Science.gov

Sample records for abrupt warming events

  1. North Pacific deglacial hypoxic events linked to abrupt ocean warming.

    PubMed

    Praetorius, S K; Mix, A C; Walczak, M H; Wolhowe, M D; Addison, J A; Prahl, F G

    2015-11-19

    Marine sediments from the North Pacific document two episodes of expansion and strengthening of the subsurface oxygen minimum zone (OMZ) accompanied by seafloor hypoxia during the last deglacial transition. The mechanisms driving this hypoxia remain under debate. We present a new high-resolution alkenone palaeotemperature reconstruction from the Gulf of Alaska that reveals two abrupt warming events of 4-5 degrees Celsius at the onset of the Bølling and Holocene intervals that coincide with sudden shifts to hypoxia at intermediate depths. The presence of diatomaceous laminations and hypoxia-tolerant benthic foraminiferal species, peaks in redox-sensitive trace metals, and enhanced (15)N/(14)N ratio of organic matter, collectively suggest association with high export production. A decrease in (18)O/(16)O values of benthic foraminifera accompanying the most severe deoxygenation event indicates subsurface warming of up to about 2 degrees Celsius. We infer that abrupt warming triggered expansion of the North Pacific OMZ through reduced oxygen solubility and increased marine productivity via physiological effects; following initiation of hypoxia, remobilization of iron from hypoxic sediments could have provided a positive feedback on ocean deoxygenation through increased nutrient utilization and carbon export. Such a biogeochemical amplification process implies high sensitivity of OMZ expansion to warming.

  2. PALEOECOLOGY. Abrupt warming events drove Late Pleistocene Holarctic megafaunal turnover.

    PubMed

    Cooper, Alan; Turney, Chris; Hughen, Konrad A; Brook, Barry W; McDonald, H Gregory; Bradshaw, Corey J A

    2015-08-07

    The mechanisms of Late Pleistocene megafauna extinctions remain fiercely contested, with human impact or climate change cited as principal drivers. We compared ancient DNA and radiocarbon data from 31 detailed time series of regional megafaunal extinctions and replacements over the past 56,000 years with standard and new combined records of Northern Hemisphere climate in the Late Pleistocene. Unexpectedly, rapid climate changes associated with interstadial warming events are strongly associated with the regional replacement or extinction of major genetic clades or species of megafauna. The presence of many cryptic biotic transitions before the Pleistocene/Holocene boundary revealed by ancient DNA confirms the importance of climate change in megafaunal population extinctions and suggests that metapopulation structures necessary to survive such repeated and rapid climatic shifts were susceptible to human impacts. Copyright © 2015, American Association for the Advancement of Science.

  3. Minimal geological methane emissions during the Younger Dryas-Preboreal abrupt warming event.

    PubMed

    Petrenko, Vasilii V; Smith, Andrew M; Schaefer, Hinrich; Riedel, Katja; Brook, Edward; Baggenstos, Daniel; Harth, Christina; Hua, Quan; Buizert, Christo; Schilt, Adrian; Fain, Xavier; Mitchell, Logan; Bauska, Thomas; Orsi, Anais; Weiss, Ray F; Severinghaus, Jeffrey P

    2017-08-23

    Methane (CH4) is a powerful greenhouse gas and plays a key part in global atmospheric chemistry. Natural geological emissions (fossil methane vented naturally from marine and terrestrial seeps and mud volcanoes) are thought to contribute around 52 teragrams of methane per year to the global methane source, about 10 per cent of the total, but both bottom-up methods (measuring emissions) and top-down approaches (measuring atmospheric mole fractions and isotopes) for constraining these geological emissions have been associated with large uncertainties. Here we use ice core measurements to quantify the absolute amount of radiocarbon-containing methane ((14)CH4) in the past atmosphere and show that geological methane emissions were no higher than 15.4 teragrams per year (95 per cent confidence), averaged over the abrupt warming event that occurred between the Younger Dryas and Preboreal intervals, approximately 11,600 years ago. Assuming that past geological methane emissions were no lower than today, our results indicate that current estimates of today's natural geological methane emissions (about 52 teragrams per year) are too high and, by extension, that current estimates of anthropogenic fossil methane emissions are too low. Our results also improve on and confirm earlier findings that the rapid increase of about 50 per cent in mole fraction of atmospheric methane at the Younger Dryas-Preboreal event was driven by contemporaneous methane from sources such as wetlands; our findings constrain the contribution from old carbon reservoirs (marine methane hydrates, permafrost and methane trapped under ice) to 19 per cent or less (95 per cent confidence). To the extent that the characteristics of the most recent deglaciation and the Younger Dryas-Preboreal warming are comparable to those of the current anthropogenic warming, our measurements suggest that large future atmospheric releases of methane from old carbon sources are unlikely to occur.

  4. Minimal geological methane emissions during the Younger Dryas-Preboreal abrupt warming event

    NASA Astrophysics Data System (ADS)

    Petrenko, Vasilii V.; Smith, Andrew M.; Schaefer, Hinrich; Riedel, Katja; Brook, Edward; Baggenstos, Daniel; Harth, Christina; Hua, Quan; Buizert, Christo; Schilt, Adrian; Fain, Xavier; Mitchell, Logan; Bauska, Thomas; Orsi, Anais; Weiss, Ray F.; Severinghaus, Jeffrey P.

    2017-08-01

    Methane (CH4) is a powerful greenhouse gas and plays a key part in global atmospheric chemistry. Natural geological emissions (fossil methane vented naturally from marine and terrestrial seeps and mud volcanoes) are thought to contribute around 52 teragrams of methane per year to the global methane source, about 10 per cent of the total, but both bottom-up methods (measuring emissions) and top-down approaches (measuring atmospheric mole fractions and isotopes) for constraining these geological emissions have been associated with large uncertainties. Here we use ice core measurements to quantify the absolute amount of radiocarbon-containing methane (14CH4) in the past atmosphere and show that geological methane emissions were no higher than 15.4 teragrams per year (95 per cent confidence), averaged over the abrupt warming event that occurred between the Younger Dryas and Preboreal intervals, approximately 11,600 years ago. Assuming that past geological methane emissions were no lower than today, our results indicate that current estimates of today’s natural geological methane emissions (about 52 teragrams per year) are too high and, by extension, that current estimates of anthropogenic fossil methane emissions are too low. Our results also improve on and confirm earlier findings that the rapid increase of about 50 per cent in mole fraction of atmospheric methane at the Younger Dryas-Preboreal event was driven by contemporaneous methane from sources such as wetlands; our findings constrain the contribution from old carbon reservoirs (marine methane hydrates, permafrost and methane trapped under ice) to 19 per cent or less (95 per cent confidence). To the extent that the characteristics of the most recent deglaciation and the Younger Dryas-Preboreal warming are comparable to those of the current anthropogenic warming, our measurements suggest that large future atmospheric releases of methane from old carbon sources are unlikely to occur.

  5. Atmospheric CO2 and abrupt climate change in Antarctic warming events 3 and 4 (65 ~ 48 kyrBP)

    NASA Astrophysics Data System (ADS)

    Ahn, J.; Brook, E. J.

    2006-12-01

    Understanding phase relationship between atmospheric CO2 and abrupt climate change (e.g., Dansgaard- Oeschger [D-O] and Heinrich events) in the last glacial period has been hampered by uncertain chronology of CO2 records from Antarctic ice cores. We developed a new extraction/analytical system to measure CO2 in ice cores, and are using it to examine millennial variations of atmospheric CO2 in the Byrd ice core, which has an age scale well synchronized to Greenland cores using CH4 records. Duplicate measurements of the Byrd ice show average standard error of the mean and pooled standard deviation of 1.55 and 1.98 ppm CO2, respectively. Our preliminary data cover Antarctic warming events A3 and A4, the onset of which precedes D-O events 14 and 17. For A3 and A4 the initial CO2 rise precedes the corresponding D-O events by 2 and 4 kyrs, respectively. CO2 reaches final interstadial levels during A4 approximately 2 kyrs before the onset of D-O 17, but the CO2 rise during A3 is more abrupt, with over half of the ~17 ppm change occurring in a <600 year step immediately preceding D-O event 14. Further high time-resolution measurements of CO2 concentration in the Byrd ice core are in progress and may help us understand the carbon cycle, teleconnection of climate-related factors such as CH4 and biological productivity recorded in marine sediments and temperatures in northern and southern hemispheres, and the chronology of other Antarctic ice cores using CO2 as a correlation tool.

  6. Response to Comment on "Abrupt warming events drove Late Pleistocene Holarctic megafaunal turnover".

    PubMed

    Cooper, Alan; Turney, Chris; Hughen, Konrad

    2016-02-26

    Rasmussen and Svensson correctly point out that there is currently no satisfactory method to fully align the Greenland and Cariaco Basin records of climate change. However, our approach using interstadial onsets as tie-points allows direct comparison between radiocarbon dates and Greenland climate records. Crucially, both the standard Greenland and the merged Greenland-Cariaco time scales show that interstadial warming was associated with megafaunal genetic transitions.

  7. Abrupt warming of the Red Sea

    NASA Astrophysics Data System (ADS)

    Raitsos, D. E.; Hoteit, I.; Prihartato, P. K.; Chronis, T.; Triantafyllou, G.; Abualnaja, Y.

    2011-07-01

    Coral reef ecosystems, often referred to as “marine rainforests,” concentrate the most diverse life in the oceans. Red Sea reef dwellers are adapted in a very warm environment, fact that makes them vulnerable to further and rapid warming. The detection and understanding of abrupt temperature changes is an important task, as ecosystems have more chances to adapt in a slowly rather than in a rapid changing environment. Using satellite derived sea surface and ground based air temperatures, it is shown that the Red Sea is going through an intense warming initiated in the mid-90s, with evidence for an abrupt increase after 1994 (0.7°C difference pre and post the shift). The air temperature is found to be a key parameter that influences the Red Sea marine temperature. The comparisons with Northern Hemisphere temperatures revealed that the observed warming is part of global climate change trends. The hitherto results also raise additional questions regarding other broader climatic impacts over the area.

  8. Abrupt climate change and extinction events

    NASA Technical Reports Server (NTRS)

    Crowley, Thomas J.

    1988-01-01

    There is a growing body of theoretical and empirical support for the concept of instabilities in the climate system, and indications that abrupt climate change may in some cases contribute to abrupt extinctions. Theoretical indications of instabilities can be found in a broad spectrum of climate models (energy balance models, a thermohaline model of deep-water circulation, atmospheric general circulation models, and coupled ocean-atmosphere models). Abrupt transitions can be of several types and affect the environment in different ways. There is increasing evidence for abrupt climate change in the geologic record and involves both interglacial-glacial scale transitions and the longer-term evolution of climate over the last 100 million years. Records from the Cenozoic clearly show that the long-term trend is characterized by numerous abrupt steps where the system appears to be rapidly moving to a new equilibrium state. The long-term trend probably is due to changes associated with plate tectonic processes, but the abrupt steps most likely reflect instabilities in the climate system as the slowly changing boundary conditions caused the climate to reach some threshold critical point. A more detailed analysis of abrupt steps comes from high-resolution studies of glacial-interglacial fluctuations in the Pleistocene. Comparison of climate transitions with the extinction record indicates that many climate and biotic transitions coincide. The Cretaceous-Tertiary extinction is not a candidate for an extinction event due to instabilities in the climate system. It is quite possible that more detailed comparisons and analysis will indicate some flaws in the climate instability-extinction hypothesis, but at present it appears to be a viable candidate as an alternate mechanism for causing abrupt environmental changes and extinctions.

  9. Abrupt pre-Bølling-Allerød warming and circulation changes in the deep ocean.

    PubMed

    Thiagarajan, Nivedita; Subhas, Adam V; Southon, John R; Eiler, John M; Adkins, Jess F

    2014-07-03

    Several large and rapid changes in atmospheric temperature and the partial pressure of carbon dioxide in the atmosphere--probably linked to changes in deep ocean circulation--occurred during the last deglaciation. The abrupt temperature rise in the Northern Hemisphere and the restart of the Atlantic meridional overturning circulation at the start of the Bølling-Allerød interstadial, 14,700 years ago, are among the most dramatic deglacial events, but their underlying physical causes are not known. Here we show that the release of heat from warm waters in the deep North Atlantic Ocean probably triggered the Bølling-Allerød warming and reinvigoration of the Atlantic meridional overturning circulation. Our results are based on coupled radiocarbon and uranium-series dates, along with clumped isotope temperature estimates, from water column profiles of fossil deep-sea corals in a limited area of the western North Atlantic. We find that during Heinrich stadial 1 (the cool period immediately before the Bølling-Allerød interstadial), the deep ocean was about three degrees Celsius warmer than shallower waters above. This reversal of the ocean's usual thermal stratification pre-dates the Bølling-Allerød warming and must have been associated with increased salinity at depth to preserve the static stability of the water column. The depleted radiocarbon content of the warm and salty water mass implies a long-term disconnect from rapid surface exchanges, and, although uncertainties remain, is most consistent with a Southern Ocean source. The Heinrich stadial 1 ocean profile is distinct from the modern water column, that for the Last Glacial Maximum and that for the Younger Dryas, suggesting that the patterns we observe are a unique feature of the deglacial climate system. Our observations indicate that the deep ocean influenced dramatic Northern Hemisphere warming by storing heat at depth that preconditioned the system for a subsequent abrupt overturning event during the

  10. Voluminous Icelandic Basaltic Eruptions Appear To Cause Abrupt Global Warming

    NASA Astrophysics Data System (ADS)

    Ward, P. L.

    2011-12-01

    Beginning on June 21, 1783, Laki volcano in southern Iceland erupted 14.7 km3 basalt, ejecting 24 Mt SO_{2} into the stratosphere where it was blown eastward and northward and 98 Mt into the troposphere where the jet stream transported it southeastward to Europe. The "dry fog" observed in Europe with an estimated mean concentration of 60 ppbv SO2, raised daytime temperatures as much as 3.3^{o}C, causing the warmest July in England from 1659 when measurements began until 1983. SO2, tropospheric O_{3}, NO2, and fine ash absorb ultraviolet energy from the sun that causes the bonds between and within their atoms to oscillate at 47 times higher frequency than the bonds in CO_{2} absorbing infrared radiation. Temperature is proportional to the kinetic energy of these oscillations, i.e. the frequency squared. Thus these gases are raised to much higher temperatures than greenhouse gases. The Stefan-Boltzmann law says that radiation from these molecules is a constant times temperature raised to the fourth power. As a result, SO2 and ash radiate far more energy back to earth than CO_{2}, causing warming. Another way to look at the energy involved shows that 15 ppbv SO2 in the 0.3-0.42 μm wavelength band absorbs as much solar energy per unit volume as 388,000 ppbv CO_{2} absorbs infrared energy in the 12.7-17.5 μm band. Basaltic volcanoes such as Laki emit 10 to 100 times more SO2 than more evolved magmas and are less explosive, leaving most of the SO_{2} in the troposphere. All 14 Dansgaard-Oeschger (DO) sudden warmings between 46 and 11 ka are contemporaneous with the highest levels of sulfate in the GISP2 drill hole near Summit Greenland. These DO events typically warmed the northern hemisphere out of the ice age within decades, but as volcanism waned, ocean temperatures cooled the world back into an ice age within centuries. The world finally exited the ice age when voluminous volcanism continued from 11.6 to 9.6 ka. Basaltic table mountains or tuyas in Iceland document

  11. Abrupt reversal in ocean overturning during the Palaeocene/Eocene warm period.

    PubMed

    Nunes, Flavia; Norris, Richard D

    2006-01-05

    An exceptional analogue for the study of the causes and consequences of global warming occurs at the Palaeocene/Eocene Thermal Maximum, 55 million years ago. A rapid rise of global temperatures during this event accompanied turnovers in both marine and terrestrial biota, as well as significant changes in ocean chemistry and circulation. Here we present evidence for an abrupt shift in deep-ocean circulation using carbon isotope records from fourteen sites. These records indicate that deep-ocean circulation patterns changed from Southern Hemisphere overturning to Northern Hemisphere overturning at the start of the Palaeocene/Eocene Thermal Maximum. This shift in the location of deep-water formation persisted for at least 40,000 years, but eventually recovered to original circulation patterns. These results corroborate climate model inferences that a shift in deep-ocean circulation would deliver relatively warmer waters to the deep sea, thus producing further warming. Greenhouse conditions can thus initiate abrupt deep-ocean circulation changes in less than a few thousand years, but may have lasting effects; in this case taking 100,000 years to revert to background conditions.

  12. Precise Interhemispheric Phasing of the Bipolar Seesaw during Abrupt Dansgaard-Oeschger Events

    NASA Astrophysics Data System (ADS)

    Buizert, C.; Baggenstos, D.; Brook, E.; Cuffey, K. M.; Fudge, T. J.; Markle, B. R.; McConnell, J. R.; Rhodes, R.; Severinghaus, J. P.; Sowers, T. A.; Steig, E. J.; Taylor, K.

    2014-12-01

    Late Pleistocene glacial periods exhibit abrupt Dansgaard-Oeschger (DO) climatic oscillations, evidence of which is preserved in a variety of northern hemisphere (NH) palaeoclimatic archives. Ice cores show Antarctica is cooling during the warm phases of the Greenland DO cycle and vice versa, suggesting an interhemispheric redistribution of heat through a mechanism dubbed the bipolar seesaw. While it is generally accepted that variations in the Atlantic meridional overturning circulation (AMOC) strength play an important role, great uncertainty remains regarding the dynamics and trigger of the abrupt events. Key information is contained in the relative phasing of hemispheric climate variations, yet the large and poorly constrained ice age-gas age difference (Dage) in Antarctic ice cores has precluded methane-based synchronization at the required sub-centennial precision. Here we present a new high accumulation deep Antarctic ice core, the West Antarctic Ice Sheet (WAIS)-Divide core, that is used to resolve the timing of the bipolar seesaw at unprecedented temporal resolution. We find that the abrupt Greenland warming phase leads the corresponding Antarctic cooling by 195 ± 59 years for DO-events, including the Bølling period; Greenland cooling leads the corresponding Antarctic warming by 179 ± 61 years. The centennial NH lead time shows that the abrupt phases of the DO cycle are initiated in the NH, after which the temperature anomaly is propagated to the southern hemisphere (SH) high latitudes via an oceanic teleconnection. The similar phasing of warming and cooling events suggests that to first order the transfer time of the climatic signal is independent of the AMOC background state. Our findings confirm the central role ocean circulation plays in the seesaw, and provide a clear criterion for testing hypotheses and model simulations of DO dynamics.

  13. Abrupt Atmospheric Methane Increases Associated With Hudson Strait Heinrich Events

    NASA Astrophysics Data System (ADS)

    Rhodes, R.; Brook, E.; Chiang, J. C. H.; Blunier, T.; Maselli, O. J.; McConnell, J. R.; Romanini, D.; Severinghaus, J. P.

    2015-12-01

    The drivers of abrupt climate change during the Last Glacial Period are not well understood. While Dansgaard-Oeschger (DO) cycles are thought to be linked to variations in the strength of the Atlantic Meridional Ocean Circulation (AMOC), it is not clear how or if Heinrich Events—extensive influxes of icebergs into the North Atlantic Ocean that impacted global climate and biogeochemistry—are related. An enduring problem is the difficultly in dating iceberg rafted debris deposits that typically lack foraminifera. Here we present an ultra-high resolution record of methane from the West Antarctic Ice Sheet Divide ice core at unprecedented, continuous temporal resolution from 67.2-9.8 ka BP, which we propose constrains the timing of Heinrich events. Our methane record essentially mirrors Greenland ice core stable isotope variability across D-O events, except during Heinrich stadials 1, 2, 4 and 5. Partway through these stadials only, methane increases abruptly and rapidly, as at the onset of a D-O event but Greenland temperature exhibits no equivalent response. Speleothem records exhibit signatures of drought in the Northern extra-tropics and intensified monsoonal activity over South America at these times. We use a simple heuristic model to propose that cold air temperatures and extensive sea ice in the North, resulting from Heinrich events, caused extreme reorganization of tropical hydroclimate. This involved curtailment of the seasonal northerly migration of tropical rain belts, leading to intensification of rainfall over Southern Hemisphere tropical wetlands, thus allowing production of excess methane relative to a 'normal' Greenland stadial. We note that this mechanism can operate if AMOC is already in a slowed state when a Heinrich event occurs, as paleo-evidence suggests it was. Heinrich events and associated sea ice cover would therefore act to prolong the duration of this AMOC state. Our findings place the big four Heinrich events of Hudson Strait origin

  14. Fluvial response to abrupt global warming at the Palaeocene/Eocene boundary.

    PubMed

    Foreman, Brady Z; Heller, Paul L; Clementz, Mark T

    2012-11-01

    Climate strongly affects the production of sediment from mountain catchments as well as its transport and deposition within adjacent sedimentary basins. However, identifying climatic influences on basin stratigraphy is complicated by nonlinearities, feedback loops, lag times, buffering and convergence among processes within the sediment routeing system. The Palaeocene/Eocene thermal maximum (PETM) arguably represents the most abrupt and dramatic instance of global warming in the Cenozoic era and has been proposed to be a geologic analogue for anthropogenic climate change. Here we evaluate the fluvial response in western Colorado to the PETM. Concomitant with the carbon isotope excursion marking the PETM we document a basin-wide shift to thick, multistoried, sheets of sandstone characterized by variable channel dimensions, dominance of upper flow regime sedimentary structures, and prevalent crevasse splay deposits. This progradation of coarse-grained lithofacies matches model predictions for rapid increases in sediment flux and discharge, instigated by regional vegetation overturn and enhanced monsoon precipitation. Yet the change in fluvial deposition persisted long after the approximately 200,000-year-long PETM with its increased carbon dioxide levels in the atmosphere, emphasizing the strong role the protracted transmission of catchment responses to distant depositional systems has in constructing large-scale basin stratigraphy. Our results, combined with evidence for increased dissolved loads and terrestrial clay export to world oceans, indicate that the transient hyper-greenhouse climate of the PETM may represent a major geomorphic 'system-clearing event', involving a global mobilization of dissolved and solid sediment loads on Earth's surface.

  15. Repetitive mammalian dwarfing during ancient greenhouse warming events

    PubMed Central

    D’Ambrosia, Abigail R.; Clyde, William C.; Fricke, Henry C.; Gingerich, Philip D.; Abels, Hemmo A.

    2017-01-01

    Abrupt perturbations of the global carbon cycle during the early Eocene are associated with rapid global warming events, which are analogous in many ways to present greenhouse warming. Mammal dwarfing has been observed, along with other changes in community structure, during the largest of these ancient global warming events, known as the Paleocene-Eocene Thermal Maximum [PETM; ~56 million years ago (Ma)]. We show that mammalian dwarfing accompanied the subsequent, smaller-magnitude warming event known as Eocene Thermal Maximum 2 [ETM2 (~53 Ma)]. Statistically significant decrease in body size during ETM2 is observed in two of four taxonomic groups analyzed in this study and is most clearly observed in early equids (horses). During ETM2, the best-sampled lineage of equids decreased in size by ~14%, as opposed to ~30% during the PETM. Thus, dwarfing appears to be a common evolutionary response of some mammals during past global warming events, and the extent of dwarfing seems related to the magnitude of the event. PMID:28345031

  16. Repetitive mammalian dwarfing during ancient greenhouse warming events.

    PubMed

    D'Ambrosia, Abigail R; Clyde, William C; Fricke, Henry C; Gingerich, Philip D; Abels, Hemmo A

    2017-03-01

    Abrupt perturbations of the global carbon cycle during the early Eocene are associated with rapid global warming events, which are analogous in many ways to present greenhouse warming. Mammal dwarfing has been observed, along with other changes in community structure, during the largest of these ancient global warming events, known as the Paleocene-Eocene Thermal Maximum [PETM; ~56 million years ago (Ma)]. We show that mammalian dwarfing accompanied the subsequent, smaller-magnitude warming event known as Eocene Thermal Maximum 2 [ETM2 (~53 Ma)]. Statistically significant decrease in body size during ETM2 is observed in two of four taxonomic groups analyzed in this study and is most clearly observed in early equids (horses). During ETM2, the best-sampled lineage of equids decreased in size by ~14%, as opposed to ~30% during the PETM. Thus, dwarfing appears to be a common evolutionary response of some mammals during past global warming events, and the extent of dwarfing seems related to the magnitude of the event.

  17. Abrupt termination of the 2012 Pacific warming and its implication on ENSO prediction

    NASA Astrophysics Data System (ADS)

    Su, Jingzhi; Xiang, Baoqiang; Wang, Bin; Li, Tim

    2014-12-01

    In the summer of 2012, there was a clear signal of the developing El Niño over the equatorial Pacific, and many climate models forecasted the occurrence of El Niño with a peak phase in the subsequent winter. However, the warming was aborted abruptly in late fall. Here we show that the abrupt termination of the 2012 Pacific warming was largely attributed to the anomalous sea surface temperature (SST) cooling in the northeastern and southeastern subtropical Pacific. The anomalous SST cooling induced strong easterly and low-level divergence anomalies, suppressing the development of westerly and convection anomalies over the equatorial central Pacific. Thus, the surface warming over the equatorial Pacific was decoupled from the surface wind forcing and subsurface thermocline variability, inhibiting its further development into a mature El Niño in the winter of 2012-2013. This study highlights the importance of the SST anomaly in the subtropical Pacific in El Niño prediction.

  18. Paradox of the peak-PCIM (Paleocene Carbon Isotope Maxima; ~57.8Ma) and Abrupt Global Warming

    NASA Astrophysics Data System (ADS)

    Harper, D. T.; Hoenisch, B.; Zachos, J. C.

    2015-12-01

    The Paleocene Carbon Isotope Maxima (PCIM; ~57.8Ma) represents a major transition in global δ13C during the late Paleocene, when the long-term positive trend in δ13C reversed from positive to negative. The peak-PCIM (~57.7Ma) has been tightly resolved in new high-resolution, astronomically-tuned benthic isotope records from IODP Sites 1209 (Pacific) and 1262 (Atlantic), which show the final phase of δ13C enrichment as abrupt (~1‰ in <100kyrs) and coinciding with a 0.5‰ decline in benthic δ18O indicative of 2-3ºC of bottom water warming, effectively marking the onset of a gradual 8Myr long warming trend [Littler et al., EPSL 2014]. Typically, during the Paleogene on orbital time scales, warming is observed during intervals of δ13C depletion, consistent with release of isotopically light carbon to the atmosphere. This event, which has the appearance of a bifurcation in the long-term coupling of climate system and the carbon cycle, poses an interesting paradox as any rapid carbon release to the atmosphere should, in theory, create a negative excursion because all of the major carbon sources are isotopically light, whether volcanic outgassing, weathering/oxidation of organic carbon, or methane release [Dunkley-Jones et al., Phil. Trans. R. Soc. A 2010]. If global, there are several testable mechanisms that may explain the shift including increase in burial flux of light carbon, a reduction in heavy carbon burial flux, or a large-scale circulation change perhaps associated with the transition of a major oceanic gateway. Using trace metal (B/Ca and Mg/Ca) and stable isotope (δ11B, δ18O, and δ13C) geochemistry, here we establish the nature of the peak-PCIM at sites from 3 different ocean basins (IODP Sites 690, 1209, and 1262) and begin to test several of the possible mechanisms for change. Mg/Ca in mixed-layer planktonic foraminifera show 2-3°C of sea surface warming coinciding with, and abrupt as, the benthic carbon isotope enrichment at all sites. Bottom

  19. Abrupt changes in the southern extent of North Atlantic Deep Water during Dansgaard-Oeschger events

    NASA Astrophysics Data System (ADS)

    Gottschalk, Julia; Skinner, Luke C.; Misra, Sambuddha; Waelbroeck, Claire; Menviel, Laurie; Timmermann, Axel

    2015-12-01

    The glacial climate system transitioned rapidly between cold (stadial) and warm (interstadial) conditions in the Northern Hemisphere. This variability, referred to as Dansgaard-Oeschger variability, is widely believed to arise from perturbations of the Atlantic Meridional Overturning Circulation. Evidence for such changes during the longer Heinrich stadials has been identified, but direct evidence for overturning circulation changes during Dansgaard-Oeschger events has proven elusive. Here we reconstruct bottom water [CO32-] variability from B/Ca ratios of benthic foraminifera and indicators of sedimentary dissolution, and use these reconstructions to infer the flow of northern-sourced deep water to the deep central sub-Antarctic Atlantic Ocean. We find that nearly every Dansgaard-Oeschger interstadial is accompanied by a rapid incursion of North Atlantic Deep Water into the deep South Atlantic. Based on these results and transient climate model simulations, we conclude that North Atlantic stadial-interstadial climate variability was associated with significant Atlantic overturning circulation changes that were rapidly transmitted across the Atlantic. However, by demonstrating the persistent role of Atlantic overturning circulation changes in past abrupt climate variability, our reconstructions of carbonate chemistry further indicate that the carbon cycle response to abrupt climate change was not a simple function of North Atlantic overturning.

  20. Gradual Warming in the North Atlantic during D-O Events Synchronous with Antarctic and Southern Hemisphere Warmings

    NASA Astrophysics Data System (ADS)

    Rasmussen, T. L.; Thomsen, E.; Moros, M.

    2016-12-01

    The climate of the last glacial period was interrupted by about 25 rapid oscillations, called Dansgaard-Oeschger events. In the Greenland ice cores, the events consist of an abrupt warming to warm interstadial conditions followed by a more gradual return to cold stadial conditions. Similar abrupt warmings are seen in paleoceanographic proxies from the Nordic seas, and the shifts are apparently linked to perturbations in the ocean thermohaline circulation. The events also occur in the Antarctic ice cores, but the amplitudes here are smaller and the warmings are more gradual and initiated earlier than in the north. The out-of-phase relationship between the north and south is often referred to as the `Bipolar seesaw'. We have studied core SO2 from the Reykjanes Ridge in the central northernmost Atlantic. The results are compared with previously published records from the North Atlantic and correlated with the Greenland and Antarctic ice cores. By means of transfer function analysis and δ18O values from planktic and benthic foraminifera we show that surface and bottom water temperatures in SO2 increased gradually during the Greenland stadials to a maximum at the beginning of the interstadials. The warmings in SO2 follow the timing and gradual warmings observed in the Antarctic ice cores and they are clearly out of phase with the abrupt, delayed warmings over Greenland. Apparently, the surface and intermediate water over most of the Atlantic from the Antarctica to the Scotland-Greenland Ridge warmed and pressed northward at a time when the atmospheric temperatures over Greenland were at minimum and the convection in the Nordic seas stopped. The system appears to function more as a `push-and-pull' system than as a seesaw with a `pull' during the warm interstadials, when convection in the Nordic seas was active and a `push' during the cold stadials, when warm water from the south-central Atlantic pushed northward gradually warming the northernmost Atlantic and Nordic

  1. Linear sea-level response to abrupt ocean warming of major West Antarctic ice basin

    NASA Astrophysics Data System (ADS)

    Mengel, M.; Feldmann, J.; Levermann, A.

    2016-01-01

    Antarctica's contribution to global sea-level rise has recently been increasing. Whether its ice discharge will become unstable and decouple from anthropogenic forcing or increase linearly with the warming of the surrounding ocean is of fundamental importance. Under unabated greenhouse-gas emissions, ocean models indicate an abrupt intrusion of warm circumpolar deep water into the cavity below West Antarctica's Filchner-Ronne ice shelf within the next two centuries. The ice basin's retrograde bed slope would allow for an unstable ice-sheet retreat, but the buttressing of the large ice shelf and the narrow glacier troughs tend to inhibit such instability. It is unclear whether future ice loss will be dominated by ice instability or anthropogenic forcing. Here we show in regional and continental-scale ice-sheet simulations, which are capable of resolving unstable grounding-line retreat, that the sea-level response of the Filchner-Ronne ice basin is not dominated by ice instability and follows the strength of the forcing quasi-linearly. We find that the ice loss reduces after each pulse of projected warm water intrusion. The long-term sea-level contribution is approximately proportional to the total shelf-ice melt. Although the local instabilities might dominate the ice loss for weak oceanic warming, we find that the upper limit of ice discharge from the region is determined by the forcing and not by the marine ice-sheet instability.

  2. Abrupt Climate Events in Britain and the North Atlantic during Marine Isotope Stage 11

    NASA Astrophysics Data System (ADS)

    Candy, I.; Tye, G.; Coxon, P.; Palmer, A.; Hardiman, M.; Matthews, I.; Loakes, K.; Ryves, D.; McClymont, E.

    2016-12-01

    The Holocene has been punctuated by numerous abrupt climatic events, whilst abrupt change may also occur in the future as ice-sheet decay interacts with ocean-circulation. It is unclear whether abrupt events are a common phenomenon in pre-Holocene interglacials and whether such events occur in association with terminal ice-sheet decay in the very early interglacial and/or in association with largescale melting of ice sheets, such as Greenland, during peak interglacial conditions. The best preserved abrupt climatic event in a pre-Holocene interglacial in western/central Europe comes from annually-laminated lake deposits of MIS 11c. These sequences are, however, fragmented and difficult to place into the context of the long/continuous benthic δ18O records of glacial interglacial cycles. This study presents; 1) a high-resolution record of an MIS 11c abrupt event from Britain and 2) the first high-precision correlation between European MIS11c deposits and the marine records of the North Atlantic (ODP 980) through the application of tephra chronology. Both the structure of this event and its position within the benthic δ18O stratigraphy of MIS11 implies that it is analogous to the 8.2ka event. However, the occurrence of other abrupt events later in MIS11c in Europe indicate the possibility that climatic instability occurred later in this interglacial too, possibly in association with the thermal maximum, and the ice volume minima, of this interglacial.

  3. H4 abrupt event and late Neanderthal presence in Iberia

    NASA Astrophysics Data System (ADS)

    Sepulchre, Pierre; Ramstein, Gilles; Kageyama, Masa; Vanhaeren, Marian; Krinner, Gerhard; Sánchez-Goñi, María-Fernanda; d'Errico, Francesco

    2007-06-01

    Heinrich event 4 (H4) is well documented in the North Atlantic Ocean and the adjacent continents as a cooling event 39,000 yr before present (BP). To quantify the impact of this event with respect to climate and vegetation over the Iberian Peninsula, we perform numerical experiments using a high-resolution general circulation model forced by sea surface temperatures before and during H4. Our model simulates an expansion of aridity over the peninsula during H4, a desertification of the south, and a replacement of arboreal by herbaceous plants in the north, all of which are in agreement with contemporaneous pollen sequences from marine cores located off the Iberian Peninsula. Our simulations demonstrate that the H4 marine event imprinted drastic changes over Southern Iberia, which would not have favoured its occupation by Anatomically Modern Humans, therefore providing a plausible explanation for the delayed extinction of Neanderthals in this region inferred from the archaeological record.

  4. Sea-level response to abrupt ocean warming of Antarctic ice shelves

    NASA Astrophysics Data System (ADS)

    Pattyn, Frank

    2016-04-01

    Antarctica's contribution to global sea-level rise increases steadily. A fundamental question remains whether the ice discharge will lead to marine ice sheet instability (MISI) and collapse of certain sectors of the ice sheet or whether ice loss will increase linearly with the warming trends. Therefore, we employ a newly developed ice sheet model of the Antarctic ice sheet, called f.ETISh (fast Elementary Thermomechanical Ice Sheet model) to simulate ice sheet response to abrupt perturbations in ocean and atmospheric temperature. The f.ETISh model is a vertically integrated hybrid (SSA/SIA) ice sheet model including ice shelves. Although vertically integrated, thermomechanical coupling is ensured through a simplified representation of ice sheet thermodynamics based on an analytical solution of the vertical temperature profile, including strain heating and horizontal advection. The marine boundary is represented by a flux condition either coherent with power-law basal sliding (Pollard & Deconto (2012) based on Schoof (2007)) or according to Coulomb basal friction (Tsai et al., 2015), both taking into account ice-shelf buttressing. Model initialization is based on optimization of the basal friction field. Besides the traditional MISMIP tests, new tests with respect to MISI in plan-view models have been devised. The model is forced with stepwise ocean and atmosphere temperature perturbations. The former is based on a parametrised sub-shelf melt (limited to ice shelves), while the latter is based on present-day mass balance/surface temperature and corrected for elevation changes. Surface melting is introduced using a PDD model. Results show a general linear response in mass loss to ocean warming. Nonlinear response due to MISI occurs under specific conditions and is highly sensitive to the basal conditions near the grounding line, governed by both the initial conditions and the basal sliding/deformation model. The Coulomb friction model leads to significantly higher

  5. Paleoclimate. Synchronization of North Pacific and Greenland climates preceded abrupt deglacial warming.

    PubMed

    Praetorius, Summer K; Mix, Alan C

    2014-07-25

    Some proposed mechanisms for transmission of major climate change events between the North Pacific and North Atlantic predict opposing patterns of variations; others suggest synchronization. Resolving this conflict has implications for regulation of poleward heat transport and global climate change. New multidecadal-resolution foraminiferal oxygen isotope records from the Gulf of Alaska (GOA) reveal sudden shifts between intervals of synchroneity and asynchroneity with the North Greenland Ice Core Project (NGRIP) δ(18)O record over the past 18,000 years. Synchronization of these regions occurred 15,500 to 11,000 years ago, just prior to and throughout the most abrupt climate transitions of the last 20,000 years, suggesting that dynamic coupling of North Pacific and North Atlantic climates may lead to critical transitions in Earth's climate system.

  6. Classical and quantum cosmology of the little rip abrupt event

    NASA Astrophysics Data System (ADS)

    Albarran, Imanol; Bouhmadi-López, Mariam; Kiefer, Claus; Marto, João; Vargas Moniz, Paulo

    2016-09-01

    We analyze from a classical and quantum point of view the behavior of the Universe close to a little rip, which can be interpreted as a big rip sent towards the infinite future. Like a big rip singularity, a little rip implies the destruction of all bounded structures in the Universe and is thus an event where quantum effects could be important. We present here a new phantom scalar field model for the little rip. The quantum analysis is performed in quantum geometrodynamics, with the Wheeler-DeWitt equation as its central equation. We find that the little rip can be avoided in the sense of the DeWitt criterion, that is, by having a vanishing wave function at the place of the little rip. Therefore our analysis completes the answer to the question: can quantum cosmology smoothen or avoid the divergent behavior genuinely caused by phantom matter? We show that this can indeed happen for the little rip, similar to the avoidance of a big rip and a little sibling of the big rip.

  7. Investigation of the Impact of a Heinrich-Event-like Abrupt Event Superimposed Onto the RCP 8.5 Scenario

    NASA Astrophysics Data System (ADS)

    Defrance, D.; Ramstein, G.; Dumas, C.; Charbit, S.

    2014-12-01

    The CMIP5/IPCC (AR5) projections of climate change showed the temperatures should increase by between 1.3 °C and 4.4 °C by 2100 and the sea level rise between 26 cm and 82 cm on average. Superimposed on these climatic and hydrologic trends associated with the RCP 8.5 most pessimistic scenario, it is important to investigate the possible effect of an abrupt event like an ice-sheet surge. This is first justified by the recent collapse of the Larsen B ice shelf which illustrates that a non-linear response of the cryosphere may occur in a warming world. Furthermore, in glacial periods, ice-sheets have been unstable and huge surges of icebergs did occur and deeply modified the climate. The aim of this presentation is to show the hypothetical climatic consequences of such a Heinrich-type event on future climate change. To achieve this goal, 3 scenarios of rapid ice-sheet deglaciation have been designed, corresponding to an additional sea level rise of around 3 m : - S1 corresponds to a contribution from Greenland only; - S2 from West-Antarctica only; - S3 from both ice-sheets. We use the global atmosphere-ocean general circulation model (OAGCM) IPSL-CM5A-LR. The freshwater perturbation is applied near the ice-sheet(s) during 20 years from 2050 to 2070 during an RCP8.5 perturbation. The RCP8.5 scenario is then continued until 2100 (without freshwater). For these types of scenarios, previous experiments for paleoclimatic cases help us diagnose the most vulnerable areas. The North Atlantic and the collapse of thermohaline circulation is one key issue, but far field teleconnections with the Asian monsoon will also be explored. We will investigate the timing and amplitude of the climate impacts due to the perturbations, which may be quite different in our 3 scenarios. These abrupt events consequences can be important for the populations and the consideration of rapid changes should improve the reliability of IPCC predictions.

  8. Gradual onset and recovery of the Younger Dryas abrupt climate event in the tropics

    PubMed Central

    Partin, J.W.; Quinn, T.M.; Shen, C.-C.; Okumura, Y.; Cardenas, M.B.; Siringan, F.P.; Banner, J.L.; Lin, K.; Hu, H.-M.; Taylor, F.W.

    2015-01-01

    Proxy records of temperature from the Atlantic clearly show that the Younger Dryas was an abrupt climate change event during the last deglaciation, but records of hydroclimate are underutilized in defining the event. Here we combine a new hydroclimate record from Palawan, Philippines, in the tropical Pacific, with previously published records to highlight a difference between hydroclimate and temperature responses to the Younger Dryas. Although the onset and termination are synchronous across the records, tropical hydroclimate changes are more gradual (>100 years) than the abrupt (10–100 years) temperature changes in the northern Atlantic Ocean. The abrupt recovery of Greenland temperatures likely reflects changes in regional sea ice extent. Proxy data and transient climate model simulations support the hypothesis that freshwater forced a reduction in the Atlantic meridional overturning circulation, thereby causing the Younger Dryas. However, changes in ocean overturning may not produce the same effects globally as in Greenland. PMID:26329911

  9. Gradual onset and recovery of the Younger Dryas abrupt climate event in the tropics

    NASA Astrophysics Data System (ADS)

    Partin, J. W.; Quinn, T. M.; Shen, C.-C.; Okumura, Y.; Cardenas, M. B.; Siringan, F. P.; Banner, J. L.; Lin, K.; Hu, H.-M.; Taylor, F. W.

    2015-09-01

    Proxy records of temperature from the Atlantic clearly show that the Younger Dryas was an abrupt climate change event during the last deglaciation, but records of hydroclimate are underutilized in defining the event. Here we combine a new hydroclimate record from Palawan, Philippines, in the tropical Pacific, with previously published records to highlight a difference between hydroclimate and temperature responses to the Younger Dryas. Although the onset and termination are synchronous across the records, tropical hydroclimate changes are more gradual (>100 years) than the abrupt (10-100 years) temperature changes in the northern Atlantic Ocean. The abrupt recovery of Greenland temperatures likely reflects changes in regional sea ice extent. Proxy data and transient climate model simulations support the hypothesis that freshwater forced a reduction in the Atlantic meridional overturning circulation, thereby causing the Younger Dryas. However, changes in ocean overturning may not produce the same effects globally as in Greenland.

  10. Gradual onset and recovery of the Younger Dryas abrupt climate event in the tropics.

    PubMed

    Partin, J W; Quinn, T M; Shen, C-C; Okumura, Y; Cardenas, M B; Siringan, F P; Banner, J L; Lin, K; Hu, H-M; Taylor, F W

    2015-09-02

    Proxy records of temperature from the Atlantic clearly show that the Younger Dryas was an abrupt climate change event during the last deglaciation, but records of hydroclimate are underutilized in defining the event. Here we combine a new hydroclimate record from Palawan, Philippines, in the tropical Pacific, with previously published records to highlight a difference between hydroclimate and temperature responses to the Younger Dryas. Although the onset and termination are synchronous across the records, tropical hydroclimate changes are more gradual (>100 years) than the abrupt (10-100 years) temperature changes in the northern Atlantic Ocean. The abrupt recovery of Greenland temperatures likely reflects changes in regional sea ice extent. Proxy data and transient climate model simulations support the hypothesis that freshwater forced a reduction in the Atlantic meridional overturning circulation, thereby causing the Younger Dryas. However, changes in ocean overturning may not produce the same effects globally as in Greenland.

  11. Abrupt summer warming and changes in temperature extremes over Northeast Asia since the mid-1990s: Drivers and physical processes

    NASA Astrophysics Data System (ADS)

    Dong, Buwen; Sutton, Rowan T.; Chen, Wei; Liu, Xiaodong; Lu, Riyu; Sun, Ying

    2016-09-01

    This study investigated the drivers and physical processes for the abrupt decadal summer surface warming and increases in hot temperature extremes that occurred over Northeast Asia in the mid-1990s. Observations indicate an abrupt increase in summer mean surface air temperature (SAT) over Northeast Asia since the mid-1990s. Accompanying this abrupt surface warming, significant changes in some temperature extremes, characterized by increases in summer mean daily maximum temperature (Tmax), daily minimum temperature (Tmin), annual hottest day temperature (TXx), and annual warmest night temperature (TNx) were observed. There were also increases in the frequency of summer days (SU) and tropical nights (TR). Atmospheric general circulation model experiments forced by changes in sea surface temperature (SST)/sea ice extent (SIE), anthropogenic greenhouse gas (GHG) concentrations, and anthropogenic aerosol (AA) forcing, relative to the period 1964-93, reproduced the general patterns of observed summer mean SAT changes and associated changes in temperature extremes, although the abrupt decrease in precipitation since the mid-1990s was not simulated. Additional model experiments with different forcings indicated that changes in SST/SIE explained 76% of the area-averaged summer mean surface warming signal over Northeast Asia, while the direct impact of changes in GHG and AA explained the remaining 24% of the surface warming signal. Analysis of physical processes indicated that the direct impact of the changes in AA (through aerosol-radiation and aerosol-cloud interactions), mainly related to the reduction of AA precursor emissions over Europe, played a dominant role in the increase in TXx and a similarly important role as SST/SIE changes in the increase in the frequency of SU over Northeast Asia via AA-induced coupled atmosphere-land surface and cloud feedbacks, rather than through a direct impact of AA changes on cloud condensation nuclei. The modelling results also imply

  12. Consistent simulations of multiple proxy responses to an abrupt climate change event.

    PubMed

    LeGrande, A N; Schmidt, G A; Shindell, D T; Field, C V; Miller, R L; Koch, D M; Faluvegi, G; Hoffmann, G

    2006-01-24

    Isotope, aerosol, and methane records document an abrupt cooling event across the Northern Hemisphere at 8.2 kiloyears before present (kyr), while separate geologic lines of evidence document the catastrophic drainage of the glacial Lakes Agassiz and Ojibway into the Hudson Bay at approximately the same time. This melt water pulse may have been the catalyst for a decrease in North Atlantic Deep Water formation and subsequent cooling around the Northern Hemisphere. However, lack of direct evidence for ocean cooling has lead to speculation that this abrupt event was purely local to Greenland and called into question this proposed mechanism. We simulate the response to this melt water pulse using a coupled general circulation model that explicitly tracks water isotopes and with atmosphere-only experiments that calculate changes in atmospheric aerosol deposition (specifically (10)Be and dust) and wetland methane emissions. The simulations produce a short period of significantly diminished North Atlantic Deep Water and are able to quantitatively match paleoclimate observations, including the lack of isotopic signal in the North Atlantic. This direct comparison with multiple proxy records provides compelling evidence that changes in ocean circulation played a major role in this abrupt climate change event.

  13. Consistent simulations of multiple proxy responses to an abrupt climate change event

    PubMed Central

    LeGrande, A. N.; Schmidt, G. A.; Shindell, D. T.; Field, C. V.; Miller, R. L.; Koch, D. M.; Faluvegi, G.; Hoffmann, G.

    2006-01-01

    Isotope, aerosol, and methane records document an abrupt cooling event across the Northern Hemisphere at 8.2 kiloyears before present (kyr), while separate geologic lines of evidence document the catastrophic drainage of the glacial Lakes Agassiz and Ojibway into the Hudson Bay at approximately the same time. This melt water pulse may have been the catalyst for a decrease in North Atlantic Deep Water formation and subsequent cooling around the Northern Hemisphere. However, lack of direct evidence for ocean cooling has lead to speculation that this abrupt event was purely local to Greenland and called into question this proposed mechanism. We simulate the response to this melt water pulse using a coupled general circulation model that explicitly tracks water isotopes and with atmosphere-only experiments that calculate changes in atmospheric aerosol deposition (specifically 10Be and dust) and wetland methane emissions. The simulations produce a short period of significantly diminished North Atlantic Deep Water and are able to quantitatively match paleoclimate observations, including the lack of isotopic signal in the North Atlantic. This direct comparison with multiple proxy records provides compelling evidence that changes in ocean circulation played a major role in this abrupt climate change event. PMID:16415159

  14. Partitioning the influence of regional warming and feedbacks in the global response to abrupt CO2 forcing

    NASA Astrophysics Data System (ADS)

    Hedemann, Christopher; Mauritsen, Thorsten; Jungclaus, Johann; Marotzke, Jochem

    2017-04-01

    We present a new analytical framework for diagnosing the regional causes of state-dependence in global radiative feedbacks. We apply this framework in long runs (˜1000 years) with the coupled climate model MPI-ESM-LR 1.2, subject to abrupt increases in CO2 concentration, including 2-, 4-, 8- and 16-times the pre-industrial levels. Two existing theories link a changing global feedback parameter to regional processes: either changing regional warming patterns activate constant regional feedbacks - "the pattern effect" - or the regional feedbacks themselves change -"regional state-dependence". Previous studies have typically tested one theory under particular conditions; we apply our method to diagnose both effects across a range of timescales and forcing strengths. Preliminary results indicate that the influence of the pattern effect is restricted to the initial warming phase. During the first decades of warming, ocean heat uptake allows regional warming to be non-linear with respect to the global mean, which our framework indicates is a necessary condition for the pattern effect. The evolution of global feedbacks over the remainder of the warming response is dominated by regional state-dependence and determined by the forcing strength. By identifying the conditions necessary for these effects to influence the global radiative response, we propose a link between both theories.

  15. Competition between global warming and an abrupt collapse of the AMOC in Earth's energy imbalance.

    PubMed

    Drijfhout, Sybren

    2015-10-06

    A collapse of the Atlantic Meridional Overturning Circulation (AMOC) leads to global cooling through fast feedbacks that selectively amplify the response in the Northern Hemisphere (NH). How such cooling competes with global warming has long been a topic for speculation, but was never addressed using a climate model. Here it is shown that global cooling due to a collapsing AMOC obliterates global warming for a period of 15-20 years. Thereafter, the global mean temperature trend is reversed and becomes similar to a simulation without an AMOC collapse. The resulting surface warming hiatus lasts for 40-50 years. Global warming and AMOC-induced NH cooling are governed by similar feedbacks, giving rise to a global net radiative imbalance of similar sign, although the former is associated with surface warming, the latter with cooling. Their footprints in outgoing longwave and absorbed shortwave radiation are very distinct, making attribution possible.

  16. Tree ring correlation between prehistoric landslides and abrupt tectonic events in Seattle, washington.

    PubMed

    Jacoby, G C; Williams, P L; Buckley, B M

    1992-12-04

    Radiocarbon ages of submerged trees on landslide deposits in Lake Washington, Seattle, indicate that the most recent slides in three separate areas may have occurred simultaneously about 1000 years ago. Tree ring crossdating shows that seven bark-bearing trees from one of these recent slides and a tree 23 kilometers to the northwest in a probable tsunami deposit on the shore of Puget Sound died in the same season of the same year. The close coincidence among the most recent lake landslides, a probable tsunami, abrupt subsidence, and other possible seismic events gives evidence for a strong prehistoric earthquake in the Seattle region.

  17. Synchronous centennial abrupt events in the ocean and atmosphere during the last deglaciation.

    PubMed

    Chen, Tianyu; Robinson, Laura F; Burke, Andrea; Southon, John; Spooner, Peter; Morris, Paul J; Ng, Hong Chin

    2015-09-25

    Antarctic ice-core data reveal that the atmosphere experienced abrupt centennial increases in CO2 concentration during the last deglaciation (~18 thousand to 11 thousand years ago). Establishing the role of ocean circulation in these changes requires high-resolution, accurately dated marine records. Here, we report radiocarbon data from uranium-thorium-dated deep-sea corals in the Equatorial Atlantic and Drake Passage over the past 25,000 years. Two major deglacial radiocarbon shifts occurred in phase with centennial atmospheric CO2 rises at 14.8 thousand and 11.7 thousand years ago. We interpret these radiocarbon-enriched signals to represent two short-lived (less than 500 years) "overshoot" events, with Atlantic meridional overturning stronger than that of the modern era. These results provide compelling evidence for a close coupling of ocean circulation and centennial climate events during the last deglaciation.

  18. Abrupt Bølling warming and ice saddle collapse contributions to the Meltwater Pulse 1a rapid sea level rise

    NASA Astrophysics Data System (ADS)

    Gregoire, Lauren J.; Otto-Bliesner, Bette; Valdes, Paul J.; Ivanovic, Ruza

    2016-09-01

    Elucidating the source(s) of Meltwater Pulse 1a, the largest rapid sea level rise caused by ice melt (14-18 m in less than 340 years, 14,600 years ago), is important for understanding mechanisms of rapid ice melt and the links with abrupt climate change. Here we quantify how much and by what mechanisms the North American ice sheet could have contributed to Meltwater Pulse 1a, by driving an ice sheet model with two transient climate simulations of the last 21,000 years. Ice sheet perturbed physics ensembles were run to account for model uncertainties, constraining ice extent and volume with reconstructions of 21,000 years ago to present. We determine that the North American ice sheet produced 3-4 m global mean sea level rise in 340 years due to the abrupt Bølling warming, but this response is amplified to 5-6 m when it triggers the ice sheet saddle collapse.

  19. Abrupt Bølling warming and ice saddle collapse contributions to the Meltwater Pulse 1a rapid sea level rise

    PubMed Central

    Otto‐Bliesner, Bette; Valdes, Paul J.; Ivanovic, Ruza

    2016-01-01

    Abstract Elucidating the source(s) of Meltwater Pulse 1a, the largest rapid sea level rise caused by ice melt (14–18 m in less than 340 years, 14,600 years ago), is important for understanding mechanisms of rapid ice melt and the links with abrupt climate change. Here we quantify how much and by what mechanisms the North American ice sheet could have contributed to Meltwater Pulse 1a, by driving an ice sheet model with two transient climate simulations of the last 21,000 years. Ice sheet perturbed physics ensembles were run to account for model uncertainties, constraining ice extent and volume with reconstructions of 21,000 years ago to present. We determine that the North American ice sheet produced 3–4 m global mean sea level rise in 340 years due to the abrupt Bølling warming, but this response is amplified to 5–6 m when it triggers the ice sheet saddle collapse. PMID:27773954

  20. Abrupt Bølling warming and ice saddle collapse contributions to the Meltwater Pulse 1a rapid sea level rise.

    PubMed

    Gregoire, Lauren J; Otto-Bliesner, Bette; Valdes, Paul J; Ivanovic, Ruza

    2016-09-16

    Elucidating the source(s) of Meltwater Pulse 1a, the largest rapid sea level rise caused by ice melt (14-18 m in less than 340 years, 14,600 years ago), is important for understanding mechanisms of rapid ice melt and the links with abrupt climate change. Here we quantify how much and by what mechanisms the North American ice sheet could have contributed to Meltwater Pulse 1a, by driving an ice sheet model with two transient climate simulations of the last 21,000 years. Ice sheet perturbed physics ensembles were run to account for model uncertainties, constraining ice extent and volume with reconstructions of 21,000 years ago to present. We determine that the North American ice sheet produced 3-4 m global mean sea level rise in 340 years due to the abrupt Bølling warming, but this response is amplified to 5-6 m when it triggers the ice sheet saddle collapse.

  1. Abrupt climate change: Past, present and the search for precursors as an aid to predicting events in the future (Hans Oeschger Medal Lecture)

    NASA Astrophysics Data System (ADS)

    Mayewski, Paul Andrew

    2016-04-01

    The demonstration using Greenland ice cores that abrupt shifts in climate, Dansgaard-Oeschger (D-O) events, existed during the last glacial period has had a transformational impact on our understanding of climate change in the naturally forced world. The demonstration that D-O events are globally distributed and that they operated during previous glacial periods has led to extensive research into the relative hemispheric timing and causes of these events. The emergence of civilization during our current interglacial, the Holocene, has been attributed to the "relative climate quiescence" of this period relative to the massive, abrupt shifts in climate that characterized glacial periods in the form of D-O events. But, everything is relative and climate change is no exception. The demise of past civilizations, (eg., Mesopatamian, Mayan and Norse) is integrally tied to abrupt climate change (ACC) events operating at regional scales. Regionally to globally distributed ACC events have punctuated the Holocene and extreme events have always posed significant challenges to humans and ecosystems. Current warming of the Arctic, in terms of length of the summer season, is as abrupt and massive, albeit not as extensive, as the transition from the last major D-O event, the Younger Dryas into the Holocene (Mayewski et al., 2013). Tropospheric source greenhouse gas rise and ozone depletion in the stratosphere over Antarctica are triggers for the modern advent of human emission instigated ACCs. Arctic warming and Antarctic ozone depletion have resulted in significance changes to the atmospheric circulation systems that transport heat, moisture, and pollutants in both hemispheres. Climate models offer a critical tool for assessing trends, but they cannot as yet predict ACC events, as evidenced by the inability of these models to predict the rapid onset of Arctic warming and resulting changes in atmospheric circulation; and in the model vs past analog differences in projections for

  2. Response of atmospheric CO2 to the abrupt cooling event 8200 years ago

    NASA Astrophysics Data System (ADS)

    Ahn, J.; Brook, E.; Buizert, C.

    2013-12-01

    The abrupt cooling event 8200 years ago (8.2 ka event) is the most prominent centennial scale climate event during the Holocene and was likely caused by a reduction in the Atlantic meridional overturning circulation (AMOC). Atmospheric CO2 records for this event may help us understand climate-carbon cycle feedbacks under interglacial conditions, which are important for understanding future climate, but existing ice core records do not provide enough detail and natural smoothing of the CO2 time series by diffusion and gradual bubble close-off in the firn layer (unconsolidated snow layer in the top of ice sheets) limits their resolution. Studies of leaf stomata records suggest a CO2 decrease of up to ~25 ppm during the 8.2 ka event, but relatively large uncertainties in reconstructed CO2 levels from leaves and dating make firm conclusions difficult. Here we present a new CO2 record from the Siple Dome ice core, Antarctica, that covers 7.4-9.0 ka with 8- to 16-year resolution. The relatively high snow accumulation rate at Siple Dome results minimizes smoothing relative to other records and the timing of the 8.2 ka event is precisely constrained by a CH4 record from the same core. We observe a small, ~2 ppm, increase of atmospheric CO2 during the 8.2 ka event. The increase is not remarkable when compared to other centennial variations in the Holocene that are not linked to large temperature changes. Our results imply that the sensitivity of atmospheric CO2 to the primarily northern hemisphere cooling of the 8.2 ka event was limited.

  3. Examining the potential impact of a warming ocean on food insecure Africa: concerns and mechanisms for abrupt climate change

    NASA Astrophysics Data System (ADS)

    Funk, C.; Dettinger, M.; Verdin, J.

    2007-12-01

    Given that more than 200 million sub-Saharan Africans are food insecure, abrupt climate change in Africa could be devastating. Recent observations for eastern and southern Africa suggest substantial declines in main growing season rainfall over the past 20 years. In this talk we present research from a multi-year study that examined the causes and implications of these drying trends. Our statistical and dynamic modeling results suggest that warming in the Indian Ocean has been linked to increased oceanic convection and disruptions in onshore moisture transports. These moisture transport disruptions, in turn, are probably associated with an increased frequency in agricultural drought in sub-tropical countries along Africa's eastern seaboard. This 'warm ocean-dry Africa' dipole appears to be a major driver of decadal variability. An evaluation of 11 climate change models suggests that increased tropical Indian Ocean precipitation, and the associated moisture transport disruptions, may in fact be anthropogenic, accounting for at least part of the regional drought tendencies in eastern and southern Africa over the past 20 years. These simulations also suggest continued increases in oceanic convection will be very likely over the next century. This diabatic forcing will likely produce continuing rainfall declines across 7 food insecure nations. These drying trends, combined with declining per capita agricultural capacity, are likely to contribute to a ~250 percent increase in food shortages over the next 30 years. Modest agricultural and market development, however, could alleviate the food problem substantially.

  4. Abrupt onset and prolongation of aragonite undersaturation events in the Southern Ocean

    NASA Astrophysics Data System (ADS)

    Hauri, Claudine; Friedrich, Tobias; Timmermann, Axel

    2016-02-01

    Ocean acidification may lead to seasonal aragonite undersaturation in surface waters of the Southern Ocean as early as 2030 (ref. ). These conditions are harmful to key organisms such as pteropods, which contribute significantly to the pelagic foodweb and carbon export fluxes in this region. Although the severity of ocean acidification impacts is mainly determined by the duration, intensity and spatial extent of aragonite undersaturation events, little is known about the nature of these events, their evolving attributes and the timing of their onset in the Southern Ocean. Using an ensemble of ten Earth system models, we show that starting around 2030, aragonite undersaturation events will spread rapidly, affecting ~30% of Southern Ocean surface waters by 2060 and >70% by 2100, including the Patagonian Shelf. On their onset, the duration of these events will increase abruptly from 1 month to 6 months per year in less than 20 years in >75% of the area affected by end-of-century aragonite undersaturation. This is likely to decrease the ability of organisms to adapt to a quickly evolving environment. The rapid equatorward progression of surface aragonite undersaturation can be explained by the uptake of anthropogenic CO2, whereas climate-driven physical or biological changes will play a minor role.

  5. Agriculture, Settlement, and Abrupt Climate Change: The 4.2ka BP event in Northern Mesopotamia

    NASA Astrophysics Data System (ADS)

    Ristvet, L.

    2003-12-01

    An abrupt aridification event at 4200 BP has been recorded in 41 paleoclimate proxies in the Old World, from Kilmanjaro, Tanzania to Rajasthan, India, East Asia and the Pacific. This event is particularly well defined for Western Asia, where it has been associated with the abandonment of settlements across the Fertile Crescent and the collapse of states on the Levantine coast and in the dry-farming plains of Northern Mesopotamia, including the Akkadian Empire. Adaptations to climate change are constrained by both local environmental and social factors. Agriculturalists, especially those living in pre-industrial societies, are particularly susceptible to changes in precipitation. The Tell Leilan Regional Survey, which systematically studied sites in a 1650km2 area of Northeastern Syria, records one set of adaptations to this event in an area where dry-farming provided the subsistence base. The survey transect crosses ecotones, from the present 500mm isohyet in the North to the 250mm isohyet in the South, and contains diverse wadi systems, ground water resources, soil profiles, and an ancient marsh/lake-- all of which allow this region to be taken as a microcosm of Northern Mesopotamia. In order to contextualize our study of human response to abrupt climate change, it is necessary to consider how the economic and social systems that were previously in place were transformed by this event. This study attempts to quantify climate change and model its effects on agricultural, pastoral, and settlement systems in Northeastern Syria from 2400-1700 BC. From 2400-2300 BC, optimal climate conditions coincided with the consolidation of an indigenous state. The next century witnessed the Akkadian conquest and imperialization of the Habur plains, which resulted in both the intensification and extensification of agro-production. During the next 300 years, (2200-1900 BC), rainfall plummeted to 70% of the climatic optimum, triggering the abandonment of cities along with their

  6. Increasing frequency and duration of Arctic winter warming events

    NASA Astrophysics Data System (ADS)

    Graham, Robert M.; Cohen, Lana; Petty, Alek A.; Boisvert, Linette N.; Rinke, Annette; Hudson, Stephen R.; Nicolaus, Marcel; Granskog, Mats A.

