Science.gov

Sample records for abrupt climate shifts

  1. 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.

  2. Abrupt glacial climate shifts controlled by ice sheet changes

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

    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.

  3. 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. PMID:25119027

  4. Abrupt climate shift in the Western Mediterranean Sea

    PubMed Central

    Schroeder, K.; Chiggiato, J.; Bryden, H. L.; Borghini, M.; Ben Ismail, S.

    2016-01-01

    One century of oceanographic measurements has evidenced gradual increases in temperature and salinity of western Mediterranean water masses, even though the vertical stratification has basically remained unchanged. Starting in 2005, the basic structure of the intermediate and deep layers abruptly changed. We report here evidence of reinforced thermohaline variability in the deep western basin with significant dense water formation events producing large amounts of warmer, saltier and denser water masses than ever before. We provide a detailed chronological order to these changes, giving an overview of the new water masses and following their route from the central basin interior to the east (toward the Tyrrhenian) and toward the Atlantic Ocean. As a consequence of this climate shift, new deep waters outflowing through Gibraltar will impact the North Atlantic in terms of salt and heat input. In addition, modifications in the Mediterranean abyssal ecosystems and biogeochemical cycles are to be expected. PMID:26965790

  5. Abrupt climate shift in the Western Mediterranean Sea.

    PubMed

    Schroeder, K; Chiggiato, J; Bryden, H L; Borghini, M; Ben Ismail, S

    2016-01-01

    One century of oceanographic measurements has evidenced gradual increases in temperature and salinity of western Mediterranean water masses, even though the vertical stratification has basically remained unchanged. Starting in 2005, the basic structure of the intermediate and deep layers abruptly changed. We report here evidence of reinforced thermohaline variability in the deep western basin with significant dense water formation events producing large amounts of warmer, saltier and denser water masses than ever before. We provide a detailed chronological order to these changes, giving an overview of the new water masses and following their route from the central basin interior to the east (toward the Tyrrhenian) and toward the Atlantic Ocean. As a consequence of this climate shift, new deep waters outflowing through Gibraltar will impact the North Atlantic in terms of salt and heat input. In addition, modifications in the Mediterranean abyssal ecosystems and biogeochemical cycles are to be expected. PMID:26965790

  6. Abrupt climate shift in the Western Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Schroeder, K.; Chiggiato, J.; Bryden, H. L.; Borghini, M.; Ben Ismail, S.

    2016-03-01

    One century of oceanographic measurements has evidenced gradual increases in temperature and salinity of western Mediterranean water masses, even though the vertical stratification has basically remained unchanged. Starting in 2005, the basic structure of the intermediate and deep layers abruptly changed. We report here evidence of reinforced thermohaline variability in the deep western basin with significant dense water formation events producing large amounts of warmer, saltier and denser water masses than ever before. We provide a detailed chronological order to these changes, giving an overview of the new water masses and following their route from the central basin interior to the east (toward the Tyrrhenian) and toward the Atlantic Ocean. As a consequence of this climate shift, new deep waters outflowing through Gibraltar will impact the North Atlantic in terms of salt and heat input. In addition, modifications in the Mediterranean abyssal ecosystems and biogeochemical cycles are to be expected.

  7. Catalogue of abrupt shifts in Intergovernmental Panel on Climate Change climate models.

    PubMed

    Drijfhout, Sybren; Bathiany, Sebastian; Beaulieu, Claudie; Brovkin, Victor; Claussen, Martin; Huntingford, Chris; Scheffer, Marten; Sgubin, Giovanni; Swingedouw, Didier

    2015-10-27

    Abrupt transitions of regional climate in response to the gradual rise in atmospheric greenhouse gas concentrations are notoriously difficult to foresee. However, such events could be particularly challenging in view of the capacity required for society and ecosystems to adapt to them. We present, to our knowledge, the first systematic screening of the massive climate model ensemble informing the recent Intergovernmental Panel on Climate Change report, and reveal evidence of 37 forced regional abrupt changes in the ocean, sea ice, snow cover, permafrost, and terrestrial biosphere that arise after a certain global temperature increase. Eighteen out of 37 events occur for global warming levels of less than 2°, a threshold sometimes presented as a safe limit. Although most models predict one or more such events, any specific occurrence typically appears in only a few models. We find no compelling evidence for a general relation between the overall number of abrupt shifts and the level of global warming. However, we do note that abrupt changes in ocean circulation occur more often for moderate warming (less than 2°), whereas over land they occur more often for warming larger than 2°. Using a basic proportion test, however, we find that the number of abrupt shifts identified in Representative Concentration Pathway (RCP) 8.5 scenarios is significantly larger than in other scenarios of lower radiative forcing. This suggests the potential for a gradual trend of destabilization of the climate with respect to such shifts, due to increasing global mean temperature change. PMID:26460042

  8. Catalogue of abrupt shifts in Intergovernmental Panel on Climate Change climate models

    PubMed Central

    Drijfhout, Sybren; Bathiany, Sebastian; Beaulieu, Claudie; Brovkin, Victor; Claussen, Martin; Huntingford, Chris; Scheffer, Marten; Sgubin, Giovanni; Swingedouw, Didier

    2015-01-01

    Abrupt transitions of regional climate in response to the gradual rise in atmospheric greenhouse gas concentrations are notoriously difficult to foresee. However, such events could be particularly challenging in view of the capacity required for society and ecosystems to adapt to them. We present, to our knowledge, the first systematic screening of the massive climate model ensemble informing the recent Intergovernmental Panel on Climate Change report, and reveal evidence of 37 forced regional abrupt changes in the ocean, sea ice, snow cover, permafrost, and terrestrial biosphere that arise after a certain global temperature increase. Eighteen out of 37 events occur for global warming levels of less than 2°, a threshold sometimes presented as a safe limit. Although most models predict one or more such events, any specific occurrence typically appears in only a few models. We find no compelling evidence for a general relation between the overall number of abrupt shifts and the level of global warming. However, we do note that abrupt changes in ocean circulation occur more often for moderate warming (less than 2°), whereas over land they occur more often for warming larger than 2°. Using a basic proportion test, however, we find that the number of abrupt shifts identified in Representative Concentration Pathway (RCP) 8.5 scenarios is significantly larger than in other scenarios of lower radiative forcing. This suggests the potential for a gradual trend of destabilization of the climate with respect to such shifts, due to increasing global mean temperature change. PMID:26460042

  9. Catalogue of abrupt shifts in Intergovernmental Panel on Climate Change climate models.

    PubMed

    Drijfhout, Sybren; Bathiany, Sebastian; Beaulieu, Claudie; Brovkin, Victor; Claussen, Martin; Huntingford, Chris; Scheffer, Marten; Sgubin, Giovanni; Swingedouw, Didier

    2015-10-27

    Abrupt transitions of regional climate in response to the gradual rise in atmospheric greenhouse gas concentrations are notoriously difficult to foresee. However, such events could be particularly challenging in view of the capacity required for society and ecosystems to adapt to them. We present, to our knowledge, the first systematic screening of the massive climate model ensemble informing the recent Intergovernmental Panel on Climate Change report, and reveal evidence of 37 forced regional abrupt changes in the ocean, sea ice, snow cover, permafrost, and terrestrial biosphere that arise after a certain global temperature increase. Eighteen out of 37 events occur for global warming levels of less than 2°, a threshold sometimes presented as a safe limit. Although most models predict one or more such events, any specific occurrence typically appears in only a few models. We find no compelling evidence for a general relation between the overall number of abrupt shifts and the level of global warming. However, we do note that abrupt changes in ocean circulation occur more often for moderate warming (less than 2°), whereas over land they occur more often for warming larger than 2°. Using a basic proportion test, however, we find that the number of abrupt shifts identified in Representative Concentration Pathway (RCP) 8.5 scenarios is significantly larger than in other scenarios of lower radiative forcing. This suggests the potential for a gradual trend of destabilization of the climate with respect to such shifts, due to increasing global mean temperature change.

  10. Phase-locked states and abrupt shifts in Pacific climate indices

    NASA Astrophysics Data System (ADS)

    Douglass, David H.

    2013-10-01

    Douglass has shown that ENSO index aNino3.4 contains segments phase locked to subharmonics of the annual solar cycle and also that a set of indices including aNino3.4 shows abrupt shifts between these phase-locked states. Here, four additional Pacific indices are studied. These five indices show that the Pacific climate system alternates between two regimes: (1) Solar cycle (SOL), (2) Teleconnections (TEL). During SOL each index shows two components that are phase locked to the solar cycle. The first is at the annual cycle, while the second is at a subharmonic of the annual cycle. During TEL abrupt climate shifts occur.

  11. Causes and projections of abrupt climate-driven ecosystem shifts in the North Atlantic.

    PubMed

    Beaugrand, Grégory; Edwards, Martin; Brander, Keith; Luczak, Christophe; Ibanez, Frederic

    2008-11-01

    Warming of the global climate is now unequivocal and its impact on Earth' functional units has become more apparent. Here, we show that marine ecosystems are not equally sensitive to climate change and reveal a critical thermal boundary where a small increase in temperature triggers abrupt ecosystem shifts seen across multiple trophic levels. This large-scale boundary is located in regions where abrupt ecosystem shifts have been reported in the North Atlantic sector and thereby allows us to link these shifts by a global common phenomenon. We show that these changes alter the biodiversity and carrying capacity of ecosystems and may, combined with fishing, precipitate the reduction of some stocks of Atlantic cod already severely impacted by exploitation. These findings offer a way to anticipate major ecosystem changes and to propose adaptive strategies for marine exploited resources such as cod in order to minimize social and economic consequences.

  12. Theoretical basis for predicting climate-induced abrupt shifts in the oceans

    PubMed Central

    Beaugrand, Gregory

    2015-01-01

    Among the responses of marine species and their ecosystems to climate change, abrupt community shifts (ACSs), also called regime shifts, have often been observed. However, despite their effects for ecosystem functioning and both provisioning and regulating services, our understanding of the underlying mechanisms involved remains elusive. This paper proposes a theory showing that some ACSs originate from the interaction between climate-induced environmental changes and the species ecological niche. The theory predicts that a substantial stepwise shift in the thermal regime of a marine ecosystem leads indubitably to an ACS and explains why some species do not change during the phenomenon. It also explicates why the timing of ACSs may differ or why some studies may detect or not detect a shift in the same ecosystem, independently of the statistical method of detection and simply because they focus on different species or taxonomic groups. The present theory offers a way to predict future climate-induced community shifts and their potential associated trophic cascades and amplifications.

  13. Tracking abrupt climate shifts with stable isotopes: geochemical evidence for dynamic temperature, precipitation and seasonality regimes during the last deglaciation (8 to 15ka BP)

    NASA Astrophysics Data System (ADS)

    Candy, I.; Blockley, S.; Matthews, I.; Palmer, A.; Darvill, C.

    2012-12-01

    The interval between the Last Glacial Maximum (LGM) and the stabilisation of climatic conditions during the Holocene (ca 8ka BP) is well-known to have been punctuated with abrupt climatic shifts on a range of different time scales. This is clearly seen in the oxygen and deuterium isotope signal of the Greenland ice core records (e.g. NGRIP). How the magnitude and duration of these events translates across a region, such as western Europe, is however, unclear, primarily because many traditional proxies do not respond rapidly enough to provide a clear expression of abrupt climatic events. In this paper, we present a range of new oxygen and carbon isotopic records from lacustrine carbonate sequences, and a review of existing datasets, spanning the interval 8 to 15ka BP. These records lie on W-E and N-S transects across the British Isles allowing the spatial variability of the structure and magnitude of abrupt climatic events to be investigated. The oxygen isotopic signal is primarily driven by temperature and indicates that the climatic structure of abrupt events, such as the Lateglacial interstadial, is highly variable over relatively short spatial scales. Records from eastern Britain suggest patterns of warming and cooling in the Lateglacial interstadial (GI-1) comparable to those observed in Greenland, where a temperature maxima occurs early in GI-1. However records in western Britain provide evidence for more subdued climatic oscillations with peak temperatures occurring later in GI-1. Spatial variability in the isotopic expression of abrupt climatic events allows the role of different factors such as the position of the polar front, the influence of the thermohaline conveyer and the influence of maritime versus continental climates, to be investigated. This study also indicates that a major depletion event occurs in the δ18O value of lake carbonates during the early Holocene which affects all currently known sequences. This depletion event cannot be explained by

  14. Tracking abrupt climate shifts with stable isotopes in lacustrine sediments: geochemical evidence for dynamic temperature, precipitation and seasonality regimes during the last deglaciation (8 to 15ka BP)

    NASA Astrophysics Data System (ADS)

    Candy, Ian; Blockley, Simon; Matthews, Ian; Palmer, Adrian; Darvill, Chris

    2013-04-01

    The interval between the Last Glacial Maximum (L.G.M.) and the stabilisation of climatic conditions during the Holocene (ca 8ka BP) is well-known to have been punctuated with abrupt climatic shifts on a range of time scales. This is clearly seen in the oxygen and deuterium isotope signal of the Greenland ice core records (e.g. NGRIP). How the magnitude and duration of these events translates across a region, such as western Europe, is however, unclear, primarily because many traditional proxies do not respond rapidly enough to provide a clear expression of abrupt climatic events. In this paper we present a range of new oxygen and carbon isotopic records, and a review of existing datasets, from lacustrine carbonate sequences spanning the interval 8 to 15ka BP. These records lie on W-E and N-S transects across the British Isles allowing the spatial variability of the structure and magnitude of abrupt climatic events to be investigated. The oxygen isotopic signal is primarily driven by temperature and indicates that the climatic structure of abrupt events in this time interval, the Lateglacial interstadial for example, is highly variable over relatively small distances. Records from the east of Britain suggest patterns of warming and cooling in the Lateglacial interstadial comparable to that observable in Greenland (e.g. a temperature maximum occurring early in the interstadial), whilst record in the west provide evidence for more subdued climatic oscillations with peak temperatures occurring late in the interstadial. Spatial variability in the isotopic expression of abrupt climatic events allows the role of different factors; i.e. the position of the polar front, the influence of the thermohaline conveyer and the influence of maritime versus continental climates, to be investigated. This work also indicates that a major depletion event occurs in the δ18O value of lake carbonates during the early Holocene which effects all currently known sequences. This depletion

  15. Climate-driven shifts in continental net primary production implicated as a driver of a recent abrupt increase in the land carbon sink

    NASA Astrophysics Data System (ADS)

    Buermann, Wolfgang; Beaulieu, Claudie; Parida, Bikash; Medvigy, David; Collatz, George J.; Sheffield, Justin; Sarmiento, Jorge L.

    2016-03-01

    The world's ocean and land ecosystems act as sinks for anthropogenic CO2, and over the last half century their combined sink strength grew steadily with increasing CO2 emissions. Recent analyses of the global carbon budget, however, have uncovered an abrupt, substantial ( ˜ 1 PgC yr-1) and sustained increase in the land sink in the late 1980s whose origin remains unclear. In the absence of this prominent shift in the land sink, increases in atmospheric CO2 concentrations since the late 1980s would have been ˜ 30 % larger than observed (or ˜ 12 ppm above current levels). Global data analyses are limited in regards to attributing causes to changes in the land sink because different regions are likely responding to different drivers. Here, we address this challenge by using terrestrial biosphere models constrained by observations to determine if there is independent evidence for the abrupt strengthening of the land sink. We find that net primary production significantly increased in the late 1980s (more so than heterotrophic respiration), consistent with the inferred increase in the global land sink, and that large-scale climate anomalies are responsible for this shift. We identify two key regions in which climatic constraints on plant growth have eased: northern Eurasia experienced warming, and northern Africa received increased precipitation. Whether these changes in continental climates are connected is uncertain, but North Atlantic climate variability is important. Our findings suggest that improved understanding of climate variability in the North Atlantic may be essential for more credible projections of the land sink under climate change.

  16. Approaching the Edge of Abrupt Climate Change

    NASA Astrophysics Data System (ADS)

    Ramadhin, C.; Yi, C.

    2015-12-01

    The phenomenon of Abrupt Climate Change (ACC) became evident as paleoclimate data analyses began revealing that Earth's climate has the ability to rapidly switch from one state to the next in just a few decades after thresholds are crossed. Previously paleo-climatologists thought these switches were gradual but now there is growing concern to identify thresholds and the dominant feedback mechanisms that propel systems toward thresholds. Current human civilization relies heavily on climate stability and ACC threatens immense disruption with potentially disastrous consequences for all ecosystems. Therefore, prediction of the climate system's approach to threshold values would prove vital for the resilience of civilization through development of appropriate adaptation strategies when that shift occurs. Numerous studies now establish that earth systems are experiencing dramatic changes both by system interactions and anthropogenic sources adding urgency for comprehensive knowledge of tipping point identification. Despite this, predictions are difficult due to the immensity of interactions among feedback mechanisms. In this paper, we attempt to narrow this broad spectrum of critical feedback mechanisms by reviewing several publications on role of feedbacks in initiating past climate transitions establishing the most critical ones and significance in current climate changes. Using a compilation of paleoclimate datasets we compared the rates of deglaciations with that of glacial inceptions, which are approximately 5-10 times slower. We hypothesize that the critical feedbacks are unique to each type of transition such that warmings are dominated by the ice-albedo feedback while coolings are a combination of temperature - CO2 and temperature-precipitation followed by the ice-albedo feedbacks. Additionally, we propose the existence of a commonality in the dominant trigger feedbacks for astronomical and millennial timescale abrupt climate shifts and as such future studies

  17. Abrupt climate-independent fire regime changes

    USGS Publications Warehouse

    Pausas, Juli G.; Keeley, Jon E.

    2014-01-01

    Wildfires have played a determining role in distribution, composition and structure of many ecosystems worldwide and climatic changes are widely considered to be a major driver of future fire regime changes. However, forecasting future climatic change induced impacts on fire regimes will require a clearer understanding of other drivers of abrupt fire regime changes. Here, we focus on evidence from different environmental and temporal settings of fire regimes changes that are not directly attributed to climatic changes. We review key cases of these abrupt fire regime changes at different spatial and temporal scales, including those directly driven (i) by fauna, (ii) by invasive plant species, and (iii) by socio-economic and policy changes. All these drivers might generate non-linear effects of landscape changes in fuel structure; that is, they generate fuel changes that can cross thresholds of landscape continuity, and thus drastically change fire activity. Although climatic changes might contribute to some of these changes, there are also many instances that are not primarily linked to climatic shifts. Understanding the mechanism driving fire regime changes should contribute to our ability to better assess future fire regimes.

  18. Abrupt climate change and extinction events

    NASA Technical Reports Server (NTRS)

    Crowley, Thomas J.

    1988-01-01

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

  19. Abrupt climate change: can society cope?

    PubMed

    Hulme, Mike

    2003-09-15

    Consideration of abrupt climate change has generally been incorporated neither in analyses of climate-change impacts nor in the design of climate adaptation strategies. Yet the possibility of abrupt climate change triggered by human perturbation of the climate system is used to support the position of both those who urge stronger and earlier mitigative action than is currently being contemplated and those who argue that the unknowns in the Earth system are too large to justify such early action. This paper explores the question of abrupt climate change in terms of its potential implications for society, focusing on the UK and northwest Europe in particular. The nature of abrupt climate change and the different ways in which it has been defined and perceived are examined. Using the example of the collapse of the thermohaline circulation (THC), the suggested implications for society of abrupt climate change are reviewed; previous work has been largely speculative and has generally considered the implications only from economic and ecological perspectives. Some observations about the implications from a more social and behavioural science perspective are made. If abrupt climate change simply implies changes in the occurrence or intensity of extreme weather events, or an accelerated unidirectional change in climate, the design of adaptation to climate change can proceed within the existing paradigm, with appropriate adjustments. Limits to adaptation in some sectors or regions may be reached, and the costs of appropriate adaptive behaviour may be large, but strategy can develop on the basis of a predicted long-term unidirectional change in climate. It would be more challenging, however, if abrupt climate change implied a directional change in climate, as, for example, may well occur in northwest Europe following a collapse of the THC. There are two fundamental problems for society associated with such an outcome: first, the future changes in climate currently being

  20. Abrupt climate change: can society cope?

    PubMed

    Hulme, Mike

    2003-09-15

    Consideration of abrupt climate change has generally been incorporated neither in analyses of climate-change impacts nor in the design of climate adaptation strategies. Yet the possibility of abrupt climate change triggered by human perturbation of the climate system is used to support the position of both those who urge stronger and earlier mitigative action than is currently being contemplated and those who argue that the unknowns in the Earth system are too large to justify such early action. This paper explores the question of abrupt climate change in terms of its potential implications for society, focusing on the UK and northwest Europe in particular. The nature of abrupt climate change and the different ways in which it has been defined and perceived are examined. Using the example of the collapse of the thermohaline circulation (THC), the suggested implications for society of abrupt climate change are reviewed; previous work has been largely speculative and has generally considered the implications only from economic and ecological perspectives. Some observations about the implications from a more social and behavioural science perspective are made. If abrupt climate change simply implies changes in the occurrence or intensity of extreme weather events, or an accelerated unidirectional change in climate, the design of adaptation to climate change can proceed within the existing paradigm, with appropriate adjustments. Limits to adaptation in some sectors or regions may be reached, and the costs of appropriate adaptive behaviour may be large, but strategy can develop on the basis of a predicted long-term unidirectional change in climate. It would be more challenging, however, if abrupt climate change implied a directional change in climate, as, for example, may well occur in northwest Europe following a collapse of the THC. There are two fundamental problems for society associated with such an outcome: first, the future changes in climate currently being

  1. Can ice sheets trigger abrupt climatic change?

    SciTech Connect

    Hughes, T.

    1996-11-01

    The discovery in recent years of abrupt climatic changes in climate proxy records from Greenland ice cores and North Atlantic sediment cores, and from other sites around the world, has diverted attention from gradual insolation changes caused by Earth`s orbital variations to more rapid processes on Earth`s surface as forcing Quaternary climatic change. In particular, forcing by ice sheets has been quantified for a major ice stream that drained the Laurentide Ice Sheet along Hudson Strait. The history of these recent discoveries leading to an interest in ice sheets is reviewed, and a case is made that ice sheets may drive abrupt climatic change that is virtually synchronous worldwide. Attention is focused on abrupt inception and termination of a Quaternary glaciation cycle, abrupt changes recorded as stadials and interstadials within the cycle, abrupt changes in ice streams that trigger stadials and interstadials, and abrupt changes in the Laurentide Ice Sheet linked to effectively simultaneous abrupt changes in its ice streams. Remaining work needed to quantify further these changes is discussed. 90 refs., 14 figs.

  2. Abrupt Impacts of Climate Change: Anticipating Surprises

    NASA Astrophysics Data System (ADS)

    White, James W. C.; Alley, Richard B.; Archer, David E.; Barnosky, Anthony D.; Dunlea, Edward; Foley, Jonathan; Fu, Rong; Holland, Marika M.; Lozier, M. Susan; Schmitt, Johanna; Smith, Laurence C.; Sugihara, George; Thompson, David W. J.; Weaver, Andrew J.; Wofsy, Steven C.

    2014-05-01

    Levels of carbon dioxide and other greenhouse gases in Earth's atmosphere are exceeding levels recorded in the past millions of years, and thus climate is being forced beyond the range of the recent geological era. Lacking concerted action by the world's nations, it is clear that the future climate will be warmer, sea levels will rise, global rainfall patterns will change, and ecosystems will be altered. However, there is still uncertainty about how we will arrive at that future climate state. Although many projections of future climatic conditions have predicted steadily changing conditions giving the impression that communities have time to gradually adapt, the scientific community has been paying increasing attention to the possibility that at least some changes will be abrupt, perhaps crossing a threshold or "tipping point" to change so quickly that there will be little time to react. This presentation will synopsize the new US National Research Council Report, Abrupt Impacts of Climate Change: Anticipating Surprises, highlighting areas of increased and decreased concern, as well as areas of new concern. Emphasis is placed on not only abrupt change in physical climate, but on abrupt changes in human and natural systems that can occur as a result of a slowly changing climate. The report calls for action now on an abrupt change early warning system (ACEWS) if societies are to be resilient to climate change.

  3. The economics of abrupt climate change.

    PubMed

    Perrings, Charles

    2003-09-15

    The US National Research Council defines abrupt climate change as a change of state that is sufficiently rapid and sufficiently widespread in its effects that economies are unprepared or incapable of adapting. This may be too restrictive a definition, but abrupt climate change does have implications for the choice between the main response options: mitigation (which reduces the risks of climate change) and adaptation (which reduces the costs of climate change). The paper argues that by (i) increasing the costs of change and the potential growth of consumption, and (ii) reducing the time to change, abrupt climate change favours mitigation over adaptation. Furthermore, because the implications of change are fundamentally uncertain and potentially very high, it favours a precautionary approach in which mitigation buys time for learning. Adaptation-oriented decision tools, such as scenario planning, are inappropriate in these circumstances. Hence learning implies the use of probabilistic models that include socioeconomic feedbacks.

  4. Abrupt climate change: Mechanisms, patterns, and impacts

    NASA Astrophysics Data System (ADS)

    Schultz, Colin

    2012-08-01

    In the span of only a few decades, the global temperature can soar by more than a dozen degrees Celsius, a feat that 20 years ago was considered improbable, if not impossible. But recent research in the nascent field of rapid climate change has upended the dominant views of decades past. Focusing primarily on events during and after the most recent glaciation, from 80,000 years ago, the AGU monograph Abrupt Climate Change: Mechanisms, Patterns, and Impacts, edited by Harunur Rashid, Leonid Polyak, and Ellen Mosley-Thompson, explores the transient climate transitions that were only recently uncovered in climate proxies around the world. In this interview, Eos talks to Harunur Rashid about piecing together ancient climes, the effect of abrupt change on historical civilizations, and why younger researchers may be more worried about modern warming than their teachers.

  5. Abrupt shifts in Horn of Africa hydroclimate since the Last Glacial Maximum.

    PubMed

    Tierney, Jessica E; deMenocal, Peter B

    2013-11-15

    The timing and abruptness of the initiation and termination of the Early Holocene African Humid Period are subjects of ongoing debate, with direct consequences for our understanding of abrupt climate change, paleoenvironments, and early human cultural development. Here, we provide proxy evidence from the Horn of Africa region that documents abrupt transitions into and out of the African Humid Period in northeast Africa. Similar and generally synchronous abrupt transitions at other East African sites suggest that rapid shifts in hydroclimate are a regionally coherent feature. Our analysis suggests that the termination of the African Humid Period in the Horn of Africa occurred within centuries, underscoring the nonlinearity of the region's hydroclimate. PMID:24114782

  6. Abrupt tropical climate change: Past and present

    PubMed Central

    Thompson, Lonnie G.; Mosley-Thompson, Ellen; Brecher, Henry; Davis, Mary; León, Blanca; Les, Don; Lin, Ping-Nan; Mashiotta, Tracy; Mountain, Keith

    2006-01-01

    Three lines of evidence for abrupt tropical climate change, both past and present, are presented. First, annually and decadally averaged δ18O and net mass-balance histories for the last 400 and 2,000 yr, respectively, demonstrate that the current warming at high elevations in the mid- to low latitudes is unprecedented for at least the last 2 millennia. Second, the continuing retreat of most mid- to low-latitude glaciers, many having persisted for thousands of years, signals a recent and abrupt change in the Earth’s climate system. Finally, rooted, soft-bodied wetland plants, now exposed along the margins as the Quelccaya ice cap (Peru) retreats, have been radiocarbon dated and, when coupled with other widespread proxy evidence, provide strong evidence for an abrupt mid-Holocene climate event that marked the transition from early Holocene (pre-5,000-yr-B.P.) conditions to cooler, late Holocene (post-5,000-yr-B.P.) conditions. This abrupt event, ≈5,200 yr ago, was widespread and spatially coherent through much of the tropics and was coincident with structural changes in several civilizations. These three lines of evidence argue that the present warming and associated glacier retreat are unprecedented in some areas for at least 5,200 yr. The ongoing global-scale, rapid retreat of mountain glaciers is not only contributing to global sea-level rise but also threatening freshwater supplies in many of the world’s most populous regions. PMID:16815970

  7. Abrupt tropical climate change: past and present.

    PubMed

    Thompson, Lonnie G; Mosley-Thompson, Ellen; Brecher, Henry; Davis, Mary; León, Blanca; Les, Don; Lin, Ping-Nan; Mashiotta, Tracy; Mountain, Keith

    2006-07-11

    Three lines of evidence for abrupt tropical climate change, both past and present, are presented. First, annually and decadally averaged delta(18)O and net mass-balance histories for the last 400 and 2,000 yr, respectively, demonstrate that the current warming at high elevations in the mid- to low latitudes is unprecedented for at least the last 2 millennia. Second, the continuing retreat of most mid- to low-latitude glaciers, many having persisted for thousands of years, signals a recent and abrupt change in the Earth's climate system. Finally, rooted, soft-bodied wetland plants, now exposed along the margins as the Quelccaya ice cap (Peru) retreats, have been radiocarbon dated and, when coupled with other widespread proxy evidence, provide strong evidence for an abrupt mid-Holocene climate event that marked the transition from early Holocene (pre-5,000-yr-B.P.) conditions to cooler, late Holocene (post-5,000-yr-B.P.) conditions. This abrupt event, approximately 5,200 yr ago, was widespread and spatially coherent through much of the tropics and was coincident with structural changes in several civilizations. These three lines of evidence argue that the present warming and associated glacier retreat are unprecedented in some areas for at least 5,200 yr. The ongoing global-scale, rapid retreat of mountain glaciers is not only contributing to global sea-level rise but also threatening freshwater supplies in many of the world's most populous regions.

  8. The Arctic Grand Challenge: Abrupt Climate Change

    NASA Astrophysics Data System (ADS)

    Wilkniss, P. E.

    2003-12-01

    Trouble in polar paradise (Science, 08/30/02), significant changes in the Arctic environment are scientifically documented (R.E. Moritz et al. ibid.). More trouble, lots more, "abrupt climate change," (R. B. Alley, et al. Science 03/28/03). R. Corell, Arctic Climate Impact Assessment team (ACIA), "If you want to see what will happen in the rest of the world 25 years from now just look what's happening in the Arctic," (Arctic Council meeting, Iceland, 08/03). What to do? Make abrupt Arctic climate change a grand challenge for the IPY-4 and beyond! Scientifically:Describe the "state" of the Arctic climate system as succinctly as possible and accept it as the point of departure.Develop a hypothesis and criteria what constitutes "abrupt climate change," in the Arctic that can be tested with observations. Observations: Bring to bear existing observations and coordinate new investments in observations through an IPY-4 scientific management committee. Make the new Barrow, Alaska, Global Climate Change Research Facility a major U.S. contribution and focal point for the IPY-4 in the U.S Arctic. Arctic populations, Native peoples: The people of the North are living already, daily, with wrenching change, encroaching on their habitats and cultures. For them "the earth is faster now," (I. Krupnik and D. Jolly, ARCUS, 2002). From a political, economic, social and entirely realistic perspective, an Arctic grand challenge without the total integration of the Native peoples in this effort cannot succeed. Therefore: Communications must be established, and the respective Native entities must be approached with the determination to create well founded, well functioning, enduring partnerships. In the U.S. Arctic, Barrow with its long history of involvement and active support of science and with the new global climate change research facility should be the focal point of choice Private industry: Resource extraction in the Arctic followed by oil and gas consumption, return the combustion

  9. Abrupt climate change in the computer: Is it real?

    PubMed Central

    Stocker, Thomas F.; Marchal, Olivier

    2000-01-01

    Models suggest that dramatic changes in the ocean circulation are responsible for abrupt climate changes during the last ice age and may possibly alter the relative climate stability of the last 10,000 years. PMID:10677468

  10. Abrupt transitions of the top-down controlled Black Sea pelagic ecosystem during 1960 2000: Evidence for regime-shifts under strong fishery exploitation and nutrient enrichment modulated by climate-induced variations

    NASA Astrophysics Data System (ADS)

    Oguz, Temel; Gilbert, Denis

    2007-02-01

    Functioning of the Black Sea ecosystem has profoundly changed since the early 1970s under cumulative effects of excessive nutrient enrichment, strong cooling/warming, over-exploitation of pelagic fish stocks, and population outbreak of gelatinous carnivores. Applying a set of criteria to the long-term (1960-2000) ecological time-series data, the present study demonstrates that the Black Sea ecosystem was reorganised during this transition phase in different forms of top-down controlled food web structure through successive regime-shifts of distinct ecological properties. The Secchi disc depth, oxic-anoxic interface zone, dissolved oxygen and hydrogen sulphide concentrations also exhibit abrupt transition between their alternate regimes, and indicate tight coupling between the lower trophic food web structure and the biogeochemical pump in terms of regime-shift events. The first shift, in 1973-1974, marks a switch from large predatory fish to small planktivore fish-controlled system, which persisted until 1989 in the form of increasing small pelagic and phytoplankton biomass and decreasing zooplankton biomass. The increase in phytoplankton biomass is further supported by a bottom-up contribution due to the cumulative response to high anthropogenic nutrient load and the concurrent shift of the physical system to the "cold climate regime" following its ˜20-year persistence in the "warm climate regime". The end of the 1980s signifies the depletion of small planktivores and the transition to a gelatinous carnivore-controlled system. By the end of the 1990s, small planktivore populations take over control of the system again. Concomitantly, their top-down pressure when combined with diminishing anthropogenic nutrient load and more limited nutrient supply into the surface waters due to stabilizing effects of relatively warm winter conditions switched the "high production" regime of phytoplankton to its background "low production" regime. The Black Sea regime-shifts

  11. Abrupt climate change and the decline of Indus urbanism

    NASA Astrophysics Data System (ADS)

    Hodell, D. A.; Dixit, Y.; Petrie, C. A.

