Vegetation history and palaeoclimate of the last glacial period at Lago Grande di Monticchio, Southern Italy

NASA Astrophysics Data System (ADS)

Watts, W. A.; Allen, J. R. M.; Huntley, B.

A high-resolution palynological study of a 51 m core from Lago Grande di Monticchio, southern Italy, has provided a palaeonvironmental record for the last glacill. A annual lamination based chronology, supported by radiometric and tephrochronological dates, provides an absolute timescale for this record that spans 76,300 years. Correlations are established between the pollen stratigraphy, the GRIP ice core δ18O record and foraminiferal assemblages from Atlantic core V23-81. Both Dansgaard-Oeschger and Heinrich events are reflected by changes in the pollen stratigraphy. Revised dates are estimated for Heinrich events H1-H6. A quantitative palaeoclimate reconstruction based upon the pollen data provides evidence of the climate changes in southern Italy associated with these and other fluctuations during the last glacial.

Interpreting the power spectrum of Dansgaard-Oeschger events via stochastic dynamical systems

NASA Astrophysics Data System (ADS)

Mitsui, Takahito; Lenoir, Guillaume; Crucifix, Michel

2017-04-01

Dansgaard-Oeschger (DO) events are abrupt climate shifts, which are particularly pronounced in the North Atlantic region during glacial periods [Dansgaard et al. 1993]. The signals are most clearly found in δ 18O or log [Ca2+] records of Greenland ice cores. The power spectrum S(f) of DO events has attracted attention over two decades with debates on the apparent 1.5-kyr periodicity [Grootes & Stuiver 1997; Schultz et al. 2002; Ditlevsen et al. 2007] and scaling property over several time scales [Schmitt, Lovejoy, & Schertzer 1995; Rypdal & Rypdal 2016]. The scaling property is written most simply as S(f)˜ f-β , β ≈ 1.4. However, physical as well as underlying dynamics of the periodicity and the scaling property are still not clear. Pioneering works for modelling the spectrum of DO events are done by Cessi (1994) and Ditlevsen (1999), but their model-data comparisons of the spectra are rather qualitative. Here, we show that simple stochastic dynamical systems can generate power spectra statistically consistent with the observed spectra over a wide range of frequency from orbital to the Nyquist frequency (=1/40 yr-1). We characterize the scaling property of the spectrum by defining a local scaling exponentβ _loc. For the NGRIP log [Ca2+] record, the local scaling exponent β _loc increases from ˜ 1 to ˜ 2 as the frequency increases from ˜ 1/5000 yr-1 to ˜ 1/500 yr-1, and β _loc decreases toward zero as the frequency increases from ˜ 1/500 yr-1 to the Nyquist frequency. For the δ 18O record, the local scaling exponent β _loc increases from ˜ 1 to ˜ 1.5 as the frequency increases from ˜ 1/5000 yr^{-1 to ˜ 1/1000 yr-1, and β _loc decreases toward zero as the frequency increases from ˜ 1/1000 yr-1 to the Nyquist frequency. This systematic breaking of a single scaling is reproduced by the simple stochastic models. Especially, the models suggest that the flattening of the spectra starting from multi-centennial scale and ending at the Nyquist frequency results from both non-dynamical (or non-system) noise and 20-yr binning of the ice core records. The modelling part of this research is partially based on the following work: Takahito Mitsui and Michel Crucifix, Influence of external forcings on abrupt millennial-scale climate changes: a statistical modelling study, Climate Dynamics (first online). doi:10.1007/s00382-016-3235-z

Temperature and seawater isotopic controls on two stalagmite records since 83 ka from maritime Japan

NASA Astrophysics Data System (ADS)

Mori, Taiki; Kashiwagi, Kenji; Amekawa, Shota; Kato, Hirokazu; Okumura, Tomoyo; Takashima, Chiduru; Wu, Chung-Che; Shen, Chuan-Chou; Quade, Jay; Kano, Akihiro

2018-07-01

Millennial-scale interstadial Dansgaard-Oeschger (D-O) cycles and Heinrich (H) stadial events are pronounced paleoclimatic features during the last glacial period, which were first demonstrated in the North Atlantic region. These stadial and interstadial events are expressed in marine and terrestrial high-resolution records elsewhere in the world, but the magnitude and mode of the regional climate changes are still poorly quantified. Here we present new replicated stalagmite δ18O profiles from two caves in central Japan, which extend back to 83.4 ka. The records clearly display the H7 to H3 events, but not D-O cycles. An important feature of the two Japanese stalagmites is the small difference (∼2.9‰) in δ18O values between the mid-Holocene and the Last Glacial Maximum (LGM). Long-term trends of the stalagmite δ18O values at the more maritime site generally follow that of the δ18O record of seawater, which is responsible for ∼1.1‰ of the ∼2.9‰ difference between mid-Holocene and LGM. The remaining 1.8‰ in the difference can be accounted for by +9 °C of warming between the LGM and mid-Holocene and -3 °C cooling at H events, which are comparable with the previous estimates of land paleo-temperature in the Japanese Islands. The attenuated isotopic signal associated with D-O interstadials indicates that the warming in the Atlantic did not significantly transfer to the maritime Japan. These unique features of the isotopic records of the Japanese stalagmites are due to the geographic position at the vicinity of the moisture source, Kuroshio warm current.

Evidence of Methane Outgassing During MIS3 in the Bering Sea

NASA Astrophysics Data System (ADS)

Cook, M. S.; Keigwin, L. D.

2005-12-01

There are multiple negative excursions in planktonic and benthic foraminifer δ13C in a core from 1467m in the southeast Bering Sea. These excursions occur episodically during the last glacial period, and may coincide with Dansgaard-Oeschger (D-O) events. Measured foraminifer δ13C during the excursions is as low as -14‰ and are probably the result of overgrowths of diagenetic calcium carbonate. We estimate overgrowth δ13C is -23‰, and hypothesize that the occurrence of overgrowths is associated with anaerobic oxidation of biogenic methane. The likely pressure and temperature conditions at this site and during the last glacial period were well within the zone of methane-hydrate stability, so the source of methane is probably not from destabilization of methane hydrate at this depth. The methane may have originated from increased in-situ methanogenesis resulting from greater burial of organic carbon, or from destabilization of methane hydrate at shallower sites near the methane-hydrate stability threshold. Both these scenarios could be active, consistent with the ``Clathrate Gun Hypothesis'' (Kennett et al., 2003), in which there is widespread destabilization of marine methane hydrates during D-O events, where methane gas both is oxidized within the water column and escapes to the atmosphere.

Millennial-scale variability in vegetation records from the East Asian Islands: Taiwan, Japan and Sakhalin

NASA Astrophysics Data System (ADS)

Takahara, Hikaru; Igarashi, Yaeko; Hayashi, Ryoma; Kumon, Fujio; Liew, Ping-Mei; Yamamoto, Masanobu; Kawai, Sayuri; Oba, Tadamichi; Irino, Tomohisa

2010-10-01

High-resolution pollen records from Taiwan, Japan and Sakhalin document regional vegetation changes during Dansgaard-Oeschger (D-O) cycles during the last glacial. During the period from the cold phase (GS 18/19) to warm phase (D-O 19), the biome shift from temperate conifer forest to cold/cool conifer forest in Japan and from subtropical forest to temperate deciduous/conifer forest in Taiwan. The vegetation in D-O 17, cool mixed forest in central Japan, temperate deciduous broadleaf forest in western Japan and subtropical forest in Taiwan, indicates warm condition but not wet in all area. These vegetation changes lead to biome shift from MIS (Marine Isotope Stage) 4 to MIS 3. The abundance of Cryptomeria japonica and Fagus crenata in D-O 12 and D-O 8 indicates wet conditions brought by the strong summer monsoon through the Islands and high snowfall brought by the inflow of the Tsushima Warm Current into the Sea of Japan. The registration of other D-O warming events in MIS 3, although reflected by shifts in the abundance of key species, is not sufficient to produce changes in biomes. Development of cold deciduous forest in HS (Heinrich events) 1 in Sakhalin, Hokkaido and central Japan was conspicuous and was much larger than that in YD. Vegetation response in YD was small scale and within the same biome in the East Asian Islands. In D-O 1 at the termination of the last glacial, the same taxa that developed in the early Holocene, cold evergreen needleleaf trees in northern region, temperate deciduous broadleaf trees in central and western Japan, and warm-temperate evergreen trees in Taiwan, increased.

Rapid subtropical North Atlantic salinity oscillations across Dansgaard-Oeschger cycles.

PubMed

Schmidt, Matthew W; Vautravers, Maryline J; Spero, Howard J

2006-10-05

Geochemical and sedimentological evidence suggest that the rapid climate warming oscillations of the last ice age, the Dansgaard-Oeschger cycles, were coupled to fluctuations in North Atlantic meridional overturning circulation through its regulation of poleward heat flux. The balance between cold meltwater from the north and warm, salty subtropical gyre waters from the south influenced the strength and location of North Atlantic overturning circulation during this period of highly variable climate. Here we investigate how rapid reorganizations of the ocean-atmosphere system across these cycles are linked to salinity changes in the subtropical North Atlantic gyre. We combine Mg/Ca palaeothermometry and oxygen isotope ratio measurements on planktonic foraminifera across four Dansgaard-Oeschger cycles (spanning 45.9-59.2 kyr ago) to generate a seawater salinity proxy record from a subtropical gyre deep-sea sediment core. We show that North Atlantic gyre surface salinities oscillated rapidly between saltier stadial conditions and fresher interstadials, covarying with inferred shifts in the Tropical Atlantic hydrologic cycle and North Atlantic overturning circulation. These salinity oscillations suggest a reduction in precipitation into the North Atlantic and/or reduced export of deep salty thermohaline waters during stadials. We hypothesize that increased stadial salinities preconditioned the North Atlantic Ocean for a rapid return to deep overturning circulation and high-latitude warming by contributing to increased North Atlantic surface-water density on interstadial transitions.

Variations in productivity and eolian fluxes in the northeastern Arabian Sea during the past 110 ka

NASA Astrophysics Data System (ADS)

Pourmand, Ali; Marcantonio, Franco; Schulz, Hartmut

2004-04-01

High-resolution (one to two samples/ka) radionuclide proxy records from core 93KL in the northeastern Arabian Sea provide evidence for millennial climate variability over the past 110 ka. We interpret 230Th-normalized 232Th fluxes as a proxy for eolian input, and authigenic uranium concentrations as a proxy for past productivity. We attribute orbital and suborbital variations in both proxies to changes in the intensity of the southwest Indian Ocean monsoon. The highest 230Th-normalized 232Th fluxes occur at times that are consistent with the timing of the Younger Dryas, Heinrich events 1-7 and cold Dansgaard-Oeschger stadial events recorded in the GISP2 ice core. Such high dust fluxes may be due to a weakened southwest monsoon in conjunction with strengthened northwesterlies from the Arabian Peninsula and Mesopotamia. Authigenic uranium concentrations, on the other hand, are highest during warm Dansgaard-Oeschger interstadials when the southwest monsoon is intensified relative to the northwesterly winds. Our results also indicate that on orbital timescales maximum average eolian fluxes coincide with the timing of marine isotopic stage (MIS) 2 and 4, while minimum fluxes occur during MIS 1, 3 and 5. Although the forcing mechanism(s) controlling suborbital variabilities in monsoonal intensity is still debated, our findings suggest an atmospheric teleconnection between the low-latitude southwest monsoon and North Atlantic climate.

Millennial-scale precipitation variability over Easter Island (South Pacific) during MIS 3: inter-hemispheric teleconnections with North Atlantic abrupt cold events

NASA Astrophysics Data System (ADS)

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.

2015-04-01

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 abrupt cooling events in the North Atlantic known as Heinrich events. Although both the timing and dynamics of these events 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 events of enhanced precipitation between 38 and 65 kyr BP. These events 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 events and consistent with a reorganization of Southern Pacific atmospheric and oceanic circulation also at higher latitudes during Heinrich and Dansgaard-Oeschger stadials.

Ice sheet runoff and Dansgaard-Oeschger Cycles

NASA Astrophysics Data System (ADS)

Hewitt, Ian; Wolff, Eric; Fowler, Andrew; Clark, Chris; Evatt, Geoff; Johnson, Helen; Munday, David; Rickaby, Ros; Stokes, Chris

2016-04-01

Many northern hemisphere climate records, particularly those from around the North Atlantic, show a series of rapid climate changes that recurred on centennial to millennial timescales throughout most of the last glacial period. These Dansgaard-Oeschger (D-O) sequences are observed most prominently in Greenland ice cores, although they have a global signature, including an out of phase Antarctic signal. They consist of warming jumps of order 10°C, occurring in typically 40 years, followed generally by a slow cooling (Greenland Interstadial, GI) lasting between a few centuries and a few millennia, and then a final rapid temperature drop into a cold Greenland Stadial (GS) that lasts for a similar period. Most explanations for D-O events call on changes in Atlantic meridional overturning circulation strength, and the majority of such explanations use changes in freshwater delivery from ice sheets as a trigger. Many have relied on large inputs of freshwater from singular events (such as lake outbursts or iceberg armadas) to push the AMOC into its cold state. However the evidence for such events at the right time in each cycle is sparse. Here we investigate mechanisms that would arise from a change in the rate of ice sheet runoff, which would be a natural feedback from each rapid warming or cooling event. Recent work has suggested that AMOC is most easily disrupted by freshwater delivered through the Arctic. We investigate whether the proposed AMOC changes could have occurred as part of a natural oscillation, in which runoff from the Laurentide ice sheet into the Arctic is controlled by temperature around the North Atlantic. The Arctic buffers the salinity changes, but under warm conditions, high runoff eventually leads to water entering the North Atlantic with low enough salinity to switch AMOC into its weaker state. Under the colder conditions now prevailing, the Arctic is starved of runoff, and the salinity rises until a further switch occurs. Contrary to many previous studies, this mechanism does not require large freshwater pulses to the North Atlantic. Instead, steady changes in ice-sheet runoff, driven by the AMOC, lead to a naturally arising oscillator, in which the rapid warmings come about because the Arctic Ocean is starved of freshwater. The changing size of the ice sheets would have affected the magnitude and extent of runoff, and we suggest that this could provide a simple explanation for the absence of the events during interglacials and around the time of glacial maxima. We construct a simple model to investigate whether the timescales and magnitudes would in practice make this a viable mechanism, and we consider other roles that runoff could play. Heinrich events, delivering additional freshwater into the Atlantic during a Greenland stadial, play no direct role in this mechanism, but would serve to delay the switch to faster AMOC.

Southern Ocean Control of Glacial AMOC Stability and Dansgaard-Oeschger Interstadial Duration

NASA Astrophysics Data System (ADS)

Buizert, C.; Schmittner, A.

2016-12-01

Glacial periods exhibit abrupt Dansgaard-Oeschger (DO) climatic oscillations that are thought to be linked to instabilities in the Atlantic meridional overturning circulation (AMOC). Great uncertainty remains regarding the dynamics of the DO cycle, as well as controls on the timing and duration of individual events. Using ice core data we show that the duration of warm (interstadial) periods is strongly correlated with Antarctic climate, and presumably with Southern Ocean (SO) temperature and the position of the Southern Hemisphere (SH) westerlies. We propose a SO control on AMOC stability and interstadial duration via the rate of Antarctic bottom water formation, meridional density/pressure gradients, Agulhas Leakage, and SO adiabatic upwelling. This hypothesis is supported by climate model experiments that demonstrate SO warming leads to a stronger AMOC that is less susceptible to freshwater perturbations. In the AMOC stability diagram, SO warming and strengthening of the SH westerlies both shift the vigorous AMOC branch toward higher freshwater values, thus raising the threshold for AMOC collapse. The proposed mechanism could provide a consistent explanation for several diverse observations, including maximum DO activity during intermediate ice volume/SH temperature, and successively shorter DO durations within each Bond cycle. It may further have implications for the fate of the AMOC under future global warming.

Glacial Isostatic Adjustment Derived Boundary Conditions for Paleoclimate Simulation: the Refined ICE-6G_D (VM5a) Model and the Dansgaard-Oeschger Oscillation

NASA Astrophysics Data System (ADS)

Peltier, W. R.; Vettoretti, G.; Argus, D. F.

2017-12-01

Global models of the glacial isostatic adjustment (GIA) process are designed to fit a wide range of geophysical and geomorphological observations that simultaneously constrain the internal viscoelastic structure of Earths interior and the history of grounded ice thickness variations that has occurred over the most recent ice-age cycle of the Late Quaternary interval of time. The most recent refinement of the ICE-NG (VMX) series of such global models from the University of Toronto, ICE-6G_C (VM5a), has recently been slightly modified insofar as its Antarctic component is concerned to produce a "_D" version of the structure. This has been chosen to provide the boundary conditions for the next round of model-data inter-comparisons in the context of the international Paleoclimate Modeling Inter-comparison Project (PMIP). The output of PMIP will contribute to the Sixth Assessment Report (AR6) of the Intergovernmental Panel on Climate Change which is now under way. A highly significant test of the utility of this latest model has recently been performed that is focused upon the Dansgaard-Oeschger oscillation that was the primary source of climate variability during Marine Isotope Stage 3 (MIS3) of the most recent glacial cycle. By introducing the surface boundary conditions for paleotopography and paleobathymetry, land-sea mask and surface albedo into the NCAR CESM1 coupled climate model configured at full one degree by one degree CMIP5 resolution, together with the appropriate trace gas and orbital insolation forcing, we show that the millennium timescale Dansgard-Oeschger oscillation naturally develops following spin- up of the model into the glacial state.

Investigating the Influence of Climate Changes on Rodent Communities at a Regional-Scale (MIS 1-3, Southwestern France)

PubMed Central

Royer, Aurélien; Montuire, Sophie; Legendre, Serge; Discamps, Emmanuel; Jeannet, Marcel; Lécuyer, Christophe

2016-01-01

Terrestrial ecosystems have continuously evolved throughout the Late Pleistocene and the Holocene, deeply affected by both progressive environmental and climatic modifications, as well as by abrupt and large climatic changes such as the Heinrich or Dansgaard-Oeschger events. Yet, the impacts of these different events on terrestrial mammalian communities are poorly known, as is the role played by potential refugia on geographical species distributions. This study examines community changes in rodents of southwestern France between 50 and 10 ky BP by integrating 94 dated faunal assemblages coming from 37 archaeological sites. This work reveals that faunal distributions were modified in response to abrupt and brief climatic events, such as Heinrich events, without actually modifying the rodent community on a regional scale. However, the succession of events which operated between the Late Pleistocene and the Holocene gradually led to establishing a new rodent community at the regional scale, with intermediate communities occurring between the Bølling and the Allerød. PMID:26789523

Decadal-scale progression of Dansgaard-Oeschger warming events - Are warmings at the end of Heinrich-Stadials different from others?

NASA Astrophysics Data System (ADS)

Erhardt, T.; Capron, E.; Rasmussen, S.; Schuepbach, S.; Bigler, M.; Fischer, H.

2017-12-01

During the last glacial period proxy records throughout the Northern Hemisphere document a succession of rapid millennial-scale warming events, called Dansgaard Oeschger (DO) events. Marine proxy records from the Atlantic also reveal, that some of the warming events where preceded by large ice rafting events, referred to as Heinrich events. Different mechanisms have been proposed, that can produce DO-like warming in model experiments, however the progression and plausible trigger of the events and their possible interplay with the Heinrich events is still unknown. Because of their fast nature, the progression is challenging to reconstruct from paleoclimate data due to the temporal resolution achievable in many archives and cross-dating uncertainties between records. We use new high-resolution multi-proxy records of sea-salt and terrestrial aerosol concentrations over the period 10-60 ka from two Greenland deep ice cores in conjunction with local precipitation and temperature proxy records from one of the cores to investigate the progression of environmental changes at the onset of the individual warming events. The timing differences are then used to explore whether the DO warming events that terminate Heinrich-Stadials progressed differently in comparison to those after Non-Heinrich-Stadials. Our analysis indicates no difference in the progression of the warming terminating Heinrich-Stadials and Non-Heinrich-Stadials. Combining the evidence from all warming events in the period, our analysis shows a consistent lead of the changes in both local precipitation and terrestrial dust aerosol concentrations over the change in sea-salt aerosol concentrations and local temperature by approximately one decade. This implies that both the moisture transport to Greenland and the intensity of the Asian winter monsoon changed before the sea-ice cover in the North Atlantic was reduced, rendering a collapse of the sea-ice cover as a trigger for the DO events unlikely.

A stratigraphic framework for abrupt climatic changes during the Last Glacial period based on three synchronized Greenland ice-core records: refining and extending the INTIMATE event stratigraphy

NASA Astrophysics Data System (ADS)

Rasmussen, Sune O.; Bigler, Matthias; Blockley, Simon P.; Blunier, Thomas; Buchardt, Susanne L.; Clausen, Henrik B.; Cvijanovic, Ivana; Dahl-Jensen, Dorthe; Johnsen, Sigfus J.; Fischer, Hubertus; Gkinis, Vasileios; Guillevic, Myriam; Hoek, Wim Z.; Lowe, J. John; Pedro, Joel B.; Popp, Trevor; Seierstad, Inger K.; Steffensen, Jørgen Peder; Svensson, Anders M.; Vallelonga, Paul; Vinther, Bo M.; Walker, Mike J. C.; Wheatley, Joe J.; Winstrup, Mai

2014-12-01

Due to their outstanding resolution and well-constrained chronologies, Greenland ice-core records provide a master record of past climatic changes throughout the Last Interglacial-Glacial cycle in the North Atlantic region. As part of the INTIMATE (INTegration of Ice-core, MArine and TErrestrial records) project, protocols have been proposed to ensure consistent and robust correlation between different records of past climate. A key element of these protocols has been the formal definition and ordinal numbering of the sequence of Greenland Stadials (GS) and Greenland Interstadials (GI) within the most recent glacial period. The GS and GI periods are the Greenland expressions of the characteristic Dansgaard-Oeschger events that represent cold and warm phases of the North Atlantic region, respectively. We present here a more detailed and extended GS/GI template for the whole of the Last Glacial period. It is based on a synchronization of the NGRIP, GRIP, and GISP2 ice-core records that allows the parallel analysis of all three records on a common time scale. The boundaries of the GS and GI periods are defined based on a combination of stable-oxygen isotope ratios of the ice (δ18O, reflecting mainly local temperature) and calcium ion concentrations (reflecting mainly atmospheric dust loading) measured in the ice. The data not only resolve the well-known sequence of Dansgaard-Oeschger events that were first defined and numbered in the ice-core records more than two decades ago, but also better resolve a number of short-lived climatic oscillations, some defined here for the first time. Using this revised scheme, we propose a consistent approach for discriminating and naming all the significant abrupt climatic events of the Last Glacial period that are represented in the Greenland ice records. The final product constitutes an extended and better resolved Greenland stratotype sequence, against which other proxy records can be compared and correlated. It also provides a more secure basis for investigating the dynamics and fundamental causes of these climatic perturbations.

Periodic fluctuations in deep water formation due to sea ice

NASA Astrophysics Data System (ADS)

Saha, R.

2012-12-01

During the last ice age, several abrupt warming events took place, known as Dansgaard-Oeschger (D-O) events. Their effects were felt globally, although the North Atlantic experienced the largest temperature increase. The leading hypothesis to explain their occurrence postulates that the warming was caused by abrupt disruptions of the North Atlantic Current due to meltwater discharge from destabilized ice sheets (Heinrich events). However, the number of warming events outnumber the those of ice-sheet collapse. Thus, the majority of D-O events are not attributed to surface freshwater anomalies, and the underlying mechanism behind their occurrence remain unexplained. Using a simple dynamical model of sea ice and an overturning circulation, I show the existence of self-sustained relaxation oscillations in the overturning circulation. The insulating effect of sea ice is shown to paradoxically lead to a net loss of heat from the top layer of the polar ocean when sea ice retreats. Repeated heat loss results in a denser top layer and a destabilized water column, which triggers convection. The convective state pulls the system out of its preferred mode of circulation, setting up relaxation oscillations. The period of oscillations in this case is linked to the geometry of the ocean basin, if solar forcing is assumed to remain constant. If appropriate glacial freshwater forcing is applied to the model, a pattern of oscillation is produced that bears remarkable similarity to the observed fluctuations in North Atlantic climate between 50,000 and 30,000 years before present.; Comparison of NGRIP δ 18-O (proxy for near surface air temperature) between 50,000 and 30,000 years before present, showing Bond cycles (left) with the model output when forced with appropriate glacial freshwater forcing (right).

Vegetation and climate variability in tropical and subtropical South America during the late Quaternary

NASA Astrophysics Data System (ADS)

Behling, H.

2013-05-01

Detailed palynological studies from different ecosystems in tropical and subtropical South America reflect interesting vegetation and climate dynamics, in particular during glacial and late glacial times. Records from ecosystems such as the Amazon rainforest, savanna, Caatinga, Atlantic rainforest, Araucaria forest and grasslands provide interesting insight of past climate variability. The influence of events such as Dansgaard-Oeschger, Heinnrich stadials, changes in the thermohaline circulation (THC) will be discussed. In particular the Younger Dryas (YD) period shows at different places distinct vegetational changes, revealing unexpected past climatic conditions.

The INTIMATE event stratigraphy of the last glacial period

NASA Astrophysics Data System (ADS)

Olander Rasmussen, Sune; Svensson, Anders

2015-04-01

The North Atlantic INTIMATE (INtegration of Ice-core, MArine and TErrestrial records) group has previously recommended an Event Stratigraphy approach for the synchronisation of records of the Last Termination using the Greenland ice core records as the regional stratotypes. A key element of these protocols has been the formal definition of numbered Greenland Stadials (GS) and Greenland Interstadials (GI) within the past glacial period as the Greenland expressions of the characteristic Dansgaard-Oeschger events that represent cold and warm phases of the North Atlantic region, respectively. Using a recent synchronization of the NGRIP, GRIP, and GISP2 ice cores that allows the parallel analysis of all three records on a common time scale, we here present an extension of the GS/GI stratigraphic template to the entire glacial period. In addition to the well-known sequence of Dansgaard-Oeschger events that were first defined and numbered in the ice core records more than two decades ago, a number of short-lived climatic oscillations have been identified in the three synchronized records. Some of these events have been observed in other studies, but we here propose a consistent scheme for discriminating and naming all the significant climatic events of the last glacial period that are represented in the Greenland ice cores. In addition to presenting the updated event stratigraphy, we make a series of recommendations on how to refer to these periods in a way that promotes unambiguous comparison and correlation between different proxy records, providing a more secure basis for investigating the dynamics and fundamental causes of these climatic perturbations. The work presented is a part of a newly published paper in an INTIMATE special issue of Quaternary Science Reviews: Rasmussen et al., 'A stratigraphic framework for abrupt climatic changes during the Last Glacial period based on three synchronized Greenland ice-core records: refining and extending the INTIMATE event stratigraphy', Quaternary Science Reviews, vol. 106, p. 14-24, 2014.

Dansgaard Oeschger Dynamics: Clearly Revealed in a Comprehensive Model of Glacial Climate

NASA Astrophysics Data System (ADS)

Peltier, W. Richard; Vettoretti, Guido

2017-04-01

More than 30 years ago, Willi Dansgaard in Copenhagen and Hans Oeschger in Bern established the existence of millennium timescale oscillations in oxygen isotope stratigraphies from Greenland ice cores. This isotopic signal was interpreted as implying large amplitude variations in surface air temperature. Until the publication of Peltier and Vettoretti (2014, GRL) the prevalent view had been that this exclusively ice-age phenomenon, thought to be linked to variability in the strength of the Atlantic MOC, was considered to be forced by the episodic release of freshwater from the continental ice sheets, each oscillation requiring its own freshwater input. In Peltier and Vettoretti (2014) this phenomenon was recovered for the first time in a comprehensive model of glacial climate, specifically the CESM1 model of the NCAR laboratory. Attention was drawn to the fact that individual D-O oscillations, or Bond Cycle clusters of such oscillations, were inevitably preceded by individual Heinrich events. In Peltier and Vettoretti (2014) it was shown that, following the "spin-up" of CESM1 into the glacial state, with continental ice sheet volume held fixed, a sequence of nonlinear unforced and therefor "free" oscillations of the MOC occurred, following a sharp Heinrich event-like sharp suppression of MOC strength. All of the salient characteristics of the D-O process inferred on the basis of ice core evidence from both hemispheres were fully captured in these high (CMIP5) resolution simulations, namely: (i) the pulse shape of the individual oscillations characterized by an extremely rapid shift from cold stadial to warm interstadial conditions followed by a slow return to the stadial state, (ii) the peak-to-peak variations in Greenland surface air temperature of 10-15 degrees Centigrade during individual oscillations, (iii) the "bi-polar see saw" connection between this Northern Hemisphere process and that recorded in the EDML and WAIS Divide ice cores from Antarctica, (iv) the reduced amplitude of the oxygen isotopic swings in the Antarctic ice cores, by approximately a factor of 10, from those in Greenland cores. Because the coupled climate model fully captures the phenomenon, it has been possible to fully understand the dynamical mechanism involved. In Peltier and Vettoretti (2014) this was described as a "kicked" salt oscillator, in which individual D-O cycles involved an oscillatory out of phase relationship between the salinity of the North Atlantic sub-tropical gyre and the salinity of a North Atlantic halocline. As shown more recently by Vettoretti and Peltier (2016, GRL), transitions from cold stadial to warm interstadial conditions involve the opening of a massive "super polynya" north of the southern edge of the sea ice front which, under stadial conditions, extends as far south as the south coast of the Bay of Biscaye. This polynya is opened by the onset of a thermohaline convective instability of the water column beneath the sea ice, which is accompanied by a sharp re-invigoration of the intensity of the MOC, thereby initiating a sharp rise of air temperature over Greenland. Several further issues remain with this now fully articulated theory of the D-O process and these will be summarized.

Correlation of Late-Pleistocene Lake-Level Oscillations in Mono Lake, California, with North Atlantic Climate Events

NASA Astrophysics Data System (ADS)

Benson, Larry V.; Lund, Steve P.; Burdett, James W.; Kashgarian, Michaele; Rose, Timothy P.; Smoot, Joseph P.; Schwartz, Martha

1998-01-01

Oxygen-18 ( 18O) values of sediment from the Wilson Creek Formation, Mono Basin, California, indicate three scales of temporal variation (Dansgaard-Oeschger, Heinrich, and Milankovitch) in the hydrologic balance of Mono Lake between 35,400 and 12,900 14C yr B.P. During this interval, Mono Lake experienced four lowstands each lasting from 1000 to 2000 yr. The youngest lowstand, which occurred between 15,500 and 14,000 14C yr B.P., was nearly synchronous with a desiccation of Owens Lake, California. Paleomagnetic secular variation (PSV) data indicate that three of four persistent lowstands occurred at the same times as Heinrich events H1, H2, and H4. 18O data indicate the two highest lake levels occurred ˜18,000 and ˜13,100 14C yr B.P., corresponding to passages of the mean position of the polar jet stream over the Mono Basin. Extremely low values of total inorganic carbon between 26,000 and 14,000 14C yr B.P. indicate glacial activity, corresponding to a time when summer insolation was much reduced.

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 the state of atmospheric circulation in the Southern Hemisphere that will result as a consequence of greenhouse gas rise and "healing" of the Antarctic ozone hole (Mayewski et al., 2015). Climate change perspective gained from instrumentally calibrated ice core and other past climate proxies is essential to the construction of plausible scenarios for future climate and actionable planning. More ACC events are in our future and the early manifestation of these events is apparent in the emerging change in the severity and frequency of extreme events. Searching for a precursor for ACC events is a major challenge for the scientific community and humanity. For the climate community to undertake this challenge it is necessary to investigate both past and present sub-seasonal and longer extreme events associated with past D-O and ACC events and their impact on societies. Examples of sub-seasonal scale investigation of these events will be included in the presentation. Mayewski, P.A., Sneed, S.B., Birkel, S.D., Kurbatov, A.V. and Maasch, Holocene warming marked by longer summers and reduced storm frequency around Greenland, Journal of Quaternary Science, 267-8179. DOl: I 0.1002/jqs.2684, 2013. Mayewski, P.A., Bertler, N., Birkel, S., Bracegirdle, T., Carleton, A., England, M., Goodwin, I., Kang, J-H., Mayewski, P., Russell, J., Schneider, S., Turner, J. and Vellicogna, I., 2015, Potential for Southern Hemisphere climate surprises, Journal of Quaternary Science (Rapid Communication) 30, 391-395, DOI: 10.1002/jqs.2794.

Basin-wide Millennial Cycles in Arabian Sea Climate Over the Last Glacial

NASA Astrophysics Data System (ADS)

Pourmand, A.; Marcantonio, F.

2005-05-01

High-frequency Dansgaard-Oeschger (D-O) and Heinrich cycles first discovered in the records of North Atlantic ice and marine sediments have been found to extend beyond the North Atlantic There is ample evidence for these millennial cycles of climate variability in the sediments of the Arabian Sea. We employ uranium-series radionuclide proxies to determine changes in the fluxes of sedimentary components in two cores from the western (W) and northeastern (NE) Arabian Sea in order to investigate fluctuations of export production and wind strength on a large regional scale during the last glacial period. In the NE Arabian Sea off of the Pakistani margin, 230Th-derived detrital (eolian) fluxes are highest during periods consistent with the timing of North Atlantic D-O stadial and H 1-7 events. Authigenic uranium concentrations, which we interpret as a proxy for primary productivity, also show an increase during North Atlantic D-O interstadials. Preliminary results from W Arabian Sea sediments off of the Oman margin corroborate that these millennial cycles in productivity and eolian fluxes are indeed basin-wide events. Authigenic U concentrations in these sediments are, on average, about twice those measured in the NE Arabian Sea, suggesting, qualitatively, an enhancement of primary productivity in the western part of the basin. In contrast, fluxes of eolian material to the Oman margin are, on average, more than 10 times lower than those delivered to the Pakistani margin, even though the patterns of millennial variability are virtually identical. We associate enhanced export production and a decreased eolian input during relatively warmer D-O interstadials with an intensification of southwest monsoonal winds. Similarly, decreased export production is coincident with an increase in eolian fluxes during North Atlantic stadial and H events. These results provide strong evidence for a basin-wide atmospheric teleconnection between Arabian Sea and North Atlantic climate on sub-Milankovitch timescales.

Environmental magnetic record and paleosecular variation data for the last 40 kyrs from the Lake Biwa sediments, Central Japan

NASA Astrophysics Data System (ADS)

Hayashida, Akira; Ali, Mohammed; Kuniko, Yoshiki; Kitagawa, Hiroyuki; Torii, Masayuki; Takemura, Keiji

2007-07-01

We have conducted paleomagnetic and environmental magnetic analysis of a sediment piston core recovered from Lake Biwa, central Japan. Tephrochronology and AMS radiocarbon dating showed that this core covers the time period since about 40 kyr BP. The variation of paleomagnetic direction shows a good agreement with the PSV record for the last 10 kyrs from the deeper water site (BIWA SV-3; Ali et al., 1999), although the amplitudes are subdued probably due to the relatively lower accumulation rate at the shallower site. Inclination lows of the pre-Holocene interval are correlated to PSV records reported from the marine sediments off Shikoku and in the Japan Sea. In addition, the variation of magnetic mineral concentration reflects environmental changes during the last glacial period. It is suggested that the flux of fine-grained magnetite, probably associated with greater precipitation, was increased during interstadial periods. The variation of anhysteretic remanent magnetization is likely correlated to the Dansgaard-Oeschger (D-O) cycles recorded in Greenland ice cores. An apparent swing of the PSV curve is recognized at about 27 ka, but evidence for the Mono Lake excursion at 32 ka around the D-O events 6 and 7 is unclear. Combination of the detailed paleomagnetic record and the sub-Milankovitch climate cycles thus provides better resolution for understanding geomagnetic secular variation and polarity excursions in space and time.

Unstable AMOC during glacial intervals and millennial variability: The role of mean sea ice extent

NASA Astrophysics Data System (ADS)

Sévellec, Florian; Fedorov, Alexey V.

2015-11-01

A striking feature of paleoclimate records is the greater stability of the Holocene epoch relative to the preceding glacial interval, especially apparent in the North Atlantic region. In particular, strong irregular variability with an approximately 1500 yr period, known as the Dansgaard-Oeschger (D-O) events, punctuates the last glaciation, but is absent during the interglacial. Prevailing theories, modeling and data suggest that these events, seen as abrupt warming episodes in Greenland ice cores and sea surface temperature records in the North Atlantic, are linked to reorganizations of the Atlantic Meridional Overturning Circulation (AMOC). In this study, using a new low-order ocean model that reproduces a realistic power spectrum of millennial variability, we explore differences in the AMOC stability between glacial and interglacial intervals of the 100 kyr glacial cycle of the Late Pleistocene (1 kyr = 1000 yr). Previous modeling studies show that the edge of sea ice in the North Atlantic shifts southward during glacial intervals, moving the region of the North Atlantic Deep Water formation and the AMOC also southward. Here we demonstrate that, by shifting the AMOC with respect to the mean atmospheric precipitation field, such a displacement makes the system unstable, which explains chaotic millennial variability during the glacials and the persistence of stable ocean conditions during the interglacials.

Millennial-scale variability during the last glacial in vegetation records from North America

USGS Publications Warehouse

Jiménez-Moreno, Gonzalo; Anderson, R. Scott; Desprat, S.; Grigg, L.D.; Grimm, E.C.; Heusser, L.E.; Jacobs, Brian F.; Lopez-Martinez, C.; Whitlock, C.L.; Willard, D.A.

2010-01-01

High-resolution pollen records from North America show that terrestrial environments were affected by Dansgaard-Oeschger (D-O) and Heinrich climate variability during the last glacial. In the western, more mountainous regions, these climate changes are generally observed in the pollen records as altitudinal movements of climate-sensitive plant species, whereas in the southeast, they are recorded as latitudinal shifts in vegetation. Heinrich (HS) and Greenland (GS) stadials are generally correlated with cold and dry climate and Greenland interstadials (GI) with warm-wet phases. The pollen records from North America confirm that vegetation responds rapidly to millennial-scale climate variability, although the difficulties in establishing independent age models for the pollen records make determination of the absolute phasing of the records to surface temperatures in Greenland somewhat uncertain. ?? 2009 Elsevier Ltd.

Multi-proxy evidence of millennial climate variability from multiple Bahamian speleothems

NASA Astrophysics Data System (ADS)

Arienzo, Monica M.; Swart, Peter K.; Broad, Kenneth; Clement, Amy C.; Pourmand, Ali; Kakuk, Brian

2017-04-01

Northern Hemisphere tropical paleoclimate records support significant changes associated with Dansgaard Oeschger (D/O) events and Heinrich stadials 1 to 6 during the last 64,000 years. However, few absolutely dated terrestrial records from the western Atlantic span the last six Heinrich stadials. Here we present geochemical results from three new stalagmites collected from a cave in the Bahamas which encompass Heinrich stadials 1 to 6. We build on a previous study of the δ13C and δ18O values of the calcite and δ18O value of fluid inclusions from a single stalagmite from the same cave spanning the last three Heinrich stadials. Absolute geochronometry using U-Th equilibrium series demonstrates that the stalagmites formed between 63.8 and 13.8 kyr BP. The δ13C and δ18O values of the calcite show higher values associated with Heinrich stadials 1-6, and lower values during the D/O interstadial events. The Sr/Ca ratios of the calcite are shown to be relatively invariant, while in two of the samples the Mg/Ca ratios track the δ13C values. Increases in the δ18O values across Heinrich stadials 1-6 are interpreted as being driven by lower temperatures. The two deeper occurring stalagmites demonstrate increased Mg/Ca ratios and δ13C values during Heinrich stadials 1 and 2 which are interpreted as a signal of reduced flow rates in the epikarst and increased water/rock interactions as a result of increased aridity which potentially occurred across all six Heinrich stadials. The observed reductions in mean annual temperature and amount of precipitation across Heinrich stadials are proposed to be driven by a reduction in sea surface temperatures in the North Atlantic and an expanded Bermuda High. During D/O interstadials, the Bahamas cave records likely indicate warmer and/or wetter climate; however the isotopic shifts are not as significant as the isotopic excursions associated with Heinrich stadials.

The ACER pollen and charcoal database: a global resource to document vegetation and fire response to abrupt climate changes during the last glacial period

NASA Astrophysics Data System (ADS)

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

2017-09-01

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 warming events 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 (Abrupt 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 event 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 Microsoft AccessTM at https://doi.org/10.1594/PANGAEA.870867.

Millennial Scale Rapid Climate Change Events of the last 60kya as Observed in Multiple Stalagmites from The Bahamas

NASA Astrophysics Data System (ADS)

Mehterian, S.; Arienzo, M. M.; Pourmand, A.; Broad, K.; Kakuk, B.; Swart, P. K.

2016-12-01

Nine stalagmites collected from various depths of a submerged cave system on the island of Abaco, Bahamas comprise a continuous record of oxygen isotopic variation between 7.3 to 63kyr. The depths from which the speleothems were collected range from 12m to 37m. The youngest age of the speleothems reflect the inundation of the cave system by rising sea level. Millennial scale rapid climate change events can be seen in the δ18O record of the Bahamian stalagmites as Heinrich Stadials H0 to H6 and Dansgaard Oeschger Events. This collection of stalagmites represents different depths in a cave in Abaco, and their collective geochemical record reflects the global climatic effects as experienced locally in the subtropical islands of the Bahamas. Separately, various stalagmites that grew during the same time periods reflect similar patterns in the δ18O values of their calcite mineralogy despite having been located at vastly different depth elevations relative to each other. In general, the average δ18O value for the stalagmites collected from this cave is -2.5‰ VPDB with a maximum and minimum δ18O value between 0.5 ‰ and -5.5‰ VPDB respectively during Heinrich stadials and D/O events. In addition to δ18O values measured in these stalagmites, ratios of Sr/Ca, Mg/Ca, and Ba/Ca are also compared with one another. This study attempts to elucidate differences, if any, that locations in a cave relative to sea level would have on recording the true climate signals of a region. Finally, results from this study are compared with stalagmites collected from Eleuthera, another Bahamian island with speleothems younger than those from Abaco in order to create a mostly continuous record of rapid climate change events dating back from present day to 63,000 years.

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 firmly within ice core chronologies and suggest that their impacts on AMOC and tropical hydroclimate persisted for 740-1520 yr.

Correlation of Late-Pleistocene Lake-Level Oscillations in Mono Lake, California, with North Atlantic Climate Events

USGS Publications Warehouse

Benson, L.V.; Lund, S.P.; Burdett, J.W.; Kashgarian, Michaele; Rose, T.P.; Smoot, J.P.; Schwartz, M.

1998-01-01

Oxygen-18 (18O) values of sediment from the Wilson Creek Formation, Mono Basin, California, indicate three scales of temporal variation (Dansgaard-Oeschger, Heinrich, and Milankovitch) in the hydrologic balance of Mono Lake between 35,400 and 12,900 14C yr B.P. During this interval, Mono Lake experienced four lowstands each lasting from 1000 to 2000 yr. The youngest low-stand, which occurred between 15,500 and 14,000 14C yr B.P., was nearly synchronous with a desiccation of Owens Lake, California. Paleomagnetic secular variation (PSV) data indicate that three of four persistent lowstands occurred at the same times as Heinrich events H1, H2, and H4. 18O data indicate the two highest lake levels occurred ???18,000 and ???13,100 14C yr B.P., corresponding to passages of the mean position of the polar jet stream over the Mono Basin. Extremely low values of total inorganic carbon between 26,000 and 14,000 14C yr B.P. indicate glacial activity, corresponding to a time when summer insolation was much reduced. ?? 1998 University of Washington.

A speleothem record of South Pacific Convergence Zone dynamics during MIS 3 - Evidence for non-stationary coupling between the southern tropical Pacific and Greenland?

NASA Astrophysics Data System (ADS)

Sinclair, D. J.; Sherrell, R. M.; Rowe, H. D.; Wright, J. D.; Mortlock, R. A.; Hellstrom, J. C.; Cheng, H.; Min, A.; Edwards, R. L.

2014-12-01

The South Pacific Convergence Zone (SPCZ) is the largest component of the Intertropical Convergence Zone (ITCZ), and its impact on global climate rivals that of the deep convection at the heart of the Western Pacific Warm Pool. Rapid glacial climate fluctuations, such as Dansgaard-Oeschger (D-O) Events, would have triggered a reorganization of tropical systems such as the SPCZ, manifesting as significantly altered rainfall across the tropical south Pacific. However, a critical lack of high-resolution glacial records from this region means the dynamics of the SPCZ are largely unknown. We present a decade-resolution, absolute-dated speleothem rainfall record from the Island of Niue in the southern Tropical Pacific spanning 25-45 ka. Sr, Mg, δ18O and δ13C variations show that Niue experienced large, rapid fluctuations in rainfall lasting up to 1200 years. Between 40 and 45 ka, these show a remarkable concordance with the timing, duration and shape of D-O events 9-11. Rapid warming in Greenland was accompanied by a sudden increase in rainfall in Niue, implying that the SPCZ was strongly coupled with climate in the high Northern latitudes. These changes are not consistent with a wholesale northward shift in the SPCZ, which would have resulted in drying in Niue, and instead imply that the SPCZ underwent a more complex reorganization, perhaps rotating around its western edge in a manner analogous to modern-day extreme ENSO events. The speleothem record between 25-40 ka also shows large changes in rainfall, with D-O events identifiable. However, these changes are less well matched to Greenland, and include events not captured by the ice cores. It is clear that the SPCZ response to global climate change is complex: while it can closely couple with high-northern latitude climate for periods, this coupling may not be stationary with time. We speculate that this might result from changing precession, influencing which teleconnections dominate climate changes in the south tropical Pacific.

Sea surface temperatures in the North Atlantic Ocean from 30ka to 10ka

NASA Astrophysics Data System (ADS)

Barrack, Kerr; Greenop, Rosanna; Burke, Andrea; Barker, Stephen; Chalk, Thomas; Crocker, Anya

2016-04-01

Some of the most striking features of the Late Pleistocene interval are the rapid changes in climate between warmer interstadial and cold stadial periods which, when coupled, are termed Dansgaard-Oeschger (D-O) events. This shift between warm and cold climates has been interpreted to result from changes in the thermohaline circulation (Broecker et al., 1985) triggered by, for instance, freshwater input from the collapse of the Laurentide ice sheet (Zahn et al., 1997). However, a recent study suggests that major ice rafting events cannot be the 'trigger' for the centennial to millennial scale cooling events identified over the past 500kyr (Barker at al., 2015). Polar planktic foraminiferal and lithogenic/terrigenous grain counts reveal that the southward migration of the polar front occurs before the deposition of ice rafted debris and therefore the rafting of ice during stadial periods. Based upon this evidence, Barker et al. suggest that the transition to a stadial state is a non-linear response to gradual cooling in the region. In order to test this hypothesis, our study reconstructs sea surface temperature across D-O events and the deglaciation in the North Atlantic between 30ka and 10ka using Mg/ Ca paleothermometry in Globigerina bulloides at ODP Sites 980 and 983 (the same sites as used in Barker et al., 2015) with an average sampling resolution of 300 years. With our new record we evaluate the timing of surface ocean temperature change, frontal shift movement, and ice rafting to investigate variations in the temperature gradient across the polar front over D-O events. References: Barker, S., Chen, J., Gong, X., Jonkers, L., Knorr, G., Thornalley, D., 2015. Icebergs not the trigger for North Atlantic cold events. Nature, 520(7547), pp.333-336. Broecker, W.S., Peteer, D.M., Rind, D., 1985. Does the ocean-atmosphere system have more than one stable mode of operation? Nature, 315 (6014), pp.21-26. Zahn, R., Schönfeld, J., Kudrass, H.-R., Park, M.-H., Erlenkeuser, H., Grootes, P, 1997. Thermohaline instability in the North Atlantic during meltwater events: Stable isotope and ice-rafted detritus records from Core SO75-26KL, Portuguese Margin. Paleoceanography, 12(5), pp.696-710.

Abrupt changes of intermediate water properties on the northeastern slope of the Bering Sea during the last glacial and deglacial period

NASA Astrophysics Data System (ADS)

Rella, Stephan F.; Tada, Ryuji; Nagashima, Kana; Ikehara, Minoru; Itaki, Takuya; Ohkushi, Ken'ichi; Sakamoto, Tatsuhiko; Harada, Naomi; Uchida, Masao

2012-09-01

Millennial-scale variability in the behavior of North Pacific Intermediate Water during the last glacial and deglacial period, and its association with Dansgaard-Oeschger (D-O) cycles and Heinrich events, are examined based on benthic foraminiferal oxygen and carbon isotopes (δ18Obf and δ13Cbf) and %CaCO3 using a sediment core recovered from the northeastern slope of the Bering Sea. A suite of positive δ18Obf excursions at intermediate depths of the Bering Sea, which seem at least in part associated with increases in the δ18Obf gradients between the Bering and Okhotsk Seas, suggest the Bering Sea as a proximate source of intermediate water during several severe stadial episodes in the last glacial and deglacial period. Absence of such δ18Obf gradients during periods of high surface productivity in the Bering and Okhotsk Seas, which we correlate to D-O interstadials, suggests a reduction in intermediate water production in the Bering Sea and subsequent introduction of nutrient-rich deep waters from the North Pacific into intermediate depths of the Bering Sea. We argue that a reorganization of atmospheric circulation in the high-latitude North Pacific during severe cold episodes in the last glacial and deglacial period created favorable conditions for brine rejection in the northeastern Bering Sea. The resulting salinity increase in the cold surface waters could have initiated intermediate (and deep) water formation that spread out to the North Pacific.

Unstable AMOC during glacial intervals and millennial variability: The role of mean sea ice extent

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sevellec, Florian; Fedorov, Alexey V.

A striking feature of paleoclimate records is the greater stability of the Holocene epoch relative to the preceding glacial interval, especially apparent in the North Atlantic region. In particular, strong irregular variability with an approximately 1500 yr period, known as the Dansgaard-Oeschger (D-O) events, punctuates the last glaciation, but is absent during the interglacial. Prevailing theories, modeling and data suggest that these events, seen as abrupt warming episodes in Greenland ice cores and sea surface temperature records in the North Atlantic, are linked to reorganizations of the Atlantic Meridional Overturning Circulation (AMOC). In this study, using a new low-order oceanmore » model that reproduces a realistic power spectrum of millennial variability, we explore differences in the AMOC stability between glacial and interglacial intervals of the 100 kyr glacial cycle of the Late Pleistocene (1 kyr = 1000 yr). Previous modeling studies show that the edge of sea ice in the North Atlantic shifts southward during glacial intervals, moving the region of the North Atlantic Deep Water formation and the AMOC also southward. Finally, here we demonstrate that, by shifting the AMOC with respect to the mean atmospheric precipitation field, such a displacement makes the system unstable, which explains chaotic millennial variability during the glacials and the persistence of stable ocean conditions during the interglacials.« less

Unstable AMOC during glacial intervals and millennial variability: The role of mean sea ice extent

DOE PAGES

Sevellec, Florian; Fedorov, Alexey V.

2015-11-01

A striking feature of paleoclimate records is the greater stability of the Holocene epoch relative to the preceding glacial interval, especially apparent in the North Atlantic region. In particular, strong irregular variability with an approximately 1500 yr period, known as the Dansgaard-Oeschger (D-O) events, punctuates the last glaciation, but is absent during the interglacial. Prevailing theories, modeling and data suggest that these events, seen as abrupt warming episodes in Greenland ice cores and sea surface temperature records in the North Atlantic, are linked to reorganizations of the Atlantic Meridional Overturning Circulation (AMOC). In this study, using a new low-order oceanmore » model that reproduces a realistic power spectrum of millennial variability, we explore differences in the AMOC stability between glacial and interglacial intervals of the 100 kyr glacial cycle of the Late Pleistocene (1 kyr = 1000 yr). Previous modeling studies show that the edge of sea ice in the North Atlantic shifts southward during glacial intervals, moving the region of the North Atlantic Deep Water formation and the AMOC also southward. Finally, here we demonstrate that, by shifting the AMOC with respect to the mean atmospheric precipitation field, such a displacement makes the system unstable, which explains chaotic millennial variability during the glacials and the persistence of stable ocean conditions during the interglacials.« less

The Atlantic Meridional Overturning Circulation and Abrupt Climate Change.

PubMed

Lynch-Stieglitz, Jean

2017-01-03

Abrupt 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 abrupt events. The evidence for changes in the strength and structure of the AMOC associated with the Younger Dryas and many of the Heinrich events is strong. Although it has been difficult to directly document changes in the AMOC over the relatively short Dansgaard-Oeschger events, 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 events leaves open the possibility of other driving mechanisms for millennial-scale climate variability.

Rapid changes in ice core gas records - Part 1: On the accuracy of methane synchronisation of ice cores

NASA Astrophysics Data System (ADS)

Köhler, P.

2010-08-01

Methane synchronisation is a concept to align ice core records during rapid climate changes of the Dansgaard/Oeschger (D/O) events onto a common age scale. However, atmospheric gases are recorded in ice cores with a log-normal-shaped age distribution probability density function, whose exact shape depends mainly on the accumulation rate on the drilling site. This age distribution effectively shifts the mid-transition points of rapid changes in CH4 measured in situ in ice by about 58% of the width of the age distribution with respect to the atmospheric signal. A minimum dating uncertainty, or artefact, in the CH4 synchronisation is therefore embedded in the concept itself, which was not accounted for in previous error estimates. This synchronisation artefact between Greenland and Antarctic ice cores is for GRIP and Byrd less than 40 years, well within the dating uncertainty of CH4, and therefore does not calls the overall concept of the bipolar seesaw into question. However, if the EPICA Dome C ice core is aligned via CH4 to NGRIP this synchronisation artefact is in the most recent unified ice core age scale (Lemieux-Dudon et al., 2010) for LGM climate conditions of the order of three centuries and might need consideration in future gas chronologies.

Enhanced aridity and atmospheric high-pressure stability over the western Mediterranean during the North Atlantic cold events of the past 50 k.y.

NASA Astrophysics Data System (ADS)

Combourieu Nebout, N.; Turon, J. L.; Zahn, R.; Capotondi, L.; Londeix, L.; Pahnke, K.

2002-10-01

Multiproxy paleoenvironmental records (pollen and planktonic isotope) from Ocean Drilling Program Site 976 (Alboran Sea) document rapid ocean and climate variations during the last glacial that follow the Dansgaard-Oeschger climate oscillations seen in the Greenland ice core records, thus suggesting a close link of the Mediterranean climate swings with North Atlantic climates. Continental conditions rapidly oscillated through cold-arid and warm-wet conditions in the course of stadial-interstadial climate jumps. At the time of Heinrich events, i.e., maximum meltwater flux to the North Atlantic, western Mediterranean marine microflora and microfauna show rapid cooling correlated with increasing continental dryness. Enhanced aridity conceivably points to prolonged wintertime stability of atmospheric high-pressure systems over the southwestern Mediterranean in conjunction with cooling of the North Atlantic.

To what extent can global warming events influence scaling properties of climatic fluctuations in glacial periods?

NASA Astrophysics Data System (ADS)

Alberti, Tommaso; Lepreti, Fabio; Vecchio, Antonio; Carbone, Vincenzo

2017-04-01

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) events 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 event 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 events, and a low-frequency one, associated to the cooling/warming phase switch [Alberti et al., 2014]. Here, we investigate the scaling properties of the climate fluctuations within the Last Glacial Period, where abrupt climate changes, characterized by fast increase of temperature usually called Dansgaard-Oeschger (DO) events, have been particularly pronounced. By using the MultiFractal Detrended Fluctuation Analysis (MF-DFA), we show that a multifractal structure exists for both high- and low-frequency fluctuations in Northern and Southern hemispheres, with different scaling exponents, thus indicating a long-range persistence of the climatic variability within the whole Last Glacial Period. Our results evidence that both DO events and cooling/warming cycles must be considered as processes of the internal component of the Earth's climate, rather than processes related to external forcings. This study should be helpful for investigation of the internal origin of climate changes. References Shao, Z.G. and Ditlevsen, P.D., Nature Commun., 7, 10951, (2016). Alberti, T., Lepreti, F., Vecchio, A., Bevacqua, E., Capparelli, V. and Carbone, V., Clim. Past, 10, 1751 (2014).

Northern Hemisphere Influence on the Position of the SPCZ During MIS3: a High Resolution Glacial Rainfall Record from a Niuean Speleothem

NASA Astrophysics Data System (ADS)

Sinclair, D.; Sherrell, R. M.; Tremaine, D. M.; Sweeney, J. R.; Rowe, H.; Wright, J. D.; Mortlock, R. A.; Hellstrom, J. C.; Cheng, H.; Min, A.; Edwards, R. L.

2017-12-01

Here we present a high-resolution glacial paleorainfall record from the heart of the South Pacific Convergence Zone (SPCZ) extracted from a stalagmite from the remote island of Niue (19°03'S 169°52'W). The record spans much of MIS3 (25-45 ka) and captures rapid rainfall changes associated with shifts in the SPCZ. It is clear that rapid climate shifts in the Northern Hemisphere have a strong influence on the SPCZ. All of the warm Dansgaard-Oeschger (`D-O') interstadials across this period are represented by rainfall increases, with D-O Events 9-11 particularly strongly represented. Since Niue lies south of the core of the SPCZ, this implies that rather than shifting northwards (as the ITCZ does), the SPCZ instead rotates clockwise in response to northern Hemisphere warming (analogous to a shift between modern El Nino and La Nina states). We propose that changes to surface ocean temperature gradients in the Eastern Pacific modulate the strength of the Wind Evaporation SST feedback, changing the size and westward penetration of the eastern Pacific dry zone, resulting in changes to the diagonality of the SPCZ. Our record also captures a response to strong northern Hemisphere cooling. The 25-45 ka record is bounded by large hiatuses (inferred dry conditions) coincident with cold Heinrich Stadials (HS) 2 and 5, while HS3 and HS4 are captured as distinct reductions in speleothem growth rate and proxy evidence for declining rainfall. This is consistent with a counter-clockwise rotation of the SPCZ during Northern cooling, supporting our proposed mechanism. Interestingly, our record also captures several other (non-Heinrich) cooling events, including a strong 500-year dry interval at 26ka that is seen in Chinese and Brazilian speleothems and coincides with a strong cooling over Asia (inferred from Greenland dust records). We note the (possibly coincidental) timing between this event and the Oruanui super-eruption at 25.6 ka.

Sea ice and millennial-scale climate variability in the Nordic seas 90 kyr ago to present

PubMed Central

Hoff, Ulrike; Rasmussen, Tine L.; Stein, Ruediger; Ezat, Mohamed M.; Fahl, Kirsten

2016-01-01

In the light of rapidly diminishing sea ice cover in the Arctic during the present atmospheric warming, it is imperative to study the distribution of sea ice in the past in relation to rapid climate change. Here we focus on glacial millennial-scale climatic events (Dansgaard/Oeschger events) using the sea ice proxy IP25 in combination with phytoplankton proxy data and quantification of diatom species in a record from the southeast Norwegian Sea. We demonstrate that expansion and retreat of sea ice varies consistently in pace with the rapid climate changes 90 kyr ago to present. Sea ice retreats abruptly at the start of warm interstadials, but spreads rapidly during cooling phases of the interstadials and becomes near perennial and perennial during cold stadials and Heinrich events, respectively. Low-salinity surface water and the sea ice edge spreads to the Greenland–Scotland Ridge, and during the largest Heinrich events, probably far into the Atlantic Ocean. PMID:27456826

Sea ice and millennial-scale climate variability in the Nordic seas 90 kyr ago to present.

PubMed

Hoff, Ulrike; Rasmussen, Tine L; Stein, Ruediger; Ezat, Mohamed M; Fahl, Kirsten

2016-07-26

In the light of rapidly diminishing sea ice cover in the Arctic during the present atmospheric warming, it is imperative to study the distribution of sea ice in the past in relation to rapid climate change. Here we focus on glacial millennial-scale climatic events (Dansgaard/Oeschger events) using the sea ice proxy IP25 in combination with phytoplankton proxy data and quantification of diatom species in a record from the southeast Norwegian Sea. We demonstrate that expansion and retreat of sea ice varies consistently in pace with the rapid climate changes 90 kyr ago to present. Sea ice retreats abruptly at the start of warm interstadials, but spreads rapidly during cooling phases of the interstadials and becomes near perennial and perennial during cold stadials and Heinrich events, respectively. Low-salinity surface water and the sea ice edge spreads to the Greenland-Scotland Ridge, and during the largest Heinrich events, probably far into the Atlantic Ocean.

Millennial-scale variations of late Pleistocene radiolarian assemblages in the Bering Sea related to environments in shallow and deep waters

NASA Astrophysics Data System (ADS)

Itaki, Takuya; Kim, Sunghan; Rella, Stephan F.; Uchida, Masao; Tada, Ryuji; Khim, Boo-Keun

2012-02-01

A high-resolution record of the radiolarian assemblage from 60 to 10 ka was investigated using a piston core (PC-23A) obtained from the northern slope of the Bering Sea. Faunal changes based on the 29 major radiolarian taxa demonstrated that the surface and deep water conditions in the Bering Sea were related to the orbital and millennial-scale climatic variations known as glacial-interglacial and Dansgaard-Oeschger (D-O) cycles, respectively. During interstadial periods of the D-O cycles, the assemblage was characterized by increases in the high-latitude coastal species Rhizoplegma boreale and the upper-intermediate water species Cycladophora davisiana, while the sea-ice related species Actinomma boreale and A. leptodermum and many deep-water species such as Dictyophimus crisiae and D. hirundo tended to be reduced. This trend was more apparent in two laminated intervals at 15-13.5 and 11.5-11 ka, which were correlated with well-known ice-sheet collapse events that occurred during the last deglaciation: melt-water pulse (MWP)-1A and MWP-1B, respectively. The radiolarian faunal composition in these periods suggests that oceanic conditions were different from today: (1) surface water was affected by increased melt-water discharge from continental ice-sheet, occurring at the same time as an abrupt increase in atmospheric temperature, (2) upper-intermediate water (ca. 200-500 m) was well-ventilated and organic-rich, and (3) lower-intermediate water (ca. 500-1000 m) was oxygen-poor. Conversely, the sea-ice season might have been longer during stadial periods of the D-O cycles and the last glacial maximum (LGM) compared to the interstadial periods and the earliest Holocene. In these colder periods, deep-water species were very abundant, and this corresponded to increases in the oxygen isotope value of benthic foraminifera. Our findings suggest that the oxygen-rich water was present in the lower-intermediate layer resulting from intensified ventilation.

Abrupt climatic events recorded by the Ili loess during the last glaciation in Central Asia: Evidence from grain-size and minerals

NASA Astrophysics Data System (ADS)

Song, Yougui; Zeng, Mengxiu; Chen, Xiuling; Li, Yue; Chang, Hong; An, Zhisheng; Guo, Xiaohua

2018-04-01

The loess record of Central Asia provides an important archive of regional climate and environmental changes. In contrast to the widely investigated loess deposits in the Chinese Loess Plateau, Central Asian loess-paleosol sequences remain poorly understood. Here, we present an aeolian loess section in the southern Ili Basin. Based on granularity and mineralogical analyses, we reconstruct climatic changes during the last glaciation. The results indicated that most of the abrupt climatic events (such as Dansgaard-Oeschger events and Heinrich events) were imprinted in this loess section, although their amplitudes and ages showed some differences. Compared with the millennial oscillations recoded in loess and stalagmites in East Asia, the arid Central Asia responded more sensitively to the warming events than to the cooling events. The shifting trajectory of westerlies across Central Asia played an important role in dust deposition during the stadials. The North Atlantic climatic signals may have been transmitted from Central Asia to the East Asian monsoon regions via the westerlies.

Obliquity-driven expansion of North Atlantic sea ice controls structure of the last glacial

NASA Astrophysics Data System (ADS)

Turney, Chris; Thomas, Zoe; Hutchinson, David; Bradshaw, Corey; Brook, Barry; England, Matthew; Fogwill, Christopher; Jones, Richard; Palmer, Jonathan; Hughen, Konrad; Cooper, Alan

2015-04-01

North Atlantic late-Pleistocene climate was characterised by a series of abrupt climate changes, the most extreme of which were the Dansgaard-Oeschger (D-O) events; millennial-scale oscillations that switched rapidly between cold and warm atmospheric conditions of up to Δ16°C, most strongly expressed during the period 60-30 ka. Time series analysis of palaeoclimate ice core records is one of the best ways to detect threshold behaviour in the climate system; however, some of these techniques can be age model dependent. Spectral analysis of a new Greenland-Cariaco GICC05 age model (GICC05-CB), generated by combining the GICC05 and Cariaco ∂18O chronologies, reveals a change in the dominant periodicities at ~31 ka, consistent with the cessation of the D-O events. While the GICC05-CB has the same ∂18O structure as GICC05, the different periodicity profile reveals a change in the climate system at 31 ka. Stability analysis of the ∂18O time series over the last 60 ka determines the number of states the climate experienced over time, and reveals a bifurcation in the climate system at 31 ka, switching from a bistable to a monostable state. Early warning signals of this bifurcation are also detected starting 10,000 years before the shift in the form of increasing autocorrelation and variance. This is consistent with the climate system experiencing a slow forcing towards a critical threshold. These signals are found in both the GICC05-CB and GICC05 chronologies, though the timing of the bifurcation point varies slightly. We suggest that this bifurcation is linked to a minima in obliquity, causing greatly expanded sea ice in the Labrador sea. Modelling runs from the CSIRO Mk3L Earth-system model indicates that extensive sea ice cover is established in the Labrador Sea and North Pacific at the obliquity minima centred on 28.5 ka. This expanded sea ice is thus responsible for shifting the Northern Hemisphere westerlies southwards and reducing the strength of the AMOC, preventing the establishment of the cold state from 31 ka.

A simple conceptual model to interpret the 100 000 years dynamics of paleo-climate records

NASA Astrophysics Data System (ADS)

Quiroga Lombard, C. S.; Balenzuela, P.; Braun, H.; Chialvo, D. R.

2010-10-01

Spectral analyses performed on records of cosmogenic nuclides reveal a group of dominant spectral components during the Holocene period. Only a few of them are related to known solar cycles, i.e., the De Vries/Suess, Gleissberg and Hallstatt cycles. The origin of the others remains uncertain. On the other hand, time series of North Atlantic atmospheric/sea surface temperatures during the last ice age display the existence of repeated large-scale warming events, called Dansgaard-Oeschger (DO) events, spaced around multiples of 1470 years. The De Vries/Suess and Gleissberg cycles with periods close to 1470/7 (~210) and 1470/17 (~86.5) years have been proposed to explain these observations. In this work we found that a conceptual bistable model forced with the De Vries/Suess and Gleissberg cycles plus noise displays a group of dominant frequencies similar to those obtained in the Fourier spectra from paleo-climate during the Holocene. Moreover, we show that simply changing the noise amplitude in the model we obtain similar power spectra to those corresponding to GISP2 δ18O (Greenland Ice Sheet Project 2) during the last ice age. These results give a general dynamical framework which allows us to interpret the main characteristic of paleoclimate records from the last 100 000 years.

Inverse stochastic-dynamic models for high-resolution Greenland ice core records

NASA Astrophysics Data System (ADS)

Boers, Niklas; Chekroun, Mickael D.; Liu, Honghu; Kondrashov, Dmitri; Rousseau, Denis-Didier; Svensson, Anders; Bigler, Matthias; Ghil, Michael

2017-12-01

Proxy records from Greenland ice cores have been studied for several decades, yet many open questions remain regarding the climate variability encoded therein. Here, we use a Bayesian framework for inferring inverse, stochastic-dynamic models from δ18O and dust records of unprecedented, subdecadal temporal resolution. The records stem from the North Greenland Ice Core Project (NGRIP), and we focus on the time interval 59-22 ka b2k. Our model reproduces the dynamical characteristics of both the δ18O and dust proxy records, including the millennial-scale Dansgaard-Oeschger variability, as well as statistical properties such as probability density functions, waiting times and power spectra, with no need for any external forcing. The crucial ingredients for capturing these properties are (i) high-resolution training data, (ii) cubic drift terms, (iii) nonlinear coupling terms between the δ18O and dust time series, and (iv) non-Markovian contributions that represent short-term memory effects.

Contrasting scaling properties of interglacial and glacial climates

NASA Astrophysics Data System (ADS)

Ditlevsen, Peter; Shao, Zhi-Gang

2017-04-01

Understanding natural climate variability is essential for assessments of climate change. This is reflected in the scaling properties of climate records. The scaling exponents of the interglacial and the glacial climates are fundamentally different. The Holocene record is monofractal, with a scaling exponent H˜0.7. On the contrary, the glacial record is multifractal, with a significantly higher scaling exponent H˜1.2, indicating a longer persistence time and stronger nonlinearities in the glacial climate. The glacial climate is dominated by the strong multi-millennial Dansgaard-Oeschger (DO) events influencing the long-time correlation. However, by separately analysing the last glacial maximum lacking DO events, here we find the same scaling for that period as for the full glacial period. The unbroken scaling thus indicates that the DO events are part of the natural variability and not externally triggered. At glacial time scales, there is a scale break to a trivial scaling, contrasting the DO events from the similarly saw-tooth-shaped glacial cycles. Ref: Zhi-Gang Shao and Peter Ditlevsen, Nature Comm. 7, 10951, 2016

Abrupt Climate Change in the Southern Great Plains during the Last Glacial Interval

NASA Astrophysics Data System (ADS)

Housson, A. L.; Maupin, C. R.; Roark, B.; Shen, C. C.; Baykara, O.; White, K.; Kampen-Lewis, S. V.; McChesney, C. L.

2016-12-01

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 abrupt global climate events, 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 Events 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 warming.

Role of the Bering Strait on the hysteresis of the ocean conveyor belt circulation and glacial climate stability.

PubMed

Hu, Aixue; Meehl, Gerald A; Han, Weiqing; Timmermann, Axel; Otto-Bliesner, Bette; Liu, Zhengyu; Washington, Warren M; Large, William; Abe-Ouchi, Ayako; Kimoto, Masahide; Lambeck, Kurt; Wu, Bingyi

2012-04-24

Abrupt climate transitions, known as Dansgaard-Oeschger and Heinrich events, occurred frequently during the last glacial period, specifically from 80-11 thousand years before present, but were nearly absent during interglacial periods and the early stages of glacial periods, when major ice-sheets were still forming. Here we show, with a fully coupled state-of-the-art climate model, that closing the Bering Strait and preventing its throughflow between the Pacific and Arctic Oceans during the glacial period can lead to the emergence of stronger hysteresis behavior of the ocean conveyor belt circulation to create conditions that are conducive to triggering abrupt climate transitions. Hence, it is argued that even for greenhouse warming, abrupt climate transitions similar to those in the last glacial time are unlikely to occur as the Bering Strait remains open.

Tropical North Atlantic subsurface temperature anomalies: evidence for AMOC variability across Dansgaard-Oscheger events?

NASA Astrophysics Data System (ADS)

Parker, A. O.; Schmidt, M. W.; Chang, P.

2013-12-01

A common mechanism often proposed to explain the abrupt climate events of Marine Isotope Stage 3 (MIS 3), known as Dansgaard-Oscheger (D-O) cycles, invokes variability in the strength of the Atlantic Meridional Overturning Circulation (AMOC). Although proxy evidence shows that D-O cycles resulted in large-scale changes in atmospheric circulation patterns around the planet, an understanding of how the AMOC varied across these events remains unclear. Coupled ocean-atmosphere models demonstrate that AMOC variability is linked to abrupt change in the tropical North Atlantic (TNA) through both oceanic and atmospheric processes. A reduction in AMOC causes a subsurface oceanic warming in the TNA as the western boundary current slows, allowing the warm salinity maximum waters to enter the deep tropics. Recently, Schmidt et al. (2012) identified an abrupt subsurface warming at the onset of AMOC slow down during both Heinrich 1 and the Younger Dryas, suggesting this signal may be a robust feature of AMOC variability in the TNA. In order to determine if AMOC variability was the driver of D-O cycles during MIS 3, we present new, high-resolution Mg/Ca and δ18O records from the near-surface dwelling planktonic foraminifera G. ruber and the lower-thermocline dwelling planktonic foraminifera G. crassaformis from 22 - 52 ka BP in southern Caribbean core VM12-107 (11.33oN, 66.63oW, 1079m depth). Sedimentation rates in VM12-107 average 24cm/kyr, providing high temporal resolution able to resolve millennial-scale events. The G. ruber δ18O record shows abrupt oscillations up to 1‰ as well as Mg/Ca-based SST changes of 1.5 - 2oC that are synchronous with some D-O cycles recorded in the Greenland ice cores. Given our ability to resolve D-O cycles in the planktonic record, we find that Mg/Ca ratios from G. crassaformis were, on average, 0.13 × 0.04 mmol/mol higher during stadials. This equates to a temperature increase during stadials of up to 1.5oC. These results imply that AMOC variability played an important role in at least some millennial-scale D-O cycles during MIS 3.

Methane and nitrous oxide in the ice core record.

PubMed

Wolff, Eric; Spahni, Renato

2007-07-15

Polar ice cores contain, in trapped air bubbles, an archive of the concentrations of stable atmospheric gases. Of the major non-CO2 greenhouse gases, methane is measured quite routinely, while nitrous oxide is more challenging, with some artefacts occurring in the ice and so far limited interpretation. In the recent past, the ice cores provide the only direct measure of the changes that have occurred during the industrial period; they show that the current concentration of methane in the atmosphere is far outside the range experienced in the last 650,000 years; nitrous oxide is also elevated above its natural levels. There is controversy about whether changes in the pre-industrial Holocene are natural or anthropogenic in origin. Changes in wetland emissions are generally cited as the main cause of the large glacial-interglacial change in methane. However, changing sinks must also be considered, and the impact of possible newly described sources evaluated. Recent isotopic data appear to finally rule out any major impact of clathrate releases on methane at these time-scales. Any explanation must take into account that, at the rapid Dansgaard-Oeschger warmings of the last glacial period, methane rose by around half its glacial-interglacial range in only a few decades. The recent EPICA Dome C (Antarctica) record shows that methane tracked climate over the last 650,000 years, with lower methane concentrations in glacials than interglacials, and lower concentrations in cooler interglacials than in warmer ones. Nitrous oxide also shows Dansgaard-Oeschger and glacial-interglacial periodicity, but the pattern is less clear.

Carbon and hydrogen isotope composition of plant biomarkers as proxies for precipitation changes across Heinrich Events in the subtropics

NASA Astrophysics Data System (ADS)

Arnold, T. E.; Freeman, K.; Brenner, M.; Diefendorf, A. F.

2014-12-01

Lake Tulane is a relatively deep (~23 m) solution lake in south-central Florida. Its depth and location on a structural high, the Lake Wales Ridge, enabled continuous lacustrine sediment accumulation over the past >60,000 years. Pollen in the lake sediments indicate repeated major shifts in the vegetation community, with six peaks in Pinus (pine) abundance that coincide with the most intense cold phases of Dansgaard-Oeschger cycles and the Heinrich events that terminate them. Alternating with Pinus peaks are zones with high relative percentages of Quercus (oak), Ambrosia (ragweed), Lyonia (staggerbush) and Ceratiola (rosemary) pollen, genera that today occupy the most xeric sites on the Florida landscape. This suggests the pollen record indicates the Pinus phases, and therefore Heinrich Events, were wetter than the intervening Quercus phases. To test the connection between Heinrich Events and precipitation in Florida, we analyzed the carbon (δ13C) and hydrogen (δD) isotope signatures of plant biomarkers extracted from the Lake Tulane sediment core as proxies of paleohydrology. The δ13C of plant biomarkers, such as n-alkanes and terpenoids, are determined, in part, by changes in water-use efficiency (WUE = Assimilation/Transpiration) in plant communities, which changes in response to shifts in mean annual precipitation. Plant δ13C values can, therefore, provide a rough indication of precipitation changes when other factors, such as plant community, are relatively stable throughout time. Paleohydrology is also recorded in the δD of plant leaf waxes, which are strongly controlled by precipitation δD. In this region, precipitation δD is negatively correlated with rainfall amount (i.e. the "amount" effect) and positively correlated with aridity. Thus, the δ13C and δD signatures of molecular plant biomarkers provide relative indicators of precipitation change, and when combined, provide a test of our hypothesis that vegetation changes in this region are driven by changes in aridity.

Carbon and hydrogen isotope composition of plant biomarkers from lake sediments as proxies for precipitation changes across Heinrich Events in the subtropics

NASA Astrophysics Data System (ADS)

Arnold, T. E.; Diefendorf, A. F.; Brenner, M.; Freeman, K. H.; Curtis, J. H.

2015-12-01

Lake Tulane is a relatively deep (~23 m) solution lake in south-central Florida. Its depth and location on a structural high, the Lake Wales Ridge, enabled continuous lacustrine sediment accumulation over the past >60,000 years. Pollen in the lake sediments indicate repeated major shifts in the vegetation community, with six peaks in Pinus (pine) abundance that coincide with the most intense cold phases of Dansgaard-Oeschger cycles and the Heinrich events that terminate them. Alternating with Pinus peaks are zones with high relative percentages of Quercus (oak), Ambrosia (ragweed), Lyonia (staggerbush) and Ceratiola (rosemary) pollen, genera that today occupy the most xeric sites on the Florida landscape. This suggests the pollen record indicates the Pinus phases, and therefore Heinrich Events, were wetter than the intervening Quercus phases. To test the connection between Heinrich Events and precipitation in Florida, we analyzed the carbon (δ13C) and hydrogen (δD) isotope signatures of plant biomarkers extracted from the Lake Tulane sediment core as proxies of paleohydrology. The δ13C of plant biomarkers, such as n-alkanes and terpenoids, are determined, in part, by changes in water-use efficiency (WUE = Assimilation/Transpiration) in plant communities, which changes in response to shifts in mean annual precipitation. Plant δ13C values can, therefore, provide a rough indication of precipitation changes when other factors, such as plant community, are relatively stable throughout time. Paleohydrology is also recorded in the δD of plant leaf waxes, which are strongly controlled by precipitation δD. In this region, precipitation δD is negatively correlated with rainfall amount (i.e. the "amount" effect) and positively correlated with aridity. Thus, the δ13C and δD signatures of molecular plant biomarkers provide relative indicators of precipitation change, and when combined, provide a test of our hypothesis that vegetation changes in this region are driven by changes in aridity.

How Will Sea Ice Loss Affect the Greenland Ice Sheet? On the Puzzling Features of Greenland Ice-Core Isotopic Composition

NASA Technical Reports Server (NTRS)

Pausata, Francesco S. R.; Legrande, Allegra N.; Roberts, William H. G.

2016-01-01

The modern cryosphere, Earth's frozen water regime, is in fast transition. Greenland ice cores show how fast theses changes can be, presenting evidence of up to 15 C warming events over timescales of less than a decade. These events, called Dansgaard/Oeschger (D/O) events, are believed to be associated with rapid changes in Arctic sea ice, although the underlying mechanisms are still unclear. The modern demise of Arctic sea ice may, in turn, instigate abrupt changes on the Greenland Ice Sheet. The Arctic Sea Ice and Greenland Ice Sheet Sensitivity (Ice2Ice Chttps://ice2ice.b.uib.noD) initiative, sponsored by the European Research Council, seeks to quantify these past rapid changes to improve our understanding of what the future may hold for the Arctic. Twenty scientists gathered in Copenhagen as part of this initiative to discuss the most recent observational, technological, and model developments toward quantifying the mechanisms behind past climate changes in Greenland. Much of the discussion focused on the causes behind the changes in stable water isotopes recorded in ice cores. The participants discussed sources of variability for stable water isotopes and framed ways that new studies could improve understanding of modern climate. The participants also discussed how climate models could provide insights into the relative roles of local and nonlocal processes in affecting stable water isotopes within the Greenland Ice Sheet. Presentations of modeling results showed how a change in the source or seasonality of precipitation could occur not only between glacial and modern climates but also between abrupt events. Recent fieldwork campaigns illustrate an important role of stable isotopes in atmospheric vapor and diffusion in the final stable isotope signal in ice. Further, indications from recent fieldwork campaigns illustrate an important role of stable isotopes in atmospheric vapor and diffusion in the final stable isotope signal in ice. This feature complicates the quantitative interpretation of ice core signals but also makes the stable ice isotope signal a more robust regional indicator of climate, speakers noted. Meeting participants agreed that to further our understanding of these relationships, we need more process-focused field and laboratory campaigns.

Tropical North Atlantic subsurface warming events as a fingerprint for AMOC variability during Marine Isotope Stage 3

NASA Astrophysics Data System (ADS)

Parker, Andrew O.; Schmidt, Matthew W.; Chang, Ping

2015-11-01

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 events 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 warming 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 warm 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 abrupt increases in Mg/Ca ratios (the largest equal to a 4°C warming) during the interstadial-stadial transition of most DO events during this period. This change is consistent with reconstructions of subsurface warming events associated with cold events 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 events 2 and 3. This record presents some of the first high-resolution marine sediment derived evidence for variable AMOC during MIS 3.

Suborbital timescale variability of North Atlantic Deep Water during the past 200,000 years

NASA Astrophysics Data System (ADS)

Oppo, Delia W.; Lehman, Scott J.

1995-10-01

We generated ˜200-kyr-long proxy records of surface and deepwater variability from a subpolar North Atlantic core (V29-202), enabling us to assess the linkage between surface and deepwater changes on suborbital timescales. In particular, we used a benthic δ13C record to evaluate the deep water response to Dansgaard-Oeschger temperature oscillations and to Heinrich events, times of massive iceberg delivery to the North Atlantic. We found that the reduction of North Atlantic Deep Water (NADW) production was generally associated with cold or dropping sea surface temperatures (SSTs) as indicated by planktonic foraminiferal assemblages. The NADW contribution to the site did not drop appreciably during Heinrich events H4 through H2, probably because these events followed intervals of prolonged surface cooling already characterized by low rates of NADW production. By contrast NADW reduction appears to have been synchronous with H5. SST rise associated with both Dansgaard-Oeschger oscillations and Heinrich events was usually accompanied by increasing NADW strength. In a few cases the NADW recovery appeared to lag the SST rise; however, the apparent delay is most likely an artefact of the sedimentary record (low concentrations of benthic foraminifera). As a result of low benthic foraminiferal abundances during stage 6, the stage 6 benthic foraminiferal δ13C record is of lower resolution than the younger part of the record. The stage 6 proxy records for surface hydrography nevertheless reveal millennial-scale oscillations similar to those seen in stage 3. The available δ13C data suggest that NADW weakened in association with the cold portions of stage 6 SST oscillations. We also sought to confirm a recent study which concluded that there was little NADW variability during the peak of the last interglaciation, marine oxygen isotope substage 5e (Eemian). Isotope stage 5 was marked by a trend of increasing benthic δ13C in V29-202. Rising δ13C through isotope stage 5 is also seen in tropical surface water records and at some deep Atlantic sites and may reflect the common derivation of these water masses. Variations of ≥ 0.5 ‰ superimposed on this rising δ13C trend within substage 5e in V29-202 are so far not evident in tropical feed waters and may therefore indicate that NADW production was weaker during the late than mid-Eemian. An electronic supplement of this material may be obtained on a diskette or Anonymous FTP from KOSMOS.AGU.ORG. (LOGIN to AGU's FTP account using ANONYMOUS as the username and GUEST as the password. Go to the right directory by typing CD APEND. Type LS to see what files are available. Type GET and the name of the file to get it. Finally, type QUIT to leave the system.) (Paper 95PA02089, Suborbital timescale variability of North Atlantic Deep Water during the past 200,000 years, by D. W. Oppo and S. J. Lehman) Diskette may be ordered from American Geophysical Union, 2000 Florida Avenue, N.W., Washington, DC 20009; $15.00. Payment must accompany order.

Reconstructing Eastern Tropical Pacific productivity across Marine Isotope Stage 3 using foraminifera faunal counts

NASA Astrophysics Data System (ADS)

McCourty, M.; Schmidt, M. W.; Glaubke, R.; Hertzberg, J. E.; Marcantonio, F.; Bianchi, T. S.

2017-12-01

The El Niño-Southern Oscillation is one of Earth's largest sources of interannual climate variability that has many global environmental impacts. Furthermore, the mean state of the tropical Pacific has the potential to change in the near future due to anthropogenic warming of the planet. In order to provide an analogue for future climate states, there is a critical need to understand how the tropical Pacific evolved across abrupt warming events in Earth's recent past. While most studies have focused on the evolution of ENSO across Marine Isotope Stages (MIS) 1 and 2, the dynamics of the tropical Pacific across the abrupt climate events of MIS 3 are still highly contentious. To develop a record of past changes in upwelling intensity in the EEP, a parameter critically linked to the tropical Pacific mean state, we quantify the faunal abundances of 6 planktonic foraminifera species from piston core MV1014-02-17JC (00° 10.83'S, 85° 52.00'W; 2846 m depth) on the Carnegie Ridge from 35 - 59 kyr. The relative abundance of Globigerina bulloides, a species associated with upwelling conditions, and 5 other planktonic foraminifera suggest an increase in water column productivity during Heinrich Event 4 and across several Dansgaard-Oeschger stadial intervals. Initial results suggest that stadials in the North Atlantic are associated with more permanent La Niña-like conditions in the EEP. However, multiple lines of evidence suggest that depth intervals in our core between 43.7 - 55.7 kyr were impacted by intense dissolution due to changes in bottom water chemistry, impacting the fidelity of our faunal count records across this interval. Future work includes extending our faunal record back to 100 kyr to include Heinrich Events 6 - 8.

Late Quaternary Palaeoceanographic Changes in Sea Surface Conditions in the Tropical Atlantic

NASA Astrophysics Data System (ADS)

Fischel, Andrea; Seidenkrantz, Marit-Solveig; Kuijpers, Antoon; Nürnberg, Dirk

2013-04-01

Palaeoceanographic changes and the variability in surface water mass hydrography are reconstructed in order to track tropical ocean and climate variability and inter-hemispheric heat exchange through the last 42,000 year BP. Our studies are based on the relative abundance of planktonic foraminifera combined with sea surface temperature approximation based Mg/Ca measurements, XRF scanning and stable oxygen isotope analyses in a 5 m long gravity core Ga307-Win-12GC (17°50.80N, 64°48.7290W), retrieved in the Virgin Island Basin in approx. 3,960 m water depth. The Virgin Island Basin is the deepest part of the Anegada-Jungfern Passage in the northeast Caribbean, one of the most important pathways for water mass exchange between the Central Atlantic and the Caribbean Sea. Due to its bathymetry surface waters as well as deep water mass strata from the northern and southern hemisphere enter the basin, comprising Caribbean Surface Water (CSW), Antarctic Intermediate Water (AAIW), Atlantic Intermediate Water (AIW) and North Atlantic Deep Water (NADW). The planktonic foraminiferal assemblage suggests rather stable sea-surface conditions during the Holocene in the NE Caribbean. However, major changes in the hydrographic setting could be identified within the glacial period. During the glacial period, clear millennial-scale variability in sea-surface temperature and productivity are present. Fluctuations in the relative abundance of Globigerinoides ruber in the sediment core may be correlated to Dansgaard-Oeschger events in the northern North Atlantic. Furthermore an increase in relative abundance of Globorotalia rubescens occurs synchronous with ice rafted debris layers described from the North Atlantic. The faunal changes in the tropical Atlantic may thus be correlated to major climate changes in the North Atlantic, mainly D-O cyclicity as well as Heinrich events. Thus, the synchronous change in water mass distribution and hydrographic cyclicity suggests a possible linkage between tropical and North Atlantic Ocean variability during the Late Quaternary.

Isotopic evidence of multiple controls on atmospheric oxidants over climate transitions

NASA Astrophysics Data System (ADS)

Geng, Lei; Murray, Lee T.; Mickley, Loretta J.; Lin, Pu; Fu, Qiang; Schauer, Andrew J.; Alexander, Becky

2017-06-01

The abundance of tropospheric oxidants, such as ozone (O3) and hydroxyl (OH) and peroxy radicals (HO2 + RO2), determines the lifetimes of reduced trace gases such as methane and the production of particulate matter important for climate and human health. The response of tropospheric oxidants to climate change is poorly constrained owing to large uncertainties in the degree to which processes that influence oxidants may change with climate and owing to a lack of palaeo-records with which to constrain levels of atmospheric oxidants during past climate transitions. At present, it is thought that temperature-dependent emissions of tropospheric O3 precursors and water vapour abundance determine the climate response of oxidants, resulting in lower tropospheric O3 in cold climates while HOx (= OH + HO2 + RO2) remains relatively buffered. Here we report observations of oxygen-17 excess of nitrate (a proxy for the relative abundance of atmospheric O3 and HOx) from a Greenland ice core over the most recent glacial-interglacial cycle and for two Dansgaard-Oeschger events. We find that tropospheric oxidants are sensitive to climate change with an increase in the O3/HOx ratio in cold climates, the opposite of current expectations. We hypothesize that the observed increase in O3/HOx in cold climates is driven by enhanced stratosphere-to-troposphere transport of O3, and that reactive halogen chemistry is also enhanced in cold climates. Reactive halogens influence the oxidative capacity of the troposphere directly as oxidants themselves and indirectly via their influence on O3 and HOx. The strength of stratosphere-to-troposphere transport is largely controlled by the Brewer-Dobson circulation, which may be enhanced in colder climates owing to a stronger meridional gradient of sea surface temperatures, with implications for the response of tropospheric oxidants and stratospheric thermal and mass balance. These two processes may represent important, yet relatively unexplored, climate feedback mechanisms during major climate transitions.

100,000-year-long terrestrial record of millennial-scale linkage between eastern North American mid-latitude paleovegetation shifts and Greenland ice-core oxygen isotope trends

USGS Publications Warehouse

Litwin, Ronald J.; Smoot, Joseph P.; Pavich, Milan J.; Markewich, Helaine Walsh; Brook, George; Durika, Nancy J.

2013-01-01

We document frequent, rapid, strong, millennial-scale paleovegetation shifts throughout the late Pleistocene, within a 100,000+ yr interval (~ 115–15 ka) of terrestrial sediments from the mid-Atlantic Region (MAR) of North America. High-resolution analyses of fossil pollen from one core locality revealed a continuously shifting sequence of thermally dependent forest assemblages, ranging between two endmembers: subtropical oak-tupelo-bald cypress-gum forest and high boreal spruce-pine forest. Sedimentary textural evidence indicates fluvial, paludal, and loess deposition, and paleosol formation, representing sequential freshwater to subaerial environments in which this record was deposited. Its total age"depth model, based on radiocarbon and optically stimulated luminescence ages, ranges from terrestrial oxygen isotope stages (OIS) 6 to 1. The particular core sub-interval presented here is correlative in trend and timing to that portion of the oxygen isotope sequence common among several Greenland ice cores: interstades GI2 to GI24 (≈ OIS2–5 d). This site thus provides the first evidence for an essentially complete series of "Dansgaard"Oeschger" climate events in the MAR. These data reveal that the ~ 100,000 yr preceding the Late Glacial and Holocene in the MAR of North America were characterized by frequently and dynamically changing climate states, and by vegetation shifts that closely tracked the Greenland paleoclimate sequence.

Variations of the paleo-productivity in benthic foraminifera records in MIS 3 from western South China Sea

NASA Astrophysics Data System (ADS)

Niu, Y.; Du, J.; Huang, B.; Chen, M.

2010-12-01

Understanding climate change of last glacial age as the background information of climate forecasting is particularly important in climate research. Marine Isotope Stage 3 (MIS 3, 61-24 ka B.P.) is a relative warm and unstable period in the last glacial. Millennium scale abrupt climate changes, such as Heinrich events and Dansgaard-Oeschger (D-O) cycles, are identified in this period. Research topic on the variations of monsoon during the glacial cycles, especially in MIS 3, is critical for understanding low latitude climatic change and the global paleo-environment as a whole. Fortunately, high resolution sedimentary records in western South China Sea provide us valuable materials to uncover how East Asia Summer Monsoon (EASM) system acts in a highly fluctuating climate ambient like MIS 3. Core 17954 is located in the modern summer upwelling area off the Vietnam coast in western South China Sea (SCS), its sediments record the variations of upwelling generated by EASM. In this work, we carry out paleo-ecological analyses on planktonic ( Neogloboquadrina dutertrei, Globigerina bulloides) and benthic foraminifera (Bulimina aculeate, Uvigerina peregrina, Cibicidoides wuellerstorfi, ect.) sampled from Core 17954 to investigate paleo-productivity and nutrition change of western SCS and its relation to EASM. The results show that benthic and planktonic foraminifera have similar responses to nutrition change. Various indicators of productivity on the basis of benthic foraminiferal analyses reflect an overall three stage change trend: productivity gradually increases from the beginning of MIS 3 (60-40 ka) to its maximum during 35-30 ka, and finally declines after 30 ka. There is also another important discovery, if we observe the climate change in MIS 3 as a whole, we can also find western SCS and Northern Hemisphere High latitude have strong correspondences in such changes: Heinrich events coincided with high productivity events in the western SCS. Further, the result of this study also support precious study’s conclusion of five strengthened EASM periods (referred as S1-5) because productivity inferred form benthic foraminiferal analysis during these periods are relative high.

Lake level and climate records of the last 90 ka from the Northern Basin of Lake Van, eastern Turkey

NASA Astrophysics Data System (ADS)

Çağatay, M. N.; Öğretmen, N.; Damcı, E.; Stockhecke, M.; Sancar, Ü.; Eriş, K. K.; Özeren, S.

2014-11-01

Sedimentary, geochemical and mineralogical analyses of the ICDP cores recovered from the Northern Basin (NB) of Lake Van provide evidence of lake level and climatic changes related to orbital and North Atlantic climate system over the last 90 ka. High lake levels are generally observed during the interglacial and interstadial periods, which are marked by deposition of varved sediments with high total organic carbon (TOC), total inorganic carbon (TIC), low detrital influx (high Ca/F) and high δ18O and δ13C values of authigenic carbonate. During the glacial and stadial periods of 71-58 ka BP (Marine Isotope Stage 4, MIS4) and end of last glaciation-deglaciation (30-14.5 ka BP; MIS3) relatively low lake levels prevailed, and grey homogeneous to faintly laminated clayey silts were deposited at high sedimentation and low organic productivity rates. Millennial-scale variability of the proxies during 60-30 ka BP (MIS3 is correlated with the Dansgaard-Oeschger (D-O)) and Holocene abrupt climate events in the Atlantic. These events are characterized by laminated sediments, with high TOC, TIC, Ca/Fe, δ18O and δ13C values. The Lake Van NB records correlate well in the region with the climate records from the lakes Zeribar and Urmia in Iran and the Sofular Cave in NW Anatolia, but are in general in anti-phase to those from the Dead Sea Basin (Lake Lisan) in the Levant. The relatively higher δ18O values (0 to -0.4‰) for the interglacial and interstadial periods in the Lake Van NB section are due to the higher temperature and seasonality of precipitation and higher evaporation, whereas the lower values (-0.8 to -2‰) during the glacial and stadial periods are caused mainly by relative decrease in both temperature and seasonality of precipitation. The high δ18O values (up to 4.2‰) during the Younger Dryas, together with the presence of dolomite and low TOC contents, supports evaporative conditions and low lake level. A gradual decrease in the δ18O values from an average of -0.4‰ during the humid early Holocene to an average of -3.5‰ during the more arid late Holocene suggests an increasing contribution of winter precipitation. The changes in the seasonality of precipitation in eastern Anatolia are probably caused by changes in the temperatures of North Atlantic and Mediterranean and in the strength of Siberian High.

Dolni Vestonice (Czech Republic) an intermédiate loess series between Western and eastern European records

NASA Astrophysics Data System (ADS)

Rousseau, D.; Antoine, P.; Hatte, C.; Lagroix, F.; Fuchs, M.; Moine, O.; Gauthier, C.; Svoboda, J.; Lisa, L.

2010-12-01

Previous investigations on western and eastern European loess series have shown similarities at least for the main loess deposition during the last climate cycle, recording North-Atlantic abrupt climate changes, the Dansgaard-Oeschger and Heinrich events. To address the question of how such record occurred through modeling experiments (Sima et al., QSR, 2009), we need reference series located in an intermediary position between the Nussloch (Germany - Antoine et al, QI 2001, QSR, 2009; Rousseau et al, GRL 2007) and Stayky (Ukraine -Rousseau et al, Clim Past D 2010) loess series at about 50°N latitude, location of the main deposits. The key sequence of Dolni Vestonice in southern Czech Republic, had been investigated previously and described by many authors since 1961, and more especially by G Kukla and B Klima. Here we present the preliminary results of the new study of this key sequence by a multidisciplinary study, supported by ANR-ACTES project, combining the detailed stratigraphy, AMS 14C and IRSL dating, rock magnetic property, grain size, d13C and mollusks analyses. We applied the same sampling protocol than previously developed, by carefully cleaning the sequence on a vertical panel, 15m high and 5m wide in order to have parallel samples (on continuous columns) easily comparable. The results show similar patterns, high frequency variations of the different proxies in the upper part of the record corresponding to MIS 3 and 2, as observed in western and eastern European sequences supporting then our assumption of the recording of N Atlantic abrupt changes over Europe. Other interesting variations are clearly demonstrated for every proxy making these results remarkable new data for individual in deep studies. Moreover our detailed investigation also shows new data about abrupt dust events, markers, in the lower part of the sequence, and previously interpreted as strong dust events, and how they appear within sedimentary cycles linked to the cyclicity at the base of the last climate cycle.

Was millennial scale climate change during the Last Glacial triggered by explosive volcanism?

PubMed Central

Baldini, James U.L.; Brown, Richard J.; McElwaine, Jim N.

2015-01-01

The mechanisms responsible for millennial scale climate change within glacial time intervals are equivocal. Here we show that all eight known radiometrically-dated Tambora-sized or larger NH eruptions over the interval 30 to 80 ka BP are associated with abrupt Greenland cooling (>95% confidence). Additionally, previous research reported a strong statistical correlation between the timing of Southern Hemisphere volcanism and Dansgaard-Oeschger (DO) events (>99% confidence), but did not identify a causative mechanism. Volcanic aerosol-induced asymmetrical hemispheric cooling over the last few hundred years restructured atmospheric circulation in a similar fashion as that associated with Last Glacial millennial-scale shifts (albeit on a smaller scale). We hypothesise that following both recent and Last Glacial NH eruptions, volcanogenic sulphate injections into the stratosphere cooled the NH preferentially, inducing a hemispheric temperature asymmetry that shifted atmospheric circulation cells southward. This resulted in Greenland cooling, Antarctic warming, and a southward shifted ITCZ. However, during the Last Glacial, the initial eruption-induced climate response was prolonged by NH glacier and sea ice expansion, increased NH albedo, AMOC weakening, more NH cooling, and a consequent positive feedback. Conversely, preferential SH cooling following large SH eruptions shifted atmospheric circulation to the north, resulting in the characteristic features of DO events. PMID:26616338

Was millennial scale climate change during the Last Glacial triggered by explosive volcanism?

PubMed

Baldini, James U L; Brown, Richard J; McElwaine, Jim N

2015-11-30

The mechanisms responsible for millennial scale climate change within glacial time intervals are equivocal. Here we show that all eight known radiometrically-dated Tambora-sized or larger NH eruptions over the interval 30 to 80 ka BP are associated with abrupt Greenland cooling (>95% confidence). Additionally, previous research reported a strong statistical correlation between the timing of Southern Hemisphere volcanism and Dansgaard-Oeschger (DO) events (>99% confidence), but did not identify a causative mechanism. Volcanic aerosol-induced asymmetrical hemispheric cooling over the last few hundred years restructured atmospheric circulation in a similar fashion as that associated with Last Glacial millennial-scale shifts (albeit on a smaller scale). We hypothesise that following both recent and Last Glacial NH eruptions, volcanogenic sulphate injections into the stratosphere cooled the NH preferentially, inducing a hemispheric temperature asymmetry that shifted atmospheric circulation cells southward. This resulted in Greenland cooling, Antarctic warming, and a southward shifted ITCZ. However, during the Last Glacial, the initial eruption-induced climate response was prolonged by NH glacier and sea ice expansion, increased NH albedo, AMOC weakening, more NH cooling, and a consequent positive feedback. Conversely, preferential SH cooling following large SH eruptions shifted atmospheric circulation to the north, resulting in the characteristic features of DO events.