    2017-07-01

    Near-surface air temperatures close to 0°C were observed in situ over sea ice in the central Arctic during the last three winter seasons. Here we use in situ winter (December-March) temperature observations, such as those from Soviet North Pole drifting stations and ocean buoys, to determine how common Arctic winter warming events are. Observations of winter warming events exist over most of the Arctic Basin. Temperatures exceeding -5°C were observed during >30% of winters from 1954 to 2010 by North Pole drifting stations or ocean buoys. Using the ERA-Interim record (1979-2016), we show that the North Pole (NP) region typically experiences 10 warming events (T2m > -10°C) per winter, compared with only five in the Pacific Central Arctic (PCA). There is a positive trend in the overall duration of winter warming events for both the NP region (4.25 days/decade) and PCA (1.16 days/decade), due to an increased number of events of longer duration.Plain Language SummaryDuring the last three winter seasons, extreme <span class="hlt">warming</span> <span class="hlt">events</span> were observed over sea ice in the central Arctic Ocean. Each of these <span class="hlt">warming</span> <span class="hlt">events</span> were associated with temperatures close to or above 0°C, which lasted for between 1 and 3 days. Typically temperatures in the Arctic at this time of year are below -30°C. Here we study past temperature observations in the Arctic to investigate how common winter <span class="hlt">warming</span> <span class="hlt">events</span> are. We use time temperature observations from expeditions such as Fram (1893-1896) and manned Soviet North Pole drifting ice stations from 1937 to 1991. These historic temperature records show that winter <span class="hlt">warming</span> <span class="hlt">events</span> have been observed over most of the Arctic Ocean. Despite a thin network of observation sites, winter time temperatures above -5°C were directly observed approximately once every 3 years in the central Arctic Ocean between 1954 and 2010. Winter <span class="hlt">warming</span> <span class="hlt">events</span> are associated with storm systems originating in either the Atlantic</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..1512793M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..1512793M"><span><span class="hlt">Abrupt</span> Climate <span class="hlt">Events</span> Recorded in Chinese and Central Asian Loess Sequences</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Machalett, Bjoern; Oches, Eric A.; Haam, Eddie; Lai, Zhongping; Endlicher, Wilfried</p> <p>2013-04-01</p> <p>Past climate dynamics associated with the Eurasian continent have been extensively studied. However, the impact of intra-hemispheric-scale climate variability on the entire Eurasian landmass, as well as the self-generated effects of the continent on the global climate system, is still a matter of investigation . While western Atlantic polar and tropical air masses penetrate into the continent and are transformed as they cross Eurasia, the interior regions of Eurasia strongly influence Earth's climate system. Significant cooling and heating of Central and High Asia drive interactions between atmospheric and oceanic processes and regulate teleconnection patterns across the Northern Hemisphere. This paper utilizes high resolution particle size data from the Central Asian loess sequence at Remisowka, Kazakhstan, and the long studied, monsoon-influenced Chinese loess sequence at Xifeng, to reconstruct past atmospheric circulation and aeolian dust dynamics within interior Eurasia since the last interglacial period. The observed dynamics in aeolian dust transport closely mirror d18O and fine dust variations measured in Greenland ice cores, suggesting a correlation with short-term climate oscillations (DO <span class="hlt">events</span>) recorded therein. An Asian origin of fine aeolian dust preserved in Greenland ice cores has been discussed previously, and recent papers reveal a close link between Asian aeolian dust dynamics and DO <span class="hlt">events</span> recorded in Greenland ice cores. In this context, data presented here represent the first Central and East Asian aeolian dust records in which DO <span class="hlt">events</span> are recorded, providing a means to test hypothesized links between short-term climate variability recorded in Greenland and associated climate dynamics at Asian dust source areas. Ultimately, the data extend existing hypotheses, suggesting that the Central and High Asian mountains are a crucial element within the sensitive glacier-desert-dust response system in interior Eurasia and may be considered a pacemaker</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMPP11B1810M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMPP11B1810M"><span><span class="hlt">Abrupt</span> Climate <span class="hlt">Events</span> Recorded in Chinese and Central Asian Loess Sequences</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Machalett, B.; Oches, E. A.; Haam, E. K.; Lai, Z.; Endlicher, W.</p> <p>2013-12-01</p> <p>Past climate dynamics associated with the Eurasian continent have been extensively studied. However, the impact of intra-hemispheric-scale climate variability on the entire Eurasian landmass, as well as the self-generated effects of the continent on the global climate system, is still a matter of investigation . While western Atlantic polar and tropical air masses penetrate into the continent and are transformed as they cross Eurasia, the interior regions of Eurasia strongly influence Earth's climate system. Significant cooling and heating of Central and High Asia drive interactions between atmospheric and oceanic processes and regulate teleconnection patterns across the Northern Hemisphere. This paper utilizes high resolution particle size data from the Central Asian loess sequence at Remisowka, Kazakhstan, and the long studied, monsoon-influenced Chinese loess sequence at Xifeng, to reconstruct past atmospheric circulation and aeolian dust dynamics within interior Eurasia since the last interglacial period. The observed dynamics in aeolian dust transport closely mirror d18O and fine dust variations measured in Greenland ice cores, suggesting a correlation with short-term climate oscillations (DO <span class="hlt">events</span>) recorded therein. An Asian origin of fine aeolian dust preserved in Greenland ice cores has been discussed previously, and recent papers reveal a close link between Asian aeolian dust dynamics and DO <span class="hlt">events</span> recorded in Greenland ice cores. In this context, data presented here represent the first Central and East Asian aeolian dust records in which DO <span class="hlt">events</span> are recorded, providing a means to test hypothesized links between short-term climate variability recorded in Greenland and associated climate dynamics at Asian dust source areas. Ultimately, the data extend existing hypotheses, suggesting that the Central and High Asian mountains are a crucial element within the sensitive glacier-desert-dust response system in interior Eurasia and may be considered a pacemaker</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4742819','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4742819"><span>North Atlantic <span class="hlt">warming</span> during Dansgaard-Oeschger <span class="hlt">events</span> synchronous with Antarctic <span class="hlt">warming</span> and out-of-phase with Greenland climate</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Rasmussen, Tine L.; Thomsen, Erik; Moros, Matthias</p> <p>2016-01-01</p> <p>The precise reason for the differences and out-of-phase relationship between the <span class="hlt">abrupt</span> Dansgaard-Oeschger <span class="hlt">warmings</span> in the Nordic seas and Greenland ice cores and the gradual <span class="hlt">warmings</span> in the south-central Atlantic and Antarctic ice cores is poorly understood. Termed the bipolar seesaw, the differences are apparently linked to perturbations in the ocean circulation pattern. Here we show that surface and intermediate-depth water south of Iceland <span class="hlt">warmed</span> gradually synchronously with the Antarctic <span class="hlt">warming</span> and out of phase with the <span class="hlt">abrupt</span> <span class="hlt">warming</span> of the Nordic seas and over Greenland. The hinge line between areas showing <span class="hlt">abrupt</span> and gradual <span class="hlt">warming</span> was close to the Greenland-Scotland Ridge and the marine system appears to be a ‘push-and-pull’ system rather than a seesaw system. ‘Pull’ during the <span class="hlt">warm</span> interstadials, when convection in the Nordic seas was active; ‘push’ during the cold stadials, when convection stopped and <span class="hlt">warm</span> water from the south-central Atlantic pushed northward gradually <span class="hlt">warming</span> the North Atlantic and Nordic seas. PMID:26847384</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26847384','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26847384"><span>North Atlantic <span class="hlt">warming</span> during Dansgaard-Oeschger <span class="hlt">events</span> synchronous with Antarctic <span class="hlt">warming</span> and out-of-phase with Greenland climate.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Rasmussen, Tine L; Thomsen, Erik; Moros, Matthias</p> <p>2016-02-05</p> <p>The precise reason for the differences and out-of-phase relationship between the <span class="hlt">abrupt</span> Dansgaard-Oeschger <span class="hlt">warmings</span> in the Nordic seas and Greenland ice cores and the gradual <span class="hlt">warmings</span> in the south-central Atlantic and Antarctic ice cores is poorly understood. Termed the bipolar seesaw, the differences are apparently linked to perturbations in the ocean circulation pattern. Here we show that surface and intermediate-depth water south of Iceland <span class="hlt">warmed</span> gradually synchronously with the Antarctic <span class="hlt">warming</span> and out of phase with the <span class="hlt">abrupt</span> <span class="hlt">warming</span> of the Nordic seas and over Greenland. The hinge line between areas showing <span class="hlt">abrupt</span> and gradual <span class="hlt">warming</span> was close to the Greenland-Scotland Ridge and the marine system appears to be a 'push-and-pull' system rather than a seesaw system. 'Pull' during the <span class="hlt">warm</span> interstadials, when convection in the Nordic seas was active; 'push' during the cold stadials, when convection stopped and <span class="hlt">warm</span> water from the south-central Atlantic pushed northward gradually <span class="hlt">warming</span> the North Atlantic and Nordic seas.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMPP31C1155S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMPP31C1155S"><span>Diatoms as Proxies for <span class="hlt">Abrupt</span> <span class="hlt">Events</span> in the Hudson River Estuary</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Skorski, W.; Abbott, D. H.; Recasens, C.; Breger, D. L.</p> <p>2014-12-01</p> <p>The Hudson River estuary has been subject to many <span class="hlt">abrupt</span> <span class="hlt">events</span> throughout its history including hurricanes, droughts and pluvials. Hurricanes in particular are rare, discrete <span class="hlt">events</span> that if fingerprinted can be used to develop better age models for Hudson River sediments. Proxies use observed physical characteristics or biological assemblages (e.g. diatom and foraminiferal assemblages) as tools to reconstruct past conditions prior to the modern instrumental record. Using a sediment core taken from the Hudson River (CDO2-29A), in New York City, drought and pluvial layers were selected based on Cs-137 dating while hurricane layers were determined from occurrences of tropical to subtropical foraminifera. Contrary to previous studies (Weaver, 1970, Weiss et al, 1978), more than sixty different diatom species have been identified using a scanning electron microscope (SEM). Cosmopolitan, hurricane and drought assemblages have begun to be identified after observing multiple layers (Table 1). Tropical foraminifera dominated by Globigerinoides ruber pink were also found in a hurricane layer that we infer was deposited during Hurricane Belle in 1976. More diatom abundance analyses and cataloged SEM pictures will provide further insight into these proxies. Table 1 Diatom Genera and Species Environment Clarification Cyclotella caspia Planktonic, marine-brackish Cosmopolitan Karayevia clevei Freshwater Cosmopolitan Melosira sp Planktonic, marine Cosmopolitan Thalassiosira sp Marine, brackish Cosmopolitan Staurosirella leptostauron Benthic, freshwater Cosmopolitan Actinoptychus senarius Planktonic or benthic, freshwater to brackish Hurricane and pluvial layers Amphora aff. sp Benthic, marine or freshwater Hurricane layers only Nitzschia sp Benthic, marine or freshwater Hurricane layers only Gomphonema sp Freshwater Hurricane layers only Surirella sp Marine-brackish Drought layer only Triceratium sp Marine Drought layer only Other Genera and species Environment Clarification</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26655642','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26655642"><span>Reduction in the Reverse-Bias Effect by an <span class="hlt">Abrupt</span> Break in the Sequential Regularity of Visual <span class="hlt">Events</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Urakawa, Tomokazu; Hirose, Noboyuki; Mori, Shuji</p> <p>2016-04-01</p> <p>A bistable image is more likely to be initially perceived as the reversal of its preceding unambiguous version presented for a prolonged period. This perceptual bias is called the reverse-bias effect. We hypothesized that an <span class="hlt">abrupt</span> break in the sequential regularity of visual <span class="hlt">events</span>, synchronized with the onset of a bistable image, counteracts the reverse-bias effect in a similar manner to the disturbing effect of noise in the perceptual process. Under the condition in which the reverse-bias effect was achieved with the Necker lattice, the orientation of the bars around the lattice was simultaneously changed at the onset of the lattice, yielding an <span class="hlt">abrupt</span> break in the sequential regularity of visual <span class="hlt">events</span> besides the lattice. The results obtained showed that the reverse-bias effect was significantly reduced by the <span class="hlt">abrupt</span> break, suggesting that an <span class="hlt">abrupt</span> break in the sequential regularity of visual <span class="hlt">events</span> perturbs the perceptual bias of the bistable image, similar to that caused by noise.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013JGRA..118.1190O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013JGRA..118.1190O"><span>Equatorial ionospheric electrodynamic perturbations during Southern Hemisphere stratospheric <span class="hlt">warming</span> <span class="hlt">events</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Olson, M. E.; Fejer, B. G.; Stolle, C.; Lühr, H.; Chau, J. L.</p> <p>2013-03-01</p> <p>use ground-based and satellite measurements to examine, for the first time, the characteristics of equatorial electrodynamic perturbations measured during the 2002 major and 2010 minor Southern Hemisphere sudden stratospheric <span class="hlt">warming</span> (SSW) <span class="hlt">events</span>. Our data suggest the occurrence of enhanced quasi 2 day fluctuations during the 2002 early autumnal equinoctial <span class="hlt">warming</span>. They also show a moderately large multi-day perturbation pattern, resembling those during arctic SSW <span class="hlt">events</span>, during 2002 late equinox, as the major SSW was weakening. We also compare these data with extensive recent results that showed the fundamentally important role of lunar semidiurnal tidal effects on low latitude electrodynamic perturbations during arctic SSW <span class="hlt">events</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMOS44A..04P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMOS44A..04P"><span>Ice core measurements of 14CH4 show no evidence of methane release to atmosphere from methane hydrates during a large <span class="hlt">warming</span> <span class="hlt">event</span> 11,600 years ago</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Petrenko, V. V.; Severinghaus, J. P.; Smith, A.; Riedel, K.; Brook, E.; Schaefer, H.; Baggenstos, D.; Harth, C. M.; Hua, Q.; Buizert, C.; Schilt, A.; Fain, X.; Mitchell, L.; Bauska, T. K.; Orsi, A. J.; Weiss, R. F.</p> <p>2016-12-01</p> <p>Marine methane hydrate destabilization has been proposed as a potentially large source of methane to the atmosphere in response to both past and future <span class="hlt">warming</span>. We present new measurements of 14C of paleoatmospheric methane (CH4) over the Younger Dryas - Preboreal (YD - PB) <span class="hlt">abrupt</span> <span class="hlt">warming</span> <span class="hlt">event</span> (≈11,600 years ago) from ancient ice outcropping at Taylor Glacier, Antarctica. The YD - PB <span class="hlt">abrupt</span> <span class="hlt">warming</span> was centered in the North Atlantic, occurred partway through the global <span class="hlt">warming</span> of last deglaciation and was associated with a ≈ 50% increase in atmospheric CH4 concentrations. 14C can unambiguously identify CH4 emissions from "old carbon" sources, such as CH4 hydrates. All samples from before, during and after the <span class="hlt">abrupt</span> <span class="hlt">warming</span> and associated CH4 increase yielded 14CH4 values that are consistent with 14C of atmospheric CO2 at that time, indicating a purely contemporaneous methane source. Our results show that neither the <span class="hlt">abrupt</span> regional <span class="hlt">warming</span> nor the gradual global <span class="hlt">warming</span> that preceded it resulted in detectable CH4 release to the atmosphere from CH4 hydrates during the YD - PB transition. Our results are thus consistent with the hypothesis that the vast majority of CH4 that is released from dissociating hydrates or other old-carbon seafloor CH4 sources is oxidized prior to reaching the atmosphere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006AGUFMPP23C1775N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006AGUFMPP23C1775N"><span>Variability of oceanic productivity in the North Atlantic during <span class="hlt">abrupt</span> climate changes (Heinrich <span class="hlt">Events</span>)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nave, S.; Labeyrie, L.; Gherardi, J.; Cortijo, E.; Abrantes, F.; Kissel, C.</p> <p>2006-12-01</p> <p>Evidences of strong millennial-scale climate variability, especially marked during MIS3, have been reported worldwide in high-resolution records. These pronounced climate changes, known as Dansgaard-Oeschger cycles, are characterized by sudden shifts in temperature, dust content and concentration of methane. Some of the longest Dansgaard-Oescher stadials are closely related to massive iceberg surges, the Heinrich <span class="hlt">Events</span> (HE), recognized by anomalous concentrations in ice-rafted debris in six peculiar layers in the North Atlantic. Besides the well-documented changes in hydrology, these iceberg discharges had probably a major impact on the marine ecosystem, but data to constrain this variability is lacking. In order to further our understanding on productivity feedbacks to massive iceberg discharges and associated hydrologic adjustments, we have done a high-resolution diatom and organic carbon analysis focused on 7 sedimentary sequences between 40ºN and 65ºN, each of them representative of a North Atlantic region. This study was conducted over two <span class="hlt">abrupt</span> climate <span class="hlt">events</span> of the last glacial period, Heinrich <span class="hlt">Event</span> 1 (H1) and Heinrich <span class="hlt">Event</span> 4 (H4). Our results show that during H4 <span class="hlt">event</span>, productivity decreased drastically at all latitudes. No major blooms of siliceous phytoplankton were recorded during iceberg discharges, and hence production resulting from high nutrient supply does not seem to have occurred during HE as suggested by previous studies (Sancetta, 1992). Instead, the severe productivity decrease during H4 could be due to the establishment of a strong halocline and the consequent slowdown of the thermohaline circulation (reducing the mixed layer and therefore preventing the nutrient supply from deeper waters to the upper layer). However, during H1, although hydrologically similar, productivity was apparently not affected in northern latitudes, showing a progressive increase during the deglaciation period. Hence, our results suggest that the orbital forcing</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..16.7984R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16.7984R"><span>Continuous methane record of <span class="hlt">abrupt</span> climate change 10-68 ka: sighting Heinrich <span class="hlt">events</span> in the ice core record</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rhodes, Rachael; Brook, Edward; Chiang, John; Blunier, Thomas; Cheng, Hai; Edwards, R. Lawrence; Maselli, Olivia; McConnell, Joseph; Romanini, Daniele; Severinghaus, Jeffrey; Sowers, Todd; Stowasser, Christopher</p> <p>2014-05-01</p> <p>The Last Glacial period was punctuated by millennial scale <span class="hlt">abrupt</span> climate changes - Dansgaard-Oeschger (D-O) cycles and Heinrich <span class="hlt">events</span>. Controls on the magnitude and frequency of these climate perturbations, and how they may be inter-related, remain unclear. Specific problems include the difficulty of dating Heinrich sediment layers and local bias of key paleoclimate archives. We present a highly detailed and precise record of ice core methane (CH4), a globally integrated signal, which resolves climatic features in unprecedented resolution. <span class="hlt">Abrupt</span> CH4 increases are resolved in Heinrich Stadials (HS) 1, 2, 4 and 5 where, in contrast to all D-O cycles, there are no concurrent <span class="hlt">abrupt</span> changes in Greenland temperature. Using modern-day tropical rainfall variability as an analog, we propose that strong cooling in the North Atlantic severely restricted the northerly range of the Intertropical Convergence Zone (ITCZ), leading to an enhanced wet season over Southern Hemisphere tropical land areas, and consequently driving production of excess CH4 in tropical wetlands. Our findings place four Heinrich <span class="hlt">events</span> firmly within ice core chronologies and suggest maximum durations of 778 to 1606 yr. CH4 anomalies are only associated with Heinrich <span class="hlt">events</span> of Hudson Strait provenance, indicating that the tropical impacts of Heinrich <span class="hlt">events</span> were not uniform.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ACP....17..615K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ACP....17..615K"><span>Stratospheric tropical <span class="hlt">warming</span> <span class="hlt">event</span> and its impact on the polar and tropical troposphere</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kodera, Kunihiko; Eguchi, Nawo; Mukougawa, Hitoshi; Nasuno, Tomoe; Hirooka, Toshihiko</p> <p>2017-01-01</p> <p>Stratosphere-troposphere coupling is investigated in relation to middle atmospheric subtropical jet (MASTJ) variations in boreal winter. An exceptional strengthening of the MASTJ occurred in association with a sudden equatorward shift of the stratospheric polar night jet (PNJ) in early December 2011. This <span class="hlt">abrupt</span> transformation of the MASTJ and PNJ had no apparent relation to the upward propagation of planetary waves from the troposphere. The impact of this stratospheric <span class="hlt">event</span> penetrated into the troposphere in two regions: in the northern polar region and the tropics. Due to the strong MASTJ, planetary waves at higher latitudes were deflected and trapped in the northern polar region. Trapping of the planetary waves resulted in amplification of zonal wave number 1 component, which appeared in the troposphere as the development of a trough over the Atlantic sector and a ridge over the Eurasian sector. A strong MASTJ also suppressed the equatorward propagation of planetary waves, which resulted in weaker tropical stratospheric upwelling and produced anomalous <span class="hlt">warming</span> in the tropical stratosphere. In the tropical tropopause layer (TTL), however, sublimation of ice clouds kept the temperature change minor. In the troposphere, an <span class="hlt">abrupt</span> termination of a Madden-Julian Oscillation (MJO) <span class="hlt">event</span> occurred following the static stability increase in the TTL. This termination suggests that the stratospheric <span class="hlt">event</span> affected the convective episode in the troposphere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AtmRe.123..197G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AtmRe.123..197G"><span><span class="hlt">Warm</span>-season severe wind <span class="hlt">events</span> in Germany</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gatzen, Christoph</p> <p>2013-04-01</p> <p>A 15-year data set of wind measurements was analyzed with regard to <span class="hlt">warm</span> season severe wind gusts in Germany. For April to September of the years 1997 to 2011, 1035 wind measurements of 26 m/s or greater were found. These wind reports were associated with 268 wind <span class="hlt">events</span>. In total, 252 convective wind <span class="hlt">events</span> contributed to 837 (81%) of the wind reports, 16 non-convective synoptic-scale wind <span class="hlt">events</span> contributed to 198 reports (19%). Severe wind <span class="hlt">events</span> were found with synoptic situations characterized by rather strong mid-level flow and advancing mid-level troughs. Severe convective wind <span class="hlt">events</span> were analyzed using radar images and classified with respect to the observed radar structure. The most important convective mode was squall lines that were associated with one third of all severe wind gusts, followed by groups, bow echo complexes, and bow echoes. Supercells and cells were not associated with many wind reports. The low contribution of isolated cells indicates that rather large-scale forcing by synoptic-scale features like fronts is important for German severe wind <span class="hlt">events</span>. Bow echoes were found to be present for 58% of all wind reports. The movement speed of bow echoes indicated a large variation with a maximum speed of 33 m/s. Extreme wind <span class="hlt">events</span> as well as <span class="hlt">events</span> with more than 15 wind reports were found to be related to higher movement speeds. Concentrating on the most intense <span class="hlt">events</span>, derechos seem to be very important to the <span class="hlt">warm</span> season wind threat in Germany. Convective <span class="hlt">events</span> with a path length of more than 400 km contributed to 36% of all <span class="hlt">warm</span>-season wind gusts in this data set. Furthermore, eight of nine extreme gusts exceeding 40 m/s were recorded with derecho <span class="hlt">events</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19860018268&hterms=quiroz&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dquiroz','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19860018268&hterms=quiroz&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dquiroz"><span>Discrimination of a major stratospheric <span class="hlt">warming</span> <span class="hlt">event</span> in February-March 1984 from earlier minor <span class="hlt">warmings</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Johnson, K. W.; Quiroz, R. S.; Gelman, M. E.</p> <p>1985-01-01</p> <p>As part of its responsibility for stratospheric monitoring, the Climate Analysis Center derives time trends of various dynamic parameters from NMC stratospheric analyses. Selected figures from this stratospheric monitoring data base are published in Climate Diagnostics Bulletin in March and October, after each hemispheric winter. During the Northern Hemisphere winter of December 1983-February 1984 several <span class="hlt">warming</span> <span class="hlt">events</span> may be seen in the plot of 60 deg. N zonal mean temperatures for 10 mb. Minor <span class="hlt">warmings</span> may be noted in early December, late December, mid January and early February. A major <span class="hlt">warming</span> with the 60 deg. N zonal mean temperatures reaching -40C is observed in late February, associated with a circulation reversal. In all of the minor <span class="hlt">warming</span> episodes, there is a polarward movement of the Aleutian anticyclone; however, at 10 mb the North Pole remains in the cyclonic circulation of the stratospheric vortex which is not displaced far from its usual position. In the case of the later February major <span class="hlt">warming</span>, the 10 mb circulation pattern over the North Pole is anticyclonic, and the cyclonic circulation has moved to the south and east with a considerable elongation. Cross sections of heat transport and momentum transport are not dramatically different for the minor and major <span class="hlt">warming</span> episodes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19860018268&hterms=Gelman&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAuthor-Name%26N%3D0%26No%3D30%26Ntt%3DGelman','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19860018268&hterms=Gelman&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAuthor-Name%26N%3D0%26No%3D30%26Ntt%3DGelman"><span>Discrimination of a major stratospheric <span class="hlt">warming</span> <span class="hlt">event</span> in February-March 1984 from earlier minor <span class="hlt">warmings</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Johnson, K. W.; Quiroz, R. S.; Gelman, M. E.</p> <p>1985-01-01</p> <p>As part of its responsibility for stratospheric monitoring, the Climate Analysis Center derives time trends of various dynamic parameters from NMC stratospheric analyses. Selected figures from this stratospheric monitoring data base are published in Climate Diagnostics Bulletin in March and October, after each hemispheric winter. During the Northern Hemisphere winter of December 1983-February 1984 several <span class="hlt">warming</span> <span class="hlt">events</span> may be seen in the plot of 60 deg. N zonal mean temperatures for 10 mb. Minor <span class="hlt">warmings</span> may be noted in early December, late December, mid January and early February. A major <span class="hlt">warming</span> with the 60 deg. N zonal mean temperatures reaching -40C is observed in late February, associated with a circulation reversal. In all of the minor <span class="hlt">warming</span> episodes, there is a polarward movement of the Aleutian anticyclone; however, at 10 mb the North Pole remains in the cyclonic circulation of the stratospheric vortex which is not displaced far from its usual position. In the case of the later February major <span class="hlt">warming</span>, the 10 mb circulation pattern over the North Pole is anticyclonic, and the cyclonic circulation has moved to the south and east with a considerable elongation. Cross sections of heat transport and momentum transport are not dramatically different for the minor and major <span class="hlt">warming</span> episodes.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_1");'>1</a></li> <li><a href="#" onclick='return showDiv("page_2");'>2</a></li> <li class="active"><span>3</span></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_3 --> <div id="page_4" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_2");'>2</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li class="active"><span>4</span></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="61"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950040891&hterms=global+warming&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dglobal%2Bwarming','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950040891&hterms=global+warming&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dglobal%2Bwarming"><span>Global variations of zonal mean ozone during stratospheric <span class="hlt">warming</span> <span class="hlt">events</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Randel, William J.</p> <p>1993-01-01</p> <p>Eight years of Solar Backscatter Ultraviolet (SBUV) ozone data are examined to study zonal mean variations associated with stratospheric planetary wave (<span class="hlt">warming</span>) <span class="hlt">events</span>. These fluctuations are found to be nearly global in extent, with relatively large variations in the tropics, and coherent signatures reaching up to 50 deg in the opposite (summer) hemisphere. These ozone variations are a manifestation of the global circulation cells associated with stratospheric <span class="hlt">warming</span> <span class="hlt">events</span>; the ozone responds dynamically in the lower stratosphere to transport, and photochemically in the upper stratosphere to the circulation-induced temperature changes. The observed ozone variations in the tropics are of particular interest because transport is dominated by zonal-mean vertical motions (eddy flux divergences and mean meridional transports are negligible), and hence, substantial simplifications to the governing equations occur. The response of the atmosphere to these impulsive circulation changes provides a situation for robust estimates of the ozone-temperature sensitivity in the upper stratosphere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5602576','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5602576"><span>Global variations of zonal mean ozone during stratospheric <span class="hlt">warming</span> <span class="hlt">events</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Randel, W.J. )</p> <p>1993-10-01</p> <p>Eight years of Solar Backscatter Ultraviolet ozone data are examined to study zonal mean ozone variations associated with stratospheric planetary wave (<span class="hlt">warming</span>) <span class="hlt">events</span>. These fluctuations are found to be nearly global in extent, with relatively large variations in the tropics, and coherent signatures reaching up to 50[degrees] in the opposite (summer) hemisphere. These ozone variations are a manifestation of the global circulation cells associated with stratospheric <span class="hlt">warming</span> <span class="hlt">events</span>; the ozone responds dynamically in the lower stratosphere to transport, and photochemically in the upper stratosphere to the circulation-induced temperature changes. The observed ozone variations in the tropics are of particular interest because transport is dominated by zonal-mean vertical motions (eddy flux divergences and mean meridional transports are negligible), and hence, substantial simplifications to the governing equations occur. The response of the atmosphere to these impulsive circulation changes provides a situation for robust estimates of ozone-temperature sensitivity in the upper stratosphere. 39 refs., 16 rigs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950040891&hterms=zonal+circulation&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dzonal%2Bcirculation','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950040891&hterms=zonal+circulation&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dzonal%2Bcirculation"><span>Global variations of zonal mean ozone during stratospheric <span class="hlt">warming</span> <span class="hlt">events</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Randel, William J.</p> <p>1993-01-01</p> <p>Eight years of Solar Backscatter Ultraviolet (SBUV) ozone data are examined to study zonal mean variations associated with stratospheric planetary wave (<span class="hlt">warming</span>) <span class="hlt">events</span>. These fluctuations are found to be nearly global in extent, with relatively large variations in the tropics, and coherent signatures reaching up to 50 deg in the opposite (summer) hemisphere. These ozone variations are a manifestation of the global circulation cells associated with stratospheric <span class="hlt">warming</span> <span class="hlt">events</span>; the ozone responds dynamically in the lower stratosphere to transport, and photochemically in the upper stratosphere to the circulation-induced temperature changes. The observed ozone variations in the tropics are of particular interest because transport is dominated by zonal-mean vertical motions (eddy flux divergences and mean meridional transports are negligible), and hence, substantial simplifications to the governing equations occur. The response of the atmosphere to these impulsive circulation changes provides a situation for robust estimates of the ozone-temperature sensitivity in the upper stratosphere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.9729V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.9729V"><span>Changes in winter <span class="hlt">warming</span> <span class="hlt">events</span> in the Nordic Arctic Region</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vikhamar-Schuler, Dagrun; Isaksen, Ketil; Haugen, Jan Erik; Bjerke, Jarle Werner; Tømmervik, Hans</p> <p>2015-04-01</p> <p>In recent years winter <span class="hlt">warming</span> <span class="hlt">events</span> are frequently reported from Arctic areas. Extraordinarily <span class="hlt">warm</span> weather episodes, occasionally combined with intense rainfall, cause severe ecological disturbance and great challenges for Arctic infrastructure. For example, the formation of ground ice due to winter rain or melting prevents reindeer from grazing, leads to vegetation browning, and impacts soil temperatures. The infrastructure may be affected by avalanches and floods resulting from intense snowmelt. The aim of our analysis is to study changes in <span class="hlt">warm</span> spells during winter in the Nordic Arctic Region, here defined as the regions in Norway, Sweden and Finland north of the Arctic circle (66.5°N), including the Arctic islands Svalbard and Jan Mayen. Within this study area we have selected the longest available high quality observation series with daily temperature and precipitation. For studying future climate we use available regionally downscaled scenarios. We analyse three time periods: 1) the past 50-100 years, 2) the present (last 15 years, 2000-2014) and 3) the future (next 50-100 years). We define an extended winter season (October-April) and further divide it into three subseasons: 1) Early winter (October and November), 2) Mid-winter (December, January and February) and 3) Late-winter (March and April). We identify <span class="hlt">warm</span> spells using two different classification criteria: a) days with temperature above 0°C (the melting temperature); and b) days with temperature in excess of the 90th percentile of the 1985-2014 temperature for each subseason. Both wet and dry <span class="hlt">warm</span> spells are analysed. We compare the results for the mainland stations (maritime and inland stations) with the Arctic islands. All stations have very high frequency of <span class="hlt">warm</span> weather <span class="hlt">events</span> in the period 1930-1940s and for the last 15 years (2000-2014). For the most recent period the largest increase in number of <span class="hlt">warm</span> spells are observed at the northernmost stations. We also find a continuation of this</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.B43F..04Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.B43F..04Y"><span>Global <span class="hlt">warming</span>, drought <span class="hlt">events</span>, and GPP performance (Invited)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yi, C.; Jensen, K.; Wei, S.; Hendrey, G.</p> <p>2013-12-01</p> <p>The first decade of the 21st century was the warmest decade recorded since the start of modern measurements in 1850, according to a new report on July 3, 2013 by the World Meteorological Organization (WMO). Global <span class="hlt">warming</span> may now be exacerbating droughts in the world, and leading to more reduction in crop production, plant growth and hence carbon fixation, and further <span class="hlt">warming</span> climate. How do we quantify the relationship between drought <span class="hlt">event</span> and ecosystem performance? Here, we developed a method called 'perfect-deficit approach' and a local dryness index based on eddy-flux measurements. We applied these concepts and mathematical method to remote sensing observations (MODIS) to examine the world ecosystem performance in the first decade of 21st century and identify the associated climate extremes. The initial results show that the deficits of ecosystem performances in lower latitudes were caused mainly by drought <span class="hlt">events</span>, while at high latitudes cold/<span class="hlt">warm</span> <span class="hlt">events</span> also exert substantial influences on ecosystem performances, particularly in spring season. Acknowledgements This research was financially supported by PSC-CUNY Award (PSC-CUNY-ENHC-44-83)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26917761','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26917761"><span>Comment on "<span class="hlt">Abrupt</span> <span class="hlt">warming</span> <span class="hlt">events</span> drove Late Pleistocene Holarctic megafaunal turnover".</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Rasmussen, Sune O; Svensson, Anders M</p> <p>2016-02-26</p> <p>Cooper et al. (Research Article, 7 August 2015, p. 602) combined the annual-layer-counted Greenland Ice Core Chronology 2005 with chronological information from the Hulu Cave and Cariaco Basin records to produce a "revised" time scale. We argue that their time scale is incompatible with the nature of annual-layer-counted time scales and may lead to seriously flawed conclusions if used elsewhere at face value.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4594299','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4594299"><span>Competition between global <span class="hlt">warming</span> and an <span class="hlt">abrupt</span> collapse of the AMOC in Earth’s energy imbalance</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Drijfhout, Sybren</p> <p>2015-01-01</p> <p>A collapse of the Atlantic Meridional Overturning Circulation (AMOC) leads to global cooling through fast feedbacks that selectively amplify the response in the Northern Hemisphere (NH). How such cooling competes with global <span class="hlt">warming</span> has long been a topic for speculation, but was never addressed using a climate model. Here it is shown that global cooling due to a collapsing AMOC obliterates global <span class="hlt">warming</span> for a period of 15–20 years. Thereafter, the global mean temperature trend is reversed and becomes similar to a simulation without an AMOC collapse. The resulting surface <span class="hlt">warming</span> hiatus lasts for 40–50 years. Global <span class="hlt">warming</span> and AMOC-induced NH cooling are governed by similar feedbacks, giving rise to a global net radiative imbalance of similar sign, although the former is associated with surface <span class="hlt">warming</span>, the latter with cooling. Their footprints in outgoing longwave and absorbed shortwave radiation are very distinct, making attribution possible. PMID:26437599</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015NatSR...514877D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015NatSR...514877D"><span>Competition between global <span class="hlt">warming</span> and an <span class="hlt">abrupt</span> collapse of the AMOC in Earth’s energy imbalance</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Drijfhout, Sybren</p> <p>2015-10-01</p> <p>A collapse of the Atlantic Meridional Overturning Circulation (AMOC) leads to global cooling through fast feedbacks that selectively amplify the response in the Northern Hemisphere (NH). How such cooling competes with global <span class="hlt">warming</span> has long been a topic for speculation, but was never addressed using a climate model. Here it is shown that global cooling due to a collapsing AMOC obliterates global <span class="hlt">warming</span> for a period of 15-20 years. Thereafter, the global mean temperature trend is reversed and becomes similar to a simulation without an AMOC collapse. The resulting surface <span class="hlt">warming</span> hiatus lasts for 40-50 years. Global <span class="hlt">warming</span> and AMOC-induced NH cooling are governed by similar feedbacks, giving rise to a global net radiative imbalance of similar sign, although the former is associated with surface <span class="hlt">warming</span>, the latter with cooling. Their footprints in outgoing longwave and absorbed shortwave radiation are very distinct, making attribution possible.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1711159M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1711159M"><span>Properties of stratospheric <span class="hlt">warming</span> <span class="hlt">events</span> during northern winter.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Maury, Pauline; Claud, Chantal; Manzini, Elisa; Hauchecorne, Alain; Keckhut, Philippe</p> <p>2015-04-01</p> <p>During wintertime the polar mid-stratosphere is characterized by the setting up of westerly winds around the pole; the so-called polar vortex. The polar vortex is one of the most variable features of the zonal-mean circulation of the earth atmosphere, due to a highly non linear interaction between planetary-scale Rossby waves and the zonal flow. Indeed, the interaction between the upward tropospheric propagating waves and the polar vortex leads to a zonal flow weakening, implying a large day to day vortex variability. In the most dramatic cases the polar vortex breaks down, the stratospheric polar flow can reverse its direction and the temperatures can rise locally by more than 50K in a span of a few days. Such phenomena are known as Sudden Stratospheric <span class="hlt">Warmings</span> (SSWs) and constitute, since their discovery, the most impressive dynamical <span class="hlt">events</span> in the physical climate system. There are however situations where the polar vortex does not break down, but temperatures increase dramatically. In this study, we propose a global characterization of stratospheric <span class="hlt">warmings</span> situations based on a temperature threshold in the 50-10hPa layer, in order to assess the properties of daily stratospheric temperature variability during the northern winter. The originality of this approch consists in evaluating the wintertime positive temperature anomalies in terms of intensity and duration. We will show that there is a wide spectrum of <span class="hlt">warming</span> types. The major SSWs are the most extreme, but there are other <span class="hlt">events</span> that share some common properties with the major ones. Though neglected, these latter <span class="hlt">warmings</span> may play a key role in the coupling of the stratosphere-troposphere system.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017CliPa..13..729W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017CliPa..13..729W"><span>Regional seesaw between the North Atlantic and Nordic Seas during the last glacial <span class="hlt">abrupt</span> climate <span class="hlt">events</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wary, Mélanie; Eynaud, Frédérique; Swingedouw, Didier; Masson-Delmotte, Valérie; Matthiessen, Jens; Kissel, Catherine; Zumaque, Jena; Rossignol, Linda; Jouzel, Jean</p> <p>2017-06-01</p> <p>Dansgaard-Oeschger oscillations constitute one of the most enigmatic features of the last glacial cycle. Their cold atmospheric phases have been commonly associated with cold sea-surface temperatures and expansion of sea ice in the North Atlantic and adjacent seas. Here, based on dinocyst analyses from the 48-30 ka interval of four sediment cores from the northern Northeast Atlantic and southern Norwegian Sea, we provide direct and quantitative evidence of a regional paradoxical seesaw pattern: cold Greenland and North Atlantic phases coincide with warmer sea-surface conditions and shorter seasonal sea-ice cover durations in the Norwegian Sea as compared to <span class="hlt">warm</span> phases. Combined with additional palaeorecords and multi-model hosing simulations, our results suggest that during cold Greenland phases, reduced Atlantic meridional overturning circulation and cold North Atlantic sea-surface conditions were accompanied by the subsurface propagation of <span class="hlt">warm</span> Atlantic waters that re-emerged in the Nordic Seas and provided moisture towards Greenland summit.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003EAEJA....12663H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003EAEJA....12663H"><span>The glaciology of IRD <span class="hlt">events</span>: <span class="hlt">warming</span> and ice dynamics</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hindmarsh, R. C. A.</p> <p>2003-04-01</p> <p>Heinrich <span class="hlt">events</span>, the enormous glacial-period ice-rafting episodeshave been posited to be due to large-scale surges of the Laurentide ice-sheet (3). However, more frequent <span class="hlt">events</span> such as the Bond <span class="hlt">events</span> are difficult to explain this way. Recently acquired geological evidence (2,4) suggests that climatic perturbations are correlated with some N. Atlantic IRD <span class="hlt">events</span>. A model (1) which show how climate perturbations can lead to IRD <span class="hlt">events</span> is reviewed. The model shows how 20-50km retreats induced by ablation rates of 2 m/yr provide sufficient debris flux through the grounding line to produce large sedimentation <span class="hlt">events</span>. Such ablation would reduce ice-shelf extent markedly, permitting debris to reach the calving front and be transported by icebergs leading to ice-rafted debris (IRD) <span class="hlt">events</span>. Surges are not necessary conditions for the production of large IRD <span class="hlt">events</span>. The glacial dynamics of this climate perturbation model is compared with the surge theory, with particular emphasis on the amount of sediment that either method can deliver to the oceans. Consideration of the non-exclusivety and consistency of the two mechanisms is emphasised. (1) R.C.A. Hindmarsh and A. Jenkins, Centurial-millenial ice-rafted debris pulses from ablating marine ice sheets, Geophys Res. Lett 22(12), 2477-2480, 2001; (2) Paul C. Knutz et al. G3 Multidecadal ocean variability and NW European ice sheet surges during the last deglaciation G3 3(12) 17 December 2002 1077, doi:10.1029/2002GC000351; (3) MacAyeal,D.R. Binge/purge oscillations of the Laurentide ice-sheet as a cause of the North-Atlantic's Heinrich <span class="hlt">events</span>, Paleoceanography, 8(6), p.775-784, (1993); (4) M. Moros, et. al. Were glacial iceberg surges in the North Atlantic triggered by climatic <span class="hlt">warming</span>?, Marine Geology, 192(4), 2002, p.393-417</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMSA13B2355L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMSA13B2355L"><span>Wave Dynamical Coupling of Atmospheres During Sudden Stratospheric <span class="hlt">Warming</span> <span class="hlt">Events</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Laskar, F. I.; Duggirala, P. R.</p> <p>2015-12-01</p> <p>The electrodynamic and neutral dynamic behavior of the low-latitude upper atmosphere during sudden stratospheric <span class="hlt">warming</span> (SSW) <span class="hlt">events</span> has been investigated. The equatorial electrojet (EEJ) strength and the total electron content (TEC) data from low latitudes, over Indian longitudes, during the mid-winter season in the years 2005 to 2013 are used in this study. Five major and three minor SSW <span class="hlt">events</span> occurred in the observation duration, wherein the solar activity had varied from minimum (almost no sunspots) to mini-maximum (approximately 50 sunspots of the solar cycle 24). Spectral powers of the quasi-16-day waves in the EEJ and the TEC have been found to be dominant and varying with solar activity and SSW strengths. Specifically, the spectral powers of quasi-16-day type variations during the three dramatic strong SSW <span class="hlt">events</span> in the years 2006, 2009, and 2013 were found to be very high in comparison with those of other years. For these major <span class="hlt">events</span>, the amplitudes of the semi-diurnal tides and quasi-16-day waves were found to be highly correlated and were maximum around the peak of SSW, suggesting a strong interaction between the two waves. However, this correlation was poor and the quasi-16-day spectral power was low for the minor <span class="hlt">events</span>. A strong vertical coupling of atmospheres was noted in spite of the solar activity being relatively higher during 2013, which was, however, explained to be due to the occurrence of a strong SSW <span class="hlt">event</span>. These results suggest that the wave dynamical vertical coupling of atmospheres is stronger during strong major SSW <span class="hlt">events</span> and weaker during minor <span class="hlt">events</span>. Also, SSW <span class="hlt">events</span> play an important role in enabling the upward coupling of atmospheres even during high solar activity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014GeoRL..41..604A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014GeoRL..41..604A"><span>Response of atmospheric CO2 to the <span class="hlt">abrupt</span> cooling <span class="hlt">event</span> 8200 years ago</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ahn, Jinho; Brook, Edward J.; Buizert, Christo</p> <p>2014-01-01</p> <p>Atmospheric CO2 records for the centennial scale cooling <span class="hlt">event</span> 8200 years ago (8.2 ka <span class="hlt">event</span>) may help us understand climate-carbon cycle feedbacks under interglacial conditions, which are important for understanding future climate, but existing records do not provide enough detail. Here we present a new CO2 record from the Siple Dome ice core, Antarctica, that covers 7.4-9.0 ka with 8 to 16 year resolution. We observe a small, about 1-2 ppm, increase of atmospheric CO2 during the 8.2 ka <span class="hlt">event</span>. The increase is not significant when compared to other centennial variations in the Holocene that are not linked to large temperature changes. Our results do not agree with leaf stomata records that suggest a CO2 decrease of up to ~25 ppm and imply that the sensitivity of atmospheric CO2 to the primarily Northern Hemisphere cooling of the 8.2 ka <span class="hlt">event</span> was limited.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006QSRv...25.2197G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006QSRv...25.2197G"><span>Evidence for <span class="hlt">warm</span> wet Heinrich <span class="hlt">events</span> in Florida</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Grimm, Eric C.; Watts, William A.; Jacobson, George L.; Hansen, Barbara C. S.; Almquist, Heather R.; Dieffenbacher-Krall, Ann C.</p> <p>2006-09-01</p> <p>Analyses of pollen and plant macrofossils from a new core spanning the past 60,000 years from Lake Tulane, Florida show a strong antiphase relationship in temperature between Florida and the North Atlantic region. During the Pleistocene, oak-scrub and prairie phases were coeval with long, intense Dansgaard-Oeschger interstadials (<span class="hlt">warm</span> periods) that initiated Bond cycles. Pine phases were coeval with the North Atlantic long stadials (cold periods) that ended Bond cycles and were terminated by Heinrich <span class="hlt">events</span>. Lake levels were higher during pine phases, and climate was wetter. However, climate in Florida was also warmer during these phases, which were cold periods in the North Atlantic. Perhaps diminution of thermohaline circulation before and during Heinrich <span class="hlt">events</span> reduced northward heat transport and retained warmth in the subtropical Atlantic and Gulf of Mexico.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.7849M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.7849M"><span>The December 2015 and 2016 North Pole <span class="hlt">Warming</span> <span class="hlt">Events</span> and the Increasing Occurrence of Such <span class="hlt">Events</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Moore, Kent</p> <p>2017-04-01</p> <p>In late December 2015 and 2016, widespread media interest revolved around forecasts that the surface air temperature at the North Pole would rise above freezing. Although there has been significant interest in the enhanced <span class="hlt">warming</span> that is occurring at high northern latitudes, a process known as arctic amplification, remarkably little is known about these midwinter <span class="hlt">warming</span> <span class="hlt">events</span> at the pole including their frequency, duration and magnitude as well as the environmental conditions responsible for their occurrence. Here we use buoy and radiosonde data along with operational weather forecasts and atmospheric reanalyses to show that such <span class="hlt">events</span> are associated with surface cyclones near the pole that advect <span class="hlt">warm</span> and moist air polewards as well as a highly perturbed polar vortex. In addition to 2015 and 2016, a similar <span class="hlt">event</span> occurred in December 2014 as well. On average, they occur once or twice each decade with the earliest identified <span class="hlt">event</span> taking place in 1959. In addition, the warmest midwinter temperatures at the North Pole have been increasing at a rate that is twice as large as that for mean midwinter temperatures at the pole. It is argued that this enhanced trend is consistent with the loss of winter sea ice from the Nordic Seas that moves the reservoir of <span class="hlt">warm</span> air over this region northwards making it easier for weather systems to transport this heat polewards.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.1450V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.1450V"><span><span class="hlt">Abrupt</span> drying <span class="hlt">events</span> in the Caribbean related to large Laurentide meltwater pulses during the glacial-to-Holocene transition</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vieten, Rolf; Warken, Sophie; Winter, Amos; Scholz, Denis; Black, David; Zanchettin, Davide; Miller, Thomas E.</p> <p>2017-04-01</p> <p>At the end of the last deglaciation North Atlantic meltwater pulses from the retreating Laurentide ice sheet triggered a chain of oceanic and atmospheric responses including temporary slow-down of the thermohaline circulation and hemispheric-scale alterations of the atmospheric circulation. The 8.2 ka <span class="hlt">event</span> (occurring about 8.2 ka BP) is the most pronounced meltwater pulse during the Holocene and serves as an analogue to understand how North Atlantic fresh water influxes can affect the ocean-atmosphere coupled system on a basin, hemispheric or global scale. This <span class="hlt">event</span> left strong regional climate imprints, such as <span class="hlt">abrupt</span> cooling reconstructed over the North Atlantic and Europe lasting 100 to 150 years and drying in the northern hemispheric tropics. However, there is a lack of high resolution proxies to learn about the <span class="hlt">event</span>'s temporal structure especially in the tropics. We present geochemical evidence from a stalagmite indicating sudden climate fluctuations towards drier conditions in the northeastern Caribbean possibly related to rapid cooling in the high northern latitudes and a southward shift of the Inter-Tropical Convergence Zone (ITCZ). Stalagmite PR-PA-1 was collected in Palco cave, Puerto Rico, and it is a remarkable record of the 8.2 ka <span class="hlt">event</span> because 15 MC-ICPMS 230Th/U-dates produce a precise chronology of its Holocene period growing solely between 9.0 ka BP to 7.5 ka BP. Based on 240 trace element and stable isotope ratio measurement we reconstructed hydrological changes with sub-decadal resolution. Our proxy data show large and rapid climate variations before 8.0 ka. Pronounced peaks in the Mg/Ca and δ13C records indicate three major <span class="hlt">events</span> of <span class="hlt">abrupt</span> drying. These fluctuations towards drier conditions took place in less than 10 years and the climate remained drier than the natural range for 10 to 20 years, before it returned to pre-fluctuation conditions again. Our observations confirm previous studies suggesting that repeated meltwater pulses</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMOS12A..07F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMOS12A..07F"><span>Imminent onset and <span class="hlt">abrupt</span> increase in duration of low aragonite and calcite saturation state <span class="hlt">events</span> in the Southern Ocean</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Friedrich, T.; Hauri, C.; Timmermann, A.</p> <p>2015-12-01</p> <p>Rapid progression of ocean acidification is a threat to key organisms of the Southern Ocean ecosystem. While the severity of ocean acidification impacts is mainly determined by the duration, intensity, and spatial extent of low aragonite or calcite saturation state <span class="hlt">events</span>, little is known about the nature of these <span class="hlt">events</span>, their evolving attributes, and the timing of their onset. Using output of historical and RCP 8.5 simulations from ten Earth System Models from CMIP5, we found that aragonite undersaturation, which decreases the calcification rate of pteropods and causes dissolution of their aragonitic shell, will spread rapidly after 2035, covering 70 % of the Southern Ocean surface waters by 2095. Surface aragonite undersaturation <span class="hlt">events</span> will last for about 5 months in areas south of 60°S by 2055, and for more than 8 months by the end of the century. Overall, the duration of these <span class="hlt">events</span> increases from 1 month to more than 6 months within fewer than 20 years in >75 % of the affected area. This <span class="hlt">abrupt</span> change in exposure duration to unfavorable conditions may be too fast for pteropods to adapt, as these chemical changes will occur within just a few generations. As a result of two month-long calcite undersaturation <span class="hlt">events</span> projected for the end of this century, even organisms built of the more stable calcium carbonate mineral calcite will face prolonged chemical dissolution. The threat of ocean acidification to the Southern Ocean ecosystem may be more imminent than previously thought, and may spread quickly to the southern tips of New Zealand, South America, and South Africa, with potentially far-reaching consequences to fisheries, local economies, and livelihoods.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20010007151&hterms=tempo&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dtempo','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20010007151&hterms=tempo&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dtempo"><span><span class="hlt">Abrupt</span> Changes at the Permian/Triassic Boundary: Tempo of <span class="hlt">Events</span> from High-Resolution Cyclostratigraphy</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Rampino, M. R.; Prokoph, A.; Adler, A. C.</p> <p>2000-01-01</p> <p> the nearby Reppwand outcrop section, the same faunal changes occurs over only 0.8 m or about 8,000 years, close to the limit of time-resolution induced by bioturbation and reworking in these sediments. The sharp negative global carbon-isotope shift took place within less than or equal to 40,000 yr, and the isotope excursions persisted for approximately 480,000 yr into the Early Triassic. The results indicate that the severe marine faunal <span class="hlt">event</span> that marks the P/Tr boundary was very sudden, perhaps less than the resolution window in the GK-1 core, and suggest a catastrophic cause. The wavelet-analysis approach to high-resolution cyclostratigraphy can be applied to other P/Tr boundary sections, and when combined with precise absolute dating and magnetostratigraphic methods promises a significant increase in resolution in determining the correlation and tempo of the end-Permian extinctions and related <span class="hlt">events</span> worldwide.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PalOc..30.1425P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PalOc..30.1425P"><span>Tropical North Atlantic subsurface <span class="hlt">warming</span> <span class="hlt">events</span> as a fingerprint for AMOC variability during Marine Isotope Stage 3</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Parker, Andrew O.; Schmidt, Matthew W.; Chang, Ping</p> <p>2015-11-01</p> <p>The role of Atlantic Meridional Overturning Circulation (AMOC) as the driver of Dansgaard-Oeschger (DO) variability that characterized Marine Isotope Stage 3 (MIS 3) has long been hypothesized. Although there is ample proxy evidence suggesting that DO <span class="hlt">events</span> were robust features of glacial climate, there is little data supporting a link with AMOC. Recently, modeling studies and subsurface temperature reconstructions have suggested that subsurface <span class="hlt">warming</span> across the tropical North Atlantic can be used to fingerprint a weakened AMOC during the deglacial because a reduction in the strength of the western boundary current allows <span class="hlt">warm</span> salinity maximum water of the subtropical gyre to enter the deep tropics. To determine if AMOC variability played a role during the DO cycles of MIS 3, we present new, high-resolution Mg/Ca and δ18O records spanning 24-52 kyr from the near-surface dwelling planktonic foraminifera Globigerinoides ruber and the lower thermocline dwelling planktonic foraminifera Globorotalia truncatulinoides in Southern Caribbean core VM12-107 (11.33°N, 66.63°W, 1079 m depth). Our subsurface Mg/Ca record reveals <span class="hlt">abrupt</span> increases in Mg/Ca ratios (the largest equal to a 4°C <span class="hlt">warming</span>) during the interstadial-stadial transition of most DO <span class="hlt">events</span> during this period. This change is consistent with reconstructions of subsurface <span class="hlt">warming</span> <span class="hlt">events</span> associated with cold <span class="hlt">events</span> across the deglacial using the same core. Additionally, our data support the conclusion reached by a recently published study from the Florida Straits that AMOC did not undergo significant reductions during Heinrich <span class="hlt">events</span> 2 and 3. This record presents some of the first high-resolution marine sediment derived evidence for variable AMOC during MIS 3.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016NatSR...639084M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016NatSR...639084M"><span>The December 2015 North Pole <span class="hlt">Warming</span> <span class="hlt">Event</span> and the Increasing Occurrence of Such <span class="hlt">Events</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Moore, G. W. K.</p> <p>2016-12-01</p> <p>In late December 2015, widespread media interest revolved around forecasts that the surface air temperature at the North Pole would rise above freezing. Although there has been significant interest in the enhanced <span class="hlt">warming</span> that is occurring at high northern latitudes, a process known as arctic amplification, remarkably little is known about these midwinter <span class="hlt">warming</span> <span class="hlt">events</span> at the pole including their frequency, duration and magnitude as well as the environmental conditions responsible for their occurrence. Here we use buoy and radiosonde data along with operational weather forecasts and atmospheric reanalyses to show that such <span class="hlt">events</span> are associated with surface cyclones near the pole as well as a highly perturbed polar vortex. They occur once or twice each decade with the earliest identified <span class="hlt">event</span> taking place in 1959. In addition, the warmest midwinter temperatures at the North Pole have been increasing at a rate that is twice as large as that for mean midwinter temperatures at the pole. It is argued that this enhanced trend is consistent with the loss of winter sea ice from the Nordic Seas that moves the reservoir of <span class="hlt">warm</span> air over this region northwards making it easier for weather systems to transport this heat polewards.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_2");'>2</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li class="active"><span>4</span></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_4 --> <div id="page_5" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li class="active"><span>5</span></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="81"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5157030','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5157030"><span>The December 2015 North Pole <span class="hlt">Warming</span> <span class="hlt">Event</span> and the Increasing Occurrence of Such <span class="hlt">Events</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Moore, G. W. K.</p> <p>2016-01-01</p> <p>In late December 2015, widespread media interest revolved around forecasts that the surface air temperature at the North Pole would rise above freezing. Although there has been significant interest in the enhanced <span class="hlt">warming</span> that is occurring at high northern latitudes, a process known as arctic amplification, remarkably little is known about these midwinter <span class="hlt">warming</span> <span class="hlt">events</span> at the pole including their frequency, duration and magnitude as well as the environmental conditions responsible for their occurrence. Here we use buoy and radiosonde data along with operational weather forecasts and atmospheric reanalyses to show that such <span class="hlt">events</span> are associated with surface cyclones near the pole as well as a highly perturbed polar vortex. They occur once or twice each decade with the earliest identified <span class="hlt">event</span> taking place in 1959. In addition, the warmest midwinter temperatures at the North Pole have been increasing at a rate that is twice as large as that for mean midwinter temperatures at the pole. It is argued that this enhanced trend is consistent with the loss of winter sea ice from the Nordic Seas that moves the reservoir of <span class="hlt">warm</span> air over this region northwards making it easier for weather systems to transport this heat polewards. PMID:27976745</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27976745','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27976745"><span>The December 2015 North Pole <span class="hlt">Warming</span> <span class="hlt">Event</span> and the Increasing Occurrence of Such <span class="hlt">Events</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Moore, G W K</p> <p>2016-12-15</p> <p>In late December 2015, widespread media interest revolved around forecasts that the surface air temperature at the North Pole would rise above freezing. Although there has been significant interest in the enhanced <span class="hlt">warming</span> that is occurring at high northern latitudes, a process known as arctic amplification, remarkably little is known about these midwinter <span class="hlt">warming</span> <span class="hlt">events</span> at the pole including their frequency, duration and magnitude as well as the environmental conditions responsible for their occurrence. Here we use buoy and radiosonde data along with operational weather forecasts and atmospheric reanalyses to show that such <span class="hlt">events</span> are associated with surface cyclones near the pole as well as a highly perturbed polar vortex. They occur once or twice each decade with the earliest identified <span class="hlt">event</span> taking place in 1959. In addition, the warmest midwinter temperatures at the North Pole have been increasing at a rate that is twice as large as that for mean midwinter temperatures at the pole. It is argued that this enhanced trend is consistent with the loss of winter sea ice from the Nordic Seas that moves the reservoir of <span class="hlt">warm</span> air over this region northwards making it easier for weather systems to transport this heat polewards.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1912919A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1912919A"><span>To what extent can global <span class="hlt">warming</span> <span class="hlt">events</span> influence scaling properties of climatic fluctuations in glacial periods?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Alberti, Tommaso; Lepreti, Fabio; Vecchio, Antonio; Carbone, Vincenzo</p> <p>2017-04-01</p> <p>The Earth's climate is an extremely unstable complex system consisting of nonlinear and still rather unknown interactions among atmosphere, land surface, ice and oceans. The system is mainly driven by solar irradiance, even if internal components as volcanic eruptions and human activities affect the atmospheric composition thus acting as a driver for climate changes. Since the extreme climate variability is the result of a set of phenomena operating from daily to multi-millennial timescales, with different correlation times, a study of the scaling properties of the system can evidence non-trivial persistent structures, internal or external physical processes. Recently, the scaling properties of the paleoclimate changes have been analyzed by distinguish between interglacial and glacial climates [Shao and Ditlevsen, 2016]. The results show that the last glacial record (20-120 kyr BP) presents some elements of multifractality, while the last interglacial period (0-10 kyr BP), say the Holocene period, seems to be characterized by a mono-fractal structure. This is associated to the absence of Dansgaard-Oeschger (DO) <span class="hlt">events</span> in the interglacial climate that could be the cause for the absence of multifractality. This hypothesis is supported by the analysis of the period between 18 and 27 kyr BP, i.e. during the Last Glacial Period, in which a single DO <span class="hlt">event</span> have been registred. Through the Empirical Mode Decomposition (EMD) we were able to detect a timescale separation within the Last Glacial Period (20-120 kyr BP) in two main components: a high-frequency component, related to the occurrence of DO <span class="hlt">events</span>, and a low-frequency one, associated to the cooling/<span class="hlt">warming</span> phase switch [Alberti et al., 2014]. Here, we investigate the scaling properties of the climate fluctuations within the Last Glacial Period, where <span class="hlt">abrupt</span> climate changes, characterized by fast increase of temperature usually called Dansgaard-Oeschger (DO) <span class="hlt">events</span>, have been particularly pronounced. By using the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..15.7271M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..15.7271M"><span>Millennial scale precipitation changes over Easter Island (Southern Pacific) during MIS 3: Inter-hemispheric connections during North Atlantic <span class="hlt">abrupt</span> cold <span class="hlt">events</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Margalef, Olga; Cacho, Isabel; Pla-Rabes, Sergi; Cañellas-Boltà, Núria; Pueyo, Juan Jose; Sáez, Alberto; Valero-Garcés, Blas L.; Giralt, Santiago</p> <p>2013-04-01</p> <p>Marine Isotope Stage (MIS) 3 climate has been globally characterized by the occurrence of millennial-scale climate variations defined over North Atlantic as Dansgaard-Oeschger and Heinrich <span class="hlt">events</span>. Despite climate variability has been broadly explored over North Atlantic records, the response of the tropical and subtropical latitudes, especially in the Southern Hemisphere, still remains as a matter of debate. Rano Aroi peat record (Easter Island, Chile, 27°S) provides a unique opportunity to understand Southern Pacific atmospheric and oceanic changes during these stadial-interstadial transitions because of its exceptional location on the interplay of the South Pacific Convergence Zone (SPCZ), the Intertropical Convergence Zone (ITCZ), the South Pacific Anticyclone (SPA) and the Southern Westerlies (SW). Rano Aroi record contains 8 main enhanced precipitation <span class="hlt">events</span> between 70 and 40 kyr BP that can be correlated with the timing of Heinrich <span class="hlt">events</span> 5, 5a and 6 as well as other cold stadials. These humid <span class="hlt">events</span> are also present in other Southern Hemisphere continental sites and correspond to dry periods on Northern Hemisphere records. This opposite hydrologic trend has been explained by the latitudinal migration of ITCZ and has been supported by several climatic models. As Easter Island precipitation is mainly dependent on SPCZ storm track belt activity, we suggest that the southern migration of the ITCZ is associated to an expansion of SPCZ to the east. This process should be intimately related to a weakening of the Walker circulation, which is further supported by an estimation of d18Osw gradient along the equator for the same time period. Consequently, atmospheric and oceanic responses during these cold stadials and Heinrich <span class="hlt">events</span> might lead to a configuration that resembles the <span class="hlt">warm</span> ENSO state over Southern Pacific, as previously suggested by some global climatic models. Rano Aroi record clearly points out that shifts in hydrological cycle in tropical Southern</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/16815970','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/16815970"><span><span class="hlt">Abrupt</span> tropical climate change: past and present.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Thompson, Lonnie G; Mosley-Thompson, Ellen; Brecher, Henry; Davis, Mary; León, Blanca; Les, Don; Lin, Ping-Nan; Mashiotta, Tracy; Mountain, Keith</p> <p>2006-07-11</p> <p>Three lines of evidence for <span class="hlt">abrupt</span> tropical climate change, both past and present, are presented. First, annually and decadally averaged delta(18)O and net mass-balance histories for the last 400 and 2,000 yr, respectively, demonstrate that the current <span class="hlt">warming</span> at high elevations in the mid- to low latitudes is unprecedented for at least the last 2 millennia. Second, the continuing retreat of most mid- to low-latitude glaciers, many having persisted for thousands of years, signals a recent and <span class="hlt">abrupt</span> change in the Earth's climate system. Finally, rooted, soft-bodied wetland plants, now exposed along the margins as the Quelccaya ice cap (Peru) retreats, have been radiocarbon dated and, when coupled with other widespread proxy evidence, provide strong evidence for an <span class="hlt">abrupt</span> mid-Holocene climate <span class="hlt">event</span> that marked the transition from early Holocene (pre-5,000-yr-B.P.) conditions to cooler, late Holocene (post-5,000-yr-B.P.) conditions. This <span class="hlt">abrupt</span> <span class="hlt">event</span>, approximately 5,200 yr ago, was widespread and spatially coherent through much of the tropics and was coincident with structural changes in several civilizations. These three lines of evidence argue that the present <span class="hlt">warming</span> and associated glacier retreat are unprecedented in some areas for at least 5,200 yr. The ongoing global-scale, rapid retreat of mountain glaciers is not only contributing to global sea-level rise but also threatening freshwater supplies in many of the world's most populous regions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1484420','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1484420"><span><span class="hlt">Abrupt</span> tropical climate change: Past and present</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Thompson, Lonnie G.; Mosley-Thompson, Ellen; Brecher, Henry; Davis, Mary; León, Blanca; Les, Don; Lin, Ping-Nan; Mashiotta, Tracy; Mountain, Keith</p> <p>2006-01-01</p> <p>Three lines of evidence for <span class="hlt">abrupt</span> tropical climate change, both past and present, are presented. First, annually and decadally averaged δ18O and net mass-balance histories for the last 400 and 2,000 yr, respectively, demonstrate that the current <span class="hlt">warming</span> at high elevations in the mid- to low latitudes is unprecedented for at least the last 2 millennia. Second, the continuing retreat of most mid- to low-latitude glaciers, many having persisted for thousands of years, signals a recent and <span class="hlt">abrupt</span> change in the Earth’s climate system. Finally, rooted, soft-bodied wetland plants, now exposed along the margins as the Quelccaya ice cap (Peru) retreats, have been radiocarbon dated and, when coupled with other widespread proxy evidence, provide strong evidence for an <span class="hlt">abrupt</span> mid-Holocene climate <span class="hlt">event</span> that marked the transition from early Holocene (pre-5,000-yr-B.P.) conditions to cooler, late Holocene (post-5,000-yr-B.P.) conditions. This <span class="hlt">abrupt</span> <span class="hlt">event</span>, ≈5,200 yr ago, was widespread and spatially coherent through much of the tropics and was coincident with structural changes in several civilizations. These three lines of evidence argue that the present <span class="hlt">warming</span> and associated glacier retreat are unprecedented in some areas for at least 5,200 yr. The ongoing global-scale, rapid retreat of mountain glaciers is not only contributing to global sea-level rise but also threatening freshwater supplies in many of the world’s most populous regions. PMID:16815970</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24599259','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24599259"><span>An <span class="hlt">abrupt</span> centennial-scale drought <span class="hlt">event</span> and mid-holocene climate change patterns in monsoon marginal zones of East Asia.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Li, Yu; Wang, Nai'ang; Zhang, Chengqi</p> <p>2014-01-01</p> <p>The mid-latitudes of East Asia are characterized by the interaction between the Asian summer monsoon and the westerly winds. Understanding long-term climate change in the marginal regions of the Asian monsoon is critical for understanding the millennial-scale interactions between the Asian monsoon and the westerly winds. <span class="hlt">Abrupt</span> climate <span class="hlt">events</span> are always associated with changes in large-scale circulation patterns; therefore, investigations into <span class="hlt">abrupt</span> climate changes provide clues for responses of circulation patterns to extreme climate <span class="hlt">events</span>. In this paper, we examined the time scale and mid-Holocene climatic background of an <span class="hlt">abrupt</span> dry mid-Holocene <span class="hlt">event</span> in the Shiyang River drainage basin in the northwest margin of the Asian monsoon. Mid-Holocene lacustrine records were collected from the middle reaches and the terminal lake of the basin. Using radiocarbon and OSL ages, a centennial-scale drought <span class="hlt">event</span>, which is characterized by a sand layer in lacustrine sediments both from the middle and lower reaches of the basin, was absolutely dated between 8.0-7.0 cal kyr BP. Grain size data suggest an <span class="hlt">abrupt</span> decline in lake level and a dry environment in the middle reaches of the basin during the dry interval. Previous studies have shown mid-Holocene drought <span class="hlt">events</span> in other places of monsoon marginal zones; however, their chronologies are not strong enough to study the mechanism. According to the absolutely dated records, we proposed a new hypothesis that the mid-Holocene dry interval can be related to the weakening Asian summer monsoon and the relatively arid environment in arid Central Asia. Furthermore, <span class="hlt">abrupt</span> dry climatic <span class="hlt">events</span> are directly linked to the basin-wide effective moisture change in semi-arid and arid regions. Effective moisture is affected by basin-wide precipitation, evapotranspiration, lake surface evaporation and other geographical settings. As a result, the time scales of the dry interval could vary according to locations due to different geographical</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3943949','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3943949"><span>An <span class="hlt">Abrupt</span> Centennial-Scale Drought <span class="hlt">Event</span> and Mid-Holocene Climate Change Patterns in Monsoon Marginal Zones of East Asia</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Li, Yu; Wang, Nai'ang; Zhang, Chengqi</p> <p>2014-01-01</p> <p>The mid-latitudes of East Asia are characterized by the interaction between the Asian summer monsoon and the westerly winds. Understanding long-term climate change in the marginal regions of the Asian monsoon is critical for understanding the millennial-scale interactions between the Asian monsoon and the westerly winds. <span class="hlt">Abrupt</span> climate <span class="hlt">events</span> are always associated with changes in large-scale circulation patterns; therefore, investigations into <span class="hlt">abrupt</span> climate changes provide clues for responses of circulation patterns to extreme climate <span class="hlt">events</span>. In this paper, we examined the time scale and mid-Holocene climatic background of an <span class="hlt">abrupt</span> dry mid-Holocene <span class="hlt">event</span> in the Shiyang River drainage basin in the northwest margin of the Asian monsoon. Mid-Holocene lacustrine records were collected from the middle reaches and the terminal lake of the basin. Using radiocarbon and OSL ages, a centennial-scale drought <span class="hlt">event</span>, which is characterized by a sand layer in lacustrine sediments both from the middle and lower reaches of the basin, was absolutely dated between 8.0–7.0 cal kyr BP. Grain size data suggest an <span class="hlt">abrupt</span> decline in lake level and a dry environment in the middle reaches of the basin during the dry interval. Previous studies have shown mid-Holocene drought <span class="hlt">events</span> in other places of monsoon marginal zones; however, their chronologies are not strong enough to study the mechanism. According to the absolutely dated records, we proposed a new hypothesis that the mid-Holocene dry interval can be related to the weakening Asian summer monsoon and the relatively arid environment in arid Central Asia. Furthermore, <span class="hlt">abrupt</span> dry climatic <span class="hlt">events</span> are directly linked to the basin-wide effective moisture change in semi-arid and arid regions. Effective moisture is affected by basin-wide precipitation, evapotranspiration, lake surface evaporation and other geographical settings. As a result, the time scales of the dry interval could vary according to locations due to different</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014CliPD..10.4033H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014CliPD..10.4033H"><span>Subsurface North Atlantic <span class="hlt">warming</span> as a trigger of rapid cooling <span class="hlt">events</span>: evidences from the Early Pleistocene (MIS 31-19)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hernández-Almeida, I.; Sierro, F.-J.; Cacho, I.; Flores, J.-A.</p> <p>2014-10-01</p> <p>Subsurface water column dynamics in the subpolar North Atlantic were reconstructed in order to improve the understanding of the cause of <span class="hlt">abrupt</span> IRD <span class="hlt">events</span> during cold periods of the Early Pleistocene. We used Mg / Ca-based temperatures of deep-dwelling (Neogloboquadrina pachyderma sinistral) planktonic foraminifera and paired Mg / Ca-δ18O measurements to estimate the subsurface temperatures and δ18O of seawater at Site U1314. Carbon isotopes on benthic and planktonic foraminifera from the same site provide information about the ventilation and water column nutrient gradient. Mg / Ca-based temperatures and δ18O of seawater suggest increased temperatures and salinities during ice-rafting, likely due to enhanced northward subsurface transport of subtropical waters during periods of AMOC reduction. Planktonic carbon isotopes support this suggestion, showing coincident increased subsurface ventilation during deposition of ice-rafted detritus (IRD). <span class="hlt">Warm</span> waters accumulated at subsurface would result in basal <span class="hlt">warming</span> and break-up of ice-shelves, leading to massive iceberg discharges in the North Atlantic. Release of heat and salt stored at subsurface would help to restart the AMOC. This mechanism is in agreement with modelling and proxy studies that observe a subsurface <span class="hlt">warming</span> in the North Atlantic in response to AMOC slowdown during the MIS3.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015CliPa..11..687H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015CliPa..11..687H"><span>Subsurface North Atlantic <span class="hlt">warming</span> as a trigger of rapid cooling <span class="hlt">events</span>: evidence from the early Pleistocene (MIS 31-19)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hernández-Almeida, I.; Sierro, F.-J.; Cacho, I.; Flores, J.-A.</p> <p>2015-04-01</p> <p>Subsurface water column dynamics in the subpolar North Atlantic were reconstructed in order to improve the understanding of the cause of <span class="hlt">abrupt</span> ice-rafted detritus (IRD) <span class="hlt">events</span> during cold periods of the early Pleistocene. We used paired Mg / Ca and δ18O measurements of Neogloboquadrina pachyderma (sinistral - sin.), deep-dwelling planktonic foraminifera, to estimate the subsurface temperatures and seawater δ18O from a sediment core from Gardar Drift, in the subpolar North Atlantic. Carbon isotopes of benthic and planktonic foraminifera from the same site provide information about the ventilation and water column nutrient gradient. Mg / Ca-based temperatures and seawater δ18O suggest increased subsurface temperatures and salinities during ice-rafting, likely due to northward subsurface transport of subtropical waters during periods of weaker Atlantic Meridional Overturning Circulation (AMOC). Planktonic carbon isotopes support this suggestion, showing coincident increased subsurface ventilation during deposition of IRD. Subsurface accumulation of <span class="hlt">warm</span> waters would have resulted in basal <span class="hlt">warming</span> and break-up of ice-shelves, leading to massive iceberg discharges in the North Atlantic. The release of heat stored at the subsurface to the atmosphere would have helped to restart the AMOC. This mechanism is in agreement with modelling and proxy studies that observe a subsurface <span class="hlt">warming</span> in the North Atlantic in response to AMOC slowdown during Marine Isotope Stage (MIS) 3.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PrOce.130...75B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PrOce.130...75B"><span>Heat budget in the North Atlantic subpolar gyre: Impacts of atmospheric weather regimes on the 1995 <span class="hlt">warming</span> <span class="hlt">event</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Barrier, Nicolas; Deshayes, Julie; Treguier, Anne-Marie; Cassou, Christophe</p> <p>2015-01-01</p> <p>In the mid 1990s, the North Atlantic subpolar gyre has shown a dramatic <span class="hlt">warming</span> <span class="hlt">event</span> that has been thoroughly investigated from observations and numerical simulations. Some studies suggest that it was due to an interannual, wind-driven weakening and shrinking of the gyre that facilitated the penetration of <span class="hlt">warm</span> Atlantic Water, the weakening of the gyre being attributed to changes in the North Atlantic Oscillation (NAO) and in the East Atlantic Pattern, which are the two dominant modes of atmospheric variability in the North Atlantic. However, other studies suggest that the <span class="hlt">warming</span> <span class="hlt">event</span> was due to a decadal, buoyancy-driven strengthening of the meridional overturning circulation and subsequent intensification of the poleward heat transport, in response to the positive NAO conditions of 1988-1995. To reconcile this discrepancy, the heat budget in the North Atlantic subpolar gyre is reconstructed from four ocean hindcast simulations sharing the same modelling platform but using different settings. The novelty of this work is the decomposition of the subpolar gyre into a western and an eastern subregion, which is motivated by water mass distribution around Reykjanes Ridge and by the fact that deep convection only occurs in the western subpolar gyre. In the western subpolar gyre, the 1995 <span class="hlt">warming</span> <span class="hlt">event</span> is the decadal, baroclinic ocean response to positive NAO conditions from 1988 to 1995. The latter induced increased surface heat loss in the Labrador Sea that intensified deep convection hence strengthened the meridional overturning circulation and the associated poleward heat transport. In the eastern subregion, a concomittant <span class="hlt">warming</span> is induced by an interannual, barotropic adjustment of the gyre circulation to an <span class="hlt">abrupt</span> switch from positive NAO conditions in winter 1995 to negative NAO conditions in winter 1996. Indeed, the gyre response to negative NAO conditions is a cyclonic intergyre-gyre that increases northward volume and heat transports at the southeastern</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.P11C3785L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.P11C3785L"><span>Investigating Potential Causes for An <span class="hlt">Abrupt</span> Change of Thermal State in Earth's Upper Mantle During the Great Oxygenation <span class="hlt">Event</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, M.; McNamara, A. K.</p> <p>2014-12-01</p> <p>The oxygenic photosynthesis might have well evolved about 3 billion years ago, but there seems no great increase of atmospheric oxygen until the great oxygenation <span class="hlt">event</span> (GOE) at about 2.4 Ga. One possibility for the suppressing of atmospheric oxygen level before the GOE is through consumption of oxygen by reduced volcanic gasses. The amount of atmospheric oxygen that could be consumed by volcanic gases depends on the absolute amount of volcanic gases as well as the redox state of the upper mantle. Evidence from the redox sensitive V/Sc ratio have shown that the redox state of the upper mantle have remained constant for the last 3.5 billion years (e.g., Li and Lee, 2004). If so, <span class="hlt">abrupt</span> changes in thermal state of Earth's upper mantle could explain the rapid changes of degassing rate at the time of GOE. The Earth's lowermost mantle has been shown to be compositionally heterogeneous, which could be caused by the presence of dense, primordial material resulting from early differentiation processes. An important question is how do chemical heterogeneities in the lowermost mantle influence the secular cooling of the upper mantle. Here, we performed numerical calculations to explore the effects of themochemical convection on the thermal evolution of Earth's upper mantle. A large parameter space is explored, with varying Rayleigh number, viscosity, internal heating and density of chemical heterogeneities. We start with an initially hot mantle with a layer of dense material in the lowermost mantle. We found that when the mantle is hot, the dense material remains layered and covers the entire CMB, leading to low CMB heat flux. In this stage, the upper mantle cools down rapidly. However, as the mantle cools, the dense material is swept into discrete thermochemical piles by cold downwellings, leading to increasing CMB heat flux. The cooling rate of the mantle is temporarily reduced as this transition occurs. This occurs at a time consistent with the GOE <span class="hlt">event</span>. Li, Z. X. A. and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17060975','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17060975"><span>Implications of <span class="hlt">abrupt</span> climate change.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Alley, Richard B</p> <p>2004-01-01</p> <p>Records of past climates contained in ice cores, ocean sediments, and other archives show that large, <span class="hlt">abrupt</span>, widespread climate changes have occurred repeatedly in the past. These changes were especially prominent during the cooling into and <span class="hlt">warming</span> out of the last ice age, but persisted into the modern <span class="hlt">warm</span> interval. Changes have especially affected water availability in <span class="hlt">warm</span> regions and temperature in cold regions, but have affected almost all climatic variables across much or all of the Earth. Impacts of climate changes are smaller if the changes are slower or more-expected. The rapidity of <span class="hlt">abrupt</span> climate changes, together with the difficulty of predicting such changes, means that impacts on the health of humans, economies and ecosystems will be larger if <span class="hlt">abrupt</span> climate changes occur. Most projections of future climate include only gradual changes, whereas paleoclimatic data plus models indicate that <span class="hlt">abrupt</span> changes remain possible; thus, policy is being made based on a view of the future that may be optimistic.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19990069572&hterms=nino+regions&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dnino%2Bregions','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19990069572&hterms=nino+regions&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dnino%2Bregions"><span>Recent <span class="hlt">Warming</span> <span class="hlt">Event</span> in the Pacific May be an El Nino</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Liu, W. Timothy; Tang, Wenqing; Fu, Lee-Lueng</p> <p>1995-01-01</p> <p>A recent anomalous <span class="hlt">warming</span> <span class="hlt">event</span> in the tropical Pacific consist of a series of intraseasonal episodes, observations from four spaceborne sensors and simulation by an ocean general circulation model show. Four distinct groups of equatorial westerly wind anomalies near the date line were observed by scatterometer. Anomalous integrated water vapor was observed by a microwave radiometer. To study the <span class="hlt">warming</span> <span class="hlt">event</span>, the anomalous sea level and sea surface temperature were simulated with an ocean general circulation model forced by realistic winds.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19990069572&hterms=warming+sea+levels&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dwarming%2Bsea%2Blevels','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19990069572&hterms=warming+sea+levels&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dwarming%2Bsea%2Blevels"><span>Recent <span class="hlt">Warming</span> <span class="hlt">Event</span> in the Pacific May be an El Nino</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Liu, W. Timothy; Tang, Wenqing; Fu, Lee-Lueng</p> <p>1995-01-01</p> <p>A recent anomalous <span class="hlt">warming</span> <span class="hlt">event</span> in the tropical Pacific consist of a series of intraseasonal episodes, observations from four spaceborne sensors and simulation by an ocean general circulation model show. Four distinct groups of equatorial westerly wind anomalies near the date line were observed by scatterometer. Anomalous integrated water vapor was observed by a microwave radiometer. To study the <span class="hlt">warming</span> <span class="hlt">event</span>, the anomalous sea level and sea surface temperature were simulated with an ocean general circulation model forced by realistic winds.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009GeoRL..36.3819S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009GeoRL..36.3819S"><span>Downward influence of stratospheric final <span class="hlt">warming</span> <span class="hlt">events</span> in an idealized model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sun, Lantao; Robinson, Walter A.</p> <p>2009-02-01</p> <p>The stratospheric final <span class="hlt">warming</span> is the final transition of the zonal winds from wintertime westerlies to summertime easterlies as solar heating of the high latitude stratosphere increases. Here the stratospheric influence on the tropospheric circulation during the stratospheric final <span class="hlt">warming</span> <span class="hlt">events</span> is investigated through ensemble model integrations of a simple dynamical core general circulation model. When the radiative equilibrium temperature in the stratosphere alone is gradually changed from a winter to a summer profile, the model generates realistic final <span class="hlt">warmings</span>. As in the observations, the simulated final <span class="hlt">warmings</span> occur at different ``dates'' in different realizations. Following previously published analyses of observed final <span class="hlt">warmings</span>, we form a climatological springtime transition and compute composite anomalies centered on the final <span class="hlt">warmings</span>. Simulations for both non-topographic and topographic cases show that starting five days before the final <span class="hlt">warming</span>, the stratospheric zonal wind rapidly decelerates, in association with a strong upward Eliassen-Palm (EP) flux anomaly and EP flux convergence. Precursor <span class="hlt">events</span> of wave driven zonal-wind deceleration occur, but at different times in simulations with and without topography. The composite zonal wind anomalies for final <span class="hlt">warmings</span> with and without topography are compared with each other and with observations. In both cases, a statistically significant zonal wind anomaly extends downward to the surface, similarly to what is observed in the Northern Hemisphere (NH). These tropospheric zonal wind anomalies are stronger in the simulations with topography. Tropospheric geopotential height anomalies across the final <span class="hlt">warming</span> also resemble NH observations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/20497369','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/20497369"><span>Impacts of extreme winter <span class="hlt">warming</span> <span class="hlt">events</span> on plant physiology in a sub-Arctic heath community.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Bokhorst, Stef; Bjerke, Jarle W; Davey, Matthew P; Taulavuori, Kari; Taulavuori, Erja; Laine, Kari; Callaghan, Terry V; Phoenix, Gareth K</p> <p>2010-10-01</p> <p>Insulation provided by snow cover and tolerance of freezing by physiological acclimation allows Arctic plants to survive cold winter temperatures. However, both the protection mechanisms may be lost with winter climate change, especially during extreme winter <span class="hlt">warming</span> <span class="hlt">events</span> where loss of snow cover from snow melt results in exposure of plants to <span class="hlt">warm</span> temperatures and then returning extreme cold in the absence of insulating snow. These <span class="hlt">events</span> cause considerable damage to Arctic plants, but physiological responses behind such damage remain unknown. Here, we report simulations of extreme winter <span class="hlt">warming</span> <span class="hlt">events</span> using infrared heating lamps and soil <span class="hlt">warming</span> cables in a sub-Arctic heathland. During these <span class="hlt">events</span>, we measured maximum quantum yield of photosystem II (PSII), photosynthesis, respiration, bud swelling and associated bud carbohydrate changes and lipid peroxidation to identify physiological responses during and after the winter <span class="hlt">warming</span> <span class="hlt">events</span> in three dwarf shrub species: Empetrum hermaphroditum, Vaccinium vitis-idaea and Vaccinium myrtillus. Winter <span class="hlt">warming</span> increased maximum quantum yield of PSII, and photosynthesis was initiated for E. hermaphroditum and V. vitis-idaea. Bud swelling, bud carbohydrate decreases and lipid peroxidation were largest for E. hermaphroditum, whereas V. myrtillus and V. vitis-idaea showed no or less strong responses. Increased physiological activity and bud swelling suggest that sub-Arctic plants can initiate spring-like development in response to a short winter <span class="hlt">warming</span> <span class="hlt">event</span>. Lipid peroxidation suggests that plants experience increased winter stress. The observed differences between species in physiological responses are broadly consistent with interspecific differences in damage seen in previous studies, with E. hermaphroditum and V. myrtillus tending to be most sensitive. This suggests that initiation of spring-like development may be a major driver in the damage caused by winter <span class="hlt">warming</span> <span class="hlt">events</span> that are predicted to become more</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.A14F..03N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.A14F..03N"><span>Changes in Large Precipitation <span class="hlt">Events</span> Under Global <span class="hlt">Warming</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Neelin, J. D.; Sahany, S.; Stechmann, S. N.; Bernstein, D. N.</p> <p>2014-12-01</p> <p>Model-based studies have suggested that changes may occur in hydrologic variables associated with increased probability of high precipitation occurrences, such as the 95th percentile of daily precipitation intensity. It has been common to discuss changes in extreme <span class="hlt">events</span> in terms of consequences of the shift of the mean of the distribution, or an increase in variance. Here we present a prototype for the behavior of changes in the distribution of precipitation <span class="hlt">event</span> size, i.e., of the precipitation integrated from onset to termination of an <span class="hlt">event</span>. It has been noted in observations that <span class="hlt">event</span> size distributions exhibit a scale-free, approximately power-law range with a cutoff at large <span class="hlt">event</span> sizes (Peters et al, 2010). A simple stochastic model for an atmospheric column moisture budget shows how this behavior arises and how the cutoff is controlled by the physical parameters of the system. A simple set of conditions implies that the frequency of the very largest <span class="hlt">events</span> may be expected to exhibit disproportionate sensitivity to changes. Any increase in the variance of the moisture convergence, as is projected to occur in the warmer climate, is predicted to yield changes in the very largest <span class="hlt">event</span>-size portion of the distribution. Precipitation <span class="hlt">event</span> size distributions computed from high time-resolution output from the Community Earth System Model appear to fit this prototype well in current climate, consistent with the form of observed <span class="hlt">event</span> size distributions. In an ensemble of 15 simulations under Representative Concentration Pathway 8.5 for anthropogenic forcing increases, the very largest <span class="hlt">event</span> portion of the distribution shows marked sensitivity, consistent with the simple prototype, with increases over most of the globe and strong regional increases. The theory suggests a set of conditions to evaluate for other climate quantities under which one should expect such sensitivity of probability of the very largest <span class="hlt">events</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..16.7249H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16.7249H"><span>Subsurface <span class="hlt">warming</span> in the subpolar North Atlantic during rapid climate <span class="hlt">events</span> in the Early and Mid-Pleistocene</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hernández-Almeida, Iván; Sierro, Francisco; Cacho, Isabel; Abel Flores, José</p> <p>2014-05-01</p> <p>A new high-resolution reconstruction of the temperature and salinity of the subsurface waters using paired Mg/Ca-δ18O measurements on the planktonic foraminifera Neogloboquadrina pachyderma sinistrorsa (sin.) was conducted on a deep-sea sediment core in the subpolar North Atlantic (Site U1314). This study aims to reconstruct millennial-scale subsurface hydrography variations during the Early and Mid-Pleistocene (MIS 31-19). These rapid climate <span class="hlt">events</span> are characterized by <span class="hlt">abrupt</span> shifts between <span class="hlt">warm</span>/cold conditions, and ice-sheet oscillations, as evidenced by major ice rafting <span class="hlt">events</span> recorded in the North Atlantic sediments (Hernández-Almeida et al., 2012), similar to those found during the Last Glacial period (Marcott et al, 2011). The Mg/Ca derived paleotemperature and salinity oscillations prior and during IRD discharges at Site U1314 are related to changes in intermediate circulation. The increases in Mg/Ca paleotemperatures and salinities during the IRD <span class="hlt">event</span> are preceded by short episodes of cooling and freshening of subsurface waters. The response of the AMOC to this perturbation is an increased of <span class="hlt">warm</span> and salty water coming from the south, transported to high latitudes in the North Atlantic beneath the thermocline. This process is accompanied by a southward shift in the convection cell from the Nordic Seas to the subpolar North Atlantic and better ventilation of the North Atlantic at mid-depths. Poleward transport of <span class="hlt">warm</span> and salty subsurface subtropical waters causes intense basal melting and thinning of marine ice-shelves, that culminates in large-scale instability of the ice sheets, retreat of the grounding line and iceberg discharge. The mechanism proposed involves the coupling of the AMOC with ice-sheet dynamics, and would explain the presence of these fluctuations before the establishment of high-amplitude 100-kyr glacial cycles. Hernández-Almeida, I., Sierro, F.J., Cacho, I., Flores, J.A., 2012. Impact of suborbital climate changes in the North</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EOSTr..93..313S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EOSTr..93..313S"><span><span class="hlt">Abrupt</span> climate change: Mechanisms, patterns, and impacts</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schultz, Colin</p> <p>2012-08-01</p> <p>In the span of only a few decades, the global temperature can soar by more than a dozen degrees Celsius, a feat that 20 years ago was considered improbable, if not impossible. But recent research in the nascent field of rapid climate change has upended the dominant views of decades past. Focusing primarily on <span class="hlt">events</span> during and after the most recent glaciation, from 80,000 years ago, the AGU monograph <span class="hlt">Abrupt</span> Climate Change: Mechanisms, Patterns, and Impacts, edited by Harunur Rashid, Leonid Polyak, and Ellen Mosley-Thompson, explores the transient climate transitions that were only recently uncovered in climate proxies around the world. In this interview, Eos talks to Harunur Rashid about piecing together ancient climes, the effect of <span class="hlt">abrupt</span> change on historical civilizations, and why younger researchers may be more worried about modern <span class="hlt">warming</span> than their teachers.