    2012-12-01

    Climate change has been suggested as a cause for the decline of the cities of the Indus Civilization, which is believed to have begun ~4.0 to 3.9 ky B.P. Previous studies have centered on paleoclimatic records obtained from areas outside the geographic limits of the Indus Civilization, raising questions about their suitability for evaluating past climate-cultural linkages. Here we report a detailed climate record from paleolake Kotla Dahar, Haryana (28°00'095'' N, 76°57'173'' E), located at the eastern edge of the distribution of Indus settlements and ~100km to the east of the city-site of Rakhigarhi in NW India. Regional hydrologic changes are inferred using oxygen-isotope measurements of gastropod aragonite from a 2.88-m sediment section. A permanent ~4‰ increase in δ18O of shell aragonite occurred at ~4.1±0.1 ky B.P., marking an abrupt increase in evaporation/precipitation in the lake catchment. These data provide evidence for a weakening of the monsoon and shift toward drier climate on the plains of northwest (NW) India at ~4.1±0.1 ky B.P. Decreased monsoon rainfall at this time may have been linked to increased ENSO variability, and supports a possible role of climate in the transformation of the Indus Civilization from an urbanized (mature or urban Indus) to a rural (post-urban) society.

  12. The Role of the Tropics in Abrupt Climate Changes

    SciTech Connect

    Fedorov, Alexey

    2013-12-07

    Topics addressed include: abrupt climate changes and ocean circulation in the tropics; what controls the ocean thermal structure in the tropics; a permanent El Niño in paleoclimates; the energetics of the tropical ocean.

  13. International policy implications of abrupt climate change scenarios

    SciTech Connect

    Molitor, M.R.

    1997-12-31

    New theoretical and empirical evidence supports the view that in the recent past [Holocene] abrupt climate changes occurred over very short [decadal] time periods. One leading possibility of future changes involves the North Atlantic Ocean conveyor that transfers warm surface waters from the equator to northern latitudes and helps maintain Europe`s climate. The predicted abrupt climate change scenario theorizes that the conveyor may be modified as a result of disruption of the thermohaline circulation driving North, Atlantic Deep Water. This would lead, the theory contends, to a rapid cooling of Europe`s climate. In light of the EPCC`s 1995 Second Assessment Report conclusion that there is a {open_quotes}discernible{close_quotes} human influence on the global climate system, there are many emerging questions concerning possible abrupt climate change scenarios.

  14. Abrupt changes in North American climate during early Holocene times

    NASA Astrophysics Data System (ADS)

    Hu, F. S.; Slawinski, D.; Wright, H. E.; Ito, E.; Johnson, R. G.; Kelts, K. R.; McEwan, R. F.; Boedigheimer, A.

    1999-07-01

    Recent studies of the Greenland ice cores have offered many insights into Holocene climatic dynamics at decadal to century timescales. Despite the abundance of continental records of Holocene climate, few have sufficient chronological control and sampling resolution to compare with the Greenland findings. Butannually laminated sediments (varves) from lakes can provide high-resolution continental palaeoclimate data with secure chronologies. Here we present analyses of varved sediments from Deep Lake in Minnesota, USA. Trends in the stable oxygen-isotope composition of the sedimentary carbonate indicate a pronounced climate cooling from 8.9 to 8.3kyr before present, probably characterized by increased outbreaks of polar air, decreased precipitation temperatures, and a higher fraction of the annual precipitation falling as snow. The abrupt onset of this climate reversal, over several decades, was probably caused by a reorganization of atmospheric circulation and cooling of the Arctic airmass in summer that resulted from the final collapse of the Laurentide ice near Hudson Bay and the discharge of icebergs from the Quebec and Keewatin centres into the Tyrell Sea. The timing and duration of this climate reversal suggest that it is distinct from the prominent widespread cold snap that occurred 8,200 years ago in Greenland and other regions,,. No shifts in the oxygen-isotope composition of sediment carbonate occurred at 8.2kyr before present at Deep Lake, but varve thickness increased dramatically, probably as a result of increased deposition of aeolian dust. Taken together, our data suggest that two separate regional-scale climate reversals occurred between 9,000 and 8,000 years ago, and that they were driven by different mechanisms.

  15. Sea-ice switches and abrupt climate change.

    PubMed

    Gildor, Hezi; Tziperman, Eli

    2003-09-15

    We propose that past abrupt climate changes were probably a result of rapid and extensive variations in sea-ice cover. We explain why this seems a perhaps more likely explanation than a purely thermohaline circulation mechanism. We emphasize that because of the significant influence of sea ice on the climate system, it seems that high priority should be given to developing ways for reconstructing high-resolution (in space and time) sea-ice extent for past climate-change events. If proxy data can confirm that sea ice was indeed the major player in past abrupt climate-change events, it seems less likely that such dramatic abrupt changes will occur due to global warming, when extensive sea-ice cover will not be present.

  16. Sea-ice switches and abrupt climate change.

    PubMed

    Gildor, Hezi; Tziperman, Eli

    2003-09-15

    We propose that past abrupt climate changes were probably a result of rapid and extensive variations in sea-ice cover. We explain why this seems a perhaps more likely explanation than a purely thermohaline circulation mechanism. We emphasize that because of the significant influence of sea ice on the climate system, it seems that high priority should be given to developing ways for reconstructing high-resolution (in space and time) sea-ice extent for past climate-change events. If proxy data can confirm that sea ice was indeed the major player in past abrupt climate-change events, it seems less likely that such dramatic abrupt changes will occur due to global warming, when extensive sea-ice cover will not be present. PMID:14558902

  17. Abrupt climate change in southeast tropical Africa influenced by Indian monsoon variability and ITCZ migration

    NASA Astrophysics Data System (ADS)

    Tierney, Jessica E.; Russell, James M.

    2007-08-01

    The timing and magnitude of abrupt climate change in tropical Africa during the last glacial termination remains poorly understood. High-resolution paleolimnological data from Lake Tanganyika, Southeast Africa show that wind-driven seasonal mixing in the lake was reduced during the Younger Dryas, Inter-Allerød Cool Period, Older Dryas, and Heinrich Event 1, suggesting a weakened southwest Indian monsoon and a more southerly position of the Inter-Tropical Convergence Zone over Africa during these intervals. These events in Lake Tanganyika, coeval with millennial and centennial-scale climate shifts in the high latitudes, suggest that changes in ITCZ location and Indian monsoon strength are important components of abrupt global climate change and that their effects are felt south of the equator in Africa. However, we observe additional events in Lake Tanganyika of equal magnitude that are not correlated with high-latitude changes, indicating the potential for abrupt climate change to originate from within tropical systems.

  18. Ecological forecasting in the presence of abrupt regime shifts

    NASA Astrophysics Data System (ADS)

    Dippner, Joachim W.; Kröncke, Ingrid

    2015-10-01

    Regime shifts may cause an intrinsic decrease in the potential predictability of marine ecosystems. In such cases, forecasts of biological variables fail. To improve prediction of long-term variability in environmental variables, we constructed a multivariate climate index and applied it to forecast ecological time series. The concept is demonstrated herein using climate and macrozoobenthos data from the southern North Sea. Special emphasis is given to the influence of selection of length of fitting period to the quality of forecast skill especially in the presence of regime shifts. Our results indicate that the performance of multivariate predictors in biological forecasts is much better than that of single large-scale climate indices, especially in the presence of regime shifts. The approach used to develop the index is generally applicable to all geographical regions in the world and to all areas of marine biology, from the species level up to biodiversity. Such forecasts are of vital interest for practical aspects of the sustainable management of marine ecosystems and the conservation of ecosystem goods and services.

  19. Anticipating abrupt shifts in temporal evolution of probability of eruption

    NASA Astrophysics Data System (ADS)

    Rohmer, Jeremy; Loschetter, Annick

    2016-04-01

    Estimating the probability of eruption by jointly accounting for different sources of monitoring parameters over time is a key component for volcano risk management. In the present study, we are interested in the transition from a state of low-to-moderate probability value and to the one of high probability value: the latter value generally supports the call for evacuation. By using the data of MESIMEX exercise at the Vesuvius volcano, we investigated the potential for time-varying indicators related to the correlation structure or to the variability of the probability time series for detecting in advance this critical transition. We found that changes in the power spectra and in the standard deviation estimated over a rolling time window both present an abrupt increase, which marks the approaching shift. Our numerical experiments revealed that the transition from an eruption probability of 10-15% to >70% could be identified up 4 hours in advance, ~2.5 days before the evacuation call (decided for an eruption probability >80% during the MESIMEX exercise). This additional lead time could be useful to place different key services (e.g., emergency services for vulnerable groups, commandeering additional transportation means, etc.) on a higher level of alert before the actual call for evacuation.

  20. Anticipating abrupt shifts in temporal evolution of probability of eruption

    NASA Astrophysics Data System (ADS)

    Rohmer, J.; Loschetter, A.

    2016-04-01

    Estimating the probability of eruption by jointly accounting for different sources of monitoring parameters over time is a key component for volcano risk management. In the present study, we are interested in the transition from a state of low-to-moderate probability value to a state of high probability value. By using the data of MESIMEX exercise at the Vesuvius volcano, we investigated the potential for time-varying indicators related to the correlation structure or to the variability of the probability time series for detecting in advance this critical transition. We found that changes in the power spectra and in the standard deviation estimated over a rolling time window both present an abrupt increase, which marks the approaching shift. Our numerical experiments revealed that the transition from an eruption probability of 10-15% to > 70% could be identified up to 1-3 h in advance. This additional lead time could be useful to place different key services (e.g., emergency services for vulnerable groups, commandeering additional transportation means, etc.) on a higher level of alert before the actual call for evacuation.

  1. Abrupt climate change and thermohaline circulation: mechanisms and predictability.

    PubMed

    Marotzke, J

    2000-02-15

    The ocean's thermohaline circulation has long been recognized as potentially unstable and has consequently been invoked as a potential cause of abrupt climate change on all timescales of decades and longer. However, fundamental aspects of thermohaline circulation changes remain poorly understood.

  2. Abrupt climate change and thermohaline circulation: mechanisms and predictability.

    PubMed

    Marotzke, J

    2000-02-15

    The ocean's thermohaline circulation has long been recognized as potentially unstable and has consequently been invoked as a potential cause of abrupt climate change on all timescales of decades and longer. However, fundamental aspects of thermohaline circulation changes remain poorly understood. PMID:10677464

  3. The role of the thermohaline circulation in abrupt climate change.

    PubMed

    Clark, Peter U; Pisias, Nicklas G; Stocker, Thomas F; Weaver, Andrew J

    2002-02-21

    The possibility of a reduced Atlantic thermohaline circulation in response to increases in greenhouse-gas concentrations has been demonstrated in a number of simulations with general circulation models of the coupled ocean-atmosphere system. But it remains difficult to assess the likelihood of future changes in the thermohaline circulation, mainly owing to poorly constrained model parameterizations and uncertainties in the response of the climate system to greenhouse warming. Analyses of past abrupt climate changes help to solve these problems. Data and models both suggest that abrupt climate change during the last glaciation originated through changes in the Atlantic thermohaline circulation in response to small changes in the hydrological cycle. Atmospheric and oceanic responses to these changes were then transmitted globally through a number of feedbacks. The palaeoclimate data and the model results also indicate that the stability of the thermohaline circulation depends on the mean climate state.

  4. The role of the thermohaline circulation in abrupt climate change.

    PubMed

    Clark, Peter U; Pisias, Nicklas G; Stocker, Thomas F; Weaver, Andrew J

    2002-02-21

    The possibility of a reduced Atlantic thermohaline circulation in response to increases in greenhouse-gas concentrations has been demonstrated in a number of simulations with general circulation models of the coupled ocean-atmosphere system. But it remains difficult to assess the likelihood of future changes in the thermohaline circulation, mainly owing to poorly constrained model parameterizations and uncertainties in the response of the climate system to greenhouse warming. Analyses of past abrupt climate changes help to solve these problems. Data and models both suggest that abrupt climate change during the last glaciation originated through changes in the Atlantic thermohaline circulation in response to small changes in the hydrological cycle. Atmospheric and oceanic responses to these changes were then transmitted globally through a number of feedbacks. The palaeoclimate data and the model results also indicate that the stability of the thermohaline circulation depends on the mean climate state. PMID:11859359

  5. Hydrological response to an abrupt shift in surface air temperature over France in 1987/88

    NASA Astrophysics Data System (ADS)

    Brulebois, Etienne; Castel, Thierry; Richard, Yves; Chateau-Smith, Carmela; Amiotte-Suchet, Philippe

    2015-12-01

    During the last few decades, Europe has seen a faster increase of observed temperature than that simulated by models. The air temperature over Western Europe showed an abrupt shift at the end of the 1980s, still insufficiently documented. The aim of this study is to assess the characteristics of this shift and its potential impacts on the hydrological cycle over France. Such an assessment is essential for a better understanding of past and future climatic changes and their impact on water resources. A subset of 119 temperature, 122 rainfall, and 30 hydrometric stations was studied, over the entire French metropolitan territory. Several change-point detection tests were applied to temperature, rainfall and runoff time series. A shift in annual mean air temperature was detected in 1987/88, for more than 75% of the stations, and for both minimum and maximum temperatures. An abrupt increase of about 1 °C in minimum and maximum temperature provides evidence of this shift, which shows strong seasonality, with significant increases for DJF, MAM and JJA. Its detection is not affected by the length of the time series or any potential artefacts associated to the conditions of measurement. Cluster analysis of the rainfall stations was used to take account of regional variability in rainfall evolution. Two climate areas were obtained from this analysis: Mediterranean and temperate. No shift was detected in rainfall for either area. However, at annual and quarterly scales, several changes in runoff were observed between the periods 1969-87 and 1988-09. The significant changes occurred from January to July, in agreement with maximum increases in temperature. Evapotranspiration could well play a key role in these changes in the hydrological cycle, as a response to temperature increases in the watersheds studied.

  6. Mechanisms of abrupt climate change of the last glacial period

    NASA Astrophysics Data System (ADS)

    Clement, Amy C.; Peterson, Larry C.

    2008-12-01

    More than a decade ago, ice core records from Greenland revealed that the last glacial period was characterized by abrupt climate changes that recurred on millennial time scales. Since their discovery, there has been a large effort to determine whether these climate events were a global phenomenon or were just confined to the North Atlantic region and also to reveal the mechanisms that were responsible for them. In this paper, we review the available paleoclimate observations of abrupt change during the last glacial period in order to place constraints on possible mechanisms. Three different mechanisms are then reviewed: ocean thermohaline circulation, sea ice feedbacks, and tropical processes. Each mechanism is tested for its ability to explain the key features of the observations, particularly with regard to the abruptness, millennial recurrence, and geographical extent of the observed changes. It is found that each of these mechanisms has explanatory strengths and weaknesses, and key areas in which progress could be made in improving the understanding of their long-term behavior, both from observational and modeling approaches, are suggested. Finally, it is proposed that a complete understanding of the mechanisms of abrupt change requires inclusion of processes at both low and high latitudes, as well as the potential for feedbacks between them. Some suggestions for experimental approaches to test for such feedbacks with coupled climate models are given.

  7. Abrupt shifts in Horn of Africa hydroclimate and the influence of the Indian Ocean (Invited)

    NASA Astrophysics Data System (ADS)

    Tierney, J. E.; deMenocal, P. B.

    2013-12-01

    The timing and abruptness with which Northeast Africa transitioned into and out of the Early Holocene African Humid Period is a subject of ongoing debate, with direct consequences for our understanding of climate stability and paleoenvironments. Here we present a new proxy record of regional hydroclimate, based on the hydrogen isotopic composition of leaf waxes, from a marine core in the Gulf of Aden that documents rapid, century-scale transitions into and out of the African Humid Period across the Horn of Africa. The Gulf of Aden record also documents large drying events during the last deglacial, synchronous with Heinrich Event 1 and the Younger Dryas. Similar and generally synchronous abrupt transitions at other East African sites suggest that rapid shifts in hydroclimate are regionally coherent. In addition, the termination of the African Humid Period in East Africa is synchronous with the termination along the western Saharan margin. A probabilistic analysis of the abruptness of the transitions in East Africa suggests that they likely occurred within centuries, underscoring the sensitivity of northeast African hydroclimate to external forcings. We speculate that the non-linear behavior of hydroclimate in the Horn of Africa is related to convection thresholds in the western Indian Ocean, and test this hypothesis with preliminary SST proxy data.

  8. Response of seafloor ecosystems to abrupt global climate change

    PubMed Central

    Moffitt, Sarah E.; Hill, Tessa M.; Roopnarine, Peter D.; Kennett, James P.

    2015-01-01

    Anthropogenic climate change is predicted to decrease oceanic oxygen (O2) concentrations, with potentially significant effects on marine ecosystems. Geologically recent episodes of abrupt climatic warming provide opportunities to assess the effects of changing oxygenation on marine communities. Thus far, this knowledge has been largely restricted to investigations using Foraminifera, with little being known about ecosystem-scale responses to abrupt, climate-forced deoxygenation. We here present high-resolution records based on the first comprehensive quantitative analysis, to our knowledge, of changes in marine metazoans (Mollusca, Echinodermata, Arthropoda, and Annelida; >5,400 fossils and trace fossils) in response to the global warming associated with the last glacial to interglacial episode. The molluscan archive is dominated by extremophile taxa, including those containing endosymbiotic sulfur-oxidizing bacteria (Lucinoma aequizonatum) and those that graze on filamentous sulfur-oxidizing benthic bacterial mats (Alia permodesta). This record, from 16,100 to 3,400 y ago, demonstrates that seafloor invertebrate communities are subject to major turnover in response to relatively minor inferred changes in oxygenation (>1.5 to <0.5 mL⋅L−1 [O2]) associated with abrupt (<100 y) warming of the eastern Pacific. The biotic turnover and recovery events within the record expand known rates of marine biological recovery by an order of magnitude, from <100 to >1,000 y, and illustrate the crucial role of climate and oceanographic change in driving long-term successional changes in ocean ecosystems. PMID:25825727

  9. Response of seafloor ecosystems to abrupt global climate change

    NASA Astrophysics Data System (ADS)

    Moffitt, Sarah E.; Hill, Tessa M.; Roopnarine, Peter D.; Kennett, James P.

    2015-04-01

    Anthropogenic climate change is predicted to decrease oceanic oxygen (O2) concentrations, with potentially significant effects on marine ecosystems. Geologically recent episodes of abrupt climatic warming provide opportunities to assess the effects of changing oxygenation on marine communities. Thus far, this knowledge has been largely restricted to investigations using Foraminifera, with little being known about ecosystem-scale responses to abrupt, climate-forced deoxygenation. We here present high-resolution records based on the first comprehensive quantitative analysis, to our knowledge, of changes in marine metazoans (Mollusca, Echinodermata, Arthropoda, and Annelida; >5,400 fossils and trace fossils) in response to the global warming associated with the last glacial to interglacial episode. The molluscan archive is dominated by extremophile taxa, including those containing endosymbiotic sulfur-oxidizing bacteria (Lucinoma aequizonatum) and those that graze on filamentous sulfur-oxidizing benthic bacterial mats (Alia permodesta). This record, from 16,100 to 3,400 y ago, demonstrates that seafloor invertebrate communities are subject to major turnover in response to relatively minor inferred changes in oxygenation (>1.5 to <0.5 mLṡL-1 [O2]) associated with abrupt (<100 y) warming of the eastern Pacific. The biotic turnover and recovery events within the record expand known rates of marine biological recovery by an order of magnitude, from <100 to >1,000 y, and illustrate the crucial role of climate and oceanographic change in driving long-term successional changes in ocean ecosystems.

  10. Response of seafloor ecosystems to abrupt global climate change.

    PubMed

    Moffitt, Sarah E; Hill, Tessa M; Roopnarine, Peter D; Kennett, James P

    2015-04-14

    Anthropogenic climate change is predicted to decrease oceanic oxygen (O2) concentrations, with potentially significant effects on marine ecosystems. Geologically recent episodes of abrupt climatic warming provide opportunities to assess the effects of changing oxygenation on marine communities. Thus far, this knowledge has been largely restricted to investigations using Foraminifera, with little being known about ecosystem-scale responses to abrupt, climate-forced deoxygenation. We here present high-resolution records based on the first comprehensive quantitative analysis, to our knowledge, of changes in marine metazoans (Mollusca, Echinodermata, Arthropoda, and Annelida; >5,400 fossils and trace fossils) in response to the global warming associated with the last glacial to interglacial episode. The molluscan archive is dominated by extremophile taxa, including those containing endosymbiotic sulfur-oxidizing bacteria (Lucinoma aequizonatum) and those that graze on filamentous sulfur-oxidizing benthic bacterial mats (Alia permodesta). This record, from 16,100 to 3,400 y ago, demonstrates that seafloor invertebrate communities are subject to major turnover in response to relatively minor inferred changes in oxygenation (>1.5 to <0.5 mL⋅L(-1) [O2]) associated with abrupt (<100 y) warming of the eastern Pacific. The biotic turnover and recovery events within the record expand known rates of marine biological recovery by an order of magnitude, from <100 to >1,000 y, and illustrate the crucial role of climate and oceanographic change in driving long-term successional changes in ocean ecosystems.

  11. Response of seafloor ecosystems to abrupt global climate change.

    PubMed

    Moffitt, Sarah E; Hill, Tessa M; Roopnarine, Peter D; Kennett, James P

    2015-04-14

    Anthropogenic climate change is predicted to decrease oceanic oxygen (O2) concentrations, with potentially significant effects on marine ecosystems. Geologically recent episodes of abrupt climatic warming provide opportunities to assess the effects of changing oxygenation on marine communities. Thus far, this knowledge has been largely restricted to investigations using Foraminifera, with little being known about ecosystem-scale responses to abrupt, climate-forced deoxygenation. We here present high-resolution records based on the first comprehensive quantitative analysis, to our knowledge, of changes in marine metazoans (Mollusca, Echinodermata, Arthropoda, and Annelida; >5,400 fossils and trace fossils) in response to the global warming associated with the last glacial to interglacial episode. The molluscan archive is dominated by extremophile taxa, including those containing endosymbiotic sulfur-oxidizing bacteria (Lucinoma aequizonatum) and those that graze on filamentous sulfur-oxidizing benthic bacterial mats (Alia permodesta). This record, from 16,100 to 3,400 y ago, demonstrates that seafloor invertebrate communities are subject to major turnover in response to relatively minor inferred changes in oxygenation (>1.5 to <0.5 mL⋅L(-1) [O2]) associated with abrupt (<100 y) warming of the eastern Pacific. The biotic turnover and recovery events within the record expand known rates of marine biological recovery by an order of magnitude, from <100 to >1,000 y, and illustrate the crucial role of climate and oceanographic change in driving long-term successional changes in ocean ecosystems. PMID:25825727

  12. Extrinsic regime shifts drive abrupt changes in regeneration dynamics at upper treeline in the Rocky Mountains, U.S.A.

    PubMed

    Elliott, Grant P

    2012-07-01

    Given the widespread and often dramatic influence of climate change on terrestrial ecosystems, it is increasingly common for abrupt threshold changes to occur, yet explicitly testing for climate and ecological regime shifts is lacking in climatically sensitive upper treeline ecotones. In this study, quantitative evidence based on empirical data is provided to support the key role of extrinsic, climate-induced thresholds in governing the spatial and temporal patterns of tree establishment in these high-elevation environments. Dendroecological techniques were used to reconstruct a 420-year history of regeneration dynamics within upper treeline ecotones along a latitudinal gradient (approximately 44-35 degrees N) in the Rocky Mountains. Correlation analysis was used to assess the possible influence of minimum and maximum temperature indices and cool-season (November-April) precipitation on regional age-structure data. Regime-shift analysis was used to detect thresholds in tree establishment during the entire period of record (1580-2000), temperature variables significantly Correlated with establishment during the 20th century, and cool-season precipitation. Tree establishment was significantly correlated with minimum temperature during the spring (March-May) and cool season. Regime-shift analysis identified an abrupt increase in regional tree establishment in 1950 (1950-1954 age class). Coincident with this period was a shift toward reduced cool-season precipitation. The alignment of these climate conditions apparently triggered an abrupt increase in establishment that was unprecedented during the period of record. Two main findings emerge from this research that underscore the critical role of climate in governing regeneration dynamics within upper treeline ecotones. (1) Regional climate variability is capable of exceeding bioclimatic thresholds, thereby initiating synchronous and abrupt changes in the spatial and temporal patterns of tree establishment at broad

  13. Extrinsic regime shifts drive abrupt changes in regeneration dynamics at upper treeline in the Rocky Mountains, U.S.A.

    PubMed

    Elliott, Grant P

    2012-07-01

    Given the widespread and often dramatic influence of climate change on terrestrial ecosystems, it is increasingly common for abrupt threshold changes to occur, yet explicitly testing for climate and ecological regime shifts is lacking in climatically sensitive upper treeline ecotones. In this study, quantitative evidence based on empirical data is provided to support the key role of extrinsic, climate-induced thresholds in governing the spatial and temporal patterns of tree establishment in these high-elevation environments. Dendroecological techniques were used to reconstruct a 420-year history of regeneration dynamics within upper treeline ecotones along a latitudinal gradient (approximately 44-35 degrees N) in the Rocky Mountains. Correlation analysis was used to assess the possible influence of minimum and maximum temperature indices and cool-season (November-April) precipitation on regional age-structure data. Regime-shift analysis was used to detect thresholds in tree establishment during the entire period of record (1580-2000), temperature variables significantly Correlated with establishment during the 20th century, and cool-season precipitation. Tree establishment was significantly correlated with minimum temperature during the spring (March-May) and cool season. Regime-shift analysis identified an abrupt increase in regional tree establishment in 1950 (1950-1954 age class). Coincident with this period was a shift toward reduced cool-season precipitation. The alignment of these climate conditions apparently triggered an abrupt increase in establishment that was unprecedented during the period of record. Two main findings emerge from this research that underscore the critical role of climate in governing regeneration dynamics within upper treeline ecotones. (1) Regional climate variability is capable of exceeding bioclimatic thresholds, thereby initiating synchronous and abrupt changes in the spatial and temporal patterns of tree establishment at broad

  14. Regional Abrupt Climate Change in the U.S.: Comparing the Colorado and Columbia River Basins

    NASA Astrophysics Data System (ADS)

    Lund, D.

    2001-12-01

    Paleoclimatic evidence and historical experience indicate the earth's climate system is capable of switching rapidly from one quasi-stable state to another. Current global assessments of anthropogenic climate change, however, do not fully account for such abrupt shifts, and instead generally assume the earth's climate will gradually warm over the next several centuries. Integrated assessments of abrupt climate change exist, but on a regional level. Here we discuss two examples where abrupt climate change information was applied to the management of natural resources, including water in the Colorado Basin and salmon in the Columbia Basin. Tree-ring data imply that a massive 20-yr drought occurred in the Colorado Basin during the late sixteenth century. The Severe-Sustained Drought assessment (SSD) evaluated the socioeconomic impacts of this historically-unprecedented drought in the context of modern water allocation policy in the Colorado Basin. Based on semi-structured, open-ended interviews with assessment participants and regional stakeholders, the SSD clarified positions of competing water interests and expanded awareness of potential drought impacts, but did not modify Colorado River water management or policies. Assessment design characteristics had limited influence on effectiveness; the timing of publication and political and legal factors constraining alternative policy options for water distribution were more influential determinants. Absent a crisis, there are few incentives for water managers to implement SSD policy recommendations. The lack of a basin wide commission and long-term climate assessment group in the Colorado Basin appear to limit stakeholder ability to utilize technical information related to abrupt climate change. In the Columbia River Basin, the crisis of declining salmon stocks motivated the consideration of alternative policies which recognize the role of unpredictable and abrupt decadal shifts in oceanic productivity. Although actual

  15. Abrupt Holocene climate change and potential response to solar forcing in western Canada

    NASA Astrophysics Data System (ADS)

    Gavin, Daniel G.; Henderson, Andrew C. G.; Westover, Karlyn S.; Fritz, Sherilyn C.; Walker, Ian R.; Leng, Melanie J.; Hu, Feng Sheng

    2011-05-01

    Several abrupt climate events during the Holocene, including the widely documented oscillation at 8.2 thousand years before present (ka), are attributed to changes in the North Atlantic thermohaline circulation. Additional mechanisms, such as interactions between atmospheric circulation, ice-sheet dynamics, and the influence of solar irradiance, also have been proposed to explain abrupt climatic events, but evidence remains elusive. This study presents evidence from multi-proxy analyses on the Holocene sediments of Eleanor Lake, interior British Columbia. Climatic inferences from our decadal-resolution record of biogenic silica (BSi) abundance are supported by changes in diatom and pollen assemblages from the same core and correlations with existing regional climate records. The BSi record reveals abrupt and persistent climatic shifts at 10.2, 9.3, and 8.5 ka, the latter two of which are coeval with major collapses of the Laurentide Ice Sheet. The record also reveals a short-term cooling at 8.2 ka that is distinct from the 8.5 ka event and similar in magnitude to several other late-Holocene coolings. BSi is correlated with solar-irradiance indices ( r = 0.43-0.61), but the correlation is opposite in sign to that expected from direct solar forcing and weakens after 8 ka. Possible mechanisms causing the abrupt and persistent climate changes of the early Holocene include 1) sudden losses of ice and proglacial lake extent, causing a shift in the meridional structure of atmospheric circulation, 2) a possible link between solar minima and El Niño-like conditions that are correlated with warm spring temperature in interior British Columbia, and 3) the influence of solar irradiance variability on the position of the polar jet, possibly via effects on the strength of the glacial anticyclone.

  16. Abrupt climate change and collapse of deep-sea ecosystems

    USGS Publications Warehouse

    Yasuhara, Moriaki; Cronin, T. M.; Demenocal, P.B.; Okahashi, H.; Linsley, B.K.

    2008-01-01

    We investigated the deep-sea fossil record of benthic ostracodes during periods of rapid climate and oceanographic change over the past 20,000 years in a core from intermediate depth in the northwestern Atlantic. Results show that deep-sea benthic community "collapses" occur with faunal turnover of up to 50% during major climatically driven oceanographic changes. Species diversity as measured by the Shannon-Wiener index falls from 3 to as low as 1.6 during these events. Major disruptions in the benthic communities commenced with Heinrich Event 1, the Inter-Aller??d Cold Period (IACP: 13.1 ka), the Younger Dryas (YD: 12.9-11.5 ka), and several Holocene Bond events when changes in deep-water circulation occurred. The largest collapse is associated with the YD/IACP and is characterized by an abrupt two-step decrease in both the upper North Atlantic Deep Water assemblage and species diversity at 13.1 ka and at 12.2 ka. The ostracode fauna at this site did not fully recover until ???8 ka, with the establishment of Labrador Sea Water ventilation. Ecologically opportunistic slope species prospered during this community collapse. Other abrupt community collapses during the past 20 ka generally correspond to millennial climate events. These results indicate that deep-sea ecosystems are not immune to the effects of rapid climate changes occurring over centuries or less. ?? 2008 by The National Academy of Sciences of the USA.

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

    PubMed

    Praetorius, Summer K; Mix, Alan C

    2014-07-25

    Some proposed mechanisms for transmission of major climate change events between the North Pacific and North Atlantic predict opposing patterns of variations; others suggest synchronization. Resolving this conflict has implications for regulation of poleward heat transport and global climate change. New multidecadal-resolution foraminiferal oxygen isotope records from the Gulf of Alaska (GOA) reveal sudden shifts between intervals of synchroneity and asynchroneity with the North Greenland Ice Core Project (NGRIP) δ(18)O record over the past 18,000 years. Synchronization of these regions occurred 15,500 to 11,000 years ago, just prior to and throughout the most abrupt climate transitions of the last 20,000 years, suggesting that dynamic coupling of North Pacific and North Atlantic climates may lead to critical transitions in Earth's climate system. PMID:25061208

  18. Low-latitude mountain glacier evidence for abrupt climate changes

    NASA Astrophysics Data System (ADS)

    Thompson, L. G.; Mosley-Thompson, E. S.; Lin, P.; Davis, M. E.; Mashiotta, T. A.; Brecher, H. H.

    2004-12-01

    Clear evidence that a widespread warming of Earth's climate system is now underway comes from low latitude mountain glaciers. Proxy temperature histories reconstructed from ice cores, and the rapidly accelerating loss of both the total ice area and ice volume on a near global scale suggest that these glaciers responding to increasing rates of melting. In situ observations reveal the startling rates at which many tropical glaciers are disappearing. For example, the retreat of the terminus of the Qori Kalis Glacier in Peru is roughly 200 meters per year, 40 times faster than its retreat rate in 1978. Similarly, in 1912 the ice on Mount Kilimanjaro covered 12.1 km2, but today it covers only 2.6 km2. If the current rate of retreat continues, the perennial ice fields may disappear within the next few decades, making this the first time in the past 11,700 years that Kilimanjaro will be devoid of the ice that shrouds its summit. Tropical glaciers may be considered ``the canaries in the coal mine'' for the global climate system as they integrate and respond to key climatological variables, such as temperature, precipitation, cloudiness, humidity, and incident solar radiation. A composite of the decadally-averaged oxygen isotopic records from three Andean and three Tibetan ice cores extending back over the last two millennia shows an isotopic enrichment in the 20th century that suggests a large-scale warming is underway at lower latitudes. Multiple lines of evidence from Africa, the Middle East, Europe and South America indicate an abrupt mid-Holocene climate event in the low latitudes. If such an event were to occur now with a global human population of 6.3 billion people, the consequences could be severe. Clearly, we need to understand the nature and cause of abrupt climate events.

  19. Dynamic response of desert wetlands to abrupt climate change

    PubMed Central

    Springer, Kathleen B.; Manker, Craig R.; Pigati, Jeffrey S.