Effect of the Bering Strait on the AMOC hysteresis and glacial climate stability (Invited)

NASA Astrophysics Data System (ADS)

Hu, A.; Meehl, G. A.; Han, W.; Timmermann, A.; Otto-Bliesner, B. L.; Liu, Z.; Abe-Ouchi, A.

2013-12-01

Abrupt climate transitions, such as Dansgaard-Oeschger and Heinrich events, occurred frequently during the last glacial period, especially from 80 - 11 thousand years before present, but were nearly absent during Holocene and the early stages of last glacial period. Here we show, with a fully coupled climate model, that closing the Bering Strait and preventing its throughflow between the Pacific and Arctic Oceans during the glacial period can lead to the emergence of stronger hysteresis behavior of the Atlantic meridional overturning circulation (AMOC) to create conditions that are conducive to triggering abrupt climate transitions. Hence, it is argued that even for greenhouse warming, abrupt climate transitions similar to those in the last glacial time are unlikely to occur as the Bering Strait remains open. Qualitatively the same result is arrived in new simulations by employing the glacial background conditions using the same climate model. Theoretical and simulated AMOC hysteresis curves (a, b) and the associated changes of Greenland surface temperature and meridional heat transport at 65°N in the Atlantic (c, d). In panel a), 'S' is the bifurcation point beyond which AMOC collapses and the '+/-F' values indicate the freshwater forcing strength. In panels b), c), and d), the black/red (blue/green) lines are for the closed (open) BS simulation. The black/blue (red/green) lines represent the phase of freshwater forcing increase (decrease) in these simulations. Note that a change of the freshwater forcing by 0.1 Sv (Sv≡106m3s-1) in this figure takes place over 500 model years.

The Quaternary fossil-pollen record and global change

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grimm, E.C.

Fossil pollen provide one of the most valuable records of vegetation and climate change during the recent geological past. Advantages of the fossil-pollen record are that deposits containing fossil pollen are widespread, especially in areas having natural lakes, that fossil pollen occurs in continuous stratigraphic sequences spanning millennia, and that fossil pollen occurs in quantitative assemblages permitting a multivariate approach for reconstructing past vegetation and climates. Because of stratigraphic continuity, fossil pollen records climate cycles on a wide range of scales, from annual to the 100 ka Milankovitch cycles. Receiving particular emphasis recently are decadal to century scale changes, possiblemore » from the sediments of varved lakes, and late Pleistocene events on a 5--10 ka scale possibly correlating with the Heinrich events in the North Atlantic marine record or the Dansgaard-Oeschger events in the Greenland ice-core record. Researchers have long reconstructed vegetation and climate by qualitative interpretation of the fossil-pollen record. Recently quantitative interpretation has developed with the aid of large fossil-pollen databases and sophisticated numerical models. In addition, fossil pollen are important climate proxy data for validating General Circulation Models, which are used for predicting the possible magnitude future climate change. Fossil-pollen data also contribute to an understanding of ecological issues associated with global climate change, including questions of how and how rapidly ecosystems might respond to abrupt climate change.« less

On the use of δ18Oatm for ice core dating

NASA Astrophysics Data System (ADS)

Extier, Thomas; Landais, Amaelle; Bréant, Camille; Prié, Frédéric; Bazin, Lucie; Dreyfus, Gabrielle; Roche, Didier M.; Leuenberger, Markus

2018-04-01

Deep ice core chronologies have been improved over the past years through the addition of new age constraints. However, dating methods are still associated with large uncertainties for ice cores from the East Antarctic plateau where layer counting is not possible. Indeed, an uncertainty up to 6 ka is associated with AICC2012 chronology of EPICA Dome C (EDC) ice core, which mostly arises from uncertainty on the delay between changes recorded in δ18Oatm and in June 21st insolation variations at 65°N used for ice core orbital dating. Consequently, we need to enhance the knowledge of this delay to improve ice core chronologies. We present new high-resolution EDC δ18Oatm record (153-374 ka) and δO2/N2 measurements (163-332 ka) performed on well-stored ice to provide continuous records of δ18Oatm and δO2/N2 between 100 and 800 ka. The comparison of δ18Oatm with the δ18Ocalcite from East Asian speleothems shows that both signals present similar orbital and millennial variabilities, which may represent shifts in the InterTropical Convergence Zone position, themselves associated with Heinrich events. We thus propose to use the δ18Ocalcite as target for δ18Oatm orbital dating. Such a tuning method improves the ice core chronology of the last glacial inception compared to AICC2012 by reconciling NGRIP and mid-latitude climatic records. It is especially marked during Dansgaard-Oeschger 25 where the proposed chronology is 2.2 ka older than AICC2012. This δ18Oatm - δ18Ocalcite alignment method applied between 100 and 640 ka improves the EDC ice core chronology, especially over MIS 11, and leads to lower ice age uncertainties compared to AICC2012.

Periglacial fires and trees in a continental setting of Central Canada, Upper Pleistocene.

PubMed

Bélanger, N; Carcaillet, C; Padbury, G A; Harvey-Schafer, A N; Van Rees, K J C

2014-03-01

Fire is a key factor controlling global vegetation patterns and carbon cycling. It mostly occurs under warm periods during which fuel builds up with sufficient moisture, whereas such conditions stimulate fire ignition and spread. Biomass burning increased globally with warming periods since the last glacial era. Data confirming periglacial fires during glacial periods are very sparse because such climates are likely too cold to favour fires. Here, tree occurrence and fires during the Upper Pleistocene glacial periods in Central Canada are inferred from botanical identification and calibrated radiocarbon dates of charcoal fragments. Charcoal fragments were archived in sandy dunes of central Saskatchewan and were dated >50000-26600 cal BP. Fragments were mostly gymnosperms. Parallels between radiocarbon dates and GISP2-δ¹⁸O records deciphered relationships between fire and climate. Fires occurred either hundreds to thousands of years after Dansgaard-Oeschger (DO) interstadial warming events (i.e., the time needed to build enough fuel for fire ignition and spread) or at the onset of the DO event. The chronological uncertainties result from the dated material not precisely matching the fires and from the low residual ¹⁴C associated with old sample material. Dominance of high-pressure systems and low effective moisture during post-DO coolings likely triggered flammable periglacial ecosystems, while lower moisture and the relative abundance of fuel overshadowed lower temperatures for fire spread. Laurentide ice sheet (LIS) limits during DO events are difficult to assess in Central Canada due to sparse radiocarbon dates. Our radiocarbon data set constrains the extent of LIS. Central Saskatchewan was not covered by LIS throughout the Upper Pleistocene and was not a continental desert. Instead, our results suggest long-lasting periods where fluctuations of the northern tree limits and fires after interstadials occurred persistently. © 2014 John Wiley & Sons Ltd.

Beyond the bipolar seesaw: Toward a process understanding of interhemispheric coupling

NASA Astrophysics Data System (ADS)

Pedro, Joel B.; Jochum, Markus; Buizert, Christo; He, Feng; Barker, Stephen; Rasmussen, Sune O.

2018-07-01

The thermal bipolar ocean seesaw hypothesis was advanced by Stocker and Johnsen (2003) as the 'simplest possible thermodynamic model' to explain the time relationship between Dansgaard-Oeschger (DO) and Antarctic Isotope Maxima (AIM) events. In this review we combine palaeoclimate observations, theory and general circulation model experiments to advance from the conceptual model toward a process understanding of interhemispheric coupling and the forcing of AIM events. We present four main results: (1) Changes in Atlantic heat transport invoked by the thermal seesaw are partially compensated by opposing changes in heat transport by the global atmosphere and Pacific Ocean. This compensation is an integral part of interhemispheric coupling, with a major influence on the global pattern of climate anomalies. (2) We support the role of a heat reservoir in interhemispheric coupling but argue that its location is the global interior ocean to the north of the Antarctic Circumpolar Current (ACC), not the commonly assumed Southern Ocean. (3) Energy budget analysis indicates that the process driving Antarctic warming during AIM events is an increase in poleward atmospheric heat and moisture transport following sea ice retreat and surface warming over the Southern Ocean. (4) The Antarctic sea ice retreat is itself driven by eddy-heat fluxes across the ACC, amplified by sea-ice-albedo feedbacks. The lag of Antarctic warming after AMOC collapse reflects the time required for heat to accumulate in the ocean interior north of the ACC (predominantly the upper 1500 m), before it can be mixed across this dynamic barrier by eddies.

Intermitted Occurrence of Millennial-scale Variability of East Asian Summer Monsoon before 1.45 Ma based on the High-resolution Br Record of the Japan Sea Sediments

NASA Astrophysics Data System (ADS)

Tada, R.; Seki, A.; Ikeda, M.; Irino, T.; Ikehara, K.; Karasuda, A.; Sugisaki, S.; Sagawa, T.; Itaki, T.; Kubota, Y.; Murayama, M.; Lu, S.; Murray, R. W.; Alvarez Zarikian, C. A.

2017-12-01

It is well-known that Dansgaard-Oeschger Cycles (DOC) and East Asian Summer Monsoon (EASM) are closely linked during the last glacial period, and that Atlantic Meridional Ocean Circulation (AMOC) played a key role to amplify and propagate the DOC signal. Climatic model studies also suggested that on and off of AMOC caused simultaneous north-south shifts of westerly jets (WJ) in both hemispheres and ITCZ. Since WJ over East Asia bounds the northern limit of EASM front, it is likely that N-S shifts of WJ caused millennial-scale variability of EASM precipitation distribution. This linkage can be traced back to ca. 0.4 Ma based on comparison of synthetic Greenland temperature record of Barker et al. (2011) with d18O record of Chinese speleothems, and back to 0.8 Ma based on comparison of synthetic Greenland temperature record with Br profile of the hemipelagic sediments of the Japan Sea (reflecting marine organic carbon content and considered as a proxy of EASM) retrieved from Site U1424 during IODP Exp. 346. Br profile of the Japan Sea sediments also implies that millennial-scale variability of EASM was persistent since ca. 1.45 Ma ago, which was probably linked with AMOC variability. However, presence/absence of millennial-scale variability of EASM and possibility of its linkage with AMOC variability are not known for the period before 1.45 Ma. Here we extend our Br record of Site U1424 back to ca. 3 Ma and demonstrate that there was intermitted occurrence of millennial-scale EASM variability since ca. 2.5 Ma when LR04 glacial d18O value first exceeded ca. 4 permil. This may suggest the presence of threshold of ice volume to cause millennial-scale variability of AMOC and EASM.

The rise and fall of Lake Bonneville between 45 and 10.5 ka

USGS Publications Warehouse

Benson, L.V.; Lund, S.P.; Smoot, J.P.; Rhode, D.E.; Spencer, R.J.; Verosub, K.L.; Louderback, L.A.; Johnson, C.A.; Rye, R.O.; Negrini, R.M.

2011-01-01

A sediment core taken from the western edge of the Bonneville Basin has provided high-resolution proxy records of relative lake-size change for the period 45.1-10.5 calendar ka (hereafter ka). Age control was provided by a paleomagnetic secular variation (PSV)-based age model for Blue Lake core BL04-4. Continuous records of ??18O and total inorganic carbon (TIC) generally match an earlier lake-level envelope based on outcrops and geomorphic features, but with differences in the timing of some hydrologic events/states. The Stansbury Oscillation was found to consist of two oscillations centered on 25 and 24 ka. Lake Bonneville appears to have reached its geomorphic highstand and began spilling at 18.5 ka. The fall from the highstand to the Provo level occurred at 17.0 ka and the lake intermittently overflowed at the Provo level until 15.2 ka, at which time the lake fell again, bottoming out at ~14.7 ka. The lake also fell briefly below the Provo level at ~15.9 ka. Carbonate and ??18O data indicate that between 14.7 and 13.1 ka the lake slowly rose to the Gilbert shoreline and remained at about that elevation until 11.6 ka, when it fell again. Chemical and sedimentological data indicate that a marsh formed in the Blue Lake area at 10.5 ka.Relatively dry periods in the BL04-4 records are associated with Heinrich events H1-H4, suggesting that either the warming that closely followed a Heinrich event increased the evaporation rate in the Bonneville Basin and (or) that the core of the polar jet stream (PJS) shifted north of the Bonneville Basin in response to massive losses of ice from the Laurentide Ice Sheet (LIS) during the Heinrich event. The second Stansbury Oscillation occurred during Heinrich event H2, and the Gilbert wet event occurred during the Younger Dryas cold interval. Several relatively wet events in BL04-4 occur during Dansgaard-Oeschger (DO) warm events.The growth of the Bear River glacier between 32 and 17 ka paralleled changes in the values of proxy indicators of Bonneville Basin wetness and terminal moraines on the western side of the Wasatch Mountains have ages ranging from 16.9 to 15.2 ka. This suggests a near synchroneity of change in the hydrologic and cryologic balances occurring in the Bonneville drainage system and that glacial extent was linked to lake size. ?? 2010.

Shell We Date? ESR Dating Sangamon Interglacial Episode Deposits at Hopwood Farm, IL.

PubMed

Blackwell, Bonnie A B; Kim, Danny M K; Curry, B Brandon; Grimley, David A; Blickstein, Joel I B; Skinner, Anne R

2016-12-01

During the Sangamon Episode, North America occasionally experienced warm climates. At Hopwood Farm, IL, a small kettle lake filled with sediment after the Illinois Episode glaciers retreated from southern Illinois. To date those deposits, 14 mollusc samples newly collected with associated sediment from three depths at Hopwood Farm were dated by standard electron spin resonance (ESR) dating. ESR can date molluscs from ~0.5 ka to >2 Ma in age with 5-10% precision, by comparing the accumulated radiation dose with the total radiation dose rate from the mollusc and its environment. Because all molluscs contained ≤0.6 ppm U, their ages do not depend on the assumed U uptake model. Using five different species, ESR analyses for 14 mollusc subsamples from Hopwood Farm showed that Unit 3, a layer rich in lacustrine molluscs, dates at 102 ± 7 ka to 90 ± 6 ka, which correlates with Marine (Oxygen) Isotope Stage 5c-b. Thus, the period with the highest non-arboreal pollen at Hopwood also correlates with the European Brørup, Dansgaard-Oeschger Event DO 23, a time period when climates were cooling and drying somewhat over the same period. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Late Pleistocene climate drivers of early human migration.

PubMed

Timmermann, Axel; Friedrich, Tobias

2016-10-06

On the basis of fossil and archaeological data it has been hypothesized that the exodus of Homo sapiens out of Africa and into Eurasia between ~50-120 thousand years ago occurred in several orbitally paced migration episodes. Crossing vegetated pluvial corridors from northeastern Africa into the Arabian Peninsula and the Levant and expanding further into Eurasia, Australia and the Americas, early H. sapiens experienced massive time-varying climate and sea level conditions on a variety of timescales. Hitherto it has remained difficult to quantify the effect of glacial- and millennial-scale climate variability on early human dispersal and evolution. Here we present results from a numerical human dispersal model, which is forced by spatiotemporal estimates of climate and sea level changes over the past 125 thousand years. The model simulates the overall dispersal of H. sapiens in close agreement with archaeological and fossil data and features prominent glacial migration waves across the Arabian Peninsula and the Levant region around 106-94, 89-73, 59-47 and 45-29 thousand years ago. The findings document that orbital-scale global climate swings played a key role in shaping Late Pleistocene global population distributions, whereas millennial-scale abrupt climate changes, associated with Dansgaard-Oeschger events, had a more limited regional effect.

Late Pleistocene climate drivers of early human migration

NASA Astrophysics Data System (ADS)

Timmermann, Axel; Friedrich, Tobias

2016-10-01

On the basis of fossil and archaeological data it has been hypothesized that the exodus of Homo sapiens out of Africa and into Eurasia between ~50-120 thousand years ago occurred in several orbitally paced migration episodes. Crossing vegetated pluvial corridors from northeastern Africa into the Arabian Peninsula and the Levant and expanding further into Eurasia, Australia and the Americas, early H. sapiens experienced massive time-varying climate and sea level conditions on a variety of timescales. Hitherto it has remained difficult to quantify the effect of glacial- and millennial-scale climate variability on early human dispersal and evolution. Here we present results from a numerical human dispersal model, which is forced by spatiotemporal estimates of climate and sea level changes over the past 125 thousand years. The model simulates the overall dispersal of H. sapiens in close agreement with archaeological and fossil data and features prominent glacial migration waves across the Arabian Peninsula and the Levant region around 106-94, 89-73, 59-47 and 45-29 thousand years ago. The findings document that orbital-scale global climate swings played a key role in shaping Late Pleistocene global population distributions, whereas millennial-scale abrupt climate changes, associated with Dansgaard-Oeschger events, had a more limited regional effect.

Similar millennial climate variability on the Iberian margin during two early Pleistocene glacials and MIS 3

NASA Astrophysics Data System (ADS)

Birner, B.; Hodell, D. A.; Tzedakis, P. C.; Skinner, L. C.

2016-01-01

Although millennial-scale climate variability (<10 ka) has been well studied during the last glacial cycles, little is known about this important aspect of climate in the early Pleistocene, prior to the Middle Pleistocene Transition. Here we present an early Pleistocene climate record at centennial resolution for two representative glacials (marine isotope stages (MIS) 37-41 from approximately 1235 to 1320 ka) during the "41 ka world" at Integrated Ocean Drilling Program Site U1385 (the "Shackleton Site") on the southwest Iberian margin. Millennial-scale climate variability was suppressed during interglacial periods (MIS 37, MIS 39, and MIS 41) and activated during glacial inceptions when benthic δ18O exceeded 3.2‰. Millennial variability during glacials MIS 38 and MIS 40 closely resembled Dansgaard-Oeschger events from the last glacial (MIS 3) in amplitude, shape, and pacing. The phasing of oxygen and carbon isotope variability is consistent with an active oceanic thermal bipolar see-saw between the Northern and Southern Hemispheres during most of the prominent stadials. Surface cooling was associated with systematic decreases in benthic carbon isotopes, indicating concomitant changes in the meridional overturning circulation. A comparison to other North Atlantic records of ice rafting during the early Pleistocene suggests that freshwater forcing, as proposed for the late Pleistocene, was involved in triggering or amplifying perturbations of the North Atlantic circulation that elicited a bipolar see-saw response. Our findings support similarities in the operation of the climate system occurring on millennial time scales before and after the Middle Pleistocene Transition despite the increases in global ice volume and duration of the glacial cycles.

Spatio-temporal dynamics of hydrographic reorganizations and iceberg discharges at the junction between the Northeast Atlantic and Norwegian Sea basins surrounding Heinrich event 4

NASA Astrophysics Data System (ADS)

Wary, Mélanie; Eynaud, Frédérique; Kissel, Catherine; Londeix, Laurent; Rossignol, Linda; Lapuyade, Joanna; Castéra, Marie-Hélène; Billy, Isabelle

2018-01-01

Dansgaard-Oeschger and Heinrich events constitute ones of the most enigmatic features of the last glacial period. Many studies have focused on their characteristic millennial climatic variability, testing atmospheric/cryospheric/oceanic couplings, but major uncertainties and discrepancies still remain. A new scenario, robustly supported by an approach coupling paleoreconstructions and freshwater hosing experiments simulating Heinrich-type perturbations, has recently emerged. Reconciling most of the up to now hypothesized theories, it suggests the occurrence of a regional seesaw between a cooled-down North Atlantic Ocean and warmed-up Nordic Seas during cold atmospheric phases, in relation to enhanced subsurface advection of warm Atlantic waters re-emerging in the Norwegian Sea. The associated ocean warming, thus reaching Nordic basins at a critical location beyond the Faeroe-Shetland sill, is proposed to be involved in the concomitant release of European icebergs. Here we further investigate this promising scenario over the 35-41 ka BP interval by (i) outlining its precise spatial pattern in a crucial area, i.e. the junction between the North Atlantic and the Norwegian Sea close to European ice-sheets, (ii) resolving its very fine temporal and regional evolution during critical transitions associated with the onset of warm advection, i.e. Greenland Interstadial to Greenland Stadial and Greenland Interstadial to Heinrich Stadial, and (iii) assessing its impact on the spatio-temporal dynamic of iceberg discharges from the European and Laurentide ice-sheets during cold stadial episodes especially including Heinrich event 4.

A tephra lattice for Greenland and a reconstruction of volcanic events spanning 25-45 ka b2k

NASA Astrophysics Data System (ADS)

Bourne, A. J.; Cook, E.; Abbott, P. M.; Seierstad, I. K.; Steffensen, J. P.; Svensson, A.; Fischer, H.; Schüpbach, S.; Davies, S. M.

2015-06-01

Tephra layers preserved within the Greenland ice-cores are crucial for the independent synchronisation of these high-resolution records to other palaeoclimatic archives. Here we present a new and detailed tephrochronological framework for the time period 25,000-45,000 a b2k that brings together results from 4 deep Greenland ice-cores. In total, 99 tephra deposits, the majority of which are preserved as cryptotephra, are described from the NGRIP, NEEM, GRIP and DYE-3 records. The major element signatures of single glass shards within these deposits indicate that 93 are basaltic in composition all originating from Iceland. Specifically, 43 originate from Grimsvötn, 20 are thought to be sourced from the Katla volcanic system and 17 show affinity to the Kverkfjöll system. Robust geochemical characterisations, independent ages derived from the GICC05 ice-core chronology, and the stratigraphic positions of these deposits relative to the Dansgaard-Oeschger climate events represent a key framework that provides new information on the frequency and nature of volcanic events in the North Atlantic region between GS-3 and GI-12. Of particular importance are 19 tephra deposits that lie on the rapid climatic transitions that punctuate the last glacial period. This framework of well-constrained, time-synchronous tie-lines represents an important step towards the independent synchronisation of marine, terrestrial and ice-core records from the North Atlantic region, in order to assess the phasing of rapid climatic changes during the last glacial period.

Ocean-Ice Sheet Interactions in the Norwegian Sea and Teleconnections to Low Latitude Hydrology and Atmospheric Circulation

NASA Astrophysics Data System (ADS)

Brendryen, J.; Hannisdal, B.; Haaga, K. A.; Haflidason, H.; Castro, D. D.; Grasmo, K. J.; Sejrup, H. P.; Edwards, R. L.; Cheng, H.; Kelly, M. J.; Lu, Y.

2016-12-01

Abrupt millennial scale climatic events known as Dansgaard-Oeschger events are a defining feature of the Quaternary climate system dynamics in the North Atlantic and beyond. We present a high-resolution multi-proxy record of ocean-ice sheet interactions in the Norwegian Sea spanning the interval between 50 and 150 ka BP. A comparison with low latitude records indicates a very close connection between the high northern latitude ocean-ice sheet interactions and large scale changes in low latitude atmospheric circulation and hydrology even on sub-millennial scales. The records are placed on a common precise radiometric chronology based on correlations to U/Th dated speleothem records from China and the Alps. This enables a comparison of the records to orbital and other climatically important parameters such as U/Th dated sea-level data from corals and speleothems. We explore the drive-response relationships in these coupled systems with the information transfer (IT) and the convergent cross mapping (CCM) analytical techniques. These methods employ conceptually different approaches to detect the relative strength and directionality of potentially chaotic and nonlinearly coupled systems. IT is a non-parametric measure of information transfer between data records based on transfer entropy, while CCM relies on delay reconstructions using Takens' theorem. This approach enables us to address how the climate system processes interact and how this interaction is affected by external forcing from for example greenhouse gases and orbital variability.

History of Larix decidua Mill. (European larch) since 130 ka

NASA Astrophysics Data System (ADS)

Wagner, Stefanie; Litt, Thomas; Sánchez-Goñi, Maria-Fernanda; Petit, Rémy J.

2015-09-01

Retrospective studies focussing on forest dynamics using fossil and genetic data can provide important keys to prepare forests for the future. In this study we analyse the impact of past climate and anthropogenic changes on Larix decidua Mill. (European larch) populations based on a new range-wide fossil compilation encompassing the last 130 ka and on recently produced genetic data (nuclear, mitochondrial). Results demonstrate that during the last 130 ka L. decidua persisted close to its current distribution range and colonized vast areas outside this range during the first two early Weichselian interstadials (c. 87-109 ka and c. 83-78 ka), reaching a distributional maxima in the north-central European lowlands. Some fossil sites point to notably rapid responses to some abrupt climate events (Dansgaard-Oeschger cycles and Heinrich Events). Combined fossil and genetic data identify at least six MIS 2 refuges and postglacial recolonization pathways. The establishment of extant L. decidua forests dates back to the first two millennia of the Holocene (c. 11.5-9.5 ka) and the onset of anthropogenic impact was inferred since the late Neolithic (c. 6 ka), with major changes occurring since the Bronze Age (c. 4 ka). During the last 300 years human-induced translocations resulted in recent admixture of populations originating from separate refuges. Altogether, the results of this study provide valuable clues for developing sustainable conservation and management strategies targeting ancient genetic lineages and for studying evolutionary issues.

Persistent millennial-scale link between Greenland climate and northern Pacific Oxygen Minimum Zone under interglacial conditions

NASA Astrophysics Data System (ADS)

Cartapanis, O.; Tachikawa, K.; Romero, O. E.; Bard, E.

2014-02-01

The intensity and/or extent of the northeastern Pacific Oxygen Minimum Zone (OMZ) varied in-phase with the Northern Hemisphere high latitude climate on millennial timescales during the last glacial period, indicating the occurrence of atmospheric and oceanic connections under glacial conditions. While millennial variability was reported for both the Greenland and the northern Atlantic Ocean during the last interglacial period, the climatic connections with the northeastern Pacific OMZ has not yet been observed under warm interglacial conditions. Here we present a new geochemical dataset, spanning the past 120 ka, for major components (terrigenous fraction, marine organic matter, biogenic opal, and carbonates) generated by X-ray fluorescence scanning alongside with biological productivity and redox sensitive trace element content (Mo, Ni, Cd) of sediment core MD02-2508 at 23° N, retrieved from the northern limit of the modern OMZ. Based on elemental ratios Si / Ti (proxy for opal), Cd / Al and Ni / Al, we suggest that biological productivity was high during the last interglacial (MIS5). Highly resolved opal reconstruction presents millennial variability corresponding to all the Dansgaard-Oeschger interstadial events over the last interglacial, while the Mo / Al ratio indicates reduced oxygenation during these events. Extremely high opal content during warm interstadials suggests high diatom productivity. Despite the different climatic and oceanic background between glacial and interglacial periods, rapid variability in the northeastern Pacific OMZ seems to be tightly related to Northern Hemisphere high latitude climate via atmospheric and possibly oceanic processes.

Controls on Cyclic Formation of Quaternary Early Diagenetic Dolomite

NASA Astrophysics Data System (ADS)

McCormack, J.; Bontognali, T. R. R.; Immenhauser, A.; Kwiecien, O.

2018-04-01

The origin of sedimentary dolomite and the factors that control its formation within the geological record remain speculative. In most models, dolomite formation is linked to evaporative conditions, high water temperature, increasing Mg/Ca ratio, increasing alkalinity, and high amounts of biomass. Here we challenge these archetypal views, by documenting a case example of Quaternary dolomite which formed in Lake Van at constantly low temperature (<4°C) and without direct control of the latter conditions. Dolomite occurs within highstand sediments related to suborbital climate variability (Dansgaard-Oeschger cycles). We propose that dolomite precipitation is a product of a microbially influenced process, triggered by ecological stress, resulting from reventilation of the water-sediment interface. Independently from the validity of this hypothesis, our results call for a reevaluation of the paleoenvironmental conditions often invoked for early diagenetic dolomite-rich intervals within sedimentary sequences and for caution when interpreting time series of subrecent lacustrine carbonates.

Glacial-Interglacial, Orbital and Millennial-Scale Climate Variability for the Last Glacial Cycle at Shackleton Site U1385 based on Dinoflagellate Cysts

NASA Astrophysics Data System (ADS)

Datema, M.

2015-12-01

The Shackleton Site (IODP Expedition 339 Site U1385), located off the West-Portuguese Margin, preserves a continuous high-fidelity record of millennial-scale climate variability for the last several glacial cycles (~1.4 Myr) that can be correlated precisely to patterns observed in polar ice cores. In addition, rapid delivery of terrestrial material to the deep-sea environment allows the correlation of these marine records to European terrestrial climate records. This unique marine-ice-terrestrial linkage makes the Shackleton Site the ideal reference section for studying Quaternary abrupt climate change. The main objective of studying Site U1385 is to establish a marine reference section of Pleistocene climate change. We generated (sub)millennial-scale (~600 year interval) dinoflagellate cyst (dinocyst) assemblage records from Shackleton Site U1385 (IODP Expedition 339) to reconstruct sea surface temperature (SST) and productivity/upwelling over the last 152 kyrs. In addition, our approach allows for detailed land-sea correlations, because we also counted assemblages of pollen and spores from higher plants. Dinocyst SST and upwelling proxies, as well as warm/cold pollen proxies from Site U1385 show glacial-interglacial, orbital and stadial-interstadial climate variability and correlate very well to Uk'37, planktic foraminifer δ18O and Ca/Ti proxies of previously drilled Shackleton Sites and Greenland Ice Core δ18O. The palynological proxies capture (almost) all Dansgaard-Oeschger events of the last glacial cycle, also before ~70 ka, where millennial-scale variability is overprinted by precession. We compare the performance and results of the palynology of Site U1385 to proxies of previously drilled Shackleton Sites and conclude that palynology strengthens the potential of this site to form a multi-proxy reference section for millennial scale climate variability across the Pleistocene-Holocene. Finally, we will present a long-term paleoceanographic perspective down to ~150 ka.

Insights from a synthesis of old and new climate-proxy data from the Pyramid and Winnemucca lake basins for the period 48 to 11.5 cal ka

USGS Publications Warehouse

Benson, Larry; Smoot, J.P.; Lund, S.P.; Mensing, S.A.; Foit, F.F.; Rye, R.O.

2013-01-01

A synthesis of old and new paleoclimatic data from the Pyramid and Winnemucca lake basins indicates that, between 48.0 and 11.5·103 calibrated years BP (hereafter ka), the climate of the western Great Basin was, to a degree, linked with the climate of the North Atlantic. Paleomagnetic secular variation (PSV) records from Pyramid Lake core PLC08-1 were tied to the GISP2 ice-core record via PSV matches to North Atlantic sediment cores whose isotopic and(or) carbonate records could be linked to the GISP2 δ18O record. Relatively dry intervals in the western Great Basin were associated with cold Heinrich events and relatively wet intervals were associated with warm Dansgaard-Oeschger (DO) oscillations. The association of western Great Basin dry events with North Atlantic cold events (and vice versa) switched sometime after the Laurentide Ice Sheet (LIS) reached its maximum extent. For example, the Lahontan highstand, which culminated at 15.5 ka, and a period of elevated lake level between 13.1 and 11.7 ka were associated with cold North Atlantic conditions, the latter period with the Youngest Dryas event. Relatively dry periods were associated with the Bølling and Allerød warm events. A large percentage of the LIS may have been lost to the North Atlantic during Heinrich events 1 and 2 and may have resulted in the repositioning of the Polar Jet Stream over North America. The Trego Hot Springs, Wono, Carson Sink, and Marble Bluff tephras found in core PLC08-1 have been assigned GISP2 calendar ages of respectively, 29.9, 33.7, 34.1, and 43.2 ka. Given its unique trace-element chemistry, the Carson Sink Bed is the same as Wilson Creek Ash 15 in the Mono Lake Basin. This implies that the Mono Lake magnetic excursion occurred at approximately 34 ka and it is not the Laschamp magnetic excursion. The entrance of the First Americans into the northern Great Basin is dated to approximately 14.4 ka, a time when the climate was relatively dry. Evidence for human occupation of the Great Basin is lacking for the next 1100 years (y); i.e., the oldest western stemmed point site in the Great Basin dates to 13.3 ka. Two hypotheses are suggested for this cultural hiatus: (1) the climate had deteriorated to the point that people vacated the Great Basin, or (2) people moved to basin-bottom wetlands that persisted during the dry period, and then the subsequent Younger Dryas wet event erased the archaeological evidence deposited around the low-elevation wetland sites.

Global Implications of late Pleistocene Megafaunal Extinctions in the Holarctic

NASA Astrophysics Data System (ADS)

Cooper, Alan; Turney, Chris

2017-04-01

Improved resolution data from radiocarbon, climate and ancient DNA studies of megafauna and humans is providing the first ability to disentangle the roles of climate change and human impact in the Late Pleistocene megafaunal extinctions. In the Holarctic we find that megafaunal populations underwent repeated local or global extinctions apparently associated with abrupt, centennial to millennial duration warming events (Dansgaard-Oeschger interstadials). Importantly, the extinction events took place both before and after the arrival of modern humans in the landscape. Here we look at the possible role of human activity in Holarctic and suggest it may be through the disruption of metapopulation processes which stabilize ecosystems and may have evolved to provide resilience to rapid and frequent climate shifts in the past. The observed relationship between climate and humans on megafaunal populations may provide a model for global extinction. Fortunately in this regard, the rapid movement of the first Native Americans throughout both American continents during the Last Deglaciation provides a powerful and unique model system for testing the competing roles on extinction because the opposing climate trends in each hemisphere at the time. Here we show that while megafaunal extinctions were associated with warming trends in both cases, the out-of-phase climate patterns caused the sequence and timing of events to be mirrored, providing a unique high-resolution view of the interactions of human colonization and rapid climate change on megafaunal ecosystems, with implications for future warming scenarios. References: Cooper, A., Turney, C., Hughen, K.A., Brook, B.W., McDonald, H.G., Bradshaw, C.J.A., 2015. Abrupt warming events drove Late Pleistocene Holarctic megafaunal turnover. Science 349, 602-606. Metcalf, J.L., Turney, C., Barnett, R., Martin, F., Bray, S.C., Vilstrup, J.T., Orlando, L., Salas-Gismondi, R., Loponte, D., Medina, M., De Nigris, M., Civalero, T., Fernández, P.M., Gasco, A., Duran, V., Seymour, K.L., Otaola, C., Gil, A., Paunero, R., Prevosti, F.J., Bradshaw, C.J.A., Wheeler, J.C., Borrero, L., Austin, J.J., Cooper, A., 2016. Synergistic roles of climate warming and human occupation in Patagonian megafaunal extinctions during the Last Deglaciation. Science Advances 2, doi: 10.1126/sciadv.1501682.

Paleomagnetism and environmental magnetism of GLAD800 sediment cores from Bear Lake, Utah and Idaho

USGS Publications Warehouse

Heil, C.W.; King, J.W.; Rosenbaum, J.G.; Reynolds, R.L.; Colman, Steven M.

2009-01-01

A ???220,000-year record recovered in a 120-m-long sediment core from Bear Lake, Utah and Idaho, provides an opportunity to reconstruct climate change in the Great Basin and compare it with global climate records. Paleomagnetic data exhibit a geomagnetic feature that possibly occurred during the Laschamp excursion (ca. 40 ka). Although the feature does not exhibit excursional behavior (???40?? departure from the expected value), it might provide an additional age constraint for the sequence. Temporal changes in salinity, which are likely related to changes in freshwater input (mainly through the Bear River) or evaporation, are indicated by variations in mineral magnetic properties. These changes are represented by intervals with preserved detrital Fe-oxide minerals and with varying degrees of diagenetic alteration, including sulfidization. On the basis of these changes, the Bear Lake sequence is divided into seven mineral magnetic zones. The differing magnetic mineralogies among these zones reflect changes in deposition, preservation, and formation of magnetic phases related to factors such as lake level, river input, and water chemistry. The occurrence of greigite and pyrite in the lake sediments corresponds to periods of higher salinity. Pyrite is most abundant in intervals of highest salinity, suggesting that the extent of sulfidization is limited by the availability of SO42-. During MIS 2 (zone II), Bear Lake transgressed to capture the Bear River, resulting in deposition of glacially derived hematite-rich detritus from the Uinta Mountains. Millennial-scale variations in the hematite content of Bear Lake sediments during the last glacial maximum (zone II) resemble Dansgaard-Oeschger (D-O) oscillations and Heinrich events (within dating uncertainties), suggesting that the influence of millennial-scale climate oscillations can extend beyond the North Atlantic and influence climate of the Great Basin. The magnetic mineralogy of zones IV-VII (MIS 5, 6, and 7) indicates varying degrees of post-depositional alteration between cold and warm substages, with greigite forming in fresher conditions and pyrite in the more saline conditions. Copyright ?? 2009 The Geological Society of America.

Climate Stability: Pathway to understand abrupt glacial climate shifts

NASA Astrophysics Data System (ADS)

Zhang, X.; Knorr, G.; Barker, S.; Lohmann, G.

2017-12-01

Glacial climate is marked by abrupt, millennial-scale climate changes known as Dansgaard-Oeschger (DO) cycles that have been linked to variations in the Atlantic meridional overturning circulation (AMOC). The most pronounced stadial coolings, Heinrich Stadials (HSs), are associated with massive iceberg discharges to the North Atlantic. This motivates scientists to consider that the North Atlantic freshwater perturbations is a common trigger of the associated abrupt transitions between weak and strong AMOC states. However, recent studies suggest that the Heinrich ice-surging events are triggered by ocean subsurface warming associated with an AMOC slow-down. Furthermore, the duration of ice-rafting events does not systematically coincide with the beginning and end of the pronounced cold conditions during HSs. In this context, we show that both, changes in atmospheric CO2 and ice sheet configuration can provide important control on the stability of the AMOC, using a coupled atmosphere-ocean model. Our simulations reveal that gradual changes in Northern Hemisphere ice sheet height and atmospheric CO2 can act as a trigger of abrupt glacial/deglacial climate changes. The simulated global climate responses—including abrupt warming in the North Atlantic, a northward shift of the tropical rain belts, and Southern Hemisphere cooling related to the bipolar seesaw—are generally consistent with empirical evidence. We further find that under a delicate configuration of atmospheric CO2 and ice sheet height the AMOC can be characterized by a self-oscillation (resonance) feature (Hopf Bifucation) with a 1000-year cycle that is comparable with observed small DO events during the MIS 3. This provides an alternative explanation for millennial-scale DO variability during glacial periods.

Astronomically calibrated 40Ar/39Ar age for the Toba supereruption and global synchronization of late Quaternary records

NASA Astrophysics Data System (ADS)

Storey, Michael; Roberts, Richard G.; Saidin, Mokhtar

2012-11-01

The Toba supereruption in Sumatra, ∼74 thousand years (ka) ago, was the largest terrestrial volcanic event of the Quaternary. Ash and sulfate aerosols were deposited in both hemispheres, forming a time-marker horizon that can be used to synchronize late Quaternary records globally. A precise numerical age for this event has proved elusive, with dating uncertainties larger than the millennial-scale climate cycles that characterized this period. We report an astronomically calibrated 40Ar/39Ar age of 73.88 ± 0.32 ka (1σ, full external errors) for sanidine crystals extracted from Toba deposits in the Lenggong Valley, Malaysia, 350 km from the eruption source and 6 km from an archaeological site with stone artifacts buried by ash. If these artifacts were made by Homo sapiens, as has been suggested, then our age indicates that modern humans had reached Southeast Asia by ∼74 ka ago. Our 40Ar/39Ar age is an order-of-magnitude more precise than previous estimates, resolving the timing of the eruption to the middle of the cold interval between Dansgaard-Oeschger events 20 and 19, when a peak in sulfate concentration occurred as registered by Greenland ice cores. This peak is followed by a ∼10 °C drop in the Greenland surface temperature over ∼150 y, revealing the possible climatic impact of the eruption. Our 40Ar/39Ar age also provides a high-precision calibration point for other ice, marine, and terrestrial archives containing Toba sulfates and ash, facilitating their global synchronization at unprecedented resolution for a critical period in Earth and human history beyond the range of 14C dating.

Astronomically calibrated 40Ar/39Ar age for the Toba supereruption and global synchronization of late Quaternary records.

PubMed

Storey, Michael; Roberts, Richard G; Saidin, Mokhtar

2012-11-13

The Toba supereruption in Sumatra, ∼74 thousand years (ka) ago, was the largest terrestrial volcanic event of the Quaternary. Ash and sulfate aerosols were deposited in both hemispheres, forming a time-marker horizon that can be used to synchronize late Quaternary records globally. A precise numerical age for this event has proved elusive, with dating uncertainties larger than the millennial-scale climate cycles that characterized this period. We report an astronomically calibrated (40)Ar/(39)Ar age of 73.88 ± 0.32 ka (1σ, full external errors) for sanidine crystals extracted from Toba deposits in the Lenggong Valley, Malaysia, 350 km from the eruption source and 6 km from an archaeological site with stone artifacts buried by ash. If these artifacts were made by Homo sapiens, as has been suggested, then our age indicates that modern humans had reached Southeast Asia by ∼74 ka ago. Our (40)Ar/(39)Ar age is an order-of-magnitude more precise than previous estimates, resolving the timing of the eruption to the middle of the cold interval between Dansgaard-Oeschger events 20 and 19, when a peak in sulfate concentration occurred as registered by Greenland ice cores. This peak is followed by a ∼10 °C drop in the Greenland surface temperature over ∼150 y, revealing the possible climatic impact of the eruption. Our (40)Ar/(39)Ar age also provides a high-precision calibration point for other ice, marine, and terrestrial archives containing Toba sulfates and ash, facilitating their global synchronization at unprecedented resolution for a critical period in Earth and human history beyond the range of (14)C dating.

Centennial-to-millennial scale climate change during the last 100,000 years: a Southern Hemisphere perspective

NASA Astrophysics Data System (ADS)

van den Bos, Valerie; Rees, Andrew; Newnham, Rewi; Augustinus, Paul

2017-04-01

The response of past terrestrial ecosystems to abrupt climate change is central to the debate surrounding the consequences of future climate change. Many centennial-to-millennial scale episodes of rapid change over the past 117,000 years have been reported, notably the Dansgaard-Oeschger events of Greenland and the North Atlantic and Antarctic Isotope Maxima. Best expressed in past climate records from the polar and tropical regions, the timing, amplitude and duration of these changes are variable on a global scale, and it is unclear how the events are generated and transmitted to cause such asynchronous patterns. The southern mid-latitudes form a poorly understood piece of the puzzle. Our Marsden-funded project aims to increase understanding of the New Zealand climate system in relation to global patterns over the last 100 kyr by developing high-resolution climate records from the lake sediments contained within Auckland's maars. These crater lakes are unique, because their sediments are laminated throughout and the sedimentation rate is very high. Additionally, the numerous (>50) volcanic ash layers contained within the sediments act as anchor points in our chronologies. We have adopted a multiproxy approach that combines data from biotic, molecular biomarker isotope and geochemical analyses. The remit of my doctorate is to produce two independent, but complementary, temperature reconstructions from chironomid remains (mean summer temperatures) and pollen (mean annual temperatures) from Lake Pupuke sediments. This approach will eventually help us to address whether abrupt climate change events or changes in seasonality influenced climate and biota over the past 100,000 years in northern New Zealand, and whether these changes were driven by triggers from the North Atlantic, Antarctica or the tropics.

Influence of external forcings on abrupt millennial-scale climate changes: a statistical modelling study

NASA Astrophysics Data System (ADS)

Mitsui, Takahito; Crucifix, Michel

2017-04-01

The last glacial period was punctuated by a series of abrupt climate shifts, the so-called Dansgaard-Oeschger (DO) events. The frequency of DO events varied in time, supposedly because of changes in background climate conditions. Here, the influence of external forcings on DO events 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 warming 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 warming 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 abrupt 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 abrupt millennial-scale climate changes in older glacial periods (MISs 6, 8, and 10) might be larger than inferred from the SST record.

The effect of millennial-scale changes in Arabian Sea denitrification on atmospheric CO2.

PubMed

Altabet, Mark A; Higginson, Matthew J; Murray, David W

2002-01-10

Most global biogeochemical processes are known to respond to climate change, some of which have the capacity to produce feedbacks through the regulation of atmospheric greenhouse gases. Marine denitrification-the reduction of nitrate to gaseous nitrogen-is an important process in this regard, affecting greenhouse gas concentrations directly through the incidental production of nitrous oxide, and indirectly through modification of the marine nitrogen inventory and hence the biological pump for CO2. Although denitrification has been shown to vary with glacial-interglacial cycles, its response to more rapid climate change has not yet been well characterized. Here we present nitrogen isotope ratio, nitrogen content and chlorin abundance data from sediment cores with high accumulation rates on the Oman continental margin that reveal substantial millennial-scale variability in Arabian Sea denitrification and productivity during the last glacial period. The detailed correspondence of these changes with Dansgaard-Oeschger events recorded in Greenland ice cores indicates rapid, century-scale reorganization of the Arabian Sea ecosystem in response to climate excursions, mediated through the intensity of summer monsoonal upwelling. Considering the several-thousand-year residence time of fixed nitrogen in the ocean, the response of global marine productivity to changes in denitrification would have occurred at lower frequency and appears to be related to climatic and atmospheric CO2 oscillations observed in Antarctic ice cores between 20 and 60 kyr ago.

Abrupt glacial climate shifts controlled by ice sheet changes.

PubMed

Zhang, Xu; Lohmann, Gerrit; Knorr, Gregor; Purcell, Conor

2014-08-21

During glacial periods of the Late Pleistocene, an abundance of proxy data demonstrates the existence of large and repeated millennial-scale warming episodes, known as Dansgaard-Oeschger (DO) events. 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 events. The simulated global climate responses--including abrupt warming 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 abrupt climate changes in the coupled atmosphere-ocean system, as well as their linkages to the volume of the intermediate ice sheets during glacials.

Pink marine sediments reveal rapid ice melt and Arctic meltwater discharge during Dansgaard-Oeschger warmings.

PubMed

Rasmussen, Tine L; Thomsen, Erik

2013-01-01

The climate of the last glaciation was interrupted by numerous abrupt temperature fluctuations, referred to as Greenland interstadials and stadials. During warm interstadials the meridional overturning circulation was active transferring heat to the north, whereas during cold stadials the Nordic Seas were ice-covered and the overturning circulation was disrupted. Meltwater discharge, from ice sheets surrounding the Nordic Seas, is implicated as a cause of this ocean instability, yet very little is known regarding this proposed discharge during warmings. Here we show that, during warmings, pink clay from Devonian Red Beds is transported in suspension by meltwater from the surrounding ice sheet and replaces the greenish silt that is normally deposited on the north-western slope of Svalbard during interstadials. The magnitude of the outpourings is comparable to the size of the outbursts during the deglaciation. Decreasing concentrations of ice-rafted debris during the interstadials signify that the ice sheet retreats as the meltwater production increases.

Controls on the East Asian monsoon during the last glacial cycle, based on comparison between Hulu Cave and polar ice-core records

NASA Astrophysics Data System (ADS)

Rohling, E. J.; Liu, Q. S.; Roberts, A. P.; Stanford, J. D.; Rasmussen, S. O.; Langen, P. L.; Siddall, M.

2009-12-01

Previous studies have suggested a sound chronological correlation between the Hulu Cave record (East Asian monsoon) and Greenland ice-core records, which implies a dominant control of northern hemisphere climate processes on monsoon intensity. We present an objective, straightforward statistical evaluation that challenges this generally accepted paradigm for sub-orbital variability. We propose a more flexible, global interpretation, which takes into account a broad range of variability in the signal structures in the Hulu Cave and polar ice-core records, rather than a limited number of major transitions. Our analysis employs the layer-counted Greenland Ice-Core Chronology 2005 (GICC05), which was developed for Greenland records and has since been applied - via methane synchronisation - to the high-resolution δ 18O ice series from EPICA Dronning Maud Land (EDML). The GICC05 chronology allows these ice-core records to be compared to the U-Th dated Hulu Cave record within relatively narrow (˜3%) bounds of age uncertainty. Following previous suggestions, our proposed interpretation suggests that the East Asian monsoon is influenced by a combination of northern hemisphere 'pull' (which is more intense during boreal warm periods), and southern hemisphere 'push' (which is more intense monsoon during austral cold periods). Our analysis strongly suggests a dominant control on millennial-scale monsoon variability by southern hemisphere climate changes during glacial times when the monsoon is weak overall, and control by northern hemisphere climate changes during deglacial and interglacial times when the monsoon is strong. The deduced temporally variable relationship with southern hemisphere climate records offers a statistically more plausible reason for the apparent coincidence of major East Asian monsoon transitions with northern hemisphere (Dansgaard-Oeschger, DO) climate events during glacial times, than the traditional a priori interpretation of strict northern hemisphere control.

Temperature variations in Greenland from 10 to 110 kyr b2k derived from the NGRIP ice core

NASA Astrophysics Data System (ADS)

Kindler, Philippe; Leuenberger, Markus; Landais, Amaelle; Guillevic, Myriam

2013-04-01

During the last ice age dramatic temperature variations of up to 16 °C took place in Greenland which are now known as Dansgaard-Oeschger-events (DO-events). They most probably originate from the North Atlantic oceanic and atmospheric circulation system and are characterised by an abrupt warming within decades followed by a gradual cooling over hundreds to thousands of years. We have determined local temperature variations for DO-event 1 to 25 in Greenland based on δ15N measurements from the NorthGRIP ice core, corresponding to the period from 10 to 110 kyr b2k. The record is a composite of measurements from two laboratories, Laboratoire des Sciences du Climat et de l'Environnement, Paris (DO 18 to 25) and the Climate and Environmental Physics Division of the Physics Institute of the University of Bern (DO 1 to 17) with new measurements from the beginning of the Holocene to DO 8. Temperature variations were reconstructed by reproducing the measured 15N/14N ratio of air enclosed in ice bubbles by the firn densification and heat diffusion model from Schwander. The reconstruction show temperature amplitudes for the DO-events ranging from 5 to 16 °C, thereby the corresponding rates of change can exceed 0.5 °C/decade. In order get an agreement between measured δ15N, Δdepth and Δage values with their modelled analogues, a lower accumulation rate than the one associated with the used ss09sea06bm1 time scale had to be assumed. We had to reduce the accumulation rate time dependently by 0 to nearly 40% with a mean reduction over the whole time period of 16%. With these adjustments both the Δdepth and the Δage values agree between model and measurements.

Orbital- and Millennial-Scale Changes in the Australasian Monsoon over the Last 470,000 Years

NASA Astrophysics Data System (ADS)

Gagan, M. K.; Ayliffe, L.; Drysdale, R.; Zhao, J.; Griffiths, M. L.; Hellstrom, J.; Dunbar, G.; Hantoro, W.; Edwards, R.; Cheng, H.; Suwargadi, B.

2011-12-01

Speleothem 18O/16O records from China have revealed changes in East Asian monsoon rainfall over the last ~390,000 years (e.g. Wang et al. 2008, Cheng et al. 2010), yet little is known about orbital- and millennial-scale climate change in the 'southern half' of the Australasian monsoon domain. To fill this gap, we aim to build speleothem 18O/16O records for the seasonal monsoon rainfall belt of south-central Indonesia. Between 2006 and 2009, we sampled speleothems in Flores and southwest Sulawesi (latitudes 5-9 S) with U-series ages extending to ~90,000 yBP and ~470,000 yBP, respectively. Development of the 18O/16O records for Sulawesi is in progress, but the basal ages of the speleothems (onset of stalagmite growth) are intriguing because they cluster around glacial terminations, when the East Asian monsoon is known to have been weak (Cheng et al. 2010). There is clear antiphasing of the Flores and China speleothem 18O/16O records on precession time-scales over the last ~90,000 years. A distinct maximum in monsoon rainfall in Flores occurred ~21,000 yBP, suggesting the ITCZ moved south during the Last Glacial Maximum in response to the southern hemisphere summer insolation maximum. This important finding indicates that ITCZ positioning in tropical Australasia, through its influence on large-scale oceanic-atmospheric circulation, could have played a key role in the rapid rise of atmospheric CO2 and global warming that ultimately led to the demise of the ice age, as summarised by Denton et al. (2010) and others. The new Flores speleothem 18O/16O records also show that climate change in the North Atlantic region and Australasian monsoon rainfall are inextricably linked on millennial timescales (Griffiths et al. 2009, Lewis et al. 2011). For example, rapid warming in the North Atlantic region during Dansgaard-Oeschger Event 21 (~86,000 yBP) was linked to a synchronous northward shift of the Australasian ITCZ, marking the final demise of MIS 5b. In contrast, cooling in the North Atlantic during Heinrich Events 3 (~30,000 yBP) and 1 (~16,000 yBP) and the YD (12,800-11,500 yBP) correlates with southward shifts in the Australasian ITCZ. However, the 8,200 yBP cold snap in the North Atlantic produced drying and cooling around Flores. The key difference here is that sea level was relatively high, and cooler sea-surface temperatures in the Indonesian maritime continent at that time (based on nearby coral records) may have suppressed a southward migration of the ITCZ. Cheng, H. et al. (2010), Science, 326, 248-. Denton, G.H. et al. (2010), Science, 328, 1652-. Griffiths, M.L. et al. (2009), Nature Geoscience, 2, 636-. Lewis, S.C. et al. (2011), Earth Planet. Sci. Lett., 303, 133-. Wang, Y. et al. (2008), Nature, 451, 1090-.

Patterns of Late Quaternary hydrologic variability and atmospheric change inferred from a Northern California speleothem

NASA Astrophysics Data System (ADS)

Oster, J. L.; Weisman, I. E.; Sharp, W. D.; Ibarra, D. E.

2017-12-01

The synthesis of hydrologically sensitive proxy records across western North America reveals spatial patterns of variability that persist, with some variation, over multiple temporal scales. For example, tree ring records from the last century highlight a distinct north-south dipole pattern in the response of regional precipitation anomalies to ENSO and the PDO, while a similar dipole pattern of wet and dry precipitation anomalies developed across the region in response to climate forcing at the Last Glacial Maximum (LGM). Hydrologically sensitive proxy records from the intervening transition zone can shed light on the stationarity and spatial scale of this pattern over time. Here we present records of δ18O and δ13C from a Lake Shasta Caverns stalagmite (LSC3) from Northern California that grew from 36 to 14 ka. This cave, located at 40.8°N, is situated within the transition zone and is well-positioned to enhance our understanding of regional precipitation patterns and moisture transport variability during the last glacial period and deglaciation. Six years of weekly rain isotope data indicate that varying atmospheric temperatures and moisture sources are primary controls on δ18O in Northern California precipitation. Increased δ18O and δ13C in LSC3 and slower stalagmite growth rates during MIS 2 suggest increased subtropical moisture but also dry conditions in Northern California. The δ13C record displays distinct millennial-scale oscillations during MIS 3, suggesting drier conditions also occurred during interstadials associated with Dansgaard-Oeschger cycles. The LSC3 δ18O record documents changes synchronous with δ18O in the Fort Stanton stalagmite in New Mexico, though sometimes in phase (e.g. during Heinrich Stadial 1; HS1) and sometimes anti-phased (e.g. during the Bölling-Alleröd). Likewise, the LSC3 δ13C record suggests a transition from wet to drier conditions during HS1 in marked contrast to many more southerly records that indicate wetter conditions later in HS1. These comparisons show that changes in Northern California climate were both in and out of phase with hydroclimate variations occurring to the south and southeast. Thus, the LSC3 record refines our understanding of spatial patterns of hydroclimatic change in western North America.

The impact of Last Glacial climate variability in west-European loess revealed by radiocarbon dating of fossil earthworm granules.

PubMed

Moine, Olivier; Antoine, Pierre; Hatté, Christine; Landais, Amaëlle; Mathieu, Jérôme; Prud'homme, Charlotte; Rousseau, Denis-Didier

2017-06-13

The characterization of Last Glacial millennial-timescale warming phases, known as interstadials or Dansgaard-Oeschger events, requires precise chronologies for the study of paleoclimate records. On the European continent, such chronologies are only available for several Last Glacial pollen and rare speleothem archives principally located in the Mediterranean domain. Farther north, in continental lowlands, numerous high-resolution records of loess and paleosols sequences show a consistent environmental response to stadial-interstadial cycles. However, the limited precision and accuracy of luminescence dating methods commonly used in loess deposits preclude exact correlations of paleosol horizons with Greenland interstadials. To overcome this problem, a radiocarbon dating protocol has been developed to date earthworm calcite granules from the reference loess sequence of Nussloch (Germany). Its application yields a consistent radiocarbon chronology of all soil horizons formed between 47 and 20 ka and unambiguously shows the correlation of every Greenland interstadial identified in isotope records with specific soil horizons. Furthermore, eight additional minor soil horizons dated between 27.5 and 21 ka only correlate with minor decreases in Greenland dust records. This dating strategy reveals the high sensitivity of loess paleoenvironments to Northern Hemisphere climate changes. A connection between loess sedimentation rate, Fennoscandian ice sheet dynamics, and sea level changes is proposed. The chronological improvements enabled by the radiocarbon "earthworm clock" thus strongly enhance our understanding of loess records to a better perception of the impact of Last Glacial climate changes on European paleoenvironments.

Polar synchrony and the climatic history of Antarctica deduced from Greenland's

NASA Astrophysics Data System (ADS)

Oh, J.; Rial, J. A.; Reischmann, E.

2012-12-01

Polar synchronization brings new insights into the dynamic processes that link Greenland's Dansgaard-Oeschger (DO) abrupt temperature fluctuations to Antarctic temperature variability. The term synchronization as used here describes how two or more coupled nonlinear oscillators adjust their (initially different) natural rhythms to a common frequency and constant relative phase. It is shown that, consistent with the presence of polar synchronization, the time series of the most representative abrupt climate events of the last glaciation recorded in Greenland and Antarctica can be transformed into one another by a pi/2 phase shift at millennial scale, with Antarctica temperature variations leading Greenland's. For this study we employ Van der Pol Synchronizing Oscillators model to simulate Antarctic temperature proxy based on the synchronized relationship between two poles for the last 800ky after removing ~100ky glaciation cycles. The separated long period (~100ky) signal is reproduced by frequency modulation. As separation techniques, Singular Spectrum Analysis and Empirical Mode Decomposition are adopted and decomposed long period signals are compared with them from linear filter. It is shown that remarkable close simulations of Antarctic temperature proxy are obtained with a model consisting of a few nonlinear differential equations especially when coupling terms have strong effects. This, plus the close reproduction of glaciation cycles by frequency modulation suggests the intriguing possibility that there are simple rules governing the complex behavior of global paleoclimate such as heat and mass transfer through the intervening ocean and atmosphere.

Dansgaard-Oeschger cycles observed in the Greenland ReCAP ice core project

NASA Astrophysics Data System (ADS)

Kjær, Helle Astrid; Vallelonga, Paul; Vinther, Bo; Simonsen, Marius; Maffezzoli, Niccoló; Gkinis, Vasileios; Svensson, Anders; Jensen, Camilla Marie; Dallmayr, Remi; Spolaor, Andrea; Edwards, Ross

2017-04-01

The new REnland ice CAP (RECAP) ice core was drilled in summer 2015 in Greenland and measured by means of Continuous flow analysis (CFA) during the last 3 months of 2015. The Renland ice core was obtained as part of the ReCAP project, extending 584.11 meters to the bottom of the Renland ice cap located in east Greenland. The unique position on a mountain saddle above 2000 meters altitude, but close to the coast, ensures that the Renland ice core offers high accumulation, but also reaches far back in time. Results show that despite the short length the RECAP ice core holds ice all the way back to the past warm interglacial period, the Eemian. The glacial section is strongly thinned and covers on 20 meters of the ReCAP core, but nonetheless due to the high resolution of the measurements all 25 expected DO events could be identified. The record was analyzed for multiple elements including the water isotopes, forest fire tracers NH4+ and black carbon, insoluble dust particles by means of Abakus laser particle counter and the dust ion Ca2+, sea salt Na+, and sea ice proxies as well as acidity useful for finding volcanic layers to date the core. Below the glacial section another 20 meters of warm Eemian ice have been analysed. Here we present the chemistry results as obtained by continuous flow analysis (CFA) and compare the glacial section with the chemistry profile from other Greenland ice cores.

A lacustrine record from Lop Nur, Xinjiang, China: Implications for paleoclimate change during Late Pleistocene

USGS Publications Warehouse

Chao, L.; Zicheng, P.; Dong, Y.; Weiguo, L.; Zhaofeng, Z.; Jianfeng, H.; Chenlin, C.

2009-01-01

Climate variability during the Late Pleistocene is studied from the proxies in core CK-2 drilled from the Luobei Depression (91??03???E, 40??47???N), Lop Nur in the eastern Tarim Basin, Xinjiang, China. Geophysical and geochemical properties, including magnetic susceptibility, granularity, chroma, carbonate content, loss on ignition and trace elements, have been determined to reconstruct the environmental evolution of the area during 32-9 ka BP. The chronology is established by uranium-thorium disequilibrium dating techniques. Our data suggest four paleoclimate stages, indicating glacial variations between cold-humid and warm-arid environments. A period of extreme humidity occurred during 31,900-19,200 yr BP is attributed the last glacial maximum (LGM). The period was followed by a warm-arid episode during 19,200-13,500 yr BP. Then a cold-humid interval during 13,500-12,700 yr BP may correspond to another cooling phases at high latitudes of the Northern Hemisphere. The last stage from 12,700 to 9000 yr BP has a trend that the climate turned warm and arid. The Lop Nur region is characterized by particularly humid stadials and arid interstadials. The climate variability in Lop Nur was constrained by global climate change because it is correlated with Dansgaard-Oeschger and Heinrich events, which were observed at the northern high latitudes. The synchroneity of the palaeoclimatic events suggested that cold air activity at the northern high latitudes was the most important factor that influenced the climate evolution in the Lop Nur region. A probable mechanism that involves the migration of westerly winds is proposed to interpret this synchroneity. ?? 2008 Elsevier Ltd.

A 62 ka record from the WAIS Divide ice core with annual resolution to 30 ka (so far)

NASA Astrophysics Data System (ADS)

Fudge, T. J.; Taylor, K.; McGwire, K.; Brook, E.; Sowers, T.; Steig, E.; White, J.; Vaughn, B.; Bay, R.; McConnell, J.; Waddington, E.; Conway, H.; Clow, G.; Cuffey, K.; Cole-Dai, J.; Ferris, D.; Severinghaus, J.

2012-04-01

Drilling of the West Antarctic Ice Sheet (WAIS) Divide ice core has been completed to a depth of 3400 m, about 60 meters above the bed. We present an annually resolved time scale for the most recent 30ka (to 2800 m) based on electrical conductivity measurements, called "timescale WDC06A-5". Below 2800 m the ice is dated by matching isotopes, methane, and/or dust records to other ice cores. Optical borehole logging provides stratigraphic ties to other cores for the bottom-most 75 m that was drilled in December 2011, and indicates the bottom-most ice has an age of 62 ka. The relatively young ice at depth is likely the result of basal melting. The inferred annual layer thickness of the deep ice is >1 cm, suggesting that annual layer counting throughout the entire core may be possible with continuous flow analysis of the ice core chemistry; however, the annual signal in the electrical measurements fades at about 30 ka. We compare the WDC06A-5 timescale through the glacial-interglacial transition with the Greenland GICC05 and GISP2 timescales via rapid variations in methane. We calculate a preliminary delta-age with: 1) accumulation rate inferred from the annual layer thicknesses and thinning functions computed with a 1-D ice flow model, and 2) surface temperature inferred from the low resolution d18O record and a preliminary borehole temperature profile. The WDC06A-5 timescale agrees with the GICC05 and GISP2 timescales to within decades at the 8.2k event and the ACR termination (Younger Dryas/Preboreal transition, 11.7 ka). This is within the delta-age and correlation uncertainties. At the rapid methane drop at ~12.8 ka, the WDC06A-5 timescale is ~150 years older than GICC05 and ~90 older than GISP2; while at ~14.8 ka, the timescales once again agree within the delta-age and correlation uncertainties. The cause of the age discrepancy at 12.8 ka is unclear. We also compare the WDC06A-5 timescale at Dansgaard-Oeschger events 3 and 4 (~27.5 and 29 ka) to the radiometrically-dated speolethem records from Hulu Cave, China (Larry Edwards and Hai Cheng, personal communication). To make such a comparison, we assume that the rapid variations in methane from the WAIS Divide core are synchronous with the rapid variations in d18O in the speleothem record. We find that the WDC06A-5 timescale is multiple hundreds of years older than the Hulu Cave record. As the GICC05 timescale is younger than the Hulu timescale, this puts the WDC06A-5 timescale even older than the GICC05. The uncertainties in the comparison are large both because of the uncertainty in the synchroneity of the ice core methane and speleothem isotope variations and because of the larger delta-age for the ice core in the glacial period. The timescale for the WAIS Divide core will be revised when the CFA results become available.

Atmospheric CO2 and abrupt climate change on submillennial timescales

NASA Astrophysics Data System (ADS)

Ahn, Jinho; Brook, Edward

2010-05-01

How atmospheric CO2 varies and is controlled on various time scales and under various boundary conditions is important for understanding how the carbon cycle and climate change are linked. Ancient air preserved in ice cores provides important information on past variations in atmospheric CO2. In particular, concentration records for intervals of abrupt climate change may improve understanding of mechanisms that govern atmospheric CO2. We present new multi-decadal CO2 records that cover Greenland stadial 9 (between Dansgaard-Oeschger (DO) events 8 and 9) and the abrupt cooling event at 8.2 ka. The CO2 records come from Antarctic ice cores but are well synchronized with Greenland ice core records using new high-resolution CH4 records,precisely defining the timing of CO2 change with respect to abrupt climate events in Greenland. Previous work showed that during stadial 9 (40~38 ka), CO2 rose by about 15~20 ppm over around 2,000 years, and at the same time temperatures in Antarctica increased. Dust proxies indicate a decrease in dust flux over the same period. With more detailed data and better age controls we now find that approximately half of the CO2 increase during stadial 9 occurred abruptly, over the course of decades to a century at ~39.6 ka. The step increase of CO2 is synchronous with a similar step increase of Antarctic isotopic temperature and a small abrupt change in CH4, and lags after the onset of decrease in dust flux by ~400 years. New atmospheric CO2 records at the well-known ~8.2 ka cooling event were obtained from Siple Dome ice core, Antarctica. Our preliminary CO2 data span 900 years and include 19 data points within the 8.2 ka cooling event, which persisted for ~160 years (Thomas et al., Quarternary Sci. Rev., 2007). We find that CO2 increased by 2~4 ppm during that cooling event. Further analyses will improve the resolution and better constrain the CO2 variability during other times in the early Holocene to determine if the variations observed during at 8.2 ka event are significant.

Past climate variability between 97 and 7 ka reconstructed from a multi proxy speleothem record from Western Cuba

NASA Astrophysics Data System (ADS)

Winterhalder, Sophie; Scholz, Denis; Mangini, Augusto; Spötl, Christoph; Jochum, Klaus Peter; Pajón, Jesús M.

2016-04-01

The tropical hydrological cycle plays a key role in regulating global climate, mainly through the export of heat and moisture to higher latitudes, and is highly sensitive to climate change, for instance due to changes in the position of the Intertropical Convergence Zone (ITCZ). Previous work on Caribbean stalagmites suggests a strong connection of precipitation variability to North Atlantic (NA) sea surface temperatures on multidecadal to millenial timescales (Fensterer et al., 2012; Fensterer et al., 2013; Winter et al., 2011). Cold phases in the NA potentially lead to a southward shift of the ITCZ and thus drier conditions in Cuba. On orbital timescales, Cuban stalagmites suggest a relation of speleothem δ18O values with the δ18O value of Caribbean surface waters (Fensterer et al., 2013). Here we present an expansion of the Cuban speleothem record covering the whole last glacial period from the end of MIS5c (97 ka BP) until 7 ka with hiatuses between 93-80 ka, 37-35 ka and 13-10 ka. Stalagmite Cuba medio (CM) has been precisely dated with 60 230Th/U-ages, mainly performed by the MC-ICPMS technique. The δ18O and δ13C records are completed by a continuous, high resolution LA-ICPMS trace element profile. These data allow for the first time to establish a multi-proxy climate reconstruction for the North Western Caribbean at decadal to centennial resolution for this period. The long-term variability of the δ18O values probably reflects rainfall amount in Cuba. The response to some Dansgaard/Oeschger and Heinrich stadials confirms the previously observed correlation between Caribbean and NA climate variability. However, this connection is not clearly imprinted throughout the record. Furthermore, trace elements, such as Mg, do not proof without ambiguity drier conditions in Cuba during NA cold events, such as the Heinrich stadials. This suggests that climate variability in Cuba was more complex during the last 100ka, and that the NA was not the only driving factor. Due to the competing influence of the NA, the Gulf of Mexico and the Pacific Ocean, the proposed severe changes in the tropical hydrological cycle during that time (such as variations of the ITCZ, insolation and the thermohaline circulation (THC)) have potentially lead to significant changes in sources and trajectories of precipitation in Western Cuba. Our record, thus, provides an important contribution towards understanding and differentiating these parameters on Caribbean climate during glacial climate changes. References: Fensterer, C., Scholz, D., Hoffmann, D., Spötl, C., Pajón, J.M., Mangini, A., 2012. Cuban stalagmite suggests relationship between Caribbean precipitation and the Atlantic Multidecadal Oscillation during the past 1.3 ka. The Holocene, 0959683612449759. Fensterer, C., Scholz, D., Hoffmann, D.L., Spötl, C., Schröder-Ritzrau, A., Horn, C., Pajón, J.M., Mangini, A., 2013. Millennial-scale climate variability during the last 12.5 ka recorded in a Caribbean speleothem. Earth and Planetary Science Letters 361, 143-151. Winter, A., Miller, T., Kushnir, Y., Sinha, A., Timmermann, A., Jury, M.R., Gallup, C., Cheng, H., Edwards, R.L., 2011. Evidence for 800years of North Atlantic multi-decadal variability from a Puerto Rican speleothem. Earth and Planetary Science Letters 308, 23-28.

Extending the application of deuterium excess as a tracer in surface and groundwaters

NASA Astrophysics Data System (ADS)

Hurst, S.; Krishnamurthy, R. V.

2017-12-01

Stable isotopes of surface and ground waters provide invaluable information on the processes involved in their genesis. A starting point in these applications is the relationship between hydrogen (δ2H) and oxygen (δ18O), exemplified in the so-called Global Meteoric Water Line where δ2H=8δ18O+10 [1]. From this line Dansgaard [2] defined the parameter deuterium excess where d=δ2H-8δ18O. Generally, the d-excess value is fixed at the source, predominantly the equatorial oceans and retained. At an average humidity of about 85% the expected d-excess value is 10. Deviations indicate secondary changes in the air mass or a water body thus making d-excess a useful geophysical tracer. For instance, evaporation results in a higher d-excess in the vapor. Mixing of this water vapor with overhead air mass results in precipitation exhibiting d-excess values higher than Global Meteoric Water Line [3]. Alternatively, the fraction of liquid remaining will have low d-excess and in extreme cases negative d-excess. In this case a plot of d-excess-δ2H will give a straight line with a negative slope. This can be demonstrated from pan evaporation experiments [4]. Deviation from a perfect straight line on the d-excess-δ2H plot indicates a combination of mixing from various source waters and evaporation. This study will discuss various case studies from multiple environments applying this approach using d-excess. References [1] Craig, H. Standard for Reporting Concentrations of Deuterium and Oxygen-18 in Natural Waters. Science 133, 1833-1834 (1961). [2] Dansgaard, W. Stable isotopes in precipitation. Tellus A 16: 436-468 (1964). [3] Machavaram, M. &, Krishnamurthy, R.V. Earth surface evaporative process: a case study from the Great Lakes region of the United States based on deuterium excess in precipitation. Geochim. et Cosmochem. Acta 59, 4279-4283 (1995). [4] Simpson, H.J., Hamza, M.S., & White, J.W.C. Evaporative enrichment of deuterium and 18O in arid zone irrigation. IAEA, 241-256 (1987).

Sub-Milankovitch millennial-scale climate variability in Middle Eocene deep-marine sediments

NASA Astrophysics Data System (ADS)

Scotchman, J. I.; Pickering, K. T.; Robinson, S. A.

2009-12-01

Sub-Milankovitch millennial scale climate variability appears ubiquitous throughout the Quaternary and Pleistocene palaeoenvironmental records (e.g. McManus et al., 1999) yet the driving mechanism remains elusive. Possible mechanisms are generally linked to Quaternary-specific oceanic and cryospheric conditions (e.g. Maslin et al., 2001). An alternative external control, such as solar forcing, however, remains a compelling alternative hypothesis (e.g. Bond et al., 2001). This would imply that millennial-scale cycles are an intrinsic part of the Earth’s climatic system and not restricted to any specific period of time. Determining which of these hypotheses is correct impacts on our understanding of the climate system and its role as a driver of cyclic sedimentation during both icehouse and greenhouse climates. Here we show that Middle Eocene, laminated deep-marine sediments deposited in the Ainsa Basin, Spanish Pyrenees, contain 1,565-year (469 mm) cycles modulated by a 7,141-year (2157 mm) period. Climatic oscillations of 1,565-years recorded by element/Al ratios, are interpreted as representing climatically driven variation in sediment supply (terrigenous run-off) to the Ainsa basin. Climatic oscillations with this period are comparable to Quaternary Bond (~1,500-year), Dansgaard-Oeschger (~1,470-year) and Heinrich (~7,200-year) climatic events. Recognition of similar millennial-scale oscillations in the greenhouse climate of the Middle Eocene would appear inconsistent with an origin dependent upon Quaternary-specific conditions. Our observations lend support for pervasive millennial-scale climatic variability present throughout geologic time likely driven by an external forcing mechanism such as solar forcing. References Bond, G., Kromer, B., Beer, J., Muscheler, R., Evans, M.N., Showers, W., Hoffmann, S., Lotti-Bond, R., Hajdas, I., Bonani, G. 2001. Persistent Solar Influence on North Atlantic Climate During the Holocene. Science, 294, 2130-2136 Maslin, M., Seidov, D., Lowe, J. 2001. Synthesis of the nature and causes of rapid climate transitions during the Quaternary. In: The Oceans and rapid climate change: Past, present and future, (Seidov, D., Haupt, B. J. & Maslin, M., Eds.), AGU, Washington, D. C. McManus, J.F., Oppo, D.W. & Cullen, J.L. 1999. A 0.5-Million-Year Record of Millennial-Scale Climate Variability in the North Atlantic. Science, 283, 971-975

Centennial- to millennial-scale ice-ocean interactions in the subpolar northeast Atlantic 18-41 kyr ago

NASA Astrophysics Data System (ADS)

Hall, I. R.; Colmenero-Hidalgo, E.; Zahn, R.; Peck, V. L.; Hemming, S. R.

2011-06-01

In order to monitor the evolution of the British-Irish Ice Sheet (BIIS) and its influence in surface ocean structure during marine isotopic stages (MIS) 2 and 3, we have analyzed the sediments recovered in core MD04-2829CQ (Rosemary Bank, north Rockall Trough, northeast Atlantic) dated between ˜41 and ˜18 ka B.P. Ice-rafted debris flux and composition, 40Ar/39Ar ages of individual hornblende grains, multispecies planktonic stable isotope records, planktonic foraminifera assemblage data and faunal-based sea surface temperatures (SSTs) demonstrate a close interaction between BIIS dynamics and surface ocean structure and water properties in this region. The core location lies beneath the North Atlantic Current (NAC) and is ideal for monitoring the shifts in the position of its associated oceanic fronts, as recorded by faunal changes. These data reveal a succession of BIIS-sourced iceberg calving events related to low SST, usually synchronous with dramatic changes in the composition of the planktonic foraminifera assemblage and with variations in the stable isotope records of the taxa Neogloboquadrina pachyderma (sinistral coiling) and Globigerina bulloides. The pacing of the calving events, from typically Dansgaard-Oeschger millennial timescales during late MIS 3 to multicentennial cyclicity from ˜28 ka B.P., represents the build-up of the BIIS and its growing instability toward Heinrich Event (HE) 2 and the Last Glacial Maximum. Our data confirm the strong coupling between BIIS instabilities and the temperature and salinity of surface waters in the adjacent northeast Atlantic and demonstrate the BIIS's ability to modify the NAC on its flow toward the Nordic Seas. In contrast, subsurface water masses were less affected except during the Greenland stadials that contain HEs, when most intense water column reorganizations occurred simultaneously with the deposition of cream-colored carbonate sourced from the Laurentide Ice Sheet.

Precise interpolar phasing of abrupt climate change during the last ice age

USGS Publications Warehouse

,; 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.

2015-01-01

The last glacial period exhibited abrupt 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 warm 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 abrupt events7, 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, abrupt Greenland warming leads the corresponding Antarctic cooling onset by 218 ± 92 years (2σ) for Dansgaard–Oeschger events, including the Bølling event; Greenland cooling leads the corresponding onset of Antarctic warming by 208 ± 96 years. Our results demonstrate a north-to-south directionality of the abrupt climatic signal, which is propagated to the Southern Hemisphere high latitudes by oceanic rather than atmospheric processes. The similar interpolar phasing of warming 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.

Orbital- and Millennial-Scale Changes in the Australasian Monsoon Through the Late Pleistocene

NASA Astrophysics Data System (ADS)

Gagan, M. K.; Ayliffe, L. K.; Scroxton, N. G.; Krause, C. E.; Kimbrough, A. K.; Hantoro, W. S.; Drysdale, R.; Hellstrom, J.; Cheng, H.; Edwards, R.; Zhao, J.; Griffiths, M. L.

2012-12-01

Speleothem 18O/16O records from China and Borneo have revealed changes in Asian monsoon rainfall over the last ~570,000 years (e.g. Wang et al. 2008, Cheng et al. 2010, Meckler et al. 2012), yet little is known about orbital- and millennial-scale climate change in the 'southern half' of the Australasian monsoon domain. To fill this gap, we aim to build speleothem 18O/16O records for the seasonal monsoon rainfall belt of south-central Indonesia. Between 2006 and 2011, we sampled speleothems in Flores and southwest Sulawesi (latitudes 5-9oS) with U-series ages extending to 92,000 yBP and ~470,000 yBP, respectively. Development of the 18O/16O records for Sulawesi is in progress, but the basal ages of the speleothems (onset of stalagmite growth) are intriguing because they cluster around glacial terminations, when the East Asian monsoon is known to have been weak (Cheng et al. 2010). There is clear antiphasing of the Flores and China speleothem 18O/16O records on precession time-scales over the last ~90,000 years. A distinct maximum in monsoon rainfall in Flores occurred ~21,000 yBP, suggesting the ITCZ moved south during the Last Glacial Maximum in response to the southern hemisphere summer insolation maximum. This finding indicates that ITCZ positioning in tropical Australasia, through its influence on large-scale oceanic-atmospheric circulation, could have played a key role in the rapid rise of atmospheric CO2 and global warming that ultimately led to the demise of the last ice age, as summarised by Denton et al. (2010) and others. The new Flores speleothem 18O/16O records also show that climate change in the North Atlantic region and Australasian monsoon rainfall are inextricably linked on millennial timescales (Griffiths et al. 2009, Lewis et al. 2011). For example, rapid warming in the North Atlantic region during Dansgaard-Oeschger Event 21 (~86,000 yBP) was linked to a synchronous northward shift of the Australasian ITCZ, marking the final demise of MIS 5b. In contrast, cooling in the North Atlantic during Heinrich Events 3 (~30,000 yBP) and 1 (~16,000 yBP) and the YD (12,800-11,500 yBP) correlates with southward shifts in the Australasian ITCZ. However, the 8,200 yBP cold snap in the North Atlantic produced drying and cooling around Flores. The key difference here is that sea level was relatively high, and cooler sea-surface temperatures in the Indonesian maritime continent at that time (based on nearby coral records) may have suppressed a southward migration of the ITCZ. Cheng, H. et al. (2010), Science, 326, 248-. Denton, G.H. et al. (2010), Science, 328, 1652-. Griffiths, M.L. et al. (2009), Nature Geoscience, 2, 636-. Lewis, S.C. et al. (2011), Earth Planet. Sci. Lett., 303, 133-. Meckler et al. (2012), Science, 336, 1301-. Wang, Y. et al. (2008), Nature, 451, 1090-.

Climate oscillations reflected in the Arabian Sea subseafloor microbiome

NASA Astrophysics Data System (ADS)

Orsi, William; Coolen, Marco; He, Lijun; Wuchter, Cornelia; Irigoien, Xabier; Chust, Guillem; Johnson, Carl; Hemingway, Jordon; Lee, Mitchell; Galy, Valier; Giosan, Liviu

2016-04-01

Marine sediment contains a vast microbial biosphere that influences global biogeochemical cycles over geological timescales. However, the environmental factors controlling the stratigraphy of subseafloor microbial communities are poorly understood. We studied a sediment core directly underlying the Arabian Sea oxygen minimum zone (OMZ), which exhibits organic carbon rich sapropelic laminae deposited under low oxygen conditions. Consistent with several other cores from the same location, age dating revealed the sapropelic layers coincide with warm North Atlantic millennial-scale Dansgaard-Oeschger events, indicating a direct link between the strength of the OMZ and paleoclimate. A total of 214 samples spanning 13 m and 52 Kyr of deposition were selected for geochemical analyses and paleoclimate proxy measurements, as well as high-throughput metagenomic DNA sequencing of bacteria and archaea. A novel DNA extraction protocol was developed that allowed for direct (unamplified) metagenomic sequencing of DNA from each sample. This dataset represents the highest resolved sedimentary metagenomic sampling profile to date. Analysis of these data together with multiple paleoceanographic proxies show that millennial-scale paleoenvironmental conditions correlate with the metabolism and diversity of bacteria and archaea over the last glacial-interglacial cycle in the Arabian Sea. The metabolic potential for bacterial denitrification correlates with climate-driven OMZ strength and concomitant nitrogen stable isotope fractionation, whereas catabolic potential reflects changing marine organic matter sources across the Last Glacial Maximum. These results indicate that the subsisting microbial communities had been stratified to a large extent by paleoceanographic conditions at the time of deposition. Paleoenvironmental conditions should thus be considered as a mechanism that can help explain microbiome stratigraphy in marine sediment.

Matlab based automatization of an inverse surface temperature modelling procedure for Greenland ice cores using an existing firn densification and heat diffusion model

NASA Astrophysics Data System (ADS)

Döring, Michael; Kobashi, Takuro; Kindler, Philippe; Guillevic, Myriam; Leuenberger, Markus

2016-04-01

In order to study Northern Hemisphere (NH) climate interactions and variability, getting access to high resolution surface temperature records of the Greenland ice sheet is an integral condition. For example, understanding the causes for changes in the strength of the Atlantic meridional overturning circulation (AMOC) and related effects for the NH [Broecker et al. (1985); Rahmstorf (2002)] or the origin and processes leading the so called Dansgaard-Oeschger events in glacial conditions [Johnsen et al. (1992); Dansgaard et al., 1982] demand accurate and reproducible temperature data. To reveal the surface temperature history, it is suitable to use the isotopic composition of nitrogen (δ15N) from ancient air extracted from ice cores drilled at the Greenland ice sheet. The measured δ15N record of an ice core can be used as a paleothermometer due to the nearly constant isotopic composition of nitrogen in the atmosphere at orbital timescales changes only through firn processes [Severinghaus et. al. (1998); Mariotti (1983)]. To reconstruct the surface temperature for a special drilling site the use of firn models describing gas and temperature diffusion throughout the ice sheet is necessary. For this an existing firn densification and heat diffusion model [Schwander et. al. (1997)] is used. Thereby, a theoretical δ15N record is generated for different temperature and accumulation rate scenarios and compared with measurement data in terms of mean square error (MSE), which leads finally to an optimization problem, namely the finding of a minimal MSE. The goal of the presented study is a Matlab based automatization of this inverse modelling procedure. The crucial point hereby is to find the temperature and accumulation rate input time series which minimizes the MSE. For that, we follow two approaches. The first one is a Monte Carlo type input generator which varies each point in the input time series and calculates the MSE. Then the solutions that fulfil a given limit or the best solutions for a given number of iterations are saved and used as a new input for the next model run. This procedure is repeated until the MSE undercuts a given threshold (e.g. the analytical error of the measurement data). For the second approach, different Matlab based derivative free optimization algorithms (DFOAs) (i.a. the Nelder-Mead Simplex Method, [Lagarias et al. (1998)]) are studied with an adaptation of the manual method of Kindler et al. (2013). For that the DFOAs are used to find those values for the temperature sensitivity and offset for calculating the surface temperature from the oxygen isotope records of the ice core water samples minimizing the MSE. Finally, a comparison to surface temperature records gained with different other methods for Glacial as well as Holocene data is planned. References: Broecker, W. S., Peteet, D., and Rind, D. (1985). Does the ocean-atmosphere system have more than one stable mode of operation? Nature, 315(6014):21-26. Dansgaard, W., Clausen, H., Gundestrup, N., Hammer, C., Johnsen, S., Gristinsdottir, P., and Reeh, N. (1982). A new Greenland deep ice core. Science, 218(4579):1273-1277. Johnsen, S. J., Clausen, H. B., Dansgaard, W., Fuhrer, K., Gundestrup, N., Hammer, C. U., Iversen, P., Jouzel, J., Stauffer, B., and Steffensen, J.P. (1992). Irregular glacial interstadials recorded in new Greenland ice core. Nature, 359:311- 313. Kindler, P., Guillevic, M., Baumgartner M., Schwander J., Landais A. and Leuenberger, M. (2013). NGRIP Temperature Reconstruction from 10 to 120 kyr b2k. Clim. Past, 9:4099-4143. Lagarias, J.C., Reeds, J. A., Wright, M. H., and Wright, P. E. (1998). Convergence Properties of the Nelder-Mead Simplex Method in Low Dimensions. SIAM Journal of Optimization, Vol. 9 Number 1, pp. 112-147. Mariotti, A. (1983). Atmospheric nitrogen is a reliable standard for natural 15N abundance measurements. Nature, 303:685- 687. Rahmstorf, S. (2002). Ocean circulation and climate during the past 120,000 years. Nature,419(6903):207-214. Severinghaus, J. P., Sowers, T., Brook, E. J., Alley, R. B., and Bender, M. L. (1998). Timing of abrupt climate change at the end of the Younger Dryas interval from thermally fractionated gases in polar ice. Nature, 391:141-146. Schwander, J., Sowers, T., Barnola, J., Blunier, T., Fuchs, A., and Malaizé, B. (1997). Age scale of the air in the summit ice: implication for glacial-interglacial temperature change. J. Geophys. Res-Atmos., 102(D16):19483-19493.

Observation and modelling of stable isotopes in precipitation for midlatitude weather systems in Melbourne, Australia

NASA Astrophysics Data System (ADS)

Barras, Vaughan; Simmonds, Ian

2010-05-01

The application of stable water isotopes as tracers of moisture throughout the hydrological cycle is often hindered by the relatively coarse temporal and spatial resolution of observational data. Intensive observation periods (IOPs) of isotopes in precipitation have been valuable in this regard enabling the quantification of the effects of vapour recycling, convection, cloud top height and droplet reevaporation (Dansgaard, 1953; Miyake et al., 1968; Gedzelman and Lawrence, 1982; 1990; Pionke and DeWalle, 1992; Risi et al., 2008; 2009) and have been used as a basis to develop isotope models of varying complexity (Lee and Fung, 2008; Bony et al., 2008). This study took a unified approach combining observation and modelling of stable isotopes in precipitation in an investigation of three key circulation types that typically bring rainfall to southeastern Australia. The observational component of this study involved the establishment of the Melbourne University Network of Isotopes in Precipitation (MUNIP). MUNIP was devised to sample rainwater simultaneously at a number of collection sites across greater Melbourne to record the spatial and temporal isotopic variability of precipitation during the passage of particular events. Samples were collected at half-hourly intervals for three specific rain events referred to as (1) mixed-frontal, (2) convective, and (3) stratiform. It was found that the isotopic content for each event varied over both high and low frequencies due to influences from local changes in rain intensity and large scale rainout respectively. Of particular note was a positive relationship between deuterium excess and rainfall amount under convective conditions. This association was less well defined for stratiform rainfall. As a supplement to the data coverage of the observations, the events were simulated using a version of NCAR CAM3 running with an isotope hydrology scheme. This was done by periodically nudging the model dynamics with data from the NCEP Reanalysis (Noone, 2006). Results from the simulations showed that the model represented well the large scale evolution of vapour profiles of deuterium excess and 18O for the mixed-frontal and stratiform events. Reconstruction of air mass trajectories provided further detail of the evolution and structure of the vapour profiles revealing a convergence of air masses from different source regions for the mixed-frontal event. By combining observations and modelling in this way, much detail of the structure and isotope moisture history of the observed events was provided that would be unavailable from the sampling of precipitation alone. References Bony, S., C. Risi, and F. Vimeux (2008), Influence of convective processes on the isotopic composition (?18O and ?D) of precipitation and water vapor in the tropics: 1. Radiative-convective equilibrium and Tropical Ocean-Global Atmosphere-Coupled Ocean-Atmosphere Response (TOGA-COARE) simulations, J. Geophys. Res., 113, D19305, doi:10.1029/2008JD009942. Dansgaard, W. (1953), The abundance of 18O in atmospheric water and water vapor. Tellus, 5, 461-469. Gedzelman, S. D., and J. R. Lawrence (1982), The isotopic composition of cyclonic precipitation. J. App. Met., 21, 1385-1404. Gedzelman, S. D., and J. R. Lawrence (1990), The isotopic composition of precipitation from two extratropical cyclones, Mon. Weather Rev., 118 , 495-509. Lee, J., and I. Fung (2008), 'Amount effect' of water isotopes and quantitative analysis of post-condensation processes, Hydrol. Process., 22, 1-8. Miyake, Y., O. Matsubaya, and C. Nishihara (1968), An isotopic study on meteoric precipitation, Pap. Meteorol. Geophys., 19, 243-266. Noone, D. (2006), Isotopic composition of water vapor modeled by constraining global climate simulations with reanalyses, in Research activities in atmospheric and oceanic modeling, J. Côté (ed.), Report No. 36, WMO/TD-No. 1347, p. 2.37-2.38. Pionke, H. B., and D. R. DeWalle (1992), Intra- and inter-storm 18O trends for selected rainstorms in Pennsylvania. J. Hydrol., 138, 131-143. Risi, C., S. Bony, and F. Vimeux (2008), Influence of convective processes on the isotopic composition (?18O and ?D) of precipitation and water vapor in the tropics: 2. Physical interpretation of the amount effect. J. Geophys. Res., 113, D19306, doi:10.1029/2008JD009943. Risi, C., S. Bony, F. Vimeux, M. Chong, and L. Descroix (2009), Evolution of the water stable isotopic composition of the rain sampled along Sahelian squall lines, Q. J. Roy. Meteor. Soc., doi:10.1002/qj.485, (in press).

Sediment geochemical records of productivity and oxygen depletion along the margin of western North America during the past 60,000 years: teleconnections with Greenland Ice and the Cariaco Basin

USGS Publications Warehouse

Dean, W.E.

2007-01-01

Many sediment records from the margins of the Californias (Alta and Baja) collected in water depths between 60 and 1200 m contain anoxic intervals (laminated sediments) that can be correlated with interstadial intervals as defined by the oxygen-isotope composition of Greenland ice (Dansgaard-Oeschger, D-O, cycles). These intervals include all or parts of Oxygen Isotope Stage 3 (OIS3; 60-24 cal ka), the Bo??lling/Allero??d warm interval (B/A; 15-13 cal ka), and the Holocene. This study uses organic carbon (Corg) and trace-element proxies for anoxia and productivity, namely elevated concentrations and accumulation rates of molybdenum and cadmium, in these laminated sediments to suggest that productivity may be more important than ventilation in producing changes in bottom-water oxygen (BWO) conditions on open, highly productive continental margins. The main conclusion from these proxies is that during the last glacial interval (LGI; 24-15 cal ka) and the Younger Dryas cold interval (YD; 13-11.6 cal ka) productivity was lower and BWO levels were higher than during OIS3, the B/A, and the Holocene on all margins of the Californias. The Corg and trace-element profiles in the LGI-B/A-Holocene transition in the Cariaco Basin on the margin of northern Venezuela are remarkably similar to those in the transition on the northern California margin. Correlation between D-O cycles in Greenland ice with gray-scale measurements in varved sediments in the Cariaco Basin also is well established. Synchronous climate-driven changes as recorded in the sediments on the margins of the Californias, sediments from the Cariaco Basin, and in the GISP-2 Greenland ice core support the hypothesis that changes in atmospheric dynamics played a major role in abrupt climate change during the last 60 ka. Millennial-scale cycles in productivity and oxygen depletion on the margins of the Californias demonstrate that the California Current System was poised at a threshold whereby perturbations of atmospheric circulation produced rapid changes in circulation in the eastern North Pacific Ocean. It is likely that the Pacific and Atlantic Oceans were linked through the atmosphere. Warmer air temperatures during interstadials would have strengthened Hadley and Walker circulations, which, in turn, would have strengthened the subtropical high pressure systems in both the North Pacific and the North Atlantic, producing increased rainfall over the Cariaco Basin and increased upwelling along the margins of the Californias. ?? 2006 Elsevier Ltd. All rights reserved.

Vegetation responses to abrupt climatic changes during the Last Interglacial Complex (Marine Isotope Stage 5) at Tenaghi Philippon, NE Greece

NASA Astrophysics Data System (ADS)

Milner, A. M.; Roucoux, K. H.; Collier, R. E. L.; Müller, U. C.; Pross, J.; Tzedakis, P. C.

2016-12-01

The discovery that climate variability during the Last Glacial shifted rapidly between climate states has intensified efforts to understand the distribution, timing and impact of abrupt climate change under a wide range of boundary conditions. In contribution to this, we investigate the nature of abrupt environmental changes in terrestrial settings of the Mediterranean region during the Last Interglacial Complex (Marine Isotope Stage [MIS] 5) and explore the relationships of these changes to high-latitude climate events. We present a new, temporally highly resolved (mean: 170 years) pollen record for the Last Interglacial Complex from Tenaghi Philippon, north-east Greece. The new pollen record, which spans the interval from 130,000 to 65,000 years ago, forms part of an exceptionally long polleniferous sediment archive covering the last 1.35 million years. The pollen data reveal an interglacial followed by alternating forest and steppe phases representing the interstadials and stadials of the Early Glacial. Superimposed on these millennial-scale changes is evidence of persistent sub-millennial-scale variability. We identify ten high-amplitude abrupt events in the pollen record, characterised by rapid contractions of closed forest to open steppe environment and interpreted to indicate major changes in moisture availability and temperature. The contractions in forest cover on millennial timescales appear associated with cooling events in the Mediterranean Sea, North Atlantic and Greenland regions, linked to the Dansgaard-Oeschger (DO) cycles of the Early Glacial. On sub-millennial timescales, the pattern of changes in forest cover at Tenaghi Philippon display a structure similar to the pattern of short-lived precursor and rebound-type events detected in the Greenland ice-core record. Our findings indicate that persistent, high-amplitude environmental variability occurred throughout the Early Glacial, on both millennial and submillennial timescales. Furthermore, the similarity of the pattern of change between Tenaghi Philippon and Greenland on sub-millennial timescales suggests that teleconnections between the high-latitudes and the Mediterranean region operate on sub-millennial timescales and that some terrestrial archives, such as Tenaghi Philippon, are particularly sensitive recorders of these abrupt climate changes.

A high-resolution paleosecular variation record from Black Sea sediments indicating fast directional changes associated with low field intensities during marine isotope stage (MIS) 4

NASA Astrophysics Data System (ADS)

Nowaczyk, Norbert R.; Jiabo, Liu; Frank, Ute; Arz, Helge W.

2018-02-01

A total of nine sediment cores recovered from the Archangelsky Ridge in the SE Black Sea were systematically subjected to intense paleo- and mineral magnetic analyses. Besides 16 accelerator mass spectrometry (AMS) 14C ages available for another core from this area, dating was accomplished by correlation of short-term warming events during the last glacial monitored by high-resolution X-ray fluorescence (XRF) scanning as maxima in both Ca/Ti and K/Ti ratios in Black Sea sediments to the so-called 'Dansgaard-Oeschger events' recognized from Greenland ice cores. Thus, several hiatuses could be identified in the various cores during the last glacial/interglacial cycle. Finally, core sections documenting marine isotope stage (MIS) 4 at high resolution back to 69 ka were selected for detailed analyses. At 64.5 ka, according to obtained results from Black Sea sediments, the second deepest minimum in relative paleointensity during the past 69 ka occurred, with the Laschamp geomagnetic excursion at 41 ka being associated with the lowest field intensities. The field minimum during MIS 4 is associated with large declination swings beginning about 3 ka before the minimum. While a swing to 50°E is associated with steep inclinations (50-60°) according to the coring site at 42°N, the subsequent declination swing to 30°W is associated with shallow inclinations of down to 40°. Nevertheless, these large deviations from the direction of a geocentric axial dipole field (I = 61 °, D = 0 °) still can not yet be termed as 'excursional', since latitudes of corresponding virtual geomagnetic poles (VGP) only reach down to 51.5°N (120°E) and 61.5°N (75°W), respectively. However, these VGP positions at opposite sides of the globe are linked with VGP drift rates of up to 0.2° per year in between. These extreme secular variations might be the mid-latitude expression of a geomagnetic excursion with partly reversed inclinations found at several sites much further North in Arctic marine sediments between 69°N and 81°N. Thus, the pronounced intensity minimum at 64.5 ka and described directional variations might be the effect of a weak geomagnetic field with a multi-polar geometry in the middle of MIS 4.

Continuous-flow water sampler for real-time isotopic water measurements

NASA Astrophysics Data System (ADS)

Carter, J.; Dennis, K.

2013-12-01

Measuring the stable isotopes of liquid water (δ18O and δD) is a tool familiar to many Earth scientists, but most current techniques require discrete sampling. For example, isotope ratio mass spectrometry requires the collection of aliquots of water that are then converted to CO2, CO or H2 for analysis. Similarly, laser-based techniques, such as Cavity Ring-Down Spectroscopy (CRDS) convert discrete samples (typically < 2μL) of liquid water to water vapor using a flash vaporization process. By requiring the use of discrete samples fine-scale spatial and temporal studies of changes in δ18O and δD are limited. Here we present a continuous-flow water sampler that will enable scientists to probe isotopic changes in real-time, with applications including, but not limited to, quantification of the 'amount effect' (Dansgaard, 1964) during an individual precipitation event or storm track, real-time mixing of water in river systems, and shipboard continuous water measurements (Munksgaard et al., 2012). Due to the inherent ability of CRDS to measure a continuous flow of water vapor it is an ideal candidate for interfacing with a continuous water sampling system. Here we present results from the first commercially available continuous-flow water sampler, developed by engineers at Picarro. This peripheral device is compatible with Picarro CRDS isotopic water analyzers, allowing real-time, continuous isotopic measurements of liquid water. The new device, which expands upon the design of Munskgaard et al. (2011), utilizes expanded polytetrafluoroethylene (ePTFE) membrane technology to continuously generate gas-phase water, while liquid water is pumped through the system. The water vapor subsequently travels to the CRDS analyzer where the isotopic ratios are measured and recorded. The generation of water vapor using membrane technology is sensitive to environmental conditions, which if not actively control, lead to sustainable experimental noise and drift. Consequently, our continuous-flow water sample employs active control for all pertinent parameters, significantly increasing its stability and usability. We will present data from controlled laboratory experiments demonstrating sample-to-sample precision and long-term stability. We will also show experimental data that highlights the instrumental sample-to-sample memory, which we have decreased significantly from previous implementations of this technology. Additionally, we will present field results from the Sacramento River, CA. Dansgaard, W. (1964) 'Stable isotopes in precipitation', Tellus, 16(4), p. 436-468. Munksgaard, N.C., Wurster, C.M., Bass, A., Zagorskis, I., and Bird, M.I. (2012) 'First continuous shipboard d18O and dD measurements in seawater by diffusion sampling--cavity ring-down spectrometry', Environmental Chemistry Letters, 10, p.301-307. Munksgaard, N.C., Wurster, C.M., and Bird, M.I., (2011), 'Continuous analysis of δ18O and δD values of water by diffusion sampling cavity ring-down spectrometry: a novel sampling device for unattended field monitoring of precipitation, ground and surface waters', Rapid Communications in Mass Spectrometry, 25, p. 3706-3712.