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li class="active"><span>5</span></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_5 --> <div id="page_6" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li class="active"><span>6</span></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="101"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003AGUFMPP22C..01W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003AGUFMPP22C..01W"><span>Work More? The 8.2 kaBP <span class="hlt">Abrupt</span> Climate Change <span class="hlt">Event</span> and the Origins of Irrigation Agriculture and Surplus Agro-Production in Mesopotamia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Weiss, H.</p> <p>2003-12-01</p> <p>The West Asian archaeological record is of sufficient transparency and resolution to permit observation of the social responses to the major Holocene <span class="hlt">abrupt</span> climate change <span class="hlt">events</span> at 8.2, 5.2 and 4.2 kaBP. The 8.2kaBP <span class="hlt">abrupt</span> climate change <span class="hlt">event</span> in West Asia was a three hundred year aridification and cooling episode. During this period rain-fed agriculture, established for over a millennium in northern Mesopotamia, suddenly collapsed. Irrigation agriculture, pastoral nomadism, or migration were the only subsistence alternatives for populations previously supported by cereal dry-farming. Irrigation agriculture was not, however, possible along the northern alluvial plains of the Tigris and Euphrates Rivers, where incised riverbeds were several meters below plain level. Exploitable plain-level levees were only accessible in southern-most alluvial plain, at the head of the present-day Persian Gulf. The archaeological data from this region documents the first irrigation agriculture settlement of the plain during the 8.2 kaBP <span class="hlt">event</span>. Irrigation agriculture provides about twice the yield of dry-farming in Mesopotamia, but at considerable labor costs relative to dry-farming. With irrigation agriculture surplus production was now available for deployment. But why work more? The 8.2 kaBP <span class="hlt">event</span> provided the natural force for Mesopotamian irrigation agriculture and surplus production that were essential for the earliest class-formation and urban life.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/14558902','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/14558902"><span>Sea-ice switches and <span class="hlt">abrupt</span> climate change.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Gildor, Hezi; Tziperman, Eli</p> <p>2003-09-15</p> <p>We propose that past <span class="hlt">abrupt</span> climate changes were probably a result of rapid and extensive variations in sea-ice cover. We explain why this seems a perhaps more likely explanation than a purely thermohaline circulation mechanism. We emphasize that because of the significant influence of sea ice on the climate system, it seems that high priority should be given to developing ways for reconstructing high-resolution (in space and time) sea-ice extent for past climate-change <span class="hlt">events</span>. If proxy data can confirm that sea ice was indeed the major player in past <span class="hlt">abrupt</span> climate-change <span class="hlt">events</span>, it seems less likely that such dramatic <span class="hlt">abrupt</span> changes will occur due to global <span class="hlt">warming</span>, when extensive sea-ice cover will not be present.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26460042','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26460042"><span>Catalogue of <span class="hlt">abrupt</span> shifts in Intergovernmental Panel on Climate Change climate models.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Drijfhout, Sybren; Bathiany, Sebastian; Beaulieu, Claudie; Brovkin, Victor; Claussen, Martin; Huntingford, Chris; Scheffer, Marten; Sgubin, Giovanni; Swingedouw, Didier</p> <p>2015-10-27</p> <p><span class="hlt">Abrupt</span> transitions of regional climate in response to the gradual rise in atmospheric greenhouse gas concentrations are notoriously difficult to foresee. However, such <span class="hlt">events</span> could be particularly challenging in view of the capacity required for society and ecosystems to adapt to them. We present, to our knowledge, the first systematic screening of the massive climate model ensemble informing the recent Intergovernmental Panel on Climate Change report, and reveal evidence of 37 forced regional <span class="hlt">abrupt</span> changes in the ocean, sea ice, snow cover, permafrost, and terrestrial biosphere that arise after a certain global temperature increase. Eighteen out of 37 <span class="hlt">events</span> occur for global <span class="hlt">warming</span> levels of less than 2°, a threshold sometimes presented as a safe limit. Although most models predict one or more such <span class="hlt">events</span>, any specific occurrence typically appears in only a few models. We find no compelling evidence for a general relation between the overall number of <span class="hlt">abrupt</span> shifts and the level of global <span class="hlt">warming</span>. However, we do note that <span class="hlt">abrupt</span> changes in ocean circulation occur more often for moderate <span class="hlt">warming</span> (less than 2°), whereas over land they occur more often for <span class="hlt">warming</span> larger than 2°. Using a basic proportion test, however, we find that the number of <span class="hlt">abrupt</span> shifts identified in Representative Concentration Pathway (RCP) 8.5 scenarios is significantly larger than in other scenarios of lower radiative forcing. This suggests the potential for a gradual trend of destabilization of the climate with respect to such shifts, due to increasing global mean temperature change.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4629371','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4629371"><span>Catalogue of <span class="hlt">abrupt</span> shifts in Intergovernmental Panel on Climate Change climate models</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Drijfhout, Sybren; Bathiany, Sebastian; Beaulieu, Claudie; Brovkin, Victor; Claussen, Martin; Huntingford, Chris; Scheffer, Marten; Sgubin, Giovanni; Swingedouw, Didier</p> <p>2015-01-01</p> <p><span class="hlt">Abrupt</span> transitions of regional climate in response to the gradual rise in atmospheric greenhouse gas concentrations are notoriously difficult to foresee. However, such <span class="hlt">events</span> could be particularly challenging in view of the capacity required for society and ecosystems to adapt to them. We present, to our knowledge, the first systematic screening of the massive climate model ensemble informing the recent Intergovernmental Panel on Climate Change report, and reveal evidence of 37 forced regional <span class="hlt">abrupt</span> changes in the ocean, sea ice, snow cover, permafrost, and terrestrial biosphere that arise after a certain global temperature increase. Eighteen out of 37 <span class="hlt">events</span> occur for global <span class="hlt">warming</span> levels of less than 2°, a threshold sometimes presented as a safe limit. Although most models predict one or more such <span class="hlt">events</span>, any specific occurrence typically appears in only a few models. We find no compelling evidence for a general relation between the overall number of <span class="hlt">abrupt</span> shifts and the level of global <span class="hlt">warming</span>. However, we do note that <span class="hlt">abrupt</span> changes in ocean circulation occur more often for moderate <span class="hlt">warming</span> (less than 2°), whereas over land they occur more often for <span class="hlt">warming</span> larger than 2°. Using a basic proportion test, however, we find that the number of <span class="hlt">abrupt</span> shifts identified in Representative Concentration Pathway (RCP) 8.5 scenarios is significantly larger than in other scenarios of lower radiative forcing. This suggests the potential for a gradual trend of destabilization of the climate with respect to such shifts, due to increasing global mean temperature change. PMID:26460042</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012DSRII..65....6O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012DSRII..65....6O"><span>Recent Bering Sea <span class="hlt">warm</span> and cold <span class="hlt">events</span> in a 95-year context</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Overland, James E.; Wang, Muyin; Wood, Kevin R.; Percival, Donald B.; Bond, Nicholas A.</p> <p>2012-06-01</p> <p>The meteorology and oceanography of the southeastern Bering Sea shelf was recently dominated by a multi-year <span class="hlt">warm</span> <span class="hlt">event</span> (2000-2005) followed by a multi-year cold <span class="hlt">event</span> (2007-2010). We put these recent <span class="hlt">events</span> into the context of the 95-year air temperature record from St. Paul Island and with concurrent spatial meteorological fields. For March 2000-2005 the mean air temperature anomaly at St. Paul was 2.1 °C above the long-term mean, and for March 2007-2010 the mean temperature anomaly at St. Paul was 4.7 °C below the long-term mean. The only multi-year temperature deviations comparable to the first decade of the 2000s are a cold <span class="hlt">event</span> from 1971 to 1976 followed by a <span class="hlt">warm</span> <span class="hlt">event</span> from 1978 to 1983. There was also a short <span class="hlt">warm</span> <span class="hlt">event</span> 1935-1937. The temperature transition between <span class="hlt">warm</span> and cold <span class="hlt">events</span> in the 1970s and 2000s took two years. While there are theoretical arguments for some physical memory processes in the North Pacific climate system, we cannot rule out that the recent <span class="hlt">warm</span> and cold <span class="hlt">events</span> are of a random nature: they are rare in the St. Paul temperature record, they are dominated by North Pacific-wide sea level pressure <span class="hlt">events</span> rather than local Bering Sea processes, and they are consistent with a red noise model of climate variability. The 1970s transition appears to have an ENSO (El Niño-Southern Oscillation) influence, while the recent <span class="hlt">events</span> are likely connected to Arctic-wide <span class="hlt">warming</span>. Evidence provided by the 95-year St. Paul meteorological record reinforces the idea that a red-noise model of climate variability is appropriate for the North Pacific and southeastern Bering Sea. We stress the importance of relatively rare sub-decadal <span class="hlt">events</span> and shifts, rather than multi-decadal variability associated with the Pacific Decadal Oscillation (PDO). Thus, in the future we can expect large positive and negative excursions in the region that can last for multiple years, but there is as yet little predictability for their timing and duration.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110008490','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110008490"><span>Response of the Antarctic Stratosphere to <span class="hlt">Warm</span> Pool EI Nino <span class="hlt">Events</span> in the GEOS CCM</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hurwitz, Margaret M.; Song, In-Sun; Oman, Luke D.; Newman, Paul A.; Molod, Andrea M.; Frith, Stacey M.; Nielsen, J. Eric</p> <p>2011-01-01</p> <p>A new type of EI Nino <span class="hlt">event</span> has been identified in the last decade. During "<span class="hlt">warm</span> pool" EI Nino (WPEN) <span class="hlt">events</span>, sea surface temperatures (SSTs) in the central equatorial Pacific are warmer than average. The EI Nino signal propagates poleward and upward as large-scale atmospheric waves, causing unusual weather patterns and <span class="hlt">warming</span> the polar stratosphere. In austral summer, observations show that the Antarctic lower stratosphere is several degrees (K) warmer during WPEN <span class="hlt">events</span> than during the neutral phase of EI Nino/Southern Oscillation (ENSO). Furthermore, the stratospheric response to WPEN <span class="hlt">events</span> depends of the direction of tropical stratospheric winds: the Antarctic <span class="hlt">warming</span> is largest when WPEN <span class="hlt">events</span> are coincident with westward winds in the tropical lower and middle stratosphere i.e., the westward phase of the quasi-biennial oscillation (QBO). Westward winds are associated with enhanced convection in the subtropics, and with increased poleward wave activity. In this paper, a new formulation of the Goddard Earth Observing System Chemistry-Climate Model, Version 2 (GEOS V2 CCM) is used to substantiate the observed stratospheric response to WPEN <span class="hlt">events</span>. One simulation is driven by SSTs typical of a WPEN <span class="hlt">event</span>, while another simulation is driven by ENSO neutral SSTs; both represent a present-day climate. Differences between the two simulations can be directly attributed to the anomalous WPEN SSTs. During WPEN <span class="hlt">events</span>, relative to ENSO neutral, the model simulates the observed increase in poleward planetary wave activity in the South Pacific during austral spring, as well as the relative <span class="hlt">warming</span> of the Antarctic lower stratosphere in austral summer. However, the modeled response to WPEN does not depend on the phase of the QBO. The modeled tropical wind oscillation does not extend far enough into the lower stratosphere and upper troposphere, likely explaining the model's insensitivity to the phase of the QBO during WPEN <span class="hlt">events</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008Sci...321..680S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008Sci...321..680S"><span>High-Resolution Greenland Ice Core Data Show <span class="hlt">Abrupt</span> Climate Change Happens in Few Years</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Steffensen, Jørgen Peder; Andersen, Katrine K.; Bigler, Matthias; Clausen, Henrik B.; Dahl-Jensen, Dorthe; Fischer, Hubertus; Goto-Azuma, Kumiko; Hansson, Margareta; Johnsen, Sigfús J.; Jouzel, Jean; Masson-Delmotte, Valérie; Popp, Trevor; Rasmussen, Sune O.; Röthlisberger, Regine; Ruth, Urs; Stauffer, Bernhard; Siggaard-Andersen, Marie-Louise; Sveinbjörnsdóttir, Árný E.; Svensson, Anders; White, James W. C.</p> <p>2008-08-01</p> <p>The last two <span class="hlt">abrupt</span> <span class="hlt">warmings</span> at the onset of our present <span class="hlt">warm</span> interglacial period, interrupted by the Younger Dryas cooling <span class="hlt">event</span>, were investigated at high temporal resolution from the North Greenland Ice Core Project ice core. The deuterium excess, a proxy of Greenland precipitation moisture source, switched mode within 1 to 3 years over these transitions and initiated a more gradual change (over 50 years) of the Greenland air temperature, as recorded by stable water isotopes. The onsets of both <span class="hlt">abrupt</span> Greenland <span class="hlt">warmings</span> were slightly preceded by decreasing Greenland dust deposition, reflecting the wetting of Asian deserts. A northern shift of the Intertropical Convergence Zone could be the trigger of these <span class="hlt">abrupt</span> shifts of Northern Hemisphere atmospheric circulation, resulting in changes of 2 to 4 kelvin in Greenland moisture source temperature from one year to the next.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18566247','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18566247"><span>High-resolution Greenland ice core data show <span class="hlt">abrupt</span> climate change happens in few years.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Steffensen, Jørgen Peder; Andersen, Katrine K; Bigler, Matthias; Clausen, Henrik B; Dahl-Jensen, Dorthe; Fischer, Hubertus; Goto-Azuma, Kumiko; Hansson, Margareta; Johnsen, Sigfús J; Jouzel, Jean; Masson-Delmotte, Valérie; Popp, Trevor; Rasmussen, Sune O; Röthlisberger, Regine; Ruth, Urs; Stauffer, Bernhard; Siggaard-Andersen, Marie-Louise; Sveinbjörnsdóttir, Arny E; Svensson, Anders; White, James W C</p> <p>2008-08-01</p> <p>The last two <span class="hlt">abrupt</span> <span class="hlt">warmings</span> at the onset of our present <span class="hlt">warm</span> interglacial period, interrupted by the Younger Dryas cooling <span class="hlt">event</span>, were investigated at high temporal resolution from the North Greenland Ice Core Project ice core. The deuterium excess, a proxy of Greenland precipitation moisture source, switched mode within 1 to 3 years over these transitions and initiated a more gradual change (over 50 years) of the Greenland air temperature, as recorded by stable water isotopes. The onsets of both <span class="hlt">abrupt</span> Greenland <span class="hlt">warmings</span> were slightly preceded by decreasing Greenland dust deposition, reflecting the wetting of Asian deserts. A northern shift of the Intertropical Convergence Zone could be the trigger of these <span class="hlt">abrupt</span> shifts of Northern Hemisphere atmospheric circulation, resulting in changes of 2 to 4 kelvin in Greenland moisture source temperature from one year to the next.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/576867','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/576867"><span><span class="hlt">Abrupt</span> climate <span class="hlt">events</span> 500,000 to 340,000 years ago: Evidence from subpolar North Atlantic sediments</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Oppo, D.W.; McManus, J.F.; Cullen, J.L.</p> <p>1998-02-27</p> <p>Subpolar North Atlantic proxy records document millennial-scale climate variations 500,000 to 340,000 years ago. The cycles have an approximately constant pacing that is similar to that documented for the last glacial cycle. These findings suggest that such climate variations are inherent to the late Pleistocene, regardless of glacial state. Sea surface temperature during the <span class="hlt">warm</span> peak of Marine Isotope Stage 11 (MIS 11) varied by 0.5{degree} to 1{degree}C, less than the 4{degree} to 4.5{degree}C estimated during times of ice growth and the 3{degree}C estimated for glacial maxima. Coherent deep ocean circulation changes were associated with glacial oscillations in sea surface temperature. 31 refs., 3 figs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/7552108','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/7552108"><span>ENSO and disaster: droughts, floods and El Niño/Southern Oscillation <span class="hlt">warm</span> <span class="hlt">events</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Dilley, M; Heyman, B N</p> <p>1995-09-01</p> <p>The connection between El Niño/Southern Oscillation (ENSO) <span class="hlt">events</span> and precipitation and temperature variability worldwide is increasingly well understood. ENSO has been linked to droughts and flooding in some regions. This paper uses the disaster history database of the U.S. Agency for International Development's Office of U.S. Foreign Disaster Assistance to examine the link between ENSO <span class="hlt">events</span> and droughts or floods of sufficient magnitude to trigger international disasters. Worldwide, disasters triggered by droughts are twice as frequent during year two of ENSO <span class="hlt">warm</span> <span class="hlt">events</span> than during other years. No such relationship is apparent in the case of flood disasters. Drought disasters occur during year two of ENSO <span class="hlt">warm</span> <span class="hlt">events</span> significantly more frequently than in other years in Southern Africa and Southeast Asia. No regional pattern emerges from a comparable analysis of flood disasters. Those places likely to be affected by ENSO-triggered droughts can take proactive measures to mitigate the impacts.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2263775','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2263775"><span>Implications of <span class="hlt">abrupt</span> climate change.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Alley, Richard B.</p> <p>2004-01-01</p> <p>Records of past climates contained in ice cores, ocean sediments, and other archives show that large, <span class="hlt">abrupt</span>, widespread climate changes have occurred repeatedly in the past. These changes were especially prominent during the cooling into and <span class="hlt">warming</span> out of the last ice age, but persisted into the modern <span class="hlt">warm</span> interval. Changes have especially affected water availability in <span class="hlt">warm</span> regions and temperature in cold regions, but have affected almost all climatic variables across much or all of the Earth. Impacts of climate changes are smaller if the changes are slower or more-expected. The rapidity of <span class="hlt">abrupt</span> climate changes, together with the difficulty of predicting such changes, means that impacts on the health of humans, economies and ecosystems will be larger if <span class="hlt">abrupt</span> climate changes occur. Most projections of future climate include only gradual changes, whereas paleoclimatic data plus models indicate that <span class="hlt">abrupt</span> changes remain possible; thus, policy is being made based on a view of the future that may be optimistic. PMID:17060975</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015CliPD..11.1407M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015CliPD..11.1407M"><span>Millennial-scale precipitation variability over Easter Island (South Pacific) during MIS 3: inter-hemispheric teleconnections with North Atlantic <span class="hlt">abrupt</span> cold <span class="hlt">events</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Margalef, O.; Cacho, I.; Pla-Rabes, S.; Cañellas-Boltà, N.; Pueyo, J. J.; Sáez, A.; Pena, L. D.; Valero-Garcés, B. L.; Rull, V.; Giralt, S.</p> <p>2015-04-01</p> <p>Marine Isotope Stage 3 (MIS 3, 59.4-27.8 kyr BP) is characterized by the occurrence of rapid millennial-scale climate oscillations known as Dansgaard-Oeschger cycles (DO) and by <span class="hlt">abrupt</span> cooling <span class="hlt">events</span> in the North Atlantic known as Heinrich <span class="hlt">events</span>. Although both the timing and dynamics of these <span class="hlt">events</span> have been broadly explored in North Atlantic records, the response of the tropical and subtropical latitudes to these rapid climatic excursions, particularly in the Southern Hemisphere, still remains unclear. The Rano Aroi peat record (Easter Island, 27° S) provides a unique opportunity to understand atmospheric and oceanic changes in the South Pacific during these DO cycles because of its singular location, which is influenced by the South Pacific Anticyclone (SPA), the Southern Westerlies (SW), and the Intertropical Convergence Zone (ITCZ) linked to the South Pacific Convergence Zone (SPCZ). The Rano Aroi sequence records 6 major <span class="hlt">events</span> of enhanced precipitation between 38 and 65 kyr BP. These <span class="hlt">events</span> are compared with other hydrological records from the tropical and subtropical band supporting a coherent regional picture, with the dominance of humid conditions in Southern Hemisphere tropical band during Heinrich Stadials (HS) 5, 5a and 6 and other Stadials while dry conditions prevailed in the Northern tropics. This antiphased hydrological pattern between hemispheres has been attributed to ITCZ migration, which in turn might be associated with an eastward expansion of the SPCZ storm track, leading to an increased intensity of cyclogenic storms reaching Easter Island. Low Pacific Sea Surface Temperature (SST) gradients across the Equator were coincident with the here-defined Rano Aroi humid <span class="hlt">events</span> and consistent with a reorganization of Southern Pacific atmospheric and oceanic circulation also at higher latitudes during Heinrich and Dansgaard-Oeschger stadials.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GeoRL..4310489C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GeoRL..4310489C"><span>Do strong <span class="hlt">warm</span> ENSO <span class="hlt">events</span> control the phase of the stratospheric QBO?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Christiansen, Bo; Yang, Shuting; Madsen, Marianne Sloth</p> <p>2016-10-01</p> <p>Although there in general are no significant long-term correlations between the quasi-biennial oscillation (QBO) and the El Niño-Southern Oscillation (ENSO) in observations, we find that the QBO and the ENSO were aligned in the 3 to 4 years after the three <span class="hlt">warm</span> ENSO <span class="hlt">events</span> in 1982, 1997, and 2015. We investigate this indicated relationship with a version of the EC-Earth climate model which includes nonorographic gravity waves. We analyze the modeled QBO in ensembles forced with climatological sea surface temperatures (SSTs) and observed SSTs. In the ensemble with observed SSTs we find a strong and significant alignment of the ensemble members in the equatorial stratospheric winds in the 2 to 4 years after the strong ENSO <span class="hlt">event</span> in 1997. This alignment also includes the observed QBO. No such alignment is found in the ensemble with climatological SSTs. These results indicate that strong <span class="hlt">warm</span> ENSO <span class="hlt">events</span> can lock the phase of the QBO.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..1510084E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..1510084E"><span><span class="hlt">Abrupt</span> Changes in the Marmara Pelagic Ecosystem during the recent jellyfish Liriope tetraphylla invasion and mucilage <span class="hlt">events</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Erkan Kideys, Ahmet; Yüksek, Ahsen; Sur, Halil Ibrahim</p> <p>2013-04-01</p> <p>In this study, meteorological and hydrographical conditions as well as chemical and biological parameters have been examined for the period 2005-2009 to determine the impact and cause of the massive mucilage phenomenon observed in the Sea of Marmara in October 2007. Results showed that there is a decrease pattern in chl concentration as well as both phytoplankton and zooplankton abundances from August till October in 2007 whilst the jellyfish Liriope tetraphylla had bloom levels. This period coincided with the maximum intensity of pelagic fishing throughout the years. Nitrogen/phosphate ratio increased prior to the mucilage formation. Invasive Liriope tetraphylla abundance increased exponentially in August and died in masses as a result of starvation and meteorological / oceanographic conditions. In October, following the mucilage matter production another new species for the region Gonyaulax fragilis was observed in high abundance through the basin. It is worthy to note that during basin wide samplings conducted in the Sea of Marmara in both 2005 and 2006, high abundances of Liriope tetraphylla have been detected particularly at the northern parts where no mucilage <span class="hlt">event</span> was observed. We suggest that overfishing in the Sea of Marmara provided a ground for the establishment of the invasive jellyfish and accompanying mucilage <span class="hlt">event</span> was due to by synergic combinations of several factors.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27859198','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27859198"><span>Relatively stable response of fruiting stage to <span class="hlt">warming</span> and cooling relative to other phenological <span class="hlt">events</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Jiang, L L; Wang, S P; Meng, F D; Duan, J C; Niu, H S; Xu, G P; Zhu, X X; Zhang, Z H; Luo, C Y; Cui, S J; Li, Y M; Li, X E; Wang, Q; Zhou, Y; Bao, X Y; Li, Y N; Dorji, T; Piao, S L; Ciais, P; Peñuelas, J; Du, M Y; Zhao, X Q; Zhao, L; Zhang, F W; Wang, G J</p> <p>2016-08-01</p> <p>The timing of the fruit-set stage (i.e., start and end of fruit set) is crucial in a plant's life cycle, but its response to temperature change is still unclear. We investigated the timing of seven phenological <span class="hlt">events</span>, including fruit-set dates during 3 yr for six alpine plants transplanted to warmer (approximately +3.5°C in soils) and cooler (approximately -3.5°C in soils) locations along an altitudinal gradient in the Tibetan area. We found that fruit-set dates remained relatively stable under both <span class="hlt">warming</span> and cooling during the 3-yr transplant experiment. Three earlier phenological <span class="hlt">events</span> (emergence of first leaf, first bud set, and first flowering) and two later phenological <span class="hlt">events</span> (first leaf coloring and complete leaf coloring) were earlier by 4.8-8.2 d/°C and later by 3.2-7.1 d/°C in response to <span class="hlt">warming</span>. Conversely, cooling delayed the three earlier <span class="hlt">events</span> by 3.8-6.9 d/°C and advanced the two later <span class="hlt">events</span> by 3.2-8.1 d/°C for all plant species. The timing of the first and/or last fruit-set dates, however, did not change significantly compared to earlier and later phenological <span class="hlt">events</span>. Statistical analyses also showed that the dates of fruit set were not significantly correlated or had lower correlations with changes of soil temperature relative to the earlier and later phenological <span class="hlt">events</span>. Alpine plants may thus acclimate to changes in temperature for their fruiting function by maintaining relatively stable timings of fruit set compared with other phenological <span class="hlt">events</span> to maximize the success of seed maturation and dispersal in response to short-term <span class="hlt">warming</span> or cooling. © 2016 by the Ecological Society of America.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUFMGC13A0950N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUFMGC13A0950N"><span><span class="hlt">Abrupt</span> changes in rainfall during the twentieth century</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Narisma, G.; Foley, J.; Licker, R.; Ramankutty, N.</p> <p>2007-12-01</p> <p>A sudden change in climate is brought about by complex interactions in the climate system, including interactions between land and atmosphere, that can give rise to strong positive feedback mechanisms. Paleoclimatic studies have shown that <span class="hlt">abrupt</span> climate changes have happened in the geologic past. Studies of future climate change under global <span class="hlt">warming</span> scenarios indicate the possibility of the sudden collapse of the thermohaline circulation, which will have major implications for the climate of Europe. However, <span class="hlt">abrupt</span> climatic changes are not <span class="hlt">events</span> of the geologic past or a computer-simulated future: they have occurred in recent history and have had serious consequences on society and the environment. The prolonged Sahel drought in the late 1960s and the Dust Bowl of the 1930s are examples of <span class="hlt">abrupt</span> climatic changes of the twentieth century. Apart from these <span class="hlt">events</span>, however, there has been no systematic survey of recent climate history to determine the prevalence of <span class="hlt">abrupt</span> climatic changes. Given the potential cost of these <span class="hlt">abrupt</span> changes, there is a need to investigate historical records for evidence of other sudden climatic changes in the more recent past. Here we analyze the Climate Research Unit global historical rainfall observations (covering the years 1901-2000) using wavelet analysis to detect regions that have undergone large, sudden decreases in rainfall. We show that in the twentieth century, aside from the Sahel and the US midwest, at least 30 regions in the world have experienced sudden climatic changes. These <span class="hlt">events</span> are statistically significant at the 99 percent level, are persistent for at least ten years, and most have magnitudes of change that are 10 percent lower than the climatological normal (1901-2000 rainfall average). We also illustrate some of the potential consequences of these <span class="hlt">abrupt</span> changes and show that these <span class="hlt">events</span> had major impacts on social and environmental conditions. Interestingly, these regions of <span class="hlt">abrupt</span> precipitation changes are</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFMPP24A..03P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFMPP24A..03P"><span>AMS Chronology Reveals Ice Sheet Retreat at 15.5 kyr; Provides North Atlantic Chill and Feedbacks for <span class="hlt">Abrupt</span> Climate <span class="hlt">Warming</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Peteet, D. M.; Beh, M.; Orr, C.; Kurdyla, D.; Guilderson, T. P.</p> <p>2009-12-01</p> <p>The timing of the southeastern Laurentide ice sheet collapse is critical to understanding ocean-atmosphere-ice dynamics. Yet at present an enigma remains based on conflicting evidence including radiocarbon ages on bulk and identifiable macrofossils in lakes, 10Be cosmogenic dating results, and glacial lake varve sequences. Disparate data sources offer conflicting chronologies concerning when ice began retreating from the Laurentide New York - New Jersey -Pennsylvania Last Glacial Maximum (LGM) position. Our study, an investigation of lake basal clays and silts (0.5-8% organic), finds the deglaciation at 15 kyr. These results are 5-8 kyr later than previous deglaciation chronology (23-20 kyr) based upon bulk radiocarbon dating of lake sediments and extrapolation, 8-12 kyr later than varve chronologies, and 4-8kyr later than 10Be results. Our surprising result is generated by 15 accelerator mass spectrometry 14C dates from tundra/spruce macrofossils in 9 basal lake sediments. These dates indicate pioneer plant colonization from areas south and west as the landscape stabilized, just prior to widespread (Bolling) <span class="hlt">warming</span> which induced rapid limnic organic sedimentation. While <span class="hlt">warming</span> began as early as 17kyr as evidenced by terrestrial and marine records south of the ice margin, this cold meltwater lid on the N. Atlantic may have delayed the southern margin retreat to 15 kyr, when ice-free soils/lakes provided positive terrestrial/water vapor feedback for the swift pronounced <span class="hlt">warming</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008cosp...37.2034M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008cosp...37.2034M"><span>A study of the airglow and the sporadic E layers during stratospheric <span class="hlt">warming</span> <span class="hlt">events</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mikhalev, Alexander; Ratovsky, Konstantin; Medvedev, Andrey; Medvedeva, Irina; Kurkin, Vladimir; Chernigovskaya, Marina; Kostyleva, Nadegda</p> <p></p> <p>In the present work the <span class="hlt">events</span> of disturbances of the 557.7 nm and 630 nm airglow and occurrence of sporadic E layer in middle latitudes of Asian region during sudden stratospheric <span class="hlt">warmings</span> in December 2006 and January-February 2008 are analyzed. Ionosphere data were obtained with the DPS-4 ionosonde located in Irkutsk (52.3N, 104.3E). Airglow measurements were made by the 4-channel zenith photometer and colour CCD imager at ISTP Geophysical observatory located 130 km southwest of Irkutsk. To identify the stratospheric <span class="hlt">warming</span> <span class="hlt">events</span> the Berlin Meteorological University data (http://strat-www.met.fu-berlin.de) on stratospheric <span class="hlt">warming</span> at standard isobaric levels and the atmospheric temperature height profiles measured by the Microwave Limb Sounder (MLS) aboard the EOS Aura spacecraft were used. In some cases we observed correlated diurnal variations of 557.7 nm airglow intensity and Es characteristics. The fact that the correlation between 557.7 nm and Es layer characteristics did not always happen probably can be explained by the different spatial localization of Es layer and emitting layer as well as by the features of their dynamics. During a maximal rise of 557.7 nm airglow its spatial inhomogeneity registered by CCD imager in a continuum was observed. The possible mechanisms of the airglow disturbances and occurrence of sporadic E layers during sudden stratospheric <span class="hlt">warming</span> are discussed. The work was supported by RAS Presidium Program 16 (Part 3).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110008725','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110008725"><span>The Impact of <span class="hlt">Warm</span> Pool El Nino <span class="hlt">Events</span> on Antarctic Ozone</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hurwitz, Margaret M.; Newman, P. A.; Song, In-Sun; Frith, Stacey M.</p> <p>2011-01-01</p> <p><span class="hlt">Warm</span> pool El Nino (WPEN) <span class="hlt">events</span> are characterized by positive sea surface temperature (SST) anomalies in the central equatorial Pacific in austral spring and summer. Previous work found an enhancement in planetary wave activity in the South Pacific in austral spring, and a <span class="hlt">warming</span> of 3-5 K in the Antarctic lower stratosphere during austral summer, in WPEN <span class="hlt">events</span> as compared with ENSO neutral. In this presentation, we show that weakening of the Antarctic vortex during WPEN affects the structure and magnitude of high-latitude total ozone. We use total ozone data from TOMS and OMI, as well as station data from Argentina and Antarctica, to identify shifts in the longitudinal location of the springtime ozone minimum from its climatological position. In addition, we examine the sensitivity of the WPEN-related ozone response to the phase of the quasi-biennial oscillation (QBO). We then compare the observed response to WPEN <span class="hlt">events</span> with Goddard Earth Observing System chemistry-climate model, version 2 (GEOS V2 CCM) simulations. Two, 50-year time-slice simulations are forced by annually repeating SST and sea ice climatologies, one set representing observed WPEN <span class="hlt">events</span> and the second set representing neutral ENSO <span class="hlt">events</span>, in a present-day climate. By comparing the two simulations, we isolate the impact of WPEN <span class="hlt">events</span> on lower stratospheric ozone, and furthermore, examine the sensitivity of the WPEN ozone response to the phase of the QBO.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25825727','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25825727"><span>Response of seafloor ecosystems to <span class="hlt">abrupt</span> global climate change.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Moffitt, Sarah E; Hill, Tessa M; Roopnarine, Peter D; Kennett, James P</p> <p>2015-04-14</p> <p>Anthropogenic climate change is predicted to decrease oceanic oxygen (O2) concentrations, with potentially significant effects on marine ecosystems. Geologically recent episodes of <span class="hlt">abrupt</span> climatic <span class="hlt">warming</span> provide opportunities to assess the effects of changing oxygenation on marine communities. Thus far, this knowledge has been largely restricted to investigations using Foraminifera, with little being known about ecosystem-scale responses to <span class="hlt">abrupt</span>, climate-forced deoxygenation. We here present high-resolution records based on the first comprehensive quantitative analysis, to our knowledge, of changes in marine metazoans (Mollusca, Echinodermata, Arthropoda, and Annelida; >5,400 fossils and trace fossils) in response to the global <span class="hlt">warming</span> associated with the last glacial to interglacial episode. The molluscan archive is dominated by extremophile taxa, including those containing endosymbiotic sulfur-oxidizing bacteria (Lucinoma aequizonatum) and those that graze on filamentous sulfur-oxidizing benthic bacterial mats (Alia permodesta). This record, from 16,100 to 3,400 y ago, demonstrates that seafloor invertebrate communities are subject to major turnover in response to relatively minor inferred changes in oxygenation (>1.5 to <0.5 mL⋅L(-1) [O2]) associated with <span class="hlt">abrupt</span> (<100 y) <span class="hlt">warming</span> of the eastern Pacific. The biotic turnover and recovery <span class="hlt">events</span> within the record expand known rates of marine biological recovery by an order of magnitude, from <100 to >1,000 y, and illustrate the crucial role of climate and oceanographic change in driving long-term successional changes in ocean ecosystems.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li class="active"><span>6</span></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_6 --> <div id="page_7" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li class="active"><span>7</span></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="121"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PNAS..112.4684M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PNAS..112.4684M"><span>Response of seafloor ecosystems to <span class="hlt">abrupt</span> global climate change</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Moffitt, Sarah E.; Hill, Tessa M.; Roopnarine, Peter D.; Kennett, James P.</p> <p>2015-04-01</p> <p>Anthropogenic climate change is predicted to decrease oceanic oxygen (O2) concentrations, with potentially significant effects on marine ecosystems. Geologically recent episodes of <span class="hlt">abrupt</span> climatic <span class="hlt">warming</span> provide opportunities to assess the effects of changing oxygenation on marine communities. Thus far, this knowledge has been largely restricted to investigations using Foraminifera, with little being known about ecosystem-scale responses to <span class="hlt">abrupt</span>, climate-forced deoxygenation. We here present high-resolution records based on the first comprehensive quantitative analysis, to our knowledge, of changes in marine metazoans (Mollusca, Echinodermata, Arthropoda, and Annelida; >5,400 fossils and trace fossils) in response to the global <span class="hlt">warming</span> associated with the last glacial to interglacial episode. The molluscan archive is dominated by extremophile taxa, including those containing endosymbiotic sulfur-oxidizing bacteria (Lucinoma aequizonatum) and those that graze on filamentous sulfur-oxidizing benthic bacterial mats (Alia permodesta). This record, from 16,100 to 3,400 y ago, demonstrates that seafloor invertebrate communities are subject to major turnover in response to relatively minor inferred changes in oxygenation (>1.5 to <0.5 mLṡL-1 [O2]) associated with <span class="hlt">abrupt</span> (<100 y) <span class="hlt">warming</span> of the eastern Pacific. The biotic turnover and recovery <span class="hlt">events</span> within the record expand known rates of marine biological recovery by an order of magnitude, from <100 to >1,000 y, and illustrate the crucial role of climate and oceanographic change in driving long-term successional changes in ocean ecosystems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4403169','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4403169"><span>Response of seafloor ecosystems to <span class="hlt">abrupt</span> global climate change</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Moffitt, Sarah E.; Hill, Tessa M.; Roopnarine, Peter D.; Kennett, James P.</p> <p>2015-01-01</p> <p>Anthropogenic climate change is predicted to decrease oceanic oxygen (O2) concentrations, with potentially significant effects on marine ecosystems. Geologically recent episodes of <span class="hlt">abrupt</span> climatic <span class="hlt">warming</span> provide opportunities to assess the effects of changing oxygenation on marine communities. Thus far, this knowledge has been largely restricted to investigations using Foraminifera, with little being known about ecosystem-scale responses to <span class="hlt">abrupt</span>, climate-forced deoxygenation. We here present high-resolution records based on the first comprehensive quantitative analysis, to our knowledge, of changes in marine metazoans (Mollusca, Echinodermata, Arthropoda, and Annelida; >5,400 fossils and trace fossils) in response to the global <span class="hlt">warming</span> associated with the last glacial to interglacial episode. The molluscan archive is dominated by extremophile taxa, including those containing endosymbiotic sulfur-oxidizing bacteria (Lucinoma aequizonatum) and those that graze on filamentous sulfur-oxidizing benthic bacterial mats (Alia permodesta). This record, from 16,100 to 3,400 y ago, demonstrates that seafloor invertebrate communities are subject to major turnover in response to relatively minor inferred changes in oxygenation (>1.5 to <0.5 mL⋅L−1 [O2]) associated with <span class="hlt">abrupt</span> (<100 y) <span class="hlt">warming</span> of the eastern Pacific. The biotic turnover and recovery <span class="hlt">events</span> within the record expand known rates of marine biological recovery by an order of magnitude, from <100 to >1,000 y, and illustrate the crucial role of climate and oceanographic change in driving long-term successional changes in ocean ecosystems. PMID:25825727</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PNAS..114.4881D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PNAS..114.4881D"><span>Quantifying the influence of global <span class="hlt">warming</span> on unprecedented extreme climate <span class="hlt">events</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Diffenbaugh, Noah S.; Singh, Deepti; Mankin, Justin S.; Horton, Daniel E.; Swain, Daniel L.; Touma, Danielle; Charland, Allison; Liu, Yunjie; Haugen, Matz; Tsiang, Michael; Rajaratnam, Bala</p> <p>2017-05-01</p> <p>Efforts to understand the influence of historical global <span class="hlt">warming</span> on individual extreme climate <span class="hlt">events</span> have increased over the past decade. However, despite substantial progress, <span class="hlt">events</span> that are unprecedented in the local observational record remain a persistent challenge. Leveraging observations and a large climate model ensemble, we quantify uncertainty in the influence of global <span class="hlt">warming</span> on the severity and probability of the historically hottest month, hottest day, driest year, and wettest 5-d period for different areas of the globe. We find that historical <span class="hlt">warming</span> has increased the severity and probability of the hottest month and hottest day of the year at >80% of the available observational area. Our framework also suggests that the historical climate forcing has increased the probability of the driest year and wettest 5-d period at 57% and 41% of the observed area, respectively, although we note important caveats. For the most protracted hot and dry <span class="hlt">events</span>, the strongest and most widespread contributions of anthropogenic climate forcing occur in the tropics, including increases in probability of at least a factor of 4 for the hottest month and at least a factor of 2 for the driest year. We also demonstrate the ability of our framework to systematically evaluate the role of dynamic and thermodynamic factors such as atmospheric circulation patterns and atmospheric water vapor, and find extremely high statistical confidence that anthropogenic forcing increased the probability of record-low Arctic sea ice extent.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28439005','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28439005"><span>Quantifying the influence of global <span class="hlt">warming</span> on unprecedented extreme climate <span class="hlt">events</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Diffenbaugh, Noah S; Singh, Deepti; Mankin, Justin S; Horton, Daniel E; Swain, Daniel L; Touma, Danielle; Charland, Allison; Liu, Yunjie; Haugen, Matz; Tsiang, Michael; Rajaratnam, Bala</p> <p>2017-05-09</p> <p>Efforts to understand the influence of historical global <span class="hlt">warming</span> on individual extreme climate <span class="hlt">events</span> have increased over the past decade. However, despite substantial progress, <span class="hlt">events</span> that are unprecedented in the local observational record remain a persistent challenge. Leveraging observations and a large climate model ensemble, we quantify uncertainty in the influence of global <span class="hlt">warming</span> on the severity and probability of the historically hottest month, hottest day, driest year, and wettest 5-d period for different areas of the globe. We find that historical <span class="hlt">warming</span> has increased the severity and probability of the hottest month and hottest day of the year at >80% of the available observational area. Our framework also suggests that the historical climate forcing has increased the probability of the driest year and wettest 5-d period at 57% and 41% of the observed area, respectively, although we note important caveats. For the most protracted hot and dry <span class="hlt">events</span>, the strongest and most widespread contributions of anthropogenic climate forcing occur in the tropics, including increases in probability of at least a factor of 4 for the hottest month and at least a factor of 2 for the driest year. We also demonstrate the ability of our framework to systematically evaluate the role of dynamic and thermodynamic factors such as atmospheric circulation patterns and atmospheric water vapor, and find extremely high statistical confidence that anthropogenic forcing increased the probability of record-low Arctic sea ice extent.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5441735','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5441735"><span>Quantifying the influence of global <span class="hlt">warming</span> on unprecedented extreme climate <span class="hlt">events</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Singh, Deepti; Horton, Daniel E.; Swain, Daniel L.; Touma, Danielle; Charland, Allison; Liu, Yunjie; Haugen, Matz; Tsiang, Michael; Rajaratnam, Bala</p> <p>2017-01-01</p> <p>Efforts to understand the influence of historical global <span class="hlt">warming</span> on individual extreme climate <span class="hlt">events</span> have increased over the past decade. However, despite substantial progress, <span class="hlt">events</span> that are unprecedented in the local observational record remain a persistent challenge. Leveraging observations and a large climate model ensemble, we quantify uncertainty in the influence of global <span class="hlt">warming</span> on the severity and probability of the historically hottest month, hottest day, driest year, and wettest 5-d period for different areas of the globe. We find that historical <span class="hlt">warming</span> has increased the severity and probability of the hottest month and hottest day of the year at >80% of the available observational area. Our framework also suggests that the historical climate forcing has increased the probability of the driest year and wettest 5-d period at 57% and 41% of the observed area, respectively, although we note important caveats. For the most protracted hot and dry <span class="hlt">events</span>, the strongest and most widespread contributions of anthropogenic climate forcing occur in the tropics, including increases in probability of at least a factor of 4 for the hottest month and at least a factor of 2 for the driest year. We also demonstrate the ability of our framework to systematically evaluate the role of dynamic and thermodynamic factors such as atmospheric circulation patterns and atmospheric water vapor, and find extremely high statistical confidence that anthropogenic forcing increased the probability of record-low Arctic sea ice extent. PMID:28439005</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/20403836','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/20403836"><span>Recent and future <span class="hlt">warm</span> extreme <span class="hlt">events</span> and high-mountain slope stability.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Huggel, C; Salzmann, N; Allen, S; Caplan-Auerbach, J; Fischer, L; Haeberli, W; Larsen, C; Schneider, D; Wessels, R</p> <p>2010-05-28</p> <p>The number of large slope failures in some high-mountain regions such as the European Alps has increased during the past two to three decades. There is concern that recent climate change is driving this increase in slope failures, thus possibly further exacerbating the hazard in the future. Although the effects of a gradual temperature rise on glaciers and permafrost have been extensively studied, the impacts of short-term, unusually <span class="hlt">warm</span> temperature increases on slope stability in high mountains remain largely unexplored. We describe several large slope failures in rock and ice in recent years in Alaska, New Zealand and the European Alps, and analyse weather patterns in the days and weeks before the failures. Although we did not find one general temperature pattern, all the failures were preceded by unusually <span class="hlt">warm</span> periods; some happened immediately after temperatures suddenly dropped to freezing. We assessed the frequency of <span class="hlt">warm</span> extremes in the future by analysing eight regional climate models from the recently completed European Union programme ENSEMBLES for the central Swiss Alps. The models show an increase in the higher frequency of high-temperature <span class="hlt">events</span> for the period 2001-2050 compared with a 1951-2000 reference period. <span class="hlt">Warm</span> <span class="hlt">events</span> lasting 5, 10 and 30 days are projected to increase by about 1.5-4 times by 2050 and in some models by up to 10 times. <span class="hlt">Warm</span> extremes can trigger large landslides in temperature-sensitive high mountains by enhancing the production of water by melt of snow and ice, and by rapid thaw. Although these processes reduce slope strength, they must be considered within the local geological, glaciological and topographic context of a slope.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.A23F0380H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.A23F0380H"><span>Observed Circulation Changes up to the Mesopause during Sudden <span class="hlt">Warming</span> <span class="hlt">Events</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hirooka, T.; Ohata, T.; Iida, C.; Eguchi, N.</p> <p>2013-12-01</p> <p>Large circulation changes are caused in association with stratospheric sudden <span class="hlt">warming</span> (SSW) <span class="hlt">events</span> and many studies have been devoted for the region up to the stratopause level from both observational and theoretical aspects. However, observational evidence is still fragmentary in the mesosphere during SSW <span class="hlt">events</span>, because global data capable of comprehensive analyses are still insufficient for the region. Hence, in this study, we make global gridpoint data for geopotential and temperature fields up to the mesopause level derived from Aura MLS data, to make dynamical analyses for global wind and temperature changes during recent SSW <span class="hlt">events</span>. It is found that large circulation changes also occur in the polar mesosphere, which might be caused by large-scale waves internally formed in the lower mesosphere and/or propagating upward from the stratosphere. Such enhancement of large-scale wave activity in the mesosphere seems to be owing to changing background wind structure of the lower mesosphere associated with the SSW occurrence. In addition, equatorial circulations might be also modulated by SSW <span class="hlt">events</span>, e.g., the strength of semi-annual oscillations (SAOs) near the stratopause as well as in the mesosphere. In the equatorial regions, enhanced poleward flows of the residual meridional circulation associated with SSW <span class="hlt">events</span> leads to temperature perturbations consisting of a cooling in the stratosphere and a <span class="hlt">warming</span> in the mesosphere. Such temperature perturbations may bring about opposite changes of SAOs near the stratopause and in the mesosphere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMSA54A..05A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMSA54A..05A"><span>Comparison of global ionospheric response to Sudden Stratospheric <span class="hlt">Warming</span> <span class="hlt">events</span> in 2009 and 2013</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Azeem, S. I.; Honniball, C.</p> <p>2014-12-01</p> <p>Recent studies have shown variations in the low latitude ionosphere that are linked to Sudden Stratospheric <span class="hlt">Warming</span> (SSW) <span class="hlt">events</span>. Although previous studies have provided important information on the ionospheric response to SSW <span class="hlt">events</span>, they have been fairly localized. Therefore, broader observational capabilities and data are required that can unambiguously reveal the instantaneous global response of the ionosphere to SSW <span class="hlt">events</span>. In this paper, we present results from ASTRA's Ionospheric Data Assimilation Four-Dimensional (IDA4D) algorithm to describe a global view of the ionospheric variability during SSW <span class="hlt">events</span> in 2009 and 2013. In both years, the response is characterized by above normal TECs during the day-time and below average TECs during the night-time. In this study, we also show that even though the 2009 SSW was stronger than the 2013 SSW, the ionospheric response in 2009 was significantly weaker than that in 2013.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19332777','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19332777"><span>Global <span class="hlt">warming</span>-enhanced stratification and mass mortality <span class="hlt">events</span> in the Mediterranean.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Coma, Rafel; Ribes, Marta; Serrano, Eduard; Jiménez, Eroteida; Salat, Jordi; Pascual, Josep</p> <p>2009-04-14</p> <p>Summer conditions in the Mediterranean Sea are characterized by high temperatures and low food availability. This leads to "summer dormancy" in many benthic suspension feeders due to energetic constraints. Analysis of the most recent 33-year temperature time series demonstrated enhanced stratification due to global <span class="hlt">warming</span>, which produced a approximately 40% lengthening of summer conditions. Many biological processes are expected to be affected by this trend, culminating in such <span class="hlt">events</span> as mass mortality of invertebrates. Climatic anomalies concomitant with the occurrence of these <span class="hlt">events</span> represent prolonged exposure to warmer summer conditions coupled with reduced food resources. Simulation of the effects of these conditions on a model organism demonstrated a biomass loss of >35%. Losses of this magnitude result in mortality similar to that noted in field observations during mass mortality <span class="hlt">events</span>. These results indicate that temperature anomalies are the underlying cause of the <span class="hlt">events</span>, with energetic constraints serving as the main triggering mechanism.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22481362','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22481362"><span>Past extreme <span class="hlt">warming</span> <span class="hlt">events</span> linked to massive carbon release from thawing permafrost.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>DeConto, Robert M; Galeotti, Simone; Pagani, Mark; Tracy, David; Schaefer, Kevin; Zhang, Tingjun; Pollard, David; Beerling, David J</p> <p>2012-04-04</p> <p>Between about 55.5 and 52 million years ago, Earth experienced a series of sudden and extreme global <span class="hlt">warming</span> <span class="hlt">events</span> (hyperthermals) superimposed on a long-term <span class="hlt">warming</span> trend. The first and largest of these <span class="hlt">events</span>, the Palaeocene-Eocene Thermal Maximum (PETM), is characterized by a massive input of carbon, ocean acidification and an increase in global temperature of about 5 °C within a few thousand years. Although various explanations for the PETM have been proposed, a satisfactory model that accounts for the source, magnitude and timing of carbon release at the PETM and successive hyperthermals remains elusive. Here we use a new astronomically calibrated cyclostratigraphic record from central Italy to show that the Early Eocene hyperthermals occurred during orbits with a combination of high eccentricity and high obliquity. Corresponding climate-ecosystem-soil simulations accounting for rising concentrations of background greenhouse gases and orbital forcing show that the magnitude and timing of the PETM and subsequent hyperthermals can be explained by the orbitally triggered decomposition of soil organic carbon in circum-Arctic and Antarctic terrestrial permafrost. This massive carbon reservoir had the potential to repeatedly release thousands of petagrams (10(15) grams) of carbon to the atmosphere-ocean system, once a long-term <span class="hlt">warming</span> threshold had been reached just before the PETM. Replenishment of permafrost soil carbon stocks following peak <span class="hlt">warming</span> probably contributed to the rapid recovery from each <span class="hlt">event</span>, while providing a sensitive carbon reservoir for the next hyperthermal. As background temperatures continued to rise following the PETM, the areal extent of permafrost steadily declined, resulting in an incrementally smaller available carbon pool and smaller hyperthermals at each successive orbital forcing maximum. A mechanism linking Earth's orbital properties with release of soil carbon from permafrost provides a unifying model accounting for the salient</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/20566887','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/20566887"><span><span class="hlt">Abrupt</span> change of Antarctic moisture origin at the end of Termination II.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Masson-Delmotte, V; Stenni, B; Blunier, T; Cattani, O; Chappellaz, J; Cheng, H; Dreyfus, G; Edwards, R L; Falourd, S; Govin, A; Kawamura, K; Johnsen, S J; Jouzel, J; Landais, A; Lemieux-Dudon, B; Lourantou, A; Marshall, G; Minster, B; Mudelsee, M; Pol, K; Röthlisberger, R; Selmo, E; Waelbroeck, C</p> <p>2010-07-06</p> <p>The deuterium excess of polar ice cores documents past changes in evaporation conditions and moisture origin. New data obtained from the European Project for Ice Coring in Antarctica Dome C East Antarctic ice core provide new insights on the sequence of <span class="hlt">events</span> involved in Termination II, the transition between the penultimate glacial and interglacial periods. This termination is marked by a north-south seesaw behavior, with first a slow methane concentration rise associated with a strong Antarctic temperature <span class="hlt">warming</span> and a slow deuterium excess rise. This first step is followed by an <span class="hlt">abrupt</span> north Atlantic <span class="hlt">warming</span>, an <span class="hlt">abrupt</span> resumption of the East Asian summer monsoon, a sharp methane rise, and a CO(2) overshoot, which coincide within dating uncertainties with the end of Antarctic optimum. Here, we show that this second phase is marked by a very sharp Dome C centennial deuterium excess rise, revealing <span class="hlt">abrupt</span> reorganization of atmospheric circulation in the southern Indian Ocean sector.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24769900','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24769900"><span>Evidence that the insertion <span class="hlt">events</span> of IS2 transposition are biased towards <span class="hlt">abrupt</span> compositional shifts in target DNA and modulated by a diverse set of culture parameters.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Gonçalves, Geisa A L; Oliveira, Pedro H; Gomes, Ana G; Prather, Kristala L J; Lewis, Leslie A; Prazeres, Duarte M F; Monteiro, Gabriel A</p> <p>2014-08-01</p> <p>Insertion specificity of mobile genetic elements is a rather complex aspect of DNA transposition, which, despite much progress towards its elucidation, still remains incompletely understood. We report here the results of a meta-analysis of IS2 target sites from genomic, phage, and plasmid DNA and find that newly acquired IS2 elements are consistently inserted around <span class="hlt">abrupt</span> DNA compositional shifts, particularly in the form of switch sites of GC skew. The results presented in this study not only corroborate our previous observations that both the insertion sequence (IS) minicircle junction and target region adopt intrinsically bent conformations in IS2, but most interestingly, extend this requirement to other families of IS elements. Using this information, we were able to pinpoint regions with high propensity for transposition and to predict and detect, de novo, a novel IS2 insertion <span class="hlt">event</span> in the 3' region of the gfp gene of a reporter plasmid. We also found that during amplification of this plasmid, process parameters such as scale, culture growth phase, and medium composition exacerbate IS2 transposition, leading to contamination levels with potentially detrimental clinical effects. Overall, our findings provide new insights into the role of target DNA structure in the mechanism of transposition of IS elements and extend our understanding of how culture conditions are a relevant factor in the induction of genetic instability.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016APS..DPPPO6007B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016APS..DPPPO6007B"><span>Self-consistent long-time simulation of chirping energetic particle modes and <span class="hlt">abrupt</span> large <span class="hlt">events</span> in beam-driven JT-60U tokamak plasmas</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bierwage, A.; Shinohara, K.; Todo, Y.; Aiba, N.; Ishikawa, M.; Matsunaga, G.; Takechi, M.; Yagi, M.</p> <p>2016-10-01</p> <p>Recurring bursts of chirping Alfvén modes as well as so-called <span class="hlt">Abrupt</span> Large <span class="hlt">Events</span> (ALE) that were observed in JT-60U tokamak plasmas driven by negative-ion-based neutral beams (N-NB) are reproduced in first-principle simulations performed with an extended version of the hybrid code MEGA. This code simulates the interactions between gyrokinetic fast ions and magnetohydrodynamic (MHD) modes in the presence of a realistic fast ion source and collisions, so that it self-consistently captures dynamics across a wide range of time scales (0.01-100 ms). Detailed comparisons with experimental measurements are performed. On the long time scale (10-100 ms) the simulation reproduces ALEs with the associated avalanche-like transport of fast ions. ALEs are shown to occur when multiple modes with toroidal mode numbers n = 1 , 2 , 3 are excited to large amplitudes. On the meso time scale (1-10 ms), bursts of chirping modes are reproduced, which are shown to be n = 1 energetic particle modes (EPM). On the short time scale (0.01-0.1 ms), pulsations and phase jumps are reproduced, which we interpret as the result of beating between multiple resonant wave packets. JSPS Grant-in-Aid for Scientific Research (No. 25820443, 16K18341). NIFS Collaborative Research Program (NIFS12KNTT016).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFMNH33B1144S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFMNH33B1144S"><span>On the PETM and ETM2 global <span class="hlt">warming</span> <span class="hlt">events</span>: New evidence for a tectonic-magmatic trigger mechanism (Invited)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Storey, M.; Condon, D.; Stecher, O.; Hald, N.</p> <p>2009-12-01</p> <p>The climate record covering the past 70 my shows that global temperatures peaked during the Early Eocene around ˜54 to 52 Ma; the Early Eocene Climatic Optimum (EECO) (1). Preceding and during the EECO were three ephemeral global <span class="hlt">warming</span> <span class="hlt">events</span>, each with approximately half the intensity of its predecessor: the Paleocene Eocene Thermal Maximum (PETM), the Eocene Thermal Maximum 2 (ETM2) and the Eocene Thermal Maximum 3 (ETM3). Each is marked by an <span class="hlt">abrupt</span> decrease in the δ13C of sedimentary carbon, consistent with the rapid addition of massive amounts of 13C-depleted C, in the form of carbon dioxide and/or methane, into the hydrosphere/atmosphere. These <span class="hlt">events</span> are regarded as the best deep-time analogues to future climate scenarios through higher CO2 concentration in the atmosphere. There is, however, no consensus on the source of the carbon for these ancient <span class="hlt">warming</span> <span class="hlt">events</span> or the triggering mechanism/s for the release. Two ideas are (i) breakdown of marine methane hydrate (2), possibly related to orbital cycles forcing and/or (ii) for the PETM, thermogenic release of methane by massive sill intrusion into C-rich sedimentary basins, with the gas being released via a complex of thousands of hydrothermal vents (3). These two potential carbon sources have quite different isotopic ratios, which in mass balance calculations determine the amount of carbon required to account for the carbon isotope excursions. Better knowledge of the carbon sources/s is essential if these <span class="hlt">events</span> are to be factored in to models of climate sensitivity to atmospheric CO2 concentration. The PETM has been shown to be synchronous with the onset of peak, continental-breakup related, magmatic activity during the formation of the East Greenland and the Faeroes flood basalt province (4), supporting the sill intrusion model for the source of the methane/CO2 (3). One perceived weakness of this explanation, however, is that it apparently fails to explain the younger ETM2 and ETM3 <span class="hlt">events</span>. Here we</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMSA23A2034M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMSA23A2034M"><span>Modeling Sudden Stratospheric <span class="hlt">Warming</span> <span class="hlt">Events</span> Using the Ionosphere-Plasmasphere-Electrodynamics (IPE) Model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Millholland, S. C.; Maruyama, N.; Maute, A. I.; Goncharenko, L. P.; Burns, A. G.; Richards, P. G.; Fang, T.; Fuller-Rowell, T. J.</p> <p>2013-12-01</p> <p>Sudden Stratospheric <span class="hlt">Warming</span> (SSW) <span class="hlt">events</span> are large meteorological disturbances where the northern winter stratospheric westerly winds slow down or reverse direction. The perturbation is associated with a breakdown in the northern polar vortex and has been observed to cause various anomalies in the upper atmosphere. SSW <span class="hlt">events</span> occur nearly every year to varying degrees of strength. Understanding the connection between the terrestrial and space weathers during these <span class="hlt">events</span> has become more important with increased solar activity, particularly in an effort to separate out forcing from the <span class="hlt">events</span> and from geomagnetic and solar activities. In this work, the Ionosphere-Plasmasphere Electrodynamics (IPE) model is used to investigate the response of the ionosphere during SSW <span class="hlt">events</span>. The Jicamarca 150km echo observation is used to describe the main ionospheric forcing during the SSW <span class="hlt">event</span>. The IPE model reproduces the observed ionospheric response to the large SSW <span class="hlt">event</span> of January 2009. Our results illustrate the direct impact of the equatorial drift deviations during the SSW <span class="hlt">event</span> on the variations of main ionospheric parameters. Furthermore, we evaluate the role of the coupling between ionosphere and plasmasphere during the solar minimum in reproducing the observations. The global drift from Thermosphere-Ionosphere-Mesosphere-Electrodynamics General Circulation Model (TIMEGCM) is also used to evaluate the role of the latitudinal and local time variations of the ExB drift. Finally, we compare the ionospheric responses between 2009 and 2013 to understand the different ionospheric responses depending on the solar flux conditions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24919920','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24919920"><span>Increased frequency of extreme Indian Ocean Dipole <span class="hlt">events</span> due to greenhouse <span class="hlt">warming</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Cai, Wenju; Santoso, Agus; Wang, Guojian; Weller, Evan; Wu, Lixin; Ashok, Karumuri; Masumoto, Yukio; Yamagata, Toshio</p> <p>2014-06-12</p> <p>The Indian Ocean dipole is a prominent mode of coupled ocean-atmosphere variability, affecting the lives of millions of people in Indian Ocean rim countries. In its positive phase, sea surface temperatures are lower than normal off the Sumatra-Java coast, but higher in the western tropical Indian Ocean. During the extreme positive-IOD (pIOD) <span class="hlt">events</span> of 1961, 1994 and 1997, the eastern cooling strengthened and extended westward along the equatorial Indian Ocean through strong reversal of both the mean westerly winds and the associated eastward-flowing upper ocean currents. This created anomalously dry conditions from the eastern to the central Indian Ocean along the Equator and atmospheric convergence farther west, leading to catastrophic floods in eastern tropical African countries but devastating droughts in eastern Indian Ocean rim countries. Despite these serious consequences, the response of pIOD <span class="hlt">events</span> to greenhouse <span class="hlt">warming</span> is unknown. Here, using an ensemble of climate models forced by a scenario of high greenhouse gas emissions (Representative Concentration Pathway 8.5), we project that the frequency of extreme pIOD <span class="hlt">events</span> will increase by almost a factor of three, from one <span class="hlt">event</span> every 17.3 years over the twentieth century to one <span class="hlt">event</span> every 6.3 years over the twenty-first century. We find that a mean state change--with weakening of both equatorial westerly winds and eastward oceanic currents in association with a faster <span class="hlt">warming</span> in the western than the eastern equatorial Indian Ocean--facilitates more frequent occurrences of wind and oceanic current reversal. This leads to more frequent extreme pIOD <span class="hlt">events</span>, suggesting an increasing frequency of extreme climate and weather <span class="hlt">events</span> in regions affected by the pIOD.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015NatCC...5..132C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015NatCC...5..132C"><span>Increased frequency of extreme La Niña <span class="hlt">events</span> under greenhouse <span class="hlt">warming</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cai, Wenju; Wang, Guojian; Santoso, Agus; McPhaden, Michael J.; Wu, Lixin; Jin, Fei-Fei; Timmermann, Axel; Collins, Mat; Vecchi, Gabriel; Lengaigne, Matthieu; England, Matthew H.; Dommenget, Dietmar; Takahashi, Ken; Guilyardi, Eric</p> <p>2015-02-01</p> <p>The El Niño/Southern Oscillation is Earth’s most prominent source of interannual climate variability, alternating irregularly between El Niño and La Niña, and resulting in global disruption of weather patterns, ecosystems, fisheries and agriculture. The 1998-1999 extreme La Niña <span class="hlt">event</span> that followed the 1997-1998 extreme El Niño <span class="hlt">event</span> switched extreme El Niño-induced severe droughts to devastating floods in western Pacific countries, and vice versa in the southwestern United States. During extreme La Niña <span class="hlt">events</span>, cold sea surface conditions develop in the central Pacific, creating an enhanced temperature gradient from the Maritime continent to the central Pacific. Recent studies have revealed robust changes in El Niño characteristics in response to simulated future greenhouse <span class="hlt">warming</span>, but how La Niña will change remains unclear. Here we present climate modelling evidence, from simulations conducted for the Coupled Model Intercomparison Project phase 5 (ref. ), for a near doubling in the frequency of future extreme La Niña <span class="hlt">events</span>, from one in every 23 years to one in every 13 years. This occurs because projected faster mean <span class="hlt">warming</span> of the Maritime continent than the central Pacific, enhanced upper ocean vertical temperature gradients, and increased frequency of extreme El Niño <span class="hlt">events</span> are conducive to development of the extreme La Niña <span class="hlt">events</span>. Approximately 75% of the increase occurs in years following extreme El Niño <span class="hlt">events</span>, thus projecting more frequent swings between opposite extremes from one year to the next.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ClDy..tmp...81X','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ClDy..tmp...81X"><span>Extreme subsurface <span class="hlt">warm</span> <span class="hlt">events</span> in the South China Sea during 1998/99 and 2006/07: observations and mechanisms</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Xiao, Fuan; Zeng, Lili; Liu, Qin-Yan; Zhou, Wen; Wang, Dongxiao</p> <p>2017-03-01</p> <p>Conductivity-temperature-depth observations, objectively analyzed data, and model output are used to investigate the variability of subsurface temperature in the South China Sea (SCS) during 1948-2010. Two extreme subsurface <span class="hlt">warm</span> <span class="hlt">events</span> are identified during 1998/99 and 2006/07, with no corresponding extreme surface <span class="hlt">warming</span> except in 1998. Mixed-layer heat budget analysis reveals that the lack of significant heat input from surface net heat flux or from current advection is responsible for the absence of extreme surface <span class="hlt">warming</span> during 1999, and 2006/07. The surface net heat flux alone cannot explain the first phases of subsurface <span class="hlt">warming</span> during 1998/99 and 2006/07. <span class="hlt">Warm</span> advection from the southern SCS in 1998/99 and from the Kuroshio intrusion in 2006/07, induced by anomalous ocean currents, is likely the major contributor to <span class="hlt">warming</span> of the subsurface water. During the second phase of <span class="hlt">warming</span>, the surface net heat flux plays a damping role to cool the subsurface water, and the <span class="hlt">warm</span> advection induced by anomalous SCS western boundary currents from the southern SCS leads to extremely <span class="hlt">warm</span> subsurface water anomalies. The results show the importance of the Pacific western boundary currents, especially the Kuroshio, in maintaining extreme subsurface <span class="hlt">warm</span> <span class="hlt">events</span> in the SCS.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20120016994&hterms=Embedded&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DEmbedded','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20120016994&hterms=Embedded&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DEmbedded"><span><span class="hlt">Warm</span> and Saline <span class="hlt">Events</span> Embedded in the Meridional Circulation of the Northern North Atlantic</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hakkinen, Sirpa; Rhines, Peter B.; Worthen, Denise L.</p> <p>2011-01-01</p> <p>Ocean state estimates from 1958 to 2005 from the Simple Ocean Assimilation System (SODA) system are analyzed to understand circulation between subtropical and subpolar Atlantic and their connection with atmospheric forcing. This analysis shows three periods (1960s, around 1980, and 2000s) with enhanced <span class="hlt">warm</span>, saline waters reaching high latitudes, alternating with freshwater <span class="hlt">events</span> originating at high latitudes. It complements surface drifter and altimetry data showing the subtropical -subpolar exchange leading to a significant temperature and salinity increase in the northeast Atlantic after 2001. The <span class="hlt">warm</span> water limb of the Atlantic meridional overturning cell represented by SODA expanded in density/salinity space during these <span class="hlt">warm</span> <span class="hlt">events</span>. Tracer simulations using SODA velocities also show decadal variation of the Gulf Stream waters reaching the subpolar gyre and Nordic seas. The negative phase of the North Atlantic Oscillation index, usually invoked in such variability, fails to predict the <span class="hlt">warming</span> and salinization in the early 2000s, with salinities not seen since the 1960s. Wind stress curl variability provided a linkage to this subtropical/subpolar gyre exchange as illustrated using an idealized two ]layer circulation model. The ocean response to the modulation of the climatological wind stress curl pattern was found to be such that the northward penetration of subtropical tracers is enhanced when amplitude of the wind stress curl is weaker than normal. In this case both the subtropical and subpolar gyres weaken and the subpolar density surfaces relax; hence, the polar front moves westward, opening an enhanced northward access of the subtropical waters in the eastern boundary current.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20120016994&hterms=current+events&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dcurrent%2Bevents','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20120016994&hterms=current+events&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dcurrent%2Bevents"><span><span class="hlt">Warm</span> and Saline <span class="hlt">Events</span> Embedded in the Meridional Circulation of the Northern North Atlantic</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hakkinen, Sirpa; Rhines, Peter B.; Worthen, Denise L.</p> <p>2011-01-01</p> <p>Ocean state estimates from 1958 to 2005 from the Simple Ocean Assimilation System (SODA) system are analyzed to understand circulation between subtropical and subpolar Atlantic and their connection with atmospheric forcing. This analysis shows three periods (1960s, around 1980, and 2000s) with enhanced <span class="hlt">warm</span>, saline waters reaching high latitudes, alternating with freshwater <span class="hlt">events</span> originating at high latitudes. It complements surface drifter and altimetry data showing the subtropical -subpolar exchange leading to a significant temperature and salinity increase in the northeast Atlantic after 2001. The <span class="hlt">warm</span> water limb of the Atlantic meridional overturning cell represented by SODA expanded in density/salinity space during these <span class="hlt">warm</span> <span class="hlt">events</span>. Tracer simulations using SODA velocities also show decadal variation of the Gulf Stream waters reaching the subpolar gyre and Nordic seas. The negative phase of the North Atlantic Oscillation index, usually invoked in such variability, fails to predict the <span class="hlt">warming</span> and salinization in the early 2000s, with salinities not seen since the 1960s. Wind stress curl variability provided a linkage to this subtropical/subpolar gyre exchange as illustrated using an idealized two ]layer circulation model. The ocean response to the modulation of the climatological wind stress curl pattern was found to be such that the northward penetration of subtropical tracers is enhanced when amplitude of the wind stress curl is weaker than normal. In this case both the subtropical and subpolar gyres weaken and the subpolar density surfaces relax; hence, the polar front moves westward, opening an enhanced northward access of the subtropical waters in the eastern boundary current.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li class="active"><span>7</span></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_7 --> <div id="page_8" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li class="active"><span>8</span></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="141"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17735247','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17735247"><span>The appearance of sustained equatorial surface westerlies during the 1982 pacific <span class="hlt">warm</span> <span class="hlt">event</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Harrison, D E</p> <p>1984-06-08</p> <p>In June 1982 a band of anomalous southerly surface wind, extending from the equator as far south as the Tasman Sea, formed east of Australia (150 degrees E to 160 degrees E). This flow crossed the equator just before the appearance of sustained westerly winds on the equator somewhat west of the date line. Because these westerly winds induced the initial strong equatorial <span class="hlt">warming</span> of the ocean east of the date line during the 1982 El Niño-Southern Oscillation (ENSO) <span class="hlt">event</span>, the southerly jet appears to be an important atmospheric component leading to the onset of the vigorous phase of this <span class="hlt">event</span>. Some historical evidence suggests that anomalous southerly winds in the same region occurred prior to the appearance of sustained equatorial westerly winds in the major ENSO <span class="hlt">events</span> of 1957, 1965, and 1972.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007JASTP..69.2355H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007JASTP..69.2355H"><span>Latitudinal and longitudinal variability of mesospheric winds and temperatures during stratospheric <span class="hlt">warming</span> <span class="hlt">events</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hoffmann, P.; Singer, W.; Keuer, D.; Hocking, W. K.; Kunze, M.; Murayama, Y.</p> <p>2007-12-01</p> <p>Continuous MF and meteor radar observations allow detailed studies of winds in the mesosphere and lower thermosphere (MLT) as well as temperatures around the mesopause. This height region is characterized by a strong variability in winter due to enhanced planetary wave activity and related stratospheric <span class="hlt">warming</span> <span class="hlt">events</span>, which are distinct coupling processes between lower, middle and upper atmosphere. Here the variability of mesospheric winds and temperatures is discussed in relation with major and minor stratospheric <span class="hlt">warmings</span> as observed during winter 2005/06 in comparison with results during winter 1998/99. Our studies are based on MF radar wind measurements at Andenes (69°N, 16°E), Poker Flat (65°N, 147°W) and Juliusruh (55°N, 13°E) as well as on meteor radar observations of winds and temperatures at Resolute Bay (75°N, 95°W), Andenes (69°N, 16°E) and Kühlungsborn (54°N, 12°E). Additionally, energy dissipation rates have been estimated from spectral width measurements using a 3 MHz Doppler radar near Andenes. Particular attention is directed to the changes of winds, turbulence and the gravity wave activity in the mesosphere in relation to the planetary wave activity in the stratosphere. Observations indicate an enhancement of planetary wave 1 activity in the mesosphere at high latitudes during major stratospheric <span class="hlt">warmings</span>. Daily mean temperatures derived from meteor decay times indicate that strong <span class="hlt">warming</span> <span class="hlt">events</span> are connected with a cooling of the 90 km region by about 10 20 K. The onset of these cooling processes and the reversals of the mesospheric circulation to easterly winds occur some days before the changes of the zonal circulation in the stratosphere start indicating a downward propagation of the circulation disturbances from the MLT region to the stratosphere and troposphere during the stratospheric <span class="hlt">warming</span> <span class="hlt">events</span>. The short-term reversal of the mesospheric winds is followed by a period of strong westerly winds connected with enhanced</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1811033K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1811033K"><span>Absorbing and reflecting sudden stratospheric <span class="hlt">warming</span> <span class="hlt">events</span> and their relationship with tropospheric circulation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kodera, Kunihiko; Mukougawa, Hitoshi; Maury, Pauline; Claud, Chantal; Ueda, Manabu</p> <p>2016-04-01</p> <p>Sudden stratospheric <span class="hlt">warming</span> (SSW) <span class="hlt">events</span> have received increased attention since their impacts on the troposphere became evident recently. Studies of SSW usually focus on polar stratospheric conditions; however, understanding the global impact of these <span class="hlt">events</span> requires studying them from a wider perspective. Case studies are used to clarify the characteristics of the stratosphere-troposphere dynamical coupling, and the meridional extent of the phenomena associated with SSW. Results show that differences in the recovery phase can be used to classify SSW <span class="hlt">events</span> into two types. The first is the absorbing type of SSW, which has a longer timescale as well as a larger meridional extent due to the persistent incoming planetary waves from the troposphere. The absorbing type of SSW is related to the annular mode on the surface through poleward and downward migration of the deceleration region of the polar-night jet. The other is the reflecting type. This is characterized by a quick termination of the <span class="hlt">warming</span> episode due to the reflection of planetary waves in the stratosphere, which leads to an amplification of tropospheric planetary waves inducing strong westerlies over the North Atlantic and blocking over the North Pacific sector. Differences in the tropospheric impact of the absorbing and reflecting SSWs are also confirmed with composite analysis of 22 major SSWs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JGRD..121...80K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JGRD..121...80K"><span>Absorbing and reflecting sudden stratospheric <span class="hlt">warming</span> <span class="hlt">events</span> and their relationship with tropospheric circulation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kodera, Kunihiko; Mukougawa, Hitoshi; Maury, Pauline; Ueda, Manabu; Claud, Chantal</p> <p>2016-01-01</p> <p>Sudden stratospheric <span class="hlt">warming</span> (SSW) <span class="hlt">events</span> have received increased attention since their impacts on the troposphere became evident recently. Studies of SSW usually focus on polar stratospheric conditions; however, understanding the global impact of these <span class="hlt">events</span> requires studying them from a wider perspective. Case studies are used to clarify the characteristics of the stratosphere-troposphere dynamical coupling, and the meridional extent of the phenomena associated with SSW. Results show that differences in the recovery phase can be used to classify SSW <span class="hlt">events</span> into two types. The first is the absorbing type of SSW, which has a longer timescale as well as a larger meridional extent due to the persistent incoming planetary waves from the troposphere. The absorbing type of SSW is related to the annular mode on the surface through poleward and downward migration of the deceleration region of the polar night jet. The other is the reflecting type. This is characterized by a quick termination of the <span class="hlt">warming</span> episode due to the reflection of planetary waves in the stratosphere, which leads to an amplification of tropospheric planetary waves inducing strong westerlies over the North Atlantic and blocking over the North Pacific sector. Differences in the tropospheric impact of the absorbing and reflecting SSWs are also confirmed with composite analysis of 22 major SSWs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23526779','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23526779"><span>Persistent versus transient tree encroachment of temperate peat bogs: effects of climate <span class="hlt">warming</span> and drought <span class="hlt">events</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Heijmans, Monique M P D; van der Knaap, Yasmijn A M; Holmgren, Milena; Limpens, Juul</p> <p>2013-07-01</p> <p>Peatlands store approximately 30% of global soil carbon, most in moss-dominated bogs. Future climatic changes, such as changes in precipitation patterns and <span class="hlt">warming</span>, are expected to affect peat bog vegetation composition and thereby its long-term carbon sequestration capacity. Theoretical work suggests that an episode of rapid environmental change is more likely to trigger transitions to alternative ecosystem states than a gradual, but equally large, change in conditions. We used a dynamic vegetation model to explore the impacts of drought <span class="hlt">events</span> and increased temperature on vegetation composition of temperate peat bogs. We analyzed the consequences of six patterns of summer drought <span class="hlt">events</span> combined with five temperature scenarios to test whether an open peat bog dominated by moss (Sphagnum) could shift to a tree-dominated state. Unexpectedly, neither a gradual decrease in the amount of summer precipitation nor the occurrence of a number of extremely dry summers in a row could shift the moss-dominated peat bog permanently into a tree-dominated peat bog. The increase in tree biomass during drought <span class="hlt">events</span> was unable to trigger positive feedbacks that keep the ecosystem in a tree-dominated state after a return to previous 'normal' rainfall conditions. In contrast, temperature increases from 1 °C onward already shifted peat bogs into tree-dominated ecosystems. In our simulations, drought <span class="hlt">events</span> facilitated tree establishment, but temperature determined how much tree biomass could develop. Our results suggest that under current climatic conditions, peat bog vegetation is rather resilient to drought <span class="hlt">events</span>, but very sensitive to temperature increases, indicating that future <span class="hlt">warming</span> is likely to trigger persistent vegetation shifts. © 2013 Blackwell Publishing Ltd.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/15576615','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/15576615"><span><span class="hlt">Abrupt</span> temperature changes in the Western Mediterranean over the past 250,000 years.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Martrat, Belen; Grimalt, Joan O; Lopez-Martinez, Constancia; Cacho, Isabel; Sierro, Francisco J; Flores, Jose Abel; Zahn, Rainer; Canals, Miquel; Curtis, Jason H; Hodell, David A</p> <p>2004-12-03</p> <p>A continuous high-resolution Western Mediterranean sea surface temperature (SST) alkenone record spanning the past 250,000 years shows that <span class="hlt">abrupt</span> changes were more common at <span class="hlt">warming</span> than at cooling. During marine isotope stage (MIS) 6, SST oscillated following a stadial-interstadial pattern but at lower intensities and rates of change than in the Dansgaard/Oeschger <span class="hlt">events</span> of MIS 3. Some of the most prominent <span class="hlt">events</span> occurred over MISs 5 and 7, after prolonged <span class="hlt">warm</span> periods of high stability. Climate during the whole period was predominantly maintained in interglacial-interstadial conditions, whereas the duration of stadials was much shorter.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMGC54A..03S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMGC54A..03S"><span>Changes in Large Spatiotemporal Climatic Extreme <span class="hlt">Events</span> Beyond the Mean <span class="hlt">Warming</span> Signal</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sippel, S.; Mahecha, M. D.; Otto, F. E. L.</p> <p>2014-12-01</p> <p>Weather and climate extremes impose substantial impacts on human societies and ecosystems. In particular, <span class="hlt">events</span> that are large in space (areal extent), time (duration) or both are likely to be associated with highly significant consequences. Hence, a better detection, characterization and understanding of such anomalous <span class="hlt">events</span> is crucial. There is widespread consensus on a global and continental-scale <span class="hlt">warming</span> trend, which leads to increases in the number, magnitude and frequency of temperature extremes (Hansen et al., 2012). It is less clear, however, if this <span class="hlt">warming</span> also coincides with a broadening of temperature distributions (Huntingford et al., 2013). Moreover, the question whether other climate variables, such as large-scale precipitation deficits, likewise change, remains largely unanswered (Sheffield et al., 2012; Seneviratne 2012). In this study, we address this issue by investigating the characteristics of large extremes, using an algorithm that detects the n largest spatiotemporally connected climate extremes for any time period. The deployed algorithm detects, depending on the chosen time step and variable, major heat waves, cold spells or droughts. We find a robust increase in the magnitude of large hot temperature extremes on a global and European scale in observations and reanalysis products, whereas the duration and affected area of those extremes does not show any pronounced changes. These results reveal that there is a detectable signal in temperature distributions beyond the mean <span class="hlt">warming</span> trend, which might imply a structural change in the making of large extreme <span class="hlt">events</span>. Furthermore, we use the CMIP5 ensemble of models and an ensemble of 100+ members of a regional climate model for Europe (HadRM3P within the weather@home framework[1]) in order to conduct a global and continental-scale analysis of large extreme <span class="hlt">events</span> in temperature and precipitation. The employment of those model ensembles allows to sample more reliably the tails of the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27535205','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27535205"><span>Responses of sequential and hierarchical phenological <span class="hlt">events</span> to <span class="hlt">warming</span> and cooling in alpine meadows.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Li, Xine; Jiang, Lili; Meng, Fandong; Wang, Shiping; Niu, Haishan; Iler, Amy M; Duan, Jichuan; Zhang, Zhenhua; Luo, Caiyun; Cui, Shujuan; Zhang, Lirong; Li, Yaoming; Wang, Qi; Zhou, Yang; Bao, Xiaoying; Dorji, Tsechoe; Li, Yingnian; Peñuelas, Josep; Du, Mingyuan; Zhao, Xinquan; Zhao, Liang; Wang, Guojie</p> <p>2016-08-18</p> <p>Organisms' life cycles consist of hierarchical stages, from a single phenological stage (for example, flowering within a season), to vegetative and reproductive phases, to the total lifespan of the individual. Yet phenological <span class="hlt">events</span> are typically studied in isolation, limiting our understanding of life history responses to climate change. Here, we reciprocally transfer plant communities along an elevation gradient to investigate plastic changes in the duration of sequential phenological <span class="hlt">events</span> for six alpine species. We show that prolonged flowering leads to longer reproductive phases and activity periods when plants are moved to warmer locations. In contrast, shorter post-fruiting leaf and flowering stages led to shorter vegetative and reproductive phases, respectively, which resulted in shorter activity periods when plants were moved to cooler conditions. Therefore, phenological responses to <span class="hlt">warming</span> and cooling do not simply mirror one another in the opposite direction, and low temperature may limit reproductive allocation in the alpine region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4992149','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4992149"><span>Responses of sequential and hierarchical phenological <span class="hlt">events</span> to <span class="hlt">warming</span> and cooling in alpine meadows</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Li, Xine; Jiang, Lili; Meng, Fandong; Wang, Shiping; Niu, Haishan; Iler, Amy M.; Duan, Jichuan; Zhang, Zhenhua; Luo, Caiyun; Cui, Shujuan; Zhang, Lirong; Li, Yaoming; Wang, Qi; Zhou, Yang; Bao, Xiaoying; Dorji, Tsechoe; Li, Yingnian; Peñuelas, Josep; Du, Mingyuan; Zhao, Xinquan; Zhao, Liang; Wang, Guojie</p> <p>2016-01-01</p> <p>Organisms' life cycles consist of hierarchical stages, from a single phenological stage (for example, flowering within a season), to vegetative and reproductive phases, to the total lifespan of the individual. Yet phenological <span class="hlt">events</span> are typically studied in isolation, limiting our understanding of life history responses to climate change. Here, we reciprocally transfer plant communities along an elevation gradient to investigate plastic changes in the duration of sequential phenological <span class="hlt">events</span> for six alpine species. We show that prolonged flowering leads to longer reproductive phases and activity periods when plants are moved to warmer locations. In contrast, shorter post-fruiting leaf and flowering stages led to shorter vegetative and reproductive phases, respectively, which resulted in shorter activity periods when plants were moved to cooler conditions. Therefore, phenological responses to <span class="hlt">warming</span> and cooling do not simply mirror one another in the opposite direction, and low temperature may limit reproductive allocation in the alpine region. PMID:27535205</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMPA21B1869C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMPA21B1869C"><span>Communicating Climate Uncertainties: Challenges and Opportunities Related to Spatial Scales, Extreme <span class="hlt">Events</span>, and the <span class="hlt">Warming</span> 'Hiatus'</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Casola, J. H.; Huber, D.</p> <p>2013-12-01</p> <p>Many media, academic, government, and advocacy organizations have achieved sophistication in developing effective messages based on scientific information, and can quickly translate salient aspects of emerging climate research and evolving observations. However, there are several ways in which valid messages can be misconstrued by decision makers, leading them to inaccurate conclusions about the risks associated with climate impacts. Three cases will be discussed: 1) Issues of spatial scale in interpreting climate observations: Local climate observations may contradict summary statements about the effects of climate change on larger regional or global spatial scales. Effectively addressing these differences often requires communicators to understand local and regional climate drivers, and the distinction between a 'signal' associated with climate change and local climate 'noise.' Hydrological statistics in Missouri and California are shown to illustrate this case. 2) Issues of complexity related to extreme <span class="hlt">events</span>: Climate change is typically invoked following a wide range of damaging meteorological <span class="hlt">events</span> (e.g., heat waves, landfalling hurricanes, tornadoes), regardless of the strength of the relationship between anthropogenic climate change and the frequency or severity of that type of <span class="hlt">event</span>. Examples are drawn from media coverage of several recent <span class="hlt">events</span>, contrasting useful and potentially confusing word choices and frames. 3) Issues revolving around climate sensitivity: The so-called 'pause' or 'hiatus' in global <span class="hlt">warming</span> has reverberated strongly through political and business discussions of climate change. Addressing the recent slowdown in <span class="hlt">warming</span> yields an important opportunity to raise climate literacy in these communities. Attempts to use recent observations as a wedge between climate 'believers' and 'deniers' is likely to be counterproductive. Examples are drawn from Congressional testimony and media stories. All three cases illustrate ways that decision</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010GeoRL..3717702L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010GeoRL..3717702L"><span>On the impact of central Pacific <span class="hlt">warming</span> <span class="hlt">events</span> on Atlantic tropical storm activity</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lee, Sang-Ki; Wang, Chunzai; Enfield, David B.</p> <p>2010-09-01</p> <p>A recent study by Kim et al. (2009) claim that central Pacific <span class="hlt">warming</span> (CPW) <span class="hlt">events</span> in 1969, 1991, 1994, 2002 and 2004 are associated with a greater-than-average frequency of tropical storms and increasing landfall potential along the Gulf of Mexico coast and Central America. Based on an independent data analysis of tropical cyclone activity in the five CPW years, it is shown here that only 1969, 2002 and 2004 were characterized with significantly greater-than-average cyclone activity in the Gulf of Mexico and Caribbean Sea, whereas 1991 and 1994 were characterized with significantly lower-than-average activity. Coincidently, the Atlantic <span class="hlt">warm</span> pool (AWP) was significantly larger than average during 1969 and 2004, and significantly smaller than average during 1991 and 1994. By performing multiple sets of ensemble model experiments using the NCAR atmospheric general circulation model, it is shown here that the increased tropical storm frequency in 1969 and 2004 can be readily explained by a large AWP and the associated vertical wind shear reduction and enhanced moist convective instability in the main development region for Atlantic hurricanes, without invoking a remote influence from the tropical Pacific. Therefore, we conclude that it is premature to associate CPW <span class="hlt">events</span> to an increasing frequency of cyclone activity in the Gulf of Mexico and Caribbean Sea.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.4539T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.4539T"><span>Towards Greenland Glaciation: cumulative or <span class="hlt">abrupt</span> transition?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tan, Ning; Dumas, Christophe; Ladant, Jean-Baptiste; Ramstein, Gilles; Contoux, Camille</p> <p>2016-04-01</p> <p>During the mid-Pliocene <span class="hlt">warming</span> period (3-3.3 Ma BP), global annual mean temperature is warmer by 2-3 degree than pre-industrial. Greenland ice sheet volume is supposed to be a 50% reduction compared to nowadays [Haywood et al. 2010]. Around 2.7-2.6 Ma BP, just ~ 500 kyr after the <span class="hlt">warming</span> peak of mid-Pliocene, there is already full Greenland Glaciation [Lunt et al. 2008]. How does Greenland ice sheet evolve from a half size to a glaciation level during 3 Ma - 2.5 Ma? Data show that there is a decreasing trend of atmospheric CO2 concentration from 3 Ma to 2.5 Ma [Seki et al.2010; Bartoli et al. 2011; Martinez et al. 2015]. However, a recent study [Contoux et al. 2015] suggests that a lowering of CO2 is not sufficient to initiate a perennial glaciation on Greenland and must be combined to low summer insolation, to preserve the ice sheet during insolation maximum, suggesting a cumulative process. In order to diagnose whether the ice sheet build-up is an <span class="hlt">abrupt</span> <span class="hlt">event</span> or a cumulative process, we carry on, for the first time, a transient simulation of climate and ice sheet evolutions from 3 Ma to 2.5 Ma. This strategy enables to investigate waxing and waning of the ice sheet during several orbital cycles. To reach this goal, we use a tri-dimensional interpolation method designed by Ladant et al. (2014) which combines the evolution of CO2 concentration, orbital parameters and Greenland ice sheet sizes in an off-line way by interpolating snapshots simulations. Thanks to this new method, we can build a transient like simulation through asynchronous coupling between GCM and ice sheet model. With this method, we may consistently answer the question of the build-up of Greenland: <span class="hlt">abrupt</span> or cumulative process.