    2015-01-01

    Desert wetlands are keystone ecosystems in arid environments and are preserved in the geologic record as groundwater discharge (GWD) deposits. GWD deposits are inherently discontinuous and stratigraphically complex, which has limited our understanding of how desert wetlands responded to past episodes of rapid climate change. Previous studies have shown that wetlands responded to climate change on glacial to interglacial timescales, but their sensitivity to short-lived climate perturbations is largely unknown. Here, we show that GWD deposits in the Las Vegas Valley (southern Nevada, United States) provide a detailed and nearly complete record of dynamic hydrologic changes during the past 35 ka (thousands of calibrated 14C years before present), including cycles of wetland expansion and contraction that correlate tightly with climatic oscillations recorded in the Greenland ice cores. Cessation of discharge associated with rapid warming events resulted in the collapse of entire wetland systems in the Las Vegas Valley at multiple times during the late Quaternary. On average, drought-like conditions, as recorded by widespread erosion and the formation of desert soils, lasted for a few centuries. This record illustrates the vulnerability of desert wetland flora and fauna to abrupt climate change. It also shows that GWD deposits can be used to reconstruct paleohydrologic conditions at millennial to submillennial timescales and informs conservation efforts aimed at protecting these fragile ecosystems in the face of anthropogenic warming. PMID:26554007

  20. Dynamic response of desert wetlands to abrupt climate change.

    PubMed

    Springer, Kathleen B; Manker, Craig R; Pigati, Jeffrey S

    2015-11-24

    Desert wetlands are keystone ecosystems in arid environments and are preserved in the geologic record as groundwater discharge (GWD) deposits. GWD deposits are inherently discontinuous and stratigraphically complex, which has limited our understanding of how desert wetlands responded to past episodes of rapid climate change. Previous studies have shown that wetlands responded to climate change on glacial to interglacial timescales, but their sensitivity to short-lived climate perturbations is largely unknown. Here, we show that GWD deposits in the Las Vegas Valley (southern Nevada, United States) provide a detailed and nearly complete record of dynamic hydrologic changes during the past 35 ka (thousands of calibrated (14)C years before present), including cycles of wetland expansion and contraction that correlate tightly with climatic oscillations recorded in the Greenland ice cores. Cessation of discharge associated with rapid warming events resulted in the collapse of entire wetland systems in the Las Vegas Valley at multiple times during the late Quaternary. On average, drought-like conditions, as recorded by widespread erosion and the formation of desert soils, lasted for a few centuries. This record illustrates the vulnerability of desert wetland flora and fauna to abrupt climate change. It also shows that GWD deposits can be used to reconstruct paleohydrologic conditions at millennial to submillennial timescales and informs conservation efforts aimed at protecting these fragile ecosystems in the face of anthropogenic warming. PMID:26554007

  1. Dynamic response of desert wetlands to abrupt climate change

    USGS Publications Warehouse

    Springer, Kathleen; Manker, Craig; Pigati, Jeff

    2015-01-01

    Desert wetlands are keystone ecosystems in arid environments and are preserved in the geologic record as groundwater discharge (GWD) deposits. GWD deposits are inherently discontinuous and stratigraphically complex, which has limited our understanding of how desert wetlands responded to past episodes of rapid climate change. Previous studies have shown that wetlands responded to climate change on glacial to interglacial timescales, but their sensitivity to short-lived climate perturbations is largely unknown. Here, we show that GWD deposits in the Las Vegas Valley (southern Nevada, United States) provide a detailed and nearly complete record of dynamic hydrologic changes during the past 35 ka (thousands of calibrated 14C years before present), including cycles of wetland expansion and contraction that correlate tightly with climatic oscillations recorded in the Greenland ice cores. Cessation of discharge associated with rapid warming events resulted in the collapse of entire wetland systems in the Las Vegas Valley at multiple times during the late Quaternary. On average, drought-like conditions, as recorded by widespread erosion and the formation of desert soils, lasted for a few centuries. This record illustrates the vulnerability of desert wetland flora and fauna to abrupt climate change. It also shows that GWD deposits can be used to reconstruct paleohydrologic conditions at millennial to submillennial timescales and informs conservation efforts aimed at protecting these fragile ecosystems in the face of anthropogenic warming.

  2. Dynamic response of desert wetlands to abrupt climate change.

    PubMed

    Springer, Kathleen B; Manker, Craig R; Pigati, Jeffrey S

    2015-11-24

    Desert wetlands are keystone ecosystems in arid environments and are preserved in the geologic record as groundwater discharge (GWD) deposits. GWD deposits are inherently discontinuous and stratigraphically complex, which has limited our understanding of how desert wetlands responded to past episodes of rapid climate change. Previous studies have shown that wetlands responded to climate change on glacial to interglacial timescales, but their sensitivity to short-lived climate perturbations is largely unknown. Here, we show that GWD deposits in the Las Vegas Valley (southern Nevada, United States) provide a detailed and nearly complete record of dynamic hydrologic changes during the past 35 ka (thousands of calibrated (14)C years before present), including cycles of wetland expansion and contraction that correlate tightly with climatic oscillations recorded in the Greenland ice cores. Cessation of discharge associated with rapid warming events resulted in the collapse of entire wetland systems in the Las Vegas Valley at multiple times during the late Quaternary. On average, drought-like conditions, as recorded by widespread erosion and the formation of desert soils, lasted for a few centuries. This record illustrates the vulnerability of desert wetland flora and fauna to abrupt climate change. It also shows that GWD deposits can be used to reconstruct paleohydrologic conditions at millennial to submillennial timescales and informs conservation efforts aimed at protecting these fragile ecosystems in the face of anthropogenic warming.

  3. Glacial climate states and abrupt climate change in MIROC AOGCM

    NASA Astrophysics Data System (ADS)

    Abe-Ouchi, Ayako; Ohgaito, Rumi; Takahashi, Kunio; Yoshimori, Masa; Kawamura, Kenji; Oka, Akira; Chan, Wing-Le; Sherriff-Tadano, Sam

    2016-04-01

    Millennial climate change such as D-O cycles and AIM recorded in ice cores in both Hemispheres is known to show a relatively higher amplitude in the middle-level of a glacial cycle than in the interglacial state or severe glacial state. Here we ran several sensitivity experiments using a coupled atmosphere and ocean GCM (MIROC4m, renamed from MIROC3.2.2) and show that the response to fresh water release to the ocean and bipolar response is highly dependent on the background climate. The experiments were conducted with 500 years water hosing of 0.05 to 0.1 Sv (where 1 Sv is equivalent to the water flux of 10m sea level rise in 100 years) in the North Atlantic 50-70N under different basic states; modern climate state with the pre-industrial condition, middle glacial climate state and full glacial condition, mainly differing in the ice sheet configuration and atmospheric amount of Greenhouse Gases. The results under middle glacial condition show largest cooling/warming response in North Atlantic and a reasonable bipolar warming/cooling signal revealed in the ice core data of the both hemisphere. We discuss the responses under different background climates which involve the strong coupling between atmosphere, ocean and sea ice and their dependence on the configuration of ice sheet.

  4. Wildfire responses to abrupt climate change in North America.

    PubMed

    Marlon, J R; Bartlein, P J; Walsh, M K; Harrison, S P; Brown, K J; Edwards, M E; Higuera, P E; Power, M J; Anderson, R S; Briles, C; Brunelle, A; Carcaillet, C; Daniels, M; Hu, F S; Lavoie, M; Long, C; Minckley, T; Richard, P J H; Scott, A C; Shafer, D S; Tinner, W; Umbanhowar, C E; Whitlock, C

    2009-02-24

    It is widely accepted, based on data from the last few decades and on model simulations, that anthropogenic climate change will cause increased fire activity. However, less attention has been paid to the relationship between abrupt climate changes and heightened fire activity in the paleorecord. We use 35 charcoal and pollen records to assess how fire regimes in North America changed during the last glacial-interglacial transition (15 to 10 ka), a time of large and rapid climate changes. We also test the hypothesis that a comet impact initiated continental-scale wildfires at 12.9 ka; the data do not support this idea, nor are continent-wide fires indicated at any time during deglaciation. There are, however, clear links between large climate changes and fire activity. Biomass burning gradually increased from the glacial period to the beginning of the Younger Dryas. Although there are changes in biomass burning during the Younger Dryas, there is no systematic trend. There is a further increase in biomass burning after the Younger Dryas. Intervals of rapid climate change at 13.9, 13.2, and 11.7 ka are marked by large increases in fire activity. The timing of changes in fire is not coincident with changes in human population density or the timing of the extinction of the megafauna. Although these factors could have contributed to fire-regime changes at individual sites or at specific times, the charcoal data indicate an important role for climate, and particularly rapid climate change, in determining broad-scale levels of fire activity.

  5. Climate oscillations and abrupt changes in C14 data

    NASA Astrophysics Data System (ADS)

    Kuznetsova, T. V.; Tsirulnik, L. B.

    2004-01-01

    The radiocarbon series are analysed by a method of non-linear spectral analysis to detect time intervals of appearance of non-stationary oscillations of large amplitude, and the times of abrupt changes of their oscillation regime. The analysis shows that the most powerful cycles of the spectra can be interpreted in terms of periods (and their respective higher harmonics) of astronomical origin. An intense stationary sinusoid from the spectrum with period T˜6500 yr, the 4th harmonic of the period of equinox precession, correlates with the time variations of the geomagnetic dipole moment. The most powerful non-stationary sinusoid with mean period T=2230 yr, reflects oscillations in C14 data related to the non-dipole part of the geomagnetic field, and correlates with periods of climate warming/cooling. The apparent regularities that can be inferred in the interaction of such two powerful cycles (i.e. stationary and non-stationary parts of the uniform mechanism of the geomagnetic field generation) permit to forecast a tendency of the climate changes. A possible physical mechanism is presented based on a possible transformation, of some signals caused by perturbation of the tidal forces of astronomical origin (that can arise along the orbit of the Earth), into effects that control geophysical systems through small variations of the dissipative parameters of a dynamo system.

  6. A comparison of two methods for detecting abrupt changes in the variance of climatic time series

    NASA Astrophysics Data System (ADS)

    Rodionov, Sergei N.

    2016-06-01

    Two methods for detecting abrupt shifts in the variance - Integrated Cumulative Sum of Squares (ICSS) and Sequential Regime Shift Detector (SRSD) - have been compared on both synthetic and observed time series. In Monte Carlo experiments, SRSD outperformed ICSS in the overwhelming majority of the modeled scenarios with different sequences of variance regimes. The SRSD advantage was particularly apparent in the case of outliers in the series. On the other hand, SRSD has more parameters to adjust than ICSS, which requires more experience from the user in order to select those parameters properly. Therefore, ICSS can serve as a good starting point of a regime shift analysis. When tested on climatic time series, in most cases both methods detected the same change points in the longer series (252-787 monthly values). The only exception was the Arctic Ocean sea surface temperature (SST) series, when ICSS found one extra change point that appeared to be spurious. As for the shorter time series (66-136 yearly values), ICSS failed to detect any change points even when the variance doubled or tripled from one regime to another. For these time series, SRSD is recommended. Interestingly, all the climatic time series tested, from the Arctic to the tropics, had one thing in common: the last shift detected in each of these series was toward a high-variance regime. This is consistent with other findings of increased climate variability in recent decades.

  7. Testing massive Arctic sea ice export as a trigger for abrupt climate change

    NASA Astrophysics Data System (ADS)

    Coletti, Anthony; Condron, Alan; Bradley, Raymond

    2014-05-01

    The discharge of freshwater from glacial lakes to the North Atlantic is repeatedly cited as the main trigger for abrupt centennial to millennial length climate change during the last deglaciation. Broecker et al., (1989) was a proponent of this idea suggesting that abrupt re-routing of pro-glacial lake freshwater to the North Atlantic through the St. Lawrence Valley weakened the strength of the AMOC. Yet, evidence for this is lacking, freshwater estimates in these lakes are relatively small and flood durations are rather short (<5 years), suggesting that floods may not have been the only mechanism driving these climate shifts. Using sophisticated ocean modeling, it has been shown that the release of freshwater originating from the Arctic is more effective at weakening the AMOC compared to freshwater released further south. Here we investigate whether the break-up and mobilization of thick Arctic sea-ice would have supplied enough freshwater to the Nordic Seas to sufficiently cause dampening of the AMOC and hinder NADW formation in the sub-polar North Atlantic. We use numerical climate models to assess 1) the maximum thickness of sea ice that can be formed during glacial periods and the volume of freshwater in the ice, 2) the mechanism which caused the collapse and mobilization of arctic sea-ice into the North Atlantic and 3) the impact of melting sea-ice on global ocean circulation. This hypothesis focuses on the potential impacts of sea-ice as a forcing mechanism for abrupt climate change events on geologic time scales.

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

    NASA Astrophysics Data System (ADS)

    Mitsui, Takahito; Crucifix, Michel

    2016-07-01

    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.

  9. Climatic and Societal Causes for Abrupt Environmental Change in the Mediterranean During the Common Era

    NASA Astrophysics Data System (ADS)

    Mensing, S. A.; Tunno, I.; Sagnotti, L.; Florindo, F.; Noble, P. J.; Archer, C.; Zimmerman, S. R. H.; Pavón-Carrasco, F. J.; Cifnani, G.; Passigli, S.; Piovesan, G.

    2015-12-01

    We compare climatic and societal causes for abrupt environmental change for the last 2000 years in the Rieti Basin, central Italy using high-resolution sedimentary paleoenvironmental proxies, historical documents, and annually resolved independent climate reconstructions of temperature and precipitation. Pollen zones, identified from temporally constrained cluster analysis, coincide with historic periods developed from well-established ceramic sequences corresponding to the Roman Imperial through Late Antique (1 to 600 CE) Early Medieval (600 to 875 CE), Medieval through Late Medieval (875 to 1400 CE), Renaissance and Modern (1400 to 1725 CE), and Contemporary periods (1725 CE to present). Non-metric dimensional scaling (NMDS) ordination showed that each temporal period occupied a unique ecologic space suggesting that a new landscape was created during each successive historic period. During Roman time, between 1 and 500 CE, a modest decline in forest coincides with a positive phase of the North Atlantic Oscillation (NAO) and drier climate; however mesophyllous forest is preserved. Steep decline in forest cover between 850 and 950 CE coincides with positive temperature anomalies in Europe and a positive NAO. Although this would seem to suggest climate as a cause, temperature and precipitation changes are modest and the magnitude and rapidity of the vegetation change suggests climate played a small role. Archaeological evidence from across Europe identifies socioeconomic factors that produced forest clearing. In contrast, cooler temperatures and a negative NAO (increased ppt) appears to have been a catalyst for land abandonment and forest recovery in the 13th to 14th centuries. The NAO produces opposite effects on societies in the eastern and western Mediterranean with the negative phase in 1400 CE leading to cool wet climate and land abandonment in central Italy but an abrupt shift to drier conditions and change from sedentary village life to nomadism in Syria.

  10. Abrupt shifts in ecosystem function and intensification of global biogeochemical cycle driven by hydroclimatic extremes

    NASA Astrophysics Data System (ADS)

    Ma, Xuanlong; Huete, Alfredo; Ponce-Campos, Guillermo; Zhang, Yongguang; Xie, Zunyi; Giovannini, Leandro; Cleverly, James; Eamus, Derek

    2016-04-01

    Amplification of the hydrologic cycle as a consequence of global warming is increasing the frequency, intensity, and spatial extent of extreme climate events globally. The potential influences resulting from amplification of the hydro-climatic cycle, coupled with an accelerating warming trend, pose great concerns on the sustainability of terrestrial ecosystems to sequester carbon, maintain biodiversity, provide ecosystem services, food security, and support human livelihood. Despite the great implications, the magnitude, direction, and carry-over effect of these extreme climate events on ecosystem function, remain largely uncertain. To address these pressing issues, we conducted an observational, interdisciplinary study using satellite retrievals of atmospheric CO2 and photosynthesis (chlorophyll fluorescence), and in-situ flux tower measures of ecosystem-atmosphere carbon exchange, to reveal the shifts in ecosystem function across extreme drought and wet periods. We further determine the factors that govern ecosystem sensitivity to hydroclimatic extremes. We focus on Australia but extended our analyses to other global dryland regions due to their significant role in global biogeochemical cycles. Our results revealed dramatic impacts of drought and wet hydroclimatic extremes on ecosystem function, with abrupt changes in vegetation productivity, carbon uptake, and water-use-efficiency between years. Drought resulted in widespread reductions or collapse in the normal patterns of vegetation growth seasonality such that in many cases there was no detectable phenological cycle during extreme drought years. We further identified a significant increasing trend (p < 0.001) in extreme wet year precipitation amounts over Australia and many other global regions, resulting in an increasing trend in magnitude of the episodic carbon sink pulses coupled to each La Niña-induced wet years. This finding is of global biogeochemical significance, with the consequence of amplifying

  11. Climate changes, shifting ranges

    USGS Publications Warehouse

    Romanach, Stephanie

    2015-01-01

    Even a fleeting mention of the Everglades conjures colorful images of alligators, panthers, flamingos, and manatees. Over the centuries, this familiar cast of characters has become synonymous with life in south Florida. But the workings of a changing climate have the potential to significantly alter the menagerie of animals that call this area home. Global projections suggest south Florida wildlife will need to contend with higher temperatures, drier conditions, and rising seas in the years ahead. Recent modeling efforts shed new light on the potential outcomes these changes may have for threatened and endangered species in the area.

  12. Slowing down of North Pacific climate variability and its implications for abrupt ecosystem change.

    PubMed

    Boulton, Chris A; Lenton, Timothy M

    2015-09-15

    Marine ecosystems are sensitive to stochastic environmental variability, with higher-amplitude, lower-frequency--i.e., "redder"--variability posing a greater threat of triggering large ecosystem changes. Here we show that fluctuations in the Pacific Decadal Oscillation (PDO) index have slowed down markedly over the observational record (1900-present), as indicated by a robust increase in autocorrelation. This "reddening" of the spectrum of climate variability is also found in regionally averaged North Pacific sea surface temperatures (SSTs), and can be at least partly explained by observed deepening of the ocean mixed layer. The progressive reddening of North Pacific climate variability has important implications for marine ecosystems. Ecosystem variables that respond linearly to climate forcing will have become prone to much larger variations over the observational record, whereas ecosystem variables that respond nonlinearly to climate forcing will have become prone to more frequent "regime shifts." Thus, slowing down of North Pacific climate variability can help explain the large magnitude and potentially the quick succession of well-known abrupt changes in North Pacific ecosystems in 1977 and 1989. When looking ahead, despite model limitations in simulating mixed layer depth (MLD) in the North Pacific, global warming is robustly expected to decrease MLD. This could potentially reverse the observed trend of slowing down of North Pacific climate variability and its effects on marine ecosystems.

  13. Slowing down of North Pacific climate variability and its implications for abrupt ecosystem change

    PubMed Central

    Boulton, Chris A.; Lenton, Timothy M.

    2015-01-01

    Marine ecosystems are sensitive to stochastic environmental variability, with higher-amplitude, lower-frequency––i.e., “redder”––variability posing a greater threat of triggering large ecosystem changes. Here we show that fluctuations in the Pacific Decadal Oscillation (PDO) index have slowed down markedly over the observational record (1900–present), as indicated by a robust increase in autocorrelation. This “reddening” of the spectrum of climate variability is also found in regionally averaged North Pacific sea surface temperatures (SSTs), and can be at least partly explained by observed deepening of the ocean mixed layer. The progressive reddening of North Pacific climate variability has important implications for marine ecosystems. Ecosystem variables that respond linearly to climate forcing will have become prone to much larger variations over the observational record, whereas ecosystem variables that respond nonlinearly to climate forcing will have become prone to more frequent “regime shifts.” Thus, slowing down of North Pacific climate variability can help explain the large magnitude and potentially the quick succession of well-known abrupt changes in North Pacific ecosystems in 1977 and 1989. When looking ahead, despite model limitations in simulating mixed layer depth (MLD) in the North Pacific, global warming is robustly expected to decrease MLD. This could potentially reverse the observed trend of slowing down of North Pacific climate variability and its effects on marine ecosystems. PMID:26324900

  14. Antarctic Forcing of Abrupt Global Climate Change During Isotope Stage 3

    NASA Astrophysics Data System (ADS)

    Turney, Christian; Jones, Richard; Phipps, Steven; Thomas, Zoë; Hogg, Alan; Kershaw, Peter; Fogwill, Christopher; Palmer, Jonathan; Bronk Ramsey, Christopher; Adolphi, Florian; Muscheler, Raimund; Hughen, Konrad; Staff, Richard; Grosvenor, Mark; Golledge, Nicholas; Haberle, Simon

    2016-04-01

    Contrasting Greenland and Antarctic temperature trends during the late Pleistocene (60,000 to 11,650 years ago) are thought to be driven by imbalances in the rate of formation of North Atlantic and Antarctic Deep Water (the 'bipolar seesaw'), with millennial-scale cooling Dansgaard-Oeschger (D-O) events in the north leading warming in the south. An alternative origin for these abrupt climate shifts, however, is the Southern Hemisphere whereby changes are transmitted globally via atmospheric and/or oceanic teleconnections. Testing these competing hypotheses is challenging given the relatively large uncertainties associated with dating terrestrial, marine and ice core chronologies. Here we use a fully coupled climate system model to investigate whether freshening of the Southern Ocean has extra-regional climate impacts. Focusing on an Isotope Stage 3 cooling event preserved in Antarctic ice cores immediately prior to Antarctic Isotope Maximum 4 (AIM 4; around 29,000 years ago) we undertook an ensemble of transient meltwater simulations. We observe no impact on the Atlantic Meridional Overturning Circulation (AMOC) from freshwater hosing in the Southern Ocean but a dramatic warming over the North Atlantic and contrasting precipitation patterns across the low latitudes. Exploiting a new bidecadally-resolved 14C calibration dataset obtained from New Zealand kauri (Agathis australis) we undertook intensive radiocarbon dating and high-resolution multiproxy analysis of the tropical Australia Lynch's Crater terrestrial peat sequence spanning this same period and find a synchronous change in hydroclimate to the purported meltwater event in the Southern Ocean. Our results imply Southern Ocean dynamics played a significant role in driving global climate change across this period via atmospheric teleconnections, with implications for other abrupt events through the late Pleistocene.

  15. Arctic Ocean freshwater as a trigger for abrupt climate change

    NASA Astrophysics Data System (ADS)

    Bradley, Raymond; Condron, Alan; Coletti, Anthony

    2016-04-01

    The cause of the Younger Dryas cooling remains unresolved despite decades of debate. Current arguments focus on either freshwater from Glacial Lake Agassiz drainage through the St Lawrence or the MacKenzie river systems. High resolution ocean modeling suggests that freshwater delivered to the North Atlantic from the Arctic Ocean through Fram Strait would have had more of an impact on Atlantic Meridional Overturning Circulation (AMOC) than freshwater from the St Lawrence. This has been interpreted as an argument for a MacKenzie River /Lake Agassiz freshwater source. However, it is important to note that although the modeling identifies Fram Strait as the optimum location for delivery of freshwater to disrupt the AMOC, this does not mean the freshwater source came from Lake Agassiz. Another potential source of freshwater is the Arctic Ocean ice cover itself. During the LGM, ice cover was extremely thick - many tens of meters in the Canada Basin (at least), resulting in a hiatus in sediment deposition there. Extreme ice thickness was related to a stagnant circulation, very low temperatures and continuous accumulation of snow on top of a base of sea-ice. This resulted in a large accumulation of freshwater in the Arctic Basin. As sea-level rose and a more modern circulation regime became established in the Arctic, this freshwater was released from the Arctic Ocean through Fram Strait, leading to extensive sea-ice formation in the North Atlantic (Greenland Sea) and a major reduction in the AMOC. Here we present new model results and a review of the paleoceanographic evidence to support this hypothesis. The bottom line is that the Arctic Ocean was likely a major player in causing abrupt climate change in the past, via its influence on the AMOC. Although we focus here on the Younger Dryas, the Arctic Ocean has been repeatedly isolated from the world ocean during glacial periods of the past. When these periods of isolation ended, it is probable that there were significant

  16. Abrupt climate change and transient climates during the Paleogene: a marine perspective

    NASA Technical Reports Server (NTRS)

    Zachos, J. C.; Lohmann, K. C.; Walker, J. C.; Wise, S. W.

    1993-01-01

    Detailed investigations of high latitude sequences recently collected by the Ocean Drilling Program (ODP) indicate that periods of rapid climate change often culminated in brief transient climates, with more extreme conditions than subsequent long term climates. Two examples of such events have been identified in the Paleogene; the first in latest Paleocene time in the middle of a warming trend that began several million years earlier: the second in earliest Oligocene time near the end of a Middle Eocene to Late Oligocene global cooling trend. Superimposed on the earlier event was a sudden and extreme warming of both high latitude sea surface and deep ocean waters. Imbedded in the latter transition was an abrupt decline in high latitude temperatures and the brief appearance of a full size continental ice-sheet on Antarctica. In both cases the climate extremes were not stable, lasting for less than a few hundred thousand years, indicating a temporary or transient climate state. Geochemical and sedimentological evidence suggest that both Paleogene climate events were accompanied by reorganizations in ocean circulation, and major perturbations in marine productivity and the global carbon cycle. The Paleocene-Eocene thermal maximum was marked by reduced oceanic turnover and decreases in global delta 13C and in marine productivity, while the Early Oligocene glacial maximum was accompanied by intensification of deep ocean circulation and elevated delta 13C and productivity. It has been suggested that sudden changes in climate and/or ocean circulation might occur as a result of gradual forcing as certain physical thresholds are exceeded. We investigate the possibility that sudden reorganizations in ocean and/or atmosphere circulation during these abrupt transitions generated short-term positive feedbacks that briefly sustained these transient climatic states.

  17. Sensitivity and rapidity of vegetational response to abrupt climate change

    NASA Technical Reports Server (NTRS)

    Peteet, D.

    2000-01-01

    Rapid climate change characterizes numerous terrestrial sediment records during and since the last glaciation. Vegetational response is best expressed in terrestrial records near ecotones, where sensitivity to climate change is greatest, and response times are as short as decades.

  18. Dynamics of climate and ecosystem coupling: abrupt changes and multiple equilibria.

    PubMed Central

    Higgins, Paul A T; Mastrandrea, Michael D; Schneider, Stephen H

    2002-01-01

    Interactions between subunits of the global climate-biosphere system (e.g. atmosphere, ocean, biosphere and cryosphere) often lead to behaviour that is not evident when each subunit is viewed in isolation. This newly evident behaviour is an emergent property of the coupled subsystems. Interactions between thermohaline circulation and climate illustrate one emergent property of coupling ocean and atmospheric circulation. The multiple thermohaline circulation equilibria that result caused abrupt climate changes in the past and may cause abrupt climate changes in the future. Similarly, coupling between the climate system and ecosystem structure and function produces complex behaviour in certain regions. For example, atmosphere-biosphere interactions in the Sahel region of West Africa lead to multiple stable equilibria. Either wet or dry climate equilibria can occur under otherwise identical forcing conditions. The equilibrium reached is dependent on past history (i.e. initial conditions), and relatively small perturbations to either climate or vegetation can cause switching between the two equilibria. Both thermohaline circulation and the climate-vegetation system in the Sahel are prone to abrupt changes that may be irreversible. This complicates the relatively linear view of global changes held in many scientific and policy communities. Emergent properties of coupled socio-natural systems add yet another layer of complexity to the policy debate. As a result, the social and economic consequences of possible global changes are likely to be underestimated in most conventional analyses because these nonlinear, abrupt and irreversible responses are insufficiently considered. PMID:12079526

  19. Dynamics of climate and ecosystem coupling: abrupt changes and multiple equilibria.

    PubMed

    Higgins, Paul A T; Mastrandrea, Michael D; Schneider, Stephen H

    2002-05-29

    Interactions between subunits of the global climate-biosphere system (e.g. atmosphere, ocean, biosphere and cryosphere) often lead to behaviour that is not evident when each subunit is viewed in isolation. This newly evident behaviour is an emergent property of the coupled subsystems. Interactions between thermohaline circulation and climate illustrate one emergent property of coupling ocean and atmospheric circulation. The multiple thermohaline circulation equilibria that result caused abrupt climate changes in the past and may cause abrupt climate changes in the future. Similarly, coupling between the climate system and ecosystem structure and function produces complex behaviour in certain regions. For example, atmosphere-biosphere interactions in the Sahel region of West Africa lead to multiple stable equilibria. Either wet or dry climate equilibria can occur under otherwise identical forcing conditions. The equilibrium reached is dependent on past history (i.e. initial conditions), and relatively small perturbations to either climate or vegetation can cause switching between the two equilibria. Both thermohaline circulation and the climate-vegetation system in the Sahel are prone to abrupt changes that may be irreversible. This complicates the relatively linear view of global changes held in many scientific and policy communities. Emergent properties of coupled socio-natural systems add yet another layer of complexity to the policy debate. As a result, the social and economic consequences of possible global changes are likely to be underestimated in most conventional analyses because these nonlinear, abrupt and irreversible responses are insufficiently considered.

  20. Dynamics of climate and ecosystem coupling: abrupt changes and multiple equilibria.

    PubMed

    Higgins, Paul A T; Mastrandrea, Michael D; Schneider, Stephen H

    2002-05-29

    Interactions between subunits of the global climate-biosphere system (e.g. atmosphere, ocean, biosphere and cryosphere) often lead to behaviour that is not evident when each subunit is viewed in isolation. This newly evident behaviour is an emergent property of the coupled subsystems. Interactions between thermohaline circulation and climate illustrate one emergent property of coupling ocean and atmospheric circulation. The multiple thermohaline circulation equilibria that result caused abrupt climate changes in the past and may cause abrupt climate changes in the future. Similarly, coupling between the climate system and ecosystem structure and function produces complex behaviour in certain regions. For example, atmosphere-biosphere interactions in the Sahel region of West Africa lead to multiple stable equilibria. Either wet or dry climate equilibria can occur under otherwise identical forcing conditions. The equilibrium reached is dependent on past history (i.e. initial conditions), and relatively small perturbations to either climate or vegetation can cause switching between the two equilibria. Both thermohaline circulation and the climate-vegetation system in the Sahel are prone to abrupt changes that may be irreversible. This complicates the relatively linear view of global changes held in many scientific and policy communities. Emergent properties of coupled socio-natural systems add yet another layer of complexity to the policy debate. As a result, the social and economic consequences of possible global changes are likely to be underestimated in most conventional analyses because these nonlinear, abrupt and irreversible responses are insufficiently considered. PMID:12079526

  1. Abrupt climate changes and its oscillations in solar-terrestrial data

    NASA Astrophysics Data System (ADS)

    Kuznetsova, T.

    2003-04-01

    Time series of different solar-terrestrial data (on solar activity, geomagnetic field variations, Be-10, C-14, anomaly of global surface temperature,) are analysed by a method of non-linear spectral analysis (named by the MGM method) to detect time intervals of appearance of non-stationary oscillations of large amplitude and times of abrupt changes of their oscillation regime. Analysis shows that the most power cycles of the calculated spectra can be interpreted by periods (and overtones) of astronomical origin. The powerest non-stationary (with varying phase and amplitude) sinusoid at mean period T~2230 yr. (and its overtones), reflecting oscillations of non-dipole part of the geomagnetic field in C14 data and variations of long-term solar activity), is connected with climate variability and its abrupt changes. Derived regularities in behaviour of this cycle allow forecasting the tendency of climate changes in the future. Analysis of different studies shows that this cycle was detected in many geophysical data (governed by different physical mechanisms). It is shown that the time intervals of regime change of oscillations of the 2230-year cycle is reflected in all geophysical data synchro. It is generally recognized that climate regime shifts are connected with sudden changes of other geophysical systems although these systems are controlled by different physical mechanisms. However, this speed and the global synchronicity of climate changes are the major problems in understanding links between the Milankovich forcing of astronomical origin and climate data. It is possible to separate in orbital motion of each celestial body non-perturbed (Kepler's) part and perturbed one. The non-perturbed part of tide force characterizes non-evolving orbital motion (analogous to normal part of geophysical fields, for instance, gravitational and geomagnetic); respectively, perturbed part of tide force characterizes evolving orbital motion (analogous of anomalous part that can be

  2. Reducing The Risk Of Abrupt Climate Change: Emission Corridors Preserving The Thermohaline Circulation

    NASA Astrophysics Data System (ADS)

    Zickfeld, K.

    Paleo-reconstructions have shown that large and abrupt climate changes have occurred throughout the last ice-age cycles. This evidence, supplemented by insights into the complex and nonlinear nature of the climate system, gives raise to the concern that anthropogenic forcing may trigger such events in the future. A prominent example for such a potential climatic shift is the collapse of the North Atlantic thermohaline circu- lation (THC), which would cause a major cooling of the northern North Atlantic and north-western Europe and considerable regional sea level rise, with possibly severe consequences on, e.g., fisheries, agriculture and ecosystems. In this paper we present emission corridors for the 21st century preserving the THC. Emission corridors embrace the range of future emissions beyond which either the THC collapses or the mitigation burden becomes intolerable. They are calculated along the conceptual and methodological lines of the tolerable windows approach. We investigate the sensitivity of the emission corridors to the main uncertain parame- ters (climate and North Atlantic hydrological sensitivities as well as emissions of non CO_2 greenhouse gases). Results show a high dependence of the size of the emis- sion corridors on hydrological and climate sensitivities. For the best-guess values of both parameters we find that the emission corridors are wider than the range spanned by the SRES emissions scenarios. Thus, no immediate mitigation seems necessary in order to preserve the THC. For high but still realistic values of the sensitivities, however, even the low SRES emissions scenarios transgress the corridor boundaries. These findings imply that under 'business as usual' a non-negligible risk of either a THC collapse or an intolerable mitigation burden exists.

  3. Climate-driven regime shifts in Arctic marine benthos.

    PubMed

    Kortsch, Susanne; Primicerio, Raul; Beuchel, Frank; Renaud, Paul E; Rodrigues, João; Lønne, Ole Jørgen; Gulliksen, Bjørn

    2012-08-28

    Climate warming can trigger abrupt ecosystem changes in the Arctic. Despite the considerable interest in characterizing and understanding the ecological impact of rapid climate warming in the Arctic, few long time series exist that allow addressing these research goals. During a 30-y period (1980-2010) of gradually increasing seawater temperature and decreasing sea ice cover in Svalbard, we document rapid and extensive structural changes in the rocky-bottom communities of two Arctic fjords. The most striking component of the benthic reorganization was an abrupt fivefold increase in macroalgal cover in 1995 in Kongsfjord and an eightfold increase in 2000 in Smeerenburgfjord. Simultaneous changes in the abundance of benthic invertebrates suggest that the macroalgae played a key structuring role in these communities. The abrupt, substantial, and persistent nature of the changes observed is indicative of a climate-driven ecological regime shift. The ecological processes thought to drive the observed regime shifts are likely to promote the borealization of these Arctic marine communities in the coming years. PMID:22891319

  4. Atmospheric CO2 forces abrupt vegetation shifts locally, but not globally.

    PubMed

    Higgins, Steven I; Scheiter, Simon

    2012-08-01

    It is possible that anthropogenic climate change will drive the Earth system into a qualitatively different state. Although different types of uncertainty limit our capacity to assess this risk, Earth system scientists are particularly concerned about tipping elements, large-scale components of the Earth system that can be switched into qualitatively different states by small perturbations. Despite growing evidence that tipping elements exist in the climate system, whether large-scale vegetation systems can tip into alternative states is poorly understood. Here we show that tropical grassland, savanna and forest ecosystems, areas large enough to have powerful impacts on the Earth system, are likely to shift to alternative states. Specifically, we show that increasing atmospheric CO2 concentration will force transitions to vegetation states characterized by higher biomass and/or woody-plant dominance. The timing of these critical transitions varies as a result of between-site variance in the rate of temperature increase, as well as a dependence on stochastic variation in fire severity and rainfall. We further show that the locations of bistable vegetation zones (zones where alternative vegetation states can exist) will shift as climate changes. We conclude that even though large-scale directional regime shifts in terrestrial ecosystems are likely, asynchrony in the timing of these shifts may serve to dampen, but not nullify, the shock that these changes may represent to the Earth system.