Mode change of millennial CO2 variability during the last glacial cycle associated with a bipolar marine carbon seesaw

PubMed Central

Bereiter, Bernhard; Lüthi, Dieter; Siegrist, Michael; Schüpbach, Simon; Stocker, Thomas F.; Fischer, Hubertus

2012-01-01

Important elements of natural climate variations during the last ice age are abrupt temperature increases over Greenland and related warming and cooling periods over Antarctica. Records from Antarctic ice cores have shown that the global carbon cycle also plays a role in these changes. The available data shows that atmospheric CO2 follows closely temperatures reconstructed from Antarctic ice cores during these variations. Here, we present new high-resolution CO2 data from Antarctic ice cores, which cover the period between 115,000 and 38,000 y before present. Our measurements show that also smaller Antarctic warming events have an imprint in CO2 concentrations. Moreover, they indicate that during Marine Isotope Stage (MIS) 5, the peak of millennial CO2 variations lags the onset of Dansgaard/Oeschger warmings by 250 ± 190 y. During MIS 3, this lag increases significantly to 870 ± 90 y. Considerations of the ocean circulation suggest that the millennial variability associated with the Atlantic Meridional Overturning Circulation (AMOC) undergoes a mode change from MIS 5 to MIS 4 and 3. Ocean carbon inventory estimates imply that during MIS 3 additional carbon is derived from an extended mass of carbon-enriched Antarctic Bottom Water. The absence of such a carbon-enriched water mass in the North Atlantic during MIS 5 can explain the smaller amount of carbon released to the atmosphere after the Antarctic temperature maximum and, hence, the shorter lag. Our new data provides further constraints for transient coupled carbon cycle-climate simulations during the entire last glacial cycle. PMID:22675123

Mode change of millennial CO2 variability during the last glacial cycle associated with a bipolar marine carbon seesaw.

PubMed

Bereiter, Bernhard; Lüthi, Dieter; Siegrist, Michael; Schüpbach, Simon; Stocker, Thomas F; Fischer, Hubertus

2012-06-19

Important elements of natural climate variations during the last ice age are abrupt temperature increases over Greenland and related warming and cooling periods over Antarctica. Records from Antarctic ice cores have shown that the global carbon cycle also plays a role in these changes. The available data shows that atmospheric CO(2) follows closely temperatures reconstructed from Antarctic ice cores during these variations. Here, we present new high-resolution CO(2) data from Antarctic ice cores, which cover the period between 115,000 and 38,000 y before present. Our measurements show that also smaller Antarctic warming events have an imprint in CO(2) concentrations. Moreover, they indicate that during Marine Isotope Stage (MIS) 5, the peak of millennial CO(2) variations lags the onset of Dansgaard/Oeschger warmings by 250 ± 190 y. During MIS 3, this lag increases significantly to 870 ± 90 y. Considerations of the ocean circulation suggest that the millennial variability associated with the Atlantic Meridional Overturning Circulation (AMOC) undergoes a mode change from MIS 5 to MIS 4 and 3. Ocean carbon inventory estimates imply that during MIS 3 additional carbon is derived from an extended mass of carbon-enriched Antarctic Bottom Water. The absence of such a carbon-enriched water mass in the North Atlantic during MIS 5 can explain the smaller amount of carbon released to the atmosphere after the Antarctic temperature maximum and, hence, the shorter lag. Our new data provides further constraints for transient coupled carbon cycle-climate simulations during the entire last glacial cycle.

The interaction between sea ice and salinity-dominated ocean circulation: implications for halocline stability and rapid changes of sea ice cover

NASA Astrophysics Data System (ADS)

Jensen, Mari F.; Nilsson, Johan; Nisancioglu, Kerim H.

2016-11-01

Changes in the sea ice cover of the Nordic Seas have been proposed to play a key role for the dramatic temperature excursions associated with the Dansgaard-Oeschger events during the last glacial. In this study, we develop a simple conceptual model to examine how interactions between sea ice and oceanic heat and freshwater transports affect the stability of an upper-ocean halocline in a semi-enclosed basin. The model represents a sea ice covered and salinity stratified Nordic Seas, and consists of a sea ice component and a two-layer ocean. The sea ice thickness depends on the atmospheric energy fluxes as well as the ocean heat flux. We introduce a thickness-dependent sea ice export. Whether sea ice stabilizes or destabilizes against a freshwater perturbation is shown to depend on the representation of the diapycnal flow. In a system where the diapycnal flow increases with density differences, the sea ice acts as a positive feedback on a freshwater perturbation. If the diapycnal flow decreases with density differences, the sea ice acts as a negative feedback. However, both representations lead to a circulation that breaks down when the freshwater input at the surface is small. As a consequence, we get rapid changes in sea ice. In addition to low freshwater forcing, increasing deep-ocean temperatures promote instability and the disappearance of sea ice. Generally, the unstable state is reached before the vertical density difference disappears, and the temperature of the deep ocean do not need to increase as much as previously thought to provoke abrupt changes in sea ice.

Influence of tropical atmospheric variability on Weddell Sea deep water convection

NASA Astrophysics Data System (ADS)

Kleppin, H.

2016-02-01

Climate reconstructions from ice core records in Greenland and Antarctica have revealed a series of abrupt climate transitions, showing a distinct relationship between northern and southern hemisphere climate during the last glacial period. The recent ice core records from West Antarctica (WAIS) point towards an atmospheric teleconnection as a possible trigger for the interhemispheric climate variability (Markle et al., 2015). An unforced simulation of the Community Climate System Model, version 4 (CCSM4) reveals Greenland warming and cooling events, caused by stochastic atmospheric forcing, that resemble Dansgaard-Oeschger cycles in pattern and magnitude (Kleppin et al., 2015). Anti-phased temperature changes in the Southern Hemisphere are small in magnitude and have a spatially varying pattern. We argue that both north and south high latitude climate variability is triggered by changes in tropical atmospheric deep convection in the western tropical Pacific. The atmospheric wave guide provides a fast communication pathway connecting the deep tropics and the polar regions. In the Southern Hemisphere this is manifested as a distinct pressure pattern over West Antarctica. These altered atmospheric surface conditions over the convective region can lead to destabilization of the water column and thus to convective overturning in the Weddell Sea. However, opposed to what is seen in the Northern Hemisphere no centennial scale variability can establish, due to the absence of a strong feedback mechanism between ocean, atmosphere and sea ice. Kleppin, H., Jochum, M., Otto-Bliesner, B., Shields, C. A., & Yeager, S. (2015). Stochastic Atmospheric Forcing as a Cause of Greenland Climate Transitions. Journal of Climate, (2015). Markle, B. and Coauthors (2015, April). Atmospheric teleconnections between the tropics and high southern latitudes during millennial climate change. In EGU General Assembly Conference Abstracts (Vol. 17, p. 2569).

40Ar/ 39Ar, K-Ar and 230Th- 238U dating of the Laschamp excursion: A radioisotopic tie-point for ice core and climate chronologies

NASA Astrophysics Data System (ADS)

Singer, Brad S.; Guillou, Hervé; Jicha, Brian R.; Laj, Carlo; Kissel, Catherine; Beard, Brian L.; Johnson, Clark M.

2009-08-01

A brief period of enhanced 10Be flux that straddles the interstadial warm period known as Dansgaard-Oeschger event 10 in Greenland and its counterpart in Antarctica, the Antarctic Isotope Maximum 10 is but one consequence of the weakening of Earth's magnetic field associated with the Laschamp excursion. This 10Be peak measured in the GRIP ice core is dated at 41,250 y b2k (= before year 2000 AD) in the most recent GICC05 age model obtained from the NorthGRIP core via multi-parameter counting of annual layers. Uncertainty in the age of the 10Be peak is, however, no better than ± 1630 y at the 95% confidence level, reflecting accumulated error in identifying annual layers. The age of the Laschamp excursion [Guillou, H., Singer, B.S., Laj, C., Kissel, C., Scaillet, S., Jicha, B., 2004. On the age of the Laschamp geomagnetic excursion. Earth Planet. Sci. Lett. 227, 331-343.] is revised on the basis of new 40Ar/ 39Ar, unspiked K-Ar and 238U- 230Th data from three lava flows in the Massif Central, France, together with the 40Ar/ 39Ar age of a transitionally magnetized lava flow at Auckland, New Zealand. Combined, these data yield an age of 40,700 ± 950 y b2k, where the uncertainty includes both analytical and systematic ( 40K and 230Th decay constant) errors. Taking the radioisotopic age as a calibration tie point suggests that the layer-counting chronologies for the NorthGRIP and GISP2 ice cores are more accurate and precise than previously thought at depths corresponding to the Laschamp excursion.

Palaeoclimate dynamics : a voyage through scales

NASA Astrophysics Data System (ADS)

Crucifix, Michel; Mitsui, Takahito

2015-04-01

Our knowledge of climate dynamics depends on indirect observations of past climate evolution, as well as on what can be inferred from theoretical arguments. At the scale of the Cenozoic, it is common to define a framework of nested time scales, the longest time scale of interest being related to the slow tectonic evolution, then variability associated with or controlled by the astronomical forcing, and finally the fastest dynamics associated with the natural modes of variability of the ocean and the atmosphere. For example, in a model, the astronomical modes of variability may be simulated with deterministic equations under fixed boundary conditions representing the tectonic state, and associated with stochastic parameterisations of the ocean-atmosphere (chaotic) modes of motion. Bifurcations or, more generally, qualitative changes in climate dynamics may be scanned by changing slowly the tectonic state, in order to provide explanations to observed changes in regimes such as the appearance of ice ages and their changes in length or amplitude. The above framework, largely theorized by B. Saltzman, may still be partly justified but is in need of a review. We address here specifically three questions: To what extent astronomical variability interacts with natural modes of ocean - atmosphere variability ? Specifically, how does millennial variability (e.g.: Dansgaard-Oeschger events) fit the Saltzman scheme ? The astronomical forcing is quasi-periodic, and we recently showed that it may produce somewhat counter-intuitive dynamics associated with the emergence of strange non-chaotic attractors. What are the consequences on the spectrum of climate variability ? What are the effects of centennial climate variability on the slow variability of climate ? These three questions are addressed by reference to recently published material, with the objective of emphasising research questions to be explored in the near future.

The Southern Ocean's role in ocean circulation and climate transients

NASA Astrophysics Data System (ADS)

Thompson, A. F.; Stewart, A.; Hines, S.; Adkins, J. F.

2017-12-01

The ventilation of deep and intermediate density classes at the surface of the Southern Ocean impacts water mass modification and the air-sea exchange of heat and trace gases, which in turn influences the global overturning circulation and Earth's climate. Zonal variability occurs along the Antarctic Circumpolar Current and the Antarctic margins related to flow-topography interactions, variations in surface boundary conditions, and exchange with northern basins. Information about these zonal variations, and their impact on mass and tracer transport, are suppressed when the overturning is depicted as a two-dimensional (depth-latitude) streamfunction. Here we present an idealized, multi-basin, time-dependent circulation model that applies residual circulation theory in the Southern Ocean and allows for zonal water mass transfer between different ocean basins. This model efficiently determines the temporal evolution of the ocean's stratification, ventilation and overturning strength in response to perturbations in the external forcing. With this model we explore the dynamics that lead to transitions in the circulation structure between multiple, isolated cells and a three-dimensional, "figure-of-eight," circulation in which traditional upper and lower cells are interleaved. The transient model is also used to support a mechanistic explanation of the hemispheric asymmetry and phase lag associated with Dansgaard-Oeschger (DO) events during the last glacial period. In particular, the 200 year lag in southern hemisphere temperatures, following a perturbation in North Atlantic deep water formation, depends critically on the migration of Southern Ocean isopycnal outcropping in response to low-latitude stratification changes. Our results provide a self-consistent dynamical framework to explain various ocean overturning transitions that have occurred over the Earth's last 100,000 years, and motivate an exploration of these mechanisms in more sophisticated climate models.

EPICA Dome C deuterium record of orbital and millennial Antarctic climate variability over the last 800 000 years

NASA Astrophysics Data System (ADS)

Masson-Delmotte, V.

2006-12-01

The detailed deuterium record of the EPICA (European Project for Ice Coring in Antarctica) Dome C ice core from East Antarctica has been measured at a 55 cm resolution down to a depth of 3260 m, covering ~800 000 years. Several lines of evidence support a reliable use of deuterium fluctuations in central Antarctic ice to reconstruct past temperature changes. The magnitude of the temperature fluctuations range between -9°C and +5°C compared to the late Holocene level. At the orbital scale, the imprint of obliquity changes in the EPICA Dome C record is highlighted and compared to simulations conducted with the ECBILT-CLIO intermediate complexity climate model. We discuss the comparison between the current interglacial period and the long interglacial corresponding to marine isotopic stage 11, ~400 kyr BP. Previous studies had focused on the role of precession and the thresholds required to induce glacial inceptions. We suggest that, due to the low eccentricity configuration of MIS 11 and the Holocene, the effect of precession on the incoming solar radiation is damped and that changes in obliquity must be taken into account. The EPICA Dome C alignment of terminations I and V published in 2004 corresponds to a phasing of the obliquity signals. A relationship is observed between an index of interglacial intensity and the cumulative annual mean insolation at high latitudes, mainly as a result of the modulation of amplitude of obliquity fluctuations. We suggest that this long term changes in obliquity may be involved in the change in magnitude of glacial-interglacial fluctuations between the first and second halves of the EPICA Dome C record. At the high frequency scale, the detailed EPICA Dome C deuterium record clearly shows a one-to-one correspondence between each Greenland ice core Dansgaard-Oeschger event and their smoothed Antarctic counterparts. A methodology to detect objectively rapid events from the EPICA Dome C records is developed and applied for the earlier glacial periods, suggesting a stable magnitude and pacing of Antarctic rapid events along the EPICA Dome C record.

Sedimentary organic matter and carbonate variations in the Chukchi Borderland in association with ice sheet and ocean-atmosphere dynamics over the last 155 kyr

NASA Astrophysics Data System (ADS)

Rella, S. F.; Uchida, M.

2012-12-01

Knowledge on past variability of sedimentary organic carbon in the Arctic Ocean is important to assess natural carbon cycling and transport processes related to global climate changes. However, the late Pleistocene oceanographic history of the Arctic is still poorly understood. In the present study we show sedimentary records of total organic carbon (TOC), CaCO3, benthic foraminiferal δ18O and the coarse grain size fraction from a piston core recovered from the northern Northwind Ridge in the far western Arctic Ocean. TOC shows orbital-scale increases and decreases during the past ~155 kyr that can be respectively correlated to the waxing and waning of large ice sheets dominating the Eurasian Arctic, suggesting advection of fine suspended matter derived from glacial erosion to the Northwind Ridge by eastward flowing intermediate water and/or surface water and sea ice during cold periods. At millennial scales, increases in TOC might correlate to a suite of Dansgaard-Oeschger Stadials between 120 and 45 ka BP indicating a possible response to abrupt northern hemispheric temperature changes. Between 70 and 45 ka BP, closures and openings of the Bering Strait could have additionally influenced TOC variability. CaCO3 contents tend to anti-correlate with TOC on both orbital and millennial time scales, which we interpret in terms of enhanced sediment advection from the carbonate-rich Canadian Arctic via an extended Beaufort Gyre during warm periods and increased organic carbon advection from the Siberian Arctic during cold periods when the Beaufort Gyre contracted. We propose that this pattern may be related to orbital- and millennial-scale variations of dominant atmospheric surface pressure systems expressed in mode shifts of the Arctic Oscillation.

The nature of abrupt climate change during the last glacial period from detailed isotopic records from the NGRIP ice core

NASA Astrophysics Data System (ADS)

Popp, T. J.; Svensson, A.; Steffensen, J. P.; Johnsen, S. J.; White, J. W. C.

2009-04-01

Isotopic and chemical impurity records from Greenland ice cores with sub-annual resolution across three fast climate transitions of the last deglacial termination reveal complex patterns of environmental change for the onset of Greenland Interstadial 1 (GI-1 or Bølling), the onset of Greenland Stadial 1 (GS-1 or Younger Dryas), and the onset of the Holocene. In the NGRIP ice core each of these transitions is initiated by a 1-3 year mode shift in deuterium excess, which is a proxy for the Greenland precipitation moisture source. These mode shifts in deuterium excess are decoupled in time from the isotopic (deuterium and oxygen-18) transitions from which they are derived. In general the abrupt isotopic transitions follow the corresponding deuterium excess shifts and span decades rather than years. Similar data from GISP2 confirms the clear deuterium excess mode shifts for transitions from cold states to warm states; however the abrupt deuterium excess transition at the onset of GS-1 is not expressed in a similar way at GISP2. Ironically, it appears that this cooling at the beginning of the Younger Dryas, for which we have theories of the triggering event, is less clearly recorded than warming events, the triggering of which is still poorly understood. Along with other available paleo-data, these results indicate that the sum of an abrupt climate change is composed of multiple responses from different parts of the climate system. These responses can be separated by as little as a single year to a few decades and the collection of these responses result in a variety of abrupt transitions giving each a unique anatomy. Here we expand this type of analysis with new isotope, deuterium excess, and accumulation rate time series from NGRIP across the abrupt transitions associated with several interstadial events of the Last Glacial period (Dansgaard-Oeschger events). Indeed the temporal phasing of deuterium excess and the isotopic content of the ice can vary from one event to the next and emerging patterns may depend on the conditions associated with specific events such as Heinrich Events and ice volume boundary conditions. Together with modeling and chemical impurity data, these patterns will provide clues to the timing and origin of ocean and atmospheric changes that comprise an abrupt climate change. The emerging picture indicates that abrupt climate changes have both a temporal and geographic anatomy that can change from one event to the next in how they are recorded across Greenland.

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 major sub-glacial eruptions that occurred during DO 0, A, and 1 (11.6, 13.1, and 14.6 ka) and similar but less well dated activity at least over the past million years. Massive melting of a thick ice sheet by volcanoes would decrease overburden pressure on the magma chambers, potentially increasing volcanism. Continued basaltic eruptions over decades enhanced by such a feedback c8ould explain why the intervals between DO events (1300 to 8800 years) are more random than cyclic and the evidence for sudden influxes of fresh water into the North Atlantic documented during DO events. Concentrations of sulfate in Greenland were as high from 1928 to 1985 as during the largest DO event. Trace element analysis shows this sulfate came from smoke stacks in northern Russia, Europe, and central North America. Observed levels of SO2, NO_{x}, tropospheric O$_{3} and black carbon are more than sufficient to have been the primary cause of 20th century global warming. Efforts to reduce acid rain by reducing emissions of these pollutants "accidentally" slowed global warming by 1998. Mean global surface temperatures have remained high but have not increased since then.

Pollen from the Deep-Sea: A Breakthrough in the Mystery of the Ice Ages

PubMed Central

Sánchez Goñi, María F.; Desprat, Stéphanie; Fletcher, William J.; Morales-Molino, César; Naughton, Filipa; Oliveira, Dulce; Urrego, Dunia H.; Zorzi, Coralie

2018-01-01

Pollen from deep-sea sedimentary sequences provides an integrated regional reconstruction of vegetation and climate (temperature, precipitation, and seasonality) on the adjacent continent. More importantly, the direct correlation of pollen, marine and ice indicators allows comparison of the atmospheric climatic changes that have affected the continent with the response of the Earth’s other reservoirs, i.e., the oceans and cryosphere, without any chronological uncertainty. The study of long continuous pollen records from the European margin has revealed a changing and complex interplay between European climate, North Atlantic sea surface temperatures (SSTs), ice growth and decay, and high- and low-latitude forcing at orbital and millennial timescales. These records have shown that the amplitude of the last five terrestrial interglacials was similar above 40°N, while below 40°N their magnitude differed due to precession-modulated changes in seasonality and, particularly, winter precipitation. These records also showed that vegetation response was in dynamic equilibrium with rapid climate changes such as the Dangaard-Oeschger (D-O) cycles and Heinrich events, similar in magnitude and velocity to the ongoing global warming. However, the magnitude of the millennial-scale warming events of the last glacial period was regionally-specific. Precession seems to have imprinted regions below 40°N while obliquity, which controls average annual temperature, probably mediated the impact of D-O warming events above 40°N. A decoupling between high- and low-latitude climate was also observed within last glacial warm (Greenland interstadials) and cold phases (Greenland stadials). The synchronous response of western European vegetation/climate and eastern North Atlantic SSTs to D-O cycles was not a pervasive feature throughout the Quaternary. During periods of ice growth such as MIS 5a/4, MIS 11c/b and MIS 19c/b, repeated millennial-scale cold-air/warm-sea decoupling events occurred on the European margin superimposed to a long-term air-sea decoupling trend. Strong air-sea thermal contrasts promoted the production of water vapor that was then transported northward by the westerlies and fed ice sheets. This interaction between long-term and shorter time-scale climatic variability may have amplified insolation decreases and thus explain the Ice Ages. This hypothesis should be tested by the integration of stochastic processes in Earth models of intermediate complexity. PMID:29434616

Pollen from the Deep-Sea: A Breakthrough in the Mystery of the Ice Ages.

PubMed

Sánchez Goñi, María F; Desprat, Stéphanie; Fletcher, William J; Morales-Molino, César; Naughton, Filipa; Oliveira, Dulce; Urrego, Dunia H; Zorzi, Coralie

2018-01-01

Pollen from deep-sea sedimentary sequences provides an integrated regional reconstruction of vegetation and climate (temperature, precipitation, and seasonality) on the adjacent continent. More importantly, the direct correlation of pollen, marine and ice indicators allows comparison of the atmospheric climatic changes that have affected the continent with the response of the Earth's other reservoirs, i.e., the oceans and cryosphere, without any chronological uncertainty. The study of long continuous pollen records from the European margin has revealed a changing and complex interplay between European climate, North Atlantic sea surface temperatures (SSTs), ice growth and decay, and high- and low-latitude forcing at orbital and millennial timescales. These records have shown that the amplitude of the last five terrestrial interglacials was similar above 40°N, while below 40°N their magnitude differed due to precession-modulated changes in seasonality and, particularly, winter precipitation. These records also showed that vegetation response was in dynamic equilibrium with rapid climate changes such as the Dangaard-Oeschger (D-O) cycles and Heinrich events, similar in magnitude and velocity to the ongoing global warming. However, the magnitude of the millennial-scale warming events of the last glacial period was regionally-specific. Precession seems to have imprinted regions below 40°N while obliquity, which controls average annual temperature, probably mediated the impact of D-O warming events above 40°N. A decoupling between high- and low-latitude climate was also observed within last glacial warm (Greenland interstadials) and cold phases (Greenland stadials). The synchronous response of western European vegetation/climate and eastern North Atlantic SSTs to D-O cycles was not a pervasive feature throughout the Quaternary. During periods of ice growth such as MIS 5a/4, MIS 11c/b and MIS 19c/b, repeated millennial-scale cold-air/warm-sea decoupling events occurred on the European margin superimposed to a long-term air-sea decoupling trend. Strong air-sea thermal contrasts promoted the production of water vapor that was then transported northward by the westerlies and fed ice sheets. This interaction between long-term and shorter time-scale climatic variability may have amplified insolation decreases and thus explain the Ice Ages. This hypothesis should be tested by the integration of stochastic processes in Earth models of intermediate complexity.

Bayesian comparison of conceptual models of abrupt climate changes during the last glacial period

NASA Astrophysics Data System (ADS)

Boers, Niklas; Ghil, Michael; Rousseau, Denis-Didier

2017-04-01

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) events, during which Arctic temperatures increased by up to 10 K within a few decades. These warming events 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 abrupt 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. [1] Kindler et al., Clim. Past (2014) [2] WAIS, Nature (2015) [3] Henry et al., Science (2016) [4] Gildor and Tziperman, Phil. Trans. R. Soc. (2003) [5] Petersen et al., Paleoceanography (2013)

The environmental and evolutionary history of Lake Ohrid (FYROM/Albania): interim results from the SCOPSCO deep drilling project

NASA Astrophysics Data System (ADS)

Wagner, Bernd; Wilke, Thomas; Francke, Alexander; Albrecht, Christian; Baumgarten, Henrike; Bertini, Adele; Combourieu-Nebout, Nathalie; Cvetkoska, Aleksandra; D'Addabbo, Michele; Donders, Timme H.; Föller, Kirstin; Giaccio, Biagio; Grazhdani, Andon; Hauffe, Torsten; Holtvoeth, Jens; Joannin, Sebastien; Jovanovska, Elena; Just, Janna; Kouli, Katerina; Koutsodendris, Andreas; Krastel, Sebastian; Lacey, Jack H.; Leicher, Niklas; Leng, Melanie J.; Levkov, Zlatko; Lindhorst, Katja; Masi, Alessia; Mercuri, Anna M.; Nomade, Sebastien; Nowaczyk, Norbert; Panagiotopoulos, Konstantinos; Peyron, Odile; Reed, Jane M.; Regattieri, Eleonora; Sadori, Laura; Sagnotti, Leonardo; Stelbrink, Björn; Sulpizio, Roberto; Tofilovska, Slavica; Torri, Paola; Vogel, Hendrik; Wagner, Thomas; Wagner-Cremer, Friederike; Wolff, George A.; Wonik, Thomas; Zanchetta, Giovanni; Zhang, Xiaosen S.

2017-04-01

This study reviews and synthesises existing information generated within the SCOPSCO (Scientific Collaboration on Past Speciation Conditions in Lake Ohrid) deep drilling project. The four main aims of the project are to infer (i) the age and origin of Lake Ohrid (Former Yugoslav Republic of Macedonia/Republic of Albania), (ii) its regional seismotectonic history, (iii) volcanic activity and climate change in the central northern Mediterranean region, and (iv) the influence of major geological events on the evolution of its endemic species. The Ohrid basin formed by transtension during the Miocene, opened during the Pliocene and Pleistocene, and the lake established de novo in the still relatively narrow valley between 1.9 and 1.3 Ma. The lake history is recorded in a 584 m long sediment sequence, which was recovered within the framework of the International Continental Scientific Drilling Program (ICDP) from the central part (DEEP site) of the lake in spring 2013. To date, 54 tephra and cryptotephra horizons have been found in the upper 460 m of this sequence. Tephrochronology and tuning biogeochemical proxy data to orbital parameters revealed that the upper 247.8 m represent the last 637 kyr. The multi-proxy data set covering these 637 kyr indicates long-term variability. Some proxies show a change from generally cooler and wetter to drier and warmer glacial and interglacial periods around 300 ka. Short-term environmental change caused, for example, by tephra deposition or the climatic impact of millennial-scale Dansgaard-Oeschger and Heinrich events are superimposed on the long-term trends. Evolutionary studies on the extant fauna indicate that Lake Ohrid was not a refugial area for regional freshwater animals. This differs from the surrounding catchment, where the mountainous setting with relatively high water availability provided a refuge for temperate and montane trees during the relatively cold and dry glacial periods. Although Lake Ohrid experienced significant environmental change over the last 637 kyr, preliminary molecular data from extant microgastropod species do not indicate significant changes in diversification rate during this period. The reasons for this constant rate remain largely unknown, but a possible lack of environmentally induced extinction events in Lake Ohrid and/or the high resilience of the ecosystems may have played a role.

Late Quaternary vegetational and climate dynamics in northeastern Brazil, inferences from marine core GeoB 3104-1

NASA Astrophysics Data System (ADS)

Behling, Hermann; W. Arz, Helge; Pätzold, Jürgen; Wefer, Gerold

2000-06-01

Late Quaternary paleoenvironments from northeastern (NE) Brazil have been studied by pollen analysis of marine sediment. The studied core GeoB 3104-1 (3°40' S, 37°43' W, 767 m b.s.l.) from the upper continental slope off NE Brazil is 517 cm long and >42,000 14C yr BP old. Chronological control was obtained by 12 radiocarbon (AMS) dates from individuals of the foraminiferal species Globigerinoides sacculifer. Modern pollen analogs were received from 15 river, lake and forest soil surface samples from NE Brazil. Marine pollen dates indicate the predominance of semi-arid caatinga vegetation in NE Brazil during the recorded period between >42,000 and 8500 14C yr BP. The increased fluvial input of terrigenous material, with high concentrations of pollen and specially fern spores, into the marine deposits, about 40,000, 33,000 and 24,000 14C yr BP and between 15,500 and 11,800 14C yr BP, indicate short-term periods of strong rainfall on the NE Brazilian continent. The expansion of mountain, floodplain and gallery forests characterize the interval between 15,500 and 11,800 14C yr BP as the wettest recorded period in NE Brazil, which allowed floristic exchanges between Atlantic rain forest and Amazonian rain forest, and vice versa. The paleodata from core GeoB 3104-1 confirm the, in general, dry pre-Last Glacial Maximum (LGM) and LGM conditions and the change to wet Lateglacial environments in tropical South America. The annual movement of the intertropical convergence zone over NE Brazil, the strong influence of the Antarctic cold fronts and changes of the high-pressure cell over the southern Atlantic, may explain the very wet Lateglacial period in NE Brazil. The documented NE Brazilian short-term signals correlate with the documented Dansgaard-Oeschger cycles and Heinrich events from the northern Hemisphere and suggest strong teleconnections.

Insights into the Toba Super-Eruption using SEM Analysis of Ash Deposits

NASA Astrophysics Data System (ADS)

Gatti, E.; Achyuthan, H.; Durant, A. J.; Gibbard, P.; Mokhtar, S.; Oppenheimer, C.; Raj, R.; Shridar, A.

2010-12-01

The ~74 ka Youngest Toba Tuff (YTT) super-eruption of Toba volcano, Northern Sumatra, was the largest eruption of the Quaternary (magnitude M= 8.8) and injected massive quantities of volcanic gases and ash into the stratosphere. YTT deposits covered at least 40,000,000 km2 of Southeast Asia and are preserved in river valleys across peninsular India and Malaysia, and in deep-sea tephra layers in the Indian Ocean, Bay of Bengal and South China Sea. Initial studies hypothesized the eruption caused immediate and substantial global cooling during the ~ 1 kyr between Dansgaard-Oeschger events 19 and 20 which devastated ecosystems and hominid populations. A more recent review argues against severe post-YTT climatic deterioration and cannot find clear evidence for considerable impacts on ecosystems or bio-diversity. The determination of the eruptive parameters is crucial in this issue to document the eruption and understand the potential impacts from future super-volcanic eruptions. Volcanic ash deposits can offer dramatic insights into key eruptive parameters, including magnitude, duration and plume height. The composition and shape of volcanic ashes can be used to interpret physical properties of an erupting magma and tephra transport, while textural characteristics such as grain roughness and surface vescicularity can provide insights into degassing history, volatile content and explosive activity of the volcano. We present a stratigraphic and sedimentological analysis of YTT deposits in stratified contexts at three localities in India, at two sites in Peninsular Malaysia, and at several localities around Lake Toba and on Samosir Island, Sumatra. These sites offer excellent constraints on the spatial distribution of YTT deposits which can be used to infer dispersal directions of the cloud, and provide insights into environmental controls on preservation of tephra beds. The research aims at a systematic interpretation of the Toba tephra to understand the volcanic processes and environmental impacts of the largest known Quaternary volcanic eruption.

Sea-ice cover in the Nordic Seas and the sensitivity to Atlantic water temperatures

NASA Astrophysics Data System (ADS)

Jensen, Mari F.; Nisancioglu, Kerim H.; Spall, Michael A.

2017-04-01

Changes in the sea-ice cover of the Nordic Seas have been proposed to play a key role for the dramatic temperature excursions associated with the Dansgaard-Oeschger events during the last glacial. However, with its proximity to the warm Atlantic water, how a sea-ice cover can persist in the Nordic Seas is not well understood. In this study, we apply an eddy-resolving configuration of the Massachusetts Institute of Technology general circulation model with an idealized topography to study the presence of sea ice in a Nordic Seas-like domain. We assume an infinite amount of warm Atlantic water present in the south by restoring the southern area to constant temperatures. The sea-surface temperatures are restored toward cold, atmospheric temperatures, and as a result, sea ice is present in the interior of the domain. However, the sea-ice cover in the margins of the Nordic Seas, an area with a warm, cyclonic boundary current, is sensitive to the amount of heat entering the domain, i.e., the restoring temperature in the south. When the temperature of the warm, cyclonic boundary current is high, the margins are free of sea ice and heat is released to the atmosphere. We show that with a small reduction in the temperature of the incoming Atlantic water, the Nordic Seas-like domain is fully covered in sea ice. Warm water is still entering the Nordic Seas, however, this happens at depths below a cold, fresh surface layer produced by melted sea ice. Consequently, the heat release to the atmosphere is reduced along with the eddy heat fluxes. Results suggest a threshold value in the amount of heat entering the Nordic Seas before the sea-ice cover disappears in the margins. We study the sensitivity of this threshold to changes in atmospheric temperatures and vertical diffusivity.

Saving Humanity from Catastrophic Cooling with Geo-Engineering

NASA Astrophysics Data System (ADS)

Haapala, K.; Singer, S. F.

2016-02-01

There are two kinds of ice ages; they are fundamentally different and therefore require different methods of mitigation: (i) Major (Milankovitch-style) glaciations occur on a 100,000-year time-scale and are controlled astronomically. (ii) "Little" ice ages were discovered in ice cores; they have been occurring on an approx. 1000-1500-yr cycle and are likely controlled by the Sun [Ref: Singer & Avery 2007. Unstoppable Global Warming: Every 1500 years]. The current cycle's cooling phase may be imminent - hence there may be urgent need for action. To stop onset of a major (Milankovitch) glaciation 1. Locate a "trigger" - a growing perennial snow/ice field - using satellites 2. Spread soot, to lower the albedo, and use Sun to melt 3. How much soot? How to apply soot? Learn by experimentation To lessen (regional, intermittent) cooling of DOB (Dansgaard-Oeschger-Bond) cycles1. Use greenhouse effect of manmade cirrus (ice particles) [Ref: Singer 1988. Meteorology and Atmospheric Physics 38:228 - 239]2. Inject water droplets (mist) near tropopause 3. Trace dispersion of cirrus cloud by satellite and observe warming at surface 4. How much water; over what area? How often to inject? Learn by experimentation Many scientific questions remain. While certainly interesting and important, there is really no need to delay the crucial and urgent tests of geo-engineering, designed to validate schemes of mitigation. Such proposed tests involve only minor costs and present negligible risks to the environment.

Testing the Hypothesis of Fire Use for Ecosystem Management by Neanderthal and Upper Palaeolithic Modern Human Populations

PubMed Central

Daniau, Anne-Laure; d'Errico, Francesco; Sánchez Goñi, Maria Fernanda

2010-01-01

Background It has been proposed that a greater control and more extensive use of fire was one of the behavioral innovations that emerged in Africa among early Modern Humans, favouring their spread throughout the world and determining their eventual evolutionary success. We would expect, if extensive fire use for ecosystem management were a component of the modern human technical and cognitive package, as suggested for Australia, to find major disturbances in the natural biomass burning variability associated with the colonisation of Europe by Modern Humans. Methodology/Principal Findings Analyses of microcharcoal preserved in two deep-sea cores located off Iberia and France were used to reconstruct changes in biomass burning between 70 and 10 kyr cal BP. Results indicate that fire regime follows the Dansgaard-Oeschger climatic variability and its impacts on fuel load. No major disturbance in natural fire regime variability is observed at the time of the arrival of Modern Humans in Europe or during the remainder of the Upper Palaeolithic (40–10 kyr cal BP). Conclusions/Significance Results indicate that either Neanderthals and Modern humans did not influence fire regime or that, if they did, their respective influence was comparable at a regional scale, and not as pronounced as that observed in the biomass burning history of Southeast Asia. PMID:20161786

Large fluctuations of dissolved oxygen in the Indian and Pacific oceans during Dansgaard-Oeschger oscillations caused by variations of North Atlantic Deep Water subduction

NASA Astrophysics Data System (ADS)

Schmittner, Andreas; Galbraith, Eric D.; Hostetler, Steven W.; Pedersen, Thomas F.; Zhang, Rong

2007-09-01

Paleoclimate records from glacial Indian and Pacific oceans sediments document millennial-scale fluctuations of subsurface dissolved oxygen levels and denitrification coherent with North Atlantic temperature oscillations. Yet the mechanism of this teleconnection between the remote ocean basins remains elusive. Here we present model simulations of the oxygen and nitrogen cycles that explain how changes in deepwater subduction in the North Atlantic can cause large and synchronous variations of oxygen minimum zones throughout the Northern Hemisphere of the Indian and Pacific oceans, consistent with the paleoclimate records. Cold periods in the North Atlantic are associated with reduced nutrient delivery to the upper Indo-Pacific oceans, thereby decreasing productivity. Reduced export production diminishes subsurface respiration of organic matter leading to higher oxygen concentrations and less denitrification. This effect of reduced oxygen consumption dominates at low latitudes. At high latitudes in the Southern Ocean and North Pacific, increased mixed layer depths and steepening of isopycnals improve ocean ventilation and oxygen supply to the subsurface. Atmospheric teleconnections through changes in wind-driven ocean circulation modify this basin-scale pattern regionally. These results suggest that changes in the Atlantic Ocean circulation, similar to those projected by climate models to possibly occur in the centuries to come because of anthropogenic climate warming, can have large effects on marine ecosystems and biogeochemical cycles even in remote areas.

Provenance Changes Over Glacial-Interglacial Timescales Recorded in Japan Sea Sediments (IODP Site U1430)

NASA Astrophysics Data System (ADS)

Kinsley, C. W.; McGee, D.; Anderson, C. H.; Murray, R. W.; Tada, R.; Alvarez Zarikian, C. A.

2017-12-01

Recent work has shown a mechanistic relationship between the Westerly Jet (WJ) and East Asian Monsoon (EAM) precipitation, as migration of the WJ to the northern edge of the Tibetan Plateau during spring and early summer appears to be essential for driving convective rainfall over eastern China. Chiang et al. (2015) has proposed the "Jet Transition Hypothesis" wherein it is put forward that changes to the seasonal meridional position of the WJ relative to the Tibetan Plateau drives rainfall climate changes over East Asia on paleoclimate timescales. This hypothesis would predict that in extreme scenarios such as cold phases of Dansgaard-Oeschger (D-O) stadials and during periods of low Northern Hemisphere summer insolation that the Jet would not move north of the Tibetan Plateau, keeping East Asia in prolonged spring conditions. Conversely, during periods of high Northern Hemisphere summer insolation it would be predicted that the Jet would move more quickly north of the Tibetan Plateau and remain there longer, keeping East Asia in prolonged summer conditions. Westerly Jet behavior can be reconstructed using sediments from the Japan Sea, as the WJ path and intensity determines dust emissions and transport paths from Chinese and Mongolian dust source areas, which is the primary source of terrigenous material to the Japan Sea. Radiogenic isotopes of Pb, Nd and Sr can be been applied to fingerprint the dust sources from Asia, and measurements of these isotopes downcore in the Japan Sea will allow reconstruction of the changing dust source area and thus behavior of the WJ. By coupling dust reconstructions lending insight to the behavior of the Westerly Jet with complementary records reflecting EAM intensity and precipitation distribution, the mean state and variability of the WJ and its coupling with the EAM can be examined. This study will measure a suite of samples for Pb, Nd and Sr isotopes from IODP Site U1430 over glacial-interglacial timescales, allowing detailed insights into changes in eolian sediment source regions in the Japan Sea and laying a foundation for future work examining millennial- and orbital-scale variability. Chiang, J.C.H., et al. 2015. Role of Seasonal Transitions and Westerly Jets in East Asian Paleoclimate, QSR, 108, 111-129.

Records of millennial-scale climate change from the Great Basin of the Western United States

NASA Astrophysics Data System (ADS)

Benson, Larry

High-resolution (decadal) records of climate change from the Owens, Mono, and Pyramid Lake basins of California and Nevada indicate that millennialscale oscillations in climate of the Great Basin occurred between 52.6 and 9.2 14C ka. Climate records from the Owens and Pyramid Lake basins indicate that most, but not all, glacier advances (stades) between 52.6 and ˜15.0 14C ka occurred during relatively dry times. During the last alpine glacial period (˜60.0 to ˜14.0 14C ka), stadial/interstadial oscillations were recorded in Owens and Pyramid Lake sediments by the negative response of phytoplankton productivity to the influx of glacially derived silicates. During glacier advances, rock flour diluted the TOC fraction of lake sediments and introduction of glacially derived suspended sediment also increased the turbidity of lake water, decreasing light penetration and photosynthetic production of organic carbon. It is not possible to correlate objectively peaks in the Owens and Pyramid Lake TOC records (interstades) with Dansgaard-Oeschger interstades in the GISP2 ice-core δ18O record given uncertainties in age control and difference in the shapes of the OL90, PLC92 and GISP2 records. In the North Atlantic region, some climate records have clearly defined variability/cyclicity with periodicities of 102 to 103 yr; these records are correlatable over several thousand km. In the Great Basin, climate proxies also have clearly defined variability with similar time constants, but the distance over which this variability can be correlated remains unknown. Globally, there may be minimal spatial scales (domains) within which climate varies coherently on centennial and millennial scales, but it is likely that the sizes of these domains vary with geographic setting and time. A more comprehensive understanding of the mechanisms of climate forcing and the physical linkages between climate forcing and system response is needed in order to predict the spatial scale(s) over which climate varies coherently.

Large fluctuations of dissolved oxygen in the Indian and Pacific oceans during Dansgaard-Oeschger oscillations caused by variations of North Atlantic Deep Water subduction

USGS Publications Warehouse

Schmittner, A.; Galbraith, E.D.; Hostetler, S.W.; Pedersen, Thomas F.; Zhang, R.

2007-01-01

Paleoclimate records from glacial Indian and Pacific oceans sediments document millennial-scale fluctuations of subsurface dissolved oxygen levels and denitrification coherent with North Atlantic temperature oscillations. Yet the mechanism of this teleconnection between the remote ocean basins remains elusive. Here we present model simulations of the oxygen and nitrogen cycles that explain how changes in deepwater subduction in the North Atlantic can cause large and synchronous variations of oxygen minimum zones, throughout the Northern Hemisphere of the Indian and Pacific oceans, consistent with the paleoclimate records. Cold periods in the North Atlantic are associated with reduced nutrient delivery to the upper Indo-Pacific oceans, thereby decreasing productivity. Reduced export production diminishes subsurface respiration of organic matter leading to higher oxygen concentrations and less denitrification. This effect of reduced oxygen consumption dominates at low latitudes. At high latitudes in the Southern Ocean and North Pacific, increased mixed layer depths and steepening of isopycnals improve ocean ventilation and oxygen supply to the subsurface. Atmospheric teleconnections through changes in wind-driven ocean circulation modify this basin-scale pattern regionally. These results suggest that changes in the Atlantic Ocean circulation, similar to those projected by climate models to possibly occur in the centuries to come because of anthropogenic climate warming, can have large effects on marine ecosystems and biogeochemical cycles even in remote areas. Copyright 2007 by the American Geophysical Union.

A Model-based Interpretation of Low-frequency Changes in the Carbon Cycle during the Last 120,000 years and its Implications for the Reconstruction of Atmospheric (delta) 14-C

NASA Technical Reports Server (NTRS)

Koehler, Peter; Muscheler, Raimund; Fischer, Hubertus

2006-01-01

A main caveat in the interpretation of observed changes in atmospheric (Delta)C-l4 during the last 50,000 years is the unknown variability of the carbon cycle, which together with changes in the C-14 production rates determines the C-14 dynamics. A plausible scenario explaining glacial/interglacial dynamics seen in atmospheric CO2 and (delta)C-13 was proposed recently (Kohler et al., 2005a). A similar approach that expands its interpretation to the C-14 cycle is an important step toward a deeper understanding of (Delta)C-14 variability. This approach is based on an ocean/atmosphere/biosphere box model of the global carbon cycle (BICYCLE) to reproduce low-frequency changes in atmospheric CO2 as seen in Antarctic ice cores. The model is forced forward in time by various paleoclimatic records derived from ice and sediment cores. The simulation results of our proposed scenario match a compiled CO2 record from various ice cores during the last 120,000 years with high accuracy (r(sup 2) = 0.89). We analyze scenarios with different C-14 production rates, which are either constant or based on Be-10 measured in Greenland ice cores or the recent high-resolution geomagnetic field reconstruction GLOPIS-75 and compare them with the available (Delta)C-14 data covering the last 50,000 years. Our results suggest that during the last glacial cycle in general less than 110%0o f the increased atmospheric (Delta)C-14 is based on variations in the carbon cycle, while the largest part (5/6) of the variations has to be explained by other factors. Glacial atmospheric (Delta)C-14 larger than 700% cannot not be explained within our framework, neither through carbon cycle-based changes nor through variable C-14 production. Superimposed on these general trends might lie positive anomalies in atmospheric (Delta)C-14 of approx. 50% caused by millennial-scale variability of the northern deep water production during Heinrich events and Dansgaard/Oeschger climate fluctuations. According to our model, the dominant processes that increase glacial (Delta)C-14 are a reduced glacial ocean circulation (+ approx.40%0), a restricted glacial gas exchange between the atmosphere and the surface ocean through sea ice coverage (+ approx. 20%), and the enrichment of dissolved inorganic carbon with C-14 in the surface waters through isotopic fractionation during higher glacial marine export production caused by iron fertilization (+ approx.10%).

Impact of convective activity on precipitation δ18O in isotope-enabled models

NASA Astrophysics Data System (ADS)

Hu, J.; Emile-Geay, J.; Dee, S.

2017-12-01

The ^18O signal preserved in paleo-archives (e.g. speleothem, tree ring cellulose, ice cores) is widely used to reconstruct precipitation or temperature. In the tropics, the inverse relationship between precipitation ^18O and rainfall amount, namely "amount effect" [Dansgaard, Tellus, 1964], is often used to interpret precipitation ^18O. However, recent studies have shown that precipitation ^18O is also influenced by precipitation type [Kurita et al, JGR, 2009; Moerman et al, EPSL, 2013], and recent observations indicate that it is negatively correlated with the fraction of precipitation associated with stratiform clouds [Aggarwal et al, Nature Geosci, 2016]. It is thus important to determine to what extent isotope-enabled climate models can reproduce these relationships. Here we do so using output from LMDZ, CAM2, and isoGSM from the Stable Water Isotope Intercomparison Group, Phase 2 (SWING2) project and results of SPEEDY-IER [Dee et al, JGR, 2015] from an AMIP-style experiment. The results show that these models simulate the "amount effect" well in the tropics, and the relationship between precipitation ^18O and precipitation is reversed in many places in mid-latitudes, in accordance with observations [Bowen, JGR, 2008]. Also, these models can all reproduce the negative correlation between monthly precipitation ^18O and stratiform precipitation proportion in mid-latitude (30°N-50°N; 50°S-30°S), but in the tropics (30°S-30°N), models show a positive correlation instead. The reason for this bias will be investigated within idealized experiments with SPEEDY-IER. The correct simulations of the impact of convective activity on precipitation ^18O in isotope-enabled models will improve our interpretation of paleoclimate proxies with respect to hydroclimate variability. P. K. Aggarwal et al. (2016), Nature Geosci., 9, 624-629, doi:10.1038/ngeo2739. G. J. Bowen. (2008), J. Geophys. Res., 113, D05113, doi:10.1029/2007JD009295. W. Dansgaard (1964), Tellus, 16(4), 436-468. S. Dee et al. (2015), J. Geophys. Res. Atmos., 120, 73-91, doi:10.1002/2014JD022194. N. Kurita. (2013), J. Geophys. Res. Atmos. 118, 10,376-10,390, doi:10.1002/jgrd.50754. J. W. Moerman et al. (2013), Earth Planet. Sci. Lett., 369, 108-119.

Rapid climate change from north Andean Lake Fúquene pollen records driven by obliquity: implications for a basin-wide biostratigraphic zonation for the last 284 ka

NASA Astrophysics Data System (ADS)

Bogotá-A, R. G.; Groot, M. H. M.; Hooghiemstra, H.; Lourens, L. J.; Van der Linden, M.; Berrio, J. C.

2011-11-01

This paper compares a new super-high resolution pollen record from a central location in Lake Fúquene (4°N) with 3 pollen records from marginal sites from the same lake basin, located at 2540 m elevation in the Eastern Cordillera of Colombia. We harmonized the pollen sum of all records, and provided previously published records of climate change with an improved age model using a new approach for long continental pollen records. We dissociated from subjective curve matching and applied a more objective procedure including radiocarbon ages, cyclostratigraphy, and orbital tuning using the new 284 ka long Fúquene Basin Composite record (Fq-BC) as the backbone ( Groot et al., 2011). We showed that a common ˜9 m cycle in the arboreal pollen percentage (AP%) records reflects obliquity forcing and drives vegetational and climatic change. The AP% records were tuned to the 41 kyr component filtered from standard benthic δ 18O LR04 record. Changes in sediment supply to the lake are reflected in concert by the four records making frequency analysis in the depth domain an adequate method to compare records from the same basin. We calibrated the original 14C ages and used where necessary biostratigraphic correlation, i.e. for records shorter than one obliquity cycle. Pollen records from the periphery of the lake showed changes in the abundance of Alnus and Weinmannia forests more clearly while centrally located record Fq-9C shows a more integrated signal of regional vegetation change. The revised age models show that core Fq-2 reflects the last 44 ka and composite record Fq-7C the last 85.5 ka. Marginally located core Fq-3 has an age of 133 ka at 32 m core depth and the lowermost 11 m of sediments appear of older but unknown age. The longest record Fq-BC shows ˜60 yr resolution over the period of 284-27 ka. All pollen records are in support of a common regional vegetation development leading to a robust reconstruction of long series of submillennial climate oscillations reflecting Dansgaard-Oeschger (DO) cycles. Reconstructed climate variability in the tropical Andes since marine isotope stage (MIS) 8 compares well with NGRIP (δ 18O based), Epica Dome C (δD based) and the Mediterranean sea surface temperature record MD01-2443/44 (U K'37 based) underpinning the global significance of the climate record from this tropical Andean lake. A basin-wide biostratigraphy is presented and we concluded although with varying robustness that each core is representative of regional vegetational and climatic change.

Directly dated MIS 3 lake-level record from Lake Manix, Mojave Desert, California, USA

USGS Publications Warehouse

Reheis, Marith; Miller, David M.; McGeehin, John P.; Redwine, Joanna R.; Oviatt, Charles G.; Bright, Jordon E.

2015-01-01

An outcrop-based lake-level curve, constrained by ~ 70 calibrated 14C ages on Anodonta shells, indicates at least 8 highstands between 45 and 25 cal ka BP within 10 m of the 543-m upper threshold of Lake Manix in the Mojave Desert of southern California. Correlations of Manix highstands with ice, marine, and speleothem records suggest that at least the youngest three highstands coincide with Dansgaard–Oeschger (D–O) stadials and Heinrich events 3 and 4. The lake-level record is consistent with results from speleothem studies in the Southwest that indicate cool wet conditions during D–O stadials. Notably, highstands between 43 and 25 ka apparently occurred at times of generally low levels of pluvial lakes farther north as interpreted from core-based proxies. Mojave lakes may have been supported by tropical moisture sources during oxygen-isotope stage 3, perhaps controlled by southerly deflection of Pacific storm tracks due to weakening of the sea-surface temperature gradient in response to North Atlantic climate perturbations.

Sedimentary organic matter and carbonate variations in the Chukchi Borderland in association with ice sheet and ocean-atmosphere dynamics over the last 155 kyr

NASA Astrophysics Data System (ADS)

Rella, S. F.; Uchida, M.

2011-12-01

Knowledge on past variability of sedimentary organic carbon in the Arctic Ocean is important to assess natural carbon cycling and transport processes related to global climate changes. However, the late Pleistocene oceanographic history of the Arctic is still poorly understood. In the present study we show sedimentary records of total organic carbon (TOC), CaCO3, benthic foraminiferal δ18O and the coarse grain size fraction from a piston core recovered from the northern Northwind Ridge in the far western Arctic Ocean, a region potentially sensitively responding to past variability in surface current regimes and sedimentary processes such as coastal erosion. An age model based on oxygen stratigraphy, radiocarbon dating and lithological constraints suggests that the piston core records paleoenvironmental changes of the last 155 kyr. TOC shows orbital-scale increases and decreases that can be respectively correlated to the waxing and waning of large ice sheets dominating the Eurasian Arctic, suggesting advection of fine suspended matter derived from glacial erosion to the Northwind Ridge by eastward flowing intermediate water and/or surface water and sea ice during cold episodes of the last two glacial-interglacial cycles. At millennial scales, increases in TOC might correlate to a suite of Dansgaard-Oeschger Stadials between 120 and 45 ka before present (BP) indicating a possible response to abrupt northern hemispheric temperature changes. Between 70 and 45 ka BP, closures and openings of the Bering Strait could have additionally influenced TOC variability. CaCO3 content tends to anti-correlate with TOC on both orbital and millennial time scales, which we interpret in terms of enhanced sediment advection from the carbonate-rich Canadian Arctic via an extended Beaufort Gyre during warm periods of the last two glacial-interglacial cycles and increased organic carbon advection from the Siberian Arctic during cold periods when the Beaufort Gyre contracted. We propose that this pattern may be related to orbital- and millennial-scale variations of dominant atmospheric surface pressure systems expressed in mode shifts of the Arctic Oscillation.

Sedimentary organic matter variations in the Chukchi Borderland over the last 155 kyr

NASA Astrophysics Data System (ADS)

Rella, S. F.; Uchida, M.

2011-03-01

Knowledge on past variability of sedimentary organic carbon in the Arctic Ocean is important to assess natural carbon cycling and transport processes related to global climate changes. However, the late Pleistocene oceanographic history of the Arctic is still poorly understood. In the present study we show sedimentary records of total organic carbon (TOC), C/N and CaCO3 from a piston core recovered from the northern Northwind Ridge in the far western Arctic Ocean, a region potentially sensitively responding to past variability in surface current regimes and sedimentary processes such as coastal erosion. An age model based on correlation of our CaCO3 record with the benthic δ18O stack, supplemented by lithological constraints, suggests that the piston core records paleoenvironmental changes of the last 155 kyr. According to this age model, TOC and C/N show orbital-scale increases and decreases that can be respectively correlated to the waxing and waning of large ice sheets dominating the Eurasian Arctic, suggesting advection of fine suspended matter derived from glacial erosion to the Northwind Ridge by eastward flowing intermediate water and/or surface water and sea ice during cold episodes of the last two glacial-interglacial cycles. At millennial scales, increases in TOC and C/N appear to correlate to a suite of Dansgaard-Oeschger Stadials between 120 and 40 ka before present (BP) and thus seem to respond to abrupt northern hemispheric temperature changes. Between 65 and 40 ka BP, closures and openings of the Bering Strait could have additionally influenced TOC and C/N variability. CaCO3 content tends to anti-correlate with TOC and C/N on both orbital and millennial time scales, which we interpret as enhanced sediment advection from the carbonate-rich Canadian Arctic via an extended Beaufort Gyre during warm periods of the last two glacial-interglacial cycles and increased terrestrial organic carbon advection from the Siberian Arctic during cold periods when the Beaufort Gyre contracted. We propose that this pattern may be related to orbital- and millennial-scale variations of dominant atmospheric surface pressure systems expressed in mode shifts of the Arctic Oscillation.

Linkages between ocean circulation, heat uptake and transient warming: a sensitivity study

NASA Astrophysics Data System (ADS)

Pfister, Patrik; Stocker, Thomas

2016-04-01

Transient global warming due to greenhouse gas radiative forcing is substantially reduced by ocean heat uptake (OHU). However, the fraction of equilibrium warming that is realized in transient climate model simulations differs strongly between models (Frölicher and Paynter 2015). It has been shown that this difference is not only related to the magnitude of OHU, but also to the radiative response the OHU causes, measured by the OHU efficacy (Winton et al., 2010). This efficacy is strongly influenced by the spatial pattern of the OHU and its changes (Rose et al. 2014, Winton et al. 2013), predominantly caused by changes in the Atlantic meridional overturning circulation (AMOC). Even in absence of external greenhouse gas forcing, an AMOC weakening causes a radiative imbalance at the top of the atmosphere (Peltier and Vettoretti, 2014), inducing in a net warming of the Earth System. We investigate linkages between those findings by performing both freshwater and greenhouse gas experiments in an Earth System Model of Intermediate Complexity. To assess the sensitivity of the results to ocean and atmospheric transport as well as climate sensitivity, we use an ensemble of model versions, systematically varying key parameters. We analyze circulation changes and radiative adjustments in conjunction with traditional warming metrics such as the transient climate response and the equilibrium climate sensitivity. This aims to improve the understanding of the influence of ocean circulation and OHU on transient climate change, and of the relevance of different metrics for describing this influence. References: Frölicher, T. L. and D.J. Paynter (2015), Extending the relationship between global warming and cumulative carbon emissions to multi-millennial timescales, Environ. Res. Lett., 10, 075022 Peltier, W. R., and G. Vettoretti (2014), Dansgaard-Oeschger oscillations predicted in a comprehensive model of glacial climate: A "kicked" salt oscillator in the Atlantic, Geophys. Res. Lett., 41, 7306-7313 Rose, B. E. J., K. C. Armour, D. S. Battisti, N. Feldl, and D. D. B. Koll (2014), The dependence of transient climate sensitivity and radiative feedbacks on the spatial pattern of ocean heat uptake, Geophys. Res. Lett., 41, 1071-1078 Winton M., K. Takahashi and I. M. Held (2010), Importance of ocean heat uptake efficacy to transient climate change, J. Clim., 23, 2333-44 Winton, M., S. M. Griffies, B. Samuels, J. L. Sarmiento and T. L. Frölicher (2013) Connecting changing ocean circulation with changing climate, J. Clim., 26, 2268-78

The Earth's Interaction With the Sun Over the Millennia From Analyses of Historical Sunspot, Auroral and Climate Records

NASA Astrophysics Data System (ADS)

Yau, K.

2001-12-01

A prolonged decrease in the Sun's irradiance during the Maunder Minimum has been proposed as a cause of the Little Ice Age ({ca} 1600-1800). Eddy [{Science} {192}, 1976, 1189] made this suggestion after noting that very few sunspots were observed from 1645 to 1715, indicative of a weakened Sun. Pre-telescopic Oriental sunspot records go back over 2200 years. Periods when no sunspots were seen have been documented by, {eg}, Clark [{Astron} {7}, 2/1979, 50]. Abundances of C 14 in tree rings and Be10 in ice cores are also good indicators of past solar activity. These isotopes are produced by cosmic rays high in the atmosphere. When the Sun is less active more of them are made and deposited at ground level. There is thus a strong {negative} correlation between their abundances and sunspot counts. Minima of solar activity in tree rings and a south polar ice core have been collated by, {eg}, Bard [{Earth Planet Sci Lett} {150} 1997, 453]; and show striking correspondence with periods when no sunspots were seen, centered at {ca} 900, 1050, 1500, 1700. Pang and Yau [{Eos} {79}, #45, 1998, F149] investigated the Medieval Minimum at 700, using in addition the frequency of auroral sighting7s, a good indicator of solar activity too [Yau, PhD thesis, 1988]; and found that the progression of minima in solar activity goes back to 700. Auroral frequency, C 14 and Be 10 concentrations are also affected by variations in the geomagnetic field. Deposition changes can also influence C 14 and Be 10 abundances. Sunspot counts are thus the only true indicator of solar activity. The Sun's bolometric variations (-0.3% for the Maunder Minimum) can contribute to climatic changes (\\0.5° C for the Little Ice Age)[{eg}, Lean, {GRL} {22}, 1995, 3195]. For times with no thermometer data, temperature can be estimated from, {eg}, Oxygen 18 isotopic abundance in ice cores, which in turn depends on the temperature of the ocean water it evaporated from. We have linked the Medieval Minimum to the cold spell, dated to {ca} 700 by Dansgaard [{Nature} {255}, 1974, 24]. Using records of advances and retreats of glaciers, previous researchers have linked it to a cold spell in the previous two centuries instead, thus requiring an offset in timescales. Our literature search has yielded more records of sunspot sightings, and established the fifth century as a minimum of solar activity, ending in a maximum at {ca} 500. These features and the minimum at 700 match contemporary deviations of atmospheric C 14 from a secular trend, due primarily to long-term changes in the strength of the Earth's magnetic moment [Stuiver, {Radiocarbon} {35}, 215]. Pang has shown that the climate of Eurasia was cold in the 5th century, due partly to volcanic cooling [{Eos} {80}, #46, 1999, F220]. Reduced solar luminosity may have contributed to that too. The cold apparently forced massive southward migrations of Teutonic and Asian barbarians into the Roman Empire, ending it in 476. Europe was plunged into the Dark Age, from which it did not recover until the climate warmed up again toward the end of the millennium. Finally, climate changes can also be produced by greenhouse warming, reorganization of ocean current systems "Dansgaard-Oeschger events," the Earth's orbital variations "Milankovitch effects," {etc}. Continued analysis of historical records, in conjunction with other proxy data, can help shed light on the nature of the Earth's interactions with the Sun, and the causes of past climate changes.

The Big Chills

NASA Astrophysics Data System (ADS)

Bond, G. C.; Dwyer, G. S.; Bauch, H. A.

2002-12-01

At the end of the last glacial, the Earth's climate system abruptly shifted into the Younger Dryas, a 1500-year long cold snap known in the popular media as the Big Chill. Following an abrupt warming ending the Younger Dryas about 11,600 years ago, the climate system has remained in an interglacial state, thought to have been relatively stable and devoid, with possibly one or two exceptions, of abrupt climate change. A growing amount of evidence suggests that this benign view of interglacial climate is incorrect. High resolution records of North Atlantic ice rafted sediment, now regarded as evidence of extreme multiyear sea ice drift, reveal abrupt shifts on centennial and millennial time scales. These have been traced from the end of the Younger Dryas to the present, revealing evidence of significant climate variability through all of the last two millennia. Correlatives of these events have been found in drift ice records from the Arctic's Laptev Sea, in the isotopic composition of North Grip ice, and in dissolved K from the GISP2 ice core, attesting to their regional extent and imprint in proxies of very different origins. Measurements of Mg/Ca ratios in planktic foraminifera over the last two millennia in the eastern North Atlantic demonstrate that increases in drifting multiyear sea ice were accompanied by abrupt decreases in sea surface temperatures, especially during the Little Ice Age. Estimated rates of temperature change are on the order of two degrees centigrade, more than thirty percent of the regional glacial to interglacial change, within a few decades. When compared at the same resolution, these interglacial variations are as abrupt as the last glacial's Dansgaard-Oeschger cycles. The interglacial abrupt changes are especially striking because they occurred within the core of the warm North Atlantic Current. The changes may have been triggered by variations in solar irradiance, but if so their large magnitude and regional extent requires amplifying mechanisms that have not yet been identified. While the Younger Dryas event is dramatic, the Big Chills of the Holocene are clearly significant abrupt changes in their own right. Because they were a recurring feature of the interglacial climate we live in presently, they are especially relevant to the prediction of sudden changes in the future, more so probably than abrupt changes during the last glacial which took place within boundary conditions that are not likely to occur again soon, perhaps within tens of thousands of years.

Investigating the direct meltwater effect in oxygen-isotope records using an isotope-enabled Earth system model

NASA Astrophysics Data System (ADS)

Zhu, J.; Liu, Z.; Brady, E. C.; Otto-Bliesner, B. L.; Marcott, S. A.; Zhang, J.; Wang, X.; Noone, D.; Nusbaumer, J. M.; Wong, T. E.; Jahn, A.

2017-12-01

Oxygen isotopes (δ18O) in both terrestrial and marine paleoclimate archives have long been used to study the climate evolution of the late Quaternary. Based on the high-latitude "temperature effect" and the tropical "amount effect", the δ18O variations in ice cores and speleothems have been primarily interpreted as changes in surface air temperature and regional precipitation amount, respectively, although recent studies suggest that other climate processes may also play a role. However, one long-overlooked assumption for these climatic interpretations is that the δ18O variations in the terrestrial records can be exclusively explained by changes in climate variables. This assumption could be violated during past glacial meltwater events, as the meltwater discharged into the ocean by icebergs or surface runoff is considerably depleted in δ18O compared to the surface ocean. This depleted meltwater can significantly decrease the isotope composition of the seawater it deposits and propagate within the hydrological cycle to directly influence the δ18O values in adjacent precipitation (the direct effect), without involving any changes in the climate state (the indirect effect). Here, by conducting water isotope-enabled climate simulations, we aim to quantify the direct meltwater effect on the terrestrial δ18O records. We find that, for large meltwater events in the northern North Atlantic Ocean (e.g., around 0.25 Sv lasting 300 years), the direct meltwater effect contributes more than 15% and 35% of the total δ18O changes in the precipitation over Greenland and the eastern Brazil, respectively. Model simulations further demonstrate that the direct meltwater effect increases with the magnitude and duration of meltwater, and it is sensitive to both the location and the shape of the freshwater forcing. We argue that the direct meltwater effect on δ18O records could also be significant in other regions and for other terrestrial oxygen-isotope records, as long as the meltwater can decrease the isotope composition of seawater over the major moisture source regions for the precipitation at the record sites. These new modeling results have important implications for the interpretation of δ18O changes during past glacial meltwater events (e.g., the Heinrich events, Meltwater Pulses and the Dansgaard-Oeshger cycles).

Late Pliocene - Early Pleistocene paleoenvironmental reconstruction based on stable isotope compositions of Stephanorhinus sp. and Mammut sp. teeth

NASA Astrophysics Data System (ADS)

Szabó, Péter; Kovács, János; Kocsis, László; Gasparik, Mihály; Vennemann, Torsten; Demény, Attila; Virág, Attila

2014-05-01

Stable isotope measurements of skeletal apatite from herbivorous mammals are often used to provide information on the terrestrial paleoenvironment and paleoclimate. In this study fossil teeth of Stephanorhinus Kretzoi 1942 (rhinoceros) and Mammut Blumenbach 1799 (mastodon), amongst others, were investigated from the Carpathian Basin. According to the biostratigraphy, the age of the samples has a range from Late Pliocene to Early Pleistocene. Reconstructing paleoclimate and paleoenvironment of this era is important as it can be an analogue for the future climate. Oxygen and carbon isotopic compositions were measured from the tooth enamel, because it is believed to be the most resistant to diagenetic alteration (e.g., Kohn & Cerling, 2002). The carbon isotopic composition in the carbonate fraction of apatite can be related to the diet of the animal (Kohn & Cerling, 2002). Hence, it can reflect the photosynthetic pathway (C3 or C4) of the plants consumed by these herbivores. The δ18O values were determined in the phosphate fraction of apatite. In the case of large mammals that are obligate drinkers, the δ18O values closely track those of the environmental water (Bryant & Froelich, 1995). Knowing the δ18O values of environmental water and relating it to local precipitation, the mean annual temperature (MAT) of the site can be calculated (Dansgaard, 1964). The δ13C values range from -10 to -15 o (VPDB). The result clearly shows that these animals consumed C3 plants. Most of the δ13C values indicate mixed grassland-open woodland rather than a closed canopy forest. Although there is variation in the δ18O values (mean 14.2 ± 1.0 o VSMOW, n=17), most of the samples would support a MAT range of 8-12 ° C. This is in good agreement with other proxies for the localities and time period (Kovács et al., 2013). Bryant, D.J. & Froelich, P.N. (1995) A model of oxygen-isotope fractionation in bodywater of large-mammals. Geochimica et Cosmochimica Acta 59, 4523-4537. Dansgaard, W. (1964) Stable isotopes in precipitation. Tellus 16, 436-468. Kohn, M.J. & Cerling, T.E. (2002) Stable isotope compositions of biological apatite. Reviews in Mineralogy and Geochemistry 48, 455-488. Kovács, J. et al. (2013) Clay Mineralogy of Red Clay Deposits from the Central Carpathian Basin (Hungary): Implications for Plio/Pleistocene Chemical Weathering and Paleoclimate. Turkish J. Earth. Sci. 22, 414-426.

Strong and deep Atlantic meridional overturning circulation during the last glacial cycle.

PubMed

Böhm, E; Lippold, J; Gutjahr, M; Frank, M; Blaser, P; Antz, B; Fohlmeister, J; Frank, N; Andersen, M B; Deininger, M

2015-01-01

Extreme, abrupt Northern Hemisphere climate oscillations during the last glacial cycle (140,000 years ago to present) were modulated by changes in ocean circulation and atmospheric forcing. However, the variability of the Atlantic meridional overturning circulation (AMOC), which has a role in controlling heat transport from low to high latitudes and in ocean CO2 storage, is still poorly constrained beyond the Last Glacial Maximum. Here we show that a deep and vigorous overturning circulation mode has persisted for most of the last glacial cycle, dominating ocean circulation in the Atlantic, whereas a shallower glacial mode with southern-sourced waters filling the deep western North Atlantic prevailed during glacial maxima. Our results are based on a reconstruction of both the strength and the direction of the AMOC during the last glacial cycle from a highly resolved marine sedimentary record in the deep western North Atlantic. Parallel measurements of two independent chemical water tracers (the isotope ratios of (231)Pa/(230)Th and (143)Nd/(144)Nd), which are not directly affected by changes in the global cycle, reveal consistent responses of the AMOC during the last two glacial terminations. Any significant deviations from this configuration, resulting in slowdowns of the AMOC, were restricted to centennial-scale excursions during catastrophic iceberg discharges of the Heinrich stadials. Severe and multicentennial weakening of North Atlantic Deep Water formation occurred only during Heinrich stadials close to glacial maxima with increased ice coverage, probably as a result of increased fresh-water input. In contrast, the AMOC was relatively insensitive to submillennial meltwater pulses during warmer climate states, and an active AMOC prevailed during Dansgaard-Oeschger interstadials (Greenland warm periods).

Holocene millennial/centennial-scale multiproxy cyclicity in temperate eastern Australian estuary sediments

NASA Astrophysics Data System (ADS)

Skilbeck, C. Gregory; Rolph, Timothy C.; Hill, Natalie; Woods, Jonathan; Wilkens, Roy H.

2005-05-01

We have undertaken a comparative study of down-core variation in multiproxy palaeoclimate data (magnetic susceptibility, calcium carbonate content and total organic carbon) from two coastal water bodies (Myall and Tuggerah Lakes) in temperate eastern Australia to identify local, regional and global-forcing factors within Holocene estuarine sediments. The two lakes lie within the same temperate climate zone adjacent to the Tasman Sea, but are not part of the same catchment and drain different geological provinces. One is essentially a freshwater coastal lake whereas the other is a brackish back-barrier lagoon. Despite these differences, data from two sites in each of the two lakes have allowed us to investigate and compare cyclicity in otherwise uniform, single facies sediments within the frequency range of 200-2000 years, limited by the sedimentation rate within the lakes and our sample requirements. We have auto- and cross-correlated strong periodicities at 360 years, 500-530 years, 270-290 years, 420-450 years and 210 years, and subordinate periods of 650 years, 1200-1400 years and 1800 years. Our thesis is that climate is the only regionally available mechanism available to control common millennial and centennial scale cyclicity in these sediments, given the geographical and other differences. However, regional climate may not be the dominant effect at any single time and either location. Within the range of frequency spectral peaks we have identified, several fall within known long-term periodical fluctuations of sun spot activity; however, feedback loops associated with short-term orbital variation, such as Dansgaard-Oeschger cycles, and the relationship between these and palaeo-ENSO variation, are also possible contributors. Copyright

Evidence for Millennial-Scale Climate Variability in the Surface Waters Above ODP Site 980, NE Atlantic Ocean During the Last Glacial Interval (MIS 4-2)

NASA Astrophysics Data System (ADS)

Michaud, J. R.; Cullen, J. L.; McManus, J. F.; Oppo, D. W.

2004-05-01

Successful efforts to recover quality high sedimentation rate deep-sea sediment sections from the North Atlantic over the last decade have produced a number of studies demonstrating that climate instability at sub-orbital and even millennial time-scales is a pervasive component of Late Pleistocene North Atlantic climate. This is particularly true during Marine Isotope Stages (MIS) 4-2, i.e., the last glacial interval. One such high sedimentation rate section was recovered at ODP Site 980, Northeast Atlantic Ocean where sedimentation rates during MIS 4-2 exceed 15cm/kyr. Recently, we have begun to generate more detailed records from MIS 4-2 at Site 980 by reducing our sampling interval from 20 to around 2.5 cm, improving the resolution of our records an order of magnitude, from 1200-1300 to 100-200 years. 300 samples were used to generate high resolution records of changes in the input of ice-rafted detritus (IRD), along with limited data documenting changes in the relative abundance of the N. pachyderma, left coiling, which can be evaluated within the context of our previously generated lower resolution planktic and benthic oxygen isotope records used to generate our age model for this interval. Our previously published low resolution IRD record enabled us to identify Heinrich events 1-6 within the sediment interval deposited during the last glacial. Each event is characterized by IRD concentrations ranging from 500 to over 2500 lithic grains >150 microns per gram sediment. Superimposing our new high resolution IRD record reveals that Heinrich events 3,2,1 occurring at approximately 32, 23, and 17 kya, respectively, are each composed of a series of separate abrupt rapid increases in IRD concentrations approaching 1,000 grains per gram. An additional comparable event occurring at approximately 20 kya has also been identified. In the early part of the last glacial H6, H5, and H4 occurring at approximately 66, 47, and 38 kya, respectively, are recorded as much more abrupt and rapid increases in IRD concentrations to 2,000 or greater lithic grains per gram than were observed in our previous record. There are two 5 kyr intervals between H6 and H5 that contain little or no IRD. An additional abrupt IRD event is recorded at approximately 34 kya. Thus, our new IRD record is recording a series of additional episodic increases in IRD concentrations comparable in intensity to the identified Heinrich events. This suggests that ODP Site 980 sediments are recording a series of more closely spaced episodic increases in IRD concentration that can be directly related to the Dansgaard/Oeschger events recorded in Greenland ice cores. Comparison of our preliminary high resolution record of changes in the relative abundance of the polar species N. pachyderma, left coiling, to our IRD record suggests that the input of iceberg bearing waters precedes the increases in the relative abundance of N. pachyderma, left coiling for the early glacial IRD events. Whereas the abrupt increases in N. pachyderma, left coiling seem to occur during the later glacial IRD events. Thus, in the early glacial the influx of icebergs seem to occur before the invasion of cooler surface waters as opposed to the same time later in the glacial.

Novel automated inversion algorithm for temperature reconstruction using gas isotopes from ice cores

NASA Astrophysics Data System (ADS)

Döring, Michael; Leuenberger, Markus C.

2018-06-01

Greenland past temperature history can be reconstructed by forcing the output of a firn-densification and heat-diffusion model to fit multiple gas-isotope data (δ15N or δ40Ar or δ15Nexcess) extracted from ancient air in Greenland ice cores using published accumulation-rate (Acc) datasets. We present here a novel methodology to solve this inverse problem, by designing a fully automated algorithm. To demonstrate the performance of this novel approach, we begin by intentionally constructing synthetic temperature histories and associated δ15N datasets, mimicking real Holocene data that we use as true values (targets) to be compared to the output of the algorithm. This allows us to quantify uncertainties originating from the algorithm itself. The presented approach is completely automated and therefore minimizes the subjective impact of manual parameter tuning, leading to reproducible temperature estimates. In contrast to many other ice-core-based temperature reconstruction methods, the presented approach is completely independent from ice-core stable-water isotopes, providing the opportunity to validate water-isotope-based reconstructions or reconstructions where water isotopes are used together with δ15N or δ40Ar. We solve the inverse problem T(δ15N, Acc) by using a combination of a Monte Carlo based iterative approach and the analysis of remaining mismatches between modelled and target data, based on cubic-spline filtering of random numbers and the laboratory-determined temperature sensitivity for nitrogen isotopes. Additionally, the presented reconstruction approach was tested by fitting measured δ40Ar and δ15Nexcess data, which led as well to a robust agreement between modelled and measured data. The obtained final mismatches follow a symmetric standard-distribution function. For the study on synthetic data, 95 % of the mismatches compared to the synthetic target data are in an envelope between 3.0 to 6.3 permeg for δ15N and 0.23 to 0.51 K for temperature (2σ, respectively). In addition to Holocene temperature reconstructions, the fitting approach can also be used for glacial temperature reconstructions. This is shown by fitting of the North Greenland Ice Core Project (NGRIP) δ15N data for two Dansgaard-Oeschger events using the presented approach, leading to results comparable to other studies.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ehhalt, D.; Knott, K.; Nagel, J. F.

The D and O¹⁸ contents of rain water are known to vary considerably with time and location. Dansgaard found a good correlation of the mean O¹⁸ content of rain with mean air temperature, which causes a latitudinal as well as a seasonal variation of O¹⁸ and a similar one for D. Under dry climatic conditions, as in South Africa, the D content appears to be strongly influenced by re-evaporation of the falling raindrops. This has the effect of obscuring the normal seasonal variations. The evaporation obviously takes place under kinetic conditions, thus increasing the separation factors especially for the oxygenmore » isotopes. A detailed study of a thunderstorm in Heidelberg shows that here too evaporation causes an enrichment in D. (auth)« less

Contrasting scaling properties of interglacial and glacial climates

PubMed Central

Shao, Zhi-Gang; Ditlevsen, Peter D.

2016-01-01

Understanding natural climate variability is essential for assessments of climate change. This is reflected in the scaling properties of climate records. The scaling exponents of the interglacial and the glacial climates are fundamentally different. The Holocene record is monofractal, with a scaling exponent H∼0.7. On the contrary, the glacial record is multifractal, with a significantly higher scaling exponent H∼1.2, indicating a longer persistence time and stronger nonlinearities in the glacial climate. The glacial climate is dominated by the strong multi-millennial Dansgaard–Oeschger (DO) events influencing the long-time correlation. However, by separately analysing the last glacial maximum lacking DO events, here we find the same scaling for that period as for the full glacial period. The unbroken scaling thus indicates that the DO events are part of the natural variability and not externally triggered. At glacial time scales, there is a scale break to a trivial scaling, contrasting the DO events from the similarly saw-tooth-shaped glacial cycles. PMID:26980084

Reconstruction of peak water levels, peak discharges and long-term occurrence of extreme- as well as smaller pre-instrumental flood events of river Aare, Limmat, Reuss, Rhine and Saane in Switzerland. Part I

NASA Astrophysics Data System (ADS)

Wetter, Oliver; Tuttenuj, Daniel

2016-04-01

Part I: Dr. Oliver Wetter. (Oeschger Centre for Climate Change Research, University of Bern, Switzerland) Part II: PhD student Daniel Tuttenuj (Oeschger Centre of Climate Change Research, University of Bern, Switzerland) The methodology developed by Wetter et al. (2011) combines different documentary and instrumental sources, retaining relevant information for the reconstruction of extreme pre-instrumental flood events. These include hydrological measurements (gauges), historic river profiles (cross and longitudinal profiles), flood marks, historic city maps, documentary flood evidence (reports in chronicles and newspapers) as well as paintings and drawings. It has been shown that extreme river Rhine flood events of the pre-instrumental period can be reconstructed in terms of peak discharges for the last 750 years by applying this methodology to the site of Basel. Pfister & Wetter (2011) furthermore demonstrated that this methodology is also principally transferable to other locations and rivers. Institutional documentary evidence has not been systematically analysed in the context of historical hydrology in Switzerland so far. The term institutional documentary evidence generally outlines sources that were produced by governments or other (public) bodies including the church, hospitals, and the office of the bridge master. Institutional bodies were typically not directly interested in describing climate or hydrological events but they were obliged to document their activities, especially if they generated financial costs (bookkeeping), and in doing so they often indirectly recorded climatologic or hydrological events. The books of weekly expenditures of Basel ("Wochenausgabenbücher der Stadt Basel") were first analysed by Fouquet (1999). He found recurring records of wage expenditures for a squad of craftsmen that was called up onto the bridge with the task of preventing the bridge from being damaged by fishing out drifting logs from the flood waters. Fouquet systematically analysed the period from 1446-1542 and could prove a large number of pre-instrumental flood events of river Rhine, Birs, Birsig and Wiese in Basel. All in all the weekly led account books contained 54 Rhine flood events, whereas chroniclers and annalists only recorded seven floods during the same period. This is a ratio of almost eight to one. This large difference points to the significantly sharper "observation skills" of the account books towards smaller floods, which may be explained by the fact that bridges can be endangered by relatively small floods because of driftwood, whereas it is known that chroniclers or annalists were predominantly focussing on spectacular (extreme) flood events. We [Oliver Wetter and Daniel Tuttenuj] are now able to present first preliminary results of reconstructed peak water levels and peak discharges of pre instrumental river Aare-, Emme-, Limmat-, Reuss-, Rhine- and Saane floods. These first results clearly show the strengths as well as the limits of the data and method used, depending mainly on the river types. Of the above mentioned rivers only the floods of river Emme could not be reconstructed whereas the long-term development of peak water levels and peak discharges of the other rivers clearly correlate with major local and supra-regional Swiss flood corrections over time. PhD student Daniel Tuttenuj is going to present the results for river Emme and Saane (see Abstract Daniel Tuttenuj), whereas Dr Oliver Wetter is going to present the results for the other rivers and gives a first insight on long-term recurring periods of smaller river Birs-, Birsig-, Rhine- and Wiese flood events based on the analysis of the weekly led account books "Wochenausgabenbücher der Stadt Basel" (see also Abstract of Daniel Tuttenuj).

Countering Ice Ages: Re-directing Public Concern from Global Warming (GW) to Global Cooling (GC)

NASA Astrophysics Data System (ADS)

Singer, S. F.

2016-02-01

I present here three arguments in favor of such a drastic shift - which involves also a shift in current policies, such as mitigation of the greenhouse (GH) gas carbon dioxide. 1. Historical evidence shows that cooling, even on a regional or local scale, is much more damaging than warming. The key threat is to agriculture, leading to failure of harvests, followed by famine, starvation, disease, and mass deaths. 2. Also, GC is reasonably sure, while GW is iffy. The evidence from deep-sea sediment cores and ice cores shows some 17 (Milankovitch-style) glaciations in the past 2 million years, each typically lasting 100,000 years, interrupted by warm inter-glacials, typically around 10,000-yr duration. The most recent glaciation ended rather suddenly about 12,000 years ago. We are now in the warm Holocene, which is expected to end soon. Most of humanity may not survive the next, inevitable glaciation. We need to consider also the warming-cooling (Dansgaard-Oeschger-Bond - DOB) cycles, which seem solar-controlled and have a period of approx 1000-1500 years; its most recent cooling phase, the "Little Ice Age" (LIA), ended about 200 years ago. For details, see Unstoppable Global Warming: Every 1500 years by Singer &Avery [2007]. 3. Available technology seems adequate to assure human survival - at least in industrialized nations. The main threat is warfare, driven by competition for food and other essential resources. With nuclear weapons and delivery systems widely dispersed, the outcome of future wars is difficult to predict. Using geo-engineering to overcome a future cooling looks promising for both types of ice ages - with relatively low cost and low risk to the physical and biological environment. I will describe how to neutralize the "trigger" of major glaciations, and propose a particular greenhouse scheme that may counter the cooling phase of DOB cycles.

Thermohaline circulation and its box models simulation

NASA Astrophysics Data System (ADS)

Bazyura, Kateryna; Polonsky, Alexander; Sannikov, Viktor

2014-05-01

Ocean Thermochaline circulation (THC) is the part of large-scale World Ocean circulation and one of the main climate system components. It is generated by global meridional density gradients, which are controlled by surface heat and freshwater fluxes. THC regulates climate variability on different timescales (from decades to thousands years) [Stocker (2000), Clark (2002)]. Study of paleoclimatic evidences of abrupt and dramatic changes in ocean-atmosphere system in the past (such as, Dansgaard-Oeschger and Heinrich events or Younger Dryas, see e.g., [Rahmstorf (2002), Alley & Clark(1999)]) shows that these events are connected with THC regimes. At different times during last 120,000 years, three THC modes have prevailed in the Atlantic. They can be labeled as stadial, interstadial and Heinrich modes or as cold, warm and off mode. THC collapse (or thermohaline catastrophe) can be one of the consequences of global warming (including modern anthropogenic climate changes occurring at the moment). The ideas underlying different box-model studies, possibility of thermochaline catastrophe in present and past are discussed in this presentation. Response of generalized four box model of North Atlantic thermohaline circulation [developing the model of Griffies & Tzippermann (1995)] on periodic, stochastic and linear forcing is studied in details. To estimate climatic parameters of the box model we used monthly salinity and temperature data of ECMWF operational Ocean Reanalysis System 3 (ORA-S3) and data from atmospheric NCEP/NCAR reanalysis on precipitation, and heat fluxes for 1959-2011. Mean values, amplitude of seasonal cycle, amplitudes and periods of typical interdecadal oscillations, white noise level, linear trend coefficients and their significance level were estimated for every hydrophysical parameter. In response to intense freshwater or heat forcing, THC regime can change resulting in thermohaline catastrophe. We analyze relevant thresholds of external forcing in cases of using linear and nonlinear seawater state equation. In the frame of four-box model it is shown that: 1) The occurrence of the thermohaline catastrophe, which is likely happened at Younger Dryas period or developed as Heinrich events in the past, is improbable in modern climate epoch. 2) Choice of nonlinear seawater equitation of state leads to stabilization of warm mode of THC, which corresponds to modern climate state. 3) Typical white noise in heat and freshwater fluxes leads to generation of multidecadal oscillations of volume transport. Time-scale of these oscillations coincides with Atlantic Multidecadal oscillation periodicity. So, it is shown that that recent climate is characterized by quasi-periodical stable multidecadal THC warm regime. Stocker, T. F., 2000: Past and future reorganisations in the climate system. Quat. Sci.Rev, Vol. 19, P.301-319. Clark U., 2002: The role of the thermohaline circulation in abrupt climate change. Nature. Vol. 415, P.863-869. Rahmstorf S., 2002: Ocean circulation and climate during the past 120000 years. Nature. Vol. 419, P.207-214. Alley, R. B. & Clark, P. U., 1999: The deglaciation of the Northern Hemisphere: a global perspective. Annu.Rev. Earth Planet. Sci. Vol. 27, P.149-182. Griffies S.M., Tziperman E., 1995: A linear thermohaline oscillator driven by stochastic atmospheric forcing. Journal of Climate. Vol. 8. P. 2440-2453.

An alluvial record of El Niño events from northern coastal Peru

NASA Astrophysics Data System (ADS)

Wells, Lisa E.

1987-12-01

Overbank flood deposits of northern coastal Peru provide the potential for the development of a late Quaternary chronology of El Niño events. Alluvial deposits from the 1982-1983 El Niño event are the basis for establishing a type El Niño deposit. Sedimentary structures suggesting depositional processes range from sheet flows to debris flows, with sheet flood deposits being the most common. The 1982-1983 deposits are characterized by a 50- to 100-cm- thick basal gravel, overlain by a 10- to 100-cm-thick sand bed, grading into a 1- to 10-cm-thick silty sand bed and capped by a very thin layer of silt or clay. The surface of the deposit commonly displays the original shear flow lines crosscut by postdepositional mud cracks and footprints (human and animal). Stacked sequences of flood deposits are present in Pleistocene and Holocene alluvial fill, suggesting that El Niño type events likely occurred throughout the late Quaternary. A relative chronology of the deposits is developed based on terrace and soil stratigraphy and on the degree of preservation of surficial features. A minimum of 15 El Niño events occurred during the Holocene; a minimum of 21 events occurred during the late Pleistocene. Timing of the Holocene events is bracketed by isochrons derived from the archaeologic stratigraphy. Corrected radiocarbon ages from included detrital wood provide the following absolute dates for El Niño events: 1720 ± 60 A.D., 1460 ± 20 A.D., 1380 ± 140 A.D. (error overlaps with the A.D. 1460 event; these may represent a single event), and 1230 ± 60 B.C.

Examination of the Asian Monsoon: Ongoing Studies from IODP Expedition 346

NASA Astrophysics Data System (ADS)

Murray, R. W.; Tada, R.; Alvarez Zarikian, C. A.

2014-12-01

IODP Expedition 346 (Asian Monsoon) tested the hypothesis that Plio-Pleistocene uplift of the Himalaya and Tibetan Plateau, and/or emergence and growth of the northern hemisphere ice sheets and establishment of the two discrete modes of Westerly Jet circulation, is the cause of the millennial-scale variability of the East Asian summer monsoon (EASM) and amplification of Dansgaard-Oeschger cycles. We also examined whether the nature and strength of flow through the Tsushima Strait (which is strongly affected by EASM precipitation, sea level changes, and EAWM cooling) influenced surface and deepwater conditions of the Japan, Yamato, and Ulleung Basins. During only six weeks of drilling, Expedition 346 recovered 6135.3 m of core, which established an IODP record for the amount of recovered material. Because of recent advances in drilling technology and newly developed analytical tools, we were able to examine records that were impossible to acquire even a few years ago. The newly engineered half piston core system recovered the deepest piston core in DSDP/ODP/IODP history (490.4 m in Hole U1427A), which was reached by continuous piston coring from the seafloor. These advances delivered new surprises. We recovered pristine dark-light laminae from approximately 8 Ma sediment from 275 m below the seafloor at Site U1425 (Yamato Rise) and from 210 m below the seafloor (10-12 Ma) at Site U1430 in the Ulleung Basin. Aggressive sampling for geochemistry provided important constraints on the diagenetic and chemical environments throughout these marginal seas, and yet did not negatively compromise paleoceanographic objectives. We are extending earlier pioneering results of the Quaternary dark and light layers in these basins and which record variations of EASM precipitation over South China. Drilling in the East China Sea is providing an excellent record of EASM precipitation because its surface water salinity and temperature during summer is significantly influenced by Yangtze River discharge. Ash records are providing calibrated stratigraphic control and improving understanding of arc history. Interpreting these and other results in the context of other IODP drilling expeditions, such as Expedition 349 to the South China Sea, will be critical to develop a holistic understanding of the Asian monsoon system.

Holocene Concentrations of Methane in the Atmosphere are in Part Proportional to Concentrations of Sulfur Dioxide and Inversely Proportional to the Oxidizing Capacity of the Atmosphere

NASA Astrophysics Data System (ADS)

Ward, P. L.

2008-12-01

The atmosphere cleans itself by oxidizing pollutants. The primary oxidant is the hydroxyl radical (OH) formed by photodissociation of ozone in the near ultra-violet. Ozone and OH are in limited supply. Sulfur dioxide (SO2) absorbs near ultraviolet light limiting production of OH and reacts immediately with any available OH, forming sulfuric acid. Methane reacts more slowly with OH and will typically not be oxidized until there is little SO2. Thus a high concentration of methane indicates low oxidizing capacity. The rate at which SO2 is injected into the atmosphere controls oxidizing capacity and climate change in four ways: 1. Moderate rate: Large volcanic eruptions (VEI >=6) lower global temperatures for a few years when they are separated by years to decades so the oxidizing capacity of the atmosphere can fully recover. In 1991, Pinatubo volcano in the Philippines erupted 20 Mt SO2 and 491 Mt H2O, the largest volcanic eruption since 1912. The SO2 was oxidized primarily by OH to form a 99% pure aerosol of sulfuric acid and water at an elevation of 20-23 km. This aerosol reflected sunlight, lowering the world's temperature on average 0.4°C for three years. Ozone levels were reduced by 10%. Methane increased by 15 ppb for a year. The e-folding time for SO2 was 35 days. 2. High rate: When large eruptions occur once to several times per year, there is insufficient oxidizing capacity leading to increases in methane and other greenhouse gases and global warming. There were 15 times in the Holocene when large volcanoes erupted on average at least every year for 7 to 21 years. Man is now putting as much SO2 from burning fossil fuels into the atmosphere every year as one large volcano, causing current global warming. The two previous times were from 818-838 AD, the onset of the Medieval Warming Period, and from 180-143 BC, the onset of the Roman Warm Period. 3. Low rate: When there are no large eruptions for decades, the oxidizing capacity can catch up, cleaning the atmosphere, removing most of the methane and other pollutants. A clean atmosphere leads to cooling and drought. The 8.2 ka event is a classic example, but similar decadal droughts around 6.2, 5.8, 5.4, 4.2, and 2.9 ka caused the demise of major civilizations. 4. Extreme rate: Whereas large volcanic eruptions produce 10-1000 km3 of andesitic and silicic tephra, flood basalt eruptions produce as much as 3,000,000 km3 of basalt containing 10 to 100 times more SO2 per km3. The result is runaway global warming, widespread acid rain, and mass extinctions. The link between SO2 and global warming is good news because we have developed many efficient technologies that burn fossil fuels with less SO2 emission and scrub SO2 out of smoke stacks. Efforts to reduce acid rain have been successful in reducing manmade emissions of SO2 by >20% since 1980 and thereby reducing methane concentrations. Sudden increases in methane during the Pleistocene Dansgaard-Oeschger events follow sudden increases in volcanism. High rainfall especially in the Sahara and high methane concentrations in the early Holocene are clearly related to increased volcanism that brought about the end of the Ice Age. Increases in global warming at 3170 BC, 161 BC, and 828 AD are contemporaneous with short-term increases in methane. The rapid increase in SO2 from burning fossil fuels since 1850 can explain much of the corresponding rapid increase in methane. But during the last 5000 years, volcanism has been relatively constant and thus it can not explain the observed gradual increase in methane.

Intra-event isotope and raindrop size data of tropical rain reveal effects concealed by event averaged data

NASA Astrophysics Data System (ADS)

Managave, S. R.; Jani, R. A.; Narayana Rao, T.; Sunilkumar, K.; Satheeshkumar, S.; Ramesh, R.

2016-08-01

Evaporation of rain is known to contribute water vapor, a potent greenhouse gas, to the atmosphere. Stable oxygen and hydrogen isotopic compositions (δ18O and, δD, respectively) of precipitation, usually measured/presented as values integrated over rain events or monthly mean values, are important tools for detecting evaporation effects. The slope ~8 of the linear relationship between such time-averaged values of δD and δ18O (called the meteoric water line) is widely accepted as a proof of condensation under isotopic equilibrium and absence of evaporation of rain during atmospheric fall. Here, through a simultaneous investigation of the isotopic and drop size distributions of seventeen rain events sampled on an intra-event scale at Gadanki (13.5°N, 79.2°E), southern India, we demonstrate that the evaporation effects, not evident in the time-averaged data, are significantly manifested in the sub-samples of individual rain events. We detect this through (1) slopes significantly less than 8 for the δD-δ18O relation on intra-event scale and (2) significant positive correlations between deuterium excess ( d-excess = δD - 8*δ18O; lower values in rain indicate evaporation) and the mass-weighted mean diameter of the raindrops ( D m ). An estimated ~44 % of rain is influenced by evaporation. This study also reveals a signature of isotopic equilibration of rain with the cloud base vapor, the processes important for modeling isotopic composition of precipitation. d-excess values of rain are modified by the post-condensation processes and the present approach offers a way to identify the d-excess values least affected by such processes. Isotope-enabled global circulation models could be improved by incorporating intra-event isotopic data and raindrop size dependent isotopic effects.

Modelingofwaterisotopesinpolarregionsandapplicationtoicecorestudies

NASA Astrophysics Data System (ADS)

Jouzel, J.

2012-04-01

Willi Dansgaard spear-headed the use of the stable isotopes of water in climatology and palaeoclimatology especially as applied to deep ice cores for which measurements of the oxygen and hydrogen isotope ratios remain the key tools for reconstructing continuous palaeotemperature records. In the line of his pioneering work on "Stable isotopes in precipitation" published in Tellus in 1964, I will review how isotopic models, either Rayleigh type or based on the implementation of water isotopes in General Circulation Models, have developed and been used for applications in polar ice core studies. This will include a discussion of the conventional approach for interpreting water isotopes in ice cores and of additional information provided by measurements of the deuterium excess and more recently of the 17O-excess.

The equivalent depth of burst for impact cratering

NASA Technical Reports Server (NTRS)

Holsapple, K. A.

1980-01-01

The concept of modeling an impact cratering event with an explosive event with the explosive buried at some equivalent depth of burst (d.o.b.) is discussed. Various and different ways to define this equivalent d.o.b. are identified. Recent experimental results for a dense quartz sand are used to determine the equivalent d.o.b. for various conditions of charge type, event size, and impact conditions. The results show a decrease in equivalent d.o.b. with increasing energy for fixed impact velocity and a decrease in equivalent d.o.b. with increasing velocity for fixed energy. The values for an iron projectile are on the order of 2-3 projectile radii for energy equal to one ton of TNT, decreasing to about 1.5 radii at a megaton of TNT. The dependence on projectile and target mass density matches that included in common jet-penetration formulas for projectile densities greater than target densities and for the higher energies.

Correspondence between North Pacific Ocean ventilation, Cordilleran Ice Sheet variations, and North Atlantic Heinrich Events

NASA Astrophysics Data System (ADS)

Walczak, M. H.; Mix, A.; Fallon, S.; Praetorius, S. K.; Cowan, E. A.; Du, J.; Hobern, T.; Padman, J.; Fifield, L. K.; Stoner, J. S.; Haley, B. A.

2017-12-01

Much remains unresolved concerning the origin and global implications of the episodes of rapid glacial failure in the North Atlantic known as Heinrich Events. Thought to occur during or at the termination of the coldest of the abrupt stadial climate events known as Dansgaard-Oschger cycles, various trigger mechanisms have been theorized, including external forcing in the form of oceanic or atmospheric warming, internal dynamics of the large Laurentide ice sheet, or the episodic failure of another (presumably European) ice sheet. Heinrich events may also be associated with a decrease in North Atlantic deep-water formation. New results from Gulf of Alaska IODP Expedition 341 reveal events of Cordilleran Ice Sheet retreat (based on ice-rafted detritus and sedimentation rates) synchronous with reorganization of ocean circulation (based on benthic-planktic 14C pairs) spanning the past 45,000 years on an independent high-resolution radiocarbon-based chronology. We document the relationship between these Pacific records and the North Atlantic Heinrich events, and find the data show an early Pacific expression of ice sheet instability in the form of pulses of Cordilleran glacial discharge. The benthic radiocarbon anomalies in the Northeast Pacific contemporaneous with Cordilleran discharge events indicate a close coupling of ice-ocean dynamics throughout Marine Isotope Stage 2. These data are hard to reconcile with triggering in the North Atlantic or internal to the Laurentide ice sheet, requiring us to re-think both the mechanisms that generate Heinrich events and their far-field impacts.

Millennial oscillations in greenland dust and Eurasian Aeolian records - a paleosol-loess perspective (Hans Oeschger Medal Lecture)

NASA Astrophysics Data System (ADS)

Rousseau, Denis-Didier

2017-04-01

Considerable interest is brought on the abrupt climate changes that punctuated the last glacial period (˜110.6-14.62 ka). Originating in the North-Atlantic area, they have been recorded in ice, marine and terrestrial records all over the world, and especially in the Northern Hemisphere, with various environmental implications. The ice-core records, of increasingly high resolution, allow specifying more precisely the timing of these abrupt changes, which have occurred within intervals equivalent to present human generations. The continental records have been mainly interpreted so far in terms of temperature, precipitation or vegetation changes between the relatively warm ("Greenland Interstadial" - GI) and the cold ("Greenland Stadial" - GS) North-Atlantic climate phases. In this presentation records from Greenland ice and northwestern European eolian deposits are compared in order to establish a link between GI and the soil development in European mid-latitudes, as recorded in loess sequences. For the different types of observed paleosols, the precise correlation with the Greenland records is applied to propose estimates of the maximum time lapses needed to achieve the different degrees of maturation and development. To identify these time lapses more precisely, two independent ice-core records are compared: δ180 and dust concentration, indicating variations of temperature and atmospheric dustiness respectively in the Greenland area. This method slightly differs from the definition of a GI event duration applied in other studies where the sharp end of the δ18O decrease gives the end of a GI. The same methodology is applied to both records (i.e., the GI last from the beginning of the abrupt δ18O increase or dust concentration decrease until when δ18O or dust reach again their initial value) determined both visually and algorithmically, and compare them to GI published estimates. Focusing on the eolian/dust intervals, the analysis of δ18O and dust in the Greenland ice cores, and a critical study of their source variations, reconciles these records with those observed on the Eurasian continent. This allows demonstrating the link between European and Chinese loess sequences, dust records in Greenland, and variations of the North Atlantic sea ice extent. The sources of the emitted and transported dust material are variable and relate to different environments corresponding to present desert areas in Asia, but also hidden regions related to lower sea level stands, dry rivers, or zones close to the frontal moraines of the main Northern Hemisphere ice sheets in Europe. As a conclusion of this presentation, I address the short term past climatic changes as preserved in the continental eolian records, in line with the Hans Oeschger medal description. Furthermore one can anticipate such study to be at the origin of more sophisticated and elaborated investigations of millennial and sub-millennial continental climate variability on the Northern Hemisphere. The overview presented during this presentation would not have been possible without the help and close collaboration of many colleagues among whom are Niklas BOERS, Adriana SIMA, Anders SVENSSON, Matthias BIGLER, France LAGROIX, Samuel TAYLOR, Pierre ANTOINE, Christine HATTE, Michael GHIL, George KUKLA, Sigfus JOHNSEN, Markus FUCHS, Andreas LANG, Gilles BERGAMETTI, Beatrice MARTICORENA and Ludwig ZOELLER.