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1998PhDT........34A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1998PhDT........34A"><span><span class="hlt">Abrupt</span> climate changes and the effects of North Atlantic deepwater formation: Results from the GENESIS global climate model and comparison with data from the Younger Dryas <span class="hlt">event</span> and the <span class="hlt">event</span> at 8200 years bp and the present</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Agustsdottir, Anna Maria</p> <p>1998-10-01</p> <p><span class="hlt">Abrupt</span> changes in climate towards glacial conditions have occurred several times during the last tens of thousands of years. A reduction in ocean heat transport to the high-latitude North Atlantic, associated with reduction, shutdown, or southward shift in formation of North Atlantic Deepwater, is hypothesized to have caused or amplified <span class="hlt">abrupt</span> cooling <span class="hlt">events</span>. The model-data comparisons reported here provide strong support for this hypothesis for the Younger Dryas interval and the cold <span class="hlt">event</span> about 8200 years ago, and show likely changes were such an oceanic change to occur in the near future. Different levels of North Atlantic ocean heat transport were specified in age-appropriate simulations using the GENESIS GCM climate model. For the Younger Dryas, simulated reduction in GENESIS ocean heat transport (in versions 1.02A and 2.0) from modern levels produces climate-anomaly patterns, including many seasonal changes, that closely match observations, however, observed changes far from the North Atlantic are somewhat larger than modeled. Both model and data indicate stronger winds during cold times. Modeled cold-time winds produce about 10% more tropical-ocean Ekman divergence in regions and at times of prominent upwelling. The cooling associated with this, but not calculated for the mixed- layer GENESIS model ocean, probably is important in model-data differences. Because of the success of GENESIS in simulating Younger Dryas changes around the North Atlantic but underestimating those beyond this region, the large changes simulated for a modern reduction of North Atlantic ocean heat transport likely march or underestimate those that would occur if such a change occurred in the near future. Reduction in ocean heat transport for 8200 years ago form modern levels produces an anomaly pattern somewhat like observations, but reduction form heat transport higher than modern produces a much better match. Together with other evidence, this suggests that this cold climate <span class="hlt">event</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JMetR..29..747M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JMetR..29..747M"><span>Characteristics and mechanisms of the sudden <span class="hlt">warming</span> <span class="hlt">events</span> in the nocturnal atmospheric boundary layer: A case study using WRF</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ma, Yuanyuan; Yang, Yi; Hu, Xiao-Ming; Gan, Ruhui</p> <p>2015-10-01</p> <p>Although sudden nocturnal <span class="hlt">warming</span> <span class="hlt">events</span> near the earth's surface in Australia and the United States have been examined in previous studies, similar <span class="hlt">events</span> observed occasionally over the Loess Plateau of Northwest China have not yet been investigated. The factors that lead to these <span class="hlt">warming</span> <span class="hlt">events</span> in such areas with their unique topography and climate remain not clear. To understand the formation mechanisms and associated thermal and dynamical features, a nocturnal <span class="hlt">warming</span> <span class="hlt">event</span> recorded in Gansu Province (northwest of the Loess Plateau) in June 2007 was investigated by using observations and model simulations with the Weather Research and Forecasting (WRF) model. Observations showed that this near-surface <span class="hlt">warming</span> <span class="hlt">event</span> lasted for 4 h and the temperature increased by 2.5°C. During this <span class="hlt">event</span>, a decrease in humidity occurred simultaneously with the increase of temperature. The model simulation showed that the nocturnal <span class="hlt">warming</span> was caused mainly by the transport of warmer and drier air aloft downward to the surface through enhanced vertical mixing. Wind shear played an important role in inducing the elevated vertical mixing, and it was enhanced by the continuous development of the atmospheric baroclinicity, which converted more potential energy to kinetic energy.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011ThApC.105..445M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011ThApC.105..445M"><span>Detecting <span class="hlt">abrupt</span> climate changes on different time scales</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Matyasovszky, István</p> <p>2011-10-01</p> <p>Two concepts are introduced for detecting <span class="hlt">abrupt</span> climate changes. In the first case, the sampling frequency of climate data is high as compared to the frequency of climate <span class="hlt">events</span> examined. The method is based on a separation of trend and noise in the data and is applicable to any dataset that satisfies some mild smoothness and statistical dependence conditions for the trend and the noise, respectively. We say that an <span class="hlt">abrupt</span> change occurs when the first derivative of the trend function has a discontinuity and the task is to identify such points. The technique is applied to Northern Hemisphere temperature data from 1850 to 2009, Northern Hemisphere temperature data from proxy data, a.d. 200-1995 and Holocene δ18O values going back to 11,700 years BP. Several <span class="hlt">abrupt</span> changes are detected that are, among other things, beneficial for determining the Medieval <span class="hlt">Warm</span> Period, Little Ice Age and Holocene Climate Optimum. In the second case, the sampling frequency is low relative to the frequency of climate <span class="hlt">events</span> studied. A typical example includes Dansgaard-Oeschger <span class="hlt">events</span>. The methodology used here is based on a refinement of autoregressive conditional heteroscedastic models. The key element of this approach is the volatility that characterises the time-varying variance, and <span class="hlt">abrupt</span> changes are defined by high volatilities. The technique applied to δ18O values going back to 122,950 years BP is suitable for identifying DO <span class="hlt">events</span>. These two approaches for the two cases are closely related despite the fact that at first glance, they seem quite different.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3158189','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3158189"><span>Ice-shelf collapse from subsurface <span class="hlt">warming</span> as a trigger for Heinrich <span class="hlt">events</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Marcott, Shaun A.; Clark, Peter U.; Padman, Laurie; Klinkhammer, Gary P.; Springer, Scott R.; Liu, Zhengyu; Otto-Bliesner, Bette L.; Carlson, Anders E.; Ungerer, Andy; Padman, June; He, Feng; Cheng, Jun; Schmittner, Andreas</p> <p>2011-01-01</p> <p>Episodic iceberg-discharge <span class="hlt">events</span> from the Hudson Strait Ice Stream (HSIS) of the Laurentide Ice Sheet, referred to as Heinrich <span class="hlt">events</span>, are commonly attributed to internal ice-sheet instabilities, but their systematic occurrence at the culmination of a large reduction in the Atlantic meridional overturning circulation (AMOC) indicates a climate control. We report Mg/Ca data on benthic foraminifera from an intermediate-depth site in the northwest Atlantic and results from a climate-model simulation that reveal basin-wide subsurface <span class="hlt">warming</span> at the same time as large reductions in the AMOC, with temperature increasing by approximately 2 °C over a 1–2 kyr interval prior to a Heinrich <span class="hlt">event</span>. In simulations with an ocean model coupled to a thermodynamically active ice shelf, the increase in subsurface temperature increases basal melt rate under an ice shelf fronting the HSIS by a factor of approximately 6. By analogy with recent observations in Antarctica, the resulting ice-shelf loss and attendant HSIS acceleration would produce a Heinrich <span class="hlt">event</span>. PMID:21808034</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21808034','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21808034"><span>Ice-shelf collapse from subsurface <span class="hlt">warming</span> as a trigger for Heinrich <span class="hlt">events</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Marcott, Shaun A; Clark, Peter U; Padman, Laurie; Klinkhammer, Gary P; Springer, Scott R; Liu, Zhengyu; Otto-Bliesner, Bette L; Carlson, Anders E; Ungerer, Andy; Padman, June; He, Feng; Cheng, Jun; Schmittner, Andreas</p> <p>2011-08-16</p> <p>Episodic iceberg-discharge <span class="hlt">events</span> from the Hudson Strait Ice Stream (HSIS) of the Laurentide Ice Sheet, referred to as Heinrich <span class="hlt">events</span>, are commonly attributed to internal ice-sheet instabilities, but their systematic occurrence at the culmination of a large reduction in the Atlantic meridional overturning circulation (AMOC) indicates a climate control. We report Mg/Ca data on benthic foraminifera from an intermediate-depth site in the northwest Atlantic and results from a climate-model simulation that reveal basin-wide subsurface <span class="hlt">warming</span> at the same time as large reductions in the AMOC, with temperature increasing by approximately 2 °C over a 1-2 kyr interval prior to a Heinrich <span class="hlt">event</span>. In simulations with an ocean model coupled to a thermodynamically active ice shelf, the increase in subsurface temperature increases basal melt rate under an ice shelf fronting the HSIS by a factor of approximately 6. By analogy with recent observations in Antarctica, the resulting ice-shelf loss and attendant HSIS acceleration would produce a Heinrich <span class="hlt">event</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.C31A0504G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.C31A0504G"><span>Soil responses to rapid <span class="hlt">warming</span> <span class="hlt">events</span> inside and outside of thermokarst features during the snow season in arctic Alaska</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gooseff, M. N.; Godsey, S.; Lewkowicz, A. G.; Lanan, K.</p> <p>2010-12-01</p> <p>Air temperatures in arctic Alaska are <span class="hlt">warming</span> more so in the fall and winter than in the spring and summer. Analysis of air temperature records during the snow season (September to April) indicates that there are short (~day) and infrequent (a few occurrences per year) <span class="hlt">warm</span> periods above freezing. The impact of these <span class="hlt">warm</span> pulses is not well understood and may have important implications for seasonal soil energy storage and dynamics, particularly as fall and winter climates change. Here we analyze the ground temperature responses to several <span class="hlt">warming</span> <span class="hlt">events</span> from September 2009 to March 2010 inside and outside of thermokarst erosion features. Thermokarst erosion features result in bare mineral soil surfaces and, as depressions, they accumulate deeper snow than the surrounding tundra. We find that during the snow season, the soil temperature responses are more sensitive to the rapid atmospheric <span class="hlt">warming</span> in the surrounding tundra than in the thermokarst feature.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMPP51B1113R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMPP51B1113R"><span>A Global <span class="hlt">Warming</span> <span class="hlt">Event</span> in Magnetochron C19r: New evidence from the Atlantic Ocean</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Roehl, U.; Westerhold, T.; Donner, B.; Kordesch, W.; Bohaty, S. M.</p> <p>2014-12-01</p> <p>The Chron C19r <span class="hlt">event</span> in the late middle Eocene was first described at ODP Site 1260 in the equatorial Atlantic. It is characterized by strong dissolution expressed in a dark, clay-rich layer and a distinct peak in X-ray fluorescence (XRF) scanning Fe intensities as well as by a negative carbon isotope excursion (CIE) in bulk sediment. All similar to early Paleogene hyperthermal <span class="hlt">events</span> - the Chron C19r <span class="hlt">event</span> could also be a hyperthermal <span class="hlt">event</span> but in the late middle Eocene. The dissolution of carbonate at Site 1260 prevented so far to retrieve a benthic stable isotope record with a typical CIE and <span class="hlt">warming</span> of deep water. The C19r <span class="hlt">event</span> occurred ~1.0 myr prior to the onset of the Middle Eocene Climate Optimum (MECO, 40.5 Ma) and several million years after the Early Eocene Climate Optimum (EECO, 51 Ma) during a slightly cooler climate. No significant CCD changes have been observed one million years before and after the <span class="hlt">event</span> as expressed by regular Fe cycles at Site 1260. The duration of the <span class="hlt">event</span> estimated by orbital calibration is in the order of 40-50 kyr, similar to other transient hyperthermals in the early to middle Eocene. Here we present new high-resolution bulk and benthic stable isotope data revealing the widespread nature of the <span class="hlt">event</span>. We investigated ODP Sites 702B (~2200m) near the crest of the Islas Orcadas Rise in the southern South Atlantic, 1263 (~1800 m) on Walvis Ridge in the SE Atlantic, and 1051 (2100 m) on Blake Nose in the NW Atlantic. The position of the <span class="hlt">event</span> was initially narrowed by careful analysis of magnetostratigraphy and XRF scanning data. First results of stable isotope data show a ~0.7 δ13C and ~0.4‰ δ18O excursion very similar to the pattern observed at Site 1260. Although the magnitude of the bulk δ13C excursion is comparable, the bulk δ18O excursion at Site 702B is only a third of that observed at Site 1260 which might be related to diagenetic and/or latitudinal effects. 702B benthic isotope data show a ~0.75 ‰ CIE and a ~0</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JGRD..121.4518L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JGRD..121.4518L"><span>On the composite response of the MLT to major sudden stratospheric <span class="hlt">warming</span> <span class="hlt">events</span> with elevated stratopause</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Limpasuvan, Varavut; Orsolini, Yvan J.; Chandran, Amal; Garcia, Rolando R.; Smith, Anne K.</p> <p>2016-05-01</p> <p>Based on a climate-chemistry model (constrained by reanalyses below ~50 km), the zonal-mean composite response of the mesosphere and lower thermosphere (MLT) to major sudden stratospheric <span class="hlt">warming</span> <span class="hlt">events</span> with elevated stratopauses demonstrates the role of planetary waves (PWs) in driving the mean circulation in the presence of gravity waves (GWs), helping the polar vortex recover and communicating the sudden stratospheric <span class="hlt">warming</span> (SSW) impact across the equator. With the SSW onset, strong westward PW drag appears above 80 km primarily from the dissipation of wave number 1 perturbations with westward period of 5-12 days, generated from below by the unstable westward polar stratospheric jet that develops as a result of the SSW. The filtering effect of this jet also allows eastward propagating GWs to saturate in the winter MLT, providing eastward drag that promotes winter polar mesospheric cooling. The dominant PW forcing translates to a net westward drag above the eastward mesospheric jet, which initiates downwelling over the winter pole. As the eastward polar stratospheric jet returns, this westward PW drag persists above 80 km and acts synergistically with the return of westward GW drag to drive a stronger polar downwelling that <span class="hlt">warms</span> the pole adiabatically and helps reform the stratopause at an elevated altitude. With the polar wind reversal during the SSW onset, the westward drag by the quasi-stationary PW in the winter stratosphere drives an anomalous equatorial upwelling and cooling that enhance tropical stratospheric ozone. Along with equatorial wind anomalies, this ozone enhancement subsequently amplifies the migrating semidiurnal tide amplitude in the winter midlatitudes.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li class="active"><span>8</span></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_8 --> <div id="page_9" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active"><span>9</span></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="161"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21412336','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21412336"><span>Eocene global <span class="hlt">warming</span> <span class="hlt">events</span> driven by ventilation of oceanic dissolved organic carbon.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Sexton, Philip F; Norris, Richard D; Wilson, Paul A; Pälike, Heiko; Westerhold, Thomas; Röhl, Ursula; Bolton, Clara T; Gibbs, Samantha</p> <p>2011-03-17</p> <p>'Hyperthermals' are intervals of rapid, pronounced global <span class="hlt">warming</span> known from six episodes within the Palaeocene and Eocene epochs (∼65-34 million years (Myr) ago). The most extreme hyperthermal was the ∼170 thousand year (kyr) interval of 5-7 °C global <span class="hlt">warming</span> during the Palaeocene-Eocene Thermal Maximum (PETM, 56 Myr ago). The PETM is widely attributed to massive release of greenhouse gases from buried sedimentary carbon reservoirs, and other, comparatively modest, hyperthermals have also been linked to the release of sedimentary carbon. Here we show, using new 2.4-Myr-long Eocene deep ocean records, that the comparatively modest hyperthermals are much more numerous than previously documented, paced by the eccentricity of Earth's orbit and have shorter durations (∼40 kyr) and more rapid recovery phases than the PETM. These findings point to the operation of fundamentally different forcing and feedback mechanisms than for the PETM, involving redistribution of carbon among Earth's readily exchangeable surface reservoirs rather than carbon exhumation from, and subsequent burial back into, the sedimentary reservoir. Specifically, we interpret our records to indicate repeated, large-scale releases of dissolved organic carbon (at least 1,600 gigatonnes) from the ocean by ventilation (strengthened oxidation) of the ocean interior. The rapid recovery of the carbon cycle following each Eocene hyperthermal strongly suggests that carbon was re-sequestered by the ocean, rather than the much slower process of silicate rock weathering proposed for the PETM. Our findings suggest that these pronounced climate <span class="hlt">warming</span> <span class="hlt">events</span> were driven not by repeated releases of carbon from buried sedimentary sources, but, rather, by patterns of surficial carbon redistribution familiar from younger intervals of Earth history.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009pcms.confE.120A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009pcms.confE.120A"><span>The 8th-10 th January 2009 snowfalls: a case of Mediterranean <span class="hlt">warm</span> advection <span class="hlt">event</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Aguado, F.; Ayensa, E.; Barriga, M.; Del Hoyo, J.; Fernández, A.; Garrido, N.; Martín, A.; Martín, F.; Roa, I. Martínez, A.; Pascual, R.</p> <p>2009-09-01</p> <p>From 8 th to 10 th of January 2009, significant snowfalls were reported in many areas of the Iberian Peninsula and the Balearic Islands. This relevant <span class="hlt">event</span> was very important from the meteorological and social impact point of views. The snow affected many zones, especially the regions of Madrid, Castilla & León and Castilla-La Mancha (Spanish central plateau) with the persistence and thickness of solid precipitation. Up to twenty-five centimetres of snow were reported in some places. On 9th of January the snowfalls caused great social and media impact due to the fact that they took place in the early hours in the Madrid metropolitan areas, affecting both air traffic and land transport. The "Madrid-Barajas" airport was closed and the city was collapsed during several hours. A study of this situation appears in the poster. The snowstorm was characterized by the previous irruption of an European continental polar air mass, that subsequently interacted with a wet and <span class="hlt">warm</span> air mass of Mediterranean origin, all preceded by low level easterly flows. This type of snowfall is called "<span class="hlt">warm</span> advection". These winter situations are very efficient from precipitation point of view, generating significant snowfalls and affecting a lot of areas.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMPP22B..05K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMPP22B..05K"><span>Changes in the strength of Atlantic Ocean overturning circulation across repeated Eocene <span class="hlt">warming</span> <span class="hlt">events</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kirtland Turner, S.; Sexton, P. F.; Norris, R. D.; Wilson, P. A.; Charles, C. D.; Ridgwell, A.</p> <p>2015-12-01</p> <p>The Paleogene Period (~65 to 34 Ma) was a time of acute climatic warmth, with deep ocean temperatures exceeding 12°C at the height of the Early Eocene Climatic Optimum (~53 to 50 Ma). Multiple rapid <span class="hlt">warming</span> <span class="hlt">events</span>, associated with transient deep sea temperature increases of 2 to 4°C (termed 'hyperthermals'), potentially related to orbital forcing of the carbon cycle and climate, occurred from the late Paleocene through at least the early middle Eocene and onset of long-term Cenozoic cooling (~47 Ma). While deep ocean circulation patterns associated with the great glaciations of the Plio-Pleistocene have been studied extensively, the behavior of the ocean's overturning circulation on orbital-timescales in the extreme warmth of the early Cenozoic is largely unknown. Here we present new evidence for changing patterns of ocean overturning in the southern hemisphere associated with four orbitally paced hyperthermal <span class="hlt">events</span> in the early-middle Eocene (~50 to 48 Ma) based on a combination of multi-site bulk carbonate and benthic foraminiferal stable isotope measurements and Earth system modeling. Our results suggest that southern-sourced overturning weakens and shoals in response to modest atmospheric carbon injections and consequent <span class="hlt">warming</span>, and is replaced by invasion of nutrient-rich North Atlantic-sourced deep water, leading to predictable spatial patterns in deep-sea carbon isotope records. The changes in abyssal carbon isotope 'aging' gradients associated with these hyperthermals are, in fact, two to three times larger than the change in aging gradient associated with the switch in Atlantic overturning between the Last Glacial Maximum and today. Our results suggest that the Atlantic overturning circulation was sensitive to orbital-scale climate variability during Eocene extreme warmth, not just to interglacial-glacial climatic variability of the Plio-Pleistocene.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.A34D..03T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.A34D..03T"><span>Pseudo-global <span class="hlt">warming</span> controls on the intensity and morphology of extreme convective storm <span class="hlt">events</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Trapp, R. J.</p> <p>2015-12-01</p> <p>This research seeks to answer the basic question of how current-day extreme convective storm <span class="hlt">events</span> might be represented under future anthropogenic climate change. We adapt the "pseudo-global <span class="hlt">warming</span>" (PGW) methodology employed by Lackmann (2013, 2015) and others, who have investigated flooding and tropical cyclone <span class="hlt">events</span> under climate change. Here, we exploit coupled atmosphere-ocean GCM data contributed to the CMIP5 archive, and take the mean 3D atmospheric state simulated during May 1990-1999 and subtract it from that simulated during May 2090-2099. Such 3D changes in temperature, humidity, geopotential height, and winds are added to synoptic/meso-scale analyses (NAM-ANL) of specific <span class="hlt">events</span>, and this modified atmospheric state is then used for initial and boundary conditions for real-data WRF model simulations of the <span class="hlt">events</span> at high resolution. Comparison of an ensemble of these simulations with control (CTRL) simulations facilitates assessment of PGW effects. In contrast to the robust development of supercellular convection in our CTRL simulations, the combined effects of increased CIN and decreased forcing under PGW led to a failure of convection initiation in many of our ensemble members. Those members that had sufficient matching between the CIN and forcing tended to generate stronger convective updrafts than in the CTRL simulations, because of the relatively higher CAPE under PGW. And, the members with enhanced updrafts also tended to have enhanced vertical rotation. In fact, such mesocyclonic rotation and attendant supercellular morphology were even found in simulations that were driven with PGW-reduced environmental wind shear.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25925479','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25925479"><span>Precise interpolar phasing of <span class="hlt">abrupt</span> climate change during the last ice age.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p></p> <p>2015-04-30</p> <p>The last glacial period exhibited <span class="hlt">abrupt</span> Dansgaard-Oeschger climatic oscillations, evidence of which is preserved in a variety of Northern Hemisphere palaeoclimate archives. Ice cores show that Antarctica cooled during the <span class="hlt">warm</span> phases of the Greenland Dansgaard-Oeschger cycle and vice versa, suggesting an interhemispheric redistribution of heat through a mechanism called the bipolar seesaw. Variations in the Atlantic meridional overturning circulation (AMOC) strength are thought to have been important, but much uncertainty remains regarding the dynamics and trigger of these <span class="hlt">abrupt</span> <span class="hlt">events</span>. Key information is contained in the relative phasing of hemispheric climate variations, yet the large, poorly constrained difference between gas age and ice age and the relatively low resolution of methane records from Antarctic ice cores have so far precluded methane-based synchronization at the required sub-centennial precision. Here we use a recently drilled high-accumulation Antarctic ice core to show that, on average, <span class="hlt">abrupt</span> Greenland <span class="hlt">warming</span> leads the corresponding Antarctic cooling onset by 218 ± 92 years (2σ) for Dansgaard-Oeschger <span class="hlt">events</span>, including the Bølling <span class="hlt">event</span>; Greenland cooling leads the corresponding onset of Antarctic <span class="hlt">warming</span> by 208 ± 96 years. Our results demonstrate a north-to-south directionality of the <span class="hlt">abrupt</span> climatic signal, which is propagated to the Southern Hemisphere high latitudes by oceanic rather than atmospheric processes. The similar interpolar phasing of <span class="hlt">warming</span> and cooling transitions suggests that the transfer time of the climatic signal is independent of the AMOC background state. Our findings confirm a central role for ocean circulation in the bipolar seesaw and provide clear criteria for assessing hypotheses and model simulations of Dansgaard-Oeschger dynamics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70147340','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70147340"><span>Precise interpolar phasing of <span class="hlt">abrupt</span> climate change during the last ice age</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>,; Buizert, Christo; Adrian, Betty M.; Ahn, Jinho; Albert, Mary; Alley, Richard B.; Baggenstos, Daniel; Bauska, Thomas K.; Bay, Ryan C.; Bencivengo, Brian B.; Bentley, Charles R.; Brook, Edward J.; Chellman, Nathan J.; Clow, Gary D.; Cole-Dai, Jihong; Conway, Howard; Cravens, Eric; Cuffey, Kurt M.; Dunbar, Nelia W.; Edwards, Jon S.; Fegyveresi, John M.; Ferris, Dave G.; Fitzpatrick, Joan J.; Fudge, T. J.; Gibson, Chris J.; Gkinis, Vasileios; Goetz, Joshua J.; Gregory, Stephanie; Hargreaves, Geoffrey Mill; Iverson, Nels; Johnson, Jay A.; Jones, Tyler R.; Kalk, Michael L.; Kippenhan, Matthew J.; Koffman, Bess G.; Kreutz, Karl; Kuhl, Tanner W.; Lebar, Donald A.; Lee, James E.; Marcott, Shaun A.; Markle, Bradley R.; Maselli, Olivia J.; McConnell, Joseph R.; McGwire, Kenneth C.; Mitchell, Logan E.; Mortensen, Nicolai B.; Neff, Peter D.; Nishiizumi, Kunihiko; Nunn, Richard M.; Orsi, Anais J.; Pasteris, Daniel R.; Pedro, Joel B.; Pettit, Erin C.; Price, P. Buford; Priscu, John C.; Rhodes, Rachael H.; Rosen, Julia L.; Schauer, Andrew J.; Schoenemann, Spruce W.; Sendelbach, Paul J.; Severinghaus, Jeffrey P.; Shturmakov, Alexander J.; Sigl, Michael; Slawny, Kristina R.; Souney, Joseph M.; Sowers, Todd A.; Spencer, Matthew K.; Steig, Eric J.; Taylor, Kendrick C.; Twickler, Mark S.; Vaughn, Bruce H.; Voigt, Donald E.; Waddington, Edwin D.; Welten, Kees C.; Wendricks, Anthony W.; White, James W. C.; Winstrup, Mai; Wong, Gifford J.; Woodruff, Thomas E.</p> <p>2015-01-01</p> <p>The last glacial period exhibited <span class="hlt">abrupt</span> Dansgaard–Oeschger climatic oscillations, evidence of which is preserved in a variety of Northern Hemisphere palaeoclimate archives1. Ice cores show that Antarctica cooled during the <span class="hlt">warm</span> phases of the Greenland Dansgaard–Oeschger cycle and vice versa2, 3, suggesting an interhemispheric redistribution of heat through a mechanism called the bipolar seesaw4, 5, 6. Variations in the Atlantic meridional overturning circulation (AMOC) strength are thought to have been important, but much uncertainty remains regarding the dynamics and trigger of these <span class="hlt">abrupt</span> <span class="hlt">events</span>7, 8, 9. Key information is contained in the relative phasing of hemispheric climate variations, yet the large, poorly constrained difference between gas age and ice age and the relatively low resolution of methane records from Antarctic ice cores have so far precluded methane-based synchronization at the required sub-centennial precision2, 3,10. Here we use a recently drilled high-accumulation Antarctic ice core to show that, on average, <span class="hlt">abrupt</span> Greenland <span class="hlt">warming</span> leads the corresponding Antarctic cooling onset by 218 ± 92 years (2σ) for Dansgaard–Oeschger <span class="hlt">events</span>, including the Bølling <span class="hlt">event</span>; Greenland cooling leads the corresponding onset of Antarctic <span class="hlt">warming</span> by 208 ± 96 years. Our results demonstrate a north-to-south directionality of the <span class="hlt">abrupt</span> climatic signal, which is propagated to the Southern Hemisphere high latitudes by oceanic rather than atmospheric processes. The similar interpolar phasing of <span class="hlt">warming</span> and cooling transitions suggests that the transfer time of the climatic signal is independent of the AMOC background state. Our findings confirm a central role for ocean circulation in the bipolar seesaw and provide clear criteria for assessing hypotheses and model simulations of Dansgaard–Oeschger dynamics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28694487','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28694487"><span>Evidence for rapid weathering response to climatic <span class="hlt">warming</span> during the Toarcian Oceanic Anoxic <span class="hlt">Event</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Them, Theodore R; Gill, Benjamin C; Selby, David; Gröcke, Darren R; Friedman, Richard M; Owens, Jeremy D</p> <p>2017-07-10</p> <p>Chemical weathering consumes atmospheric carbon dioxide through the breakdown of silicate minerals and is thought to stabilize Earth's long-term climate. However, the potential influence of silicate weathering on atmospheric pCO2 levels on geologically short timescales (10(3)-10(5) years) remains poorly constrained. Here we focus on the record of a transient interval of severe climatic <span class="hlt">warming</span> across the Toarcian Oceanic Anoxic <span class="hlt">Event</span> or T-OAE from an open ocean sedimentary succession from western North America. Paired osmium isotope data and numerical modelling results suggest that weathering rates may have increased by 215% and potentially up to 530% compared to the pre-<span class="hlt">event</span> baseline, which would have resulted in the sequestration of significant amounts of atmospheric CO2. This process would have also led to increased delivery of nutrients to the oceans and lakes stimulating bioproductivity and leading to the subsequent development of shallow-water anoxia, the hallmark of the T-OAE. This enhanced bioproductivity and anoxia would have resulted in elevated rates of organic matter burial that would have acted as an additional negative feedback on atmospheric pCO2 levels. Therefore, the enhanced weathering modulated by initially increased pCO2 levels would have operated as both a direct and indirect negative feedback to end the T-OAE.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.8526S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.8526S"><span>Social implications from heatwave <span class="hlt">events</span> at different levels of global <span class="hlt">warming</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sillmann, Jana; Russo, Simone</p> <p>2017-04-01</p> <p>In recent decades, many poor and highly populated regions have experienced extreme heat waves with strong impact on human mortality and agriculture. By applying the Heat Wave Magnitude Index daily (HWMId) to temperature reanalysis data, we quantify the magnitude and the spatial extent of the most extreme heatwave <span class="hlt">events</span> experienced in the world between 1979 and 2016. Results show that in the recent years many continents experienced hotter, longer and more extended heatwaves than in the last two decades of the 20th century. According to the latest multi-model climate simulations, the globally averaged near surface temperature will increase by 1.5 or 2 degree Celsius by 2030 and 2040, respectively, compared to preindustrial (1861-1880) conditions. We present a method where aspects of hazard, exposure and vulnerability can be combined to illustrate regions under risk of severe impacts due to heatwave <span class="hlt">events</span>. We show that even at modest <span class="hlt">warming</span> levels of 2 degrees versus 1.5 degrees Celsius the impacts of heatwaves can differ, particularly across region with high population density and low Gross Domestic Product (GDP).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1237098','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1237098"><span>Changes in Intense Precipitation <span class="hlt">Events</span> in West Africa and the central U.S. under Global <span class="hlt">Warming</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Cook, Kerry H.; Vizy, Edward</p> <p>2016-02-08</p> <p>The purpose of the proposed project is to improve our understanding of the physical processes and large-scale connectivity of changes in intense precipitation <span class="hlt">events</span> (high rainfall rates) under global <span class="hlt">warming</span> in West Africa and the central U.S., including relationships with low-frequency modes of variability. This is in response to the requested subject area #2 “simulation of climate extremes under a changing climate … to better quantify the frequency, duration, and intensity of extreme <span class="hlt">events</span> under climate change and elucidate the role of low frequency climate variability in modulating extremes.” We will use a regional climate model and emphasize an understanding of the physical processes that lead to an intensification of rainfall. The project objectives are as follows: 1. Understand the processes responsible for simulated changes in <span class="hlt">warm</span>-season rainfall intensity and frequency over West Africa and the Central U.S. associated with greenhouse gas-induced global <span class="hlt">warming</span> 2. Understand the relationship between changes in <span class="hlt">warm</span>-season rainfall intensity and frequency, which generally occur on regional space scales, and the larger-scale global <span class="hlt">warming</span> signal by considering modifications of low-frequency modes of variability. 3. Relate changes simulated on regional space scales to global-scale theories of how and why atmospheric moisture levels and rainfall should change as climate <span class="hlt">warms</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24567826','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24567826"><span>Snow cover and extreme winter <span class="hlt">warming</span> <span class="hlt">events</span> control flower abundance of some, but not all species in high arctic Svalbard.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Semenchuk, Philipp R; Elberling, Bo; Cooper, Elisabeth J</p> <p>2013-08-01</p> <p>The High Arctic winter is expected to be altered through ongoing and future climate change. Winter precipitation and snow depth are projected to increase and melt out dates change accordingly. Also, snow cover and depth will play an important role in protecting plant canopy from increasingly more frequent extreme winter <span class="hlt">warming</span> <span class="hlt">events</span>. Flower production of many Arctic plants is dependent on melt out timing, since season length determines resource availability for flower preformation. We erected snow fences to increase snow depth and shorten growing season, and counted flowers of six species over 5 years, during which we experienced two extreme winter <span class="hlt">warming</span> <span class="hlt">events</span>. Most species were resistant to snow cover increase, but two species reduced flower abundance due to shortened growing seasons. Cassiope tetragona responded strongly with fewer flowers in deep snow regimes during years without extreme <span class="hlt">events</span>, while Stellaria crassipes responded partly. Snow pack thickness determined whether winter <span class="hlt">warming</span> <span class="hlt">events</span> had an effect on flower abundance of some species. <span class="hlt">Warming</span> <span class="hlt">events</span> clearly reduced flower abundance in shallow but not in deep snow regimes of Cassiope tetragona, but only marginally for Dryas octopetala. However, the affected species were resilient and individuals did not experience any long term effects. In the case of short or cold summers, a subset of species suffered reduced reproductive success, which may affect future plant composition through possible cascading competition effects. Extreme winter <span class="hlt">warming</span> <span class="hlt">events</span> were shown to expose the canopy to cold winter air. The following summer most of the overwintering flower buds could not produce flowers. Thus reproductive success is reduced if this occurs in subsequent years. We conclude that snow depth influences flower abundance by altering season length and by protecting or exposing flower buds to cold winter air, but most species studied are resistant to changes. Winter <span class="hlt">warming</span> <span class="hlt">events</span>, often occurring</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3930050','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3930050"><span>Snow cover and extreme winter <span class="hlt">warming</span> <span class="hlt">events</span> control flower abundance of some, but not all species in high arctic Svalbard</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Semenchuk, Philipp R; Elberling, Bo; Cooper, Elisabeth J</p> <p>2013-01-01</p> <p>Abstract The High Arctic winter is expected to be altered through ongoing and future climate change. Winter precipitation and snow depth are projected to increase and melt out dates change accordingly. Also, snow cover and depth will play an important role in protecting plant canopy from increasingly more frequent extreme winter <span class="hlt">warming</span> <span class="hlt">events</span>. Flower production of many Arctic plants is dependent on melt out timing, since season length determines resource availability for flower preformation. We erected snow fences to increase snow depth and shorten growing season, and counted flowers of six species over 5 years, during which we experienced two extreme winter <span class="hlt">warming</span> <span class="hlt">events</span>. Most species were resistant to snow cover increase, but two species reduced flower abundance due to shortened growing seasons. Cassiope tetragona responded strongly with fewer flowers in deep snow regimes during years without extreme <span class="hlt">events</span>, while Stellaria crassipes responded partly. Snow pack thickness determined whether winter <span class="hlt">warming</span> <span class="hlt">events</span> had an effect on flower abundance of some species. <span class="hlt">Warming</span> <span class="hlt">events</span> clearly reduced flower abundance in shallow but not in deep snow regimes of Cassiope tetragona, but only marginally for Dryas octopetala. However, the affected species were resilient and individuals did not experience any long term effects. In the case of short or cold summers, a subset of species suffered reduced reproductive success, which may affect future plant composition through possible cascading competition effects. Extreme winter <span class="hlt">warming</span> <span class="hlt">events</span> were shown to expose the canopy to cold winter air. The following summer most of the overwintering flower buds could not produce flowers. Thus reproductive success is reduced if this occurs in subsequent years. We conclude that snow depth influences flower abundance by altering season length and by protecting or exposing flower buds to cold winter air, but most species studied are resistant to changes. Winter <span class="hlt">warming</span> <span class="hlt">events</span>, often</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1710094S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1710094S"><span>Subtropical influence on January 2009 major sudden stratospheric <span class="hlt">warming</span> <span class="hlt">event</span>: diagnostic analysis</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schneidereit, Andrea; Peters, Dieter; Grams, Christian; Wolf, Gabriel; Riemer, Michael; Gierth, Franziska; Quinting, Julian; Keller, Julia; Martius, Olivia</p> <p>2015-04-01</p> <p>In January 2009 a major sudden stratospheric <span class="hlt">warming</span> (MSSW) <span class="hlt">event</span> occurred with the strongest NAM anomaly ever observed at 10 hPa. Also stratospheric Eliassen-Palm flux convergence and zonal mean eddy heat fluxes of ultra-long waves at 100 hPa layer were unusually strong in the mid-latitudes just before and after the onset of the MSSW. Beside internal interactions between the background flow and planetary waves and between planetary waves among themselves the subtropical tropospheric forcing of these enhanced heat fluxes is still an open question. This study investigates in more detail the dynamical reasons for the pronounced heat fluxes based on ERA-Interim re-analysis data. Investigating the regional contributions of the eddy heat flux to the northern hemispheric zonal mean revealed a distinct spatial pattern with maxima in the Eastern Pacific/North America and the Eastern North Atlantic/ Europe in that period. The first region is related with an almost persistent tropospheric blocking high (BH) over the Gulf of Alaska dominating the upper-level flow and the second region with a weaker BH over Northern Europe. The evolution of the BH over the Gulf of Alaska can be explained by a chain of tropospheric weather <span class="hlt">events</span> linked to and maintained by subtropical and tropical influences: MJO (phase 7-8) and the developing cold phase of ENSO (La Niña), which are in coherence over the Eastern Pacific favor enhanced subtropical baroclinicity. In turn extratropical cyclone activity increases and shifts more poleward associated with an increase of the frequency of <span class="hlt">warm</span> conveyor belts (WCB). These WCBs support enhanced poleward directed eddy heat fluxes in Eastern Pacific/North-American region. The Eastern North Atlantic/European positive heat flux anomaly is associated with a blocking high over Scandinavia. This BH is maintained by an eastward propagating Rossby wave train, emanating from the block over the Gulf of Alaska. Eddy feedback processes support this high pressure</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JGRA..119.7858F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JGRA..119.7858F"><span>Ionospheric response to sudden stratospheric <span class="hlt">warming</span> <span class="hlt">events</span> at low and high solar activity</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fang, Tzu-Wei; Fuller-Rowell, Tim; Wang, Houjun; Akmaev, Rashid; Wu, Fei</p> <p>2014-09-01</p> <p>The sensitivity of the ionospheric response to a sudden stratospheric <span class="hlt">warming</span> (SSW) <span class="hlt">event</span> has been examined under conditions of low and high solar activity through simulations using the whole atmosphere model (WAM) and the global ionosphere plasmasphere model (GIP). During non-SSW conditions, simulated daytime mean vertical drifts at the magnetic equator show similar solar activity dependence as an empirical model. Model results of ionospheric total electron content (TEC) and equatorial vertical drift for the January 2009 major SSW, which occurred at very low solar activity conditions, show reasonable agreement with observations. The simulations demonstrate that the E region dynamo is capable of creating the semidiurnal variation of vertical drift. WAM and GIP were also run at high solar activity conditions, using the same lower atmosphere conditions as present in the January 2009 SSW <span class="hlt">event</span>. The simulations indicate that the amplitude and phase of migrating tides in the dynamo region during the <span class="hlt">event</span> have similar magnitudes for both solar flux conditions. However, comparing the ionospheric responses to a major SSW under low and high solar activity periods, it was found that the changes in the ionospheric vertical drifts and relative changes in TEC decreased with increasing solar activity. The simulations indicate that the F region dynamo becomes more important throughout the daytime and contributes to the upward drift in the afternoon during the <span class="hlt">event</span> when the solar activity is higher. Our test simulations also confirm that the increase of the ionospheric conductivity associated with increasing solar activity is responsible for the decrease of vertical drift changes during an SSW. In particular, first, the increase in F region conductivity allows the closure of E region currents through the F region, reducing the polarization electric field before noon. Second, the F region dynamo contributes an upward drift postnoon, maintaining upward drifts till after sunset</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JGRA..121.8055B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JGRA..121.8055B"><span>Solar quiet current response in the African sector due to a 2009 sudden stratospheric <span class="hlt">warming</span> <span class="hlt">event</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bolaji, O. S.; Oyeyemi, E. O.; Owolabi, O. P.; Yamazaki, Y.; Rabiu, A. B.; Okoh, D.; Fujimoto, A.; Amory-Mazaudier, C.; Seemala, G. K.; Yoshikawa, A.; Onanuga, O. K.</p> <p>2016-08-01</p> <p>We present solar quiet (Sq) variation of the horizontal (H) magnetic field intensity deduced from Magnetic Data Acquisition System (MAGDAS) records over Africa during an unusual strong and prolonged 2009 sudden stratospheric <span class="hlt">warming</span> (SSW) <span class="hlt">event</span>. A reduction in the SqH magnitude that enveloped the geomagnetic latitudes between 21.13°N (Fayum FYM) in Egypt and 39.51°S (Durban DRB) in South Africa was observed, while the stratospheric polar temperature was increasing and got strengthened when the stratospheric temperature reached its maximum. Another novel feature associated with the hemispheric reduction is the reversal in the north-south asymmetry of the SqH, which is indicative of higher SqH magnitude in the Northern Hemisphere compared to the Southern Hemisphere during SSW peak phase. The reversal of the equatorial electrojet (EEJ) or the counter electrojet (CEJ) was observed after the polar stratospheric temperature reached its maximum. The effect of additional currents associated with CEJ was observed in the Southern Hemisphere at middle latitude. Similar changes were observed in the EEJ at the South America, Pacific Ocean, and Central Asia sectors. The effect of the SSW is largest in the South American sector and smallest in the Central Asian sector.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5330854','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5330854"><span><span class="hlt">Abrupt</span> cooling over the North Atlantic in modern climate models</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Sgubin, Giovanni; Swingedouw, Didier; Drijfhout, Sybren; Mary, Yannick; Bennabi, Amine</p> <p>2017-01-01</p> <p>Observations over the 20th century evidence no long-term <span class="hlt">warming</span> in the subpolar North Atlantic (SPG). This region even experienced a rapid cooling around 1970, raising a debate over its potential reoccurrence. Here we assess the risk of future <span class="hlt">abrupt</span> SPG cooling in 40 climate models from the fifth Coupled Model Intercomparison Project (CMIP5). Contrary to the long-term SPG <span class="hlt">warming</span> trend evidenced by most of the models, 17.5% of the models (7/40) project a rapid SPG cooling, consistent with a collapse of the local deep-ocean convection. Uncertainty in projections is associated with the models' varying capability in simulating the present-day SPG stratification, whose realistic reproduction appears a necessary condition for the onset of a convection collapse. This <span class="hlt">event</span> occurs in 45.5% of the 11 models best able to simulate the observed SPG stratification. Thus, due to systematic model biases, the CMIP5 ensemble as a whole underestimates the chance of future <span class="hlt">abrupt</span> SPG cooling, entailing crucial implications for observation and adaptation policy. PMID:28198383</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28198383','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28198383"><span><span class="hlt">Abrupt</span> cooling over the North Atlantic in modern climate models.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Sgubin, Giovanni; Swingedouw, Didier; Drijfhout, Sybren; Mary, Yannick; Bennabi, Amine</p> <p>2017-02-15</p> <p>Observations over the 20th century evidence no long-term <span class="hlt">warming</span> in the subpolar North Atlantic (SPG). This region even experienced a rapid cooling around 1970, raising a debate over its potential reoccurrence. Here we assess the risk of future <span class="hlt">abrupt</span> SPG cooling in 40 climate models from the fifth Coupled Model Intercomparison Project (CMIP5). Contrary to the long-term SPG <span class="hlt">warming</span> trend evidenced by most of the models, 17.5% of the models (7/40) project a rapid SPG cooling, consistent with a collapse of the local deep-ocean convection. Uncertainty in projections is associated with the models' varying capability in simulating the present-day SPG stratification, whose realistic reproduction appears a necessary condition for the onset of a convection collapse. This <span class="hlt">event</span> occurs in 45.5% of the 11 models best able to simulate the observed SPG stratification. Thus, due to systematic model biases, the CMIP5 ensemble as a whole underestimates the chance of future <span class="hlt">abrupt</span> SPG cooling, entailing crucial implications for observation and adaptation policy.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017NatCo...8.....S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017NatCo...8.....S"><span><span class="hlt">Abrupt</span> cooling over the North Atlantic in modern climate models</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sgubin, Giovanni; Swingedouw, Didier; Drijfhout, Sybren; Mary, Yannick; Bennabi, Amine</p> <p>2017-02-01</p> <p>Observations over the 20th century evidence no long-term <span class="hlt">warming</span> in the subpolar North Atlantic (SPG). This region even experienced a rapid cooling around 1970, raising a debate over its potential reoccurrence. Here we assess the risk of future <span class="hlt">abrupt</span> SPG cooling in 40 climate models from the fifth Coupled Model Intercomparison Project (CMIP5). Contrary to the long-term SPG <span class="hlt">warming</span> trend evidenced by most of the models, 17.5% of the models (7/40) project a rapid SPG cooling, consistent with a collapse of the local deep-ocean convection. Uncertainty in projections is associated with the models' varying capability in simulating the present-day SPG stratification, whose realistic reproduction appears a necessary condition for the onset of a convection collapse. This <span class="hlt">event</span> occurs in 45.5% of the 11 models best able to simulate the observed SPG stratification. Thus, due to systematic model biases, the CMIP5 ensemble as a whole underestimates the chance of future <span class="hlt">abrupt</span> SPG cooling, entailing crucial implications for observation and adaptation policy.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFM.B14D..05G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.B14D..05G"><span>Exploring mass extinction <span class="hlt">events</span> and their association with global <span class="hlt">warming</span> <span class="hlt">events</span> from muliproxy biomarker and isotopic approaches</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Grice, K.; Nabbefeld, B.; Maslen, E.; Jaraula, C.; Holman, A.; Melendez, I.; Tulipani, S.; Twitchett, R.; Hays, L. E.; Summons, R. E.; Mella, L.; Williford, K. H.; McElwain, J.; Böttcher, M.</p> <p>2011-12-01</p> <p>The Late Permian mass extinction <span class="hlt">event</span> was the most profound extinctions of the entire Phanerozoic. Biomarker evidence for photic zone euxinic (PZE) conditions within Permian/Triassic (P/Tr) setions, where concentrations of sulfide, are sufficient to support anoxygenic photosynthesis, come from components derived from pigments of Chlorobi. Evidence for such conditions occurred at 6 global localities from shallow marine settings. Perturbations in the redox-state of the ancient seas are also reflected in d34S of pyrite (e.g. from China, Italy, Iran, Western Australia, East Greenland, Western Canada and Spitsbergen) supporting widespread euxinic conditions in both Palaeotethys and Panthalassa oceans. The aromatic biomarkers, dibenzothiophene, dibenzofuran and biphenyl have been detected in high abundances in samples just before the onset of the marine ecosystem collapse in East Greenland, Spitsbergen, South China and Western Canada . We have proposed that lignin derived from land plants, present during the Late Permian is their likely source. We provide sedimentological data, biomarker abundances and compound specific isotopic data (δ13C and δD) along with bulk isotopes (δ34Spyrite, δ13Ccarbonate, δ13Corg) for several sections. At two localities sedimentological and geochemical data supports a marine transgression and collapse of the marine ecosystem occurring in the Late Permian. δ13C data of algal and land-plant derived biomarkers, δ13C carbonate and organic matter support synchronous changes in δ13C of marine and atmospheric CO2, attributed to a 13C-depleted source (13C depleted methane and/or CO2 derived from degradation of organic matter due to the marine ecosystem collapse). Evidence for waxing and waning of PZE throughout the Late Permian is provided by Chlorobi derived biomarkers and δ34S pyrite implying multiple phases of H2S outgassing and potentially several prolonged pulses of extinction at several global localities. We suggest that high levels of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JGRA..120.3084C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JGRA..120.3084C"><span>Upper mesospheric lunar tides over middle and high latitudes during sudden stratospheric <span class="hlt">warming</span> <span class="hlt">events</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chau, J. L.; Hoffmann, P.; Pedatella, N. M.; Matthias, V.; Stober, G.</p> <p>2015-04-01</p> <p>In recent years there have been a series of reported ground- and satellite-based observations of lunar tide signatures in the equatorial and low latitude ionosphere/thermosphere around sudden stratospheric <span class="hlt">warming</span> (SSW) <span class="hlt">events</span>. This lower atmosphere/ionosphere coupling has been suggested to be via the E region dynamo. In this work we present the results of analyzing 6 years of hourly upper mesospheric winds from specular meteor radars over a midlatitude (54°N) station and a high latitude (69°N) station. Instead of correlating our results with typical definitions of SSWs, we use the definition of polar vortex weaking (PVW) used by Zhang and Forbes. This definition provides a better representation of the strength in middle atmospheric dynamics that should be responsible for the waves propagating to the E region. We have performed a wave decomposition on hourly wind data in 21 day segments, shifted by 1 day. In addition to the radar wind data, the analysis has been applied to simulations from Whole Atmosphere Community Climate Model Extended version and the thermosphere-ionosphere-mesosphere electrodynamics general circulation model. Our results indicate that the semidiurnal lunar tide (M2) enhances in northern hemispheric winter months, over both middle and high latitudes. The time and magnitude of M2 are highly correlated with the time and associated zonal wind of PVW. At middle/high latitudes, M2 in the upper mesosphere occurs after/before the PVW. At both latitudes, the maximum amplitude of M2 is directly proportional to the strength of PVW westward wind. We have found that M2 amplitudes could be comparable to semidiurnal solar tide amplitudes, particularly around PVW and equinoxes. Besides these general results, we have also found peculiarities in some <span class="hlt">events</span>, particularly at high latitudes. These peculiarities point to the need of considering the longitudinal features of the polar stratosphere and the upper mesosphere and lower thermosphere regions. For</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/12791974','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/12791974"><span>Does the trigger for <span class="hlt">abrupt</span> climate change reside in the ocean or in the atmosphere?</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Broecker, W S</p> <p>2003-06-06</p> <p>Two hypotheses have been put forward to explain the large and <span class="hlt">abrupt</span> climate changes that punctuated glacial time. One attributes such changes to reorganizations of the ocean's thermohaline circulation and the other to changes in tropical atmosphere-ocean dynamics. In an attempt to distinguish between these hypotheses, two lines of evidence are examined. The first involves the timing of the freshwater injections to the northern Atlantic that have been suggested as triggers for the global impacts associated with the Younger Dryas and Heinrich <span class="hlt">events</span>. The second has to do with evidence for precursory <span class="hlt">events</span> associated with the Heinrich ice-rafted debris layers in the northern Atlantic and with the <span class="hlt">abrupt</span> Dansgaard-Oeschger <span class="hlt">warmings</span> recorded in the Santa Barbara Basin.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active"><span>9</span></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_9 --> <div id="page_10" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active"><span>10</span></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="181"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004AGUFM.C44A..02T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004AGUFM.C44A..02T"><span>Low-latitude mountain glacier evidence for <span class="hlt">abrupt</span> climate changes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Thompson, L. G.; Mosley-Thompson, E. S.; Lin, P.; Davis, M. E.; Mashiotta, T. A.; Brecher, H. H.</p> <p>2004-12-01</p> <p>Clear evidence that a widespread <span class="hlt">warming</span> of Earth's climate system is now underway comes from low latitude mountain glaciers. Proxy temperature histories reconstructed from ice cores, and the rapidly accelerating loss of both the total ice area and ice volume on a near global scale suggest that these glaciers responding to increasing rates of melting. In situ observations reveal the startling rates at which many tropical glaciers are disappearing. For example, the retreat of the terminus of the Qori Kalis Glacier in Peru is roughly 200 meters per year, 40 times faster than its retreat rate in 1978. Similarly, in 1912 the ice on Mount Kilimanjaro covered 12.1 km2, but today it covers only 2.6 km2. If the current rate of retreat continues, the perennial ice fields may disappear within the next few decades, making this the first time in the past 11,700 years that Kilimanjaro will be devoid of the ice that shrouds its summit. Tropical glaciers may be considered ``the canaries in the coal mine'' for the global climate system as they integrate and respond to key climatological variables, such as temperature, precipitation, cloudiness, humidity, and incident solar radiation. A composite of the decadally-averaged oxygen isotopic records from three Andean and three Tibetan ice cores extending back over the last two millennia shows an isotopic enrichment in the 20th century that suggests a large-scale <span class="hlt">warming</span> is underway at lower latitudes. Multiple lines of evidence from Africa, the Middle East, Europe and South America indicate an <span class="hlt">abrupt</span> mid-Holocene climate <span class="hlt">event</span> in the low latitudes. If such an <span class="hlt">event</span> were to occur now with a global human population of 6.3 billion people, the consequences could be severe. Clearly, we need to understand the nature and cause of <span class="hlt">abrupt</span> climate <span class="hlt">events</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110005628','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110005628"><span>Can the GEOS CCM Simulate the Temperature Response to <span class="hlt">Warm</span> Pool El Nino <span class="hlt">Events</span> in the Antarctic Stratosphere?</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hurwitz, M. M.; Song, I.-S.; Oman, L. D.; Newman, P. A.; Molod, A. M.; Frith, S. M.; Nielsen, J. E.</p> <p>2011-01-01</p> <p>"<span class="hlt">Warm</span> pool" (WP) El Nino <span class="hlt">events</span> are characterized by positive sea surface temperature (SST) anomalies in the central equatorial Pacific. During austral spring, WP El Nino <span class="hlt">events</span> are associated with an enhancement of convective activity in the South Pacific Convergence Zone, provoking a tropospheric planetary wave response and thus increasing planetary wave driving of the Southern Hemisphere stratosphere. These conditions lead to higher polar stratospheric temperatures and to a weaker polar jet during austral summer, as compared with neutral ENSO years. Furthermore, this response is sensitive to the phase of the quasi-biennial oscillation (QBO): a stronger <span class="hlt">warming</span> is seen in WP El Nino <span class="hlt">events</span> coincident with the easterly phase of the quasi-biennial oscillation (QBO) as compared with WP El Nino <span class="hlt">events</span> coincident with a westerly or neutral QBO. The Goddard Earth Observing System (GEOS) chemistry-climate model (CCM) is used to further explore the atmospheric response to ENSO. Time-slice simulations are forced by composited SSTs from observed NP El Nino and neutral ENSO <span class="hlt">events</span>. The modeled eddy heat flux, temperature and wind responses to WP El Nino <span class="hlt">events</span> are compared with observations. A new gravity wave drag scheme has been implemented in the GEOS CCM, enabling the model to produce e realistic, internally generated QBO. By repeating the above time-slice simulations with this new model version, the sensitivity of the WP El Nino response to the phase of the quasi-biennial oscillation QBO is estimated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110005602','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110005602"><span>Can the GEOS CCM Simulate the Temperature Response to <span class="hlt">Warm</span> Pool El Nino <span class="hlt">Events</span> in the Antarctic Stratosphere?</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hurwitz, M. M.; Song, I.-S.; Oman, L. D.; Newman, P. A.; Molod, A. M.; Frith, S. M.; Nielsen, J. E.</p> <p>2010-01-01</p> <p>"<span class="hlt">Warm</span> pool" (WP) El Nino <span class="hlt">events</span> are characterized by positive sea surface temperature (SST) anomalies in the central equatorial Pacific. During austral spring. WP El Nino <span class="hlt">events</span> are associated with an enhancement of convective activity in the South Pacific Convergence Zone, provoking a tropospheric planetary wave response and thus increasing planetary wave driving of the Southern Hemisphere stratosphere. These conditions lead to higher polar stratospheric temperatures and to a weaker polar jet during austral summer, as compared with neutral ENSO years. Furthermore, this response is sensitive to the phase of the quasi-biennial oscillation (QBO): a stronger <span class="hlt">warming</span> is seen in WP El Nino <span class="hlt">events</span> coincident with the easterly phase of the quasi-biennial oscillation (QBO) as compared with WP El Nino <span class="hlt">events</span> coincident with a westerly or neutral QBO. The Goddard Earth Observing System (GEOS) chemistry-climate model (CCM) is used to further explore the atmospheric response to ENSO. Time-slice simulations are forced by composited SSTs from observed WP El Nino and neutral ENSO <span class="hlt">events</span>. The modeled eddy heat flux, temperature and wind responses to WP El Nino <span class="hlt">events</span> are compared with observations. A new gravity wave drag scheme has been implemented in the GEOS CCM, enabling the model to produce a realistic, internally generated QBO. By repeating the above time-slice simulations with this new model version, the sensitivity of the WP El Nino response to the phase of the quasi-biennial oscillation QBO is estimated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19840031293&hterms=Neubauer&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DNeubauer','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19840031293&hterms=Neubauer&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DNeubauer"><span>The sun-weather connection - Sudden stratospheric <span class="hlt">warmings</span> correlated with sudden commencements and solar proton <span class="hlt">events</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Neubauer, L.</p> <p>1983-01-01</p> <p>It has been found that a strong correlation exists between sudden stratospheric <span class="hlt">warmings</span> and sudden commencements of geomagnetic activity. This correlation follows a 22-yr cycle. The sudden <span class="hlt">warmings</span> of the lower stratosphere occur near the north magnetic pole over Siberia and the Pacific, although occasionally they do occur over North America. A mechanism explaining how the solar wind ultimately affects the surface weather through its selective interaction with the middle atmosphere is outlined.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3175371','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3175371"><span><span class="hlt">Abruption</span>-associated prematurity</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Han, Christina S.; Schatz, Frederick; Lockwood, Charles J.</p> <p>2011-01-01</p> <p>SYNOPSIS Chronic, subacute decidual hemorrhage (i.e., abruptio placenta and retrochorionic hematoma formation) is an important contributor to preterm parturition. Such hemorrhage induces thrombin from decidual tissue factor, which play a pivotal role in the development of preterm premature rupture of membranes and preterm delivery by acting through protease-activated receptors to promote the production of pro-inflammatory cytokines, and matrix-degrading metalloproteinases. Severe, acute <span class="hlt">abruption</span> can lead to maternal and fetal mortality. Current management of <span class="hlt">abruption</span> is individualized based on severity of disease, underlying etiology, and gestational age. PMID:21890016</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFM.V54A..06B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.V54A..06B"><span>The Role Of Oceanic Plateau Volcanism On Climate Change: <span class="hlt">Warming</span> And Cooling Episodes Across Early Aptian Oceanic Anoxic <span class="hlt">Event</span> 1a</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bottini, C.; Erba, E.; Mutterlose, J.</p> <p>2011-12-01</p> <p>The early Aptian is marked by a global phenomenon of organic matter burial in oxygen-depleted oceans known as Oceanic Anoxic <span class="hlt">Event</span> 1a (OAE 1a: ~120 Ma). Volcanism associated with the emplacement of the Ontong Java Plateau (OJP) is thought to be the main triggering mechanism for global anoxia, ocean acidification and greenhouse conditions. However, climate instability during OAE 1a is indicated by independent studies on TEX86, sporomorphs and oxygen-stable isotope but a direct connection between OJP volcanic phases and temperature variations has not been ascertained. A high-resolution integrated nannofossil-geochemical investigation of distant sections from the Tethys, the Pacific Ocean and the Boreal Realm has revealed systematic and synchronous changes. Specifically, the nannofossil Temperature Index and Os-isotope records allowed the reconstruction of a complex series of global <span class="hlt">warming</span> and cooling <span class="hlt">events</span> across OAE 1a and their relationships with OJP volcanism as well as weathering patterns. Two prominent volcanic phases are documented in the Os-isotope records: the first preceding OAE 1a and the second one, of major intensity, starting in the core of the negative C-isotopic anomaly. Both phases are paralleled by increased temperature, suggestive of a (super)greenhouse climate triggered by excess volcanogenic CO2. Indeed, our data indicate that the beginning of the prolonged volcanic phase during OAE 1a coincides with warmest temperatures. In the early part of OAE 1a, between the two major volcanic phases, there is a ~100 kyrs-long interval characterized by a radiogenic Os-isotope peak, suggestive of accelerated continental weathering rates, with or without volcanism cessation, following an interval of <span class="hlt">abrupt</span> <span class="hlt">warming</span> and preceding a cooling interlude. Arguably, <span class="hlt">warming</span> at OAE 1a onset promoted methane hydrate dissociation (also suggested by C-isotope and biomarkers analyses), which was perhaps instrumental in triggering continental weathering. Subsequent CO2 draw</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19930033977&hterms=remington&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dremington','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19930033977&hterms=remington&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dremington"><span>Involuntary attentional capture by <span class="hlt">abrupt</span> onsets</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Remington, Roger W.; Johnston, James C.; Yantis, Steven</p> <p>1992-01-01</p> <p>Five experiments were carried out to examine the extent to which brief <span class="hlt">abrupt</span>-onset visual stimuli involuntarily capture spatial attention. A fundumantal limitation on the conscious control of spatial attention is demonstrated. Data obtained reveal conditions under which the control of spatial attention is completely involuntary: attention is captured by an irrelevant <span class="hlt">event</span> despite subjects' intentions to ignore the <span class="hlt">event</span>. The paradigm used provided strong incentives to ignore the distracting <span class="hlt">abrupt</span> onset, but these were insufficient to prevent capture. Results suggest that voluntary control of attention is limited to focusing attention in advance on locations, objects, or properties of interest. Under appropriate conditions, spatial attention can be involantarily drawn to <span class="hlt">abrupt</span>-onset <span class="hlt">events</span> despite the intention of subjects' to ignore them.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19930033977&hterms=behavioral+intention&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dbehavioral%2Bintention','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19930033977&hterms=behavioral+intention&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dbehavioral%2Bintention"><span>Involuntary attentional capture by <span class="hlt">abrupt</span> onsets</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Remington, Roger W.; Johnston, James C.; Yantis, Steven</p> <p>1992-01-01</p> <p>Five experiments were carried out to examine the extent to which brief <span class="hlt">abrupt</span>-onset visual stimuli involuntarily capture spatial attention. A fundumantal limitation on the conscious control of spatial attention is demonstrated. Data obtained reveal conditions under which the control of spatial attention is completely involuntary: attention is captured by an irrelevant <span class="hlt">event</span> despite subjects' intentions to ignore the <span class="hlt">event</span>. The paradigm used provided strong incentives to ignore the distracting <span class="hlt">abrupt</span> onset, but these were insufficient to prevent capture. Results suggest that voluntary control of attention is limited to focusing attention in advance on locations, objects, or properties of interest. Under appropriate conditions, spatial attention can be involantarily drawn to <span class="hlt">abrupt</span>-onset <span class="hlt">events</span> despite the intention of subjects' to ignore them.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016E%26PSL.455..115R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016E%26PSL.455..115R"><span><span class="hlt">Abrupt</span> plant physiological changes in southern New Zealand at the termination of the Mi-1 <span class="hlt">event</span> reflect shifts in hydroclimate and pCO2</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Reichgelt, Tammo; D'Andrea, William J.; Fox, Bethany R. S.</p> <p>2016-12-01</p> <p>A rise in atmospheric CO2 is believed to be necessary for the termination of large-scale glaciations. Although the Antarctic Ice Sheet is estimated to have melted from ∼125% to ∼50% its modern size, there is thus far no evidence for an increase in atmospheric CO2 associated with the Mi-1 glacial termination in the earliest Miocene. Here, we present evidence from a high-resolution terrestrial record of leaf physiological change in southern New Zealand for an <span class="hlt">abrupt</span> increase in atmospheric CO2 coincident with the termination of the Mi-1 glaciation and lasting approximately 20 kyr. Quantitative pCO2 estimates, made using a leaf gas exchange model, suggest that atmospheric CO2 levels may have doubled during this period, from 516 ± 111ppm to 1144 ± 410ppm, and subsequently returned back to 425 ± 53ppm. The 20-kyr interval with high pCO2 estimates is also associated with a period of increased moisture supply to southern New Zealand, inferred from carbon and hydrogen isotopes of terrestrial leaf waxes. The results provide the first high-resolution record of terrestrial environmental change at the Oligocene/Miocene boundary, document a ∼20 kyr interval of elevated pCO2 and increased local moisture availability, and provide insight into ecosystem response to a major orbitally driven climatic transition.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.8316G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.8316G"><span>A preliminary look at the impact of <span class="hlt">warming</span> Mediterranean Sea temperatures on some aspects of extreme thunderstorm <span class="hlt">events</span> in Italy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gallus, William; Parodi, Antonio; Miglietta, Marcello; Maugeri, Maurizio</p> <p>2017-04-01</p> <p>As the global climate has <span class="hlt">warmed</span> in recent decades, interest has grown in the impacts on extreme <span class="hlt">events</span> associated with thunderstorms such as tornadoes and intense rainfall that can cause flash flooding. Because warmer temperatures allow the atmosphere to contain larger values of water vapor, it is generally accepted that short-term rainfall may become more intense in a future warmer climate. Regarding tornadoes, it is more difficult to say what might happen since although increased temperatures and humidity in the lowest part of the troposphere should increase thermodynamic instability, allowing for stronger thunderstorm updrafts, vertical wind shear necessary for storm-scale rotation may decrease as the pole to equator temperature gradient weakens. The Mediterranean Sea is an important source for moisture that fuels thunderstorms in Italy, and it has been <span class="hlt">warming</span> faster than most water bodies in recent decades. The present study uses three methods to gain preliminary insight into the role that the <span class="hlt">warming</span> Mediterranean may have on tornadoes and thunderstorms with intense rainfall in Italy. First, a historical archive of Italian tornadoes has been updated for the 1990s, and it will be used along with other data from the European Severe Weather Database to discuss possible trends in tornado occurrence. Second, convection-allowing Weather Research and Forecasting (WRF) model simulations have been performed for three extreme <span class="hlt">events</span> to examine sensitivity to both the sea surface temperatures and other model parameters. These <span class="hlt">events</span> include a flash flood-producing storm <span class="hlt">event</span> near Milan, a non-tornadic severe hail <span class="hlt">event</span> in far northeastern Italy, and the Mira EF-4 tornado of July 2015. Sensitivities in rainfall amount, radar reflectivity and storm structure, and storm rotation will be discussed. Finally, changes in the frequency of intense mesoscale convective system <span class="hlt">events</span> in and near the Ligurian Sea, inferred from the presence of strong convergence lines in EXPRESS</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/15603531','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/15603531"><span>The extraordinary <span class="hlt">events</span> of the major, sudden stratospheric <span class="hlt">warming</span>, the diminutive antarctic ozone hole, and its split in 2002.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Varotsos, Costas</p> <p>2004-01-01</p> <p>Great interest in the unprecedented <span class="hlt">events</span> of the major, sudden stratospheric <span class="hlt">warming</span> and the ozone hole split over Antarctica in September 25, 2002 motivates a necessity to analyze the current understanding on the dynamics, chemistry and climate impacts that are associated with both <span class="hlt">events</span>. Significant progress in the analysis of the observational data obtained, as well as successful development and application of dynamical modeling, which have been achieved very recently, create a basis for the first survey on the role of the major, sudden stratospheric <span class="hlt">warming</span> observed in the southern hemisphere and its relationship to the diminutive Antarctic ozone hole and its break up into two parts. Special attention has been paid to assessments of the causes of the major <span class="hlt">warming</span> <span class="hlt">event</span> and the future expectations concerning the stratospheric ozone depletion effect. Among the principal results is the fact that, as the polar vortex elongated, it became hydrodynamically unstable, and this insta-, bility affected the upper troposphere and stratosphere. During the major, sudden stratospheric <span class="hlt">warming</span>, the middle stratospheric vortex split into two pieces; one piece rapidly mixed with extra vortex air, while the other returned to the pole as a much weaker and smaller vortex. The polar night jet was considerably weaker than normal, and was displaced more poleward than has been observed in previous winters, resulting from a series of wave <span class="hlt">events</span> (propagated from the troposphere) that took place over the course of the winter. Finally, the relative ozone decrease (increase) in the eastern Antarctic is tightly associated with westerly (easterly) zonal wind anomalies near the southern tip of South America, and the unusual behavior of the ozone hole in 2002 therefore appears to be caused by great easterlies in this region. The main conclusion is that the southern polar vortex and the diminutive ozone hole split into two parts in September 2002, due to the prevalence of very strong</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMGC43B1152K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMGC43B1152K"><span>Effects of soil <span class="hlt">warming</span> on CO2 efflux in tundra soil: Response to a 2015 episodic <span class="hlt">event</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kim, Y.; Park, S. J.; Kim, B. M.; Cho, M. H.; Suzuki, R.; Lee, B. Y.; Walsh, J. E.</p> <p>2016-12-01</p> <p>Soil carbon emission is vulnerable to changes in temperature, moisture, and the organic carbon stored in tundra soil. Emissions can therefore be affected by recent Arctic climate change and <span class="hlt">warming</span>. Here, we conducted soil CO2 efflux measurements in the tundra ecosystem of western Alaska, during the growing seasons of 2014 and 2015, in order to assess the effect of soil <span class="hlt">warming</span> on soil carbon emission from a 2015 episodic <span class="hlt">warming</span> <span class="hlt">event</span>. Soil carbon emissions were greater in 2015 than in 2014, resulting from 1) a dry growing season and lower soil moisture, 2) increases in TDDs (total degree days of above 0 °C) for soil temperature at deeper active layers of 50, 70, and 80-cm depths, 3) deeper thaw depth of the active layer, and 4) stronger PAR (photosynthetically active radiation) during the growing season of 2015. These findings demonstrate the response from the decomposability of old-aged organic carbon matter from naturally occurring increased soil temperature at a deeper active layer, and subsequently, enhanced soil carbon emission to the atmosphere (e.g., 9 % higher in 2015 than in 2014) during the growing season. The findings also imply that soil <span class="hlt">warming</span>-induced soil carbon emissions contribute an additional atmospheric carbon source and an accelerating positive feedback to climate change in the Arctic during the growing season.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25119027','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25119027"><span><span class="hlt">Abrupt</span> glacial climate shifts controlled by ice sheet changes.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zhang, Xu; Lohmann, Gerrit; Knorr, Gregor; Purcell, Conor</p> <p>2014-08-21</p> <p>During glacial periods of the Late Pleistocene, an abundance of proxy data demonstrates the existence of large and repeated millennial-scale <span class="hlt">warming</span> episodes, known as Dansgaard-Oeschger (DO) <span class="hlt">events</span>. This ubiquitous feature of rapid glacial climate change can be extended back as far as 800,000 years before present (BP) in the ice core record, and has drawn broad attention within the science and policy-making communities alike. Many studies have been dedicated to investigating the underlying causes of these changes, but no coherent mechanism has yet been identified. Here we show, by using a comprehensive fully coupled model, that gradual changes in the height of the Northern Hemisphere ice sheets (NHISs) can alter the coupled atmosphere-ocean system and cause rapid glacial climate shifts closely resembling DO <span class="hlt">events</span>. The simulated global climate responses--including <span class="hlt">abrupt</span> <span class="hlt">warming</span> in the North Atlantic, a northward shift of the tropical rainbelts, and Southern Hemisphere cooling related to the bipolar seesaw--are generally consistent with empirical evidence. As a result of the coexistence of two glacial ocean circulation states at intermediate heights of the ice sheets, minor changes in the height of the NHISs and the amount of atmospheric CO2 can trigger the rapid climate transitions via a local positive atmosphere-ocean-sea-ice feedback in the North Atlantic. Our results, although based on a single model, thus provide a coherent concept for understanding the recorded millennial-scale variability and <span class="hlt">abrupt</span> climate changes in the coupled atmosphere-ocean system, as well as their linkages to the volume of the intermediate ice sheets during glacials.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMSA13A2314L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMSA13A2314L"><span>Short period airglow temperature and emission rate oscillations in the high Arctic MLT region during stratospheric <span class="hlt">warming</span> <span class="hlt">events</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lederman, J. I.</p> <p>2015-12-01</p> <p>The airglow is a photochemical glow in the upper atmosphere that occurs in thin layers corresponding to different chemical processes. The O2 Atmospheric airglow layer exists at about 94 km altitude and the hydroxyl layer at about 87 km. The intensity of the light gives information about the concentration of atomic oxygen there, while the shape of the spectrum gives accurate values of the temperature. In this investigation, these are measured above Eureka in the Canadian Arctic (80N, 86W) using an instrument called SATI (Spectral Airglow Temperature Imager). The optical data are employed to characterize short period oscillations in rotational temperatures and integral emission rates of OH (6,2) Meinel and O2 (0,1) Atm. bands during a stratospheric <span class="hlt">warming</span> <span class="hlt">event</span> from January 2015. In this presentation, SATI observations coupled with wind radiosonde data at Eureka and the ECMWF model are used to compare the January 2015 <span class="hlt">warming</span> with the major stratospheric <span class="hlt">warming</span> <span class="hlt">event</span> of January 2009, thereby providing a window into high frequency atmospheric wave dynamics at play between altitudes of 20 km - 100 km.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AtmRe.168...33S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AtmRe.168...33S"><span>Changes in extreme temperature and precipitation <span class="hlt">events</span> in the Loess Plateau (China) during 1960-2013 under global <span class="hlt">warming</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sun, Wenyi; Mu, Xingmin; Song, Xiaoyan; Wu, Dan; Cheng, Aifang; Qiu, Bing</p> <p>2016-02-01</p> <p>In recent decades, extreme climatic <span class="hlt">events</span> have been a major issue worldwide. Regional assessments on various climates and geographic regions are needed for understanding uncertainties in extreme <span class="hlt">events</span>' responses to global <span class="hlt">warming</span>. The objective of this study was to assess the annual and decadal trends in 12 extreme temperature and 10 extreme precipitation indices in terms of intensity, frequency, and duration over the Loess Plateau during 1960-2013. The results indicated that the regionally averaged trends in temperature extremes were consistent with global <span class="hlt">warming</span>. The occurrence of <span class="hlt">warm</span> extremes, including summer days (SU), tropical nights (TR), <span class="hlt">warm</span> days (TX90), and nights (TN90) and a <span class="hlt">warm</span> spell duration indicator (WSDI), increased by 2.76 (P < 0.01), 1.24 (P < 0.01), 2.60 (P = 0.0003), 3.41 (P < 0.01), and 0.68 (P = 0.0041) days/decade during the period of 1960-2013, particularly, sharp increases in these indices occurred in 1985-2000. Over the same period, the occurrence of cold extremes, including frost days (FD), ice days (ID), cold days (TX10) and nights (TN10), and a cold spell duration indicator (CSDI) exhibited decreases of - 3.22 (P < 0.01), - 2.21 (P = 0.0028), - 2.71 (P = 0.0028), - 4.31 (P < 0.01), and - 0.69 (P = 0.0951) days/decade, respectively. Moreover, extreme <span class="hlt">warm</span> <span class="hlt">events</span> in most regions tended to increase while cold indices tended to decrease in the Loess Plateau, but the trend magnitudes of cold extremes were greater than those of <span class="hlt">warm</span> extremes. The growing season (GSL) in the Loess Plateau was lengthened at a rate of 3.16 days/decade (P < 0.01). Diurnal temperature range (DTR) declined at a rate of - 0.06 °C /decade (P = 0.0931). Regarding the precipitation indices, the annual total precipitation (PRCPTOT) showed no obvious trends (P = 0.7828). The regionally averaged daily rainfall intensity (SDII) exhibited significant decreases (- 0.14 mm/day/decade, P = 0.0158), whereas consecutive dry days (CDD) significantly increased (1.96 days</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28985232','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28985232"><span>Altered cropping pattern and cultural continuation with declined prosperity following <span class="hlt">abrupt</span> and extreme arid <span class="hlt">event</span> at ~4,200 yrs BP: Evidence from an Indus archaeological site Khirsara, Gujarat, western India.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Pokharia, Anil K; Agnihotri, Rajesh; Sharma, Shalini; Bajpai, Sunil; Nath, Jitendra; Kumaran, R N; Negi, Bipin Chandra</p> <p>2017-01-01</p> <p>Archaeological sites hold important clues to complex climate-human relationships of the past. Human settlements in the peripheral zone of Indus culture (Gujarat, western India) are of considerable importance in the assessment of past monsoon-human-subsistence-culture relationships and their survival thresholds against climatic stress exerted by <span class="hlt">abrupt</span> changes. During the mature phase of Harappan culture between ~4,600-3,900yrsBP, the ~4,100±100yrsBP time slice is widely recognized as one of the major, <span class="hlt">abrupt</span> arid-<span class="hlt">events</span> imprinted innumerous well-dated palaeo records. However, the veracity of this dry <span class="hlt">event</span> has not been established from any archaeological site representing the Indus (Harappan) culture, and issues concerning timing, changes in subsistence pattern, and the likely causes of eventual abandonment (collapse) continue to be debated. Here we show a significant change in crop-pattern (from barley-wheat based agriculture to 'drought-resistant' millet-based crops) at ~4,200 yrs BP, based on abundant macrobotanical remains and C isotopes of soil organic matter (δ13CSOM) in an archaeological site at Khirsara, in the Gujarat state of western India. The crop-change appears to be intentional and was likely used as an adaptation measure in response to deteriorated monsoonal conditions. The ceramic and architectural remains of the site indicate that habitation survived and continued after the ~4,200yrsBP dry climatic phase, but with declined economic prosperity. Switching to millet-based crops initially helped inhabitants to avoid immediate collapse due to climatic stresses, but continued aridity and altered cropping pattern led to a decline in prosperity levels of inhabitants and eventual abandonment of the site at the end of the mature Harappan phase.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AtmRe.195...31W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AtmRe.195...31W"><span>The relationship of lightning activity and short-duration rainfall <span class="hlt">events</span> during <span class="hlt">warm</span> seasons over the Beijing metropolitan region</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wu, Fan; Cui, Xiaopeng; Zhang, Da-Lin; Qiao, Lin</p> <p>2017-10-01</p> <p>The relationship between lightning activity and rainfall associated with 2925 short-duration rainfall (SDR) <span class="hlt">events</span> over the Beijing metropolitan region (BMR) is examined during the <span class="hlt">warm</span> seasons of 2006-2007, using the cloud-to-ground (CG) and intracloud (IC) lightning data from Surveillance et Alerte Foudre par Interférometrie Radioélectrique (SAFIR)-3000 and 5-min rainfall data from automatic weather stations (AWSs). An optimal radius of 10 km around selected AWSs is used to determine the lightning-rainfall relationship. The lightning-rainfall correlations vary significantly, depending upon the intensity of SDR <span class="hlt">events</span>. That is, correlation coefficient (R 0.7) for the short-duration heavy rainfall (SDHR, i.e., ≥ 20 mm h- 1) <span class="hlt">events</span> is found higher than that (R 0.4) for the weak SDR (i.e., 5-10 mm h- 1) <span class="hlt">events</span>, and lower percentage of the SDHR <span class="hlt">events</span> (< 10%) than the weak SDR <span class="hlt">events</span> (40-50%) are observed with few flashes. Significant time-lagged correlations between lightning and rainfall are also found. About 80% of the SDR <span class="hlt">events</span> could reach their highest correlation coefficients when the associated lightning flashes shift at time lags of < 25 min before and after rainfall begins. Those <span class="hlt">events</span> with lightning preceding rainfall account for 50-60% of the total SDR <span class="hlt">events</span>. Better lightning-rainfall correlations can be attained when time lags are incorporated, with the use of total (CG and IC) lightning data. These results appear to have important implications for improving the nowcast of SDHR <span class="hlt">events</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AdSpR..48.1631D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AdSpR..48.1631D"><span>Signatures of the Sudden Stratospheric <span class="hlt">Warming</span> <span class="hlt">events</span> of January-February 2008 in Seoul, S. Korea</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>De Wachter, Evelyn; Hocke, Klemens; Flury, Thomas; Scheiben, Dominik; Kämpfer, Niklaus; Ka, Soohyun; Oh, Jung Jin</p> <p>2011-11-01</p> <p>The period January-February 2008 was characterized by four Sudden Stratospheric <span class="hlt">Warmings</span> (SSWs) in the Northern Hemisphere, of which the last <span class="hlt">warming</span>, at the end of February 2008, was a major <span class="hlt">warming</span>. A significant decrease in mesospheric water vapour (H 2O) of more than 2 ppmv (˜40%) was observed by the ground-based microwave (GBMW) radiometer in Seoul, S. Korea [37.3°N, 126.3°E] during the major SSW. A comparison with ground-based mesospheric H 2O observations from the mid-latitude station in Bern [46.9°N, 7°E] revealed an anticorrelation in the mesospheric H 2O data during the major SSW. In addition, prior to the major <span class="hlt">warming</span>, strong periodic fluctuations were recorded in the Aura MLS vertical temperature distribution between 15 and 0.05 hPa at Seoul. The mesospheric temperature oscillation was found to have a period of ˜10-14 days with a persistency of 3-4 cycles. The observed anticorrelation in mesospheric H 2O between the stations in Seoul and Bern is associated with an increased meridional flow. Trajectory calculations give evidence that H 2O-rich subtropical air had moved to Bern during the major SSW while H 2O-poor polar air was transported to Seoul. The results shown in this study are a possible indication of a strong coupling between the dynamic regimes of the low- and the high-latitude regions during SSWs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2901456','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2901456"><span><span class="hlt">Abrupt</span> change of Antarctic moisture origin at the end of Termination II</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Masson-Delmotte, V.; Stenni, B.; Blunier, T.; Cattani, O.; Chappellaz, J.; Cheng, H.; Dreyfus, G.; Edwards, R. L.; Falourd, S.; Govin, A.; Kawamura, K.; Johnsen, S. J.; Jouzel, J.; Landais, A.; Lemieux-Dudon, B.; Lourantou, A.; Marshall, G.; Minster, B.; Mudelsee, M.; Pol, K.; Röthlisberger, R.; Selmo, E.; Waelbroeck, C.</p> <p>2010-01-01</p> <p>The deuterium excess of polar ice cores documents past changes in evaporation conditions and moisture origin. New data obtained from the European Project for Ice Coring in Antarctica Dome C East Antarctic ice core provide new insights on the sequence of <span class="hlt">events</span> involved in Termination II, the transition between the penultimate glacial and interglacial periods. This termination is marked by a north–south seesaw behavior, with first a slow methane concentration rise associated with a strong Antarctic temperature <span class="hlt">warming</span> and a slow deuterium excess rise. This first step is followed by an <span class="hlt">abrupt</span> north Atlantic <span class="hlt">warming</span>, an <span class="hlt">abrupt</span> resumption of the East Asian summer monsoon, a sharp methane rise, and a CO2 overshoot, which coincide within dating uncertainties with the end of Antarctic optimum. Here, we show that this second phase is marked by a very sharp Dome C centennial deuterium excess rise, revealing <span class="hlt">abrupt</span> reorganization of atmospheric circulation in the southern Indian Ocean sector. PMID:20566887</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010EGUGA..1210451G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010EGUGA..1210451G"><span>The examination of a downslope <span class="hlt">warming</span> wind <span class="hlt">event</span> over the Larsen Ice Shelf in Antarctica through modeling and aircraft observations.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Grosvenor, Daniel; Choularton, Thomas; King, John; Lachlan-Cope, Thomas</p> <p>2010-05-01</p> <p>During the last 50-60 years temperatures over the Antarctic Peninsula region have increased more rapidly than anywhere else in the southern hemisphere, at several times the global average rate. At one station, the near-surface <span class="hlt">warming</span> between 1951 and 2004 was 2.94 oC compared to a global average of 0.52 oC. However, the seasonal pattern of this regional <span class="hlt">warming</span> has varied with location, with the east side having <span class="hlt">warmed</span> more than the west in the autumn and summer seasons. This is important since the process of surface melting on the Larsen ice shelves, which are located on the east side, predominately occurs in summer. Crevasse propagation due to the weight of accumulated melt water is currently thought to have been the major factor in causing the catastrophic near-total disintegration of the Larsen B ice shelf in 2002, representing a loss of ice of area 3200 km2. The larger and more southerly Larsen C ice shelf could also suffer a similar fate if the <span class="hlt">warming</span> continues, with consequences for the ecology and for increased glacier flow, leading to sea level rise. The difference in <span class="hlt">warming</span> between the east and west side in these seasons is thought to have been driven by circulation changes that have led to increases in the strength of westerly winds. The high mountains of the Antarctic Peninsula provide a climatic barrier between the warmer oceanic air of the west and the cold continental air of the east. It has been suggested that increased westerlies allow <span class="hlt">warm</span> winds to cross to the east side more frequently. The <span class="hlt">warming</span> of westerly flow can also be enhanced by latent heat release on the upslope side and/or adiabatic descent of air from above, on the downslope side. In January 2006 the British Antarctic Survey performed an aircraft flight over the Larsen C ice shelf on the east side of the Peninsula, which sampled a strong downslope <span class="hlt">warming</span> wind <span class="hlt">event</span>. Surface flux measurements over the ice shelf suggest that the sensible heat provided by the <span class="hlt">warm</span> jets would be</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active"><span>10</span></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_10 --> <div id="page_11" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="201"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.A13E0319S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.A13E0319S"><span>Inter-annual Variability of Temperature and Extreme Heat <span class="hlt">Events</span> during the Nairobi <span class="hlt">Warm</span> Season</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Scott, A.; Misiani, H. O.; Zaitchik, B. F.; Ouma, G. O.; Anyah, R. O.; Jordan, A.</p> <p>2016-12-01</p> <p>Extreme heat <span class="hlt">events</span> significantly stress all organisms in the ecosystem, and are likely to be amplified in peri-urban and urban areas. Understanding the variability and drivers behind these <span class="hlt">events</span> is key to generating early warnings, yet in Equatorial East Africa, this information is currently unavailable. This study uses daily maximum and minimum temperature records from weather stations within Nairobi and its surroundings to characterize variability in daily minimum temperatures and the number of extreme heat <span class="hlt">events</span>. ERA-Interim reanalysis is applied to assess the drivers of these <span class="hlt">events</span> at <span class="hlt">event</span> and seasonal time scales. At seasonal time scales, high temperatures in Nairobi are a function of large scale climate variability associated with the Atlantic Multi-decadal Oscillation (AMO) and Global Mean Sea Surface Temperature (GMSST). Extreme heat <span class="hlt">events</span>, however, are more strongly associated with the El Nino Southern Oscillation (ENSO). For instance, the persistence of AMO and ENSO, in particular, provide a basis for seasonal prediction of extreme heat <span class="hlt">events</span>/days in Nairobi. It is also apparent that the temporal signal from extreme heat <span class="hlt">events</span> in tropics differs from classic heat wave definitions developed in the mid-latitudes, which suggests that a new approach for defining these <span class="hlt">events</span> is necessary for tropical regions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMSA41B2342A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMSA41B2342A"><span>Understanding the Role of Planetary Waves and Tides in Atmosphere-Ionosphere Coupling Processes During Sudden Stratospheric <span class="hlt">Warming</span> <span class="hlt">Events</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Azeem, S. I.</p> <p>2015-12-01</p> <p>Recent studies have shown variations in the ionosphere that are linked to changes in the underlying dynamic meteorology during Sudden Stratospheric <span class="hlt">Warming</span> (SSW) <span class="hlt">events</span>. In this paper, we present results from ASTRA's Ionospheric Data Assimilation Four-Dimensional (IDA4D) algorithm to compare and contrast ionospheric response to the 2009 and 2013 SSW <span class="hlt">events</span>. The ionospheric response in both years was characterized by above normal TECs during the day-time and below average TECs during the night-time. We compared the IDA4D results to highlight significant differences between the ionospheric responses to the 2009 and 2013 SSWs. The ionospheric anomaly during the 2009 SSW <span class="hlt">event</span> was primarily driven by the non-migrating semidiurnal tide. This is in contrast to the ionospheric variability seen during the 2013 SSW <span class="hlt">event</span> which exhibited a distinct structure of a migrating semidiurnal tide. These results pose a question as to whether these differences were due to the differences in tides generated in the lower atmosphere or in-situ forcing. We use measurements from the NASA Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics (TIMED) mission to understand the role of various upward atmospheric tides and planetary waves on the ionosphere during the 2009 and 2013 SSW <span class="hlt">events</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140011361','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140011361"><span>Sensitivity of the Atmospheric Response to <span class="hlt">Warm</span> Pool El Nino <span class="hlt">Events</span> to Modeled SSTs and Future Climate Forcings</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hurwitz, Margaret M.; Garfinkel, Chaim I.; Newman, Paul A.; Oman, Luke D.</p> <p>2013-01-01</p> <p><span class="hlt">Warm</span> pool El Nino (WPEN) <span class="hlt">events</span> are characterized by positive sea surface temperature (SST) anomalies in the central equatorial Pacific. Under present-day climate conditions, WPEN <span class="hlt">events</span> generate poleward propagating wavetrains and enhance midlatitude planetary wave activity, weakening the stratospheric polar vortices. The late 21st century extratropical atmospheric response to WPEN <span class="hlt">events</span> is investigated using the Goddard Earth Observing System Chemistry-Climate Model (GEOSCCM), version 2. GEOSCCM simulations are forced by projected late 21st century concentrations of greenhouse gases (GHGs) and ozone-depleting substances (ODSs) and by SSTs and sea ice concentrations from an existing ocean-atmosphere simulation. Despite known ocean-atmosphere model biases, the prescribed SST fields represent a best estimate of the structure of late 21st century WPEN <span class="hlt">events</span>. The future Arctic vortex response is qualitatively similar to that observed in recent decades but is weaker in late winter. This response reflects the weaker SST forcing in the Nino 3.4 region and subsequently weaker Northern Hemisphere tropospheric teleconnections. The Antarctic stratosphere does not respond to WPEN <span class="hlt">events</span> in a future climate, reflecting a change in tropospheric teleconnections: The meridional wavetrain weakens while a more zonal wavetrain originates near Australia. Sensitivity simulations show that a strong poleward wavetrain response to WPEN requires a strengthening and southeastward extension of the South Pacific Convergence Zone; this feature is not captured by the late 21st century modeled SSTs. Expected future increases in GHGs and decreases in ODSs do not affect the polar stratospheric responses to WPEN.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/20159396','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/20159396"><span>The impact of <span class="hlt">warm</span> weather on mass <span class="hlt">event</span> medical need: a review of the literature.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Baird, Matthew B; O'Connor, Robert E; Williamson, Allen L; Sojka, Benjamin; Alibertis, Kostas; Brady, William J</p> <p>2010-02-01</p> <p>Over the last 20 years, interest in medical need at mass <span class="hlt">events</span> has increased. Many studies have been published identifying the characteristics of such <span class="hlt">events</span> that significantly impact the number of patients who seek care. Investigators agree that weather is one of the most important variables. We performed a literature search using several biomedical databases (MEDLINE via PubMed, the Cochrane database, BMJ's Clinical Evidence compendium, and Google Scholar) for articles addressing the effect of weather on medical need at mass <span class="hlt">events</span>. This search resulted in 8 focused articles and several other resources from the reference sections of these publications. We found that the early literature is composed of case reports and predominantly subjective observations concerning the impact of weather on medical need. Most investigators agree upon a positive relationship between heat/humidity and the frequency of patient presentation. More recent authors make attempts at quantifying the relationship and propose prediction models for patient volume and medical personnel requirements. We present an ancestral review of these studies, discuss their results collectively, and propose a simplified algorithm for predicting patient volume at mass <span class="hlt">events</span>. This review is intended for <span class="hlt">event</span> planners and mass <span class="hlt">event</span> emergency medical personnel for planning future <span class="hlt">events</span>. We also hope to stimulate further study to develop and verify prediction models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1912525R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1912525R"><span>Towards Greenland Glaciation: cumulative or <span class="hlt">abrupt</span> transition?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ramstein, Gilles; Tan, Ning; Ladant, Jean-baptiste; Dumas, Christophe; Contoux, Camille</p> <p>2017-04-01</p> <p>During the mid-Pliocene <span class="hlt">warming</span> period (3-3.3 Ma BP), the global annual mean temperatures inferred by data and model studies were 2-3° warmer than pre-industrial values. Accordingly, Greenland ice sheet volume is supposed to reach at the most, only half of that of present-day [Haywood et al. 2010]. Around 2.7-2.6 Ma BP, just ˜ 500 kyr after the <span class="hlt">warming</span> peak of mid-Pliocene, the Greenland ice sheet has reached its full size [Lunt et al. 2008]. A crucial question concerns the evolution of the Greenland ice sheet from half to full size during the 3 - 2.5 Ma period. Data show a decreasing trend of atmospheric CO2 concentration from 3 Ma to 2.5 Ma [Seki et al.2010; Bartoli et al. 2011; Martinez et al. 2015]. However, a recent study [Contoux et al. 2015] suggests that a lowering of CO2 is not sufficient to initiate a perennial glaciation on Greenland and must be combined with low summer insolation to preserve the ice sheet during insolation maxima. This suggests rather a cumulative process than an <span class="hlt">abrupt</span> <span class="hlt">event</span>. In order to diagnose the evolution of the ice sheet build-up, we carry on, for the first time, a transient simulation of climate and ice sheet evolutions from 3 Ma to 2.5 Ma. This strategy enables us to investigate the waxing and waning of the ice sheet during several orbital cycles. We use a tri-dimensional interpolation method designed by Ladant et al. (2014), which allows the evolution of CO2 concentration and of orbital parameters, and the evolution of the Greenland ice sheet size to be taken into account. By interpolating climatic snapshot simulations ran with various possible combinations of CO2, orbits and ice sheet sizes, we can build a continuous climatic forcing that is then used to provide 500 kyrs-long ice sheet simulations. With such a tool, we may offer a physically based answer to different CO2 reconstructions scenarios and analyse which one is the most consistent with Greenland ice sheet buildup.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AtmEn.140...60S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AtmEn.140...60S"><span>Nucleation <span class="hlt">events</span> at a coastal city during the <span class="hlt">warm</span> period: Kerbside versus urban background measurements</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Siakavaras, D.; Samara, C.; Petrakakis, M.; Biskos, G.