  5. Ice-core evidence of abrupt climate changes

    PubMed Central

    Alley, Richard B.

    2000-01-01

    Ice-core records show that climate changes in the past have been large, rapid, and synchronous over broad areas extending into low latitudes, with less variability over historical times. These ice-core records come from high mountain glaciers and the polar regions, including small ice caps and the large ice sheets of Greenland and Antarctica. PMID:10677460

  6. Ice-core evidence of abrupt climate changes.

    PubMed

    Alley, R B

    2000-02-15

    Ice-core records show that climate changes in the past have been large, rapid, and synchronous over broad areas extending into low latitudes, with less variability over historical times. These ice-core records come from high mountain glaciers and the polar regions, including small ice caps and the large ice sheets of Greenland and Antarctica.

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

    PubMed Central

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

    2015-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

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

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

    PubMed

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

    2015-09-02

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

  10. The applicability of research on moving cut data-approximate entropy on abrupt climate change detection

    NASA Astrophysics Data System (ADS)

    Jin, Hongmei; He, Wenping; Liu, Qunqun; Wang, Jinsong; Feng, Guolin

    2016-04-01

    In this study, the performance of moving cut data-approximate entropy (MC-ApEn) to detect abrupt dynamic changes was investigated. Numerical tests in a time series model indicate that the MC-ApEn method is suitable for the detection of abrupt dynamic changes for three types of meteorological data: daily maximum temperature, daily minimum temperature, and daily precipitation. Additionally, the MC-ApEn method was used to detect abrupt climate changes in daily precipitation data from Northwest China and the Pacific Decadal Oscillation (PDO) index. The results show an abrupt dynamic change in precipitation in 1980 and in the PDO index in 1976. The times indicated for the abrupt changes are identical to those from previous results. Application of the analysis to observational data further confirmed the performance of the MC-ApEn method. Moreover, MC-ApEn outperformed the moving t test (MTT) and the moving detrended fluctuation analysis (MDFA) methods for the detection of abrupt dynamic changes in a simulated 1000-point daily precipitation dataset.

  11. Agulhas salt-leakage oscillations during abrupt climate changes of the Late Pleistocene

    NASA Astrophysics Data System (ADS)

    Marino, Gianluca; Zahn, Rainer; Ziegler, Martin; Purcell, Conor; Knorr, Gregor; Hall, Ian R.; Ziveri, Patrizia; Elderfield, Henry

    2013-09-01

    An ensemble of new, high-resolution records of surface ocean hydrography from the Indian-Atlantic oceanic gateway, south of Africa, demonstrates recurrent and high-amplitude salinity oscillations in the Agulhas Leakage area during the penultimate glacial-interglacial cycle. A series of millennial-scale salinification events, indicating strengthened salt leakage into the South Atlantic, appear to correlate with abrupt changes in the North Atlantic climate and Atlantic Meridional Overturning Circulation (AMOC). This interhemispheric coupling, which plausibly involved changes in the Hadley Cell and midlatitude westerlies that impacted the interocean transport at the tip of Africa, suggests that the Agulhas Leakage acted as a source of negative buoyancy for the perturbed AMOC, possibly aiding its return to full strength. Our finding points to the Indian-to-Atlantic salt transport as a potentially important modulator of the AMOC during the abrupt climate changes of the Late Pleistocene.

  12. 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.

  13. Abrupt climate change in West Antarctica and Greenland during the last deglacial warming

    NASA Astrophysics Data System (ADS)

    Fudge, T. J.; Steig, E. J.; Brook, E.; Buizert, C.; Conway, H.; Ding, Q.; Markle, B. R.; McConnell, J. R.; Pedro, J. B.; Schoenemann, S. W.; Severinghaus, J. P.; Sigl, M.; Sowers, T. A.; Taylor, K.; Waddington, E. D.

    2013-12-01

    The WAIS Divide ice core is the first Southern Hemisphere record with precision similar to ice cores from Greenland. The annually resolved timescale and small gas-age ice-age difference allow the phasing of climate change in the two hemispheres to be compared with unprecedented precision. We focus on the three abrupt climate changes in Greenland during the deglacial transition and the corresponding changes at WAIS Divide. The onset of the Antarctic Cold Reversal (ACR) is clearly defined in the WAIS Divide record and lagged the Bolling-Allerod (BA) warming by 150×50 years. The phasing of the other two abrupt climate changes cannot be distinguished from synchronous with an uncertainty of ~200 years because the transitions from warming to cooling (or cooling to warming) are not distinct in the WAIS Divide record. The lead-lag relationships of no more than a couple centuries confirm the tight coupling between hemispheres during the deglaciation. The independent timescale of WAIS Divide confirms that meltwater Pulse 1a began near-coincident with the BA and ACR although the lack of direct synchronization between the annually dated ice-core imescales and the radiometrically dated coral timescale prevents the phasing from being known to better than a couple of centuries. A new observation from WAIS Divide is that accumulation increased ~40% between 12.0 and 11.6 ka, with the accumulation increase ending approximately coincident with the warming at the end of the Younger Dryas in Greenland. Other Antarctic ice cores lack timescales with sufficient resolution to identify such abrupt changes so it is unclear how much of Antarctica was affected by the increased accumulation rates. The inter-hemispheric relationships are often limited to a discussion of warming, but the WAIS Divide records suggests that the moisture transport may be another important constraint on the mechanisms that drive abrupt climate change.

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

    PubMed

    2015-04-30

    The last glacial period exhibited abrupt Dansgaard-Oeschger climatic oscillations, evidence of which is preserved in a variety of Northern Hemisphere palaeoclimate archives. Ice cores show that Antarctica cooled during the warm phases of the Greenland Dansgaard-Oeschger cycle and vice versa, suggesting an interhemispheric redistribution of heat through a mechanism called the bipolar seesaw. Variations in the Atlantic meridional overturning circulation (AMOC) strength are thought to have been important, but much uncertainty remains regarding the dynamics and trigger of these abrupt events. Key information is contained in the relative phasing of hemispheric climate variations, yet the large, poorly constrained difference between gas age and ice age and the relatively low resolution of methane records from Antarctic ice cores have so far precluded methane-based synchronization at the required sub-centennial precision. Here we use a recently drilled high-accumulation Antarctic ice core to show that, on average, 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.

  15. The role of stochastic noise in the abrupt climatic transitions of the pleistocene

    SciTech Connect

    Matteucci, G.

    1991-01-01

    Analyses of marine [delta][sup 18]O records suggest that the variations of the Earth's orbital parameters have induced and provided the timing of the Pleistocene climatic oscillations. This dissertation analyses some statistical properties of the Pleistocene climate by estimating the Probability Density Function (PDF) of the [delta][sup 18]O record. The results allow to define statistically what were the [open quotes]typical conditions[close quotes] (in a probabilistic sense) of the Quaternary, to identify the modes of the PDF as the mean glacial and interglacial climatic states, and to clarify the meaning and the abruptness of the climatic transitions. A zero-dimensional Energy Balance Model is developed. The nonlinearity of the ice albedo-temperature feedback leads to multiple steady-state equilibria. The role of stochastic perturbations and their interaction with the orbital forcing in producing the periodic and abrupt climatic transitions of the late Pleistocene are illustrated. A stochastic sensitivity analysis is used to clarify the results, especially the selective amplification of the orbitally-induced 100 kyr cycle, and the predictability of the system on the time scales of the orbital cycles. From the analysis of GCM simulations and observational zonally- averaged data a one-dimensional EBM is then developed. The strong nonlinearity of this model and the occurrence of multiple equilibria is caused by the presence of the Thin Ice Cap Instability. A discussion of the features that stochastic perturbations would introduce, follows. Finally a GCM sensitivity study to atmospheric CO[sub 2] shows how the effects of varying CO[sub 2] concentrations can be included in simple EBMs. The role that stochastic perturbations, orbital forcing, and the known past concentrations of atmospheric CO[sub 2] have played in producing the abrupt climatic transitions of the late Pleistocene is discussed.

  16. North Atlantic ocean circulation and abrupt climate change during the last glaciation

    NASA Astrophysics Data System (ADS)

    Henry, L. G.; McManus, J. F.; Curry, W. B.; Roberts, N. L.; Piotrowski, A. M.; Keigwin, L. D.

    2016-07-01

    The most recent ice age was characterized by rapid and hemispherically asynchronous climate oscillations, whose origin remains unresolved. Variations in oceanic meridional heat transport may contribute to these repeated climate changes, which were most pronounced during marine isotope stage 3, the glacial interval 25 thousand to 60 thousand years ago. We examined climate and ocean circulation proxies throughout this interval at high resolution in a deep North Atlantic sediment core, combining the kinematic tracer protactinium/thorium (Pa/Th) with the deep water-mass tracer, epibenthic δ13C. These indicators suggest reduced Atlantic overturning circulation during every cool northern stadial, with the greatest reductions during episodic Hudson Strait iceberg discharges, while sharp northern warming followed reinvigorated overturning. These results provide direct evidence for the ocean’s persistent, central role in abrupt glacial climate change.

  17. North Atlantic ocean circulation and abrupt climate change during the last glaciation.

    PubMed

    Henry, L G; McManus, J F; Curry, W B; Roberts, N L; Piotrowski, A M; Keigwin, L D

    2016-07-29

    The most recent ice age was characterized by rapid and hemispherically asynchronous climate oscillations, whose origin remains unresolved. Variations in oceanic meridional heat transport may contribute to these repeated climate changes, which were most pronounced during marine isotope stage 3, the glacial interval 25 thousand to 60 thousand years ago. We examined climate and ocean circulation proxies throughout this interval at high resolution in a deep North Atlantic sediment core, combining the kinematic tracer protactinium/thorium (Pa/Th) with the deep water-mass tracer, epibenthic δ(13)C. These indicators suggest reduced Atlantic overturning circulation during every cool northern stadial, with the greatest reductions during episodic Hudson Strait iceberg discharges, while sharp northern warming followed reinvigorated overturning. These results provide direct evidence for the ocean's persistent, central role in abrupt glacial climate change.

  18. North Atlantic ocean circulation and abrupt climate change during the last glaciation.

    PubMed

    Henry, L G; McManus, J F; Curry, W B; Roberts, N L; Piotrowski, A M; Keigwin, L D

    2016-07-29

    The most recent ice age was characterized by rapid and hemispherically asynchronous climate oscillations, whose origin remains unresolved. Variations in oceanic meridional heat transport may contribute to these repeated climate changes, which were most pronounced during marine isotope stage 3, the glacial interval 25 thousand to 60 thousand years ago. We examined climate and ocean circulation proxies throughout this interval at high resolution in a deep North Atlantic sediment core, combining the kinematic tracer protactinium/thorium (Pa/Th) with the deep water-mass tracer, epibenthic δ(13)C. These indicators suggest reduced Atlantic overturning circulation during every cool northern stadial, with the greatest reductions during episodic Hudson Strait iceberg discharges, while sharp northern warming followed reinvigorated overturning. These results provide direct evidence for the ocean's persistent, central role in abrupt glacial climate change. PMID:27365315

  19. Transition process of abrupt climate change based on global sea surface temperature over the past century

    NASA Astrophysics Data System (ADS)

    Yan, Pengcheng; Hou, Wei; Feng, Guolin

    2016-05-01

    A new detection method has been proposed to study the transition process of abrupt climate change. With this method, the climate system transiting from one stable state to another can be verified clearly. By applying this method to the global sea surface temperature over the past century, several climate changes and their processes are detected, including the start state (moment), persist time, and end state (moment). According to the spatial distribution, the locations of climate changes mainly have occurred in the Indian Ocean and western Pacific before the middle twentieth century, in the 1970s in the equatorial middle-eastern Pacific, and in the middle and southern Pacific since the end of the twentieth century. In addition, the quantitative relationship between the transition process parameters is verified in theory and practice: (1) the relationship between the rate and stability parameters is linear, and (2) the relationship between the rate and change amplitude parameters is quadratic.

  20. The Paleoceanography of Cariaco Basin and its Relationship to Deglacial and Abrupt Climate Change

    NASA Astrophysics Data System (ADS)

    Peterson, L. C.; Yurco, L. N.; Gibson, K.; Haug, G. H.; Deplazes, G.; Black, D. E.; Thunell, R.

    2011-12-01

    Sediments of the anoxic Cariaco Basin have produced important high-resolution records of climate and oceanographic change in the southern Caribbean over the last glacial-interglacial cycle. For example, the well-known Dansgaard-Oeschger (D-O) excursions of Greenland ice core fame are recorded in Cariaco Basin by alternating dark and light sediment intervals which reflect climatically-driven oscillations between anoxic and oxygenated deep basin conditions, changes in biological productivity at the surface, and rapid oscillations in the input of siliciclastic muds from local rivers. These oscillations can be related to past changes in the average position of the Intertropical Convergence Zone (ITCZ). Periods of high input of continental sediment and elevated organic carbon (OC) contents are in phase with the warm interstadials and indicate higher regional precipitation and productivity and a more northerly position of the ITCZ; periods of low siliciclastic input and low OC contents during the colder stadials are evidence of dry and less productive regional conditions and southerly displacement of the ITCZ. This now well-known pattern of change in Cariaco Basin is consistent with a mechanism driven by changes in the Atlantic's Meridional Overturning Circulation (AMOC), with a weakened AMOC leading to cooler North Atlantic sea surface temperatures, an enhanced meridional temperature gradient, and a southward shift of the ITCZ. Though every D-O excursion can be identified in Cariaco sediments, the time intervals corresponding to Heinrich ice-rafting episodes in the North Atlantic record the most arid conditions, presumably reflecting an ITCZ response to periods of most severely curtailed AMOC. This talk will review these changes as well as other lines of paleo-evidence for regional changes in the Caribbean-Gulf of Mexico system, with a particular focus on the Late Glacial and Deglacial intervals. In Cariaco Basin, evidence will be presented for a previously unidentified

  1. Spontaneous abrupt climate change due to an atmospheric blocking-sea-ice-ocean feedback in an unforced climate model simulation.

    PubMed

    Drijfhout, Sybren; Gleeson, Emily; Dijkstra, Henk A; Livina, Valerie

    2013-12-01

    Abrupt climate change is abundant in geological records, but climate models rarely have been able to simulate such events in response to realistic forcing. Here we report on a spontaneous abrupt cooling event, lasting for more than a century, with a temperature anomaly similar to that of the Little Ice Age. The event was simulated in the preindustrial control run of a high-resolution climate model, without imposing external perturbations. Initial cooling started with a period of enhanced atmospheric blocking over the eastern subpolar gyre. In response, a southward progression of the sea-ice margin occurred, and the sea-level pressure anomaly was locked to the sea-ice margin through thermal forcing. The cold-core high steered more cold air to the area, reinforcing the sea-ice concentration anomaly east of Greenland. The sea-ice surplus was carried southward by ocean currents around the tip of Greenland. South of 70 °N, sea ice already started melting and the associated freshwater anomaly was carried to the Labrador Sea, shutting off deep convection. There, surface waters were exposed longer to atmospheric cooling and sea surface temperature dropped, causing an even larger thermally forced high above the Labrador Sea. In consequence, east of Greenland, anomalous winds changed from north to south, terminating the event with similar abruptness to its onset. Our results imply that only climate models that possess sufficient resolution to correctly represent atmospheric blocking, in combination with a sensitive sea-ice model, are able to simulate this kind of abrupt climate change.

  2. Spontaneous abrupt climate change due to an atmospheric blocking-sea-ice-ocean feedback in an unforced climate model simulation.

    PubMed

    Drijfhout, Sybren; Gleeson, Emily; Dijkstra, Henk A; Livina, Valerie

    2013-12-01

    Abrupt climate change is abundant in geological records, but climate models rarely have been able to simulate such events in response to realistic forcing. Here we report on a spontaneous abrupt cooling event, lasting for more than a century, with a temperature anomaly similar to that of the Little Ice Age. The event was simulated in the preindustrial control run of a high-resolution climate model, without imposing external perturbations. Initial cooling started with a period of enhanced atmospheric blocking over the eastern subpolar gyre. In response, a southward progression of the sea-ice margin occurred, and the sea-level pressure anomaly was locked to the sea-ice margin through thermal forcing. The cold-core high steered more cold air to the area, reinforcing the sea-ice concentration anomaly east of Greenland. The sea-ice surplus was carried southward by ocean currents around the tip of Greenland. South of 70 °N, sea ice already started melting and the associated freshwater anomaly was carried to the Labrador Sea, shutting off deep convection. There, surface waters were exposed longer to atmospheric cooling and sea surface temperature dropped, causing an even larger thermally forced high above the Labrador Sea. In consequence, east of Greenland, anomalous winds changed from north to south, terminating the event with similar abruptness to its onset. Our results imply that only climate models that possess sufficient resolution to correctly represent atmospheric blocking, in combination with a sensitive sea-ice model, are able to simulate this kind of abrupt climate change. PMID:24248352

  3. Spontaneous abrupt climate change due to an atmospheric blocking–sea-ice–ocean feedback in an unforced climate model simulation

    PubMed Central

    Drijfhout, Sybren; Gleeson, Emily; Dijkstra, Henk A.; Livina, Valerie

    2013-01-01

    Abrupt climate change is abundant in geological records, but climate models rarely have been able to simulate such events in response to realistic forcing. Here we report on a spontaneous abrupt cooling event, lasting for more than a century, with a temperature anomaly similar to that of the Little Ice Age. The event was simulated in the preindustrial control run of a high-resolution climate model, without imposing external perturbations. Initial cooling started with a period of enhanced atmospheric blocking over the eastern subpolar gyre. In response, a southward progression of the sea-ice margin occurred, and the sea-level pressure anomaly was locked to the sea-ice margin through thermal forcing. The cold-core high steered more cold air to the area, reinforcing the sea-ice concentration anomaly east of Greenland. The sea-ice surplus was carried southward by ocean currents around the tip of Greenland. South of 70°N, sea ice already started melting and the associated freshwater anomaly was carried to the Labrador Sea, shutting off deep convection. There, surface waters were exposed longer to atmospheric cooling and sea surface temperature dropped, causing an even larger thermally forced high above the Labrador Sea. In consequence, east of Greenland, anomalous winds changed from north to south, terminating the event with similar abruptness to its onset. Our results imply that only climate models that possess sufficient resolution to correctly represent atmospheric blocking, in combination with a sensitive sea-ice model, are able to simulate this kind of abrupt climate change. PMID:24248352

  4. Does the trigger for abrupt climate change reside in the ocean or in the atmosphere?

    PubMed

    Broecker, W S

    2003-06-01

    Two hypotheses have been put forward to explain the large and abrupt climate changes that punctuated glacial time. One attributes such changes to reorganizations of the ocean's thermohaline circulation and the other to changes in tropical atmosphere-ocean dynamics. In an attempt to distinguish between these hypotheses, two lines of evidence are examined. The first involves the timing of the freshwater injections to the northern Atlantic that have been suggested as triggers for the global impacts associated with the Younger Dryas and Heinrich events. The second has to do with evidence for precursory events associated with the Heinrich ice-rafted debris layers in the northern Atlantic and with the abrupt Dansgaard-Oeschger warmings recorded in the Santa Barbara Basin.

  5. Does the trigger for abrupt climate change reside in the ocean or in the atmosphere?

    PubMed

    Broecker, W S

    2003-06-01

    Two hypotheses have been put forward to explain the large and abrupt climate changes that punctuated glacial time. One attributes such changes to reorganizations of the ocean's thermohaline circulation and the other to changes in tropical atmosphere-ocean dynamics. In an attempt to distinguish between these hypotheses, two lines of evidence are examined. The first involves the timing of the freshwater injections to the northern Atlantic that have been suggested as triggers for the global impacts associated with the Younger Dryas and Heinrich events. The second has to do with evidence for precursory events associated with the Heinrich ice-rafted debris layers in the northern Atlantic and with the abrupt Dansgaard-Oeschger warmings recorded in the Santa Barbara Basin. PMID:12791974

  6. Deep-Sea Biodiversity Response to Abrupt Deglacial and Holocene Climate Changes

    NASA Astrophysics Data System (ADS)

    Yasuhara, M.

    2014-12-01

    High-resolution records of microfossil assemblages from deep-sea sediment cores covering the last 20,000 years in the North Atlantic Ocean were investigated to understand biotic responses to abrupt climate changes over decadal-centennial timescales. The results show pervasive control of deep-sea benthic species diversity by rapidly changing climate. Species diversity rapidly increased during abrupt stadial events during the last deglacial and the Holocene interglacial periods. These included the well-known Heinrich 1, the Younger Dryas, and the 8.2 ka events when the strength of Atlantic Meridional Overturning Circulation (AMOC) decreased. In addition, there is evidence for quasi-cyclic changes in biodiversity at a ~1500-year periodicity. Statistical analyses revealed that AMOC-driven bottom-water-temperature variability is a primary influence on deep-sea biodiversity. Our results may portend pervasive, synchronous and sudden ecosystem responses to human-induced changes to climate and ocean circulation in this century. Exceptionally highly resolved fossil records help us to understand past, present and future ecosystem responses to climate changes by bridging the gap between biological and palaeontological time-scales.

  7. Long-term phenological shifts in raptor migration and climate.

    PubMed

    Jaffré, Mikaël; Beaugrand, Grégory; Goberville, Eric; Jiguet, Frédéric; Kjellén, Nils; Troost, Gerard; Dubois, Philippe J; Leprêtre, Alain; Luczak, Christophe

    2013-01-01

    Climate change is having a discernible effect on many biological and ecological processes. Among observed changes, modifications in bird phenology have been widely documented. However, most studies have interpreted phenological shifts as gradual biological adjustments in response to the alteration of the thermal regime. Here we analysed a long-term dataset (1980-2010) of short-distance migratory raptors in five European regions. We revealed that the responses of these birds to climate-induced changes in autumn temperatures are abrupt and synchronous at a continental scale. We found that when the temperatures increased, birds delayed their mean passage date of autumn migration. Such delay, in addition to an earlier spring migration, suggests that a significant warming may induce an extension of the breeding-area residence time of migratory raptors, which may eventually lead to residency.

  8. Long-term phenological shifts in raptor migration and climate.

    PubMed

    Jaffré, Mikaël; Beaugrand, Grégory; Goberville, Eric; Jiguet, Frédéric; Kjellén, Nils; Troost, Gerard; Dubois, Philippe J; Leprêtre, Alain; Luczak, Christophe

    2013-01-01

    Climate change is having a discernible effect on many biological and ecological processes. Among observed changes, modifications in bird phenology have been widely documented. However, most studies have interpreted phenological shifts as gradual biological adjustments in response to the alteration of the thermal regime. Here we analysed a long-term dataset (1980-2010) of short-distance migratory raptors in five European regions. We revealed that the responses of these birds to climate-induced changes in autumn temperatures are abrupt and synchronous at a continental scale. We found that when the temperatures increased, birds delayed their mean passage date of autumn migration. Such delay, in addition to an earlier spring migration, suggests that a significant warming may induce an extension of the breeding-area residence time of migratory raptors, which may eventually lead to residency. PMID:24223888

  9. Abrupt climate change at the end of the last glacial period inferred from trapped air in polar Ice

    PubMed

    Severinghaus; Brook

    1999-10-29

    The last glacial period was terminated by an abrupt warming event in the North Atlantic approximately 15,000 years before the present, and warming events of similar age have been reported from low latitudes. Understanding the mechanism of this termination requires that the precise relative timing of abrupt climate warming in the tropics versus the North Atlantic be known. Nitrogen and argon isotopes in trapped air in Greenland ice show that the Greenland Summit warmed 9 +/- 3 degrees C over a period of several decades, beginning 14,672 years ago. Atmospheric methane concentrations rose abruptly over a approximately 50-year period and began their increase 20 to 30 years after the onset of the abrupt Greenland warming. These data suggest that tropical climate became warmer or wetter (or both) approximately 20 to 80 years after the onset of Greenland warming, supporting a North Atlantic rather than a tropical trigger for the climate event.

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

    PubMed Central

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

    2006-01-01

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

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

    PubMed

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

    2006-01-24

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

  12. Transient Adjustment of the global climate to an abrupt Northern North Atlantic cooling

    NASA Astrophysics Data System (ADS)

    Tang, G.; Chang, P.; Panetta, R.; Saravanan, R.

    2013-12-01

    The Thermohaline Circulation (THC) is thought to play a key role in abrupt changes in Earth climate. In cold periods such as the Younger Dryas, the THC was much weaker than today. In an experiment with a fully coupled CCSM3 model an artificial freshwater flux is added to the Northern North Atlantic Ocean surface, which weakens the THC. The North Atlantic Ocean surface cools almost instantly after the freshwater flux onset. This cooling is subsequently spread throughout the Northern Hemisphere, resulting in the ITCZ moving southward. In the weakening THC, heat carried by the THC from Southern Hemisphere to the Northern Hemisphere is reduced, resulting in a cooler Northern Hemisphere. It is still questioned what role the atmosphere plays in this process. There are two possible ways the atmosphere may change the ocean surface temperature. One is that the wind changes the ocean surface wind-driven circulation, leading to a change to the ocean heat budget. Another is that the atmosphere changes the ocean-atmosphere heat flux directly. Here we look into the second possibility by comparing the effects of freshwater flux in a fully coupled model to the effects of the same flux in a model constructed by coupling an atmospheric general circulation model (CAM3) to a thermodynamic slab ocean model. With use of appropriate Q-fluxes, the coupled model with the slab ocean has the same climatology as the fully coupled CCSM3 model. Perturbation Q-fluxes are constructed for the fresh water flux experiments using a restoring technique. We find that the atmosphere interacting with a thermodynamic slab ocean can spread the cooling from the Northern North Atlantic and cause the ITCZ to move southward, and that there is a cooling front propagating southward with a speed depending on the mixed layer depth: a deeper mixed layer depth results in a slower propagation. By applying the Q-flux perturbation only in the Northern North Atlantic Ocean, the effect of the ocean circulation change on

  13. Abrupt Holocene climate change as an important factor for human migration in West Greenland

    PubMed Central

    D’Andrea, William J.; Huang, Yongsong; Fritz, Sherilyn C.; Anderson, N. John

    2011-01-01

    West Greenland has had multiple episodes of human colonization and cultural transitions over the past 4,500 y. However, the explanations for these large-scale human migrations are varied, including climatic factors, resistance to adaptation, economic marginalization, mercantile exploration, and hostile neighborhood interactions. Evaluating the potential role of climate change is complicated by the lack of quantitative paleoclimate reconstructions near settlement areas and by the relative stability of Holocene temperature derived from ice cores atop the Greenland ice sheet. Here we present high-resolution records of temperature over the past 5,600 y based on alkenone unsaturation in sediments of two lakes in West Greenland. We find that major temperature changes in the past 4,500 y occurred abruptly (within decades), and were coeval in timing with the archaeological records of settlement and abandonment of the Saqqaq, Dorset, and Norse cultures, which suggests that abrupt temperature changes profoundly impacted human civilization in the region. Temperature variations in West Greenland display an antiphased relationship to temperature changes in Ireland over centennial to millennial timescales, resembling the interannual to multidecadal temperature seesaw associated with the North Atlantic Oscillation. PMID:21628586

  14. Abrupt Climate Events Recorded in Chinese and Central Asian Loess Sequences

    NASA Astrophysics Data System (ADS)

    Machalett, B.; Oches, E. A.; Haam, E. K.; Lai, Z.; Endlicher, W.

    2013-12-01

    of suborbital global climate changes and an initiator of abrupt climate oscillations in the Northern Hemisphere.

  15. Abrupt Climate Events Recorded in Chinese and Central Asian Loess Sequences

    NASA Astrophysics Data System (ADS)

    Machalett, Bjoern; Oches, Eric A.; Haam, Eddie; Lai, Zhongping; Endlicher, Wilfried

    2013-04-01

    of suborbital global climate changes and an initiator of abrupt climate oscillations in the Northern Hemisphere.

  16. Laurentide Ice Sheet meltwater and abrupt climate change during the last glaciation

    SciTech Connect

    Hill, H W; Flower, B P; Quinn, T M; Hollander, D J; Guilderson, T P

    2005-10-02

    A leading hypothesis to explain abrupt climate change during the last glacial cycle calls on fluctuations in the margin of the North American Laurentide Ice Sheet (LIS), which may have routed freshwater between the Gulf of Mexico (GOM) and North Atlantic, affecting North Atlantic Deep Water (NADW) variability and regional climate. Paired measurements of {delta}O and Mg/Ca of foraminiferal calcite from GOM sediments reveal five episodes of LIS meltwater input from 28-45 thousand years ago (ka) that do not match the millennial-scale Dansgaard-Oeschger (D/O) warmings recorded in Greenland ice. We suggest that summer melting of the LIS may occur during Antarctic warming and likely contributed to sea-level variability during Marine Isotope Stage 3 (MIS 3).

  17. The chronology of abrupt climate change and Late Upper Palaeolithic human adaptation in Europe

    NASA Astrophysics Data System (ADS)

    Blockley, S. P. E.; Blockley, S. M.; Donahue, R. E.; Lane, C. S.; Lowe, J. J.; Pollard, A. M.

    2006-07-01

    This paper addresses the possible connections between the onset of human expansion in Europe following the Last Glacial Maximum, and the timing of abrupt climate warming at the onset of the Lateglacial (Bölling/Allerød) Interstadial. There are opposing views as to whether or not human populations and activities were directly forced by climate change, based on different comparisons between archaeological and environmental data. We review the geochronological assumptions and approaches on which data comparisons have been attempted in the past, and argue that the uncertainties presently associated with age models based on calibrated radiocarbon dates preclude robust testing of the competing models, particularly when comparing the data to non-radiocarbon-based timescales such as the Greenland ice core records. The paper concludes with some suggestions as to the steps that will be necessary if more robust tests of the models are to be developed in the future. Copyright

  18. Abrupt climate-triggered lake ecosystem changes recorded in late glacial lake sediments in northern Poland

    NASA Astrophysics Data System (ADS)

    Slowinski, M. M.; Zawiska, I.; Ott, F.; Noryskiewicz, A. M.; Apolinarska, K.; Lutynska, M.; Michczynska, D. J.; Brauer, A.; Wulf, S.; Skubala, P.; Blaszkiewicz, M.

    2013-12-01

    The aim of this study was to better understand how local lake ecosystems responded to abrupt climate changes through applying multi-proxy sediment analyses. Therefore, we carried out a detailed and high-resolution case study on the late glacial sediment from the Trzechowskie palaeolake located in the eastern part of the Pomeranian Lakeland, northern Poland. We reconstructed climate induced environmental changes in the paleolake and its catchment using biotic proxies (macrofossils, pollen, cladocera, diatoms, oribatidae mite) and classical geochemical proxies (δ18O, δ13C, loss-on-ignition, CaCO3 content) in combination with high-resolution μ-XRF element core scanning. The core chronology has been established by means of biostratigraphy, AMS 14C-dating on plant macro remains, varve counting in laminated intervals and tephrochronology. The latter was possible by the discovery of the late Allerød Laacher See Tephra for the first time at such eastern location. Biogenic accumulation in the lake started rather late during the lateglacial interstadial at 13903×170 cal yrs BP. The rapid and pronounced cooling at the beginning of the Younger Dryas had a major impact on the lake and its catchment as clearly reflected by both, biotic and geochemical proxies. The depositional environment of the lake abruptly changed from a varved to massive gytjia. The pronounced warming at the demise of Younger Dryas cooling is well-reflected in all environmental indicators but with conspicuous leads and lags reflecting complex responses of lake ecosystems to climate warming. The research was supported by the National Science Centre Poland - NN306085037. This study is a contribution to the Virtual Institute ICLEA (Integrated Climate and Landscape Evolution Analysis) funded by the Helmholtz Association.

  19. Postglacial Response of Terrestrial Neotropical Vegetation to Abrupt Climate Change as Recorded by Pollen from a Marine Core, Cariaco Basin

    NASA Astrophysics Data System (ADS)

    Delusina, I.; Peterson, L. C.; Spero, H. J.