Modeling of water isotopes in polar regions and application to ice core studies

NASA Astrophysics Data System (ADS)

Jouzel, J.

2012-04-01

Willi Dansgaard spear-headed the use of the stable isotopes of water in climatology and palaeoclimatology especially as applied to deep ice cores for which measurements of the oxygen and hydrogen isotope ratios remain the key tools for reconstructing continuous palaeotemperature records. In the line of his pioneering work on "Stable isotopes in precipitation" published in Tellus in 1964, I will review how isotopic models, either Rayleigh type or based on the implementation of water isotopes in General Circulation Models, have developed and been used for applications in polar ice core studies. This will include a discussion of the conventional approach for interpreting water isotopes in ice cores and of additional information provided by measurements of the deuterium excess and more recently of the 17O-excess.

Flowstones from SE Spain document a close relationship between North Atlantic temperature and precipitation in the Western Mediterranean between 7 and 112 ka

NASA Astrophysics Data System (ADS)

Budsky, Alexander; Scholz, Denis; Mertz-Kraus, Regina; Spötl, Christoph; Gibert, Luis; Jochum, Klaus Peter

2017-04-01

Here we present three flowstone records from Cueva Victoria, SE Spain, covering the period between Marine Isotope Stage (MIS) 5 and MIS 3, the Late Glacial and the Holocene. The flowstones were precisely dated by the MC-ICPMS 230Th/U-method. In addition, stable oxygen and carbon isotope ratios as well as trace element concentrations were determined at high resolution (centennial to decadal scale). Present-day climate of SE Spain is classified as semi-arid with dry summer months (<10 mm/month precipitation) and sparsely developed vegetation. A large dataset of 230Th/U ages on several flowstones from Cueva Victoria indicates preferential flowstone growth during warm phases (i.e., interglacials as well as warm interstadials), whereas flowstone growth is interrupted during glacial phases (Budsky et al., 2015). One of the drill cores shows more or less continuous flowstone growth between the Last Interglacial (MIS 5) and MIS 3 (112 - 46 ka). A flowstone from another part of the cave only records the time span from 86 to 50 ka including several growth interruptions. However, both flowstones cover the transition from MIS 4 to 3 including D/O events 17 to 13 at high resolution. Each D/O event is reflected by a remarkable decrease in both δ18O and δ13C values (both up to 3‰ ) accompanied by decreasing concentrations of Mg and Sr. In particular, longer D/O events, lasting several thousands of years (e.g., D/O 14, 19, 20 and 21), are well represented in the δ18O and δ13C records. The timing is in good agreement with the NGRIP ice core and sea-surface temperatures from the Iberian margin. δ18O values are around -3.5 ‰ and decrease to -5 to -6 ‰ during D/O events, while δ13C values are around -9 ‰ and decrease to -10 to -11 ‰ ) during D/O events. We interpret these changes as more humid conditions during D/O events, with elevated sea-surface temperatures in the North Atlantic and the Mediterranean Sea leading to increased moisture transport and precipitation on the SE Iberian Peninsula. As a consequence, vegetation density increased, which is reflected by the decrease in δ13C values and Mg and Sr concentrations and an increase in P content. In the Holocene, the flowstone grew continuously from the Bølling/Allerød to the mid-Holocene (7 ka). Stable isotopes record a trend of increasing temperatures with decreasing values towards the mid-Holocene (δ18O ≈ - 6.4 ‰ , δ13C ≈ -11 ‰ ). However, δ13C values record a significant excursion with elevated values (up to -3.8 ‰ ) during a period from 9.5 to 7.7 ka related to cold Bond-events in the North Atlantic, which is interpreted as a dry period in SE Spain. Budsky, A., Scholz, D., Gibert, L., Mertz-Kraus, R., 2015. 230Th/U-dating of the Cueva Victoria flowstone sequence: Preliminary results and paleoclimate implications, in: Gibert, L., Ferràndez-Canadell, C. (Eds.), Geology and Paleontology of Cueva Victoria. Mastia 11-13, Cartagena, pp. 101-109.

Oscillators and relaxation phenomena in Pleistocene climate theory

PubMed Central

Crucifix, Michel

2012-01-01

Ice sheets appeared in the northern hemisphere around 3 Ma (million years) ago and glacial–interglacial cycles have paced Earth's climate since then. Superimposed on these long glacial cycles comes an intricate pattern of millennial and sub-millennial variability, including Dansgaard–Oeschger and Heinrich events. There are numerous theories about these oscillations. Here, we review a number of them in order to draw a parallel between climatic concepts and dynamical system concepts, including, in particular, the relaxation oscillator, excitability, slow–fast dynamics and homoclinic orbits. Namely, almost all theories of ice ages reviewed here feature a phenomenon of synchronization between internal climate dynamics and astronomical forcing. However, these theories differ in their bifurcation structure and this has an effect on the way the ice age phenomenon could grow 3 Ma ago. All theories on rapid events reviewed here rely on the concept of a limit cycle excited by changes in the surface freshwater balance of the ocean. The article also reviews basic effects of stochastic fluctuations on these models, including the phenomenon of phase dispersion, shortening of the limit cycle and stochastic resonance. It concludes with a more personal statement about the potential for inference with simple stochastic dynamical systems in palaeoclimate science. PMID:22291227

Hydrochemical Characteristics of Groundwater in an Agricultural Area in South Korea

NASA Astrophysics Data System (ADS)

Kim, N.; Hamm, S.; An, J.; Lee, J.; Jang, S.

2008-12-01

The study area, Sacheon-Hadong area, is located in the southern part of the Korean peninsula, which is bounded by the South Sea and surrounded by the Seomjin River in the west. The study area utilized for agricultural work for a long time. That resulted in vulnerable situation of groundwater due to contamination by fertilizer, insecticide and other human activities. In addition, groundwater is in the risk of seawater intrusion because of the study area's location nearby the South Sea. In Sacheon and Hadong area, the EC values were higher in alluvial aquifer than bedrock aquifer. The higher EC values in the alluvial groundwater than the bedrock groundwater were influenced by agricultural activity in near-surface. Water types of two groundwaters belong to Ca-Cl and Na-Cl types due to saline-water influence. EC values are raised, becoming close to the coast. The correlation analysis showed that EC had positive relationship with Na+, Ca2+, Mg2+, Fe2+, Mn2+, SO42-, and Cl-, indicating mixing with seawater. In Sacheon area, nitrogen isotope ratios in the alluvial groundwater ranged between -0.40 and 12.80‰, with 0.05~2.49 mg/l of NO3-N concentration; the range of nitrogen isotopes in the bedrock groundwater was between 3.30 and 17.60‰, with 0.12~2.14 mg/l of NO3-N concentration. Nitrogen was originated from organic source in soils, manures, and domestic wastes (Mueller and Helsel, 1996; Kim and Woo, 2003). In Hadong area, the nitrogen isotopes in the alluvial groundwater ranged from -0.50 to 19.10‰, and NO3-N concentration was between 0.63 and 6.68 mg/l. And these may be originated from anthropogenic pollutants (Mueller and Helsel, 1996). In Sacheon area, average δ18O and δD in alluvial groundwater were analyzed as - 6.77‰ and -47.50‰; average isotope ratios in bedrock groundwater were -7.73‰ and - 53.46‰. In Hadong area, average δ18O and δD in the alluvial groundwater were - 7.32‰ and -49.80‰; average isotope ratios in the bedrock groundwater exhibited - 7.35‰ and -49.40‰. The δ18O in function of δD was plotted parallel with and slightly lower than the meteoric water line (Dansgaard, 1964). In general, deep groundwater displays higher δ18O ratios than shallow groundwater does (Freeze and Cherry, 1979), since deep groundwater reacts with bedrock which commonly emits more 18O than 16O. However, δ18O ratios in the bedrock groundwater in this area opposed to general trend, indicating not enough time to react with bedrock and diffusion effect probably (Hoefs, 1997). Keywords: alluvial groundwater, bedrock groundwater, nitrogen isotope, hydrogen isotope, agricultural area Acknowledgement This work was financially supported by the 21st Century Frontier R&D Program (project no. 3~4~3 of the Sustainable Water Resources Research Center), and also supported by the agricultural groundwater management project, Korea Rural Community & Agriculture Corporation and Ministry of agriculture & Forestry, Republic of Korea.

Resurgence and dynamics of O(N) and Grassmannian sigma models

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dunne, Gerald V.; Unsal, Mithat

Here, we study the non-perturbative dynamics of the two dimensional O( N) and Grassmannian sigma models by using compactification with twisted boundary conditions on R× S 1, semi-classical techniques and resurgence. While the O(N) model has no instantons for N > 3, it has (non-instanton) saddles on R 2, which we call 2d-saddles. On R× S 1, the resurgent relation between perturbation theory and non-perturbative physics is encoded in new saddles, which are associated with the affine root system of the o( N) algebra. These events may be viewed as fractionalizations of the 2d-saddles. The first beta function coefficient, givenmore » by the dual Coxeter number, can then be intepreted as the sum of the multiplicities (dual Kac labels) of these fractionalized objects. Surprisingly, the new saddles in O( N) models in compactified space are in one-to-one correspondence with monopole-instanton saddles in SO( N) gauge theory on R 3×S 1. The Grassmannian sigma models Gr( N, M) have 2d instantons, which fractionalize into N kink-instantons. The small circle dynamics of both sigma models can be described as a dilute gas of the one-events and two-events, bions. One-events are the leading source of a variety of non-perturbative effects, and produce the strong scale of the 2d theory in the compactified theory. We show that in both types of sigma models the neutral bion emulates the role of IR-renormalons. We also study the topological theta angle dependence in both the O(3) model and Gr( N, M), and describe the multi-branched structure of the observables in terms of the theta-angle dependence of the saddle amplitudes, providing a microscopic argument for Haldane’s conjecture.« less

Resurgence and dynamics of O(N) and Grassmannian sigma models

DOE PAGES

Dunne, Gerald V.; Unsal, Mithat

2015-09-29

Here, we study the non-perturbative dynamics of the two dimensional O( N) and Grassmannian sigma models by using compactification with twisted boundary conditions on R× S 1, semi-classical techniques and resurgence. While the O(N) model has no instantons for N > 3, it has (non-instanton) saddles on R 2, which we call 2d-saddles. On R× S 1, the resurgent relation between perturbation theory and non-perturbative physics is encoded in new saddles, which are associated with the affine root system of the o( N) algebra. These events may be viewed as fractionalizations of the 2d-saddles. The first beta function coefficient, givenmore » by the dual Coxeter number, can then be intepreted as the sum of the multiplicities (dual Kac labels) of these fractionalized objects. Surprisingly, the new saddles in O( N) models in compactified space are in one-to-one correspondence with monopole-instanton saddles in SO( N) gauge theory on R 3×S 1. The Grassmannian sigma models Gr( N, M) have 2d instantons, which fractionalize into N kink-instantons. The small circle dynamics of both sigma models can be described as a dilute gas of the one-events and two-events, bions. One-events are the leading source of a variety of non-perturbative effects, and produce the strong scale of the 2d theory in the compactified theory. We show that in both types of sigma models the neutral bion emulates the role of IR-renormalons. We also study the topological theta angle dependence in both the O(3) model and Gr( N, M), and describe the multi-branched structure of the observables in terms of the theta-angle dependence of the saddle amplitudes, providing a microscopic argument for Haldane’s conjecture.« less

Occurrence of oxygen desaturation events during preterm infant bottle feeding near discharge

PubMed Central

Thoyre, Suzanne M.; Carlson, John

2010-01-01

Aims The purpose of this study was to examine the occurrence, severity, pattern, and moderators of oxygen desaturation during preterm infant bottle feeding near the time of discharge from the neonatal intensive care unit (NICU) when fed by mothers. Study design Twenty-two very low birthweight (VLBW) infants [birthweight 1155 ± 293 g, gestational age (GA) 28.1 ± 2.0, postconceptional age (PCA) 36.5 ± 1.6 weeks] were videotaped being bottle-fed by their mothers. Most infants (86%) were discharged within 6 days of the study. Oxygen saturation was continuously monitored and infant feeding behaviors were coded. Oxygen desaturation events (SpO2 < 90%) were identified and analyzed. Results Infants averaged 10.8 events during feeding (range 1–28, S.D. 8.9) and spent, on average, 20% of their feeding time (range 0–70%, S.D. 17.98%) with oxygen levels below 90%. One hundred forty of the desaturation events (59%) were classified as mild (SpO2 85–89), 47 events (20%) were classified as moderate (SpO2 81–84), and 51 events (21%) were classified as severe (SpO2 ≤ 80). Events were evenly distributed across infants’ feeding time. Receiving supplemental oxygen, beginning the feeding with a higher baseline SpO2, and being of older PCA predicted lower percentage of feeding time with SpO2 below 90% (R2 = 0.57). Receiving supplemental oxygen and beginning the feeding with a higher baseline SpO2 predicted less number of desaturation events during the feeding (R2 = 0.44). Despite similar baseline SpO2 levels, infants who were on supplemental oxygen had 50% less oxygen desaturation events and spent 33% less time with SpO2 less than 90%. Conclusion VLBW infants continue to have desaturation events during feeding when fed by their mothers near the time of discharge. Further research is needed to understand the effect of hypoxemia on the preterm infant’s development of oral feeding skills, to study the effects of supplemental oxygen during feeding, and to further develop interventions to minimize desaturation during feeding. PMID:12706309

Atmospheric nitrous oxide produced by solar protons and relativistic electrons

NASA Technical Reports Server (NTRS)

Prasad, S. S.; Zipf, E. C.

1981-01-01

A mechanism by which solar proton (SP) events and relativistic electron precipitation (REP) events may lead to the production of stratospheric NO is described. The process comprises the production of N2O in the mesosphere, its downward migration, and conversion in the stratosphere to NO by the reaction N2O + O(D) yields 2NO. This process would amplify direct NO production by more than 10%.

Ab initio molecular dynamics simulations of low energy recoil events in MgO

DOE PAGES

Petersen, B. A.; Liu, B.; Weber, W. J.; ...

2017-01-11

In this paper, low-energy recoil events in MgO are studied using ab initio molecular dynamics simulations to reveal the dynamic displacement processes and final defect configurations. Threshold displacement energies, E d, are obtained for Mg and O along three low-index crystallographic directions, [100], [110], and [111]. The minimum values for E d are found along the [110] direction consisting of the same element, either Mg or O atoms. Minimum threshold values of 29.5 eV for Mg and 25.5 eV for O, respectively, are suggested from the calculations. For other directions, the threshold energies are considerably higher, 65.5 and 150.0 eVmore » for O along [111] and [100], and 122.5 eV for Mg along both [111] and [100] directions, respectively. These results show that the recoil events in MgO are partial-charge transfer assisted processes where the charge transfer plays an important role. Finally, there is a similar trend found in other oxide materials, where the threshold displacement energy correlates linearly with the peak partial-charge transfer, suggesting this behavior might be universal in ceramic oxides.« less

Stable water isotopes suggest sub-canopy water recycling in a northern forested catchment

Treesearch

Mark B. Green; Bethany K. Laursen; John L. Campbell; Kevin J. McGuire; Eric P. Kelsey

2015-01-01

Stable water isotopes provide a means of tracing many hydrologic processes, including poorly understood dynamics like soil water interactions with the atmosphere. We present a four-year dataset of biweekly water isotope samples from eight fluxes and stores in a headwater catchment at the Hubbard Brook Experimental Forest, New Hampshire, USA. We use Dansgaard's...

Oxygen Isotopes and Meltwater: Younger Dryas and 8.2 ka Event

NASA Astrophysics Data System (ADS)

Keigwin, L. D.

2015-12-01

Delta 18-O is one of our most powerful and widely used proxies, with, arguably, the fewest likely unknown unknowns. Here I will consider the d18-O evidence for the two best-known floods of mostly liquid water to the ocean, the Younger Dryas (YD) and the 8.2 ka event. The first d18-O signal of a meltwater flood in the ocean was reported 40 years ago by Kennett and Shackleton (1975) and that paper led directly to the meltwater diversion hypothesis for the origin of the YD cooling. It was later suggested by Rooth (1982) that such a flood could interrupt Nordic seas convection and trigger the YD cold episode. It was reported at this meeting last year that a candidate flood has been found in the Mackenzie River region of the western Arctic based on low d18-O and multiple other lines of evidence. The 8.2 ka event was about one-tenth the duration of the YD but with possibly higher transport, and is more difficult to detect in open marine sediments. As with the YD, it has been modeled by hosing and low salinities have been derived by temperature correcting the d18-O. The resulting low salinity was shown not to follow the prediction of the highest resolution modeling, and theory, that the fresh water would be transported mostly equatorward along the continental shelf. However, I report here that the low d18-O signal of the 8.2 ka flooding is present in new cores from near Logan Canyon on the Scotian shelf break, and in Jordan Basin, Gulf of Maine. These results substantially validate the modeling of Condron and Winsor that fresh water transport must have been along the continental shelf.

78 FR 55777 - Proposed Information Collection (VA, National Veterans Sports Programs and Special Events, Event...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-09-11

... 0928j. o. National Veteran Creative Arts Festival Event Application, VA0929a, b, c, d, e, f, g, h. OMB... Creative Arts Festival, National Veterans TEE Tournament, National Disabled Veterans Winter Sports Clinic...

On smoothness of black saturns

NASA Astrophysics Data System (ADS)

Chruściel, Piotr T.; Eckstein, Michał; Szybka, Sebastian J.

2010-11-01

We prove smoothness of the domain of outer communications (d.o.c.) of the Black Saturn solutions of Elvang and Figueras. We show that the metric on the d.o.c. extends smoothly across two disjoint event horizons with topology mathbb{R} × {S^3} and mathbb{R} × {S^1} × {S^2} . We establish stable causality of the d.o.c. when the Komar angular momentum of the spherical component of the horizon vanishes, and present numerical evidence for stable causality in general.

Development of a Regional 3-D Velocity Model of the Pakistan Region for Improved Seismic Event Location

DTIC Science & Technology

2006-04-01

the Engdahl, el al. (1998) database . Our results show that the new model better fits the data COm~ared to both the initial model and the alobal l -D...34SOUICU" m the cal-. Tbe Podvh-Lemmte method sohns the eikonal equation m a 3-D medium using a htd&mme . . spprmimatian. It c a n ~ e l y m o d e l ~ ~ o

Ulysses Observations of Tripolar Guide-Magnetic Field Perturbations Across Solar Wind Reconnection Exhausts

NASA Astrophysics Data System (ADS)

Eriksson, S.; Peng, B.; Markidis, S.; Gosling, J. T.; McComas, D. J.; Lapenta, G.; Newman, D. L.

2014-12-01

We report observations from 15 solar wind reconnection exhausts encountered along the Ulysses orbit beyond 4 AU in 1996-1999 and 2002-2005. The events, which lasted between 17 and 45 min, were found at heliospheric latitudes between -36o and 21o with one event detected as high as 58o. All events shared a common characteristic of a tripolar guide-magnetic field perturbation being detected across the observed exhausts. The signature consists of an enhanced guide field magnitude within the exhaust center and two regions of significantly depressed guide-fields adjacent to the center region. The events displayed magnetic field shear angles as low as 37o with a mean of 89o. This corresponds to a strong external guide field relative to the anti-parallel reconnecting component of the magnetic field with a mean ratio of 1.3 and a maximum ratio of 3.1. A 2-D kinetic reconnection simulation for realistic solar wind conditions reveals that tripolar guide fields form at current sheets in the presence of multiple X-lines as two magnetic islands interact with one another for such strong guide fields. The Ulysses observations are also compared with the results of a 3-D kinetic simulation of multiple flux ropes in a strong guide field.

The Expected Cardiovascular Benefit of Plasma Cholesterol Lowering with or Without LDL-C Targets in Healthy Individuals at Higher Cardiovascular Risk.

PubMed

Cesena, Fernando Henpin Yue; Laurinavicius, Antonio Gabriele; Valente, Viviane A; Conceição, Raquel D; Santos, Raul D; Bittencourt, Marcio S

2017-06-01

There is controversy whether management of blood cholesterol should be based or not on LDL-cholesterol (LDL-c) target concentrations. To compare the estimated impact of different lipid-lowering strategies, based or not on LDL-c targets, on the risk of major cardiovascular events in a population with higher cardiovascular risk. We included consecutive individuals undergoing a routine health screening in a single center who had a 10-year risk for atherosclerotic cardiovascular disease (ASCVD) ≥ 7.5% (pooled cohort equations, ACC/AHA, 2013). For each individual, we simulated two strategies based on LDL-c target (≤ 100 mg/dL [Starget-100] or ≤ 70 mg/dL [Starget-70]) and two strategies based on percent LDL-c reduction (30% [S30%] or 50% [S50%]). In 1,897 subjects (57 ± 7 years, 96% men, 10-year ASCVD risk 13.7 ± 7.1%), LDL-c would be lowered from 141 ± 33 mg/dL to 99 ± 23 mg/dL in S30%, 71 ± 16 mg/dL in S50%, 98 ± 9 mg/dL in Starget-100, and 70 ± 2 mg/dL in Starget-70. Ten-year ASCVD risk would be reduced to 8.8 ± 4.8% in S50% and 8.9 ± 5.2 in Starget-70. The number of major cardiovascular events prevented in 10 years per 1,000 individuals would be 32 in S30%, 31 in Starget-100, 49 in S50%, and 48 in Starget-70. Compared with Starget-70, S50% would prevent more events in the lower LDL-c tertile and fewer events in the higher LDL-c tertile. The more aggressive lipid-lowering approaches simulated in this study, based on LDL-c target or percent reduction, may potentially prevent approximately 50% more hard cardiovascular events in the population compared with the less intensive treatments. Baseline LDL-c determines which strategy (based or not on LDL-c target) is more appropriate at the individual level. Há controvérsias sobre se o controle do colesterol plasmático deve ou não se basear em metas de concentração de colesterol LDL (LDL-c). Comparar o impacto estimado de diferentes estratégias hipolipemiantes, baseadas ou não em metas de LDL-c, sobre o risco de eventos cardiovasculares maiores em uma população de risco cardiovascular mais elevado. Foram incluídos indivíduos consecutivamente submetidos a uma avaliação rotineira de saúde em um único centro e que apresentavam um risco em 10 anos de doença cardiovascular aterosclerótica (DCVAS) ≥ 7,5% ("pooled cohort equations", ACC/AHA, 2013). Para cada indivíduo, foram simuladas duas estratégias baseadas em meta de LDL-c (≤ 100 mg/dL [Emeta-100] ou ≤ 70 mg/dL [Emeta-70]) e duas estratégias baseadas em redução percentual do LDL-c (30% [E30%] ou 50% [E50%]). Em 1.897 indivíduos (57 ± 7 anos, 96% homens, risco em 10 anos de DCVAS 13,7 ± 7,1%), o LDL-c seria reduzido de 141 ± 33 mg/dL para 99 ± 23 mg/dL na E30%, 71 ± 16 mg/dL na E50%, 98 ± 9 mg/dL na Emeta-100 e 70 ± 2 mg/dL na Emeta-70. O risco em 10 anos de DCVAS seria reduzido para 8,8 ± 4,8% na E50% e para 8,9 ± 5,2 na Emeta-70. O número de eventos cardiovasculares maiores prevenidos em 10 anos por 1.000 indivíduos seria de 32 na E30%, 31 na Emeta-100, 49 na E50% e 48 na Emeta-70. Em comparação com a Emeta-70, a E50% evitaria mais eventos no tercil inferior de LDL-c e menos eventos no tercil superior de LDL-c. As abordagens hipolipemiantes mais agressivas simuladas neste estudo, com base em meta de LDL-c ou redução percentual, podem potencialmente prevenir cerca de 50% mais eventos cardiovasculares graves na população em comparação com os tratamentos menos intensivos. Os níveis basais de LDL-c determinam qual estratégia (baseada ou não em meta de LDL-c) é mais apropriada para cada indivíduo.

Chemistry of CCl 4 on Fe 3O 4(1 1 1)-(2 × 2) surfaces in the presence of adsorbed D 2O studied by temperature programmed desorption

NASA Astrophysics Data System (ADS)

Adib, K.; Totir, G. G.; Fitts, J. P.; Rim, K. T.; Mueller, T.; Flynn, G. W.; Joyce, S. A.; Osgood, R. M.

2003-07-01

Temperature programmed desorption (TPD) was used to study surface reactions of Fe 3O 4(1 1 1)-(2 × 2) sequentially exposed, at ˜100 K, to vapor-phase D 2O and CCl 4. Previous TPD and XPS results have indicated that in the absence of D 2O, CCl 4 dissociatively adsorbs on Fe 3O 4(1 1 1) producing chemisorbed Cl and CCl 2. Subsequent heating of the surface results in abstraction of lattice iron and oxygen atoms and causes them to desorb as FeCl 2 and OCCl 2, respectively. This study shows that when this Fe 3O 4 surface is exposed only to D 2O, TPD measures a rich surface chemistry with multiple desorption events extending as high as ˜800 K, indicating dissociative adsorption of D 2O on the Fe 3O 4(1 1 1) surface. After sequential exposure to D 2O and then CCl 4, the production of FeCl 2 and OCCl 2 from adsorbed CCl 4 is suppressed, indicating that D 2O fragments block the surface reactive sites.

The Effect of Task Characteristics on the Availability Heuristic for Judgments under Uncertainty.

DTIC Science & Technology

1983-05-01

RICE UNIVERSITY Houston, Texas 7 7001 * Department of Psycholgsy ~ A0 Reserch Report Series dAOTbik has eD dis~fuomis =liited. -~~~ ~ - - 0...The experimental design Involved the manipulation of event characteristics in order to induce a heuristic processing strategy for designated available...40 References .... .......... .o.................. o...................... 41 Appendix A. Experimental Questionnaires

Heart rate at first postdischarge visit and outcomes in patients with heart failure.

PubMed

Kim, Tae-Hun; Kim, Hyungseop; Kim, In-Cheol; Yoon, Hyuck-Jun; Park, Hyoung-Seob; Cho, Yun-Kyeong; Nam, Chang-Wook; Han, Seongwook; Hur, Seung-Ho; Kim, Yoon-Nyun

2018-07-01

Heart rate control is important to prevent adverse outcomes in patients with heart failure (HF). However, postdischarge activity may worsen heart rate control, resulting in readmission. This study aimed to explore the implications of the heart rate differences between discharge and the first outpatient visit (D-O diff). We retrospectively identified 458 patients (male: 46%; mean age: 72 years) discharged after HF. The heart rates at admission, discharge and first outpatient visit were analysed. The primary outcome was a composite of cardiovascular (CV) death and readmission of non-fatal myocardial infarction (MI), non-fatal stroke or non-fatal HF over a mean follow-up of 16 months. During follow-up, the clinical outcomes were noted in 223 patients (49%): HF, 199; stroke, 9; MI, 6; CV death, 9. The heart rate at the first outpatient visit (r=-0.311, P<0.001) and D-O diff (r=0.416, P<0.001) showed a better correlation with the time-to-clinical event than the heart rate at admission or discharge. The events group displayed a pronounced heart rate increase (13 beats/min) from discharge to the first outpatient visit compared with the event-free group (a decrease of 2 beats/min). A decrease less than -15 in the D-O diff showed a 4.5-fold risk of clinical outcomes during follow-up (P<0.001). A decreased D-O diff was related to the adverse outcomes of HF. The failure of heart rate control within more than 15 beats/min at the first outpatient visit was an independent factor for CV events. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

A decadal time series of water vapor and D / H isotope ratios above Zugspitze: transport patterns to central Europe

NASA Astrophysics Data System (ADS)

Hausmann, Petra; Sussmann, Ralf; Trickl, Thomas; Schneider, Matthias

2017-06-01

We present vertical soundings (2005-2015) of tropospheric water vapor (H2O) and its D / H isotope ratio (δD) derived from ground-based solar Fourier transform infrared (FTIR) measurements at Zugspitze (47° N, 11° E, 2964 m a.s.l.). Beside water vapor profiles with optimized vertical resolution (degrees of freedom for signal, DOFS, = 2.8), {H2O, δD} pairs with consistent vertical resolution (DOFS = 1.6 for H2O and δD) applied in this study. The integrated water vapor (IWV) trend of 2.4 [-5.8, 10.6] % decade-1 is statistically insignificant (95 % confidence interval). Under this caveat, the IWV trend estimate is conditionally consistent with the 2005-2015 temperature increase at Zugspitze (1.3 [0.5, 2.1] K decade-1), assuming constant relative humidity. Seasonal variations in free-tropospheric H2O and δD exhibit amplitudes of 140 and 50 % of the respective overall means. The minima (maxima) in January (July) are in agreement with changing sea surface temperature of the Atlantic Ocean. Using extensive backward-trajectory analysis, distinct moisture pathways are identified depending on observed δD levels: low column-based δD values (δDcol < 5th percentile) are associated with air masses originating at higher latitudes (62° N on average) and altitudes (6.5 km)than high δD values (δDcol > 95th percentile: 46° N, 4.6 km). Backward-trajectory classification indicates that {H2O, δD} observations are influenced by three long-range-transport patterns towards Zugspitze assessed in previous studies: (i) intercontinental transport from North America (TUS; source region: 25-45° N, 70-110° W, 0-2 km altitude), (ii) intercontinental transport from northern Africa (TNA; source region: 15-30° N, 15° W-35° E, 0-2 km altitude), and (iii) stratospheric air intrusions (STIs; source region: > 20° N, above zonal mean tropopause). The FTIR data exhibit significantly differing signatures in free-tropospheric {H2O, δD} pairs (5 km a.s.l.) - given as the mean with uncertainty of ±2 standard error (SE) - for TUS (VMRH2O = 2.4 [2.3, 2.6] × 103 ppmv, δD = -315 [-326, -303] ‰), TNA (2.8 [2.6, 2.9] × 103 ppmv, -251 [-257, -246] ‰), and STIs (1.2 [1.1, 1.3] × 103 ppmv, -384 [-397, -372] ‰). For TUS events, {H2O, δD} observations depend on surface temperature in the source region and the degree of dehydration having occurred during updraft in warm conveyor belts. During TNA events (dry convection of boundary layer air) relatively moist and weakly HDO-depleted air masses are imported. In contrast, STI events are associated with import of predominantly dry and HDO-depleted air masses. These long-range-transport patterns potentially involve the import of various trace constituents to the central European free troposphere, i.e., import of pollution from North America (e.g., aerosol, ozone, carbon monoxide), Saharan mineral dust, stratospheric ozone, and other airborne species such as pollen. Our results provide evidence that {H2O, δD} observations are a valuable proxy for the transport of such tracers. To validate this finding, we consult a database of transport events (TNA and STI) covering 2013-2015 deduced by data filtering from in situ measurements at Zugspitze and lidar profiles at nearby Garmisch. Indeed, the FTIR data related to these verified TNA events (27 days) exhibit characteristic fingerprints in IWV (5.5 [4.9, 6.1] mm) and δDcol (-266 [-284, -247] ‰), which are significantly distinguishable from the rest of the time series (4.3 [4.1, 4.5] mm, -316 [-324, -308] ‰). This holds true for 136 STI days considering uncertainties of ±1 SE (4.2 [4.0, 4.3] mm, -322 [-327, -316] ‰) with respect to the remainder (4.6 [4.5, 4.8] mm, -302 [-307, -297] ‰). Furthermore, deep stratospheric intrusions to the Zugspitze summit (in situ humidity and beryllium-7 data filtering) show a significantly lower mean value (-334 [-337, -330] ‰) of lower-tropospheric δD (3-5 km a.s.l.) than the rest of the 2005-2015 time series (-284 [-286, -282] ‰) considering uncertainty of ±2 SE. Our results show that consistent {H2O, δD} observations at Zugspitze can serve as an operational indicator for long-range-transport events potentially affecting regional climate and air quality, as well as human health in central Europe.

Marine radiocarbon reservoir age variation in Donax obesulus shells from northern Peru: late Holocene evidence for extended El Niño

USGS Publications Warehouse

Etayo-Cadavid, Miguel F.; Andrus, C. Fred T.; Jones, Kevin B.; Hodgins, Gregory W. L.; Sandweiss, Daniel H.; Uceda-Castillo, Sandiago; Quilter, Jeffrey

2013-01-01

For at least 6 m.y., El Niño events have posed the greatest environmental risk on the Peruvian coast. A better understanding of El Niño is essential for predicting future risk and growth in this tropical desert. To achieve this we analyzed archaeological and modern pre-bomb shells from the surf clam Donax for the radiocarbon reservoir effect (ΔR) to characterize late Holocene coastal upwelling conditions in northern Peru (8°14′S). Mean ΔR values from these shells suggest that modern upwelling conditions in this region were likely established between A.D. 539 and A.D. 1578. Our radiocarbon data suggest that upwelling conditions ca. A.D. 539 were less intense than those in modern times. The observed coastal water enrichment in 14C may be consequence of frequent strong El Niño events or extended El Niño–like conditions. These ΔR-inferred marine conditions are in agreement with proposed extended El Niño activity in proxy and archaeological records of ca. A.D. 475–530. Extended El Niño conditions have been linked to political destabilization, societal transformation, and collapse of the Moche civilization in northern Peru. A return to such conditions would have significant impacts on the dense population of this region today and in the near future.

Cross-continental triple oxygen isotope analysis of tropospheric CO2

NASA Astrophysics Data System (ADS)

Liang, M. C.; Rangarajan, R.; Newman, S.; Laskar, A. H.

2016-12-01

The abundance variations of near surface atmospheric CO2 isotopologues (primarily 16O12C16O, 16O13C16O, 17O12C16O, and 18O12C16O) represent an integrated signal from anthropogenic/biogeochemical processes, including fossil fuel burning, biospheric photosynthesis and respiration, hydrospheric isotope exchange with water, and stratospheric photochemistry. Oxygen isotopes, in particular, are affected by the carbon and water cycles. Being a useful tracer that directly probes governing processes in CO2 biogeochemical cycles, D17O (= ln(1+d17O) - 0.516´ln(1+d18O)) provides an alternative constraint on the strengths of the associated cycles involving CO2. Here, we report more than one year of data obtained from Taiwan (Taipei), South China Sea, and USA (Pasadena, CA and Palos Verdes, CA). On average, the D17O values from these locations are similar and show no significant influence from the 2014-2016 El Nino event, in contrast to what has been reported for the 1997-1998 El Nino from the CO2 data collected from La Jolla, CA. Implications for utilizing the new tracer D17O for carbon cycling studies will be made.

AlphaACT

DTIC Science & Technology

2014-07-20

t**k HOUM 1i7iOSh»d, uro .*fto»d ^Sunflower V«()*Uil«n Rviiauiani :{31 Chkn Bii^ R:ad •Pel Lov*ri Cotnpanton ^&i«na’i RMUuram 1U17 VVtMjltfl...Select a case to tailor • Click Customize CUSTOMIZE lO ) Alpha j[~:: 0:09:15 3 .~^’’ I ~J^’ Purpose Tasks Tailor the case to scenario...present o o ® =T Does the event area have tall buildings o o ® a^ ^KBPPB^ or choose up lo 3 n«nts Irom the VKiii^P Knowledge Base bela» Tim

Variations of the relative abundances of He, (C,N,O) and Fe-group nuclei in solar cosmic rays and their relationship to solar particle acceleration

NASA Technical Reports Server (NTRS)

Bertsch, D. L.; Biswas, S.; Fichtel, C. E.; Pellerin, C. J.; Reames, D. V.

1973-01-01

Measurements of the flux of helium nuclei in the 24 January 1971 event and of helium and (C,N,O) nuclei in the 1 September 1971 event are combined with previous measurements to obtain the relative abundances of helium, (C,N,O), and Fe-group nuclei in these events. These data are then summarized together with previously reported results to show that, even when the same detector system using a dE/dx plus range technique is used, differences in the He/(C,N,O) value in the same energy/nucleon interval are observed in solar cosmic ray events. Further, when the He/(C,N,O) value is lower the He/(Fe-group nuclei) value is also systematically lower in these large events. When solar particle acceleration theory is analyzed, it is seen that the results suggest that, for large events, Coulomb energy loss probably does not play a major role in determining solar particle composition at higher energies (10 MeV). The variations in multicharged nuclei composition are more likely due to partial ionization during the acceleration phase.

Moisture sources of the Mono Lake deglacial pluvial events

NASA Astrophysics Data System (ADS)

Wang, X.; Liang, M. C.; Ali, G.; Shen, C. C.; Cai, Y.; Ke, L.; Hemming, S. R.

2016-12-01

Enormously expanded lakes existed in the today's dry western US Great Basin during the last glacial period. The ancient shorelines located well above modern lake levels suggest that precipitation in lake basins must have been substantially higher in the past. It is however under debate whether the subtropical North Pacific or the tropical Pacific is the major moisture source that contributed to the pluvial events, particularly during the deglaciation. Here, we collected a suite of tufa carbonate samples deposited at the 2,080 meter terrace ( 135 meters above today's lake level) in the Mono Basin, California, a closed lake basin for the last 130 thousand years (kyr). At Goat Ranch, we discovered white, shiny, laminated botryoidal carbonate coatings on tufa mounds. Most of these coatings present two generations of formation separated by a hiatus, which indicates lake level fluctuations. Using high-precision U-Th dating techniques, we found that the lower layer was formed 14.1-14.4 kyr BP (corresponding to the North Atlantic Bølling warming period). The upper layer of the coating was formed 11.9-12.3 kyr BP (within the Younger Dryas event). We then obtained d18O, d13C, D47 and 17O-excess values for the two carbonate layers. The upper part is characterized by low d18O values, -8 to -12 ‰ VPDB, whereas the lower one has higher d18O values, -5 to -6 ‰ VPDB. Both share similar d13C values ( 1-2‰ VPDB). D47 analysis on the carbonates suggests that both layers were deposited in a water temperature of 9±2 oC (1s, n = 4 and 8, respectively). The two generations of carbonates present 17O-excess of moisture in values of 50±5 (1s, n=4) and 25±5 (1s, n=8) per meg VSMOW-SLAP, respectively. The large difference in 17O-excess of parent meteoric water points to different origins of moisture for the tufa carbonate formations. The high 17O-excess values during YD suggest a moisture source with a low relative humidity, consistent with the conventional view that the moisture was brought from the subtropical North Pacific, aided by a strong southward shift of the jet stream. In contrast, the lower 17O-excess values during Bølling indicate a moisture source with a high relative humidity or strong continental recycling; each suggests a southern moisture source in the tropical Pacific.

Vegetation and Channel Morphology Responses to Ordinary High Water Discharge Events in Arid West Stream Channels

DTIC Science & Technology

2009-05-01

a rc h a n d E n gi n e e ri n g La b o ra to ry Approved for public release; distribution is unlimited. ERDC/CRREL TR-09-5 May 2009...21 Appendix B . Aerial Imagery and Discharge Events..........................................................................22 Appendix C...3 Figure 2. The Arid West region as defined by Land Resource Regions B , C, and D

Triple oxygen isotope analysis of tropospheric CO2 on the two sides of the Pacific Ocean

NASA Astrophysics Data System (ADS)

Liang, M. C.; Newman, S.; Laskar, A. H.

2017-12-01

The abundance variations of near surface atmospheric CO2 isotopologues (primarily 16O12C16O, 16O13C16O, 17O12C16O, and 18O12C16O) represent an integrated signal from anthropogenic/biogeochemical processes, including fossil fuel burning, biospheric photosynthesis and respiration, hydrospheric isotope exchange with water, stratospheric photochemistry, cross-tropopause exchange, and subsequent vertical mixing between the free troposphere and planetary boundary. Oxygen isotopes, in particular, are affected by both the carbon and water cycles. Being a useful tracer that directly probes governing processes in CO2 biogeochemical cycles, D17O (= ln(1+d17O) - 0.516 ln(1+d18O)) provides a powerful constraint on the strengths of the associated cycles involving CO2. Here, we report and compare summer to winter seasons CO2 isotopic composition from Taiwan (Taipei) and USA (Palos Verdes, CA). On average, the D17O values from Taiwan are significantly higher than those in USA. Analysis shows that the impact of 2014-2016 El Nino event on the observed D17O values is not visible, in contrast to what was reported for the 1997-1998 El Nino from the CO2 data collected from La Jolla, CA. Attempts are made to understand the elevated D17O values in the eastern Pacific compared to those in the western Pacific. Implications for utilizing the new tracer D17O along with the conventional d18O for carbon cycling studies are also discussed.

DoD Biometrics Collaboration Forum 25-27 Jan 2011. Event Report

DTIC Science & Technology

2011-03-01

GS-15 Level Staffing Marine Corps Action Tracking System ( MCATS ) Entered Staffing 21 December 2010 HQ USMC Receiving Staff Comments GO...SES Level Staffing MCATS TBD HQ USMC Assistant Commandant of the TBD HQ USMC 2011 DoD Biometrics Collaboration Forum Event Report 13...O-6/GS-15 Staffing MCATS Late March 2011 HQ USMC GO/SES Staffing MCATS Early April 2011 HQ USMC ACMC Signature TBD HQ USMC USMC

Influence of northwest Pacific productivity on North Pacific Intermediate Water oxygen concentrations during the Bølling-Ållerød interval (14.7-12.9 ka)

USGS Publications Warehouse

Crusius, John; Pedersen, Thomas F.; Kienast, Stephanie; Keigwin, Lloyd D.; Labeyrie, Laurent

2004-01-01

Elevated productivity in the northwest Pacific is suggested as a new possible control driving past intervals of low-O2 intermediate water along the western continental margin of North America. According to this mechanism, O2 consumption would occur near the site of formation of North Pacific Intermediate Water (NPIW), due to increased respiration of organic carbon in response to a high-productivity event. Evidence is provided for such a productivity increase during the Bølling-Ållerød interval (14.7–12.9 ka), a time when laminated sediments were deposited along the northern California margin. By this mechanism, low-O2 events in intermediate waters off the western North American margin could occur without significant changes in the rate of NPIW ventilation.

Combat Aircraft Noise held in Bonn, Germany on 23-25 October 1991 (Le Bruit Genere par les Avions de Combat)

DTIC Science & Technology

1992-04-01

study suggeet that the penalty in needed Important factors see"m to be the onset but it may be neceesary to extend the rate of the flyovers. In aerieas...the average will underestimate the impcat at laboratOry studies the onset and decay those operations. These two factors . rates have the eams level at...events st a SEL of 115 studies and found that fundamentally all dO gives an Leq(8h) of 88 d8 while Oil tended to support a 10 LagioN event factor events

Global MHD Test Particle Simulations of 10 MeV Radiation Belt Electrons During Sudden Storm Commencement

DTIC Science & Technology

2007-09-22

9 0 , a n d I t o 2 m n h t o b d i c r a l al h e o w q u o i l p t hthe SC lectic ieldpule ispreominntl in he 1 to 2 months to be discemable at the...correlation with sharp increase in the H -component, ground B dx(A, magnetometer perturbation which is the signature of an SSC event. The March 1991...Parametric study of shock- Press, W. H ., B . P. Flannery, S. A. Teukolsky, and W. T. Vetterling (1992),induced transport and energization of relativistic

D-region ion-neutral coupled chemistry (Sodankylä Ion Chemistry, SIC) within the Whole Atmosphere Community Climate Model (WACCM 4) - WACCM-SIC and WACCM-rSIC

NASA Astrophysics Data System (ADS)

Kovács, Tamás; Plane, John M. C.; Feng, Wuhu; Nagy, Tibor; Chipperfield, Martyn P.; Verronen, Pekka T.; Andersson, Monika E.; Newnham, David A.; Clilverd, Mark A.; Marsh, Daniel R.

2016-09-01

This study presents a new ion-neutral chemical model coupled into the Whole Atmosphere Community Climate Model (WACCM). The ionospheric D-region (altitudes ˜ 50-90 km) chemistry is based on the Sodankylä Ion Chemistry (SIC) model, a one-dimensional model containing 307 ion-neutral and ion recombination, 16 photodissociation and 7 photoionization reactions of neutral species, positive and negative ions, and electrons. The SIC mechanism was reduced using the simulation error minimization connectivity method (SEM-CM) to produce a reaction scheme of 181 ion-molecule reactions of 181 ion-molecule reactions of 27 positive and 18 negative ions. This scheme describes the concentration profiles at altitudes between 20 km and 120 km of a set of major neutral species (HNO3, O3, H2O2, NO, NO2, HO2, OH, N2O5) and ions (O2+, O4+, NO+, NO+(H2O), O2+(H2O), H+(H2O), H+(H2O)2, H+(H2O)3, H+(H2O)4, O3-, NO2-, O-, O2, OH-, O2-(H2O), O2-(H2O)2, O4-, CO3-, CO3-(H2O), CO4-, HCO3-, NO2-, NO3-, NO3-(H2O), NO3-(H2O)2, NO3-(HNO3), NO3-(HNO3)2, Cl-, ClO-), which agree with the full SIC mechanism within a 5 % tolerance. Four 3-D model simulations were then performed, using the impact of the January 2005 solar proton event (SPE) on D-region HOx and NOx chemistry as a test case of four different model versions: the standard WACCM (no negative ions and a very limited set of positive ions); WACCM-SIC (standard WACCM with the full SIC chemistry of positive and negative ions); WACCM-D (standard WACCM with a heuristic reduction of the SIC chemistry, recently used to examine HNO3 formation following an SPE); and WACCM-rSIC (standard WACCM with a reduction of SIC chemistry using the SEM-CM method). The standard WACCM misses the HNO3 enhancement during the SPE, while the full and reduced model versions predict significant NOx, HOx and HNO3 enhancements in the mesosphere during solar proton events. The SEM-CM reduction also identifies the important ion-molecule reactions that affect the partitioning of odd nitrogen (NOx), odd hydrogen (HOx) and O3 in the stratosphere and mesosphere.

Observation of the Top Quark

DOE R&D Accomplishments Database

Kim, S. B.

1995-08-01

Top quark production is observed in{bar p}p collisions at{radical}s= 1.8 TeV at the Fermilab Tevatron. The Collider Detector at Fermilab (CDF) and D{O} observe signals consistent with t{bar t} to WWb{bar b}, but inconsistent with the background prediction by 4.8{sigma} (CDF), 4.6a (D{O}). Additional evidence for the top quark Is provided by a peak in the reconstructed mass distribution. The kinematic properties of the excess events are consistent with the top quark decay. They measure the top quark mass to be 176{plus_minus}8(stat.){plus_minus}10(sys.) GeV/c{sup 2} (CDF), 199{sub -21}{sup+19}(stat.){plus_minus}22(sys.) GeV/c{sup 2} (D{O}), and the t{bar t} production cross section to be 6.8{sub -2.4}{sup+3.6}pb (CDF), 6.4{plus_minus}2.2 pb (D{O}).

Association of deformation and fluid events in the central Brooks Range fold-and-thrust belt, Northern Alaska

USGS Publications Warehouse

Moore, Thomas E.; Potter, Christopher J.; O'Sullivan, Paul B.; Shelton, Kevin L.; Underwood, Michael B.

2003-01-01

Ocentral Brooks Range consists of two superposed north-directed contractional orogens, one formed between 140-120 Ma and the other at ~60-45 Ma. The older orogen was an arc-continent collisional zone characterized by far-traveled allochthons and relatively low structural relief. The younger orogen is a retroarc thrust belt with relatively low amounts of shortening and high structural relief. Folding and thrusting of the younger episode is superimposed on the thin-skinned deformational wedge of the earlier orogen and also produced a frontal triangle zone in a thick sequence of mid-Cretaceous foreland basin sediments to the north. Stable isotope compositions of calcite and quartz veins indicate two fluid events including: (1) an earlier, higher-temperature (~250-300° C) event that produced veins in deformed Devonian clastic rocks, and (2) a younger, lower-temperature (~150° C) event that deposited veins in deformed Mississippian through Albian strata. The fluids in the first event had variable d18O values, but nearly constant d13C values buffered by limestone lithologies. The vein-forming fluids in the second event had similarly variable d18O values, but with distinctly lower d13C values as a result of oxidation of organic matter and/or methane. Zircon fission track ages demonstrate cooling to temperatures below 200° C between 140-120 Ma for the Devonian rocks, whereas zircon and apatite fission track ages show that Mississippian to Albian rocks were never heated above 200° C and cooled below 110-90° C at ~60-45 Ma. These data are interpreted as indicating that the older, high-temperature fluid event was active during thrusting at 120-140 Ma, and the younger fluid event during deformation at ~60-45 Ma. The data and results presented in this poster will be published in early 2004 in Moore and others (in press).

Insights into hydroclimatic variability of Southern California since 125 ka, from multi-proxy analyses of alpine lakes

NASA Astrophysics Data System (ADS)

Glover, K. C.; MacDonald, G. M.; Kirby, M.

2016-12-01

Hydroclimatic variability is especially important in California, a water-stressed and increasingly populous region. We assess the range of past hydroclimatic sensitivity and variability in the San Bernardino Mountains of Southern California based on 125 ka of lacustrine sediment records. Geochemistry, charcoal and pollen highlight periods of sustained moisture, aridity and sudden variability driven by orbital and oceanic variations. Marine Isotope Stage 3 (MIS 3) is one such period of greater moisture availability that lasted c. 30 kyr, with smaller-scale perturbations likely reflect North Atlantic Dansgaard-Oeschgar events. Past glacial periods, MIS 4 and MIS 2, display high-amplitude changes. These include periods of reduced forest cover that span millennia, indicating long-lasting aridity. Rapid forest expansion also occurs, marking sudden shifts towards wet conditions. Fire regimes have also changed in tandem with hydroclimate and vegetation. Higher-resolution analysis of the past 10 ka shows that Southern California hydroclimate was broadly similar to other regions of the Southwest and Great Basin, including an orbital and oceanic-driven wet Early Holocene, dry Mid-Holocene, and highly variable Late Holocene. Shorter-term pluvial conditions occur throughout the Holocene, with episodic moisture likely derived from a Pacific source.

Astronomically calibrated 40Ar/39Ar age for the Toba supereruption and global synchronization of late Quaternary records

PubMed Central

Storey, Michael; Roberts, Richard G.; Saidin, Mokhtar

2012-01-01

The Toba supereruption in Sumatra, ∼74 thousand years (ka) ago, was the largest terrestrial volcanic event of the Quaternary. Ash and sulfate aerosols were deposited in both hemispheres, forming a time-marker horizon that can be used to synchronize late Quaternary records globally. A precise numerical age for this event has proved elusive, with dating uncertainties larger than the millennial-scale climate cycles that characterized this period. We report an astronomically calibrated 40Ar/39Ar age of 73.88 ± 0.32 ka (1σ, full external errors) for sanidine crystals extracted from Toba deposits in the Lenggong Valley, Malaysia, 350 km from the eruption source and 6 km from an archaeological site with stone artifacts buried by ash. If these artifacts were made by Homo sapiens, as has been suggested, then our age indicates that modern humans had reached Southeast Asia by ∼74 ka ago. Our 40Ar/39Ar age is an order-of-magnitude more precise than previous estimates, resolving the timing of the eruption to the middle of the cold interval between Dansgaard–Oeschger events 20 and 19, when a peak in sulfate concentration occurred as registered by Greenland ice cores. This peak is followed by a ∼10 °C drop in the Greenland surface temperature over ∼150 y, revealing the possible climatic impact of the eruption. Our 40Ar/39Ar age also provides a high-precision calibration point for other ice, marine, and terrestrial archives containing Toba sulfates and ash, facilitating their global synchronization at unprecedented resolution for a critical period in Earth and human history beyond the range of 14C dating. PMID:23112159

Safety and immunogenicity of the killed bivalent (O1 and O139) whole-cell cholera vaccine in the Philippines.

PubMed

Capeding, Maria Rosario Z; Gonzales, Maria Liza Antoinette M; Dhingra, Mandeep Singh; D'Cor, Naveena Aloysia; Midde, Venkat Jayanth; Patnaik, Badri Narayan; Thollot, Yaël; Desauziers, Eric

2017-10-03

The killed bivalent (O1 and O139) whole cell oral cholera vaccine (OCV) (Shanchol™) was first licensed in India in 2009 and World Health Organization pre-qualified in 2011. We assessed the safety and immunogenicity of this OCV in the Philippines. This was a phase IV, single-arm, descriptive, open-label study. We recruited 336 participants from 2 centers: 112 participants in each age group (1-4, 5-14 and ≥ 15 years). Participants received 2 OCV doses 14 d apart. Safety was monitored throughout the trial. Blood samples were collected at baseline (pre-vaccination) and 14 d after each dose. Serum vibriocidal antibody titers to V. cholerae O1 (El Tor Inaba and El Tor Ogawa) and O139 strains were assessed, with seroconversion defined as ≥ 4-fold increase from baseline in titers. No immediate unsolicited systemic adverse events/reactions were observed. Unsolicited systemic adverse events were mostly grade 1 intensity. One serious adverse event occurred after the first dose, but was unrelated to vaccination. High seroconversion rates (range 69-92%) were achieved against the O1 serotypes with a trend toward higher rates in the 1-4 y (86-92%) and 5-14 y (86-88%) age groups than the ≥ 15 y age group (69-83%). Lower seroconversion rates were achieved against the O139 serotype (35-70%), particularly in those aged ≥ 15 y (35-42%). The 2-dose regimen of the killed bivalent whole cell OCV was well-tolerated in this study conducted in the Philippines, a cholera-endemic country. Robust immune responses were observed even after a single-dose.

Ice-Ocean Environmental Buoys (IOEB); Technology and Deployment in 1991- 1992

DTIC Science & Technology

1993-10-01

110 Appendix D Sedim ent trap and W TS schedules ...ICE(15 ICZ 15 ICEPTTb STES TRSSI (42) (42) (42) ICE ICE ICESLAXAT & THEIRMS SEACAT k THMISd SEACAT & THEMJ (6,o) (10 (6 (1o0) (56) (,11o) Schedule ...user to schedule the time between filtering events, as well as the characteristics and limitations of the pumping operation. During the deployment of

Comparison of broiler performance and carcass yields when fed transgenic maize grain containing event DP-O9814O-6 and processed fractions from transgenic soybeans containing event DP-356O43-5.

PubMed

McNaughton, J; Roberts, M; Rice, D; Smith, B; Hinds, M; Delaney, B; Iiams, C; Sauber, T

2011-08-01

The performance of broilers fed diets containing maize grain from event DP-Ø9814Ø-6 (98140; gat4621 and zm-hra genes) and processed fractions (meal, hulls, and oil) from soybeans containing event DP-356Ø43-5 (356043; gat4601 and gm-hra genes) was evaluated in a 42-d feeding study. Diets were produced with nontransgenic maize grain and soybean fractions from controls with comparable genetic backgrounds to 98140 and 356043 (control), 98140 maize and 356043 soybean (98140 + 356043), or 3 commercially available nontransgenic maize and soybean combinations. Ross 708 broilers (n = 120/group; 50% male, 50% female) were fed diets in 3 phases: starter (d 0 to 21), grower (d 22 to 35), and finisher (d 36 to 42). Starter diets contained (on average) 63% maize and 28% soybean meal, grower diets 66% maize and 26% soybean meal, and finisher diets 72% maize and 21% soybean meal; soybean hulls and oils were held constant at 1.0 and 0.5%, respectively, across all diets in all phases. Weight gain, feed intake, and mortality-adjusted feed efficiency were calculated for d 0 to 42. Standard organ and carcass yield data were collected on d 42. Data were analyzed using a mixed model ANOVA with differences between control and 98140 + 356043 group means considered significant at P < 0.05. Reference group data were used only to estimate experimental variability and to generate tolerance intervals. No significant differences were observed in weight gain, mortality, mortality-adjusted feed efficiency, organ yields, or carcass yields between broilers consuming diets produced with 98140 + 356043 and those consuming diets produced with control maize and soybean fractions. All values of response variables evaluated in the control and 98140 + 356043 groups fell within calculated tolerance intervals. Based on these results, it was concluded that the combination of genetically modified 98140 maize and 356043 soybean fractions was nutritionally equivalent to nontransgenic maize and soybean controls with comparable genetic backgrounds.

Fasting Glycemia in Sleep Disordered Breathing: Lowering the Threshold on Oxyhemoglobin Desaturation

PubMed Central

Stamatakis, Katherine; Sanders, Mark H.; Caffo, Brian; Resnick, Helaine E.; Gottlieb, Dan J.; Mehra, Reena; Punjabi, Naresh M.

2008-01-01

Study Objectives: Commonly used definitions of sleep-disordered breathing (SDB) are based on identifying discrete events of breathing abnormalities during sleep that are accompanied by an oxyhemoglobin desaturation (ΔSaO2) of at least 4%. However, it is not known whether disordered breathing events with oxyhemoglobin desaturation less than 4% are associated with clinical sequelae such as abnormalities in fasting glycemia. Design: Cross-sectional study. Subjects and Setting: Participants from the Sleep Heart Health Study (SHHS) with a fasting glucose measurement made within a year of the baseline polysomnogram. Measurements and Results: SDB severity was defined using the apnea-hypopnea index (AHI) and the hypopnea index (HI) by counting events with different levels of oxyhemoglobin desaturation (0.0%–1.9%, 2.0%–2.9%, 3.0%–3.9%, >4.0%). Fasting glucose levels were used to classify individuals into normal (<100 mg/dL), impaired (100–125 mg/dL), and diabetic (>126 mg/dL) groups. Ordinal logistic regression was used to determine the adjusted relative odds of an abnormal glucose value across quartiles of the hypopnea index, independent of factors such as age, body mass index, waist circumference, and usual sleep duration. The prevalence of impaired and diabetic fasting glucose in the analytical sample was 32.9% and 5.8%, respectively. The covariate-adjusted relative odds of impaired or diabetic fasting glucose in the highest versus the lowest AHI quartile was 1.35 (95% CI: 1.04–1.76) for events with a ΔSaO2 ≥ 4.0%, 1.72 (95% CI: 1.20–2.48) for events with a ΔSaO2 between 3.0%-3.9%, 1.41 (95% CI: 1.07–1.86) for events with a ΔSaO2 between 2.0%–2.9%, and 1.07 (95% CI: 0.84–1.37) for events with a ΔSaO2 between 0.0%–1.9%. The corresponding odds ratios for the HI were 1.47 (95% CI: 1.13–1.92), 2.25 (95% CI: 1.59–3.19), 1.44 (95% CI: 1.09–1.90), and 1.15 (95% CI: 0.90–1.47), respectively. Conclusions: The results of this study indicate that SDB events accompanied by oxyhemoglobin desaturation of between 2% to 4% are associated with fasting hyperglycemia. These findings suggest that milder degrees of SDB may predispose to adverse metabolic outcomes. Citation: Stamatakis K; Sanders MH; Caffo B; Resnick HE; Gottlieb DJ; Mehra R; Punjabi NM. Fasting glycemia in sleep disordered breathing:lowering the threshold on oxyhemoglobin desaturation. SLEEP 2008;31(7):1018-1024. PMID:18652097

NOAA research finds new way to identify which El Niño events will have

Science.gov Websites

atmospheric El Niño signal that is very strongly associated with U.S. winter weather impacts. Download here weather impacts. Ed Harrison, Ph.D. of the NOAA Pacific Marine Environmental Laboratory in Seattle and University of Washington, co-authored the paper. "When it comes to El Niño's weather impacts, we are

The aeronomy of odd nitrogen in the thermosphere. II - Twilight emissions

NASA Technical Reports Server (NTRS)

Strobel, D. F.; Oran, E. S.; Feldman, P. D.

1976-01-01

A model developed for the aeronomy of odd nitrogen in the thermosphere is used to analyze rocket measurements of N(4S) and NO densities. Data from Atmosphere Explorer were used to develop a consistent reaction kinetics model for odd nitrogen chemistry. It is concluded that most NO(+) dissociative recombination events must produce N(2D), that N(2D) is quenched by O at a rate of 1 trillionth cu cm per sec, and that the atmospheric O2 quenching rate of N(2D) is consistent with the laboratory rate. The major quenching agent of N(2D) between 140 and 220 km is atomic oxygen, and this reaction is the major source of N(4S). Peak N(4S) densities of about (20-60) million per cu cm at 140-150 km are predicted, with the variability being indicative of the model sensitivity to a factor of 2 change in the O/O2 ratio in the thermosphere.

Last Millennium ENSO-Mean State Interactions in the Tropical Pacific

NASA Astrophysics Data System (ADS)

Wyman, D. A.; Conroy, J. L.; Karamperidou, C.

2017-12-01

The nature and degree of interaction between the mean state of the tropical Pacific and ENSO remains an open question. Here we use high temporal resolution, tropical Pacific sea surface temperature (SST) records from the last millennium to investigate the relationship between ENSO and the tropical Pacific zonal sea surface temperature gradient (hereafter dSST). A dSST time series was created by standardizing, interpolating, and compositing 7 SST records from the western and 3 SST records from the eastern tropical Pacific. Propagating the age uncertainty of each of these records was accomplished through a Monte Carlo Empirical Orthogonal Function analysis. We find last millennium dSST is strong from 700 to 1300 CE, begins to weaken at approximately 1300 CE, and decreases more rapidly at 1700 CE. dSST was compared to 14 different ENSO reconstructions, independent of the records used to create dSST, to assess the nature of the ENSO-mean state relationship. dSST correlations with 50-year standard deviations of ENSO reconstructions are consistently negative, suggesting that more frequent, strong El Niño events on this timescale reduces dSST. To further assess the strength and direction of the ENSO-dSST relationship, moving 100-year standard deviations of ENSO reconstructions were compared to moving 100-year averages of dSST using Cohen's Kappa statistic, which measures categorical agreement. The Li et al. (2011) and Li et al. (2013) Nino 3.4 ENSO reconstructions had the highest agreement with dSST (k=0.80 and 0.70, respectively), with greater ENSO standard deviation coincident with periods of weak dSST. Other ENSO reconstructions showed weaker agreement with dSST, which may be partly due to low sample size. The consistent directional agreement of dSST with ENSO, coupled with the inability of strong ENSO events to develop under a weak SST gradient, suggests periods of more frequent strong El Niño events reduced tropical Pacific dSST on centennial timescales over the last millennium.

Evaluation of Visibility Sensors at the Eglin Air Force Base Climatic Chamber.

DTIC Science & Technology

1983-10-01

s o t LI a of to -NAIC 6/81- -11 * VIow:1710 tons e- I: l - llO 26 5 6 Os *15 eeas IIg " 25 l5 .0 36 15 lOI (C) RYC (d) FIGURE 5-15. HOMOGENEITY OF...4 inch thick white plastic scattering disk. Since the exact attenuation of a filter can vary by as much as a factor of two, there was no way to...translucent plastic disk as scatterer and was found to be unchanged. The difference in calibration between Event 1 (slope - 0.88) and Event 2 (slope

A 10-yr record of stable isotope ratios of hydrogen and oxygen in precipitation at Calgary, Alberta, Canada

NASA Astrophysics Data System (ADS)

Peng, Haidong; Mayer, Bernhard; Harris, Stuart; Krouse, H. Roy

2004-04-01

Short-term (0.5 3 d) precipitation samples were collected from January 1992 to December 2001 in Calgary, Alberta, Canada, and the stable isotope ratios of hydrogen (2H/1H) and oxygen (18O/16O) for these samples were determined. The 10-yr amount-weighted average δ2H and δ18O values of precipitation were -136.1‰ and -17.9‰, respectively. Consistent with International Atomic Energy Agency (IAEA) established practice, the following local meteoric water line (LMWL) for Calgary was derived using amount-weighted monthly average δ2H and δ18O values: δ2H = 7.68 δ18O -0.21 (r2= 0.96, n= 104). The correlation equation between δ2H and δ18O values from individual samples was found to be δ2H = 7.10 δ18O -13.64 (r2= 0.95, n= 839), which is different from the LMWL, exhibiting lower slope and intercept values. A comparison of δ2H and δ18O correlation equations with temperature during precipitation events showed a trend of decreasing slopes and intercepts with increasing temperature. Our data suggest that this is caused by incorporation of moisture derived from evaporation from water bodies and soils along the storm paths and by secondary evaporation between the cloud base and the ground during precipitation events. These processes compromise the usefulness of d-excess values as an indicator for the meteorological conditions in the maritime source regions. The δ18O temperature dependence at Calgary was found to be 0.44‰°C1. The study shows that short-term sampling of individual precipitation events yields valuable information, which is not obtainable by the widely used monthly collection programs.

O-GlcNAc modification is essential for the regulation of autophagy in Drosophila melanogaster.

PubMed

Park, Sujin; Lee, Yangsin; Pak, Jin Won; Kim, Hanbyeol; Choi, Hyeonjin; Kim, Jae-woo; Roth, Jürgen; Cho, Jin Won

2015-08-01

O-GlcNAcylation is a dynamic post-translational modification that takes place on ser/thr residues of nucleocytoplasmic proteins. O-GlcNAcylation regulates almost all cellular events as a nutrient sensor, a transcriptional and translational regulator, and a disease-related factor. Although the role of O-GlcNAcylation in insulin signaling and metabolism are well established, the relationship between O-GlcNAcylation and autophagy is largely unknown. Here, we manipulated O-GlcNAcylation in Drosophila and found that it regulates autophagy through Akt/dFOXO signaling. We demonstrate that O-GlcNAcylation and the levels of O-GlcNAc transferase (OGT) are increased during starvation. Furthermore, Atg proteins and autolysosomes are increased in OGT-reduced flies without fasting. Atg proteins and autophagosomes are reduced in OGT-overexpressing flies. Our results suggest that not only autophagy gene expression but also autophagic structures are regulated by OGT through Akt and dFOXO. These data imply that O-GlcNAcylation is important in modulating autophagy as well as insulin signaling in Drosophila.

Southern Greenland water vapour isotopic composition at the crossroads of Atlantic and Arctic moisture

NASA Astrophysics Data System (ADS)

Bonne, J. L.; Steen-Larsen, H. C.; Risi, C. M.; Werner, M.; Sodemann, H.; Lacour, J. L.; Fettweis, X.; Cesana, G.; Delmotte, M.; Cattani, O.; Clerbaux, C.; Sveinbjörnsdottir, A. E.; Masson-Delmotte, V.

2014-12-01

Since September 2011, a continuous water vapour isotopic composition monitoring instrument has been remotely operated in Ivittuut (61.21°N, 48.17°W), southern Greenland. Meteorological parameters are monitored and precipitation has been sampled and analysed for isotopic composition, suggesting equilibrium between surface vapour and precipitation. The data depict small summer diurnal variations. δ18O and deuterium excess (d-excess) are generally anti-correlated and show important seasonal variations (with respective amplitudes of 10 and 20 ‰), and large synoptic variations associated to low-pressure systems (typically +5‰ on δ18O and -15‰ on d-excess). The moisture sources, estimated based on Lagrangian back-trajectories, are primarily influenced by the western North Atlantic, and north-eastern American continent. Notable are important seasonal and synoptic shifts of the moisture sources, and sporadic influences of the Arctic or the eastern North Atlantic. Moisture sources variations can be related to changes in water vapour isotopic composition, and the isotopic fingerprints can be attributed to the areas of moisture origins. Isotopic enabled AGCMs nudged to meteorology (LMDZiso, ECHAM5-wiso), despite biases, correctly capture the δ18O changes, but underestimate the d-excess changes. They allow to identify a high correlation between the southern Greenland d-excess and the simulated relative humidity and d-excess in the moisture source region south of Greenland. An extreme high temperature event in July 2012 affecting all Greenland, similar to ice sheet melt events during the medieval periods and one event in 1889 documented by Greenland ice core records, has been analysed regarding water vapour isotopic composition, using remote sensing (IASI) and in situ observations from Bermuda to northern Greenland (NEEM station). Our southern Greenland observations allow to track the water vapour evolution during this event along the moisture transport path, depicting the northward propagation of an isotopic signal inherited from the meteorological conditions during evaporation. Overall, our observations provide valuable information for interpreting Greenland ice core records as well as for evaluating water vapour isotopic simulations in atmospheric models.

Upcoming Events

Science.gov Websites

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z D2L PAWS Email My UW-System About UWM UWM Jobs D2L PAWS Email My UW-System University of Wisconsin-Milwaukee College ofEngineering & Olympiad Girls Who Code Club FIRST Tech Challenge NSF I-Corps Site of Southeastern Wisconsin UW-Milwaukee

Initial Chemical Events in CL-20 Under Extreme Conditions: An Ab Initio Molecular Dynamics Study

DTIC Science & Technology

2006-11-01

M.; Ehara, M.; Toyota , K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Klene, M.; Li, X.; Knox, J. E...M.P.; Nissan , R.A.; Vanderah, D.J.; Gilardi, R.D.; George, C. F.; Flippen-Anderson, J. L. Tetrahedron, 1998, 54, 11793- 11812. 27. Okovytyy, S

From precipitation to ice cores: an isotopic comparison at Summit, Greenland

NASA Astrophysics Data System (ADS)

Kopec, B. G.; Feng, X.; Adolph, A. C.; Virginia, R. A.; Posmentier, E. S.

2015-12-01

The observed deuterium excess (d-excess) in ice cores from Summit, Greenland has high summer values and low winter values, which is opposite of the seasonal variations of most northern hemisphere locations. The interpretation of this d-excess seasonality in the context of moisture source changes is made more complicated by possible post-depositional modifications. We investigate potential post-depositional modifications within 3-4 years after precipitation events by collecting precipitation samples and comparing them with snow pit profiles at Summit. Precipitation was sampled on a storm-by-storm basis from July 2011 to September 2014. To assess the effect of wind blown snow on cross-storm contamination, we sampled at three heights (1, 2, and 4 m). Snow pits were sampled in the summers of 2013 and 2015 to span the entirety of our precipitation record. All samples were analyzed for δD and δ18O and d-excess was calculated. Mixing of snow between different storms was identified only for samples collected at the lowest height. We thus use the samples collected at the top height for interpretation. The annual cycle of precipitation isotopes follow the established seasonal relationship with the average summer enrichment of -217 and -29‰, and winter depletion of -317 and -40‰ for δD and δ18O, respectively. The d-excess shows an average summer maximum of 16‰ and winter minimum of 3‰. In the snow pit, the seasonal amplitude and phase of both oxygen and hydrogen isotopic ratios as well as the d-excess compare remarkably well with those of the precipitation. The profile appeared to be devoid of major post depositional effects except for a thin layer that changed during a melt event in 2012. However, this type of event is extremely rare at Summit, and should not significantly compromise the interpretation of precipitation isotopes in ice cores, except perhaps during climatic warm period summers. The precipitation d-excess seasonality is typically interpreted as resulting from changing moisture sources, but this does not explain the positive relationship between d-excess and d18O at Summit, Greenland. We propose that moisture sublimated from the snow surface, which typically has high d-excess values, may be an important moisture source captured in the isotope record.

Patrick Air Force Base Storm Water Pollution Prevention Plan.

DTIC Science & Technology

1994-09-01

CE 00 0O L 2- E0 .0 cl ci = 0 L) cz C C 00 H cz - ~.CIn U -. 0 0 - - E o nC .C) 0 2;l C)i En C) u C CIO cz _ C>) C) 0 u E-) a) Z L) 0o~bo coo 0 - . cn...as soon as practi-distated and lo dal c rq ir nts anderas, cable after significant modification areS tate, an d local req u irem en ts an d asm a e t...the duration between the storm event and fecal coliform (counts per 100 mL). sampled and the end of the previous measur- able (greater than 0.1 inch

Effect of severe weather events on the shedding of Shiga toxigenic Escherichia coli in slaughter cattle and phenotype of serogroup O157 isolates.

PubMed

Stanford, Kim; Reuter, Tim; Bach, Susan J; Chui, Linda; Ma, Angela; Conrad, Cheyenne C; Tostes, Renata; McAllister, Tim A

2017-09-01

High-event periods (HEPs) occur sporadically when beef carcasses and meat have episodes of acute contamination with Shiga toxin-producing Escherichia coli (STEC). In this study, severe weather events were investigated as catalysts for HEPs based on PCR and isolate prevalence of seven E. coli serogroups in slaughter cattle feces. Winter ambient temperatures with daily means 10.5oC warmer or 12.3°C colder than seasonal norms (-10.4°C) most altered STEC shedding. Fecal samples yielded increased proportions (P < 0.05) of O26 and O157 isolates during winter warm periods, and reduced (P < 0.05) O45 isolates during cold periods compared to samplings during seasonal norms. Based on changing PCR prevalence and isolates collected, O157 was the serogroup most responsive to severe weather events. Consequently, O157 isolates (n = 219) were evaluated for heat resistance, biofilm-forming potential and virulence gene subtypes. Two isolates had heat-resistant phenotypes with thermal death time at 60°C (D60) > 10 min and one also had strong biofilm-forming potential. However, this isolate lacked eae and stx genes. Severe weather can influence STEC shedding, particularly of O157, and could possibly trigger HEPs. However, our data suggest that it is unlikely for isolates to carry virulence genes and possess phenotypes capable of evading post-harvest microbiological interventions. © FEMS 2017. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Geochemical characteristics of cave drip water respond to ENSO based on a 6-year monitoring work in Yangkou Cave, Southwest China

NASA Astrophysics Data System (ADS)

Chen, Chao-Jun; Li, Ting-Yong

2018-06-01

The scientific explanation of speleothem δ18O in Chinese monsoon region is a greatly debated issue. Modern cave monitoring combined with instrument observation maybe is an essential solution to deal with this issue. During the period from 2011 to 2016, we monitored local precipitation, soil water in three soil profiles, and six drip water sites in Yangkou Cave, which is located in Chongqing City, Southwest China. This article presents measurements about δ18O, δD and Mg/Ca ratios of drip water and compared these geochemical proxies with contemporaneous atmospheric circulations. The main conclusions are: (1) As water migrates from precipitation to soil water to cave drip water, the amplitudes of seasonal variations in δD and δ18O decreased gradually. Due to the existence of complex hydrogeological conditions, the range of variation and the seasonal characteristics of δD and δ18O differ among the drip sites where samples were collected, but the interannual variability is nearly the same. The drip water Mg/Ca ratios are mainly regulated by changes in hydrological conditions in the epikarst zone, with higher values during winter months than that during summer months. (2) When an El Niño event occurs, the Western Pacific Subtropical High (WPSH) is migrated westward, and the production of near-source water vapor from the western Pacific and the South China Sea increases, leading to higher δ18O values in the precipitation and the cave drip water. The drip water Mg/Ca ratios were significantly lower with increased summer precipitation. On the other hand, during La Niña events, the WPSH is migrated eastward, and inputs of water vapor that has traveled greater distances (from the Indian Ocean) become comparatively important, resulting in lower δ18O values in the precipitation and the cave drip water. The drip water Mg/Ca ratios were higher with decreased summer precipitation. In summary, the interannual variability of δ18O in the drip waters of Yangkou Cave reflects changes in water vapor sources caused by atmospheric circulation patterns. Mg/Ca ratios respond to changes of precipitation and CO2 in soil and can be used to reconstruct abnormal drought or flood events.

Error control techniques for satellite and space communications

NASA Technical Reports Server (NTRS)

Costello, Daniel J., Jr.

1990-01-01

An expurgated upper bound on the event error probability of trellis coded modulation is presented. This bound is used to derive a lower bound on the minimum achievable free Euclidean distance d sub (free) of trellis codes. It is shown that the dominant parameters for both bounds, the expurgated error exponent and the asymptotic d sub (free) growth rate, respectively, can be obtained from the cutoff-rate R sub O of the transmission channel by a simple geometric construction, making R sub O the central parameter for finding good trellis codes. Several constellations are optimized with respect to the bounds.

Eastern Tropical Pacific Precipitation Response to Zonal SPCZ events

NASA Astrophysics Data System (ADS)

Durán-Quesada, A. M.; Lintner, B. R.

2014-12-01

Extreme El Niño events and warming conditions in the eastern tropical Pacific have been linked to pronounced spatial displacements of the South Pacific Convergence Zone known as "zonal SPCZ" events.. Using a global dataset of Lagrangian back trajectories computed with the FLEXPART model for the period 1980-2013, comprehensive analysis of the 3D circulation characteristics associated with the SPCZ is undertaken. Ten days history of along-trajectory specific humidity, potential vorticity and temperature are reconstructed for zonal SPCZ events as well as other states,, with differences related to El Niño intensity and development stage as well as the state of the Western Hemisphere Warm Pool. How zonal events influence precipitation over the Eastern Tropical Pacific is examined using back trajectories, reanalysis, TRMM precipitation, and additional satellite derived cloud information. It is found that SPCZ displacements are associated with enhanced convection over the Eastern Tropical Pacific in good agreement with prior work. The connection between intensification of precipitation over the eastern Tropical Pacific during zonal events and suppression of rainfall over the Maritime continent is also described.

The Cauaburi magmatic arc: Litho-stratigraphic review and evolution of the Imeri Domain, Rio Negro Province, Amazonian Craton

NASA Astrophysics Data System (ADS)

Carneiro, Marcia C. R.; Nascimento, Rielva S. C.; Almeida, Marcelo E.; Salazar, Carlos A.; Trindade, Ivaldo Rodrigues da; Rodrigues, Vanisse de Oliveira; Passos, Marcel S.

2017-08-01

A lithostratigraphic review of the Cauaburi Complex was carried out by means of field, tectono-metamorphic and geochemical data, which were the basis for the sub-division of the Cauaburi Complex orthogneisses into the Santa Izabel do Rio Negro, Cumati and São Jorge facies. These rocks crop out between São Gabriel da Cachoeira and Santa Izabel do Rio Negro, Amazonas, Brazil. The gneisses of the Santa Izabel do Rio Negro and Cumati facies are metaluminous and of calc-alkaline affinity; in turn, the rocks of the São Jorge facies are peraluminous and of alkaline affinity. They vary from (amphibole)-biotite granodiorites/monzogranites (Cumati and Santa Izabel do Rio Negro facies) to spessartite-bearing biotite monzogranites (São Jorge facies). The Cauaburi Complex geochemical signature is compatible with that of granites generated in collisional settings (magmatic arc?) and its evolution is related to three distinct tectono-metamorphic events: D1, causing foliation S1, which developed during the Cauaburi Complex syn-tectonic emplacement in the Cauaburi Orogeny; D2/M2, causing foliation S2, which was generated under amphibolite facies conditions (717.9 °C and 5.84 kbars), and the emplacement of I- and S-type granite during the Içana Orogen, and low-temperature D3, associated with the K'Mudku Event, which caused foliation S3 and reworking via transcurrent shear zones under greenschist facies conditions.

Nutrient Concentrations and Stable Isotopes of Runoff from a Midwest Tile-Drained Corn Field

NASA Astrophysics Data System (ADS)

Wilkins, B. P.; Woo, D.; Li, J.; Michalski, G. M.; Kumar, P.; Conroy, J. L.; Keefer, D. A.; Keefer, L. L.; Hodson, T. O.

2017-12-01

Tile drains are a common crop drainage device used in Midwest agroecosystems. While efficient at drainage, the tiles provide a quick path for nutrient runoff, reducing the time available for microbes to use nutrients (e.g., NO3- and PO43-) and reduce export to riverine systems. Thus, understanding the effects of tile drains on nutrient runoff is critical to achieve nutrient reduction goals. Here we present isotopic and concentration data collected from tile drain runoff of a corn field located near Monticello, IL. Tile flow samples were measured for anion concentrations and stable isotopes of H2O and NO3-, while precipitation was measured for dual isotopes of H2O. Results demonstrate early tile flow from rain events have a low Cl- concentration (<20ppm) with water isotopic values reflecting precipitation, indicating preferential flow (>60% contribution) in the beginning of the hydrograph. As flow continues H2O isotopic values reflect pre-event water (ground and soil water), and Cl- concentrations increase representing a greater influence by matrix flow (60-90% contribution). Nitrate concentrations change dramatically, especially during the growing season, and do not follow a similar trend as the conservative Cl-, often decreasing days before, which represents missing nitrate in the upper surface portion of the soil. Nitrate isotopic data shows significant changes in 15N (4‰) and 18O (4‰) during individual hydrological events, representing that in addition to plant uptake and leaching, considerate NO3- is lost through denitrification. It is notable, that throughout the season d15N and d18O of nitrate change significantly representing that seasonally, substantial denitrification occurs.

Collision-induced dissociation of protonated water clusters

NASA Astrophysics Data System (ADS)

Berthias, F.; Buridon, V.; Abdoul-Carime, H.; Farizon, B.; Farizon, M.; Dinh, P. M.; Reinhard, P.-G.; Suraud, E.; Märk, T. D.

2014-06-01

Collision-induced dissociation (CID) has been studied for protonated water clusters H+(H2O)n, with n = 2-8, colliding with argon atoms at a laboratory energy of 8 keV. The experimental data have been taken with an apparatus (Device for Irradiation of Molecular Clusters, `Dispositif d'Irradiation d'Agrégats Moléculaire,' DIAM) that has been recently constructed at the Institut de Physique Nucléaire de Lyon. It includes an event-by-event mass spectrometry detection technique, COINTOF (correlated ion and neutral fragment time of flight). The latter device allows, for each collision event, to detect and identify in a correlated manner all produced neutral and charged fragments. For all the studied cluster ions, it has allowed us to identify branching ratios for the loss of i = 1 to i = n water molecules, leading to fragment ions ranging from H+(H2O)i=n-1 all the way down to the production of protons. Using a corresponding calibration technique we determine total charged fragment production cross sections for incident protonated water clusters H+(H2O)n, with n = 2-7. Observed trends for branching ratios and cross sections, and a comparison with earlier data on measured attenuation cross sections for water clusters colliding with other noble gases (He and Xe), give insight into the underlying dissociation mechanisms.

The Relationships of Climate and Terrain to Maintenance of Way on the Norfolk Southern Railroad between Norfolk, Virginia, and Portsmouth, Ohio

DTIC Science & Technology

1990-08-01

M,@mrq f. 1* cw iO 11erWurev SUo - NT1 wq~fag u’q e oseir ofv At AW MOWt aa d T its C0d CAi of dr"idlr. .- t I sq ao ’Or voduJafort 6 nW . to thWqnoV...The Atlantic, Mississippi, and Ohio Railroad had depended on the products of an agrarian South, such as cotton, lumber, tobacco , grains, and cattle...thunderstorm cells , one can say that intense precipitation events are demonstrably capable of producing slope failures, particularly when these events follow

Tropical Pacific climate variability over the last 6000 years as recorded in Bainbridge Crater Lake, Galápagos

NASA Astrophysics Data System (ADS)

Thompson, Diane M.; Conroy, Jessica L.; Collins, Aaron; Hlohowskyj, Stephan R.; Overpeck, Jonathan T.; Riedinger-Whitmore, Melanie; Cole, Julia E.; Bush, Mark B.; Whitney, H.; Corley, Timothy L.; Kannan, Miriam Steinitz

2017-08-01

Finely laminated sediments within Bainbridge Crater Lake, Galápagos, provide a record of El Niño-Southern Oscillation (ENSO) events over the Holocene. Despite the importance of this sediment record, hypotheses for how climate variability is preserved in the lake sediments have not been tested. Here we present results of long-term monitoring of the local climate and limnology and a revised interpretation of the sediment record. Brown-green, organic-rich, siliciclastic laminae reflect warm, wet conditions typical of El Niño events, whereas carbonate and gypsum precipitate during cool, dry La Niña events and persistent dry periods, respectively. Applying this new interpretation, we find that ENSO events of both phases were generally less frequent during the mid-Holocene ( 6100-4000 calendar years B.P.) relative to the last 1500 calendar years. Abundant carbonate laminations between 3500 and 3000 calendar years B.P. imply that conditions in the Galápagos region were cool and dry during this period when the tropical Pacific E-W sea surface temperature (SST) gradient likely strengthened. The frequency of El Niño and La Niña events then intensified dramatically around 1750-2000 calendar years B.P., consistent with a weaker SST gradient and an increased frequency of ENSO events in other regional records. This strong interannual variability persisted until 700 calendar years B.P., when ENSO-related variability at the lake decreased as the SST gradient strengthened. Persistent, dry conditions then dominated between 300 and 50 calendar years B.P. (A.D. 1650-1900, ± 100 years), whereas wetter conditions and frequent El Niño events dominated in the most recent century.

Participation of 3-O-sulfated heparan sulfates in the protection of macrophages by herpes simplex virus-1 glycoprotein D and cyclophilin B against apoptosis.

PubMed

Delos, Maxime; Hellec, Charles; Foulquier, François; Carpentier, Mathieu; Allain, Fabrice; Denys, Agnès

2017-02-01

Heparan sulfates (HS) are involved in numerous biological processes, which rely on their ability to interact with a large panel of proteins. Although the reaction of 3-O-sulfation can be catalysed by the largest family of HS sulfotransferases, very few mechanisms have been associated with this modification and to date, only glycoprotein D (gD) of herpes simplex virus-1 (HSV-1 gD) and cyclophilin B (CyPB) have been well-described as ligands for 3- O -sulfated HS. Here, we hypothesized that both ligands could induce the same responses via a mechanism dependent on 3- O -sulfated HS. First, we checked that HSV-1 gD was as efficient as CyPB to induce the activation of the same signalling events in primary macrophages. We then demonstrated that both ligands efficiently reduced staurosporin-induced apoptosis and modulated the expression of apoptotic genes. In addition to 3- O -sulfated HS, HSV-1 gD was reported to interact with other receptors, including herpes virus entry mediator (HVEM), nectin-1 and -2. Thus, we decided to identify the contribution of each binding site in the responses triggered by HSV-1 gD and CyPB. We found that knock-down of 3- O -sulfotransferase 2, which is the main 3- O -sulfated HS-generating enzyme in macrophages, strongly reduced the responses induced by both ligands. Moreover, silencing the expression of HVEM rendered macrophages unresponsive to either HSV-1 gD and CyPB, thus indicating that both proteins induced the same responses by interacting with a complex formed by 3- O -sulfated HS and HVEM. Collectively, our results suggest that HSV-1 might hijack the binding sites for CyPB in order to protect macrophages against apoptosis for efficient infection.

New mineralogical and geochemical evidence for the Middle Eocene Climatic Optimum (MECO) in the Neo-Tethys (Central Turkey)

NASA Astrophysics Data System (ADS)

Rego, E. S.; Jovane, L.; Giorgioni, M.; Hein, J. R.; Sant'Anna, L. G.; Rodelli, D.; Özcan, E.; Frontalini, F.; Coccioni, R.

2016-12-01

The Middle Eocene Climatic Optimum (MECO) is one of several climate warming events that occurred during the Paleogene. It started at 40.5 Ma and produced a global temperature increase over a period of 500 kyr. However, the duration and the d13C signature of this event are not consistent with the models commonly proposed to explain warming events in the Cenozoic, and thus challenge our understanding of carbon cycling and climatic processes. Here we present data of a new section from central Turkey, recording the MECO in the eastern part of the Neo-Tethys. The stratigraphic extent and continuity, as well as the exceptional preservation of various types of microfossils, allow us to obtain a multi-proxy record of unprecedented high resolution for this interval. We integrate data from stable isotopes, X-ray diffraction mineralogy, XRF chemistry, and magnetic properties to obtain a complete paleoclimatic and paleoceanographic reconstruction. Stable isotopes (d13C and d18O) allow us to clearly define the geochemical signature of the MECO. A divergence between the d18O curves of the shallow- and deep-water dwelling planktonic foraminifera after the event suggests a more stratified water column in the Neo-Tethys. Bulk and clay mineralogy reveal changing weathering conditions on land. Higher amounts of chlorite and illite (physical weathering) occur prior and after the event, while the MECO interval displays greater amounts of illite and smectite (chemical weathering). Additionally, the inverse relationship between detrital minerals and calcite suggests that carbonate productivity might have suffered at that time, or an increase in detrital input could have diluted the carbonate fraction. An increase in ARM and magnetic particle grain size also suggests an increase in productivity or preservation of biogenic magnetite. Our results confirm the global nature of the MECO, affecting both oceans and continents. However, different from other events, warming conditions were not produced by a sudden release of greenhouse gasses, but probably by a change in circulation amplified by orbital forcing.

Aprepitant in adolescent patients for prevention of chemotherapy-induced nausea and vomiting: a randomized, double-blind, placebo-controlled study of efficacy and tolerability.

PubMed

Gore, Lia; Chawla, Sant; Petrilli, Antonio; Hemenway, Molly; Schissel, Debra; Chua, Vickey; Carides, Alexandra D; Taylor, Arlene; Devandry, Suzanne; Valentine, Jack; Evans, Judith K; Oxenius, Bettina

2009-02-01

The neurokinin-1 receptor antagonist aprepitant, plus a 5HT3 antagonist and corticosteroid is well-tolerated and effective in preventing chemotherapy-induced nausea and vomiting in adults but has not been formally assessed in adolescents. Patients age 11-19 years old receiving emetogenic chemotherapy were randomized 2:1 to aprepitant triple therapy (aprepitant [A] 125 mg p.o., dexamethasone [D] 8 mg p.o., and ondansetron [O] 0.15 mg/kg i.v. t.i.d. day 1; A 80 mg, D 4 mg, and O 0.15 mg/kg t.i.d. day 2; A 80 mg and D 4 mg day 3; and D 4 mg day 4) or a control regimen (D 16 mg and O 0.15 mg/kg t.i.d. day 1; D 8 mg and O 0.15 mg/kg t.i.d. day 2; and D 8 mg days 3 and 4). The primary endpoint was the difference in drug-related adverse events during and for 14 days following treatment. Efficacy and aprepitant pharmacokinetics were assessed. Baseline characteristics were similar between aprepitant (N = 28) and control (N = 18) groups. Febrile neutropenia was more frequent in the aprepitant group (25% vs. 11.1%). Complete response (CR) rates were 35.7% for aprepitant triple therapy versus 5.6% for the control group. Mean plasma aprepitant AUC(0-24 hr) and C(max) on day 1 and mean trough concentrations on days 2 and 3 were consistently lower compared to historical data obtained from healthy adults; however, the differences were not clinically significant. Aprepitant triple therapy was generally well tolerated; CR were greater with aprepitant, although not statistically significant. Pharmacokinetics suggest that the adult dosing regimen is appropriate for adolescents. (c) 2008 Wiley-Liss, Inc.

The MEM of spectral analysis applied to L.O.D.

NASA Astrophysics Data System (ADS)

Fernandez, L. I.; Arias, E. F.

The maximum entropy method (MEM) has been widely applied for polar motion studies taking advantage of its performance on the management of complex time series. The authors used the algorithm of the MEM to estimate Cross Spectral function in order to compare interannual Length-of-Day (LOD) time series with Southern Oscillation Index (SOI) and Sea Surface Temperature (SST) series, which are close related to El Niño-Southern Oscillation (ENSO) events.

Isotopic Variability in Central Valley Precipitation Events

NASA Astrophysics Data System (ADS)

Keene, D.; Sowers, T.; Wagner, A. J.

2017-12-01

Wintertime precipitation in the Sacramento Valley is characterized by two regimes: northerly storms generated by the polar jet stream and southerly storms generated by subtropical atmospheric rivers (ARs). Polar jet stream storms account for the majority of storm activity in the central valley, but the amount of subtropical moisture available for transport tends to increase during El Niño years. However, during the El Niño of 2015-2016, California continued to experience drought conditions with the Sacramento area receiving below average wintertime precipitation. Although the 2016-2017 winter was not an El Niño year, the Sacramento area received more than 190% of its average precipitation from ARs in the opening months of 2017. While this suggests that ARs are a significant part of California's hydrologic cycle independent of El Niño, it has not been established whether these storms have an isotopically distinct signature compared to those generated by the polar jet stream or if their signature covaries with ENSO. To investigate the potential isotopic variability of ARs, rainwater was collected over a period of three years in the Sacramento Valley and the surrounding areas and analyzed for δD and δ18O. Since El Niño is generally considered to cause an increase in the amount of available subtropical moisture delivered to the Sacramento valley, we would expect precipitation during those years to be less depleted than precipitation in non-El Niño years. On average, δD and δ18O values of precipitation during the 2015-2016 winter were not significantly different compared to precipitation from 2016-2017 even though 2016-2017 was dominated by historic amounts of AR rainfall. This suggests that the frequency and intensity of atmospheric river storm events may not be intimately linked with the ENSO cycle.

Investigating the Source Mechanisms of Deflation-Inflation Events at Kilauea Volcano, Hawai`i

NASA Astrophysics Data System (ADS)

Johnson, J. H.; Anderson, K. R.; Poland, M. P.; Miklius, A.

2012-12-01

At Kilauea Volcano, Hawai`i, cyclic deflation-inflation ("DI") events have been observed on tiltmeters since 1988. Most DI events begin with deflation at the summit that generally lasts 12-72 hours and accumulate ~1-5 microradians of tilt as measured on the rim of Kilauea Caldera, followed by inflation that is initially rapid but wanes over the course of 12-48 hours as the net deformation approaches pre-event levels. This gives the tilt events a V- or U-shaped appearance in the tilt time series, depending on the onset deflation rates. DI events are also manifested at the Pu`u `O`o eruptive vent on Kilauea's east rift zone, about 20 km along the rift from the summit, and lag summit deformation by approximately 30-90 minutes (except during 2005-2007, when summit DI events were not detected at Pu`u `O`o). The temporal correlation of tilt at the caldera and east rift zone indicates that these events affect much of Kilauea's magma plumbing system, from the summit magma reservoir to the eruption site. Large-magnitude DI events are visible in data from continuously-recording GPS stations both at Kilauea's summit and at Pu`u `O`o, and some DI events have been imaged using InSAR. Tilt events with long-lived (several days) deflation phases are usually associated with decreases in lava effusion or even eruptive pauses on the east rift zone, while large inflationary phases are often accompanied by surges in lava effusion, new breakouts, and thus increased lava flow hazard. The lava level within the summit eruptive vent, which has been continuously visible since early 2010, correlates with tilt deformation associated with DI events. Seismic tremor levels measured at Kilauea summit at times also display a relation with DI events, sometimes correlated and sometimes anti-correlated. Tilt events have become more common since the onset of Kilauea's summit eruption in March 2008, increasing from about 5-10 per year before 2008 to more than 80 in the 8 months of 2012. Two possibly inter-related mechanisms have been suggested to explain the DI events: (1) blockage and subsequent clearing of the transport pathway that feeds the shallow summit magma system and conduit to Pu`u `O`o, and (2) convective overturns caused by replacement of degassed magma with gas-rich magma. Using a simple kinematic forward model, we invert deformation data from more than 400 DI events to estimate the location and volume change of the shallow summit source generating the ground tilt, and look for changes associated with the evolution of eruptive behaviour at Kilauea. More insight into the DI events can be gained by developing a physics-based model capable of linking magmatic processes with the temporal evolution of individual DI events. We will construct multiphysics finite element models (FEMs) to simulate deformation caused by the two proposed mechanisms to link the observations to the physical processes that drive DI events. The FEMs allow us to investigate complicated model configurations that account for 3D geometric configurations, distributions of rheologic properties, and multiple deformation sources. Crucially, the models also allow for temporal variation of fluid flow and subsurface pressurization, which will provide insights into the unique patterns of tilt observed at Kilauea.

A decrease in D-dimer concentration and an occurrence of skin rash as iatrogenic events and complementary predictors of survival in lung cancer patients treated with EGFR tyrosine kinase inhibitors.

PubMed

Zaborowska-Szmit, Magdalena; Kowalski, Dariusz M; Piórek, Aleksandra; Krzakowski, Maciej; Szmit, Sebastian

2016-12-01

Progression of lung cancer is associated with some abnormalities in coagulation. The aim of the study was to determine the predictive and prognostic value of changes in D-dimer concentration in non-small cell lung cancer (NSCLC) patients on anti-EGFR targeted therapy. The analysis included fifty two NSCLC patients treated with EGFR tyrosine kinase inhibitors (TKIs): erlotinib or gefitinib. All clinical data were collected before treatment and after 2 cycles (60days) of therapy and correlated with progression free and overall survival (PFS, OS). Two iatrogenic events were noted within the first 60days of anti-EGFR treatment: typical skin rash in 38 (73.1%) and a decrease in D-dimer concentration in 26 (50%) patients. Multivariate analysis revealed a decrease of D-dimer concentration as the strongest factor associated with longer PFS (HR=0.39; 95%CI: 0.16-0.91; p=0.029) and OS (HR=0.33; 95%CI: 0.13-0.82, p=0.017) independently of skin rash, baseline level of D-dimer and other clinical characteristics. Coexisting a decrease in D-dimer concentration with an occurrence of skin rash correlated significantly with the positive objective response after 60days of anti-EGFR therapy (p=0.0175) and indicated the longest PFS (HR=0.31; 95%CI: 0.16-0.60, p=0.0005) as well as OS (HR=0.30; 95%CI: 0.15-0.59, p=0.0005). Adverse events may predict the outcomes of cancer patients. Apart from skin rash, change in D-dimer concentration may be valuable parameter in creation of predictive and prognostic models in NSCLC patients receiving anti-EGFR targeted therapy. Copyright © 2016. Published by Elsevier Urban & Partner Sp. z o.o.

Applications of a Conditional Event Algebra to Data Fusion

DTIC Science & Technology

1988-05-01

FUNDING NUMBERS APPLICATIONS OF A CONDITIONAL EVENT ALGEBRA TO DATA FUSION- In-house funding 6. AUTOR(S)C 1. R. Goodman 7. PERFORMING ORGANIZATION NAME...S) AND ADDRESS(ES) EL C E llk 8. PERFORMING ORGAiIIZATION REPORT NUMBER 9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(Eq 10. SPONSORING...of the corresponding quantitative descript- D . CO N -R o ion. In effect , this entails choosing both an appropri- SNODE 6 ate relational syntax and a

Simulation Crisis Team Training Effect on Rural Hospital Safety Climate (SIMCRITTER)

DTIC Science & Technology

2008-09-01

etc. 8. Aid Run labs, get chart, assist ICU RN Central Venous Cannulation Training S b t ti l d ti fu s an a re uc on o Related Infections Health...accurately Y Y % 100% 100% Deliver meds to bedside assistant Defibrillate/cardiovert/pace Treatment leader 0 Acquire history : AMPLE Yes 0 0 Make diagnostic...cardiac cause. Prioritize intervening in myocardial event. III. Educational Level: All levels IV. Pre-event History and Physical: See below

Major Solar Proton Event during September 24-30, 2001 using Imaging Riometer Technique (P42)

NASA Astrophysics Data System (ADS)

Sharma, A. K.; Vhatkar, R. S.

2006-11-01

sharma_ashokkumar@yahoo.com Major outbursts of mass and energy i.e. a fast full halo CME with speed of 2402 km/sec from region 9632, located on the Sun at S16 E23 was observed at 1030 UT by SOHO/LASCO C3 coronagraph on September 24, 2001. The proton event at greater than 100 MeV began at 1440 UT on 24 September, reached a maximum of 31.2 PFU at 0755 UT on 25 September and ended at 1940 UT on 26 September 2001. The protons event at greater than 10 MeV began at 1215 UT on 24 September, reached a maximum of 12,900 PFU at 2235 UT on 25 September and ended at 1710 UT on 30 September 2001. These extremely high energetic protons accelerated during CMEs produces significant ionization in the D region of the ionosphere at high latitudes. Increase in ionization in the D region causes cosmic noise absorption. The major Polar Cap Absorption (PCA) observed during SEPTEMBER 24 -30, 2001 will be discussed in this paper. Imaging riometer observations were made from Kilpisjarvi (69.05oN; 20.79oW), Northern Finland during the PCA event. For this the remote and insitu data have been used. The imaging riometer for ionospheric studies (IRIS) is used to quantify the intensity, time of occurrence and location of CME effects on the ionosphere.