</p> <p>2016-09-01</p> <p>Number size distributions of atmospheric aerosol particles were simultaneously measured at a kerbside and an urban background site in the city of Thessaloniki, Greece, from June to October 2009. New particle formation <span class="hlt">events</span> were observed ca. 27% of the days at the urban kerbside site and 29% of the days at the urban background site. In almost all the cases the <span class="hlt">events</span> started between 10:00 and 12:00, and continued for several hours. The total number concentration (TNC) of the particles having diameters from 10 to ca. 500 nm during the <span class="hlt">events</span> increased from 1.4 × 104 to 6.5 × 104 #/cm3 at the urban kerbside site, and from 0.2 × 104 to 2.4 × 104 #/cm3 at the urban background site. At the urban kerbside site, 9% of the days exhibited class I <span class="hlt">events</span> (i.e., <span class="hlt">events</span> followed by a clear growth of the newly formed particles), 10% class II (i.e., <span class="hlt">events</span> during which the concentration of nucleation mode particles were high but their growth was not continuous), 67% were characterised as non-<span class="hlt">event</span> days, and 14% of the days exhibited no clear particle formation pattern (undefined). At the urban background site, 15% of the days were classified as class I, 5% as class II, 75% of the days showed no nucleation, whereas only 5% of the days were undefined. While the fraction of <span class="hlt">event</span> days (both class I and class II) at both sites was similar (ca. 20%), the higher fraction of class I <span class="hlt">events</span> observed at Eptapyrgio can be attributed to the cleaner environment of the urban background site that allows better identification of the particle concentration increase. The nucleation bursts show a similar pattern at both sites, with the newly formed particles reaching a final size of ca. 80-100 nm. A distinct difference between the two stations was that the smallest particles observed during the new-particle formation <span class="hlt">events</span> had a diameter of ca. 10 nm (i.e., the smallest particles we could observe) at the kerbside site and ca. 20 nm at the urban background site. This is an indication that</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1997GeoRL..24.2303T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1997GeoRL..24.2303T"><span>Freezing of polar stratospheric clouds in orographically induced strong <span class="hlt">warming</span> <span class="hlt">events</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tsias, A.; Prenni, A. J.; Carslaw, K. S.; Onasch, T. P.; Luo, B. P.; Tolbert, M. A.; Peter, Th.</p> <p>1997-09-01</p> <p>Results from laboratory experiments and microphysical modeling are presented that suggest a potential freezing nucleation mechanism for polar stratospheric cloud (PSC) particles above the water ice frost point (Tice). The mechanism requires very high HNO3 concentrations of about 58 wt% in the droplets, and leads to the freezing of nitric acid dihydrate (NAD) in a highly selective manner in the smallest droplets of an ensemble. In the stratosphere such liquid compositions are predicted to occur in aerosol droplets which are <span class="hlt">warmed</span> adiabatically with rates of about +150 K/h from below 190 K to 194 K. Such rapid temperature changes have been observed in mountain leewaves that occur frequently in the stratosphere, clearly demonstrating the need for a stratospheric gravity wave climatology.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GeoRL..43.2192P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GeoRL..43.2192P"><span>Southern Ocean deep convection as a driver of Antarctic <span class="hlt">warming</span> <span class="hlt">events</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pedro, J. B.; Martin, T.; Steig, E. J.; Jochum, M.; Park, W.; Rasmussen, S. O.</p> <p>2016-03-01</p> <p>Simulations with a free-running coupled climate model show that heat release associated with Southern Ocean deep convection variability can drive centennial-scale Antarctic temperature variations of up to 2.0°C. The mechanism involves three steps: Preconditioning: heat accumulates at depth in the Southern Ocean; Convection onset: wind and/or sea ice changes tip the buoyantly unstable system into the convective state; and Antarctic <span class="hlt">warming</span>: fast sea ice-albedo feedbacks (on annual-decadal time scales) and slow Southern Ocean frontal and sea surface temperature adjustments to convective heat release (on multidecadal-century time scales) drive an increase in atmospheric heat and moisture transport toward Antarctica. We discuss the potential of this mechanism to help drive and amplify climate variability as observed in Antarctic ice core records.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4823715','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4823715"><span>Dynamics of 2013 Sudden Stratospheric <span class="hlt">Warming</span> <span class="hlt">event</span> and its impact on cold weather over Eurasia: Role of planetary wave reflection</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Nath, Debashis; Chen, Wen; Zelin, Cai; Pogoreltsev, Alexander Ivanovich; Wei, Ke</p> <p>2016-01-01</p> <p>In the present study, we investigate the impact of stratospheric planetary wave reflection on tropospheric weather over Central Eurasia during the 2013 Sudden Stratospheric <span class="hlt">Warming</span> (SSW) <span class="hlt">event</span>. We analyze EP fluxes and Plumb wave activity fluxes to study the two and three dimensional aspects of wave propagation, respectively. The 2013 SSW <span class="hlt">event</span> is excited by the combined influence of wavenumber 1 (WN1) and wavenumber 2 (WN2) planetary waves, which makes the <span class="hlt">event</span> an unusual one and seems to have significant impact on tropospheric weather regime. We observe an extraordinary development of a ridge over the Siberian Tundra and the North Pacific during first development stage (last week of December 2012) and later from the North Atlantic in the second development stage (first week of January 2013), and these waves appear to be responsible for the excitation of the WN2 pattern during the SSW. The wave packets propagated upward and were then reflected back down to central Eurasia due to strong negative wind shear in the upper stratospheric polar jet, caused by the SSW <span class="hlt">event</span>. Waves that propagated downward led to the formation of a deep trough over Eurasia and brought extreme cold weather over Kazakhstan, the Southern part of Russia and the Northwestern part of China during mid-January 2013. PMID:27051997</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016NatSR...624174N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016NatSR...624174N"><span>Dynamics of 2013 Sudden Stratospheric <span class="hlt">Warming</span> <span class="hlt">event</span> and its impact on cold weather over Eurasia: Role of planetary wave reflection</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nath, Debashis; Chen, Wen; Zelin, Cai; Pogoreltsev, Alexander Ivanovich; Wei, Ke</p> <p>2016-04-01</p> <p>In the present study, we investigate the impact of stratospheric planetary wave reflection on tropospheric weather over Central Eurasia during the 2013 Sudden Stratospheric <span class="hlt">Warming</span> (SSW) <span class="hlt">event</span>. We analyze EP fluxes and Plumb wave activity fluxes to study the two and three dimensional aspects of wave propagation, respectively. The 2013 SSW <span class="hlt">event</span> is excited by the combined influence of wavenumber 1 (WN1) and wavenumber 2 (WN2) planetary waves, which makes the <span class="hlt">event</span> an unusual one and seems to have significant impact on tropospheric weather regime. We observe an extraordinary development of a ridge over the Siberian Tundra and the North Pacific during first development stage (last week of December 2012) and later from the North Atlantic in the second development stage (first week of January 2013), and these waves appear to be responsible for the excitation of the WN2 pattern during the SSW. The wave packets propagated upward and were then reflected back down to central Eurasia due to strong negative wind shear in the upper stratospheric polar jet, caused by the SSW <span class="hlt">event</span>. Waves that propagated downward led to the formation of a deep trough over Eurasia and brought extreme cold weather over Kazakhstan, the Southern part of Russia and the Northwestern part of China during mid-January 2013.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27051997','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27051997"><span>Dynamics of 2013 Sudden Stratospheric <span class="hlt">Warming</span> <span class="hlt">event</span> and its impact on cold weather over Eurasia: Role of planetary wave reflection.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Nath, Debashis; Chen, Wen; Zelin, Cai; Pogoreltsev, Alexander Ivanovich; Wei, Ke</p> <p>2016-04-07</p> <p>In the present study, we investigate the impact of stratospheric planetary wave reflection on tropospheric weather over Central Eurasia during the 2013 Sudden Stratospheric <span class="hlt">Warming</span> (SSW) <span class="hlt">event</span>. We analyze EP fluxes and Plumb wave activity fluxes to study the two and three dimensional aspects of wave propagation, respectively. The 2013 SSW <span class="hlt">event</span> is excited by the combined influence of wavenumber 1 (WN1) and wavenumber 2 (WN2) planetary waves, which makes the <span class="hlt">event</span> an unusual one and seems to have significant impact on tropospheric weather regime. We observe an extraordinary development of a ridge over the Siberian Tundra and the North Pacific during first development stage (last week of December 2012) and later from the North Atlantic in the second development stage (first week of January 2013), and these waves appear to be responsible for the excitation of the WN2 pattern during the SSW. The wave packets propagated upward and were then reflected back down to central Eurasia due to strong negative wind shear in the upper stratospheric polar jet, caused by the SSW <span class="hlt">event</span>. Waves that propagated downward led to the formation of a deep trough over Eurasia and brought extreme cold weather over Kazakhstan, the Southern part of Russia and the Northwestern part of China during mid-January 2013.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/12528824','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/12528824"><span>Mechanical transmission of porcine reproductive and respiratory syndrome virus throughout a coordinated sequence of <span class="hlt">events</span> during <span class="hlt">warm</span> weather.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Dee, Scott; Deen, John; Rossow, Kurt; Weise, Carrie; Eliason, Roger; Otake, Satoshi; Joo, Han Soo; Pijoan, Carlos</p> <p>2003-01-01</p> <p>Mechanical transmission of porcine reproductive and respiratory syndrome virus (PRRSV) throughout a coordinated sequence of <span class="hlt">events</span> that replicated common farm worker behavior during <span class="hlt">warm</span> weather (10 degrees C to 16 degrees C) was assessed using a field-based model. The model involved fomites (boots and containers), vehicle sanitation, transport, and personnel movement. In a previous study, the model successfully demonstrated mechanical transmission of PRRSV in 8 out of 10 replicates during cold weather. A field strain of PRRSV was inoculated into carriers consisting of soil samples, which were adhered to the undercarriage of a vehicle. The vehicle was driven approximately 50 km to a commercial truck washing facility where the driver's boots contacted the carriers during washing, introducing the virus to the vehicle interior. The vehicle was then driven 50 km to a simulated farm site, and the driver's boots mechanically spread virus into the farm anteroom. Types of containers frequently employed in swine farms contacted drippings from the footwear on the anteroom floor. The truck wash floor, vehicle cab floor mats, boot soles, anteroom floor, and the ventral surface of containers were sampled to track the virus throughout the model. Ten replicates were conducted, along with sham-inoculated controls, and control replicates. In 2 replicates, infectious PRRSV was detected on the anteroom floor and in 1 replicate, infectious PRRSV was detected on the surface of the container by swine bioassay. All sham-inoculated controls and protocol controls were negative. These results indicate that mechanical transmission of PRRSV throughout a coordinated sequence of <span class="hlt">events</span> in <span class="hlt">warm</span> weather can occur, but in contrast to data from studies conducted during cold weather, it appears to be a relatively infrequent <span class="hlt">event</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..1513981A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..1513981A"><span>Thermokarst processes in west-European loess series: new evidences for rapid climatic <span class="hlt">warming</span> <span class="hlt">events</span> during the Last Glacial</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Antoine, Pierre; Moine, Olivier; Didier Rousseau, Denis; Hatté, Christine</p> <p>2013-04-01</p> <p>For a long time, the imprint of millennial climatic cycles (D/O cycles) in the Last Glacial loess sequences has been related to the alternation of loess layers and arctic brown soil horizons, especially between about 60 and 30 ka BP (± MIS 3). Nevertheless, owing to erosion gaps and strong reductions in the sedimentation rate, there are always less individual soil horizons than D/O cycles during the same period, which makes correlations very difficult. The discovery in the Nussloch loess sequence (Germany) of a thermokarst structure including well preserved vegetal remains, mollusc shells, and relicts of former ice wedge casts, provides new evidences for a rapid climatic <span class="hlt">warming</span> at the origin of a major erosion <span class="hlt">event</span> during the Middle Pleniglacial (±MIS 3). This elongated thermokarst erosion gully incised the underlying deposits. The presence of deformed ice-wedge relicts along its very sharp and irregular lower boundary indicates a formation by thermal erosion linked to a rapid melting of the permafrost ice. The analysis of the biological data (vegetal remains and mollusc shells) allows to evidence interstadial conditions strongly contrasting with the over- and underlying loess environments. Radiocarbon dates from wood remains (average 32.26 14C / ± 37.7 cal. BP) allow the correlation of the main thermokarst formation and infilling with GIS-8 from the GRIP ice core, following H4 <span class="hlt">event</span>. Similar structures have been evidenced in other west-European loess sequences, most of them at the base of the Middle Pleniglacial formations. On the basis of a comparison with present day analogues from Alaska and Siberia permafrost areas, past "thermokarst <span class="hlt">events</span>" are related to thermal erosion processes and proposed as markers for rapid <span class="hlt">warming</span> periods in Last Glacial European loess sequences.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/12695904','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/12695904"><span>Dominant cold desert plants do not partition <span class="hlt">warm</span> season precipitation by <span class="hlt">event</span> size.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Schwinning, Susanne; Starr, Benjamin I; Ehleringer, James R</p> <p>2003-07-01</p> <p>We conducted experiments to examine the quantitative relationships between rainfall <span class="hlt">event</span> size and rainwater uptake and use by four common native plant species of the Colorado Plateau, including two perennial grasses, Hilaria jamesii (C(4)) and Oryzopsis hymenoides (C(3)), and two shrubs, Ceratoides lanata (C(3)), and Gutierrezia sarothrae (C(3)). Specifically, we tested the hypothesis that grasses use small rainfall <span class="hlt">events</span> more efficiently than shrubs and lose this advantage when <span class="hlt">events</span> are large. Rainfall <span class="hlt">events</span> between 2 and 20 mm were simulated in spring and summer by applying pulses of deuterium-labeled irrigation water. Afterwards, pulse water fractions in stems and the rates of leaf gas exchange were monitored for 9 days. Cumulative pulse water uptake over this interval (estimated by integrating the product of pulse fraction in stem water and daytime transpiration rate over time) was approximately linearly related to the amount of pulse water added to the ground in all four species. Across species, consistently more pulse water was taken up in summer than in spring. Relative to their leaf areas, the two grass species took up more pulse water than the two shrub species, across all <span class="hlt">event</span> sizes and in both seasons, thus refuting the initial hypothesis. In spring, pulse water uptake did not significantly increase photosynthetic rates and in summer, pulse water uptake had similar, but relatively small effects on the photosynthetic rates of the three C(3) plants, and a larger effect on the C(4) plant H. jamesii. Based on these data, we introduce an alternative hypothesis for the responses of plant functional types to rainfall <span class="hlt">events</span> of different sizes, building on cost-benefit considerations for active physiological responses to sudden, unpredictable changes in water availability.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70159608','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70159608"><span>Dynamic response of desert wetlands to <span class="hlt">abrupt</span> climate change</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Springer, Kathleen; Manker, Craig; Pigati, Jeff</p> <p>2015-01-01</p> <p>Desert wetlands are keystone ecosystems in arid environments and are preserved in the geologic record as groundwater discharge (GWD) deposits. GWD deposits are inherently discontinuous and stratigraphically complex, which has limited our understanding of how desert wetlands responded to past episodes of rapid climate change. Previous studies have shown that wetlands responded to climate change on glacial to interglacial timescales, but their sensitivity to short-lived climate perturbations is largely unknown. Here, we show that GWD deposits in the Las Vegas Valley (southern Nevada, United States) provide a detailed and nearly complete record of dynamic hydrologic changes during the past 35 ka (thousands of calibrated 14C years before present), including cycles of wetland expansion and contraction that correlate tightly with climatic oscillations recorded in the Greenland ice cores. Cessation of discharge associated with rapid <span class="hlt">warming</span> <span class="hlt">events</span> resulted in the collapse of entire wetland systems in the Las Vegas Valley at multiple times during the late Quaternary. On average, drought-like conditions, as recorded by widespread erosion and the formation of desert soils, lasted for a few centuries. This record illustrates the vulnerability of desert wetland flora and fauna to <span class="hlt">abrupt</span> climate change. It also shows that GWD deposits can be used to reconstruct paleohydrologic conditions at millennial to submillennial timescales and informs conservation efforts aimed at protecting these fragile ecosystems in the face of anthropogenic <span class="hlt">warming</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4664373','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4664373"><span>Dynamic response of desert wetlands to <span class="hlt">abrupt</span> climate change</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Springer, Kathleen B.; Manker, Craig R.; Pigati, Jeffrey S.</p> <p>2015-01-01</p> <p>Desert wetlands are keystone ecosystems in arid environments and are preserved in the geologic record as groundwater discharge (GWD) deposits. GWD deposits are inherently discontinuous and stratigraphically complex, which has limited our understanding of how desert wetlands responded to past episodes of rapid climate change. Previous studies have shown that wetlands responded to climate change on glacial to interglacial timescales, but their sensitivity to short-lived climate perturbations is largely unknown. Here, we show that GWD deposits in the Las Vegas Valley (southern Nevada, United States) provide a detailed and nearly complete record of dynamic hydrologic changes during the past 35 ka (thousands of calibrated 14C years before present), including cycles of wetland expansion and contraction that correlate tightly with climatic oscillations recorded in the Greenland ice cores. Cessation of discharge associated with rapid <span class="hlt">warming</span> <span class="hlt">events</span> resulted in the collapse of entire wetland systems in the Las Vegas Valley at multiple times during the late Quaternary. On average, drought-like conditions, as recorded by widespread erosion and the formation of desert soils, lasted for a few centuries. This record illustrates the vulnerability of desert wetland flora and fauna to <span class="hlt">abrupt</span> climate change. It also shows that GWD deposits can be used to reconstruct paleohydrologic conditions at millennial to submillennial timescales and informs conservation efforts aimed at protecting these fragile ecosystems in the face of anthropogenic <span class="hlt">warming</span>. PMID:26554007</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26554007','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26554007"><span>Dynamic response of desert wetlands to <span class="hlt">abrupt</span> climate change.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Springer, Kathleen B; Manker, Craig R; Pigati, Jeffrey S</p> <p>2015-11-24</p> <p>Desert wetlands are keystone ecosystems in arid environments and are preserved in the geologic record as groundwater discharge (GWD) deposits. GWD deposits are inherently discontinuous and stratigraphically complex, which has limited our understanding of how desert wetlands responded to past episodes of rapid climate change. Previous studies have shown that wetlands responded to climate change on glacial to interglacial timescales, but their sensitivity to short-lived climate perturbations is largely unknown. Here, we show that GWD deposits in the Las Vegas Valley (southern Nevada, United States) provide a detailed and nearly complete record of dynamic hydrologic changes during the past 35 ka (thousands of calibrated (14)C years before present), including cycles of wetland expansion and contraction that correlate tightly with climatic oscillations recorded in the Greenland ice cores. Cessation of discharge associated with rapid <span class="hlt">warming</span> <span class="hlt">events</span> resulted in the collapse of entire wetland systems in the Las Vegas Valley at multiple times during the late Quaternary. On average, drought-like conditions, as recorded by widespread erosion and the formation of desert soils, lasted for a few centuries. This record illustrates the vulnerability of desert wetland flora and fauna to <span class="hlt">abrupt</span> climate change. It also shows that GWD deposits can be used to reconstruct paleohydrologic conditions at millennial to submillennial timescales and informs conservation efforts aimed at protecting these fragile ecosystems in the face of anthropogenic <span class="hlt">warming</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMSA23A2036S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMSA23A2036S"><span>Daily Variations of Lower Thermospheric Tides at Middle Latitude and Their Association with Sudden Stratospheric <span class="hlt">Warming</span> <span class="hlt">Events</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Steeves, R.; Goncharenko, L. P.</p> <p>2013-12-01</p> <p>Sudden Stratospheric <span class="hlt">Warming</span> (SSW) <span class="hlt">events</span> have been shown by both observations and model results to couple the polar stratosphere to the low latitude ionosphere. Studies have suggested that a partial driver of the connection is the amplification of tides due to the SSW that reaches maximum at mid-latitudes. This study aims to increase the understanding of the coupling processes at mid-latitudes to establish possible SSW effects on dominant tidal structures. We utilize lower thermospheric (100-130 km) data collected from the Millstone Hill Incoherent Scatter Radar (ISR) (42.6N, 288.5E) during the Northern Hemispheric winter experimental campaigns classified as either SSW <span class="hlt">events</span> or non-SSW <span class="hlt">events</span>. The campaign set is comprised of two SSW <span class="hlt">events</span>, one minor and one major, along with three non-SSW <span class="hlt">events</span>. We also examine environmental characteristics such as temperature, zonal wind, and planetary wave activity (zonal wave numbers 1 and 2) from National Center for Environmental Prediction (NCEP) data for each campaign to distinguish any noteworthy characteristics. Comparison of the campaigns concentrates on the amplitudes and phases in the zonal and meridional winds. The altitudes of analysis lie in the range between 100 km and 124 km where the dominant tides were extracted at 3 km increments. Dominant tidal structures are the 12-hour tide and 6-hour tide, indicated by the Lomb-Scargle spectral analysis. The study focuses on these tides to show differences between campaigns and daily variations. A common trend found among the campaigns, both SSW and non-SSW <span class="hlt">events</span>, is large day-to-day variability and evidence of oscillations with periods on the order of 2-4 days. Differences in phases show the most distinction between campaign subsets, especially in the meridional component.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/20962843','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/20962843"><span>Continental <span class="hlt">warming</span> preceding the Palaeocene-Eocene thermal maximum.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Secord, Ross; Gingerich, Philip D; Lohmann, Kyger C; Macleod, Kenneth G</p> <p>2010-10-21</p> <p>Marine and continental records show an <span class="hlt">abrupt</span> negative shift in carbon isotope values at ∼55.8 Myr ago. This carbon isotope excursion (CIE) is consistent with the release of a massive amount of isotopically light carbon into the atmosphere and was associated with a dramatic rise in global temperatures termed the Palaeocene-Eocene thermal maximum (PETM). Greenhouse gases released during the CIE, probably including methane, have often been considered the main cause of PETM <span class="hlt">warming</span>. However, some evidence from the marine record suggests that <span class="hlt">warming</span> directly preceded the CIE, raising the possibility that the CIE and PETM may have been linked to earlier <span class="hlt">warming</span> with different origins. Yet pre-CIE <span class="hlt">warming</span> is still uncertain. Disentangling the sequence of <span class="hlt">events</span> before and during the CIE and PETM is important for understanding the causes of, and Earth system responses to, <span class="hlt">abrupt</span> climate change. Here we show that continental <span class="hlt">warming</span> of about 5 °C preceded the CIE in the Bighorn Basin, Wyoming. Our evidence, based on oxygen isotopes in mammal teeth (which reflect temperature-sensitive fractionation processes) and other proxies, reveals a marked temperature increase directly below the CIE, and again in the CIE. Pre-CIE <span class="hlt">warming</span> is also supported by a negative amplification of δ(13)C values in soil carbonates below the CIE. Our results suggest that at least two sources of <span class="hlt">warming</span>-the earlier of which is unlikely to have been methane-contributed to the PETM.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016NatSR...622543M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016NatSR...622543M"><span>Linkage Between Hourly Precipitation <span class="hlt">Events</span> and Atmospheric Temperature Changes over China during the <span class="hlt">Warm</span> Season</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Miao, Chiyuan; Sun, Qiaohong; Borthwick, Alistair G. L.; Duan, Qingyun</p> <p>2016-03-01</p> <p>We investigated changes in the temporospatial features of hourly precipitation during the <span class="hlt">warm</span> season over mainland China. The frequency and amount of hourly precipitation displayed latitudinal zonation, especially for light and moderate precipitation, which showed successive downward change over time in northeastern and southern China. Changes in the precipitation amount resulted mainly from changes in frequency rather than changes in intensity. We also evaluated the linkage between hourly precipitation and temperature variations and found that hourly precipitation extreme was more sensitive to temperature than other categories of precipitation. A strong dependency of hourly precipitation on temperature occurred at temperatures colder than the median daily temperature; in such cases, regression slopes were greater than the Clausius-Clapeyron (C-C) relation of 7% per degree Celsius. Regression slopes for 31.6%, 59.8%, 96.9%, and 99.1% of all stations were greater than 7% per degree Celsius for the 75th, 90th, 99th, and 99.9th percentiles for precipitation, respectively. The mean regression slopes within the 99.9th percentile of precipitation were three times the C-C rate. Hourly precipitation showed a strong negative relationship with daily maximum temperature and the diurnal temperature range at most stations, whereas the equivalent correlation for daily minimum temperature was weak.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_11 --> <div id="page_12" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="221"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4773837','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4773837"><span>Linkage Between Hourly Precipitation <span class="hlt">Events</span> and Atmospheric Temperature Changes over China during the <span class="hlt">Warm</span> Season</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Miao, Chiyuan; Sun, Qiaohong; Borthwick, Alistair G. L.; Duan, Qingyun</p> <p>2016-01-01</p> <p>We investigated changes in the temporospatial features of hourly precipitation during the <span class="hlt">warm</span> season over mainland China. The frequency and amount of hourly precipitation displayed latitudinal zonation, especially for light and moderate precipitation, which showed successive downward change over time in northeastern and southern China. Changes in the precipitation amount resulted mainly from changes in frequency rather than changes in intensity. We also evaluated the linkage between hourly precipitation and temperature variations and found that hourly precipitation extreme was more sensitive to temperature than other categories of precipitation. A strong dependency of hourly precipitation on temperature occurred at temperatures colder than the median daily temperature; in such cases, regression slopes were greater than the Clausius-Clapeyron (C-C) relation of 7% per degree Celsius. Regression slopes for 31.6%, 59.8%, 96.9%, and 99.1% of all stations were greater than 7% per degree Celsius for the 75th, 90th, 99th, and 99.9th percentiles for precipitation, respectively. The mean regression slopes within the 99.9th percentile of precipitation were three times the C-C rate. Hourly precipitation showed a strong negative relationship with daily maximum temperature and the diurnal temperature range at most stations, whereas the equivalent correlation for daily minimum temperature was weak. PMID:26931350</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26931350','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26931350"><span>Linkage Between Hourly Precipitation <span class="hlt">Events</span> and Atmospheric Temperature Changes over China during the <span class="hlt">Warm</span> Season.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Miao, Chiyuan; Sun, Qiaohong; Borthwick, Alistair G L; Duan, Qingyun</p> <p>2016-03-02</p> <p>We investigated changes in the temporospatial features of hourly precipitation during the <span class="hlt">warm</span> season over mainland China. The frequency and amount of hourly precipitation displayed latitudinal zonation, especially for light and moderate precipitation, which showed successive downward change over time in northeastern and southern China. Changes in the precipitation amount resulted mainly from changes in frequency rather than changes in intensity. We also evaluated the linkage between hourly precipitation and temperature variations and found that hourly precipitation extreme was more sensitive to temperature than other categories of precipitation. A strong dependency of hourly precipitation on temperature occurred at temperatures colder than the median daily temperature; in such cases, regression slopes were greater than the Clausius-Clapeyron (C-C) relation of 7% per degree Celsius. Regression slopes for 31.6%, 59.8%, 96.9%, and 99.1% of all stations were greater than 7% per degree Celsius for the 75th, 90th, 99th, and 99.9th percentiles for precipitation, respectively. The mean regression slopes within the 99.9th percentile of precipitation were three times the C-C rate. Hourly precipitation showed a strong negative relationship with daily maximum temperature and the diurnal temperature range at most stations, whereas the equivalent correlation for daily minimum temperature was weak.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22524630','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22524630"><span>Seasonal variation in placental <span class="hlt">abruption</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Mankita, Ronen; Friger, Michael; Pariente, Gali; Sheiner, Eyal</p> <p>2012-11-01</p> <p>To characterize seasonal patterns of placental <span class="hlt">abruption</span> among Jewish and Bedouin parturients in the Southern part of Israel. A retrospective population-based study comparing all singleton pregnancies of patients with and without placental <span class="hlt">abruption</span> was conducted. Deliveries occurred between the years 1988 and 2010. A 'classical' model of time series was used, allowing to assess trend and periodic patterns of placental <span class="hlt">abruption</span>. During the study period, 241,408 deliveries took place, of which 1685 (0.7%) were complicated with placental <span class="hlt">abruption</span>. Placental <span class="hlt">abruption</span> was significantly more common among Bedouin parturients: 0.77% (n = 948) vs. 0.623% (n = 737), p < 0.001. A non-linear negative correlation was noted in the incidence of placental <span class="hlt">abruption</span> (coefficient = -0.002) during the entire study period. Time series analysis demonstrated annual cycle frequency, seasonal cycle and weekly cycle of placental <span class="hlt">abruption</span>. The seasonal incidence of placental <span class="hlt">abruption</span> was higher during spring (B = 7.15) and lower during summer (reference) for both populations (Jewish and Bedouins). Weekly cycle showed significantly higher incidence on Saturday (B = 3.4) and lowest on Tuesday (B = -4.66) for both groups. The daily differences were accentuated in the Bedouin population (B = 3.7 vs. B = 2.93 in the Jewish population). Placental <span class="hlt">abruption</span> was significantly more common in the Bedouin population. Both populations demonstrated the same annual and seasonal patterns, with higher incidence in spring and autumn.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ClDy..tmp..301M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ClDy..tmp..301M"><span>Influence of external forcings on <span class="hlt">abrupt</span> millennial-scale climate changes: a statistical modelling study</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mitsui, Takahito; Crucifix, Michel</p> <p>2016-07-01</p> <p>The last glacial period was punctuated by a series of <span class="hlt">abrupt</span> climate shifts, the so-called Dansgaard-Oeschger (DO) <span class="hlt">events</span>. The frequency of DO <span class="hlt">events</span> varied in time, supposedly because of changes in background climate conditions. Here, the influence of external forcings on DO <span class="hlt">events</span> is investigated with statistical modelling. We assume two types of simple stochastic dynamical systems models (double-well potential-type and oscillator-type), forced by the northern hemisphere summer insolation change and/or the global ice volume change. The model parameters are estimated by using the maximum likelihood method with the NGRIP Ca^{2+} record. The stochastic oscillator model with at least the ice volume forcing reproduces well the sample autocorrelation function of the record and the frequency changes of <span class="hlt">warming</span> transitions in the last glacial period across MISs 2, 3, and 4. The model performance is improved with the additional insolation forcing. The BIC scores also suggest that the ice volume forcing is relatively more important than the insolation forcing, though the strength of evidence depends on the model assumption. Finally, we simulate the average number of <span class="hlt">warming</span> transitions in the past four glacial periods, assuming the model can be extended beyond the last glacial, and compare the result with an Iberian margin sea-surface temperature (SST) record (Martrat et al. in Science 317(5837): 502-507, 2007). The simulation result supports the previous observation that <span class="hlt">abrupt</span> millennial-scale climate changes in the penultimate glacial (MIS 6) are less frequent than in the last glacial (MISs 2-4). On the other hand, it suggests that the number of <span class="hlt">abrupt</span> millennial-scale climate changes in older glacial periods (MISs 6, 8, and 10) might be larger than inferred from the SST record.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ClDy...48.2729M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ClDy...48.2729M"><span>Influence of external forcings on <span class="hlt">abrupt</span> millennial-scale climate changes: a statistical modelling study</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mitsui, Takahito; Crucifix, Michel</p> <p>2017-04-01</p> <p>The last glacial period was punctuated by a series of <span class="hlt">abrupt</span> climate shifts, the so-called Dansgaard-Oeschger (DO) <span class="hlt">events</span>. The frequency of DO <span class="hlt">events</span> varied in time, supposedly because of changes in background climate conditions. Here, the influence of external forcings on DO <span class="hlt">events</span> is investigated with statistical modelling. We assume two types of simple stochastic dynamical systems models (double-well potential-type and oscillator-type), forced by the northern hemisphere summer insolation change and/or the global ice volume change. The model parameters are estimated by using the maximum likelihood method with the NGRIP Ca^{2+} record. The stochastic oscillator model with at least the ice volume forcing reproduces well the sample autocorrelation function of the record and the frequency changes of <span class="hlt">warming</span> transitions in the last glacial period across MISs 2, 3, and 4. The model performance is improved with the additional insolation forcing. The BIC scores also suggest that the ice volume forcing is relatively more important than the insolation forcing, though the strength of evidence depends on the model assumption. Finally, we simulate the average number of <span class="hlt">warming</span> transitions in the past four glacial periods, assuming the model can be extended beyond the last glacial, and compare the result with an Iberian margin sea-surface temperature (SST) record (Martrat et al. in Science 317(5837): 502-507, 2007). The simulation result supports the previous observation that <span class="hlt">abrupt</span> millennial-scale climate changes in the penultimate glacial (MIS 6) are less frequent than in the last glacial (MISs 2-4). On the other hand, it suggests that the number of <span class="hlt">abrupt</span> millennial-scale climate changes in older glacial periods (MISs 6, 8, and 10) might be larger than inferred from the SST record.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016cosp...41E2004V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016cosp...41E2004V"><span>Total Electron Content (TEC) disturbances over Brazilian region during the minor sudden stratospheric <span class="hlt">warming</span> (SSW 2012) <span class="hlt">event</span> of January 2012</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vieira, Francisco; Fagundes, Paulo Roberto; Kavutarapu, Venkatesh; Gil Pillat, Valdir</p> <p>2016-07-01</p> <p>The effects of Sudden Stratospheric <span class="hlt">Warming</span> on ionosphere have been investigated by several scientists, using different observational techniques and model simulations. However, the 2011-2012 minor <span class="hlt">event</span> is one of those that are less studied. Since, the zonal westward wind is slowed without reversing to eastward, this SSW was consider as a minor <span class="hlt">event</span>. The stratospheric temperature started increasing on December 26, 2011, reached its peak on January 18, 2012, and afterwards started decreasing slowly. In addition, there was moderate geomagnetic storm on January 22-25, 2012, after the SSW temperature peak. In the present study, the GPS-TEC measurements from a network of 72 receivers over the Brazilian region are considered. This network of 72 GPS-TEC locations lies between 5 N and 30 S (35 degrees) latitudes and 35 W and 65 W (30 degrees) longitudes. Further, two chains of GPS receivers are used to study the response of Equatorial Ionization Anomaly (EIA) changes in the Brazilian East and West sectors, as well as its day-to-day variability before and during the SSW2012. It was noted that the TEC is depleted to the order of 30% all over the Brazilian region, from equator to beyond the EIA regions and from East to West sectors. It is also noticed that the EIA strengths at East and West sectors were suppressed after the stratospheric temperature peak. However, the Brazilian West sector was found to be more disturbed compared to the East sector during this SSW <span class="hlt">event</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28725352','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28725352"><span>Management adaptation of invertebrate fisheries to an extreme marine heat wave <span class="hlt">event</span> at a global <span class="hlt">warming</span> hot spot.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Caputi, Nick; Kangas, Mervi; Denham, Ainslie; Feng, Ming; Pearce, Alan; Hetzel, Yasha; Chandrapavan, Arani</p> <p>2016-06-01</p> <p>An extreme marine heat wave which affected 2000 km of the midwest coast of Australia occurred in the 2010/11 austral summer, with sea-surface temperature (SST) anomalies of 2-5°C above normal climatology. The heat wave was influenced by a strong Leeuwin Current during an extreme La Niña <span class="hlt">event</span> at a global <span class="hlt">warming</span> hot spot in the Indian Ocean. This <span class="hlt">event</span> had a significant effect on the marine ecosystem with changes to seagrass/algae and coral habitats, as well as fish kills and southern extension of the range of some tropical species. The effect has been exacerbated by above-average SST in the following two summers, 2011/12 and 2012/13. This study examined the major impact the <span class="hlt">event</span> had on invertebrate fisheries and the management adaption applied. A 99% mortality of Roei abalone (Haliotis roei) and major reductions in recruitment of scallops (Amusium balloti), king (Penaeus latisulcatus) and tiger (P. esculentus) prawns, and blue swimmer crabs were detected with management adapting with effort reductions or spatial/temporal closures to protect the spawning stock and restocking being evaluated. This study illustrates that fisheries management under extreme temperature <span class="hlt">events</span> requires an early identification of temperature hot spots, early detection of abundance changes (preferably using pre-recruit surveys), and flexible harvest strategies which allow a quick response to minimize the effect of heavy fishing on poor recruitment to enable protection of the spawning stock. This has required researchers, managers, and industry to adapt to fish stocks affected by an extreme environmental <span class="hlt">event</span> that may become more frequent due to climate change.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26430383','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26430383"><span>Extinction of an introduced <span class="hlt">warm</span>-climate alien species, Xenopus laevis, by extreme weather <span class="hlt">events</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Tinsley, Richard C; Stott, Lucy C; Viney, Mark E; Mable, Barbara K; Tinsley, Matthew C</p> <p></p> <p>Invasive, non-native species represent a major threat to biodiversity worldwide. The African amphibian Xenopus laevis is widely regarded as an invasive species and a threat to local faunas. Populations originating at the Western Cape, South Africa, have been introduced on four continents, mostly in areas with a similar Mediterranean climate. Some introduced populations are also established in cooler environments where persistence for many decades suggests a capacity for long-term adaptation. In these cases, recent climate <span class="hlt">warming</span> might enhance invasion ability, favouring range expansion, population growth and negative effects on native faunas. In the cool temperate UK, populations have been established for about 50 years in Wales and for an unknown period, probably >20 years, in England (Lincolnshire). Our field studies over 30 and 10 years, respectively, show that in favourable conditions there may be good recruitment, fast individual growth rates and large body size; maximum longevity exceeds 23 years. Nevertheless, areas of distribution remained limited, with numbers <500 in each population. In 2010, only a single individual was captured at each locality and further searching failed to record any others in repeated sampling up to 2014. We conclude that both populations are now extinct. The winters of 2009-2010 and 2010-2011 experienced extreme cold and drought (December 2010 was the coldest in 120 years and the third driest in 100 years). The extinction of X. laevis in these areas indicates that even relatively long-established alien species remain vulnerable to rare extreme weather conditions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/14558906','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/14558906"><span><span class="hlt">Abrupt</span> climate change: can society cope?</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hulme, Mike</p> <p>2003-09-15</p> <p>Consideration of <span class="hlt">abrupt</span> climate change has generally been incorporated neither in analyses of climate-change impacts nor in the design of climate adaptation strategies. Yet the possibility of <span class="hlt">abrupt</span> climate change triggered by human perturbation of the climate system is used to support the position of both those who urge stronger and earlier mitigative action than is currently being contemplated and those who argue that the unknowns in the Earth system are too large to justify such early action. This paper explores the question of <span class="hlt">abrupt</span> climate change in terms of its potential implications for society, focusing on the UK and northwest Europe in particular. The nature of <span class="hlt">abrupt</span> climate change and the different ways in which it has been defined and perceived are examined. Using the example of the collapse of the thermohaline circulation (THC), the suggested implications for society of <span class="hlt">abrupt</span> climate change are reviewed; previous work has been largely speculative and has generally considered the implications only from economic and ecological perspectives. Some observations about the implications from a more social and behavioural science perspective are made. If <span class="hlt">abrupt</span> climate change simply implies changes in the occurrence or intensity of extreme weather <span class="hlt">events</span>, or an accelerated unidirectional change in climate, the design of adaptation to climate change can proceed within the existing paradigm, with appropriate adjustments. Limits to adaptation in some sectors or regions may be reached, and the costs of appropriate adaptive behaviour may be large, but strategy can develop on the basis of a predicted long-term unidirectional change in climate. It would be more challenging, however, if <span class="hlt">abrupt</span> climate change implied a directional change in climate, as, for example, may well occur in northwest Europe following a collapse of the THC. There are two fundamental problems for society associated with such an outcome: first, the future changes in climate currently being</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27258011','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27258011"><span>Response of a Habitat-Forming Marine Plant to a Simulated <span class="hlt">Warming</span> <span class="hlt">Event</span> Is Delayed, Genotype Specific, and Varies with Phenology.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Reynolds, Laura K; DuBois, Katherine; Abbott, Jessica M; Williams, Susan L; Stachowicz, John J</p> <p>2016-01-01</p> <p>Growing evidence shows that increasing global temperature causes population declines and latitudinal shifts in geographical distribution for plants living near their thermal limits. Yet, even populations living well within established thermal limits of a species may suffer as the frequency and intensity of <span class="hlt">warming</span> <span class="hlt">events</span> increase with climate change. Adaptive response to this stress at the population level depends on the presence of genetic variation in thermal tolerance in the populations in question, yet few data exist to evaluate this. In this study, we examined the immediate effects of a moderate <span class="hlt">warming</span> <span class="hlt">event</span> of 4.5°C lasting 5 weeks and the legacy effects after a 5 week recovery on different genotypes of the marine plant Zostera marina (eelgrass). We conducted the experiment in Bodega Bay, CA USA, where average summer water temperatures are 14-15°C, but extended <span class="hlt">warming</span> periods of 17-18°C occur episodically. Experimental <span class="hlt">warming</span> increased shoot production by 14% compared to controls held at ambient temperature. However, after returning temperature to ambient levels, we found strongly negative, delayed effects of <span class="hlt">warming</span> on production: shoot production declined by 27% and total biomass decreased by 50% relative to individuals that had not been <span class="hlt">warmed</span>. While all genotypes' production decreased in the recovery phase, genotypes that grew the most rapidly under benign thermal conditions (control) were the most susceptible to the detrimental effects of <span class="hlt">warming</span>. This suggests a potential tradeoff in relative performance at normal vs. elevated temperatures. Modest short-term increases in water temperature have potentially prolonged negative effects within the species' thermal envelope, but genetic variation within these populations may allow for population persistence and adaptation. Further, intraspecific variation in phenology can result in maintenance of population diversity and lead to enhanced production in diverse stands given sufficient frequency of <span class="hlt">warming</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4892549','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4892549"><span>Response of a Habitat-Forming Marine Plant to a Simulated <span class="hlt">Warming</span> <span class="hlt">Event</span> Is Delayed, Genotype Specific, and Varies with Phenology</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Reynolds, Laura K.; DuBois, Katherine; Abbott, Jessica M.; Williams, Susan L.; Stachowicz, John J.</p> <p>2016-01-01</p> <p>Growing evidence shows that increasing global temperature causes population declines and latitudinal shifts in geographical distribution for plants living near their thermal limits. Yet, even populations living well within established thermal limits of a species may suffer as the frequency and intensity of <span class="hlt">warming</span> <span class="hlt">events</span> increase with climate change. Adaptive response to this stress at the population level depends on the presence of genetic variation in thermal tolerance in the populations in question, yet few data exist to evaluate this. In this study, we examined the immediate effects of a moderate <span class="hlt">warming</span> <span class="hlt">event</span> of 4.5°C lasting 5 weeks and the legacy effects after a 5 week recovery on different genotypes of the marine plant Zostera marina (eelgrass). We conducted the experiment in Bodega Bay, CA USA, where average summer water temperatures are 14–15°C, but extended <span class="hlt">warming</span> periods of 17–18°C occur episodically. Experimental <span class="hlt">warming</span> increased shoot production by 14% compared to controls held at ambient temperature. However, after returning temperature to ambient levels, we found strongly negative, delayed effects of <span class="hlt">warming</span> on production: shoot production declined by 27% and total biomass decreased by 50% relative to individuals that had not been <span class="hlt">warmed</span>. While all genotypes’ production decreased in the recovery phase, genotypes that grew the most rapidly under benign thermal conditions (control) were the most susceptible to the detrimental effects of <span class="hlt">warming</span>. This suggests a potential tradeoff in relative performance at normal vs. elevated temperatures. Modest short-term increases in water temperature have potentially prolonged negative effects within the species’ thermal envelope, but genetic variation within these populations may allow for population persistence and adaptation. Further, intraspecific variation in phenology can result in maintenance of population diversity and lead to enhanced production in diverse stands given sufficient frequency of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70155275','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70155275"><span>The regional forcing of Northern hemisphere drought during recent <span class="hlt">warm</span> tropical west Pacific Ocean La Niña <span class="hlt">events</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Hoell, Andrew; Funk, Christopher C.; Mathew Barlow,</p> <p>2014-01-01</p> <p>Northern Hemisphere circulations differ considerably between individual El Niño-Southern Oscillation <span class="hlt">events</span> due to internal atmospheric variability and variation in the zonal location of sea surface temperature forcing over the tropical Pacific Ocean. This study examines the similarities between recent Northern Hemisphere droughts associated with La Niña <span class="hlt">events</span> and anomalously <span class="hlt">warm</span> tropical west Pacific sea surface temperatures during 1988–1989, 1998–2000, 2007–2008 and 2010–2011 in terms of the hemispheric-scale circulations and the regional forcing of precipitation over North America and Asia during the cold season of November through April. The continental precipitation reductions associated with recent central Pacific La Niña <span class="hlt">events</span> were most severe over North America, eastern Africa, the Middle East and southwest Asia. High pressure dominated the entire Northern Hemisphere mid-latitudes and weakened and displaced storm tracks northward over North America into central Canada. Regionally over North America and Asia, the position of anomalous circulations within the zonal band of mid-latitude high pressure varied between each La Niña <span class="hlt">event</span>. Over the northwestern and southeastern United States and southern Asia, the interactions of anomalous circulations resulted in consistent regional temperature advection, which was subsequently balanced by similar precipitation-modifying vertical motions. Over the central and northeastern United States, the spatial variation of anomalous circulations resulted in modest inter-seasonal temperature advection variations, which were balanced by varying vertical motion and precipitation patterns. Over the Middle East and eastern Africa, the divergence of moisture and the advection of dry air due to anomalous circulations enhanced each of the droughts.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25945617','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25945617"><span>Short-term thermal stratification and partial overturning <span class="hlt">events</span> in a <span class="hlt">warm</span> polymictic reservoir: effects on distribution of phytoplankton community.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Santos, R M; Saggio, A A; Silva, T L R; Negreiros, N F; Rocha, O</p> <p>2015-01-01</p> <p>In lentic freshwater ecosystems, patterns of thermal stratification play a considerable part in determining the population dynamics of phytoplankton. In this study we investigated how these thermal patterns and the associated hydrodynamic processes affect the vertical distribution of phytoplankton during two consecutive diel cycles in a <span class="hlt">warm</span> polymictic urban reservoir in the metropolitan region of São Paulo, Brazil. Water samples were taken and physical, chemical and biological data collected at half-meter intervals of depth along a water column at a fixed site, every 3 hours throughout the 48-hour period. Two <span class="hlt">events</span> of stratification, followed by deepening of the thermocline occurred during the study period and led to changes in the vertical distribution of phytoplankton populations. Aphanocapsa delicatissima Nägeli was the single dominant species throughout the 48-hour period. In the second diel cycle, the density gradient induced by temperature differences avoided the sedimentation of Mougeotia sp. C. Agardh to the deepest layers. On the other hand, Pseudanabaena galeata Böcher remained in the 4.0-5.5 m deep layer. The thermal structure of the water was directly affected by two meteorological factors: air temperature and wind speed. Changes in the cell density and vertical distribution of the phytoplankton were controlled by the thermal and hydrodynamic <span class="hlt">events</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AtmRe.196..108W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AtmRe.196..108W"><span>Linear trend and <span class="hlt">abrupt</span> changes of climate indices in the arid region of northwestern China</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Huaijun; Pan, Yingping; Chen, Yaning; Ye, Zhengwei</p> <p>2017-11-01</p> <p>In recent years, climate extreme <span class="hlt">events</span> have caused increasing direct economic and social losses in the arid region of northwestern China. Based on daily temperature and precipitation data from 1960 to 2010, this paper discussed the linear trend and <span class="hlt">abrupt</span> changes of climate indices. The general evolution was obtained by the empirical orthogonal function (EOF), the Mann-Kendall test, and the distribution-free cumulative sum chart (CUSUM) test. The results are as follows: (1) climate showed a <span class="hlt">warming</span> trend at annual and seasonal scale, with all temperature indices exhibiting statistically significant changes. The <span class="hlt">warm</span> indices have increased, with 1.37%days/decade of <span class="hlt">warm</span> days (TX90p), 0.17 °C/decade of warmest days (TXx) and 1.97 days/decade of <span class="hlt">warm</span> spell duration indicator (WSDI), respectively. The cold indices have decreased, with - 1.89%days/decade, 0.65 °C/decade and - 0.66 days/decade for cold nights (TN10p), coldest nights (TNn) and cold spell duration indicator (CSDI), respectively. The precipitation indices have also increased significantly, coupled with the changes of magnitude (max 1-day precipitation amount (RX1day)), frequency (rain day (R0.1)), and duration (consecutive dry days (CDD)). (2) <span class="hlt">Abrupt</span> changes of the annual regional precipitation indices and the minimum temperature indices were observed around 1986, and that of the maximum temperature indices were observed in 1996. (3) The EOF1 indicated the overall coherent distribution for the whole study area, and its principal component (PC1) was also observed, showing a significant linear trend with an <span class="hlt">abrupt</span> change, which were in accordance with the regional observation results. EOF2 and EOF3 show contrasts between the southern and northern study areas, and between the eastern and western study areas, respectively, whereas no significant tendency was observed for their PCs. Hence, the climate indices have changed significantly, with linear trends and <span class="hlt">abrupt</span> changes noted for all climate indices</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1815815B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1815815B"><span>Simulating the response of glacial ice-sheets to past <span class="hlt">abrupt</span> climate changes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Banderas, Rubén; Álvarez-Solas, Jorge; Robinson, Alexander; Montoya, Marisa</p> <p>2016-04-01</p> <p>Dansgaard-Oeschger (D/O) <span class="hlt">events</span> were recurrent glacial <span class="hlt">abrupt</span> climatic transitions between cold and <span class="hlt">warm</span> conditions over Greenland with an approximate characteristic time of a thousand years. The uncertainties among the available sea level reconstructions hinder our understanding of the interactions between climate and global ice volume. In addition, only limited highly-resolved and continuous sea level records exist. Thus, the millennial time-scale response of glacial ice-sheets to past <span class="hlt">abrupt</span> climate changes is not well known. Here, we use a hybrid ice sheet-ice shelf model in order to investigate the response of glacial ice-sheets to the influence of millennial-scale climate variability. An ensemble of simulations is performed by forcing the model with a wide range of time-varying climatologies derived from proxy data and from some of the currently available climate model simulations. The assessment of the resulting suite of transient simulations will contribute to constrain the inadequacies of sea level reconstructions in terms of amplitude and timing and will help to understand the implications of glacial <span class="hlt">abrupt</span> climate changes in past sea level variability. Furthermore, our experiments could be useful to elucidate the mechanisms that involve the interactions between climate and ice sheets on millennial time scales, including future climate change.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009NatGe...2..206W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009NatGe...2..206W"><span>Glacial terminations as southern <span class="hlt">warmings</span> without northern control</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wolff, E. W.; Fischer, H.; Röthlisberger, R.</p> <p>2009-03-01</p> <p>The change from a glacial to an interglacial climate is paced by variations in Earth's orbit. However, the detailed sequence of <span class="hlt">events</span> that leads to a glacial termination remains controversial. It is particularly unclear whether the northern or southern hemisphere leads the termination. Here we present a hypothesis for the beginning and continuation of glacial terminations, which relies on the observation that the initial stages of terminations are indistinguishable from the <span class="hlt">warming</span> stage of <span class="hlt">events</span> in Antarctica known as Antarctic Isotopic Maxima, which occur frequently during glacial periods. Such <span class="hlt">warmings</span> in Antarctica generally begin to reverse with the onset of a <span class="hlt">warm</span> Dansgaard-Oeschger <span class="hlt">event</span> in the northern hemisphere. However, in the early stages of a termination, Antarctic <span class="hlt">warming</span> is not followed by any <span class="hlt">abrupt</span> <span class="hlt">warming</span> in the north. We propose that the lack of an Antarctic climate reversal enables southern <span class="hlt">warming</span> and the associated atmospheric carbon dioxide rise to reach a point at which full deglaciation becomes inevitable. In our view, glacial terminations, in common with other <span class="hlt">warmings</span> that do not lead to termination, are led from the southern hemisphere, but only specific conditions in the northern hemisphere enable the climate state to complete its shift to interglacial conditions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013HESSD..10.8365T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013HESSD..10.8365T"><span>Coupled prediction of flood response and debris flow initiation during <span class="hlt">warm</span> and cold season <span class="hlt">events</span> in the Southern Appalachians, USA</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tao, J.; Barros, A. P.</p> <p>2013-07-01</p> <p>Debris flows associated with rainstorms are a frequent and devastating hazard in the Southern Appalachians in the United States. Whereas <span class="hlt">warm</span> season <span class="hlt">events</span> are clearly associated with heavy rainfall intensity, the same cannot be said for the cold season <span class="hlt">events</span>. Instead, there is a relationship between large (cumulative) rainfall <span class="hlt">events</span> independently of season, and thus hydrometeorological regime, and debris flows. This suggests that the dynamics of subsurface hydrologic processes play an important role as a trigger mechanism, specifically through soil moisture redistribution by interflow. The first objective of this study is to investigate this hypothesis. The second objective is to assess the physical basis for a regional coupled flood prediction and debris flow warning system. For this purpose, uncalibrated model simulations of well-documented debris flows in headwater catchments of the Southern Appalachians using a 3-D surface-groundwater hydrologic model coupled with slope stability models are examined in detail. Specifically, we focus on two vulnerable headwater catchments that experience frequent debris flows, the Big Creek and the Jonathan Creek in the Upper Pigeon River Basin, North Carolina, and three distinct weather systems: an extremely heavy summertime convective storm in 2011; a persistent winter storm lasting several days; and a severe winter storm in 2009. These <span class="hlt">events</span> were selected due to the optimal availability of rainfall observations, availability of detailed field surveys of the landslides shortly after they occurred, which can be used to evaluate model predictions, and because they are representative of <span class="hlt">events</span> that cause major economic losses in the region. The model results substantiate that interflow is a useful prognostic of conditions necessary for the initiation of slope instability, and should therefore be considered explicitly in landslide hazard assessments. Moreover, the relationships between slope stability and interflow are</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009EGUGA..11.5554W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009EGUGA..11.5554W"><span>20th century global <span class="hlt">warming</span> favoured enhanced intensity of extreme torrential <span class="hlt">events</span> - a proglacial sediment record in NW French Alps</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wilhelm, B.; Arnaud, F.; Legaz, A.; Allignol, F.; Enters, D.; Revillon, S.</p> <p>2009-04-01</p> <p>During the past few yeas, considerable climate changes have been observed at high elevation areas of the European Alps. Additionally, one of the main results of high resolution climate modelling is a trend towards both dryer summer conditions and enhanced risk of extreme floods. This should have particularly dramatic consequences in alpine areas. Indeed, the development of tourism during the 20th century in the Alps and the rise of population density resulted in an increasing potential risk from natural hazards. Among them, torrential floods are some of the most common and widespread ones. They cause both loss of human life and high damage to property and infrastructure and are particularly destructive in mountain areas. For example, in August 2005, an unusual meteorological situation resulted in a series of catastrophic floods in most regions of the European Alps and particularly in the catchment of the Vorz river, downstream of proglacial Lac Blanc (2170 m a.s.l., Belledonne range, NW French Alps). We studied a series of sediment cores from Lac Blanc, spanning the last ca. 250 years. Through a coupled high resolution sedimentological and geochemical approach we documented about 100 flood deposits and measured their thickness. The age of each deposit has been assessed by radiochemical dating and the recognition of historically-known <span class="hlt">events</span> - major earthquakes and historical atmospheric lead deposition. Furthermore, a detailed study of regional and local historical archives was conducted allowing us to relate the recognised flood deposits to the ones reported by local population. We hence obtained a flood calendar from 1740 to 2005 with the respective intensity of each <span class="hlt">event</span> assessed by the thickness of the associated deposit. The flood frequency shows an important and punctual increase at the early end of the Little Ice Age (1830 - 1860) as a response to the beginning <span class="hlt">warming</span> period, which was emphasized by the synchronous local glacier retreat. On the other hand</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..1613182E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..1613182E"><span>Rapid increases of CO and H2O in the tropical lower stratosphere during January 2010 stratospheric sudden <span class="hlt">warming</span> <span class="hlt">event</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Eguchi, Nawo; Kodera, Kunihiko; Ueyama, Rei; Li, Qian</p> <p>2014-05-01</p> <p>A potential transport mechanism of various tracers from the tropical troposphere to the lower stratosphere (LS) across the tropical tropopause layer (TTL) is the overshooting convective clouds which inject air with tropospheric characteristics (high CO, high H2O, low O3) into the LS over a period of a few days. Evidence of such convective intrusions extending up to the 90 hPa level are observed over the southern African continent at the end of January 2010 in MLS and CALIOP satellite measurements. Rapid increases of CO and water vapor concentrations over Africa are associated with increased convective activity over the region a few days prior to the onset of stratospheric sudden <span class="hlt">warming</span> (SSW) <span class="hlt">event</span> and contribute to enhancements in their zonal tropical mean concentrations during January and February 2010. The modulation of tropical upwelling by SSW appears to force stronger and deeper tropical convection, particularly in the Southern Hemisphere tropics. The January 2010 SSW <span class="hlt">event</span> induced the lowest recorded LS temperature in MLS history (2004-13), allowing an unprecedented clear detection of stratosphere-troposphere exchange process by way of CO, H2O and O3 intrusions. The present study suggests that short duration, overshooting clouds can have a large impact on the zonally averaged fields of LS composition (zonally-averaged tracer fields in the tropical LS). In this presentation, we present the simulated CO, water vapor and ozone mixing ratios during Jan 2010 SSW using GEOS-Chem model. We further investigate the transport pathways based on trajectory analysis of air parcels in convective regions of the tropics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006AGUFM.U13A0806W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006AGUFM.U13A0806W"><span>Proxy records of Late Holocene climate <span class="hlt">events</span> in the eastern United States: Medieval <span class="hlt">Warm</span> Period and Little Ice Age</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Willard, D. A.; Cronin, T. M.; Hayo, K. M.</p> <p>2006-12-01</p> <p>We are conducting a multiproxy, regional reconstruction of climate variability during the last two millennia including the Medieval <span class="hlt">Warm</span> Period (MWP) and Little Ice Age (LIA) in eastern North America. Pollen, benthic foraminifers, ostracodes, and other proxies were analyzed from high-resolution sampling of continuous sedimentary records from lakes, wetlands, and estuaries in Florida, North Carolina, Chesapeake Bay, and Lake Champlain. These records document multi-decadal changes in vegetation, temperature, precipitation, and estuarine salinity across a latitudinal transect. During both the MWP and LIA, decreased precipitation altered plant community composition and distribution in the southeastern United States, and the LIA triggered threshold changes in vegetation that persisted until anthropogenic land-cover change overwhelmed the climate signature. In the mid-Atlantic region, progressively cooler and wetter late Holocene springs culminated in a cool, wet LIA; this trend correlates with observed oceanic changes. Trend analysis of the data suggest that inter-regional correlation of multi-decadal and centennial-scale Holocene climate <span class="hlt">events</span> will be forthcoming.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_12 --> <div id="page_13" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="241"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMPP13B1426B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMPP13B1426B"><span><span class="hlt">Abrupt</span> climate variability in the North Atlantic region: Did the icebergs do it?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Barker, S.; Chen, J.; Gong, X.; Jonkers, L.; Knorr, G.; Thornalley, D. J.</p> <p>2014-12-01</p> <p>We present high resolution records of temperature and ice rafted debris over the last ~440Kyr from a sediment core retrieved from the NE Atlantic. Our records reveal that episodes of ice rafting typically occurred after <span class="hlt">abrupt</span> cooling at the site. Because the site is sensitive to the earliest phases of ice rafting as recorded by other sites across the wider Atlantic, this suggests that icebergs were not the trigger for North Atlantic cold <span class="hlt">events</span>. Moreover we find a different relationship between cooling and the arrival of rafted ice at a site ~750km to the SE of ours. We suggest that asynchronous cooling between these locations can be explained by the more gradual southward migration of the North Atlantic polar front. We describe a mechanism that can explain the occurrence of <span class="hlt">abrupt</span> stadial <span class="hlt">events</span> over Greenland as a non-linear response as regional cooling continues beyond the threshold necessary for sustaining ocean circulation in its '<span class="hlt">warm</span>' mode with active convection north of Iceland. Thus while the freshwater derived from melting icebergs may provide a positive feedback for enhancing and prolonging stadial conditions, it is probably not the trigger for northern stadial <span class="hlt">events</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010EGUGA..12.5819A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010EGUGA..12.5819A"><span>The role of oceanic heat transport in <span class="hlt">abrupt</span> millennial-scale climate transitions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Arzel, Olivier; de Verdière, Alain Colin; England, Matthew H.</p> <p>2010-05-01</p> <p>The last glacial period was punctuated by rapid climate shifts, known as Dansgaard-Oeschger <span class="hlt">events</span>, with strong imprint in the North Atlantic sector suggesting that they were linked with the Atlantic Meridional Overturning Circulation. Here an idealized single-hemisphere three-dimensional ocean-atmosphere-sea ice coupled model is used to explore the possible origin of the instability driving these <span class="hlt">abrupt</span> <span class="hlt">events</span> and to provide a plausible explanation for the relative stability of the Holocene. Focusing on the physics of noise-free millennial oscillations under steady external (solar) forcing, we show that cold climates become unstable, that is, exhibit <span class="hlt">abrupt</span> millennial-scale transitions, for significantly lower freshwater fluxes than <span class="hlt">warm</span> climates, in agreement with previous studies making use of zonally-averaged coupled models. This fundamental difference is a direct consequence of the weaker temperature stratification of the glacial ocean, mainly caused by upper ocean cooling. With similar overturning strengths between the cold and <span class="hlt">warm</span> climates, this weaker temperature stratification implies a weaker baroclinic heat transport that ultimately leads to a weaker stabilization of the circulation by the negative temperature advection feedback. Using a two-hemisphere configuration of a coupled climate model of intermediate complexity, we show that this result is robust to the added presence of a bottom water mass of southern origin. The analysis reveals that under particular conditions, a pronounced interdecadal variability develops during <span class="hlt">warm</span> interstadials, with maximum variance in the northern extension of the western boundary current in the North Atlantic. While the nature of the instability driving the millennial oscillations is identical to that found in ocean models under mixed boundary conditions, these interstadial-interdecadal oscillations share the same characteristics as those previously found in ocean models forced by fixed surface fluxes: they originate</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1811182T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1811182T"><span>Antarctic Forcing of <span class="hlt">Abrupt</span> Global Climate Change During Isotope Stage 3</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Turney, Christian; Jones, Richard; Phipps, Steven; Thomas, Zoë; Hogg, Alan; Kershaw, Peter; Fogwill, Christopher; Palmer, Jonathan; Bronk Ramsey, Christopher; Adolphi, Florian; Muscheler, Raimund; Hughen, Konrad; Staff, Richard; Grosvenor, Mark; Golledge, Nicholas; Haberle, Simon</p> <p>2016-04-01</p> <p>Contrasting Greenland and Antarctic temperature trends during the late Pleistocene (60,000 to 11,650 years ago) are thought to be driven by imbalances in the rate of formation of North Atlantic and Antarctic Deep Water (the 'bipolar seesaw'), with millennial-scale cooling Dansgaard-Oeschger (D-O) <span class="hlt">events</span> in the north leading <span class="hlt">warming</span> in the south. An alternative origin for these <span class="hlt">abrupt</span> climate shifts, however, is the Southern Hemisphere whereby changes are transmitted globally via atmospheric and/or oceanic teleconnections. Testing these competing hypotheses is challenging given the relatively large uncertainties associated with dating terrestrial, marine and ice core chronologies. Here we use a fully coupled climate system model to investigate whether freshening of the Southern Ocean has extra-regional climate impacts. Focusing on an Isotope Stage 3 cooling <span class="hlt">event</span> preserved in Antarctic ice cores immediately prior to Antarctic Isotope Maximum 4 (AIM 4; around 29,000 years ago) we undertook an ensemble of transient meltwater simulations. We observe no impact on the Atlantic Meridional Overturning Circulation (AMOC) from freshwater hosing in the Southern Ocean but a dramatic <span class="hlt">warming</span> over the North Atlantic and contrasting precipitation patterns across the low latitudes. Exploiting a new bidecadally-resolved 14C calibration dataset obtained from New Zealand kauri (Agathis australis) we undertook intensive radiocarbon dating and high-resolution multiproxy analysis of the tropical Australia Lynch's Crater terrestrial peat sequence spanning this same period and find a synchronous change in hydroclimate to the purported meltwater <span class="hlt">event</span> in the Southern Ocean. Our results imply Southern Ocean dynamics played a significant role in driving global climate change across this period via atmospheric teleconnections, with implications for other <span class="hlt">abrupt</span> <span class="hlt">events</span> through the late Pleistocene.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMPP13B1431R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMPP13B1431R"><span>Persistent Intermediate Water <span class="hlt">Warming</span> during Cold Stadials in the SE Nordic Seas during the Last 65 Kyr</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rasmussen, T. L.; Ezat, M.; Groeneveld, J.</p> <p>2014-12-01</p> <p>In the Nordic seas, conversion of inflowing <span class="hlt">warm</span> Atlantic surface water to deep cold water through convection is closely linked with climate. During the last glacial period climate underwent rapid millennial-scale variability known as Dansgaard-Oeschger (DO) <span class="hlt">events</span>, consisting of <span class="hlt">warm</span> interstadials and cold stadials. Here we present the first benthic foraminiferal Mg/Ca-d18O record from the Nordic seas in order to reconstruct the ocean circulation on DO timescales. The record confirms that modern-like convection took place in the Nordic seas during interstadials with cold bottom water temperatures (BWT) close to modern temperatures. The results show gradual and pronounced BWT increases by 2-5 °C during stadials indicating a stop or near-stop in convection. The BWT peaks are followed by an <span class="hlt">abrupt</span> drop in temperature at the onset of interstadials indicating the <span class="hlt">abrupt</span> start of convection and renewed generation of cold deep water. The rise in BWT during stadials confirms earlier interpretations of subsurface inflow of <span class="hlt">warm</span> Atlantic water below a halocline reaching >1.2 km water depth. The results suggest that <span class="hlt">warm</span> Atlantic Water never ceased to flow into the Nordic seas during the glacial period with inflow at the surface during the Holocene and <span class="hlt">warm</span> interstadials switching to subsurface and intermediate inflow during cold stadials. Our results suggest that it is the vertical shifts in the position of the <span class="hlt">warm</span> Atlantic Water that cause the <span class="hlt">abrupt</span> surface <span class="hlt">warmings</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/11251114','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/11251114"><span>Synchronous tropical South China Sea SST change and Greenland <span class="hlt">warming</span> during deglaciation.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kienast, M; Steinke, S; Stattegger, K; Calvert, S E</p> <p>2001-03-16</p> <p>The tropical ocean plays a major role in global climate. It is therefore crucial to establish the precise phase between tropical and high-latitude climate variability during past <span class="hlt">abrupt</span> climate <span class="hlt">events</span> in order to gain insight into the mechanisms of global climate change. Here we present alkenone sea surface temperature (SST) records from the tropical South China Sea that show an <span class="hlt">abrupt</span> temperature increase of at least 1 degrees C at the end of the last glacial period. Within the recognized dating uncertainties, this SST increase is synchronous with the Bølling <span class="hlt">warming</span> observed at 14.6 thousand years ago in the Greenland Ice Sheet Project 2 ice core.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMPP41A2210R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMPP41A2210R"><span>Approaching the Edge of <span class="hlt">Abrupt</span> Climate Change</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ramadhin, C.; Yi, C.</p> <p>2015-12-01</p> <p>The phenomenon of <span class="hlt">Abrupt</span> Climate Change (ACC) became evident as paleoclimate data analyses began revealing that Earth's climate has the ability to rapidly switch from one state to the next in just a few decades after thresholds are crossed. Previously paleo-climatologists thought these switches were gradual but now there is growing concern to identify thresholds and the dominant feedback mechanisms that propel systems toward thresholds. Current human civilization relies heavily on climate stability and ACC threatens immense disruption with potentially disastrous consequences for all ecosystems. Therefore, prediction of the climate system's approach to threshold values would prove vital for the resilience of civilization through development of appropriate adaptation strategies when that shift occurs. Numerous studies now establish that earth systems are experiencing dramatic changes both by system interactions and anthropogenic sources adding urgency for comprehensive knowledge of tipping point identification. Despite this, predictions are difficult due to the immensity of interactions among feedback mechanisms. In this paper, we attempt to narrow this broad spectrum of critical feedback mechanisms by reviewing several publications on role of feedbacks in initiating past climate transitions establishing the most critical ones and significance in current climate changes. Using a compilation of paleoclimate datasets we compared the rates of deglaciations with that of glacial inceptions, which are approximately 5-10 times slower. We hypothesize that the critical feedbacks are unique to each type of transition such that <span class="hlt">warmings</span> are dominated by the ice-albedo feedback while coolings are a combination of temperature - CO2 and temperature-precipitation followed by the ice-albedo feedbacks. Additionally, we propose the existence of a commonality in the dominant trigger feedbacks for astronomical and millennial timescale <span class="hlt">abrupt</span> climate shifts and as such future studies</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010avh..confE..40M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010avh..confE..40M"><span><span class="hlt">Abrupt</span> shutdown of the Atlantic meridional overturning circulation and rainfall patterns in Mexico</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Martinez-Lopez, B.; Garcia, C. Gay</p> <p>2010-03-01</p> <p><span class="hlt">Abrupt</span> shutdown of the Atlantic meridional overturning circulation and rainfall patterns in Mexico. Model simulations agree that the <span class="hlt">warming</span> and the resulting freshening of the surface waters will significantly reduce deep water formation in the Labrador Sea during the next decades. A complete collapse of the Atlantic meridional overturning circulation (AMOC) would be associated with a strong cooling of several degrees in the North Atlantic region (Winton 2003). The future response of the AMOC, however, is predictable only within a broad range due to the existence of a critical threshold in the system and the large uncertainty about both the location of this threshold on the freshwater axis and the freshwater forcing (Zickfeld et al., 2007). According to Meehl et al. (2007), the probability of an <span class="hlt">abrupt</span> slowdown or shutdown of the AMOC triggered by greenhouse gas forcing is low, but it is considered a high-impact <span class="hlt">event</span> (Wood et al., 2003). An <span class="hlt">abrupt</span> change in the AMOC could occur so unexpectedly and quickly that natural systems would have difficulty adapting to them (NRC, 2002). In this work we use coupled ocean-atmosphere models to asses the response of rainfall patterns in Mexico to an <span class="hlt">abrupt</span> shutdown of the AMOC. First, a cooling pattern, triggered by a freshwater flux perturbation in the North Atlantic, is simulated by an isopycnic ocean model coupled to an atmospheric energy balance model. Then, this anomalous surface temperature pattern is used as a surface boundary condition for a numerical experiment performed using the simplified global atmospheric circulation model PUMA (Portable University Model of the Atmosphere; Fraedrich et al., 1998), which compute the perturbed rainfall patterns in Mexico.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JGRG..120.2036M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JGRG..120.2036M"><span><span class="hlt">Abrupt</span> shifts in phenology and vegetation productivity under climate extremes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ma, Xuanlong; Huete, Alfredo; Moran, Susan; Ponce-Campos, Guillermo; Eamus, Derek</p> <p>2015-10-01</p> <p>Amplification of the hydrologic cycle as a consequence of global <span class="hlt">warming</span> is predicted to increase climate variability and the frequency and severity of droughts. Recent large-scale drought and flooding over numerous continents provide unique opportunities to understand ecosystem responses to climatic extremes. In this study, we investigated the impacts of the early 21st century extreme hydroclimatic variations in southeastern Australia on phenology and vegetation productivity using Moderate Resolution Imaging Spectroradiometer Enhanced Vegetation Index and Standardized Precipitation-Evapotranspiration Index. Results revealed dramatic impacts of drought and wet extremes on vegetation dynamics, with <span class="hlt">abrupt</span> between year changes in phenology. Drought resulted in widespread reductions or collapse in the normal patterns of seasonality such that in many cases there was no detectable phenological cycle during drought years. Across the full range of biomes examined, we found semiarid ecosystems to exhibit the largest sensitivity to hydroclimatic variations, exceeding that of arid and humid ecosystems. This result demonstrated the vulnerability of semiarid ecosystems to climatic extremes and potential loss of ecosystem resilience with future mega-drought <span class="hlt">events</span>. A skewed distribution of hydroclimatic sensitivity with aridity is of global biogeochemical significance because it suggests that current drying trends in semiarid regions will reduce hydroclimatic sensitivity and suppress the large carbon sink that has been reported during recent wet periods (e.g., 2011 La Niña).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/577308','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/577308"><span>International policy implications of <span class="hlt">abrupt</span> climate change scenarios</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Molitor, M.R.</p> <p>1997-12-31</p> <p>New theoretical and empirical evidence supports the view that in the recent past [Holocene] <span class="hlt">abrupt</span> climate changes occurred over very short [decadal] time periods. One leading possibility of future changes involves the North Atlantic Ocean conveyor that transfers <span class="hlt">warm</span> surface waters from the equator to northern latitudes and helps maintain Europe`s climate. The predicted <span class="hlt">abrupt</span> climate change scenario theorizes that the conveyor may be modified as a result of disruption of the thermohaline circulation driving North, Atlantic Deep Water. This would lead, the theory contends, to a rapid cooling of Europe`s climate. In light of the EPCC`s 1995 Second Assessment Report conclusion that there is a {open_quotes}discernible{close_quotes} human influence on the global climate system, there are many emerging questions concerning possible <span class="hlt">abrupt</span> climate change scenarios.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JGRA..121.8995W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JGRA..121.8995W"><span>Observations and simulations of midlatitude ionospheric and thermospheric response to the January 2013 stratospheric sudden <span class="hlt">warming</span> <span class="hlt">event</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wu, Qian; Maute, A.; Yudin, V.; Goncharenko, L.; Noto, J.; Kerr, R.; Jacobi, Christoph</p> <p>2016-09-01</p> <p>Using observations from midlatitudes, we examine the ionospheric and thermospheric responses to the 2013 stratospheric sudden <span class="hlt">warming</span> <span class="hlt">event</span> by comparing data with four simulations performed by the Whole Atmosphere Community Climate Model eXtended (WACCM-X), Thermosphere-Ionosphere Mesosphere Electrodynamics General Circulation Model (TIMEGCM), and Thermosphere-Ionosphere Electrodynamics General Circulation Model (TIEGCM). The WACCM-X simulation was nudged by the GEOS-5 data. The two TIMEGCM simulations were nudged by the Modern-Era Retrospective analysis for Research and Applications data and by the aforementioned WACCM-X outputs, respectively. The standard TIEGCM simulation was also performed. These four simulations were compared with Millstone Hill (42.6°N, 71.4°W) incoherent scatter radar data, Millstone Hill and Boulder (40.1°N, 105.2°W) upper and lower thermospheric wind data. The meteor radar data from Collm (51.3°N, 13°E) were also used to examine the zonal wave number of the semidiurnal tide (SD). We evaluate the model simulations of the mesospheric and thermospheric responses to the 2013 SSW. The TIMEGCM simulation nudged with the WACCM-X output has suitable stratospheric input and ionospheric dynamics and can reproduce a sharp rise of hmf2 on January 12 observed by the Millstone Hill radar. The comparison of different models with the lower thermospheric SD tide yielded mixed results. The SD tide maintained mostly as a migrating tide for most of the time and matched the TIEGCM simulation very well. The WACCM-X appeared to perform better when the observed SD tide displays the large phase shift. It also has larger and more variable SD tide amplitude. The two TIMEGCM simulations have smaller SD amplitudes in general. Observations showed complex SD tide patterns after 20 January, which was difficult to characterize as a migrating tidal mode.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013JGRC..118.4600Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013JGRC..118.4600Z"><span>Atmospheric forcing intensifies the effects of regional ocean <span class="hlt">warming</span> on reef-scale temperature anomalies during a coral bleaching <span class="hlt">event</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, Zhenlin; Falter, James; Lowe, Ryan; Ivey, Greg; McCulloch, Malcolm</p> <p>2013-09-01</p> <p>We investigate how local atmospheric conditions and hydrodynamic forcing contributed to local variations in water temperature within a fringing coral reef-lagoon system during the peak of a marine heat wave in 2010-2011 that caused mass coral bleaching across Western Australia. A three-dimensional circulation model Regional Ocean Modeling System (ROMS) with a built-in air-sea heat flux exchange module Coupled Ocean Atmosphere Experiment (COARE) was coupled with a spectral wave model Simulating Waves Nearshore (SWAN) to resolve the surface heat exchange and wave-driven reef circulation in Coral Bay, Ningaloo Reef. Using realistic oceanic and atmospheric forcing, the model predictions were in good agreement with measured time series of water temperature at various locations in the coral reef system during the bleaching <span class="hlt">event</span>. Through a series of sensitivity analyses, we found that the difference in temperature between the reef and surrounding offshore waters (ΔT) was predominantly a function of both the daily mean net heat flux (Qnet>¯) and residence time, whereas diurnal variations in reef water temperature were dependent on the diurnal fluctuation in the net heat flux. We found that reef temperatures were substantially higher than offshore in the inner lagoon under normal weather conditions and over the entire reef domain under more extreme weather conditions (0.7°C-1.5°C). Although these temperature elevations were still less than that caused by the regional ocean <span class="hlt">warming</span> (2°C-3°C), the arrival of peak seasonal temperatures in the summer of 2010-2011 (when net atmospheric heat fluxes were positive and abnormally high) caused substantially higher thermal stresses than would have otherwise occurred if offshore temperatures had reached their normal seasonal maxima in autumn (when net atmospheric heat fluxes were negative or cooling). Therefore, the degree heating weeks calculated based on offshore temperature substantially underestimated the thermal stresses</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040090320&hterms=marine+biology&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dmarine%2Bbiology','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040090320&hterms=marine+biology&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dmarine%2Bbiology"><span><span class="hlt">Abrupt</span> climate change and transient climates during the Paleogene: a marine perspective</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Zachos, J. C.; Lohmann, K. C.; Walker, J. C.; Wise, S. W.</p> <p>1993-01-01</p> <p>Detailed investigations of high latitude sequences recently collected by the Ocean Drilling Program (ODP) indicate that periods of rapid climate change often culminated in brief transient climates, with more extreme conditions than subsequent long term climates. Two examples of such <span class="hlt">events</span> have been identified in the Paleogene; the first in latest Paleocene time in the middle of a <span class="hlt">warming</span> trend that began several million years earlier: the second in earliest Oligocene time near the end of a Middle Eocene to Late Oligocene global cooling trend. Superimposed on the earlier <span class="hlt">event</span> was a sudden and extreme <span class="hlt">warming</span> of both high latitude sea surface and deep ocean waters. Imbedded in the latter transition was an <span class="hlt">abrupt</span> decline in high latitude temperatures and the brief appearance of a full size continental ice-sheet on Antarctica. In both cases the climate extremes were not stable, lasting for less than a few hundred thousand years, indicating a temporary or transient climate state. Geochemical and sedimentological evidence suggest that both Paleogene climate <span class="hlt">events</span> were accompanied by reorganizations in ocean circulation, and major perturbations in marine productivity and the global carbon cycle. The Paleocene-Eocene thermal maximum was marked by reduced oceanic turnover and decreases in global delta 13C and in marine productivity, while the Early Oligocene glacial maximum was accompanied by intensification of deep ocean circulation and elevated delta 13C and productivity. It has been suggested that sudden changes in climate and/or ocean circulation might occur as a result of gradual forcing as certain physical thresholds are exceeded. We investigate the possibility that sudden reorganizations in ocean and/or atmosphere circulation during these <span class="hlt">abrupt</span> transitions generated short-term positive feedbacks that briefly sustained these transient climatic states.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/11537739','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/11537739"><span><span class="hlt">Abrupt</span> climate change and transient climates during the Paleogene: a marine perspective.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zachos, J C; Lohmann, K C; Walker, J C; Wise, S W</p> <p>1993-03-01</p> <p>Detailed investigations of high latitude sequences recently collected by the Ocean Drilling Program (ODP) indicate that periods of rapid climate change often culminated in brief transient climates, with more extreme conditions than subsequent long term climates. Two examples of such <span class="hlt">events</span> have been identified in the Paleogene; the first in latest Paleocene time in the middle of a <span class="hlt">warming</span> trend that began several million years earlier: the second in earliest Oligocene time near the end of a Middle Eocene to Late Oligocene global cooling trend. Superimposed on the earlier <span class="hlt">event</span> was a sudden and extreme <span class="hlt">warming</span> of both high latitude sea surface and deep ocean waters. Imbedded in the latter transition was an <span class="hlt">abrupt</span> decline in high latitude temperatures and the brief appearance of a full size continental ice-sheet on Antarctica. In both cases the climate extremes were not stable, lasting for less than a few hundred thousand years, indicating a temporary or transient climate state. Geochemical and sedimentological evidence suggest that both Paleogene climate <span class="hlt">events</span> were accompanied by reorganizations in ocean circulation, and major perturbations in marine productivity and the global carbon cycle. The Paleocene-Eocene thermal maximum was marked by reduced oceanic turnover and decreases in global delta 13C and in marine productivity, while the Early Oligocene glacial maximum was accompanied by intensification of deep ocean circulation and elevated delta 13C and productivity. It has been suggested that sudden changes in climate and/or ocean circulation might occur as a result of gradual forcing as certain physical thresholds are exceeded. We investigate the possibility that sudden reorganizations in ocean and/or atmosphere circulation during these <span class="hlt">abrupt</span> transitions generated short-term positive feedbacks that briefly sustained these transient climatic states.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JGRC..119..165K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JGRC..119..165K"><span>A closer look at the central Pacific El Niño and <span class="hlt">warm</span> pool migration <span class="hlt">events</span> from 1982 to 2011</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kidwell, Autumn; Jo, Young-Heon; Yan, Xiao-Hai</p> <p>2014-01-01</p> <p>In recent years, it has been observed that there are different types of El Niño <span class="hlt">events</span>. The <span class="hlt">warm</span> <span class="hlt">events</span> can be divided into two categories: those centered in the central Pacific (CP) and those centered in the eastern Pacific (EP). We examined the variability of western Pacific <span class="hlt">warm</span> pool (WPWP) horizontal migration and size from January 1982 to December 2011 by applying Ensemble Empirical Mode Decomposition (EEMD) and Hilbert-Huang Spectrum (HHS) to the optimally interpolated sea surface temperature (OISST) data set. The analysis shows that the long-term residual trend of the zonal centroid movement is migrating to the west by 3.78° from the mean location during the past 30 years. The size of the <span class="hlt">warm</span> pool has also increased 18% during this period. These analysis techniques isolated two separate time series for the migration of the zonal component of the WPWP for both CP and EP <span class="hlt">events</span> and showed that these two types of El Niño generally operate at different time scales. The EP time series shows the strong traditional EP El Niño and the transition between strong El Niño conditions and La Niña conditions. The CP time series shows that CP El Niños occur more often than EP El Niños. The changes of El Niño type in conjunction with westward drift and increasing <span class="hlt">warm</span> pool size shows an interesting multidecadal change in the <span class="hlt">warm</span> pool. Potential mechanisms relating the Pacific Decadal Oscillation to El Niño typologies were also discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5209705','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5209705"><span>Major cause of unprecedented Arctic <span class="hlt">warming</span> in January 2016: Critical role of an Atlantic windstorm</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Kim, Baek-Min; Hong, Ja-Young; Jun, Sang-Yoon; Zhang, Xiangdong; Kwon, Hataek; Kim, Seong-Joong; Kim, Joo-Hong; Kim, Sang-Woo; Kim, Hyun-Kyung</p> <p>2017-01-01</p> <p>In January 2016, the Arctic experienced an extremely anomalous <span class="hlt">warming</span> <span class="hlt">event</span> after an extraordinary increase in air temperature at the end of 2015. During this <span class="hlt">event</span>, a strong intrusion of <span class="hlt">warm</span> and moist air and an increase in downward longwave radiation, as well as a loss of sea ice in the Barents and Kara seas, were observed. Observational analyses revealed that the <span class="hlt">abrupt</span> <span class="hlt">warming</span> was triggered by the entry of a strong Atlantic windstorm into the Arctic in late December 2015, which brought enormous moist and <span class="hlt">warm</span> air masses to the Arctic. Although the storm terminated at the eastern coast of Greenland in late December, it was followed by a prolonged blocking period in early 2016 that sustained the extreme Arctic <span class="hlt">warming</span>. Numerical experiments indicate that the <span class="hlt">warming</span> effect of sea ice loss and associated upward turbulent heat fluxes are relatively minor in this <span class="hlt">event</span>. This result suggests the importance of the synoptically driven <span class="hlt">warm</span> and moist air intrusion into the Arctic as a primary contributing factor of this extreme Arctic <span class="hlt">warming</span> <span class="hlt">event</span>. PMID:28051170</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017NatSR...740051K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017NatSR...740051K"><span>Major cause of unprecedented Arctic <span class="hlt">warming</span> in January 2016: Critical role of an Atlantic windstorm</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kim, Baek-Min; Hong, Ja-Young; Jun, Sang-Yoon; Zhang, Xiangdong; Kwon, Hataek; Kim, Seong-Joong; Kim, Joo-Hong; Kim, Sang-Woo; Kim, Hyun-Kyung</p> <p>2017-01-01</p> <p>In January 2016, the Arctic experienced an extremely anomalous <span class="hlt">warming</span> <span class="hlt">event</span> after an extraordinary increase in air temperature at the end of 2015. During this <span class="hlt">event</span>, a strong intrusion of <span class="hlt">warm</span> and moist air and an increase in downward longwave radiation, as well as a loss of sea ice in the Barents and Kara seas, were observed. Observational analyses revealed that the <span class="hlt">abrupt</span> <span class="hlt">warming</span> was triggered by the entry of a strong Atlantic windstorm into the Arctic in late December 2015, which brought enormous moist and <span class="hlt">warm</span> air masses to the Arctic. Although the storm terminated at the eastern coast of Greenland in late December, it was followed by a prolonged blocking period in early 2016 that sustained the extreme Arctic <span class="hlt">warming</span>. Numerical experiments indicate that the <span class="hlt">warming</span> effect of sea ice loss and associated upward turbulent heat fluxes are relatively minor in this <span class="hlt">event</span>. This result suggests the importance of the synoptically driven <span class="hlt">warm</span> and moist air intrusion into the Arctic as a primary contributing factor of this extreme Arctic <span class="hlt">warming</span> <span class="hlt">event</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28051170','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28051170"><span>Major cause of unprecedented Arctic <span class="hlt">warming</span> in January 2016: Critical role of an Atlantic windstorm.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kim, Baek-Min; Hong, Ja-Young; Jun, Sang-Yoon; Zhang, Xiangdong; Kwon, Hataek; Kim, Seong-Joong; Kim, Joo-Hong; Kim, Sang-Woo; Kim, Hyun-Kyung</p> <p>2017-01-04</p> <p>In January 2016, the Arctic experienced an extremely anomalous <span class="hlt">warming</span> <span class="hlt">event</span> after an extraordinary increase in air temperature at the end of 2015. During this <span class="hlt">event</span>, a strong intrusion of <span class="hlt">warm</span> and moist air and an increase in downward longwave radiation, as well as a loss of sea ice in the Barents and Kara seas, were observed. Observational analyses revealed that the <span class="hlt">abrupt</span> <span class="hlt">warming</span> was triggered by the entry of a strong Atlantic windstorm into the Arctic in late December 2015, which brought enormous moist and <span class="hlt">warm</span> air masses to the Arctic. Although the storm terminated at the eastern coast of Greenland in late December, it was followed by a prolonged blocking period in early 2016 that sustained the extreme Arctic <span class="hlt">warming</span>. Numerical experiments indicate that the <span class="hlt">warming</span> effect of sea ice loss and associated upward turbulent heat fluxes are relatively minor in this <span class="hlt">event</span>. This result suggests the importance of the synoptically driven <span class="hlt">warm</span> and moist air intrusion into the Arctic as a primary contributing factor of this extreme Arctic <span class="hlt">warming</span> <span class="hlt">event</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1915414N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1915414N"><span>The role of sea ice in <span class="hlt">abrupt</span> climate changes following the last glacial maximum</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nisancioglu, Kerim; Dokken, Trond</p> <p>2017-04-01</p> <p>Climate changes following the last glacial maximum ( 21-10ka BP) are considered some of the most dramatic and wide reaching <span class="hlt">abrupt</span> <span class="hlt">events</span> of the geological past. On Greenland the transition from the last glacial maximum to the Bølling-Allerød (BA) <span class="hlt">warm</span> period was extremely <span class="hlt">abrupt</span>, as is the transitions in and out of the Younger Dryas (YD) cold period. In terms of ocean changes, there are indications from proxy records that the large scale Atlantic Meridional Overturning Circulation (AMOC) was significantly reduced a few thousand years before the BA and again at the start of the YD. However, the link between changes in AMOC and climate in the Northern Hemisphere and in particular on Greenland is unclear. Here, we study changes to climate and circulation in the North Atlantic across these key climate transitions based on a sediment core from the Nordic Seas as well as sensitivity studies with a global climate model. Preliminary results suggest that changes in sea ice and stratification of the Nordic Seas played a key role in the observed climate changes during and preceding the deglaciation of the large land based ice sheets. In particular the cold period following Heinrich <span class="hlt">Event</span> 1 (H1) and ending at the BA as well as the cold YD are associated with expansions of Arctic sea ice into the Nordic Seas region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003EAEJA.....8091C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003EAEJA.....8091C"><span>Ice Sheet Forcing of <span class="hlt">Abrupt</span> Climate Change: Lessons from the Last Deglaciation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Clark, P. U.; Weaver, A. J.; Mitrovica, J. X.