    2011-12-01

    The response of terrestrial vegetation to the climatic shift that followed the Last Glacial Maximum is a critical component of the Neotropical climate system: it is linked to the carbon cycle and makes it possible to trace the impact of climatic alterations. We analyzed fossil pollen from high-resolution marine core MD03-2620 from the anoxic Cariaco Basin, off the coast of Venezuela. The study covers the period from Last Glacial Maximum (LGM) to the mid-Holocene. Previous paleoreconstructions from Cariaco Basin sediments emphasized that the abrupt climatic change that followed the LGM was associated with a shift of the ITCZ, subsequent sea level oscillations and alteration in a thermohaline circulation. We maintain that pollen from the marine core reflects vegetation trends of a large regional area, which smooths out local peculiarities in vegetation and allows us to trace the Cold/Dry-Warm/Wet dynamic in the pollen assemblages of the Cariaco sediments. Our pollen analysis indicates an interval of clear dominance of C4-type plants between ca 19.0 - 17.5 kyr BP, representing the transition from salt-marshes to steppe/savanna on the lowland. The onset of the Mystery Interval MI (17.5 to ~14.5 kyr BP) caused the most dramatic changes in vegetation for all postglacial time and was characterized sequentially by both a wet and dry signal, resulting in the reduction of forest vegetation, and later with the expansion of salt marshes in the littoral zone. According to the pollen data, MI consisted of two clearly recognized parts with a bridge in the middle: 1) H1-a. Dry interval between ~17.5 and 16.5 kyr BP with gradually growing humidity, that reaches a plateau at ~16.6 kyr BP. 2) Middle of the MI: ~ 16.5 - 15.8 kyr BP, exhibiting warm, humid conditions. 3) H1-b. Dry period after ~15.8 kyr BP, to ~14.5 kyr BP. The largest abrupt change in the pollen record is the transition to the Bølling/Allerød Stade, where our results are well correlated with plant wax biomarker

  20. Vegetation zones shift in changing climate

    NASA Astrophysics Data System (ADS)

    Belda, Michal; Halenka, Tomas; Kalvova, Jaroslava; Holtanova, Eva

    2016-04-01

    The analysis of climate patterns can be performed for each climate variable separately or the data can be aggregated using e.g. some kind of climate classification. These classifications usually correspond to vegetation distribution in the sense that each climate type is dominated by one vegetation zone or eco-region. In case of the Köppen-Trewartha classification it is integrated assessment of temperature and precipitation together with their annual cycle as well. This way climate classifications also represent a convenient tool for the assessment and validation of climate models and for the analysis of simulated future climate changes. The Köppen-Trewartha classification is used on full CMIP5 family of more than 40 GCM simulations and CRU dataset for comparison. This evaluation provides insight on the GCM performance and errors for simulations of the 20th century climate. Common regions are identified, such as Australia or Amazonia, where many state-of-the-art models perform inadequately. Furthermore, the analysis of the CMIP5 ensemble for RCP 4.5 and 8.5 is performed to assess the climate change for future. There are significant changes for some types in most models e.g. increase of savanna and decrease of tundra for the future climate. For some types significant shifts in latitude can be seen when studying their geographical location in selected continental areas, e.g. toward higher latitudes for boreal climate. For Europe, EuroCORDEX results for both 0.11 and 0.44 degree resolution are validated using Köppen-Trewartha types in comparison to E-OBS based classification. ERA-Interim driven simulations are compared to both present conditions of CMIP5 models as well as their downscaling by EuroCORDEX RCMs. Finally, the climate change signal assessment is provided using the individual climate types. In addition to the changes assessed similarly as for GCMs analysis in terms of the area of individual types, in the continental scale some shifts of boundaries

  1. Abrupt Climate Changes Caused by a Collapse of the North Atlantic Thermohaline Circulation: Implications for Optimal Economic Climate Policies

    NASA Astrophysics Data System (ADS)

    Keller, K.; Bradford, D. F.

    2001-12-01

    Climate modelers have recognized the possibility of abrupt climate changes caused by a collapse of the North Atlantic thermohaline circulation (THC). This circulation system now warms northwestern Europe and transports carbon dioxide to the deep oceans. The posited THC collapse could produce severe cooling in northwestern Europe, even when general global warming is in progress. Here we use a simple integrated assessment model to investigate the optimal policy response to this risk. Our analysis shows that significantly reducing carbon dioxide emissions may be justified to avoid or delay even small (and arguably realistic) damages from an uncertain THC collapse. Detecting a change in the THC before a potential collapse enables the policy maker to improve climate policy (as measured by an increased per-capita consumption). The considerable economic value of detecting a potential THC collapse early enough has implications for the design of an ocean observation system.

  2. Abrupt Climate Change and the Atlantic Meridional Overturning Circulation: sensitivity and non-linear response to Arctic/sub-Arctic freshwater pulses. Collaborative research. Final report

    SciTech Connect

    Hill, Christopher

    2015-06-15

    This project investigated possible mechanisms by which melt-water pulses can induce abrupt change in the Atlantic Meridional Overturning Circulation (AMOC) magnitude. AMOC magnitude is an important ingredient in present day climate. Previous studies have hypothesized abrupt reduction in AMOC magnitude in response to influxes of glacial melt water into the North Atlantic. Notable fresh-water influxes are associated with the terminus of the last ice age. During this period large volumes of melt water accumulated behind retreating ice sheets and subsequently drained rapidly when the ice weakened sufficiently. Rapid draining of glacial lakes into the North Atlantic is a possible origin of a number of paleo-record abrupt climate shifts. These include the Younger-Dryas cooling event and the 8,200 year cooling event. The studies undertaken focused on whether the mechanistic sequence by which glacial melt-water impacts AMOC, which then impacts Northern Hemisphere global mean surface temperature, is dynamically plausible. The work has implications for better understanding past climate stability. The work also has relevance for today’s environment, in which high-latitude ice melting in Greenland appears to be driving fresh water outflows at an accelerating pace.

  3. Abrupt Transitions in Climate Throughout the Holocene from a Lake Sediment Record in se Greenland

    NASA Astrophysics Data System (ADS)

    de Wet, G.; Bradley, R. S.; Balascio, N. L.

    2012-12-01

    Arctic climate variability over the Holocene has been both extensive and, at times, abrupt. Current understanding of these changes is still quite limited with few high-resolution paleoclimate records available for this period. In order to place observed and predicted 21st century climate change in perspective, reliable and highly resolved paleo-reconstructions of Arctic climate are essential. Using an 8.5 m sediment core from Nanerersarpik Lake, this project will characterize climate changes during the Holocene, including the deglacial transition, the rapid changes that are known to have occurred around 8,200 years ago, the transition from Holocene thermal maximum (HTM) to the colder Neoglacial period, and intervals of abrupt climate change during the late Holocene such as the Medieval Warm Period and Little Ice Age. The 8.5 m sediment core from Nanerersarpik contains a dense gray clay in the lower 0.5m. The upper 8.0m of sediment is light brown and organic-rich with centimeter to half-centimeter laminations, interrupted by mass-movement events. Paleoenvironmental conditions have been interpreted using magnetic susceptibility, grain size, biogenic silica, TOC, C/N, and δ13Corg, as well as with high-resolution spectral reflectance and scanning XRF profiles. These parameters allow us to interpret changes in autochthonous productivity and clastic input throughout the Holocene. A chronology for the record has been established using 210Pb and 11 radiocarbon dates. Cryptotephra analysis will also be carried out to improve the chronology during the Late Holocene. The age-model indicates Nanerersarpik Lake contains an ~8,500-yr sediment record with a linear age/depth relationship and a sedimentation rate of 0.1cm/yr, allowing for potentially decadal scale resolution of environmental changes. Preliminary results show an abrupt transition from dense glacial clay to laminated organic rich sediment near the base of the core. This is interpreted as marking the retreat of

  4. Abrupt shifts in the fish community of the hydrologically variable upper estuary of the Swan River

    NASA Astrophysics Data System (ADS)

    Kanandjembo, A. N.; Potter, I. C.; Platell, M. E.

    2001-09-01

    Fish were sampled in nearshore, shallow waters (<1·5 m deep) and offshore, deeper waters (2·5-5 m) of the saline lower reaches of the Swan and Canning Rivers, which collectively represent the upper Swan-Canning Estuary, by using seine and gill nets, respectively, in each season between winter 1995 and autumn 1997. Seventeen of the 34 fish species caught during the study spawn in the upper estuaries. These species, which include the semi-anadromous Nematalosa vlaminghi, comprised 50·0% of the number of species and 88·8% of the number of fish in shallow waters and 43·8 and 89·9%, respectively, of those in deeper waters. The two most abundant species in shallow waters, Engraulis australis and N. vlaminghi, contributed 36·0 and 19·6%, respectively, to the total numbers of fish in those waters, and the latter species comprised nearly 50% of the catch in deeper waters. During winter, when freshwater discharge increased sharply and salinities declined precipitously, the number of species and abundance of fish in shallow and deeper waters were generally at their lowest and the species composition was the most discrete. This reflected the downstream movement out of the upper estuary of substantial numbers of individuals of species such as N. vlaminghi, Acanthopagrus butcheri, Amniataba caudavittata, Atherinomorus ogilbyi, Atherinosoma elongata and Craterocephalus mugiloides and the upstream movement into the upper estuary of juvenile Mugil cephalus. The overall fish fauna then changed quite abruptly in spring, when large N. vlaminghi, A. butcheri and A. caudavittata became abundant as they migrated into the upper estuary where they then spawned. During summer and autumn, the fauna in the shallows then changed more gradually through, inter alia, the recruitment of juvenile abrupt change in the fish community in winter contrasts with the

  5. An abrupt and prominent climatic reversal at 9.2 ka in the northeastern North America

    NASA Astrophysics Data System (ADS)

    Hou, J.; Huang, Y.; Shuman, B. N.; Oswald, W.; Foster, D. R.

    2008-12-01

    Continental climate during the early Holocene (from 10 to 7 ka) is characterized by multiple abrupt climatic reversals such as the well-known 8.2 ka event that has been observed worldwide and attributed to the terminal collapse of the Laurentide Ice Sheet (LIS) in the North American continent. However, many episodes of meltwater releases occurred prior to the final collapse of LIS, their impact on the continental climate is much less understood. We present in this paper decadal-scale hydrogen isotopic records of aquatic and terrestrial plant biomarkers from Blood Pond, Massachusetts during the early Holocene. Our isotopic records infer a cooling of 3~4 degree between 9.3 and 9.1 ka against the millennial scale climate background, mainly induced by changes in precipitation seasonality. In comparison, the 8.2 ka event displays smaller amplitude of temperature cooling of 1~2 degree at our southern New England site. We interpret our observed climatic reversal at ~ 9.2 ka as representing increased proportion of winter precipitation in conjunction with a drier and cooler summer, triggered by slowdown in thermohaline circulation as a result of freshwater release from the proglacial lakes. We attribute the difference in climate response at 8.2 ka and 9.2 ka events to the configuration of LIS, with 9.2 ka LIS having a much stronger blocking effect on the moisture from the Gulf of Mexico during the summer. Our data suggest that the seasonality of the precipitation at the southern New England was highly sensitive to meltwater releases, especially prior to the final collapse of the LIS.

  6. Abrupt climate changes for Iceland during the last millennium: Evidence from high resolution sea ice reconstructions

    NASA Astrophysics Data System (ADS)

    Massé, Guillaume; Rowland, Steven J.; Sicre, Marie-Alexandrine; Jacob, Jeremy; Jansen, Eystein; Belt, Simon T.

    2008-05-01

    A high resolution account of Icelandic sea ice over the last millennium has been constructed using a novel proxy based on the presence in sediments of a biomarker (IP 25) produced by sea ice algae. Comparison with historical sea ice records demonstrates a strong correlation between documented sea ice occurrences and the IP 25 proxy. An excellent agreement is also observed between the IP 25 record and a diatom-based sea surface temperature reconstruction obtained from the same core and the Crowley and Lowery Northern Hemisphere temperature reconstruction. Using this approach, we provide new historical sea ice data for periods where records are scarce or absent and evidence for abrupt changes to sea ice and/or climate conditions around Iceland during the Little Ice Age.

  7. Impact of abrupt deglacial climate change on tropical Atlantic subsurface temperatures.

    PubMed

    Schmidt, Matthew W; Chang, Ping; Hertzberg, Jennifer E; Them, Theodore R; Ji, Link; J, Link; Otto-Bliesner, Bette L

    2012-09-01

    Both instrumental data analyses and coupled ocean-atmosphere models indicate that Atlantic meridional overturning circulation (AMOC) variability is tightly linked to abrupt tropical North Atlantic (TNA) climate change through both atmospheric and oceanic processes. Although a slowdown of AMOC results in an atmospheric-induced surface cooling in the entire TNA, the subsurface experiences an even larger warming because of rapid reorganizations of ocean circulation patterns at intermediate water depths. Here, we reconstruct high-resolution temperature records using oxygen isotope values and Mg/Ca ratios in both surface- and subthermocline-dwelling planktonic foraminifera from a sediment core located in the TNA over the last 22 ky. Our results show significant changes in the vertical thermal gradient of the upper water column, with the warmest subsurface temperatures of the last deglacial transition corresponding to the onset of the Younger Dryas. Furthermore, we present new analyses of a climate model simulation forced with freshwater discharge into the North Atlantic under Last Glacial Maximum forcings and boundary conditions that reveal a maximum subsurface warming in the vicinity of the core site and a vertical thermal gradient change at the onset of AMOC weakening, consistent with the reconstructed record. Together, our proxy reconstructions and modeling results provide convincing evidence for a subsurface oceanic teleconnection linking high-latitude North Atlantic climate to the tropical Atlantic during periods of reduced AMOC across the last deglacial transition. PMID:22908256

  8. An abrupt climate event in a coupled ocean-atmosphere simulation without external forcing.

    PubMed

    Hall, A; Stouffer, R J

    2001-01-11

    Temperature reconstructions from the North Atlantic region indicate frequent abrupt and severe climate fluctuations during the last glacial and Holocene periods. The driving forces for these events are unclear and coupled atmosphere-ocean models of global circulation have only simulated such events by inserting large amounts of fresh water into the northern North Atlantic Ocean. Here we report a drastic cooling event in a 15,000-yr simulation of global circulation with present-day climate conditions without the use of such external forcing. In our simulation, the annual average surface temperature near southern Greenland spontaneously fell 6-10 standard deviations below its mean value for a period of 30-40 yr. The event was triggered by a persistent northwesterly wind that transported large amounts of buoyant cold and fresh water into the northern North Atlantic Ocean. Oceanic convection shut down in response to this flow, concentrating the entire cooling of the northern North Atlantic by the colder atmosphere in the uppermost ocean layer. Given the similarity between our simulation and observed records of rapid cooling events, our results indicate that internal atmospheric variability alone could have generated the extreme climate disruptions in this region. PMID:11196636

  9. Impact of abrupt deglacial climate change on tropical Atlantic subsurface temperatures

    PubMed Central

    Schmidt, Matthew W.; Chang, Ping; Hertzberg, Jennifer E.; Them, Theodore R.; Ji, Link; Otto-Bliesner, Bette L.

    2012-01-01

    Both instrumental data analyses and coupled ocean-atmosphere models indicate that Atlantic meridional overturning circulation (AMOC) variability is tightly linked to abrupt tropical North Atlantic (TNA) climate change through both atmospheric and oceanic processes. Although a slowdown of AMOC results in an atmospheric-induced surface cooling in the entire TNA, the subsurface experiences an even larger warming because of rapid reorganizations of ocean circulation patterns at intermediate water depths. Here, we reconstruct high-resolution temperature records using oxygen isotope values and Mg/Ca ratios in both surface- and subthermocline-dwelling planktonic foraminifera from a sediment core located in the TNA over the last 22 ky. Our results show significant changes in the vertical thermal gradient of the upper water column, with the warmest subsurface temperatures of the last deglacial transition corresponding to the onset of the Younger Dryas. Furthermore, we present new analyses of a climate model simulation forced with freshwater discharge into the North Atlantic under Last Glacial Maximum forcings and boundary conditions that reveal a maximum subsurface warming in the vicinity of the core site and a vertical thermal gradient change at the onset of AMOC weakening, consistent with the reconstructed record. Together, our proxy reconstructions and modeling results provide convincing evidence for a subsurface oceanic teleconnection linking high-latitude North Atlantic climate to the tropical Atlantic during periods of reduced AMOC across the last deglacial transition. PMID:22908256

  10. Impact of abrupt deglacial climate change on tropical Atlantic subsurface temperatures.

    PubMed

    Schmidt, Matthew W; Chang, Ping; Hertzberg, Jennifer E; Them, Theodore R; Ji, Link; J, Link; Otto-Bliesner, Bette L

    2012-09-01

    Both instrumental data analyses and coupled ocean-atmosphere models indicate that Atlantic meridional overturning circulation (AMOC) variability is tightly linked to abrupt tropical North Atlantic (TNA) climate change through both atmospheric and oceanic processes. Although a slowdown of AMOC results in an atmospheric-induced surface cooling in the entire TNA, the subsurface experiences an even larger warming because of rapid reorganizations of ocean circulation patterns at intermediate water depths. Here, we reconstruct high-resolution temperature records using oxygen isotope values and Mg/Ca ratios in both surface- and subthermocline-dwelling planktonic foraminifera from a sediment core located in the TNA over the last 22 ky. Our results show significant changes in the vertical thermal gradient of the upper water column, with the warmest subsurface temperatures of the last deglacial transition corresponding to the onset of the Younger Dryas. Furthermore, we present new analyses of a climate model simulation forced with freshwater discharge into the North Atlantic under Last Glacial Maximum forcings and boundary conditions that reveal a maximum subsurface warming in the vicinity of the core site and a vertical thermal gradient change at the onset of AMOC weakening, consistent with the reconstructed record. Together, our proxy reconstructions and modeling results provide convincing evidence for a subsurface oceanic teleconnection linking high-latitude North Atlantic climate to the tropical Atlantic during periods of reduced AMOC across the last deglacial transition.

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

    NASA Astrophysics Data System (ADS)

    Ristvet, L.

    2003-12-01

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

  12. Shifting seasons, climate change and ecosystem consequences

    NASA Astrophysics Data System (ADS)

    Thackeray, Stephen; Henrys, Peter; Hemming, Deborah; Huntingford, Chris; Bell, James; Leech, David; Wanless, Sarah

    2014-05-01

    In recent decades, the seasonal timing of many biological events (e.g. flowering, breeding, migration) has shifted. These phenological changes are believed to be one of the most conspicuous biological indicators of climate change. Rates and directions of phenological change have differed markedly among species, potentially threatening the seasonal synchrony of key species interactions and ultimately ecosystem functioning. Differences in phenological change among-species at different trophic levels, and with respect to other broad species traits, are likely to be driven by variations in the climatic sensitivity of phenological events. However, as yet, inconsistencies in analytical methods have hampered broad-scale assessments of variation in climate sensitivity among taxonomic and functional groups of organisms. In this presentation, results will be presented from a current collaborative project (http://www.ceh.ac.uk/sci_programmes/shifting-seasons-uk.html) in which many UK long-term data sets are being integrated in order to assess relationships between temperature/precipitation, and the timing of seasonal events for a wide range of plants and animals. Our aim is to assess which organism groups (in which locations/habitats) are most sensitive to climate. Furthermore, the role of anthropogenic climate change as a driver of phenological change is being assessed.

  13. North Atlantic Meridional Overturning Circulation (AMOC) and Abrupt Climate Change through the Last Glaciation

    NASA Astrophysics Data System (ADS)

    Henry, G., III; McManus, J. F.; Curry, W. B.; Keigwin, L. D.; Giosan, L.

    2014-12-01

    The climate of the glacial North Atlantic was punctuated by catastrophic discharges of icebergs (Heinrich events), as well as by more mysterious, abrupt warming events associated with Dansgaard-Oeschger oscillations. These events are suspected to be related to changes in AMOC and its influence on heat transport and the regional and global heat budget. Investigation of these rapid oscillations is often limited by the resolution of sediment records. High accumulation rates at our study site (33.69°N, 57.58°W, 4583m water depth) on the Bermuda Rise allow improved resolution by one to two orders of magnitude. Cores CDH19 (38.81m) and CDH13 (36.70m), were recovered during KNR191, the initial deployment of the RV Knorr's long coring system developed at the Woods Hole Oceanographic Institution with support from the NSF. These cores contain high quality sediment sections that allow high resolution studies extending through the last glacial cycle at a key location for monitoring past oceanographic and climatic variability. Here we present detailed multi-proxy data from Bermuda Rise sediments reflecting deep ocean chemistry and dynamics of the last glaciation, and combine them with published data to produce a continuous, high resolution record spanning the last 70,000 years. CaCO3 burial fluxes, foraminifera stable isotopes, and sedimentary uranium-series disequilibria (including seawater-derived 231Pa /230Th), display coherent, complementary variability throughout the last glaciation. Glacial values in each proxy are consistent with reduced ventilation and overturning compared to the Holocene, with intervals that indicate substantial millennial reductions in each, and others when they briefly approach Holocene levels. In multiple instances, particularly spanning interstadials eight through twelve (IS8-IS12) our results are consistent with an abrupt, subcentennial acceleration in the export of excess 231Pa from the North Atlantic during stadial-interstadial transitions

  14. Impact of Climate and Fires on Abrupt Permafrost Thaw in Alaskan Tundra

    NASA Astrophysics Data System (ADS)

    Chipman, M. L.; Reents, C.; Greenberg, J. A.; Hu, F.

    2015-12-01

    Thermo-erosion from abrupt permafrost thaw is a key pulse disturbance in the Arctic that may impact the global carbon cycle. Abrupt thaw can occur when the permafrost active layer expands in response to climate warming and/or increased wildfire activity. Understanding these drivers of thermo-erosion is necessary to anticipate feedbacks in the Arctic, where summer temperature and fire frequency are predicted to increase. We examine modern and late-Holocene thermo-erosion in high-fire (Noatak) and low-fire (North Slope) tundra ecoregions of Alaska using a combination of remote-sensing and paleo-records. Lakes with active thaw features were identified through Landsat-7 image classification and time-series analysis based on observed 0.52-0.60 μm reflectance peaks following slump formation. We identified 1067 and 1705 lakes with active features between CE 2000-2012 in the Noatak and North Slope ecoregions, respectively. The density of features was higher in the highly flammable Noatak (0.04 versus 0.01 features km-2, respectively), suggesting that warmer climate and/or fires likely promote high thermo-erosional activity at present. To assess modern signals of thermo-erosion and identify past events, we analyzed soil profiles and lake-sediment cores from both ecoregions using X-ray fluorescence. The ratios of Ca:K and Ca:Sr increased with depth in permafrost soils, were higher in soils from younger versus older slump surfaces, and were significantly correlated with the ratio of carbonate to feldspar and clay minerals in lake sediments (r=0.96 and 0.93, P<0.0001, n=15). We interpret past increases in Ca:K, Ca:Sr, and δ13C as enhanced weathering of carbonate-rich permafrost soils associated with thermo-erosion. At the North Slope site, we identified ten episodes of thermoerosion over the past 6000 years and found strong correspondence to summer temperature trends. Events were more frequent at the Noatak site, where 15 thermo-erosional episodes and 26 fires occurred over

  15. Abrupt shift in δ18O values at Medicine Lake volcano (California, USA)

    USGS Publications Warehouse

    Donnelly-Nolan, J. M.

    1998-01-01

     Oxygen-isotope analyses of lavas from Medicine Lake volcano (MLV), in the southern Cascade Range, indicate a significant change in δ18O in Holocene time. In the Pleistocene, basaltic lavas with <52% SiO2 averaged +5.9‰, intermediate lavas averaged +5.7‰, and silicic lavas (≥63.0%SiO2) averaged +5.6‰. No analyzed Pleistocene rhyolites or dacites have values greater than +6.3‰. In post-glacial time, basalts were similar at +5.7‰ to those erupted in the Pleistocene, but intermediate lavas average +6.8‰ and silicic lavas +7.4‰ with some values as high as +8.5‰. The results indicate a change in the magmatic system supplying the volcano. During the Pleistocene, silicic lavas resulted either from melting of low-18O crust or from fractionation combined with assimilation of very-low-18O crustal material such as hydrothermally altered rocks similar to those found in drill holes under the center of the volcano. By contrast, Holocene silicic lavas were produced by assimilation and/or wholesale melting of high-18O crustal material such as that represented by inclusions of granite in lavas on the upper flanks of MLV. This sudden shift in assimilant indicates a fundamental change in the magmatic system. Magmas are apparently ponding in the crust at a very different level than in Pleistocene time.

  16. Abrupt climate changes in northwestern Colombia during the Lateglacial and Holocene transition

    NASA Astrophysics Data System (ADS)

    Velasquez Ruiz, C.

    2013-05-01

    High resolution pollen/spores records from Paramo de Frontino (6, 29N, 76, 6W) and Paramo de Belmira (6,42'N, 75,40'W) in Colombia (Velásquez C. and H. Hooghiemstra, Paleobotany, 2012 in press; Velásquez C., et al., in preparation) spanning 17300 and 34000 cal yr BP; are studied for abrupt climatic change and compared with a La Cocha diatom record (Gonzalez, Z, et al., 2012), Frontino and Cariaco Basin (offshore Venezuela) titanium records and a Cariaco sea surface temperatures record (Gorin, G., et al, in preparation; Haug, et al., 2001; Lea D., et al., 2003; respectively); in reference to detected vegetation and climate variations. The most remarkable events occurred at 8200, 9300, 10400, 12000, 13500, 14.5-14.7, 16.2 and 21.4 cal yr BP. Low frequency cycles of 1500-2500 yr are present along the records suggesting that the North Atlantic Bond Cycles are also registered in northwestern South American terrestrial records. Some of these changes were dry while others wet, showing that both patterns "Cold poles, dry tropics" and "Cold poles, wet tropics" can be expressed. It was also found that the estimated temperatures from Paramo de Frontino (pollen based) and sea surface temperatures in Cariaco followed a similar trend during the the Late Glacial and Early Holocene. However, in the case of moisture, the Titanium record (indicative of rainfall) from the Cariaco Basin, the aquatic vegetation pollen and titanium records from Paramo de Frontino and diatoms record from La Cocha lake, showed a clear antiphase behavior during the same periods. Position and shape of Intertropical Convergence Zone are postulated as responsible for this variation. Keywords: palinology, Intertropical Convergence Zone, titanium, Colombia, climatic and vegetation changes.

  17. Reducing abrupt climate change risk using the Montreal Protocol and other regulatory actions to complement cuts in CO2 emissions.

    PubMed

    Molina, Mario; Zaelke, Durwood; Sarma, K Madhava; Andersen, Stephen O; Ramanathan, Veerabhadran; Kaniaru, Donald

    2009-12-01

    Current emissions of anthropogenic greenhouse gases (GHGs) have already committed the planet to an increase in average surface temperature by the end of the century that may be above the critical threshold for tipping elements of the climate system into abrupt change with potentially irreversible and unmanageable consequences. This would mean that the climate system is close to entering if not already within the zone of "dangerous anthropogenic interference" (DAI). Scientific and policy literature refers to the need for "early," "urgent," "rapid," and "fast-action" mitigation to help avoid DAI and abrupt climate changes. We define "fast-action" to include regulatory measures that can begin within 2-3 years, be substantially implemented in 5-10 years, and produce a climate response within decades. We discuss strategies for short-lived non-CO(2) GHGs and particles, where existing agreements can be used to accomplish mitigation objectives. Policy makers can amend the Montreal Protocol to phase down the production and consumption of hydrofluorocarbons (HFCs) with high global warming potential. Other fast-action strategies can reduce emissions of black carbon particles and precursor gases that lead to ozone formation in the lower atmosphere, and increase biosequestration, including through biochar. These and other fast-action strategies may reduce the risk of abrupt climate change in the next few decades by complementing cuts in CO(2) emissions.

  18. Reducing abrupt climate change risk using the Montreal Protocol and other regulatory actions to complement cuts in CO2 emissions

    PubMed Central

    Molina, Mario; Zaelke, Durwood; Sarma, K. Madhava; Andersen, Stephen O.; Ramanathan, Veerabhadran; Kaniaru, Donald

    2009-01-01

    Current emissions of anthropogenic greenhouse gases (GHGs) have already committed the planet to an increase in average surface temperature by the end of the century that may be above the critical threshold for tipping elements of the climate system into abrupt change with potentially irreversible and unmanageable consequences. This would mean that the climate system is close to entering if not already within the zone of “dangerous anthropogenic interference” (DAI). Scientific and policy literature refers to the need for “early,” “urgent,” “rapid,” and “fast-action” mitigation to help avoid DAI and abrupt climate changes. We define “fast-action” to include regulatory measures that can begin within 2–3 years, be substantially implemented in 5–10 years, and produce a climate response within decades. We discuss strategies for short-lived non-CO2 GHGs and particles, where existing agreements can be used to accomplish mitigation objectives. Policy makers can amend the Montreal Protocol to phase down the production and consumption of hydrofluorocarbons (HFCs) with high global warming potential. Other fast-action strategies can reduce emissions of black carbon particles and precursor gases that lead to ozone formation in the lower atmosphere, and increase biosequestration, including through biochar. These and other fast-action strategies may reduce the risk of abrupt climate change in the next few decades by complementing cuts in CO2 emissions. PMID:19822751

  19. Rapid Climate Shifts during last Deglaciation over Central to Northern Europe

    NASA Astrophysics Data System (ADS)

    Schenk, F.; Muschitiello, F.; Brandefelt, J.; Wohlfarth, B.; Tarasov, L.; Naslund, J. O.; Johansson, A. V.

    2014-12-01

    Abrupt climate shifts during the last deglaciation provide test cases for analyzing the transient response of our climate system to changes in external forcings and internal feedbacks. The regional imprints of rapid climate shifts, their timing and hence connection to local vs. large-scale mechanisms are however still poorly understood owing to a limited number of records with usually large age uncertainties and low sampling rates. In this study we examine the spatiotemporal evolution of rapid climate shifts over central Europe and Scandinavia during Bølling-Allerød (14.7-12.7kyr BP) and Younger Dryas (~12kyr BP) by means of pollen data and climate simulations. For a better understanding of physical mechanisms behind regional imprints of climate shifts, time slice experiments with the Community Earth System Model (CCSM1.0.5) are set up at high resolution (1°x1°) using different topographies and ice sheets (ICE-5G and a new version of GLAC). Matching these time slice experiments with the spatial temperature pattern derived from pollen records, we estimate the extent to which environmental conditions (pollen) represent the direct large-scale influence of climate over the Euro-Atlantic sector vs. regional-scale climate effects e.g. caused by shrinking ice sheets and coastal transgression due to sea-level rise.

  20. Abrupt Climate Change Caused by Global Fires from a Large Meteor Impact

    NASA Astrophysics Data System (ADS)

    Bardeen, C.; Toon, O. B.; Garcia, R. R.; Otto-Bliesner, B. L.; Wolf, E. T.

    2015-12-01

    Global or near-global fires like those that are thought to have occurred after the Chicxulub asteroid impact are associated with abrupt climate change and the K-Pg mass extinction event. Using the Community Earth System Model (CESM), a three-dimensional coupled climate model with interactive chemistry, we have simulated the climate response to global fires assuming a burden of 70,000 Tg, as estimated from the K-Pg layer sediments by Wolbach et al. (1988). Soot aerosols are lofted by solar heating and remain in the atmosphere for about 6 years, warming the stratosphere by more than 240 K and suppressing completely solar radiation at the surface for 2 years. Global average land surface temperatures cool by -28 K after 3 years and ocean temperatures by -11 K after 4 years. Precipitation is reduced by 80 % for 5 years, and the ozone column is reduced by 80 % for 4 years. The tropical tropopause cold point disappears for a few years, leading to water vapor mixing ratios of > 1000 ppmv in the stratosphere. There is a rapid recovery around year 6, when the soot is removed by wet deposition as stratospheric water condenses and precipitates, but this is followed by a peak in the UV Index in the tropics of over 40 before stratospheric ozone recovers. Ocean temperature cools by more than -2 K to a depth of 300 m, and sea ice develops in the Black Sea, Caspian Sea, and Baltic Sea. Global fires, two years of darkness, extreme surface cooling, significant ocean cooling, increases in sea ice extent and a large short-term increase in UV Index would have been catastrophic for many life forms. This work is the first step in an effort to simulate the climatic effects of all of the aerosols and gases that may have been generated by the Chicxulub impact in a model that has been configured for late-Cretaceous conditions to help assess the role of the Chicxulub impact in the K-Pg extinction.

  1. Early Heritage-Language Education and the Abrupt Shift to a Dominant-Language Classroom: Impact on the Personal and Collective Esteem of Inuit Children in Arctic Quebec

    ERIC Educational Resources Information Center

    Bougie, Evelyne; Wright, Stephen C.; Taylor, Donald M.

    2003-01-01

    This research explored the impact of the abrupt shift from heritage-language to dominant-language education on Inuit children's personal and collective self-esteem. Specifically, the following question was addressed: will early heritage-language education serve as an inoculation against the potential negative impact of being submerged in a…

  2. 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

  3. Abrupt Late Holocene Shift in Atmospheric Circulation Recorded by Mineral Dust in the Siple Dome Ice Core, Antarctica

    NASA Astrophysics Data System (ADS)

    Koffman, B. G.; Goldstein, S. L.; Kaplan, M. R.; Winckler, G.; Bory, A. J. M.; Biscaye, P.

    2015-12-01

    Atmospheric dust directly influences Earth's climate by altering the radiative balance and by depositing micronutrients in the surface ocean, affecting global biogeochemical cycling. In addition, mineral dust particles provide observational evidence constraining past atmospheric circulation patterns. Because dust can originate from both local and distant terrestrial sources, knowledge of dust provenance can substantially inform our understanding of past climate history, atmospheric transport pathways, and differences in aerosol characteristics between glacial and interglacial climate states. Dust provenance information from Antarctic ice cores has until now been limited to sites in East Antarctica. Here we present some of the first provenance data from West Antarctica. We use Sr-Nd isotopes to characterize dust extracted from late Holocene ice (~1000-1800 C.E.) from the Siple Dome ice core. The data form a tight array in Sr-Nd isotope space, with 87Sr/86Sr ranging between ~0.7087 and 0.7102, and ɛNd ranging between ~ -7 and -16. This combination is unique for Antarctica, with low Nd and low Sr isotope ratios compared to high-elevation East Antarctic sites, requiring a dust source from ancient (Archean to early Proterozoic) and unweathered continental crust, which mixes with young volcanic material. Both components are likely sourced from Antarctica. We also observe significant, systematic variability in Sr and Nd isotopic signatures through time, reflecting changes in the mixing ratio of these sources, and hypothesize that these changes are driven by shifts in circulation patterns. A large change occurs over about 10 years at ca. 1125 C.E. (ΔɛNd = +3 and Δ87Sr/86Sr = -0.0014). This shift coincides with changes in climate proxies in Southern Hemisphere paleoclimate records reflecting variability in the Westerlies. We therefore interpret the shift in dust provenance at Siple Dome to be related to larger-scale circulation changes. In general, the observed shifts

  4. Dansgaard-Oeschger-like abrupt climate transition in a coupled GCM

    NASA Astrophysics Data System (ADS)

    Tziperman, E.; Eisenman, I.; Bitz, C.