Inverse kinetic solvent isotope effect in TiO2 photocatalytic dehalogenation of non-adsorbable aromatic halides: a proton-induced pathway.

PubMed

Chang, Wei; Sun, Chunyan; Pang, Xibin; Sheng, Hua; Li, Yue; Ji, Hongwei; Song, Wenjing; Chen, Chuncheng; Ma, Wanhong; Zhao, Jincai

2015-02-09

An efficient redox reaction between organic substrates in solution and photoinduced h(+) vb /e(-) cb on the surface of photocatalysts requires the substrates or solvent to be adsorbed onto the surface, and is consequentially marked by a normal kinetic solvent isotope effect (KSIE ≥ 1). Reported herein is a universal inverse KSIE (0.6-0.8 at 298 K) for the reductive dehalogenation of aromatic halides which cannot adsorb onto TiO2 in a [D0 ]methanol/[D4 ]methanol solution. Combined with in situ ATR-FTIR spectroscopy investigations, a previously unknown pathway for the transformation of these aromatic halides in TiO2 photocatalysis was identified: a proton adduct intermediate, induced by released H(+) /D(+) from solvent oxidation, accompanies a change in hybridization from sp(2) to sp(3) at a carbon atom of the aromatic halides. The protonation event leads these aromatic halides to adsorb onto the TiO2 surface and an ET reaction to form dehalogenated products follows. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Heterogeneous Production of Sulfate Aerosol over China.

NASA Astrophysics Data System (ADS)

Shao, J.; Alexander, B.; Chen, Q.; Zhang, L.; Wang, Y.; Xie, Z.; He, P.

2017-12-01

Sulfate is thought to be the main contributor to the growth of PM2.5 during the severe haze pollution over China, but most studies have shown that traditional gas- and aqueous-phase chemistry cannot explain the rapid sulfate production during haze events, suggesting a missing heterogeneous oxidation mechanism. In this work, we implement heterogeneous sulfate formation into a 3-D global chemical transport model (GEOS-Chem) to evaluate the different pathways for global and regional sulfate production, including SO2 oxidation by NO2, O3, H2O2, and TMI+O2. Heterogeneous sulfate production rates and the dominant heterogeneous sulfate formation mechanism depends on calculations of aerosol pH, which is in turn is dependent upon thermodynamic state assumptions. We evaluate the influence of aerosol pH and potential impacts of aerosol ionic strength on sulfate production rates and mechanisms in the model, and its implications for PM2.5 in Chinese haze events.

The effect of saline groundwater exchange, evaporation and variable river flows and on stable isotopes (18O and 2H) and major ion concentrations along the Darling River, NSW, Australia

NASA Astrophysics Data System (ADS)

Meredith, K. T.; Hughes, C. E.; Hollins, S. E.; Cendón, D. I.; Hankin, S.

2009-04-01

Australia's longest river, the Darling River, faces extreme pressure from drought and over extraction of water from its catchment. The lack of detailed baseline hydrochemical and isotopic data for the Darling River has prompted research aimed at using hydrological tracers to assess water gains and losses within the Darling River Drainage Basin. This study uses temporal hydrochemical and stable isotope data (18O and 2H) that has been monitored from gauging stations along the Barwon-Darling catchment over a five-year period from 2002 to 2007 as part of the Global Network for Isotopes in Rivers (GNIR) monitoring programme. Stream flow data, monthly δ18O and δ2H values and major ion chemistry is presented. Individual flow events were found to be isotopically distinct but the LELs that develop after these events have a very similar slope indicating similar climatic conditions across this region. During low flow conditions, salt concentrations increase systematically, δ18O and δ2H become enriched and d-excess becomes more negative indicating significant evaporation. Flow events input isotopically depleted fresh waters to the system and the d-excess returns towards the local meteoric water line. The major ions increase in concentration at a greater rate at Louth than they do at upstream at Bourke or downstream at Wilcannia, despite similar decreases in flow rates for all three sites. The hydrological response of the river to drought has had detrimental affects on the surface water system because it provides a pathway for saline groundwater to discharge into the river system.

A STUDY OF IMPACT OF STRESSFUL LIFE-EVENTS IN NEUROTIC PATIENTS1

PubMed Central

Gautam, Shiv; Kamal, Preet

1990-01-01

SUMMARY Stressful life events preceding neurotic disorders, their impact on neurotic patients in comparison to normal subjects and relationship of impact of stressful life-events to depression and anxiety scores were studied prospectively in 100 consecutive neurotic patients, diagnosed according to ICD-9 and 100 matched normal subjects in psychiatric O.P.D. of S.M.S. Hospital, Jaipur, by administering presumptive stressful life event scale, Beck's depression inventory and Max Hamilton anxiety rating scale. It was found that number of stressful life events was higher in neurotic patients and their impact was also perceived significantly higher in them. Significantly higher depression and anxiety scores had positive corelation to number and impact of stressful life events in-neurotic patients. Cause and effect relationship of impact of stressful life events to neuroses has been discussed. PMID:21927491

Spatial patterns of throughfall isotopic composition at the event and seasonal timescales

NASA Astrophysics Data System (ADS)

Allen, Scott T.; Keim, Richard F.; McDonnell, Jeffrey J.

2015-03-01

Spatial variability of throughfall isotopic composition in forests is indicative of complex processes occurring in the canopy and remains insufficiently understood to properly characterize precipitation inputs to the catchment water balance. Here we investigate variability of throughfall isotopic composition with the objectives: (1) to quantify the spatial variability in event-scale samples, (2) to determine if there are persistent controls over the variability and how these affect variability of seasonally accumulated throughfall, and (3) to analyze the distribution of measured throughfall isotopic composition associated with varying sampling regimes. We measured throughfall over two, three-month periods in western Oregon, USA under a Douglas-fir canopy. The mean spatial range of δ18O for each event was 1.6‰ and 1.2‰ through Fall 2009 (11 events) and Spring 2010 (7 events), respectively. However, the spatial pattern of isotopic composition was not temporally stable causing season-total throughfall to be less variable than event throughfall (1.0‰; range of cumulative δ18O for Fall 2009). Isotopic composition was not spatially autocorrelated and not explained by location relative to tree stems. Sampling error analysis for both field measurements and Monte-Carlo simulated datasets representing different sampling schemes revealed the standard deviation of differences from the true mean as high as 0.45‰ (δ18O) and 1.29‰ (d-excess). The magnitude of this isotopic variation suggests that small sample sizes are a source of substantial experimental error.

Differential Consequences of Tramadol in Overdosing: Dilemma of a Polymorphic Cytochrome P450 2D6-Mediated Substrate.

PubMed

Srinivas, Nuggehally R

2015-09-01

Tramadol is a centrally acting opioid analgesic that is prone to polymorphic metabolism via cytochrome P450 (CYP) 2D6. The generation of the active metabolite, O-desmethyltramadol, which occurs through the CYP 2D6 pathway, significantly contributes to the drug's activity. However, dosage adjustments of tramadol are typically not practiced in the clinic when treating patients who are homozygous extensive metabolizers, heterozygous extensive metabolizers, or poor metabolizers. In the event of a tramadol overdose, the consequences may be influenced importantly by the genotype or phenotype status of the subject. Depending on the individual subject's CYP 2D6 status, one may see excessive miotic-related toxicity driven by the excessive availability of O-desmethyltramadol or one may manifest mydriatic-related toxicity driven by the excessive availability of tramadol. This report provides pharmacokinetic perspectives in situations of tramadol overdosing.

Assessment of DoD Enterprise Resource Planning Business Systems

DTIC Science & Technology

2011-02-01

activities, and processes to the organizational units that execute them • Architecture standards, such as application of the BPMN • Recommended...Recommendation: • Create and use style guides for the development of BPMN based process models. The style guide would probably include specifications such as...o All processes must have ‘entry points’ or ‘triggers’ in the form of BPMN Events o All processes must have ‘outcomes’ also in the form of BPMN

Measurement of the $$b \\bar{b}$$ Cross-Section and Correlations using Dimuon Events in $$p \\bar{p}$$ Collisions at $$\\sqrt{s}$$ = 1.8-TeV

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fein, David Kevin

1996-01-01

We have measured the b-quark production cross section formore » $$\\mid y \\mid$$ < 1 using a sample of dimuon events collected with the D0 detector in $$p\\bar{p}$$ collisions at $$\\sqrt{s}$$ = 1:8 TeV at the Fermilab Tevatron. The measured b-quark cross section is consistent with $$O(\\alpha^3_s$$) QCD predictions, but lies at the upper limit of the theoretical uncertainties which is a factor of 1.5 above the mean value. A study of the difference in azimuthal angle of the two muons is in good qualitative agreement with the $$O(\\alpha^3_s$$) QCD predictions« less

Visualizing the Fundamental Physics of Rapid Earth Penetration Using Transparent Soils

DTIC Science & Technology

2015-03-01

L R E P O R T DTRA-TR-14-80 Visualizing the Fundamental Physics of Rapid Earth Penetration Using Transparent Soils Approved for public... ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER 5e. TASK NUMBER 5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS...dose absorbed) roentgen shake slug torr (mm Hg, 0 C) *The bacquerel (Bq) is the SI unit of radioactivity ; 1 Bq = 1 event/s. **The Gray (GY) is

Release of E.coli D21g with transients in water content

USDA-ARS?s Scientific Manuscript database

Transients in water content are well known to mobilize microorganisms that are retained in the vadose zone. However, there is no consensus on the relative importance of drainage and imbibition events on microorganism release. To overcome this limitation, we have systematically studied the release o...

Impact Induced Climate Change on Venus: The Role of Large Comets

NASA Astrophysics Data System (ADS)

Grinspoon, D. H.; Bullock, M. A.

2000-10-01

The surface temperature of Venus is a sensitive function of the abundances of greenhouse gases and also of cloud structure. In previous work we have studied the climate impact of past and continued outgassing of greenhouse and cloud-forming gases (1) and tectonic signatures that may have resulted from volcanically induced climate change (2). These studies showed that in outgassing events where large amounts of both H2O and SO2 are released, the increased albedo that arises from thickening of the clouds can, to some extent, ameliorate the greenhouse warming expected from increased abundances of these IR absorbing gases. The largest warming typically arises several hundred million years after an outgassing event when most of the excess SO2 has been removed by reaction with surface minerals, but much of the atmospheric H2O remains (because it is removed by exospheric escape on longer time scales). This combination - enhanced H2O abundance with SO2 returned to 'normal' - leads to maximum warming because the cloud thickness, and thus the albedo, is limited by the availability of SO2, whereas IR absorption in CO2 windows by enhanced H2O can cause warming on the order of 100 K. It seems likely that large comet impacts should also produce such a situation. The atmosphere of Venus currently contains 7 x 1018 grams of water, about as much as in a 25 km diameter comet. Comets may have been an important contributor to the current water inventory on Venus. Much of this may have been supplied by a few large comet impacts in the last several hundred million years (3). We will report on new runs of our Venus Evolutionary Climate Model which simulate the volatile input from large comet impacts and investigate the climate effects of these events. Calculation will be done with cometary delivery alone, and in conjunction with various outgassing scenarios. This allows us to examine how the vulnerability of the Venusian climate system to impact induced climate change is affected by the relative timing of large magmatic and impact events. (1) Bullock, M.A., and D.H. Grinspoon, J. Geophys. Res. 101, 7521-7529, 1996. (2) Solomon, S.C., M. A. Bullock, and D. H. Grinspoon, Science, 286: 87-90, 1999. (3) Grinspoon, D.H. and J.S. Lewis, Icarus, 74, 21-35, 1988.

Water isotope variability across single rainfall events in the tropical Pacific

NASA Astrophysics Data System (ADS)

Cobb, K. M.; Moerman, J. W.; Ellis, S. A.; Bennett, L.; Bosma, C.; Hitt, N. T.

2017-12-01

Water isotopologues provide a powerful diagnostic tool for probing the dynamical processes involved in the initiation and evolution of tropical convective events, yet water isotope observations rarely meet the temporal resolution required to resolve such processes. Here we present timeseries of rainfall oxygen and hydrogen isotopologues across over 30 individual convective events sampled at 1- to 5-minute intervals at both terrestrial (Gunung Mulu National Park, 4N, 115W) and maritime (Kiritimati Island, 2N, 157W) sites located in the equatorial Pacific. The sites are the loci of significant paleoclimate research that employ water isotopologues to reconstruct a variety of climatic parameters of interest over the last century, in the case of coral d18O, to hundreds of thousands of years before present, in the case of stalagmite d18O. As such, there is significant scientific value in refining our understanding of water isotope controls at these particular sites. Our results illustrate large, short-term excursions in water isotope values that far exceed the signals recovered in daily timeseries of rainfall isotopologues from the sites, illustrating the fundamental contribution of mesoscale processes in driving rainfall isotope variability. That said, the cross-event profiles exhibit a broad range of trajectories, even for events collected at the same time of day on adjoining days. Profiles collected at different phases of the 2015-2017 strong El Nino-Southern Oscillation cycle also exhibit appreciable variability. We compare our observations to hypothetical profiles from a 1-dimensional model of each rainfall event, as well as to output from 4-dimensional isotope-equipped, ocean-atmosphere coupled models of rainfall isotope variability in the tropical Pacific. We discuss the implications of our findings for the interpretation of water isotope-based reconstructions of hydroclimate in the tropics.

Medicanes in an ocean-atmosphere coupled regional climate model

NASA Astrophysics Data System (ADS)

Akhtar, Naveed; Brauch, Jennifer; Ahrens, Bodo

2014-05-01

So-called medicanes (Mediterranean hurricanes) are meso-scale, marine and warm core Mediterranean cyclones which exhibit some similarities with tropical cyclones. The strong cyclonic winds associated with them are a potential thread for highly populated coastal areas around the Mediterranean basin. In this study we employ an atmospheric limited-area model (COSMO-CLM) coupled with a one-dimensional ocean model (NEMO-1d) to simulate medicanes. The goal of this study is to assess the robustness of the coupled model to simulate these extreme events. For this purpose 11 historical medicane events are simulated by the atmosphere-only and the coupled models using different set-ups (horizontal grid-spacings: 0.44o, 0.22o, 0.088o; with/with-out spectral nudging). The results show that at high resolution the coupled model is not only able to simulate all medicane events but also improves the simulated track length, warm core, and wind speed of simulated medicanes compared to atmosphere-only simulations. In most of the cases the medicanes trajectories and structures are better represented in coupled simulations compared to atmosphere-only simulations. We conclude that the coupled model is a suitable tool for systemic and detailed study of historical medicane events and also for future projections.

Geographical Distribution of Thundersnow and their Properties from GPM Ku-band Radar

NASA Astrophysics Data System (ADS)

Adhikari, A.; Liu, C.

2017-12-01

Lightning in snow and freezing rain are relatively uncommon, compared to the warm season thunderstorm. These events can be identified by lightning with the surface temperature colder than 0oC, or named as "cold lightning", A six-years of "cold lightning" characteristics and climatology, including seasonal, diurnal, and surface temperature distribution, are generated after collocating WWLLN and NLDN lightning with ERA-Interim 2 meter temperature. The thundersnow cases are further identified with all vertical temperature profile below 0oC, and the freezing rain cases have temperature warmer than 4oC somewhere in the column above the freezing surface. The statistics of thundersnow events from WWLLN and NLDN are compared over the United States (US). Though with different detection efficiency, WWLLN and NLDN demonstrate almost identical geographical distribution of thundersnow over the US. Taking the full advantage of the Global Precipitation Measuring Mission (GPM) Ku band radar, Thunder Snow Features (TSFs) are defined with contiguous area of non-zero near surface snow precipitation derived from Ku radar along with the collocated WWLLN lightning strikes. Though only a small number of TSFs are identified with three year GPM data, all TSFs have maximum radar reflectivity above 30 dBZ at temperature colder than -10oC, which indicates the importance of non-inductive charging in these events.

The Caldas Novas dome, central Brazil: structural evolution and implications for the evolution of the Neoproterozoic Brasília belt

NASA Astrophysics Data System (ADS)

D'el-Rey Silva, Luiz José Homem; Wolf Klein, Percy Boris; Walde, Detlef Hans-Gert

2004-10-01

The Caldas Novas dome (Goiaás state, central Brazil) lies in the southern segment of the Neoproterozoic Brasília belt (center of the Tocantins Province) between the Goiás magmatic arc and the margin of the ancient São Francisco plate. The core of the dome comprises rocks of the Meso-Neoproterozoic Paranoá group (passive margin psamitic-pelitic sediments and subgreenschist facies) covered by a nappe of the Neoproterozoic Araxá group (backarc basin pelitic-psamitic sediments and volcanics of greenschist facies, bitotite zone). Hot underground waters that emerge along fractures in the Paranoá quartzite and wells in the Araxá schist have made the Caldas Novas dome an international tourist attraction. A recent detailed structural analysis demonstrates that the dome area was affected by a D 1-D 3 Brasiliano cycle progressive deformation in the ˜750-600 Ma interval (published U-Pb and Sm-Nd data). During event D 1, a pervasive layer-parallel foliation developed coeval the regional metamorphism. Event D 2 (intense F 2 isoclinal folding) was responsible for the emplacement of the nappe. D 1 and D 2 record a regime of simple shear (top-to-SE relative regional movement) due to a WNW-ESE subhorizontal compression ( σ1). Event D 3 records a WSW-ENE compression, during which the dome rose as a large-scale F 3 fold, possibly associated with a duplex structure at depth. During the dome's uplift, the layers slid back and down in all directions, giving way to gravity-slide folds and an extensional crenulation cleavage. A set of brittle fractures and quartz veins constitutes the record of a late-stage D 4 event important for understanding the thermal water reservoir.

Response of a comprehensive climate model to a broad range of external forcings: relevance for deep ocean ventilation and the development of late Cenozoic ice ages

NASA Astrophysics Data System (ADS)

Galbraith, Eric; de Lavergne, Casimir

2018-03-01

Over the past few million years, the Earth descended from the relatively warm and stable climate of the Pliocene into the increasingly dramatic ice age cycles of the Pleistocene. The influences of orbital forcing and atmospheric CO2 on land-based ice sheets have long been considered as the key drivers of the ice ages, but less attention has been paid to their direct influences on the circulation of the deep ocean. Here we provide a broad view on the influences of CO2, orbital forcing and ice sheet size according to a comprehensive Earth system model, by integrating the model to equilibrium under 40 different combinations of the three external forcings. We find that the volume contribution of Antarctic (AABW) vs. North Atlantic (NADW) waters to the deep ocean varies widely among the simulations, and can be predicted from the difference between the surface densities at AABW and NADW deep water formation sites. Minima of both the AABW-NADW density difference and the AABW volume occur near interglacial CO2 (270-400 ppm). At low CO2, abundant formation and northward export of sea ice in the Southern Ocean contributes to very salty and dense Antarctic waters that dominate the global deep ocean. Furthermore, when the Earth is cold, low obliquity (i.e. a reduced tilt of Earth's rotational axis) enhances the Antarctic water volume by expanding sea ice further. At high CO2, AABW dominance is favoured due to relatively warm subpolar North Atlantic waters, with more dependence on precession. Meanwhile, a large Laurentide ice sheet steers atmospheric circulation as to strengthen the Atlantic Meridional Overturning Circulation, but cools the Southern Ocean remotely, enhancing Antarctic sea ice export and leading to very salty and expanded AABW. Together, these results suggest that a `sweet spot' of low CO2, low obliquity and relatively small ice sheets would have poised the AMOC for interruption, promoting Dansgaard-Oeschger-type abrupt change. The deep ocean temperature and salinity simulated under the most representative `glacial' state agree very well with reconstructions from the Last Glacial Maximum (LGM), which lends confidence in the ability of the model to estimate large-scale changes in water-mass geometry. The model also simulates a circulation-driven increase of preformed radiocarbon reservoir age, which could explain most of the reconstructed LGM-preindustrial ocean radiocarbon change. However, the radiocarbon content of the simulated glacial ocean is still higher than reconstructed for the LGM, and the model does not reproduce reconstructed LGM deep ocean oxygen depletions. These ventilation-related disagreements probably reflect unresolved physical aspects of ventilation and ecosystem processes, but also raise the possibility that the LGM ocean circulation was not in equilibrium. Finally, the simulations display an increased sensitivity of both surface air temperature and AABW volume to orbital forcing under low CO2. We suggest that this enhanced orbital sensitivity contributed to the development of the ice age cycles by amplifying the responses of climate and the carbon cycle to orbital forcing, following a gradual downward trend of CO2.

Joint Ne/O and Fe/O Analysis to Diagnose Large Solar Energetic Particle Events during Solar Cycle 23

NASA Astrophysics Data System (ADS)

Malandraki, Olga; Tan, Lun C.; Shao, Xi

2017-04-01

In this work we have examined 29 large SEP events with the peak proton intensity Jpp(>60MeV) >1 pfu during the solar cycle 23. The emphasis of our examination is put on a joint analysis of the Ne/O and Fe/O data in the 3-40 MeV/nucleon energy range as covered by the Wind/LEMT and ACE/SIS sensors in order to differentiate between the Fe-poor and Fe-rich events emerged from the CME-driven shock acceleration process. Some of our main findings are: (1) An improved ion ratio calculation can be carried out by re-binning ion intensity data into the form of equal bin widths in the logarithmic energy scale, (2) through the analysis we find that the variability of Ne/O and Fe/O ratios can be used to investigate the accelerating shock properties, (3) in particular, we observe a good correlation of the high-energy Ne/O ratio with the source plasma temperature T recently reported by Reames (2016). Therefore, the (Ne/O)n value at high energies should be a proxy of the injection energy in the shock acceleration process, and hence the shock θBn according to the models of Tylka & Lee (2006) as well as Schwadron et al. (2015). Acknowledgements. We gratefully acknowledge the source plasma temperature data provided by D. Reames, Wind/EPACT/LEMT data provided by the NASA/Space Physics Data Facility (SPDF)/CDAWeb, and the ACE/SIS data provided by the ACE Science Center. This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 637324.

Thrust exhumation of the Southern Marginal Zone of the Limpopo Complex in the Neoarchaean: link of distinct high-grade shear zones with DC and IC P-T-t paths

NASA Astrophysics Data System (ADS)

Smit, C. Andre; van Reenen, Dirk D.

2010-05-01

The Limpopo Complex is a ~750km long E-W trending zone of predominantly granulite facies rocks situated between the Archaean Kaapvaal and Zimbabwe cratons of southern Africa. Large ductile shear zones are an integral part of the Limpopo architecture, defining the boundaries between the belt and the adjacent cratons and are interpreted to have been responsible for uplift (exhumation) of over thickened crust during the Neoarchaean [10 and references therein; 1]. The Hout River Shear Zone forms the terrane boundary between the granite-greenstone terrane of the Kaapvaal craton in the south and the high-grade Southern Marginal Zone (SMZ) of the Limpopo Complex in the north. Integrated structural, metamorphic, magmatic and age data collected over a period of more than 30 years provide convincing evidence for a Neoarchean high-grade tectono-metamorphic event that affected the SMZ in the interval ~2.72 - 2.60 Ga [4; 5, 6; 7; 2; 8; 9; 11]. The thrust-controlled exhumation of the SMZ is demonstrated by the convergence of a retrograde P-T path in the hanging wall (SMZ) and a prograde P-T loop in the footwall (Kaapvaal Craton) of the steeply SW-verging Hout River Shear Zone [4; 5]. The coeval ages (~2.69 Ga) of the two contrasting metamorphic histories are indicated by geochronological data [2; 3]. In addition, the establishment of a retrograde isograd and zone of rehydrated granulites in the hanging wall by hydrous CO2-rich fluids derived by dehydration of the low-grade rocks in the footwall provides another convincing link between the two contrasting metamorphic environments [10]. Distinct retrograde P-T paths [4; 6; 8] linked to distinct shear deformational events document evidence for a two-stage post-peak exhumation history of the SMZ: (i) granulites sampled far from the contact with the cool rocks of the Kaapvaal Craton are characterized by P-T paths with two distinct decompression-cooling (DC) stages (DC=>DC paths), (ii) granulites sampled close to this contact are characterized by P-T paths with an inflection that reflects near-isobaric cooling (IC) (DC=>IC paths). The early (2.69-2.664Ga) DC stage (P ~8 kbar, T ~825oC to P ~6.5 kbar, T ~750oC) of exhumation is linked to the transportation of the high-grade rocks up the steep ramp section of the Hout River Shear Zone that controlled their emplacement to upper crustal levels. The later (~2.62-2.6Ga) near-IC stage (P ~6.5kbar, T ~700oC to P ~ 5kbar, T ~500oC) of exhumation is linked to the flat section of SW-verging thrusts that reflect the emplacement of the high-grade rocks over the cool rocks of the adjacent craton. These low-angle thrusts also account for the presence of high-grade klippen [10] located on the craton far south of the Hout River Shear Zone. Peak UHT metamorphic conditions (T > 900oC at P > 10kbar) recently reported for the SMZ [9] might have been reached at ~2.72 Ga, as is suggested by shallow northerly verging ~2.72Ga thrusts on the Kaapvaal Craton [3]. These thrusts, which are truncated by the steeply SW-verging ~2.69Ga Hout River Shear Zone are probably linked to a crustal thickening event that controlled the initial burial of SMZ granulites to depths >30 km. Integrated D-P-T-t paths constructed for hanging wall granulites and footwall greenstones provide evidence in support of a tectonic model for the evolution of the SMZ (and of the Limpopo Complex as a whole) that is either linked to a crustal thickening event involving the collision in the Neoarchean of the Kaapvaal and Zimbabwe cratons [10] or to a gravitational redistribution model [1]. References: [1] Gerya, T.V., Perchuk, L.L., Van Reenen, D.D., and Smit, C.A. 2000. J. Geodynamics, 30, 17-35. [2] Kreissig, K., Holzer, L., Frei, R., Villa, I.M., Kramers, J.D., Smit, C.A., and Van Reenen, D.D. 2001. Precambrian Resarch, 109, 145-173. [3] Passeraub, M., Wuest, T., Kreissig, K., Smit, C.A., Kramers, J.D. 1999. S. Afr. J. Geology 102, n.4, 323-334. [4] Perchuk, L.L., Gerya., T.V., Van Reenen, D.D., Sefanov, O.G., and Smit, C.A. 1996. Petrology, 4, 571-599. [5] Perchuk, L.L., Gerya, T.V., Van Reenen, D.D., Smit, C.A., Krotov, A.V., and Safanov, O.G. 2000. Mineralogy and Petrology, 69, 69-108 [6] Perchuk, L.L., Gerya, T.V., Van Reenen, D.D., Smit, C.A., and Krotov, A.V. 2000. Min. Pet, 69, 109-141. [7] Perchuk, L.L., Gerya, T.V., Van Reenen, D.D., and Smit, C.A., 2001. Gondwana Research, 4, 729-732. [8] Smit, C.A., Van Reenen, D.D, Gerya, T.V., and Perchuk, L.L. 2001. J. Metamorphic Geololgy, 19, 249-268. [9] Tsunogae,T., Miyano, T., Van Reenen, D. D., and Smit, C.A., 2004. J. Mineralogy and Petrology, 99, 213-224. [10] Van Reenen, D.D., Roering, C., Ashwal, L.D., and de Wit, M.J. 1992 (Eds). Precambrian Research, 55, 1-587.

Model simulations of the impact of energetic particle precipitation onto the upper and middle atmosphere

NASA Astrophysics Data System (ADS)

Wieters, Nadine; Sinnhuber, Miriam; Winkler, Holger; Berger, Uwe; Maik Wissing, Jan; Stiller, Gabriele; Funke, Bernd; Notholt, Justus

Solar eruptions and geomagnetic storms can produce fluxes of high-energy protons and elec-trons, so-called Solar Energetic Particle Events, which can enter the Earth's atmosphere espe-cially in polar regions. These particle fluxes primarily cause ionisation and excitation in the upper atmosphere, and thereby the production of HOx and NOx species, which are catalysts for the reduction of ozone. To simulate such particle events, ionisation rates, calculated by the Atmospheric Ionization Module Osnabrück AIMOS (University of Osnabrück), have been implemented into the Bremen 3D Chemistry and Transport Model. To cover altitudes up to the mesopause, the model is driven by meteorological data, provided by the Leibniz-Institute Middle Atmosphere Model LIMA (IAP Kühlungsborn). For several electron and proton events during the highly solar-active period 2003/2004, model calculations have been carried out. To investigate the accordance of modeled to observed changes for atmospheric constituents like NO, NO2 , HNO3 , N2 O5 , ClO, and O3 , results of these calculations will be compared to measurements by the Michelson Interferometer for Passive Atmospheric Sounding MIPAS (ENVISAT) instrument. Computed model results and comparisons with measurements will be presented.

Impact of topography, climate and moisture sources on isotopic composition (δ18O &δD) of rivers in the Pyrenees: Implications for topographic reconstructions in small orogens

NASA Astrophysics Data System (ADS)

Huyghe, Damien; Mouthereau, Frédéric; Sébilo, Mathieu; Vacherat, Arnaud; Ségalen, Loïc; Richard, Patricia; Biron, Philippe; Bariac, Thierry

2018-02-01

Understanding how orogenic topography controls the spatial distribution and isotopic composition of precipitation is critical for paleoaltitudinal reconstructions. Here, we determine the isotopic composition (δ18O and δD) of 82 small rivers and springs from small catchments in the Pyrenees. Calculation of the deuterium excess (d-excess) parameter allows the distinction of four distinct isotopic provinces with d-excess values of between 15 and 22‰ in the northwest, between 7 and 14‰ in the central northern Pyrenees and between 3 and 11‰ in the northeast. The southern Pyrenees have a homogenous d-excess signature ranging from 7 to 14‰. Our results show significant local moisture recycling and/or rain amount effect in the northwestern Pyrenees, and control by evaporation processes during rainfall events in the southern Pyrenees and for low elevated samples of the northeast of the range. Based on the distribution of d-excess values, we estimate contrasting isotope lapse rates of -2.9/-21.4‰/km (δ18O/δD) in the northwest, -2.7/-21.4‰/km (δ18O/δD) in the north central and -3.7/-31.7‰/km (δ18O/δD) in the northeastern Pyrenees. The southern Pyrenees show distinctly higher lapse rates of -9.5/-77.5‰/km (δ18O/δD), indicating that in this area the altitudinal effect in not the only parameter driving isotopic composition of rivers. Despite their relatively low topographic gradient, the Pyrenees exert a direct control on the isotopic composition of river waters, especially on their northern side. The variations in isotopic composition-elevation relationships documented along the strike of the range are interpreted to reflect an increasing continentality effect driven by wind trajectories parallel to the range, and mixing with Mediterranean air masses. Despite these effects, the measurable orographic effect on precipitation in the Pyrenees proves that the isotopic composition approach for reconstructing past topography is applicable to low-elevation orogens.

On-Die Sensors for Transient Events

NASA Astrophysics Data System (ADS)

Suchak, Mihir Vimal

Failures caused by transient electromagnetic events like Electrostatic Discharge (ESD) are a major concern for embedded systems. The component often failing is an integrated circuit (IC). Determining which IC is affected in a multi-device system is a challenging task. Debugging errors often requires sophisticated lab setups which require intentionally disturbing and probing various parts of the system which might not be easily accessible. Opening the system and adding probes may change its response to the transient event, which further compounds the problem. On-die transient event sensors were developed that require relatively little area on die, making them inexpensive, they consume negligible static current, and do not interfere with normal operation of the IC. These circuits can be used to determine the pin involved and the level of the event in the event of a transient event affecting the IC, thus allowing the user to debug system-level transient events without modifying the system. The circuit and detection scheme design has been completed and verified in simulations with Cadence Virtuoso environment. Simulations accounted for the impact of the ESD protection circuits, parasitics from the I/O pin, package and I/O ring, and included a model of an ESD gun to test the circuit's response to an ESD pulse as specified in IEC 61000-4-2. Multiple detection schemes are proposed. The final detection scheme consists of an event detector and a level sensor. The event detector latches on the presence of an event at a pad, to determine on which pin an event occurred. The level sensor generates current proportional to the level of the event. This current is converted to a voltage and digitized at the A/D converter to be read by the microprocessor. Detection scheme shows good performance in simulations when checked against process variations and different kind of events.

Toward the Inference of Deglacial Ocean Dynamics from the Spatial Pattern of LGM-to-Modern d13C and d18O Change

NASA Astrophysics Data System (ADS)

Gebbie, G.; Peterson, C. D.; Lisiecki, L. E.; Spero, H. J.

2014-12-01

Estimates of the whole-ocean d13C change between the Last Glacial Maximum (LGM) and the modern-day are converging to values of about 0.4 per mil, and are of great use in partitioning land versus ocean contributions to the deglacial carbon cycle. To determine which specific oceanic processes are at play, however, knowledge of the spatial pattern of LGM-to-modern d13C and d18O change is critical. Spatial maps have mostly focused on Atlantic d13C, with less progress for d18O and the Pacific and Indian sectors, due to the concentration of sediment-core observations in the Atlantic and the difficulty in making meaningful maps from sparse data. Here, we demonstrate that a state estimation (or data assimilation) method based on recently compiled data and a simple kinematic ocean model simultaneously produces reasonable results for: 1) global maps of d13C and d18O, 2) uncertainty in the estimated properties, and 3) oceanic water-mass geometry. The observations include benthic d13C and d18O data from 493 marine sediment cores that were collected from the scientific literature and NOAA, PANGEA, and Delphi databases. The kinematic model permits each data point to have influence both up- and downstream along a water-mass pathway, typically allowing a larger geographical range than a statistical interpolation method. No assumption regarding the state of the circulation is necessary, and the modern-day circulation need not be assumed to be representative of the LGM. With this method, meridional (or other) sections can be compared between ocean basins. Furthermore, the internally-consistent d18O and d13C maps are used to determine the LGM-to-modern spatial changes that are robust given the uncertainty and sparsity of data. Rather than simply focus on property maps, we suggest that the link between observations and circulation changes (as reflected by the paths that water travels), points the way toward dynamical processes that must be explained. A particular application of our result is the geographic constraint of possible unobserved reservoirs of d13C or radiocarbon and calculation of their potential impact on the global chain of events during the deglaciation.

Photodissociation dynamics of the simplest alkyl peroxy radicals, CH 3OO and C 2H 5OO, at 248 nm

DOE PAGES

Sullivan, Erin N.; Nichols, Bethan; Neumark, Daniel M.

2018-01-28

The photodissociation dynamics of the simplest alkyl peroxy radicals, methyl peroxy (CH 3OO) and ethyl peroxy C 2H 5OO , are investigated using fast beam photofragment translational spectroscopy. A fast beam of CH3OO- or C2H5OO- anions is photodetached to generate neutral radicals that are subsequently dissociated using 248 nm photons. The coincident detection of the photofragment positions and arrival times allows for the determination of mass, translational energy, and angular distributions for both two-body and three-body dissociation events. CH3OO exhibits repulsive O loss resulting in the formation of O(1D) + CH3O with high translational energy release. Minor two-body channels leadingmore » to OH + CH2O and CH3O + O(3P) formation are also detected. In addition, small amounts of H + O(3P) + CH2O are observed and attributed to O loss followed by CH3O dissociation. C2H5OO exhibits more complex dissociation dynamics, in which O loss and OH loss occur in roughly equivalent amounts with O(1D) formed as the dominant O atom electronic state via dissociation on a repulsive surface. Minor two-body channels leading to the formation of O2 + C2H5 and HO2 + C2H4 are also observed and attributed to a ground state dissociation pathway following internal conversion. Additionally, C2H5OO dissociation yields a three-body product channel, CH3 + O(3P) + CH2O, for which the proposed mechanism is repulsive O loss followed by the dissociation of C2H5O over a barrier. These results are compared to a recent study of tert-butyl peroxy (t-BuOO) in which 248 nm excitation results in three-body dissociatio n and ground state two-body dissociation but no O(1D) production.« less

Photodissociation dynamics of the simplest alkyl peroxy radicals, CH 3OO and C 2H 5OO, at 248 nm

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sullivan, Erin N.; Nichols, Bethan; Neumark, Daniel M.

The photodissociation dynamics of the simplest alkyl peroxy radicals, methyl peroxy (CH 3OO) and ethyl peroxy C 2H 5OO , are investigated using fast beam photofragment translational spectroscopy. A fast beam of CH3OO- or C2H5OO- anions is photodetached to generate neutral radicals that are subsequently dissociated using 248 nm photons. The coincident detection of the photofragment positions and arrival times allows for the determination of mass, translational energy, and angular distributions for both two-body and three-body dissociation events. CH3OO exhibits repulsive O loss resulting in the formation of O(1D) + CH3O with high translational energy release. Minor two-body channels leadingmore » to OH + CH2O and CH3O + O(3P) formation are also detected. In addition, small amounts of H + O(3P) + CH2O are observed and attributed to O loss followed by CH3O dissociation. C2H5OO exhibits more complex dissociation dynamics, in which O loss and OH loss occur in roughly equivalent amounts with O(1D) formed as the dominant O atom electronic state via dissociation on a repulsive surface. Minor two-body channels leading to the formation of O2 + C2H5 and HO2 + C2H4 are also observed and attributed to a ground state dissociation pathway following internal conversion. Additionally, C2H5OO dissociation yields a three-body product channel, CH3 + O(3P) + CH2O, for which the proposed mechanism is repulsive O loss followed by the dissociation of C2H5O over a barrier. These results are compared to a recent study of tert-butyl peroxy (t-BuOO) in which 248 nm excitation results in three-body dissociatio n and ground state two-body dissociation but no O(1D) production.« less

The Relativistic Solar Proton Event of 11 June 1991

DTIC Science & Technology

1993-01-01

A D-A 78 6 2 ATON ~ t ~e~~orForm Approved ""MB No 0, ,0188 u~ii..iuuum ii~uu u~i o zj r~1 cmments rojaraing’ -ts ouc~er *ýtjm.,te )-, ther 3ýo’ ) s...8217L1G..4f~i ,,4eC~ j . rt ’Cr ntorr-jriop6#norr jE tr~ 4Orq , ?left~f ,n IIIIIIIIIIII| |I I II ~~e-Gr .... ýC •O . ....... Ŕ .... %8...Apatity, Russia and Mawson , Antarctica recorded an - 7 percent increase while stations viewing in the probable "reverse" direction such as Tixie Bay

Morphology controlled synthesis of nanoporous Co3O4 nanostructures and their charge storage characteristics in supercapacitors.

PubMed

Deori, Kalyanjyoti; Ujjain, Sanjeev Kumar; Sharma, Raj Kishore; Deka, Sasanka

2013-11-13

Cubic spinel Co3O4 nanoparticles with spherical (0D) and hexagonal platelet (2D) morphologies were synthesized using a simple solvothermal method by tuning the reaction time. XRD and HRTEM analyses revealed pure phase with growth of Co3O4 particles along [111] and [110] directions. UV-vis studies showed two clear optical absorption peaks corresponding to two optical band gaps in the range of 400-500 nm and 700-800 nm, respectively, related to the ligand to metal charge transfer events (O(2-) → Co(2+,3+)). Under the electrochemical study in two electrode assembly system (Co3O4/KOH/Co3O4) without adding any large area support or a conductive filler, the hexagonal platelet Co3O4 particles exhibited comparatively better characteristics with high specific capacitance (476 F g(-1)), energy density 42.3 Wh kg(-1) and power density 1.56 kW kg(-1) at current density of 0.5 Ag(-1), that suited for potential applications in supercapacitors. The observed better electrochemical properties of the nanoporous Co3O4 particles is attributed to the layered platelet structural arrangement of the hexagonal platelet and the presence of exceptionally high numbers of regularly ordered pores.

Are abrupt climate changes predictable?

NASA Astrophysics Data System (ADS)

Ditlevsen, Peter

2013-04-01

It is taken for granted that the limited predictability in the initial value problem, the weather prediction, and the predictability of the statistics are two distinct problems. Lorenz (1975) dubbed this predictability of the first and the second kind respectively. Predictability of the first kind in a chaotic dynamical system is limited due to the well-known critical dependence on initial conditions. Predictability of the second kind is possible in an ergodic system, where either the dynamics is known and the phase space attractor can be characterized by simulation or the system can be observed for such long times that the statistics can be obtained from temporal averaging, assuming that the attractor does not change in time. For the climate system the distinction between predictability of the first and the second kind is fuzzy. This difficulty in distinction between predictability of the first and of the second kind is related to the lack of scale separation between fast and slow components of the climate system. The non-linear nature of the problem furthermore opens the possibility of multiple attractors, or multiple quasi-steady states. As the ice-core records show, the climate has been jumping between different quasi-stationary climates, stadials and interstadials through the Dansgaard-Oechger events. Such a jump happens very fast when a critical tipping point has been reached. The question is: Can such a tipping point be predicted? This is a new kind of predictability: the third kind. If the tipping point is reached through a bifurcation, where the stability of the system is governed by some control parameter, changing in a predictable way to a critical value, the tipping is predictable. If the sudden jump occurs because internal chaotic fluctuations, noise, push the system across a barrier, the tipping is as unpredictable as the triggering noise. In order to hint at an answer to this question, a careful analysis of the high temporal resolution NGRIP isotope record is presented. The result of the analysis points to a fundamental limitation in predictability of the third kind. Reference: P. D. Ditlevsen and S. Johnsen, "Tipping points: Early warning and wishful thinking", Geophys. Res. Lett., 37, 2010

Production of odd nitrogen in the stratosphere and mesosphere - An intercomparison of source strengths

NASA Technical Reports Server (NTRS)

Jackman, C. H.; Frederick, J. E.; Stolarski, R. S.

1980-01-01

Galactic cosmic rays (GCRs), nuclear explosions, lightning, solar proton events (SPEs), relativistic electron precipitation, and meteors are related to the oxidation of nitrous oxide by comparing several sources of odd nitrogen (ON) in the stratosphere and mesosphere. Published O3 and N2O data show that ON produced by the reaction of O(1D) with N2O peaks between 25 and 35 km; the GCRs add approximately the same amount of ON as N2O oxidation at the solar minimum for geographic latitudes over 50 deg. Nuclear explosions in 1961-1962 added 1.1 and 2.2 x 10 to the 34th NO molecules each, and SPEs produced greater amounts of ON above 50 deg than N2O oxidation during 1958 through 1960, and in 1972.

77 FR 45675 - Margy Temponeras, M.D.; Decision and Order

Federal Register 2010, 2011, 2012, 2013, 2014

2012-08-01

..., under DEA regulations, ``[i]n the event a person commences business with no controlled substances on... further noted that it was ``[o]f significance, [that] no invoices, DEA Form 222s, or dispensing logs were... requires that a registrant retain its invoices, form 222s, as well as a dispensing log, for at least two...

Naval Health Research Center/NPRU Command Bibliography 1962 to 1985

DTIC Science & Technology

1986-09-01

Sokoloff, R~ger L. 78 Nelson, Dennis P i5 Spaulding, Raymond C. 78 Nelson, Paul D. 63 Spinweber, Cheryl L. 19 Neuman, Thomas S. 64 Spreng, Lawrence...WC McCallum & JR Knott (uds), Thu Reuponsive Brain. Proceedings, Third International Congress on Event-Related Slow Potean1i-oFh-’Erarn. Bristol: John

Critical role for the mitochondrial permeability transition pore and cyclophilin D in platelet activation and thrombosis

PubMed Central

Wilson, Katina M.; Leo, Lorie; Raimondi, Alejandro; Molkentin, Jeffery D.; Lentz, Steven R.; Di Paola, Jorge

2008-01-01

Many of the cellular responses that occur in activated platelets resemble events that take place following activation of cell-death pathways in nucleated cells. We tested the hypothesis that formation of the mitochondrial permeability transition pore (MPTP), a key signaling event during cell death, also plays a critical role in platelet activation. Stimulation of murine platelets with thrombin plus the glycoprotein VI agonist convulxin resulted in a rapid loss of mitochondrial transmembrane potential (Δψm) in a subpopulation of activated platelets. In the absence of cyclophilin D (CypD), an essential regulator of MPTP formation, murine platelet activation responses were altered. CypD-deficient platelets exhibited defects in phosphatidylserine externalization, high-level surface fibrinogen retention, membrane vesiculation, and procoagulant activity. Also, in CypD-deficient platelet-rich plasma, clot retraction was altered. Stimulation with thrombin plus H2O2, a known activator of MPTP formation, also increased high-level surface fibrinogen retention, phosphatidylserine externalization, and platelet procoagulant activity in a CypD-dependent manner. In a model of carotid artery photochemical injury, thrombosis was markedly accelerated in CypD-deficient mice. These results implicate CypD and the MPTP as critical regulators of platelet activation and suggest a novel CypD-dependent negative-feedback mechanism regulating arterial thrombosis. PMID:17989312

Effect of extreme storm-enhanced chemical weathering in a subtropical catchment, southeast China, during Typhoon Meranti (2016)

NASA Astrophysics Data System (ADS)

Su, N.; Yang, S.

2017-12-01

We used time-series major cations (Ca2+, Na+, Mg2+ and K+), inorganic nutrient species (nitrogen, phosphorus and silica), stable isotopes of hydrogen and oxygen of water (δD and δ18O) along with nitrogen (N) and oxygen (O) of nitrate (δ18O-NO3- and δ15N-NO3-) to understand the water chemistry variability and chemical weathering in the Mulanxi River, southeast China, during a typhoon-induced stormwater runoff on 13-19 September, 2016. Abrupt increase of water level, discharge and concentration of suspended particulate matter coincided with the intensive storm surge. A remarkable drop in the δD and δ18O isotopes, the concentration of major ions and nutrients was also observed during the heavy rainfall, a result of both rainout effect and resultant dilution by precipitation. The results from a simple three component mixing model showed the first 6 h of increases in stream discharge comprising over 70% event water. During typhoon-induced flooding, the dissolved silica flux ( 74% of the total) associated CO2 consumption by silicate weathering (28.7×103 mol km-2 in a 96 h storm) reflected a dominant contribution of terrestrial inputs from the watershed by surface runoffs. In contrast to normal conditions, water chemistry in the Mulanxi River underwent significant stable isotopic changes in increasing of δ18O-NO3- and decreasing of δ15N-NO3- corresponding to potential NO3-N sources under typhoon-enhanced silicate weathering. This is one of the major sticking points in using isotope techniques to identify the sources and mechanisms by which extreme weather events take place to induce more dynamic watershed-scale processes.

The impact of Last Glacial climate variability in west-European loess revealed by radiocarbon dating of fossil earthworm granules

PubMed Central

Moine, Olivier; Antoine, Pierre; Hatté, Christine; Landais, Amaëlle; Mathieu, Jérôme; Prud’homme, Charlotte

2017-01-01

The characterization of Last Glacial millennial-timescale warming phases, known as interstadials or Dansgaard–Oeschger events, requires precise chronologies for the study of paleoclimate records. On the European continent, such chronologies are only available for several Last Glacial pollen and rare speleothem archives principally located in the Mediterranean domain. Farther north, in continental lowlands, numerous high-resolution records of loess and paleosols sequences show a consistent environmental response to stadial–interstadial cycles. However, the limited precision and accuracy of luminescence dating methods commonly used in loess deposits preclude exact correlations of paleosol horizons with Greenland interstadials. To overcome this problem, a radiocarbon dating protocol has been developed to date earthworm calcite granules from the reference loess sequence of Nussloch (Germany). Its application yields a consistent radiocarbon chronology of all soil horizons formed between 47 and 20 ka and unambiguously shows the correlation of every Greenland interstadial identified in isotope records with specific soil horizons. Furthermore, eight additional minor soil horizons dated between 27.5 and 21 ka only correlate with minor decreases in Greenland dust records. This dating strategy reveals the high sensitivity of loess paleoenvironments to Northern Hemisphere climate changes. A connection between loess sedimentation rate, Fennoscandian ice sheet dynamics, and sea level changes is proposed. The chronological improvements enabled by the radiocarbon “earthworm clock” thus strongly enhance our understanding of loess records to a better perception of the impact of Last Glacial climate changes on European paleoenvironments. PMID:28559353

Two Types of Transpolar Arc Development, Event Studies with Data Set of ASTRID-2, DMSP, FAST, and SuperDARN

NASA Technical Reports Server (NTRS)

Narita, Yasuhito; Maezawa, Kiyoshi; Toshinori, Mukai; Kullen, A.; Ivchenko, N.; Marklund, G.; Frederick, R.; Carlson, C. W.; Spann, J. F.; Parks, G. K.;

Reproducing the scaling laws for Slow and Fast ruptures

NASA Astrophysics Data System (ADS)

Romanet, Pierre; Bhat, Harsha; Madariaga, Raúl

2017-04-01

Modelling long term behaviour of large, natural fault systems, that are geometrically complex, is a challenging problem. This is why most of the research so far has concentrated on modelling the long term response of single planar fault system. To overcome this limitation, we appeal to a novel algorithm called the Fast Multipole Method which was developed in the context of modelling gravitational N-body problems. This method allows us to decrease the computational complexity of the calculation from O(N2) to O(N log N), N being the number of discretised elements on the fault. We then adapted this method to model the long term quasi-dynamic response of two faults, with step-over like geometry, that are governed by rate and state friction laws. We assume the faults have spatially uniform rate weakening friction. The results show that when stress interaction between faults is accounted, a complex spectrum of slip (including slow-slip events, dynamic ruptures and partial ruptures) emerges naturally. The simulated slow-slip and dynamic events follow the scaling law inferred by Ide et al. 2007 i. e. M ∝ T for slow-slip events and M ∝ T2 (in 2D) for dynamic events.

Should Variations of d2H, d18O and d17O in Precipitation be Considered 'Settled Science' or a 'New Frontier' For Understanding Cloud Dynamics and Microphysics?

NASA Astrophysics Data System (ADS)

Aggarwal, P. K.; araguas Araguas, L.; Belachew, D.; Terzer, S.; Wassenaar, L. I.; Longstaffe, F. J.; Schumacher, C.; Funk, A. B.; Steinacker, R.; Kaltenboeck, R.

2017-12-01

After more than 60 years of isotope measurements in precipitation, there are relatively well established patterns of variation, but their origin and controlling parameters remain a matter of debate, preventing a fuller integration of isotope-based information in meteorology. The prevailing hypothesis based on temperature and Rayleigh distillation has been successful in explaining many of the patterns, particularly at a seasonal or annual scale, and attempts to explain variances by 'tweaking' the prevailing hypothesis suggest that the underlying science may be considered to be 'settled'. A rigorous evaluation at the storm event scale, where precipitation acquires its isotope composition, however, does not provide a satisfactory explanation in most cases. We have conducted an year-long study with high-frequency sampling (5-15 min) of mid-latitude precipitation at Vienna and more than 1000 samples have been analyzed for d2H, d18O and d17O. We have also collected profiles of reflectivity and doppler velocity using a vertically pointed micro-rain radar, particle size distribution in precipitation using a disdrometer, and conducted aerological analysis of air and moisture circulation using sounding data. A combined evaluation of isotope and meteorological data provides a detailed understanding of isotope variability. We will discuss these results and the light they shed on boundary layer and tropospheric moisture circulation in frontal or convective precipitation, the relative roles of vapor deposition and riming growth of precipitation, and the origin of d-excess. The agreement between meteorological observations and isotopic variability is extremely promising and may help open a new frontier in the use of isotopes for weather and climate studies.

Why Are Most Ground Level Events Associated with High Fe/O Ratios?

NASA Technical Reports Server (NTRS)

von Rosenvinge, Tycho T.; Richardson, Ian G.; Cane, Hilary V.

2010-01-01

In a seminal paper about Ground Level Events (GLEs), Dietrich and Lopate (1999) reported on 24 GLEs from April, 1973 to May, 1998. They noted that alt but one of these GLEs, June 15, 1991, were associated with a Solar Energetic Particle (SEP) event with an enhanced Fe/O ratio. The Fe/O ratio observed for the June 15, 1991 event was only 0.03, well below the nominal coronal abundance of Fe/O = 0.134. For the remaining events, Fe/O ranged from 0.27 to over 3, welt over the nominal coronal value. During Solar Cycle 23, 14 more GLEs were observed, only one of which had very low Fe/O. This was the event of January 20, 2005, the largest ground-level neutron monitor event in 49 years. We will report on our efforts to find out whether the events of June 15, 1991 and January 20, 2005 have features in common, besides high Fe/O, that distinguish them from all other GLE events and may help determine the cause of elevated Fe/O in almost all GLE events. We will use energetic particle, magnetic field, and solar wind plasma data from NASA's IMP-8 Wind, and ACE spacecraft.

Charge states of low energy ions from the sun. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Sciambi, R. K.

1975-01-01

Measurements of ionization states and energy spectra of carbon, oxygen, and iron accelerated in ten solar flare particle events are reported, for energies between 15 keV per nucleon and 600 keV per nucleon. The ionization states were remarkably constant from flare to flare, despite great variations in other event parameters. The mean ionization state for carbon was 5.7, for oxygen 6.2, and for iron 11.7, values which are similar to the respective ionization states in the solar wind. The time profile of the He/C+N+O ratio was examined, and it was found that the ratio was small early in the event, and increased with time. The energy spectra of the medium ions showed a flattening below 100 keV per nucleon, which was highly correlated with event size as measured by the event averaged flux of 130 to 220 keV protons.

Temporal variation in stable isotopes ( 18O and 2H) and major ion concentrations within the Darling River between Bourke and Wilcannia due to variable flows, saline groundwater influx and evaporation

NASA Astrophysics Data System (ADS)

Meredith, K. T.; Hollins, S. E.; Hughes, C. E.; Cendón, D. I.; Hankin, S.; Stone, D. J. M.

2009-11-01

SummaryThe Darling River faces environmental pressures from both climate change and anthropogenic influences leading to a reduction in fresh water availability for the river system. This study uses temporal hydrochemical and stable isotope data ( 18O and 2H) that has been collected over a five-year period (2002 to 2007), as part of the Global Network for Isotopes in Rivers (GNIR) programme, which is aimed at monitoring hydrological processes in large river systems throughout the world. Daily stream flow, monthly stable isotope and major ion chemistry data is presented for sampling locations along the Darling River at Bourke, Louth and Wilcannia, as well as additional more detailed data from locations near Glen Villa. The hydrochemical data is used to partition groundwater influx that is not readily separable by using only the available isotopic data. Individual flow events in the river were found to be isotopically distinct but the Local Evaporation Lines (LELs) that develop after these events have a similar slope indicating similar climatic conditions across this region. After a storm event, fresh waters that are isotopically depleted are introduced to the system and d-excess ( d) values return towards meteoric values. During low flow, the Cl -, Na +, Mg 2+, SO 42-, δ 18O and δ 2H values all increase systematically, and d values become more negative. Hydrochemical and isotopic tracers in conjunction with high resolution sampling strategies have been used to quantify the contribution of evaporation, bank storage release and saline groundwater influx to the evolution of the river waters. Fractional contributions (% of volume) of groundwater to the river water were calculated for different reaches using Cl - concentrations, δ 18O and d values and it was found that river waters comprised of approximately 60-99% saline groundwater during zero flow. The reduced water levels in the river during the drought conditions experienced in the period of this study had detrimental impacts on the surface water system by providing a pathway for saline groundwaters to discharge into the river system. Persistent drought and continued over-abstraction of surface waters will lead to further saline groundwater intrusion along this reach of the river. This work shows that a suite of hydrochemical and isotopic tracers are needed on spatially and temporally significant scales to unravel the hydrological complexities of dryland river systems such as the Darling River.

A preliminary summary of a seismic-refraction survey in the vicinity of the Tonto Forest Observatory, Arizona

USGS Publications Warehouse

Roller, J.C.; Jackson, W.H.; Warren, D.H.; Healy, J.H.

1964-01-01

The U.S. Geological Survey complete d a seismic-refraction survey in the vicinity of the Tonto Forest Seismological Observatory (T.F.S.O.) in April and May 1964. More than 1200 km of reversed profiles were surveyed to determine the crustal structure and crustal and upper mantle velocities in this area. The purpose of this work was to provide information on wave-propagation paths of seismic events recorded at T.F.S.O. and to improve the performance of the Observatory in locating and identifying these events. First arrivals indicate that the Mohorovicic discontinuity dips to the northeast by as much as 6 degrees under T.F.S.O., and may even be displaced vertically by as much as 5 km immediately north of the Observatory near the boundary of the Basin and Range a n d t he Colorado Plateau Provinces. A preliminary examination of the first arrivals indicates that the crust at T.F.S.O. is at least 30 km thick and is made up of at least two seismic layers. A thin veneer at the surface with a velocity of approximately 4 km/sec is underlain by a layer with a velocity of approximately 5.9 km/sec to 6.1 km/sec. An intermediate layer with velocity of 6.6 to 7.0 km/sec is probably present in the lower crust, but is not revealed by first arrivals. The velocity of seismic waves in the upper mantle is about 7.9 km/sec.

Heat flow and heat generation in greenstone belts

NASA Technical Reports Server (NTRS)

Drury, M. J.

1986-01-01

Heat flow has been measured in Precambrian shields in both greenstone belts and crystalline terrains. Values are generally low, reflecting the great age and tectonic stability of the shields; they range typically between 30 and 50 mW/sq m, although extreme values of 18 and 79 mW/sq m have been reported. For large areas of the Earth's surface that are assumed to have been subjected to a common thermotectonic event, plots of heat flow against heat generation appear to be linear, although there may be considerable scatter in the data. The relationship is expressed as: Q = Q sub o + D A sub o in which Q is the observed heat flow, A sub o is the measured heat generation at the surface, Q sub o is the reduced heat flow from the lower crust and mantle, and D, which has the dimension of length, represents a scale depth for the distribution of radiogenic elements. Most authors have not used data from greenstone belts in attempting to define the relationship within shields, considering them unrepresentative and preferring to use data from relatively homogeneous crystalline rocks. A discussion follows.

Lidar observations revealing transport of O3 in the presence of a nocturnal low-level jet: Regional implications for ;next-day; pollution

NASA Astrophysics Data System (ADS)

Sullivan, John T.; Rabenhorst, Scott D.; Dreessen, Joel; McGee, Thomas J.; Delgado, Ruben; Twigg, Laurence; Sumnicht, Grant

2017-06-01

Remotely sensed profiles of ozone (O3) and wind are presented continuously for the first time during a nocturnal low-level jet (NLLJ) event occurring after a severe O3 episode in the Baltimore-Washington D.C. (BW) urban corridor throughout 11-12 June 2015. High-resolution O3 lidar observations indicate a well-mixed and polluted daytime O3 reservoir, which decayed into a contaminated nocturnal residual layer (RL) with concentrations between 70 and 100 ppbv near 1 km above the surface. Observations indicate the onset of the NLLJ was responsible for transporting polluted O3 away from the region, while simultaneously affecting the height and location of the nocturnal residual layer. High-resolution modeling analyses and next-day (12 June) lidar, surface, and balloon-borne observations indicate the trajectory of the NLLJ and polluted residual layer corresponds with "next-day" high O3 at sites throughout the southern New England region (New York, Connecticut, Massachusetts). The novel O3 lidar observations are evidence of both nocturnal advection (via high NLLJ wind fields) and entrainment of the polluted residual layer in the presence of the "next-day" convectively growing boundary layer. In the greater context, the novel observational suite described in this work has shown that the chemical budget in areas downwind of major urban centers can be altered significantly overnight during transport events such as the NLLJ.

δ(15)N and δ(18)O Reveal the Sources of Nitrate-Nitrogen in Urban Residential Stormwater Runoff.

PubMed

Yang, Yun-Ya; Toor, Gurpal S

2016-03-15

Nitrogen (N) sources are widely distributed in the complex urban environment. High-resolution data elucidating N sources in the residential catchments are not available. We used stable isotopes of N and oxygen (O) of nitrate (δ(18)O-NO3(-) and δ(15)N-NO3(-)) along with δ(18)O and hydrogen (δD) of water (H2O) to understand the sources and transformations of N in residential stormwater runoff. Stormwater runoff samples were collected over 25 stormwater events at 5 min intervals using an autosampler installed at the residential catchment outlet pipe that drained 31 low-density homes with a total drainage area of 0.11 km(2). Bayesian mixing model results indicated that atmospheric deposition (range 43-71%) and chemical N fertilizers (range <1-49%) were the dominant NO3-N sources in the stormwater runoff and that there was a continuum of source changes during the stormwater events. Further, the NO3-N transport in the stormwater runoff from the residential catchment was driven by mixing of multiple sources and biotic (i.e., nitrification) processes. This work suggests that a better understanding of N transport and sources is needed to reduce N export and improve water quality in urban water systems.

From Abrupt Change to the Future (Hans Oeschger Medal Lecture)

NASA Astrophysics Data System (ADS)

Stocker, T.

2009-04-01

The award of the Oeschger Medal 2009 is a particular honor and pleasure for me as I was given the chance to take over from Hans Oeschger the lead of a wonderful Institute at the University of Bern in 1993. Very apprehensive first, in front of the huge expectations and challenges, I quickly found dear colleagues, close collaborators and extremely supportive staff who all dedicated their time and creativity to work for the common goal of better understanding the Earth System, its variations in the past and its sensitivity to perturbations that man is inflicting on it today. Although met with innate skepticism first by the experimental physicists, our efforts in modelling, particularly the approach of using climate models of reduced complexity, quickly paid off and provided added value to the hard won data and measurements from polar ice cores. It is clear that modelling in such a diverse environment is so much more stimulating and enriching than working on a sophisticated parameterisation in a big modelling centre. Simple models have suggested that the Earth System may have limited stability and that rather fundamental changes could be triggered by the increase of greenhouse gases. However, it is the unique results from polar ice cores, particularly from Greenland that showed that, indeed, the Earth System has limited stability and can react in extremely abrupt ways to changes in forcing. Likewise, the Antarctic ice cores have provided one of the corner stones of our knowledge about climate change: Concentrations of CO2 are today 29% higher than ever during the last 800,000 years. These two fundamental insights from the paleoclimatic archive call for accelerated research into the sensitivity of the climate system and its components to perturbations, as well as the investigation of feedback mechanisms in the biogeochemical cycles that are disturbed by the input of CO2 into the atmosphere by burning fossil fuels and land use change. Our research has only scratched the surface and many questions are still unresolved. A consistent simulation of ice age cycles including the remarkable transition from the 40 kyr to 100 kyr world is still missing. Evidence for interhemispheric connection, a persistent feature of the last ice age, remains circumstantial during earlier ice ages. Recent ice core analyses suggest extremely rapid climate change in the high latitude which is faster than any model has suggested. Sea ice changes must play an important role in that they may operate as an efficient accelerator. Modelling results are reviewed which suggest that instabilities in sea ice coverage can occur in response to relatively slow changes of the background climate. Such behaviour has been demonstrated in simulations of future climate, but it may well apply to past abrupt climate change. The paleoclimate record may therefore hold much more and more detailed information about instabilities and surprises if marine and atmospheric proxies are combined. However, only through the combination of highest-resolution paleoclimatic data and a clever hierarchy of models are we able to address and resolve these questions.

[Variations and simulation of stable isotopes in precipitation in the Heihe River basin].

PubMed

Wu, Jin-Kui; Yang, Qi-Yue; Ding, Yong-Jian; Ye, Bai-Sheng; Zhang, Ming-Quan

2011-07-01

To study the variations of deltaD and delta18O in precipitation, 301 samples were sampled during 2002-2004 in 6 sites in the Heihe River basin, Northwestern China. The deltaD and delta18O values ranged from 59 per thousand to -254 per thousand and 6.5 per thousand to -33.4 per thousand, respectively. This wide range indicated that stable isotopes in precipitation were controlled by different condensation mechanisms as a function of air temperature and varying sources of moisture. delta18O in precipitation had a close positive relationship with the air temperature, i. e., a clear temperature effect existed in this area. At a monthly scale, no precipitation effect existed. On the other hand, a weak precipitation effect still accrued at precipitation events scale. The spatial variation of delta18O showed that the weighted average delta18O values decreased with the increasing altitude of sampling sites at a gradient of -0. 47 per thousand/100m. A regional Meteoric Water Line, deltaD = 7.82 delta18O + 7.63, was nearly identical to the Meteoric Water Line in the Northern China. The results of backward trajectory of each precipitation day at Xishui showed that the moisture of the precipitation in cold season (October to March) mainly originated from the west while the moisture source was more complicated in warm season (April to September). The simulation of seasonal delta18O variation showed that the stable isotope composition of precipitation tended to a clear sine-wave seasonal variation.

Orbital and suborbital variability in North Atlantic bottom water temperature obtained from deep-sea ostracod Mg/Ca ratios

USGS Publications Warehouse

Cronin, T. M.; Dwyer, G.S.; Baker, P.A.; Rodriguez-Lazaro, J.; DeMartino, D.M.

2000-01-01

Magnesium/calcium (Mg/Ca) ratios were measured in the deep-sea ostracod (Crustacea) genus Krithe from Chain core 82-24-4PC from the western mid-Atlantic Ridge (3427 m) in order to estimate ocean circulation and bottom water temperature (BWT) variability over the past 200,000 years. Mg/Ca ratios have been used as a paleothermometer because the ratios are controlled primarily by ambient water temperatures at the time the organism secretes its adult carapace. Over the past two glacial–interglacial cycles, Mg/Ca values oscillated between about 7 mmol/mol and 12 mmol/mol, equivalent to a BWT range of 0 to >3.5°C. The lowest values were obtained on specimens from glacial marine isotope stages (MISs) 2, 4 and 6; the highest values were obtained from specimens from the early part of the Holocene interglacial (MIS 1), and also from MISs 5 and 7. These trends suggest that BWTs in the North Atlantic Ocean fluctuate over orbital time scales.Suborbital variability in Mg/Ca ratios and BWT was also observed for the past 100,000 years. Ratios rose from ∼8 mmol/mol to ∼10 mmol/mol (implying a BWT increase of ∼1 to 3°C) during 14 Mg/Ca excursions. The highest ratios were found in Krithe dated at approximately 32, 36–38, 43, 48, 73, 85 and 93 ka. Although the age model for the Chain 82-24-4PC and temporal resolution do not allow precise correlation, some of these deep-sea bottom temperature excursions appear to correspond to Heinrich events recorded in other regions of the North Atlantic and perhaps Dansgaard–Oeschger interstadial events recorded in Greenland ice cores. If confirmed, this would support the hypothesis that millennial-scale oscillations of climate in the North Atlantic are capable of affecting global climate via thermohaline circulation changes.

A Zn(2+)-responsive highly sensitive fluorescent probe and 1D coordination polymer based on a coumarin platform.

PubMed

Kumar, Virendra; Kumar, Ajit; Diwan, Uzra; Upadhyay, K K

2013-09-28

A coumarin-based Schiff base (receptor 1) exhibited fluorescence enhancement selectively with Zn(2+) at a nanomolar level in near-aqueous medium (EtOH-H2O; 1:1, v/v). The response was instantaneous with a detection limit of 3.26 × 10(-9) M. The sensing event is supposed to incorporate a combinational effect of intramolecular charge transfer (ICT), chelation-enhanced fluorescence (CHEF) and C[double bond, length as m-dash]N isomerization mechanisms. Various spectroscopic methods, viz. IR, UV-visible, fluorescence and NMR in association with single crystal XRD studies, were used for thorough investigation of the structure of receptor 1 as well as of the sensing event. The Zn(2+) complex of receptor 1 exhibited a very nice 1D chain coordination polymeric framework in its single crystal XRD.

Analysis of the light-water flooding of the HFBR thimble tubes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carew, J.F.; Aronson, A.L.; Cokinos, D.M.

The fuel elements surrounding the central vertical thimble tubes in the Brookhaven National Laboratory High-Flux Beam Reactor (HFBR) are highly undermoderated, and light-water flooding of these irradiation thimbles results in a positive core reactivity insertion. The light-water contamination of the D{sub 2}O thimble tube coolant is the result of a postulated double-ended guillotine break of a U tube in the experimental facilities heat exchanger during the HFBR light-water flooding (LWF) event. While this event has a low probability (1.3 x 10{sup {minus}4}/yr), the HFBR protection system must ensure adequate thermal margin during the power transient. This paper summarizes the analysismore » of the HFBR thimble-tube LWF event.« less

Understanding key drivers controlling daily stable isotope variations in precipitation of Costa Rica, Central America

NASA Astrophysics Data System (ADS)

Sanchez-Murillo, Ricardo; Welsh, Kristin; Birkel, Christian; Esquivel-Hernández, Germain; Corrales-Salazar, Jose; Boll, Jan; Brooks, Erin; Roupsard, Olivier; Katchan, Irina; Arce-Mesén, Rafael; Soulsby, Chris; Araguás-Araguás, Luis

2015-04-01

Costa Rica is located on the Central American Isthmus, which receives direct moisture inputs from the Caribbean Sea and the Pacific Ocean. The relatively narrow, but high relief Central American land bridge is characterized by unique mountainous and lowland microclimates. However, only limited knowledge exists about the impact of relief and regional atmospheric circulation patterns on precipitation origin, transport, and isotopic composition in this tropical region. Therefore, the main scope of this study is to identify the key drivers controlling variations in meteoric waters of Costa Rica using stable isotopes based on daily sample collection for the year 2013. The monitoring sites comprise three strategic locations across Costa Rica: Heredia (Central Valley), Turrialba (Caribbean slope), and Caño Seco (South Pacific slope). Sporadic dry season rain is mostly related to isolated enriched events ranging from -5.8‰ d18O up to -0.9‰ d18O. By mid-May, the Intertropical Convergence Zone reaches Costa Rica resulting in a notable depletion in isotope ratios (up to -18.5‰ d18O). HYSPLIT back air mass trajectories indicate the strong influence on the origin and transport of precipitation of two main moisture transport mechanisms, the Caribbean Low Level Jet and the Colombian Low Level Jet as well as localized convection events. Multiple linear regression models constructed based on Random Forests of surface meteorological information and atmospheric sounding profiles suggest that Lifted Condensation Level and surface relative humidity are the main factors controlling isotopic variations. These findings diverge from the recognized 'amount effect' in monthly composite samples across the tropics. Understanding of stable isotope dynamics in tropical precipitation can be used to enhance catchment and groundwater modeling efforts in ungauged basins where scarcity of long-term monitoring data drastically limit current and future water resources management.

Initial results from the ICDP SCOPSCO drilling project, Lake Ohrid (Macedonia, Albania)

NASA Astrophysics Data System (ADS)

Francke, A.; Wagner, B.; Krastel, S.; Lindhorst, K.; Wilke, T.; Zanchetta, G.; Sulpizio, R.; Grazhdani, A.; Reicherter, K. R.

2013-12-01

Lake Ohrid (Macedonia, Albania) is about 30 km long and 15 km wide and up to 290 m deep. Formed within a tectonic graben, Lake Ohrid is considered to be the oldest lake in Europe, providing a high-resolution, continuous archive of environmental change and tectonic and tephrostratigraphic history in the Eastern Mediterranean Region. The deep drilling campaign at Lake Ohrid in spring 2013 within the scope of the ICDP project SCOPSCO (Scientific Collaboration of Past Speciation Conditions in Lake Ohrid) aimed (a) to obtain more precise information about the age and origin of the lake, (b) to unravel the seismotectonic history of the lake area including effects of major earthquakes and associated mass wasting events, (c) to obtain a continuous record containing information on volcanic activities and climate changes in the central northern Mediterranean region, and (d) to better understand the impact of major geological/environmental events on general evolutionary patterns and shaping an extraordinary degree of endemic biodiversity as a matter of global significance. Drilling was carried out by DOSECC (Salt Lake City, USA) using the DLDS (Deep Lake Drilling System) with a hydraulic piston corer for surface sediments and rotation drilling for harder, deeper sediments. Overall, about 2,100 m of sediment were recovered from 4 drill sites. At the 'DEEP' site in the center of the lake, seismic data implied a maximum sediment fill of ca. 700 m, of which the uppermost 568 m sediment were recovered. Coarse-grained gravel and pebbles underlying clay and shallow water facies sediments hampered deeper penetration. 6 boreholes at the 'DEEP' site resulted in a total of 1526 m of sediment cores and a composite field recovery of 544 m (95%). Initial geochemical and magnetic susceptibility data imply that the sediments from 'DEEP' site are highly sensitive to climate and environmental variations in the Balkan area probably over the last 1.5 Mio years. Long-term climate oscillations on a glacial/interglacial timescale and also short-term events such as Dansgaard-Oescher cycles during the last glacial period can be inferred from the initial data. Although a high amount of greigite complicates the paleomagnetic dating of the recovered sediments, a robust age model can likely be inferred from numerous tephras and cryptotephras, which are indicated by spikes in the magnetic susceptibility data. Three additional sites at lateral parts of Lake Ohrid were drilled to un-ravel lake level fluctuations, catchment dynamics, biodiversity and evolution processes ('Cerava', deepest drilled depth: 90 m), active tectonics and spring dynamics ('Gradiste', deepest drilled depth: 123 m), and the early development of the Ohrid Basin ('Pestani', deepest drilled depth: 194 m). The composite field recovery is >90% at each site. The initial results obtained from the field campaign indicate that Lake Ohrid provides an extraordinary record of environmental change in the northern Mediterranean and will become a key site for a better understanding of speciation triggers.

Signals of El Niño Modoki in the tropical tropopause layer and stratosphere

NASA Astrophysics Data System (ADS)

Xie, F.; Li, J.; Tian, W.; Feng, J.; Huo, Y.

2012-06-01

The effects of El Niño Modoki events on the tropical tropopause layer (TTL) and on the stratosphere were investigated using European Center for Medium Range Weather Forecasting (ECMWF) reanalysis data, oceanic El Niño indices, and general climate model outputs. El Niño Modoki events tend to depress convective activities in the western and eastern Pacific but enhance convective activities in the central and northern Pacific. Consequently, during El Niño Modoki events, negative water vapor anomalies occur in the western and eastern Pacific upper troposphere, whereas there are positive anomalies in the central and northern Pacific upper troposphere. The spatial patterns of the outgoing longwave radiation (OLR) and upper tropospheric water vapor anomalies exhibit a tripolar form. The empirical orthogonal function (EOF) analysis of the OLR and upper tropospheric water vapor anomalies reveals that canonical El Niño events are associated with the leading mode of the EOF, while El Niño Modoki events correspond to the second mode. The composite analysis based on ERA-interim data indicate that El Niño Modoki events have a reverse effect on middle-high latitudes stratosphere, as compared with the effect of typical El Niño events, i.e., the northern polar vortex is stronger and colder but the southern polar vortex is weaker and warmer during El Niño Modoki events. According to the simulation' results, we found that the reverse effect on the middle-high latitudes stratosphere is resulted from a complicated interaction between quasi-biennial oscillation (QBO) signal of east phase and El Niño Modoki signal. This interaction is not a simply linear overlay of QBO signal and El Niño Modoki signal in the stratosphere, it is El Niño Modoki that leads to different tropospheric zonal wind anomalies with QBO forcing from that caused by typical El Niño, thus, the planetary wave propagation from troposphere to the stratosphere during El Niño Modoki events is different from that during canonical El Niño events. However, when QBO is in its west phase, El Niño Modoki events have the same effect on middle-high latitudes stratosphere as the typical El Niño events. Our simulations also suggest that canonical El Niño and El Niño Modoki activities actually have the same influence on the middle-high latitudes stratosphere when in the absence of QBO forcing.

Uranium, yttrium, and rare earth elements accumulation during the Cretaceous anoxic events in carbonaceous rocks in the Pacific Ocean

NASA Astrophysics Data System (ADS)

Savelyeva, Olga; Philosofova, Tatyana; Bergal-Kuvikas, Olga; Savelyeva, Svetlana

2017-04-01

We have studied the carbonate-siliceous section of paleooceanic Albian-Cenomanian deposits on the Kamchatsky Mys peninsula (Eastern Kamchatka, Russia) [1].The section is represented by a rhythmic alternation of planktonic limestones and jaspers, accumulated in the open ocean environment. The rhythmicity can be attributed to climate variations that reflect a fluctuation of astronomical parameters (Milankovitch cycles) [2, 3].The section contains two beds enriched in organic carbon, corresponding to the two oceanic anoxic events - MCE and OAE2 [3]. The maximum content of organic matter in those beds reaches 68%. Our geochemical studies revealed an enrichment of the carbonaceous rocks in some major and trace elements including PGE, in comparison with the surrounding limestone and jasper [4].The accumulation of the ore elements in carbonaceous beds is caused by euxinic conditions during sedimentation.The content of uranium, yttrium, and rare earth elements in carbonaceous rocks is up to 60, 142 and 312 ppm respectively. Phosphate grains (bone detritus) with microinclusions of yttrium and uranium minerals were revealed in the carbonaceous rocks using the scanning electron microscope. These data prove the hypothesis of the sorbtion of U and Y by phosphate detritus from seawater. Microprobe analysis also showed an increased content of Cu, Zn, V in some pyrite framboids, which indicates that these elements are fixed in rocks by Fe-sulphide phase or organic matter under euxinic conditions. Our research may bring us closer to understanding the mechanism of syngenetic accumulation of metals in the black shales. This work was supported by the RFBR (No. 16-05-00546). [1] Palechek, T.N., Savelyev, D.P., Savelyeva, O.L. (2010) Stratigraphy and Geological Correlation 18, (1) 63-82. [2] Savelyeva, O.L. (2010). Vestnik Kraunts. Nauki o zemle 1 (15), 45-55 (in Russian). [3] Savelyev, D.P., Savelyeva, O.L., Palechek, T.N., Pokrovsky, B.G. (2012) Geophysical Research Abstracts, 14, EGU2012-1940. [4] Savelyeva, O., Palesskiy, S., Savelyev, D. (2015) Goldschmidt Abstracts, 2015. 2779.

Seasonal isotope hydrology of a coffee agroforestry watershed in Costa Rica

NASA Astrophysics Data System (ADS)

Welsh Unwala, K.; Boll, J.; Roupsard, O.

2014-12-01

Improved information of seasonal variations in watershed hydrology in the tropics can strengthen models and understanding of hydrology of these areas. Seasonality in the tropics produces rainy seasons versus dry seasons, leading to different hydrologic and water quality processes throughout the year. We questioned whether stable isotopes in water can be used to trace the seasonality in this region, despite experiencing a "drier" season, such as in a Tropical Humid location. This study examines the fluctuations of stable isotope compositions (δ18O and δD) in water balance components in a small (<1 km2) coffee agroforestry watershed located in central Costa Rica on the Caribbean side. Samples were collected in precipitation, groundwater, and stream water for more than two years, across seasons and at an hourly frequency during storm events to better characterize spatial and temporal variations of the isotopic composition and of the respective contribution of surface and deeper groundwater to streamflow in the watershed. Isotope composition in precipitation ranged from -18.5 to -0.3‰ (∂18O) and -136.4 to 13.7‰ (∂D), and data indicate that atmospheric moisture cycling plays an important role in this region. A distinct seasonality was observed in monthly-averaged data between enriched dry season events as compared with the rainy season events. Streamflow data indicate that a deep groundwater system contributes significantly to baseflow, although a shallow, spring-driven system also contributes to stream water within the watershed. During storm events, precipitation contributes to stormflow in the short-term, confirming the role of superficial runoff. These results indicate that isotopes are helpful to partition the water balance even in a Tropical Humid situation where the rainfall seasonality is weak.

Downscaling 20th century flooding events in complex terrain (Switzerland) using the WRF regional climate model

NASA Astrophysics Data System (ADS)

Heikkilä, Ulla; Gómez Navarro, Juan Jose; Franke, Jörg; Brönnimann, Stefan; Cattin, Réne

2016-04-01

Switzerland has experienced a number of severe precipitation events during the last few decades, such as during the 14-16 November of 2002 or during the 21-22 August of 2005. Both events, and subsequent extreme floods, caused fatalities and severe financial losses, and have been well studied both in terms of atmospheric conditions leading to extreme precipitation, and their consequences [e.g. Hohenegger et al., 2008, Stucki et al., 2012]. These examples highlight the need to better characterise the frequency and severity of flooding in the Alpine area. In a larger framework we will ultimately produce a high-resolution data set covering the entire 20th century to be used for detailed hydrological studies including all atmospheric parameters relevant for flooding events. In a first step, we downscale the aforementioned two events of 2002 and 2005 to assess the model performance regarding precipitation extremes. The complexity of the topography in the Alpine area demands high resolution datasets. To achieve a sufficient detail in resolution we employ the Weather Research and Forecasting regional climate model (WRF). A set of 4 nested domains is used with a 2-km resolution horizontal resolution over Switzerland. The NCAR 20th century reanalysis (20CR) with a horizontal resolution of 2.5° serves as boundary condition [Compo et al., 2011]. First results of the downscaling the 2002 and 2005 extreme precipitation events show that, compared to station observations provided by the Swiss Meteorological Office MeteoSwiss, the model strongly underestimates the strength of these events. This is mainly due to the coarse resolution of the 20CR data, which underestimates the moisture fluxes during these events. We tested driving WRF with the higher-resolved NCEP reanalysis and found a significant improvement in the amount of precipitation of the 2005 event. In a next step we will downscale the precipitation and wind fields during a 6-year period 2002-2007 to investigate and validate the model performance during a larger number of events. Compo, G. P., J. S. Whitaker, P. D. Sardeshmukh, N. Matsui, R. J. Allan, X. Yin,B. E. Gleason, R. S. Vose, G. Rutledge, P. Bessemoulin, S. Bronnimann, M. Brunet, R. I. Crouthamel, A. N. Grant, P. Y. Groisman, P. D. Jones, M. C. Kruk, A. C. Kruger, G. J. Marshall, M. Maugeri, H. Y. Mok, O. Nordli, T. F. Ross, R. M. Trigo, X. L. Wang, S. D. Woodruff, S. J. Worley, 2011: The Twentieth Century Reanalysis Project. Quarterly J. Roy. Met. Soc., 137, 1-28, DOI: 10.1002/qj.776. Hohenegger, C., Walser, A., Langhans, H. and Schär, C., 2008, Cloud-resolving ensemble simulations of the August 2005 Alpine flood, Q. J. R. Meteorol. Soc. 2008, DOI: 10.1002/qj.252 Stucki, P., Rickli, R., Brönnimann, S., Martius, O., Wanner, H., Grebner, D. and Luterbacher, J., 2012, Weather patterns and hydro-climatological precursors of extreme floods in Switzerland since 1868, Meteorologische Zeitschrift, Vol. 21, No. 6, 531-550.

Domain 4 (D4) of Perfringolysin O to Visualize Cholesterol in Cellular Membranes-The Update.

PubMed

Maekawa, Masashi

2017-03-03

The cellular membrane of eukaryotes consists of phospholipids, sphingolipids, cholesterol and membrane proteins. Among them, cholesterol is crucial for various cellular events (e.g., signaling, viral/bacterial infection, and membrane trafficking) in addition to its essential role as an ingredient of steroid hormones, vitamin D, and bile acids. From a micro-perspective, at the plasma membrane, recent emerging evidence strongly suggests the existence of lipid nanodomains formed with cholesterol and phospholipids (e.g., sphingomyelin, phosphatidylserine). Thus, it is important to elucidate how cholesterol behaves in membranes and how the behavior of cholesterol is regulated at the molecular level. To elucidate the complexed characteristics of cholesterol in cellular membranes, a couple of useful biosensors that enable us to visualize cholesterol in cellular membranes have been recently developed by utilizing domain 4 (D4) of Perfringolysin O (PFO, theta toxin), a cholesterol-binding toxin. This review highlights the current progress on development of novel cholesterol biosensors that uncover new insights of cholesterol in cellular membranes.

Modern Analogs for Prehistoric El Niño Variability: Evidence from two Short-Lived Bivalve Species, Donax obesulus and Mesodesma donacium

NASA Astrophysics Data System (ADS)

Warner, J.; DeLong, K. L.; Chicoine, D.; Wanamaker, A. D.; Thirumalai, K.

2017-12-01

The January-April 2017 El Niño-costero, which brought elevated sea surface temperatures (SSTs) to the Niño 1+2 region and sudden rainfall, highlights the need for eastern Pacific oriented El Niño-Southern Oscillation (ENSO) proxies along the Peruvian coast. Unfortunately paleoclimatological archive options for this coast are limited because there are few long-lived (>50 years) organisms suitable for reconstructions; however, short-lived (<5 years) intertidal bivalve species are abundant. Monte Carlo simulations suggest that these bivalves live long enough to record seasonal and thus ENSO variability. Reconstructions have been created using Mesodesma donacium, an intertidal clam; however, M. donacium populations are vulnerable to die-offs from warmer SSTs during El Niño events, possibly biasing its seasonal δ18O cycle towards ENSO-neutral and La Niña conditions. M. donacium are also functionally extinct north of 14°S, limiting the geographic range for modern analog studies. Here we present another short-lived intertidal clam species, Donax obesulus, as a complimentary archive to M. donacium for reconstructing ENSO variability in modern and prehistoric Peru. D. obesulus lives in warmer SSTs and survives north of 14°S, yet may be sensitive to colder La Niña conditions. Both clam species are found in archaeological sites along the north-central coast of Peru, providing a comparison between modern and prehistoric ENSO variability in an under-researched area. We collected D. obesulus from the Nepeña Valley, department of Ancash, Peru, in 2012, 2014, and 2016 (La Niña, ENSO-neutral, and El Niño years, respectively) for a modern analog study. We also obtained M. donacium and D. obesulus specimens excavated from a prehistoric ( 2300±100 BP) site (Caylán) in the same valley for comparison to modern ENSO conditions. Our results indicate that modern D. obesulus have a seasonal δ18O range of 0.8‰, which is less than modern M. donacium from previous studies (1.1‰). Archaeological D. obesulus had a larger seasonal δ18O range ( 1.8‰), indicating greater ENSO variability. Caylán M. donacium have a seasonal range of 1.1‰, within the range of previous studies (seasonal δ18O range = 0.3-1.3‰, 2900 BP). Our results also indicate a shift in modern D. obesulus mean shell δ18O (+0.77‰) compared to 2300 BP at Caylán.

Department of Defense Implementation Plan for Pandemic Influenza

DTIC Science & Technology

2006-08-01

and Low Intensity Conflict (ASD(SO/LIC)) will provide policy oversight of the DoD Pandemic Influenza bilateral and multilateral international...flexible worksites (e.g., telecommuting ) and flexible work hours (e.g., staggered shifts) in the event of a pandemic. o Ensure development of active...however, special consideration must be given to “social distancing” in the workplace through 74 telecommuting , or other means, as an

Ultra high resolution cation analysis of NGRIP deep ice via cryo-cell UV-laser-ablation ICPMS

NASA Astrophysics Data System (ADS)

Della Lunga, Damiano; Muller, Wolfgang; Olander Rasmussen, Sune; Svensson, Anders

2014-05-01

During glacial periods, Earth experienced abrupt climate change events that led to rapid natural warming/ cooling over a few years only (Steffensen et al., 2008). In order to investigate these rapid climate events especially in old thinned ice, highest spatial/time resolution analysis of climate proxies is required. A recently developed methodology at Royal Holloway University of London (Müller et al., 2011), which permits in situ chemical analysis of frozen ice with spatial (and thus time) resolution up to 0.1 mm (100 ?m) using cryo-cell UV-laser ablation inductively-coupled-plasma mass spectrometry (UV-LA-ICPMS), has been optimized and utilized for analysis of (major) elements indicative of dust and/or sea salt (e.g. Fe, Al, Ca, Mg, Na), while maintaining detection limits in the low(est) ppb-range. NGRIP samples of Greenland Stadial GS22 (~86 ka, depth of ~2690 m), representing a minor δ18O shift (of about ± 4) within the stadial phase of D-O event 22, have been selected and analysed. With a single storm-event resolution capability, seasonal, annual and multiannual periodicity of elements have been identified and will be presented with particular focus on the phasing of the climate proxies. Corresponding results include also an optimized UV-LA-ICPMS methodology, particularly with reference to depth-profiling, assessing contamination of the sample surface and standardization. Finally, the location and distribution of soluble and insoluble micro-inclusions in deep ice have also been assessed concerning the partitioning of elements between grain boundaries and grain interiors. Results show that impurities tend to be concentrated along boundaries in clear (winter) ice, whereas in cloudy bands ('dirtier' ice) they distribute equally between boundaries and interiors. References Müller, W., Shelley, J.M.G., Rasmussen, S.O., 2011. Direct chemical analysis of frozen ice cores by UV-laser ablation ICPMS. J. Anal. At. Spectrom. 26, 2391-2395. Steffensen, J.P., Andersen, K.K., Bigler, M., Clausen, H.B., Dahl-Jensen, D., Fischer, H., Goto-Azuma, K., Hansson, M., Johnsen, S.J., Jouzel, J., Masson-Delmotte, V., Popp, T., Rasmussen, S.O., Rothlisberger, R., Ruth, U., Stauffer, B., Siggaard-Andersen, M.L., Sveinbjornsdottir, A.E., Svensson, A., White, J.W.C., 2008. High-resolution Greenland Ice Core data show abrupt climate change happens in few years. Science 321, 680-684.

Succession of structural events in the Goren greenstone belt (Burkina Faso): Implications for West African tectonics

NASA Astrophysics Data System (ADS)

Hein, Kim A. A.

2010-02-01

Ten years after field investigations in the SE Goren greenstone belt (GGB) of Burkina Faso by the Sanmatenga J.V., sponsored field studies conducted in 2007 have significantly enhanced structural datasets. The studies in 2007 were conducted across an expanded area of the GGB that included both southwestern and northeastern domains, and portions of the Pissila batholith to the west of the GGB. A revision of tectonic models proposed by Hein et al. [Hein, K.A.A., Morel, V., Kagoné, O., Kiemde, F., Mayes, K., 2004. Birimian lithological succession and structural evolution in the Goren Segment of the Boromo-Goren Greenstone Belt, Burkina Faso. Journal of African Earth Sciences 39, 1-23] is now possible. Three deformation events characterise the Goren greenstone belt. The deformation, D1 (previously D3) resulted in the formation of NW to NNW-trending steeply-dipping dextral-reverse shear zones folds and a penetrative S1-C schistosity that formed during a period of NE-SW shortening. The event is termed the Tangaean Event because it can be correlated across NE Burkina Faso in the Boromo, Bouroum, Yalago and Oudalan-Gorouol greenstone belts. The deformation, D2 (previously D2) resulted in the progressive development of NNE to NE-trending macroscopic to mesoscopic folds and a penetrative axial planar cleavage (S2), which was followed by the formation of dextral- and sinistral-reverse shears and a pervasive schistosity (S2-C). The first-order crustal-scale Sabce Shear Zone, which traverses the northern portion of the study area, is associated with macroscopic anticlockwise drag rotation of NW to NNW-trending D1 shears and folds: (the macroscopic fold was previously classified as D1). D2 in the GGB corresponds with the Eburnean Orogeny at 2130-1980 Ma, as described by [Feybesse, J.-L., Billa, M., Guerrot, C., Duguey, E., Lescuyer, J.-L, Milesi, J.-P., Bouchot, V., 2006, The paleoproterozoic Ghanian province: geodynamic model and ore controls, including regional stress modelling. Precambrian Research, 149-196]. The deformation D3 (previously D4) is recognised throughout the GGB. It is characterised by the formation of kinks and chevron folds (F3), or crenulation cleavage (S3) that are hosted by narrow WNW-trending shear zones. These formed during a period of north-south shortening termed the Wabo-Tampelse Event that post-dates the Eburnean Orogeny.

Effects of a beaver pond on runoff processes: comparison of two headwater catchments

USGS Publications Warehouse

Burns, Douglas A.; McDonnell, Jeffery J.

1998-01-01

Natural variations in concentrations of 18O, D, and H4SiO4 in two tributary catchments of Woods Lake in the west-central Adirondack Mountains of New York were measured during 1989–1991 to examine runoff processes and their implications for the neutralization of acidic precipitation by calcium carbonate treatment. The two catchments are similar except that one contained a 1.3 ha beaver pond. Evaporation from the beaver pond caused a seasonal decrease in the slope of the meteoric water line in stream water from the catchment with a beaver pond (WO2). No corresponding change in slope of the meteoric water line was evident in stream water from the other catchment (WO4), nor in ground water nor soil water from either catchment, indicating that evaporative fractionation was not significant. Application of a best-fit sine curve to δ18O data indicated that base flow in both catchments had a residence time of about 100 days. Ground water from a well finished in thick till had the longest residence time (160 days); soil water from the O-horizon and B-horizon had residence times of 63 and 80 days, respectively. Water previously stored within each catchment (pre-event water) was the predominant component of streamflow during spring snowmelt and during spring and autumn rainfall events, but the proportion of streamflow that consisted of pre-event water differed significantly in the two catchments. The proportion of event water (rain and snowmelt) in WO2 was smaller than at WO4 early in the spring snowmelt of March 13–17, 1990, but the proportions of source water components for the two catchments were almost indistinguishable by the peak flow on the third day of the melt. The event water was further separated into surface-water and subsurface-water components by utilizing measured changes in H4SiO4 concentrations in stream water during the snowmelt. Results indicated that subsurface flow was the dominant pathway by which event water reached the stream except during the peak flow of a rain-on-snow event on the last day of the melt. Streamflow from a spring rain storm with dry antecendent conditions two months later (May 16–18, 1990), was less than 5% event water at peak flow in WO2 and 26% in WO4. This change from the runoff pattern in March is attributed to retention of event water in the beaver pond favored by relatively low pre-event storage and isothermal (nonstratified) conditions in the pond that allowed mixing. Streamflow during several autumn storms was about 15–25% event water at peak flow in WO4; the highest values for event water were associated with wet antecedent moisture conditions. These results indicate that a beaver pond can significantly affect the downstream delivery of event water through evaporation and mixing, but provides minimal retention during large runoff events such as snowmelt. Beaver ponds are expected to provide greater opportunity for neutralization of acidic waters during most of the year in catchments treated with calcium carbonate, but little neutralization effect during snowmelt.

A new index for identifying different types of El Niño Modoki events

NASA Astrophysics Data System (ADS)

Wang, Xin; Tan, Wei; Wang, Chunzai

2018-04-01

El Niño Modoki events can be further classified into El Niño Modoki I and II in terms of their opposite impacts on southern China rainfall (Wang and Wang, J Clim 26:1322-1338, 2013) and the Indian Ocean dipole mode (Wang and Wang, Clim Dyn 42:991-1005, 2014). The present paper develops an index to identify the types of El Niño events. The El Niño Modoki II (MII) index is defined as the leading principle component of multivariate empirical orthogonal function analysis of the normalized El Niño Modoki index, Niño4 index and 850 hPa relative vorticity anomalies averaged near the Philippine Sea during autumn. The MII index exhibits dominant variations on interannual (2-3 and 4-5 years) and decadal (10-20 years) timescales. El Niño Modoki II events can be well identified by using the MII index value being larger than 1 standard deviation. Further analyses and numerical model experiments confirm that the MII index can portray the major oceanic and atmospheric features of El Niño Modoki II events. The constructed MII index along with previous ENSO indices can be used for classifying and identifying all types of El Niño events. Because of distinct impacts induced by different types of El Niño events, the implication of the present study is that climate prediction and future climate projection under global warming can be improved by using the MII index and other indices to identify the types of El Niño events.

Emotional reactivity to daily events in youth with anxiety disorders.

PubMed

Herres, Joanna; Caporino, Nicole E; Cummings, Colleen M; Kendall, Philip C

2018-05-07

Although research supports associations between anxiety and emotional reactivity in adults (Cisler, J. M., Olatunji, B. O., Feldner, M. T., & Forsyth, J. P. (2010). Emotion regulation and the anxiety disorders: an integrative review. Journal of Psychopathology and Behavioral Assessment, 32(1), 68-82.), few studies have examined emotional reactivity in anxious youth (e.g., Carthy et al., 2010; Tan, P. Z., Forbes, E. E., Dahl, R. E., Ryan, N. D., Siegle, G. J., Ladouceur, C. D., & Silk, J. S. (2012). Emotional reactivity and regulation in anxious and nonanxious youth: a cell-phone ecological momentary assessment study. Journal of Child Psychology and Psychiatry, 53(2), 197-206.). Using daily diary methodology, this study examined both negative affect (NA) and positive affect (PA) reactivity to daily events in youth diagnosed with anxiety (N = 68; 60% female; 78% non-Hispanic White; M age = 11.18 years, SD = 3.17). We also examined whether parent-reported emotion regulation would predict emotional reactivity. Participants reported more NA on days they experienced more negative parent and teacher events and less PA on days that they experienced more negative peer events. Additionally, better emotion regulation was associated with less NA reactivity to negative teacher events and to both negative and positive academic events. Interpersonal events have a salient effect on daily affect for anxious youth. Youth anxiety therapists should target emotion regulation associated with negative events involving adults and address barriers to developing and maintaining positive peer relationships.

Assessing Precipitation Isotope Variations during Atmospheric River Events to Reveal Dominant Atmospheric/Hydrologic Processes

NASA Astrophysics Data System (ADS)

McCabe-Glynn, S. E.; Johnson, K. R.; Yoshimura, K.; Buenning, N. H.; Welker, J. M.

2015-12-01

Extreme precipitation events across the Western US commonly associated with atmospheric rivers (ARs), whereby extensive fluxes of moisture are transported from the subtropics, can result in major damage and are projected by most climate models to increase in frequency and severity. However, they are difficult to project beyond ~ten days and the location of landfall and topographically induced precipitation is even more uncertain. Water isotopes, often used to reconstruct past rainfall variability, are useful natural tracers of atmospheric hydrologic processes. Because of the typical tropical and sub-tropical origins, ARs can carry unique water isotope (δ18O and δ2H, d-excess) signatures that can be utilized to provide source and process information that can lead to improving AR predictions. Recent analysis of the top 10 weekly precipitation total samples from Sequoia National Park, CA, of which 9 contained AR events, shows a high variability in the isotopic values. NOAA Hysplit back trajectory analyses reveals a variety of trajectories and varying latitudinal source regions contributed to moisture delivered to this site, which may explain part of the high variability (δ2H = -150.03 to -49.52 ‰, δ18O = -19.27 to -7.20 ‰, d-excess = 4.1 to 25.8). Here we examine the top precipitation totals occurring during AR events and the associated isotopic composition of precipitation samples from several sites across the Western US. We utilize IsoGSM, an isotope-enabled atmospheric general circulation model, to characterize the hydrologic processes and physical dynamics contributing to the observed isotopic variations. We investigate isotopic influences from moisture source location, AR speed, condensation height, and associated temperature. We explore the dominant controls on spatial and temporal variations of the isotopic composition of AR precipitation which highlights different physical processes for different AR events.

Impacts of the January 2005 solar particle events on middle atmospheric chlorine species

NASA Astrophysics Data System (ADS)

Winkler, Holger; Sinnhuber, Miriam; Notholt, Justus; Maik Wissing, Jan; Kallenrode, May-Britt; Santee, Michelle

It is well established that solar particle events (SPEs) are sources of significant chemical dis-turbances in the Earth's polar atmosphere. The observed SPE effects on nitrogen, hydrogen and oxygen compounds have been investigated in some detail in recent years, and they can be reproduced by atmospheric models using basic parametrizations for NOx and HOx produc-tion as a funtion of the particle impact ionisation. However, there are considerable differences between model predictions and measurements concerning several other trace gases including chlorine species. Two major SPEs occurred on January 17, and January 20, 2005. The latter had an exceptionally hard energy spectrum which caused maximum particle impact ionization at stratospheric altitudes. The Microwave Limb Sounder (MLS) instrument on-board the Aura satellite has measured a short-term decrease of HCl in the northern polar region corresponding to January 2005 SPEs. The peak HCl depletion is ˜300 ppt at 35-40 km. This is comparable to the depletion of messopheric HCl observed by the HALOE instrument during the July 2000 SPE. We will present simulation results of the University of Bremen Ion Chemistry (UBIC) model for the SPEs in January 2005 focusing on chlorine species. The simulations indicate that the observed short-term decrease of middle atmospheric HCl is due to a conversion into active chlorine species such as Cl, ClO and HOCl. The magnitude of the observed HCl loss can only be reproduced if reactions of negative chlorine species and the production of O(1 D) from the reaction N(2 D) + O2 are taken into account. The model results will be compared to MLS/Aura data of HCl, HOCl and ClO. Additionally, the impacts of the observed chlorine activation, e.g. on ozone, will be assessed.

Some aspects of stratospheric chemical response to solar particle precipitations. I - Potential roles of N2/A3Sigma/ and ion-chemistry

NASA Technical Reports Server (NTRS)

Prasad, S. S.