</p> <p>2003-04-01</p> <p>Ice sheets are known to influence climate through their impact on the hydrological cycle and attendant changes in the thermohaline circulation. Large and rapid releases of freshwater from ice sheets to sensitive areas of deepwater formation may arise from several mechanisms. The last deglaciation provides the level of preservation necessary to identify specific mechanisms of ice-sheet forcing and attendant climatic responses. Here, we discuss the primary mechanisms and how they have contributed to the <span class="hlt">abrupt</span> climate changes of the last deglaciation. Sea level records suggest that the start of the deglacial sea-level rise began 19 ka with an <span class="hlt">abrupt</span> 10--15 m sea-level rise occurring over less than 500 years. We suggest that <span class="hlt">warming</span> that began >21 ka led to the <span class="hlt">abrupt</span> collapse of a part of the Northern Hemisphere ice sheet system at 19 ka, perhaps through destabilizing ice shelves. A number of climate records reveal responses at this time that are consistent with this 19-ka meltwater pulse being released into the North Atlantic and disrupting North Atlantic deepwater formation. Subsequent cooling and reduced Atlantic thermohaline circulation caused the Oldest Dryas cold interval that was sustained by Heinrich <span class="hlt">event</span> 1 at 17.7 ka. During this interval, global sea level rose at ˜2.3 mm yr-1. Subsequently, during mwp-1A, sea level rose at rates exceeding 40 mm yr-1. We suggest that mwp-1A occurred in response to a prolonged interval of Southern Hemisphere <span class="hlt">warming</span> that began ˜19 ka. Some of this <span class="hlt">warming</span> may have originated in response to a bipolar seesaw triggered by the large reduction in Atlantic thermohaline circulation that caused the Oldest Dryas. The rise in CO_2 and methane beginning at ˜17.5 ka may have amplified Southern Hemisphere <span class="hlt">warming</span> prior to mwp-1A. In any <span class="hlt">event</span>, this <span class="hlt">warming</span> may have triggered a partial collapse of the Antarctic ice sheet, perhaps by destabilizing ice shelves. By freshening the AAIW formation region, our model results show that mwp-1A</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PalOc..30.1373D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PalOc..30.1373D"><span><span class="hlt">Abrupt</span> termination of Marine Isotope Stage 16 (Termination VII) at 631.5 ka in Santa Barbara Basin, California</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dean, Walter E.; Kennett, James P.; Behl, Richard J.; Nicholson, Craig; Sorlien, Christopher C.</p> <p>2015-10-01</p> <p>The Marine Isotope Stage 16-15 boundary (Termination VII) is the first deglacial <span class="hlt">warming</span> step of the late Quaternary following the mid-Pleistocene transition (MPT), when 41 kyr climatic cycles shifted to strong 100 kyr cycles. The detailed structure of this important climatic <span class="hlt">event</span> has remained unknown until now. Core MV0508-19JPC from Santa Barbara Basin, California, contains a decadal-scale climatic and geochemical sediment record of 4000 years duration that includes the early part of this deglacial episode. This record reveals that the climatic shift during the early deglacial occurred rapidly (<700 years), in a progression of three <span class="hlt">abrupt</span> <span class="hlt">warming</span> steps. The onset of Marine Isotope Stage (MIS) 15 was remarkably <span class="hlt">abrupt</span> with 4-5°C sea surface <span class="hlt">warming</span> in ~50 years. The deglacial sequence contains the well-dated Lava Creek tephra (631.3 ± 4 ka) from Yellowstone Caldera used to date the onset of Termination VII at 631.5 ka. The late MIS 16 and early MIS 15 interval exhibits multiple decadal-scale negative excursions in δ13C of planktic foraminifera, likely the result of repeated discharges of methane from methane hydrates associated with both ocean <span class="hlt">warming</span> and low sea level. A <span class="hlt">warm</span> interstadial that interrupts late MIS 16 is marked by elevated concentrations of redox-sensitive elements indicating sulfidic, oxygen-deficient bottom and pore-waters, and elevated concentrations of total organic carbon and Cd, reflecting increased surface productivity. Unlike younger sediments on the California margin, these indicators of increased productivity and low dissolved oxygen do not consistently correspond with each other or with preserved laminations, possibly reflecting instability of a still evolving ocean-atmosphere system following the MPT.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_13 --> <div id="page_14" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="261"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUFM.U21F..08S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUFM.U21F..08S"><span>Persistent Atlantic cold-water spells into the Mediterranean caused <span class="hlt">abrupt</span> aridities in the late Quaternary Levant</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stein, M.; Bartov, Y.; Enzel, Y.; Goldstein, S. L.; Torfstein, A.; Waldmann, N.</p> <p>2007-12-01</p> <p>The late Quaternary Levant paleohydrology and paleoclimate were recorded in the sedimentary and level history of lakes that occupied the tectonic depressions along the Dead Sea rift. The region was characterized by cold - wet climate conditions during glacials and <span class="hlt">warm</span>-dry conditions during interglacials. This pattern was punctuated by <span class="hlt">abrupt</span> arid <span class="hlt">events</span> (< 200 y) that are correlated with intrusions of cold Atlantic-water into the east Mediterranean. Important examples are the <span class="hlt">abrupt</span> falls of Lake Lisan during the Heinrich <span class="hlt">events</span>, the catastrophic falls of Lake Lisan at the 14 and 11th millennium BP that were linked to "melt water pulses" MWP1-A and B. The Allerod fall marked the severest catastrophic aridity that prevailed in the late Quaternary Levant where the intruding cold waters enhanced the post-glacial <span class="hlt">warming</span> - aridification trend. Subsequently, during the YD, the North Atlantic-cooling imposed a strong deviation from the post-Glacial <span class="hlt">warming</span>-aridification trend of the Levant leading to enhanced-rain precipitation (return to the "glacial mode"). Bartov et al. (2003) proposed that the intruding cold water stopped the cyclonic uptake of vapor from the Mediterranean to the atmosphere, shutting the Levant rains. It seems that the YD cooling was associated with atmospheric changes, probably stronger effects of the Polar fronts and Westerlies that brought more rains to the Levant. Similar effects of cold seawater intrusions on the regional climate can be detected throughout the Holocene causing possibly the significant aridities of ca. 8.1, 3.5 and possibly the Medieval <span class="hlt">warming</span>. The rapidity of the response of the regional hydrological systems to the global climate changes and the sensitivity of past human cultures to these changes (e.g. the collapse of the Natufian culture during the Allerod aridity) are certainly important lessons and alarming signals for our human society.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1815087L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1815087L"><span>Contribution of the land-use forcing to the increase in risk of <span class="hlt">warm</span> extreme <span class="hlt">events</span> since 1850 over North America from constrained CMIP5 simulations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lejeune, Quentin; Davin, Edouard; Seneviratne, Sonia</p> <p>2016-04-01</p> <p>During the industrial period, large areas of North America experienced a reduction in forest cover and an expansion of agricultural areas. There is indication that this has affected the intensity and frequency of temperature extremes through changes in biophysical land surface properties (Christidis et al., 2013, Pitman et al., 2012). However, it has never been addressed in the context of a multi-model transient experiment ensemble. Here we intend to constrain CMIP5 models with observations in order to assess the contribution of historical land-cover changes (LCC) to changes in the risk of <span class="hlt">warm</span> extreme <span class="hlt">events</span> over North America. We have retained only six models from the CMIP5 ensemble that can reproduce the local <span class="hlt">warming</span> effect of deforestation during daytime, which was identified in present-day observations of the impact of deforestation on mean summer temperature (Lee et al, 2011). As for its observed cooling effect during nighttime, we kept the sole model that is able to simulate it. Using a framework derived from the Fraction of Attributable Risk methodology, we have then quantified by how much the increase in risk of getting a particular extreme <span class="hlt">event</span> driven by increased greenhouse gas concentrations (GHG) was damped or amplified over areas which were largely affected by LCC, compared to surrounding ones that experienced few LCC over the same period. We find that the constrained model ensemble indicates an amplification by between 10 and more than 100% by local LCC of the increase in risk of occurrence of a <span class="hlt">warm</span> extreme <span class="hlt">event</span> corresponding to the 90th percentile during the pre-industrial period, depending on the model. This amplification factor gets higher for more extreme <span class="hlt">events</span>, rising to at least 20% for the 995th permille. Regarding nighttime temperatures, the retained model indicates that historical LCC have locally more than cancelled the effect of increased GHG concentrations on the frequency of <span class="hlt">warm</span> extreme <span class="hlt">events</span> corresponding to between the 90th</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.B51I0122M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.B51I0122M"><span>Remote Detection and Modeling of <span class="hlt">Abrupt</span> and Gradual Tree Mortality in the Southwestern USA</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Muss, J. D.; Xu, C.; McDowell, N. G.</p> <p>2014-12-01</p> <p>Current climate models predict a <span class="hlt">warming</span> and drying trend that has a high probability of increasing the frequency and spatial extent of tree mortality <span class="hlt">events</span>. Field surveys can be used to identify, date, and attribute a cause of mortality to specific trees, but monetary and time constraints prevent broad-scale surveys, which are necessary to establish regional or global trends in tree mortality. This is significant because widespread forest mortality will likely lead to radical changes in evapotranspiration and surface albedo, which could compound climate change. While understanding the causes and mechanisms of tree mortality <span class="hlt">events</span> is crucial, it is equally important to be able to detect and monitor mortality and subsequent changes to the ecosystem at broad spatial- and temporal-scales. Over the past five years our ability to remotely detect <span class="hlt">abrupt</span> forest mortality <span class="hlt">events</span> has improved greatly, but gradual events—such as those caused by drought or certain types of insects—are still difficult to identify. Moreover, it is virtually impossible to quantify the amount of mortality that has occurred within a mixed pixel. We have developed a system that fuses climate and satellite-derived spectral data to identify both the date and the agent of forest mortality <span class="hlt">events</span>. This system has been used with Landsat time series data to detect both <span class="hlt">abrupt</span> and general trends in tree loss that have occurred during the past quarter-century in northern New Mexico. It has also been used with MODIS data to identify pixels with a high likelihood of drought-caused tree mortality in the Southwestern US. These candidate pixels were then fed to ED-FRT, a coupled forest dynamics-radiative transfer model, to generate estimates of drought-induced. We demonstrate a multi-scale approach that can produce results that will be instrumental in advancing our understanding of tree mortality-climate feedbacks, and improve our ability to predict what forests could look like in the future.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..15.4905O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..15.4905O"><span><span class="hlt">Warm</span> water <span class="hlt">events</span> in the southeast Atlantic and their impact on regional and large-scale atmospheric conditions in the CMIP5 model output</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ott, Irena; Lutz, Karin; Rathmann, Joachim; Jacobeit, Jucundus</p> <p>2013-04-01</p> <p>Two types of El Niño-like <span class="hlt">events</span> are described in the South Atlantic: the Atlantic Niño in the equatorial Atlantic and the Benguela Niño off the Namibian and Angolan coast. These <span class="hlt">warm</span> water <span class="hlt">events</span> are known to be associated with rainfall anomalies at the West and Southwest African coastal region and harm marine ecosystems and fish populations. The two phenomena are handled separately so far, but the identification of <span class="hlt">warm</span> water <span class="hlt">events</span> in our study - via similar variabilities of sea surface temperatures (SST) - based on observed SST data (HadISST1.1) as well as global climate model output from CMIP5, involved the definition of an area mean index that includes both Niño types from the Atlantic region. A multi-model ensemble of the CMIP5 output is used to investigate the impact of Atlantic Niño <span class="hlt">events</span> on regional atmospheric conditions. Based on the Atlantic SST index, composite analyses give information about anomalous precipitation, air pressure, humidity, evaporation, horizontal wind and vertical air motion patterns over the African continent and the South Atlantic. The Atlantic variability mode is similar to the Pacific El Niño system, but more irregular and less intense. However, recent studies show that the Atlantic influences the El Niño Southern Oscillation (ENSO) in the Pacific Ocean by the modification of the Walker and Hadley circulations and associated wind stress, thermocline and SST anomalies, further amplified by the Bjerknes positive feedback. As a result, an Atlantic Niño is followed by a La Niña-like phenomenon in the Pacific area with a lag of six months. In our study, the CMIP5 output is considered with respect to its ability of describing the complex connection between the Atlantic and Pacific variability modes. For that purpose, the inter-ocean teleconnection is studied with correlation analyses of the ensemble members of the CMIP5 output by means of the Atlantic index, the Southern Oscillation (SOI) and the Pacific El Niño indices (Ni</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFMPP31B2031B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFMPP31B2031B"><span>Drivers and Dynamics of Ecological Responses to <span class="hlt">Abrupt</span> Environmental Change on the Early Miocene Oregon Shelf</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Belanger, C. L.</p> <p>2012-12-01</p> <p>We know that the biosphere responds to <span class="hlt">abrupt</span> climate change, but know less about the dynamics of those changes and their proximal drivers. Studies of well-preserved fossil time-series spanning past climate <span class="hlt">events</span> that utilize multiple environmental proxies and examine multiple taxonomic groups can provide critical insight into (a) the specific environmental factors to which the biota respond, (b) the rate and tempo of those responses, and (c) whether taxonomic groups respond similarly or differently to the same stresses. I examine the drivers and dynamics of ecological changes in continental shelf benthic foraminifera and molluscs from the Early Miocene Newport Member of the Astoria Formation in Oregon (20.3-16.3 mya), which spans a time of global <span class="hlt">warming</span> leading into the Middle Miocene Climate Optimum. Stable isotope (δ18O) data from three species of benthic foraminifera from the Astoria sediments indicate that the region <span class="hlt">abruptly</span> <span class="hlt">warmed</span> by 2-4°C approximately 19 mya. In addition, δ13C values from epifaunal and infaunal foraminifera indicate an increase in productivity and organic carbon flux over time. Further, an increase in δ15N from bulk sediment and an increase in sedimentary laminations suggest oxygen levels declined. Multivariate analyses demonstrate a strong correlation between foraminiferal community metrics and δ15N suggesting that the foraminiferal community is tracking oxygenation levels while correlations to productivity changes appear indirect. Molluscan community metrics also have an approximately linear relationship to δ15N. Temperature itself had little direct influence on community composition. Changes in community composition and structure of both the foraminifera and the molluscs are <span class="hlt">abrupt</span> relative to the duration of community states, but each group responds differently to the climate change. The foraminiferal community increases in the number of species and the evenness of species abundances while the molluscan community decreases in</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24733909','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24733909"><span>Younger Dryas deglaciation of Scotland driven by <span class="hlt">warming</span> summers.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Bromley, Gordon R M; Putnam, Aaron E; Rademaker, Kurt M; Lowell, Thomas V; Schaefer, Joerg M; Hall, Brenda; Winckler, Gisela; Birkel, Sean D; Borns, Harold W</p> <p>2014-04-29</p> <p>The Younger Dryas Stadial (YDS; ∼ 12,900-11,600 y ago) in the Northern Hemisphere is classically defined by <span class="hlt">abrupt</span> cooling and renewed glaciation during the last glacial-interglacial transition. Although this <span class="hlt">event</span> involved a global reorganization of atmospheric and oceanic circulation [Denton GH, Alley RB, Comer GC, Broecker WS (2005) Quat Sci Rev 24:1159-1182], the magnitude, seasonality, and geographical footprint of YDS cooling remain unresolved and pose a challenge to our understanding of <span class="hlt">abrupt</span> climate change. Here, we present a deglacial chronology from Scotland, immediately downwind of the North Atlantic Ocean, indicating that the Scottish ice cap disintegrated during the first half of the YDS. We suggest that stratification of the North Atlantic Ocean resulted in amplified seasonality that, paradoxically, stimulated a severe wintertime climate while promoting <span class="hlt">warming</span> summers through solar heating of the mixed layer. This latter process drove deglaciation of downwind landmasses to completion well before the end of the YDS.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004GPC....41...95R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004GPC....41...95R"><span><span class="hlt">Abrupt</span> climate change: chaos and order at orbital and millennial scales</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rial, J. A.</p> <p>2004-04-01</p> <p>Successful prediction of future global climate is critically dependent on understanding its complex history, some of which is displayed in paleoclimate time series extracted from deep-sea sediment and ice cores. These recordings exhibit frequent episodes of <span class="hlt">abrupt</span> climate change believed to be the result of nonlinear response of the climate system to internal or external forcing, yet, neither the physical mechanisms nor the nature of the nonlinearities involved are well understood. At the orbital (10 4-10 5 years) and millennial scales, <span class="hlt">abrupt</span> climate change appears as sudden, rapid <span class="hlt">warming</span> <span class="hlt">events</span>, each followed by periods of slow cooling. The sequence often forms a distinctive saw-tooth shaped time series, epitomized by the deep-sea records of the last million years and the Dansgaard-Oeschger (D/O) oscillations of the last glacial. Here I introduce a simplified mathematical model consisting of a novel arrangement of coupled nonlinear differential equations that appears to capture some important physics of climate change at Milankovitch and millennial scales, closely reproducing the saw-tooth shape of the deep-sea sediment and ice core time series, the relatively <span class="hlt">abrupt</span> mid-Pleistocene climate switch, and the intriguing D/O oscillations. Named LODE for its use of the logistic-delayed differential equation, the model combines simplicity in the formulation (two equations, small number of adjustable parameters) and sufficient complexity in the dynamics (infinite-dimensional nonlinear delay differential equation) to accurately simulate details of climate change other simplified models cannot. Close agreement with available data suggests that the D/O oscillations are frequency modulated by the third harmonic of the precession forcing, and by the precession itself, but the entrained response is intermittent, mixed with intervals of noise, which corresponds well with the idea that the climate operates at the edge between chaos and order. LODE also predicts a persistent </p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ARMS....9...83L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ARMS....9...83L"><span>The Atlantic Meridional Overturning Circulation and <span class="hlt">Abrupt</span> Climate Change</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lynch-Stieglitz, Jean</p> <p>2017-01-01</p> <p><span class="hlt">Abrupt</span> changes in climate have occurred in many locations around the globe over the last glacial cycle, with pronounced temperature swings on timescales of decades or less in the North Atlantic. The global pattern of these changes suggests that they reflect variability in the Atlantic meridional overturning circulation (AMOC). This review examines the evidence from ocean sediments for ocean circulation change over these <span class="hlt">abrupt</span> <span class="hlt">events</span>. The evidence for changes in the strength and structure of the AMOC associated with the Younger Dryas and many of the Heinrich <span class="hlt">events</span> is strong. Although it has been difficult to directly document changes in the AMOC over the relatively short Dansgaard-Oeschger <span class="hlt">events</span>, there is recent evidence supporting AMOC changes over most of these oscillations as well. The lack of direct evidence for circulation changes over the shortest <span class="hlt">events</span> leaves open the possibility of other driving mechanisms for millennial-scale climate variability.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27814029','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27814029"><span>The Atlantic Meridional Overturning Circulation and <span class="hlt">Abrupt</span> Climate Change.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lynch-Stieglitz, Jean</p> <p>2017-01-03</p> <p><span class="hlt">Abrupt</span> changes in climate have occurred in many locations around the globe over the last glacial cycle, with pronounced temperature swings on timescales of decades or less in the North Atlantic. The global pattern of these changes suggests that they reflect variability in the Atlantic meridional overturning circulation (AMOC). This review examines the evidence from ocean sediments for ocean circulation change over these <span class="hlt">abrupt</span> <span class="hlt">events</span>. The evidence for changes in the strength and structure of the AMOC associated with the Younger Dryas and many of the Heinrich <span class="hlt">events</span> is strong. Although it has been difficult to directly document changes in the AMOC over the relatively short Dansgaard-Oeschger <span class="hlt">events</span>, there is recent evidence supporting AMOC changes over most of these oscillations as well. The lack of direct evidence for circulation changes over the shortest <span class="hlt">events</span> leaves open the possibility of other driving mechanisms for millennial-scale climate variability.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMPP23A1381M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMPP23A1381M"><span>Contribution of enhanced Antarctic Bottom Water formation to Antarctic <span class="hlt">warm</span> <span class="hlt">events</span> and millennial-scale atmospheric CO2 increase</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Menviel, L.; Spence, P.; England, M. H.</p> <p>2014-12-01</p> <p>During Marine Isotope Stage 3, the Atlantic Meridional Overturning Circulation (AMOC) weakened significantly on a millennial time-scale leading to Dansgaard-Oeschger (DO) and Heinrich stadials. Ice core records reveal that each Northern Hemisphere stadial is associated with a <span class="hlt">warming</span> over Antarctica, so-called Antarctic Isotope Maximum (AIM), and that atmospheric CO2 varies in phase with Antarctic temperature. Here we perform transient simulations spanning the period 50-34 ka B.P. with two Earth System Models (LOVECLIM and the UVic ESCM) to understand the link between changes in the AMOC, changes in high latitude Southern Hemispheric climate and evolution of atmospheric CO2. Given the latest Antarctic ice core chronology, we find that part of the atmospheric CO2 increase occurring during AIM12 (DO12, ~48 ka B.P.) and at the end of AIM8 (DO8, 38 ka B.P.) can be attributed to the AMOC resumption. In contrast, the atmospheric CO2 increase observed at the beginning of AIM8 (~39.6 ka B.P.) occurs during a period of weak AMOC and can instead be explained by enhanced Antarctic Bottom Water production. Enhanced Antarctic Bottom Water formation is shown to effectively ventilate the deep Pacific carbon and thus lead to CO2 outgassing into the atmosphere. In addition, changes in the AMOC alone are not sufficient to explain the largest Antarctic Isotope Maxima (namely AIM12 and AIM8). Stronger formation of Antarctic Bottom Water during AIM12 and AIM8 enhances the southern high latitude <span class="hlt">warming</span> and leads to a better agreement with high southern latitude paleoproxy records. The robustness of this southern <span class="hlt">warming</span> response is tested using an eddy-permitting coupled ocean sea-ice model. We show that stronger Antarctic Bottom Water formation contributes to Southern Ocean surface <span class="hlt">warming</span> by increasing the Southern Ocean meridional heat transport. Finally, our simulations also suggest that the Antarctic cooling should be in phase, or lag by a maximum of ~200 years, the North Atlantic</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JASTP.154...92D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JASTP.154...92D"><span>Ionospheric response to the 2006 sudden stratospheric <span class="hlt">warming</span> <span class="hlt">event</span> over the equatorial and low latitudes in the Brazilian sector using GPS observations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>de Jesus, R.; Batista, I. S.; Fagundes, P. R.; Venkatesh, K.; de Abreu, A. J.</p> <p>2017-02-01</p> <p>The main purpose of this paper is to study the response of the ionospheric F-region using GPS-TEC measurements at equatorial and low latitude regions over the Brazilian sector during an sudden stratospheric <span class="hlt">warming</span> (SSW) <span class="hlt">event</span> in the year 2006. In this work, we present vertical total electron content (VTEC) and phase fluctuations derived from GPS network in Brazil. The continuous wavelet transform (CWT) was employed to check the periodicities of the ∆VTEC during the SSW <span class="hlt">event</span>. The results show a strong decrease in VTEC and ∆VTEC values in the afternoon over low latitudes from DOY 05-39 (during the SSW <span class="hlt">event</span>) mainly after the second SSW temperature peak. The ionospheric ∆VTEC pattern over Brazilian sector shows diurnal and semidiurnal oscillations during the 2006 SSW <span class="hlt">event</span>. In addition, for the first time, variations in ∆VTEC (low latitude stations) with periods of about 02-08 day have been reported during an SSW <span class="hlt">event</span>. Using GPS stations located in the Brazilian sector, it is reported for the first time that equatorial ionospheric irregularities were not suppressed by the SSW <span class="hlt">event</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016APS..DFD.A1004K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016APS..DFD.A1004K"><span>Parameterizing turbulence over <span class="hlt">abrupt</span> topography</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Klymak, Jody</p> <p>2016-11-01</p> <p>Stratified flow over <span class="hlt">abrupt</span> topography generates a spectrum of propagating internal waves at large scales, and non-linear overturning breaking waves at small scales. For oscillating flows, the large scale waves propagate away as internal tides, for steady flows the large-scale waves propagate away as standing "columnar modes". At small-scales, the breaking waves appear to be similar for either oscillating or steady flows, so long as in the oscillating case the topography is significantly steeper than the internal tide angle of propagation. The size and energy lost to the breaking waves can be predicted relatively well from assuming that internal modes that propagate horizontally more slowly than the barotropic internal tide speed are arrested and their energy goes to turbulence. This leads to a recipe for dissipation of internal tides at <span class="hlt">abrupt</span> topography that is quite robust for both the local internal tide generation problem (barotropic forcing) and for the scattering problem (internal tides incident on <span class="hlt">abrupt</span> topography). Limitations arise when linear generation models break down, an example of which is interference between two ridges. A single "super-critical" ridge is well-modeled by a single knife-edge topography, regardless of its actual shape, but two supercritical ridges in close proximity demonstrate interference of the high modes that makes knife-edfe approximations invalid. Future direction of this research will be to use more complicated linear models to estimate the local dissipation. Of course, despite the large local dissipation, many ridges radiate most of their energy into the deep ocean, so tracking this low-mode radiated energy is very important, particularly as it means dissipation parameterizations in the open ocean due to these sinks from the surface tide cannot be parameterized locally to where they are lost from the surface tide, but instead lead to non-local parameterizations. US Office of Naval Research; Canadian National Science and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007GeoRL..34.6710N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007GeoRL..34.6710N"><span><span class="hlt">Abrupt</span> changes in rainfall during the twentieth century</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Narisma, Gemma T.; Foley, Jonathan A.; Licker, Rachel; Ramankutty, Navin</p> <p>2007-03-01</p> <p>Complex interactions in the climate system can give rise to strong positive feedback mechanisms that may lead to sudden climatic changes. The prolonged Sahel drought and the Dust Bowl are examples of 20th century <span class="hlt">abrupt</span> climatic changes that had serious effects on ecosystems and societies. Here we analyze global historical rainfall observations to detect regions that have undergone large, sudden decreases in rainfall. Our results show that in the 20th century about 30 regions in the world have experienced such changes. These <span class="hlt">events</span> are statistically significant at the 99% level, are persistent for at least ten years, and most have magnitudes of change that are 10% lower than the climatological normal (1901-2000 rainfall average). This analysis illustrates the extent and magnitude of <span class="hlt">abrupt</span> climate changes across the globe during the 20th century and may be used for studying the dynamics of and the mechanisms behind these <span class="hlt">abrupt</span> changes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/11859359','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/11859359"><span>The role of the thermohaline circulation in <span class="hlt">abrupt</span> climate change.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Clark, Peter U; Pisias, Nicklas G; Stocker, Thomas F; Weaver, Andrew J</p> <p>2002-02-21</p> <p>The possibility of a reduced Atlantic thermohaline circulation in response to increases in greenhouse-gas concentrations has been demonstrated in a number of simulations with general circulation models of the coupled ocean-atmosphere system. But it remains difficult to assess the likelihood of future changes in the thermohaline circulation, mainly owing to poorly constrained model parameterizations and uncertainties in the response of the climate system to greenhouse <span class="hlt">warming</span>. Analyses of past <span class="hlt">abrupt</span> climate changes help to solve these problems. Data and models both suggest that <span class="hlt">abrupt</span> climate change during the last glaciation originated through changes in the Atlantic thermohaline circulation in response to small changes in the hydrological cycle. Atmospheric and oceanic responses to these changes were then transmitted globally through a number of feedbacks. The palaeoclimate data and the model results also indicate that the stability of the thermohaline circulation depends on the mean climate state.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ClDy...46...71L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ClDy...46...71L"><span><span class="hlt">Warm</span> season heavy rainfall <span class="hlt">events</span> over the Huaihe River Valley and their linkage with wintertime thermal condition of the tropical oceans</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, Laifang; Li, Wenhong; Tang, Qiuhong; Zhang, Pengfei; Liu, Yimin</p> <p>2016-01-01</p> <p><span class="hlt">Warm</span> season heavy rainfall <span class="hlt">events</span> over the Huaihe River Valley (HRV) of China are amongst the top causes of agriculture and economic loss in this region. Thus, there is a pressing need for accurate seasonal prediction of HRV heavy rainfall <span class="hlt">events</span>. This study improves the seasonal prediction of HRV heavy rainfall by implementing a novel rainfall framework, which overcomes the limitation of traditional probability models and advances the statistical inference on HRV heavy rainfall <span class="hlt">events</span>. The framework is built on a three-cluster Normal mixture model, whose distribution parameters are sampled using Bayesian inference and Markov Chain Monte Carlo algorithm. The three rainfall clusters reflect probability behaviors of light, moderate, and heavy rainfall, respectively. Our analysis indicates that heavy rainfall <span class="hlt">events</span> make the largest contribution to the total amount of seasonal precipitation. Furthermore, the interannual variation of summer precipitation is attributable to the variation of heavy rainfall frequency over the HRV. The heavy rainfall frequency, in turn, is influenced by sea surface temperature anomalies (SSTAs) over the north Indian Ocean, equatorial western Pacific, and the tropical Atlantic. The tropical SSTAs modulate the HRV heavy rainfall <span class="hlt">events</span> by influencing atmospheric circulation favorable for the onset and maintenance of heavy rainfall <span class="hlt">events</span>. Occurring 5 months prior to the summer season, these tropical SSTAs provide potential sources of prediction skill for heavy rainfall <span class="hlt">events</span> over the HRV. Using these preceding SSTA signals, we show that the support vector machine algorithm can predict HRV heavy rainfall satisfactorily. The improved prediction skill has important implication for the nation's disaster early warning system.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20070035973&hterms=abrupt+change+temperature&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dabrupt%2Bchange%2Btemperature','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20070035973&hterms=abrupt+change+temperature&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dabrupt%2Bchange%2Btemperature"><span>The 1997-1999 <span class="hlt">Abrupt</span> Change of the Upper Ocean Temperature in the North Central Pacific</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kim, Seung-Bum; Lee, Tong; Fukumori, Ichiro</p> <p>2004-01-01</p> <p>The <span class="hlt">abrupt</span> <span class="hlt">warming</span> of the north central Pacific Ocean from 1997 to 1999 is studied using an ocean data assimilation product. During this period, the average mixed-layer temperature in the region of 170-210(deg)E, 25-40(deg)N rises by 1.8 K. The major contributors to the <span class="hlt">warming</span> are surface heat flux (1.3 K), geostrophic advection (0.7 K), and entrainment (0.7 K). For the geostrophic advection, the contributions by the zonal, meridional, and vertical components are 0.4, -0.1 and 0.3 K, respectively. Mixing and meridional Ekman advection have cooling effect. The significance of the geostrophic advection indicates the importance of ocean dynamics in controlling the <span class="hlt">abrupt</span> <span class="hlt">warming</span> tendency during the 1997-99 period and the inadequacy of a slab-mixed-layer model in simulating such <span class="hlt">warming</span> tendency.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20070035973&hterms=EKMAN&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DEKMAN','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20070035973&hterms=EKMAN&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DEKMAN"><span>The 1997-1999 <span class="hlt">Abrupt</span> Change of the Upper Ocean Temperature in the North Central Pacific</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kim, Seung-Bum; Lee, Tong; Fukumori, Ichiro</p> <p>2004-01-01</p> <p>The <span class="hlt">abrupt</span> <span class="hlt">warming</span> of the north central Pacific Ocean from 1997 to 1999 is studied using an ocean data assimilation product. During this period, the average mixed-layer temperature in the region of 170-210(deg)E, 25-40(deg)N rises by 1.8 K. The major contributors to the <span class="hlt">warming</span> are surface heat flux (1.3 K), geostrophic advection (0.7 K), and entrainment (0.7 K). For the geostrophic advection, the contributions by the zonal, meridional, and vertical components are 0.4, -0.1 and 0.3 K, respectively. Mixing and meridional Ekman advection have cooling effect. The significance of the geostrophic advection indicates the importance of ocean dynamics in controlling the <span class="hlt">abrupt</span> <span class="hlt">warming</span> tendency during the 1997-99 period and the inadequacy of a slab-mixed-layer model in simulating such <span class="hlt">warming</span> tendency.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMPP11D..04B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMPP11D..04B"><span><span class="hlt">Abrupt</span> changes in atmospheric methane and carbon dioxide during Heinrich Stadials from very high resolution ice core data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brook, E.; Lee, J. E.; Bauska, T. K.; Rhodes, R.; Marcott, S. A.; Ahn, J.; Petrenko, V. V.; Severinghaus, J. P.; Kalk, M.; Fischer, H.; Schmitt, J.</p> <p>2016-12-01</p> <p>It is now well-known that the stadial-interstadial cycles of the last ice age were associated with changes in atmospheric methane and carbon dioxide. <span class="hlt">Abrupt</span> <span class="hlt">warming</span> in Greenland is typically accompanied by rising methane within a few decades, and shorter-term climate changes in Greenland have counterparts in the methane record. Carbon dioxide generally follows the patterns of Antarctic temperature change, rising during the major Greenland stadials. Small increases in carbon dioxide are also associated with some Greenland <span class="hlt">warmings</span>. Recent work has illuminated another pattern of variability - <span class="hlt">abrupt</span> shifts in these two gases during the so-called "Heinrich Stadials", implying rapid reorganization of biogeochemical cycles during these times. Relevant observations from the WAIS Divide ice core include <span class="hlt">abrupt</span> methane increases during HS 1, 2, 4, and 5 (Rhodes et al., 2015, Science), and similarly fast changes in carbon dioxide during HS1, 4, and 5 (CO2 change at HS2 is muted) that are synchronous with the methane changes (Marcott et al., 2014, Nature, and new results). δ13C-CO2 for HS1 (Bauska et al., 2015, PNAS) and new results for HS 4 show an associated light anomaly, and intriguingly, new δ13C-CH4 results suggest a heavy isotopic anomaly at the time of the <span class="hlt">abrupt</span> methane increase. The interhemispheric methane gradient decreases slightly across this <span class="hlt">event</span>, suggesting enhanced tropical sources. A working hypothesis to explain these related observations involves a southward shift of the tropical rain belts associated with the Heinrich <span class="hlt">events</span> themselves. In this view the uptick in methane is due to a southerly shift of rain belts activating southern hemisphere methane sources. The synchronous carbon dioxide increase with light isotopic signature could also be sourced from the land biosphere due to drying in the northern tropics. The isotopic composition of atmospheric molecular oxygen exhibits heavy anomalies during Heinrich Stadials (Severinghaus et al, 2009, Science</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C31B0747D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C31B0747D"><span>Paleoceanographic Synthesis of <span class="hlt">Abrupt</span> Sea Ice and Temperature Changes in the Subarctic Pacific and Marginal Seas through the Past 20,000 Years</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Davis, C. V.; Myhre, S. E.; Borreggine, M. J.; Caissie, B.; Praetorius, S. K.; Katsuki, K.; Moffitt, R.; Deutsch, C.</p> <p>2016-12-01</p> <p>Substantial efforts have been concentrated over the last half-century on the paleoceaongraphy of the North Pacific. Here we synthesize existing paleoceanographic records of temperature and sea ice extent across the Subarctic Pacific and marginal seas, including the Bering Sea, Alaskan Gyre, and Sea of Okhotsk. We focus on 26 cores collected between 1988-2009 and from 36-60°N with well-developed chronologies to reconstruct the <span class="hlt">abrupt</span> climate transitions of the last 20,000 years, including the <span class="hlt">abrupt</span> <span class="hlt">warming</span> <span class="hlt">events</span> of the Northern Hemisphere glacial terminations (Termination IA, IB). Specifically, we utilize foraminiferal (δ18O & Mg/Ca) and coccolithophore (Uk'37) derived proxies for near-surface temperature reconstructions, and diatom assemblages and indicator species to reconstruct sea ice extent and marginal sea ice environments. Sea-ice associated diatom species peaked in compositional dominance mid-way through the deglaciation from the mid-Bølling ( 14.5 ka) to the early Allerød ( 13.8 ka). Even at the lowest latitude site (36°01.4'N, core MD01-2421), sea-ice affiliated diatoms peak in the Last Glacial Maximum ( 18 ka) and the early Bølling ( 13.8 ka). Biogeochemical proxies for late-spring to late-summer temperatures across the Subarctic Pacific indicate surface ocean <span class="hlt">warming</span> between the Last Glacial Maximum ( 6°) and the Holocene (12-18°C) at all sites. However, region-specific, latitudinal differences in the timing and magnitude of <span class="hlt">warming</span> and millennial scale deglacial oscillations are evident. For example, in the Western Subarctic Pacific the higher-latitude sites show lower amplitude <span class="hlt">warming</span> through the deglaciation, but greater expression of ephemeral mid-Bølling cooling than lower latitude sites. Sea ice and temperature are important primary metrics for understanding the rate and magnitude of surface ocean response to <span class="hlt">abrupt</span> <span class="hlt">warming</span> <span class="hlt">events</span>, including the response of subpolar environments to <span class="hlt">warming</span> in the modern ocean.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005RPPh...68.1343H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005RPPh...68.1343H"><span>Global <span class="hlt">warming</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Houghton, John</p> <p>2005-06-01</p> <p>'Global <span class="hlt">warming</span>' is a phrase that refers to the effect on the climate of human activities, in particular the burning of fossil fuels (coal, oil and gas) and large-scale deforestation, which cause emissions to the atmosphere of large amounts of 'greenhouse gases', of which the most important is carbon dioxide. Such gases absorb infrared radiation emitted by the Earth's surface and act as blankets over the surface keeping it warmer than it would otherwise be. Associated with this <span class="hlt">warming</span> are changes of climate. The basic science of the 'greenhouse effect' that leads to the <span class="hlt">warming</span> is well understood. More detailed understanding relies on numerical models of the climate that integrate the basic dynamical and physical equations describing the complete climate system. Many of the likely characteristics of the resulting changes in climate (such as more frequent heat waves, increases in rainfall, increase in frequency and intensity of many extreme climate <span class="hlt">events</span>) can be identified. Substantial uncertainties remain in knowledge of some of the feedbacks within the climate system (that affect the overall magnitude of change) and in much of the detail of likely regional change. Because of its negative impacts on human communities (including for instance substantial sea-level rise) and on ecosystems, global <span class="hlt">warming</span> is the most important environmental problem the world faces. Adaptation to the inevitable impacts and mitigation to reduce their magnitude are both necessary. International action is being taken by the world's scientific and political communities. Because of the need for urgent action, the greatest challenge is to move rapidly to much increased energy efficiency and to non-fossil-fuel energy sources.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_14 --> <div id="page_15" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="281"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMPP21A2262C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMPP21A2262C"><span>New insights on the anatomy of <span class="hlt">abrupt</span> climate changes based on high-resolution ice core records from NorthGRIP (Greenland)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Capron, E.; Rasmussen, S.; Popp, T. J.; Vaughn, B. H.; Gkinis, V.; Erhardt, T.; Fischer, H.; Blunier, T.; Landais, A.; Pedro, J. B.; Steffensen, J. P.; Svensson, A.; Vinther, B.</p> <p>2016-12-01</p> <p>The millennial-scale succession of Greenland Stadials (GS) and Greenland Interstadials (GI) illustrates the Greenland expression of the well-known sequence of Dansgaard-Oeschger (DO) <span class="hlt">events</span>, within which we observe additional climate variations of decadal to centennial-scale duration. Various paradigms, mostly based on interactions between the cryosphere and the ocean, have been proposed to explain the existence and evolution of DO <span class="hlt">events</span>. Annual to decadal scale records of environmental and climatic regional changes over the rapid transitions are needed to assess whether climate model outputs based on a particular mechanism are consistent with the observed spatial pattern and temporal phasing. Here we present new multiannual resolution stable water isotope measurements (ice δ18O and δD) and annually resolved ion chemistry records from the NorthGRIP ice core. Because these tracers imprint the signatures of different parts of the Northern Hemisphere climate system, we can map the anatomy - the spatial and temporal signature of climate and environmental changes - associated with <span class="hlt">abrupt</span> transitions (from GS to GI and vice-versa) occurring during Marine Isotopic Stage (MIS) 4. We determine via a statistical approach the timing and duration of the transitions, along with the amplitude of the local and regional changes associated with each Greenland <span class="hlt">warming</span> and cooling phase. We quantify similarities and differences in the sequences of <span class="hlt">events</span> through a comparison with results obtained for MIS 3 <span class="hlt">abrupt</span> transitions and results from the NEEM ice core for selected transitions. The anatomy of <span class="hlt">abrupt</span> climate changes appears to be different from one <span class="hlt">event</span> to the next, suggesting that the mechanisms at play are not identical for all of them. We discuss the possible influence of (1) the Heinrich Stadials (i.e. GS during which a Heinrich <span class="hlt">Event</span> occurred) and of (2) the long term evolution of the climate system on the different decadal to centennial-scale sequences of <span class="hlt">events</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.8684H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.8684H"><span>Ecosystem resilience to <span class="hlt">abrupt</span> late Quaternary change in continental southern Siberia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Harding, Poppy; Mackay, Anson; Bezrukova, Elena; Shchetnikov, Alexander</p> <p>2017-04-01</p> <p>Quaternary climate variability is dominated by long term orbital forcing along with <span class="hlt">abrupt</span> sub-Milankovitch <span class="hlt">events</span> on the scales of millennia to centuries, driven by internal feedback mechanisms, volcanic forcing and fluctuating solar activity. Although these are well documented in the North Atlantic region, their expression is poorly understood in Siberia, particularly in relation to <span class="hlt">abrupt</span> climatic <span class="hlt">events</span>. Siberia has the world's highest level of continentality offering an opportunity to study changes remote from oceanic influences and improving understanding of interactions between the Siberian High and other atmospheric systems including the Aleutian Low, Arctic oscillation and Icelandic Low1 and ENSO2. Understanding of palaeoenvironmental change in Siberia is essential due to the region's high sensitivity to climatic change, with <span class="hlt">warming</span> rates considerably higher than the global average over the past 50 years3, triggering significant environmental changes, including permafrost degradation, shifts in the forest-steppe biome, increases in forest fires and <span class="hlt">warming</span> of seasonally ice-covered lakes. Additionally, the region provides essential palaeoenvironmental context for early hominins, for example at globally important sites such as Denisova cave4, and megafauna extinctions5. This presentation outlines ongoing work at Lake Baunt, SE Siberia including: key quaternary climate forcings, the site and its regional context, the key methods and preliminary results. These include a dated record back to ˜30ka BP (based on multiple 14C dates and Bayesian age modelling), multiproxy indicators of palaeoproductivity (e.g. biogenic silica and diatom analyses) and lake mixing regimes (inferred from diatom analyses). Together these highlight several key Quaternary fluctuations potentially correlated to <span class="hlt">events</span> recorded in Greenland Ice Cores (GS2, GS2.1, GI1, GS1), and these are considered against key Quaternary records including those from nearby Lake Baikal and Hulu Cave in</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70187397','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70187397"><span><span class="hlt">Abrupt</span> termination of Marine Isotope Stage 16 (Termination VII) at 631.5 ka in Santa Barbara Basin, Californi</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Dean, Walter E.; Kennett, James P.; Behl, Richard J.; Nicholson, Craig; Sorlien, Christopher C.</p> <p>2015-01-01</p> <p>The Marine Isotope Stage 16–15 boundary (Termination VII) is the first deglacial <span class="hlt">warming</span> step of the late Quaternary following the mid-Pleistocene transition (MPT), when 41 kyr climatic cycles shifted to strong 100 kyr cycles. The detailed structure of this important climatic <span class="hlt">event</span> has remained unknown until now. Core MV0508-19JPC from Santa Barbara Basin, California, contains a decadal-scale climatic and geochemical sediment record of 4000 years duration that includes the early part of this deglacial episode. This record reveals that the climatic shift during the early deglacial occurred rapidly (<700 years), in a progression of three <span class="hlt">abrupt</span> <span class="hlt">warming</span> steps. The onset of Marine Isotope Stage (MIS) 15 was remarkably <span class="hlt">abrupt</span> with 4–5°C sea surface <span class="hlt">warming</span> in ~50 years. The deglacial sequence contains the well-dated Lava Creek tephra (631.3 ± 4 ka) from Yellowstone Caldera used to date the onset of Termination VII at 631.5 ka. The late MIS 16 and early MIS 15 interval exhibits multiple decadal-scale negative excursions in δ13C of planktic foraminifera, likely the result of repeated discharges of methane from methane hydrates associated with both ocean <span class="hlt">warming</span> and low sea level. A <span class="hlt">warm</span> interstadial that interrupts late MIS 16 is marked by elevated concentrations of redox-sensitive elements indicating sulfidic, oxygen-deficient bottom and pore-waters, and elevated concentrations of total organic carbon and Cd, reflecting increased surface productivity. Unlike younger sediments on the California margin, these indicators of increased productivity and low dissolved oxygen do not consistently correspond with each other or with preserved laminations, possibly reflecting instability of a still evolving ocean-atmosphere system following the MPT.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006AGUFMED31A1363S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006AGUFMED31A1363S"><span>Global <span class="hlt">Warming</span> and Energy Transition: A Public Policy Imperative</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stone, G. T.</p> <p>2006-12-01</p> <p>The historic transition from fossil fuels to alternative energy resources has begun. This development is commonly attributed to increasing energy costs and the need for energy security. Looming ever larger, however, is the issue that will soon drive the third energy revolution: global <span class="hlt">warming</span>. A preponderance of evidence documents accelerating <span class="hlt">warming</span>, enlarging impacts, and human causes -- principally combustion of fossil fuels. The carbon dioxide (C02) content of Earth's atmosphere has increased more than 35 percent since the beginning of the industrial revolution and is the highest in 650,000 years. This dramatic rise of C02 and attendant positive feedbacks are already forcing significant impacts worldwide. These include atmospheric <span class="hlt">warming</span> with shifting climatic and habitat zones, spreading tropical disease, and more extreme weather <span class="hlt">events</span>; rapid ice loss at high latitude and high altitude; ocean <span class="hlt">warming</span> and acidification with coral reef bleaching and intensifying tropical storms; rising sea level; and accelerating extinction rates. The 2007 draft report of the Intergovernmental Panel on Climate Change (IPCC) predicts greater <span class="hlt">warming</span> than in previous models. A tipping point to <span class="hlt">abrupt</span> climate change may be imminent. It is incumbent upon geoscientists and geoscience educators to assume leadership in addressing this challenge through public outreach and general education. The following topics should be integrated into all appropriate courses: the evidence of global <span class="hlt">warming</span> and its causes; observed present and predicted future impacts of global <span class="hlt">warming</span>; mitigation and adaptation strategies; and implications for energy policies and economic opportunities. New entry-level science and general education courses -- such as Climate Change Fundamentals and Energy in Nature, Technology, and Society -- are proving to be effective should be widely developed In addition, by workshops and presentations to civic and business organizations and by demonstrated examples of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/publication/?seqNo115=272539','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/publication/?seqNo115=272539"><span>Analysis of <span class="hlt">abrupt</span> transitions in ecological systems</span></a></p> <p><a target="_blank" href="https://www.ars.usda.gov/research/publications/find-a-publication/">USDA-ARS?s Scientific Manuscript database</a></p> <p></p> <p></p> <p>The occurrence and causes of <span class="hlt">abrupt</span> transitions, thresholds, or regime shifts between ecosystem states are of great concern and the likelihood of such transitions is increasing for many ecological systems. General understanding of <span class="hlt">abrupt</span> transitions has been advanced by theory, but hindered by the l...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.8649L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.8649L"><span>Excess <span class="hlt">warming</span> in Central Europe after the 8.2 ka cold <span class="hlt">event</span>: evidence from a varve-dated ostracod δ18O record from Mondsee (Austria)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lauterbach, Stefan; Andersen, Nils; Erlenkeuser, Helmut; Danielopol, Dan L.; Namiotko, Tadeusz; Hüls, Matthias; Belmecheri, Soumaya; Nantke, Carla; Meyer, Hanno; Chapligin, Bernhard; von Grafenstein, Uli; Brauer, Achim</p> <p>2017-04-01</p> <p>As evidenced by numerous palaeoclimate records worldwide, the Holocene <span class="hlt">warm</span> period has been punctuated by several short, low-amplitude cold episodes. Among these, the so-called 8.2 ka cold <span class="hlt">event</span> represents a particularly prominent climate anomaly. Accordingly, several proxy-based and modeling studies have addressed its causal mechanisms, absolute dating, duration, amplitude, spatio-temporal characteristics and environmental consequences so far. However, knowledge about the dynamics and causes of subsequent climate recovery is still limited although this is essential for understanding rapid climate change. Here we present a new sub-decadally resolved and precisely dated oxygen isotope (δ18O) record for the interval 7.7-8.7 ka BP derived from benthic ostracods preserved in the varved lake sediments of pre-Alpine Mondsee (Austria), providing new insights into climate development around the 8.2 ka cold <span class="hlt">event</span> in Central Europe. The high-resolution Mondsee δ18O record reveals the occurrence of a pronounced cold spell around 8.2 ka BP, whose amplitude (˜1.0 ‰ , equivalent to a 1.5-2.0 ˚ C cooling), total duration (151 years) and absolute dating (8231-8080 varve years BP, i.e. calendar years before AD 1950) agrees well with results from other Northern Hemisphere palaeoclimate archives, e.g. the Greenland ice cores. In addition, the Mondsee data set provides evidence for a 75-year-long δ18O overshoot directly following the 8.2 ka <span class="hlt">event</span> (between 8080 and 8005 varve years BP), which is interpreted as a period of excess <span class="hlt">warming</span> (about 0.5-0.6 ˚ C above the pre-8.2 ka <span class="hlt">event</span> level) in Central Europe. Though so far not been explicitly described elsewhere, this observation is consistent with evidence from other proxy records in the North Atlantic realm, therefore likely reflecting a hemispheric-scale signal rather than a local phenomenon. As a possible trigger we suggest an enhanced resumption of the Atlantic meridional overturning circulation (AMOC), supporting</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/377245','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/377245"><span><span class="hlt">Warm</span> climate surprises</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Overpeck, J.T.</p> <p>1996-03-29</p> <p>Over the last decade, paleoclimatic data from ice cores and sediments have shown that the climate system is capable of switching between significantly different modes, suggesting that climatic surprises may lie ahead. Most attention in the growing area of <span class="hlt">abrupt</span> climatic change research continues to be focused on large changes observed during glacial periods. The weight of paleoclimatic evidence now suggests that conforting conclusions of benign <span class="hlt">warm</span> climate variability may be incorrect. The article goes on to discuss the evidence for this. 17 refs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006AGUFM.A53E0255Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006AGUFM.A53E0255Y"><span>Responses to Global <span class="hlt">Warming</span> Over the Eastern and Central Tibetan Plateau as Reflected in Day-time and Night-time Temperatures, Extreme Temperature <span class="hlt">Events</span>, and Growing Season Length During 1961-2003</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yin, Z.; Liu, X.; Shao, X.</p> <p>2006-12-01</p> <p>This study examines the trends and variation patterns in daily maximum (day-time) and minimum (night-time) temperatures (hereafter referred to as Tm and Tn), extreme <span class="hlt">events</span>, and growing season lengths over the eastern and central Tibetan Plateau (TP), in comparison with the results from other regions. Data during the period 1961-2003 from 66 weather stations over the eastern and central TP with elevations above 2000 m are used in this study, after going through rigorous quality assessment/quality control procedures. Statistically significant <span class="hlt">warming</span> trends are identified in various measures of the temperature regime, especially in night- time temperatures, extreme <span class="hlt">warm</span>/cold <span class="hlt">events</span>, and diurnal temperature range (DTR). We find that the trends in Tn and Tm display distinct spatial patterns in the study region. The <span class="hlt">warming</span> trends in winter night-time temperatures are among the highest when compared with studies conducted in other regions. Our results also confirm the asymmetric pattern of greater <span class="hlt">warming</span> trends in minimum or night-time temperatures as compared to the day-time temperatures, which reduces the DTR in the region. Based on the time-varying percentiles of Tn and Tm, prominent <span class="hlt">warming</span> trends are found in Tn during cold season months across the relative temperature scale of both <span class="hlt">warm</span> and cold <span class="hlt">events</span>. The <span class="hlt">warming</span> in night-time temperatures causes the number of frost days to decrease significantly and the number of <span class="hlt">warm</span> days to increase. The mean length of growing season has increased by approximately 17 days during the 43-year study period for the region. Most of the record-setting months for cold <span class="hlt">events</span> are found in the earlier part of the study period, while that of the <span class="hlt">warm</span> <span class="hlt">events</span> have occurred mostly in the later half, especially since the 1990s. The changes in the temperature regime in this region may have brought regional-specific impacts on the ecosystems. It is found that grain production in Qinghai Province, located in the northeastern part of the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMGC34B..01A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMGC34B..01A"><span><span class="hlt">Abrupt</span> Climate Change in the Arctic (and Beyond): An Update (Invited)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Alley, R. B.</p> <p>2013-12-01</p> <p>Our understanding of future Arctic change is informed by the history of past changes, which often have been both large and <span class="hlt">abrupt</span>. The well-known ice-age <span class="hlt">events</span> such as the Younger Dryas show how sea-ice changes can amplify forcing to produce very large responses, with wintertime sea ice especially important. These changes are increasingly seen to have played a central role in the ice-age cycling through their global impact on CO2 storage in the deep ocean. The Heinrich <span class="hlt">events</span> reveal processes of ice-sheet/ocean interaction, some of which are being played out in Greenland and Antarctica now, and which may have large future effects on sea-level rise. The paleoclimatic record plus physical understanding greatly reduce the worst worries about instabilities from methane stored in cold places, but tend to support a role in amplifying future <span class="hlt">warming</span>. Overall, the very large impacts of past Arctic changes, and the likelihood that future changes under business-as-usual fossil-fuel emissions will be unprecedented in combined size and speed, raise important questions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017GGG....18.1794C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017GGG....18.1794C"><span>Differential response of corals to regional mass-<span class="hlt">warming</span> <span class="hlt">events</span> as evident from skeletal Sr/Ca and Mg/Ca ratios</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Clarke, Harry; D'Olivo, Juan Pablo; Falter, James; Zinke, Jens; Lowe, Ryan; McCulloch, Malcolm</p> <p>2017-05-01</p> <p>During the summer of 2010/2011, a regional marine heat wave resulted in coral bleaching of variable severity along much of the western coastline of Australia. At Ningaloo Reef, a 300 km long fringing reef system and World Heritage site, highly contrasting coral bleaching was observed between two morphologically distinct nearshore reef communities located on either side of the Ningaloo Peninsula: Tantabiddi (˜20% bleaching) and Bundegi (˜90% bleaching). For this study, we collected coral cores (Porites sp.) from Tantabiddi and Bundegi reef sites to assess the response of the Sr/Ca temperature proxy and Mg/Ca ratios to the variable levels of thermal stress imposed at these two sites during the 2010/2011 <span class="hlt">warming</span> <span class="hlt">event</span>. We found that there was an anomalous increase in Sr/Ca and decrease in Mg/Ca ratios in the Bundegi record that was coincident with the timing of severe coral bleaching at the site, while no significant changes were observed in the Tantabiddi record. We show that the change in the relationship of Sr/Ca and Mg/Ca ratios with temperature at Bundegi during the 2010/2011 <span class="hlt">event</span> reflects changes in related coral "vital" processes during periods of environmental stress. These changes were found to be consistent with a reduction in active transport of Ca2+ to the site of calcification leading to a reduction in calcification rates and reduced Rayleigh fractionation of incorporated trace elements.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.B34B..05C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.B34B..05C"><span>Impact of Climate and Fires on <span class="hlt">Abrupt</span> Permafrost Thaw in Alaskan Tundra</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chipman, M. L.; Reents, C.; Greenberg, J. A.; Hu, F.</p> <p>2015-12-01</p> <p>Thermo-erosion from <span class="hlt">abrupt</span> permafrost thaw is a key pulse disturbance in the Arctic that may impact the global carbon cycle. <span class="hlt">Abrupt</span> thaw can occur when the permafrost active layer expands in response to climate <span class="hlt">warming</span> and/or increased wildfire activity. Understanding these drivers of thermo-erosion is necessary to anticipate feedbacks in the Arctic, where summer temperature and fire frequency are predicted to increase. We examine modern and late-Holocene thermo-erosion in high-fire (Noatak) and low-fire (North Slope) tundra ecoregions of Alaska using a combination of remote-sensing and paleo-records. Lakes with active thaw features were identified through Landsat-7 image classification and time-series analysis based on observed 0.52-0.60 μm reflectance peaks following slump formation. We identified 1067 and 1705 lakes with active features between CE 2000-2012 in the Noatak and North Slope ecoregions, respectively. The density of features was higher in the highly flammable Noatak (0.04 versus 0.01 features km-2, respectively), suggesting that warmer climate and/or fires likely promote high thermo-erosional activity at present. To assess modern signals of thermo-erosion and identify past <span class="hlt">events</span>, we analyzed soil profiles and lake-sediment cores from both ecoregions using X-ray fluorescence. The ratios of Ca:K and Ca:Sr increased with depth in permafrost soils, were higher in soils from younger versus older slump surfaces, and were significantly correlated with the ratio of carbonate to feldspar and clay minerals in lake sediments (r=0.96 and 0.93, P<0.0001, n=15). We interpret past increases in Ca:K, Ca:Sr, and δ13C as enhanced weathering of carbonate-rich permafrost soils associated with thermo-erosion. At the North Slope site, we identified ten episodes of thermoerosion over the past 6000 years and found strong correspondence to summer temperature trends. <span class="hlt">Events</span> were more frequent at the Noatak site, where 15 thermo-erosional episodes and 26 fires occurred over</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/471503','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/471503"><span>Can ice sheets trigger <span class="hlt">abrupt</span> climatic change?</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Hughes, T.</p> <p>1996-11-01</p> <p>The discovery in recent years of <span class="hlt">abrupt</span> climatic changes in climate proxy records from Greenland ice cores and North Atlantic sediment cores, and from other sites around the world, has diverted attention from gradual insolation changes caused by Earth`s orbital variations to more rapid processes on Earth`s surface as forcing Quaternary climatic change. In particular, forcing by ice sheets has been quantified for a major ice stream that drained the Laurentide Ice Sheet along Hudson Strait. The history of these recent discoveries leading to an interest in ice sheets is reviewed, and a case is made that ice sheets may drive <span class="hlt">abrupt</span> climatic change that is virtually synchronous worldwide. Attention is focused on <span class="hlt">abrupt</span> inception and termination of a Quaternary glaciation cycle, <span class="hlt">abrupt</span> changes recorded as stadials and interstadials within the cycle, <span class="hlt">abrupt</span> changes in ice streams that trigger stadials and interstadials, and <span class="hlt">abrupt</span> changes in the Laurentide Ice Sheet linked to effectively simultaneous <span class="hlt">abrupt</span> changes in its ice streams. Remaining work needed to quantify further these changes is discussed. 90 refs., 14 figs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMPP33B1232T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMPP33B1232T"><span>Towards Greenland Glaciation: Cumulative or <span class="hlt">Abrupt</span> Transition?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tan, N.; Ramstein, G.; Contoux, C.; Ladant, J. B.; Dumas, C.; Donnadieu, Y.</p> <p>2014-12-01</p> <p>The insolation evolution [Laskar 2004] from 4 to 2.5 Ma depicts a series of three summer solstice insolation minima between 2.7 and 2.6 Ma, but there are other more important summer solstice minima notably around 3.82 and 3.05 Ma. On such a time span of more than 1 Ma, data shows that there are variations in the evolution of atmospheric CO2 concentration with a local maximum around 3 Ma [Seki et al.2010; Bartoli et al. 2011], before a decrease between 3 and 2.6 Ma. The latter, suggesting an <span class="hlt">abrupt</span> ice sheet inception around 2.7 Ma, has been shown to be a major culprit for the full Greenland Glaciation [Lunt et al. 2008]. However, a recent study [Contoux et al. 2014, in review] suggests that a lowering of CO2 is not sufficient to initiate a glaciation on Greenland and must be combined to low summer insolation, with surviving ice during insolation maximum, suggesting a cumulative process in the first place, which could further lead to full glaciation at 2.7 Ma. Through a new tri-dimensional interpolation method implemented within the asynchronous coupling between an atmosphere ocean general circulation model (IPSL-CM5A) and an ice sheet model (GRISLI), we investigate the transient evolution of Greenland ice sheet during the Pliocene to diagnose whether the ice sheet inception is an <span class="hlt">abrupt</span> <span class="hlt">event</span> or rather a cumulative process, involving waxing and waning of the ice sheet during several orbital cycles. ReferencesBartoli, G., Hönisch, B., & Zeebe, R. E. (2011). Atmospheric CO2 decline during the Pliocene intensification of Northern Hemisphere glaciations. Paleoceanography, 26(4). Contoux C, Dumas C, Ramstein G, Jost A, Dolan A. M. (2014) Modelling Greenland Ice sheet inception and sustainability during the late Pliocene. (in review for Earth and Planetary Science Letters.).Laskar, J., Robutel, P., Joutel, F., Gastineau, M., Correia, A. C. M., & Levrard, B. (2004). A long-term numerical solution for the insolation quantities of the Earth. Astronomy & Astrophysics, 428</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70043335','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70043335"><span>Discussion of “Deglacial paleoclimate in the southwestern United States: an <span class="hlt">abrupt</span> 18.6 cold <span class="hlt">event</span> and evidence for a North Atlantic forcing of Termination I” by M.S. Lachniet, Y. Asmerom and V. Polyak</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Winograd, Isaac J.</p> <p>2012-01-01</p> <p>Utilizing a stable isotopic time series obtained from a speleothem (PC-1), which grew between 20.1 and 15.6 ka, Lachniet, Asmeron and Polyak (2011; hereafter LAP) present evidence for a significant cold <span class="hlt">event</span> in the southern Great Basin at 18.6 ka, a finding that we accept. Supplementing this short record with a literature review, they go on to claim, as their central thesis, that the paleoclimate of the southwestern US was driven by “the transmission of atmospheric anomalies to the southwest…that coincided with deglacial climate changes in Greenland and the North Atlantic region”, not by a “dominant Pacific Ocean SST control” as suggested by SST time series off California and by the Devils Hole δ18O time series from the southern Great Basin. We do not find their central thesis supportable.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GGG....17..846V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GGG....17..846V"><span>Impact of <span class="hlt">warming</span> <span class="hlt">events</span> on reef-scale temperature variability as captured in two Little Cayman coral Sr/Ca records</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>von Reumont, J.; Hetzinger, S.; Garbe-Schönberg, D.; Manfrino, C.; Dullo, W.-Chr.</p> <p>2016-03-01</p> <p>The rising temperature of the world's oceans is affecting coral reef ecosystems by increasing the frequency and severity of bleaching and mortality <span class="hlt">events</span>. The susceptibility of corals to temperature stress varies on local and regional scales. Insights into potential controlling parameters are hampered by a lack of long term in situ data in most coral reef environments and sea surface temperature (SST) products often do not resolve reef-scale variations. Here we use 42 years (1970-2012) of coral Sr/Ca data to reconstruct seasonal- to decadal-scale SST variations in two adjacent but distinct reef environments at Little Cayman, Cayman Islands. Our results indicate that two massive Diploria strigosa corals growing in the lagoon and in the fore reef responded differently to past <span class="hlt">warming</span> <span class="hlt">events</span>. Coral Sr/Ca data from the shallow lagoon successfully record high summer temperatures confirmed by in situ observations (>33°C). Surprisingly, coral Sr/Ca from the deeper fore reef is strongly affected by thermal stress <span class="hlt">events</span>, although seasonal temperature extremes and mean SSTs at this site are reduced compared to the lagoon. The shallow lagoon coral showed decadal variations in Sr/Ca, supposedly related to the modulation of lagoonal temperature through varying tidal water exchange, influenced by the 18.6 year lunar nodal cycle. Our results show that reef-scale SST variability can be much larger than suggested by satellite SST measurements. Thus, using coral SST proxy records from different reef zones combined with in situ observations will improve conservation programs that are developed to monitor and predict potential thermal stress on coral reefs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017NatGe..10...36M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017NatGe..10...36M"><span>Global atmospheric teleconnections during Dansgaard-Oeschger <span class="hlt">events</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Markle, Bradley R.; Steig, Eric J.; Buizert, Christo; Schoenemann, Spruce W.; Bitz, Cecilia M.; Fudge, T. J.; Pedro, Joel B.; Ding, Qinghua; Jones, Tyler R.; White, James W. C.; Sowers, Todd</p> <p>2017-01-01</p> <p>During the last glacial period, the North Atlantic region experienced a series of Dansgaard-Oeschger cycles in which climate <span class="hlt">abruptly</span> alternated between <span class="hlt">warm</span> and cold periods. Corresponding variations in Antarctic surface temperature were out of phase with their Northern Hemisphere counterparts. The temperature relationship between the hemispheres is commonly attributed to an interhemispheric redistribution of heat by the ocean overturning circulation. Changes in ocean heat transport should be accompanied by changes in atmospheric circulation to satisfy global energy budget constraints. Although changes in tropical atmospheric circulation linked to <span class="hlt">abrupt</span> <span class="hlt">events</span> in the Northern Hemisphere are well documented, evidence for predicted changes in the Southern Hemisphere’s atmospheric circulation during Dansgaard-Oeschger cycles is lacking. Here we use a high-resolution deuterium-excess record from West Antarctica to show that the latitude of the mean moisture source for Antarctic precipitation changed in phase with <span class="hlt">abrupt</span> shifts in Northern Hemisphere climate, and significantly before Antarctic temperature change. This provides direct evidence that Southern Hemisphere mid-latitude storm tracks shifted within decades of <span class="hlt">abrupt</span> changes in the North Atlantic, in parallel with meridional migrations of the intertropical convergence zone. We conclude that both oceanic and atmospheric processes, operating on different timescales, link the hemispheres during <span class="hlt">abrupt</span> climate change.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5070534','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5070534"><span>Possible mechanism of <span class="hlt">abrupt</span> jump in winter surface air temperature in the late 1980s over the Northern Hemisphere</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Kim, Yeon‐Hee; Lau, William K. M.; Kim, Kyu‐Myong; Cho, Chun‐Ho</p> <p>2015-01-01</p> <p>Abstract Possible cause of an <span class="hlt">abrupt</span> <span class="hlt">warming</span> in winter mean surface air temperature in the midlatitudes of the Northern Hemisphere in the late 1980s is investigated using observation and reanalysis data. To determine the timing of <span class="hlt">abrupt</span> <span class="hlt">warming</span>, we use a regime shift index based on detection of the largest significant differences between the mean values of two contiguous periods. Results show that the <span class="hlt">abrupt</span> <span class="hlt">warming</span> occurred in association with a regime shift after the 1980's in which the zonal mean sea level pressure (SLP) is significantly increased (decreased) at the latitude 25–35°N (60–70°N), in the form of north‐south dipole‐like SLP anomaly spanning the subtropics and high latitude. The dipole SLP anomaly can be attributed to a northward expansion of Hadley cell, a poleward broadening and intensification of the Ferrel cell, coupled with a collapse of polar cell. During the <span class="hlt">abrupt</span> <span class="hlt">warming</span>, strong anomalous southerly <span class="hlt">warm</span> advection at the surface was induced by an enhanced and expanded Ferrel circulation, in association with a northward and downward shift of maximum center of northward eddy heat flux over the midlatitudes. An intensification of polar jet subsequent to regime shift may be instrumental in sustaining the <span class="hlt">warming</span> up to more than 5 years. PMID:27818850</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JGRD..12012474K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JGRD..12012474K"><span>Possible mechanism of <span class="hlt">abrupt</span> jump in winter surface air temperature in the late 1980s over the Northern Hemisphere</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kim, Yeon-Hee; Kim, Maeng-Ki; Lau, William K. M.; Kim, Kyu-Myong; Cho, Chun-Ho</p> <p>2015-12-01</p> <p>Possible cause of an <span class="hlt">abrupt</span> <span class="hlt">warming</span> in winter mean surface air temperature in the midlatitudes of the Northern Hemisphere in the late 1980s is investigated using observation and reanalysis data. To determine the timing of <span class="hlt">abrupt</span> <span class="hlt">warming</span>, we use a regime shift index based on detection of the largest significant differences between the mean values of two contiguous periods. Results show that the <span class="hlt">abrupt</span> <span class="hlt">warming</span> occurred in association with a regime shift after the 1980's in which the zonal mean sea level pressure (SLP) is significantly increased (decreased) at the latitude 25-35°N (60-70°N), in the form of north-south dipole-like SLP anomaly spanning the subtropics and high latitude. The dipole SLP anomaly can be attributed to a northward expansion of Hadley cell, a poleward broadening and intensification of the Ferrel cell, coupled with a collapse of polar cell. During the <span class="hlt">abrupt</span> <span class="hlt">warming</span>, strong anomalous southerly <span class="hlt">warm</span> advection at the surface was induced by an enhanced and expanded Ferrel circulation, in association with a northward and downward shift of maximum center of northward eddy heat flux over the midlatitudes. An intensification of polar jet subsequent to regime shift may be instrumental in sustaining the <span class="hlt">warming</span> up to more than 5 years.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27818850','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27818850"><span>Possible mechanism of <span class="hlt">abrupt</span> jump in winter surface air temperature in the late 1980s over the Northern Hemisphere.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kim, Yeon-Hee; Kim, Maeng-Ki; Lau, William K M; Kim, Kyu-Myong; Cho, Chun-Ho</p> <p>2015-12-27</p> <p>Possible cause of an <span class="hlt">abrupt</span> <span class="hlt">warming</span> in winter mean surface air temperature in the midlatitudes of the Northern Hemisphere in the late 1980s is investigated using observation and reanalysis data. To determine the timing of <span class="hlt">abrupt</span> <span class="hlt">warming</span>, we use a regime shift index based on detection of the largest significant differences between the mean values of two contiguous periods. Results show that the <span class="hlt">abrupt</span> <span class="hlt">warming</span> occurred in association with a regime shift after the 1980's in which the zonal mean sea level pressure (SLP) is significantly increased (decreased) at the latitude 25-35°N (60-70°N), in the form of north-south dipole-like SLP anomaly spanning the subtropics and high latitude. The dipole SLP anomaly can be attributed to a northward expansion of Hadley cell, a poleward broadening and intensification of the Ferrel cell, coupled with a collapse of polar cell. During the <span class="hlt">abrupt</span> <span class="hlt">warming</span>, strong anomalous southerly <span class="hlt">warm</span> advection at the surface was induced by an enhanced and expanded Ferrel circulation, in association with a northward and downward shift of maximum center of northward eddy heat flux over the midlatitudes. An intensification of polar jet subsequent to regime shift may be instrumental in sustaining the <span class="hlt">warming</span> up to more than 5 years.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ThApC.tmp..181L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ThApC.tmp..181L"><span>Detecting <span class="hlt">abrupt</span> dynamic change based on changes in the fractal properties of spatial images</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liu, Qunqun; He, Wenping; Gu, Bin; Jiang, Yundi</p> <p>2016-08-01</p> <p>Many <span class="hlt">abrupt</span> climate change <span class="hlt">events</span> often cannot be detected timely by conventional <span class="hlt">abrupt</span> detection methods until a few years after these <span class="hlt">events</span> have occurred. The reason for this lag in detection is that abundant and long-term observational data are required for accurate <span class="hlt">abrupt</span> change detection by these methods, especially for the detection of a regime shift. So, these methods cannot help us understand and forecast the evolution of the climate system in a timely manner. Obviously, spatial images, generated by a coupled spatiotemporal dynamical model, contain more information about a dynamic system than a single time series, and we find that spatial images show the fractal properties. The fractal properties of spatial images can be quantitatively characterized by the Hurst exponent, which can be estimated by two-dimensional detrended fluctuation analysis (TD-DFA). Based on this, TD-DFA is used to detect an <span class="hlt">abrupt</span> dynamic change of a coupled spatiotemporal model. The results show that the TD-DFA method can effectively detect <span class="hlt">abrupt</span> parameter changes in the coupled model by monitoring the changing in the fractal properties of spatial images. The present method provides a new way for <span class="hlt">abrupt</span> dynamic change detection, which can achieve timely and efficient <span class="hlt">abrupt</span> change detection results.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_15 --> <div id="page_16" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="301"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014HESS...18..367T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014HESS...18..367T"><span>Coupled prediction of flood response and debris flow initiation during <span class="hlt">warm</span>- and cold-season <span class="hlt">events</span> in the Southern Appalachians, USA</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tao, J.; Barros, A. P.</p> <p>2014-01-01</p> <p>Debris flows associated with rainstorms are a frequent and devastating hazard in the Southern Appalachians in the United States. Whereas <span class="hlt">warm</span>-season <span class="hlt">events</span> are clearly associated with heavy rainfall intensity, the same cannot be said for the cold-season <span class="hlt">events</span>. Instead, there is a relationship between large (cumulative) rainfall <span class="hlt">events</span> independently of season, and thus hydrometeorological regime, and debris flows. This suggests that the dynamics of subsurface hydrologic processes play an important role as a trigger mechanism, specifically through soil moisture redistribution by interflow. We further hypothesize that the transient mass fluxes associated with the temporal-spatial dynamics of interflow govern the timing of shallow landslide initiation, and subsequent debris flow mobilization. The first objective of this study is to investigate this relationship. The second objective is to assess the physical basis for a regional coupled flood prediction and debris flow warning system. For this purpose, uncalibrated model simulations of well-documented debris flows in headwater catchments of the Southern Appalachians using a 3-D surface-groundwater hydrologic model coupled with slope stability models are examined in detail. Specifically, we focus on two vulnerable headwater catchments that experience frequent debris flows, the Big Creek and the Jonathan Creek in the Upper Pigeon River Basin, North Carolina, and three distinct weather systems: an extremely heavy summertime convective storm in 2011; a persistent winter storm lasting several days; and a severe winter storm in 2009. These <span class="hlt">events</span> were selected due to the optimal availability of rainfall observations; availability of detailed field surveys of the landslides shortly after they occurred, which can be used to evaluate model predictions; and because they are representative of <span class="hlt">events</span> that cause major economic losses in the region. The model results substantiate that interflow is a useful prognostic of conditions</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.8673B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.8673B"><span>Postglacial Human resilience and susceptibility to <span class="hlt">abrupt</span> climate change new insights from Star Carr</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Blockley, Simon; Abrook, Ashley; Bayliss, Alex; Candy, Ian; Conneller, Chantal; Darvill, Chris; Deeprose, Laura; Kearney, Rebecca; Langdon, Pete; Langdon Langdon, Cath; Lincoln, Paul; Macleod, Alison; Matthews, Ian; Palmer, Adrian; Schreve, Danielle; Taylor, Barry; Milner, Nicky</p> <p>2017-04-01</p> <p>We know little about the lives of the early humans who lived during the early Postglacial period (the Lateglacial and Early Holocene), a time characterised by <span class="hlt">abrupt</span> climate change after 16,000, which includes a series of <span class="hlt">abrupt</span> climatic transitions linked to the reorganisation of the global environment after the glacial maximum and the last major global <span class="hlt">warming</span> <span class="hlt">event</span> at the onset of the Holocene. The hunter-gatherers who lived during the early Postglacial have been characterised as highly mobile, dispersed and living within small groups, and there is much debate as to how they adapted to climatic and environmental change: did they move in response to climatic transitions (and if so what was the climatic threshold), or instead adapt their lifeways to the new environmental conditions? A key area for examining these ideas is the British Isles as it sits on the Atlantic fringe of Northwest Europe with a climate that is highly responsive to the wider climate forcing experienced in the northern Hemisphere. Furthermore, in this period, Britain is directly linked to continental Europe due to lowered global sea levels allowing for the ease of human migration in and out of this region. In general the British record has been seen as being dominated by abandonment and reoccupation in the Postglacial during periods of climatic transition with hunter-gatherer mobility being closely linked to the prevailing environment. Recent discoveries at the Early Mesolithic site of Star Carr and surrounding area, linked to local and regional climate records, based on isotopic, chironomid and pollen proxy data and dated at high chronological resolution, offer a new picture. Postglacial human occupation of the area commences at the Pleistocene/Holocene transition but is short lived and appears to end close to the Pre-Boreal Oscillation, However, this is followed by a period where hunter-gatherers occupy Star Carr and settle and invest time and effort into building huts and large scale wooden</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003GeoRL..30.2251C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003GeoRL..30.2251C"><span>Noble gas thermometry and hydrologic ages: Evidence for late Holocene <span class="hlt">warming</span> in Southwest Texas</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Castro, Maria Clara; Goblet, Patrick</p> <p>2003-12-01</p> <p>Paleoclimatic reconstruction using noble gas concentrations in the Carrizo aquifer of southwest Texas and water ages determined through simulation of groundwater age reveals <span class="hlt">abrupt</span> late Holocene temperature increases previously unidentified through 14C dating. Of particular interest is a temperature increase of up to 3.4°C in the first half of the last millennium following a cold period between ~3.7 and 0.9 Kyrs BP. Wet, cool periods in the region are associated with El-Nino dominated conditions, while <span class="hlt">warm</span>, arid <span class="hlt">events</span> are linked to multi-decade La-Nina dominant <span class="hlt">events</span>. The data shows a slow decrease in temperature between ~1,200 and 200 Kyrs BP, a decrease that accelerated in the late Pleistocene and early Holocene. This decrease was followed by <span class="hlt">warming</span> in the last millennium, that seems to be continuing today.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017GeoRL..44.6959M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017GeoRL..44.6959M"><span>The role of the Southern Hemisphere semiannual oscillation in the development of a precursor to central and eastern Pacific Southern Oscillation <span class="hlt">warm</span> <span class="hlt">events</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Meehl, Gerald A.; van Loon, Harry; Arblaster, Julie M.</p> <p>2017-07-01</p> <p>The semiannual oscillation (SAO) is a twice-yearly northward movement (in May-June-July (MJJ) and November-December-January (NDJ)) of the circumpolar trough of sea level pressure (SLP) in the Southern Hemisphere with effects throughout the troposphere. During MJJ the second harmonic of SLP, describing the SAO, has low values of SLP north of 50°S in the subtropical South Pacific, while the first harmonic, which is dominant over the Australian sector, increases to its peak. This once-a-year peak in negative SLP gradients (decreasing to the east) between Australia and the ocean to its east extends to the equatorial Pacific. Southern Oscillation <span class="hlt">warm</span> <span class="hlt">events</span> since 1950, with an intensification of this seasonal cycle, have larger-amplitude SST anomalies in the eastern equatorial Pacific in MJJ and during the following mature phase in NDJ. Weak amplification of the seasonal cycle in MJJ tends to be followed by larger-amplitude SST anomalies in the central equatorial Pacific during NDJ.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JGRA..121.5571G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JGRA..121.5571G"><span>An incoherent scatter radar study of the midnight temperature maximum that occurred at Arecibo during a sudden stratospheric <span class="hlt">warming</span> <span class="hlt">event</span> in January 2010</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gong, Yun; Zhou, Qihou; Zhang, Shaodong; Aponte, Nestor; Sulzer, Michael</p> <p>2016-06-01</p> <p>We present an analysis of the thermospheric midnight temperature maximum, a large increment of temperature around midnight. The analysis is based on data collected from the Arecibo incoherent scatter radar during 14-21 January 2010. The experiment overlaps with a major sudden stratospheric <span class="hlt">warming</span> (SSW) <span class="hlt">event</span> which commenced on 18 January 2010. Throughout the observation, the ion temperature exhibited moderate increase around postmidnight during 14-17 January, while it showed more intense increment during 18-21 January. In particular, on 20 January, the amplitude of the midnight temperature maximum (MTM) is 310 K, which is seldom seen at Arecibo. During the SSW, the meridional wind reverses toward the pole just before the commencement of the MTM. Then, the poleward wind and the ion temperature maximize almost at the same time. The variation of meridional wind and the MTM are consistent with the Whole Atmosphere Model (WAM) studies, which suggested that the variation is due to effects from an upward propagating terdiurnal tide. On the nights of 18-19 January, the MTM showed clear phase variation at the heights of 265, 303, and 342 km. A strong terdiurnal tide has been observed during the SSW and it is likely generated from low atmosphere and propagating upward. Our results provide direct observational evidence that the propagating upward terdiurnal tide plays an important role in causing the MTM, which supports the WAM simulations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70031947','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70031947"><span><span class="hlt">Abrupt</span> climate change and collapse of deep-sea ecosystems</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Yasuhara, Moriaki; Cronin, T. M.; Demenocal, P.B.; Okahashi, H.; Linsley, B.K.</p> <p>2008-01-01</p> <p>We investigated the deep-sea fossil record of benthic ostracodes during periods of rapid climate and oceanographic change over the past 20,000 years in a core from intermediate depth in the northwestern Atlantic. Results show that deep-sea benthic community "collapses" occur with faunal turnover of up to 50% during major climatically driven oceanographic changes. Species diversity as measured by the Shannon-Wiener index falls from 3 to as low as 1.6 during these <span class="hlt">events</span>. Major disruptions in the benthic communities commenced with Heinrich <span class="hlt">Event</span> 1, the Inter-Aller??d Cold Period (IACP: 13.1 ka), the Younger Dryas (YD: 12.9-11.5 ka), and several Holocene Bond <span class="hlt">events</span> when changes in deep-water circulation occurred. The largest collapse is associated with the YD/IACP and is characterized by an <span class="hlt">abrupt</span> two-step decrease in both the upper North Atlantic Deep Water assemblage and species diversity at 13.1 ka and at 12.2 ka. The ostracode fauna at this site did not fully recover until ???8 ka, with the establishment of Labrador Sea Water ventilation. Ecologically opportunistic slope species prospered during this community collapse. Other <span class="hlt">abrupt</span> community collapses during the past 20 ka generally correspond to millennial climate <span class="hlt">events</span>. These results indicate that deep-sea ecosystems are not immune to the effects of rapid climate changes occurring over centuries or less. ?? 2008 by The National Academy of Sciences of the USA.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18227517','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18227517"><span><span class="hlt">Abrupt</span> climate change and collapse of deep-sea ecosystems.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Yasuhara, Moriaki; Cronin, Thomas M; Demenocal, Peter B; Okahashi, Hisayo; Linsley, Braddock K</p> <p>2008-02-05</p> <p>We investigated the deep-sea fossil record of benthic ostracodes during periods of rapid climate and oceanographic change over the past 20,000 years in a core from intermediate depth in the northwestern Atlantic. Results show that deep-sea benthic community "collapses" occur with faunal turnover of up to 50% during major climatically driven oceanographic changes. Species diversity as measured by the Shannon-Wiener index falls from 3 to as low as 1.6 during these <span class="hlt">events</span>. Major disruptions in the benthic communities commenced with Heinrich <span class="hlt">Event</span> 1, the Inter-Allerød Cold Period (IACP: 13.1 ka), the Younger Dryas (YD: 12.9-11.5 ka), and several Holocene Bond <span class="hlt">events</span> when changes in deep-water circulation occurred. The largest collapse is associated with the YD/IACP and is characterized by an <span class="hlt">abrupt</span> two-step decrease in both the upper North Atlantic Deep Water assemblage and species diversity at 13.1 ka and at 12.2 ka. The ostracode fauna at this site did not fully recover until approximately 8 ka, with the establishment of Labrador Sea Water ventilation. Ecologically opportunistic slope species prospered during this community collapse. Other <span class="hlt">abrupt</span> community collapses during the past 20 ka generally correspond to millennial climate <span class="hlt">events</span>. These results indicate that deep-sea ecosystems are not immune to the effects of rapid climate changes occurring over centuries or less.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=global+AND+warming+AND+united+AND+states&id=EJ391198','ERIC'); return false;" href="http://eric.ed.gov/?q=global+AND+warming+AND+united+AND+states&id=EJ391198"><span>Global <span class="hlt">Warming</span>.</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Hileman, Bette</p> <p>1989-01-01</p> <p>States the foundations of the theory of global <span class="hlt">warming</span>. Describes methodologies used to measure the changes in the atmosphere. Discusses steps currently being taken in the United States and the world to slow the <span class="hlt">warming</span> trend. Recognizes many sources for the <span class="hlt">warming</span> and the possible effects on the earth. (MVL)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://eric.ed.gov/?q=AIR+AND+POLLUTION+AND+Climate+AND+change&pg=4&id=EJ391198','ERIC'); return false;" href="https://eric.ed.gov/?q=AIR+AND+POLLUTION+AND+Climate+AND+change&pg=4&id=EJ391198"><span>Global <span class="hlt">Warming</span>.</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Hileman, Bette</p> <p>1989-01-01</p> <p>States the foundations of the theory of global <span class="hlt">warming</span>. Describes methodologies used to measure the changes in the atmosphere. Discusses steps currently being taken in the United States and the world to slow the <span class="hlt">warming</span> trend. Recognizes many sources for the <span class="hlt">warming</span> and the possible effects on the earth. (MVL)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMOS42B..03H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMOS42B..03H"><span>North Atlantic Meridional Overturning Circulation (AMOC) and <span class="hlt">Abrupt</span> Climate Change through the Last Glaciation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Henry, G., III; McManus, J. F.; Curry, W. B.; Keigwin, L. D.; Giosan, L.</p> <p>2014-12-01</p> <p>The climate of the glacial North Atlantic was punctuated by catastrophic discharges of icebergs (Heinrich <span class="hlt">events</span>), as well as by more mysterious, <span class="hlt">abrupt</span> <span class="hlt">warming</span> <span class="hlt">events</span> associated with Dansgaard-Oeschger oscillations. These <span class="hlt">events</span> are suspected to be related to changes in AMOC and its influence on heat transport and the regional and global heat budget. Investigation of these rapid oscillations is often limited by the resolution of sediment records. High accumulation rates at our study site (33.69°N, 57.58°W, 4583m water depth) on the Bermuda Rise allow improved resolution by one to two orders of magnitude. Cores CDH19 (38.81m) and CDH13 (36.70m), were recovered during KNR191, the initial deployment of the RV Knorr's long coring system developed at the Woods Hole Oceanographic Institution with support from the NSF. These cores contain high quality sediment sections that allow high resolution studies extending through the last glacial cycle at a key location for monitoring past oceanographic and climatic variability. Here we present detailed multi-proxy data from Bermuda Rise sediments reflecting deep ocean chemistry and dynamics of the last glaciation, and combine them with published data to produce a continuous, high resolution record spanning the last 70,000 years. CaCO3 burial fluxes, foraminifera stable isotopes, and sedimentary uranium-series disequilibria (including seawater-derived 231Pa /230Th), display coherent, complementary variability throughout the last glaciation. Glacial values in each proxy are consistent with reduced ventilation and overturning compared to the Holocene, with intervals that indicate substantial millennial reductions in each, and others when they briefly approach Holocene levels. In multiple instances, particularly spanning interstadials eight through twelve (IS8-IS12) our results are consistent with an <span class="hlt">abrupt</span>, subcentennial acceleration in the export of excess 231Pa from the North Atlantic during stadial-interstadial transitions</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMPP31C2261H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMPP31C2261H"><span>Stalagmite-inferred <span class="hlt">abrupt</span> hydroclimate changes in the central Mediterranean over the past 6500 years</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hu, H. M.; Shen, C. C.; Jiang, X.; Wang, Y.; Mii, H. S.</p> <p>2015-12-01</p> <p>Mediterranean, as one of the global climate change "hot spots", was faced with severe drought over the recent decades. Investigation of regional paleo-hydroclimate evolution helps improve climate projection and adaption strategy. Here, we present a new decadal-resolved record documenting hydroclimate in the central Mediterranean from an Italian stalagmite since 6500 years ago. Eighty high-precision absolute U-Th dates with 2-sigma uncertainty better than ±20 years and 560 oxygen isotopic ratio data show several <span class="hlt">abrupt</span> drying <span class="hlt">events</span> with an average of 600 mm precipitation decrease in less than 80 years since the mid-Holocene. North Atlantic Oscillation (NAO) could dominantly govern the centennial-scale hydroclimate variability, especially for a period of 4500 to 2000 years ago. Total solar irradiance (TSI) also partially affected this regional precipitation. The obscure relationship between stalagmite and global/local mean surface temperature sequences, in contradict to previous studies, implies complex internal feedback of global <span class="hlt">warming</span> and atmospheric circulation in the Mediterranean. Our result suggests that the twenty-first century Mediterranean drying trend is significant but not unprecedented in the past six thousand years.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015QuRes..83..315T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015QuRes..83..315T"><span>Sedimentary proxy evidence of a mid-Holocene hypsithermal <span class="hlt">event</span> in the location of a current <span class="hlt">warming</span> hole, North Carolina, USA</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tanner, Benjamin R.; Lane, Chad S.; Martin, Elizabeth M.; Young, Robert; Collins, Beverly</p> <p>2015-03-01</p> <p>A wetland deposit from the southern Appalachian mountains of North Carolina, USA, has been radiocarbon dated and shows continuous deposition from the early Holocene to the present. Non-coastal records of Holocene paleoenvironments are rare from the southeastern USA. Increased stable carbon isotope ratios (δ13C) of sedimentary organic matter and pollen percentages indicate <span class="hlt">warm</span>, dry early- to mid-Holocene conditions. This interpretation is also supported by n-alkane biomarker data and bulk sedimentary C/N ratios. These <span class="hlt">warm</span>, dry conditions coincide with a mid-Holocene hypsithermal, or altithermal, documented elsewhere in North America. Our data indicate that the southeastern USA <span class="hlt">warmed</span> concurrently with much of the rest of the continent during the mid-Holocene. If the current "<span class="hlt">warming</span> hole" in the southeastern USA persists, during a time of greenhouse gas-induced <span class="hlt">warming</span> elsewhere, it will be anomalous both in space and time.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1810625M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1810625M"><span><span class="hlt">Abrupt</span> shifts in ecosystem function and intensification of global biogeochemical cycle driven by hydroclimatic extremes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ma, Xuanlong; Huete, Alfredo; Ponce-Campos, Guillermo; Zhang, Yongguang; Xie, Zunyi; Giovannini, Leandro; Cleverly, James; Eamus, Derek</p> <p>2016-04-01</p> <p>Amplification of the hydrologic cycle as a consequence of global <span class="hlt">warming</span> is increasing the frequency, intensity, and spatial extent of extreme climate <span class="hlt">events</span> globally. The potential influences resulting from amplification of the hydro-climatic cycle, coupled with an accelerating <span class="hlt">warming</span> trend, pose great concerns on the sustainability of terrestrial ecosystems to sequester carbon, maintain biodiversity, provide ecosystem services, food security, and support human livelihood. Despite the great implications, the magnitude, direction, and carry-over effect of these extreme climate <span class="hlt">events</span> on ecosystem function, remain largely uncertain. To address these pressing issues, we conducted an observational, interdisciplinary study using satellite retrievals of atmospheric CO2 and photosynthesis (chlorophyll fluorescence), and in-situ flux tower measures of ecosystem-atmosphere carbon exchange, to reveal the shifts in ecosystem function across extreme drought and wet periods. We further determine the factors that govern ecosystem sensitivity to hydroclimatic extremes. We focus on Australia but extended our analyses to other global dryland regions due to their significant role in global biogeochemical cycles. Our results revealed dramatic impacts of drought and wet hydroclimatic extremes on ecosystem function, with <span class="hlt">abrupt</span> changes in vegetation productivity, carbon uptake, and water-use-efficiency between years. Drought resulted in widespread reductions or collapse in the normal patterns of vegetation growth seasonality such that in many cases there was no detectable phenological cycle during extreme drought years. We further identified a significant increasing trend (p < 0.001) in extreme wet year precipitation amounts over Australia and many other global regions, resulting in an increasing trend in magnitude of the episodic carbon sink pulses coupled to each La Niña-induced wet years. This finding is of global biogeochemical significance, with the consequence of amplifying</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/14558908','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/14558908"><span>The economics of <span class="hlt">abrupt</span> climate change.