    2006-12-01

    The last glaciation (80-10 kyr BP) was punctuated by dramatic switches between warm and cold climates characterized by abrupt warming events recorded in Greenland ice cores. A leading hypothesis attributes these Dansgaard-Oeschger (DO) events to internal variability in the North Atlantic meridional overturning circulation (MOC), but theories have struggled to explain how these changes in MOC are capable of inducing such a large signal in Greenland. We present the results of two simulations using the CCSM3 coupled atmosphere-ocean-sea ice model. Both simulations are forced by land ice distributions characteristic of periods midway between glacial and interglacial states, but one simulation is initialized with a warm interglacial ocean initial condition while the other has a cold glacial ocean initial condition. The main difference between the surface temperatures in the two simulations is the presence of a warm region covering southern Greenland and the Greenland and Norwegian Seas in the warm-initiated simulation. The simulations have differing MOC for about 700 years which appears to cause differences in sea ice cover leading to an annual mean temperature disparity of 10° C in southern Greenland, in agreement with proxy reconstructions of the temperature change associated with DO events. The cold-initiated simulation quickly adjusts to a fairly constant state characterized by weak MOC, large sea ice area, and cold Greenland temperature. In contrast to this, the warm-initiated simulation displays an initial excitation of the MOC amplitude which then decreases over the next several hundred years. At this point we reduce the CO2 by 15ppm to represent further evolution of a developing glaciation, after which the MOC grows and then gradually decreases again. These results provide falsifiable predictions regarding the regional and seasonal distribution of DO events which can be compared directly with proxy data.

  5. Continuous methane record of abrupt climate change 10-68 ka: sighting Heinrich events in the ice core record

    NASA Astrophysics Data System (ADS)

    Rhodes, Rachael; Brook, Edward; Chiang, John; Blunier, Thomas; Cheng, Hai; Edwards, R. Lawrence; Maselli, Olivia; McConnell, Joseph; Romanini, Daniele; Severinghaus, Jeffrey; Sowers, Todd; Stowasser, Christopher

    2014-05-01

    The Last Glacial period was punctuated by millennial scale abrupt climate changes - Dansgaard-Oeschger (D-O) cycles and Heinrich events. Controls on the magnitude and frequency of these climate perturbations, and how they may be inter-related, remain unclear. Specific problems include the difficulty of dating Heinrich sediment layers and local bias of key paleoclimate archives. We present a highly detailed and precise record of ice core methane (CH4), a globally integrated signal, which resolves climatic features in unprecedented resolution. Abrupt CH4 increases are resolved in Heinrich Stadials (HS) 1, 2, 4 and 5 where, in contrast to all D-O cycles, there are no concurrent abrupt changes in Greenland temperature. Using modern-day tropical rainfall variability as an analog, we propose that strong cooling in the North Atlantic severely restricted the northerly range of the Intertropical Convergence Zone (ITCZ), leading to an enhanced wet season over Southern Hemisphere tropical land areas, and consequently driving production of excess CH4 in tropical wetlands. Our findings place four Heinrich events firmly within ice core chronologies and suggest maximum durations of 778 to 1606 yr. CH4 anomalies are only associated with Heinrich events of Hudson Strait provenance, indicating that the tropical impacts of Heinrich events were not uniform.

  6. Modeling past abrupt climate changes: driven oscillators and synchronization phenomena in Paleoclimate theory

    NASA Astrophysics Data System (ADS)

    Marchionne, Arianna

    2014-05-01

    According to Milankovitch theory of ice ages, summer insolation at high northern latitudes drives the glacial cycles, i.e. the growth and reduction of Northern Hemisphere ice sheets, and there is evidence that astronomical forcing controls indeed the timing of Pleistocene glacial-interglacial cycles. However, the δ18Otime series (the δ18O is a proxy for global ice volume) available for the last few million years reveal a non-linear response of the climate to the external forcing: transitions from the glacial to the interglacial states occur more rapidly than the transitions from the interglacials to the glacials, resulting in the so-called saw-tooth shape of the signal. These terminations were very abrupt compared to the smooth changes in insolation. Moreover, insolation alone cannot explain the Mid-Pleistocene transition. During this event, occurred about one million years ago, the dominant 41 kyr glacial cycles, were replaced by longer saw-tooth shaped cycles with a time scale around 100 kyr. The asymmetry in the oscillations indicates a non-linear response to the orbital forcing, expressed through a bifurcation, or tipping point. As an introduction to the problem, we studied simple driven oscillators that can exhibit asymmetric oscillations between the glacial and interglacial states under the effect of the astronomical forcing, such as the Van der Pool and the Duffing oscillators. In order to understand how these simple low-dimensional models enter theories of ice ages and rapid events, we studied synchronization phenomena between simple driven oscillators and astronomical forcing, focusing on distinguishing between the so-called resonance scenario and the so-called phase locking scenario. We next examined the possible mechanisms for the Mid-Pleistocene transition. Here we show that the transition could be explained as a result of frequency-locking to the external forcing. This change can be interpreted as a result of an internal change in climate response

  7. Insolation and Abrupt Climate Change Effects on the Western Pacific Maritime Monsoon

    NASA Astrophysics Data System (ADS)

    Partin, J. W.; Quinn, T. M.; Shen, C.; Cardenas, M.; Siringan, F. P.; Hori, M.; Okumura, Y.; Banner, J. L.; Lin, K.; Jiang, X.; Taylor, F. W.

    2013-12-01

    Many monsoon-sensitive paleoclimate archives capture the response of the Asian-Australian monsoon system to changes in summer insolation, as well as abrupt climate changes such as the Younger Dryas (YD). The response is commonly a direct one in Holocene and YD archives. In the case of insolation, increased summer insolation leads to increased monsoon rainfall over land, as captured in stalagmite δ18O records from Oman and China. We evaluate this direct response using maritime stalagmite records from the island of Palawan, Philippines (10 N, 119 E). The wet season in Palawan occurs over the same months (June-October) as in Oman, India and China. Therefore, we expected the Palawan stalagmite δ18O record, a proxy of rainfall, to have a similar response to changing insolation and hence, a trend of decreasing monsoon rainfall over the Holocene. However, the Holocene trend in two partially replicated stalagmite δ18O records is opposite to that expected: rainfall increases over the Holocene, despite the decrease of summer insolation over the Holocene. We interpret the Holocene trend observed at Palawan to be the result of an increase in the maritime monsoon that balances the reduction in the land monsoon; an interpretation that is consistent with previously published results from coupled ocean-atmosphere general circulation model runs. Seawater δ18O reconstructions from marine sediment cores in the western tropical Pacific contain a freshening trend over the Holocene, also supporting the hypothesis of increase maritime monsoon rainfall. The direct relationship between monsoon rainfall over land as recorded in the YD interval in Chinese stalagmite records is also observed in maritime monsoon rainfall during the YD at Palawan: both records get drier during the YD cold interval. This agreement between YD stalagmite records from China and Palawan contrasts sharply with the inverse relationship between these records over the Holocene. We further investigate the nature of

  8. "What Controls the Structure and Stability of the Ocean Meridional Overturning Circulation: Implications for Abrupt Climate Change?"

    SciTech Connect

    Fedorov, Alexey

    2013-11-23

    The central goal of this research project is to understand the properties of the ocean meridional overturning circulation (MOC) – a topic critical for understanding climate variability and stability on a variety of timescales (from decadal to centennial and longer). Specifically, we have explored various factors that control the MOC stability and decadal variability in the Atlantic and the ocean thermal structure in general, including the possibility abrupt climate change. We have also continued efforts on improving the performance of coupled ocean-atmosphere GCMs.

  9. The abrupt climate change near 4,400 yr BP on the cultural transition in Yuchisi, China and its global linkage

    NASA Astrophysics Data System (ADS)

    Wang, Jianjun; Sun, Liguang; Chen, Liqi; Xu, Libin; Wang, Yuhong; Wang, Xinming

    2016-06-01

    Extreme climatic events have profound impacts on human society. Here we present the results of a study of organic biomarkers within a sedimentary section at the archaeological site of Yuchisi, eastern China, in order to reconstruct climatic variability during the Dawenkou (5,050–4,400 yr BP) and Longshan (4,400–4,000 yr BP) cultures. At ~4,400 yr BP, within the cultural transition horizon, abrupt changes in biomarkers, such as the fatty acid ratio C18:2/C18:0, 2C31/(C27 + C29), n-C18-ol and n-C30-ol, indicate the occurrence of local climate changes over the course of a few decades. These changes occurred during the transition from the Holocene warm period to a subsequent cold period which lasted for the following 600 years. This climatic shift has been recorded at numerous sites worldwide, and it is likely to have been the main cause of the widespread collapse of many isolated cultures at that time. The palaeoclimatic and archaeological data from the Yuchisi sediments may provide new insights into the relationship between climate change and prehistoric cultural transitions.

  10. The abrupt climate change near 4,400 yr BP on the cultural transition in Yuchisi, China and its global linkage.

    PubMed

    Wang, Jianjun; Sun, Liguang; Chen, Liqi; Xu, Libin; Wang, Yuhong; Wang, Xinming

    2016-01-01

    Extreme climatic events have profound impacts on human society. Here we present the results of a study of organic biomarkers within a sedimentary section at the archaeological site of Yuchisi, eastern China, in order to reconstruct climatic variability during the Dawenkou (5,050-4,400 yr BP) and Longshan (4,400-4,000 yr BP) cultures. At ~4,400 yr BP, within the cultural transition horizon, abrupt changes in biomarkers, such as the fatty acid ratio C18:2/C18:0, 2C31/(C27 + C29), n-C18-ol and n-C30-ol, indicate the occurrence of local climate changes over the course of a few decades. These changes occurred during the transition from the Holocene warm period to a subsequent cold period which lasted for the following 600 years. This climatic shift has been recorded at numerous sites worldwide, and it is likely to have been the main cause of the widespread collapse of many isolated cultures at that time. The palaeoclimatic and archaeological data from the Yuchisi sediments may provide new insights into the relationship between climate change and prehistoric cultural transitions. PMID:27283832

  11. The abrupt climate change near 4,400 yr BP on the cultural transition in Yuchisi, China and its global linkage

    PubMed Central

    Wang, Jianjun; Sun, Liguang; Chen, Liqi; Xu, Libin; Wang, Yuhong; Wang, Xinming

    2016-01-01

    Extreme climatic events have profound impacts on human society. Here we present the results of a study of organic biomarkers within a sedimentary section at the archaeological site of Yuchisi, eastern China, in order to reconstruct climatic variability during the Dawenkou (5,050–4,400 yr BP) and Longshan (4,400–4,000 yr BP) cultures. At ~4,400 yr BP, within the cultural transition horizon, abrupt changes in biomarkers, such as the fatty acid ratio C18:2/C18:0, 2C31/(C27 + C29), n-C18-ol and n-C30-ol, indicate the occurrence of local climate changes over the course of a few decades. These changes occurred during the transition from the Holocene warm period to a subsequent cold period which lasted for the following 600 years. This climatic shift has been recorded at numerous sites worldwide, and it is likely to have been the main cause of the widespread collapse of many isolated cultures at that time. The palaeoclimatic and archaeological data from the Yuchisi sediments may provide new insights into the relationship between climate change and prehistoric cultural transitions. PMID:27283832

  12. A Generalized Stability Analysis of the AMOC in Earth System Models: Implication for Decadal Variability and Abrupt Climate Change

    SciTech Connect

    Fedorov, Alexey V.

    2015-01-14

    The central goal of this research project was to understand the mechanisms of decadal and multi-decadal variability of the Atlantic Meridional Overturning Circulation (AMOC) as related to climate variability and abrupt climate change within a hierarchy of climate models ranging from realistic ocean models to comprehensive Earth system models. Generalized Stability Analysis, a method that quantifies the transient and asymptotic growth of perturbations in the system, is one of the main approaches used throughout this project. The topics we have explored range from physical mechanisms that control AMOC variability to the factors that determine AMOC predictability in the Earth system models, to the stability and variability of the AMOC in past climates.

  13. Abrupt climatic events during OIS-3 recorded in terrestrial sediments in the Netherlands: a multi-proxy approach

    NASA Astrophysics Data System (ADS)

    Bos, J. A. A.; Bohncke, S. J. P.; Kasse, C.; van Huissteden, J.; Schokker, J.; Bunnik, F. P. M.; Wallinga, J.

    2009-04-01

    Abrupt climatic changes during Oxygen Isotope Stage 3 (OIS-3 or Weichselian Middle Pleniglacial) are revealed in the oxygen isotope records of the Greenland ice cores and in the North Atlantic marine cores. In the Greenland ice cores, these so-called D/O cycles start with a rapid warming of 5-10˚C within a few decades, followed by a phase of gradual cooling over several hundred to more than a thousand years and often end with a final reduction in temperature back to cold, stadial conditions. On the adjacent European continent, however, climatic variability during this time interval is poorly known. High-resolution terrestrial records are scarce and the discontinuous nature of sedimentation and repeated erosion on the continent combined with poor dating control often hampers a detailed study of the vegetation and climate. In this contribution, a Middle Weichselian sequence with shallow lacustrine deposits, intercalated by fluvial sediments with permafrost features, is presented from the Netherlands. Within this Middle Weichselian sequence, rapid warming events are assumed to have given rise to thawlake formation and/or deposition of organic-rich lacustrine sediments, while the extreme cooling events of the D/O cycles are probably represented in the sequences by clastic intervals during which periglacial features developed. In the sixties of the last century, two warming events or "interstadials" were first recognized and described from terrestrial Middle Weichselian sequences from the Hengelo basin in the Netherlands, the Hengelo- and Denekamp interstadials, respectively. The shift from a polar desert to shrub tundra (i.e. Hengelo interstadial) and tundra to shrub tundra (i.e. Denekamp interstadial), visible in the pollen diagrams of this area, was interpreted as a temporary amelioration of the climate and were therefore given the names of interstadials. In time the Hengelo- and Denekamp interstadials were also correlated with D/O cycles 12 respectively 8 in the

  14. Evidence of Abrupt Climatic Variability Across Heinrich Events from Multiple Bahamian Stalagmites

    NASA Astrophysics Data System (ADS)

    Arienzo, M. M.; Swart, P. K.; Pourmand, A.; Broad, K.; Clement, A. C.; Murphy, L.; Kakuk, B.

    2013-12-01

    δ18O of the carbonate associated with all Heinrich events, the δ18O of the water obtained from the fluid inclusions supports minimal change in δ18O of the water during these events. The fluid inclusion data suggest that temperature, rather than precipitation amount, is the primary driver of the shift in the oxygen isotopes of the carbonate. Based on our preliminary results, there is good geochemical agreement between stalagmites from the same cave across the studied time interval. This validates that the geochemical proxies in the stalagmites record climatic changes and are not influenced by kinetic effects. These records support the teleconnection between the high latitude North Atlantic and the subtropics.

  15. Have abrupt climate variations of the last glacial possibly been muted in the south-west African tropics by counteracting mechanisms?

    NASA Astrophysics Data System (ADS)

    Hessler, I.; Dupont, L.; Handiani, D.; Steinke, S.; Groeneveld, J.; Merkel, U.; Paul, A.

    2012-04-01

    The last glacial period including the last deglaciation (73.5-10 ka BP) is characterised by abrupt shifts between extreme climatic conditions. Millennial-scale climate variations associated with North Atlantic Heinrich Stadials (HSs) are thought to be transmitted by both the atmospheric and oceanic circulation resulting in a near-global footprint. It is further thought that HSs are closely related to a reduction or shut-down of the Atlantic Meridional Overturning Circulation, which, according to the bipolar-seesaw hypothesis, leads to the accumulation of heat in the South Atlantic. In addition, it is hypothesised that HSs result in a southward shift of the Intertropical Convergence Zone which then would likely influence the vegetation composition in the African tropics. To investigate the impact of HSs on the terrestrial African realm and the south-east Atlantic we reconstructed the vegetation development in Angola and the southern Congo Basin as well as the sea surface temperatures (SST) of the south-east Atlantic using marine sediments of ODP Site 1078 (11° 55'S, 13° 24'E, 427 m water depth). Two species of planktonic foraminifera were selected to reconstruct variations in surface water conditions in the south-east Atlantic. Due the ecological and seasonal preferences of Globigerinoides ruber (pink) this species provides a good tool to estimate SST variations during the southern hemisphere summer. In contrast, Globigerina bulloides is representing the Benguela Upwelling System during the southern hemisphere winter. While Mg/Ca-based SSTs of G. ruber (pink) were significantly higher by 1° -2° C during periods of abrupt climate change, the impact of HSs during southern hemisphere winter is less obvious. However, although there are several vegetation records that show an impact of HSs in the African tropics, our high-resolution pollen record from ODP Site 1078 reflects no vegetation changes during periods of HSs. Model simulations conducted with an Earth System

  16. The fluvial system response to abrupt climate change during the last cold stage: the Upper Pleistocene River Thames fluvial succession at Ashton Keynes, UK

    NASA Astrophysics Data System (ADS)

    Lewis, S. G.; Maddy, D.; Scaife, R. G.

    2001-02-01

    The last interglacial-glacial cycle (125-10 ka BP) is characterised by numerous rapid shifts in global climate on sub-Milankovitch timescales, recorded in the ocean and ice core records. These climatic fluctuations are clearly recorded in those European terrestrial sedimentary sequences that span this time period without interruption. In the UK, only fragmentary Upper Pleistocene sequences exist, mainly within the fluvial archive of the major river systems such as the Thames. The response of the upper River Thames to abrupt fluctuations in climate is documented in the fluvial sediments beneath the Floodplain Terrace (Northmoor Member of the Upper Thames Formation) at Ashton Keynes, Wiltshire. A number of criteria are set out by which significant changes in the fluvial system may be established from the sedimentological, palaeoecological and geochronological information contained within the succession. The sedimentary succession is divisible into four facies associations, on the basis of their sedimentology and bounding surface characteristics. These represent distinct phases of fluvial activity at the site and allow changes in fluvial style to be inferred. Palaeoecological reconstructions from pollen analysis of peats within the sequence provides an indication of the nature and direction of Late Glacial environmental change and optically stimulated luminescence and radiocarbon dating methods provide chronological control on the sequence. These data suggest that major changes in fluvial style are recorded within the succession, which can be related to the climatic fluctuations that took place on the oxygen isotope stage 5a/4 transition (approximately 70 ka BP) and the Devensian Late Glacial climatic warm-cold-warm oscillation (13-11 ka BP). The changes in fluvial style are a result of variations in sediment supply to the river resulting from changes in slope stability, vegetation cover and cold-climate mass movement processes and variations in discharge regime

  17. A Collaborative Proposal: Simulating and Understanding Abrupt Climate-Ecosystem Changes During Holocene with NCAR-CCSM3.

    SciTech Connect

    Zhengyu Liu, Bette Otto-Bliesner

    2013-02-01

    We have made significant progress in our proposed work in the last 4 years (3 years plus 1 year of no cost extension). In anticipation of the next phase of study, we have spent time on the abrupt changes since the last glacial maximum. First, we have performed further model-data comparison based on our baseline TRACE-21 simulation and made important progress towards the understanding of several major climate transitions. Second, we have made a significant effort in processing the model output of TRACE-21 and have put this output on a website for access by the community. Third, we have completed many additional sensitivity experiments. In addition, we have organized synthesis workshops to facilitate and promote transient model-data comparison for the international community. Finally, we have identified new areas of interest for Holocene climate changes.

  18. The abrupt climate change at the Eocene–Oligocene boundary and the emergence of South-East Asia triggered the spread of sapindaceous lineages

    PubMed Central

    Buerki, Sven; Forest, Félix; Stadler, Tanja; Alvarez, Nadir

    2013-01-01

    Background and Aims Paleoclimatic data indicate that an abrupt climate change occurred at the Eocene–Oligocene (E–O) boundary affecting the distribution of tropical forests on Earth. The same period has seen the emergence of South-East (SE) Asia, caused by the collision of the Eurasian and Australian plates. How the combination of these climatic and geomorphological factors affected the spatio-temporal history of angiosperms is little known. This topic is investigated by using the worldwide sapindaceous clade as a case study. Methods Analyses of divergence time inference, diversification and biogeography (constrained by paleogeography) are applied to a combined plastid and nuclear DNA sequence data set. Biogeographical and diversification analyses are performed over a set of trees to take phylogenetic and dating uncertainty into account. Results are analysed in the context of past climatic fluctuations. Key Results An increase in the number of dispersal events at the E–O boundary is recorded, which intensified during the Miocene. This pattern is associated with a higher rate in the emergence of new genera. These results are discussed in light of the geomorphological importance of SE Asia, which acted as a tropical bridge allowing multiple contacts between areas and additional speciation across landmasses derived from Laurasia and Gondwana. Conclusions This study demonstrates the importance of the combined effect of geomorphological (the emergence of most islands in SE Asia approx. 30 million years ago) and climatic (the dramatic E–O climate change that shifted the tropical belt and reduced sea levels) factors in shaping species distribution within the sapindaceous clade. PMID:23723259

  19. Pollen dispersal slows geographical range shift and accelerates ecological niche shift under climate change.

    PubMed

    Aguilée, Robin; Raoul, Gaël; Rousset, François; Ronce, Ophélie

    2016-09-27

    Species may survive climate change by migrating to track favorable climates and/or adapting to different climates. Several quantitative genetics models predict that species escaping extinction will change their geographical distribution while keeping the same ecological niche. We introduce pollen dispersal in these models, which affects gene flow but not directly colonization. We show that plant populations may escape extinction because of both spatial range and ecological niche shifts. Exact analytical formulas predict that increasing pollen dispersal distance slows the expected spatial range shift and accelerates the ecological niche shift. There is an optimal distance of pollen dispersal, which maximizes the sustainable rate of climate change. These conclusions hold in simulations relaxing several strong assumptions of our analytical model. Our results imply that, for plants with long distance of pollen dispersal, models assuming niche conservatism may not accurately predict their future distribution under climate change.

  20. Pollen dispersal slows geographical range shift and accelerates ecological niche shift under climate change.

    PubMed

    Aguilée, Robin; Raoul, Gaël; Rousset, François; Ronce, Ophélie

    2016-09-27

    Species may survive climate change by migrating to track favorable climates and/or adapting to different climates. Several quantitative genetics models predict that species escaping extinction will change their geographical distribution while keeping the same ecological niche. We introduce pollen dispersal in these models, which affects gene flow but not directly colonization. We show that plant populations may escape extinction because of both spatial range and ecological niche shifts. Exact analytical formulas predict that increasing pollen dispersal distance slows the expected spatial range shift and accelerates the ecological niche shift. There is an optimal distance of pollen dispersal, which maximizes the sustainable rate of climate change. These conclusions hold in simulations relaxing several strong assumptions of our analytical model. Our results imply that, for plants with long distance of pollen dispersal, models assuming niche conservatism may not accurately predict their future distribution under climate change. PMID:27621443

  1. Revisiting Lake Hämelsee: reconstructing abrupt Lateglacial climate transitions using state- of-the-art palaeoclimatological proxies

    NASA Astrophysics Data System (ADS)

    Engels, Stefan; Hoek, Wim; Lane, Christine; Sachse, Dirk; Wagner-Cremer, Friederike

    2015-04-01

    Lake Hämelsee (Germany) is one of the northernmost sites in NW Europe that has varved sediments throughout large parts of its Lateglacial and Early Holocene sediment sequence. Previous research on this site has shown its potential, in terms of chronological resolution and palaeoecological reconstructions, for reconstructing the abrupt transitions into and out of the Younger Dryas, the last cold period of the last glacial. The site was revisited during a 1-week summer school for Early Stage Researchers (2013), within the INTIMATE Example training and research project, supported by EU Cost Action ES0907. Two overlapping sediment sequences were retrieved from the centre of the lake during the summer school. These sediments have since formed the basis for follow-up research projects, which have sparked the collaboration of around 30 researchers in 12 laboratories across Europe. A chronological framework for the core has been composed from a combination of varve counting, radiocarbon dating and tephrochronology. Tephrostratigraphic correlations allow direct correlation and precise comparison of the record to marine and ice core records from the North Atlantic region, and other terrestrial European archives. Furthermore, the core is has been subjected to multiple sedimentological (e.g. XRF, loss-on-ignition), geochemical (e.g. lipid biomarkers, GDGTs) and palaeoecological (e.g. pollen, chironomids) proxy-based reconstructions of past environmental and climatic conditions. The results provide important insights into the nature of the abrupt climate transitions of the Lateglacial and Early Holocene, both locally and on a continental scale. The INTIMATE Example participants: Illaria Baneschi, Achim Brauer, Christopher Bronk Ramsey, Renee de Bruijn, Siwan Davies, Aritina Haliuc, Katalin Hubay, Gwydion Jones, Meike Müller, Johanna Menges, Josef Merkt, Tom Peters, Francien Peterse, Anneke ter Schure, Kathrin Schuetrumpf, Richard Staff, Falko Turner, Valerie van den Bos.

  2. Abrupt Climate Change in the Arctic (and Beyond): An Update (Invited)

    NASA Astrophysics Data System (ADS)

    Alley, R. B.

    2013-12-01

    Our understanding of future Arctic change is informed by the history of past changes, which often have been both large and abrupt. The well-known ice-age events such as the Younger Dryas show how sea-ice changes can amplify forcing to produce very large responses, with wintertime sea ice especially important. These changes are increasingly seen to have played a central role in the ice-age cycling through their global impact on CO2 storage in the deep ocean. The Heinrich events reveal processes of ice-sheet/ocean interaction, some of which are being played out in Greenland and Antarctica now, and which may have large future effects on sea-level rise. The paleoclimatic record plus physical understanding greatly reduce the worst worries about instabilities from methane stored in cold places, but tend to support a role in amplifying future warming. Overall, the very large impacts of past Arctic changes, and the likelihood that future changes under business-as-usual fossil-fuel emissions will be unprecedented in combined size and speed, raise important questions.

  3. Quantifying Climate Feedbacks from Abrupt Changes in High-Latitude Trace-Gas Emissions

    SciTech Connect

    Schlosser, Courtney Adam; Walter-Anthony, Katey; Zhuang, Qianlai; Melillo, Jerry

    2013-04-26

    Our overall goal was to quantify the potential for threshold changes in natural emission rates of trace gases, particularly methane and carbon dioxide, from pan-arctic terrestrial systems under the spectrum of anthropogenically forced climate warming, and the extent to which these emissions provide a strong feedback mechanism to global climate warming. This goal is motivated under the premise that polar amplification of global climate warming will induce widespread thaw and degradation of the permafrost, and would thus cause substantial changes in the extent of wetlands and lakes, especially thermokarst (thaw) lakes, over the Arctic. Through a coordinated effort of field measurements, model development, and numerical experimentation with an integrated assessment model framework, we have investigated the following hypothesis: There exists a climate-warming threshold beyond which permafrost degradation becomes widespread and thus instigates strong and/or sharp increases in methane emissions (via thermokarst lakes and wetland expansion). These would outweigh any increased uptake of carbon (e.g. from peatlands) and would result in a strong, positive feedback to global climate warming.

  4. Abrupt climate change around 4 ka BP: Role of the Thermohaline circulation as indicated by a GCM experiment

    NASA Astrophysics Data System (ADS)

    Wang, Shaowu; Zhou, Tianjun; Cai, Jingning; Zhu, Jinhong; Xie, Zhihui; Gong, Daoyi

    2004-04-01

    A great deal of palaeoenvironmental and palaeoclimatic evidence suggests that a predominant temperature drop and an aridification occurred at ca. 4.0 ka BP. Palaeoclimate studies in China support this dedution. The collapse of ancient civilizations at ca. 4.0 ka BP in the Nile Valley and Mesopotamia has been attributed to climate-induced aridification. A widespread alternation of the ancient cultures was also found in China at ca. 4.0 ka BP in concert with the collapse of the civilizations in the Old World. Palaeoclimatic studies indicate that the abrupt climate change at 4.0 ka BP is one of the realizations of the cold phase in millennial scale climate oscillations, which may be related to the modulation of the Thermohaline Circulation (THC) over the Atlantic Ocean. Therefore, this study conducts a numerical experiment of a GCM with SST forcing to simulate the impact of the weakening of the THC. Results show a drop in temperature from North Europe, the northern middle East Asia, and northern East Asia and a significant reduction of precipitation in East Africa, the Middle East, the Indian Peninsula, and the Yellow River Valley. This seems to support the idea that coldness and aridification at ca. 4.0 ka BP was caused by the weakening of the THC.

  5. Geomorphic Expression of Abrupt Climate Change in Southwestern North America at the Glacial Termination

    NASA Astrophysics Data System (ADS)

    Anderson, Roger Y.; Allen, Bruce D.; Menking, Kirsten M.

    2002-05-01

    Eolian and subaqueous landforms composed of gypsum sand provide geomorphic evidence for a wet episode at the termination of glacial climate in southwestern North America. Drying of pluvial Lake Estancia, central New Mexico, occurred after ca. 12,000 14C yr B.P. Thereafter, eolian landforms on the old lake floor, constructed of gypsum sand, were overridden by rising lake water, modified by subaqueous processes, and organized into beach ridges along the lake's eastern shore. Preservation of preexisting eolian landforms in the shallow lake suggests abupt changes in lake level and climate. Available radiocarbon ages suggest that the final highstand recorded by beach ridges may have developed during the Younger Dryas (YD) stade. The beach ridges provide information about lake surface area, which was 45% of the lake area reached during the maximum highstands of the late Pleistocene. A similar proportional response has been reported for YD climate changes outside the North Atlantic region.

  6. Food Security Under Shifting Economic, Demographic, and Climatic Conditions (Invited)

    NASA Astrophysics Data System (ADS)

    Naylor, R. L.

    2013-12-01

    Global demand for food, feed, and fuel will continue to rise in a more populous and affluent world. Meeting this demand in the future will become increasingly challenging with global climate change; when production shocks stemming from climate variability are added to the new mean climate state, food markets could become more volatile. This talk will focus on the interacting market effects of demand and supply for major food commodities, with an eye on climate-related supply trends and shocks. Lessons from historical patterns of climate variability (e.g., ENSO and its global teleconnections) will be used to infer potential food security outcomes in the event of abrupt changes in the mean climate state. Domestic food and trade policy responses to crop output and price volatility in key producing and consuming nations, such as export bans and import tariffs, will be discussed as a potentially major destabilizing force, underscoring the important influence of uncertainty in achieving--or failing to achieve--food security.

  7. Iceberg discharges and oceanic circulation changes during glacial abrupt climate changes

    NASA Astrophysics Data System (ADS)

    Alvarez-Solas, Jorge; Robinson, Alexander; Banderas, Rubén; Montoya, Marisa

    2015-04-01

    Proxy data reveal the existence of episodes of increased deposition of ice-rafted debris in the North Atlantic Ocean during the last glacial period. These are interpreted as massive iceberg discharges mainly from the Laurentide Ice Sheet. Although these have long been attributed to self-sustained ice sheet oscillations, growing evidence points to an active role of the oceanic circulation. Here we will present simulations of the last glacial period carried out with a hybrid ice sheet-ice shelf model. Two mechanisms producing iceberg discharges are compared. First, we reproduce the classic binge-purge by which the iceberg surges are produced thanks to the existence of an internal thermo-mechanical feedback that allows the ice sheet to behave under an oscillatory regime. Second, our ice-sheet model is forced by an oceanic warming index derived from proxy data that accounts for the impact of past ocean circulation changes on ocean temperatures. In this case, the model generates a time series of iceberg calving that agrees with ice-rafted debris records over the past 80 ka. We compare the two theories and discuss their advantages and weaknesses in terms of both the robustness of the physics on which they are based and their comparison with proxies. This comparison highlights the importance of considering past oceanic circulation changes in order to understand the ice-sheet dynamics. However, the ultimate processes determining abrupt changes in the Atlantic Meridional Overturning Circulation (AMOC) remain elusive. Therefore we will also analyze several proposed mechanisms that aims to explain such AMOC reorganizations, focusing on those that do not require freshwater flux forcing.

  8. Climate penalty for shifting shipping to the Arctic.

    PubMed

    Fuglestvedt, Jan S; Dalsøren, Stig Bjørløw; Samset, Bjørn Hallvard; Berntsen, Terje; Myhre, Gunnar; Hodnebrog, Øivind; Eide, Magnus Strandmyr; Bergh, Trond Flisnes

    2014-11-18

    The changing climate in the Arctic opens new shipping routes. A shift to shorter Arctic transit will, however, incur a climate penalty over the first one and a half centuries. We investigate the net climate effect of diverting a segment of Europe-Asia container traffic from the Suez to an Arctic transit route. We find an initial net warming for the first one-and-a-half centuries, which gradually declines and transitions to net cooling as the effects of CO2 reductions become dominant, resulting in climate mitigation only in the long term. Thus, the possibilities for shifting shipping to the Arctic confront policymakers with the question of how to weigh a century-scale warming with large uncertainties versus a long-term climate benefit from CO2 reductions. PMID:25347302

  9. An abrupt centennial-scale drought event and mid-holocene climate change patterns in monsoon marginal zones of East Asia.

    PubMed

    Li, Yu; Wang, Nai'ang; Zhang, Chengqi

    2014-01-01

    The mid-latitudes of East Asia are characterized by the interaction between the Asian summer monsoon and the westerly winds. Understanding long-term climate change in the marginal regions of the Asian monsoon is critical for understanding the millennial-scale interactions between the Asian monsoon and the westerly winds. Abrupt climate events are always associated with changes in large-scale circulation patterns; therefore, investigations into abrupt climate changes provide clues for responses of circulation patterns to extreme climate events. In this paper, we examined the time scale and mid-Holocene climatic background of an abrupt dry mid-Holocene event in the Shiyang River drainage basin in the northwest margin of the Asian monsoon. Mid-Holocene lacustrine records were collected from the middle reaches and the terminal lake of the basin. Using radiocarbon and OSL ages, a centennial-scale drought event, which is characterized by a sand layer in lacustrine sediments both from the middle and lower reaches of the basin, was absolutely dated between 8.0-7.0 cal kyr BP. Grain size data suggest an abrupt decline in lake level and a dry environment in the middle reaches of the basin during the dry interval. Previous studies have shown mid-Holocene drought events in other places of monsoon marginal zones; however, their chronologies are not strong enough to study the mechanism. According to the absolutely dated records, we proposed a new hypothesis that the mid-Holocene dry interval can be related to the weakening Asian summer monsoon and the relatively arid environment in arid Central Asia. Furthermore, abrupt dry climatic events are directly linked to the basin-wide effective moisture change in semi-arid and arid regions. Effective moisture is affected by basin-wide precipitation, evapotranspiration, lake surface evaporation and other geographical settings. As a result, the time scales of the dry interval could vary according to locations due to different geographical

  10. An abrupt centennial-scale drought event and mid-holocene climate change patterns in monsoon marginal zones of East Asia.