1979-01-01

Large amounts of long lived N2(A3Sigma) are created by the energy degradation of precipitating solar particles. Laboratory data suggest that in the stratosphere N2(A3Sigma) are efficiently converted into N2O. Through reactions with O(1D), N2O may gradually release NO and thereby influence the long term aspects of stratospheric chemical response. During the daytime, negative ions may transform an active NO(x) into an inactive HNO3. At night both negative and positive ion chemistry generate HO(x). Omission of ionic chemistry results in considerable underestimation of O3 depletion during the initial phases of solar particle events, and thereby introduces significant error in the estimation of the nature of the prompt response.

Composition Changes After the "Halloween" Solar Proton Event: The High-Energy Particle Precipitation in the Atmosphere (HEPPA) Model Versus MIPAS Data Intercomparison Study

NASA Technical Reports Server (NTRS)

Funke, B.; Baumgaertner, A.; Calisto, M.; Egorova, T.; Jackman, C. H.; Kieser, J.; Krivolutsky, A.; Lopez-Puertas, M.; Marsh. D. R.; Reddmann, T.;

Repeated deflation-inflation events at Kilauea Volcano, Hawai'i: What's up (and down) with that?

NASA Astrophysics Data System (ADS)

Poland, M. P.; Miklius, A.; Lundgren, P.; Sutton, A. J.

2011-12-01

Cyclic deflation-inflation ("DI") events are a common occurrence at Kilauea Volcano. Most DI events begin with deflation at the summit that generally lasts 12-72 hours and accumulate ~1-5 microradians of tilt as measured on the rim of Kilauea caldera, followed by inflation that is initially rapid but wanes as the net deformation approaches pre-event levels over the course of 12-48 hours. In rare cases, the initial deflation is followed by large-magnitude (~20 microradians) inflation over a few hours followed by hours to days of deflation to pre-event levels. Such DID events have only been recorded during 2000-2004. DI events are also manifested at the Pu'u 'O'o eruptive vent on Kilauea's east rift zone, about 15 km from the summit, and lag summit deformation by about 1-2 hours. For DI events with relatively large-magnitudes (i.e., several microradians) and long-durations (i.e., several days), deformation is manifested along the east rift zone between Pu'u 'O'o and the summit, and eruptive activity at Pu'u 'O'o is impacted with long periods of deflation and inflation associated with eruptive pauses and surges, respectively. During a period of increased magma transport between the summit and Pu'u 'O'o in 2005-2007, DI events recorded at the summit were not detected at Pu'u 'O'o. Since the March 2008 start of Kilauea's ongoing summit eruption, the number of DI events per year has increased from about 5-10 to about 50-60. The level of the summit lava column (continuously visible since early 2010), has generally tracked DI deformation. Surface deformation associated with DI events is measured by tilt, GPS, and InSAR. At the summit, preliminary source models suggest a depth of 1-2 km and a sill-like geometry beneath the center of the caldera, with volume loss and subsequent recovery on the order of tens of thousands of cubic meters with each DI cycle. The localized nature of the DI signal at Pu'u 'O'o argues for a shallow source that is probably less than 1 km deep. At least two mechanisms are consistent with the occurrence of DI events at Kilauea. First, blockage and subsequent clearing of the transport pathway that feeds the shallow summit magma system and conduit to Pu'u 'O'o could cause the observed deformation. A second possibility is that DI events represent convective overturns caused by replacement of degassed magma with gas-rich magma. Such a model is consistent with the increased number of DI events following the onset of Kilauea's summit eruption, when summit gas emissions increased by a factor of about 5, but there have been no changes in degassing rates during periods of frequent (i.e., daily) or rare (i.e., monthly) DI events during 2008-2011. The source of DI events therefore remains a target of continued study.

A Framework for Resilient Remote Monitoring

DTIC Science & Technology

2014-08-01

of low-level observables are availa- ble, audited , and recorded. This establishes the need for a re- mote monitoring framework that can integrate with...Security, WS-Policy, SAML, XML Signature, and XML Encryption. Pearson Higher Education, 2004. [3] OMG, “Common Secure Interoperability Protocol...www.darpa.mil/Our_Work/I2O/Programs/Integrated_Cyb er_Analysis_System_%28ICAS%29.aspx. [8] D. Miller and B. Pearson , Security information and event man

Contrasting serpentinization processes in the eastern Central Alps

USGS Publications Warehouse

Burkhard, D.J.M.; O'Neil, J.R.

1988-01-01

Stable isotope compositions have been determined for serpentinites from between Davos (Arosa-Platta nappe, Switzerland) and the Valmalenco (Italy). ??D and ??18O values (-120 to -60 and 6-10???, respectively) in the Arosa-Platta nappe indicate that serpentinization took place on the continent at relatively low temperatures in the presence of limited amounts of metamorphic fluids that contained a component of meteoric water. One sample of chrysotile has a ??18O value of 13??? providing evidence of high W/R ratios and low formation temperature of lizardite-chrysotile in this area. In contrast, relatively high ??D values (-42 to -34???) and low ??18O values (4.4-7.4???) for serpentine in the eastern part of the Valmalenco suggest a serpentinization process that took place at moderate temperatures in fluids that were dominated by ocean water. The antigorite in the Valmalenco is the first reported example of continental antigorite with an ocean water signature. An amphibole sample from a metasomatically overprinted contact zone to metasediments (??D=-36???) indicates that the metasomatic event also took place in the presence of ocean water. Lower ??D values (-93 to -60???) of serpentines in the western part of the Valmalenco suggest a different alteration history possibly influenced by fluids associated with contact metamorphism. Low water/rock ratios during regional metamorphism (and metasomatism) have to be assumed for both regions. ?? 1988 Springer-Verlag.

Contrasting serpentinization processes in the eastern Central Alps

NASA Astrophysics Data System (ADS)

Burkhard, Dorothee J. M.; O'Neil, James R.

1988-08-01

Stable isotope compositions have been determined for serpentinites from between Davos (Arosa-Platta nappe, Switzerland) and the Valmalenco (Italy). δD and δ 18O values (-120 to -60 and 6 10‰, respectively) in the Arosa-Platta nappe indicate that serpentinization took place on the continent at relatively low temperatures in the presence of limited amounts of metamorphic fluids that contained a component of meteoric water. One sample of chrysotile has a δ 18O value of 13‰ providing evidence of high W/R ratios and low formation temperature of lizardite-chrysotile in this area. In contrast, relatively high δD values (-42 to -34‰) and low δ 18O values (4.4 7.4‰) for serpentine in the eastern part of the Valmalenco suggest a serpentinization process that took place at moderate temperatures in fluids that were dominated by ocean water. The antigorite in the Valmalenco is the first reported example of continental antigorite with an ocean water signature. An amphibole sample from a metasomatically overprinted contact zone to metasediments ( δD=-36‰) indicates that the metasomatic event also took place in the presence of ocean water. Lower δD values (-93 to -60‰) of serpentines in the western part of the Valmalenco suggest a different alteration history possibly influenced by fluids associated with contact metamorphism. Low water/rock ratios during regional metamorphism (and metasomatism) have to be assumed for both regions.

Zonal wind indices to reconstruct United States winter precipitation during El Niño

NASA Astrophysics Data System (ADS)

Farnham, D. J.; Steinschneider, S.; Lall, U.

2017-12-01

The highly discussed 2015/16 El Niño event, which many likened to the similarly strong 1997/98 El Niño event, led to precipitation impacts over the continental United States (CONUS) inconsistent with general expectations given past events and model-based forecasts. This presents a challenge for regional water managers and others who use seasonal precipitation forecasts who previously viewed El Niño events as times of enhanced confidence in seasonal water availability and flood risk forecasts. It is therefore useful to understand the extent to which wintertime CONUS precipitation during El Niño events can be explained by seasonal sea surface temperature heating patterns and the extent to which the precipitation is a product of natural variability. In this work, we define two seasonal indices based on the zonal wind field spanning from the eastern Pacific to the western Atlantic over CONUS that can explain El Niño precipitation variation spatially throughout CONUS over 11 historic El Niño events from 1950 to 2016. The indices reconstruct El Niño event wintertime (Jan-Mar) gridded precipitation over CONUS through cross-validated regression much better than the traditional ENSO sea surface temperature indices or other known modes of variability. Lastly, we show strong relationships between sea surface temperature patterns and the phases of the zonal wind indices, which in turn suggests that some of the disparate CONUS precipitation during El Niño events can be explained by different heating patterns. The primary contribution of this work is the identification of intermediate variables (in the form of zonal wind indices) that can facilitate further studies into the distinct hydroclimatic response to specific El Niño events.

Role of Deep Convection in Establishing the Isotopic Composition of Water Vapor in the Tropical Transition Layer

NASA Technical Reports Server (NTRS)

Smith, Jamison A.; Ackerman, Andrew S.; Jensen, Eric J.; Toon, Owen B.

2006-01-01

The transport of H2O and HDO within deep convection is investigated with 3-D large eddy simulations (LES) using bin microphysics. The lofting and sublimation of HDO-rich ice invalidate the Rayleigh fractionation model of isotopologue distribution within deep convection. Bootstrapping the correlation of the ratio of HDO to H2O (deltaD) to water vapor mixing ratio (q(sub v)) through a sequence of convective events produced non-Rayleigh correlations resembling observations. These results support two mechanisms for stratospheric entry. Deep convection can inject air with water vapor of stratospheric character directly into the tropical transition layer (TTL). Alternatively, moister air detraining from convection may be dehydrated via cirrus formation n the TTL to produce stratospheric water vapor. Significant production of subsaturated air in the TTL via convective dehydration is not observed in these simulations, nor is it necessary to resolve the stratospheric isotope paradox.

CCl 4 chemistry on the magnetite selvedge of single-crystal hematite: competitive surface reactions

NASA Astrophysics Data System (ADS)

Adib, K.; Camillone, N., III; Fitts, J. P.; Rim, K. T.; Flynn, G. W.; Joyce, S. A.; Osgood, R. M., Jr.

2002-01-01

Temperature programmed reaction/desorption (TPR/D) studies were undertaken to characterize the surface chemistry which occurs between CCl 4 and the Fe 3O 4 (1 1 1) selvedge of single crystal α-Fe 2O 3 (0 0 0 1). Six separate desorption events are clearly observed and four desorbing species are identified: CCl 4, OCCl 2, C 2Cl 4 and FeCl 2. It is proposed that OCCl 2, CCl 4 and C 2Cl 4 are produced in reactions involving the same precursor, CCl 2. Three reaction paths compete for the CCl 2 precursor: oxygen atom abstraction (for OCCl 2), molecular recombinative desorption (for CCl 4) and associative desorption (for C 2Cl 4). During the TPR/D temperature ramp, the branching ratio is observed to depend upon temperature and the availability of reactive sites. The data are consistent with a rich site-dependent chemistry.

Computer Programs for Producing Single-Event Aircraft Noise Data for Specific Engine Power and Meteorological Conditions for Use with USAF (United States Air Force) Community Noise Model (NOISEMAP).

DTIC Science & Technology

1983-04-01

containing the atmospheric ab- sorption coefficients in dB per 1000 for standard day temperature and relative humidity. ATN8(24) Atmospheric...t L% Ias0% ar.. r- N0%aO CD -F PFa -N CaN.F F-S I-.6 0CP-. NF O3rIl DN X C CP.4 (a.,MJ-Nft In0 0N M66 %L 0% P- .FK..4 N t-4 DC2 a OAa*A e Sn U fU 4 0

Signals of El Niño Modoki in the tropical tropopause layer and stratosphere

NASA Astrophysics Data System (ADS)

Xie, F.; Li, J.; Tian, W.; Feng, J.

2012-02-01

The effects of El Niño Modoki events on the tropical tropopause layer (TTL) and on the stratosphere were investigated using European Center for Medium Range Weather Forecasting (ECMWF) reanalysis data, satellite observations from the Aura satellite Microwave Limb Sounder (MLS), oceanic El Niño indices, and general climate model outputs. El Niño Modoki events tend to depress convective activities in the western and eastern Pacific but enhance convective activities in the central and northern Pacific. Consequently, during Modoki events, negative water vapor anomalies occur in the western and eastern Pacific upper troposphere, whereas there are positive anomalies in the central and northern Pacific upper troposphere. The spatial patterns of the outgoing longwave radiation (OLR) and upper tropospheric water vapor anomalies exhibit a tripolar form. The empirical orthogonal function (EOF) analysis of the OLR and upper tropospheric water vapor anomalies reveals that canonical El Niño events are associated with the leading mode of the EOF, while El Niño Modoki events correspond to the second mode. El Niño Modoki activities tend to moisten the lower and middle stratosphere, but dry the upper stratosphere. It was also found that the canonical El Niño signal can overlay linearly on the QBO signal in the stratosphere, whereas the interaction between the El Niño Modoki and QBO signals is non-linear. Because of these non-linear interactions, El Niño Modoki events have a reverse effect on high latitudes stratosphere, as compared with the effects of typical Modoki events, i.e. the northern polar vortex is stronger and colder but the southern polar vortex is weaker and warmer during El Niño Modoki events. However, simulations suggest that canonical El Niño and El Niño Modoki activities actually have the same influence on high latitudes stratosphere, in the absence of interactions between QBO and ENSO signals. The present results also reveal that canonical El Niño events have a greater impact on the high-latitude Northern Hemisphere stratosphere than on the high-latitude Southern Hemisphere stratosphere. However, El Niño Modoki events can more profoundly influence the high-latitude Southern Hemisphere stratosphere than the high-latitude Northern Hemisphere stratosphere.

Superposed epoch analysis of O+ auroral outflow during sawtooth events and substorms

NASA Astrophysics Data System (ADS)

Nowrouzi, N.; Kistler, L. M.; Lund, E. J.; Cai, X.

2017-12-01

Sawtooth events are repeated injection of energetic particles at geosynchronous orbit. Studies have shown that 94% of sawtooth events occurred during magnetic storm times. The main factor that causes a sawtooth event is still an open question. Simulations have suggested that heavy ions like O+ may play a role in triggering the injections. One of the sources of the O+ in the Earth's magnetosphere is the nightside aurora. O+ ions coming from the nightside auroral region have direct access to the near-earth magnetotail. A model (Brambles et al. 2013) for interplanetary coronal mass ejection driven sawtooth events found that nightside O+ outflow caused the subsequent teeth of the sawtooth event through a feedback mechanism. This work is a superposed epoch analysis to test whether the observed auroral outflow supports this model. Using FAST spacecraft data from 1997-2007, we examine the auroral O+ outflow as a function of time relative to an injection onset. Then we determine whether the profile of outflow flux of O+ during sawtooth events is different from the outflow observed during isolated substorms. The auroral region boundaries are estimated using the method of (Andersson et al. 2004). Subsequently the O+ outflow flux inside these boundaries are calculated and binned as a function of superposed epoch time for substorms and sawtooth "teeth". In this way, we will determine if sawtooth events do in fact have greater O+ outflow, and if that outflow is predominantly from the nightside, as suggested by the model results.

A salt oscillator in the glacial Atlantic? 1. The concept

NASA Astrophysics Data System (ADS)

Broecker, Wallace S.; Bond, Gerard; Klas, Millie; Bonani, Georges; Wolfli, Willy

1990-08-01

As shown by the work of Dansgaard and his colleagues, climate oscillations of one or so millennia duration punctuate much of glacial section of the Greenland ice cores. These oscillations are characterized by 5°C air temperature changes, severalfold dust content changes and 50 ppm CO2 changes. Both the temperature and CO2 change are best explained by changes in the mode of operation of the ocean. In this paper we provide evidence which suggests that oscillations in surface water conditions of similar duration are present in the record from a deep sea core at 50°N. Based on this finding, we suggest that the Greenland climate changes are driven by oscillations in the salinity of the Atlantic Ocean which modulate the strength of the Atlantic's conveyor circulation.

Search For the Rare Decay K L → π 0π 0γ

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smith, David Edward

2006-08-01

This thesis describes a search for the rare decay K L → π 0π 0γ using data from the KTeV experiment, using the topology K L → π 0πmore » $$0\\atop{D}$$γ (where π$$0\\atop{D}$$ → γe +e -). Due to Bose statistics and the real nature of the photon, the K L → π 0π 0γ decay can proceed at lowest order only by the Cp conserving direct emission of an E2 photon. The decay vanishes to O(p 4) in chiral perturbation theory and is a probe of the theory to the sixth order. The primary background to this decay consists of K L → π 0π$$0\\atop{D}$$ events with one lost photon. The upper limit for the decay K L π 0π 0γ presented in this thesis is 2.32 x 10 -7 at the 90% confidence level. This upper limit was derived from both 1997 and 1999 data, using a blind analysis. The upper limit was derived from a Feldman-Cousins method, based on a weighted total of 0.53 data events in the signal region with an expected K L → π 0π 0π$$0\\atop{D}$$ background of 0.37 ± 0.28 events. The previous upper limit for this decay was 5.6 x 10 -6 at the 90% confidence level.« less

Fluid inclusion studies of ejected nodules from plinian eruptions of Mt. Somma-Vesuvius

USGS Publications Warehouse

Belkin, H.E.; de Vivo, B.

1993-01-01

Mt. Somma-Vesuvius (Naples, Italy) has erupted potassium-rich and silica-undersaturated products during a complicated history of plinian and non-plinian events. Coarse-grained cognate nodules are commonly found in the pyroclastics and are upper crustal in origin. We examined cumulate and subeffusive nodules from the 3800 y.B.P. Avellino. A.D. 79 Pompei, and A.D. 472 Pollena eruptions. Silicate-melt and liquid-vapor fluid inclusion studies in clinopyroxene from both types of nodules have been used to assess the fluids attending crystallization and to place constraints on the pressure and temperature of nodule formation. Thermometric and volumetric data from primary and pseudosecondary CO2-H2O and CO2 and coeval silicate-melt fluid inclusions indicate that they were trapped at a pressure of ???1 to ???2.5 kbar at ???1200??C. This suggests a crystallization depth of ???4 to ???10 km. The H2O-bearing fluid inclusions are abundant from plinian eruptions in contrast to non-plinian eruptions where H2O-bearing fluid inclusions were rare. The presence of primary H2O-CO2 fluid inclusions indicates that an immiscible, supercritical H2O-CO2 fluid was in the nodule-forming environment. The H2O-bearing fluid inclusions in plinian nodules may record a higher pre-eruptive H2O content in the bulk magma that is dramatically reflected in the eruption dynamics. ?? 1993.

Use of isotopic spike from Tropical Storm to understand water exchange on large scale: study case of Rafael Storm in the Lesser Antilles archipelago, October 2012.

NASA Astrophysics Data System (ADS)

Lambs, Luc

2014-05-01

Aim The tracking of the rainfall from Tropical Storm Raphael of mid October 2012 was used to better understand how the eco-hydrology and the water cycle function in wet areas, such as mangrove growing in salty ponds on a number of tropical islands. Location Guadeloupe and Saint Martin Islands in the Leeward Islands archipelago, Lesser Antilles. Methods Compared to normal tropical rainfall, tropical storms display distinct depleted heavy stable water isotopes which can be used as isotopic spikes to understand these special rainfall inflows. Rainfall, groundwater, river and pond water were sampled before, during and after the storm. Results In Guadeloupe where the tropical storm started, the rainfall isotopic signal reached values of d18O= -9 to -8 o on October 12-14th 2012, whereas the normal range is d18O= -4 to -2 o as measured from 2009 to 2012. It was possible to detect such a depleted signal in the groundwater and in the mangrove forest during the days after the storm event. Main conclusions The use of such natural isotopic spikes provides an opportunity to obtain a dynamic and time reference on a large scale for the study of the hydro-ecosystems and the effects on the impacted tropical islands. A few days after the cyclone, the isotopic spikes were found in river, groundwater and mangrove water pools with values up to d18O= -8.6 o . For the water basins on the windward side, the downhill salty pond water was almost completely renewed. By contrast, only 20 to 50 % of the water in the ponds located on the leeward side was renewed. No specific elevation in the d-excess values was noted, certainly due to the relatively long distance from the eye of the storm (180 to 300 km), which meant that there was no spray water evaporative process.

Late Holocene Peléan-style eruption at Tacaná volcano, Mexico and Guatemala: past, present, and future hazards

USGS Publications Warehouse

Macías, J. L.; Espíndola, J. M.; Garcia-Palomo, A.; Scott, K.M.; Hughes, S.; Mora, J C.

2000-01-01

Tacaná volcano, located on the border between Mexico and Guatemala, marks the northern extent of the Central American volcanic chain. Composed of three volcanic structures, it is a volcanic complex that has had periodic explosive eruptions for at least the past 40 k.y. The most recent major eruption occurred at the San Antonio volcano, the youngest volcanic edifice forming the complex, about 1950 yr ago. The Peléan style eruption, issued from the southwest part of the dome, and swept a 30° sector with a hot block and ash flow that traveled about 14 km along the Cahoacán ravine. Deposits from this event are well exposed around the town of Mixcun and were therefore given the name of that town, the Mixcun flow deposit. The Mixcun flow deposit is, in the channel facies, a light gray, massive, thick (>10 m), matrix-supported unit with dispersed lithic clasts of gravel to boulder size, divisible in some sections into a variable number of flow units. The overbank facies is represented by a thin (2 and has a minimum estimated volume of 0.12 km3. Basaltic-andesite inclusions (54% SiO2) and various signs of disequilibrium in the mineral assemblage of the two-pyroxene andesitic products (60%–63% SiO2) suggest that magma mixing may have triggered the eruption. Following deposition of the Mixcun flow deposit andesitic to dacitic (62%–64% SiO2) lava flows were extruded and a dacitic dome (64.4% SiO2) at the San Antonio summit formed. Syn-eruptive and posteruptive lahars flooded the main drainages of the Cahoacán and Izapa-Mixcun valleys in the area of the present city of Tapachula (population 250000) and the pre-Hispanic center of Izapa. Three radiocarbon ages date this event between A.D. 25 and 72 (range ±1σ, 38 B.C.–A.D. 216), which correlates with a halt in construction at Izapa (Hato phase of ca. 50 B.C.–A.D. 100), probably due to temporary abandonment of the city caused by lahars. Another similar event would produce extensive damage to the towns (population of about 68,000 people) now built upon the Mixcun flow deposit. The main summit of Tacaná volcano continues to show signs of fumarolic activity; the most recent period of activity in 1985–1986 culminated in a minor phreatic explosion.

The Vajont disaster: a 3D numerical simulation for the slide and the waves

NASA Astrophysics Data System (ADS)

Rubino, Angelo; Androsov, Alexey; Vacondio, Renato; Zanchettin, Davide; Voltzinger, Naum

2016-04-01

A very high resolution O(5 m), 3D hydrostatic nonlinear numerical model was used to simulate the dynamics of both the slide and the surface waves produced during the Vajont disaster (north Italy, 1963), one of the major landslide-induced tsunamis ever documented. Different simulated wave phenomena like, e.g., maximum run-up on the opposite shore, maximum height, and water velocity were analyzed and compared with data available in literature, including the results of a fully 3D simulation obtained with a Smoothed Particle Hydrodynamic code. The difference between measured and simulated after-slide bathymetries was calculated and used in an attempt to quantify the relative magnitude and extension of rigid and fluid motion components during the event.

Search for high-energy neutrinos from gravitational wave event GW151226 and candidate LVT151012 with ANTARES and IceCube

NASA Astrophysics Data System (ADS)

Albert, A.; André, M.; Anghinolfi, M.; Anton, G.; Ardid, M.; Aubert, J.-J.; Avgitas, T.; Baret, B.; Barrios-Martí, J.; Basa, S.; Bertin, V.; Biagi, S.; Bormuth, R.; Bourret, S.; Bouwhuis, M. C.; Bruijn, R.; Brunner, J.; Busto, J.; Capone, A.; Caramete, L.; Carr, J.; Celli, S.; Chiarusi, T.; Circella, M.; Coelho, J. A. B.; Coleiro, A.; Coniglione, R.; Costantini, H.; Coyle, P.; Creusot, A.; Deschamps, A.; de Bonis, G.; Distefano, C.; di Palma, I.; Donzaud, C.; Dornic, D.; Drouhin, D.; Eberl, T.; El Bojaddaini, I.; Elsässer, D.; Enzenhöfer, A.; Felis, I.; Fusco, L. A.; Galatà, S.; Gay, P.; Giordano, V.; Glotin, H.; Grégoire, T.; Gracia Ruiz, R.; Graf, K.; Hallmann, S.; van Haren, H.; Heijboer, A. J.; Hello, Y.; Hernández-Rey, J. J.; Hößl, J.; Hofestädt, J.; Hugon, C.; Illuminati, G.; James, C. W.; de Jong, M.; Jongen, M.; Kadler, M.; Kalekin, O.; Katz, U.; Kießling, D.; Kouchner, A.; Kreter, M.; Kreykenbohm, I.; Kulikovskiy, V.; Lachaud, C.; Lahmann, R.; Lefèvre, D.; Leonora, E.; Lotze, M.; Loucatos, S.; Marcelin, M.; Margiotta, A.; Marinelli, A.; Martínez-Mora, J. A.; Mathieu, A.; Mele, R.; Melis, K.; Michael, T.; Migliozzi, P.; Moussa, A.; Nezri, E.; Pǎvǎlaş, G. E.; Pellegrino, C.; Perrina, C.; Piattelli, P.; Popa, V.; Pradier, T.; Quinn, L.; Racca, C.; Riccobene, G.; Sánchez-Losa, A.; Saldaña, M.; Salvadori, I.; Samtleben, D. F. E.; Sanguineti, M.; Sapienza, P.; Schüssler, F.; Sieger, C.; Spurio, M.; Stolarczyk, Th.; Taiuti, M.; Tayalati, Y.; Trovato, A.; Turpin, D.; Tönnis, C.; Vallage, B.; Vallée, C.; van Elewyck, V.; Versari, F.; Vivolo, D.; Vizzoca, A.; Wilms, J.; Zornoza, J. D.; Zúñiga, J.; Aartsen, M. G.; Ackermann, M.; Adams, J.; Aguilar, J. A.; Ahlers, M.; Ahrens, M.; Al Samarai, I.; Altmann, D.; Andeen, K.; Anderson, T.; Ansseau, I.; Anton, G.; Archinger, M.; Argüelles, C.; Auffenberg, J.; Axani, S.; Bagherpour, H.; Bai, X.; Barwick, S. W.; Baum, V.; Bay, R.; Beatty, J. J.; Becker Tjus, J.; Becker, K.-H.; Benzvi, S.; Berley, D.; Bernardini, E.; Besson, D. Z.; Binder, G.; Bindig, D.; Blaufuss, E.; Blot, S.; Bohm, C.; Börner, M.; Bos, F.; Bose, D.; Böser, S.; Botner, O.; Bradascio, F.; Braun, J.; Brayeur, L.; Bretz, H.-P.; Bron, S.; Burgman, A.; Carver, T.; Casier, M.; Cheung, E.; Chirkin, D.; Christov, A.; Clark, K.; Classen, L.; Coenders, S.; Collin, G. H.; Conrad, J. M.; Cowen, D. F.; Cross, R.; Day, M.; de André, J. P. A. M.; de Clercq, C.; Del Pino Rosendo, E.; Dembinski, H.; De Ridder, S.; Desiati, P.; de Vries, K. D.; de Wasseige, G.; de With, M.; Deyoung, T.; Díaz-Vélez, J. C.; di Lorenzo, V.; Dujmovic, H.; Dumm, J. P.; Dunkman, M.; Eberhardt, B.; Ehrhardt, T.; Eichmann, B.; Eller, P.; Euler, S.; Evenson, P. A.; Fahey, S.; Fazely, A. R.; Feintzeig, J.; Felde, J.; Filimonov, K.; Finley, C.; Flis, S.; Fösig, C.-C.; Franckowiak, A.; Friedman, E.; Fuchs, T.; Gaisser, T. K.; Gallagher, J.; Gerhardt, L.; Ghorbani, K.; Giang, W.; Gladstone, L.; Glauch, T.; Glüsenkamp, T.; Goldschmidt, A.; Gonzalez, J. G.; Grant, D.; Griffith, Z.; Haack, C.; Hallgren, A.; Halzen, F.; Hansen, E.; Hansmann, T.; Hanson, K.; Hebecker, D.; Heereman, D.; Helbing, K.; Hellauer, R.; Hickford, S.; Hignight, J.; Hill, G. C.; Hoffman, K. D.; Hoffmann, R.; Hoshina, K.; Huang, F.; Huber, M.; Hultqvist, K.; in, S.; Ishihara, A.; Jacobi, E.; Japaridze, G. S.; Jeong, M.; Jero, K.; Jones, B. J. P.; Kang, W.; Kappes, A.; Karg, T.; Karle, A.; Katz, U.; Kauer, M.; Keivani, A.; Kelley, J. L.; Kheirandish, A.; Kim, J.; Kim, M.; Kintscher, T.; Kiryluk, J.; Kittler, T.; Klein, S. R.; Kohnen, G.; Koirala, R.; Kolanoski, H.; Konietz, R.; Köpke, L.; Kopper, C.; Kopper, S.; Koskinen, D. 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V.; Fulda, P.; Fyffe, M.; Gabbard, H.; Gadre, B. U.; Gaebel, S. M.; Gair, J. R.; Gammaitoni, L.; Gaonkar, S. G.; Garufi, F.; Gaur, G.; Gayathri, V.; Gehrels, N.; Gemme, G.; Genin, E.; Gennai, A.; George, J.; Gergely, L.; Germain, V.; Ghonge, S.; Ghosh, Abhirup; Ghosh, Archisman; Ghosh, S.; Giaime, J. A.; Giardina, K. D.; Giazotto, A.; Gill, K.; Glaefke, A.; Goetz, E.; Goetz, R.; Gondan, L.; González, G.; Gonzalez Castro, J. M.; Gopakumar, A.; Gorodetsky, M. L.; Gossan, S. E.; Gosselin, M.; Gouaty, R.; Grado, A.; Graef, C.; Granata, M.; Grant, A.; Gras, S.; Gray, C.; Greco, G.; Green, A. C.; Groot, P.; Grote, H.; Grunewald, S.; Guidi, G. M.; Guo, X.; Gupta, A.; Gupta, M. K.; Gushwa, K. E.; Gustafson, E. K.; Gustafson, R.; Hacker, J. J.; Hall, B. R.; Hall, E. D.; Hammond, G.; Haney, M.; Hanke, M. M.; Hanks, J.; Hanna, C.; Hannam, M. D.; Hanson, J.; Hardwick, T.; Harms, J.; Harry, G. M.; Harry, I. W.; Hart, M. J.; Hartman, M. 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S.; Radkins, H.; Raffai, P.; Raja, S.; Rajan, C.; Rakhmanov, M.; Rapagnani, P.; Raymond, V.; Razzano, M.; Re, V.; Read, J.; Regimbau, T.; Rei, L.; Reid, S.; Reitze, D. H.; Rew, H.; Reyes, S. D.; Rhoades, E.; Ricci, F.; Riles, K.; Rizzo, M.; Robertson, N. A.; Robie, R.; Robinet, F.; Rocchi, A.; Rolland, L.; Rollins, J. G.; Roma, V. J.; Romano, R.; Romie, J. H.; Rosińska, D.; Rowan, S.; Rüdiger, A.; Ruggi, P.; Ryan, K.; Sachdev, S.; Sadecki, T.; Sadeghian, L.; Sakellariadou, M.; Salconi, L.; Saleem, M.; Salemi, F.; Samajdar, A.; Sammut, L.; Sampson, L. M.; Sanchez, E. J.; Sandberg, V.; Sanders, J. R.; Sassolas, B.; Sathyaprakash, B. S.; Saulson, P. R.; Sauter, O.; Savage, R. L.; Sawadsky, A.; Schale, P.; Scheuer, J.; Schmidt, E.; Schmidt, J.; Schmidt, P.; Schnabel, R.; Schofield, R. M. S.; Schönbeck, A.; Schreiber, E.; Schuette, D.; Schutz, B. F.; Schwalbe, S. G.; Scott, J.; Scott, S. M.; Sellers, D.; Sengupta, A. S.; Sentenac, D.; Sequino, V.; Sergeev, A.; Setyawati, Y.; Shaddock, D. A.; Shaffer, T. J.; Shahriar, M. S.; Shapiro, B.; Shawhan, P.; Sheperd, A.; Shoemaker, D. H.; Shoemaker, D. M.; Siellez, K.; Siemens, X.; Sieniawska, M.; Sigg, D.; Silva, A. D.; Singer, A.; Singer, L. P.; Singh, A.; Singh, R.; Singhal, A.; Sintes, A. M.; Slagmolen, B. J. J.; Smith, B.; Smith, J. R.; Smith, R. J. E.; Son, E. J.; Sorazu, B.; Sorrentino, F.; Souradeep, T.; Spencer, A. P.; Srivastava, A. K.; Staley, A.; Steinke, M.; Steinlechner, J.; Steinlechner, S.; Steinmeyer, D.; Stephens, B. C.; Stevenson, S. P.; Stone, R.; Strain, K. A.; Straniero, N.; Stratta, G.; Strigin, S. E.; Sturani, R.; Stuver, A. L.; Summerscales, T. Z.; Sun, L.; Sunil, S.; Sutton, P. J.; Swinkels, B. L.; Szczepańczyk, M. J.; Tacca, M.; Talukder, D.; Tanner, D. B.; Tápai, M.; Taracchini, A.; Taylor, R.; Theeg, T.; Thomas, E. G.; Thomas, M.; Thomas, P.; Thorne, K. A.; Thrane, E.; Tippens, T.; Tiwari, S.; Tiwari, V.; Tokmakov, K. V.; Toland, K.; Tomlinson, C.; Tonelli, M.; Tornasi, Z.; Torrie, C. I.; Töyrä, D.; Travasso, F.; Traylor, G.; Trifirò, D.; Trinastic, J.; Tringali, M. C.; Trozzo, L.; Tse, M.; Tso, R.; Turconi, M.; Tuyenbayev, D.; Ugolini, D.; Unnikrishnan, C. S.; Urban, A. L.; Usman, S. A.; Vahlbruch, H.; Vajente, G.; Valdes, G.; van Bakel, N.; van Beuzekom, M.; van den Brand, J. F. J.; van den Broeck, C.; Vander-Hyde, D. C.; van der Schaaf, L.; van Heijningen, J. V.; van Veggel, A. A.; Vardaro, M.; Varma, V.; Vass, S.; Vasúth, M.; Vecchio, A.; Vedovato, G.; Veitch, J.; Veitch, P. J.; Venkateswara, K.; Venugopalan, G.; Verkindt, D.; Vetrano, F.; Viceré, A.; Viets, A. D.; Vinciguerra, S.; Vine, D. J.; Vinet, J.-Y.; Vitale, S.; Vo, T.; Vocca, H.; Vorvick, C.; Voss, D. V.; Vousden, W. D.; Vyatchanin, S. P.; Wade, A. R.; Wade, L. E.; Wade, M.; Walker, M.; Wallace, L.; Walsh, S.; Wang, G.; Wang, H.; Wang, M.; Wang, Y.; Ward, R. L.; Warner, J.; Was, M.; Watchi, J.; Weaver, B.; Wei, L.-W.; Weinert, M.; Weinstein, A. J.; Weiss, R.; Wen, L.; Weßels, P.; Westphal, T.; Wette, K.; Whelan, J. T.; Whiting, B. F.; Whittle, C.; Williams, D.; Williams, R. D.; Williamson, A. R.; Willis, J. L.; Willke, B.; Wimmer, M. H.; Winkler, W.; Wipf, C. C.; Wittel, H.; Woan, G.; Woehler, J.; Worden, J.; Wright, J. L.; Wu, D. S.; Wu, G.; Yam, W.; Yamamoto, H.; Yancey, C. C.; Yap, M. J.; Yu, Hang; Yu, Haocun; Yvert, M.; Zadrożny, A.; Zangrando, L.; Zanolin, M.; Zendri, J.-P.; Zevin, M.; Zhang, L.; Zhang, M.; Zhang, T.; Zhang, Y.; Zhao, C.; Zhou, M.; Zhou, Z.; Zhu, S. J.; Zhu, X. J.; Zucker, M. E.; Zweizig, J.; ANTARES Collaboration

2017-07-01

The Advanced LIGO observatories detected gravitational waves from two binary black hole mergers during their first observation run (O1). We present a high-energy neutrino follow-up search for the second gravitational wave event, GW151226, as well as for gravitational wave candidate LVT151012. We find two and four neutrino candidates detected by IceCube, and one and zero detected by Antares, within ±500 s around the respective gravitational wave signals, consistent with the expected background rate. None of these neutrino candidates are found to be directionally coincident with GW151226 or LVT151012. We use nondetection to constrain isotropic-equivalent high-energy neutrino emission from GW151226, adopting the GW event's 3D localization, to less than 2 ×1 051- 2 ×1 054 erg .

Analysis of the 2015-16 El Niño Event Using NASA's GEOS Data Assimilation System

NASA Astrophysics Data System (ADS)

Pawson, S.; Lim, Y. K.; Kovach, R. M.; Vernieres, G.

2016-12-01

The strong El Niño event that occurred in 2015/2016 is analyzed using atmospheric and oceanic analyses produced using the Goddard Earth Observing System (GEOS) systems. A theme of the work is to compare and contrast this event with two other strong El Niños, in 1982/1983 and 1997/1998, that are included in the satellite-data era of the MERRA and MERRA-2 reanalyses produced using the GEOS system. Distribution of the maximum anomalies of tropical sea-surface temperature (SST), precipitation, Walker circulation, and cloud fraction indicate that 2015/2016 is a Central Pacific (CP) El Niño. The event had an early onset compared to the 1997/1998 El Niño, with extremely strong warming and precipitation over the Central Pacific, and was the strongest in terms of central Pacific SST anomalies. The large region of warm temperature anomalies over most of the Pacific and Indian Ocean in the 2015-2016 event were due to the accumulative impacts of the El Niño event along with a positive phase of the Pacific Decadal Oscillation and a decadal warming trend over the western Pacific, Maritime Continent, and Indian Ocean. The relatively weak development of the 2015/2016 El Niño event over the Eastern Pacific was likely due to weaker westerly wind bursts and Madden-Julian Oscillation during spring, which in 1997/1998 served to drive the warm anomalies further East towards South America, making that event the strongest Eastern Pacific El Niño (in the recent data record). This is reflected in the 2015/2016 event having a shallower thermocline over the Eastern Pacific, with a weaker zonal gradient of sub-surface water temperatures along the equatorial Pacific. The major extra-tropical teleconnections associated with the El Niño in 2015/2016 are at least comparable to those in the 1982/1983 and 1997/1998 El Niño events. Specifically, the Pacific North American (PNA) teleconnection in 2015/2016 is the strongest of these three El Niño events, leading to larger extra-tropical anomalies of geopotential height, temperature, and precipitation over North America.

Proceedings of the Military Operational Medicine Research Program Return-to-Duty Research Working Group Meeting, 19-20 September 2012

DTIC Science & Technology

2013-05-01

Defense level. o The publicized issue of repeat concussions with NFL [National Football League] players has helped to identify TBI as its own field...Neuropsychological injuries include single or multiple concussive events along with other concomitant neurological effects associated with mental health...the development of RTD standards and assessment tools addressing the most common injuries across DoD: neurosensory injury (i.e., concussion

Synthesis of methyl 3-O-alpha-D-mannopyranosyl-alpha-D-talopyranoside and methyl 3-O-alpha-D-talopyranosyl-alpha-D-talopyranoside.

PubMed

Dubey, R; Jain, R K; Abbas, S A; Matta, K L

1987-08-01

Methyl 2-O-benzyl-3-O-(2,3,4,6-tetra-O-acetyl-alpha-D-mannopyranosyl)-alpha- D-mannopyranoside (4) and methyl 2-O-benzyl-3-O-alpha-D-mannopyranosyl-alpha-D-mannopyranoside (6) were prepared from a common intermediate, namely, methyl 2-O-benzyl-4,6-O-benzylidene-3-O-(2,3,4,6-tetra-O-acetyl-alpha-D- mannopyranosyl)-alpha-D-mannopyranoside. On treatment with tert-butylchlorodiphenylsilane, in N,N-dimethylformamide in the presence of imidazole, 4 and 6 afforded methyl 2-O-benzyl-6-O-tert-butyldiphenylsilyl-3-O-(2,3,4,6-tetra-O-acetyl -alpha-D- mannopyranosyl)-alpha-D-mannopyranoside (7), and methyl 2-O-benzyl-6-O-tert-butyldiphenylsilyl-3-O-(6-O-tert- butyldiphenylsilyl-alpha-D-mannopyranosyl)-alpha-D-mannopyranoside (8), respectively. Compound 8 was converted into its 2,3-O-isopropylidene derivative (9), and oxidation of 7 and 9 with pyridinium chlorochromate, and reduction of the resulting carbonyl intermediates gave methyl 2-O-benzyl-6-O-tert-butyldiphenylsilyl-3-O-(2,3,4,6-tetra-O-acetyl -alpha-D- mannopyranosyl)-alpha-D-talopyranoside and methyl 2-O-benzyl-6-O-tert-butyldiphenylsilyl-3-O-(6-O-tert-butyldiphe nylsilyl- 2,3-O-isopropylidene-alpha-D-talopyranosyl)-alpha-D-talopyranoside , respectively. Removal of the protecting groups furnished the title disaccharides.

Isotopic signals from precipitation and denitrification in nitrate in a northern hardwood forest

NASA Astrophysics Data System (ADS)

Goodale, C. L.; Wexller, S.

2012-12-01

Denitrification can represent an important term in the nitrogen budget of small catchments; however, this process varies greatly over space and time and is notoriously difficult to quantify. Measurements of the natural abundance of stable isotopes of nitrogen and oxygen in dissolved nitrate in stream- and river water can sometimes provide evidence of denitrification, particularly in large river basins or agriculturally impacted catchments. To date, however, this approach has provided little to no evidence of denitrification in catchments in temperate forests. Here, we examined d15N and d18O of nitrate in water samples collected during summer 2011 not only from streams and precipitation, but also from groundwater from the hydrologic reference watershed (W3) drained by Paradise Brook, at the Hubbard Brook Experimental Forest, in the White Mountains, New Hampshire. Despite low nitrate concentrations (< 0.5 to 8.8 uM nitrate) dual-isotopic signals of nitrate sources and nitrogen cycle processes were clearly distinguishable, including sources from atmospheric deposition, and from nitrification of atmospheric ammonium and from or soil organic nitrogen, as well as nitrate affected by soil denitrification. An atmospheric signal from nitrate in precipitation (enriched with 18O) was observed immediately following a precipitation event in mid-July contributing roughly 22% of stream nitrate export on this date. Stream samples the day following this and other storms showed this export of event nitrate to be short-lived. Hillslope piezometers showed low nitrate concentrations and high d15N- and d18O-nitrate values (averaging 12 and 18 per mil, repectively) indicating denitrification, which preferentially removes isotopically light N and O in N gases and leaves isotopically heavy nitrate behind. These samples showed a positive relationship between nitrogen and oxygen isotopic composition with a regression line slope of 0.76 (R2 = 0.68), and an isotope enrichment factor -12.7 per mil for denitrification removal of nitrate in these hillslope soils. The isotopic composition of a time series of samples from three riparian piezometers crossing Paradise Brook shows strong connections between the riparian soil water and the stream, as well as a different dominant source of nitrate in each piezometer. Repeated surveys of stream nitrate show modest positive enrichment in N and O isotopes with a slope between 18O and 15N of 0.96, indicating either in- or near-stream denitrification or mixing between stream and hillslope water bearing a stronger denitrification signal. The dual isotope approach provides detailed information on nitrogen cycling dynamics during the summer in a northern hardwood forested catchment. Together, these observations provide strong isotopic evidence for rapid rates of denitrification during summer in the soils of this small forested catchment.

The timing and duration of the Last Interglacial Asian Monsoon

NASA Astrophysics Data System (ADS)

Yuan, D.; Cheng, H.; Edwards, R.; Kelly, M.; Qing, J.; Lin, Y.; Zhang, M.

2002-12-01

An accurate estimate for the timing and duration of regional and global climate change associated with the Last Interglacial is important for elucidating climate change mechanisms. We present a 230Th-dated δ18O record of 2 stalagmites (D3 and D4) from Dongge Cave, southern China (25°N, 109°E, an area affected by East Asian and Indian Monsoons), which record Asian Monsoon history over 3 periods, 160-110 ka, 65-43 ka and 15.5 ka - present. The stalagmites have different precipitation environments and water flow paths as indicated by different growth histories, growth rates and δ234U values. D3 grew faster between 123-118 ka (12 vs. 0.4 cm/ka), but D4 grew faster between 138-126 ka (3.4 vs. 0.7 cm/ka). The mean initial δ234U value of D3 is -272 (range of -261 to -287). D4 values are higher (mean = -78, range of -27 to -160). Despite these differences, both have similar large δ18O variations for the interval over which both were active (148 to 113 ka), suggesting that water-rock interactions and kinetic fractionation did not affect δ18O values significantly. Dongge Cave stalagmites exhibit features similar to the Younger Dryas (YD) and the Bolling/Allerod as recorded in Greenland ice cores (GISP, 1997) and stalagmites from Hulu Cave, eastern China (Wang et al., 2001). The Dongge YD lies between 12640 +/-140 and 11550 +/-80 years BP, synchronous with Greenland and Hulu Cave YD analogues. Similar to Hulu Cave, light Dongge Cave δ18O excursions correspond to heavy isotopic excursions in Greenland, consistent with a positive correlation between the intensity of the Asian summer monsoon and Greenland temperature. The most prominent feature in the Dongge record is a peak that approximates a square wave and is contemporaneous with at least portions of the Last Interglacial sea level high. Dongge Termination II is a large, abrupt negative shift in δ18O (>3 per mil). The mid-point is at 129.3 +/-0.9 ka, based on direct dating of D4. D3 gives an age indistinguishable from this value. If D4 growth rate is linear over the transition, as implied by long term stable growth rates (from 144 to 124 ka), the transition takes less than 500 y, with most of it taking less than 200 y. The Dongge Last Interglacial also ends with an abrupt δ18O shift (about 4 per mil). The midpoint is at 119.6 +/-0.6 ka based on direct dating of D3. D4 gives an age indistinguishable from this value. Assuming linear growth, the main portion of the transition took less than 700 y. Combining the onset and end ages of the Dongge Last Interglacial, the duration is 9.7 +/-1.1 ka, from 129.3 +/-0.9 ka to 119.6 +/-0.6 ka, remarkably similar to some estimates of full Last Interglacial sea levels. The timing is broadly consistent with orbital forcing of the Monsoon, although the abrupt shifts require the involvement of other mechanisms (e.g. changes in circulation). Dongge Termination II lags Devils Hole Termination II, some fraction of sea level Termination II, and likely Vostok temperature, Vostok CO2, and eastern Pacific sea surface temperature. However, there is some evidence that it coincides within error with the final rise in sea level to full Last Interglacial elevations. It may well be that Monsoon Termination II is an orbitally-forced event at the end of a sequence of events not directly caused by orbital forcing. As such it may mark the inception of full interglacial conditions world-wide. Orbital forcing may be necessary for full interglacial conditions, but not for many of the shifts toward interglacial conditions observed to prior to Dongge Termination II.

A dichotomy in primary marine organic aerosol-cloud-climate system

NASA Astrophysics Data System (ADS)

Ceburnis, D.; Ovadnevaite, J.; Martucci, G.; Bialek, J.; Monahan, C.; Rinaldi, M.; Facchini, C.; Berresheim, H.; Worsnop, D. R.; O'Dowd, C.

2011-12-01

D. Ceburnis1, J. Ovadnevaite1, G. Martucci1, J. Bialek1, C. Monahan1, M. Rinaldi2, M. C. Facchini2, H. Berresheim1, D. R. Worsnop3,4 and C. D. O'Dowd1 1School of Physics & Centre for Climate and Air Pollution Studies, National University of Ireland Galway, University Road, Galway, Ireland 2Institute of Atmospheric Sciences and Climate, National Research Council, Bologna, 20129, Italy. 3 Aerodyne Research, Inc., 45 Manning Road, Billerica, MA 01821-3976, USA 4 Physics Department, University of Helsinki, P.O. Box 64, 00014, Helsinki, Finland Organic matter has been observed to significantly contribute to particulate matter in every environment including pristine remote oceans. A significant if not dominant contribution of insoluble organic matter to marine aerosol has been proved to be of biogenic origin1,2. High time resolution measurements of marine organic matter have demonstrated a dynamic system with regular organic matter plume events occurring during summer3 as well as frequent open ocean particle formation events4. High-time resolution measurements of primary marine organic sea-spray physico-chemical properties reveal an apparent dichotomous behavior in terms of water uptake: specifically sea-spray aerosol enriched in organic matter possesses a low hygroscopic Growth Factor (GF~1.25) while simultaneously having a cloud condensation nucleus/condensation nuclei (CCN/CN) activation efficiency of between 83% at 0.25% supersaturation and 100% at 0.75%5. Simultaneous retrieval of Cloud Droplet Number Concentration (CDNC) during primary organic aerosol plumes reveal CDNC concentrations of 350 cm-3 in newly formed marine stratocumulus cloud for boundary layer organic mass concentrations of 3-4 ug m-36. It is suggested that marine hydrogels are responsible for this dichotomous behavior which has profound impacts to aerosol-cloud-climate system along with a better understood process analysis of aerosol formation by sea-spray7. A hydrophobic character of organic matter dominated aerosol in sub-saturated conditions should have significant implications for direct radiative effect while effectively forming cloud condensation nuclei should have significant contribution to indirect effect. 1 O'Dowd, C. D. et al. Nature 431, 676-680, doi:10.1038/Nature02959 (2004). 2 Ceburnis, D. et al. Atmos. Chem. Phys. Discuss. 11, 2749-2772, doi:doi:10.5194/acpd-11-2749-2011 (2011). 3 Ovadnevaite, J. et al. Geophys Res Lett 38, L02807, doi:10.1029/2010gl046083 (2011). 4 O'Dowd, C., et al. Geophys Res Lett 37, doi:L19805 10.1029/2010gl044679 (2010). 5 Ovadnevaite, J. et al. Geophys Res Lett (2011). 6 Martucci, G. and O'Dowd, C. D. Atmos. Meas. Tech. Discuss., 4, 4825-4865, doi:10.5194/amtd-4-4825-2011 (2011) 7 Gantt, B. et al. Atmos. Chem. Phys. Discuss. 11, 10525-10555, doi:10.5194/acpd-11-10525-2011 (2011).

Genome-wide investigation and expression profiling of APX gene family in Gossypium hirsutum provide new insights in redox homeostasis maintenance during different fiber development stages.

PubMed

Tao, Chengcheng; Jin, Xiang; Zhu, Liping; Xie, Quanliang; Wang, Xuchu; Li, Hongbin

2018-06-01

Ascorbate peroxidase (APX) is a member of heme-containing peroxidases which catalyze the H 2 O 2 -dependent oxidation of a wide range of substrates in plants and animals. As is known, H 2 O 2 acts as a signaling molecule in the regulation of fiber development. Our previous work reported that ascorbate peroxidase 1 (GhAPX1) was important for cotton fiber elongation. However, knowledge about APX gene family members and their evolutionary and functional characteristics in cotton is limited. Here, we report 26 GhAPX genes by genome-wide investigation of tetraploid cotton Gossypium hirsutum. Phylogenetic and gene structure analyses classified these APX members into five clades and syntenic analysis suggested two duplication events. Expression profiling of the 26 APXs revealed that ten members are expressed in cotton fibers. Notably, GhAPX10A, GhAPX10D, GhAPX12A, and GhAPX12D showed high expression levels in 30-day fiber, while GhAPX1A/D, GhAPX3A/D, and GhAPX6A/D showed very low expression levels. The enzyme activity and H 2 O 2 content assays revealed that cotton fiber kept high enzyme activity and the lowest H 2 O 2 level in 30-day fibers, indicating that other than GhAPX1, the newly reported APX members are responsible for the reactive oxygen species homeostasis in the cotton fiber maturation stages. Expression profiling of ten fiber-expressed APXs after phytohormone treatments revealed their regulation patterns by different stimuli, suggesting that GhAPX1, GhAPX12A, and GhAPX12D are responsible to most phytohormone treatments. Our data provided evolutionary and functional information of GhAPX gene family members and revealed that different members are responsible to redox homeostasis during different cotton fiber development stages.

Hydrogen and oxygen isotope constraints on hydrothermal alteration of the Trinity peridotite, Klamath Mountains, California

USGS Publications Warehouse

Liakhovitch, V.; Quick, J.E.; Gregory, R.T.

2005-01-01

The Trinity peridotite represents a rare opportunity to examine a relatively fertile plagioclase peridotite that was exhumed and later subjected to intrusive events in a seafloor environment, followed by its emplacement and incorporation into a continent. Over 250 stable isotopic determinations on whole rocks and minerals elucidate the hydrothermal evolution of the Trinity complex. All three serpentine polymorphs are present in the Trinity peridotite; these separate on the basis of their ??D values: antigorite, -46 < ??D < -82??? and lizardite and chrysotile, -90 < ??D < -106 and -110 < ??D < -136???, respectively. Antigorite coexists with chlorite, talc, and tremolite in contact aureole assemblages associated with Silurian/Devonian gabbroic plutons. Lizardite and chrysotile alteration carries a meteoric signature, which suggests association with post-emplacement serpentinization, or overprinting of earlier low-temperature seafloor serpentinization. Regionally, contours of ??D values exhibit bull's-eye patterns associated with the gabbroic plutons, with ??D maxima coinciding with the blackwall alteration at the margins on the plutons. In contrast to the hydrogen isotope behavior, oxygen isotope values of the three polymorphs are indistinguishable, spanning the range 5.3 < ??18O< 7.5, and suggesting low integrated fluid fluxes and strongly 18O-shifted fluids. Inferred primary ?? 18O values for peridotite, gabbro, and late Mesozoic granodiorite indicate a progressive 18O enrichment with time for the source regions of the rocks. These isotopic signatures are consistent with the geology, petrochemistry, and geochronology of the Trinity massif, which indicate the following history: (1) lithospheric emplacement and cooling of the peridotite in an oceanic environment ??? 472 Ma; (2) intrusion of gabbroic plutons into cold peridotite in an arc environment between 435 and 404 Ma; and finally (3) intrusion of felsic plutons between 171 and 127 Ma, long after the peridotite was incorporated into the continental crust. Copyright ?? 2005 by V. H. Winston & Son, Inc. All rights reserved.

Risk score for pediatric intensive care unit admission in children undergoing hematopoietic stem cell transplantation and analysis of predictive factors for survival.

PubMed

González-Vicent, Marta; Marín, Catalina; Madero, Luis; Sevilla, Julián; Díaz, Miguel Angel

2005-10-01

The authors retrospectively analyzed postransplantation events in 198 children who underwent hematopoietic stem cell transplantation (HSCT) between 1998 and 2002 to obtain a risk score for pediatric intensive care unit (PICU) admission and to ascertain variables predicting a poor outcome. Thirty-six patients (18%) were admitted to the PICU. Median age was 9 years (range 1-18). On univariate analysis, variables significantly associated with PICU admission were male gender (P = 0.01), more than first complete remission (P = 0.003), allogeneic transplantation (P = 0.001), engraftment syndrome (P = 0.03), and acute graft-versus-host disease grade of at least two (P = 0.05). According to this, patients were divided in two levels of risk (low and high), with a respective probability of PICU admission of 8.8 +/- 2.2% and 63.8 +/- 8.8% (P < 0.0001). Seventeen (47%) patients were discharged from the PICU. The probability of event-free survival after PICU admission at 3 years was 24.2 +/- 7%. On univariate analysis, variables with a negative impact on event-free survival were type of transplantation, inotropic support, a C-reactive protein level of at least 10 mg/dL, and a high O-PRISM score. On multivariate analysis, the only variable that influenced event-free survival was the O-PRISM score (< or =10 points, 54.6 +/- 15.3%; >10 points, 8.6 +/- 5.8%; P = 0.007). In conclusion, the risk of PICU admission may be easily estimated using simple variables. A high O-PRISM score at the time of PICU admission predicts a dismal outcome.

How strong was the 2015/2016 El Niño event?

NASA Astrophysics Data System (ADS)

Iskandar, Iskhaq; Lestari, DeniOkta; Utari, PutriAdia; Sari, QurniaWulan; Setiabudidaya, Dedi; Mardiansyah, Wijaya; Supardi; Rozirwan

2018-04-01

On the interannual timescale, the Indonesian climate is strongly influenced by a coupled ocean-atmosphere modes in the tropical Pacific Ocean. During a warm phase (El Niño event), negative sea surface temperature anomalies (SSTA) in the western tropical Pacific lead to suppress convection activities causing reduce precipitation over the maritime continent. The situation is reverse during the cold season(La Niña event). In this study, the evolution of 2015/2016 El Niño event is evaluated based on the collected data by the Tropical Atmosphere Ocean/Triangle Trans-Ocean Buoy Network (TAO/TRITON) buoys. The results show that the evolution of the event has started in boreal spring (April – May 2015). It came to thepeak in boreal fall/winter (October – December 2015). The event lasted until boreal spring before it terminated in April/May 2016. In addition, the intensity of the event is classified as a strong event, and it is one of the strongest El Niño events during the last three decades.

O-GlcNAc profiling: from proteins to proteomes

PubMed Central

2014-01-01

O-linked β-D-N-acetylglucosamine (O-GlcNAc) modification (O-GlcNAcylation) onto serine and threonine residues of proteins is an important post-translational modification (PTM), which is involved in many crucial biological processes including transcription, translation, proteasomal degradation, and signal transduction. Aberrant protein O-GlcNAcylation is directly linked to the pathological progression of chronic diseases including diabetes, cancer, and neurodegenerative disorders. Identification, site mapping, and quantification of O-GlcNAc proteins are a prerequisite to decipher their functions. In this review, we mainly focus on technological developments regarding O-GlcNAc protein profiling. Specifically, on one hand, we show how these techniques are being used for the comprehensive characterization of certain targeted proteins in which biologists are most interested. On the other hand, we present several newly developed approaches for O-GlcNAcomic profiling as well as how they provide us with a systems perspective to crosstalk amongst different PTMs and complicated biological events. Promising technical trends are also highlighted to evoke more efforts by diverse laboratories, which would further expand our understanding of the physiological and pathological roles of protein O-GlcNAcylation in chronic diseases. PMID:24593906

Tree-ring-based reconstruction of precipitation in the Bighorn Basin, Wyoming, since 1260 A.D

USGS Publications Warehouse

Gray, S.T.; Fastie, C.L.; Jackson, S.T.; Betancourt, J.L.

2004-01-01

Cores and cross sections from 79 Douglas fir (Pseudotsuga menziesii) and limber pine (Pinus flexilis) trees at four sites in the Bighorn Basin of north-central Wyoming and south-central Montana were used to develop a proxy for annual (June-June) precipitation spanning 1260-1998 A.D. The reconstruction exhibits considerable nonstationarity, and the instrumental era (post-1900) in particular fails to capture the full range of precipitation variability experienced in the past ???750 years. Both single-year and decadal-scale dry events were more severe before 1900. Dry spells in the late thirteenth and sixteenth centuries surpass both magnitude and duration of any droughts in the Bighorn Basin after 1900. Precipitation variability appears to shift to a higher-frequency mode after 1750, with 15-20-yr droughts becoming rare. Comparisons between instrumental and reconstructed values of precipitation and indices of Pacific basin variability reveal that precipitation in the Bighorn Basin generally responds to Pacific forcing in a manner similar to that of the southwestern United States (drier during La Nin??a events), but high country precipitation in areas surrounding the basin displays the opposite response (drier during El Nin??o events). ?? 2004 American Meteorological Society.

Real-Time Data Processing in the muon system of the D0 detector.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Neeti Parashar et al.

2001-07-03

This paper presents a real-time application of the 16-bit fixed point Digital Signal Processors (DSPs), in the Muon System of the D0 detector located at the Fermilab Tevatron, presently the world's highest-energy hadron collider. As part of the Upgrade for a run beginning in the year 2000, the system is required to process data at an input event rate of 10 KHz without incurring significant deadtime in readout. The ADSP21csp01 processor has high I/O bandwidth, single cycle instruction execution and fast task switching support to provide efficient multisignal processing. The processor's internal memory consists of 4K words of Program Memorymore » and 4K words of Data Memory. In addition there is an external memory of 32K words for general event buffering and 16K words of Dual port Memory for input data queuing. This DSP fulfills the requirement of the Muon subdetector systems for data readout. All error handling, buffering, formatting and transferring of the data to the various trigger levels of the data acquisition system is done in software. The algorithms developed for the system complete these tasks in about 20 {micro}s per event.« less

Causes of high O3 in the lower free troposphere over the Pacific Northwest as observed at the Mt. Bachelor Observatory

NASA Astrophysics Data System (ADS)

Ambrose, J. L.; Reidmiller, D. R.; Jaffe, D. A.

2011-09-01

We measured O3, CO, Hg, sub-micron particle scattering of mid-visible light (σsp), and water vapor (WV) at the Mt. Bachelor Observatory (MBO) in central Oregon, USA since 2004. The data were used to identify sources of large ozone enhancements in the lower free troposphere (FT). A total of 25 high-ozone events, defined as time periods when the 8-h averaged O3 mixing ratio was >70.0 ppbv, were recorded. The events occurred between early March and late September. For 18 of the 25 event days we were able to identify sources based on (1) relative enhancements of O3, CO, Hg and WV compared with the corresponding monthly distributions and (2) supporting data from the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model, the Navy Aerosol Analysis and Prediction System (NAAPS) global aerosol model, and Moderate Resolution Imaging Spectroradiometer (MODIS) satellite-derived active fire counts from the Fire Information for Resource Management System (FIRMS). Our analysis suggests that enhanced O3 levels during all the identified events were transported to MBO in the FT and were driven mostly by subsidence of O3-rich air masses from the upper troposphere/lower stratosphere (UT/LS), Asian long range transport (ALRT) and mixed ALRT + UT/LS influences. The UT/LS events were depleted in CO and total atmospheric mercury (TAM) compared to monthly median values. Levels of O3 and CO tended to be anti-correlated during UT/LS events, consistent with transport from clean regions in the UT. Conversely, the ALRT events were characterized by concomitant enhancements in CO and TAM with mean values during each event that were >70th percentile values for the months during which the events occurred. Unlike for UT/LS events, levels of O3 and CO during ALRT events tended to be correlated, consistent with photochemical O3 production in polluted air masses transported across the Pacific. The mixed ALRT + UT/LS events exhibited characteristics that were intermediate between those of the ALRT and UT/LS events. For the classifiable cases the fractional distribution of each event type was: UT/LS, ˜44% (n = 8); ALRT + UT/LS, ˜33% (n = 6); ALRT, ˜22% (n = 4). In terms of the total number of classifiable high-ozone event hours UT/LS, ALRT + UT/LS and ALRT events accounted for ˜52% (t = 85), ˜36% (t = 59) and ˜13% (t = 21), respectively. The results indicate that downward mixing of O3-rich air masses from the UT/LS together with trans-Pacific transport of urban/industrial and biomass burning emissions from the Asian continent are the most important mechanisms for delivering high O3 levels (i.e., 8-h averages >70.0 ppbv) to the lower FT in the Pacific Northwest.

Glutathione cycle activity and pyridine nucleotide levels in oxidant-induced injury of cells.

PubMed Central

Schraufstätter, I U; Hinshaw, D B; Hyslop, P A; Spragg, R G; Cochrane, C G

1985-01-01

Exposure of target cells to a bolus of H2O2 induced cell lysis after a latent period of several hours, which was prevented only when the H2O2 was removed within the first 30 min of injury by addition of catalase. This indicated that early metabolic events take place that are important in the fate of the cell exposed to oxidants. In this study, we described two early and independent events of H2O2-induced injury in P388D1 macrophagelike tumor cells: activation of the glutathione cycle and depletion of cellular NAD. Glutathione cycle and hexose monophosphate shunt (HMPS) were activated within seconds after the addition of H2O2. High HMPS activity maintained glutathione that was largely reduced. However, when HMPS activity was inhibited--by glucose depletion or by incubation at 4 degrees C--glutathione remained in the oxidized state. Total pyridine nucleotide levels were diminished when cells were exposed to H2O2, and the breakdown product, nicotinamide, was recovered in the extracellular medium. Intracellular NAD levels fell by 80% within 20 min of exposure of cells to H2O2. The loss of NADP(H) and stimulation of the HMPS could be prevented when the glutathione cycle was inhibited by either blocking glutathione synthesis with buthionine sulfoximine (BSO) or by inhibiting glutathione reductase with (1,3-bis) 2 chlorethyl-1-nitrosourea. The loss of NAD developed independently of glutathione cycle and HMPS activity, as it also occurred in BSO-treated cells. PMID:3840176

Baseflow separation in a premontane transitional rainforest using stable isotope techniques

NASA Astrophysics Data System (ADS)

Miller, G. R.; DuMont, A.; Roark, E.; Cahill, A. T.; Brumbelow, J. K.

2013-12-01

Hydrologic, geologic, and biologic processes are critical to understanding the ecosystem in the tropical premontane transitional forests of Costa Rica. Precipitation is significantly lower during the dry season, and incoming rainfall can be completely intercepted and re-evaporated by the canopy during light events. These canopy processes can affect the rates of runoff and infiltration by changing the quantity and timing of rainfall reaching the ground surface. However, the resulting partitioning of stream water sources between event-water and baseflow from groundwater is not well quantified due to limited accessibility and complex subsurface conditions. This study focuses on research conducted at the Texas A&M Soltis Center for Education and Research, near San Ramón, Costa Rica. We have monitored a 2.2 ha watershed there, measuring precipitation and transpiration rates for over two years, and groundwater levels and stream flow rates for nearly one year. Precipitation rates for the watershed averaged 4.4 m/yr since 2010. Stream flow (runoff, spring flow, and baseflow) averaged 0.09 m^3/sec during the 2012-2013 wet seasons. At 1.2 mm/day, transpiration was a relatively minor component of the water budget. Over a 40-day span during summer 2013, we collected a combination of daily and rain-event based samples from locations throughout the watershed. Sources included: the main stream and two small tributaries, groundwater from piezometers, pore water from suction lysimeters, throughfall and stemflow from under canopy collection systems, and xylem water from 8 tree species across the watershed. We then measured stable isotope fractions (δ18O and δD) in the water using a Picarro L2120i CRDS. Isotope ratios for all surface water averaged -5.50‰ for δ18O and -28.00‰ for δD, while that measured under baseflow conditions were -5.45‰ for δ18O and -29.18‰ for δD. These results indicate that baseflow is the dominate source of stream water even in the wet season. We additionally conclude that despite the ubiquity of low permeability Andisols in this watershed, groundwater transport to the stream is characterized by short residence times attributable to macropore/fracture flow in the subsurface.

Plasma characteristics of upflowing ion beams in the polar cap region

NASA Technical Reports Server (NTRS)

Chen, M. W.; Ashour-Abdalla, M.; Peterson, W. K.; Moore, T. E.; Persoon, A. M.

1990-01-01

The plasma characteristics of upflowing ion stream events with energies greater than 10 eV in the polar cap region near solar maximum are analyzed. It is found that, in 22 of the 41 polar ion streaming events studied, O(+) is the dominant ion constituent in the upflowing beam components. There are significant amounts of upflowing O(+) in the plasma even during quiet auroral conditions. In one event, the upflowing O(+) population had two components, a cold distribution and a warm one. In another event the O(+) and H(+) temperatures suggested that ionospheric ions are heated. The cold upflowing ion stream component observed in some of the polar ion streaming events exhibited a filamentary nature. A significant amount of He(+) was also found in some of the events studied.

First scintillating bolometer tests of a CLYMENE R&D on Li2MoO4 scintillators towards a large-scale double-beta decay experiment

NASA Astrophysics Data System (ADS)

Buşe, G.; Giuliani, A.; de Marcillac, P.; Marnieros, S.; Nones, C.; Novati, V.; Olivieri, E.; Poda, D. V.; Redon, T.; Sand, J.-B.; Veber, P.; Velázquez, M.; Zolotarova, A. S.

2018-05-01

A new R&D on lithium molybdate scintillators has begun within a project CLYMENE (Czochralski growth of Li2MoO4 crYstals for the scintillating boloMeters used in the rare EveNts sEarches). One of the main goals of the CLYMENE is a realization of a Li2MoO4 crystal growth line to be complementary to the one recently developed by LUMINEU in view of a mass production capacity for CUPID, a next-generation tonne-scale bolometric experiment to search for neutrinoless double-beta decay. In the present paper we report the investigation of performance and radiopurity of 158-g and 13.5-g scintillating bolometers based on a first large-mass (230 g) Li2MoO4 crystal scintillator developed within the CLYMENE project. In particular, a good energy resolution (2-7 keV FWHM in the energy range of 0.2-5 MeV), one of the highest light yield (0.97 keV/MeV) amongst Li2MoO4 scintillating bolometers, an efficient alpha particles discrimination (10 σ) and potentially low internal radioactive contamination (below 0.2-0.3 mBq/kg of U/Th, but 1.4 mBq/kg of 210Po) demonstrate prospects of the CLYMENE in the development of high quality and radiopure Li2MoO4 scintillators for CUPID.

Horizontal and vertical structure of reactive bromine events probed by bromine monoxide MAX-DOAS

NASA Astrophysics Data System (ADS)

Simpson, William R.; Peterson, Peter K.; Frieß, Udo; Sihler, Holger; Lampel, Johannes; Platt, Ulrich; Moore, Chris; Pratt, Kerri; Shepson, Paul; Halfacre, John; Nghiem, Son V.

2017-08-01

Heterogeneous photochemistry converts bromide (Br-) to reactive bromine species (Br atoms and bromine monoxide, BrO) that dominate Arctic springtime chemistry. This phenomenon has many impacts such as boundary-layer ozone depletion, mercury oxidation and deposition, and modification of the fate of hydrocarbon species. To study environmental controls on reactive bromine events, the BRomine, Ozone, and Mercury EXperiment (BROMEX) was carried out from early March to mid-April 2012 near Barrow (Utqiaġvik), Alaska. We measured horizontal and vertical gradients in BrO with multiple-axis differential optical absorption spectroscopy (MAX-DOAS) instrumentation at three sites, two mobile and one fixed. During the campaign, a large crack in the sea ice (an open lead) formed pushing one instrument package ˜ 250 km downwind from Barrow (Utqiaġvik). Convection associated with the open lead converted the BrO vertical structure from a surface-based event to a lofted event downwind of the lead influence. The column abundance of BrO downwind of the re-freezing lead was comparable to upwind amounts, indicating direct reactions on frost flowers or open seawater was not a major reactive bromine source. When these three sites were separated by ˜ 30 km length scales of unbroken sea ice, the BrO amount and vertical distributions were highly correlated for most of the time, indicating the horizontal length scales of BrO events were typically larger than ˜ 30 km in the absence of sea ice features. Although BrO amount and vertical distribution were similar between sites most of the time, rapid changes in BrO with edges significantly smaller than this ˜ 30 km length scale episodically transported between the sites, indicating BrO events were large but with sharp edge contrasts. BrO was often found in shallow layers that recycled reactive bromine via heterogeneous reactions on snowpack. Episodically, these surface-based events propagated aloft when aerosol extinction was higher (> 0.1 km-1); however, the presence of aerosol particles aloft was not sufficient to produce BrO aloft. Highly depleted ozone (< 1 nmol mol-1) repartitioned reactive bromine away from BrO and drove BrO events aloft in cases. This work demonstrates the interplay between atmospheric mixing and heterogeneous chemistry that affects the vertical structure and horizontal extent of reactive bromine events.

Aging and Visual Function of Military Pilots: A Review

DTIC Science & Technology

1982-08-01

of the Soc. for Inf. Disp. 21:219- 227. 24. Ginsburg. A. P .. M. W. Cannon, R. Sekuler, D . Evans, C . Owsley, and P ... the Institute of Medicine. This work relates to Department of Navy Contract N0OOI48O- C - 0159 issued by the Office of Naval Research under Contract...loss with age in the temporal resolving power of the visual system. Temporally con- tiguous visual events that would be seen as separate

Causes of high O3 in the lower free troposphere over the Pacific Northwest as observed at the Mt. Bachelor Observatory

NASA Astrophysics Data System (ADS)

Ambrose, J. L.; Reidmiller, D.; Jaffe, D. A.

2011-12-01

We measured O3, CO, Hg, sub-micron particle scattering of mid-visible light (σsp), and water vapor (WV) at the Mt. Bachelor Observatory (MBO) in central Oregon, USA since 2004. The data were used to identify sources of large ozone enhancements in the lower free troposphere (FT) from 2004-2009. A total of 25 high-ozone events, defined as time periods when the 8-hr averaged O3 mixing ratio was >70.0 ppbv, were recorded. The events occurred between early March and late September. For 18 of the 25 event days we were able to identify sources based on (1) relative enhancements of O3, CO, Hg and WV compared with the corresponding monthly distributions and (2) supporting data from the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model, the Navy Aerosol Analysis and Prediction System (NAAPS) global aerosol model, and Moderate Resolution Imaging Spectroradiometer (MODIS) satellite-derived active fire counts from the Fire Information for Resource Management System (FIRMS). Our analysis suggests that enhanced O3 levels during all the identified events were transported to MBO in the FT and were driven mostly by subsidence of O3-rich air masses from the upper troposphere/lower stratosphere (UT/LS), Asian long range transport (ALRT) and mixed ALRT+UT/LS influences. The UT/LS events were depleted in CO and total atmospheric mercury (TAM) compared to monthly median values. Levels of O3 and CO tended to be anti-correlated during UT/LS events, consistent with transport from clean regions in the UT. Conversely, the ALRT events were characterized by concomitant enhancements in CO and TAM with mean values during each event that were >70th percentile values for the months during which the events occurred. Unlike for UT/LS events, levels of O3 and CO during ALRT events tended to be correlated, consistent with photochemical O3 production in polluted air masses transported across the Pacific. The mixed ALRT+UT/LS events exhibited characteristics that were intermediate between those of the ALRT and UT/LS events. For the classifiable cases the fractional distribution of each event type was: UT/LS, ~44% (n=8); ALRT+UT/LS, ~33% (n=6); ALRT, ~22% (n=4). In terms of the total number of classifiable high-ozone event hours UT/LS, ALRT+UT/LS and ALRT events accounted for ~52% (t=85), ~36% (t=59) and ~13% (t=21), respectively. The results indicate that downward mixing of O3-rich air masses from the UT/LS together with trans-Pacific transport of urban/industrial and biomass burning emissions from the Asian continent are the most important mechanisms for delivering high O3 levels (i.e., 8-hr averages >70.0 ppbv) to the lower FT in the Pacific Northwest. The high-ozone event characterization methodology developed from the 2004-2009 data set is further applied to observations made at MBO during 2010 and 2011.

Diversity of moderate El Niño events evolution: role of air-sea interactions in the eastern tropical Pacific

NASA Astrophysics Data System (ADS)

Dewitte, Boris; Takahashi, Ken

2017-12-01

In this paper we investigate the evolution of moderate El Niño events during their developing phase with the objective to understand why some of them did not evolve as extreme events despite favourable conditions for the non-linear amplification of the Bjerknes feedback (i.e. warm SST in Austral winter in the eastern equatorial Pacific). Among the moderate events, two classes are considered consisting in the Eastern Pacific (EP) El Niño events and Central Pacific (CP) events. We first show that the observed SST variability across moderate El Niño events (i.e. inter-event variability) is largest in the far eastern Pacific (east of 130°W) in the Austral winter prior to their peak, which is associated to either significant warm anomaly (moderate EP El Niño) or an anomaly between weak warm and cold (moderate CP El Niño) as reveals by the EOF analysis of the SST anomaly evolution during the development phase of El Niño across the El Niño years. Singular value decomposition (SVD) analysis of SST and wind stress anomalies across the El Niño years further indicates that the inter-event SST variability is associated with an air-sea mode explaining 31% of the covariance between SST and wind stress. The associated SST pattern consists in SST anomalies developing along the coast of Ecuador in Austral fall and expanding westward as far as 130°W in Austral winter. The associated wind stress pattern features westerlies (easterlies) west of 130°W along the equator peaking around June-August for EP (CP) El Niño events. This air-sea mode is interpreted as resulting from a developing seasonal Bjerknes feedback for EP El Niño events since it is shown to be associated to a Kelvin wave response at its peak phase. However equatorial easterlies east of 130°W emerge in September that counters the growing SST anomalies associated to the air-sea mode. These have been particularly active during both the 1972 and the 2015 El Niño events. It is shown that the easterlies are connected to an off-equatorial southerly wind off the coast of Peru and Ecuador. The southerly wind is a response to the coastal SST anomalies off Peru developing from Austral fall. Implications of our results for the understanding of the seasonal ENSO dynamics and diversity are discussed in the light of the analysis of two global climate models simulating realistically ENSO diversity (GFDL_CM2.1 and CESM).

Whole Atmosphere Community Climate Model With Lower Ionospheric Chemistry: Improved Modeling of Nitric Acid and Active Chlorine During Energetic Particle Precipitation

NASA Astrophysics Data System (ADS)

Verronen, P. T.; Andersson, M. E.; Marsh, D. R.; Kovacs, T.; Plane, J. M. C.; Päivärinta, S. M.

2016-12-01

Energetic particle precipitation (EPP) and ion chemistry affect the neutral composition of the polar middle atmosphere. For example, production of odd nitrogen and odd hydrogen during EPP events can decrease ozone by tens of percent. However, the standard ion chemistry parameterizations used in atmospheric models neglect the effects on some important species, such as nitric acid. We present WACCM-D, a variant of the Whole Atmosphere Community Climate Model, which includes a set of lower ionosphere (D-region) chemistry: 307 reactions of 20 positive ions and 21 negative ions. Compared to the Sodankylä Ion and Neutral Chemistry (SIC), a state-of-the-art 1-D model of the D-region chemistry, WACCM-D represents the lower ionosphere well. Comparison of ion concentrations between the models shows that the WACCM-D bias is typically within ±10% or less below 70 km. At 70-90 km, when strong altitude gradients in ionization rates and/or ion concentrations exist, the bias can be larger for some ions but is still within tens of percent. We also compare WACCM-D results for the January 2005 solar proton event (SPE) to those from the standard WACCM and observations from the Aura/MLS and SCISAT/ACE-FTS instruments. The results indicate that WACCM-D improves the modeling of {HNO3}, {HCl}, {ClO}, {OH}, and {NOx} during the SPE. For example, Northern Hemispheric {HNO3} from WACCM-D shows an increase by two orders of magnitude at 40-70 km compared to WACCM, reaching 2.6 ppbv, in agreement with the observations. Based on our results, WACCM-D provides a state-of-the-art global representation of D-region ion chemistry and improves modeling of EPP atmospheric effects considerably.

Phenolic and lignan glycosides from the butanol extract of Averrhoa carambola L. root.

PubMed

Wen, Qingwei; Lin, Xing; Liu, Yeqi; Xu, Xiaohui; Liang, Tao; Zheng, Ni; Kintoko; Huang, Renbin

2012-10-19

Fifteen compounds, which included six chiral lignans and nine phenolic glycosides, were separated from the butanol fraction of Averrhoa carambola L. root and identified. All of the compounds, namely 3,4,5-trimethoxyphenol-1-O-β-D-glucopyranoside, benzyl-1-O-β-D-glucopyranoside, (+)-5'-methoxyisolariciresinol 3α-O-β-D-gluco-pyranoside, (+)-isolariciresinol 3α-O-β-D-glucopyranoside, koaburaside, (+)-lyoniresinol 3α-O-β-D-glucopyranoside, (-)-lyoniresinol 3α-O-β-D-glucopyranoside, (-)-5'-methoxyisolariciresinol 3α-O-β-D-glucopyranoside, (-)-isolariciresinol 3α-O-β-D-glucopyranoside, 3,5-dimethoxy-4-hydroxyphenyl 1-O-β-apiofuranosyl (1''→6')-O-β-D-glucopyranoside, 3,4,5-trimethoxyphenyl 1-O-β-apiofuranosyl (1''→6')-β-gluco-pyranoside, methoxyhydroquinone-4-β-D-glucopyranoside, (2S)-2-O-β-D-gluco-pyranosyl-2-hydroxyphenylacetic acid, 3-hydroxy-4-methoxyphenol 1-O-β-D-apio-furanosyl-(1''→6')-O-β-D-glucopyranoside and 4-hydroxy-3-methoxyphenol 1-O-β-D-apiofuranosyl-(1''→6')-O-β-D-glucopyranoside were isolated from this plant for the first time.

Synthesis of methyl 2-O-alpha-D-mannopyranosyl-alpha-D-talopyranoside and methyl 2-O-alpha-D-talopyranosyl-alpha-D-talopyranoside.

PubMed

Jain, R K; Dubey, R; Abbas, S A; Matta, K L

1987-03-15

Treatment of methyl 3-O-benzyl-2-O-(2,3,4,6-tetra-O-acetyl-alpha-D-mannopyranosyl)-alpha-D- mannopyranoside (1) with tert-butyldiphenylsilyl chloride in N,N-dimethylformamide afforded methyl 3-O-benzyl-6-O-tert-butyldiphenylsilyl-2-O-(2,3,4,6-tetra-O-acetyl -alpha-D- mannopyranosyl)-alpha-D-mannopyranoside (2). Oxidation of 2 with pyridinium chlorochromate, followed by reduction of the carbonyl group, and subsequent O-deacetylation afforded methyl 3-O-benzyl-6-O-tert-butyldiphenylsilyl-2-O-alpha-D-mannopyranosyl- alpha-D- talopyranoside (5). Cleavage of the tert-butyldiphenylsilyl group of 5 with tetrabutylammonium fluoride in oxolane, followed by hydrogenolysis, gave methyl 2-O-alpha-D-mannopyranosyl-alpha-D-talopyranoside (7). O-Deacetylation of 1 gave methyl 3-O-benzyl-2-O-alpha-D-mannopyranosyl-alpha-D-mannopyranoside (8). Treatment of 8 with tert-butyldiphenylsilyl chloride afforded a 6,6'-disilyl derivative, which was converted into a 2',3'-O-isopropylidene derivative, and then further oxidized with pyridinium chlorochromate. The resulting diketone was reduced and removal of the protecting groups gave methyl 2-O-alpha-D-talopyranosyl-alpha-D-talopyranoside (15). The structures of both 7 and 15 were established by 13C-n.m.r. spectroscopy.

Impact of nitrate-enhanced leachate recirculation on gaseous releases from a landfill bioreactor cell

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tallec, G.; Bureau, C.; Peu, P.

2009-07-15

This study evaluates the impact of nitrate injection on a full scale landfill bioreactor through the monitoring of gaseous releases and particularly N{sub 2}O emissions. During several weeks, we monitored gas concentrations in the landfill gas collection system as well as surface gas releases with a series of seven static chambers. These devices were directly connected to a gas chromatograph coupled to a flame ionisation detector and an electron capture detector (GC-FID/ECD) placed directly on the field. Measurements were performed before, during and after recirculation of raw leachate and nitrate-enhanced leachate. Raw leachate recirculation did not have a significant effectmore » on the biogas concentrations (CO{sub 2}, CH{sub 4} and N{sub 2}O) in the gas extraction network. However, nitrate-enhanced leachate recirculation induced a marked increase of the N{sub 2}O concentrations in the gas collected from the recirculation trench (100-fold increase from 0.2 ppm to 23 ppm). In the common gas collection system however, this N{sub 2}O increase was no more detectable because of dilution by gas coming from other cells or ambient air intrusion. Surface releases through the temporary cover were characterized by a large spatial and temporal variability. One automated chamber gave limited standard errors over each experimental period for N{sub 2}O releases: 8.1 {+-} 0.16 mg m{sup -2} d{sup -1} (n = 384), 4.2 {+-} 0.14 mg m{sup -2} d{sup -1} (n = 132) and 1.9 {+-} 0.10 mg m{sup -2} d{sup -1} (n = 49), during, after raw leachate and nitrate-enhanced leachate recirculation, respectively. No clear correlation between N{sub 2}O gaseous surface releases and recirculation events were evidenced. Estimated N{sub 2}O fluxes remained in the lower range of what is reported in the literature for landfill covers, even after nitrate injection.« less

Effects of titanium dioxide (TiO2 ) nanoparticles on caribbean reef-building coral (Montastraea faveolata).

PubMed

Jovanović, Boris; Guzmán, Héctor M

2014-06-01

Increased use of manufactured titanium dioxide nanoparticles (nano-TiO2 ) is causing a rise in their concentration in the aquatic environment, including coral reef ecosystems. Caribbean mountainous star coral (Montastraea faveolata) has frequently been used as a model species to study gene expression during stress and bleaching events. Specimens of M. faveolata were collected in Panama and exposed for 17 d to nano-TiO2 suspensions (0.1 mg L(-1) and 10 mg L(-1) ). Exposure to nano-TiO2 caused significant zooxanthellae expulsion in all the colonies, without mortality. Induction of the gene for heat-shock protein 70 (HSP70) was observed during an early stage of exposure (day 2), indicating acute stress. However, there was no statistical difference in HSP70 expression on day 7 or 17, indicating possible coral acclimation and recovery from stress. No other genes were significantly upregulated. Inductively coupled plasma mass spectrometry analysis revealed that nano-TiO2 was predominantly trapped and stored within the posterior layer of the coral fragment (burrowing sponges, bacterial and fungal mats). The bioconcentration factor in the posterior layer was close to 600 after exposure to 10 mg L(-1) of nano-TiO2 for 17 d. The transient increase in HSP70, expulsion of zooxanthellae, and bioaccumulation of nano-TiO2 in the microflora of the coral colony indicate the potential of such exposure to induce stress and possibly contribute to an overall decrease in coral populations. © 2014 SETAC.

Analysis of δ18O and δD values of environmental waters at high temporal and spatial resolution by continuous diffusion sampling cavity ring-down spectrometry

NASA Astrophysics Data System (ADS)

Munksgaard, Niels; Bass, Adrian; Wurster, Chris; Bird, Michael

2013-04-01

A novel sampling device utilises diffusion through porous PTFE tubing to deliver water vapour continuously from a liquid water source for analysis of δ18O and δD values by Cavity Ring-Down Spectrometry (CRDS). Comparison of isotopic data for a range of water samples analysed by Diffusion Sampling-CRDS (DS-CRDS) and Isotope Ratio Mass Spectrometry (IRMS) shows significant linear correlations between the two methods allowing for accurate standardisation of DS-CRDS data. The internal precision for an integration period of 3 min (standard deviation = 0.1 ‰ and 0.3 ‰ for δ18O and δD values, respectively) is similar to analysis of water by injection/evaporation CRDS of discrete water samples. The isotopic effects of variable air and water temperature, water vapour concentration and water pumping rate were found to be either negligible or correctable by analysis of water standards. Separation of the analysed water vapour from non-volatile dissolved and particulate contaminants in the liquid sample minimises interferences associated with CRDS analyses of many aqueous samples. Coupling of the DS-CRDS instrument to an auto sampler enables rapid analysis (10 min) of discrete water samples. The DS-CRDS system was used in the first continuous shipboard measurement of δ18O and δD of water. Combined with continuous salinity recordings, a data set of nearly 6,000 isotope measurements was made at 30-s intervals during a 3-day voyage through the Great Barrier Reef Lagoon. Precise identification of river plumes within the Great Barrier Reef Lagoon was possible because unique δ18O/δD-salinity relationships of individual plumes were measured at high spatial and temporal resolution. Continuous shipboard measurement of δ18O/δD values by DS-CRDS provides additional discriminatory power for assessing water mass formation processes and histories at a small fraction of the cost of traditional isotope analysis of discrete samples. In a second application of DS-CRDS, continuous real-time analysis, at 30-s intervals, of precipitation at an Australian tropical location revealed extreme and rapidly changing δ18O and δD values related to variations in moisture source areas, transport paths and precipitation histories. The range of δ18O (-19.6 ‰ to +2.6 ‰) and δD (-140 ‰ to +13 ‰) values from almost 6,000 measurements of nine rain events over 15 days during an 8-month period at a single location was comparable with the range measured in 1532 monthly samples from all seven Australian Global Network of Isotopes in Precipitation stations from 1962 to 2002. Extreme variations in δ18O (-8.7 ‰ to -19.6 ‰) and δD (-54 ‰ to -140 ‰) were recorded within a single 4-h period. Real-time stable isotope monitoring of environmental waters at high temporal and spatial resolution enables new and powerful tracer applications in climatology, hydrology, eco-physiology and palaeo-climatology.

Automated Screening of Children With Obstructive Sleep Apnea Using Nocturnal Oximetry: An Alternative to Respiratory Polygraphy in Unattended Settings

PubMed Central

Álvarez, Daniel; Alonso-Álvarez, María L.; Gutiérrez-Tobal, Gonzalo C.; Crespo, Andrea; Kheirandish-Gozal, Leila; Hornero, Roberto; Gozal, David; Terán-Santos, Joaquín; Del Campo, Félix

2017-01-01

Study Objectives: Nocturnal oximetry has become known as a simple, readily available, and potentially useful diagnostic tool of childhood obstructive sleep apnea (OSA). However, at-home respiratory polygraphy (HRP) remains the preferred alternative to polysomnography (PSG) in unattended settings. The aim of this study was twofold: (1) to design and assess a novel methodology for pediatric OSA screening based on automated analysis of at-home oxyhemoglobin saturation (SpO2), and (2) to compare its diagnostic performance with HRP. Methods: SpO2 recordings were parameterized by means of time, frequency, and conventional oximetric measures. Logistic regression models were optimized using genetic algorithms (GAs) for three cutoffs for OSA: 1, 3, and 5 events/h. The diagnostic performance of logistic regression models, manual obstructive apnea-hypopnea index (OAHI) from HRP, and the conventional oxygen desaturation index ≥ 3% (ODI3) were assessed. Results: For a cutoff of 1 event/h, the optimal logistic regression model significantly outperformed both conventional HRP-derived ODI3 and OAHI: 85.5% accuracy (HRP 74.6%; ODI3 65.9%) and 0.97 area under the receiver operating characteristics curve (AUC) (HRP 0.78; ODI3 0.75) were reached. For a cutoff of 3 events/h, the logistic regression model achieved 83.4% accuracy (HRP 85.0%; ODI3 74.5%) and 0.96 AUC (HRP 0.93; ODI3 0.85) whereas using a cutoff of 5 events/h, oximetry reached 82.8% accuracy (HRP 85.1%; ODI3 76.7) and 0.97 AUC (HRP 0.95; ODI3 0.84). Conclusions: Automated analysis of at-home SpO2 recordings provide accurate detection of children with high pretest probability of OSA. Thus, unsupervised nocturnal oximetry may enable a simple and effective alternative to HRP and PSG in unattended settings. Citation: Álvarez D, Alonso-Álvarez ML, Gutiérrez-Tobal GC, Crespo A, Kheirandish-Gozal L, Hornero R, Gozal D, Terán-Santos J, Del Campo F. Automated screening of children with obstructive sleep apnea using nocturnal oximetry: an alternative to respiratory polygraphy in unattended settings. J Clin Sleep Med. 2017;13(5):693–702. PMID:28356177

Cerebral oxygenation during intermittent hypoxemia and bradycardia in preterm infants.

PubMed

Schmid, Manuel B; Hopfner, Reinhard J; Lenhof, Susanne; Hummler, Helmut D; Fuchs, Hans

2015-01-01

Episodes of hypoxemia and bradycardia frequently occur with apnea of prematurity in preterm infants. Little is known about the impact of different event types on the brain. To describe the influence of hypoxemia and bradycardia, either isolated or in combination, on cerebral oxygenation. In 16 preterm infants with intermittent hypoxemia and/or bradycardia, cerebral tissue oxygen saturation (StO2, as measured by near-infrared spectroscopy), heart rate and pulse oximetric saturation (SpO2) were recorded simultaneously for 16 h. Events were classified as isolated bradycardia (type 1), isolated hypoxemia (type 2) or combined (simultaneous, type 3; bradycardia first, type 4; hypoxemia first, type 5). Primary outcome was a score representing the area below baseline for cerebral StO2 desaturation during an event. Secondary outcomes were duration and depth of cerebral desaturation. Patients had a median (range) gestational age of 25.9 (22.6-30.4) weeks and a postnatal age of 32.5 (7-58) days. The median (quartiles) number of events was 49 (34-58). Isolated hypoxemias were the most frequent events (24; 9-36) and isolated bradycardias the least common (0; 0-1). Cerebral StO2 baseline was not different between event types. Cerebral desaturation score, duration of event and depth of cerebral desaturation were smallest for isolated bradycardias and largest for combined events, especially for those starting with hypoxemia followed by bradycardia. Regardless of event type, 12/16 infants maintained cerebral StO2 >60% despite severe SpO2 desaturations. Isolated bradycardias had the lowest impact on cerebral desaturation, and combined events had the highest. Most infants preserved cerebral oxygenation >60% during events. © 2014 S. Karger AG, Basel.

JHSS Baseline Shaft and Strut (BSS) Model 5653-3 Added Resistance and Powering and Ship Motions, Sea State 6 Random Waves and Regular Waves

DTIC Science & Technology

2009-04-01

00 CM CM T- T— (OOOk/dM) 9SS ui Ja/wod (Qd) p9J3A!|aa S ( 3d ) 9A|pay3 o CO o CO o ŗ- o CM (lAJdU) peads Janadojd o o o CO o CO o o...8217 o o o o o o o o o LO o LO o LO o LO o LO CO CM CM (OOOl/dL)) J8M0d (Qd) paJaAiiaa S ( 3d ) 9A|109JJ3 t n < U u ed £ LO u o U •<r o a...aseajoui Qd S 3d CM O 00 CO ^t CM JSIW UUIBO SA ges (OOOl/dM) Qd S 3d P9PPV § § o 9 o CM (Wda) pssds jeiiadojd o o o 00 o CO o o CM 1

Reconstructing the spatio-temporal variability of the southwestern Pacific salinity front from coral d18O records

NASA Astrophysics Data System (ADS)

Hasson, A. E. A.; Dassie, E. P.; Khodri, M.; Linsley, B. K.

2016-12-01

The South Pacific Convergence Zone (SPCZ) is a major atmospheric feature of the southern hemisphere. It is a low atmospheric convergence band associated with intense precipitations. Its position and intensity responds to global changes but also modulates regional weather patterns. Interannual to long-term SPCZ modifications result in extreme events such as severe droughts or flooding with profound socio-economic consequences. The SPCZ oceanic counterpart is a large body of fresh water (SSS<34.5 pss) extending southeast from the Maritime Continent to the dateline. This freshpool is separated from the high-salinity waters of the South Pacific gyre to the west by a steep salinity front. Various studies have shown a freshening of the freshpool and its southeastward expansion since the 1950s, modulated by interannual to interdecadal variability (Cravatte et al., 2009). The scarcity of traditional SSS measurements limits our ability to describe accurately this variability. This study validates the use of coral d18O as a proxy for the reconstruction of SSS over the last 200 years. Derived SSS is validated against insitu data at 3 different locations along the SSS front (Fiji, Tonga and Rarotonga Islands). This new dataset enables us to investigate the spatio-temporal variations of the SSS front prior to the instrumental data. Two robust modes of variability are present in the reconstructed SSS datasets: interannual variability and a secular trend. The reconstructed SSS variability follows the major El Niño Southern Oscillation indices. The relative SSS anomalies at each site provide information on the possible strength of the captured El Niño events. The three sites present secular trends toward fresher conditions. Furthermore, the role of atmospheric freshwater fluxes on SSS variability is evaluated by comparing reconstructed SSS to available historical rain gauge data. Results highlight the role of both atmospheric freshwater fluxes and ocean dynamics on SSS variability.

Oxygen Isotopes in Fresh Water Biogenic Opal: Northeastern US Alleroed-Younger Dryas Temperature Shift

NASA Technical Reports Server (NTRS)

Shemesh, Aldo; Peteet, Dorothy

1997-01-01

The first oxygen isotope analysis of biogenic opal from lake sediments, from the Allerod/Younger Dryas transition in a core from Linsley Pond, Connecticut, gives an average estimate of a 6 C drop in temperature during the Younger Dryas. This shift represents temperatures during the bloom season, and may be less than the winter temperature drop. The sharp transition itself, with a duration of about 200 years, suggests that the temperature decrease may have been as large as 12 C. Previous estimates of the Allerod/Younger Dryas temperature shifts are controversial, and range from 3-20 C, suggesting that further interdisciplinary research on the same samples is warranted. One way that global climate change manifests itself is by redistributing energy throughout the globe. The Northern Hemisphere latitudinal temperature gradient during the late-glacial is at present a controversial topic. The magnitude of air temperature shifts during the Allerod/Younger Dryas (YD) oscillation are estimated from mid-latitude pollen records surrounding the North Atlantic to be 3-5 C in Europe [Lowe et al., 19941 and 3-4 C in the eastern US [Peteet et al., 1993]. In contrast, lake temperatures estimates derived from aquatic midge larvae in the Canadian eastern maritimes and Maine range from 6-20 C, with larger shifts at more southern sites [Levesque et al., 1997]. The magnitude of YD cooling in Greenland ice cores ranges from at least 7 C from the Bolling warming [Dansgaard et al., 1989] to 15 C - a more recent estimate from borehole temperatures [Cuffey et al., 1995]. The ice core geochemical records reveal that massive frequent and short-term (decadal or less) changes in atmospheric composition occurred throughout this event, suggesting a very dynamic circulation [Mayewski et al., 1993).

Genome-wide set of SNPs reveals evidence for two glacial refugia and admixture from postglacial recolonization in an alpine ungulate.

PubMed

Sim, Zijian; Hall, Jocelyn C; Jex, Bill; Hegel, Troy M; Coltman, David W

2016-08-01

Past glaciation events have played a major role in shaping the genetic diversity and distribution of wild sheep in North America. The advancement of glaciers can isolate populations in ice-free refugia, where they can survive until the recession of ice sheets. The major Beringian refugium is thought to have held thinhorn sheep (Ovis dalli) populations during times of glacial advance. While isolation in the major refugium can account for much of the genetic and morphological diversity seen in extant thinhorn sheep populations, mounting evidence suggests the persistence of populations in smaller minor refugia. We investigated the refugial origins of thinhorn sheep using ~10 000 SNPs obtained via a cross-species application of the domestic sheep ovine HD BeadChip to genotype 52 thinhorn sheep and five bighorn sheep (O. canadensis) samples. Phylogenetic inference revealed a distinct lineage of thinhorn sheep inhabiting British Columbia, which is consistent with the survival of a group of thinhorn sheep in a minor refugium separate from the Beringian refugium. Isolation in separate glacial refugia probably mediated the evolution of the two thinhorn sheep subspecies, the white Dall's sheep (O. d. dalli), which persisted in Beringia, and the dark Stone's sheep (O. d. stonei), which utilized the minor refugium. We also found the first genetic evidence for admixture between sheep from different glacial refugia in south-central Yukon as a consequence of post glacial expansion and recolonization. These results show that glaciation events can have a major role in the evolution of species inhabiting previously glaciated habitats and the need to look beyond established refugia when examining the evolutionary history of such species. © 2016 John Wiley & Sons Ltd.

Environmental change in subtropical southern Africa since the Last Glacial Maximum: a case study from Etosha Pan

NASA Astrophysics Data System (ADS)

Mauz, Barbara

2014-05-01

Millennial-scale climate shifts described by Heinrich Events and Dansgard-Oeschger Cycles occurred in the Northern and Southern Hemispheres asynchronously. It has been suggested that combined influence of the oceanic bipolar seesaw and the southward displacement of the south hemisphere (SH) westerlies, both linked to northern stadials, allowed the high southern latitudes to warm as a result of melting and collapse of NH ice sheets (Denton et al. 2010). For tropical southern Africa most terrestrial records delivering observational data for such climate scenario are derived from east African rift valley lakes (e.g. Olaka et al., 2010) but further to the west data are sparse. Here we report about a palaeoclimate proxy extracted from Etosha Pan, a vast endorheic plain in southern west Africa. It is situated at the southern border of tropical Africa, at the eastern border of the coastal area influenced by the Benguela current and at the western border of inland Africa influenced by the Indian Ocean. It is therefore supposed to be sensitive to climate change and provides the opportunity to link its lake record with the drastic hydrological changes that occurred in east African rift-valley lakes during deglaciation. Using OSL dating and sediment analysis to constrain lake shorelines of perennial lakes in time and space, we found high lake levels during the late Pleistocene and a drastic drop shortly after 10 ka. This lake water-level reconstruction is not in line with the histories of ITCZ migration and strength of Benguela current upwelling. We confirm that the linkages between the evolution of the Etosha Pan and the climate mechanisms driving hydrological changes in subtropical southwest Africa are poorly resolved and need further investigation. The paper discusses these findings in the context of SH palaeoclimate records.