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Perrings, Charles</p> <p>2003-09-15</p> <p>The US National Research Council defines <span class="hlt">abrupt</span> climate change as a change of state that is sufficiently rapid and sufficiently widespread in its effects that economies are unprepared or incapable of adapting. This may be too restrictive a definition, but <span class="hlt">abrupt</span> climate change does have implications for the choice between the main response options: mitigation (which reduces the risks of climate change) and adaptation (which reduces the costs of climate change). The paper argues that by (i) increasing the costs of change and the potential growth of consumption, and (ii) reducing the time to change, <span class="hlt">abrupt</span> climate change favours mitigation over adaptation. Furthermore, because the implications of change are fundamentally uncertain and potentially very high, it favours a precautionary approach in which mitigation buys time for learning. Adaptation-oriented decision tools, such as scenario planning, are inappropriate in these circumstances. Hence learning implies the use of probabilistic models that include socioeconomic feedbacks.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMSA34A..02C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMSA34A..02C"><span>Semi diurnal lunar tides in the MLT at mid and high northern and southern latitudes during major sudden stratospheric <span class="hlt">warming</span> <span class="hlt">events</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chau, J. L.; Hoffmann, P.; Pedatella, N. M.; Janches, D.; Murphy, D. J.; Stober, G.</p> <p>2015-12-01</p> <p>From recent ground- and satellite-based observations as well as from model results, it is well known that lunar tide signatures are amplified significantly during northern hemisphere sudden stratospheric <span class="hlt">warming</span> <span class="hlt">events</span> (SSWs). Such signatures have been observed in the equatorial and low latitude ionosphere and mesosphere, and at the mesosphere and lower thermosphere (MLT) at the northern mid and high latitude mesosphere. More recently, ionospheric signatures at mid-latitudes have been also observed in satellite instruments and such observations are corroborated with model results when the lunar tides are included. From these results (N. Pedatella, personal communication), there is a strong hemispheric asymmetry, where ionospheric perturbations occur primarily in the southern hemisphere. Motivated by these results, in this work we compare the tidal signatures in the MLT region at mid and high latitudes in both hemispheres. We make use of MLT winds obtained with specular meteor radars (SMR) at Juliusruh (54oN), Andøya (69oN), Rio Grande (54oS), and Davis (69oS) around the 2009 and 2013 major SSWs. In addition we complement our studies, with model results from the Whole Atmosphere Community Climate Model Extended version (WACCM-X) combined with the thermosphere-ionosphere-mesosphere electrodynamics general circulation model (TIME-GCM) and the inclusions of lunar tides. Besides these results, we present a brief description and preliminary results of our new approach to derive wind fields in the MLT region using multi-static, multi-frequency specular meteor radars, called MMARIA.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007GeoRL..3415709T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007GeoRL..3415709T"><span><span class="hlt">Abrupt</span> climate change in southeast tropical Africa influenced by Indian monsoon variability and ITCZ migration</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tierney, Jessica E.; Russell, James M.</p> <p>2007-08-01</p> <p>The timing and magnitude of <span class="hlt">abrupt</span> climate change in tropical Africa during the last glacial termination remains poorly understood. High-resolution paleolimnological data from Lake Tanganyika, Southeast Africa show that wind-driven seasonal mixing in the lake was reduced during the Younger Dryas, Inter-Allerød Cool Period, Older Dryas, and Heinrich <span class="hlt">Event</span> 1, suggesting a weakened southwest Indian monsoon and a more southerly position of the Inter-Tropical Convergence Zone over Africa during these intervals. These <span class="hlt">events</span> in Lake Tanganyika, coeval with millennial and centennial-scale climate shifts in the high latitudes, suggest that changes in ITCZ location and Indian monsoon strength are important components of <span class="hlt">abrupt</span> global climate change and that their effects are felt south of the equator in Africa. However, we observe additional <span class="hlt">events</span> in Lake Tanganyika of equal magnitude that are not correlated with high-latitude changes, indicating the potential for <span class="hlt">abrupt</span> climate change to originate from within tropical systems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMPP13C..01S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMPP13C..01S"><span>Coherent Sea Ice Variations in the Nordic Seas and <span class="hlt">Abrupt</span> Greenland Climate Changes over Dansgaard-Oeschger Cycles</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sadatzki, H.; Berben, S.; Dokken, T.; Stein, R.; Fahl, K.; Jansen, E.</p> <p>2016-12-01</p> <p>Rapid changes in sea ice extent in the Nordic Seas may have played a crucial role in controlling the <span class="hlt">abruptness</span> of ocean circulation and climate changes associated with Dansgaard-Oeschger (D-O) cycles during the last glacial (Li et al., 2010; Dokken et al., 2013). To investigate the role of sea ice for <span class="hlt">abrupt</span> climate changes, we produced a sea ice record from the Norwegian Sea Core MD99-2284 at a temporal resolution approaching that of ice core records, covering four D-O cycles at ca. 32-41 ka. This record is based on the sea ice diatom biomarker IP25, open-water phytoplankton biomarker dinosterol and semi-quantitative phytoplankton-IP25 (PIP25) estimates. A detailed tephrochronology of MD99-2284 corroborates the tuning-based age model and independently constrains the GS9/GIS8 transition, allowing for direct comparison between our sediment and ice core records. For cold stadials we find extremely low fluxes of total organic carbon, dinosterol and IP25, which points to a general absence of open-water phytoplankton and ice algae production under a near-permanent sea ice cover. For the interstadials, in turn, all biomarker fluxes are strongly enhanced, reflecting a highly productive sea ice edge situation and implying largely open ocean conditions for the eastern Nordic Seas. As constrained by three tephra layers, we observe that the stadial-interstadial sea ice decline was rapid and may have induced a coeval <span class="hlt">abrupt</span> northward shift in the Greenland precipitation moisture source as recorded in ice cores. The sea ice retreat also facilitated a massive heat release through deep convection in the previously stratified Nordic Seas, generating atmospheric <span class="hlt">warming</span> of the D-O <span class="hlt">events</span>. We thus conclude that rapid changes in sea ice extent in the Nordic Seas amplified oceanic reorganizations and were a key factor in controlling <span class="hlt">abrupt</span> Greenland climate changes over D-O cycles. Dokken, T.M. et al., 2013. Paleoceanography 28, 491-502 Li, C. et al., 2010. Journ. Clim. 23, 5457-5475</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA137434','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA137434"><span>Detection of <span class="hlt">Abrupt</span> Changes in Dynamic Systems,</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>1984-01-01</p> <p>the detection of <span class="hlt">abrupt</span> chnages in dynamic systems. These efforts have been motivated by a wide variety of applications includinq the detection of...34Failure Detection in Dynimic Systems," AGARD Lecture Series No. 109 on Fault Tolerance Design and Redundancy Management Technqiues, Athens, Rome, and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26528702','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26528702"><span>Spinal Surgery and <span class="hlt">Abrupt</span> Intrathecal Baclofen Withdrawal.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zheng, Karl; Brodsky, Jay B</p> <p>2015-11-01</p> <p><span class="hlt">Abrupt</span> cessation of intrathecal baclofen can lead to a serious withdrawal syndrome. The anesthesiologist must be prepared to avoid intraoperative interruption of baclofen delivery before starting spinal surgery and to recognize and treat the symptoms of baclofen withdrawal in the immediate postoperative period.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19840009920','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19840009920"><span>Detection of <span class="hlt">abrupt</span> changes in dynamic systems</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Willsky, A. S.</p> <p>1984-01-01</p> <p>Some of the basic ideas associated with the detection of <span class="hlt">abrupt</span> changes in dynamic systems are presented. Multiple filter-based techniques and residual-based method and the multiple model and generalized likelihood ratio methods are considered. Issues such as the effect of unknown onset time on algorithm complexity and structure and robustness to model uncertainty are discussed.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_16 --> <div id="page_17" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="321"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/46040','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/46040"><span>Global <span class="hlt">warming</span> elucidated</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Shen, S.</p> <p>1995-03-01</p> <p>The meaning of global <span class="hlt">warming</span> and its relevance to everyday life is explained. Simple thermodynamics is used to predict an oscillatory nature of the change in climate due to global <span class="hlt">warming</span>. Global <span class="hlt">warming</span> causes extreme <span class="hlt">events</span> and bad weather in the near term. In the long term it may cause the earth to transition to another equilibrium state through many oscillation in climatic patterns. The magnitudes of these oscillations could easily exceed the difference between the end points. The author further explains why many no longer fully understands the nature and magnitudes of common phenomena such as storms and wind speeds because of these oscillations, and the absorptive properties of clouds. The author links the increase in duration of the El Nino to global <span class="hlt">warming</span>, and further predicts public health risks as the earth transitions to another equilibrium state in its young history.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMPP23D..01H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMPP23D..01H"><span><span class="hlt">Abrupt</span> Climate Change in the Southern Great Plains during the Last Glacial Interval</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Housson, A. L.; Maupin, C. R.; Roark, B.; Shen, C. C.; Baykara, O.; White, K.; Kampen-Lewis, S. V.; McChesney, C. L.</p> <p>2016-12-01</p> <p>Understanding how the climate of the North American Great Plains may change in the future is of tremendous socioeconomic importance, yet the regional response to previous <span class="hlt">abrupt</span> global climate <span class="hlt">events</span>, such as the Dansgaard-Oeschger (DO) cycles of the last glacial interval, are poorly known. Here we present two absolutely dated (U/Th), partially replicated oxygen isotope (δ18O) records from calcite speleothems in central Texas (30° N, 98° W) that grew during marine isotope stage 3 (MIS 3) (31 to 49 ky BP). The study site experiences boreal spring and fall maxima in precipitation with rainfall moisture sourced almost exclusively from the Gulf of Mexico. The two samples exhibit reproducible δ18O means and variability during overlapping growth intervals. Weak correlations between paired oxygen and carbon isotopic values coupled with reproducible δ18O strongly suggest that dripwater δ18O and calcite formation temperatures are the primary drivers of speleothem δ18O variations through time. We interpret more depleted (enriched) δ18O values to reconstruct warmer and wetter (cooler and drier) conditions based on observations of modern rainfall stable isotope variations at the study site. We find that warmer and wetter conditions in the Southern Plains are contemporaneous with MIS 3 DO interstadials, while cooler and more arid conditions prevail during stadials and Heinrich <span class="hlt">Events</span> 4 and 5. Our results show a response opposite that of hydrologic reconstructions from the American Southwest, where wetter conditions occur with stadial conditions. Future work includes exploration of paleoclimate model results to examine potential mechanisms responsible for this opposite phasing. Our speleothem data indicate that further intensification of rainy seasons in the Southern Plains should not be ruled out as a response to anthropogenic global <span class="hlt">warming</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/12228715','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/12228715"><span>Relative timing of deglacial climate <span class="hlt">events</span> in Antarctica and Greenland.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Morgan, Vin; Delmotte, Marc; van Ommen, Tas; Jouzel, Jean; Chappellaz, Jérôme; Woon, Suenor; Masson-Delmotte, Valérie; Raynaud, Dominique</p> <p>2002-09-13</p> <p>The last deglaciation was marked by large, hemispheric, millennial-scale climate variations: the Bølling-Allerød and Younger Dryas periods in the north, and the Antarctic Cold Reversal in the south. A chronology from the high-accumulation Law Dome East Antarctic ice core constrains the relative timing of these two <span class="hlt">events</span> and provides strong evidence that the cooling at the start of the Antarctic Cold Reversal did not follow the <span class="hlt">abrupt</span> <span class="hlt">warming</span> during the northern Bølling transition around 14,500 years ago. This result suggests that southern changes are not a direct response to <span class="hlt">abrupt</span> changes in North Atlantic thermohaline circulation, as is assumed in the conventional picture of a hemispheric temperature seesaw.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007PalOc..22.1219F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007PalOc..22.1219F"><span>Tropical <span class="hlt">warming</span> and intermittent cooling during the Cenomanian/Turonian oceanic anoxic <span class="hlt">event</span> 2: Sea surface temperature records from the equatorial Atlantic</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Forster, Astrid; Schouten, Stefan; Moriya, Kazuyoshi; Wilson, Paul A.; Sinninghe Damsté, Jaap S.</p> <p>2007-03-01</p> <p>Oceanic anoxic <span class="hlt">event</span> 2 (OAE-2) occurring during the Cenomanian/Turonian (C/T) transition is evident from a globally recognized positive stable carbon isotopic excursion and is thought to represent one of the most extreme carbon cycle perturbations of the last 100 Myr. However, the impact of this major perturbation on and interaction with global climate remains unclear. Here we report new high-resolution records of sea surface temperature (SST) based on TEX86 and δ18O of excellently preserved planktic foraminifera and stable organic carbon isotopes across the C/T transition from black shales located offshore Suriname/French Guiana (Demerara Rise, Ocean Drilling Program Leg 207 Site 1260) and offshore Senegal (Cape Verde Basin, Deep Sea Drilling Project Leg 41 Site 367). At Site 1260, where both SST proxy records can be determined, a good match between conservative SST estimates from TEX86 and δ18O is observed. We find that late Cenomanian SSTs in the equatorial Atlantic Ocean (≥33°C) were substantially warmer than today (˜27°-29°C) and that the onset of OAE-2 coincided with a rapid shift to an even warmer (˜35°-36°C) regime. Within the early stages of the OAE a marked (˜4°C) cooling to temperatures lower than pre-OAE conditions is observed. However, well before the termination of OAE-2 the <span class="hlt">warm</span> regime was reestablished and persisted into the Turonian. Our findings corroborate the view that the C/T transition represents the onset of the interval of peak Cretaceous warmth. More importantly, they are consistent with the hypotheses that mid-Cretaceous warmth can be attributed to high levels of atmospheric carbon dioxide (CO2) and that major OAEs were capable of triggering global cooling through the negative feedback effect of organic carbon-burial-led CO2 sequestration. Evidently, however, the factors that gave rise to the observed shift to a warmer climate regime at the onset of OAE-2 were sufficiently powerful that they were only briefly counterbalanced</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3769652','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3769652"><span><span class="hlt">Abrupt</span> rise of new machine ecology beyond human response time</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Johnson, Neil; Zhao, Guannan; Hunsader, Eric; Qi, Hong; Johnson, Nicholas; Meng, Jing; Tivnan, Brian</p> <p>2013-01-01</p> <p>Society's techno-social systems are becoming ever faster and more computer-orientated. However, far from simply generating faster versions of existing behaviour, we show that this speed-up can generate a new behavioural regime as humans lose the ability to intervene in real time. Analyzing millisecond-scale data for the world's largest and most powerful techno-social system, the global financial market, we uncover an <span class="hlt">abrupt</span> transition to a new all-machine phase characterized by large numbers of subsecond extreme <span class="hlt">events</span>. The proliferation of these subsecond <span class="hlt">events</span> shows an intriguing correlation with the onset of the system-wide financial collapse in 2008. Our findings are consistent with an emerging ecology of competitive machines featuring ‘crowds' of predatory algorithms, and highlight the need for a new scientific theory of subsecond financial phenomena. PMID:24022120</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/981810','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/981810"><span>Transient Simulation of Last Deglaciation with a New Mechanism for B lling-Aller d <span class="hlt">Warming</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Erickson, David J</p> <p>2009-01-01</p> <p>We conducted the first synchronously coupled atmosphere-ocean general circulation model simulation from the Last Glacial Maximum to the Boelling-Alleroed (BA) <span class="hlt">warming</span>. Our model reproduces several major features of the deglacial climate evolution, suggesting a good agreement in climate sensitivity between the model and observations. In particular, our model simulates the <span class="hlt">abrupt</span> BA <span class="hlt">warming</span> as a transient response of the Atlantic meridional overturning circulation (AMOC) to a sudden termination of freshwater discharge to the North Atlantic before the BA. In contrast to previous mechanisms that invoke AMOC multiple equilibrium and Southern Hemisphere climate forcing, we propose that the BA transition is caused by the superposition of climatic responses to the transient CO{sub 2} forcing, the AMOC recovery from Heinrich <span class="hlt">Event</span> 1, and an AMOC overshoot.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016NatSR...636217I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016NatSR...636217I"><span><span class="hlt">Abrupt</span> onset of tongue deformation and phase space response of ions in magnetically-confined plasmas</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ida, K.; Kobayashi, T.; Itoh, K.; Yoshinuma, M.; Tokuzawa, T.; Akiyama, T.; Moon, C.; Tsuchiya, H.; Inagaki, S.; Itoh, S.-I.</p> <p>2016-10-01</p> <p>An <span class="hlt">abrupt</span> onset of the new tongue-shaped deformation of magnetic surface in magnetized plasmas, which was conjectured in since the 1960s but has not been observed, is experimentally identified just before an <span class="hlt">abrupt</span> onset of a large-scale collapse <span class="hlt">event</span>. Two novel properties of the <span class="hlt">event</span> are identified. First, the transition of symmetry of perturbation (rather than a growth of linearly unstable MHD modes) was found to be a key for the onset of <span class="hlt">abrupt</span> collapse, i.e., the transition of symmetry gives a new route to the collapse from stable state. Second, as a phase-space response of ions, the distortion from Maxwell-Boltzmann distribution of epithermal ions was observed for the first time.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5087079','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5087079"><span><span class="hlt">Abrupt</span> onset of tongue deformation and phase space response of ions in magnetically-confined plasmas</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Ida, K.; Kobayashi, T.; Itoh, K.; Yoshinuma, M.; Tokuzawa, T.; Akiyama, T.; Moon, C.; Tsuchiya, H.; Inagaki, S.; Itoh, S.-I.</p> <p>2016-01-01</p> <p>An <span class="hlt">abrupt</span> onset of the new tongue-shaped deformation of magnetic surface in magnetized plasmas, which was conjectured in since the 1960s but has not been observed, is experimentally identified just before an <span class="hlt">abrupt</span> onset of a large-scale collapse <span class="hlt">event</span>. Two novel properties of the <span class="hlt">event</span> are identified. First, the transition of symmetry of perturbation (rather than a growth of linearly unstable MHD modes) was found to be a key for the onset of <span class="hlt">abrupt</span> collapse, i.e., the transition of symmetry gives a new route to the collapse from stable state. Second, as a phase-space response of ions, the distortion from Maxwell-Boltzmann distribution of epithermal ions was observed for the first time. PMID:27796370</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3892437','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3892437"><span><span class="hlt">Abruptness</span> of Cascade Failures in Power Grids</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Pahwa, Sakshi; Scoglio, Caterina; Scala, Antonio</p> <p>2014-01-01</p> <p>Electric power-systems are one of the most important critical infrastructures. In recent years, they have been exposed to extreme stress due to the increasing demand, the introduction of distributed renewable energy sources, and the development of extensive interconnections. We investigate the phenomenon of <span class="hlt">abrupt</span> breakdown of an electric power-system under two scenarios: load growth (mimicking the ever-increasing customer demand) and power fluctuations (mimicking the effects of renewable sources). Our results on real, realistic and synthetic networks indicate that increasing the system size causes breakdowns to become more <span class="hlt">abrupt</span>; in fact, mapping the system to a solvable statistical-physics model indicates the occurrence of a first order transition in the large size limit. Such an enhancement for the systemic risk failures (black-outs) with increasing network size is an effect that should be considered in the current projects aiming to integrate national power-grids into “super-grids”. PMID:24424239</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24424239','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24424239"><span><span class="hlt">Abruptness</span> of cascade failures in power grids.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Pahwa, Sakshi; Scoglio, Caterina; Scala, Antonio</p> <p>2014-01-15</p> <p>Electric power-systems are one of the most important critical infrastructures. In recent years, they have been exposed to extreme stress due to the increasing demand, the introduction of distributed renewable energy sources, and the development of extensive interconnections. We investigate the phenomenon of <span class="hlt">abrupt</span> breakdown of an electric power-system under two scenarios: load growth (mimicking the ever-increasing customer demand) and power fluctuations (mimicking the effects of renewable sources). Our results on real, realistic and synthetic networks indicate that increasing the system size causes breakdowns to become more <span class="hlt">abrupt</span>; in fact, mapping the system to a solvable statistical-physics model indicates the occurrence of a first order transition in the large size limit. Such an enhancement for the systemic risk failures (black-outs) with increasing network size is an effect that should be considered in the current projects aiming to integrate national power-grids into "super-grids".</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/1007412','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/1007412"><span>Weird Weather: Large <span class="hlt">Abrupt</span> Widespread Climate Changes</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Alley, Richard B.</p> <p>2001-01-24</p> <p>Ice-core records and other paleoclimatic indicators show that large (up to 10 degrees C), <span class="hlt">abrupt</span> (in about 10 years), widespread (hemispheric to global) climate changes have been common for much of the last 100,000 years and beyond, but rare during the most recent few millennia. Changes in the coupled ocean-atmosphere system with a center of activity in the north Atlantic probably have been important, but several hypotheses remain possible including solar influence and a stochastically resonant interaction with changing freshwater fluxes. Our current understanding does not allow us to exclude the possibility that human or natural processes could 'flip the switch' of another <span class="hlt">abrupt</span> change in the future.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2791606','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2791606"><span>Basic mechanism for <span class="hlt">abrupt</span> monsoon transitions</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Levermann, Anders; Schewe, Jacob; Petoukhov, Vladimir; Held, Hermann</p> <p>2009-01-01</p> <p>Monsoon systems influence the livelihood of hundreds of millions of people. During the Holocene and last glacial period, rainfall in India and China has undergone strong and <span class="hlt">abrupt</span> changes. Though details of monsoon circulations are complicated, observations reveal a defining moisture-advection feedback that dominates the seasonal heat balance and might act as an internal amplifier, leading to <span class="hlt">abrupt</span> changes in response to relatively weak external perturbations. Here we present a minimal conceptual model capturing this positive feedback. The basic equations, motivated by observed relations, yield a threshold behavior, robust with respect to addition of other physical processes. Below this threshold in net radiative influx, R c, no conventional monsoon can develop; above R c, two stable regimes exist. We identify a nondimensional parameter l that defines the threshold and makes monsoon systems comparable with respect to the character of their <span class="hlt">abrupt</span> transition. This dynamic similitude may be helpful in understanding past and future variations in monsoon circulation. Within the restrictions of the model, we compute R c for current monsoon systems in India, China, the Bay of Bengal, West Africa, North America, and Australia, where moisture advection is the main driver of the circulation. PMID:19858472</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19858472','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19858472"><span>Basic mechanism for <span class="hlt">abrupt</span> monsoon transitions.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Levermann, Anders; Schewe, Jacob; Petoukhov, Vladimir; Held, Hermann</p> <p>2009-12-08</p> <p>Monsoon systems influence the livelihood of hundreds of millions of people. During the Holocene and last glacial period, rainfall in India and China has undergone strong and <span class="hlt">abrupt</span> changes. Though details of monsoon circulations are complicated, observations reveal a defining moisture-advection feedback that dominates the seasonal heat balance and might act as an internal amplifier, leading to <span class="hlt">abrupt</span> changes in response to relatively weak external perturbations. Here we present a minimal conceptual model capturing this positive feedback. The basic equations, motivated by observed relations, yield a threshold behavior, robust with respect to addition of other physical processes. Below this threshold in net radiative influx, R(c), no conventional monsoon can develop; above R(c), two stable regimes exist. We identify a nondimensional parameter l that defines the threshold and makes monsoon systems comparable with respect to the character of their <span class="hlt">abrupt</span> transition. This dynamic similitude may be helpful in understanding past and future variations in monsoon circulation. Within the restrictions of the model, we compute R(c) for current monsoon systems in India, China, the Bay of Bengal, West Africa, North America, and Australia, where moisture advection is the main driver of the circulation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4035952','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4035952"><span>Younger Dryas deglaciation of Scotland driven by <span class="hlt">warming</span> summers</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Bromley, Gordon R. M.; Putnam, Aaron E.; Rademaker, Kurt M.; Lowell, Thomas V.; Schaefer, Joerg M.; Hall, Brenda; Winckler, Gisela; Birkel, Sean D.; Borns, Harold W.</p> <p>2014-01-01</p> <p>The Younger Dryas Stadial (YDS; ∼12,900–11,600 y ago) in the Northern Hemisphere is classically defined by <span class="hlt">abrupt</span> cooling and renewed glaciation during the last glacial–interglacial transition. Although this <span class="hlt">event</span> involved a global reorganization of atmospheric and oceanic circulation [Denton GH, Alley RB, Comer GC, Broecker WS (2005) Quat Sci Rev 24:1159–1182], the magnitude, seasonality, and geographical footprint of YDS cooling remain unresolved and pose a challenge to our understanding of <span class="hlt">abrupt</span> climate change. Here, we present a deglacial chronology from Scotland, immediately downwind of the North Atlantic Ocean, indicating that the Scottish ice cap disintegrated during the first half of the YDS. We suggest that stratification of the North Atlantic Ocean resulted in amplified seasonality that, paradoxically, stimulated a severe wintertime climate while promoting <span class="hlt">warming</span> summers through solar heating of the mixed layer. This latter process drove deglaciation of downwind landmasses to completion well before the end of the YDS. PMID:24733909</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17949833','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17949833"><span>Transient left ventricular apical ballooning syndrome caused by <span class="hlt">abrupt</span> metoprolol withdrawal.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Jefic, Dane; Koul, Deepak; Boguszewski, Andrzej; Martini, Wisam</p> <p>2008-12-17</p> <p>Transient Left Ventricular Apical Ballooning Syndrome (TLVABS) has been described to occur in response to number of stressful <span class="hlt">events</span>, drug effects or drug withdrawal. Withdrawal of beta blockade has not been described to precipitate TLVABS. We are describing a case of TLVABS developing after <span class="hlt">abrupt</span> withdrawal of metoprolol.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ClDy...44.2897B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ClDy...44.2897B"><span>An interhemispheric mechanism for glacial <span class="hlt">abrupt</span> climate change</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Banderas, Rubén; Alvarez-Solas, Jorge; Robinson, Alexander; Montoya, Marisa</p> <p>2015-05-01</p> <p>The last glacial period was punctuated by <span class="hlt">abrupt</span> climate changes that are widely considered to result from millennial-scale variability of the Atlantic meridional overturning circulation (AMOC). However, the origin of these AMOC reorganizations remains poorly understood. The climatic connection between both hemispheres indicated by proxies suggests that the Southern Ocean (SO) could regulate this variability through changes in winds and atmospheric CO concentration. Here, we investigate this hypothesis using a coupled climate model forced by prescribed CO and SO wind-stress variations. We find that the AMOC exhibits an oscillatory behavior between weak and strong circulation regimes which is ultimately caused by changes in the meridional density gradient of the Atlantic Ocean. The evolution of the simulated climatic patterns matches the amplitude and timing of the largest <span class="hlt">events</span> that occurred during the last glacial period and their widespread climatic impacts. Our results suggest the existence of an internal interhemispheric oscillation mediated by the bipolar seesaw that could promote glacial <span class="hlt">abrupt</span> climate changes through variations in atmospheric CO levels, the strength of the SO winds and AMOC reorganizations, and provide an explanation for the pervasive Antarctic-like climate signal found in proxy records worldwide.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMPP53D..07M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMPP53D..07M"><span>Atmospheric teleconnections between the tropics and the Southern Hemisphere westerly winds during <span class="hlt">abrupt</span> climate change</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Markle, B. R.; Steig, E. J.; Buizert, C.; Schoenemann, S. W.; Bitz, C. M.; Fudge, T. J.; Pedro, J. B.; Ding, Q.; Jones, T. R.; White, J. W. C.; Sowers, T. A.</p> <p>2015-12-01</p> <p><span class="hlt">Abrupt</span>, large amplitude climate oscillations occurred in the North Atlantic region during the last deglaciation and glacial period. Antarctic temperatures show a lagged and out-of-phase response, suggesting that these climate anomalies were propagated to the Southern Hemisphere high latitudes through changes in ocean circulation. Large changes in atmospheric circulation in the tropics accompanied <span class="hlt">abrupt</span> North Atlantic climate change and modeling studies have predicted an atmospheric teleconnection between the tropics and the Southern Hemisphere westerly winds. However, consistent paleoclimate evidence for this tropical-high southern latitude atmospheric teleconnection has been lacking. Here we use a new high-resolution deuterium excess record from West Antarctica to show that moisture sources for Antarctic precipitation changed in phase with <span class="hlt">abrupt</span> shifts in Northern Hemisphere climate, significantly before Antarctic temperature change. These results suggest that Southern Hemisphere mid-latitude storm tracks and westerly winds migrated north- and southwards within decades of rapid North Atlantic <span class="hlt">warming</span> and cooling, respectively, and in parallel with the well-established migrations of the intertropical convergence zone. Both ocean and atmospheric processes, operating on different timescales, are critical to the global expression of <span class="hlt">abrupt</span> climate change and this atmospheric link between the hemispheres may be important to the underlying dynamics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.U41A..11L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.U41A..11L"><span>The Early Eocene Hyperthermal <span class="hlt">Events</span>: Magnitude, Characteristics and Orbital Chronology.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lauretano, V.; Zachos, J. C.; Lourens, L. J.</p> <p>2016-12-01</p> <p>The early Eocene was characterized by major perturbations in the global carbon cycle and fluctuations in global temperature on both short- (<104 years) and long- (> 106 years) time scales. The Paleocene- Eocene Thermal Maximum (PETM), at 56 Ma, represents the most extreme episode of <span class="hlt">abrupt</span> short-lived global <span class="hlt">warming</span> <span class="hlt">event</span> superimposed on the late Paleocene- early Eocene long-term <span class="hlt">warming</span> trend. The PETM was followed by a series of smaller "hyperthermal" <span class="hlt">events</span> showing similar characteristics, including the ETM2 (or Elmo <span class="hlt">event</span>) at 54 Ma and the ETM3 (or X-<span class="hlt">event</span>) at 52.8 Ma, leading up to the Early Eocene Climatic Optimum (EECO). These <span class="hlt">events</span> are recorded in marine and continental sedimentary archives and are marked by prominent carbon isotope excursions (CIEs). As for the PETM, the "hyperthermal" <span class="hlt">events</span> were associated with dramatic increase in temperature and perturbation of the carbon cycle, driven by the release of large amounts of isotopically light carbon into the ocean-atmosphere system, possibly triggered by a common orbital forcing mechanism. Here, we present astronomically tuned high-resolution benthic stable isotope records from ODP Site 1263, (Walvis Ridge, SE Atlantic) encompassing the early Eocene hyperthermal <span class="hlt">events</span>. We discuss the changes in deep-sea temperature and global carbon cycle associated with these <span class="hlt">events</span> in relation to the PETM, and define their timing, duration and the influence of orbital forcing.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ClDy...48..727M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ClDy...48..727M"><span>An <span class="hlt">abrupt</span> weakening of the subpolar gyre as trigger of Little Ice Age-type episodes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Moreno-Chamarro, Eduardo; Zanchettin, Davide; Lohmann, Katja; Jungclaus, Johann H.</p> <p>2017-02-01</p> <p>We investigate the mechanism of a decadal-scale weakening shift in the strength of the subpolar gyre (SPG) that is found in one among three last millennium simulations with a state-of-the-art Earth system model. The SPG shift triggers multicentennial anomalies in the North Atlantic climate driven by long-lasting internal feedbacks relating anomalous oceanic and atmospheric circulation, sea ice extent, and upper-ocean salinity in the Labrador Sea. Yet changes throughout or after the shift are not associated with a persistent weakening of the Atlantic Meridional Overturning Circulation or shifts in the North Atlantic Oscillation. The anomalous climate state of the North Atlantic simulated after the shift agrees well with climate reconstructions from within the area, which describe a transition between a stronger and weaker SPG during the relatively <span class="hlt">warm</span> medieval climate and the cold Little Ice Age respectively. However, model and data differ in the timing of the onset. The simulated SPG shift is caused by a rapid increase in the freshwater export from the Arctic and associated freshening in the upper Labrador Sea. Such freshwater anomaly relates to prominent thickening of the Arctic sea ice, following the cluster of relatively small-magnitude volcanic eruptions by 1600 CE. Sensitivity experiments without volcanic forcing can nonetheless produce similar <span class="hlt">abrupt</span> <span class="hlt">events</span>; a necessary causal link between the volcanic cluster and the SPG shift can therefore be excluded. Instead, preconditioning by internal variability explains discrepancies in the timing between the simulated SPG shift and the reconstructed estimates for the Little Ice Age onset.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.C34A..04T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.C34A..04T"><span><span class="hlt">Abrupt</span> release of terrigenous organic carbon to the Laptev Sea at termination of the Younger Dryas</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tesi, T.; Muschitiello, F.; Smittenberg, R.; Jakobsson, M.; Vonk, J.; Hill, P.; Dudarev, O.; Semiletov, I. P.; Kirchner, N.; Noormets, R.; Andersson, A.; Gustafsson, O.</p> <p>2015-12-01</p> <p>Based on analysis of a piston core collected in 2014 from the Lena River paleo delta, now Laptev Sea, we show that rapid and massive organic carbon (OC) deposition took place into the marine system at the termination of the Younger Dryas when the Arctic region experienced a large and extremely fast climate change. The highly laminated strata with absence of bioturbation further confirm the rapid <span class="hlt">event</span>-driven emplacement of this deposit which was largely dominated by terrigenous OC as indicated by depleted δ13C values and high concentrations of terrestrial fossil biomarkers (lignin phenols and cutin-derived products). Moreover, the hydrogen isotopic composition (δ2H) of HMW n-alkanes indicates that this terrestrially-derived translocated OC was produced in the watershed during a relatively cold period. The OC appears to be a few thousand years old at time of deposition (ca. 4-5000 radiocarbon years; reservoir age corrected), consistent with the radiocarbon age of pre-aged OC currently supplied by the Lena river. Altogether our results indicate that fast climate <span class="hlt">warming</span> exerts first-order control on large-scale carbon redistribution. Because the Younger Dryas-Preboreal transition occurred within a few decades, we infer that the <span class="hlt">abrupt</span> and large release of terrigenous OC was essentially driven by rapid changes in the permafrost stability (i.e., thermal collapse/thawing) and increase in precipitation over the Siberian watershed. Interestingly, only surface and sub-surface carbon pools (i.e., active layer) were remobilized while deep and old sources (radiocarbon dead) did not seem to have substantially contributed to the total land-to-ocean flux during the Younger Dryas-Preboreal transition.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_17 --> <div id="page_18" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="341"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4250116','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4250116"><span>Topography's crucial role in Heinrich <span class="hlt">Events</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Roberts, William H. G.; Valdes, Paul J.; Payne, Antony J.</p> <p>2014-01-01</p> <p>Heinrich <span class="hlt">Events</span>, the <span class="hlt">abrupt</span> changes in the Laurentide Ice Sheet that cause the appearance of the well-observed Heinrich Layers, are thought to have a strong effect on the global climate. The focus of most studies that have looked at the climate’s response to these <span class="hlt">events</span> has been the freshwater flux that results from melting icebergs. However, there is the possibility that the varying height of the ice sheet could force a change in the climate. In this study, we present results from a newly developed coupled climate/ice sheet model to show what effect this topographic change has both on its own and in concert with the flux of freshwater from melting icebergs. We show that the topographic forcing can explain a number of the climate changes that are observed during Heinrich <span class="hlt">Events</span>, such as the <span class="hlt">warming</span> and wettening in Florida and the <span class="hlt">warm</span> sea surface temperatures in the central North Atlantic, which freshwater forcing alone cannot. We also find regions, for example the tropical Atlantic, where the response is a mixture of the two: Here observations may help disentangle the relative importance of each mechanism. These results suggest that the simple paradigm of a Heinrich <span class="hlt">Event</span> causing climate change via freshwater inputs into the North Atlantic needs to be revised. PMID:25368154</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25368154','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25368154"><span>Topography's crucial role in Heinrich <span class="hlt">Events</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Roberts, William H G; Valdes, Paul J; Payne, Antony J</p> <p>2014-11-25</p> <p>Heinrich <span class="hlt">Events</span>, the <span class="hlt">abrupt</span> changes in the Laurentide Ice Sheet that cause the appearance of the well-observed Heinrich Layers, are thought to have a strong effect on the global climate. The focus of most studies that have looked at the climate's response to these <span class="hlt">events</span> has been the freshwater flux that results from melting icebergs. However, there is the possibility that the varying height of the ice sheet could force a change in the climate. In this study, we present results from a newly developed coupled climate/ice sheet model to show what effect this topographic change has both on its own and in concert with the flux of freshwater from melting icebergs. We show that the topographic forcing can explain a number of the climate changes that are observed during Heinrich <span class="hlt">Events</span>, such as the <span class="hlt">warming</span> and wettening in Florida and the <span class="hlt">warm</span> sea surface temperatures in the central North Atlantic, which freshwater forcing alone cannot. We also find regions, for example the tropical Atlantic, where the response is a mixture of the two: Here observations may help disentangle the relative importance of each mechanism. These results suggest that the simple paradigm of a Heinrich <span class="hlt">Event</span> causing climate change via freshwater inputs into the North Atlantic needs to be revised.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFMGC53D..03M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFMGC53D..03M"><span>Climate response to <span class="hlt">abrupt</span> cessation of solar radiation management</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>McCusker, K. E.; Armour, K.; Bitz, C. M.; Battisti, D. S.</p> <p>2012-12-01</p> <p>Solar radiation management (SRM) as a means to reduce or cancel the effects of increased greenhouse gases may be regarded as effective to the extent that it broadly reduces <span class="hlt">warming</span> and other related changes. Studies that have previously modeled SRM have focused on spatial inhomogeneities in the climate response, assuming that SRM is continued indefinitely and global climate is stabilized. In this study, we focus on the possible situation in which SRM is terminated (e.g. due to lack of funding, international governmental disorganization, technical failure, or unanticipated negative consequences) while greenhouse gases have continued rising. We use a global climate model (GCM) with a prescribed stratospheric sulfate burden that counteracts the Representative Concentration Pathway 8.5 (RCP8.5) - wherein the radiative forcing reaches 8.5 W/m2 above the preindustrial by 2100 - to show that upon termination of the sulfate burden, <span class="hlt">abrupt</span> and sustained <span class="hlt">warming</span> occurs that is well outside familiar 20th century bounds, especially on land. The GCM utilized has a climate sensitivity of 3.2 degrees Celsius, yet in reality climate sensitivity is unknown, its probability density distribution exhibiting a long tail at the high end of sensitivity. Using SRM to stabilize climate while greenhouse gases continue to rise has the effect of obscuring how the climate would respond to the additional gases given the opportunity - climate sensitivity would be masked. We use a simple upwelling-diffusion energy balance model to span the range of the observationally-constrained climate sensitivities to investigate the range of global mean rate of temperature rise following SRM termination, in addition to its sensitivity to termination year and background emissions scenario. We show that in fact, the distribution of temperature trends following termination could be far broader than those simulated by the GCM. These inherent dangers suggest that solar radiation management should only be</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016NatSR...623009S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016NatSR...623009S"><span><span class="hlt">Abrupt</span> climate shift in the Western Mediterranean Sea</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schroeder, K.; Chiggiato, J.; Bryden, H. L.; Borghini, M.; Ben Ismail, S.</p> <p>2016-03-01</p> <p>One century of oceanographic measurements has evidenced gradual increases in temperature and salinity of western Mediterranean water masses, even though the vertical stratification has basically remained unchanged. Starting in 2005, the basic structure of the intermediate and deep layers <span class="hlt">abruptly</span> changed. We report here evidence of reinforced thermohaline variability in the deep western basin with significant dense water formation <span class="hlt">events</span> producing large amounts of warmer, saltier and denser water masses than ever before. We provide a detailed chronological order to these changes, giving an overview of the new water masses and following their route from the central basin interior to the east (toward the Tyrrhenian) and toward the Atlantic Ocean. As a consequence of this climate shift, new deep waters outflowing through Gibraltar will impact the North Atlantic in terms of salt and heat input. In addition, modifications in the Mediterranean abyssal ecosystems and biogeochemical cycles are to be expected.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4786855','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4786855"><span><span class="hlt">Abrupt</span> climate shift in the Western Mediterranean Sea</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Schroeder, K.; Chiggiato, J.; Bryden, H. L.; Borghini, M.; Ben Ismail, S.</p> <p>2016-01-01</p> <p>One century of oceanographic measurements has evidenced gradual increases in temperature and salinity of western Mediterranean water masses, even though the vertical stratification has basically remained unchanged. Starting in 2005, the basic structure of the intermediate and deep layers <span class="hlt">abruptly</span> changed. We report here evidence of reinforced thermohaline variability in the deep western basin with significant dense water formation <span class="hlt">events</span> producing large amounts of warmer, saltier and denser water masses than ever before. We provide a detailed chronological order to these changes, giving an overview of the new water masses and following their route from the central basin interior to the east (toward the Tyrrhenian) and toward the Atlantic Ocean. As a consequence of this climate shift, new deep waters outflowing through Gibraltar will impact the North Atlantic in terms of salt and heat input. In addition, modifications in the Mediterranean abyssal ecosystems and biogeochemical cycles are to be expected. PMID:26965790</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26965790','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26965790"><span><span class="hlt">Abrupt</span> climate shift in the Western Mediterranean Sea.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Schroeder, K; Chiggiato, J; Bryden, H L; Borghini, M; Ben Ismail, S</p> <p>2016-03-11</p> <p>One century of oceanographic measurements has evidenced gradual increases in temperature and salinity of western Mediterranean water masses, even though the vertical stratification has basically remained unchanged. Starting in 2005, the basic structure of the intermediate and deep layers <span class="hlt">abruptly</span> changed. We report here evidence of reinforced thermohaline variability in the deep western basin with significant dense water formation <span class="hlt">events</span> producing large amounts of warmer, saltier and denser water masses than ever before. We provide a detailed chronological order to these changes, giving an overview of the new water masses and following their route from the central basin interior to the east (toward the Tyrrhenian) and toward the Atlantic Ocean. As a consequence of this climate shift, new deep waters outflowing through Gibraltar will impact the North Atlantic in terms of salt and heat input. In addition, modifications in the Mediterranean abyssal ecosystems and biogeochemical cycles are to be expected.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22594449','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22594449"><span>Conclusive evidence of <span class="hlt">abrupt</span> coagulation inside the void during cyclic nanoparticle formation in reactive plasma</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Wetering, F. M. J. H. van de; Nijdam, S.; Beckers, J.</p> <p>2016-07-25</p> <p>In this letter, we present scanning electron microscopy (SEM) results that confirm in a direct way our earlier explanation of an <span class="hlt">abrupt</span> coagulation <span class="hlt">event</span> as the cause for the void hiccup. In a recent paper, we reported on the fast and interrupted expansion of voids in a reactive dusty argon–acetylene plasma. The voids appeared one after the other, each showing a peculiar, though reproducible, behavior of successive periods of fast expansion, <span class="hlt">abrupt</span> contraction, and continued expansion. The <span class="hlt">abrupt</span> contraction was termed “hiccup” and was related to collective coagulation of a new generation of nanoparticles growing in the void using relatively indirect methods: electron density measurements and optical emission spectroscopy. In this letter, we present conclusive evidence using SEM of particles collected at different moments in time spanning several growth cycles, which enables us to follow the nanoparticle formation process in great detail.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ApPhL.109d3105V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ApPhL.109d3105V"><span>Conclusive evidence of <span class="hlt">abrupt</span> coagulation inside the void during cyclic nanoparticle formation in reactive plasma</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>van de Wetering, F. M. J. H.; Nijdam, S.; Beckers, J.</p> <p>2016-07-01</p> <p>In this letter, we present scanning electron microscopy (SEM) results that confirm in a direct way our earlier explanation of an <span class="hlt">abrupt</span> coagulation <span class="hlt">event</span> as the cause for the void hiccup. In a recent paper, we reported on the fast and interrupted expansion of voids in a reactive dusty argon-acetylene plasma. The voids appeared one after the other, each showing a peculiar, though reproducible, behavior of successive periods of fast expansion, <span class="hlt">abrupt</span> contraction, and continued expansion. The <span class="hlt">abrupt</span> contraction was termed "hiccup" and was related to collective coagulation of a new generation of nanoparticles growing in the void using relatively indirect methods: electron density measurements and optical emission spectroscopy. In this letter, we present conclusive evidence using SEM of particles collected at different moments in time spanning several growth cycles, which enables us to follow the nanoparticle formation process in great detail.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18647332','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18647332"><span>Causes and projections of <span class="hlt">abrupt</span> climate-driven ecosystem shifts in the North Atlantic.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Beaugrand, Grégory; Edwards, Martin; Brander, Keith; Luczak, Christophe; Ibanez, Frederic</p> <p>2008-11-01</p> <p><span class="hlt">Warming</span> of the global climate is now unequivocal and its impact on Earth' functional units has become more apparent. Here, we show that marine ecosystems are not equally sensitive to climate change and reveal a critical thermal boundary where a small increase in temperature triggers <span class="hlt">abrupt</span> ecosystem shifts seen across multiple trophic levels. This large-scale boundary is located in regions where <span class="hlt">abrupt</span> ecosystem shifts have been reported in the North Atlantic sector and thereby allows us to link these shifts by a global common phenomenon. We show that these changes alter the biodiversity and carrying capacity of ecosystems and may, combined with fishing, precipitate the reduction of some stocks of Atlantic cod already severely impacted by exploitation. These findings offer a way to anticipate major ecosystem changes and to propose adaptive strategies for marine exploited resources such as cod in order to minimize social and economic consequences.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70124267','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70124267"><span><span class="hlt">Abrupt</span> climate-independent fire regime changes</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Pausas, Juli G.; Keeley, Jon E.</p> <p>2014-01-01</p> <p>Wildfires have played a determining role in distribution, composition and structure of many ecosystems worldwide and climatic changes are widely considered to be a major driver of future fire regime changes. However, forecasting future climatic change induced impacts on fire regimes will require a clearer understanding of other drivers of <span class="hlt">abrupt</span> fire regime changes. Here, we focus on evidence from different environmental and temporal settings of fire regimes changes that are not directly attributed to climatic changes. We review key cases of these <span class="hlt">abrupt</span> fire regime changes at different spatial and temporal scales, including those directly driven (i) by fauna, (ii) by invasive plant species, and (iii) by socio-economic and policy changes. All these drivers might generate non-linear effects of landscape changes in fuel structure; that is, they generate fuel changes that can cross thresholds of landscape continuity, and thus drastically change fire activity. Although climatic changes might contribute to some of these changes, there are also many instances that are not primarily linked to climatic shifts. Understanding the mechanism driving fire regime changes should contribute to our ability to better assess future fire regimes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27437571','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27437571"><span><span class="hlt">Abrupt</span> plate accelerations shape rifted continental margins.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Brune, Sascha; Williams, Simon E; Butterworth, Nathaniel P; Müller, R Dietmar</p> <p>2016-08-11</p> <p>Rifted margins are formed by persistent stretching of continental lithosphere until breakup is achieved. It is well known that strain-rate-dependent processes control rift evolution, yet quantified extension histories of Earth's major passive margins have become available only recently. Here we investigate rift kinematics globally by applying a new geotectonic analysis technique to revised global plate reconstructions. We find that rifted margins feature an initial, slow rift phase (less than ten millimetres per year, full rate) and that an <span class="hlt">abrupt</span> increase of plate divergence introduces a fast rift phase. Plate acceleration takes place before continental rupture and considerable margin area is created during each phase. We reproduce the rapid transition from slow to fast extension using analytical and numerical modelling with constant force boundary conditions. The extension models suggest that the two-phase velocity behaviour is caused by a rift-intrinsic strength--velocity feedback, which can be robustly inferred for diverse lithosphere configurations and rheologies. Our results explain differences between proximal and distal margin areas and demonstrate that <span class="hlt">abrupt</span> plate acceleration during continental rifting is controlled by the nonlinear decay of the resistive rift strength force. This mechanism provides an explanation for several previously unexplained rapid absolute plate motion changes, offering new insights into the balance of plate driving forces through time.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013E%26PSL.369..294G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013E%26PSL.369..294G"><span>Australasian monsoon response to Dansgaard-Oeschger <span class="hlt">event</span> 21 and teleconnections to higher latitudes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Griffiths, Michael L.; Drysdale, Russell N.; Gagan, Michael K.; Hellstrom, John C.; Couchoud, Isabelle; Ayliffe, Linda K.; Vonhof, Hubert B.; Hantoro, Wahyoe S.</p> <p>2013-05-01</p> <p>Dansgaard-Oeschger (D-O) cycles were the most prominent, <span class="hlt">abrupt</span> climate <span class="hlt">events</span> of the last glacial period whose impact was most strongly felt in the high latitudes of the North Atlantic region. The climate links between the North Atlantic, the Asian and American tropics, and Antarctica during these cycles are well documented. However, the potential role of the Indo-Pacific <span class="hlt">Warm</span> Pool and Australasian monsoon system in propagating climate impacts across the hemispheres is still unclear. Here, we use tandem measurements of oxygen isotopes in calcite and fluid inclusions, as well as carbon-isotope ratios, from multiple stalagmites from Liang Luar Cave, Flores (southern Indonesia) to examine the monsoon response to D-O <span class="hlt">event</span> number 21 (~87,000-84,000 years ago), the longest and warmest <span class="hlt">event</span> recorded in Greenland ice cores. The record shows that there was a rapid decline in monsoon rainfall in Indonesia during D-O21 <span class="hlt">warming</span> in Greenland and cooling in Antarctica. At around the same time, the East Asian monsoon was intensified, indicating that the intertropical convergence zone (ITCZ) shifted <span class="hlt">abruptly</span> to the north during this <span class="hlt">event</span>. Our record also shows that there was a 2-3 °C increase in local air temperature, which would have acted to increase primary productivity and promote the generation of soil carbon for methanogenesis. Therefore, our findings indicate that ITCZ positioning in tropical Australasia—through its influence on large-scale oceanic-atmospheric circulation—played a key role in transmitting the <span class="hlt">abrupt</span> climate signal between the hemispheres, thereby facilitating the rapid rise of atmospheric CO2 and CH4 concentrations during D-O21 that ultimately led to global <span class="hlt">warming</span> and the demise of the MIS5b stadial.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=earth+AND+warming&pg=5&id=EJ484206','ERIC'); return false;" href="http://eric.ed.gov/?q=earth+AND+warming&pg=5&id=EJ484206"><span>Global <span class="hlt">Warming</span>?</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Eichman, Julia Christensen; Brown, Jeff A.</p> <p>1994-01-01</p> <p>Presents information and data on an experiment designed to test whether different atmosphere compositions are affected by light and temperature during both cooling and heating. Although flawed, the experiment should help students appreciate the difficulties that researchers face when trying to find evidence of global <span class="hlt">warming</span>. (PR)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://eric.ed.gov/?q=global+AND+warming+AND+evidence&pg=2&id=EJ484206','ERIC'); return false;" href="https://eric.ed.gov/?q=global+AND+warming+AND+evidence&pg=2&id=EJ484206"><span>Global <span class="hlt">Warming</span>?</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Eichman, Julia Christensen; Brown, Jeff A.</p> <p>1994-01-01</p> <p>Presents information and data on an experiment designed to test whether different atmosphere compositions are affected by light and temperature during both cooling and heating. Although flawed, the experiment should help students appreciate the difficulties that researchers face when trying to find evidence of global <span class="hlt">warming</span>. (PR)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017NatCC...7..238Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017NatCC...7..238Z"><span>Atmospheric science: <span class="hlt">Warming</span> boosts air pollution</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, Renhe</p> <p>2017-03-01</p> <p>Atmospheric conditions play an important role in driving severe air pollution <span class="hlt">events</span> in Beijing, China. Now research finds that global <span class="hlt">warming</span> will enhance weather conditions favouring such <span class="hlt">events</span>, increasing the chances of severe winter-time haze in the future.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUSMGC44A..01M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUSMGC44A..01M"><span>Landslides as a Delayed Signal of <span class="hlt">Warm</span> Phase of ENSO in the Aconcagua Park (32 Sl)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Moreiras, S.; Lisboa, M.</p> <p>2013-05-01</p> <p>The Aconcagua mount (6,929 m asl), the top of the Andes, is characterised by high elevations and <span class="hlt">abrupt</span> topography that seem to have favoured the occurrence of landslides affecting 25% of the Aconcagua Park (Fig 1). Concerning to triggering mechanism, rainfall are mentioned as the main cause of landslides in historical sources; but this assertion could not be confirmed on the basis of available meteorological data beginning after 1940. The most reliable rainfall threshold value corresponds to a 19 mm (daily precipitation) representing 8.7% of the annual precipitation and 8% of the mean annual precipitation for this region. However, main cause of landslides is related to terrain saturation by snow melting and ice thawing of ice-core moraines or rock glaciers during the <span class="hlt">warm</span> season (November - February). A delayed link between <span class="hlt">warm</span> phases of ENSO and slope instability could be established by a relationship found between landslides and local river stream flow (Fig. 2). The typical <span class="hlt">warm</span> phase of ENSO begins in November of one year, increasing during July—August, and ends in February of the following year. Greater snowfall and positive glacier balance has been linked to the ENSO-<span class="hlt">warm</span> phase. Consequently, increased stream flows of Andean rivers will be measured the following summer. In fact, ENSO-related features in the tropical Pacific play a major role in regulating the hydrological variability in the region with increased (decreased) summer and annual river discharges following El Niño (La Niña) <span class="hlt">events</span>.; ;</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFMPP13A1497S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFMPP13A1497S"><span>Modeling dust emission variations in Eastern Europe related to North-Atlantic <span class="hlt">abrupt</span> climate changes of the last glacial period</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sima, A.; Kageyama, M.; Rousseau, D.; Ramstein, G.; Schulz, M.; Balkanski, Y.; Antoine, P.; Dulac, F.; Hatte, C.; Lagroix, F.; Gerasimenko, N.</p> <p>2010-12-01</p> <p>The European loess sequences of the last glacial period (~ 100-15 kyr BP) show periods of strong dust accumulation alternating with episodes of reduced (or no) sedimentation, allowing soil development. For the main loess sedimentation period (~ 40 - 15 kyr BP), data indicate a correlation between these variations and the North Atlantic rapid climate changes: the Dansgaard-Oeschger (DO) and Heinrich (H) <span class="hlt">events</span>. We use numerical modeling to investigate the relationship between the North-Atlantic <span class="hlt">abrupt</span> changes and the sedimentation variations in Europe. A first study (Sima et al, QSR, 2009) focused on western Europe, and addressed the impact on dust emission of North-Atlantic SST changes as those associated to DO and H <span class="hlt">events</span>. It proposed that vegetation played a key role in modulating dust emission variations in western European source areas. Here we focus on eastern Europe, especially on the areas north and north-east of the Carpathian Mountains, where loess deposits have recorded DO and H <span class="hlt">events</span> (Rousseau et al. Clim. Past D, 2010). As in the previous study, we use the LMDZ AGCM and the SECHIBA land-surface models to simulate a reference glacial state (“stadial”), a cold (“HE”) and a <span class="hlt">warm</span> (“DO interstadial”) perturbation, all corresponding to Marine Isotope Stage 3 conditions. We follow the same protocol as for the study on the west-European sector to analyze the impact of the climate factors and surface conditions on dust emission. The simulated most active emission areas are compatible with the loess deposit distribution, and the key role of vegetation in stadial-interstadial dust emission variations is confirmed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/12762825','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/12762825"><span><span class="hlt">Warm</span> up II: performance changes following active <span class="hlt">warm</span> up and how to structure the <span class="hlt">warm</span> up.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Bishop, David</p> <p>2003-01-01</p> <p> significant increase in thermoregulatory strain. The addition of a brief, task-specific burst of activity has been reported to provide further ergogenic benefits for some tasks. By manipulating intensity, duration and recovery, many different <span class="hlt">warm</span>-up protocols may be able to achieve similar physiological and performance changes. Finally, passive <span class="hlt">warm</span>-up techniques may be important to supplement or maintain temperature increases produced by an active <span class="hlt">warm</span> up, especially if there is an unavoidable delay between the <span class="hlt">warm</span> up and the task and/or the weather is cold. Further research is required to investigate the role of <span class="hlt">warm</span> up in different environmental conditions, especially for endurance <span class="hlt">events</span> where a critical core temperature may limit performance.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMPP43B2080W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMPP43B2080W"><span>Reconstruction of hydrologic responses to late-Glacial (9-33ka) <span class="hlt">abrupt</span> climate transitions in the coastal southwest United States</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wu, M.; Feakins, S. J.; Kirby, M. E.</p> <p>2013-12-01</p> <p>A sediment core retrieved from Lake Elsinore, the largest natural freshwater lake in southern California, spans an age of 9 to 33ka BP. The period includes several late-Glacial <span class="hlt">abrupt</span> climate transitions such as the Heinrich <span class="hlt">events</span> (HEs) 1-3, the Bølling-Allerød (B-A), and the Younger Dryas (YD). This terrestrial site provides a unique opportunity to evaluate changes in hydrology in coastal southwest United States across these key <span class="hlt">abrupt</span> climate transition <span class="hlt">events</span>. Hydrogen isotopic ratios (δDwax) of the long-chain C28 alkanoic acid, a biomarker for terrestrial leaf wax, extracted from the sediments, were analyzed to reveal the δD of precipitation water in the past (δDprecip). In the modern climate, higher δDprecip values are associated with moisture sourced from the tropical Pacific, which brings a drier and warmer climate, whereas lower δDprecip values are associated with moisture sourced from north Pacific brought by polar jet stream, causing a wetter and colder climate. δDwax ranges from about -210‰ to -100‰ between late-Glacial HEs and the beginning of Holocene. The pattern generally correlates with Greenland ice core and regional speleothem records, with lower δDwax values corresponding to colder periods (HEs), and higher δDwax values corresponding to warmer periods (B-A and early Holocene). We infer cold and wet climate with north Pacific sourced moisture during the glacial, followed by gradual <span class="hlt">warming</span> and drying into the B-A and Holocene, when the moisture sources shifted to the tropical Pacific. There is no substantive response to the YD. The fluctuations of δDwax into and out of the HEs can be as large as about 60‰, suggesting greatly variable hydrology across these late-Glacial <span class="hlt">abrupt</span> climate transition <span class="hlt">events</span>. The large shifts in δDwax signal during deglaciation and HEs indicate that hydrology in the coastal southwest US has responded sensitively to climate change, and therefore has important implications for water resources in this</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4804661','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4804661"><span>Cesarean Delivery for a Life-threatening Preterm Placental <span class="hlt">Abruption</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Okafor, II; Ugwu, EO</p> <p>2015-01-01</p> <p>Placental <span class="hlt">abruption</span> is one of the major life-threatening obstetric conditions. The fetomaternal outcome of a severe placental <span class="hlt">abruption</span> depends largely on prompt maternal resuscitation and delivery. A case of severe preterm placental <span class="hlt">abruption</span> with intrauterine fetal death. Following a failed induction of labor with a deteriorating maternal condition despite resuscitation, emergency cesarean delivery was offered with good maternal outcome. Cesarean delivery could avert further disease progression and possible maternal death in cases of severe preterm placental <span class="hlt">abruption</span> where vaginal delivery is not imminent. However, further studies are necessary before this could be recommended for routine clinical practice. PMID:27057388</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_18 --> <div id="page_19" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="361"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28874530','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28874530"><span><span class="hlt">Abrupt</span> climate changes during Termination III in Southern Europe.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Pérez-Mejías, Carlos; Moreno, Ana; Sancho, Carlos; Bartolomé, Miguel; Stoll, Heather; Cacho, Isabel; Cheng, Hai; Edwards, R Lawrence</p> <p>2017-09-19</p> <p>The Late Quaternary glacial-interglacial transitions represent the highest amplitude climate changes over the last million years. Unraveling the sequence of <span class="hlt">events</span> and feedbacks at Termination III (T-III), including potential <span class="hlt">abrupt</span> climate reversals similar to those of the last Termination, has been particularly challenging due to the scarcity of well-dated records worldwide. Here, we present speleothem data from southern Europe covering the interval from 262.7 to 217.9 kyBP, including the transition from marine isotope stage (MIS) 8 to MIS 7e. High-resolution δ(13)C, δ(18)O, and Mg/Ca profiles reveal major millennial-scale changes in aridity manifested in changing water availability and vegetation productivity. uranium-thorium dates provide a solid chronology for two millennial-scale <span class="hlt">events</span> (S8.1 and S8.2) which, compared with the last two terminations, has some common features with Heinrich 1 and Heinrich 2 in Termination I (T-I).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PNAS..11410047P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PNAS..11410047P"><span><span class="hlt">Abrupt</span> climate changes during Termination III in Southern Europe</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pérez-Mejías, Carlos; Moreno, Ana; Sancho, Carlos; Bartolomé, Miguel; Stoll, Heather; Cacho, Isabel; Cheng, Hai; Edwards, R. Lawrence</p> <p>2017-09-01</p> <p>The Late Quaternary glacial–interglacial transitions represent the highest amplitude climate changes over the last million years. Unraveling the sequence of <span class="hlt">events</span> and feedbacks at Termination III (T-III), including potential <span class="hlt">abrupt</span> climate reversals similar to those of the last Termination, has been particularly challenging due to the scarcity of well-dated records worldwide. Here, we present speleothem data from southern Europe covering the interval from 262.7 to 217.9 kyBP, including the transition from marine isotope stage (MIS) 8 to MIS 7e. High-resolution δ13C, δ18O, and Mg/Ca profiles reveal major millennial-scale changes in aridity manifested in changing water availability and vegetation productivity. uranium–thorium dates provide a solid chronology for two millennial-scale <span class="hlt">events</span> (S8.1 and S8.2) which, compared with the last two terminations, has some common features with Heinrich 1 and Heinrich 2 in Termination I (T-I).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.9895B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.9895B"><span>Bayesian comparison of conceptual models of <span class="hlt">abrupt</span> climate changes during the last glacial period</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Boers, Niklas; Ghil, Michael; Rousseau, Denis-Didier</p> <p>2017-04-01</p> <p>Records of oxygen isotope ratios and dust concentrations from the North Greenland Ice Core Project (NGRIP) provide accurate proxies for the evolution of Arctic temperature and atmospheric circulation during the last glacial period (12ka to 100ka b2k) [1]. The most distinctive feature of these records are sudden transitions, called Dansgaard-Oeschger (DO) <span class="hlt">events</span>, during which Arctic temperatures increased by up to 10 K within a few decades. These <span class="hlt">warming</span> <span class="hlt">events</span> are consistently followed by more gradual cooling in Antarctica [2]. The physical mechanisms responsible for these transitions and their out-of-phase relationship between the northern and southern hemisphere remain unclear. Substantial evidence hints at variations of the Atlantic Meridional Overturning Circulation as a key mechanism [2,3], but also other mechanisms, such as variations of sea ice extent [4] or ice shelf coverage [5] may play an important role. Here, we intend to shed more light on the relevance of the different mechanisms suggested to explain the <span class="hlt">abrupt</span> climate changes and their inter-hemispheric coupling. For this purpose, several conceptual differential equation models are developed that represent the suggested physical mechanisms. Optimal parameters for each model candidate are then determined via maximum likelihood estimation with respect to the observed paleoclimatic data. Our approach is thus semi-empirical: While a model's general form is deduced from physical arguments about relevant climatic mechanisms — oceanic and atmospheric — its specific parameters are obtained by training the model on observed data. The distinct model candidates are evaluated by comparing statistical properties of time series simulated with these models to the observed statistics. In particular, Bayesian model selection criteria like Maximum Likelihood Ratio tests are used to obtain a hierarchy of the different candidates in terms of their likelihood, given the observed oxygen isotope and dust time series</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFMPP43A1801A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFMPP43A1801A"><span>The role of oceanic variability on millennial-scale iceberg discharges: focus on Heinrich <span class="hlt">events</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Alvarez-Solas, J.; Montoya, M.; Banderas, R.; Dumas, C.; Ritz, C.</p> <p>2011-12-01</p> <p>Ice core data and marine and continental records reveal the existence of pronounced millennial time-scale climate variability during the last glacial cycle. Greenland ice core records show <span class="hlt">abrupt</span> transitions known as Dansgaard-Oeschger (DO) <span class="hlt">events</span> within decades from cold (stadial) to relatively <span class="hlt">warm</span> (interstadial) conditions, followed by a slow cooling lasting several centuries and a more rapid fall through stadial conditions. Two types of explanation have been suggested: periodic external forcing and internal oscillations, for which ocean circulation is the main candidate. On the other hand, six periods of extreme cooling registered in the Northern Hemisphere, known as Heinrich <span class="hlt">events</span> (HEs), have been found to be coeval with increased deposition of ice-rafted debris, which is interpreted as enhanced discharge of icebergs into the North Atlantic Ocean. Recently, the coupled effects between ocean circulation and ice-sheets dynamics have been suggested to play a major role in triggering HEs. This interpretation of HEs being responding to changes in the oceanic patterns, takes the advantage to provide an explicit relationship between DO <span class="hlt">events</span> and the periodic iceberg surges. In particular, it has been shown in a box model that a series of DO <span class="hlt">events</span> favors the occurrence of a HE through a resonance phenomenon, giving an explanation to the denominated Bond cycle. Here this hypothesis is reassessed within a more realistic modeling framework by forcing a 3D ice-sheet/shelf model with the output of <span class="hlt">abrupt</span> climate change simulations carried out with a coupled climate model. These show the main expected characteristics of such <span class="hlt">events</span>: an <span class="hlt">abrupt</span> <span class="hlt">warming</span> of the North Atlantic and Atlantic Meridional Overturning Circulation (AMOC) intensification followed by a progressive cooling and AMOC reduction and a more drastic fall into a stadial condition. Interestingly, stadial periods are characterized by the occurrence of a subsurface <span class="hlt">warming</span> up to 3 K in regions where deep water</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/898043','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/898043"><span>Laurentide Ice Sheet meltwater and <span class="hlt">abrupt</span> climate change during the last glaciation</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Hill, H W; Flower, B P; Quinn, T M; Hollander, D J; Guilderson, T P</p> <p>2005-10-02</p> <p>A leading hypothesis to explain <span class="hlt">abrupt</span> climate change during the last glacial cycle calls on fluctuations in the margin of the North American Laurentide Ice Sheet (LIS), which may have routed freshwater between the Gulf of Mexico (GOM) and North Atlantic, affecting North Atlantic Deep Water (NADW) variability and regional climate. Paired measurements of {delta}O and Mg/Ca of foraminiferal calcite from GOM sediments reveal five episodes of LIS meltwater input from 28-45 thousand years ago (ka) that do not match the millennial-scale Dansgaard-Oeschger (D/O) <span class="hlt">warmings</span> recorded in Greenland ice. We suggest that summer melting of the LIS may occur during Antarctic <span class="hlt">warming</span> and likely contributed to sea-level variability during Marine Isotope Stage 3 (MIS 3).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMPP21F..08W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMPP21F..08W"><span>Why were Past North Atlantic <span class="hlt">Warming</span> Conditions Associated with Drier Climate in the Western United States?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wong, C. I.; Potter, G. L.; Montanez, I. P.; Otto-Bliesner, B. L.; Behling, P.; Oster, J. L.</p> <p>2014-12-01</p> <p>Investigating climate dynamics governing rainfall over the western US during past <span class="hlt">warmings</span> and coolings of the last glacial and deglaciation is pertinent to understanding how precipitation patterns might change with future global <span class="hlt">warming</span>, especially as the processes driving the global hydrological reorganization affecting this drought-prone region during these rapid temperature changes remain unresolved. We present model climates of the Bølling <span class="hlt">warm</span> <span class="hlt">event</span> (14,500 years ago) and Younger Dryas cool <span class="hlt">event</span> (12,200 years ago) that i) uniquely enable the assessment of dueling hypothesis about the atmospheric teleconnections responsible for <span class="hlt">abrupt</span> temperature shifts in the North Atlantic region to variations in moisture conditions across the western US, and ii) show that existing hypotheses about these teleconnections are unsupported. Modeling results show no evidence for a north-south shift of the Pacific winter storm track, and we argue that a tropical moisture source with evolving trajectory cannot explain alternation between wet/dry conditions, which have been reconstructed from the proxy record. Alternatively, model results support a new hypothesis that variations in the intensity of the winter storm track, corresponding to its expansion/contraction, can account for regional moisture differences between <span class="hlt">warm</span> and cool intervals of the last deglaciation. Furthermore, we demonstrate that the mechanism forcing the teleconnection between the North Atlantic and western US is the same across different boundary conditions. In our simulation, during the last deglaciation, and in simulations of future <span class="hlt">warming</span>, perturbation of the Rossby wave structure reconfigures the atmospheric state. This reconfiguration affects the Aleutian Low and high-pressure ridge over and off of the northern North American coastline driving variability in the storm track. Similarity between the processes governing the climate response during these distinct time intervals illustrates the robust nature</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003AGUFM.C41C0979W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003AGUFM.C41C0979W"><span>The Arctic Grand Challenge: <span class="hlt">Abrupt</span> Climate Change</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wilkniss, P. E.</p> <p>2003-12-01</p> <p>Trouble in polar paradise (Science, 08/30/02), significant changes in the Arctic environment are scientifically documented (R.E. Moritz et al. ibid.). More trouble, lots more, "<span class="hlt">abrupt</span> climate change," (R. B. Alley, et al. Science 03/28/03). R. Corell, Arctic Climate Impact Assessment team (ACIA), "If you want to see what will happen in the rest of the world 25 years from now just look what's happening in the Arctic," (Arctic Council meeting, Iceland, 08/03). What to do? Make <span class="hlt">abrupt</span> Arctic climate change a grand challenge for the IPY-4 and beyond! Scientifically:Describe the "state" of the Arctic climate system as succinctly as possible and accept it as the point of departure.Develop a hypothesis and criteria what constitutes "<span class="hlt">abrupt</span> climate change," in the Arctic that can be tested with observations. Observations: Bring to bear existing observations and coordinate new investments in observations through an IPY-4 scientific management committee. Make the new Barrow, Alaska, Global Climate Change Research Facility a major U.S. contribution and focal point for the IPY-4 in the U.S Arctic. Arctic populations, Native peoples: The people of the North are living already, daily, with wrenching change, encroaching on their habitats and cultures. For them "the earth is faster now," (I. Krupnik and D. Jolly, ARCUS, 2002). From a political, economic, social and entirely realistic perspective, an Arctic grand challenge without the total integration of the Native peoples in this effort cannot succeed. Therefore: Communications must be established, and the respective Native entities must be approached with the determination to create well founded, well functioning, enduring partnerships. In the U.S. Arctic, Barrow with its long history of involvement and active support of science and with the new global climate change research facility should be the focal point of choice Private industry: Resource extraction in the Arctic followed by oil and gas consumption, return the combustion</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009GPC....69..170E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009GPC....69..170E"><span>Circum-Antarctic <span class="hlt">warming</span> <span class="hlt">events</span> between 4 and 3.5 Ma recorded in marine sediments from the Prydz Bay (ODP Leg 188) and the Antarctic Peninsula (ODP Leg 178) margins</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Escutia, C.; Bárcena, M. A.; Lucchi, R. G.; Romero, O.; Ballegeer, A. M.; Gonzalez, J. J.; Harwood, D. M.</p> <p>2009-11-01</p> <p>, and 2) decrease in SSSTs (from > 5.6 °C at 3.7 Ma to 4°-2.7 °C at 3.6 Ma, and 2.5 °C at 3.5 Ma.) indicated by the silicoflagellate W/C R from Site 1165. We postulate that, although the start of a cooling trend is recorded at about 3.7-3.6-Ma, relatively <span class="hlt">warm</span> conditions prevailed until 3.5 Ma capable of maintained open marine conditions with reduced or no sea-ice and reduced ice sheet volume and extent. The information in this paper regarding the timing of continental-wide and regional <span class="hlt">warm</span> <span class="hlt">events</span> and the paleoenvironmental conditions that characterized them (i.e., SSST, extent of sea ice, and ice sheet size) are relevant to help constrain paleoclimate and ice sheet models for the early-middle Pliocene, a time period when the level of <span class="hlt">warming</span> according to the Intergovernmental Panel on Climate Change 2007 report, is within range of the estimates of the Earth's global temperature increases for the 21st century. These data, when linked to modeling studies like those of Pollard and DeConto (2009) will further our understanding of how these ice sheets may respond to future <span class="hlt">warming</span> of the southern high latitudes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28825806','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28825806"><span>Atomically <span class="hlt">Abrupt</span> Topological p-n Junction.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kim, Sung Hwan; Jin, Kyung-Hwan; Kho, Byung Woo; Park, Byeong-Gyu; Liu, Feng; Kim, Jun Sung; Yeom, Han Woong</p> <p>2017-08-24</p> <p>Topological insulators (TI's) are a new class of quantum matter with extraordinary surface electronic states, which bear great potential for spintronics and error-tolerant quantum computing. In order to put a TI into any practical use, these materials need to be fabricated into devices whose basic units are often p-n junctions. Interesting electronic properties of a 'topological' p-n junction were proposed theoretically such as the junction electronic state and the spin rectification. However, the fabrication of a lateral topological p-n junction has been challenging because of materials, process, and fundamental reasons. Here, we demonstrate an innovative approach to realize a p-n junction of topological surface states (TSS's) of a three-dimensional (3D) topological insulator (TI) with an atomically <span class="hlt">abrupt</span> interface. When a ultrathin Sb film is grown on a 3D TI of Bi2Se3 with a typical n-type TSS, the surface develops a strongly p-type TSS through the substantial hybridization between the 2D Sb film and the Bi2Se3 surface. Thus, the Bi2Se3 surface covered partially with Sb films bifurcates into areas of n- and p-type TSS's as separated by atomic step edges with a lateral electronic junction of as short as 2 nm. This approach opens a different avenue toward various electronic and spintronic devices based on well-defined topological p-n junctions with the scalability down to atomic dimensions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://eric.ed.gov/?q=visual+AND+perception+AND+errors&pg=7&id=EJ842476','ERIC'); return false;" href="https://eric.ed.gov/?q=visual+AND+perception+AND+errors&pg=7&id=EJ842476"><span>Going, Going, Gone: Localizing <span class="hlt">Abrupt</span> Offsets of Moving Objects</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Maus, Gerrit W.; Nijhawan, Romi</p> <p>2009-01-01</p> <p>When a moving object <span class="hlt">abruptly</span> disappears, this profoundly influences its localization by the visual system. In Experiment 1, 2 aligned objects moved across the screen, and 1 of them <span class="hlt">abruptly</span> disappeared. Observers reported seeing the objects misaligned at the time of the offset, with the continuing object leading. Experiment 2 showed that the…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=transient+AND+analysis&pg=3&id=EJ842476','ERIC'); return false;" href="http://eric.ed.gov/?q=transient+AND+analysis&pg=3&id=EJ842476"><span>Going, Going, Gone: Localizing <span class="hlt">Abrupt</span> Offsets of Moving Objects</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Maus, Gerrit W.; Nijhawan, Romi</p> <p>2009-01-01</p> <p>When a moving object <span class="hlt">abruptly</span> disappears, this profoundly influences its localization by the visual system. In Experiment 1, 2 aligned objects moved across the screen, and 1 of them <span class="hlt">abruptly</span> disappeared. Observers reported seeing the objects misaligned at the time of the offset, with the continuing object leading. Experiment 2 showed that the…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005AGUFMPP43C..02H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005AGUFMPP43C..02H"><span>Geological "Ground Truth" of Sea-level Highstand <span class="hlt">Events</span> During <span class="hlt">Warm</span> Interglaciations (MIS 11 and 5e): Taking the Punch out of Proxy Precision</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hearty, P. J.</p> <p>2005-12-01</p> <p>High-resolution sea-level records for marine isotope stages (MIS) 11 and 5e from coastal outcrops in Bahamas, Bermuda, Hawaii, and Western Australia provide physical confirmation of extreme ice-melting <span class="hlt">events</span> during Pleistocene interglacials. Field evidence indicates MIS 11 sea level rose in a series of oscillations to c. +20 m, while that of MIS 5e reached its maximum of +6-10 m. Because these were brief <span class="hlt">events</span> (100s yrs), their true magnitude is generally muted or obscured in deep-sea oxygen isotope records; generally averaged over thousands of years by the combined effects of sampling, bioturbation, and sedimentation rates. Further unresolvable variables such as temperature and salinity further cloud the isotope proxy record. Thus, the tangible rock record is of greatest importance in understanding the nature of these extreme <span class="hlt">events</span>. Geomorphology, sedimentary structures, taphonomy of and dating of organisms, and petrology provide ground truth at field sites. Sea-level highstands preserve terraces and benches by erosion and subsequent deposition of sub- and intertidal sediments. Fenestral porosity is a measure of intertidal wetting and drying of sand, while decimetre-scale, high-angle cross beds of poorly-sorted sand and gravel indicate shallow subtidal conditions. In situ coral heads describe similar subtidal conditions. Delicate, sometimes partially articulated skeletons of birds and reptiles in sea caves reveal a protected shoreline. An early generation of isopachous, fibrous cement verifies the presence of marine phreatic water over a sustained period of time. These features, often misinterpreted (McMurtry, 2004, AGU Fall Meeting, OS21E-06), categorically exclude emplacement by tsunami waves. Oceanic isotope records cannot produce an equivalent level of resolution of short, extreme <span class="hlt">events</span> via (in terms of age, duration, rates of sea-level and ice-volume changes), thus shifting the `burden of proof' to proxy methods to identify such <span class="hlt">events</span>. In our quest to</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25877202','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25877202"><span>Icebergs not the trigger for North Atlantic cold <span class="hlt">events</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Barker, Stephen; Chen, James; Gong, Xun; Jonkers, Lukas; Knorr, Gregor; Thornalley, David</p> <p>2015-04-16</p> <p><span class="hlt">Abrupt</span> climate change is a ubiquitous feature of the Late Pleistocene epoch. In particular, the sequence of Dansgaard-Oeschger <span class="hlt">events</span> (repeated transitions between <span class="hlt">warm</span> interstadial and cold stadial conditions), as recorded by ice cores in Greenland, are thought to be linked to changes in the mode of overturning circulation in the Atlantic Ocean. Moreover, the observed correspondence between North Atlantic cold <span class="hlt">events</span> and increased iceberg calving and dispersal from ice sheets surrounding the North Atlantic has inspired many ocean and climate modelling studies that make use of freshwater forcing scenarios to simulate <span class="hlt">abrupt</span> change across the North Atlantic region and beyond. On the other hand, previous studies identified an apparent lag between North Atlantic cooling <span class="hlt">events</span> and the appearance of ice-rafted debris over the last glacial cycle, leading to the hypothesis that iceberg discharge may be a consequence of stadial conditions rather than the cause. Here we further establish this relationship and demonstrate a systematic delay between pronounced surface cooling and the arrival of ice-rafted debris at a site southwest of Iceland over the past four glacial cycles, implying that in general icebergs arrived too late to have triggered cooling. Instead we suggest that--on the basis of our comparisons of ice-rafted debris and polar planktonic foraminifera--<span class="hlt">abrupt</span> transitions to stadial conditions should be considered as a nonlinear response to more gradual cooling across the North Atlantic. Although the freshwater derived from melting icebergs may provide a positive feedback for enhancing and or prolonging stadial conditions, it does not trigger northern stadial <span class="hlt">events</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28387042','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28387042"><span>Circumpolar dynamics of a marine top-predator track ocean <span class="hlt">warming</span> rates.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Descamps, S; Anker-Nilssen, T; Barrett, R T; Irons, D B; Merkel, F; Robertson, G J; Yoccoz, N G; Mallory, M L; Montevecchi, W A; Boertmann, D; Artukhin, Y; Christensen-Dalsgaard, S; Erikstad, K E; Gilchrist, H G; Labansen, A L; Lorentsen, S-H; Mosbech, A; Olsen, B; Petersen, A; Rail, J-F; Renner, H M; Strøm, H; Systad, G H; Wilhelm, S I; Zelenskaya, L</p> <p>2017-04-07</p> <p>Global <span class="hlt">warming</span> is a non-linear process and temperature may increase in a stepwise manner. Periods of <span class="hlt">abrupt</span> <span class="hlt">warming</span> can trigger persistent changes in the state of ecosystems, also called regime shifts. The responses of organisms to <span class="hlt">abrupt</span> <span class="hlt">warming</span> and associated regime shifts can be unlike responses to periods of slow or moderate change. Understanding of non-linearity in the biological responses to climate <span class="hlt">warming</span> is needed to assess the consequences of ongoing climate change. Here we demonstrate that the population dynamics of a long-lived, wide-ranging marine predator are associated with changes in the rate of ocean <span class="hlt">warming</span>. Data from 556 colonies of black-legged kittiwakes Rissa tridactyla distributed throughout its breeding range revealed that an <span class="hlt">abrupt</span> <span class="hlt">warming</span> of sea-surface temperature in the 1990s coincided with steep kittiwake population decline. Periods of moderate <span class="hlt">warming</span> in sea temperatures did not seem to affect kittiwake dynamics. The rapid <span class="hlt">warming</span> observed in the 1990s may have driven large-scale, circumpolar marine ecosystem shifts that strongly affected kittiwakes through bottom-up effects. Our study sheds light on the non-linear response of a circumpolar seabird to large-scale changes in oceanographic conditions and indicates that marine top predators may be more sensitive to the rate of ocean <span class="hlt">warming</span> rather than to <span class="hlt">warming</span> itself. This article is protected by copyright. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/20977769','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/20977769"><span>Risk of placental <span class="hlt">abruption</span> in relation to migraines and headaches.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Sanchez, Sixto E; Williams, Michelle A; Pacora, Percy N; Ananth, Cande V; Qiu, Chungfang; Aurora, Sheena K; Sorensen, Tanya K</p> <p>2010-10-26</p> <p>Migraine, a common chronic-intermittent disorder of idiopathic origin characterized by severe debilitating headaches and autonomic nervous system dysfunction, and placental <span class="hlt">abruption</span>, the premature separation of the placenta, share many common pathophysiological characteristics. Moreover, endothelial dysfunction, platelet activation, hypercoagulation, and inflammation are common to both disorders. We assessed risk of placental <span class="hlt">abruption</span> in relation to maternal history of migraine before and during pregnancy in Peruvian women. Cases were 375 women with pregnancies complicated by placental <span class="hlt">abruption</span>, and controls were 368 women without an <span class="hlt">abruption</span>. During in-person interviews conducted following delivery, women were asked if they had physician-diagnosed migraine, and they were asked questions that allowed headaches and migraine to be classified according to criteria established by the International Headache Society. Logistic regression procedures were used to calculate odds ratios (aOR) and 95% confidence intervals (CI) adjusted for confounders. Overall, a lifetime history of any headaches or migraine was associated with an increased odds of placental <span class="hlt">abruption</span> (aOR = 1.60; 95% CI 1.16-2.20). A lifetime history of migraine was associated with a 2.14-fold increased odds of placental <span class="hlt">abruption</span> (aOR = 2.14; 95% CI 1.22-3.75). The odds of placental <span class="hlt">abruption</span> was 2.11 (95% CI 1.00-4.45) for migraineurs without aura; and 1.59 (95% 0.70-3.62) for migraineurs with aura. A lifetime history of tension-type headache was also increased with placental <span class="hlt">abruption</span> (aOR = 1.61; 95% CI 1.01-2.57). This study adds placental <span class="hlt">abruption</span> to a growing list of pregnancy complications associated with maternal headache/migraine disorders. Nevertheless, prospective cohort studies are needed to more rigorously evaluate the extent to which migraines and/or its treatments are associated with the occurrence of placental <span class="hlt">abruption</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007GeoRL..3420603C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007GeoRL..3420603C"><span>Rapid sea level rise and ice sheet response to 8,200-year climate <span class="hlt">event</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cronin, T. M.; Vogt, P. R.; Willard, D. A.; Thunell, R.; Halka, J.; Berke, M.; Pohlman, J.</p> <p>2007-10-01</p> <p>The largest <span class="hlt">abrupt</span> climatic reversal of the Holocene interglacial, the cooling <span class="hlt">event</span> 8.6-8.2 thousand years ago (ka), was probably caused by catastrophic release of glacial Lake Agassiz-Ojibway, which slowed Atlantic meridional overturning circulation (AMOC) and cooled global climate. Geophysical surveys and sediment cores from Chesapeake Bay reveal the pattern of sea level rise during this <span class="hlt">event</span>. Sea level rose ~14 m between 9.5 to 7.5 ka, a pattern consistent with coral records and the ICE-5G glacio-isostatic adjustment model. There were two distinct periods at ~8.9-8.8 and ~8.2-7.6 ka when Chesapeake marshes were drown as sea level rose rapidly at least ~12 mm yr-1. The latter <span class="hlt">event</span> occurred after the 8.6-8.2 ka cooling <span class="hlt">event</span>, coincided with extreme <span class="hlt">warming</span> and vigorous AMOC centered on 7.9 ka, and may have been due to Antarctic Ice Sheet decay.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMPP41A2209B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMPP41A2209B"><span><span class="hlt">Abrupt</span> Climate Change Caused by Global Fires from a Large Meteor Impact</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bardeen, C.; Toon, O. B.; Garcia, R. R.; Otto-Bliesner, B. L.; Wolf, E. T.</p> <p>2015-12-01</p> <p>Global or near-global fires like those that are thought to have occurred after the Chicxulub asteroid impact are associated with <span class="hlt">abrupt</span> climate change and the K-Pg mass extinction <span class="hlt">event</span>. Using the Community Earth System Model (CESM), a three-dimensional coupled climate model with interactive chemistry, we have simulated the climate response to global fires assuming a burden of 70,000 Tg, as estimated from the K-Pg layer sediments by Wolbach et al. (1988). Soot aerosols are lofted by solar heating and remain in the atmosphere for about 6 years, <span class="hlt">warming</span> the stratosphere by more than 240 K and suppressing completely solar radiation at the surface for 2 years. Global average land surface temperatures cool by -28 K after 3 years and ocean temperatures by -11 K after 4 years. Precipitation is reduced by 80 % for 5 years, and the ozone column is reduced by 80 % for 4 years. The tropical tropopause cold point disappears for a few years, leading to water vapor mixing ratios of > 1000 ppmv in the stratosphere. There is a rapid recovery around year 6, when the soot is removed by wet deposition as stratospheric water condenses and precipitates, but this is followed by a peak in the UV Index in the tropics of over 40 before stratospheric ozone recovers. Ocean temperature cools by more than -2 K to a depth of 300 m, and sea ice develops in the Black Sea, Caspian Sea, and Baltic Sea. Global fires, two years of darkness, extreme surface cooling, significant ocean cooling, increases in sea ice extent and a large short-term increase in UV Index would have been catastrophic for many life forms. This work is the first step in an effort to simulate the climatic effects of all of the aerosols and gases that may have been generated by the Chicxulub impact in a model that has been configured for late-Cretaceous conditions to help assess the role of the Chicxulub impact in the K-Pg extinction.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19535986','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19535986"><span>Thromboembolic diseases in families of women with placental <span class="hlt">abruption</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Peltier, Morgan R; Ananth, Cande V; Oyelese, Yinka; Vintzileos, Anthony M</p> <p>2009-09-01</p> <p>We explored the incidence of thromboembolic disease in relatives of women diagnosed with placental <span class="hlt">abruption</span>, a condition that may be related to disordered coagulation. Using data from a multicenter, case-control study of placental <span class="hlt">abruption</span>, we assessed thromboembolic diseases in first-degree male and female relatives of women with and without <span class="hlt">abruption</span>. The analysis was restricted to biologic parents and full siblings, below 65 years of age, and corrected for familial clustering. The prevalence of thromboembolic disease was 7.5% in 852 relatives of 212 placental <span class="hlt">abruption</span> cases and 4.8% in 792 relatives of 206 controls. This increased risk was driven by an association among sisters of <span class="hlt">abruption</span> probands (odds ratio = 6.8 [95% confidence interval = 1.8-26.0]), and to a lesser extent, among mothers (2.0 [1.0-4.2]). The risk of thromboembolic diseases was similar among the male relatives of placental <span class="hlt">abruption</span> cases and controls. These data suggest that thromboembolic diseases aggregate within female relatives of women with placental <span class="hlt">abruption</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JGRC..121.4777B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JGRC..121.4777B"><span>Revisiting the cause of the eastern equatorial Atlantic cold <span class="hlt">event</span> in 2009</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Burmeister, Kristin; Brandt, Peter; Lübbecke, Joke F.</p> <p>2016-07-01</p> <p>An extreme cold sea surface temperature <span class="hlt">event</span> occurred in the Atlantic cold tongue region in boreal summer 2009. It was preceded by a strong negative Atlantic meridional mode <span class="hlt">event</span> associated with north-westerly wind anomalies along the equator from March to May. Although classical equatorial wave dynamics suggest that westerly wind anomalies should be followed by a <span class="hlt">warming</span> in the eastern equatorial Atlantic, an <span class="hlt">abrupt</span> cooling took place. In the literature two mechanisms—meridional advection of subsurface temperature anomalies and planetary wave reflection—are discussed as potential causes of such an <span class="hlt">event</span>. Here, for the first time we use in situ measurements in addition to satellite and reanalysis products to investigate the contribution of both mechanisms to the 2009 cold <span class="hlt">event</span>. Our results suggest that meridional advection is less important in cold <span class="hlt">events</span> than in corresponding <span class="hlt">warm</span> <span class="hlt">events</span>, and, in particular, did not cause the 2009 cold <span class="hlt">event</span>. Argo float data confirm previous findings that planetary wave reflection contributed to the onset of the 2009 cold <span class="hlt">event</span>. Additionally, our analysis suggests that higher baroclinic modes were involved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19880027641&hterms=isobars&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Disobars','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19880027641&hterms=isobars&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Disobars"><span>Simulated sudden stratospheric <span class="hlt">warming</span> - Synoptic evolution</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Blackshear, W. T.; Grose, W. L.; Turner, R. E.