    PubMed

    Li, Yu; Wang, Nai'ang; Zhang, Chengqi

    2014-01-01

    The mid-latitudes of East Asia are characterized by the interaction between the Asian summer monsoon and the westerly winds. Understanding long-term climate change in the marginal regions of the Asian monsoon is critical for understanding the millennial-scale interactions between the Asian monsoon and the westerly winds. Abrupt climate events are always associated with changes in large-scale circulation patterns; therefore, investigations into abrupt climate changes provide clues for responses of circulation patterns to extreme climate events. In this paper, we examined the time scale and mid-Holocene climatic background of an abrupt dry mid-Holocene event in the Shiyang River drainage basin in the northwest margin of the Asian monsoon. Mid-Holocene lacustrine records were collected from the middle reaches and the terminal lake of the basin. Using radiocarbon and OSL ages, a centennial-scale drought event, which is characterized by a sand layer in lacustrine sediments both from the middle and lower reaches of the basin, was absolutely dated between 8.0-7.0 cal kyr BP. Grain size data suggest an abrupt decline in lake level and a dry environment in the middle reaches of the basin during the dry interval. Previous studies have shown mid-Holocene drought events in other places of monsoon marginal zones; however, their chronologies are not strong enough to study the mechanism. According to the absolutely dated records, we proposed a new hypothesis that the mid-Holocene dry interval can be related to the weakening Asian summer monsoon and the relatively arid environment in arid Central Asia. Furthermore, abrupt dry climatic events are directly linked to the basin-wide effective moisture change in semi-arid and arid regions. Effective moisture is affected by basin-wide precipitation, evapotranspiration, lake surface evaporation and other geographical settings. As a result, the time scales of the dry interval could vary according to locations due to different geographical

  11. An Abrupt Centennial-Scale Drought Event and Mid-Holocene Climate Change Patterns in Monsoon Marginal Zones of East Asia

    PubMed Central

    Li, Yu; Wang, Nai'ang; Zhang, Chengqi

    2014-01-01

    The mid-latitudes of East Asia are characterized by the interaction between the Asian summer monsoon and the westerly winds. Understanding long-term climate change in the marginal regions of the Asian monsoon is critical for understanding the millennial-scale interactions between the Asian monsoon and the westerly winds. Abrupt climate events are always associated with changes in large-scale circulation patterns; therefore, investigations into abrupt climate changes provide clues for responses of circulation patterns to extreme climate events. In this paper, we examined the time scale and mid-Holocene climatic background of an abrupt dry mid-Holocene event in the Shiyang River drainage basin in the northwest margin of the Asian monsoon. Mid-Holocene lacustrine records were collected from the middle reaches and the terminal lake of the basin. Using radiocarbon and OSL ages, a centennial-scale drought event, which is characterized by a sand layer in lacustrine sediments both from the middle and lower reaches of the basin, was absolutely dated between 8.0–7.0 cal kyr BP. Grain size data suggest an abrupt decline in lake level and a dry environment in the middle reaches of the basin during the dry interval. Previous studies have shown mid-Holocene drought events in other places of monsoon marginal zones; however, their chronologies are not strong enough to study the mechanism. According to the absolutely dated records, we proposed a new hypothesis that the mid-Holocene dry interval can be related to the weakening Asian summer monsoon and the relatively arid environment in arid Central Asia. Furthermore, abrupt dry climatic events are directly linked to the basin-wide effective moisture change in semi-arid and arid regions. Effective moisture is affected by basin-wide precipitation, evapotranspiration, lake surface evaporation and other geographical settings. As a result, the time scales of the dry interval could vary according to locations due to different

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

    NASA Astrophysics Data System (ADS)

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

    2007-12-01

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

  13. Abrupt climate variability of eastern Anatolia vegetation during the last glacial

    NASA Astrophysics Data System (ADS)

    Pickarski, N.; Kwiecien, O.; Langgut, D.; Litt, T.

    2015-07-01

    Detailed analyses of the Lake Van pollen and stable oxygen isotope record allow the identification of millennial-scale vegetation and environmental changes in eastern Anatolia throughout the last glacial. The climate within the last glacial period (∼75-15 ka BP) was cold and dry, with low arboreal pollen (AP) levels. The driest and coldest period corresponds to Marine Isotope Stage (MIS) 2 (∼28-14.5 ka BP) dominated by the highest values of xerophytic steppe vegetation. Our high-resolution multi proxy record shows rapid expansions and contractions that mimic the stadial-interstadial pattern of the Dansgaard-Oeschger (DO) events as recorded in the Greenland ice cores, and thus, provide a linkage to North Atlantic climate oscillations. Periods of reduced moisture availability characterized at Lake Van by enhanced xerophytic species correlates well with increase in ice-rafted debris (IRD) and a decrease of sea surface temperature (SST) in the North Atlantic. Furthermore, comparison with the marine realm reveals that the complex atmosphere-ocean interaction can be recognized by the strength and position of the westerlies in eastern Anatolia. Influenced by rough topography at Lake Van, the expansion of temperate species (e.g. deciduous Quercus) was stronger during interstadials DO 19, 17-16, 14, 12 and 8. However, Heinrich events (HE), characterized by highest concentrations of ice-rafted debris in marine sediments, are identified in eastern Anatolia by AP values not lower and high steppe components not more abundant than during DO stadials. In addition, this work is a first attempt to establish a continuous microscopic charcoal record over the last glacial in the Near East, which documents an initial immediate response to millennial-scale climate and environmental variability and enables the shed light on the history of fire activity during the last glacial.

  14. Abrupt climate and vegetation variability of eastern Anatolia during the last glacial

    NASA Astrophysics Data System (ADS)

    Pickarski, N.; Kwiecien, O.; Langgut, D.; Litt, T.

    2015-11-01

    Detailed analyses of the Lake Van pollen, Ca / K ratio, and stable oxygen isotope record allow the identification of millennial-scale vegetation and environmental changes in eastern Anatolia throughout the last glacial (~ 111.5-11.7 ka BP). The climate of the last glacial was cold and dry, indicated by low arboreal pollen (AP) levels. The driest and coldest period corresponds to Marine Isotope Stage (MIS) 2 (~ 28-14.5 ka BP), which was dominated by highest values of xerophytic steppe vegetation. Our high-resolution multi-proxy record shows rapid expansions and contractions of tree populations that reflect variability in temperature and moisture availability. These rapid vegetation and environmental changes can be related to the stadial-interstadial pattern of Dansgaard-Oeschger (DO) events as recorded in the Greenland ice cores. Periods of reduced moisture availability were characterized by enhanced occurrence of xerophytic species and high terrigenous input from the Lake Van catchment area. Furthermore, the comparison with the marine realm reveals that the complex atmosphere-ocean interaction can be explained by the strength and position of the westerlies, which are responsible for the supply of humidity in eastern Anatolia. Influenced by the diverse topography of the Lake Van catchment, more pronounced DO interstadials (e.g., DO 19, 17-16, 14, 12 and 8) show the strongest expansion of temperate species within the last glacial. However, Heinrich events (HE), characterized by highest concentrations of ice-rafted debris (IRD) in marine sediments, cannot be separated from other DO stadials based on the vegetation composition in eastern Anatolia. In addition, this work is a first attempt to establish a continuous microscopic charcoal record for the last glacial in the Near East. It documents an immediate response to millennial-scale climate and environmental variability and enables us to shed light on the history of fire activity during the last glacial.

  15. Insects overshoot the expected upslope shift caused by climate warming.

    PubMed

    Bässler, Claus; Hothorn, Torsten; Brandl, Roland; Müller, Jörg

    2013-01-01

    Along elevational gradients, climate warming may lead to an upslope shift of the lower and upper range margin of organisms. A recent meta-analysis concluded that these shifts are species specific and considerably differ among taxonomic lineages. We used the opportunity to compare upper range margins of five lineages (plants, beetles, flies, hymenoptera, and birds) between 1902-1904 and 2006-2007 within one region (Bavarian Forest, Central Europe). Based on the increase in the regional mean annual temperature during this period and the regional lapse rate, the upslope shift is expected to be between 51 and 201 m. Averaged across species within lineages, the range margin of all animal lineages shifted upslope, but that of plants did not. For animals, the observed shifts were probably due to shifts in temperature and not to changes in habitat conditions. The range margin of plants is therefore apparently not constrained by temperature, a result contrasting recent findings. The mean shift of birds (165 m) was within the predicted range and consistent with a recent global meta-analysis. However, the upslope shift of the three insect lineages (>260 m) exceeded the expected shift even after considering several sources of uncertainty, which indicated a non-linear response to temperature. Our analysis demonstrated broad differences among lineages in their response to climate change even within one region. Furthermore, on the considered scale, the response of ectothermic animals was not consistent with expectations based on shifts in the mean annual temperature. Irrespective of the reasons for the overshooting of the response of the insects, these shifts lead to reorganizations in the composition of assemblages with consequences for ecosystem processes.

  16. Raised bogs, a Climate Shift, Cultural Change, and Reduced Solar Activity in the Early First Millennium BC

    NASA Astrophysics Data System (ADS)

    van Geel, B.

    2006-12-01

    Matching of a high resolution sequence of uncalibrated 14C datings with the dendro-calibration curve not only offers improved dating precision, but can also reveal relationships between atmospheric 14C variations and short-term climatic fluctuations caused by variations in solar output. Holocene shifts to cool and wet climate types in the temperate zones often correspond to phases of sharply increasing values of atmospheric radiocarbon, pointing to a link between changing solar activity and climate change. In northwest Europe at ca. 850 BC a sharp climatic shift to cooler, wetter conditions occurred. The shift is reflected in the species composition and decomposition of raised bog deposits and is chronologically linked to cultural changes and migrations at the Bronze Age/Iron Age transition. The temporary sharp rise of the atmospheric 14C content around 800 BC was caused by a sudden decline of solar activity. The solar wind declined, permitting more cosmic rays to penetrate into the atmosphere, and therefore the production of the cosmogenic isotope 14C increased. The climate shift was also recorded in Central and Eastern Europe, with rapid and total flooding of the Upper Volga region and a highstand of the Caspian Sea. In the Mississippi River basin, flooding frequencies greatly increased and there was an abrupt gap in the cultural transition from `Late Archaic' to `Early Woodland'. Paleoclimatological teleconnections point to a considerable role of solar UV in climate forcing. In the Central African rain forest belt and western India there was also a strong climate shift around 850 cal BC, but it was a shift to dryness (weakening of the summer monsoon). A possible palaeoclimatological explanation for the dry-wet transition in the temperate zones, and the contemporaneous wet-dry transition in the tropics (climatic teleconnections) will be given.

  17. Chinese stalagmites: proxies for the Indian Summer Monsoon response to an archetypal abrupt climate change

    NASA Astrophysics Data System (ADS)

    Pausata, F.; Battisti, D. S.; Nisancioglu, K. H.

    2010-12-01

    Stalagmites from Indian and Chinese caves have been widely used to infer past strength of the Indian and East Asian summer monsoon, as their oxygen isotopic composition (δ18O) is primarily controlled by the δ18O of precipitation. Here we show that a sudden increase in North Atlantic sea ice extent during the last glacial period cools the Northern Hemisphere, reduces precipitation over the Indian basin and weakens the Indian monsoon. In turn, the annual weighted δ18O of precipitation (δ18Op) is increased over India and isotopically heavier vapor is exported to China - directly by circulation and indirectly through continental recycling. The model reproduces the observed changes in climate associated with an archetypal Heinrich event and the δ18Op changes seen in stalagmites across China, which are proxies of Indian monsoon and not the East Asian monsoon as previously thought. Our results also provide insight on Dansgaard-Oeschger events and precessional cycle variations seen in these records.

  18. Sensitivity of the North Atlantic Ocean Circulation to an abrupt change in the Nordic Sea overflow in a high resolution global coupled climate model

    NASA Astrophysics Data System (ADS)

    Zhang, Rong; Delworth, Thomas L.; Rosati, Anthony; Anderson, Whit G.; Dixon, Keith W.; Lee, Hyun-Chul; Zeng, Fanrong

    2011-12-01

    The sensitivity of the North Atlantic Ocean Circulation to an abrupt change in the Nordic Sea overflow is investigated for the first time using a high resolution eddy-permitting global coupled ocean-atmosphere model (GFDL CM2.5). The Nordic Sea overflow is perturbed through the change of the bathymetry in GFDL CM2.5. We analyze the Atlantic Meridional Overturning Circulation (AMOC) adjustment process and the downstream oceanic response to the perturbation. The results suggest that north of 34°N, AMOC changes induced by changes in the Nordic Sea overflow propagate on the slow tracer advection timescale, instead of the fast Kelvin wave timescale, resulting in a time lead of several years between subpolar and subtropical AMOC changes. The results also show that a stronger and deeper-penetrating Nordic Sea overflow leads to stronger and deeper AMOC, stronger northward ocean heat transport, reduced Labrador Sea deep convection, stronger cyclonic Northern Recirculation Gyre (NRG), westward shift of the North Atlantic Current (NAC) and southward shift of the Gulf Stream, warmer sea surface temperature (SST) east of Newfoundland and colder SST south of the Grand Banks, stronger and deeper NAC and Gulf Stream, and stronger oceanic eddy activities along the NAC and the Gulf Stream paths. A stronger/weaker Nordic Sea overflow also leads to a contracted/expanded subpolar gyre (SPG). This sensitivity study points to the important role of the Nordic Sea overflow in the large scale North Atlantic ocean circulation, and it is crucial for climate models to have a correct representation of the Nordic Sea overflow.

  19. The Shifting Climate Portfolio of the Greater Yellowstone Area.

    PubMed

    Sepulveda, Adam J; Tercek, Michael T; Al-Chokhachy, Robert; Ray, Andrew M; Thoma, David P; Hossack, Blake R; Pederson, Gregory T; Rodman, Ann W; Olliff, Tom

    2015-01-01

    Knowledge of climatic variability at small spatial extents (< 50 km) is needed to assess vulnerabilities of biological reserves to climate change. We used empirical and modeled weather station data to test if climate change has increased the synchrony of surface air temperatures among 50 sites within the Greater Yellowstone Area (GYA) of the interior western United States. This important biological reserve is the largest protected area in the Lower 48 states and provides critical habitat for some of the world's most iconic wildlife. We focused our analyses on temporal shifts and shape changes in the annual distributions of seasonal minimum and maximum air temperatures among valley-bottom and higher elevation sites from 1948-2012. We documented consistent patterns of warming since 1948 at all 50 sites, with the most pronounced changes occurring during the Winter and Summer when minimum and maximum temperature distributions increased. These shifts indicate more hot temperatures and less cold temperatures would be expected across the GYA. Though the shifting statistical distributions indicate warming, little change in the shape of the temperature distributions across sites since 1948 suggest the GYA has maintained a diverse portfolio of temperatures within a year. Spatial heterogeneity in temperatures is likely maintained by the GYA's physiographic complexity and its large size, which encompasses multiple climate zones that respond differently to synoptic drivers. Having a diverse portfolio of temperatures may help biological reserves spread the extinction risk posed by climate change.

  20. The Shifting Climate Portfolio of the Greater Yellowstone Area.

    PubMed

    Sepulveda, Adam J; Tercek, Michael T; Al-Chokhachy, Robert; Ray, Andrew M; Thoma, David P; Hossack, Blake R; Pederson, Gregory T; Rodman, Ann W; Olliff, Tom

    2015-01-01

    Knowledge of climatic variability at small spatial extents (< 50 km) is needed to assess vulnerabilities of biological reserves to climate change. We used empirical and modeled weather station data to test if climate change has increased the synchrony of surface air temperatures among 50 sites within the Greater Yellowstone Area (GYA) of the interior western United States. This important biological reserve is the largest protected area in the Lower 48 states and provides critical habitat for some of the world's most iconic wildlife. We focused our analyses on temporal shifts and shape changes in the annual distributions of seasonal minimum and maximum air temperatures among valley-bottom and higher elevation sites from 1948-2012. We documented consistent patterns of warming since 1948 at all 50 sites, with the most pronounced changes occurring during the Winter and Summer when minimum and maximum temperature distributions increased. These shifts indicate more hot temperatures and less cold temperatures would be expected across the GYA. Though the shifting statistical distributions indicate warming, little change in the shape of the temperature distributions across sites since 1948 suggest the GYA has maintained a diverse portfolio of temperatures within a year. Spatial heterogeneity in temperatures is likely maintained by the GYA's physiographic complexity and its large size, which encompasses multiple climate zones that respond differently to synoptic drivers. Having a diverse portfolio of temperatures may help biological reserves spread the extinction risk posed by climate change. PMID:26674185

  1. The shifting climate portfolio of the Greater Yellowstone Area

    USGS Publications Warehouse

    Sepulveda, Adam; Tercek, Mike T; Al-Chokhachy, Robert K.; Ray, Andrew; Thoma, David P.; Hossack, Blake R.; Pederson, Gregory T.; Rodman, Ann; Olliff, Tom

    2015-01-01

    Knowledge of climatic variability at small spatial extents (< 50 km) is needed to assess vulnerabilities of biological reserves to climate change. We used empirical and modeled weather station data to test if climate change has increased the synchrony of surface air temperatures among 50 sites within the Greater Yellowstone Area (GYA) of the interior western United States. This important biological reserve is the largest protected area in the Lower 48 states and provides critical habitat for some of the world’s most iconic wildlife. We focused our analyses on temporal shifts and shape changes in the annual distributions of seasonal minimum and maximum air temperatures among valley-bottom and higher elevation sites from 1948–2012. We documented consistent patterns of warming since 1948 at all 50 sites, with the most pronounced changes occurring during the Winter and Summer when minimum and maximum temperature distributions increased. These shifts indicate more hot temperatures and less cold temperatures would be expected across the GYA. Though the shifting statistical distributions indicate warming, little change in the shape of the temperature distributions across sites since 1948 suggest the GYA has maintained a diverse portfolio of temperatures within a year. Spatial heterogeneity in temperatures is likely maintained by the GYA’s physiographic complexity and its large size, which encompasses multiple climate zones that respond differently to synoptic drivers. Having a diverse portfolio of temperatures may help biological reserves spread the extinction risk posed by climate change.

  2. The Shifting Climate Portfolio of the Greater Yellowstone Area

    PubMed Central

    Sepulveda, Adam J.; Tercek, Michael T.; Al-Chokhachy, Robert; Ray, Andrew M.; Thoma, David P.; Hossack, Blake R.; Pederson, Gregory T.; Rodman, Ann W.; Olliff, Tom

    2015-01-01

    Knowledge of climatic variability at small spatial extents (< 50 km) is needed to assess vulnerabilities of biological reserves to climate change. We used empirical and modeled weather station data to test if climate change has increased the synchrony of surface air temperatures among 50 sites within the Greater Yellowstone Area (GYA) of the interior western United States. This important biological reserve is the largest protected area in the Lower 48 states and provides critical habitat for some of the world’s most iconic wildlife. We focused our analyses on temporal shifts and shape changes in the annual distributions of seasonal minimum and maximum air temperatures among valley-bottom and higher elevation sites from 1948–2012. We documented consistent patterns of warming since 1948 at all 50 sites, with the most pronounced changes occurring during the Winter and Summer when minimum and maximum temperature distributions increased. These shifts indicate more hot temperatures and less cold temperatures would be expected across the GYA. Though the shifting statistical distributions indicate warming, little change in the shape of the temperature distributions across sites since 1948 suggest the GYA has maintained a diverse portfolio of temperatures within a year. Spatial heterogeneity in temperatures is likely maintained by the GYA’s physiographic complexity and its large size, which encompasses multiple climate zones that respond differently to synoptic drivers. Having a diverse portfolio of temperatures may help biological reserves spread the extinction risk posed by climate change. PMID:26674185

  3. Abrupt changes in rainfall during the twentieth century

    NASA Astrophysics Data System (ADS)

    Narisma, G.; Foley, J.; Licker, R.; Ramankutty, N.

    2007-12-01

    mostly located in semi-arid and arid regions (with rainfall amounts of about 350-700 mm per year). This is consistent with climate modeling results, which include the effects of dynamic vegetation cover. These studies show that arid and semi-arid regions are more likely to have multiple equilibrium states and exhibit abrupt "regime shifts" between states. Our analysis shows the extent and magnitude of sudden decreases in rainfall across the globe during the 20th century and is an important first step for studying dynamics of and the mechanisms behind these abrupt changes.

  4. The Glacial-Interglacial Deuterium Excess Signal in the Illimani ice Core (Bolivia) Reveals Long Term and Abrupt Climate Changes

    NASA Astrophysics Data System (ADS)

    Vimeux, F.; Ramirez, E.; Sylvestre, F.; Hoffmann, G.

    2006-12-01

    The Illimani ice core, located on the Bolivian Cordillera Real (16S, 67W, 6350m) and covering approximately the last 18,000 years, has provided a wealth of paleoclimate information relative to the Andean and Amazonian regions. Specifically, isotopic composition of the ice has documented well known past climate changes (the Last Glacial Maximum, the Younger Dryas period, the Holocene Optimum and the last thousand years) that might be interpreted in terms of changes in precipitation over Amazonia. Here, we present new isotopic measurements from this ice core: deuterium excess at a 1cm- depth resolution (i.e around 30-year resolution) from the bottom of the core to around 5,000 years BP present. Deuterium excess (d= delta D-8*deltaO18) is a measure of the degree to which phase change occurs away from the thermodynamic equilibrium along air masses trajectory and therefore changes with the meteorological conditions (relative humidity, surface temperature and wind) during non-total evaporation (from the ocean surface, stagnant waters as lakes, rivers or flooded soil, droplets, or canopy-intercepted water) and with the supersaturation during condensation to ice. It thus might be sensitive to climate changes 1- impacting humidity and saturation conditions of the atmosphere and 2- changing the relative moisture sources contribution of Andean precipitation (recycling versus advective moisture). Based on a calibration combining isotopic composition of modern precipitation and modeling works, we discuss the significant glacial-interglacial deuterium excess change of about 3 permil as well as the very abrupt changes (between 4 and 12 per mil) occuring during well known lacustrine Tauca phase.

  5. Abrupt State Change in Spatially-Patterned Subalpine Forests in Northern Colorado During the Medieval Climate Anomaly

    NASA Astrophysics Data System (ADS)

    Calder, W. J.; Shuman, B. N.

    2014-12-01

    Spatial patterns in many ecosystems arise from feedbacks associated with the potential for critical transitions and multiple stable states. Such systems may be susceptible to abrupt change, which could be indicated by early-warning signals, such as critical slowing down (increasingly long recovery from perturbation as a threshold approaches). Paleoecological data from ribbon forests, a type of subalpine parkland found in the Rocky Mountains, offer an opportunity to test these hypotheses. The forests consist of alternating strips of forest and meadow that form because bands of Picea and Abies trees act as snow fences with large snowdrifts forming on their lee sides. Drifts provide moisture for the adjacent trees, but also increase seedling mortality and shorten the growing season where drifts accumulate. The feedbacks between forest growth and snow accumulation maintain the ribbon forest-meadow pattern, and raise the potential for abrupt change if the feedbacks breakdown in response to factors like drought or fire. Our fossil pollen data from Summit Lake, located on the Continental Divide in the Park Range, northern Colorado, indicate that a closed forest transitioned rapidly to a ribbon forest state at ca. 1000 BP. Artemisia pollen increased (20 to 35%) and Picea and Abies pollen decreased (25 to 15%) within a century or less after a pair of charcoal peaks. Decreased charcoal influx (from 0.6 to 0.4 pieces/cm2/yr) and fire frequency (from 4.5 to 1.5 fires/ka) coincided with the pollen assemblage changes, and is consistent with decreased landscape biomass and fuel connectivity. Initial analyses show evidence of critical slowing down before the state change. After eight of eleven fires recorded by peaks in charcoal accumulation, Artemisia pollen percentages rise to a peak consistent with brief opening of the initially forested landscape. After 2000 BP, the magnitude and duration of the post-fire changes increases until no recovery is recorded after the shift at 1000

  6. A Perceptual Pathway to Bias: Interracial Exposure Reduces Abrupt Shifts in Real-Time Race Perception That Predict Mixed-Race Bias.

    PubMed

    Freeman, Jonathan B; Pauker, Kristin; Sanchez, Diana T

    2016-04-01

    In two national samples, we examined the influence of interracial exposure in one's local environment on the dynamic process underlying race perception and its evaluative consequences. Using a mouse-tracking paradigm, we found in Study 1 that White individuals with low interracial exposure exhibited a unique effect of abrupt, unstable White-Black category shifting during real-time perception of mixed-race faces, consistent with predictions from a neural-dynamic model of social categorization and computational simulations. In Study 2, this shifting effect was replicated and shown to predict a trust bias against mixed-race individuals and to mediate the effect of low interracial exposure on that trust bias. Taken together, the findings demonstrate that interracial exposure shapes the dynamics through which racial categories activate and resolve during real-time perceptions, and these initial perceptual dynamics, in turn, may help drive evaluative biases against mixed-race individuals. Thus, lower-level perceptual aspects of encounters with racial ambiguity may serve as a foundation for mixed-race prejudice. PMID:26976082

  7. Monsoon abrupt change and its dominant factors

    NASA Astrophysics Data System (ADS)

    Yao, Qiang; Fu, Conbin

    2010-05-01

    . This precipitation regime shift is in good coincidence with a significant abrupt climate change which has been extensively observed in other regions over the world as well as for other variables. The East Asia summer monsoon's abrupt change mainly result from the SST forcing which derive from pacific ocean and mid-latitude atmospheric circulation pattern's distribution. The abrupt change in late 1990s may be induced by vegetation cover change caused by the anthropogenic activity. Through analysis about Indian summer monsoon, it displays that SST forcing derived from North Atlantic Ocean plays an important role in the abrupt change or regime shift, and further research suggests that although the forcing signals are fairly weak, certain internal feedback in monsoon dynamics may have amplified the weak external forcing. On the other hand, West Africa summer monsoon has also undergone obvious abrupt change, especially in late 1960s, characterised by lasting precipitation decreasing in Sahel region approximately for 30 years. The dominant factors are the vegetation cover change and SST forcing derived from Atlantic Ocean.

  8. Microbial Community Dynamics from Permafrost Across the Pleistocene-Holocene Boundary and Response to Abrupt Climate Change

    NASA Astrophysics Data System (ADS)

    Hammad, A.; Mahony, M.; Froese, D. G.; Lanoil, B. D.

    2014-12-01

    Earth is currently undergoing rapid warming similar to that observed about 10,000 years ago at the end of the Pleistocene. We know a considerable amount about the adaptations and extinctions of mammals and plants at the Pleistocene/Holocene (P/H) boundary, but relatively little about changes at the microbial level. Due to permafrost soils' freezing anoxic conditions, they act as microbial diversity archives allowing us to determine how microbial communities adapted to the abrupt warming at the end of P. Since microbial community composition only helps differentiate viable and extant microorganisms in frozen permafrost, microbial activity in thawing permafrost must be investigated to provide a clear understanding of microbial response to climate change. Current increased temperatures will result in warming and potential thaw of permafrost and release of stored organic carbon, freeing it for microbial utilization; turning permafrost into a carbon source. Studying permafrost viable microbial communities' diversity and activity will provide a better understanding of how these microorganisms respond to soil edaphic variability due to climate change across the P/H boundary, providing insight into the changes that the soil community is currently undergoing in this modern era of rapid climate change. Modern soil, H and P permafrost cores were collected from Lucky Lady II site outside Dawson City, Yukon. 16S rRNA high throughput sequencing of permafrost DNA showed the same trends for total and viable community richness and diversity with both decreasing with permafrost depth and only the richness increasing in mid and early P. The modern, H and P soils had 50.9, 33.9, and 27.3% unique viable species and only 14% of the total number of viable species were shared by all soils. Gas flux measurements of thawed permafrost showed metabolic activity in modern and permafrost soils, aerobic CH­­4 consumption in modern, some H and P soils, and anaerobic CH­­4 production in one H

  9. Climate-driven regime shift of a temperate marine ecosystem.

    PubMed

    Wernberg, Thomas; Bennett, Scott; Babcock, Russell C; de Bettignies, Thibaut; Cure, Katherine; Depczynski, Martial; Dufois, Francois; Fromont, Jane; Fulton, Christopher J; Hovey, Renae K; Harvey, Euan S; Holmes, Thomas H; Kendrick, Gary A; Radford, Ben; Santana-Garcon, Julia; Saunders, Benjamin J; Smale, Dan A; Thomsen, Mads S; Tuckett, Chenae A; Tuya, Fernando; Vanderklift, Mathew A; Wilson, Shaun

    2016-07-01

    Ecosystem reconfigurations arising from climate-driven changes in species distributions are expected to have profound ecological, social, and economic implications. Here we reveal a rapid climate-driven regime shift of Australian temperate reef communities, which lost their defining kelp forests and became dominated by persistent seaweed turfs. After decades of ocean warming, extreme marine heat waves forced a 100-kilometer range contraction of extensive kelp forests and saw temperate species replaced by seaweeds, invertebrates, corals, and fishes characteristic of subtropical and tropical waters. This community-wide tropicalization fundamentally altered key ecological processes, suppressing the recovery of kelp forests. PMID:27387951

  10. Climate-driven regime shift of a temperate marine ecosystem.

    PubMed

    Wernberg, Thomas; Bennett, Scott; Babcock, Russell C; de Bettignies, Thibaut; Cure, Katherine; Depczynski, Martial; Dufois, Francois; Fromont, Jane; Fulton, Christopher J; Hovey, Renae K; Harvey, Euan S; Holmes, Thomas H; Kendrick, Gary A; Radford, Ben; Santana-Garcon, Julia; Saunders, Benjamin J; Smale, Dan A; Thomsen, Mads S; Tuckett, Chenae A; Tuya, Fernando; Vanderklift, Mathew A; Wilson, Shaun

    2016-07-01

    Ecosystem reconfigurations arising from climate-driven changes in species distributions are expected to have profound ecological, social, and economic implications. Here we reveal a rapid climate-driven regime shift of Australian temperate reef communities, which lost their defining kelp forests and became dominated by persistent seaweed turfs. After decades of ocean warming, extreme marine heat waves forced a 100-kilometer range contraction of extensive kelp forests and saw temperate species replaced by seaweeds, invertebrates, corals, and fishes characteristic of subtropical and tropical waters. This community-wide tropicalization fundamentally altered key ecological processes, suppressing the recovery of kelp forests.

  11. Abrupt recent shift in delta 13C and delta 15N values in Adélie penguin eggshell in Antarctica.

    PubMed

    Emslie, Steven D; Patterson, William P

    2007-07-10

    Stable isotope values of carbon (delta13C) and nitrogen (delta15N) in blood, feathers, eggshell, and bone have been used in seabird studies since the 1980s, providing a valuable source of information on diet, foraging patterns, and migratory behavior in these birds. These techniques can also be applied to fossil material when preservation of bone and other tissues is sufficient. Excavations of abandoned Adélie penguin (Pygoscelis adeliae) colonies in Antarctica often provide well preserved remains of bone, feathers, and eggshell dating from hundreds to thousands of years B.P. Herein we present an approximately 38,000-year time series of delta13C and delta15N values of Adélie penguin eggshell from abandoned colonies located in three major regions of Antarctica. Results indicate an abrupt shift to lower-trophic prey in penguin diets within the past approximately 200 years. We posit that penguins only recently began to rely on krill as a major portion of their diet, in conjunction with the removal of baleen whales and krill-eating seals during the historic whaling era. Our results support the "krill surplus" hypothesis that predicts excess krill availability in the Southern Ocean after this period of exploitation.

  12. Abrupt recent shift in δ13C and δ15N values in Adélie penguin eggshell in Antarctica

    PubMed Central

    Emslie, Steven D.; Patterson, William P.

    2007-01-01

    Stable isotope values of carbon (δ13C) and nitrogen (δ15N) in blood, feathers, eggshell, and bone have been used in seabird studies since the 1980s, providing a valuable source of information on diet, foraging patterns, and migratory behavior in these birds. These techniques can also be applied to fossil material when preservation of bone and other tissues is sufficient. Excavations of abandoned Adélie penguin (Pygoscelis adeliae) colonies in Antarctica often provide well preserved remains of bone, feathers, and eggshell dating from hundreds to thousands of years B.P. Herein we present an ≈38,000-year time series of δ13C and δ15N values of Adélie penguin eggshell from abandoned colonies located in three major regions of Antarctica. Results indicate an abrupt shift to lower-trophic prey in penguin diets within the past ≈200 years. We posit that penguins only recently began to rely on krill as a major portion of their diet, in conjunction with the removal of baleen whales and krill-eating seals during the historic whaling era. Our results support the “krill surplus” hypothesis that predicts excess krill availability in the Southern Ocean after this period of exploitation. PMID:17620620

  13. Abrupt shift toward cooler condition in the earliest 20th century detected in a 165 year coral record from Ishigaki Island, southwestern Japan

    NASA Astrophysics Data System (ADS)

    Mishima, Mari; Suzuki, Atsushi; Nagao, Masayuki; Ishimura, Toyoho; Inoue, Mayuri; Kawahata, Hodaka

    2010-08-01

    We analyzed a 165 year δ18O coral record from Ishigaki Island, southwestern Japan, and compared our results with observed sea surface temperatures, as well as with the East Asian winter monsoon and El Niño Southern Oscillation. Coral skeletal δ18O fluctuations were consistent with other available SST information since the 1890s. The coral δ18O data indicated abrupt shift toward cooler condition during 1900-1905, consistent with the extremely cold winter air temperatures observed in Japan in 1902. The cold event was also supported by coral Sr/Ca data. Development of the Siberian High may have intensified the EAWM at this time, in association with active heat convection in the tropics and weak westerlies. This cooling may also have been related to surface ocean freshening in the Ogasawara Islands in the early 20th century. Thus, several phenomena were uniquely coupled during the first few years of the 20th century in the northwestern subtropical Pacific.

  14. Has climate change shifted US maize planting times?

    NASA Astrophysics Data System (ADS)

    Butler, E.; Stine, A.; Huybers, P.