Synthetic mucin fragments: synthesis of O-sulfo and O-methyl derivatives of allyl O-(beta-D-galactopyranosyl)-(1-->3)-2-acetamido-2-deoxy-alpha-D- galactopyranoside as potential compounds for sulfotransferases.

PubMed

Jain, R K; Piskorz, C F; Matta, K L

1995-10-02

Allyl 2-acetamido-4,6-O-(4-methoxybenzylidene)-2-deoxy-alpha-D-galact opy ranoside (1) was condensed with either 2,3,4,6-tetra-O-acetyl-alpha-D-galactopyranosyl bromide (2) or 2,3,4-tri-O-benzoyl-6-O-bromoacetyl-alpha-D-galactopyranosyl bromide (14) in the presence of mercuric cyanide. Selective substitution with methyl, sulfo or both at desired positions, followed by the removal of protecting groups, afforded allyl O-(beta-D-galactopyranosyl)-(1-->3)-2-acetamido-2-deoxy-6-O-methyl-alpha -D- galactopyranoside (5), allyl O-(6-O-sulfo-beta-D-galactopyranosyl sodium salt)-(1-->3)-2-acetamido-2-deoxy-6- O-methyl-alpha-D-galactopyranoside (10), allyl O-(beta-D-galactopyranosyl)-(1-->3)-2-acetamido-2-deoxy-6-O-sulfo-alpha- D- galactopyranoside sodium salt (13), allyl O-(6-O-sulfo-beta-D-galactopyranosyl sodium salt)-(1-->3)-2-acetamido-2-deoxy- alpha-D-galactopyranoside (17) and allyl O-(3-O-sulfo-beta-D-galactopyranosyl sodium salt)-(1-->3)-2-acetamido-2-deoxy- alpha-D-galactopyranoside (22). The structures of compounds 5, 10, 13, 17 and 22 were established by 13C NMR and FAB mass spectroscopy.

1,2,4-trihydroxynaphthalene-2-O-β-D-glucopyranoside delays amyloid-β42 aggregation and reduces amyloid cytotoxicity.

PubMed

Dhouafli, Zohra; Leri, Manuela; Bucciantini, Monica; Stefani, Massimo; Gadhoumi, Hamza; Mahjoub, Borhane; Ben Jannet, Hichem; Guillard, Jérôme; Ksouri, Riadh; Saidani Tounsi, Moufida; Soto, Claudio; Hayouni, El Akrem

2018-03-26

Presently, misfolding and aggregation of amyloid-β 42 (Aβ 42 ) are considered early events in Alzheimer's disease (AD) pathogenesis. The use of natural products to inhibit the aggregation process and to protect cells from cytotoxicity of early aggregate grown at the onset of the aggregation path is one of the promising strategies against AD. Recently, we have purified a new powerful antioxidant and inhibitor of Aβ 42 aggregation from the leaves of Lawsonia inermis. The new compound was identified as a new Lawsoniaside; 1,2,4-trihydroxynaphthalene-2-O-β-D-glucopyranoside (THNG). Herein, we show that THNG interferes with Aβ 42 aggregation, inhibits its conformational change to a β-sheet-rich structure, decreases its polymerization into large fibrillar species, reduces oxidative stress, and aggregate cytotoxicity. These results indicate that THNG has great potential as a neuroprotective and therapeutic agent against AD. © 2018 BioFactors, 2018. © 2018 International Union of Biochemistry and Molecular Biology.

Oxygen isotope perspective on crustal evolution on early Earth: A record of Precambrian shales with emphasis on Paleoproterozoic glaciations and Great Oxygenation Event

NASA Astrophysics Data System (ADS)

Bindeman, I. N.; Bekker, A.; Zakharov, D. O.

2016-03-01

We present stable isotope and chemical data for 206 Precambrian bulk shale and tillite samples that were collected mostly from drillholes on all continents and span the age range from 0.5 to 3.5 Ga with a dense coverage for 2.5-2.2 Ga time interval when Earth experienced four Snowball Earth glaciations and the irreversible rise in atmospheric O2. We observe significant, downward shift of several ‰ and a smaller range of δ18 O values (7 to 9‰) in shales that are associated with the Paleoproterozoic and, potentially, Neoproterozoic glaciations. The Paleoproterozoic samples consist of more than 50% mica minerals and have equal or higher chemical index of alteration than overlying and underlying formations and thus underwent equal or greater degrees of chemical weathering. Their pervasively low δ18 O and δD (down to - 85 ‰) values provide strong evidence of alteration and diagenesis in contact with ultra-low δ18 O glacial meltwaters in lacustrine, deltaic or periglacial lake (sikussak-type) environments associated with the Paleoproterozoic glaciations. The δDsilicate values for the rest of Precambrian shales range from -75 to - 50 ‰ and are comparable to those for Phanerozoic and Archean shales. Likewise, these samples have similar ranges in δ13Corg values (-23 to - 33 ‰ PDB) and Corg content (0.0 to 10 wt%) to Phanerozoic shales. Precambrian shales have a large range of δ18 O values comparable to that of the Phanerozoic shales in each age group and formation, suggesting similar variability in the provenance and intensity of chemical weathering, except for the earliest 3.3-3.5 Ga Archean shales, which have consistently lower δ18 O values. Moreover, Paleoproterozoic shales that bracket in age the Great Oxidation Event (GOE) overlap in δ18 O values. Absence of a step-wise increase in δ18 O and δD values suggests that despite the first-order change in the composition of the atmosphere, weathering cycle was not dramatically affected by the GOE at ∼2.4-2.3 Ga. Shales do not show comparable δ18 O rise in the early Phanerozoic as is observed in the coeval δ18 O trends for cherts and carbonates. There is however a sharp increase in the average δ18 O value from the Early Archean to the Late Archean followed by a progressively decelerating increase into the Phanerozoic. This decelerating increase with time likely reflects declining contribution of mantle-extracted, normal-δ18 O crust and lends support to crustal maturation and increasing 18O sequestration into the crust and recycling of high-δ18 O (and 87Sr/86Sr) sedimentary rocks. This secular increase in the δ18 O composition of the continental crust could have also had a mild effect on seawater δ18 O composition.

Six new C21 steroidal glycosides from Asclepias curassavica L.

PubMed

Li, Jun-Zhu; Liu, Hai-Yang; Lin, Yi-Ju; Hao, Xiao-Jiang; Ni, Wei; Chen, Chang-Xiang

2008-07-01

Six new C(21) steroidal glycosides, named curassavosides A-F (3-8), were obtained from the aerial parts of Asclepias curassavica (Asclepiadaceae), along with two known oxypregnanes, 12-O-benzoyldeacylmetaplexigenin (1) and 12-O-benzoylsarcostin (2). By spectroscopic methods, the structures of the six new compounds were determined as 12-O-benzoyldeacylmetaplexigenin 3-O-beta-D-oleandropyranosyl-(1-->4)-beta-D-digitoxopyranoside (3), 12-O-benzoylsarcostin 3-O-beta-D-oleandropyranosyl-(1-->4)-beta-D-digitoxopyranoside (4), sarcostin 3-O-beta-D-oleandropyranosyl-(1-->4)-beta-D-canaropyranosyl-(1-->4)-beta-D-oleandropyranosyl-(1-->4)-beta-D-digitoxopyranoside (5), sarcostin 3-O-beta-D-oleandropyranosyl-(1-->4)-beta-D-canaropyranosyl-(1-->4)-beta-D-canaropyranosyl-(1-->4)-beta-D-digitoxopyranoside (6), 12-O-benzoyldeacylmetaplexigenin 3-O-beta-D-glucopyranosyl-(1-->4)-beta-D-oleandropyranosyl-(1-->4)-beta-D-canaropyranosyl-(1-->4)-beta-d-oleandropyranosyl-(1-->4)-beta-D-digitoxopyranoside (7), and 12-O-benzoylsarcostin 3-O-beta-D-glucopyranosyl-(1-->4)-beta-D-oleandropyranosyl-(1-->4)-beta-d-canaropyranosyl-(1-->4)-beta-D-oleandropyranosyl-(1-->4)-beta-D-digitoxopyranoside (8), respectively. All compounds (1-8) were tested for in vitro cytotoxicity; only compound 3 showed weak inhibitory activity against Raji and AGZY cell lines.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zeno, Wade F.; Johnson, Kaitlin E.; Sasaki, Darryl Y.

We use fluorescence microscopy to examine the dynamics of the crowding-induced mixing transition of liquid ordered (L o)–liquid disordered (L d) phase separated lipid bilayers when the following particles of increasing size bind to either the L o or L d phase: Ubiquitin, green fluorescent protein (GFP), and nanolipoprotein particles (NLPs) of two diameters. These proteinaceous particles contained histidine-tags, which were phase targeted by binding to iminodiacetic acid (IDA) head groups, via a Cu 2+ chelating mechanism, of lipids that specifically partition into either the Lo phase or Ld phase. The degree of steric pressure was controlled by varying themore » size of the bound particle (10–240 kDa) and the amount of binding sites present (i.e., DPIDA concentrations of 9 and 12 mol%) in the supported lipid multibilayer platform used here. We develop a mass transfer-based diffusional model to analyze the observed L o phase domain dissolution that, along with visual observations and activation energy calculations, provides insight into the sequence of events in crowding-induced mixing. Furthermore, our results suggest that the degree of steric pressure and target phase influence not only the efficacy of steric-pressure induced mixing, but the rate and controlling mechanism for which it occurs.« less

Synthesis of methyl 2-O- and 3-O-alpha-D-talopyranosyl-alpha-D-mannopyranoside.

PubMed

Rana, S S; Matta, K L

1986-09-01

Methyl 3,4,6-tri-O-benzyl-2-O-[6-O-(tert-butyldiphenylsilyl)-alpha-D- mannopyranosyl]-alpha-D-mannopyranoside (2) was synthesized by treatment of methyl 3,4,6-tri-O-benzyl-2-O-alpha-D-mannopyranosyl-alpha-D-mannopyranoside with tert-butylchlorodiphenylsilane in the presence of imidazole. Isopropylidenation, followed by oxidation with pyridinium chlorochromate, and stereoselective reduction with sodium borohydride, converted 2 into methyl 3,4,6-tri-O-benzyl-2-O-[6-O-(tert-butyldiphenylsilyl)-2,3-O-isopro pylidene- alpha-D-talopyranosyl]-alpha-D-mannopyranoside (5). Treatment of 5 with a molar solution of tetrabutylammonium fluoride in dry oxolane produced a diol which, on O-de-isopropylidenation followed by catalytic hydrogenolysis, afforded the disaccharide glycoside methyl 2-O-alpha-D-talopyranosyl-alpha-D-mannopyranoside. Synthesis of methyl 3-O-alpha-D-talopyranosyl-alpha-D-mannopyranoside was accomplished by a similar reaction-sequence. The structures of the final disaccharides, and of various other intermediates, were established by 1H- and 13C-n.m.r. spectroscopy.

3-D inversion of complex magnetotelluric data from an Archean-Proterozoic terrain in northeastern São Francisco Craton, Brazil

NASA Astrophysics Data System (ADS)

Bologna, Mauricio S.; Egbert, Gary D.; Padilha, Antonio L.; Pádua, Marcelo B.; Vitorello, Ícaro

2017-09-01

We present a magnetotelluric (MT) study in the northeastern part of the São Francisco Craton that encompasses an Archean-Proterozoic terrain, the Serrinha Block, breached by a rift basin developed mostly in Early Cretaceous times during the opening of the South Atlantic Ocean. Even though the MT sites are regularly spaced, the profiles have different orientations from one another, making the data distribution over the area highly uneven and therefore non-ideal for 3-D modeling. However, the data set is very complex, with dimensionality analysis indicating prevalence of 3-D geoelectric structure. Results from 3-D inversion are evaluated for robustness and potentiality for yielding tectonic information. At upper crustal depths, the resulting 3-D model is coherent with surface geology, whereas at mid and lower crustal depths more cryptic structures are revealed, likely of Palaeoproterozoic age. The most striking features in the model are several strong (∼1 Ωṡm) crustal conductors beneath the central part of the Serrinha Block, which we attribute to a Palaeoproterozoic oceanic plate subduction and arc-continent collision event involving the Rio Itapicuru Greenstone Belt and the basement of the Serrinha Block. The west-dipping geometry of these conductors provides a constraint on subduction polarity and gives support to tectonic evolutionary models proposing that the Rio Itapicuru Belt was formed in an island arc environment.

Redox History of Early Solar System Planetismals Recorded in the D;Orbigny Angrite

DOE Office of Scientific and Technical Information (OSTI.GOV)

King, P.L.; Sutton, S.R.; Spilde, M.N.

2012-04-02

Angrites are ancient basaltic meteorites ({approx}4.56 Ga) that preserve evidence of some of the solar system's earliest melting events. The volcanic-textured angrites such as D'Orbigny were rapidly crystallized and are relatively pristine; lacking shock, brecciation, and parent-body weathering textures. Thus, these angrites provide a unique 'window' into the petrogenesis of planetary bodies in the early solar system. Angrites may be formed by partial melting of CV chondrites under relatively oxidized sources compared to the eucrites, and therefore may document variations in fO{sub 2} conditions on carbonaceous chondrite parent bodies. Thus, understanding the intrinsic fO{sub 2} conditions of the angrites ismore » needed to determine how different early Solar System basalts form, to model separation of the core, mantle and crust, and to understand magnetic fields on planetary bodies. The D'Orbigny angrite contains a range of textures: (a) crystalline texture containing interlocking crystals of fassaite (pyroxene) with Ti-rich rims, anorthite, and Mg-olivine with Fe-rich rims; (b) cavities with protruding needle-like pyroxene and anorthite dusted by Ca-(Mg)-carbonate; (c) mesostasis with kirschsteinite, ilmenite, troilite, phosphates (e.g., merrilite, whitlockite and Casilicophosphate), rhonite and minor glass; (d) glasses ({approx} angrite composition) in vesicles, as inclusions and as beads, and also cross-cutting crystal-rich portions of the rock; (e) vesicles (e.g., {approx}1.4 vol. %, 0.0219-87.7 mm{sup 3}). Analysis of the textures and Fe{sup 3+}/Fetotal of the cavity pyroxene suggests that the oxygen fugacity (fO{sub 2}) increased in the D'Orbigny angrite perhaps due to introduction of a gas phase. Here we examine the detailed fO{sub 2} history using micro-analyses that allow us to avoid inclusions that may cause spurious results. We present analyses of both S- and V- oxidation states to complement other work using Fe-oxidation state and to avoid problems related to measuring low concentrations of Fe{sup 3+} and propagating errors when calculating fO{sub 2} in samples with low Fe{sup 3+} concentrations.« less

CMOS Life Suitability Evaluation Program

DTIC Science & Technology

1979-10-01

A B 7845 1990 118 29.9 253.6 251.3 C 1910 28.7 251.6 o 125 A 01 0.00 125.0 B 0.2 0.00 125.0 225 A 6 124 169 1.86 2.54 225.6 225.8...T a«. ^■■—. ^a^^^mmmm (1) (2) (6) (7) (11) urn uiii »nu II-S» "Q" CLOCK (14) CLOCK ENABLE (13) RESET Ch (15) ^ •rMXD...8217S- ro Ch 8 CM CM «3- LI F E R DA S IZ 00 o d d d d d d o d d d d VO d ro X UJ O _i 0 O Q. z < o r") uo i^ o o o o CM ro o

Controls of precipitation δ18O on the northwestern Tibetan Plateau: A case study at Ngari station

NASA Astrophysics Data System (ADS)

Guo, Xiaoyu; Tian, Lide; Wen, Rong; Yu, Wusheng; Qu, Dongmei

2017-06-01

The shifting atmospheric circulation between the Indian monsoon and the westerlies on the northwestern Tibetan Plateau (TP) influences precipitation as well as precipitation isotopes. Isotopic records will therefore show historical fluctuations. To understand better the factors controlling present day precipitation δ18O values on the northwestern TP, we made continuous observations of precipitation isotopes at Ngari station from 2010 to 2013. The drivers of precipitation δ18O were investigated using analyses of their statistical relations with temperature, precipitation amount, relative humidity, and convective activities based on outgoing longwave radiation (OLR) data from NOAA satellites, and downward shortwave radiation (DSR) data collected at the Ngari automatic weather station. Atmospheric circulation patterns from NCAR reanalysis, and moisture transport paths of individual events derived from the HYSPLIT model using NCEP data, were also used to trace moisture sources. The results of our study include: (1) The slope and intercept of the Local Meteoric Water Line (LMWL) at Ngari (δD = 8.51 δ18O + 11.57 (R2 = 0.97, p < 0.01)) were higher than for the Global Meteoric Water Line (GMWL), indicating drier local climatic conditions; (2) Precipitation δ18O values showed a weak ;temperature effect; and a weak ;precipitation amount effect; at Ngari; and (3) Convection (or temperature patterns) integrated over several days (0-20) preceding each event were determined to be the main driver of precipitation isotopic values in monsoon (or non-monsoon) season. The longer (shorter) periods of τm days when correlation coefficients between precipitation δ18O and OLR were at their maxima (minima) indicate deep convective activities (shorter moisture transportation pathways) in August (June, July, and September).

Rebaudiosides T and U, minor C-19 xylopyranosyl and arabinopyranosyl steviol glycoside derivatives from Stevia rebaudiana (Bertoni) Bertoni.

PubMed

Perera, Wilmer H; Ghiviriga, Ion; Rodenburg, Douglas L; Alves, Kamilla; Bowling, John J; Avula, Bharathi; Khan, Ikhlas A; McChesney, James D

2017-03-01

Two diterpene glycosides were isolated from a commercial Stevia rebaudiana leaf extract. One was found to be 13-[(2-O-β-d-glucopyranosyl-3-O-β-d-glucopyranosyl-β-d-glucopyranosyl)oxy]ent-kaur-16-en-19-oic acid-(2-O-β-d-xylopyranosyl-3-O-β-d-glucopyranosyl- β-d-glucopyranosyl) ester (rebaudioside T), whereas the other was determined to be 13-[(2-O-β-d-glucopyranosyl-3-O-β-d-glucopyranosyl-β-d-glucopyranosyl)oxy]ent-kaur-16-en-19-oic acid-(6-O-α-l-arabinopyranosyl-β-d-glucopyranosyl) ester (rebaudioside U). In addition, five C-19 sugar free derivatives were prepared and identified as follows: 13-[(2-O-α-l-rhamnopyranosyl-β-d-glucopyranosyl)]oxy]kaur-16-en-19-oic acid (dulcoside A 1 ); 13-[(2-O-β-d-xylopyranosy-3-O-β-d-glucopyranosyl-β-d-glucopyranosyl)oxy]kaur-16-en-19-oic acid; 13-[(2-O-β-d-xylopyranosyl-β-d-glucopyranosyl-)oxy]kaur-16-en-19-oic acid; 13-[(2-O-β-d-glucopyranosyl-3-O-β-d-glucopyranosyl-β-d-xylopyranosyl-)oxy]kaur-16-en-19-oic acid (rebaudioside R 1 ) and 13-[(2-O-6-deoxy-β-d-glucopyranosyl-3-O-β-d-glucopyranosyl-β-d-glucopyranosyl)oxy]kaur-16-en-19-oic acid, respectively. Chemical structures were determined by NMR experiments. HPLC analyses were also useful to differentiate different steviol-C13 sugar substituent patterns by elution position. Copyright © 2016 Elsevier Ltd. All rights reserved.

Five new triterpene saponins, polygalasaponins XXVIII-XXXII from the root of Polygala japonica Houtt.

PubMed

Zhang, D; Miyase, T; Kuroyanagi, M; Umehara, K; Ueno, A

1996-04-01

Five new oleanane-type saponins, polygalasaponins XXVIII-XXXII, along with one known saponin, polygalasaponin XXIV, and one known acylated sucrose, tenuifoliside C, were isolated from the root of Polygala japonica. The structures of these new compounds were elucidated as 3-O-beta-D-glucopyranosyl pesenegenin 28-O-beta-D-xylopyranosyl (1-->4)-alpha-L-rhamnopyranosyl (1-->2)-beta-D-fucopyranosyl ester, 3-O-beta-D-glucopyranosyl presenegenin 28-O-beta-D-galactopyranosyl (1-->5)-beta-D-apiofuranosyl (1-->4)-beta-D-xylopyranosyl (1-->4)-alpha-L-rhamno-pyranosyl (1-->2)-beta-D-fucopyranosyl ester, 3-O-beta-D-glucopyranosyl presenegenin 28-O-beta-D-galactopyranosyl (1-->4)-beta-D-xylopyranosyl (1-->4)-alpha-L-rhamnopyranosyl (1-->2)-[4-O-p-methoxycinnamoyl]-[beta-D-glucopyranosyl (1-->3)]-beta-D-fucopyranosyl ester, 3-O-beta-D-glucopyranosyl presenegenin 28-O-alpha-L-arabinopyranosyl (1-->3)-beta-D-xylopyranosyl (1-->4)-[beta-D-apiofuranosyl (1-->3)]-alpha-L-rhamnopyranosyl (1-->2)-[4-O-3,4,5-trimethoxycinnamoyl]-beta-D-fucopyranosyl ester, 3-O-beta-D-glucopyranosyl persenegenin 28-O-alpha-L-arabinopyranosyl (1-->3)-beta-D-xylopyranosyl (1-->4)-[beta-D-apiofuranosyl (1-->3)-alpha-L-rhamnopyranosyl (1-->2)-[4-O-p-methoxycinnamoyl]-[alpha-L-rhamnopyranosyl (1-->3)-beta-D-fucopyranosyl ester, respectively, on the basis of spectroscopic and chemical evidence.

Reproductive success of Mariana swiftlets (Aerodramus bartschi) on the Hawaiian island of O'ahu

USGS Publications Warehouse

Johnson, Nathan C.; Haig, Susan M.; Mosher, Stephen M.; Hollenbeck, Jeff P.

2017-01-01

Mariana Swiftlets (Aerodramus bartschi) are federally listed as endangered, with populations currently limited to just three islands in the Mariana Islands plus an introduced population on the Hawaiian island of O'ahu. Before efforts are made to reintroduce Mariana Swiftlets to other islands in the Mariana archipelago, additional information is needed concerning their breeding biology. Therefore, our objective was to examine the reproductive biology of Mariana Swiftlets over five annual cycles on the Hawaiian island of O'ahu. This introduced population used a human-made tunnel for roosting and nesting, and was studied as a surrogate to negate interference with endangered populations in the Mariana Islands. Active nests (N = 478) were observed in every month of the year, with peak nesting activity between May and September. All clutches consisted of one egg. Mean duration of incubation and nestling periods were 23.9 d (range = 18–30 d, N = 233) and 55.0 d (range = 41–84 d, N = 228), respectively. Estimated nest success was 63%. Over half (52%) of nest failures were attributed to eggs found on the tunnel floor. Predation by rats (Rattus spp.) was also an important cause of nest failure and often resulted in the loss of most active nests. However, Mariana Swiftlets did re-nest after these predation events. Our results suggest that rat predation of both nests and adults may limit growth of the Mariana Swiftlet population on O'ahu, and could also affect the chances for successful establishment of relocated populations in the Mariana Islands. Another limiting factor on O'ahu is that only one nesting site is apparently available on the island. Current goals for downlisting Mariana Swiftlets from endangered to threatened include establishing populations on Guam, Rota, Aguiguan, and Saipan. To meet these goals, the population of Mariana Swiftlets on O'ahu can be important for testing reintroduction techniques, learning more about the natural history of these swiftlets, and providing individuals for reintroduction efforts in the Mariana Islands.

New chemical constituents from Oryza sativa straw and their algicidal activities against blue-green algae.

PubMed

Ahmad, Ateeque; Kim, Seung-Hyun; Ali, Mohd; Park, Inmyoung; Kim, Jin-Seog; Kim, Eun-Hye; Lim, Ju-Jin; Kim, Seul-Ki; Chung, Ill-Min

2013-08-28

Five new constituents, 5,4'-dihydroxy-7,3'-dimethoxyflavone-4'-O-β-D-xylopyranosyl-(2a→1b)-2a-O-β-D-xylopyranosyl-(2b→1c)-2b-O-β-D-xylopyranosyl-2c-octadecanoate (1), 5,4'-dihydroxy-7,3'-dimethoxyflavone-4'-O-α-D-xylopyranosyl-(2a→1b)-2a-O-α-D-xylopyranosyl-(2b→1c)-2b-O-α-D-xylopyranosyl-(2c→1d)-2c-O-α-D-xylopyranosyl-2d-octadecanoate (2), kaempferol-3-O-α-D-xylopyranosyl-(2a→1b)-2a-O-α-D-xylopyranosyl-(2b→1c)-2b-O-α-D-xylopyranosyl-(2c→1d)-2c-O-α-D-xylopyranosyl-2d-hexadecanoate (3), methyl salicylate-2-O-α-D-xylopyranosyl-(2a→1b)-2a-O-α-D-xylopyranosyl-(2b→1c)-2b-O-α-D-xylopyranosyl-(2c→1d)-2c-O-α-D-xylopyranosyl-(2d→1e)-2d-O-α-D-xylopyranosyl-(2e→1f)-2e-O-α-D-xylopyranosyl-(2f→1g)-2f-O-α-D-xylopyranosyl-(2g→1h)-2g-O-α-D-xylopyranosyl-2h-geranilan-8',10'-dioic acid-1'-oate (4), and oleioyl-β-D-arabinoside (5), along with eight known compounds, were isolated from a methanol extract of Oryza sativa straw. The structures of the new compounds were elucidated using one- and two-dimensional NMR spectroscopies in combination with IR, ESI/MS, and HR-ESI/FTMS. In bioassays with blue-green algae, the efficacies of the algicidal activities of the five new compounds (1-5) were evaluated at concentrations of 1, 10, and 100 mg/L. Compound 5 had the highest growth inhibition (92.6 ± 0.3%) for Microcystis aeruginosa UTEX 2388 at a concentration of 100 ppm (mg/L). Compound 5 has high potential for the ecofriendly control of weeds and algae harmful to water-logged rice.

Differential bleaching of corals based on El Niño type and intensity in the Andaman Sea, southeast Bay of Bengal.

PubMed

Lix, J K; Venkatesan, R; Grinson, George; Rao, R R; Jineesh, V K; Arul, Muthiah M; Vengatesan, G; Ramasundaram, S; Sundar, R; Atmanand, M A

2016-03-01

The Andaman coral reef region experienced mass bleaching events during 1998 and 2010. The purpose of this study is to investigate the role of the El Niño in the coral reef bleaching events of the Andaman region. Both Niño 3.4 and 3 indices were examined to find out the relationship between the mass bleaching events and El Niño, and correlated with sea surface temperature (SST) anomalies in the Andaman Sea. The result shows that abnormal warming and mass bleaching events in the Andaman Sea were seen only during strong El Niño years of 1997-1998 and 2009-2010. The Andaman Sea SST was more elevated and associated with El Niño Modoki (central Pacific El Niño) than conventional El Niño (eastern Pacific El Niño) occurrences. It is suggested that the development of hot spot patterns around the Andaman Islands during May 1998 and April-May 2010 may be attributed to zonal shifts in the Walker circulation driven by El Niño during the corresponding period.

Controls on Atmospheric O2: The Anoxic Archean and the Suboxic Proterozoic

NASA Astrophysics Data System (ADS)

Kasting, J. F.

2015-12-01

Geochemists have now reached consensus that the Archean atmosphere was mostly anoxic, that a Great Oxidation Event (GOE) occurred at around 2.5 Ga, and that the ensuing Proterozoic atmosphere was consistently oxidized [1,2]. Evidence for this broad-scale change in atmospheric composition comes from a variety of sources, most importantly from multiple sulfur isotopes [3,4]. The details of both the Archean and Proterozoic environments remain controversial, however, as does the underlying cause of the GOE. Evidence of 'whiffs' of oxygen during the Archean [5] now extend back as far as 3.0 Ga, based on Cr isotopes [6]. This suggests that O2 was being produced by cyanobacteria well before the GOE and that the timing of this event may have been determined by secular changes in O2 sinks. Catling et al. [7] emphasized escape of hydrogen to space, coupled with progressive oxidation of the continents and a concomitant decrease in the flux of reduced gases from metamorphism. But hydrogen produced by serpentinization of seafloor could also have been a controlling factor [8]. Higher mantle temperatures during the Archean should have resulted in thicker, more mafic seafloor and higher H2 production; decreasing mantle temperatures during the Proterozoic should have led to seafloor more like that of today and a corresponding decrease in H2 production, perhaps by enough to trigger the GOE. Once the atmosphere became generally oxidizing, it apparently remained that way during the rest of Earth's history. But O2 levels in the mid-Proterozoic could have been as low at 10-3 times the Present Atmospheric Level (PAL) [9]. The evidence, once again, is based on Cr isotopes. Possible mechanisms for maintaining such a 'suboxic' Proterozoic atmosphere will be discussed. Refs: 1. H. D. Holland, Geochim. Cosmochim. Acta 66, 3811 (2002). 2. H. D. Holland, Philosophical Transactions of the Royal Society B-Biological Sciences 361, 903 (Jun 29, 2006). 3. J. Farquhar, H. Bao, M. Thiemans, Science 289, 756 (2000). 4. C. T. Reinhard, N. J. Planavsky, T. W. Lyons, Nature 497, 100 (May, 2013). 5. A. D. Anbar et al., Science 317, 1903 (Sep, 2007). 6. S. A. Crowe et al., Nature 501, 535 (Sep, 2013). 7. D. C. Catling, K. J. Zahnle, C. P. McKay, Science 293, 839 (2001). 8. J. F. Kasting, Chem. Geol. 362, 13 (2013). 9. N. J. Planavsky et al., Science 346, 635 (Oct, 2014).

Sawtooth events and O+ in the plasma sheet and boundary layer: CME- and SIR-driven events

NASA Astrophysics Data System (ADS)

Lund, E. J.; Nowrouzi, N.; Kistler, L. M.; Cai, X.; Liao, J.

2017-12-01

The role of ionospheric ions in sawtooth events is an open question. Simulations[1,2,3] suggest that O+ from the ionosphere produces a feedback mechanism for driving sawtooth events. However, observational evidence[4,5] suggest that the presence of O+ in the plasma sheet is neither necessary nor sufficient. In this study we investigate whether the solar wind driver of the geomagnetic storm has an effect on the result. Building on an earlier study[4] that used events for which Cluster data is available in the plasma sheet and boundary layer, we perform a superposed epoch analysis for coronal mass ejection (CME) driven storms and streaming interaction region (SIR) driven storms separately, to investigate the hypothesis that ionospheric O+ is an important contributor for CME-driven storms but not SIR-driven storms[2]. [1]O. J. Brambles et al. (2011), Science 332, 1183.[2]O. J. Brambles et al. (2013), JGR 118, 6026.[3]R. H. Varney et al. (2016), JGR 121, 9688.[4]J. Liao et al. (2014), JGR 119, 1572.[5]E. J. Lund et al. (2017), JGR, submitted.

NATO-Warsaw Pact. Force Mobilization

DTIC Science & Technology

1988-01-01

DVatxbuftln Unlimited I A R- P-4 90 11 20 0354 NATO-WARSAW PACT FORCE MOBILIZATION Aeo~lu orDTIC "Is WWI LECTEN0V2 119901 L , S~E 1 Distrib~ut i on ...2 G; 06 s1 rJ N%0’ t- N C- W 00 m C7 0 z r4 Mi .0 u ON ~ cm rt ~o rv-n- 0, 0r 2N le 00~% m 0 o Z z ’-0 Z UJ U 2 z< RD R2 6’z z D u 34 SIMON NATO (6.09...debate.’" Some Soviet works completely ignore the issue. Sukhomlinov’s proposal fell victim to rapidly unfolding events and pressure from France on

α2A- and α2C-Adrenoceptors as Potential Targets for Dopamine and Dopamine Receptor Ligands.

PubMed

Sánchez-Soto, Marta; Casadó-Anguera, Verònica; Yano, Hideaki; Bender, Brian Joseph; Cai, Ning-Sheng; Moreno, Estefanía; Canela, Enric I; Cortés, Antoni; Meiler, Jens; Casadó, Vicent; Ferré, Sergi

2018-03-18

The poor norepinephrine innervation and high density of Gi/o-coupled α 2A - and α 2C -adrenoceptors in the striatum and the dense striatal dopamine innervation have prompted the possibility that dopamine could be an effective adrenoceptor ligand. Nevertheless, the reported adrenoceptor agonistic properties of dopamine are still inconclusive. In this study, we analyzed the binding of norepinephrine, dopamine, and several compounds reported as selective dopamine D 2 -like receptor ligands, such as the D 3 receptor agonist 7-OH-PIPAT and the D 4 receptor agonist RO-105824, to α 2 -adrenoceptors in cortical and striatal tissue, which express α 2A -adrenoceptors and both α 2A - and α 2C -adrenoceptors, respectively. The affinity of dopamine for α 2 -adrenoceptors was found to be similar to that for D 1 -like and D 2 -like receptors. Moreover, the exogenous dopamine receptor ligands also showed high affinity for α 2A - and α 2C -adrenoceptors. Their ability to activate Gi/o proteins through α 2A - and α 2C -adrenoceptors was also analyzed in transfected cells with bioluminescent resonance energy transfer techniques. The relative ligand potencies and efficacies were dependent on the Gi/o protein subtype. Furthermore, dopamine binding to α 2 -adrenoceptors was functional, inducing changes in dynamic mass redistribution, adenylyl cyclase activity, and ERK1/2 phosphorylation. Binding events were further studied with computer modeling of ligand docking. Docking of dopamine at α 2A - and α 2C -adrenoceptors was nearly identical to its binding to the crystallized D 3 receptor. Therefore, we provide conclusive evidence that α 2A - and α 2C -adrenoceptors are functional receptors for norepinephrine, dopamine, and other previously assumed selective D 2 -like receptor ligands, which calls for revisiting previous studies with those ligands.

Development of Embryonic Market Squid, Doryteuthis opalescens, under Chronic Exposure to Low Environmental pH and [O2].

PubMed

Navarro, Michael O; Kwan, Garfield T; Batalov, Olga; Choi, Chelsea Y; Pierce, N Tessa; Levin, Lisa A

2016-01-01

The market squid, Doryteuthis opalescens, is an important forage species for the inshore ecosystems of the California Current System. Due to increased upwelling and expansion of the oxygen minimum zone in the California Current Ecosystem, the inshore environment is expected to experience lower pH and [O2] conditions in the future, potentially impacting the development of seafloor-attached encapsulated embryos. To understand the consequences of this co-occurring environmental pH and [O2] stress for D. opalescens encapsulated embryos, we performed two laboratory experiments. In Experiment 1, embryo capsules were chronically exposed to a treatment of higher (normal) pH (7.93) and [O2] (242 μM) or a treatment of low pH (7.57) and [O2] (80 μM), characteristic of upwelling events and/or La Niña conditions. The low pH and low [O2] treatment extended embryo development duration by 5-7 days; embryos remained at less developed stages more often and had 54.7% smaller statolith area at a given embryo size. Importantly, the embryos that did develop to mature embryonic stages grew to sizes that were similar (non-distinct) to those exposed to the high pH and high [O2] treatment. In Experiment 2, we exposed encapsulated embryos to a single stressor, low pH (7.56) or low [O2] (85 μM), to understand the importance of environmental pH and [O2] rising and falling together for squid embryogenesis. Embryos in the low pH only treatment had smaller yolk reserves and bigger statoliths compared to those in low [O2] only treatment. These results suggest that D. opalescens developmental duration and statolith size are impacted by exposure to environmental [O2] and pH (pCO2) and provide insight into embryo resilience to these effects.

Development of Embryonic Market Squid, Doryteuthis opalescens, under Chronic Exposure to Low Environmental pH and [O2

PubMed Central

Navarro, Michael O.; Kwan, Garfield T.; Batalov, Olga; Choi, Chelsea Y.; Pierce, N. Tessa; Levin, Lisa A.

2016-01-01

The market squid, Doryteuthis opalescens, is an important forage species for the inshore ecosystems of the California Current System. Due to increased upwelling and expansion of the oxygen minimum zone in the California Current Ecosystem, the inshore environment is expected to experience lower pH and [O2] conditions in the future, potentially impacting the development of seafloor-attached encapsulated embryos. To understand the consequences of this co-occurring environmental pH and [O2] stress for D. opalescens encapsulated embryos, we performed two laboratory experiments. In Experiment 1, embryo capsules were chronically exposed to a treatment of higher (normal) pH (7.93) and [O2] (242 μM) or a treatment of low pH (7.57) and [O2] (80 μM), characteristic of upwelling events and/or La Niña conditions. The low pH and low [O2] treatment extended embryo development duration by 5–7 days; embryos remained at less developed stages more often and had 54.7% smaller statolith area at a given embryo size. Importantly, the embryos that did develop to mature embryonic stages grew to sizes that were similar (non-distinct) to those exposed to the high pH and high [O2] treatment. In Experiment 2, we exposed encapsulated embryos to a single stressor, low pH (7.56) or low [O2] (85 μM), to understand the importance of environmental pH and [O2] rising and falling together for squid embryogenesis. Embryos in the low pH only treatment had smaller yolk reserves and bigger statoliths compared to those in low [O2] only treatment. These results suggest that D. opalescens developmental duration and statolith size are impacted by exposure to environmental [O2] and pH (pCO2) and provide insight into embryo resilience to these effects. PMID:27936085

TiD-Introducing and Benchmarking an Event-Delivery System for Brain-Computer Interfaces.

PubMed

Breitwieser, Christian; Tavella, Michele; Schreuder, Martijn; Cincotti, Febo; Leeb, Robert; Muller-Putz, Gernot R

2017-12-01

In this paper, we present and analyze an event distribution system for brain-computer interfaces. Events are commonly used to mark and describe incidents during an experiment and are therefore critical for later data analysis or immediate real-time processing. The presented approach, called Tools for brain-computer interaction interface D (TiD), delivers messages in XML format via a buslike system using transmission control protocol connections or shared memory. A dedicated server dispatches TiD messages to distributed or local clients. The TiD message is designed to be flexible and contains time stamps for event synchronization, whereas events describe incidents, which occur during an experiment. TiD was tested extensively toward stability and latency. The effect of an occurring event jitter was analyzed and benchmarked on a reference implementation under different conditions as gigabit and 100-Mb Ethernet or Wi-Fi with a different number of event receivers. A 3-dB signal attenuation, which occurs when averaging jitter influenced trials aligned by events, is starting to become visible at around 1-2 kHz in the case of a gigabit connection. Mean event distribution times across operating systems are ranging from 0.3 to 0.5ms for a gigabit network connection for 10 6 events. Results for other environmental conditions are available in this paper. References already using TiD for event distribution are provided showing the applicability of TiD for event delivery with distributed or local clients.

MULTI-SPACECRAFT ANALYSIS OF ENERGETIC HEAVY ION AND INTERPLANETARY SHOCK PROPERTIES IN ENERGETIC STORM PARTICLE EVENTS NEAR 1 au

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ebert, R. W.; Dayeh, M. A.; Desai, M. I.

2016-11-10

We examine the longitude distribution of and relationship between interplanetary (IP) shock properties and ∼0.1–20 MeV nucleon{sup -1} O and Fe ions during seven multi-spacecraft energetic storm particle (ESP) events at 1 au. These ESP events were observed at two spacecraft and were primarily associated with low Mach number, quasi-perpendicular shocks. Key observations include the following: (i) the Alfvén Mach number increased from east to west of the coronal mass ejection source longitude, while the shock speed, compression ratios, and obliquity showed no clear dependence; (ii) the O and Fe time intensity profiles and peak intensities varied significantly between longitudinallymore » separated spacecraft observing the same event, the peak intensities being larger near the nose and smaller along the flank of the IP shock; (iii) the O and Fe peak intensities had weak to no correlations with the shock parameters; (iv) the Fe/O time profiles showed intra-event variations upstream of the shock that disappeared downstream of the shock, where values plateaued to those comparable to the mean Fe/O of solar cycle 23; (v) the O and Fe spectral index ranged from ∼1.0 to 3.4, the Fe spectra being softer in most events; and (vi) the observed spectral index was softer than the value predicted from the shock compression ratio in most events. We conclude that while the variations in IP shock properties may account for some variations in O and Fe properties within these multi-spacecraft events, detailed examination of the upstream seed population and IP turbulence, along with modeling, are required to fully characterize these observations.« less

Pulse oximetry recorded from the Phone Oximeter for detection of obstructive sleep apnea events with and without oxygen desaturation in children.

PubMed

Garde, Ainara; Dehkordi, Parastoo; Wensley, David; Ansermino, J Mark; Dumont, Guy A

2015-01-01

Obstructive sleep apnea (OSA) disrupts normal ventilation during sleep and can lead to serious health problems in children if left untreated. Polysomnography, the gold standard for OSA diagnosis, is resource intensive and requires a specialized laboratory. Thus, we proposed to use the Phone Oximeter™, a portable device integrating pulse oximetry with a smartphone, to detect OSA events. As a proportion of OSA events occur without oxygen desaturation (defined as SpO2 decreases ≥ 3%), we suggest combining SpO2 and pulse rate variability (PRV) analysis to identify all OSA events and provide a more detailed sleep analysis. We recruited 160 children and recorded pulse oximetry consisting of SpO2 and plethysmography (PPG) using the Phone Oximeter™, alongside standard polysomnography. A sleep technician visually scored all OSA events with and without oxygen desaturation from polysomnography. We divided pulse oximetry signals into 1-min signal segments and extracted several features from SpO2 and PPG analysis in the time and frequency domain. Segments with OSA, especially the ones with oxygen desaturation, presented greater SpO2 variability and modulation reflected in the spectral domain than segments without OSA. Segments with OSA also showed higher heart rate and sympathetic activity through the PRV analysis relative to segments without OSA. PRV analysis was more sensitive than SpO2 analysis for identification of OSA events without oxygen desaturation. Combining SpO2 and PRV analysis enhanced OSA event detection through a multiple logistic regression model. The area under the ROC curve increased from 81% to 87%. Thus, the Phone Oximeter™ might be useful to monitor sleep and identify OSA events with and without oxygen desaturation at home.

Network analysis reveals strongly localized impacts of El Niño

NASA Astrophysics Data System (ADS)

Fan, Jingfang; Meng, Jun; Ashkenazy, Yosef; Havlin, Shlomo; Schellnhuber, Hans Joachim

2017-07-01

Climatic conditions influence the culture and economy of societies and the performance of economies. Specifically, El Niño as an extreme climate event is known to have notable effects on health, agriculture, industry, and conflict. Here, we construct directed and weighted climate networks based on near-surface air temperature to investigate the global impacts of El Niño and La Niña. We find that regions that are characterized by higher positive/negative network “in”-weighted links are exhibiting stronger correlations with the El Niño basin and are warmer/cooler during El Niño/La Niña periods. In contrast to non-El Niño periods, these stronger in-weighted activities are found to be concentrated in very localized areas, whereas a large fraction of the globe is not influenced by the events. The regions of localized activity vary from one El Niño (La Niña) event to another; still, some El Niño (La Niña) events are more similar to each other. We quantify this similarity using network community structure. The results and methodology reported here may be used to improve the understanding and prediction of El Niño/La Niña events and also may be applied in the investigation of other climate variables.

Network analysis reveals strongly localized impacts of El Niño.

PubMed

Fan, Jingfang; Meng, Jun; Ashkenazy, Yosef; Havlin, Shlomo; Schellnhuber, Hans Joachim

2017-07-18

Climatic conditions influence the culture and economy of societies and the performance of economies. Specifically, El Niño as an extreme climate event is known to have notable effects on health, agriculture, industry, and conflict. Here, we construct directed and weighted climate networks based on near-surface air temperature to investigate the global impacts of El Niño and La Niña. We find that regions that are characterized by higher positive/negative network "in"-weighted links are exhibiting stronger correlations with the El Niño basin and are warmer/cooler during El Niño/La Niña periods. In contrast to non-El Niño periods, these stronger in-weighted activities are found to be concentrated in very localized areas, whereas a large fraction of the globe is not influenced by the events. The regions of localized activity vary from one El Niño (La Niña) event to another; still, some El Niño (La Niña) events are more similar to each other. We quantify this similarity using network community structure. The results and methodology reported here may be used to improve the understanding and prediction of El Niño/La Niña events and also may be applied in the investigation of other climate variables.

Triterpene glycosides from the tubers of Anemone coronaria.

PubMed

Mimaki, Yoshihiro; Watanabe, Kazuki; Matsuo, Yukiko; Sakagami, Hiroshi

2009-07-01

Six new triterpene glycosides (1-6), together with 11 known ones (7-17), have been isolated from a glycoside-enriched fraction prepared from the tubers of Anemone coronaria L. (Ranunculaceae). On the basis of extensive spectroscopic analysis, including 2D NMR data, and the results of hydrolytic cleavage, the structures of 1-6 were determined to be 3beta-[(O-beta-D-glucopyranosyl-(1-->4)-O-[alpha-L-rhamnopyranosyl-(1-->2)]-alpha-L-arabinopyranosyl)oxy]-2beta,23-dihydroxyolean-12-en-28-oic acid (1), 3beta-[(O-beta-D-glucopyranosyl-(1-->3)-O-alpha-L-rhamnopyranosyl-(1-->2)-O-[beta-D-glucopyranosyl-(1-->4)]-alpha-L-arabinopyranosyl)oxy]-23-hydroxyolean-12-en-28-oic acid (2), 3beta-[(O-beta-D-glucopyranosyl-(1-->4)-O-[alpha-L-rhamnopyranosyl-(1-->2)]-alpha-L-arabinopyranosyl)oxy]-23-hydroxyolean-12-en-28-oic acid O-beta-D-glucopyranosyl-(1-->6)-beta-D-glucopyranosyl ester (3), 3beta-[(O-beta-D-glucopyranosyl-(1-->4)-O-[alpha-L-rhamnopyranosyl-(1-->2)]-alpha-L-arabinopyranosyl)oxy]-2beta,23-dihydroxyolean-12-en-28-oic acid O-alpha-L-rhamnopyranosyl-(1-->4)-O-beta-D-glucopyranosyl-(1-->6)-beta-D-glucopyranosyl ester (4), 3beta-[(O-beta-D-glucopyranosyl-(1-->4)-O-[alpha-L-rhamnopyranosyl-(1-->2)]-alpha-L-arabinopyranosyl)oxy]-2beta-hydroxyolean-12-en-28-oic acid O-alpha-L-rhamnopyranosyl-(1-->4)-O-beta-D-glucopyranosyl-(1-->6)-beta-D-glucopyranosyl ester (5), and 3beta-[(O-beta-D-glucopyranosyl-(1-->4)-O-[alpha-L-rhamnopyranosyl-(1-->2)]-alpha-L-arabinopyranosyl)oxy]-23-hydroxyolean-18-en-28-oic acid O-alpha-L-rhamnopyranosyl-(1-->4)-O-beta-D-glucopyranosyl-(1-->6)-beta-D-glucopyranosyl ester (6), respectively. Furthermore, the isolated compounds were evaluated for their cytotoxic activity against HSC-2 cells.

The impact of El Niño events on the pelagic food chain in the northern California Current.

PubMed

Fisher, Jennifer L; Peterson, William T; Rykaczewski, Ryan R

2015-12-01

The zooplankton of the northern California Current are typically characterized by an abundance of lipid-rich copepods that support rapid growth and survival of ecologically, commercially, and recreationally valued fish, birds, and mammals. Disruption of this food chain and reduced ecosystem productivity are often associated with climatic variability such as El Niño events. We examined the variability in timing, magnitude, and duration of positive temperature anomalies and changes in copepod species composition in the northern California Current in relation to 10 tropical El Niño events. Measurable impacts on mesozooplankton of the northern California Current were observed during seven of 10 of these events. The occurrence of anomalously warm water and the response of the copepod community was rapid (lag of zero to 2 months) following the initiation of canonical Eastern Pacific (EP) events, but delayed (lag of 2-8 months) following 'Modoki' Central Pacific (CP) events. The variable lags in the timing of a physical and biological response led to impacts in the northern California Current peaking in winter during EP events and in the spring during CP events. The magnitude and duration of the temperature and copepod anomalies were strongly and positively related to the magnitude and duration of El Niño events, but were also sensitive to the phase of the lower frequency Pacific Decadal Oscillation. When fisheries managers and biological oceanographers are faced with the prospect of a future El Niño event, prudent management and observation will require consideration of the background oceanographic conditions, the type of event, and both the magnitude and duration of the event when assessing the potential physical and biological impacts on the northern California Current. © 2015 John Wiley & Sons Ltd.

Preliminary seismic studies at Ceboruco Volcano

NASA Astrophysics Data System (ADS)

Escudero, C. R.; Nunez-Cornu, F. J.; Ochoa, J.; Robles, F. J.

2012-12-01

Many societies and their economies endure the disastrous consequences of destructive volcanic eruptions. The Ceboruco stratovolcano is located at the west of the Mexican volcanic belt at 21.125o north, 76 km from the pacific coast and 2,280 meters above sea level. It has an eruptive recurrence of 200 years and its last activity was at 1875. This natural hazard could affect more than eight communities and important highways. Scientific knowledge constitutes the only way to avoid or at least to mitigate the negative effects of an eventual eruptive event, accordingly the main objective of this project is monitor and analyze the potential destructive effects of the Ceboruco volcano. Seismic studies began at 2003 with the deployment of one MARSlite station equipped LE3d (1Hz) sensor. Station that works until 2009 and allow us to identify and characterize the seismic activity associated to the volcano;. Since March 2012 we installed four seismic stations, each includes a digital acquisition system TAURUS of Nanometrix and a Lennartz 3D lite seismometer. Batteries are change and data collected monthly. We use the data to establish the average seismic activity rate; we also aim to corroborate previous studies that showed four families of seismic events; and to localize and make preliminary evaluations of the events.

The Last Interglacial recorded in a Remouchamps cave speleothem (Belgium) -Information on seasonal changes and on the chronology of first climate deteriorations.

NASA Astrophysics Data System (ADS)

Verheyden, Sophie; Genty, Dominique; Blamart, Dominique; Cheng, Hai; Hodel, Florent; Vansteenberghe, Stef; McGavick, Matthew L.; Gillikin, David P.; Quinif, Yves

2015-04-01

A ~3m long stalagmite from the Remouchamps and ~15cm long stalagmite from the Han-sur-Lesse caves (Belgium) grew from ~124 to 100ka with growth rates going from 0.8mm/century to 30mm/century. Stable isotope (d18O and d13C) and growth-rate analyses suggest a rather stable climate from 122.0 to 115.8 ka. A clear climate deterioration is observed at ~115.8 ka and lasts until 111.2ka (±0.5ka, 2s), which corresponds well with Greenland Stadial 26. Several short-term but clear changes are observed in the stable isotopic composition at ~121.5, 119.5, 118.4, 117.6 (±0.5ka, 2s)) and are interpreted as climatic events of ~several hundred years long. They correspond with changes in stalagmite diameter and growth rate. Depending on the combination of changes in the d18O, d13C, growth rate and stalagmite diameter, the events are interpreted as corresponding to changes in rainfall amount or temperature. The RSM17 stalagmite exhibits visible seasonal layering during the entire 120-115ka period on which changes in Mg, Sr, Ba en P have been observed. This well pronounced lamination, likely annual as suggested by the U-Th data, demonstrates a strong seasonal character of the climate and/or vegetation activity during this period. We compare these MIS5 seasonality to the present day calcite layering observed in the cave. Both stalagmites, with a growth-rate increase after 125ka globally corresponding to the so-called Eemian optimum, seem to start later than other southern stalagmites from France, Italy or Spain. This observation raises the question of a possible late onset of interglacial conditions in north-west Europe and a progressive S-N advance of warmer conditions between 130 and 125ka through Western Europe.

Validity of using a 3-dimensional PET scanner during inhalation of 15O-labeled oxygen for quantitative assessment of regional metabolic rate of oxygen in man

NASA Astrophysics Data System (ADS)

Hori, Yuki; Hirano, Yoshiyuki; Koshino, Kazuhiro; Moriguchi, Tetsuaki; Iguchi, Satoshi; Yamamoto, Akihide; Enmi, Junichiro; Kawashima, Hidekazu; Zeniya, Tsutomu; Morita, Naomi; Nakagawara, Jyoji; Casey, Michael E.; Iida, Hidehiro

2014-09-01

Use of 15O labeled oxygen (15O2) and positron emission tomography (PET) allows quantitative assessment of the regional metabolic rate of oxygen (CMRO2) in vivo, which is essential to understanding the pathological status of patients with cerebral vascular and neurological disorders. The method has, however, been challenging, when a 3D PET scanner is employed, largely attributed to the presence of gaseous radioactivity in the trachea and the inhalation system, which results in a large amount of scatter and random events in the PET assessment. The present study was intended to evaluate the adequacy of using a recently available commercial 3D PET scanner in the assessment of regional cerebral radioactivity distribution during an inhalation of 15O2. Systematic experiments were carried out on a brain phantom. Experiments were also performed on a healthy volunteer following a recently developed protocol for simultaneous assessment of CMRO2 and cerebral blood flow, which involves sequential administration of 15O2 and C15O2. A particular intention was to evaluate the adequacy of the scatter-correction procedures. The phantom experiment demonstrated that errors were within 3% at the practically maximum radioactivity in the face mask, with the greatest radioactivity in the lung. The volunteer experiment demonstrated that the counting rate was at peak during the 15O gas inhalation period, within a verified range. Tomographic images represented good quality over the entire FOV, including the lower part of the cerebral structures and the carotid artery regions. The scatter-correction procedures appeared to be important, particularly in the process to compensate for the scatter originating outside the FOV. Reconstructed images dramatically changed if the correction was carried out using inappropriate procedures. This study demonstrated that accurate reconstruction could be obtained when the scatter compensation was appropriately carried out. This study also suggested the feasibility of using a state-of-the-art 3D PET scanner in the quantitative PET imaging during inhalation of 15O labeled oxygen.

The role of water in gas hydrate dissociation

USGS Publications Warehouse

Circone, S.; Stern, L.A.; Kirby, S.H.

2004-01-01

When raised to temperatures above the ice melting point, gas hydrates release their gas in well-defined, reproducible events that occur within self-maintained temperature ranges slightly below the ice point. This behavior is observed for structure I (carbon dioxide, methane) and structure II gas hydrates (methane-ethane, and propane), including those formed with either H2O- or D2O-host frameworks, and dissociated at either ambient or elevated pressure conditions. We hypothesize that at temperatures above the H2O (or D2O) melting point: (1) hydrate dissociation produces water + gas instead of ice + gas, (2) the endothermic dissociation reaction lowers the temperature of the sample, causing the water product to freeze, (3) this phase transition buffers the sample temperatures within a narrow temperature range just below the ice point until dissociation goes to completion, and (4) the temperature depression below the pure ice melting point correlates with the average rate of dissociation and arises from solution of the hydrate-forming gas, released by dissociation, in the water phase at elevated concentrations. In addition, for hydrate that is partially dissociated to ice + gas at lower temperatures and then heated to temperatures above the ice point, all remaining hydrate dissociates to gas + liquid water as existing barriers to dissociation disappear. The enhanced dissociation rates at warmer temperatures are probably associated with faster gas transport pathways arising from the formation of water product.

Percolation Features on Climate Network under Attacks of El Niño Events

NASA Astrophysics Data System (ADS)

Lu, Z.

2015-12-01

Percolation theory under different attacks is one of the main research areas in complex networks but never be applied to investigate climate network. In this study, for the first time we construct a climate network of surface air temperature field to analyze its percolation features. Here, we regard El Niño event as a kind of naturally attacks generated from Pacific Ocean to attack its upper climate network. We find that El Niño event leads an abrupt percolation phase transition to the climate network which makes it splitting and unstable suddenly. Comparing the results of the climate network under three different forms of attacks, including most connected attack (MA), localized attack (LA) and random attack (RA) respectively, it is found that both MA and LA lead first-order transition and RA leads second-order transition to the climate network. Furthermore, we find that most real attacks consist of all these three forms of attacks. With El Niño event emerging, the ratios of LA and MA increase and dominate the style of attack while RA decreasing. It means the percolation phase transition due to El Niño events is close to first-order transition mostly affected by LA and MA. Our research may help us further understand two questions from perspective of percolation on network: (1) Why not all warming in Pacific Ocean but El Niño events could affect the climate. (2) Why the climate affected by El Niño events changes abruptly.

Cardenolide glycosides from seeds of Corchorus olitorius.

PubMed

Nakamura, T; Goda, Y; Sakai, S; Kondo, K; Akiyama, H; Toyoda, M

1998-12-01

Three new cardenolide glycosides were isolated from the seeds of Corchorus olitorius L. On the basis of chemical and spectroscopic evidence, their structures were established as cannogenol 3-O-beta-D-glucopyranosyl-(1-->4)-O-beta-D-boivinopyranoside, periplogenin 3-O-beta-D-glucopyranosyl-(1-->4)-O-beta-D-digitoxopyranoside and digitoxigenin 3-O-beta-D-glucopyranosyl-(1-->6)-O-beta-D-glucopyranosyl-(1-->4)-O-beta - D-digitoxopyranoside.

Record of a Statherian rift-sag basin in the Central Espinhaço Range: Facies characterization and geochronology

NASA Astrophysics Data System (ADS)

Costa, Alice Fernanda de Oliveira; Danderfer, André; Bersan, Samuel Moreira

2018-03-01

Several rift-related sequences and volcanic-plutonic associations of Statherian age occur within the São Francisco block. One succession within the sedimentary record, the Terra Vermelha Group, defines one of the evolutionary stages of the Espinhaço basin in the Central Espinhaço Range. As a result of stratigraphic analyses and supported by U-Pb zircon geochronological data, the evolution of this unit has been characterized. To more effectively delimit its upper depositional interval, the sequence of this unit, which is represented by the Pau d'Arco Formation, was also studied. The sedimentary signature of the Terra Vermelha Group suggests the infilling of an intracontinental rift associated with alluvial fans as well as lacustrine and eolian environments with associated volcanism. The basal succession represented by the Cavoada do Buraco Formation mainly consists of conglomerates with interlayered sandstones and subordinate banded iron formations. Detrital zircon obtained from this unit reveals ages of 1710 ± 21 Ma. The upper succession, represented by the Espigão Formation, records aeolian sandstones with volcanic activity at the top. A volcanic rock dated at 1758 ± 4 Ma was interpreted as the timing of volcanism in this basin. The eolian deposits recorded within the Pau d'Arco Formation were caused by a renewal of the sequence, which represent a stage of post-rift thermal subsidence. The maximum age of sedimentation for this unit is 1675 ± 22 Ma. The basin-infill patterns and Statherian ages suggest a direct link with the first rifting event within the São Francisco block, which was responsible for the deposition of the Espinhaço Supergroup.

Underwater Facilities Inspection and Assessment at Naval Weapons Station, Concord, California.

DTIC Science & Technology

1983-05-01

OG 0 0 .0 0 C) 0 O 0 0 0 0 0 00 0 0 0 0 OHO (D CD 0 0 0 0 0 0 0 0 c 0 (OD OsOO0O0O0dO0O 0l JOSO(D0OOs 0 0OO~ O00 (D O 0 00 OrO 0 0 lor 00 Or~O 0 0 0o...OPO 0 0 O 0 0 O 0 Op 0 POI 0 0 OR 01 0 OR 0 0 OR 0 0 OR 0 0 OR 0 ROJOE O 0 Os S l. ) Os 0 0 Os 0 0 Os 0 0 Os 0 sOl_rN 0 0 Or rs 0 Or 0 0 Or 0 0 Or 0 0...0 0 001D El 0 0D~ ] - ,- l 0 0 D 0 0 O 0K1 0 ,0 1 0 r 0, 0 - 0O 0 00 (D >O1 H 0 0 0 -_ O O O OlE ] A 00000 0 O 0 0Ol-_ 00 oOo 00 or EOJ(0 d. GI

[Studies on chemical constituents from rhizome of Anemone flaccida].

PubMed

Zhang, Lan-tian; Takaishi, Yoshihisa; Zhang, Yan-wen; Duan, Hong-quan

2008-07-01

To study the chemical constituents from Anemone flaccida. Chemical constituents were isolated by repeated column chromatography (silica gel, Toyopearl HW-40C and preparative HPLC). The structures were elucidated on the basis of spectral data analysis. Twelve triterpenes were isolated and their structures were identified as follow: oleanolic acid (1), oleanolic acid 3-O-beta-D-glccopyranosyl-(1-->2)-beta-D-xylopyranoside (2), eleutheroside K (3), oleanolic acid 3-O-alpha-L-rhamnopyranosyl-(1-->2)-beta-D-xylopyranoside (4), oleanolic acid 3-O-beta-D-glccopyranosyl-(1-->2)-alpha-L-arabinofurnoside (5), oleanolic acid 3-O-beta-D-glccuronopyranose (6), oleanolic acid 3-O-beta-D-glccuronopyranose methyl ester (7), oleanolic acid 28-O-alpha-L-rhamnopyranosyl(1-->4)-beta-D-glccopyranosyl (1-->6)-beta-D-glccopyranosyl (8), oleanolic acid 3-O-beta-D-glccuronopyranose 28-O-alpha-L-rhamnopyranosyl (1-->4)-beta-D-glccopyranosyl (1-->6)-beta-D-glccopyranoside (9), oleanolic acid 3-O-beta-D-glccopyranosyl methyl ester 28-O-alpha-L-rhamnopyranosyl (1-->4)-beta-D-glccopyranosyl (1-->6)-beta-D-glccopyranoside (10), oleanolic acid 3-O-beta-D-glccopyranosyl-(1-->2)-beta-D-xylopyranosyl-28-O-alpha-L-rhamnopyranosyl (1-->4)-beta-D-glccopyranosyl (1-->6)-beta-D-glccopyranoside (11), oleanolic acid 3-O-alpha-L-rh-amnopyranosyl-(1-->2)-alpha-L-arabinopyrnosyl-28-O-alpha-L-rhamnopyranosyl (1-->4)-beta-D-glccopyranosyl (1-->6)-beta-D-glccopyranoside (12). compounds 5-8, 10, 12 were isolated from this plant for the first time. Compounds 2, 5 and 11 showed positive anti-tumor activities.

Spatio-temporal Evolution of On-going Tokai Slow Thrust Slip Event, Central Japan

NASA Astrophysics Data System (ADS)

Miyazaki, S.; Segall, P.; Kato, T.; McGuire, J.; Hatanaka, Y.

2003-12-01

We investigate an on-going slow thrust slip event that occurred at a subduction zone along the Nankai Trough off central Japan. The area we investimate, referred as the Tokai seismic gap, is located to the east of the 1944 Tonankai earthquake, which did not slip in the 1944 event. Continuous GPS data from April 1996 to the end of 1999 shows that the stations in this region have secular velocities of ˜ 2 cm/yr to the northwest relative to the landward plate. The GPS time series show an abrupt increase in rate in late June, 2000. The accelerated rate is currently on-going. We model this non-secular deformation, which we refer to the 2000 Tokai slow slip event, by transient slip at the plate interface and estimate their distribution with Kalman Filter based inversion methods. This event initiated around (137.3oE, 34.9oN) almost at the same time of the onset of volcanic activity on Miyake-jima in late June, 2000. This suggests that the 2000 Tokai slow slip event is triggered by the volcanic activity on Miyake-jima. Then the locus of the slip propagated to (137.5oE, 34.75oN) in second half of 2000, and kept slipping at the maximum rate of ˜ 15cm/yr through 2001. The peak slip-rate propagated to around (137.75oE, 34.9oN) in early 2002. The depth of slip zone is ˜ 25km, which may correspond to the lower edge of the seismogenic zone for the anticipated Tokai earthquake defined from seismicity. The cumulative moment magnitude of the slow slip event to date is MW ˜ 6.8. The duration of this event is longer than previously studied slow slip events using GPS data, including the 1996 Bungo slow slip event (about 1 year) and the 1996 and the 2000 Boso slow events (a few weeks).

Hydrographic and fish larvae distribution during the "Godzilla El Niño 2015-2016" in the northern end of the shallow oxygen minimum zone of the Eastern Tropical Pacific Ocean

NASA Astrophysics Data System (ADS)

Sánchez-Velasco, L.; Beier, E.; Godínez, V. M.; Barton, E. D.; Santamaría-del-Angel, E.; Jiménez-Rosemberg, S. P. A.; Marinone, S. G.

2017-03-01

Based on hydrographic data and vertical distributions of tropical species of fish larvae (Diogenichthys laternatus, Vinciguerria lucetia, Bregmaceros bathymaster, and Auxis spp.), effects of "Godzilla El Niño 2015-2016" in the shallow oxygen minimum zone off Mexico were analyzed. Zooplankton samples were collected during four cruises, before (February 2010 and April 2012) and during (June 2015 and March 2016) the warm event. Temporal series of sea surface temperature revealed that June 2015 was the warmest June of the last years. Conservative temperature was >2°C higher than normal in the surface mixed layer, and the suboxic layer (4.4 µmol/kg) reached as shallow as 100 m depth. Unexpected results were that larval abundances were relatively high during the warm event, unlike zooplankton volumes, which declined. Before the warm event, V. lucetia and Auxis spp. were more abundant in the surface mixed layer, while B. bathymaster and D. laternatus dominated in the thermocline and shallow hypoxic layer (44 µmol/kg). However, during the event in June 2015, all species were most abundant in the surface mixed layer, which implied that the species adapted to hypoxia had inverted their normal pattern of distribution, possibly as consequence of the rise of the suboxic layer; however, further observations are required to confirm this generality. Results showed no dramatic change in the total larval abundance during the warm event. Nevertheless, a differential response in their vertical distribution was evident in association with changes in the depth of the shallow hypoxic and suboxic layers. This might indicate adaptability of tropical species to prolonged periods of warming in the oceans.

Manipulating the reported age in earliest memories.

PubMed

Wessel, Ineke; Schweig, Theresa; Huntjens, Rafaële J C

2017-11-02

Previous work suggests that the estimated age in adults' earliest autobiographical memories depends on age information implied by the experimental context [e.g., Kingo, O. S., Bohn, A., & Krøjgaard, P. (2013). Warm-up questions on early childhood memories affect the reported age of earliest memories in late adolescence. Memory, 21(2), 280-284. doi: 10.1080/09658211.2012.729598 ] and that the age in decontextualised snippets of memory is younger than in more complete accounts (i.e., event memories [Bruce, D., Wilcox-O'Hearn, L. A., Robinson, J. A., Phillips-Grant, K., Francis, L., & Smith, M. C. (2005). Fragment memories mark the end of childhood amnesia. Memory & Cognition, 33(4), 567-576. doi: 10.3758/BF03195324 ]). We examined the malleability of the estimated age in undergraduates' earliest memories and its relation with memory quality. In Study 1 (n = 141), vignettes referring to events happening at age 2 rendered earlier reported ages than examples referring to age 6. Exploratory analyses suggested that event memories were more sensitive to the age manipulation than memories representing a single, isolated scene (i.e., snapshots). In Study 2 (n = 162), asking self-relevant and public-event knowledge questions about participants' preschool years prior to retrieval yielded comparable average estimated ages. Both types of semantic knowledge questions rendered earlier memories than a no-age control task. Overall, the reported age in snapshots was younger than in event memories. However, age-differences between memory types across conditions were not statistically significant. Together, the results add to the growing literature indicating that the average age in earliest memories is not as fixed as previously thought.

Synthesis of 4-O-glycosylated 1,5-anhydro-D-fructose and of 1,5-anhydro-D-tagatose from a common intermediate 2,3-O-isopropylidene-D-fructose.

PubMed

Agoston, Károly; Dékány, Gyula; Lundt, Inge

2009-05-26

Four novel disaccharides of glycosylated 1,5-anhydro-D-ketoses have been prepared: 1,5-anhydro-4-O-beta-D-glucopyranosyl-D-fructose, 1,5-anhydro-4-O-beta-D-galactopyranosyl-D-fructose, 1,5-anhydro-4-O-beta-D-glucopyranosyl-D-tagatose, and 1,5-anhydro-4-O-beta-D-galactopyranosyl-D-tagatose. The common intermediate, 1,5-anhydro-2,3-O-isopropylidene-beta-D-fructopyranose, was prepared from D-fructose and was converted into the D-tagatose derivative by oxidation followed by stereoselective reduction to the 4-epimer. The anhydroketoses thus prepared were glycosylated and deprotected to give the disaccharides.

Continuous infusion of amphotericin B: preliminary experience at Faculdade de Medicina da Fundação ABC.

PubMed

Uehara, Roberto Palermo; Sá, Victor Hugo Lara de; Koshimura, Erika Tae; Prudente, Fernanda Vilas Boas; Tucunduva, Luciana Tomanik Cardozo de Mello; Gonçalves, Marina Sahade; Samano, Eliana Sueco Tibana; del Giglio, Auro

2005-09-01

Intravenous amphotericin B deoxycholate (AmB-D) infusions, usually given over 4 hours, frequently induce nephrotoxicity and undesirable infusion-related side effects such as rigors and chills. There is evidence in the literature that the use of AmB-D in the form of continuous 24-hour infusion is less toxic than the usual four-hour infusion of this drug. Our objective was to evaluate the efficacy and safety of continuous infusion of AmB-D for the treatment of persistent fever in neutropenic patients with hematological malignancies after chemotherapy. Observational retrospective analysis of our experience with continuous infusion of AmB-D, at Faculdade de Medicina da Fundação ABC and Hospital Estadual Mário Covas in Santo André. From October 2003 to May 2004, 12 patients with hematological malignancies and chemotherapy-induced neutropenia received 13 cycles of continuous infusion of AmB-D. The median dose of AmB-D was 0.84 mg/kg/day (0.33 to 2.30 mg/kg/day). Concomitant use of nephrotoxic medications occurred in 92% of the cycles. Nephrotoxicity occurred in 30.76% of the cycles, hypokalemia in 16.67%, hepatotoxicity in 30% and adverse infusion-related events in 23%. All patients survived for at least seven days after starting continuous infusion of AmB-D, and clinical resolution occurred in 76% of the cycles. Continuous infusion of AmB-D can be used in our Institution as an alternative to the more toxic four-hour infusion of AmB-D and possibly also as an alternative to the more expensive liposomal formulations of the drug.

A Survey of the Air Facilities Available to Support a Rapidly Deploying Force from the CONUS to NATO

DTIC Science & Technology

1975-06-06

jaj o ►d P ET ff ffl F a td P c+ M >Ä t: co o CO CL t-J M...p> >» Hfl O O O fe o o o N O "T) td o o H, O 2 4 ro txl tb -o oo o o o o o O *i p ^j ^j ^ •fl •id ^1 o o o o o O hl ^ •i...O td >< o •I - o a • o rt- c CO c+ (D C c+ CD Q M ’d o 5 CD H C3 M •d (D "J (;) O <D (M * ^ O P3 • h m p. g

Lessons learnt from past Flash Floods and Debris Flow events to propose future strategies on risk management

NASA Astrophysics Data System (ADS)

Cabello, Angels; Velasco, Marc; Escaler, Isabel

2010-05-01

Floods, including flash floods and debris flow events, are one of the most important hazards in Europe regarding both economic and life loss. Moreover, changes in precipitation patterns and intensity are very likely to increase due to the observed and predicted global warming, rising the risk in areas that are already vulnerable to floods. Therefore, it is very important to carry out new strategies to improve flood protection, but it is also crucial to take into account historical data to identify high risk areas. The main objective of this paper is to show a comparative analysis of the flood risk management information compiled in four test-bed basins (Llobregat, Guadalhorce, Gardon d'Anduze and Linth basins) from three different European countries (Spain, France and Switzerland) and to identify which are the lessons learnt from their past experiences in order to propose future strategies on risk management. This work is part of the EU 7th FP project IMPRINTS which aims at reducing loss of life and economic damage through the improvement of the preparedness and the operational risk management of flash flood and debris flow (FF & DF) events. The methodology followed includes the following steps: o Specific survey on the effectivity of the implemented emergency plans and risk management procedures sent to the test-bed basin authorities that participate in the project o Analysis of the answers from the questionnaire and further research on their methodologies for risk evaluation o Compilation of available follow-up studies carried out after major flood events in the four test-bed basins analyzed o Collection of the lessons learnt through a comparative analysis of the previous information o Recommendations for future strategies on risk management based on lessons learnt and management gaps detected through the process As the Floods Directive (FD) already states, the flood risks associated to FF & DF events should be assessed through the elaboration of Flood Risk Management Plans (FRMP) with tailored solutions for each basin, evaluating their flood mitigation potential, promoting environmental objectives and increasing the efficiency of the already adopted measures. The FRMP should focus on prevention (and protection), preparedness and response, and these have been the three main risk management phases of a flood crisis that have been assessed when extracting the lessons learnt from past events. Lessons learnt concerning dissemination through the three previously mentioned phases and also related to education initiatives have also been included. A common response to most of the events described in this paper was to upgrade the meteorological and hydrological forecasting systems, making the forecasting lead-time as large as possible. Another common recommendation from the test-beds was the need to implement and accomplish the land use regulations. All the basins also detected that structural measures are necessary to increase the population's protection level, but replacing the traditional safety mentality by a risk culture based on a comprehensive analysis of the flood risk. The four basins studied have also highlighted the importance of collecting information when FF & DF events occur and creating historic databases that will provide extremely useful information in the future.

Continuous Eddy Covariance Measurements of N2O Emissions and Controls from an Intensively Grazed Dairy Farm

NASA Astrophysics Data System (ADS)

Schipper, L. A.; Liang, L. L.; Wall, A.; Campbell, D.

2017-12-01

New Zealand's greenhouse gas (GHG) inventory is disproportionally dominated by methane and nitrous oxide which account for 54% of emissions. These GHGs are derived from pastoral agriculture that supports dairying and meat production. To date, most studies on quantifying or mitigating agricultural N2O emissions have used flux chamber measurements. Recent advances in detector technology now means that routine field-to-farm scale measurements of N2O emissions might be possible using the eddy covariance technique. In late 2016, we established an eddy covariance tower that measured N2O emissions from a dairy farm under year-round grazing. An Aerodyne quantum cascade laser (QCL) was used to measure N2O, CH4 and H2O concentration at 10 Hz and housed in a weatherproof and insulated enclosure (0.9 m ´ 1.2 m) and powered by mains power (240 VAC). The enclosure maintained a stable setpoint temperature (30±0.2°C) by using underground cooling pipes, fans and recirculating instrument heat. QCL (true 10 Hz digital) and CSAT3B sonic anemometer high frequency data are aligned using Network Time Protocol and EddyPro covariance maximisation during flux processing. Fluxes generally integrated over about 6-8 ha. Stable summertime baseline N2O fluxes (FN2O) were around 12-24 g N2O-N ha-1 d-1 (0.5-1.0 nmol N2O m-2 s-1). Grazing by cows during dry summer resulted in only modest increases in FN2O to 24-48 g N2O-N ha-1 d-1 (1.0-2.0 nmol N2O m-2 s-1). However, the first rain events after grazing resulted in large, short-lived (1-3 days) FN2O pulses reaching peaks of 144-192 g N2O-N ha-1 d-1 (6-8 nmol N2O m-2 s-1). During these elevated N2O emissions, FN2O displayed a significant diurnal signal, with peak fluxes mid-afternoon which was best explained by variation in shallow soil temperature in summer. In winter (both cooler and wetter) FN2O were not as easily explained on a daily basis but were generally greater than summer. Throughout the year, FN2O was strongly dependent on water filled pore-space (WFPS) with low fluxes under dry and wet conditions and maximal at 70% WFPS. This eddy covariance approach is a very powerful way to make continuous nitrous oxide measurements over sufficiently large areas to represent farm management practices and test mitigation strategies.

Recurring OH Flares towards o Ceti - I. Location and structure of the 1990s' and 2010s' events

NASA Astrophysics Data System (ADS)

Etoka, S.; Gérard, E.; Richards, A. M. S.; Engels, D.; Brand, J.; Le Bertre, T.

2017-06-01

We present the analysis of the onset of the new 2010s OH flaring event detected in the OH ground-state main line at 1665 MHz towards o Ceti and compare its characteristics with those of the 1990s' flaring event. This is based on a series of complementary single-dish and interferometric observations both in OH and H2O obtained with the Nançay Radio telescope, the Medicina and Effelsberg Telescopes, the European VLBI Network and (e)Multi-Element Radio Linked Interferometer Network. We compare the overall characteristics of o Ceti's flaring events with those that have been observed towards other thin-shell Miras, and explore the implication of these events with respect to the standard OH circumstellar-envelope model. The role of binarity in the specific characteristics of o Ceti's flaring events is also investigated. The flaring regions are found to be less than ˜400 ± 40 mas (I.e. ≤40 ± 4 au) either side of o Ceti, with seemingly no preferential location with respect to the direction to the companion Mira B. Contrary to the usual expectation that the OH maser zone is located outside the H2O maser zone, the coincidence of the H2O and OH maser velocities suggests that both emissions arise at similar distances from the star. The OH flaring characteristics of Mira are similar to those observed in various Mira variables before, supporting the earlier results that the regions where the transient OH maser emission occurs are different from the standard OH maser zone.

Bacterial Bolsheviks: PS II and the Evolution of the Oxygenic Revolution

NASA Astrophysics Data System (ADS)

Kopp, R. E.; Kirschvink, J. L.; Newman, D. K.; Nash, C. Z.; Hilburn, I. A.

2003-12-01

After the rise of life itself, the most radical transformation of Earth's biogeochemical cycles was the transition from an anoxic to an oxic world. Though various studies have suggested O2 made its first bulk appearance in the atmosphere some time between 3.8 and 2.1 Ga, virtually all analyses agree the production of large quantities of free O2 was triggered by the evolution of oxygenic photosynthesis. We suggest the oldest strong geological evidence for O2 is the 2.22 Ga Kalahari Mn member of the Hotazel BIF (1), as in the oceans only free O2 can oxidize soluble Mn(II) into insoluble Mn(IV). Some have argued, however, that oxygenic cyanobacteria had originated by 2.7 Ga. The ˜500 Myr "gap" has often been interpreted as the timescale for gradual evolutionary improvement of the O2-generating system. Biochemical and genomic analyses of photosynthetic bacteria indicate that photosystems I and II, which operate together in cyanobacteria, had a long history of parallel development. Green sulfur bacteria and heliobacteria use PS-II, while green non-sulfur and purple bacteria use PS-I; none can use H2O as an electron donor. Recent genetic analyses show lateral gene transfer was rampant among photosynthetic lineages (2). Moreover, extant cyanobacteria shut down PS-II in the presence of an alternative electron donor like H2S. This suggests PS-I and PS-II came together with their functions intact. Hence, most `debugging' of the two systems predates their merger in the ancestor of modern cyanobacteria. The time interval between the lateral transfer events and the evolution of oxygenic photosynthesis could thus have been geologically short. We suggest the ˜500 Myr "gap" may result from misinterpretations. The presence of oxygenic photosynthesis is uncertain before the deposition of the Hotazel formation, in the aftermath of the Makganyene glaciation (1). A simple model of nutrient and reductant fluxes argues that, once triggered, the oxygenation of a reducing surface environment warmed by a CH4 greenhouse (3) should occur fairly rapidly, within ˜ 10 My. The trigger requires both the evolution of cyanobacteria and sufficiently high nutrient (mainly P) fluxes to allow O2 production to overwhelm reductant fluxes. P flux into the oceans in glaciated worlds correlates with increased continental weathering during glacial intervals (4). Thus, were cyanobacteria present during the Huronian glaciations, which predate 2.22 Ga (5), these glaciations should have triggered the oxygenation event. Instead, the oxygenation event seems to correlate with the Makganyene glaciation, at 2.22 Ga (6). The appearance of red beds in the Upper Timeball Hill formation directly underlying the Makganyene diamictite supports this interpretation. As would be expected from a glaciation associated with the destruction of a CH4 greenhouse, paleomagnetic data indicate the Makganyene glaciation was a global Snowball event (7). Cyanobacteria appear to have evolved in the short interval between the Huronian glaciations and the Makganyene glaciation. The lengthy delay between the earliest life on Earth and the appearance of cyanobacteria suggests that the oxygenic revolution was a fairly low probability event; planets with oxygenic biospheres may be quite rare. 1. J. L. Kirschvink et al., PNAS 97, 1400-1405 (2000). 2. J. Raymond et al., Science 298, 1616-1620 (2002). 3. A. A. Pavlov et al., JGR 105, 11981-11990 (2000). 4. K. B. F”llmi, Geology 23, 503-506 (1995). 5. S. R. Noble, P. C. Lightfoot, Can. J. Earth Sci. 29, 1424-1429 (1992). 6. D. H. Cornell et al., Precamb. Res. 79, 101-123 (1996). 7. D. A. Evans et al., Nature 386, 262-266 (1997).

Investigating Volcanic-Hydrothermal Systems in Dominica, Lesser Antilles: Temporal Changes in the Chemical Composition of Hydrothermal Fluids for Volcanic Monitoring Using Geothermometers

NASA Astrophysics Data System (ADS)

Onyeali, M. M. C.; Joseph, E. P.; Frey, H. M.

2017-12-01

Dominica has an abundance of volcanic activity, with nine potentially active volcanoes, many of which have highly active volcanic-hydrothermal systems. The waters are predominantly acid-sulphate in character (SO4=100-4200 mg/L, pH≤4), and likely formed because of dilution of acidic gases in near surface oxygenated groundwater. The waters are of primarily meteoric origin, but are likely affected by evaporation effects at/near the surface, with δ18O ranging from -1.75 to 10.67‰, and δD from -6.1 to 14.5‰. With updated water chemistry and isotopic data from five hydrothermal areas (Boiling Lake, Valley of Desolation, Sulphur Springs, Wotten Waven, Cold Soufriere) for the period 2014 to 2017, we will re-evaluate the characteristics of these systems, which were last reported in 2011. We will present updated reservoir temperatures using a variety of geothermometers and provide insight into water-rock interactions taking place in the reservoirs. Recent changes in chemistry of the waters have indicated that while the origin of the hydrothermal systems are still dominantly meteoric (δ18O = -3 to 8‰ and δD = -5 to 18‰), surface evaporation effects and variable amounts of mixing with shallow ground waters play an important role. Fumaroles appear to reflect a deeper source contribution as compared to thermal waters with differences in acidity, temperature, TDS, δ18O, and δD observed. The general composition of the waters for most of the hydrothermal systems studied indicate no significant changes, with the exception of the Boiling Lake, which experienced a draining event in November 2016 which lasted for 6 weeks. Decreases in temperature, pH, Na, K, and Cl were seen post draining, while SO4 remained relatively low (66 ppm), but showed a small increase. The chemistry of the Boiling Lake appears to show significant changes in response to changes in the groundwater system. Changes in the groundwater system at the lake observed during the 2004/2005 draining, which lasted for 6 months, were attributed to strain release from a nearby regional seismic event. Based on the changes observed during the recent draining events, there are likely other factors affecting the ground water system at the Boiling Lake. Of particular note is the drastic change in SO4 concentrations in the Boiling Lake, which went from 1830 ppm in 2003 to <100 ppm presently.

Cardiovascular Events Associated With SGLT-2 Inhibitors Versus Other Glucose-Lowering Drugs: The CVD-REAL 2 Study.

PubMed

Kosiborod, Mikhail; Lam, Carolyn S P; Kohsaka, Shun; Kim, Dae Jung; Karasik, Avraham; Shaw, Jonathan; Tangri, Navdeep; Goh, Su-Yen; Thuresson, Marcus; Chen, Hungta; Surmont, Filip; Hammar, Niklas; Fenici, Peter

2018-06-12

Randomized trials demonstrated a lower risk of cardiovascular (CV) events with sodium-glucose cotransporter-2 inhibitors (SGLT-2i) in patients with type 2 diabetes (T2D) at high CV risk. Prior real-world data suggested similar SGLT-2i effects in T2D patients with a broader risk profile, but these studies focused on heart failure and death and were limited to the United States and Europe. The purpose of this study was to examine a broad range of CV outcomes in patients initiated on SGLT-2i versus other glucose-lowering drugs (oGLDs) across 6 countries in the Asia Pacific, the Middle East, and North American regions. New users of SGLT-2i and oGLDs were identified via claims, medical records, and national registries in South Korea, Japan, Singapore, Israel, Australia, and Canada. Propensity scores for SGLT-2i initiation were developed in each country, with 1:1 matching. Hazard ratios (HRs) for death, hospitalization for heart failure (HHF), death or HHF, MI, and stroke were assessed by country and pooled using weighted meta-analysis. After propensity-matching, there were 235,064 episodes of treatment initiation in each group; ∼27% had established CV disease. Patient characteristics were well-balanced between groups. Dapagliflozin, empagliflozin, ipragliflozin, canagliflozin, tofogliflozin, and luseogliflozin accounted for 75%, 9%, 8%, 4%, 3%, and 1% of exposure time in the SGLT-2i group, respectively. Use of SGLT-2i versus oGLDs was associated with a lower risk of death (HR: 0.51; 95% confidence interval [CI]: 0.37 to 0.70; p < 0.001), HHF (HR: 0.64; 95% CI: 0.50 to 0.82; p = 0.001), death or HHF (HR: 0.60; 95% CI: 0.47 to 0.76; p < 0.001), MI (HR: 0.81; 95% CI: 0.74 to 0.88; p < 0.001), and stroke (HR: 0.68; 95% CI: 0.55 to 0.84; p < 0.001). Results were directionally consistent across both countries and patient subgroups, including those with and without CV disease. In this large, international study of patients with T2D from the Asia Pacific, the Middle East, and North America, initiation of SGLT-2i was associated with a lower risk of CV events across a broad range of outcomes and patient characteristics. (Comparative Effectiveness of Cardiovascular Outcomes in New Users of SGLT-2 Inhibitors [CVD-REAL]; NCT02993614). Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.

Three new triterpenoid saponins from the seeds of Aesculus turbinata.

PubMed

Yang, Xiu-Wei; Zhao, Jing; Hattori, Masao

2008-01-01

Three new triterpenoid saponins, named isoescins VIIa (1), VIa (2), and VIIIa (3), were isolated from the seeds of Aesculus turbinata and identified by spectroscopic analysis and chemical hydrolysis. Their structures were established as 21beta-O-tigloyl-28-O-acetylprotoaescigenin 3beta-O-[beta-d-galactopyranosyl(1 --> 2)][beta-d-glucopyranosyl(1 --> 4)]-beta-d-glucopyranosiduronic acid (Isoescin VIIa, 1), 21beta-O-(2-methylbutyryl)-28-O-acetylprotoaescigenin 3beta-O-[beta-d-glucopyranosyl(1 --> 2)] [beta-d-glucopyranosyl(1 --> 4)]-beta-d-glucopyranosiduronic acid (Isoescin VIa, 2), and 21beta-O-angeloyl-28-O-acetylbarringtogenol C 3beta-O-[beta-d-glucopyranosyl(1 --> 2)] [beta-d-glucopyranosyl(1 --> 4)]-beta-d-glucopyranosiduronic acid (Isoescin VIIIa, 3).

Terminal Area Forecasts, FY 1993-2005

DTIC Science & Technology

1993-07-01

0 td U) ~ 4-) 4.J.4 0 J~ :s 0- -"C4 4o U ).4CO ) 0 u *Wý44 o 41C kdQ(n v 00 UrC~ 4) -4 0 M 0~ 4j > (D M kca 41 Ř b bO CA -A~ ..O 0 .0 Cd~ bl ~ - k...o tD ~ Hr- Nr,- `4v oH f n% oM 0( ON %D ~H w H LnODH (1 O O D DO ODG OD 00 OhOh(T ma % m %0 HC4.Ch h %Ch( i % )d% HN 4J H 1-0 %D- O M (NWN DU VO D...I ~ J)I C1 F "H OD ,- V 1 D ( -r r -4 Ch’. ON 00 -4 c,4 mu) n( (n A;1 m tD b r-4 rJ’q~~ I Nr-W L o 0 ( O HM N~ - I- IV N- M M O ’ rI % NN . OD U NCh0

Infrared spectra and tunneling dynamics of the N2-D2O and OC-D2O complexes in the v2 bend region of D2O.

PubMed

Zhu, Yu; Zheng, Rui; Li, Song; Yang, Yu; Duan, Chuanxi

2013-12-07

The rovibrational spectra of the N2-D2O and OC-D2O complexes in the v2 bend region of D2O have been measured in a supersonic slit jet expansion using a rapid-scan tunable diode laser spectrometer. Both a-type and b-type transitions were observed for these two complexes. All transitions are doubled, due to the heavy water tunneling within the complexes. Assuming the tunneling splittings are the same in K(a) = 0 and K(a) = 1, the band origins, all three rotational and several distortion constants of each tunneling state were determined for N2-D2O in the ground and excited vibrational states, and for OC-D2O in the excited vibrational state, respectively. The averaged band origin of OC-D2O is blueshifted by 2.241 cm(-1) from that of the v2 band of the D2O monomer, compared with 1.247 cm(-1) for N2-D2O. The tunneling splitting of N2-D2O in the ground state is 0.16359(28) cm(-1), which is about five times that of OC-D2O. The tunneling splittings decrease by about 26% for N2-D2O and 23% for OC-D2O, respectively, upon excitation of the D2O bending vibration, indicating an increase of the tunneling barrier in the excited vibrational state. The tunneling splittings are found to have a strong dependence on intramolecular vibrational excitation as well as a weak dependence on quantum number K(a).

Three new triterpenoid saponins from Dianthus superbus.

PubMed

Luo, Jian-Guang; Chen, Xia; Kong, Ling-Yi

2011-01-01

Three new triterpenoid saponins (1-3) were isolated from the dried aerial parts of Dianthus superbus L. (Caryophyllaceae). Their structures were established as 3-O-β-D-glucopyranosyl gypsogenic acid 28-O-[β-D-6-O-((3S)-3-hydroxyl-3-methylglutaryl)glucopyranosyl(1→6)]-β-D-glucopyranoside (1), 3-O-β-D-glucopyranosyl gypsogenic acid 28-O-[β-D-glucopyranosyl(1→3)][β-D-6-O-((3S)-hydroxyl-3-methylglutaryl)glucopyranosyl(1→6)]-β-D-glucopyranoside (2), 3-O-α-L-arabinopyranosyl-3β,16α-dihydroxyolean-12-en-23,28-dioic acid 28-O-[β-D-glucopyranosyl-(1→6)]-β-D-glucopyranoside (3), on the basis of various spectroscopic analyses and chemical degradations.

The study of the geomagnetic excursions and the relative intensities from Chinese loess 10Be over the past 130 ka

NASA Astrophysics Data System (ADS)

Zhou, W.; Xian, F.; Beck, J.; An, Z.; Wu, Z.; Liu, M.; Chen, M.; Priller, A.; Kutschera, W.; Jull, A. T.; Yu, H.; Song, S.; Cheng, P.; Kong, X.

2009-12-01

Chinese loess is well-known archive for the paleogeomagnetic and paleoclimatic studies [Zhou et al., 1990; An et al., 1990; Zhu et al., 2007]. However, earlier efforts to extract weak geomagnetic excursion signals from Chinese loess 10Be were always unsuccessful due to the complexities of loess 10Be, which results in the fact that loess 10Be was only used as a climatic proxy [Shen et al., 1992; Beer et al.,1993; Gu et al.,1996]. Meanwhile, knowledge on the precise stratigraphic horizons of geomagnetic excursions with a reliable dating [Channell, 2006], on whether the short-lived excursions such as Blake can not be recorded in paleosol unit are still controversial. Here, we present the reconstructed past 130ka geomagnetic excursions and relative paleointensities for the first time from 10Be records in two Chinese loess sections. Results are comparative with those of independent geomagnetic research on Atlantic and Pacific sediments. The derived Laschamp and Blake events lie in the loess-paleosol (L1SS1 and S1SS3) corresponding to mid MIS 3 and 5e respectively. Our studies prove the potential application of the complex loess 10Be for long-term geomagnetic tracing and provide new evidence to answer the long-existing debates on the precise stratigraphic horizon of geomagnetic excursions. Our study suggests the potential application of loess-paleosol 10Be for reconstructing geomagnetic intensity variations spanning the whole Quaternary. References 1. Zhou, L. P., F. Oldfield, A. G. Wintle, S. G. Robinson, and J. T. Wang (1990), Partly pedogenic origin of magnetic variations in Chinese loess, Nature, 346, 737-739. 2. An, Z. S., T. S. Liu, Y. C. Lu, S. C. Porter, G. Kukla, X. H. Wu, and Y. M. Hua (1990), The long-term paleomonsoon variation recorded by the loess-paleosol sequence in Central China, Quat. Int., 7-8, 91-95. 3. Zhu, R. X., R. Zhang, C. L. Deng, Y. X. Pan, Q. S. Liu, and Y. B. Sun (2007), Are Chinese loess deposits essentially continuous?, Geophys. Res. Lett., 34, L17306. 4. Shen, C. D., J. Beer, T. S. Liu, H. Oeschger, G. Bonani, M. Suter, and W.Wolfli (1992), 10Be in Chinese loess, Earth Planet. Sci. Lett., 109(1-2), 169-177. 5. Gu, Z. Y., D. Lal, T. S. Liu, J. Southon, M. W. Caffee, Z. T. Guo, and M. Y.Chen (1996), Five million year 10Be record in Chinese loess and red-clay: climate and weathering relationships, Earth Planet. Sci. Lett., 144(1-2), 273-287. 6. Beer, J., C. D. Shen, F. Heller ,T.S. Liu, G. Bonani, B. Dittrich, M. Suter, and P.W. Kubik (1993), 10Be and magnetic susceptibility in Chinese Loess, Geophys. Res. Lett., 20(1), 57-60 7. Channell, J. E. T.(2006), Late Brunhes polarity excursions (Mono Lake, Laschamp, Iceland Basin and Pringle Falls) recorded at ODP Site 919 (Irminger Basin), Earth Planet. Sci. Lett., 244(1-2), 378-393.

The Practice of Organization Development.

ERIC Educational Resources Information Center

Vaill, Peter B.

An article about the men who are doing organization Development (O.D.) work is presented. It is divided into the following sections: (1) The Elements of O.D. Practice; (2) Interrelationships of the Elements of O.D. Practice; (3) Sources of Data on O.D. Practice; (4) The O.D. Practitioner and the Client; (5) The O.D. Practitioner and the Evaluator;…

Summertime ozone at Mount Washington: Meteorological controls at the highest peak in the northeast

NASA Astrophysics Data System (ADS)

Fischer, Emily V.; Talbot, Robert W.; Dibb, Jack E.; Moody, Jennie L.; Murray, Georgia L.

2004-12-01

This study examined the synoptic and regional-scale meteorological controls on summertime O3 at Mount Washington, the highest peak (1910 m) in the northeastern United States. Analysis of air mass transport to Mount Washington was conducted for the summers of 1998-2003 using backward trajectories. Distinct patterns in air mass history were revealed using this approach that helped explain extreme variations in O3 mixing ratios. Most enhanced (≥90th percentile) and depleted (≤10th percentile) O3 events were short-lived and spread out over the summer months. Enhanced O3 events at Mount Washington were generally associated with westerly transport, while depleted events corresponded to northwesterly transport. Periods of O3 greater than 80 ppbv during nighttime periods coincided with westerly (71%) and southwesterly (29%) transport. Periods of elevated O3 commonly occurred during regional warm sector flow or on the western edge of a surface anticyclone. Our analysis also identified a stratospheric contribution to a small percentage (˜5%) of extreme O3 events at the site, but more evidence is required to establish the significance of the contribution to background O3 levels in this region.

Isotopic separation of D.sub.2 O from H.sub.2 O using ruthenium adsorbent

DOEpatents

Thiel, Patricia A.

1990-04-10

A method of enrichment of D.sub.2 O in solutions of D.sub.2 O in H.sub.2 O by contacting said solutions in the steam phase with hexagonal crystalline to produce enriched D.sub.2 O. The passages may be repeated to achieve a desired amount of D.sub.2 O.

The Defining Characteristics of ENSO Extremes and the Strong 2015/2016 El Niño

NASA Astrophysics Data System (ADS)

Santoso, Agus; Mcphaden, Michael J.; Cai, Wenju

2017-12-01

The year 2015 was special for climate scientists, particularly for the El Niño Southern Oscillation (ENSO) research community, as a major El Niño finally materialized after a long pause since the 1997/1998 extreme El Niño. It was scientifically exciting since, due to the short observational record, our knowledge of an extreme El Niño has been based only on the 1982/1983 and 1997/1998 events. The 2015/2016 El Niño was marked by many environmental disasters that are consistent with what is expected for an extreme El Niño. Considering the dramatic impacts of extreme El Niño, and the risk of a potential increase in frequency of ENSO extremes under greenhouse warming, it is timely to evaluate how the recent event fits into our understanding of ENSO extremes. Here we provide a review of ENSO, its nature and dynamics, and through analysis of various observed key variables, we outline the processes that characterize its extremes. The 2015/2016 El Niño brings a useful perspective into the state of understanding of these events and highlights areas for future research. While the 2015/2016 El Niño is characteristically distinct from the 1982/1983 and 1997/1998 events, it still can be considered as the first extreme El Niño of the 21st century. Its extremity can be attributed in part to unusually warm condition in 2014 and to long-term background warming. In effect, this study provides a list of physically meaningful indices that are straightforward to compute for identifying and tracking extreme ENSO events in observations and climate models.

Mutagenic Spectra Arising from Replication Bypass of the 2,6-diamino-4-hydroxy-N5-methyl Formamidopyrimidine Adduct in Primate Cells

PubMed Central

Earley, Lauriel F.; Minko, Irina G.; Christov, Plamen P.; Rizzo, Carmelo J.; Lloyd, R. Stephen

2013-01-01

DNA exposures to electrophilic methylating agents that are commonly used during chemotherapeutic treatments cause diverse chemical modifications of nucleobases, with reaction at N7-dG being the most abundant. Although this base modification frequently results in destabilization of the glycosyl bond and spontaneous depurination, the adduct can react with hydroxide ion to yield a stable, ring-opened MeFapy-dG and this lesion has been reported to persist in animal tissues. Results from prior in vitro replication bypass investigations of the MeFapy-dG adduct had revealed complex spectra of replication errors that differed depending on the identity of DNA polymerase and the local sequence context. In this study, a series of nine site-specifically modified MeFapy-dG-containing oligodeoxynucleotides were engineered into a shuttle vector and subjected to replication in primate cells. In all nine sequence contexts examined, MeFapy-dG was shown to be associated with a strong mutator phenotype, predominantly causing base substitutions, with G to T transversions being most common. Single and dinucleotide deletions were also found in a subset of the sequence contexts. Interestingly, single-nucleotide deletions occurred not only at the adducted site, but also one nucleotide downstream of the adduct. Standard models for primer-template misalignment could account for some, but not all mutations observed. These data demonstrate that in addition to mutagenesis predicted from replication of DNAs containing O6-Me-dG and O4-Me-dT, the MeFapy-dG adduct likely contributes to mutagenic events following chemotherapeutic treatments. PMID:23763662

A role for Tn6029 in the evolution of the complex antibiotic resistance gene loci in genomic island 3 in enteroaggregative hemorrhagic Escherichia coli O104:H4.