</p> <p>1987-01-01</p> <p>An analysis is presented of a sudden stratospheric <span class="hlt">warming</span> <span class="hlt">event</span> which occurred spontaneously during a general circulation model simulation of the global atmospheric circulation. Two separate <span class="hlt">warming</span> pulses exhibit the same dynamical evolution with a 'cycle' of about two weeks. Two distinct phases of the <span class="hlt">warming</span> cycle are apparent: (1) the generation of an intense localized <span class="hlt">warm</span> cell in conjunction with significant adiabatic heating associated with cross-isobar flow which has been induced by vertically propagating long wave disturbances; and (2) the northward transport of that <span class="hlt">warm</span> cell via advection by the essentially geostrophic windfield corresponding to an intense, offset polar cyclone, in conjunction with a strong Aleutian anticyclone. During the first <span class="hlt">warming</span> pulse in January, a moderate Aleutian anticyclone was in place prior to the <span class="hlt">warming</span> cycle and was intensified by interaction with an eastward traveling anticyclone induced by the differential advection of the <span class="hlt">warm</span> cell. The second <span class="hlt">warming</span> pulse occurred in early February with a strong Aleutian anticyclone already established. In contrast to the January <span class="hlt">event</span>, the <span class="hlt">warming</span> in February culminated with reversal of the zonal westerlies to easterlies over a significant depth of the stratosphere.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_19 --> <div id="page_20" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="381"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19880027641&hterms=Meteorology+isobars&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DMeteorology%2Bisobars','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19880027641&hterms=Meteorology+isobars&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DMeteorology%2Bisobars"><span>Simulated sudden stratospheric <span class="hlt">warming</span> - Synoptic evolution</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Blackshear, W. T.; Grose, W. L.; Turner, R. E.</p> <p>1987-01-01</p> <p>An analysis is presented of a sudden stratospheric <span class="hlt">warming</span> <span class="hlt">event</span> which occurred spontaneously during a general circulation model simulation of the global atmospheric circulation. Two separate <span class="hlt">warming</span> pulses exhibit the same dynamical evolution with a 'cycle' of about two weeks. Two distinct phases of the <span class="hlt">warming</span> cycle are apparent: (1) the generation of an intense localized <span class="hlt">warm</span> cell in conjunction with significant adiabatic heating associated with cross-isobar flow which has been induced by vertically propagating long wave disturbances; and (2) the northward transport of that <span class="hlt">warm</span> cell via advection by the essentially geostrophic windfield corresponding to an intense, offset polar cyclone, in conjunction with a strong Aleutian anticyclone. During the first <span class="hlt">warming</span> pulse in January, a moderate Aleutian anticyclone was in place prior to the <span class="hlt">warming</span> cycle and was intensified by interaction with an eastward traveling anticyclone induced by the differential advection of the <span class="hlt">warm</span> cell. The second <span class="hlt">warming</span> pulse occurred in early February with a strong Aleutian anticyclone already established. In contrast to the January <span class="hlt">event</span>, the <span class="hlt">warming</span> in February culminated with reversal of the zonal westerlies to easterlies over a significant depth of the stratosphere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70028212','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70028212"><span>Globally synchronous ice core volcanic tracers and <span class="hlt">abrupt</span> cooling during the last glacial period</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Bay, R.C.; Bramall, N.E.; Price, P.B.; Clow, G.D.; Hawley, R.L.; Udisti, R.; Castellano, E.</p> <p>2006-01-01</p> <p>We perform a Monte Carlo pattern recognition analysis of the coincidence between three regional volcanic histories from ice coring of Greenland and Antarctica over the period 2 to 45 ka, using SO4 anomalies in Greenland and East Antarctica determined by continuous core chemistry, together with West Antarctic volcanic ash layers determined by remote optical borehole logging and core assays. We find that the Antarctic record of volcanism correlates with Glacial <span class="hlt">abrupt</span> climate change at a 95% to >99.8% (???3??) significance level and that volcanic depositions at the three locations match at levels exceeding 3??, likely indicating that many common horizons represent single eruptive <span class="hlt">events</span> which dispersed material world wide. These globally coincident volcanics were associated with <span class="hlt">abrupt</span> cooling, often simultaneous with onsets or sudden intensifications of millennial cold periods. The striking agreement between sites implies that the consistency of current timescales obtained by isotopic and glaciological dating methods is better than estimated. Copyright 2006 by the American Geogphysical Union.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1109182','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1109182"><span>The Role of the Tropics in <span class="hlt">Abrupt</span> Climate Changes</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Fedorov, Alexey</p> <p>2013-12-07</p> <p>Topics addressed include: <span class="hlt">abrupt</span> climate changes and ocean circulation in the tropics; what controls the ocean thermal structure in the tropics; a permanent El Niño in paleoclimates; the energetics of the tropical ocean.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AdAtS..34.1185L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AdAtS..34.1185L"><span>Evolving perspectives on <span class="hlt">abrupt</span> seasonal changes of the general circulation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lu, Jianhua; Schneider, Tapio</p> <p>2017-10-01</p> <p>Professor Duzheng YE (Tu-cheng YEH) was decades ahead of his time in proposing a model experiment to investigate whether <span class="hlt">abrupt</span> seasonal changes of the general circulation can arise through circulation feedbacks alone, unrelated to underlying inhomogeneities at the lower boundary. Here, we introduce Professor YEH's ideas during the 1950s and 1960s on the general circulation and summarize the results and suggestions of Yeh et al. (1959) on <span class="hlt">abrupt</span> seasonal changes. We then review recent advances in understanding <span class="hlt">abrupt</span> seasonal changes arising from model experiments like those proposed by Yeh et al. (1959). The model experiments show that circulation feedbacks can indeed give rise to <span class="hlt">abrupt</span> seasonal transitions. In these transitions, large-scale eddies that originate in midlatitudes and interact with the zonal mean flow and meridional overturning circulations in the tropics play central roles.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5161361','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5161361"><span>Placental <span class="hlt">Abruption</span> Revealed by Hemoperitoneum: A Case Report</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Bertholdt, C.; Vincent-Rohfritsch, A.; Tsatsaris, V.; Goffinet, F.</p> <p>2016-01-01</p> <p>Background Hemoperitoneum is a life-threatening surgical emergency. Diagnosis of the cause is often difficult, in particular, during pregnancy when it may be either obstetric or nonobstetric. Case We report the case of a hemoperitoneum caused by the backflow of blood through a uterine tube, due to placental <span class="hlt">abruption</span>. Conclusion Hemoperitoneum in pregnant women with no other signs can reveal placental <span class="hlt">abruption</span>. The difficulty in identifying the cause may delay appropriate management. PMID:27994944</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EGUGA..14.3397B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..14.3397B"><span>Global <span class="hlt">Warming</span> And Meltwater</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bratu, S.</p> <p>2012-04-01</p> <p> glaciers, permafrost and sea ice. Other likely effects of the <span class="hlt">warming</span> include more frequent occurrences of extreme weather <span class="hlt">events</span> including heat waves, droughts and heavy rainfall <span class="hlt">events</span>, species extinctions due to shifting temperature regimes, and changes in agricultural yields. Meltwater is the water released by the melting of snow or ice, including glacial ice and ice shelves in the oceans. Meltwater is often found in the ablation zone of glaciers, where the rate of snow cover is reduced. In a report published in June 2007, the United Nations Environment Program estimated that global <span class="hlt">warming</span> could lead to 40% of the world's population being affected by the loss of glaciers, snow and the associated meltwater in Asia. This is one of many activities of the physics laboratory that the students of our high school are involved in.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017Natur.548..531M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017Natur.548..531M"><span>Palaeoclimate: Volcanism caused ancient global <span class="hlt">warming</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Meissner, Katrin J.; Bralower, Timothy J.</p> <p>2017-08-01</p> <p>A study confirms that volcanism set off one of Earth's fastest global-<span class="hlt">warming</span> <span class="hlt">events</span>. But the release of greenhouse gases was slow enough for negative feedbacks to mitigate impacts such as ocean acidification. See Letter p.573</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016NatGe...9..268S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016NatGe...9..268S"><span>Carbon cycle: Global <span class="hlt">warming</span> then and now</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stassen, Peter</p> <p>2016-04-01</p> <p>A rapid <span class="hlt">warming</span> <span class="hlt">event</span> 55.8 million years ago was caused by extensive carbon emissions. The rate of change of carbon and oxygen isotopes in marine shelf sediments suggests that carbon emission rates were much slower than anthropogenic emissions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4995404','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4995404"><span>Fungal decomposition of terrestrial organic matter accelerated Early Jurassic climate <span class="hlt">warming</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Pieńkowski, Grzegorz; Hodbod, Marta; Ullmann, Clemens V.</p> <p>2016-01-01</p> <p>Soils – constituting the largest terrestrial carbon pool - are vulnerable to climatic <span class="hlt">warming</span>. Currently existing uncertainties regarding carbon fluxes within terrestrial systems can be addressed by studies of past carbon cycle dynamics and related climate change recorded in sedimentary successions. Here we show an example from the Early Jurassic (early Toarcian, c. 183 mya) marginal-marine strata from Poland, tracking the hinterland response to climatic changes through a super-greenhouse <span class="hlt">event</span>. In contrast to anoxia-related enhanced carbon storage in coeval open marine environments, Total Organic Carbon (TOC) concentrations in the Polish successions are substantially reduced during this <span class="hlt">event</span>. Increasing temperature favoured fungal-mediated decomposition of plant litter – specifically of normally resistant woody tissues. The associated injection of oxidized organic matter into the atmosphere corresponds to <span class="hlt">abrupt</span> changes in standing vegetation and may have contributed significantly to the amplified greenhouse climate on Earth. The characteristic Toarcian signature of multiple <span class="hlt">warm</span> pulses coinciding with rapidly decreasing carbon isotope ratios may in part be the result of a radical reduction of the terrestrial carbon pool as a response to climate change. PMID:27554210</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016NatSR...631930P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016NatSR...631930P"><span>Fungal decomposition of terrestrial organic matter accelerated Early Jurassic climate <span class="hlt">warming</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pieńkowski, Grzegorz; Hodbod, Marta; Ullmann, Clemens V.</p> <p>2016-08-01</p> <p>Soils – constituting the largest terrestrial carbon pool - are vulnerable to climatic <span class="hlt">warming</span>. Currently existing uncertainties regarding carbon fluxes within terrestrial systems can be addressed by studies of past carbon cycle dynamics and related climate change recorded in sedimentary successions. Here we show an example from the Early Jurassic (early Toarcian, c. 183 mya) marginal-marine strata from Poland, tracking the hinterland response to climatic changes through a super-greenhouse <span class="hlt">event</span>. In contrast to anoxia-related enhanced carbon storage in coeval open marine environments, Total Organic Carbon (TOC) concentrations in the Polish successions are substantially reduced during this <span class="hlt">event</span>. Increasing temperature favoured fungal-mediated decomposition of plant litter – specifically of normally resistant woody tissues. The associated injection of oxidized organic matter into the atmosphere corresponds to <span class="hlt">abrupt</span> changes in standing vegetation and may have contributed significantly to the amplified greenhouse climate on Earth. The characteristic Toarcian signature of multiple <span class="hlt">warm</span> pulses coinciding with rapidly decreasing carbon isotope ratios may in part be the result of a radical reduction of the terrestrial carbon pool as a response to climate change.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27554210','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27554210"><span>Fungal decomposition of terrestrial organic matter accelerated Early Jurassic climate <span class="hlt">warming</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Pieńkowski, Grzegorz; Hodbod, Marta; Ullmann, Clemens V</p> <p>2016-08-24</p> <p>Soils - constituting the largest terrestrial carbon pool - are vulnerable to climatic <span class="hlt">warming</span>. Currently existing uncertainties regarding carbon fluxes within terrestrial systems can be addressed by studies of past carbon cycle dynamics and related climate change recorded in sedimentary successions. Here we show an example from the Early Jurassic (early Toarcian, c. 183 mya) marginal-marine strata from Poland, tracking the hinterland response to climatic changes through a super-greenhouse <span class="hlt">event</span>. In contrast to anoxia-related enhanced carbon storage in coeval open marine environments, Total Organic Carbon (TOC) concentrations in the Polish successions are substantially reduced during this <span class="hlt">event</span>. Increasing temperature favoured fungal-mediated decomposition of plant litter - specifically of normally resistant woody tissues. The associated injection of oxidized organic matter into the atmosphere corresponds to <span class="hlt">abrupt</span> changes in standing vegetation and may have contributed significantly to the amplified greenhouse climate on Earth. The characteristic Toarcian signature of multiple <span class="hlt">warm</span> pulses coinciding with rapidly decreasing carbon isotope ratios may in part be the result of a radical reduction of the terrestrial carbon pool as a response to climate change.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014PhyEd..49....1.','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014PhyEd..49....1."><span>News The fabulousness of physics in 2013 Crossing boundaries, national and disciplinary Five days of Eureka! in Ethiopia <span class="hlt">Warm</span> and welcoming in Iceland New Zealand Physics Conference moves to the home of Rutherford Jupiter on high: UK Astronomy Week 2014 Physics World Cup 2013 Forthcoming <span class="hlt">Events</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p></p> <p>2014-01-01</p> <p>The fabulousness of physics in 2013 Crossing boundaries, national and disciplinary Five days of Eureka! in Ethiopia <span class="hlt">Warm</span> and welcoming in Iceland New Zealand Physics Conference moves to the home of Rutherford Jupiter on high: UK Astronomy Week 2014 Physics World Cup 2013 Forthcoming <span class="hlt">Events</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ESD.....8..495S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ESD.....8..495S"><span>Non-linear intensification of Sahel rainfall as a possible dynamic response to future <span class="hlt">warming</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schewe, Jacob; Levermann, Anders</p> <p>2017-07-01</p> <p>Projections of the response of Sahel rainfall to future global <span class="hlt">warming</span> diverge significantly. Meanwhile, paleoclimatic records suggest that Sahel rainfall is capable of <span class="hlt">abrupt</span> transitions in response to gradual forcing. Here we present climate modeling evidence for the possibility of an <span class="hlt">abrupt</span> intensification of Sahel rainfall under future climate change. Analyzing 30 coupled global climate model simulations, we identify seven models where central Sahel rainfall increases by 40 to 300 % over the 21st century, owing to a northward expansion of the West African monsoon domain. Rainfall in these models is non-linearly related to sea surface temperature (SST) in the tropical Atlantic and Mediterranean moisture source regions, intensifying <span class="hlt">abruptly</span> beyond a certain SST <span class="hlt">warming</span> level. We argue that this behavior is consistent with a self-amplifying dynamic-thermodynamical feedback, implying that the gradual increase in oceanic moisture availability under <span class="hlt">warming</span> could trigger a sudden intensification of monsoon rainfall far inland of today's core monsoon region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014NatCC...4..143Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014NatCC...4..143Z"><span>How <span class="hlt">warm</span> days increase belief in global <span class="hlt">warming</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zaval, Lisa; Keenan, Elizabeth A.; Johnson, Eric J.; Weber, Elke U.</p> <p>2014-02-01</p> <p>Climate change judgements can depend on whether today seems warmer or colder than usual, termed the local <span class="hlt">warming</span> effect. Although previous research has demonstrated that this effect occurs, studies have yet to explain why or how temperature abnormalities influence global <span class="hlt">warming</span> attitudes. A better understanding of the underlying psychology of this effect can help explain the public's reaction to climate change and inform approaches used to communicate the phenomenon. Across five studies, we find evidence of attribute substitution, whereby individuals use less relevant but available information (for example, today's temperature) in place of more diagnostic but less accessible information (for example, global climate change patterns) when making judgements. Moreover, we rule out alternative hypotheses involving climate change labelling and lay mental models. Ultimately, we show that present temperature abnormalities are given undue weight and lead to an overestimation of the frequency of similar past <span class="hlt">events</span>, thereby increasing belief in and concern for global <span class="hlt">warming</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007GGG.....8.3005T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007GGG.....8.3005T"><span>An <span class="hlt">abrupt</span> change in the African monsoon at the end of the Younger Dryas</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Talbot, Michael R.; Filippi, Maria Letizia; Jensen, Niels Bo; Tiercelin, Jean-Jacques</p> <p>2007-03-01</p> <p>High-resolution studies of variations in the elemental and stable carbon- and nitrogen-isotope composition of organic matter in cores from Lakes Malawi, Tanganyika, and Bosumtwi (tropical Africa) indicate an <span class="hlt">abrupt</span> change in the wind-driven circulation of these lakes that, within the limits of available chronologies, was contemporaneous with the end of the Younger Dryas in the northern hemisphere. The change was also coincident with shifts in surface winds recorded in cores from off the west and northeast coasts of Africa. A range of other proxies indicate that these changes in wind regime were accompanied by a marked increase in precipitation in the northern tropics. Africa south of ˜5°-10°S, on the other hand, initially suffered drought conditions. Together, the evidence suggests an <span class="hlt">abrupt</span> northward translation of the African monsoon system at circa 11.5 ± 0.25 ka B.P. The data assembled here contribute to a growing body of work showing that the Younger Dryas was a major climatic excursion in tropical Africa. Furthermore, they add substance to recent suggestions that climatic <span class="hlt">events</span> in the southern hemisphere may have played a significant role in the <span class="hlt">abrupt</span> demise of the Younger Dryas.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4901284','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4901284"><span>The <span class="hlt">abrupt</span> climate change near 4,400 yr BP on the cultural transition in Yuchisi, China and its global linkage</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Wang, Jianjun; Sun, Liguang; Chen, Liqi; Xu, Libin; Wang, Yuhong; Wang, Xinming</p> <p>2016-01-01</p> <p>Extreme climatic <span class="hlt">events</span> have profound impacts on human society. Here we present the results of a study of organic biomarkers within a sedimentary section at the archaeological site of Yuchisi, eastern China, in order to reconstruct climatic variability during the Dawenkou (5,050–4,400 yr BP) and Longshan (4,400–4,000 yr BP) cultures. At ~4,400 yr BP, within the cultural transition horizon, <span class="hlt">abrupt</span> changes in biomarkers, such as the fatty acid ratio C18:2/C18:0, 2C31/(C27 + C29), n-C18-ol and n-C30-ol, indicate the occurrence of local climate changes over the course of a few decades. These changes occurred during the transition from the Holocene <span class="hlt">warm</span> period to a subsequent cold period which lasted for the following 600 years. This climatic shift has been recorded at numerous sites worldwide, and it is likely to have been the main cause of the widespread collapse of many isolated cultures at that time. The palaeoclimatic and archaeological data from the Yuchisi sediments may provide new insights into the relationship between climate change and prehistoric cultural transitions. PMID:27283832</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016NatSR...627723W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016NatSR...627723W"><span>The <span class="hlt">abrupt</span> climate change near 4,400 yr BP on the cultural transition in Yuchisi, China and its global linkage</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Jianjun; Sun, Liguang; Chen, Liqi; Xu, Libin; Wang, Yuhong; Wang, Xinming</p> <p>2016-06-01</p> <p>Extreme climatic <span class="hlt">events</span> have profound impacts on human society. Here we present the results of a study of organic biomarkers within a sedimentary section at the archaeological site of Yuchisi, eastern China, in order to reconstruct climatic variability during the Dawenkou (5,050-4,400 yr BP) and Longshan (4,400-4,000 yr BP) cultures. At ~4,400 yr BP, within the cultural transition horizon, <span class="hlt">abrupt</span> changes in biomarkers, such as the fatty acid ratio C18:2/C18:0, 2C31/(C27 + C29), n-C18-ol and n-C30-ol, indicate the occurrence of local climate changes over the course of a few decades. These changes occurred during the transition from the Holocene <span class="hlt">warm</span> period to a subsequent cold period which lasted for the following 600 years. This climatic shift has been recorded at numerous sites worldwide, and it is likely to have been the main cause of the widespread collapse of many isolated cultures at that time. The palaeoclimatic and archaeological data from the Yuchisi sediments may provide new insights into the relationship between climate change and prehistoric cultural transitions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008GeoRL..35.8701G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008GeoRL..35.8701G"><span>Comment on ``<span class="hlt">Abrupt</span> environmental change in Canada's northernmost lake inferred from fossil diatom and pigment stratigraphy'' by Dermot Antoniades et al.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gajewski, K.</p> <p>2008-04-01</p> <p>Antoniades et al. [2007; hereinafter referred to as A07] present an analysis of a 19-cm lake sediment core from Ward Hunt Island from northern Canada. They conclude that a significant and <span class="hlt">abrupt</span> change in the aquatic communities occurred in this lake during the past 2 centuries that was unusual with respect to the previous 8ka. In the paper, and especially in quotes to the press (e.g., http://www.cbc.ca; http://www.sciencedaily.com; http://scitizen.com) the authors conclude that their results, along with those from Smol et al. [2005] provide evidence for amplification of climates with latitude due to human caused global <span class="hlt">warming</span>, an <span class="hlt">event</span> unique in the past 8 ka. However, there are a number of problems in these data and flaws in the author's interpretations that render their results questionable. Their conclusions do not hold up to scrutiny as they do not concord with other information we have about climate variability in the Arctic. I have four major comments on the data, and several on the interpretation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27365315','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27365315"><span>North Atlantic ocean circulation and <span class="hlt">abrupt</span> climate change during the last glaciation.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Henry, L G; McManus, J F; Curry, W B; Roberts, N L; Piotrowski, A M; Keigwin, L D</p> <p>2016-07-29</p> <p>The most recent ice age was characterized by rapid and hemispherically asynchronous climate oscillations, whose origin remains unresolved. Variations in oceanic meridional heat transport may contribute to these repeated climate changes, which were most pronounced during marine isotope stage 3, the glacial interval 25 thousand to 60 thousand years ago. We examined climate and ocean circulation proxies throughout this interval at high resolution in a deep North Atlantic sediment core, combining the kinematic tracer protactinium/thorium (Pa/Th) with the deep water-mass tracer, epibenthic δ(13)C. These indicators suggest reduced Atlantic overturning circulation during every cool northern stadial, with the greatest reductions during episodic Hudson Strait iceberg discharges, while sharp northern <span class="hlt">warming</span> followed reinvigorated overturning. These results provide direct evidence for the ocean's persistent, central role in <span class="hlt">abrupt</span> glacial climate change.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016Sci...353..470H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016Sci...353..470H"><span>North Atlantic ocean circulation and <span class="hlt">abrupt</span> climate change during the last glaciation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Henry, L. G.; McManus, J. F.; Curry, W. B.; Roberts, N. L.; Piotrowski, A. M.; Keigwin, L. D.</p> <p>2016-07-01</p> <p>The most recent ice age was characterized by rapid and hemispherically asynchronous climate oscillations, whose origin remains unresolved. Variations in oceanic meridional heat transport may contribute to these repeated climate changes, which were most pronounced during marine isotope stage 3, the glacial interval 25 thousand to 60 thousand years ago. We examined climate and ocean circulation proxies throughout this interval at high resolution in a deep North Atlantic sediment core, combining the kinematic tracer protactinium/thorium (Pa/Th) with the deep water-mass tracer, epibenthic δ13C. These indicators suggest reduced Atlantic overturning circulation during every cool northern stadial, with the greatest reductions during episodic Hudson Strait iceberg discharges, while sharp northern <span class="hlt">warming</span> followed reinvigorated overturning. These results provide direct evidence for the ocean’s persistent, central role in <span class="hlt">abrupt</span> glacial climate change.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_20 --> <div id="page_21" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="401"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMPP13B1427K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMPP13B1427K"><span><span class="hlt">Abrupt</span> Climate Transitions in an unforced Integration of CESM (Community Earth System Model)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kleppin, H.; Jochum, M.; Shields, C. A.; Otto-Bliesner, B. L.</p> <p>2014-12-01</p> <p>In a pre-industrial control simulation of CESM changes of Greenland temperature show an asymmetric pattern that is a slow decrease at centennial timescales and an <span class="hlt">abrupt</span> increase at decadal timescales, resembling the pattern of Dansgaard-Oeschger-cycles. A strong influence of equatorial Pacific SST anomalies on the pressure state above the North Atlantic and hence the wind forcing of the Labrador Sea gyre is found. The cooling is triggered by a stochastic anomalous pressure pattern over the North Atlantic that weakens the wind forcing of the Labrador gyre, slowing down and advecting less <span class="hlt">warm</span> and saline subtropical waters to high latitudes. Then sea ice growth commences in the Labrador Sea due to locally reduced <span class="hlt">warm</span> water transport. The sea ice anomaly above the Labrador Sea enhances the anomalous atmospheric circulation and eventually causes a cold core anticyclonic high pressure anomaly to persist during the entire 300 years that the cold North Atlantic phase lasts. Furthermore the decreased salinity transport towards the Labrador Sea induces a positive feedback that weakens the gyre circulation further and causes a reduced deep water convection. This leads to a reduced Atlantic meridional overturning circulation of about 4 Sverdrup, and eventually a reduced northward heat transport. After a 30 year period of prevailing cold SST anomalies in the east Pacific the disturbed atmospheric circulation above the North Atlantic slowly disappears, the Labrador Sea gyre circulation and deep water convection resume, melting the additional sea ice away and eventually causing an <span class="hlt">abrupt</span> increase of Greenland temperatures. First ocean-sea ice only simulations forced with the anomalous atmospheric fluxes extracted from the original simulation reproduce the climate transition and the changed ocean circulation , even if starting from background ocean conditions that differ from the original ones.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011CSR....31..685W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011CSR....31..685W"><span>Response of salinity distribution around the Yellow River mouth to <span class="hlt">abrupt</span> changes in river discharge</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Yucheng; Liu, Zhe; Gao, Huiwang; Ju, Lian; Guo, Xinyu</p> <p>2011-04-01</p> <p>To investigate how salinity changes with <span class="hlt">abrupt</span> increases and decreases in river discharge, three surveys were conducted along six sections around the Yellow River mouth before, during and after a water regulation <span class="hlt">event</span> during which the river discharge was increased from ˜200 to >3000 m 3 s -1 for the first 3 days, was maintained at >3000 m 3 s -1 for the next 9 days and was decreased to <1000 m 3 s -1 for the final 4 days. The mean salinity in the Yellow River estuary area during the <span class="hlt">event</span> varied ˜1.21, which is much larger than its seasonal variation (˜0.50) and interannual variation (˜0.05). Before the <span class="hlt">event</span>, a small plume was observed near the river mouth. During the <span class="hlt">event</span>, the plume extended over 24 km offshore in the surface layer in the direction of river water outflow. After the <span class="hlt">event</span>, the plume diminished in size but remained larger than before the <span class="hlt">event</span>. The downstream propagation of the plume (as in a Kelvin wave sense) was apparent in the bottom layer during the second survey and in both the surface and bottom layers during the third survey. The plume sizes predicted by the formulas from theoretical studies are larger than those we observed, indicating that factors neglected by theoretical studies such as the temporal variation in river discharge and vertical mixing in the sea could be very important for plume evolution. In addition to the horizontal variation of the plume, we also observed the penetration of freshwater from the surface layer into the bottom layer. A comparison of two vertical processes, wind mixing and tidal mixing, suggests that the impact of wind mixing may be comparable with that of tidal mixing in the area close to the river mouth and may be dominant over offshore areas. The change in Kelvin number indicates an alteration of plume dynamics due to the <span class="hlt">abrupt</span> change in river discharge during the water regulation <span class="hlt">event</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMPP13B1424J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMPP13B1424J"><span>Decoupling of Northern North Atlantic Sea Surface Temperature and Deep Circulation during <span class="hlt">Abrupt</span> Glacial Climate Change</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jonkers, L.; Barker, S.; Hall, I. R.</p> <p>2014-12-01</p> <p><span class="hlt">Abrupt</span> climate change is a prominent feature of the ice ages. The prevailing view is that these changes are related to fluctuations in ocean circulation, possibly triggered by changes in freshwater forcing as a result of ice-rafting <span class="hlt">events</span> in the North Atlantic. Here we investigate this view by presenting results from a sediment core in the Northern North Atlantic (ODP 983 60.4°N, 23.6°W, 1984m depth, ~12-35 kyr), which is ideally positioned to monitor changes in the flow speed of Iceland-Scotland Overflow Waters. The mean size of silt (10-63 μm) has been proposed as a useful flow speed indicator, but can be influenced the presence of ice-rafted detritus (IRD). We present grain size data obtained using a Coulter counter as well as a laser diffraction particle sizer, which we compare to the proportion of Neogloboquadrina pachyderma (proxy for sea surface temperature) and manually counted coarse IRD. Grain size results are comparable for the two techniques and the influence of IRD is clearly visible in the mean size data. We use end-member modelling to derive an IRD-free estimate of flow speed variability and find clear reductions in the flow speed associated with IRD input. Sea surface temperature however, appears to vary independently from IRD input and hence deep circulation. In particular, IRD appears and current speed decreases after the onset of cooling and additional temperature variability is observed that is not associated with IRD <span class="hlt">events</span> or changes in the deep circulation. These results question the classical view of freshwater forcing as the driver of <span class="hlt">abrupt</span> climate change. We suggest that North Atlantic temperature variability may be related to shifts in position of the polar front and that, while IRD <span class="hlt">events</span> may be coeval with changes in the deep circulation, these changes are not required to explain the <span class="hlt">abrupt</span> temperature variability in the Northern North Atlantic.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.4641M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.4641M"><span>Ocean surface conditions on the SE Greenland shelf during the last millennium - from <span class="hlt">abrupt</span> changes to centennial variability</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Miettinen, Arto; Divine, Dmitry; Husum, Katrine; Koç, Nalan; Jennings, Anne</p> <p>2016-04-01</p> <p>August sea surface temperatures (aSST) and April sea-ice concentrations (aSIC) covering the last 2900 years have been reconstructed in order to investigate the variability of summer surface conditions along possible forcing factors on the SE Greenland shelf. In this diatom-based study, we focus on the interval ca. 870-1910 Common Era (CE) reconstructed at a high temporal resolution of 3-8 years. The results demonstrate both <span class="hlt">abrupt</span> changes and a clear centennial-bicentennial variability for the last millennium. The Medieval Climate Anomaly (MCA) between 1000 and 1200 CE represents the warmest ocean surface conditions of the SE Greenland shelf over the late Holocene (880 BCE-1910 CE). MCA in the current record is characterized by <span class="hlt">abrupt</span>, decadal to multidecadal changes, such as an <span class="hlt">abrupt</span> <span class="hlt">warming</span> of ~2.4 °C in 55 years around 1000 CE. Temperature changes of these magnitudes are rarely observed in other proxy records from the North Atlantic. Compared to regional air temperature reconstructions, our results indicate a lag of about 50 years in ocean surface <span class="hlt">warming</span> either due to increased freshwater discharge from the Greenland ice sheet or intensified sea-ice export from the Arctic as a response to atmospheric <span class="hlt">warming</span> at the beginning of the MCA. A cool phase, from 1200-1890 CE, associated with the Little Ice Age (LIA), ends with the rapid <span class="hlt">warming</span> of aSST and diminished aSIC in the early 20th century. The phases of <span class="hlt">warm</span> aSST and aSIC minima on the SE Greenland shelf and solar minima of the last millennium are antiphased, suggesting that solar forcing possibly amplified by atmospheric forcing has been behind the aSST variability on the SE Greenland over the last millennium. The results might indicate decreased sea ice formation on the SE Greenland shelf due to diminished freshwater input from the Greenland Ice Sheet during the cold climate periods. The results show that the SE Greenland shelf is a climatologically sensitive area where extremely rapid changes are</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1020933','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1020933"><span>Beam losses due to <span class="hlt">abrupt</span> crab cavity failures in the LHC</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Baer, T.; Barranco, J.; Calaga, R.; Tomas, R.; Wenninger, B.; Yee, B.; Zimmermann, F.</p> <p>2011-03-28</p> <p>A major concern for the implementation of crab crossing in a future High-Luminosity LHC (HL-LHC) is machine protection in an <span class="hlt">event</span> of a fast crab-cavity failure. Certain types of <span class="hlt">abrupt</span> crab-cavity amplitude and phase changes are simulated to characterize the effect of failures on the beam and the resulting particle-loss signatures. The time-dependent beam loss distributions around the ring and particle trajectories obtained from the simulations allow for a first assessment of the resulting beam impact on LHC collimators and on sensitive components around the ring. Results for the nominal LHC lattice is presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/283181','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/283181"><span>The case of the global jitters - Even in seemingly stable times, climate can take an <span class="hlt">abrupt</span> turn</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Monastersky, R.</p> <p>1996-03-02</p> <p>Research in different parts of the world has recently revealed signs that climate has behaved erratically during the last few millennia. Conditions in various regions have shifted <span class="hlt">abruptly</span> and repeatedly, perhaps even at the time of the collapse of the Akkadian civilization in 2200 B.C. This article discusses recent work of various scientists, who are trying to forecast future conditions, to understand what is causing these shifts and whether this rhythum has played a role in recent global <span class="hlt">warming</span>. A side bar discusses signs of a solar link to climatic change.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2001AGUFM.U41B..09P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2001AGUFM.U41B..09P"><span>Sensitivity and Thresholds of Ecosystems to <span class="hlt">Abrupt</span> Climate Change</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Peteet, D. M.; Peteet, D. M.</p> <p>2001-12-01</p> <p>Rapid vegetational change is a hallmark of past <span class="hlt">abrupt</span> climate change, as evidenced from Younger Dryas records in Europe, eastern North America, and the Pacific North American rim. The potential response of future ecosystems to <span class="hlt">abrupt</span> climate change is targeted, with a focus on particular changes in the hydrological cycle. The vulnerability of ecosystems is notable when particular shifts cross thresholds of precipitation and temperature, as many plants and animals are adapted to specific climatic "windows". Significant forest species compositional changes occur at ecotonal boundaries, which are often the first locations to record a climatic response. Historical forest declines have been linked to stress, and even Pleistocene extinctions have been associated with human interaction at times of rapid climatic shifts. Environmental extremes are risky for reproductive stages, and result in nonlinearities. The role of humans in association with <span class="hlt">abrupt</span> climate change suggests that many ecosystems may cross thresholds from which they will find it difficult to recover. Sectors particularly vulnerable will be reviewed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19900033509&hterms=RATE+CHANGE&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DRATE%2BOF%2BCHANGE','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19900033509&hterms=RATE+CHANGE&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DRATE%2BOF%2BCHANGE"><span>An <span class="hlt">abrupt</span> change in ridge axis gravity with spreading rate</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Small, Christopher; Sandwell, David T.</p> <p>1989-01-01</p> <p>A total of 44 Geosat profiles over ridges with spreading rates ranging from 14 to 155 mm/yr were analyzed. In agreement with previous studies, it is found that slow spreading ridges usually have high amplitude gravity troughs, while fast spreading ridges are characterized by low-amplitude ridge axis highs. Unexpectedly, it is found that the transition from axial trough to axial high occurs <span class="hlt">abruptly</span> at a spreading rate of 60-70 mm/yr. Ridge axis gravity signatures are highly variable for rates less than 65 mm/yr and very uniform at higher rates. The transition of the gravity signature appears to get more <span class="hlt">abrupt</span> than the transition of the topographic signature, suggesting an <span class="hlt">abrupt</span> change in the style of isostatic compensation with spreading rate. Published models of ridge axis dynamics do not explain this sharp transition.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1711162M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1711162M"><span>Role of Sea Surface <span class="hlt">Warming</span> in Triggering Amplification of Coastal Rainfall Extremes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Meredith, Edmund; Semenov, Vladimir; Maraun, Douglas; Park, Wonsun; Chernokulsky, Alexander</p> <p>2015-04-01</p> <p>Whether recent changes in the occurrence of meteorological extremes are attributable to a warmer climate remains a challenging question. One area where the potential for extreme summertime convective precipitation has grown recently, along with substantial sea surface temperature (SST) increase, is the Black Sea and Mediterranean (BSM) region. To study mechanisms through which SST increase may impact BSM convective extremes, we take the July 2012 precipitation extreme near the Black Sea town of Krymsk as a recent showcase example. The <span class="hlt">event</span> was related to a slow moving low pressure system crossing the eastern Black Sea, advecting <span class="hlt">warm</span> and moist air towards the coast. Two waves of convection resulted in precipitation totals that dwarfed all previous <span class="hlt">events</span> in the instrumental record, dating back to the 1930s, and over 170 deaths. The synoptic environment which led to this <span class="hlt">event</span> is typical of that found with intense summertime precipitation in the BSM region. We carry out ensemble sensitivity experiments over an eastern Black Sea domain with the WRF regional model, using multiply nested sub-domains, increasing to 600 m convection resolving resolution. The model's ability to reproduce the <span class="hlt">event</span> with observed SST forcing is first verified, before a series of additional ensembles with altered SST is created. These ensembles consist of subtracting (adding) the 1982 - 2012 trend in Black Sea SST from (to) the observed 2012 SST field in 20% increments, giving a total of 11 ensembles whose SST differ from the observed field by between -100% and +100% of the <span class="hlt">warming</span> trend. We demonstrate that such an intense precipitation <span class="hlt">event</span> would not have been possible without the recent Black Sea <span class="hlt">warming</span>. The increased SST enhances low-level instability, allowing deep convection to be triggered and causing a more than 300% increase in precipitation. Additionally, a highly nonlinear precipitation response to incrementally increasing SST suggests that Black Sea SSTs have exceeded a</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23939066','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23939066"><span><span class="hlt">Abrupt</span> polarization transition of vector autofocusing Airy beams.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Liu, Sheng; Wang, Meirong; Li, Peng; Zhang, Peng; Zhao, Jianlin</p> <p>2013-07-15</p> <p>We experimentally and theoretically study the <span class="hlt">abrupt</span> polarization transitions of vector autofocusing Airy beams associated with the spin-orbit interactions. It is shown that when the topological charges of the polarization and the attached spiral phase are equal in number, the local polarizations undergo an <span class="hlt">abrupt</span> transition from linear to circular polarizations at the focal point, and the associated orbital angular momentum partially converts into the spin of photons. The experimental results are theoretically explained from the far-field properties of the beams in terms of Hankel transformations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.7493G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.7493G"><span><span class="hlt">Abrupt</span> transitions to a cold North Atlantic in the late Holocene</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Geirsdóttir, Áslaug; Miller, Gifford; Larsen, Darren; Florian, Christopher; Pendleton, Simon</p> <p>2015-04-01</p> <p>The Holocene provides a time interval with boundary conditions similar to present, except for greenhouse gas concentrations. Recent high-resolution Northern Hemisphere records show general cooling related to orbital terms through the late Holocene, but also highly non-linear <span class="hlt">abrupt</span> departures of centennial scale summer cold periods. These <span class="hlt">abrupt</span> departures are evident within the last two millennia (the transitions between the Roman <span class="hlt">Warm</span> Period (RWP, ~2,000 yr BP), the Dark Ages Cold Period (DACP, ~500-900 years AD), the Medieval <span class="hlt">Warm</span> Period (MWP, 1000-1200 years AD) and the Little Ice Age (LIA, ~1300-1900 AD). A series of new, high-resolution and securely dated lake records from Iceland also show <span class="hlt">abrupt</span> climate departures over the past 2 ka, characterized by shifts to persistent cold summers and an expanded cryosphere. Despite substantial differences in catchment-specific processes that dominate the lake records, the multi-proxy reconstructions are remarkably similar. After nearly a millennium with little evidence of significant climate shifts, the beginning of the first millennium AD is characterized by renewed summer cooling that leads to an expanding cryosphere. Slow summer cooling over the first five centuries is succeeded by widespread substantial cooling, with evidence for substantial expansion of glaciers and ice caps throughout our field areas between 530 and 900 AD, and an accompanying reduction in vegetation cover across much of Iceland that led to widespread landscape instability. These data suggest that the North Atlantic system began a transition into a new cold state early in the first millennium AD, which was amplified after 500 AD, until it was interrupted by warmer Medieval times between ~1000 and 1250 AD. Although severe soil erosion in Iceland is frequently associated with human settlement dated to 871 ±2 AD our reconstructions indicate that soil erosion began several centuries before settlement, during the DACP, whereas for several centuries</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMPP51B1117H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMPP51B1117H"><span>Combined effects of <span class="hlt">warming</span>, acidification and changing ocean circulation on the marine carbon cycle during the PETM</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Heinze, M.; Ilyina, T.</p> <p>2014-12-01</p> <p>We are studying the ocean biogeochemistry during the Paleocene-Eocene Thermal Maximum (PETM; 55 million years ago) with an Earth System Model (ESM). During this period of <span class="hlt">abrupt</span> environmental change the climate underwent a significant transformation within short geological timescales (~10 ky). The PETM is globally recorded in proxy-data by a negative δ13C carbon isotope excursion and carbonate dissolution in the ocean, suggesting that the occurred <span class="hlt">warming</span> was caused by massive carbon release. To investigate the marine biogeochemistry before and during the onset of the PETM we use the ESM of the Max Planck Institute for Meteorology to simulate scenarios with different rates of carbon release over several thousand years. Starting from an already warmer background climate than present, the atmospheric CO2 increase and concomitant <span class="hlt">warming</span> lead to acidification and deoxygenation of mid and deep ocean waters. Our results indicate that a weakening of deep water formation, caused by global <span class="hlt">warming</span>, plays a major role in producing inhospitable conditions for benthic organisms during the PETM. We show how the interaction between biological and physical responses to the carbon perturbation lead to the observed calcite sediment dissolution in the deep ocean. At the surface a weakening of the physical and biological carbon pump restricts the oceanic uptake capacity of atmospheric CO2 which helps to maintain elevated atmospheric CO2 concentrations and temperatures throughout the <span class="hlt">event</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017NatCC...7..316A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017NatCC...7..316A"><span>Global energy budget: Elusive origin of <span class="hlt">warming</span> slowdown</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Allan, Richard P.</p> <p>2017-04-01</p> <p>Global surface <span class="hlt">warming</span> was slower than expected in the first decade of the twenty-first century. Research attributes similar <span class="hlt">events</span> to ocean or atmosphere fluctuations, but the subtle origins of these <span class="hlt">events</span> may elude observational detection.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27450507','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27450507"><span>Factors associated with <span class="hlt">abrupt</span> discontinuation of dabigatran therapy in patients with atrial fibrillation in Malaysia.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Beshir, Semira Abdi; Chee, Kok-Han; Lo, Yoke-Lin</p> <p>2016-10-01</p> <p>Background Oral anticoagulant therapy is indicated for the prevention of stroke or other thromboembolic <span class="hlt">events</span>. Premature discontinuation of oral anticoagulants may increase the risk of thromboembolism resulting in adverse sequelae. There are sparse data on the prevalence and the predictors of dabigatran discontinuation in Malaysian patients with atrial fibrillation. Objectives Determine the reasons and identify associated factors for <span class="hlt">abrupt</span> discontinuation of dabigatran, assess the switching pattern and the occurrence of thromboembolic <span class="hlt">events</span> after dabigatran discontinuation. Setting A university-affiliated tertiary hospital in Kuala Lumpur, Malaysia. Methods The clinical and demographic data of a cohort who were initiated with dabigatran between 2010 and 2012 at the University of Malaya Medical Centre were reviewed until the date of death or on 31st December 2013. Those patients who discontinued dabigatran were further followed up until 31st December 2015 to determine the occurrence of any thromboembolic <span class="hlt">event</span>. Main outcome measure Permanent discontinuation of dabigatran for more than 8 weeks. Results 26 (14 %) of a cohort of 192 patients discontinued dabigatran therapy during a median follow-up period of 20 (range 3-45) months. About one-half of the discontinuation occurred within the first 6 months of dabigatran use. The three most cited reasons for discontinuation are bleeding <span class="hlt">events</span> (19 %), high out-of-pocket drug payment (19 %) and cardioversion (19 %). Heart failure [adjusted odds ratio 3.699 (95 % confidence interval 1.393-9.574)] or chronic kidney disease [adjusted odds ratio 5.211 (95 % confidence interval 1.068-23.475)] were found to be independent risk factors for <span class="hlt">abrupt</span> dabigatran discontinuation. Patients who discontinued dabigatran received warfarin (38 %), antiplatelet agents (16 %) or no alternative antithrombotic therapy (46 %). Five of the 26 patients who discontinued dabigatran developed an ischaemic stroke within 3-34 months after</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/14558898','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/14558898"><span>Evidence for <span class="hlt">abrupt</span> climate changes in annually laminated marine sediments.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kemp, Alan E S</p> <p>2003-09-15</p> <p>Annually laminated sediments from marine or lacustrine settings represent valuable high-resolution archives of climate change that record variation due to changing precipitation and run-off from land or variation in biological productivity and flux in the water column. Because of their annual resolution such sediments may capture <span class="hlt">abrupt</span> changes of interannual to decadal scales rivaling corals and ice cores in resolution. Laminated sediments often occur intermittently in the sediment column, and the onset and cessation of laminae commonly record the <span class="hlt">abrupt</span> crossing of thresholds related to climate change, for example, in the degree of oxygenation of bottom waters. Such records from marginal basins and continental margins have been pivotal in demonstrating that <span class="hlt">abrupt</span> changes hitherto documented only in high-latitude ice cores are synchronous with climatic change at low latitudes. These insights into global teleconnections have improved our understanding of the mechanisms of rapid climate change. In deep-sea settings, the discovery of the episodic occurrence of laminated diatom-rich sediments in the Equatorial Pacific and Southern Ocean provides evidence for massive climate-related biogeochemical excursions tied to <span class="hlt">abrupt</span> changes in the input, distribution and availability of nutrients in the oceans.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://eric.ed.gov/?q=insulator&pg=2&id=EJ202047','ERIC'); return false;" href="https://eric.ed.gov/?q=insulator&pg=2&id=EJ202047"><span><span class="hlt">Abrupt</span> Depletion Layer Approximation for the Metal Insulator Semiconductor Diode.</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Jones, Kenneth</p> <p>1979-01-01</p> <p>Determines the excess surface change carrier density, surface potential, and relative capacitance of a metal insulator semiconductor diode as a function of the gate voltage, using the precise questions and the equations derived with the <span class="hlt">abrupt</span> depletion layer approximation. (Author/GA)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=semiconductor+AND+devices&pg=4&id=EJ202047','ERIC'); return false;" href="http://eric.ed.gov/?q=semiconductor+AND+devices&pg=4&id=EJ202047"><span><span class="hlt">Abrupt</span> Depletion Layer Approximation for the Metal Insulator Semiconductor Diode.</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Jones, Kenneth</p> <p>1979-01-01</p> <p>Determines the excess surface change carrier density, surface potential, and relative capacitance of a metal insulator semiconductor diode as a function of the gate voltage, using the precise questions and the equations derived with the <span class="hlt">abrupt</span> depletion layer approximation. (Author/GA)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/AD1014405','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/AD1014405"><span>Investigating Flow Features Near <span class="hlt">Abrupt</span> Topography in the Mariana Basin</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2015-09-30</p> <p>1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Investigating Flow Features Near <span class="hlt">Abrupt</span> Topography in...waves generated by flow over topography and mesoscale eddies generated by flow past islands. Having identified the prime locations in the region for such</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/10677464','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/10677464"><span><span class="hlt">Abrupt</span> climate change and thermohaline circulation: mechanisms and predictability.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Marotzke, J</p> <p>2000-02-15</p> <p>The ocean's thermohaline circulation has long been recognized as potentially unstable and has consequently been invoked as a potential cause of <span class="hlt">abrupt</span> climate change on all timescales of decades and longer. However, fundamental aspects of thermohaline circulation changes remain poorly understood.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=34301','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=34301"><span><span class="hlt">Abrupt</span> climate change and thermohaline circulation: Mechanisms and predictability</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Marotzke, Jochem</p> <p>2000-01-01</p> <p>The ocean's thermohaline circulation has long been recognized as potentially unstable and has consequently been invoked as a potential cause of <span class="hlt">abrupt</span> climate change on all timescales of decades and longer. However, fundamental aspects of thermohaline circulation changes remain poorly understood. PMID:10677464</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_21 --> <div id="page_22" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="421"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22908256','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22908256"><span>Impact of <span class="hlt">abrupt</span> deglacial climate change on tropical Atlantic subsurface temperatures.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Schmidt, Matthew W; Chang, Ping; Hertzberg, Jennifer E; Them, Theodore R; Ji, Link; J, Link; Otto-Bliesner, Bette L</p> <p>2012-09-04</p> <p>Both instrumental data analyses and coupled ocean-atmosphere models indicate that Atlantic meridional overturning circulation (AMOC) variability is tightly linked to <span class="hlt">abrupt</span> tropical North Atlantic (TNA) climate change through both atmospheric and oceanic processes. Although a slowdown of AMOC results in an atmospheric-induced surface cooling in the entire TNA, the subsurface experiences an even larger <span class="hlt">warming</span> because of rapid reorganizations of ocean circulation patterns at intermediate water depths. Here, we reconstruct high-resolution temperature records using oxygen isotope values and Mg/Ca ratios in both surface- and subthermocline-dwelling planktonic foraminifera from a sediment core located in the TNA over the last 22 ky. Our results show significant changes in the vertical thermal gradient of the upper water column, with the warmest subsurface temperatures of the last deglacial transition corresponding to the onset of the Younger Dryas. Furthermore, we present new analyses of a climate model simulation forced with freshwater discharge into the North Atlantic under Last Glacial Maximum forcings and boundary conditions that reveal a maximum subsurface <span class="hlt">warming</span> in the vicinity of the core site and a vertical thermal gradient change at the onset of AMOC weakening, consistent with the reconstructed record. Together, our proxy reconstructions and modeling results provide convincing evidence for a subsurface oceanic teleconnection linking high-latitude North Atlantic climate to the tropical Atlantic during periods of reduced AMOC across the last deglacial transition.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3437837','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3437837"><span>Impact of <span class="hlt">abrupt</span> deglacial climate change on tropical Atlantic subsurface temperatures</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Schmidt, Matthew W.; Chang, Ping; Hertzberg, Jennifer E.; Them, Theodore R.; Ji, Link; Otto-Bliesner, Bette L.</p> <p>2012-01-01</p> <p>Both instrumental data analyses and coupled ocean-atmosphere models indicate that Atlantic meridional overturning circulation (AMOC) variability is tightly linked to <span class="hlt">abrupt</span> tropical North Atlantic (TNA) climate change through both atmospheric and oceanic processes. Although a slowdown of AMOC results in an atmospheric-induced surface cooling in the entire TNA, the subsurface experiences an even larger <span class="hlt">warming</span> because of rapid reorganizations of ocean circulation patterns at intermediate water depths. Here, we reconstruct high-resolution temperature records using oxygen isotope values and Mg/Ca ratios in both surface- and subthermocline-dwelling planktonic foraminifera from a sediment core located in the TNA over the last 22 ky. Our results show significant changes in the vertical thermal gradient of the upper water column, with the warmest subsurface temperatures of the last deglacial transition corresponding to the onset of the Younger Dryas. Furthermore, we present new analyses of a climate model simulation forced with freshwater discharge into the North Atlantic under Last Glacial Maximum forcings and boundary conditions that reveal a maximum subsurface <span class="hlt">warming</span> in the vicinity of the core site and a vertical thermal gradient change at the onset of AMOC weakening, consistent with the reconstructed record. Together, our proxy reconstructions and modeling results provide convincing evidence for a subsurface oceanic teleconnection linking high-latitude North Atlantic climate to the tropical Atlantic during periods of reduced AMOC across the last deglacial transition. PMID:22908256</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19822751','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19822751"><span>Reducing <span class="hlt">abrupt</span> climate change risk using the Montreal Protocol and other regulatory actions to complement cuts in CO2 emissions.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Molina, Mario; Zaelke, Durwood; Sarma, K Madhava; Andersen, Stephen O; Ramanathan, Veerabhadran; Kaniaru, Donald</p> <p>2009-12-08</p> <p>Current emissions of anthropogenic greenhouse gases (GHGs) have already committed the planet to an increase in average surface temperature by the end of the century that may be above the critical threshold for tipping elements of the climate system into <span class="hlt">abrupt</span> change with potentially irreversible and unmanageable consequences. This would mean that the climate system is close to entering if not already within the zone of "dangerous anthropogenic interference" (DAI). Scientific and policy literature refers to the need for "early," "urgent," "rapid," and "fast-action" mitigation to help avoid DAI and <span class="hlt">abrupt</span> climate changes. We define "fast-action" to include regulatory measures that can begin within 2-3 years, be substantially implemented in 5-10 years, and produce a climate response within decades. We discuss strategies for short-lived non-CO(2) GHGs and particles, where existing agreements can be used to accomplish mitigation objectives. Policy makers can amend the Montreal Protocol to phase down the production and consumption of hydrofluorocarbons (HFCs) with high global <span class="hlt">warming</span> potential. Other fast-action strategies can reduce emissions of black carbon particles and precursor gases that lead to ozone formation in the lower atmosphere, and increase biosequestration, including through biochar. These and other fast-action strategies may reduce the risk of <span class="hlt">abrupt</span> climate change in the next few decades by complementing cuts in CO(2) emissions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2791591','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2791591"><span>Reducing <span class="hlt">abrupt</span> climate change risk using the Montreal Protocol and other regulatory actions to complement cuts in CO2 emissions</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Molina, Mario; Zaelke, Durwood; Sarma, K. Madhava; Andersen, Stephen O.; Ramanathan, Veerabhadran; Kaniaru, Donald</p> <p>2009-01-01</p> <p>Current emissions of anthropogenic greenhouse gases (GHGs) have already committed the planet to an increase in average surface temperature by the end of the century that may be above the critical threshold for tipping elements of the climate system into <span class="hlt">abrupt</span> change with potentially irreversible and unmanageable consequences. This would mean that the climate system is close to entering if not already within the zone of “dangerous anthropogenic interference” (DAI). Scientific and policy literature refers to the need for “early,” “urgent,” “rapid,” and “fast-action” mitigation to help avoid DAI and <span class="hlt">abrupt</span> climate changes. We define “fast-action” to include regulatory measures that can begin within 2–3 years, be substantially implemented in 5–10 years, and produce a climate response within decades. We discuss strategies for short-lived non-CO2 GHGs and particles, where existing agreements can be used to accomplish mitigation objectives. Policy makers can amend the Montreal Protocol to phase down the production and consumption of hydrofluorocarbons (HFCs) with high global <span class="hlt">warming</span> potential. Other fast-action strategies can reduce emissions of black carbon particles and precursor gases that lead to ozone formation in the lower atmosphere, and increase biosequestration, including through biochar. These and other fast-action strategies may reduce the risk of <span class="hlt">abrupt</span> climate change in the next few decades by complementing cuts in CO2 emissions. PMID:19822751</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25145694','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25145694"><span>Extreme temperatures, foundation species, and <span class="hlt">abrupt</span> ecosystem change: an example from an iconic seagrass ecosystem.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Thomson, Jordan A; Burkholder, Derek A; Heithaus, Michael R; Fourqurean, James W; Fraser, Matthew W; Statton, John; Kendrick, Gary A</p> <p>2015-04-01</p> <p>Extreme climatic <span class="hlt">events</span> can trigger <span class="hlt">abrupt</span> and often lasting change in ecosystems via the reduction or elimination of foundation (i.e., habitat-forming) species. However, while the frequency/intensity of extreme <span class="hlt">events</span> is predicted to increase under climate change, the impact of these <span class="hlt">events</span> on many foundation species and the ecosystems they support remains poorly understood. Here, we use the iconic seagrass meadows of Shark Bay, Western Australia--a relatively pristine subtropical embayment whose dominant, canopy-forming seagrass, Amphibolis antarctica, is a temperate species growing near its low-latitude range limit--as a model system to investigate the impacts of extreme temperatures on ecosystems supported by thermally sensitive foundation species in a changing climate. Following an unprecedented marine heat wave in late summer 2010/11, A. antarctica experienced catastrophic (>90%) dieback in several regions of Shark Bay. Animal-borne video footage taken from the perspective of resident, seagrass-associated megafauna (sea turtles) revealed severe habitat degradation after the <span class="hlt">event</span> compared with a decade earlier. This reduction in habitat quality corresponded with a decline in the health status of largely herbivorous green turtles (Chelonia mydas) in the 2 years following the heat wave, providing evidence of long-term, community-level impacts of the <span class="hlt">event</span>. Based on these findings, and similar examples from diverse ecosystems, we argue that a generalized framework for assessing the vulnerability of ecosystems to <span class="hlt">abrupt</span> change associated with the loss of foundation species is needed to accurately predict ecosystem trajectories in a changing climate. This includes seagrass meadows, which have received relatively little attention in this context. Novel research and monitoring methods, such as the analysis of habitat and environmental data from animal-borne video and data-logging systems, can make an important contribution to this framework.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=warmup&pg=7&id=EJ404495','ERIC'); return false;" href="http://eric.ed.gov/?q=warmup&pg=7&id=EJ404495"><span><span class="hlt">Warm</span> Up with Skill.</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Hoyle, R. J.; Smith, Robert F.</p> <p>1989-01-01</p> <p>Too little time is often spent on <span class="hlt">warm</span>-up activities in the school or recreation class. <span class="hlt">Warm</span>-ups are often perfunctory and unimaginative. Several suggestions are made for <span class="hlt">warm</span>-up activities that incorporate both previously learned and new skills, while preparing the body for more vigorous activity. (IAH)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.2483B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.2483B"><span>What caused the 2009 cold <span class="hlt">event</span> in the Atlantic cold tongue region?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Burmeister, Kristin; Brandt, Peter; Lübbecke, Joke F.</p> <p>2016-04-01</p> <p>The tropical Atlantic (TA) exhibits sea surface temperature (SST) variability on seasonal to inter-annual time scales. This variability is associated with changes of atmospheric dynamics, linking it to severe flooding or droughts in South America and West Africa. This study investigates processes in the TA that might have caused the extreme cold <span class="hlt">event</span> in the Atlantic cold tongue (ACT) region in 2009. During boreal spring, a strong negative Atlantic meridional mode <span class="hlt">event</span> developed in the TA associated with northwesterly wind anomalies along the equator. Contrary to what would be expected from ENSO-like dynamics, these wind anomalies did not lead to a <span class="hlt">warming</span> in the eastern equatorial Atlantic in boreal summer. Instead, from May to August 2009, an <span class="hlt">abrupt</span> cooling took place in the ACT region resulting in the coldest August ACT SST on record. In the literature, two processes - equatorial wave reflection and meridional advection of subsurface temperatures - are discussed as potential causes of such an <span class="hlt">event</span>. Whereas previous studies are mainly based on satellite data, reanalysis products and model output, we here use in situ measurements (data from Argo floats, PIRATA buoys, and TACE moorings, as well as CTD data of various ship cruises) in addition to satellite and reanalysis products to investigate the contribution of both processes to the strong surface cooling in the ACT region in 2009. Results based on the Argo float data confirm previous findings that equatorial wave reflection contributed to the cold <span class="hlt">event</span> in the ACT region in 2009. They further indicate that higher baroclinic mode waves played an important role. The analysis of in situ and reanalysis temperature and velocity data does not suggest a significant contribution of meridional advection of subsurface temperatures for the onset of the 2009 cold <span class="hlt">event</span>. The results indicate an asymmetry in the importance of meridional advection for non-ENSO-like cold and <span class="hlt">warm</span> <span class="hlt">events</span> with <span class="hlt">warm</span> <span class="hlt">events</span> more strongly affected</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24248352','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24248352"><span>Spontaneous <span class="hlt">abrupt</span> climate change due to an atmospheric blocking-sea-ice-ocean feedback in an unforced climate model simulation.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Drijfhout, Sybren; Gleeson, Emily; Dijkstra, Henk A; Livina, Valerie</p> <p>2013-12-03</p> <p><span class="hlt">Abrupt</span> climate change is abundant in geological records, but climate models rarely have been able to simulate such <span class="hlt">events</span> in response to realistic forcing. Here we report on a spontaneous <span class="hlt">abrupt</span> cooling <span class="hlt">event</span>, lasting for more than a century, with a temperature anomaly similar to that of the Little Ice Age. The <span class="hlt">event</span> was simulated in the preindustrial control run of a high-resolution climate model, without imposing external perturbations. Initial cooling started with a period of enhanced atmospheric blocking over the eastern subpolar gyre. In response, a southward progression of the sea-ice margin occurred, and the sea-level pressure anomaly was locked to the sea-ice margin through thermal forcing. The cold-core high steered more cold air to the area, reinforcing the sea-ice concentration anomaly east of Greenland. The sea-ice surplus was carried southward by ocean currents around the tip of Greenland. South of 70 °N, sea ice already started melting and the associated freshwater anomaly was carried to the Labrador Sea, shutting off deep convection. There, surface waters were exposed longer to atmospheric cooling and sea surface temperature dropped, causing an even larger thermally forced high above the Labrador Sea. In consequence, east of Greenland, anomalous winds changed from north to south, terminating the <span class="hlt">event</span> with similar <span class="hlt">abruptness</span> to its onset. Our results imply that only climate models that possess sufficient resolution to correctly represent atmospheric blocking, in combination with a sensitive sea-ice model, are able to simulate this kind of <span class="hlt">abrupt</span> climate change.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3856815','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3856815"><span>Spontaneous <span class="hlt">abrupt</span> climate change due to an atmospheric blocking–sea-ice–ocean feedback in an unforced climate model simulation</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Drijfhout, Sybren; Gleeson, Emily; Dijkstra, Henk A.; Livina, Valerie</p> <p>2013-01-01</p> <p><span class="hlt">Abrupt</span> climate change is abundant in geological records, but climate models rarely have been able to simulate such <span class="hlt">events</span> in response to realistic forcing. Here we report on a spontaneous <span class="hlt">abrupt</span> cooling <span class="hlt">event</span>, lasting for more than a century, with a temperature anomaly similar to that of the Little Ice Age. The <span class="hlt">event</span> was simulated in the preindustrial control run of a high-resolution climate model, without imposing external perturbations. Initial cooling started with a period of enhanced atmospheric blocking over the eastern subpolar gyre. In response, a southward progression of the sea-ice margin occurred, and the sea-level pressure anomaly was locked to the sea-ice margin through thermal forcing. The cold-core high steered more cold air to the area, reinforcing the sea-ice concentration anomaly east of Greenland. The sea-ice surplus was carried southward by ocean currents around the tip of Greenland. South of 70°N, sea ice already started melting and the associated freshwater anomaly was carried to the Labrador Sea, shutting off deep convection. There, surface waters were exposed longer to atmospheric cooling and sea surface temperature dropped, causing an even larger thermally forced high above the Labrador Sea. In consequence, east of Greenland, anomalous winds changed from north to south, terminating the <span class="hlt">event</span> with similar <span class="hlt">abruptness</span> to its onset. Our results imply that only climate models that possess sufficient resolution to correctly represent atmospheric blocking, in combination with a sensitive sea-ice model, are able to simulate this kind of <span class="hlt">abrupt</span> climate change. PMID:24248352</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ESSD....9..679S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ESSD....9..679S"><span>The ACER pollen and charcoal database: a global resource to document vegetation and fire response to <span class="hlt">abrupt</span> climate changes during the last glacial period</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sánchez Goñi, María Fernanda; Desprat, Stéphanie; Daniau, Anne-Laure; Bassinot, Frank C.; Polanco-Martínez, Josué M.; Harrison, Sandy P.; Allen, Judy R. M.; Anderson, R. Scott; Behling, Hermann; Bonnefille, Raymonde; Burjachs, Francesc; Carrión, José S.; Cheddadi, Rachid; Clark, James S.; Combourieu-Nebout, Nathalie; Mustaphi, Colin. J. Courtney; Debusk, Georg H.; Dupont, Lydie M.; Finch, Jemma M.; Fletcher, William J.; Giardini, Marco; González, Catalina; Gosling, William D.; Grigg, Laurie D.; Grimm, Eric C.; Hayashi, Ryoma; Helmens, Karin; Heusser, Linda E.; Hill, Trevor; Hope, Geoffrey; Huntley, Brian; Igarashi, Yaeko; Irino, Tomohisa; Jacobs, Bonnie; Jiménez-Moreno, Gonzalo; Kawai, Sayuri; Kershaw, A. Peter; Kumon, Fujio; Lawson, Ian T.; Ledru, Marie-Pierre; Lézine, Anne-Marie; Liew, Ping Mei; Magri, Donatella; Marchant, Robert; Margari, Vasiliki; Mayle, Francis E.; Merna McKenzie, G.; Moss, Patrick; Müller, Stefanie; Müller, Ulrich C.; Naughton, Filipa; Newnham, Rewi M.; Oba, Tadamichi; Pérez-Obiol, Ramón; Pini, Roberta; Ravazzi, Cesare; Roucoux, Katy H.; Rucina, Stephen M.; Scott, Louis; Takahara, Hikaru; Tzedakis, Polichronis C.; Urrego, Dunia H.; van Geel, Bas; Valencia, B. Guido; Vandergoes, Marcus J.; Vincens, Annie; Whitlock, Cathy L.; Willard, Debra A.; Yamamoto, Masanobu</p> <p>2017-09-01</p> <p>Quaternary records provide an opportunity to examine the nature of the vegetation and fire responses to rapid past climate changes comparable in velocity and magnitude to those expected in the 21st-century. The best documented examples of rapid climate change in the past are the <span class="hlt">warming</span> <span class="hlt">events</span> associated with the Dansgaard-Oeschger (D-O) cycles during the last glacial period, which were sufficiently large to have had a potential feedback through changes in albedo and greenhouse gas emissions on climate. Previous reconstructions of vegetation and fire changes during the D-O cycles used independently constructed age models, making it difficult to compare the changes between different sites and regions. Here, we present the ACER (<span class="hlt">Abrupt</span> Climate Changes and Environmental Responses) global database, which includes 93 pollen records from the last glacial period (73-15 ka) with a temporal resolution better than 1000 years, 32 of which also provide charcoal records. A harmonized and consistent chronology based on radiometric dating (14C, 234U/230Th, optically stimulated luminescence (OSL), 40Ar/39Ar-dated tephra layers) has been constructed for 86 of these records, although in some cases additional information was derived using common control points based on <span class="hlt">event</span> stratigraphy. The ACER database compiles metadata including geospatial and dating information, pollen and charcoal counts, and pollen percentages of the characteristic biomes and is archived in <span style="" class="text">Microsoft AccessTM at <a href="https://doi.org/10.1594/PANGAEA.870867" target="_blank">https://doi.org/10.1594/PANGAEA.870867</a>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24607778','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24607778"><span>Natural and <span class="hlt">abrupt</span> involution of the mammary gland affects differently the metabolic and health consequences of weaning.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Silanikove, Nissim</p> <p>2014-04-25</p> <p>In most mammals under natural conditions weaning is gradual. Weaning occurs after the mammary gland naturally produces much less milk than it did at peak and established lactation. Involution occurs following the cessation of milk evacuation from the mammary glands. The <span class="hlt">abrupt</span> termination of the evacuation of milk from the mammary gland at peak and established lactation induces <span class="hlt">abrupt</span> involution. Evidence on mice has shown that during <span class="hlt">abrupt</span> involution, mammary gland utilizes some of the same tissue remodeling programs that are activated during wound healing. These results led to the proposition of the "involution hypothesis". According to the involution hypothesis, involution is associated with increased risk for developing breast cancer. However, the involution hypothesis is challenged by the metabolic and immunological <span class="hlt">events</span> that characterize the involution process that follows gradual weaning. It has been shown that gradual weaning is associated with pre-adaption to the forthcoming break between dam and offspring and is followed by an orderly reprogramming of the mammary gland tissue. As discussed herein, such response may actually protect the mammary glands against the development of breast cancer and thus, may explain the protective effect of extended breastfeeding. On the other hand, the termination of breastfeeding during the first 6 months of lactation is likely associated with an <span class="hlt">abrupt</span> involution and thus with an increased risk for developing breast cancer. Review of the literature on the epidemiology of breast cancer principally supports those conclusions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017NatGe..10..518Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017NatGe..10..518Z"><span><span class="hlt">Abrupt</span> North Atlantic circulation changes in response to gradual CO2 forcing in a glacial climate state</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, Xu; Knorr, Gregor; Lohmann, Gerrit; Barker, Stephen</p> <p>2017-07-01</p> <p>Glacial climate is marked by <span class="hlt">abrupt</span>, millennial-scale climate changes known as Dansgaard-Oeschger cycles. The most pronounced stadial coolings, Heinrich <span class="hlt">events</span>, are associated with massive iceberg discharges to the North Atlantic. These <span class="hlt">events</span> have been linked to variations in the strength of the Atlantic meridional overturning circulation. However, the factors that lead to <span class="hlt">abrupt</span> transitions between strong and weak circulation regimes remain unclear. Here we show that, in a fully coupled atmosphere-ocean model, gradual changes in atmospheric CO2 concentrations can trigger <span class="hlt">abrupt</span> climate changes, associated with a regime of bi-stability of the Atlantic meridional overturning circulation under intermediate glacial conditions. We find that changes in atmospheric CO2 concentrations alter the transport of atmospheric moisture across Central America, which modulates the freshwater budget of the North Atlantic and hence deep-water formation. In our simulations, a change in atmospheric CO2 levels of about 15 ppmv--comparable to variations during Dansgaard-Oeschger cycles containing Heinrich <span class="hlt">events</span>--is sufficient to cause transitions between a weak stadial and a strong interstadial circulation mode. Because changes in the Atlantic meridional overturning circulation are thought to alter atmospheric CO2 levels, we infer that atmospheric CO2 may serve as a negative feedback to transitions between strong and weak circulation modes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GeoRL..43.6538S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GeoRL..43.6538S"><span>Deep time evidence for climate sensitivity increase with <span class="hlt">warming</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shaffer, Gary; Huber, Matthew; Rondanelli, Roberto; Pepke Pedersen, Jens Olaf</p> <p>2016-06-01</p> <p>Future global <span class="hlt">warming</span> from anthropogenic greenhouse gas emissions will depend on climate feedbacks, the effect of which is expressed by climate sensitivity, the <span class="hlt">warming</span> for a doubling of atmospheric CO2 content. It is not clear how feedbacks, sensitivity, and temperature will evolve in our <span class="hlt">warming</span> world, but past <span class="hlt">warming</span> <span class="hlt">events</span> may provide insight. Here we employ paleoreconstructions and new climate-carbon model simulations in a novel framework to explore a wide scenario range for the Paleocene-Eocene Thermal Maximum (PETM) carbon release and global <span class="hlt">warming</span> <span class="hlt">event</span> 55.8 Ma ago, a possible future <span class="hlt">warming</span> analogue. We obtain constrained estimates of CO2 and climate sensitivity before and during the PETM and of the PETM carbon input amount and nature. Sensitivity increased from 3.3-5.6 to 3.7-6.5 K (Kelvin) into the PETM. When taken together with Last Glacial Maximum and modern estimates, this result indicates climate sensitivity increase with global <span class="hlt">warming</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20160013621&hterms=trees&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dtrees','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20160013621&hterms=trees&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dtrees"><span><span class="hlt">Abrupt</span> Increases in Amazonian Tree Mortality Due to Drought-Fire Interactions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Brando, Paulo Monteiro; Balch, Jennifer K.; Nepstad, Daniel C.; Morton, Douglas C.; Putz, Francis E.; Coe, Michael T.; Silverio, Divino; Macedo, Marcia N.; Davidson, Eric A.; Nobrega, Caroline C.; Alencar, Ane; Soares-Filho, Britaldo S.</p> <p>2014-01-01</p> <p>Interactions between climate and land-use change may drive widespread degradation of Amazonian forests. High-intensity fires associated with extreme weather <span class="hlt">events</span> could accelerate this degradation by <span class="hlt">abruptly</span> increasing tree mortality, but this process remains poorly understood. Here we present, to our knowledge, the first field-based evidence of a tipping point in Amazon forests due to altered fire regimes. Based on results of a large-scale, longterm experiment with annual and triennial burn regimes (B1yr and B3yr, respectively) in the Amazon, we found <span class="hlt">abrupt</span> increases in fire-induced tree mortality (226 and 462%) during a severe drought <span class="hlt">event</span>, when fuel loads and air temperatures were substantially higher and relative humidity was lower than long-term averages. This threshold mortality response had a cascading effect, causing sharp declines in canopy cover (23 and 31%) and aboveground live biomass (12 and 30%) and favoring widespread invasion by flammable grasses across the forest edge area (80 and 63%), where fires were most intense (e.g., 220 and 820 kW x m(exp -1)). During the droughts of 2007 and 2010, regional forest fires burned 12 and 5% of southeastern Amazon forests, respectively, compared with less than 1% in nondrought years. These results show that a few extreme drought <span class="hlt">events</span>, coupled with forest fragmentation and anthropogenic ignition sources, are already causing widespread fire-induced tree mortality and forest degradation across southeastern Amazon forests. Future projections of vegetation responses to climate change across drier portions of the Amazon require more than simulation of global climate forcing alone and must also include interactions of extreme weather <span class="hlt">events</span>, fire, and land-use change.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4035969','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4035969"><span><span class="hlt">Abrupt</span> increases in Amazonian tree mortality due to drought–fire interactions</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Brando, Paulo Monteiro; Balch, Jennifer K.; Nepstad, Daniel C.; Morton, Douglas C.; Putz, Francis E.; Coe, Michael T.; Silvério, Divino; Macedo, Marcia N.; Davidson, Eric A.; Nóbrega, Caroline C.; Alencar, Ane; Soares-Filho, Britaldo S.</p> <p>2014-01-01</p> <p>Interactions between climate and land-use change may drive widespread degradation of Amazonian forests. High-intensity fires associated with extreme weather <span class="hlt">events</span> could accelerate this degradation by <span class="hlt">abruptly</span> increasing tree mortality, but this process remains poorly understood. Here we present, to our knowledge, the first field-based evidence of a tipping point in Amazon forests due to altered fire regimes. Based on results of a large-scale, long-term experiment with annual and triennial burn regimes (B1yr and B3yr, respectively) in the Amazon, we found <span class="hlt">abrupt</span> increases in fire-induced tree mortality (226 and 462%) during a severe drought <span class="hlt">event</span>, when fuel loads and air temperatures were substantially higher and relative humidity was lower than long-term averages. This threshold mortality response had a cascading effect, causing sharp declines in canopy cover (23 and 31%) and aboveground live biomass (12 and 30%) and favoring widespread invasion by flammable grasses across the forest edge area (80 and 63%), where fires were most intense (e.g., 220 and 820 kW⋅m−1). During the droughts of 2007 and 2010, regional forest fires burned 12 and 5% of southeastern Amazon forests, respectively, compared with <1% in nondrought years. These results show that a few extreme drought <span class="hlt">events</span>, coupled with forest fragmentation and anthropogenic ignition sources, are already causing widespread fire-induced tree mortality and forest degradation across southeastern Amazon forests. Future projections of vegetation responses to climate change across drier portions of the Amazon require more than simulation of global climate forcing alone and must also include interactions of extreme weather <span class="hlt">events</span>, fire, and land-use change. PMID:24733937</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24733937','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24733937"><span><span class="hlt">Abrupt</span> increases in Amazonian tree mortality due to drought-fire interactions.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Brando, Paulo Monteiro; Balch, Jennifer K; Nepstad, Daniel C; Morton, Douglas C; Putz, Francis E; Coe, Michael T; Silvério, Divino; Macedo, Marcia N; Davidson, Eric A; Nóbrega, Caroline C; Alencar, Ane; Soares-Filho, Britaldo S</p> <p>2014-04-29</p> <p>Interactions between climate and land-use change may drive widespread degradation of Amazonian forests. High-intensity fires associated with extreme weather <span class="hlt">events</span> could accelerate this degradation by <span class="hlt">abruptly</span> increasing tree mortality, but this process remains poorly understood. Here we present, to our knowledge, the first field-based evidence of a tipping point in Amazon forests due to altered fire regimes. Based on results of a large-scale, long-term experiment with annual and triennial burn regimes (B1yr and B3yr, respectively) in the Amazon, we found <span class="hlt">abrupt</span> increases in fire-induced tree mortality (226 and 462%) during a severe drought <span class="hlt">event</span>, when fuel loads and air temperatures were substantially higher and relative humidity was lower than long-term averages. This threshold mortality response had a cascading effect, causing sharp declines in canopy cover (23 and 31%) and aboveground live biomass (12 and 30%) and favoring widespread invasion by flammable grasses across the forest edge area (80 and 63%), where fires were most intense (e.g., 220 and 820 kW ⋅ m(-1)). During the droughts of 2007 and 2010, regional forest fires burned 12 and 5% of southeastern Amazon forests, respectively, compared with <1% in nondrought years. These results show that a few extreme drought <span class="hlt">events</span>, coupled with forest fragmentation and anthropogenic ignition sources, are already causing widespread fire-induced tree mortality and forest degradation across southeastern Amazon forests. Future projections of vegetation responses to climate change across drier portions of the Amazon require more than simulation of global climate forcing alone and must also include interactions of extreme weather <span class="hlt">events</span>, fire, and land-use change.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20160013621&hterms=TREE&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DTREE','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20160013621&hterms=TREE&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DTREE"><span><span class="hlt">Abrupt</span> Increases in Amazonian Tree Mortality Due to Drought-Fire Interactions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Brando, Paulo Monteiro; Balch, Jennifer K.; Nepstad, Daniel C.; Morton, Douglas C.; Putz, Francis E.; Coe, Michael T.; Silverio, Divino; Macedo, Marcia N.; Davidson, Eric A.; Nobrega, Caroline C.; <a style="text-decoration: none; " href="javascript:void(0); " onClick="displayelement('author_20160013621'); toggleEditAbsImage('author_20160013621_show'); toggleEditAbsImage('author_20160013621_hide'); "> <img style="display:inline; width:12px; height:12px; " src="images/arrow-up.gif" width="12" height="12" border="0" alt="hide" id="author_20160013621_show"> <img style="width:12px; height:12px; display:none; " src="images/arrow-down.gif" width="12" height="12" border="0" alt="hide" id="author_20160013621_hide"></p> <p>2014-01-01</p> <p>Interactions between climate and land-use change may drive widespread degradation of Amazonian forests. High-intensity fires associated with extreme weather <span class="hlt">events</span> could accelerate this degradation by <span class="hlt">abruptly</span> increasing tree mortality, but this process remains poorly understood. Here we present, to our knowledge, the first field-based evidence of a tipping point in Amazon forests due to altered fire regimes. Based on results of a large-scale, longterm experiment with annual and triennial burn regimes (B1yr and B3yr, respectively) in the Amazon, we found <span class="hlt">abrupt</span> increases in fire-induced tree mortality (226 and 462%) during a severe drought <span class="hlt">event</span>, when fuel loads and air temperatures were substantially higher and relative humidity was lower than long-term averages. This threshold mortality response had a cascading effect, causing sharp declines in canopy cover (23 and 31%) and aboveground live biomass (12 and 30%) and favoring widespread invasion by flammable grasses across the forest edge area (80 and 63%), where fires were most intense (e.g., 220 and 820 kW x m(exp -1)). During the droughts of 2007 and 2010, regional forest fires burned 12 and 5% of southeastern Amazon forests, respectively, compared with less than 1% in nondrought years. These results show that a few extreme drought <span class="hlt">events</span>, coupled with forest fragmentation and anthropogenic ignition sources, are already causing widespread fire-induced tree mortality and forest degradation across southeastern Amazon forests. Future projections of vegetation responses to climate change across drier portions of the Amazon require more than simulation of global climate forcing alone and must also include interactions of extreme weather <span class="hlt">events</span>, fire, and land-use change.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2981942','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2981942"><span>Forecasting phenology under global <span class="hlt">warming</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Ibáñez, Inés; Primack, Richard B.; Miller-Rushing, Abraham J.; Ellwood, Elizabeth; Higuchi, Hiroyoshi; Lee, Sang Don; Kobori, Hiromi; Silander, John A.</p> <p>2010-01-01</p> <p>As a consequence of <span class="hlt">warming</span> temperatures around the world, spring and autumn phenologies have been shifting, with corresponding changes in the length of the growing season. Our understanding of the spatial and interspecific variation of these changes, however, is limited. Not all species are responding similarly, and there is significant spatial variation in responses even within species. This spatial and interspecific variation complicates efforts to predict phenological responses to ongoing climate change, but must be incorporated in order to build reliable forecasts. Here, we use a long-term dataset (1953–2005) of plant phenological <span class="hlt">events</span> in spring (flowering and leaf out) and autumn (leaf colouring and leaf fall) throughout Japan and South Korea to build forecasts that account for these sources of variability. Specifically, we used hierarchical models to incorporate the spatial variability in phenological responses to temperature to then forecast species' overall and site-specific responses to global <span class="hlt">warming</span>. We found that for most species, spring phenology is advancing and autumn phenology is getting later, with the timing of <span class="hlt">events</span> changing more quickly in autumn compared with the spring. Temporal trends and phenological responses to temperature in East Asia contrasted with results from comparable studies in Europe, where spring <span class="hlt">events</span> are changing more rapidly than are autumn <span class="hlt">events</span>. Our results emphasize the need to study multiple species at many sites to understand and forecast regional changes in phenology. PMID:20819816</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20030013632','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20030013632"><span>Recommended Experimental Procedures for Evaluation of <span class="hlt">Abrupt</span> Wing Stall Characteristics</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Capone, F. J.; Hall, R. M.; Owens, D. B.; Lamar, J. E.; McMillin, S. N.</p> <p>2003-01-01</p> <p>This paper presents a review of the experimental program under the <span class="hlt">Abrupt</span> Wing Stall (AWS) Program. Candidate figures of merit from conventional static tunnel tests are summarized and correlated with data obtained in unique free-to-roll tests. Where possible, free-to-roll results are also correlated with flight data. Based on extensive studies of static experimental figures of merit in the <span class="hlt">Abrupt</span> Wing Stall Program for four different aircraft configurations, no one specific figure of merit consistently flagged a warning of potential lateral activity when actual activity was seen to occur in the free-to-roll experiments. However, these studies pointed out the importance of measuring and recording the root mean square signals of the force balance.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/871562','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/871562"><span>Ultra-wideband horn antenna with <span class="hlt">abrupt</span> radiator</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>McEwan, Thomas E.</p> <p>1998-01-01</p> <p>An ultra-wideband horn antenna transmits and receives impulse waveforms for short-range radars and impulse time-of flight systems. The antenna reduces or eliminates various sources of close-in radar clutter, including pulse dispersion and ringing, sidelobe clutter, and feedline coupling into the antenna. Dispersion is minimized with an <span class="hlt">abrupt</span> launch point radiator element; sidelobe and feedline coupling are minimized by recessing the radiator into a metallic horn. Low frequency cut-off associated with a horn is extended by configuring the radiator drive impedance to approach a short circuit at low frequencies. A tapered feed plate connects at one end to a feedline, and at the other end to a launcher plate which is mounted to an inside wall of the horn. The launcher plate and feed plate join at an <span class="hlt">abrupt</span> edge which forms the single launch point of the antenna.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_22 --> <div id="page_23" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="441"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1986Geo....14..943C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1986Geo....14..943C"><span><span class="hlt">Abrupt</span> terminal Ordovician extinction in phytoplankton associations, southern Appalachians</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Colbath, G. Kent</p> <p>1986-11-01</p> <p>Study of organic-walled phytoplankton (prasinophytes and “acritarchs”) from samples spanning the Ordovician/Silurian boundary in the southern Appalachians reveals an <span class="hlt">abrupt</span> change in the composition of phytoplankton associations at the boundary, coincident with the extinction of several Ordovician species. The actual duration of the extinction is poorly constrained by available biostratigraphic evidence, but it apparently took place within the duration of one stage. Evidence from other regions suggests that the extinction was widespread and may have been worldwide. Within limits of resolution, the <span class="hlt">abrupt</span> extinction among the phytoplankton was coincident with the extinction of benthic communities. Hypotheses calling upon species-area effects, evolutionary changes in the terrestrial flora, or gradual climatic deterioration to explain the terminal Ordovician extinction are not supported by evidence from the phytoplankton. A bolide impact model cannot be excluded with available evidence, nor can models calling upon threshold effects associated with changing climate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/644405','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/biblio/644405"><span>Ultra-wideband horn antenna with <span class="hlt">abrupt</span> radiator</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>McEwan, T.E.</p> <p>1998-05-19</p> <p>An ultra-wideband horn antenna transmits and receives impulse waveforms for short-range radars and impulse time-of flight systems. The antenna reduces or eliminates various sources of close-in radar clutter, including pulse dispersion and ringing, sidelobe clutter, and feedline coupling into the antenna. Dispersion is minimized with an <span class="hlt">abrupt</span> launch point radiator element; sidelobe and feedline coupling are minimized by recessing the radiator into a metallic horn. Low frequency cut-off associated with a horn is extended by configuring the radiator drive impedance to approach a short circuit at low frequencies. A tapered feed plate connects at one end to a feedline, and at the other end to a launcher plate which is mounted to an inside wall of the horn. The launcher plate and feed plate join at an <span class="hlt">abrupt</span> edge which forms the single launch point of the antenna. 8 figs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17637210','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17637210"><span>Hallucinations after <span class="hlt">abrupt</span> withdrawal of oral and intrathecal baclofen.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>D'Aleo, Giangaetano; Cammaroto, Simona; Rifici, Carmela; Marra, Giuseppe; Sessa, Edoardo; Bramanti, Placido; Di Bella, Paolo</p> <p>2007-01-01</p> <p>Since 1977 several cases of hallucinations after <span class="hlt">abrupt</span> withdrawal of oral baclofen have been described. There are no reports of hallucinations after gradual withdrawal of oral baclofen. No one has ever described visual hallucinations after <span class="hlt">abrupt</span> interruption of intrathecal baclofen therapy. We describe five personally observed cases of visual hallucinations occurring after sudden interruption of baclofen (in two of these cases, intrathecal baclofen) therapy. The patients were immediately submitted to routine EEG, visual evoked potentials and standard brain magnetic resonance imaging (MRI). A few days later they also underwent polysomnography, fundus oculi examination and brain MRI of the temporal lobe. All these examinations were normal. We hypothesise that these symptoms could be due to biochemical and molecular changes, chiefly in glutamatergic n-methyl-d-aspartate, GABA-A, and GABA-B receptor response, leading to increased excitability and spontaneous activity as a result of chronic use of baclofen.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27152990','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27152990"><span>Extreme <span class="hlt">warm</span> temperatures alter forest phenology and productivity in Europe.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Crabbe, Richard A; Dash, Jadu; Rodriguez-Galiano, Victor F; Janous, Dalibor; Pavelka, Marian; Marek, Michal V</p> <p>2016-09-01</p> <p>Recent climate <span class="hlt">warming</span> has shifted the timing of spring and autumn vegetation phenological <span class="hlt">events</span> in the temperate and boreal forest ecosystems of Europe. In many areas spring phenological <span class="hlt">events</span> start earlier and autumn <span class="hlt">events</span> switch between earlier and later onset. Consequently, the length of growing season in mid and high latitudes of European forest is extended. However, the lagged effects (i.e. the impact of a <span class="hlt">warm</span> spring or autumn on the subsequent phenological <span class="hlt">events</span>) on vegetation phenology and productivity are less explored. In this study, we have (1) characterised extreme <span class="hlt">warm</span> spring and extreme <span class="hlt">warm</span> autumn <span class="hlt">events</span> in Europe during 2003-2011, and (2) investigated if direct impact on forest phenology and productivity due to a specific <span class="hlt">warm</span> <span class="hlt">event</span> translated to a lagged effect in subsequent phenological <span class="hlt">events</span>. We found that warmer <span class="hlt">events</span> in spring occurred extensively in high latitude Europe producing a significant earlier onset of greening (OG) in broadleaf deciduous forest (BLDF) and mixed forest (MF). However, this earlier OG did not show any significant lagged effects on autumnal senescence. Needleleaf evergreen forest (NLEF), BLDF and MF showed a significantly delayed end of senescence (EOS) as a result of extreme <span class="hlt">warm</span> autumn <span class="hlt">events</span>; and in the following year's spring phenological <span class="hlt">events</span>, OG started significantly earlier. Extreme <span class="hlt">warm</span> spring <span class="hlt">events</span> directly led to significant (p=0.0189) increases in the productivity of BLDF. In order to have a complete understanding of ecosystems response to <span class="hlt">warm</span> temperature during key phenological <span class="hlt">events</span>, particularly autumn <span class="hlt">events</span>, the lagged effect on the next growing season should be considered. Copyright © 2016 Elsevier B.V. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/966057','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/966057"><span>Hydrological consequences of global <span class="hlt">warming</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Miller, Norman L.</p> <p>2009-06-01</p> <p>The 2007 Intergovernmental Panel for Climate Change indicates there is strong evidence that the atmospheric concentration of carbon dioxide far exceeds the natural range over the last 650,000 years, and this recent <span class="hlt">warming</span> of the climate system is unequivocal, resulting in more frequent extreme precipitation <span class="hlt">events</span>, earlier snowmelt runoff, increased winter flood likelihoods, increased and widespread melting of snow and ice, longer and more widespread droughts, and rising sea level. The effects of recent <span class="hlt">warming</span> has been well documented and climate model projections indicate a range of hydrological impacts with likely to very likely probabilities (67 to 99 percent) of occurring with significant to severe consequences in response t