PubMed

Roy Chowdhury, Piklu; Charles, Ian G; Djordjevic, Steven P

2015-01-01

In enteroaggregative hemorrhagic Escherichia coli (EAHEC) O104 the complex antibiotic resistance gene loci (CRL) found in the region of divergence 1 (RD1) within E. coli genomic island 3 (GI3) contains blaTEM-1, strAB, sul2, tet(A)A, and dfrA7 genes encoding resistance to ampicillin, streptomycin, sulfamethoxazole, tetracycline and trimethoprim respectively. The precise arrangement of antibiotic resistance genes and the role of mobile elements that drove the evolutionary events and created the CRL have not been investigated. We used a combination of bioinformatics and iterative BLASTn searches to determine the micro-evolutionary events that likely led to the formation of the CRL in GI3 using the closed genome sequences of EAHEC O104:H4 strains 2011C-3493 and 2009EL-2050 and high quality draft genomes of EAHEC E. coli O104:H4 isolates from sporadic cases not associated with the initial outbreak. Our analyses indicate that the CRL in GI3 evolved from a progenitor structure that contained an In2-derived class 1 integron in a Tn21/Tn1721 hybrid backbone. Within the hybrid backbone, a Tn6029-family transposon, identified here as Tn6029C abuts the sul1 gene in the 3'-Conserved Segment (-CS) of a class 1 integron generating a unique molecular signature that has only previously been observed in pASL01a, a small plasmid found in commensal E. coli in West Africa. From this common progenitor, independent IS26-mediated events created two novel transposons identified here as Tn6029D and Tn6222 in 2011C-3493 and 2009EL-2050 respectively. Analysis of RD1 within GI3 reveals IS26 has played a crucial role in the assembly of regions within the CRL.

The effects of the Indo-Pacific warm pool on the stratosphere

NASA Astrophysics Data System (ADS)

Zhou, Xin; Li, Jianping; Xie, Fei; Ding, Ruiqiang; Li, Yanjie; Zhao, Sen; Zhang, Jiankai; Li, Yang

2017-03-01

Sea surface temperature (SST) in the Indo-Pacific warm pool (IPWP) plays a key role in influencing East Asian climate, and even affects global-scale climate change. This study defines IPWP Niño and IPWP Niña events to represent the warm and cold phases of IPWP SST anomalies, respectively, and investigates the effects of these events on stratospheric circulation and temperature. Results from simulations forced by observed SST anomalies during IPWP Niño and Niña events show that the tropical lower stratosphere tends to cool during IPWP Niño events and warm during IPWP Niña events. The responses of the northern and southern polar vortices to IPWP Niño events are fairly symmetric, as both vortices are significantly warmed and weakened. However, the responses of the two polar vortices to IPWP Niña events are of opposite sign: the northern polar vortex is warmed and weakened, but the southern polar vortex is cooled and strengthened. These features are further confirmed by composite analysis using reanalysis data. A possible dynamical mechanism connecting IPWP SST to the stratosphere is suggested, in which IPWP Niño and Niña events excite teleconnections, one similar to the Pacific-North America pattern in the Northern Hemisphere and a Rossby wave train in the Southern Hemisphere, which project onto the climatological wave in the mid-high latitudes, intensifying the upward propagation of planetary waves into the stratosphere and, in turn, affecting the polar vortex.

The role of event water, a rapid shallow flow component, and catchment size in summer stormflow

USGS Publications Warehouse

Brown, V.A.; McDonnell, Jeffery J.; Burns, Douglas A.; Kendall, C.

1999-01-01

Seven nested headwater catchments (8 to 161 ha) were monitored during five summer rain events to evaluate storm runoff components and the effect of catchment size on water sources. Two-component isotopic hydrograph separation showed that event-water contributions near the time of peakflow ranged from 49% to 62% in the 7 catchments during the highest intensity event. The proportion of event water in stormflow was greater than could be accounted for by direct precipitation onto saturated areas. DOC concentrations in stormflow were strongly correlated with stream 18O composition. Bivariate mixing diagrams indicated that the large event water contributions were likely derived from flow through the soil O-horizon. Results from two-tracer, three-component hydrograph separations showed that the throughfall and O-horizon soil-water components together could account for the estimated contributions of event water to stormflow. End-member mixing analysis confirmed these results. Estimated event-water contributions were inversely related to catchment size, but the relation was significant for only the event with greatest rainfall intensity. Our results suggest that perched, shallow subsurface flow provides a substantial contribution to summer stormflow in these small catchments, but the relative contribution of this component decreases with catchment size.Seven nested headwater catchments (8 to 161 ha) were monitored during five summer rain events to evaluate storm runoff components and the effect of catchment size on water sources. Two-component isotopic hydrograph separation showed that event-water contributions near the time of peakflow ranged from 49% to 62% in the 7 catchments during the highest intensity event. The proportion of event water in stormflow was greater than could be accounted for by direct precipitation onto saturated areas. DOC concentrations in stormflow were strongly correlated with stream 18O composition. Bivariate mixing diagrams indicated that the large event water contributions were likely derived from flow through the soil O-horizon. Results from two-tracer, three-component hydrograph separations showed that the throughfall and O-horizon soil-water components together could account for the estimated contributions of event water to stormflow. End-member mixing analysis confirmed these results. Estimated event-water contributions were inversely related to catchment size, but the relation was significant for only the event with greatest rainfall intensity. Our results suggest that perched, shallow subsurface flow provides a substantial contribution to summer stormflow in these small catchments, but the relative contribution of this component decreases with catchment size.

Climate Change and Drought Events in the Geochemical Records of the Lacustrine Deposits in the Southeastern Tibetan Plateau

PubMed Central

Shi, Zhengtao; Niu, Jie; Su, Huai

2016-01-01

Lacustrine deposits at the margin of the southeastern Tibetan Plateau (SETP) are sensitive indicators for the evolution of the southwest Asian monsoon (SWAM) during the Quaternary. Thus, they can provide insight into the Quaternary climatic history and their relationship with global climatic changes. The results of the geochemical analysis of the Xiaozhongdian Basin section at the SETP suggest that SiO2 had the highest content of the major elements followed by Al2O3. The order of the abundance of the major elements was generally as follows: SiO2>Al2O3>Fe2O3>CaO>MgO>K2O>TiO2>Na2O>MnO2. The geochemical proxies, such as chemical index of alteration (CIA), the index of compositional variability (ICV) and (CaO+K2O+Na2O)/Al2O3, indicate the weak chemical weathering and the aridification of the margin of the SETP during the Heinrich events. In addition, the aridification of the SETP during the Heinrich events may be closely related to the cold signals transmitted from the high latitudes of the North Atlantic to the TP, and the effect caused the cooling effect to be very strong on the TP as a result of the upper-level westerly jet stream and then reduced the suction action associated with the SWAM, thus accelerating the drying rate of Xiaozhongdian Basin, which was amplifying the degree of drought in Heinrich events. PMID:28033377

Psychometric assessment of the IBS-D Daily Symptom Diary and Symptom Event Log.

PubMed

Rosa, Kathleen; Delgado-Herrera, Leticia; Zeiher, Bernie; Banderas, Benjamin; Arbuckle, Rob; Spears, Glen; Hudgens, Stacie

2016-12-01

Diarrhea-predominant irritable bowel syndrome (IBS-D) can considerably impact patients' lives. Patient-reported symptoms are crucial in understanding the diagnosis and progression of IBS-D. This study psychometrically evaluates the newly developed IBS-D Daily Symptom Diary and Symptom Event Log (hereafter, "Event Log") according to US regulatory recommendations. A US-based observational field study was conducted to understand cross-sectional psychometric properties of the IBS-D Daily Symptom Diary and Event Log. Analyses included item descriptive statistics, item-to-item correlations, reliability, and construct validity. The IBS-D Daily Symptom Diary and Event Log had no items with excessive missing data. With the exception of two items ("frequency of gas" and "accidents"), moderate to high inter-item correlations were observed among all items of the IBS-D Daily Symptom Diary and Event Log (day 1 range 0.67-0.90). Item scores demonstrated reliability, with the exception of the "frequency of gas" and "accidents" items of the Diary and "incomplete evacuation" item of the Event Log. The pattern of correlations of the IBS-D Daily Symptom Diary and Event Log item scores with generic and disease-specific measures was as expected, moderate for similar constructs and low for dissimilar constructs, supporting construct validity. Known-groups methods showed statistically significant differences and monotonic trends in each of the IBS-D Daily Symptom Diary item scores among groups defined by patients' IBS-D severity ratings ("none"/"mild," "moderate," or "severe"/"very severe"), supporting construct validity. Initial psychometric results support the reliability and validity of the items of the IBS-D Daily Symptom Diary and Event Log.

The patterns and implications of diurnal variations in d-excess of plant water, shallow soil water and air moisture

NASA Astrophysics Data System (ADS)

Zhao, L.; Wang, L.; Xiao, H.; Cheng, G.; Ruan, Y.; Zhou, M.; Wang, F.

2014-04-01

Deuterium excess (d-excess) of air moisture is traditionally considered as a conservative tracer of oceanic evaporation conditions. Recent studies challenge this view and emphasize the importance of vegetation activity in controlling the dynamics of air moisture d-excess. However direct field observations supporting the role of vegetation in d-excess variations is not well documented. In this study, we quantified d-excess of air moisture, leaf and xylem water of multiple dominant species as well as shallow soil water (5 and 10 cm) at hourly interval during three extensive field campaigns at two climatically different locations within the Heihe River Basin. The results showed that with the increase of temperature (T) and decrease of relative humidity (RH), the δD-δ18O plots of leaf water, xylem water and shallow soil water deviated gradually from their corresponding local meteoric water line. There were significant differences in d-excess values among different water pools at all the study sites. The most positive d-excess values were found in air moisture (9.3‰) and the most negative d-excess values (-85.6‰) were found in leaf water. The d-excess values of air moisture (dmoisture) and leaf water (dleaf) during the sunny days, and shallow soil water (dsoil) during the first sunny day after rain event showed strong diurnal patterns. There were significantly positive relationships between dleaf and RH and negative relationships between dmoisture and RH. The correlations of dleaf and dmoisture with T were opposite to their relationships with RH. In addition, we found the opposite diurnal variations for dleaf and dmoisture during the sunny day, and for dleaf during the sunny days, and shallow soil water dsoil and dmoisture during the first sunny day after rain event. Significant negative relationships were found between dleaf and dmoisture in all the sites during the sunny day. Our results provide direct evidence that dmoisture of the surface air at continental locations can be significantly altered by local processes, especially plant transpiration during the sunny days. The role of shallow soil water on dmoisture is generally much smaller but could be large at the sunny day right after rainfall events.

Traumeel vs. diclofenac for reducing pain and improving ankle mobility after acute ankle sprain: a multicentre, randomised, blinded, controlled and non-inferiority trial.

PubMed

González de Vega, C; Speed, C; Wolfarth, B; González, J

2013-10-01

Acute ankle sprains are common and activity limiting injuries, and topical diclofenac gel has proven efficacy in alleviating pain and restoring function. This trial aimed to compare a topical natural agent, Traumeel with topical diclofenac gel (1%) in the management of acute ankle sprain. This prospective, multicentre, randomised, blinded, active-control and non-inferiority study involved 449 physically active adults sustaining unilateral grade 1 or 2 ankle sprain within the past 24 h. Participants were randomised to receive 2 g of Traumeel ointment (T-O) (n = 152) or Traumeel gel (T-G) (n = 150) or diclofenac gel (D-G) (n = 147), administered topically to the ankle three times a day for 14 days, with 6-weeks follow up. Day 7 median percentage reductions in Visual Analogue Scale pain score were 60.6%, 71.1% and 68.9% for the T-O, T-G and D-G groups, respectively. Total pain relief was reported by 12 (8.5%), 7 (5.0%) and 8 (5.9%) participants in each group, respectively. Median improvements in Foot and Ankle Ability Measure Activities of Daily Living subscale score were 26.2, 26.2 and 25.0 points for T-O, T-G and D-G groups, respectively. Mann-Whitney effect sizes and lower bound confidence intervals demonstrated non-inferiority of Traumeel vs. diclofenac for reducing pain and functional improvement. At 6 weeks, participants reported total pain relief and normal functioning. Adverse events (n = 43) were reported by 31/447 participants (6.9%). Treatments were equally well tolerated. T-O and T-G decreased pain and improved joint function to the same extent as D-G in acute ankle sprain, and were well tolerated. © 2013 The Authors. International Journal of Clinical Practice published by John Wiley & Sons Ltd.

Aquatic metabolism response to the hydrologic alteration in the Yellow River estuary, China

NASA Astrophysics Data System (ADS)

Shen, Xiaomei; Sun, Tao; Liu, Fangfang; Xu, Jing; Pang, Aiping

2015-06-01

Successful artificial hydrologic regulation and environmental flow assessments for the ecosystem protection require an accurate understanding of the linkages between flow events and biotic responses. To explore an ecosystem's functional responses to hydrologic alterations, we analysed spatial and temporal variations in aquatic metabolism and the main factors influenced by artificial hydrologic alterations based on the data collected from 2009 to 2012 in the Yellow River estuary, China. Gross primary production (GPP) ranged from 0.002 to 8.488 mg O2 L-1 d-1. Ecosystem respiration (ER) ranged from 0.382 to 8.968 mg O2 L-1 d-1. Net ecosystem production (NEP) ranged from -5.792 to 7.293 mg O2 L-1 d-1 and the mean of NEP was -0.506 mg O2 L-1 d-1, which means that the trophic status of entire estuary was near to balance. The results showed that seasonal variations in the aquatic metabolism are influenced by the hydrologic alteration in the estuary. High water temperature and solar radiation in summer are associated with low turbidity and consequently high rates of GPP and ER, making the estuary net autotrophic in summer, and that also occurred after water-sediment regulation in August. Turbidity and water temperature were identified as two particularly important factors that influenced the variation in the metabolic balance. As a result, metabolism rate did not decrease but increased after the regulation. ER increased significantly in summer and autumn and reached a maximum after the water-sediment regulation in September. GPP and NEP reached a maximum value after the water-sediment regulation in August, and then decreased in autumn. Estuarine ecosystem shifted from net heterotrophy in spring to net autotrophy in summer, and then to net heterotrophy in autumn. Our study indicated that estuarine metabolism may recover to a high level faster in summer than that in other seasons after the short-term water-sediment regulation due to higher water temperature and nutrients.

Dynamics of crowding-induced mixing in phase separated lipid bilayers

DOE PAGES

Zeno, Wade F.; Johnson, Kaitlin E.; Sasaki, Darryl Y.; ...

2016-10-10

We use fluorescence microscopy to examine the dynamics of the crowding-induced mixing transition of liquid ordered (L o)–liquid disordered (L d) phase separated lipid bilayers when the following particles of increasing size bind to either the L o or L d phase: Ubiquitin, green fluorescent protein (GFP), and nanolipoprotein particles (NLPs) of two diameters. These proteinaceous particles contained histidine-tags, which were phase targeted by binding to iminodiacetic acid (IDA) head groups, via a Cu 2+ chelating mechanism, of lipids that specifically partition into either the Lo phase or Ld phase. The degree of steric pressure was controlled by varying themore » size of the bound particle (10–240 kDa) and the amount of binding sites present (i.e., DPIDA concentrations of 9 and 12 mol%) in the supported lipid multibilayer platform used here. We develop a mass transfer-based diffusional model to analyze the observed L o phase domain dissolution that, along with visual observations and activation energy calculations, provides insight into the sequence of events in crowding-induced mixing. Furthermore, our results suggest that the degree of steric pressure and target phase influence not only the efficacy of steric-pressure induced mixing, but the rate and controlling mechanism for which it occurs.« less

Inorganic carbon fluxes on the Mackenzie Shelf of the Beaufort Sea

NASA Astrophysics Data System (ADS)

Mol, Jacoba; Thomas, Helmuth; Myers, Paul G.; Hu, Xianmin; Mucci, Alfonso

2018-02-01

The Mackenzie Shelf in the southeastern Beaufort Sea is a region that has experienced large changes in the past several decades as warming, sea-ice loss, and increased river discharge have altered carbon cycling. Upwelling and downwelling events are common on the shelf, caused by strong, fluctuating along-shore winds, resulting in cross-shelf Ekman transport, and an alternating estuarine and anti-estuarine circulation. Downwelling carries dissolved inorganic carbon (DIC) and other remineralization products off the shelf and into the deep basin for possible long-term storage in the world's oceans. Upwelling carries DIC and nutrient-rich waters from the Pacific-origin upper halocline layer (UHL) onto the shelf. Profiles of DIC and total alkalinity (TA) taken in August and September of 2014 are used to investigate the cycling of carbon on the Mackenzie Shelf. The along-shore transport of water and the cross-shelf transport of DIC are quantified using velocity field output from a simulation of the Arctic and Northern Hemisphere Atlantic (ANHA4) configuration of the Nucleus of European Modelling of the Ocean (NEMO) framework. A strong upwelling event prior to sampling on the Mackenzie Shelf took place, bringing CO2-rich (elevated pCO2) water from the UHL onto the shelf bottom. The maximum on-shelf DIC flux was estimated at 16.9×103 mol C d-1 m-2 during the event. The maximum on-shelf transport of DIC through the upwelling event was found to be 65±15×10-3 Tg C d-1. TA and the oxygen isotope ratio of water (δ18O-H2O) are used to examine water-mass distributions in the study area and to investigate the influence of Pacific Water, Mackenzie River freshwater, and sea-ice melt on carbon dynamics and air-sea fluxes of carbon dioxide (CO2) in the surface mixed layer. Understanding carbon transfer in this seasonally dynamic environment is key to quantify the importance of Arctic shelf regions to the global carbon cycle and provide a basis for understanding how it will respond to the aforementioned climate-induced changes.

Effect of the Spanish Conquest on coastal change in Northwestern Peru

PubMed Central

Belknap, Daniel F.; Sandweiss, Daniel H.

2014-01-01

When Francisco Pizarro and his small band of Spanish conquistadores landed in northern Peru in A.D. 1532 to begin their conquest of the vast Inca Empire, they initiated profound changes in the culture, language, technology, economics, and demography of western South America. They also altered anthropogenically modulated processes of shoreline change that had functioned for millennia. Beginning with the extirpation of local cultures as a result of the Spanish Conquest, and continuing through today, the intersection of demography, economy, and El Niño-driven beach-ridge formation on the Chira beach-ridge plain of Northwestern Peru has changed the nature of coastal evolution in this region. A similar event may have occurred at about 2800 calibrated y B.P. in association with increased El Niño frequency. PMID:24843118

Effect of the Spanish Conquest on coastal change in Northwestern Peru

NASA Astrophysics Data System (ADS)

Belknap, Daniel F.; Sandweiss, Daniel H.

2014-06-01

When Francisco Pizarro and his small band of Spanish conquistadores landed in northern Peru in A.D. 1532 to begin their conquest of the vast Inca Empire, they initiated profound changes in the culture, language, technology, economics, and demography of western South America. They also altered anthropogenically modulated processes of shoreline change that had functioned for millennia. Beginning with the extirpation of local cultures as a result of the Spanish Conquest, and continuing through today, the intersection of demography, economy, and El Niño-driven beach-ridge formation on the Chira beach-ridge plain of Northwestern Peru has changed the nature of coastal evolution in this region. A similar event may have occurred at about 2800 calibrated y B.P. in association with increased El Niño frequency.

Effect of the Spanish Conquest on coastal change in Northwestern Peru.

PubMed

Belknap, Daniel F; Sandweiss, Daniel H

2014-06-03

When Francisco Pizarro and his small band of Spanish conquistadores landed in northern Peru in A.D. 1532 to begin their conquest of the vast Inca Empire, they initiated profound changes in the culture, language, technology, economics, and demography of western South America. They also altered anthropogenically modulated processes of shoreline change that had functioned for millennia. Beginning with the extirpation of local cultures as a result of the Spanish Conquest, and continuing through today, the intersection of demography, economy, and El Niño-driven beach-ridge formation on the Chira beach-ridge plain of Northwestern Peru has changed the nature of coastal evolution in this region. A similar event may have occurred at about 2800 calibrated y B.P. in association with increased El Niño frequency.

Oxidative Weathering of Archean Sulfides: Implications for the Great Oxidation Event

NASA Astrophysics Data System (ADS)

Johnson, A.; Romaniello, S. J.; Reinhard, C.; Garcia-Robledo, E.; Revsbech, N. P.; Canfield, D. E.; Lyons, T. W.; Anbar, A. D.

2015-12-01

The first widely accepted evidence for oxidation of Earth's atmosphere and oceans occurs ~2.45 Ga immediately prior to the Great Oxidation Event (GOE). A major line of evidence for this transition includes the abundances and isotopic variations of redox-sensitive transition metals in marine sediments (e.g., Fe, Mo, Re, Cr, and U). It is often assumed that oxidative weathering is required to liberate these redox-sensitive elements from sulfide minerals in the crust, and hence that their presence in early Archean marine sediments signifies that oxidative weathering was stimulated by small and/or transient "whiffs" of O2 in the environment.1 However, studies of crustal sulfide reactivity have not been conducted at O2 concentrations as low as those that would have prevailed when O2 began its rise during the late Archean (estimated at <10-5 present atmospheric O2).2 As a result, it is difficult to quantify O2 concentrations implied by observed trace metal variations. As a first step toward providing more quantitative constraints on late Archean pO2, we conducted laboratory studies of pyrite and molybdenite oxidation kinetics at the nanomolar O2 concentrations that are relevant to late Archean environments. These measurements were made using recently developed, highly sensitive optical O2 sensors to monitor the rates at which the powdered minerals consumed dissolved O2 in a range of pH-buffered solutions.3Our data extend the range of experimental pyrite oxidation rates in the literature by three orders of magnitude from ~10-3 present atmospheric O2 to ~10-6. We find that molybdenite and pyrite oxidation continues to <1 nM O2 (4 x 10-6 present atmospheric O2). This implies that oxidative weathering of sulfides could occur under conditions which preserve MIF S fractionation. Furthermore, our results indicate that the rate law and reaction order of pyrite oxidation kinetics change significantly at nanomolar concentrations of O2 when compared to previous compilations.2 Our results provide new empirical data that should allow for more precise quantitative constraints on atmospheric pO2 based on the sedimentary rock record. 1Anbar, A.D. et al., 2007. Science, 317, i. 5846: 1903-1906. 2Williamson & Rimstidt, 1994. Geochim. et Cosmochim. Acta, 58, n. 24: 5443-5454. 3Lehner et al., 2015. PLoS ONE, 10, n. 6: 1-15.

Seed population for about 1 MeV per nucleon heavy ions accelerated by interplanetary shocks

NASA Technical Reports Server (NTRS)

Tan, L. C.; Mason, G. M.; Klecker, B.; Hovestadt, D.

1989-01-01

Data obtained between 1977 and 1982 by the ISEE 1 and ISEE 3 satellites on the composition of heavy ions of about 1 MeV per nucleon, accelerated in interplanetary shock events which followed solar flare events, are examined. It was found that the average relative abundances for C, O, and Fe in the shock events were very close to those found for energetic ions in the solar flares, suggesting that, at these energies, the shock accelerated particles have the solar energetic particles as their seed population. This hypothesis is supported by the fact that the Fe/O ratio in the solar particle events is very strongly correlated with the Fe/O ratio in associated diffusive shock events.

The Evolution of the 2015-16 El Niño

NASA Astrophysics Data System (ADS)

L'Heureux, Michelle

2016-04-01

The 2015-16 El Niño is in an exclusive club, ranking among the strongest events over at least the past half century. In contrast to 2014, the event was generally well predicted by operational climate services. Alerts were issued within the first half of 2015, and by mid-year, there was clearer evidence that the event would be potentially historical. The evolution of several oceanic and atmospheric measures will be presented to put this event in context and compare it with the 1982-83 and 1997-98 El Niños. While the 2015-16 El Niño was comparable to these previous events in certain ways, in other aspects it was a unique beast.

[Studies on triterpenoid saponins in the rhizome of Anemone flaccida].

PubMed

Han, Lin-Tao; Huang, Fang

2009-07-01

To study the triterpenoid saponins in the rhizome of Anemone flaccida. The constituents were separated with various chromatographic techniques and their structures were elucidated by means of physicochemical properties and the analysis of their spectral datas. Five compounds were isolated and identified as 3-O-beta-D-glucuronypyranosyl-oleanolic acid-28-O-alpha-L-rhamnopyranosyl (1 --> 4)-beta-D-glucopyranosyl(1 --> 6)-beta-D-glucopyra noside (1), 3-O-beta-D-glucuronypyranosyl-oleanolic acid-28-O-beta-D-glucopyranosyl (1 --> 6)-beta-D-glucopyranoside (2), 3-O-alpha-L-rhamnopyranosy (1 --> 2)-beta-D-glucopyranosyl-oleanolic acid-28-O-alpha-L-rhamnopyranosyl (1 --> 4)-beta-D-glucopyranosyl (1 --> 6)-beta-D-glucopyranoside (3), 3-O-alpha-L-rhamnopyranosyl (1 --> 2)-alpha-L-arabinopyrano-syl-oleanolic acid-28-O-alpha-L-rhamnopyranosyl (1 -->4)-beta-D-glucopyranosyl (1 --> 6)-beta-D-glucopyranoside (4), 3-O-alpha-L-rhamnopyranosyl (1 --> 2)-beta-D-xylopyranosyl-oleanolic acid-28-O-alpha-L-rhamnopyranosyl (1 --> 4)-beta-D-glucopyranosyl (1 --> 6)-beta-D-glucopyranoside (5). Compound 1 - 4 are isolated from this plant for the first time. Compound 1,2 are isolated from this genus for the first time.

Global patterns and impacts of El Niño events on coral reefs: A meta-analysis.

PubMed

Claar, Danielle C; Szostek, Lisa; McDevitt-Irwin, Jamie M; Schanze, Julian J; Baum, Julia K

2018-01-01

Impacts of global climate change on coral reefs are being amplified by pulse heat stress events, including El Niño, the warm phase of the El Niño Southern Oscillation (ENSO). Despite reports of extensive coral bleaching and up to 97% coral mortality induced by El Niño events, a quantitative synthesis of the nature, intensity, and drivers of El Niño and La Niña impacts on corals is lacking. Herein, we first present a global meta-analysis of studies quantifying the effects of El Niño/La Niña-warming on corals, surveying studies from both the primary literature and International Coral Reef Symposium (ICRS) Proceedings. Overall, the strongest signal for El Niño/La Niña-associated coral bleaching was long-term mean temperature; bleaching decreased with decreasing long-term mean temperature (n = 20 studies). Additionally, coral cover losses during El Niño/La Niña were shaped by localized maximum heat stress and long-term mean temperature (n = 28 studies). Second, we present a method for quantifying coral heat stress which, for any coral reef location in the world, allows extraction of remotely-sensed degree heating weeks (DHW) for any date (since 1982), quantification of the maximum DHW, and the time lag since the maximum DHW. Using this method, we show that the 2015/16 El Niño event instigated unprecedented global coral heat stress across the world's oceans. With El Niño events expected to increase in frequency and severity this century, it is imperative that we gain a clear understanding of how these thermal stress anomalies impact different coral species and coral reef regions. We therefore finish with recommendations for future coral bleaching studies that will foster improved syntheses, as well as predictive and adaptive capacity to extreme warming events.

Global patterns and impacts of El Niño events on coral reefs: A meta-analysis

PubMed Central

Szostek, Lisa; McDevitt-Irwin, Jamie M.; Schanze, Julian J.; Baum, Julia K.

2018-01-01

Impacts of global climate change on coral reefs are being amplified by pulse heat stress events, including El Niño, the warm phase of the El Niño Southern Oscillation (ENSO). Despite reports of extensive coral bleaching and up to 97% coral mortality induced by El Niño events, a quantitative synthesis of the nature, intensity, and drivers of El Niño and La Niña impacts on corals is lacking. Herein, we first present a global meta-analysis of studies quantifying the effects of El Niño/La Niña-warming on corals, surveying studies from both the primary literature and International Coral Reef Symposium (ICRS) Proceedings. Overall, the strongest signal for El Niño/La Niña-associated coral bleaching was long-term mean temperature; bleaching decreased with decreasing long-term mean temperature (n = 20 studies). Additionally, coral cover losses during El Niño/La Niña were shaped by localized maximum heat stress and long-term mean temperature (n = 28 studies). Second, we present a method for quantifying coral heat stress which, for any coral reef location in the world, allows extraction of remotely-sensed degree heating weeks (DHW) for any date (since 1982), quantification of the maximum DHW, and the time lag since the maximum DHW. Using this method, we show that the 2015/16 El Niño event instigated unprecedented global coral heat stress across the world's oceans. With El Niño events expected to increase in frequency and severity this century, it is imperative that we gain a clear understanding of how these thermal stress anomalies impact different coral species and coral reef regions. We therefore finish with recommendations for future coral bleaching studies that will foster improved syntheses, as well as predictive and adaptive capacity to extreme warming events. PMID:29401493

Warnings in the International Event Flow: EFI and ROZ as Threat Indicators

DTIC Science & Technology

1976-07-15

INSTRUCTIONS BEFORE COMPLETING PORN ) RECIPIENT’S CATALOG NUMBCR S TY^E OF «C^OdT * PimoD COVCRtO 7-1-75 to 9-30-76 Technical Report PCft’ORMINC...Kingdom initiated i*.S%, France k%, Poland 5.2%, Czechoslovakia k%, Italy 2.k%, Rumania 1.2%, the Soviet Union 15.91, the United Arab Republic 5.2...being 19.2^). So, too, were the United Arab Republic (3.8| 10 year average) and North Vietnam (6.7%). A little "above par" were the United Kingdom

Results of the SDCS (Special Data Collection System) Attenuation Experiment

DTIC Science & Technology

1981-10-30

stations one can infer the degree of anelastic attenuation under each station. The design of the experiment by DARPA is based on an implicit assumption of...complete listing of the events is shown in Appendix A. Since the SDCS experiment was designed to resolve problemR arising from a study of Ms-mb, it was... designated by different symbols as follows: Symbol A (At* - ) <-a B -0 < (At* -) < 0 C 0 < (At* P) < + D (At* -> + -52- 30 - N I 50 P 0,244 o" 0.231 cr

A Study of Carrier Based Aircraft Readiness Sustainability in the Event of External Air Logistic Support Deprivation

DTIC Science & Technology

1987-06-01

equation for 7R investment has been used in combination with the linear equation for COD/VOD delivery to produce six " iso -readiness" lines. Each iso ...readiness line represents the value of inventory investment and days since last COD/VOD delivery required to maintain a specific level of FMC. The iso ...Truett, D.B., Manaaerial Economics, second edition, South-Western Publish..ng Co., 1984, p. 65. 158 Iso -Readiness Plot o80mna4C Mad" of ?R Ve COO/VOo WO

IUPAC critical evaluation of the rotational-vibrational spectra of water vapor. Part IV. Energy levels and transition wavenumbers for D216O, D217O, and D218O

NASA Astrophysics Data System (ADS)

Tennyson, Jonathan; Bernath, Peter F.; Brown, Linda R.; Campargue, Alain; Császár, Attila G.; Daumont, Ludovic; Gamache, Robert R.; Hodges, Joseph T.; Naumenko, Olga V.; Polyansky, Oleg L.; Rothman, Laurence S.; Vandaele, Ann Carine; Zobov, Nikolai F.; Dénes, Nóra; Fazliev, Alexander Z.; Furtenbacher, Tibor; Gordon, Iouli E.; Hu, Shui-Ming; Szidarovszky, Tamás; Vasilenko, Irina A.

2014-07-01

This paper is the fourth of a series of papers reporting critically evaluated rotational-vibrational line positions, transition intensities, pressure dependences, and energy levels, with associated critically reviewed assignments and uncertainties, for all the main isotopologues of water. This paper presents energy level and transition data for the following doubly and triply substituted isotopologues of water: D216O, D217O, and D218O. The MARVEL (Measured Active Rotational-Vibrational Energy Levels) procedure is used to determine the levels, the lines, and their self-consistent uncertainties for the spectral regions 0-14 016, 0-7969, and 0-9108 cm-1 for D216O, D217O, and D218O, respectively. For D216O, D217O, and D218O, 53 534, 600, and 12 167 lines are considered, respectively, from spectra recorded in absorption at room temperature and in emission at elevated temperatures. The number of validated energy levels is 12 269, 338, and 3351 for D216O, D217O, and D218O, respectively. The energy levels have been checked against the ones determined, with an average accuracy of about 0.03 cm-1, from variational rovibrational computations employing exact kinetic energy operators and an accurate potential energy surface. Furthermore, the rovibrational labels of the energy levels have been validated by an analysis of the computed wavefunctions using the rigid-rotor decomposition (RRD) scheme. The extensive list of MARVEL lines and levels obtained is deposited in the Supplementary Material of this paper, in a distributed information system applied to water, W@DIS, and on the official MARVEL website, where they can easily be retrieved.

On Orbit Performance of the Defense Meteorological Satellite Program (DMSP) 5D3 Spacecraft Power System

DTIC Science & Technology

2011-12-30

TD O £ c c ^ co — £ °> S5 o E r^ I— E o> ^ LO o 2 O c Q. £ g * CO O =3 CO E c CX) IT) <* CD Q_ C E _Q i_...fe co oo h- O I I I CO (D CO p CO c5 "S _c co o o CO _ TD 5 *> =3 CD -K Ö) s i- CO c 2 o) o .E o CO...CD •o O 0 -4—» CO CD E Ü Q. •D o TD ^ CO O O E CD •+—. CD O CD (D >> ^ >% •4—< *§ CD -•-• O) CD _Q _£Z C CD = < •o D)

Artificial delta growth

NASA Astrophysics Data System (ADS)

Mikeš, Daniel

2010-05-01

A deltaic sedimentary system has a point source; sediment is carried over the delta plain by distributary channels away from the point source and deposited at the delta front by distributary mouth bars. The established methods to describe such a sedimentary system are "bedding analysis", "facies analysis", and "basin analysis". We shall call the ambient conditions "input" and the rock record "output". There exist a number of methods to deduce input from output, e.g. "Sequence stratigraphy" (a.o. Vail et al. 1977, Catuneanu et al. 2009), "Shoreline trajectory" (a.o. Helland-Hansen & Martinsen 1996, Helland-Hansen & Hampson 2009) on the one hand and the complex use of established techniques on the other (a.o. Miall & Miall 2001, Miall & Miall 2002). None of these deductive methods seems to be sufficient. I claim that the common errors in all these attempts are the following: (1) a sedimentary system is four-dimensional (3+1) and a lesser dimensional analysis is insufficient; (2) a sedimentary system is complex and any empirical/deductive analysis is non-unique. The proper approach to the problem is therefore the theoretical/inductive analysis. To that end we performed six scenarios of a scaled version of a passive margin delta in a flume tank. The scenarios have identical stepwise tectonic subsidence and semi-cyclic sealevel, but different supply curves, i.e. supply is: constant, highly-frequent, proportional to sealevel, inversely proportional to sealevel, lagging to sealevel, ahead of sealevel. The preliminary results are indicative. Lobe-switching occurs frequently and hence locally sedimentation occurs shortly and hiatuses are substantial; therefore events in 2D (+1) cross-sections don't correlate temporally. The number of sedimentary cycles disequals the number of sealevel cycles. Lobe-switching and stepwise tectonic subsidence cause onlap/transgression. Erosional unconformities are local diachronous events, whereas maximum flooding surfaces are regional synchronous events. The evolution of the different scenarios is significantly different. These results demonstrate that the complexity of the deltaic system merits the inductive approach. References: Catuneanu, O. et al., 2009. Towards the standardization of sequence stratigraphy. Earth-Science Reviews, v. 92, p. 1-33. Helland-Hansen, W., and Martinsen, O.J., 1996, Shoreline trajectories and sequences: description of variable depositional dip scenarios: Journal of Sedimentary Research, v. 66, p. 670-688. Helland-Hansen, W. and Hampson, G.J., 2009, Trajectory analysis: concepts and applications. In: Basin Research Special Publication 21, p. 454-483. Miall, A.D., Miall, C.E., 2001, Sequence stratigraphy as a scientific enterprise: the evolution and persistence of conflicting paradigms, Earth Science Reviews, v. 54, p. 321-348. Miall, C.E., Miall, A.D., 2002, The Exxon Factor: the roles of corporate and academic science in the emergence and success of a new global model of sequence stratigraphy, Sociological Quarterly, v. 43-3, p. 307-334. Vail, P.R., Mitchum Jr., R.M., Todd, R.G., Widmier, J.M., Thompson III, S., Sangree, J.B., Bubb, J.N., Hatlelid, W.G., 1977. Seismic stratigraphy and global changes of sea-level. In: Payton, C.E. (Ed.), Seismic Stratigraphy-Applications to Hydrocarbon Exploration. American Association of Petroleum Geologists Memoir, v. 26, p. 49-212.

Reversible Chromatic Response of Polydiacetylene Derivative Vesicles in D2O Solvent.

PubMed

Shin, Min Jae; Kim, Jong-Duk

2016-01-26

The thermal chromatic sensitivity of polydiacetylenes (PDAs) with 10,12-pentacosadiynoic acid (PCDA) derivatives, which have a hydroxyl group (HEEPCDA) and an amine group (APPCDA), were investigated using D2O and H2O as solvents. The vesicle solution with polymerized HEEPCDA exhibited a reversible chromatic response during the heating and cooling cycle in D2O, but not in H2O. On the other hand, the vesicle solution with the polymerized APPCDA exhibited a reversible chromatic response in H2O during the heating and cooling cycle, but the color of the solution did not change much in D2O. The critical vesicle concentration of HEEPCDA was lower in D2O than in H2O, and the chromatic sensitivity of the polymerized vesicles to temperature was slower in D2O than in H2O. We think that it is due to D2O being a more highly structured solvent than H2O with the hydrogen bonding in D2O stronger than that in H2O.

Major bleeding risks of different low-molecular-weight heparin agents: a cohort study in 12 934 patients treated for acute venous thrombosis.

PubMed

van Rein, N; Biedermann, J S; van der Meer, F J M; Cannegieter, S C; Wiersma, N; Vermaas, H W; Reitsma, P H; Kruip, M J H A; Lijfering, W M

2017-07-01

Essentials Low-molecular-weight-heparins (LMWH) kinetics differ which may result in different bleeding risks. A cohort of 12 934 venous thrombosis patients on LMWH was followed until major bleeding. The absolute major bleeding risk was low among patients registered at the anticoagulation clinic. Once-daily dosing was associated with a lower bleeding risk as compared with twice-daily. Background Low-molecular-weight heparins (LMWHs) are considered members of a class of drugs with similar anticoagulant properties. However, pharmacodynamics and pharmacokinetics between LMWHs differ, which may result in different bleeding risks. As these agents are used by many patients, small differences may lead to a large effect on numbers of major bleeding events. Objectives To determine major bleeding risks for different LMWH agents and dosing schedules. Methods A cohort of acute venous thrombosis patients from four anticoagulation clinics who used an LMWH and a vitamin K antagonist were followed until they ceased LMWH treatment or until major bleeding. Exposures were classified according to different types of LMWHs and for b.i.d. and o.d. use. Cumulative incidences for major bleeding per 1000 patients and risk ratios were calculated and adjusted for study center. Results The study comprised 12 934 patients with a mean age of 59 years; 6218 (48%) were men. The cumulative incidence of major bleeding was 2.5 per 1000 patients (95% confidence interval [CI], 1.7-3.5). Enoxaparin b.i.d. or o.d. was associated with a relative bleeding risk of 1.7 (95% CI, 0.2-17.5) compared with nadroparin o.d. In addition, a nadroparin b.i.d. dosing schedule was associated with a 2.0-fold increased major bleeding risk (95% CI, 0.8-5.1) as compared with a nadroparin o.d. dosing schedule. Conclusions Absolute major bleeding rates were low for all LMWH agents and dosing schedules in a large unselected cohort. Nevertheless, twice-daily dosing with nadroparin appeared to be associated with an increased major bleeding risk as compared with once-daily dosing, as also suggested in a meta-analysis of controlled clinical trials. © 2017 International Society on Thrombosis and Haemostasis.

Stable Isotopic Composition of Precipitation from 2015-2016 Central Texas Rainfall Events

NASA Astrophysics Data System (ADS)

Maupin, C. R.; McChesney, C. L.; Roark, B.; Gorman, M. K.; Housson, A. L.

2016-12-01

Central Texas lies within the Southern Great Plains, a region where rainfall is of tremendous agricultural and associated socioeconomic importance. Paleoclimate records from speleothems in central Texas caves may assist in placing historical and recent drought and pluvial events in the context of natural variability. Effective interpretation of such records requires the nature and origin of variations in the meteoric δ18O signal transmitted from cloud to speleothem to be understood. Here we present a record of meteoric δ18O and δD from each individual precipitation event (δ18Op and δDp), collected by rain gauge in Austin, Texas, USA, from April 2015 through 2016. Backwards hybrid single-particle Lagrangian integrated trajectories (HYSPLITs) indicate the broader moisture source for each precipitation event during this time was the Gulf of Mexico. The local meteoric water line is within error of the global meteoric water line, suggesting minimal sourcing of evaporated continental vapor for precipitation. Total monthly rainfall followed the climatological pattern of a dual boreal spring and fall maximum, with highly variable event δ18Op and δDp values. Surface temperature during precipitation often exerts control over continental and mid latitude δ18Op values, but is not significantly correlated to study site δ18Op (p>0.10). Amount of rain falling during each precipitation event ("amount effect") explains a significant 18% of variance in δ18Op. We hypothesize that this relationship can be attributed to the following: 1) minimal recycling of continental water vapor during the study period; 2) the presence of synoptic conditions favoring intense boreal spring and fall precipitation, driven by a developing, and subsequently in-place, strong ENSO event coupled with a southerly flow from the open Gulf of Mexico; and 3) the meteorological nature of the predominant precipitating events over Texas during this time, mesoscale convective systems, which are known to produce an "amount effect" if effective in-storm downdraft-recycling is present. Continued rainfall monitoring and isotopic measurements are required to determine whether this relationship persists during years with synoptic conditions different from 2015-2016.

The effects of resveratrol on markers of oxidative stress in patients with type 2 diabetes: a randomized, double-blind, placebo-controlled clinical trial.

PubMed

Seyyedebrahimi, ShadiSadat; Khodabandehloo, Hadi; Nasli Esfahani, Ensieh; Meshkani, Reza

2018-04-01

Oxidative stress plays a pivotal role in the pathogenesis of type 2 diabetes (T2D). In vitro and animal studies have shown that resveratrol exerts an antioxidant effect, but clinical trials addressing this effect in patients with T2D are limited. The aim of this study was to determine whether resveratrol supplementation affects oxidative stress markers in a randomized, placebo-controlled, double-blind clinical trial. A total of 48 patients with T2D randomly were assigned to receive 800 mg/day resveratrol or placebo for 2 months. Plasma total antioxidant capacity, malondialdehyde concentration, protein carbonyl and total thiol contents, intracellular superoxide anion (O 2 - ·) and hydrogen peroxide (H 2 O 2 ) in PBMCs, the expression of genes involved in oxidative stress responses (Nrf2, SOD, Cat, HO-1, RAGE, NOS) in PBMCs, and metabolic and anthropometric parameters were measured at the baseline and at the trial end. Compared with the placebo group, resveratrol reduced plasma protein carbonyl content and PBMCs O 2 - · level and significantly increased plasma total antioxidant capacity and total thiol content. Furthermore, the expression of Nrf2 and SOD was significantly increased after resveratrol consumption. Resveratrol had no significant effects on the metabolic and anthropometric parameters except for a significant reduction in weight, BMI, and blood pressure levels. Resveratrol was well tolerated, and no serious adverse event was occurred. Our study demonstrated that 8 weeks of supplementation with 800 mg/day resveratrol has an antioxidant effect in the blood and PBMCs of patients with T2D. Clinical Trial Registry number and website IRCT registration number: IRCT2015072523336N1 and http://en.search.irct.ir/view/24752 .

Hydro-meteorological extreme events in the 18th century in Portugal

NASA Astrophysics Data System (ADS)

Fragoso, Marcelo; João Alcoforado, Maria; Taborda, João Paulo

2013-04-01

The present work is carried out in the frame of the KLIMHIST PROJECT ("Reconstruction and model simulations of past climate in Portugal using documentary and early instrumental sources, 17th-19th century)", and is devoted to the study of hydro-meteorological extreme events during the last 350 years, in order to understand how they have changed in time and compare them with current analogues. More specifically, the results selected to this presentation will focus on some hydro-meteorological extreme events of the 18th century, like severe droughts, heavy precipitation episodes and windstorms. One of the most noteworthy events was the winterstorm Bárbara (3rd to 6th December 1739), already studied in prior investigations (Taborda et al, 2004; Pfister et al, 2010), a devastating storm with strong impacts in Portugal caused by violent winds and heavy rainfall. Several other extreme events were detected by searching different documentary archives, including individual, administrative and ecclesiastic sources. Moreover, a more detailed insight to the 1783-1787 period will be made with regard the Lisbon region, taking into consideration the availability of information for daily meteorological observations as well as documentary evidences, like descriptions from Gazeta de Lisboa, the periodic with more continuous publication in the 18thcentury. Key-words: Instrumental data, Documentary data, Extreme events, Klimhist Project, Portugal References Pfister, C., Garnier, E., Alcoforado, M.J., Wheeler, D. Luterbacher, J. Nunes, M.F., Taborda, J.P. (2010) The meteorological framework and the cultural memory of three severe winter-storms in early eighteenth-century Europe, Climatic Change, 101, 1-2, 281-310 Taborda, JP; Alcoforado, MJ and Garcia, JC (2004) O Clima do Sul de Portugal no Séc.XVIII, Centro de Estudos Geográficos, Área de de Investigação de Geo-Ecologia, relatório no 2

Continuous and simultaneous measurements of precipitation and vapor isotopes over two monsoon seasons during 2016-2017 in Singapore

NASA Astrophysics Data System (ADS)

Jackisch, D.; He, S.; Ong, M. R.; Goodkin, N.

2017-12-01

Water isotopes are important tracers of climate dynamics and their measurement can provide valuable insights into the relationship between isotopes and atmospheric parameters and overall convective activities. While most studies provide data on daily or even monthly time scales, high-temporal in-situ stable isotope measurements are scarce, especially in the tropics. In this study, we presented δ18O and δ2H values in precipitation and vapor continuously and simultaneously measured using laser spectroscopy in Singapore during the 2016/2017 Northeast (NE) Asian monsoon and 2017 Southwest (SW) Asian monsoon. We found that δ-values of precipitation and vapor exhibit quite different patterns during individual events, although there is a significant correlation between the δ-values of precipitation and of vapor. δ-values in precipitation during individual precipitation events show a distinct V-shape pattern, with the lowest isotope values observed in the middle of the event. However, isotopes in water vapor mostly show an L-shape and are characterized by a gradual decrease with the onset of rainfall. The difference in δ-values of precipitation and vapor is generally constant during the early stage of the events but gradually increases near the end. It is likely that vapor and precipitation are closer to equilibrium at the early stage of a rain event, but diverge at the later stages. This divergence can be largely attributed to the evaporation of raindrops. We notice a frequent drop in d-excess of precipitation, whereas d-excess in vapor increases. In addition, a significant correlation exists between outgoing longwave radiation (OLR) and isotopes in both precipitation and vapor, suggesting an influence of regional convective activity.

Soil water content drives spatiotemporal patterns of CO2 and N2O emissions from a Mediterranean riparian forest soil

NASA Astrophysics Data System (ADS)

Poblador, Sílvia; Lupon, Anna; Sabaté, Santiago; Sabater, Francesc

2017-09-01

Riparian zones play a fundamental role in regulating the amount of carbon (C) and nitrogen (N) that is exported from catchments. However, C and N removal via soil gaseous pathways can influence local budgets of greenhouse gas (GHG) emissions and contribute to climate change. Over a year, we quantified soil effluxes of carbon dioxide (CO2) and nitrous oxide (N2O) from a Mediterranean riparian forest in order to understand the role of these ecosystems on catchment GHG emissions. In addition, we evaluated the main soil microbial processes that produce GHG (mineralization, nitrification, and denitrification) and how changes in soil properties can modify the GHG production over time and space. Riparian soils emitted larger amounts of CO2 (1.2-10 g C m-2 d-1) than N2O (0.001-0.2 mg N m-2 d-1) to the atmosphere attributed to high respiration and low denitrification rates. Both CO2 and N2O emissions showed a marked (but antagonistic) spatial gradient as a result of variations in soil water content across the riparian zone. Deep groundwater tables fueled large soil CO2 effluxes near the hillslope, while N2O emissions were higher in the wet zones adjacent to the stream channel. However, both CO2 and N2O emissions peaked after spring rewetting events, when optimal conditions of soil water content, temperature, and N availability favor microbial respiration, nitrification, and denitrification. Overall, our results highlight the role of water availability on riparian soil biogeochemistry and GHG emissions and suggest that climate change alterations in hydrologic regimes can affect the microbial processes that produce GHG as well as the contribution of these systems to regional and global biogeochemical cycles.

Error-prone bypass of O6-methylguanine by DNA polymerase of Pseudomonas aeruginosa phage PaP1.

PubMed

Gu, Shiling; Xiong, Jingyuan; Shi, Ying; You, Jia; Zou, Zhenyu; Liu, Xiaoying; Zhang, Huidong

2017-09-01

O 6 -Methylguanine (O 6 -MeG) is highly mutagenic and is commonly found in DNA exposed to methylating agents, generally leads to G:C to A:T mutagenesis. To study DNA replication encountering O 6 -MeG by the DNA polymerase (gp90) of P. aeruginosa phage PaP1, we analyzed steady-state and pre-steady-state kinetics of nucleotide incorporation opposite O 6 -MeG by gp90 exo - . O 6 -MeG partially inhibited full-length extension by gp90 exo - . O 6 -MeG greatly reduces dNTP incorporation efficiency, resulting in 67-fold preferential error-prone incorporation of dTTP than dCTP. Gp90 exo - extends beyond T:O 6 -MeG 2-fold more efficiently than C:O 6 -MeG. Incorporation of dCTP opposite G and incorporation of dCTP or dTTP opposite O 6 -MeG show fast burst phases. The pre-steady-state incorporation efficiency (k pol /K d,dNTP ) is decreased in the order of dCTP:G>dTTP:O 6 -MeG>dCTP:O 6 -MeG. The presence of O 6 -MeG at template does not affect the binding affinity of polymerase to DNA but it weakened their binding in the presence of dCTP and Mg 2+ . Misincorporation of dTTP opposite O 6 -MeG further weakens the binding affinity of polymerase to DNA. The priority of dTTP incorporation opposite O 6 -MeG is originated from the fact that dTTP can induce a faster conformational change step and a faster chemical step than dCTP. This study reveals that gp90 bypasses O 6 -MeG in an error-prone manner and provides further understanding in DNA replication encountering mutagenic alkylation DNA damage for P. aeruginosa phage PaP1. Copyright © 2017 Elsevier B.V. All rights reserved.

Controlled phase evolution and the occurrence of single domain CoFe2O4 nanoparticles synthesized by PVA assisted sol-gel method

NASA Astrophysics Data System (ADS)

Srinivasa Rao, K.; Ranga Nayakulu, S. V.; Chaitanya Varma, M.; Choudary, G. S. V. R. K.; Rao, K. H.

2018-04-01

The present investigation describes the development of cobalt ferrite nanoparticles having size less than 10 nm, by a sol-gel method using polyvinyl alcohol as chelating agent. X-ray results show all the samples, annealed above 700 °C have spinel structure. The information about phase evolution with reaction temperatures was obtained by subjecting the as-prepared powder for DSC/TGA study. High saturation magnetization of 84.63 emu/g has been observed for a particle size of 8.1 nm, a rare event reported till date. The dM/dH versus H curves suggest that the transition from single domain state to multi-domain state occurs with increasing annealing temperature and the critical size for the single domain nature of CoFe2O4 is around 6.5 nm. The estimated critical diameter for single domain particle (6.7 nm) is in good agreement with that (6.5 nm) obtained from Transmission Electron Micrographs. The highest coercivity (1645 Oe) has been found for a particle of size 6.5 nm.

A new phenylpropanoid and an alkylglycoside from Piper retrofractum leaves with their antioxidant and α-glucosidase inhibitory activity.

PubMed

Luyen, Bui Thi Thuy; Tai, Bui Huu; Thao, Nguyen Phuong; Yang, Seo Young; Cuong, Nguyen Manh; Kwon, Young In; Jang, Hae Dong; Kim, Young Ho

2014-09-01

Two new compounds, piperoside (1) and isoheptanol 2(S)-O-β-D-xylopyranosyl (1→6)-O-β-D-glucopyranoside (11), along with 10 known compounds 3,4-dihydroxyallylbenzene (2), 1,2-di-O-β-D-glucopyranosyl-4-allylbenzene (3), tachioside (4), benzyl-O-β-D-glucopyranoside (5), icariside F2 (6), dihydrovomifoliol-3'-O-β-D-glucopyranoside (7), isopropyl O-β-D-glucopyranoside (8), isopropyl primeveroside (9), n-butyl O-β-D-glucopyranoside (10), isoheptanol 2(S)-O-β-D-apiofuranosyl-(1→6)-O-β-D-glucopyranoside (12), were isolated from the leaves of Piper retrofractum. Their structures were determined from 1D-NMR, 2D-NMR, and HR-ESI-MS spectral, a modified Mosher's method, and comparisons with previous reports. All of the isolated compounds showed modest α-glucosidase inhibitory (4.60±1.74% to 11.97±3.30%) and antioxidant activities under the tested conditions. Copyright © 2014 Elsevier Ltd. All rights reserved.

Oxygen as a Biosignature on Terrestrial Planets

NASA Astrophysics Data System (ADS)

Harman, Chester E., Jr.

In the search for life on Earth-like planets around other stars, the first (and likely only) information will come from the spectroscopic characterization of the planet's atmosphere. Of the countless number of chemical species terrestrial life produces, only a few have the distinct spectral features and the necessary atmospheric abundance to be detectable. The easiest of these species to observe in Earth's atmosphere is O2 (and its photochemical byproduct, O 3). But the amount of oxygen in the Earth's atmosphere has evolved with time, jumping from essentially zero free O2 in the Archean to potentially detectable amounts of O2 and O3 following the Great Oxidation Event. The anomalous abundances of sulfur isotopes in ancient sediments provide the strongest evidence for an anoxic atmosphere prior to ˜2.45 Ga, but the mechanism for producing this 'mass-independent' fractionation pattern remains in question. The prevailing hypothesis has been that it is created by differences in the UV photolysis rates of different SO2 isotopologues. We argue instead that the dominant process involves combinatorial factors in sulfur chain formation. Because two minor S isotopes rarely occur in the same chain, the longer S4 and S8 chains should be strongly, and roughly equally, depleted in all minor isotopes. This gives rise to negative D33S values and positive D36S values in elemental sulfur. The fractionations produced by the chain formation mechanism can explain many of the patterns observed in sedimentary rocks laid down during the Archean, and supports the classic interpretation that the sulfur mass-independent fractionation signal records the evolution of oxygenic photosynthesis.

What is the mechanism of the OSO ring formation in sulfur tetroxide (SO4(C2v)) molecule?

NASA Astrophysics Data System (ADS)

Goodarzi, Moein; Vahedpour, Morteza; Solimannejad, Mohammad

2012-06-01

The mechanism of SO2 + O2 and O + SO3(D3h) reactions have been investigated at the MP2/6-31 + G(d) and CCSD(T)/cc-pV(Q + d)Z//MP2 levels on the triplet and singlet PESs. Although, no stable collision complexes have been found for the SO2 + O2(3∑g-), O(3P) + SO3(D3h) and O(1D) + SO3(D3h) reactions, 1IN(O2S-O2) has been considered on the singlet PES for the SO2 + O2(1Δg) reaction. The results show that there are no favorable paths for the OSO ring formation of SO4(C2v) in the atmospheric reactions of the SO2 + O2(3∑g-), SO2 + O2(1Δg) and O(3P) + SO3(D3h) while, the O(1D) + SO3(D3h) reaction can be suitable for the SO4(C2v) formation on the singlet PES.

Structure elucidation of the O-specific polysaccharide by NMR spectroscopy and selective cleavage and genetic characterization of the O-antigen of Escherichia albertii O5.

PubMed

Naumenko, Olesya I; Zheng, Han; Wang, Jianping; Senchenkova, Sof'ya N; Wang, Hong; Shashkov, Alexander S; Chizhov, Alexander O; Li, Qun; Knirel, Yuriy A; Xiong, Yanwen

2018-03-02

The O-specific polysaccharide (O-antigen) was obtained by mild acid degradation of the lipopolysaccharide of Escherichia albertii O5 (strain T150248) and studied by sugar analysis, selective cleavages of glycosidic linkages, and 1D and 2D 1 H and 13 C NMR spectroscopy. Partial solvolysis with anh (anhydrous) CF 3 CO 2 H and hydrolysis with 0.05 M CF 3 CO 2 H cleaved predominantly the glycosidic linkage of β-GalpNAc or β-Galf, respectively, whereas the linkages of α-GlcpNAc and β-Galp were stable. Mixtures of the corresponding tri- and tetra-saccharides thus obtained were studied by NMR spectroscopy and high-resolution ESI MS. The following new structure was established for the tetrasaccharide repeat (O-unit) of the O-polysaccharide: →4)-α-d-GlcpNAc-(1 → 4)-β-d-Galp6Ac-(1 → 6)-β-d-Galf-(1 → 3)-β-d-GalpNAc-(1→where the degree of O-acetylation of d-Galp is ∼70%. The O-polysaccharide studied has a β-d-Galp-(1 → 6)-β-d-Galf-(1 → 3)-β-d-GalpNAc trisaccharide fragment in common with the O-polysaccharides of E. albertii O7, Escherichia coli O124 and O164, and Shigella dysenteriae type 3 studied earlier. The orf5-7 in the O-antigen gene cluster of E. albertii O5 are 47%, 78%, and 75% identical on the amino acid level to genes for predicted enzymes of E. albertii O7, including Galp-transferase wfeS, UDP-d-Galp mutase glf, and Galf-transferase wfeT, respectively, which are putatively involved with the synthesis of the shared trisaccharide fragment of the O-polysaccharides. The occurrence upstream of the O-antigen gene cluster of a 4-epimerase gene gnu for conversion of undecaprenyl diphosphate-linked d-GlcNAc (UndPP-d-GlcNAc) into UndPP-d-GalNAc indicates that d-GalNAc is the first monosaccharide of the O-unit, and hence the O-units are interlinked in the O-polysaccharide of E. albertii O5 by the β-d-GalpNAc-(1 → 4)-α-d-GlcpNAc linkage. Copyright © 2017. Published by Elsevier Ltd.

Plant community dynamics of lomas fog oasis of Central Peru after the extreme precipitation caused by the 1997-98 El Niño event

PubMed Central

Sánchez Infantas, Edgar; Teixeira Roth, Vanessa

2018-01-01

Despite El Niño events being one of the main forces shaping the coastal desert vegetation in South America, the impacts of the high precipitation typical of this rare but recurrent climatic event remain understudied. Here we monitored the plant community of a coastal lomas, a seasonal desert ecosystem, during 1998 and 2001 to analyse its changes during the 1997–98 El Niño and the following La Niña events. We measured species abundance and vegetation cover in 31 plots, and recorded climate variables in Lomas de Lachay, Peru. We found a significant positive correlation between precipitation and vegetation cover, density, alpha diversity (species diversity at the plot level), total richness and abundance of several key species but no correlation with gamma diversity (species diversity at the whole loma level). During the El Niño event, the seasonality, typical of the lomas ecosystem, disappeared, as evidenced by both the similarity of species composition and mean vegetation cover values between most sampling campaigns of 1998 and 1999. Moreover, total richness was lower during the El Niño event than during the humid season of 2000 and 2001 resulting from the dominance of only a few species, such as Nicotiana paniculata and Loasa urens. Temporal-spatial changes in the abundance of the dominant species caused the differences between alpha and gamma diversity, especially during 1999. Within that year, mean alpha diversity showed similar values whilst gamma diversity values were different. The reestablishment of the seasonality of most plant community characteristics and a clear difference between species composition of the humid and the dry season occurred two years after the El Niño event, suggesting a resilient community. This study provides one of the few quantifications of the Peruvian lomas’ response to the 1997–98 El Niño event and the following La Niña, one of the most extreme climatic events in the last century. PMID:29293693

What is the variability in US west coast winter precipitation during strong El Niño events?

NASA Astrophysics Data System (ADS)

Kumar, Arun; Chen, Mingyue

2017-10-01

Motivated by the fact that the spatial pattern of the observed precipitation anomalies during 2015/16 winter (a year of strong El Niño) over the west coast of the US and that of the El Niño composite precipitation pattern had considerable differences, the variability in the winter precipitation during strong El Niño events is assessed. The analysis is based on a set of hindcasts (1982-2011) and real-time forecasts (2012-2015) from NCEP Climate Forecast System version 2 (CFSv2), and the following aspects for seasonal mean precipitation variability were examined: (1) the mean signal during strong El Niño based on the composite analysis, and further, the variability from the composite on an event-to-event basis; (2) probability of occurrence for precipitation anomalies to be opposite to the signal (inferred as the composite mean); (3) the probability to have precipitation anomaly in different categories varying from wet to dry; and (4) variations in the characteristics of precipitation from OND, NDJ, to DJF (early to late boreal winter). The results show that the model forecasted seasonal mean precipitation composite for strong El Niño was similar to the linear regression signal with the Niño 3.4 index in observations, with negative anomalies over the Pacific Northwest and positive anomalies over California. However, although in response to an El Niño event, the California precipitation PDF was shifted towards positive values relative to the climatological PDF, the overlap between climatological PDF and the PDF for El Niño events was considerable. This is because of the large variability in seasonal mean outcomes of precipitation from one forecast to another, and therefore, chances to have precipitation anomalies with their sign opposite to the composite El Niño signal remain appreciable. In this paradigm, although the seasonal mean precipitation during 2015/16 winter over the west coast of the US differed from the mean signal for a strong El Niño event, the observed anomalies were well within the envelope of possible outcomes. This has significant implications for seasonal predictability and prediction skill, and further, poses challenges for decision makers in the uptake of seasonal forecast information.

Inotuzumab ozogamicin in adults with relapsed or refractory CD22-positive acute lymphoblastic leukemia: a phase 1/2 study.

PubMed

DeAngelo, Daniel J; Stock, Wendy; Stein, Anthony S; Shustov, Andrei; Liedtke, Michaela; Schiffer, Charles A; Vandendries, Erik; Liau, Katherine; Ananthakrishnan, Revathi; Boni, Joseph; Laird, A Douglas; Fostvedt, Luke; Kantarjian, Hagop M; Advani, Anjali S

2017-06-27

This study evaluated the safety, antitumor activity, pharmacokinetics, and pharmacodynamics of inotuzumab ozogamicin (InO) for CD22-positive relapsed/refractory acute lymphoblastic leukemia. In phase 1, patients received InO 1.2 (n = 3), 1.6 (n = 12), or 1.8 (n = 9) mg/m 2 per cycle on days 1, 8, and 15 over a 28-day cycle (≤6 cycles). The recommended phase 2 dose (RP2D) was confirmed (expansion cohort; n = 13); safety and activity of InO were assessed in patients receiving the RP2D in phase 2 (n = 35) and in all treated patients (n = 72). The RP2D was 1.8 mg/m 2 per cycle (0.8 mg/m 2 on day 1; 0.5 mg/m 2 on days 8 and 15), with reduction to 1.6 mg/m 2 per cycle after complete remission (CR) or CR with incomplete marrow recovery (CRi). Treatment-related toxicities were primarily cytopenias. Four patients experienced treatment-related venoocclusive disease/sinusoidal obstruction syndrome (VOD/SOS; 1 fatal). Two VOD/SOS events occurred during treatment without intervening transplant; of 24 patients proceeding to poststudy transplant, 2 experienced VOD/SOS after transplant. Forty-nine (68%) patients had CR/CRi, with 41 (84%) achieving minimal residual disease (MRD) negativity. Median progression-free survival was 3.9 (95% confidence interval, 2.9-5.4) months; median overall survival was 7.4 (5.7-9.2) months for all treated patients, with median 23.7 (range, 6.8-29.8) months of follow-up for all treated patients alive at data cutoff. Achievement of MRD negativity was associated with higher InO exposure. InO was well tolerated and demonstrated high single-agent activity and MRD-negativity rates. This trial was registered at www.clinicaltrials.gov as #NCT01363297.

Range-Wide Meta-Analysis of Red-Cockaded Woodpecker Foraging Habitat Suitability

DTIC Science & Technology

2013-12-31

a 3 3 5’ as O -s o c N’ So ^D o *o o • w || g" P D- O s.5 o o a o 1...ex tE. 3* ((5 D- O ■ a b -s —’ Q. ^ . O P .. o — » ft cro c p en -i. eg. OS ^ (J3’ w ro i.|3. ^2 8 3< -i n n o...3 n> >3 I <^ -: B •— S o Q. C o o’ 3 O o o Z1 Q OQ D. sa ca as era" P *

Nonlinear Burning Stability of Solid Propellants.

DTIC Science & Technology

1983-12-31

de f()dO dX dO dX - dx d o d do d 20"--- - f( e ) 2- dX dX dX dX2 Therefore, the steady thermal profile for the same nondimensio- nal temperature...PF ,) C ( e ) de -H )-(1-r )Fo+q (0 gis 0 -C c o out s At the crossing of qg,s(P,R) with qg,s(P,Fo,®_ ), steady solutions R(P, Fo,1 ) vs qg,s are singled...PAGE (Wbrm Dets Entered) Is.-7 *0*" UNCLASSIFIED . " E C U R ITV C L A S S IF IC A T IO N O F T 0 IS P A G rwhI e D o ra E m, -- 20. Continued

DynamO: a free O(N) general event-driven molecular dynamics simulator.

PubMed

Bannerman, M N; Sargant, R; Lue, L

2011-11-30

Molecular dynamics algorithms for systems of particles interacting through discrete or "hard" potentials are fundamentally different to the methods for continuous or "soft" potential systems. Although many software packages have been developed for continuous potential systems, software for discrete potential systems based on event-driven algorithms are relatively scarce and specialized. We present DynamO, a general event-driven simulation package, which displays the optimal O(N) asymptotic scaling of the computational cost with the number of particles N, rather than the O(N) scaling found in most standard algorithms. DynamO provides reference implementations of the best available event-driven algorithms. These techniques allow the rapid simulation of both complex and large (>10(6) particles) systems for long times. The performance of the program is benchmarked for elastic hard sphere systems, homogeneous cooling and sheared inelastic hard spheres, and equilibrium Lennard-Jones fluids. This software and its documentation are distributed under the GNU General Public license and can be freely downloaded from http://marcusbannerman.co.uk/dynamo. Copyright © 2011 Wiley Periodicals, Inc.

Millennial-scale Asian summer monsoon variations in South China since the last deglaciation

NASA Astrophysics Data System (ADS)

Wang, Xisheng; Chu, Guoqiang; Sheng, Mei; Zhang, Shuqin; Li, Jinhua; Chen, Yun; Tang, Ling; Su, Youliang; Pei, Junling; Yang, Zhenyu

2016-10-01

Characterizing spatiotemporal variability of the Asian summer monsoon (ASM) is critical for full understanding of its behavior, dynamics, and future impacts. The present knowledge about ASM variations since the last glaciation in South China largely relies on several precisely-dated speleothem stable oxygen isotope (δ18 O) records. Although these speleothem δ18 O signals provide useful evidence for regional past environmental changes, their validity for denoting ASM intensity remains a great controversy. The Huguangyan Maar Lake (HML) provides one of the most complete archives of environmental and climatic changes in the tropical-subtropical South and East Asia since the last glaciation. Here we document a continuous centennial- to millennial-scale ASM record over the past 16 ky BP from the high-sedimentation-rate HML sediments. In contrast with the low-amplitude variations of Chinese speleothem-derived δ18 O signals and the Chinese loess-based monsoon precipitation proxy indexes, our multi-proxy records reveal a pattern of high-amplitude regional climatic fluctuations, including fine-scale oscillations during the Bølling-Allerød warming, the 8.2 ka cooling event, and an abrupt climate shift from 6.5-5.9 ka. The existence of Bond-like cold/dry events indicates a distinct influence of the North Atlantic circulation on low-latitude monsoon changes. The broad comparability between the HML paleo-proxies, Chinese speleothem δ18 O records, and the northern hemisphere summer insolation throughout the Holocene, suggests that solar insolation exerts a profound influence on ASM changes. These findings reinforce a model of combined insolation and glacial forcing of the ASM.

[Study on triterpenoid saponins in the rhizome of Anemone hofengensis].

PubMed

Han, Lin-Tao; Li, Ming-Ming; Huang, Fang; Hou, An-Wei

2013-10-01

To study the triterpenoid saponins in the rhizome of Anemone hofengensis. The constituents were separated with various chromatographic techniques and their structures were elucidated by physicochemical properties and spectral data. Five compounds were isolated and identified as 3-O-alpha-L-rhamnopyranosyl-(1 --> 2)-alpha-L-arabino-pyranosyl-oleanolic acid (1), 3-O-alpha-L-rhamnopyranosyl-(1 --> 2)-beta-D-glucopyranosyl-(1 --> 2)-alpha-L-rhamnopyranosyl-oleanolic acid 28-O-alpha-L-rhamnopyranosyl-(1 --> 4) -beta-D-glucopyranosyl-(1 --> 6)-beta-D-glucopyranoside (2), 3-O-alpha-L-rhamnopyranosyl-(1 --> 2) [beta-D-glucopyranosyl-(1 --> 4)]-alpha-L-rhamnopyranosyl-oleanolic acid-28-O-beta-D-glucopyranosyl-(1 --> 6)-beta-D-gluco-pyranoside (3), 3-O-beta-D-glucopyranosyl-(1 --> 2)-beta-D-xylopyranosyl-oleanolic acid 28-O-beta-D-glucopyranosyl-(1 --> 6)-beta-D-glucopyranoside (4), oleanolic acid-28-O-alpha-L-rhamnopyra-nosyl-(1 --> 4)-beta-D-glucopyranosyl-(1 --> 6)-beta-D-glucopyranoside (5). Compound 1 - 5 are isolated from this plant for the first time.

Characterization of Pollution Transport into Texas Using OMI and TES Satellite and In Situ data, and HYSPLIT Back Trajectory Analyses: implications for TCEQ State Implementation Plans and High School/Undergraduate STEM Education

NASA Astrophysics Data System (ADS)

Boxe, C.; Bella, D.; Khaimova, J.; Culpepper, J.; Ahmed, N.; Belkalai, A.; Ealy, J.; Arroyo, I.; Lahoumh, M.; Jenkins, O.; Emmanuel, S.; Andrews, J.; Fu, D.; Wu, L.; Choi, Y.; Morris, G.; Osterman, G. B.; Johnson, L. P.; Austin, S. A.

2014-12-01

Using an online trajectory analysis tool NASA, ArcGIS, Satellite and EPA in situ data, we assess whether high pollution events in Texas are primarily sourced locally or remotely. We focus satellite data that exemplify high O3 and NO2 over Texas's lower troposphere. Four day back trajectory analyses of all dates show that upper-, mid-, and lower-tropospheric air over Texas, containing high O3, is transported from the Gulf of Mexico, Southeast USA, Midwest USA, Northeast USA, the Atlantic Ocean, Pacific Ocean, Mexico, etc. Only day showed air at 1 km is sourced within Texas. Satellite data show O3 enhancements in the boundary layer and O3 and NO2 enhancements via tropospheric column profiles. These enhancements complement four-day trajectory analysis. This study provides a viable basis for more quantifiable and accurate information for developing effective air quality State Implementation Plans. STEM Impact: (i) D. Bella was an NSF-LSAMP undergraduate research mentee with me at Medgar Evers College-CUNY; she received a B.S. in Environmental Science (and a Chemistry Minor) and is now a Ph.D. graduate student at University at Albany's School of Public Health. (ii) J. Khaimova is an undergraduate Geology and Planetary Science B.S. major at Brooklyn College-CUNY. I have supported Jessica's summer internship in summer 2013 as a CUNY Summer Research Fellow, where she is currently an NSF-REU research mentee at Pennsylvania State University's Meteorology Department. (iii) J. Culpepper received his B.S. in Environmental Science from MEC-CUNY and will be a Ph.D. student, Fall 2014 at University of Iowa's Civil and Environmental Engineering Department. (iv) S. Gentle was a high school researcher with me within ACS's Project SEED Program for high school students. S. Gentle will start her undergraduate career Fall 2014 at Pennsylvania State University and seeks to attain a B.S. in Chemistry. (v). All parties, including high school and undergraduate researchers seek to attend medical/graduate school to pursue an M.D/Ph.D. in a STEM-discipline.

In search of colonial El Niño events and a brief history of meteorology in Ecuador

NASA Astrophysics Data System (ADS)

Terneus, A.; Gioda, A.

2006-02-01

This study shows a brief overview of the development of meteorology in Ecuador from historical documentation of climatic events in the Colonial era through to modern data collection. In the colonial era (16th century-1824), historical documents of rogation ceremonies and municipal proceedings, from the Quito area, provide a rich source of climate information, including El Niño events. Our preliminary findings show that very few of the historically documented catastrophes and other marked environmental events in Quito match known El Niño episodes. Independently, the first meteorological data was collected in Ecuador (beginning with La Condamine in 1738), followed by the earliest attempts to build a national meteorological network in the 1860's, linked closely to President Gabriel García Moreno and the Jesuits. The 1925 El Niño phenomenon was the first important meteorological episode recorded with scientific instrumentation in Ecuador, with newspapers providing complementary archives about the extreme impact of this event.

RIDE vs. CLASP Comparison and Evaluation: Models and Parameters

DTIC Science & Technology

2007-04-01

the model is declared "No Decision," indicating that neither QLRM nor LLRM provides a satisfactory fit. If p-value ( i 2j ) > p-value ( flj ), then our...evaluated at A = D = loo tD (7) UA/D(70,40) = 37.35 (8) UA/D(70,100) = 22.93 (9) OUA/D = 0 when evaluated at A = 70, D = 65.7 aD Note the number of...M U) U) C)U)f-~H W 0 U) co CQ CU)QC) W W 0 O40U) El)U tq D O U) U) E U) Z 04 X L X 4j c)c: o n n , f)cj" D ,m u)o mm o:zz .o tD o U) Uti)U) ’-4 r-4

Relating isotopic composition of precipitation to atmospheric patterns and local moisture recycling

NASA Astrophysics Data System (ADS)

Logan, K. E.; Brunsell, N. A.; Nippert, J. B.

2016-12-01

Local land management practices such as irrigation significantly alter surface evapotranspiration (ET), regional boundary layer development, and potentially modify precipitation likelihood and amount. How strong this local forcing is in comparison to synoptic-scale dynamics, and how much ET is recycled locally as precipitation are areas of great uncertainty and are especially important when trying to forecast the impact of local land management strategies on drought mitigation. Stable isotope analysis has long been a useful tool for tracing movement throughout the water cycle. In this study, reanalysis data and stable isotope samples of precipitation events are used to estimate the contribution of local moisture recycling to precipitation at the Konza Prairie LTER - located in the Great Plains, downwind of intensive agricultural areas. From 2001 to 2014 samples of all precipitation events over 5mm were collected and 18O and D isotopes measured. Comparison of observed precipitation totals and MERRA and ERA-interim reanalysis totals is used to diagnose periods of strong local moisture contribution (especially from irrigation) to precipitation. Large discrepancies in precipitation between observation and reanalysis, particularly MERRA, tend to follow dry periods during the growing season, presumably because while ERA-Interim adjusts soil moisture using observed surface temperature and humidity, MERRA includes no such local soil moisture adjustment and therefore lacks potential precipitation feedbacks induced by irrigation. The δ18O and δD signature of local irrigation recycling is evaluated using these incongruous observations. Self-organizing maps (SOM) are then used to identify a comprehensive range of synoptic conditions that result in precipitation at Konza LTER. Comparison of isotopic signature and SOM classification of rainfall events allows for identification of the primary moisture source and estimation of the contribution of locally recycled moisture. The climatology of precipitation source and changes in the influence of local moisture over the course of 14 years of observation are explored.

OAE2 and the Platycopid Signal

NASA Astrophysics Data System (ADS)

Horne, David

2010-05-01

More than 20 years ago the first detailed multi-proxy investigation of the Cenomanian-Turonian Boundary Event (CTBE) in SE England revealed a distinctive pattern of changes in ostracod assemblages. Coincident with a major global positive carbon stable-isotope excursion during Oceanic Anoxic Event 2 (OAE 2), a marked reduction in floral and faunal diversity was attributed to decreasing levels of dissolved oxygen, consequent on an intensification and expansion of the oceanic Oxygen Minimum Zone into shelf seas. As podocopid ostracod taxa became locally extinct, platycopid ostracods became dominant; from this observation was developed the "Platycopid Signal" hypothesis which claimed that dominance of platycopids in ostracod assemblages signalled dysaerobic conditions on the sea floor. Subsequently this interpretation was widely accepted and applied to the recognition of other dysaerobic intervals in the geological record. However, the modern biological and ecological support claimed for the Platycopid Signal has been challenged and found wanting. In the case of the much-studied CTBE sections in SE England this effectively removes the only remaining pillar of support for the notion of bottom-water dysaerobia in the Anglo-Paris Basin during OAE2, which has already been contradicted by macrofossil, trace fossil and geochemical evidence. A new interpretation of the Platycopid Signal as indicative of oligotrophy is supported by other palaeontological proxy evidence in the CTBE and by observations that living platycopids appear to be adapted to filter-feed on nano- and picoplankton phytodetritus which predominates in oligotrophic conditions. Brandão, S.N. & Horne, D.J., 2009. The Platycopid Signal of oxygen depletion in the ocean: a critical evaluation of the evidence from modern ostracod biology, ecology and depth distribution. Palaeogeography, Palaeoclimatology, Palaeoecology, 286, 126-133. Horne, D.J., Brandão, S.N. & Slipper, I.J. The Platycopid Signal deciphered: responses of ostracod taxa to environmental change during the Cenomanian-Turonian Boundary Event (Late Cretaceous) in SE England. Submitted to Cretaceous Research…

The Interplanetary Transport Effects on the Fe/O Ratio of Large Solar Energetic Particle Events

NASA Astrophysics Data System (ADS)

Qin, G.; Wang, Y.

2016-12-01

Mason and coauthors in 2006 invested the intensities of O and Fe in large western solar energetic particle (SEP) events observed by ACE spacecraft. It was found that the Fe/O ratio decreases with time at the same kinetic energy per nucleon during the rising phase of time-intensity profile, and the Fe/O ratio gradually becomes a constant during the decay phase of intensity. However, if the O intensity is compared at a higher kinetic energy with the Fe intensity, the behaviors of intensity profiles of O and Fe are similar. So they concluded that for such kind of events the injection profiles of Fe and O are similar near the Sun, and that scattering effects dominates. With numerical simulations, we find that in order to get such kind of SEPs behavior, Fe and O have to have similar injection profiles near the Sun, and similar diffusion and adiabatic cooling processes in the interplanetary space.

Nucleation and crystallization of Ca doped basaltic glass for the production of a glass-ceramic material

NASA Astrophysics Data System (ADS)

Tarrago, Mariona; Royo, Irene; Garcia-Valles, Maite; Martínez, Salvador

2016-04-01

Sewage sludge from wastewater treatment plants is a waste with a composition roughly similar to that of a basalt. It may contain potentially toxic elements that can be inertized by vitrification. Using a glass-ceramic process, these elements will be emplaced in newly formed mineral phases. Glass-ceramic production requires an accurate knowledge of the temperatures of nucleation (TN) and crystal growth of the corresponding minerals. This work arises from the study of the addition of ions to a basaltic matrix in order to establish a model of vitrification of sewage sludge. In this case a glass-ceramic is obtained from a glass made with a basalt that has been doped with 16% CaO. Two glasses which underwent different cooling processes have been produced and compared. The first was annealed at 650oC (AG) and the second was quenched (QG). The chemical composition of the glasses is SiO2 36.11 wt%, Al2O312.19 wt%, CaO 24.44 wt%, FeO 10.06 wt%, MgO 9.19 wt%, Na2O 2.28 wt%, TiO2 2.02 wt%, K2O 1.12 wt%, P2O5 0.46 wt%. Glass transition temperature obtained by dilatometry varies from 640 oC (AG) to 700 oC (QG). The temperatures of nucleation and crystal growth of the glass have been determined by Differential Thermal Analysis (DTA). The phases formed after these treatments were identified by X-Ray Diffraction. The temperatures of exothermic and endothermic peaks measured in the quenched glass are, in average, 10 oC higher than those found for the annealed glass. The exothermic peaks provide crystallization temperatures for different phases: a first event at 857 oC corresponds to the growth of magnetite, pyroxene and nepheline, whereas a second event at 1030 oC is due to the crystallization of melilite from the reaction between previous minerals and a remaining amorphous phase. The complete melting of this system occurs at 1201 oC. This glass has been nucleated inside the DTA furnace (500-850° C/3 hours) and then heated up to 1300 oC using the fraction between 400-500μm. TN can be obtained by analysing the exothermic peak temperature (Tex) which is related to the number of nuclei per unit volume that is formed on the glass. If we represent (1000/Tex) versus TN, we obtain the range of nucleation and the temperature of maximum nucleation rate of glass. Three different nucleation events were observed for both glasses. The first event, assigned to the nucleation of magnetite starts between 550 (AG) and 600 oC (QG); the second event is linked to the start of nucleation of pyroxene at 655 oC (AG and QG); the third event is the nucleation of nepheline between 700 (QG) and 730 oC (AG). These thermal events are more evident in QG, hence it has been chosen to make the glass-ceramic. Its production would divided in 4 steps at a heating rate of 15 oC/min: is starts by heating the original glass up to 550 oC; further heating up to 655 oC; then up to 700 oC and a final heating up to 1050 oC. A 4h isothermal step was performed after each heating.

Four new triterpenoid glycosides from the seed residue of Hippophae rhamnoides subsp. sinensis.

PubMed

Chen, Chao; Gao, Wen; Cheng, Liang; Shao, Yan; Kong, De-Yun

2014-01-01

Four new triterpenoid saponins (1-4) were isolated from the seed residue of Hippophae rhamnoides subsp. sinensis, named 3-O-[β-D-glucopyranosyl(1 → 2)-β-D-glucopyranosyl-(1 → 3)]-[α-L-rhamnopyranosyl-(1 → 2)]-α-L-arabinopyranosyl-13-ene-19-one-28-oic acid 28-O-β-D-glucopyranosyl ester (1), 3-O-[β-D-glucopyranosyl(1 → 2)-β-D-glucopyranosyl-(1 → 3)]-[α-L-rhamnopyranosyl-(1 → 2)]-α-L-arabinopyranosyl-13-ene-19-one-30-hydroxyolean-28-oic acid 28-O-β-D-glucopyranosyl ester (2), 3-O-[β-D-glucopyranosyl(1 → 2)-β-D-glucopyranosyl-(1 → 3)]-[α-L-rhamnopyranosyl-(1 → 2)]-β-D-glucopyranosyl-13-ene-19-one-28-oic acid 28-O-β-D-glucopyranosyl ester (3), and 3-O-[β-D-glucopyranosyl(1 → 2)-β-D-glucopyranosyl-(1 → 3)]-[α-L-rhamnopyranosyl-(1 → 2)]-β-D-glucopyranosyl-13-ene-19-one-30-hydroxyolean-28-oic acid 28-O-β-D-glucopyranosyl ester (4), and their structures were elucidated on the basis of spectroscopic and chemical methods.

Experimental Studies on the Formation of D2O and D2O2 by Implantation of Energetic D+ Ions into Oxygen Ices

NASA Astrophysics Data System (ADS)

Bennett, Chris J.; Ennis, Courtney P.; Kaiser, Ralf I.

2014-02-01

The formation of water (H2O) in the interstellar medium is intrinsically linked to grain-surface chemistry; thought to involve reactions between atomic (or molecular) hydrogen with atomic oxygen (O), molecular oxygen (O2), and ozone (O3). Laboratory precedent suggests that H2O is produced efficiently when O2 ices are exposed to H atoms (~100 K). This leads to the sequential generation of the hydroxyperoxyl radical (HO2), then hydrogen peroxide (H2O2), and finally H2O and a hydroxyl radical (OH); despite a barrier of ~2300 K for the last step. Recent detection of the four involved species toward ρ Oph A supports this general scenario; however, the precise formation mechanism remains undetermined. Here, solid O2 ice held at 12 K is exposed to a monoenergetic beam of 5 keV D+ ions. Products formed during the irradiation period are monitored through FTIR spectroscopy. O3 is observed through seven archetypal absorptions. Three additional bands found at 2583, 2707, and 1195 cm -1 correspond to matrix isolated DO2 (ν1) and D2O2 (ν1, ν5), and D2O (ν2), respectively. During subsequent warming, the O2 ice sublimates, revealing a broad band at 2472 cm-1 characteristic of amorphous D2O (ν1, ν3). Sublimating D2, D2O, D2O2, and O3 products were confirmed through their subsequent detection via quadrupole mass spectrometry. Reaction schemes based on both thermally accessible and suprathermally induced chemistries were developed to fit the observed temporal profiles are used to elucidate possible reaction pathways for the formation of D2-water. Several alternative schemes to the hydrogenation pathway (O2→HO2→H2O2→H2O) were identified; their astrophysical implications are briefly discussed.

The Last Interglacial Climate Variability in Northern China

NASA Astrophysics Data System (ADS)

Li, X.; Lu, Y.; Sinha, A.; Ma, Z.; Tan, M.; Edwards, R.; Cheng, H.

2013-12-01

Speleothem oxygen isotope (δ18O) records can reconstruct high-resolution and absolutely dated climate history, in particular, the variability of monsoon precipitation that is associated with the changes in atmospheric circulation and, in turn, the δ18O of precipitation. In the East Asian monsoon domain, although speleothem records have been established in southeastern China over the last decade, including several records covering the last interglacial period (MIS 5e), similar records are virtually absent in northern China. This hampers our understanding of the mechanism of the East Asian monsoon changes, because the northern China δ18O record is, as recently shown by modeling work, more sensitive to changes in summer monsoon precipitation than that from southeastern China. Here we provide a high-resolution and absolutely dated speleothem δ18O record between ~129 and 119 ka BP from Kulishu cave, Beijing, northern China. It shows an abrupt onset of MIS 5e at 129.4×0.7 ka BP, similar within dating uncertainty to the Dongge, Hulu, and Sanbao records from southeastern China. However, the end of MIS 5e is rather gradual in comparison to the southern China counterparts. While overall MIS5e monsoon climate appears to be rather stable on orbital timescales, broadly following northern hemisphere summer insolation, millennial/centennial-scale events punctuate the Kulishu record. Spectral analysis reveals a significant quasi-1500 year periodicity, comparable to the Bond cycle, first observed in the North Atlantic during the Holocene, and more recently in interglacial East Asian monsoon cave records. As such, events with a ~1500 year pacing appear to be a persistent characteristic of the East Asian monsoon for good portions of the past two glacial-interglacial periods. Changes in solar output would be one possibility for the trigger; changes in ocean circulation with a ~1500-year time constant would be another. Comparison with Hulu(MSX, Cheng et al., 2006)-Dongge(D3, D4, Kelly et al., 2006)-Sanbao(SB23, SB25, Wang et al., 2008) complex.

Effect of Extremes: How El Niño Events Affect Reef Fish Population Connectivity in the Hawaiian Islands

NASA Astrophysics Data System (ADS)

Wren, J.; Toonen, R. J.

2016-02-01

As a result of climate change, scientists predict stronger, more frequent El Niño events in the future. These events in the Central Equatorial Pacific cause increased sea surface temperatures (SST), a depressed thermocline, and decreased primary production. The oceanographic effects in the Hawaiian Archipelago located in the Subtropical North Pacific, are not equally well understood, and have shown both increased and decreased SST and primary production during El Niño events. Marine larval fish development rates can be affected by factors such as food availability and temperature, thus oceanographic changes caused by El Niño can potentially alter larval dispersal patterns throughout the Hawaiian Archipelago, affecting regional population connectivity. Using a two dimensional Lagrangian particle dispersal model coupled with high resolution Hybrid Coordinate Ocean Model (HYCOM) currents for the Hawaiian Archipelago we are able to model annual settlement probabilities and self-recruitment, important metrics for understanding population dynamics and connectivity. Preliminary data comparing modeled dispersal during the 1997-98 El Niño with four years of normal state oceanographic conditions (2011-2014), showed an increase in total settlement during the El Niño years for the North Western Hawaiian Islands, and a decreased settlement success for the Main Hawaiian Islands. Self-recruitment across the archipelago was lower during El Niño and the distance the successful settlers traveled was greater, indicating that El Niño may be playing an important role in long distance dispersal and genetic exchange between distant sites not otherwise connected. We see a much greater connectivity between the Hawaiian Archipelago and Johnnston Atoll during the El Niño event, with a significant increase of larval exchange in both directions. Since these ecologically rare but extreme events can have a disproportionate influence on dispersal, it's important to understand how connectivity is affected in order to manage for diverse coral reefs in the future.

Singlet Oxygen-Mediated Oxidation during UVA Radiation Alters the Dynamic of Genomic DNA Replication

PubMed Central

Graindorge, Dany; Martineau, Sylvain; Machon, Christelle; Arnoux, Philippe; Guitton, Jérôme; Francesconi, Stefania; Frochot, Céline; Sage, Evelyne; Girard, Pierre-Marie

2015-01-01

UVA radiation (320–400 nm) is a major environmental agent that can exert its deleterious action on living organisms through absorption of the UVA photons by endogenous or exogenous photosensitizers. This leads to the production of reactive oxygen species (ROS), such as singlet oxygen (1O2) and hydrogen peroxide (H2O2), which in turn can modify reversibly or irreversibly biomolecules, such as lipids, proteins and nucleic acids. We have previously reported that UVA-induced ROS strongly inhibit DNA replication in a dose-dependent manner, but independently of the cell cycle checkpoints activation. Here, we report that the production of 1O2 by UVA radiation leads to a transient inhibition of replication fork velocity, a transient decrease in the dNTP pool, a quickly reversible GSH-dependent oxidation of the RRM1 subunit of ribonucleotide reductase and sustained inhibition of origin firing. The time of recovery post irradiation for each of these events can last from few minutes (reduction of oxidized RRM1) to several hours (replication fork velocity and origin firing). The quenching of 1O2 by sodium azide prevents the delay of DNA replication, the decrease in the dNTP pool and the oxidation of RRM1, while inhibition of Chk1 does not prevent the inhibition of origin firing. Although the molecular mechanism remains elusive, our data demonstrate that the dynamic of replication is altered by UVA photosensitization of vitamins via the production of singlet oxygen. PMID:26485711

Highly sulfated hexasaccharide sequences isolated from chondroitin sulfate of shark fin cartilage: insights into the sugar sequences with bioactivities.

PubMed

Mizumoto, Shuji; Murakoshi, Saori; Kalayanamitra, Kittiwan; Deepa, Sarama Sathyaseelan; Fukui, Shigeyuki; Kongtawelert, Prachya; Yamada, Shuhei; Sugahara, Kazuyuki

2013-02-01

Chondroitin sulfate (CS) chains regulate the development of the central nervous system in vertebrates and are linear polysaccharides consisting of variously sulfated repeating disaccharides, [-4GlcUAβ1-3GalNAcβ1-](n), where GlcUA and GalNAc represent D-glucuronic acid and N-acetyl-D-galactosamine, respectively. CS chains containing D-disaccharide units [GlcUA(2-O-sulfate)-GalNAc(6-O-sulfate)] are involved in the development of cerebellar Purkinje cells and neurite outgrowth-promoting activity through interaction with a neurotrophic factor, pleiotrophin, resulting in the regulation of signaling. In this study, to obtain further structural information on the CS chains containing d-disaccharide units involved in brain development, oligosaccharides containing D-units were isolated from a shark fin cartilage. Seven novel hexasaccharide sequences, ΔO-D-D, ΔA-D-D, ΔC-D-D, ΔE-A-D, ΔD-D-C, ΔE-D-D and ΔA-B-D, in addition to three previously reported sequences, ΔC-A-D, ΔC-D-C and ΔA-D-A, were isolated from a CS preparation of shark fin cartilage after exhaustive digestion with chondroitinase AC-I, which cannot act on the galactosaminidic linkages bound to D-units. The symbol Δ stands for a 4,5-unsaturated bond of uronic acids, whereas A, B, C, D, E and O represent [GlcUA-GalNAc(4-O-sulfate)], [GlcUA(2-O-sulfate)-GalNAc(4-O-sulfate)], [GlcUA-GalNAc(6-O-sulfate)], [GlcUA(2-O-sulfate)-GalNAc(6-O-sulfate)], [GlcUA-GalNAc(4-O-, 6-O-sulfate)] and [GlcUA-GalNAc], respectively. In binding studies using an anti-CS monoclonal antibody, MO-225, the epitopes of which are involved in cerebellar development in mammals, novel epitope structures, ΔA-D-A, ΔA-D-D and ΔA-B-D, were revealed. Hexasaccharides containing two consecutive D-units or a B-unit will be useful for the structural and functional analyses of CS chains particularly in the neuroglycobiological fields.

The influence of low latitude forcing on European Ice sheet dynamics

NASA Astrophysics Data System (ADS)

Kaboth, Stefanie; Bahr, André; Lourens, Lucas J.

2017-04-01

Distinct mid-glacial δ18O enrichment events found at Site U1386 in the Gulf of Cadiz during Marine Isotope Stages 6 and 8 represent a striking feature absent in most deep-sea benthic δ18O records studied worldwide. These δ18O enrichment events are closely related to periods of maximum precession and aligned with previous findings from the Mediterranean and Red Seas. Here we present paired planktic and benthic stable isotope (δ18O and δ13C) and Mg/Ca-based temperature records of Site U1386 of the last 300.000 years. Our results show that these δ18O enrichment events are recorded in both subsurface and bottom water masses and pre-date the largest cooling events along the Iberian Margin and associated European sourced meltwater pulses of the Drenthe and Fuhne major ice-sheet advances, suggesting that they instead correspond to periods of maximum ice volume extend in Europe.

Biological Surface Coating and Molting Inhibition as Mechanisms of TiO2 Nanoparticle Toxicity in Daphnia magna

PubMed Central

Dabrunz, André; Duester, Lars; Prasse, Carsten; Seitz, Frank; Rosenfeldt, Ricki; Schilde, Carsten; Schaumann, Gabriele E.; Schulz, Ralf

2011-01-01

The production and use of nanoparticles (NP) has steadily increased within the last decade; however, knowledge about risks of NP to human health and ecosystems is still scarce. Common knowledge concerning NP effects on freshwater organisms is largely limited to standard short-term (≤48 h) toxicity tests, which lack both NP fate characterization and an understanding of the mechanisms underlying toxicity. Employing slightly longer exposure times (72 to 96 h), we found that suspensions of nanosized (∼100 nm initial mean diameter) titanium dioxide (nTiO2) led to toxicity in Daphnia magna at nominal concentrations of 3.8 (72-h EC50) and 0.73 mg/L (96-h EC50). However, nTiO2 disappeared quickly from the ISO-medium water phase, resulting in toxicity levels as low as 0.24 mg/L (96-h EC50) based on measured concentrations. Moreover, we showed that nTiO2 (∼100 nm) is significantly more toxic than non-nanosized TiO2 (∼200 nm) prepared from the same stock suspension. Most importantly, we hypothesized a mechanistic chain of events for nTiO2 toxicity in D. magna that involves the coating of the organism surface with nTiO2 combined with a molting disruption. Neonate D. magna (≤6 h) exposed to 2 mg/L nTiO2 exhibited a “biological surface coating” that disappeared within 36 h, during which the first molting was successfully managed by 100% of the exposed organisms. Continued exposure up to 96 h led to a renewed formation of the surface coating and significantly reduced the molting rate to 10%, resulting in 90% mortality. Because coating of aquatic organisms by manmade NP might be ubiquitous in nature, this form of physical NP toxicity might result in widespread negative impacts on environmental health. PMID:21647422

Synthesis of P1-(11-phenoxyundecyl)-P2-(2-acetamido-2-deoxy-3-O-α-D-rhamnopyranosyl-α-D-glucopyranosyl) diphosphate and P1-(11-phenoxyundecyl)-P2-(2-acetamido-2-deoxy-3-O-β-D-galactopyranosyl-α-D-galactopyranosyl) diphosphate for the investigation of biosynthesis of O-antigenic polysaccharides in Pseudomonas aeruginosa and Escherichia coli O104.

PubMed

Torgov, Vladimir; Danilov, Leonid; Utkina, Natalia; Veselovsky, Vladimir; Brockhausen, Inka

2017-12-01

Two new phenoxyundecyl diphosphate sugars were synthesized for the first time: P 1 -(11-phenoxyundecyl)-P 2 - (2-acetamido-2-deoxy-3-O-α-D-rhamnopyranosyl-α-D-glucopyranosyl) diphosphate and P 1 -(11-phenoxyundecyl)-P 2 -(2-acetamido-2-deoxy-3-O-β-D-galactopyranosyl-α-D-galactopyranosyl) diphosphate to study the third step of biosynthesis of the repeating units of O-antigenic polysaccharides in Pseudomonas aeruginosa and E.coli O104 respectively. Copyright © 2017 Elsevier Ltd. All rights reserved.

Synthesis of fagopyritols A1 and B1 from D-chiro-inositol.

PubMed

Cid, M Belén; Alfonso, Francisco; Martín-Lomas, Manuel

2004-09-13

Fagopyritol A1 (3-O-alpha-d-galactopyranosyl-d-chiro-inositol) and fagopyritol B1 (2-O-alpha-d-galactopyranosyl-d-chiro-inositol) have been synthesized by glycosylation of the diequatorial diol 1,4,5,6-tetra-O-benzoyl-d-chiro-inositol, readily obtained from d-chiro-inositol, with 2,3,4,6-tetra-O-benzyl-d-galactopyranosyl trichloroacetimidate.

D/H fractionation in the H2-H2O system at supercritical water conditions: Compositional and hydrogen bonding effects

NASA Astrophysics Data System (ADS)

Foustoukos, Dionysis I.; Mysen, Bjorn O.

2012-06-01

A series of experiments has been conducted in the H2-D2-D2O-H2O-Ti-TiO2 system at temperatures ranging from 300 to 800 °C and pressures between ∼0.3 and 1.3 GPa in a hydrothermal diamond anvil cell, utilizing Raman spectroscopy as a quantitative tool to explore the relative distribution of hydrogen and deuterium isotopologues of the H2 and H2O in supercritical fluids. In detail, H2O-D2O solutions (1:1) were reacted with Ti metal (3-9 h) in the diamond cell, leading to formation of H2, D2, HD, and HDO species through Ti oxidation and H-D isotope exchange reactions. Experimental results obtained in situ and at ambient conditions on quenched samples indicate significant differences from the theoretical estimates of the equilibrium thermodynamic properties of the H-D exchange reactions. In fact, the estimated enthalpy for the H2(aq)-D2(aq) disproportionation reaction (ΔHrxn) is about -3.4 kcal/mol, which differs greatly from the +0.16 kcal/mol predicted for the exchange reaction in the gas phase by statistical mechanics models. The exothermic behavior of the exchange reaction implies enhanced stability of H2 and D2 relative to HD. Accordingly, the significant energy difference of the internal H2(aq)-D2(aq)-HD(aq) equilibrium translates to strong differences of the fractionation effects between the H2O-H2 and D2O-D2 isotope exchange relationships. The D/H fractionation factors between H2O-H2(aq) and D2O-D2(aq) differ by 365‰ in the 600-800 °C temperature range, and are indicative of the greater effect of D2O contribution to the δD isotopic composition of supercritical fluids. The negative ΔHrxn values for the H2(aq)-D2(aq)-HD(aq) equilibrium and the apparent decrease of the equilibrium constant with increasing temperature might be because of differences of the Henry’s law constant between the H- and D-bearing species dissolved in supercritical aqueous solutions. Such effects may be attributed to the stronger hydrogen bonding in the O-H⋯O relative to the O-D⋯O environment. This difference allows enhanced gas solubility in the denser and more polar H2O clusters, and thus, affects the D/H exchange between the H2-D2 volatiles and the coexisting H2O-D2O mixtures. The proposed role of temperature in promoting differences in the density and polarity of hydrogen-bonded OHO and ODO molecules may be explained with isotope-specific molar volume effects similar to those suggested to account for the hydrogen isotope fractionation between H2O and hydroxide mineral phases (e.g. brucite) across large pressure intervals.