    2012-12-01

    Global warming has been accompanied by an earlier onset of spring phenological events across a range of ecosystems. However, the degree to which humans have adapted planting schedules to a changing climate remains an open question; the leading hypotheses for earlier planting are improved hardiness of cultivars and farming equipment. Here we examine the relationship between historical temperature and precipitation from 549 weather stations from the United States Historical Climatology Network (USHCN) with planting schedules from 20 states in the United States Department of Agriculture/National Agriculture Statistics Service (USDA/NASS) database. We construct an empirical model to relate yearly weather conditions to predict planting dates and compare this to the spatial distribution of climate conditions and mean planting times. Evidence for a relationship between climate and planting schedules indicates that planting schedules for US maize have been adapted to yearly variations and overall changes in climatology. As one might expect, hotter temperatures lead to earlier plantings while greater precipitation leads to later planting. These findings serve to indicate extant adaptation between US farmers and climate change, and will aid in forecasting future shifts to planting schedules as climate continues to change. Furthermore, the statistical model should also be useful for estimating planting times for states and years for which records do not otherwise exist.

  15. Speed and Magnitude of Abrupt Climate Change at 8,200 yrs B.P. from the Greenland Ice Core (GISP2)

    NASA Astrophysics Data System (ADS)

    Kobashi, T.; Severinghaus, J. P.; Brook, E. J.; Grachev, A.

    2003-12-01

    At ˜8,200 years before present, an abrupt climate change occurred, which is believed to be the largest in the past 10,000 years. The scale of the event was probably global, as seen in reduced atmospheric methane concentration and paleoclimatic evidence around the globe indicating drying and cooling trends. The timing of the climate change also coincides with widespread abandonment of villages in southwestern Asia, which marks the end of the Pre-Pottery Neolithic B (PPNB) interval. Owing to the similarity between the warm early-Holocene and the projected warmer future climate, the 8.2 k event provides us an invaluable test case for a future potential abrupt climate change. We reconstructed the speed and magnitude of temperature change at the event, using argon and nitrogen isotopes in trapped air from the Greenland ice core coupled with the oxygen isotope record of ice. This method makes use of two isotopic fractionations, gravitational and thermal, which occur within the firn layer (snow layer above the air bubble close-off depth). The analyses of argon and nitrogen isotopes can separate the two effects, and allows us to directly retrieve temperature information (Severinghaus et al., Nature, v. 391, 141, 1998). The magnitude of temperature change in central Greenland at 8.2kyr B.P. is preliminarily estimated to be 5 +/- 2 ° C for the decadal average with the experimentally determined thermal diffusion constants (Grachev and Severinghaus, Geochim. et Cosmochim. Acta, v.67, 345, 2003; J. Phys. Chem., v.107, 4636, 2003), implying an oxygen isotope-temperature coefficient, α , of ˜0.4 permil/° C. Using oxygen isotope record of ice and α , we estimate that the abrupt cooling took place within ˜5 years with an 'instantaneous' magnitude of ˜8° C, and climate was locked in the cold phase for ˜60 years. In addition, we plan to measure methane concentration in trapped air, which will constrain the mechanisms of the abrupt climate change.

  16. Climate change-driven species' range shifts filtered by photoperiodism

    NASA Astrophysics Data System (ADS)

    Saikkonen, Kari; Taulavuori, Kari; Hyvönen, Terho; Gundel, Pedro E.; Hamilton, Cyd E.; Vänninen, Irene; Nissinen, Anne; Helander, Marjo

    2012-04-01

    Forecasts of species range shifts as a result of climate change are essential, because invasions by exotic species shape biodiversity and therefore ecosystem functions and services. Ecologists have focused on propagule pressure (for example, the number of individuals and invasion events), the characteristics of an invading species, and its new abiotic and biotic environment to predict the likelihood of range expansion and invasion. Here, we emphasize the role of photoperiodic response on the range expansion of species. Unlike temperature, the latitudinal gradient of seasonal changes in day length is a stable, abiotic environmental factor that does not change with local or global climate. Predicting range expansions across latitudes and the subsequent consequences for native communities requires a more comprehensive understanding of how species use day length to coordinate seasonal growth, reproduction, physiology and synchronization of life cycles with interacting individuals and species.

  17. The Abrupt Climatic Changes During the Last Deglaciation: Direct Land-sea Correlation From a Marine Pollen Record off Southeastern United States

    NASA Astrophysics Data System (ADS)

    Desprat, S.; McManus, J. F.; Peteet, D.

    2007-12-01

    We present a new direct land-sea correlation covering the last deglaciation in order a) to provide a better documentation of the regional vegetation changes in southeastern North America and b) more particularly to assess the connection of the continental climatic changes to North Atlantic circulation rapid variability. It was achieved using coupled analyses of pollen and marine climatic proxies from core KNR140-GGC39 (Blake Outer Ridge) at very high time-resolution. Mg/Ca ratio, planktonic δ18O, mean "sortable silt" grain size (mean S¯S¯) were analyzed in order to get records of SST, salinity and bottom current strength at the core site (Evans et al., submitted to Paleoceanography). The abrupt climatic changes which characterize the last deglaciation, in particular the major cold oscillations Heinrich event 1 (H1) and Younger Dryas (YD), have been widely documented in the North Atlantic and adjacent continents. However, in the tropical and subtropical North Atlantic and southeastern United States, the climatic signature of these events appears quite different and somehow unclear. Our direct land-sea correlation shows three configurations: 1- H1 period: cold climatic conditions in southeastern US (high percentages of boreal and herbaceous taxa) but only extremely cold at around 17 ka, accumulation of salty water in the subtropics (high δ18OSW- IVC) and weak bottom current intensity at the site (low mean S¯S¯) 2- Bolling Alleröd interval: abrupt warming in southeastern US (decrease of boreal taxa in favour of Quercus) at the beginning, synchronous to northern export of the salty water previously accumulated and to an increase of the bottom current strength at the site 3- YD period: mild and wet conditions in southeastern US (expansion of Tsuga and Quercus), decrease of the bottom current strength at the site and accumulation of salty water in the subtropical regions but less than during H1.

  18. Analysis of climate paths reveals potential limitations on species range shifts.

    PubMed

    Early, Regan; Sax, Dov F

    2011-11-01

    Forecasts of species endangerment under climate change usually ignore the processes by which species ranges shift. By analysing the 'climate paths' that range shifts might follow, and two key range-shift processes--dispersal and population persistence--we show that short-term climatic and population characteristics have dramatic effects on range-shift forecasts. By employing this approach with 15 amphibian species in the western USA, we make unexpected predictions. First, inter-decadal variability in climate change can prevent range shifts by causing gaps in climate paths, even in the absence of geographic barriers. Second, the hitherto unappreciated trait of persistence during unfavourable climatic conditions is critical to species range shifts. Third, climatic fluctuations and low persistence could lead to endangerment even if the future potential range size is large. These considerations may render habitat corridors ineffectual for some species, and conservationists may need to consider managed relocation and augmentation of in situ populations. PMID:21955643

  19. ENSO's non-stationary and non-Gaussian character: the role of climate shifts

    NASA Astrophysics Data System (ADS)

    Boucharel, J.; Dewitte, B.; Garel, B.; Du Penhoat, Y.

    2009-07-01

    El Niño Southern Oscillation (ENSO) is the dominant mode of climate variability in the Pacific, having socio-economic impacts on surrounding regions. ENSO exhibits significant modulation on decadal to inter-decadal time scales which is related to changes in its characteristics (onset, amplitude, frequency, propagation, and predictability). Some of these characteristics tend to be overlooked in ENSO studies, such as its asymmetry (the number and amplitude of warm and cold events are not equal) and the deviation of its statistics from those of the Gaussian distribution. These properties could be related to the ability of the current generation of coupled models to predict ENSO and its modulation. Here, ENSO's non-Gaussian nature and asymmetry are diagnosed from in situ data and a variety of models (from intermediate complexity models to full-physics coupled general circulation models (CGCMs)) using robust statistical tools initially designed for financial mathematics studies. In particular α-stable laws are used as theoretical background material to measure (and quantify) the non-Gaussian character of ENSO time series and to estimate the skill of ``naïve'' statistical models in producing deviation from Gaussian laws and asymmetry. The former are based on non-stationary processes dominated by abrupt changes in mean state and empirical variance. It is shown that the α-stable character of ENSO may result from the presence of climate shifts in the time series. Also, cool (warm) periods are associated with ENSO statistics having a stronger (weaker) tendency towards Gaussianity and lower (greater) asymmetry. This supports the hypothesis of ENSO being rectified by changes in mean state through nonlinear processes. The relationship between changes in mean state and nonlinearity (skewness) is further investigated both in the Zebiak and Cane (1987)'s model and the models of the Intergovernmental Panel for Climate Change (IPCC). Whereas there is a clear relationship in all

  20. Work More? The 8.2 kaBP Abrupt Climate Change Event and the Origins of Irrigation Agriculture and Surplus Agro-Production in Mesopotamia

    NASA Astrophysics Data System (ADS)

    Weiss, H.

    2003-12-01

    The West Asian archaeological record is of sufficient transparency and resolution to permit observation of the social responses to the major Holocene abrupt climate change events at 8.2, 5.2 and 4.2 kaBP. The 8.2kaBP abrupt climate change event in West Asia was a three hundred year aridification and cooling episode. During this period rain-fed agriculture, established for over a millennium in northern Mesopotamia, suddenly collapsed. Irrigation agriculture, pastoral nomadism, or migration were the only subsistence alternatives for populations previously supported by cereal dry-farming. Irrigation agriculture was not, however, possible along the northern alluvial plains of the Tigris and Euphrates Rivers, where incised riverbeds were several meters below plain level. Exploitable plain-level levees were only accessible in southern-most alluvial plain, at the head of the present-day Persian Gulf. The archaeological data from this region documents the first irrigation agriculture settlement of the plain during the 8.2 kaBP event. Irrigation agriculture provides about twice the yield of dry-farming in Mesopotamia, but at considerable labor costs relative to dry-farming. With irrigation agriculture surplus production was now available for deployment. But why work more? The 8.2 kaBP event provided the natural force for Mesopotamian irrigation agriculture and surplus production that were essential for the earliest class-formation and urban life.

  1. Ecosystem Network Shifts As Indicators of Climate Response

    NASA Astrophysics Data System (ADS)

    Goodwell, A. E.; Kumar, P.

    2014-12-01

    Ecosystem states evolve due to complex interactions over various space and time scales. Process networks, in which nodes are time series variables and directional links are measures of information transfer, provide a method to analyze an ecosystem in terms of feedbacks, information transfer, and synchronization. It has been shown using FLUXNET data and ecohydrological modeling that variables such as precipitation, soil temperature, soil moisture, and heat fluxes exhibit forcings and feedbacks that are altered during periods of climate extremes such as drought. In this study, we use methods to deal with short datasets to observe shifts in network behavior over hourly to daily timescales. We compute network properties including transfer entropy, mutual information, and net system transport. To test our methods, we first generate chaotic test networks of various sizes and connectivity structures. It is found that a single feedback between two nodes causes a "self-feedback" to be detected at both nodes, which propagates throughout the network causing complete connectivity at predictable timescales. Depending on the symmetry of feedbacks and overall connectivity, a network may partially or completely synchronize. We then apply our methods to evaluate short-term ecosystem responses to climate extremes in agricultural landscapes in Illinois. We use 30- minute flux tower data from Bondville, IL, and 1 to15-minute data from recently installed weather stations and flux tower in the Sangamon River watershed to analyze network structure before, during, and after rainfall events or dry periods. Simulations in MLCan, a plant-atmosphere-canopy model, are performed to incorporate unmeasured nodes involving photosynthesis and soil hydrology. We compare the structure of feedbacks, forcings, and synchronization to vegetation response as measured by LAI or NDVI, in addition to a comparison with our test networks. This type of analysis can identify the feedbacks and links critical for

  2. Shifting distributions and speciation: species divergence during rapid climate change.

    PubMed

    Carstens, Bryan C; Knowles, L Lacey

    2007-02-01

    Questions about how shifting distributions contribute to species diversification remain virtually without answer, even though rapid climate change during the Pleistocene clearly impacted genetic variation within many species. One factor that has prevented this question from being adequately addressed is the lack of precision associated with estimates of species divergence made from a single genetic locus and without incorporating processes that are biologically important as populations diverge. Analysis of DNA sequences from multiple variable loci in a coalescent framework that (i) corrects for gene divergence pre-dating speciation, and (ii) derives divergence-time estimates without making a priori assumptions about the processes underlying patterns of incomplete lineage sorting between species (i.e. allows for the possibility of gene flow during speciation), is critical to overcoming the inherent logistical and analytical difficulties of inferring the timing and mode of speciation during the dynamic Pleistocene. Estimates of species divergence that ignore these processes, use single locus data, or do both can dramatically overestimate species divergence. For example, using a coalescent approach with data from six loci, the divergence between two species of montane Melanoplus grasshoppers is estimated at between 200,000 and 300,000 years before present, far more recently than divergence estimates made using single-locus data or without the incorporation of population-level processes. Melanoplus grasshoppers radiated in the sky islands of the Rocky Mountains, and the analysis of divergence between these species suggests that the isolation of populations in multiple glacial refugia was an important factor in promoting speciation. Furthermore, the low estimates of gene flow between the species indicate that reproductive isolation must have evolved rapidly for the incipient species boundaries to be maintained through the subsequent glacial periods and shifts in species

  3. Shifting distributions and speciation: species divergence during rapid climate change.

    PubMed

    Carstens, Bryan C; Knowles, L Lacey

    2007-02-01

    Questions about how shifting distributions contribute to species diversification remain virtually without answer, even though rapid climate change during the Pleistocene clearly impacted genetic variation within many species. One factor that has prevented this question from being adequately addressed is the lack of precision associated with estimates of species divergence made from a single genetic locus and without incorporating processes that are biologically important as populations diverge. Analysis of DNA sequences from multiple variable loci in a coalescent framework that (i) corrects for gene divergence pre-dating speciation, and (ii) derives divergence-time estimates without making a priori assumptions about the processes underlying patterns of incomplete lineage sorting between species (i.e. allows for the possibility of gene flow during speciation), is critical to overcoming the inherent logistical and analytical difficulties of inferring the timing and mode of speciation during the dynamic Pleistocene. Estimates of species divergence that ignore these processes, use single locus data, or do both can dramatically overestimate species divergence. For example, using a coalescent approach with data from six loci, the divergence between two species of montane Melanoplus grasshoppers is estimated at between 200,000 and 300,000 years before present, far more recently than divergence estimates made using single-locus data or without the incorporation of population-level processes. Melanoplus grasshoppers radiated in the sky islands of the Rocky Mountains, and the analysis of divergence between these species suggests that the isolation of populations in multiple glacial refugia was an important factor in promoting speciation. Furthermore, the low estimates of gene flow between the species indicate that reproductive isolation must have evolved rapidly for the incipient species boundaries to be maintained through the subsequent glacial periods and shifts in species

  4. The impact of shift work and organizational work climate on health outcomes in nurses.

    PubMed

    von Treuer, Kathryn; Fuller-Tyszkiewicz, Matthew; Little, Glenn

    2014-10-01

    Shift workers have a higher rate of negative health outcomes than day shift workers. Few studies however, have examined the role of difference in workplace environment between shifts itself on such health measures. This study investigated variation in organizational climate across different types of shift work and health outcomes in nurses. Participants (n = 142) were nursing staff from a metropolitan Melbourne hospital. Demographic items elicited the type of shift worked, while the Work Environment Scale and the General Health Questionnaire measured organizational climate and health respectively. Analysis supported the hypotheses that different organizational climates occurred across different shifts, and that different organizational climate factors predicted poor health outcomes. Shift work alone was not found to predict health outcomes. Specifically, permanent night shift workers had significantly lower coworker cohesion scores compared with rotating day and evening shift workers and significantly higher managerial control scores compared with day shift workers. Further, coworker cohesion and involvement were found to be significant predictors of somatic problems. These findings suggest that differences in organizational climate between shifts accounts for the variation in health outcomes associated with shift work. Therefore, increased workplace cohesion and involvement, and decreased work pressure, may mitigate the negative health outcomes of shift workers.

  5. The Preboreal climate reversal and a subsequent solar-forced climate shift

    NASA Astrophysics Data System (ADS)

    van der Plicht, J.; van Geel, B.; Bohncke, S. J. P.; Bos, J. A. A.; Blaauw, M.; Speranza, A. O. M.; Muscheler, R.; Björck, S.

    2004-03-01

    Accurate chronologies are essential for linking palaeoclimate archives. Carbon-14 wiggle-match dating was used to produce an accurate chronology for part of an early Holocene peat sequence from the Borchert (The Netherlands). Following the Younger Dryas-Preboreal transition, two climatic shifts could be inferred. Around 11 400 cal. yr BP the expansion of birch (Betula) forest was interrupted by a dry continental phase with dominantly open grassland vegetation, coeval with the PBO (Preboreal Oscillation), as observed in the GRIP ice core. At 11 250 cal. yr BP a sudden shift to a humid climate occurred. This second change appears to be contemporaneous with: (i) a sharp increase of atmospheric 14C; (ii) a temporary decline of atmospheric CO2; and (iii) an increase in the GRIP 10Be flux. The close correspondence with excursions of cosmogenic nuclides points to a decline in solar activity, which may have forced the changes in climate and vegetation at around 11 250 cal. yr BP. Copyright

  6. New evidence from the South China Sea for an abrupt termination of the last glacial period

    NASA Technical Reports Server (NTRS)

    Broecker, W. S.; Klas, M.; Andree, M.; Bonani, G.; Wolfli, W.

    1988-01-01

    Results demonstrating an abrupt change in the rate and character of sedimentation in the South China Sea at the close of the last glacial period are presented. Radiocarbon dating and its position in the oxygen isotope shift suggest that this change may be coincident with the abrupt change in climatic conditions seen at high latitudes in the North Atlantic and the Antarctic at 13 kyr BP. These results support the contention that a major global climatic change occurred between 14 and 13 kyr BP.

  7. Analysis of abrupt transitions in ecological systems

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The occurrence and causes of abrupt transitions, thresholds, or regime shifts between ecosystem states are of great concern and the likelihood of such transitions is increasing for many ecological systems. General understanding of abrupt transitions has been advanced by theory, but hindered by the l...

  8. Detecting abrupt dynamic change based on changes in the fractal properties of spatial images

    NASA Astrophysics Data System (ADS)

    Liu, Qunqun; He, Wenping; Gu, Bin; Jiang, Yundi

    2016-08-01

    Many abrupt climate change events often cannot be detected timely by conventional abrupt detection methods until a few years after these events have occurred. The reason for this lag in detection is that abundant and long-term observational data are required for accurate abrupt change detection by these methods, especially for the detection of a regime shift. So, these methods cannot help us understand and forecast the evolution of the climate system in a timely manner. Obviously, spatial images, generated by a coupled spatiotemporal dynamical model, contain more information about a dynamic system than a single time series, and we find that spatial images show the fractal properties. The fractal properties of spatial images can be quantitatively characterized by the Hurst exponent, which can be estimated by two-dimensional detrended fluctuation analysis (TD-DFA). Based on this, TD-DFA is used to detect an abrupt dynamic change of a coupled spatiotemporal model. The results show that the TD-DFA method can effectively detect abrupt parameter changes in the coupled model by monitoring the changing in the fractal properties of spatial images. The present method provides a new way for abrupt dynamic change detection, which can achieve timely and efficient abrupt change detection results.

  9. Abrupt climate events 500,000 to 340,000 years ago: Evidence from subpolar North Atlantic sediments

    SciTech Connect

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

    1998-02-27

    Subpolar North Atlantic proxy records document millennial-scale climate variations 500,000 to 340,000 years ago. The cycles have an approximately constant pacing that is similar to that documented for the last glacial cycle. These findings suggest that such climate variations are inherent to the late Pleistocene, regardless of glacial state. Sea surface temperature during the warm peak of Marine Isotope Stage 11 (MIS 11) varied by 0.5{degree} to 1{degree}C, less than the 4{degree} to 4.5{degree}C estimated during times of ice growth and the 3{degree}C estimated for glacial maxima. Coherent deep ocean circulation changes were associated with glacial oscillations in sea surface temperature. 31 refs., 3 figs.

  10. Abrupt change of the mid-summer climate in central east China by the influence of atmospheric pollution

    NASA Astrophysics Data System (ADS)

    Xu, Qun

    Following the great flooding of summer 1998, the mid-lower Yangtze Basin further suffered from another large flooding in summer 1999. Successive droughts through 3 recent summers (1997-1999) appeared in north China in addition, leading to an abnormal summer climate pattern of "north drought with south flooding". Such southward move of the summer monsoon rainy belt in east China started in the late 1970s-early 1980s. Its main cause may not be a purely natural climate change, but the acceleration of industrialization in east China could play a major role by emitting large volumes of SO 2, especially from the rapidly growing rural factories of east China. The annual release of SO 2 in China exceeded 20 Tg during 1992-1998, so dense sulfate aerosols covered the central east China which significantly reduced the sunlight. Although present estimates for the changes of clear sky global solar radiation may include some error, they show that the negative radiative forcing of sulfate aerosols in central east China by far exceeds the effect of greenhouse warming in summer. Hence the mid-summer monsoon rainy belt of east China has a trend moving southward in 21 recent years (1979-1999), showing the very sensitive characteristic of the summer monsoon system to the change in heat equilibrium of the land surface. The occurrence rate of summer climate pattern of "north drought with south flooding" in east China during 21 recent years is the largest since AD 950; such anomalous climate has brought large losses to China. The only possible way to reverse this southward trend of summer monsoon rainy belt is to significantly reduce air pollution by using more clean energy. Recently, the PRC has paid serious attention to this problem by adopting a series of countermeasures.

  11. The Nonlinear Response of the Equatorial Pacific Ocean-Atmosphere System to Periodic Variations in Insolation and its Association with the Abrupt Climate Transitions during the Quaternary.

    NASA Astrophysics Data System (ADS)

    Lopes, P. G.

    2015-12-01

    The evidences of climate changes during the Quaternary are abundant but the physical mechanisms behind the climate transitions are controversial. The theory of Milankovitch takes into account the periodic orbital variations and the solar radiation received by the Earth as the main explanation for the glacial-interglacial cycles. However, some gaps in the theory still remain. In this study, we propose elucidating some of these gaps by approaching the Equatorial Pacific Ocean as a large oscillator, capable of triggering climate changes in different temporal scales. A mathematical model representing El Ninõ-like phenomena, based on Duffing equation and modulated by the astronomical cycle of 100 ka, was used to simulate the variability of the equatorial Pacific climate system over the last 2 Ma. The physical configuration of the Pacific Ocean, expressed in the equation, explains the temporal limit of the glacial-interglacial cycles. According to the simulation results, consistent with paleoclimate records, the amplification of the effects of the gradual variation of the Earth's orbit eccentricity - another unclear question - is due to the feedback mechanism of the Pacific ocean-atmosphere system, which responds non-linearly to small variations in insolation forcing and determines the ENSO-like phase (warm or cold) at different time scales and different intensities. The approach proposed here takes into account that the abrupt transitions between the ENSO-like phases, and the consequent changes in the sea surface temperature (SST) along the Equatorial Pacific Ocean, produce reactions that act as secondary causes of the temperature fluctuations that result in a glaciation (or deglaciation) - as the drastic change on the rate of evaporation/precipitation around the globe, and the increase (or decrease) of the atmospheric CO2 absorption by the phytoplankton. The transitional behavior between the warm and the cold phases, according to the presented model, is enhanced as

  12. Geographical limits to species-range shifts are suggested by climate velocity.

    PubMed

    Burrows, Michael T; Schoeman, David S; Richardson, Anthony J; Molinos, Jorge García; Hoffmann, Ary; Buckley, Lauren B; Moore, Pippa J; Brown, Christopher J; Bruno, John F; Duarte, Carlos M; Halpern, Benjamin S; Hoegh-Guldberg, Ove; Kappel, Carrie V; Kiessling, Wolfgang; O'Connor, Mary I; Pandolfi, John M; Parmesan, Camille; Sydeman, William J; Ferrier, Simon; Williams, Kristen J; Poloczanska, Elvira S

    2014-03-27

    The reorganization of patterns of species diversity driven by anthropogenic climate change, and the consequences for humans, are not yet fully understood or appreciated. Nevertheless, changes in climate conditions are useful for predicting shifts in species distributions at global and local scales. Here we use the velocity of climate change to derive spatial trajectories for climatic niches from 1960 to 2009 (ref. 7) and from 2006 to 2100, and use the properties of these trajectories to infer changes in species distributions. Coastlines act as barriers and locally cooler areas act as attractors for trajectories, creating source and sink areas for local climatic conditions. Climate source areas indicate where locally novel conditions are not connected to areas where similar climates previously occurred, and are thereby inaccessible to climate migrants tracking isotherms: 16% of global surface area for 1960 to 2009, and 34% of ocean for the 'business as usual' climate scenario (representative concentration pathway (RCP) 8.5) representing continued use of fossil fuels without mitigation. Climate sink areas are where climate conditions locally disappear, potentially blocking the movement of climate migrants. Sink areas comprise 1.0% of ocean area and 3.6% of land and are prevalent on coasts and high ground. Using this approach to infer shifts in species distributions gives global and regional maps of the expected direction and rate of shifts of climate migrants, and suggests areas of potential loss of species richness.

  13. The complex behavior of the Cordilleran Ice Sheet and mountain glaciers to abrupt climate change during the latest Pleistocene

    NASA Astrophysics Data System (ADS)

    Menounos, Brian; Goehring, Brent; Osborn, Gerald; Clarke, Garry K. C.; Ward, Brent; Margold, Martin; Bond, Jeff; Clague, John J.; Lakeman, Tom; Schaefer, Joerg; Koch, Joe; Gosse, John; Stroeven, Arjen P.; Seguinot, Julien; Heyman, Jakob; Fulton, Robert

    2014-05-01

    Surficial mapping and more than 70 radiometric ages 10Be, 14C] constrain the evolution of the Cordilleran Ice Sheet (CIS) and associated mountain glaciers in western Canada during the latest Pleistocene. Our data suggest that: i) there is widespread evidence for the Younger Dryas (YD) throughout the mountains of western Canada; ii) late Pleistocene climate reconstructions based solely on alpine moraines may be misleading in regions with decaying ice sheets; iii) extensive interfluves in some mountain regions were ice-free between 16 ka and 13 ka (kilo calibrated yrs BP). Initial decay of the CIS from its maximum extent around 16 ka was likely due to a combination of climatic (surface melting) and dynamical factors. Climate amelioration during the Bølling-Allerød Warm Period [14.7-12.9 ka], likely the cause for the major phase of CIS decay, resulted in ice sheet equilibrium line altitudes (ELAs) ranging from 2500 m asl in southern BC to around 2000 m asl along the BC-Yukon border. Hence, before the onset of the Younger Dryas (YD) Cold Period [12.9-11.7 ka], the ice sheet shrank and became a labyrinth of individual and coalescing valley glaciers fed by major accumulation zones centered on the Coast Mountains and other high ranges of NW Canada. The response of remnant ice and cirque glaciers to the YD climate deterioration was highly variable. In some cases, small glaciers (0.5-2 km2) built YD moraines that were only hundreds of meters beyond those constructed during the Little Ice Age (LIA) [0.30-0.15 ka]. Our dating also reveals that much larger glaciers persisted in nearby valleys that lie hundreds of meters below the cirques. Hence, we infer that many cirques were completely deglaciated prior the YD, in contrast to low-lying valleys where ice sheet remnants persisted. Glaciers also advanced in north-central British Columbia during the YD, but here glaciers constructed large terminal and lateral moraines. In the Cassiar and northern Coast mountains, for example

  14. Directionality of recent bird distribution shifts and climate change in Great Britain.

    PubMed

    Gillings, Simon; Balmer, Dawn E; Fuller, Robert J

    2015-06-01

    There is good evidence that species' distributions are shifting poleward in response to climate change and wide interest in the magnitude of such responses for scientific and conservation purposes. It has been suggested from the directions of climatic changes that species' distribution shifts may not be simply poleward, but this has been rarely tested with observed data. Here, we apply a novel approach to measuring range shifts on axes ranging through 360°, to recent data on the distributions of 122 species of British breeding birds during 1988-1991 and 2008-2011. Although previously documented poleward range shifts have continued, with an average 13.5 km shift northward, our analysis indicates this is an underestimate because it ignores common and larger shifts that occurred along axes oriented to the north-west and north-east. Trailing edges contracted from a broad range of southerly directions. Importantly, these results are derived from systematically collected data so confounding observer-effort biases can be discounted. Analyses of climate for the same period show that whilst temperature trends should drive species along a north-north-westerly trajectory, directional responses to precipitation will depend on both the time of year that is important for determining a species' distribution, and the location of the range margin. Directions of species' range centroid shift were not correlated with spatial trends in any single climate variable. We conclude that range shifts of British birds are multidirectional, individualistic and probably determined by species-specific interactions of multiple climate factors. Climate change is predicted to lead to changes in community composition through variation in the rates that species' ranges shift; our results suggest communities could change further owing to constituent species shifting along different trajectories. We recommend more studies consider directionality in climate and range dynamics to produce more

  15. 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

  16. Sensitivity of river fishes to climate change: The role of hydrological stressors on habitat range shifts.

    PubMed

    Segurado, Pedro; Branco, Paulo; Jauch, Eduardo; Neves, Ramiro; Ferreira, M Teresa

    2016-08-15

    Climate change will predictably change hydrological patterns and processes at the catchment scale, with impacts on habitat conditions for fish. The main goal of this study is to assess how shifts in fish habitat favourability under climate change scenarios are affected by hydrological stressors. The interplay between climate and hydrological stressors has important implications in river management under climate change because management actions to control hydrological parameters are more feasible than controlling climate. This study was carried out in the Tamega catchment of the Douro basin. A set of hydrological stressor variables were generated through a process-based modelling based on current climate data (2008-2014) and also considering a high-end future climate change scenario. The resulting parameters, along with climatic and site-descriptor variables were used as explanatory variables in empirical habitat models for nine fish species using boosted regression trees. Models were calibrated for the whole Douro basin using 254 fish sampling sites and predictions under future climate change scenarios were made for the Tamega catchment. Results show that models using climatic variables but not hydrological stressors produce more stringent predictions of future favourability, predicting more distribution contractions or stronger range shifts. The use of hydrological stressors strongly influences projections of habitat favourability shifts; the integration of these stressors in the models thinned shifts in range due to climate change. Hydrological stressors were retained in the models for most species and had a high importance, demonstrating that it is important to integrate hydrology in studies of impacts of climate change on freshwater fishes. This is a relevant result because it means that management actions to control hydrological parameters in rivers will have an impact on the effects of climate change and may potentially be helpful to mitigate its negative

  17. Sensitivity of river fishes to climate change: The role of hydrological stressors on habitat range shifts.

    PubMed

    Segurado, Pedro; Branco, Paulo; Jauch, Eduardo; Neves, Ramiro; Ferreira, M Teresa

    2016-08-15

    Climate change will predictably change hydrological patterns and processes at the catchment scale, with impacts on habitat conditions for fish. The main goal of this study is to assess how shifts in fish habitat favourability under climate change scenarios are affected by hydrological stressors. The interplay between climate and hydrological stressors has important implications in river management under climate change because management actions to control hydrological parameters are more feasible than controlling climate. This study was carried out in the Tamega catchment of the Douro basin. A set of hydrological stressor variables were generated through a process-based modelling based on current climate data (2008-2014) and also considering a high-end future climate change scenario. The resulting parameters, along with climatic and site-descriptor variables were used as explanatory variables in empirical habitat models for nine fish species using boosted regression trees. Models were calibrated for the whole Douro basin using 254 fish sampling sites and predictions under future climate change scenarios were made for the Tamega catchment. Results show that models using climatic variables but not hydrological stressors produce more stringent predictions of future favourability, predicting more distribution contractions or stronger range shifts. The use of hydrological stressors strongly influences projections of habitat favourability shifts; the integration of these stressors in the models thinned shifts in range due to climate change. Hydrological stressors were retained in the models for most species and had a high importance, demonstrating that it is important to integrate hydrology in studies of impacts of climate change on freshwater fishes. This is a relevant result because it means that management actions to control hydrological parameters in rivers will have an impact on the effects of climate change and may potentially be helpful to mitigate its negative

  18. PREDICTING CLIMATE-INDUCED RANGE SHIFTS: MODEL DIFFERENCES AND MODEL RELIABILITY

    EPA Science Inventory

    Predicted changes in the global climate are likely to cause large shifts in the geographic ranges of many plant and animal species. To date, predictions of future range shifts have relied on a variety of modeling approaches with different levels of model accuracy. Using a common ...

  19. PREDICTING CLIMATE-INDUCED RANGE SHIFTS FOR MAMMALS: HOW GOOD ARE THE MODELS?

    EPA Science Inventory

    In order to manage wildlife and conserve biodiversity, it is critical that we understand the potential impacts of climate change on species distributions. Several different approaches to predicting climate-induced geographic range shifts have been proposed to address this proble...

  20. The Climate Shift and the Climate Variability in the Mediterranean region

    NASA Astrophysics Data System (ADS)

    Lopez Parages, Jorge; Rodriguez-Fonseca, Belen

    2010-05-01

    The so-called "climate shift" (CS) was defined at the beginning of the nineties as a dramatic change between 1976-77 in the basic state of the tropical Pacific and in the ENSO dynamics. Nowadays, the 1976-1977 shift is interpreted as a phase change in a decadal scale oscillation (the Pacific Decadal Oscillation, PDO, Mantua et al. 1997) lasting from about 1976 to 1988 (Trenberth and Hurrell 1994, Miller et al. 1994). However, several changes in the global climate have been reported after the CS; as changes in the air-sea interactions and in the tropical and extratropical teleconnection patterns. The climate variability of the Mediterranean area is influenced by the North Atlantic Oscillation (NAO, Hurrell, 2003), which frequency and positive phase intensity has suffered an increase after the CS unprecedented in the instrumental period, in coincidence with extreme drought conditions in the Mediterranean region. This results remark the non-stationary variability of the NAO (Vicente-Serrano and López-Moreno, 2008b) and the existence of changes in the underlying dynamics. In addition, Tropical Atlantic Variability (TAV) and ENSO have also shown to exhibit a strong and non- stationary influence in the Mediterranean basin, with maximum correlations at the beginning of the twenty century and since the CS (Mariotti et al. 2002), in concordance with the Atlantic Multidecadal Oscillation (AMO) evolution. A recent singular discovery show the influence of the Atlantic Niño on its Pacific counterpart (Rodríguez-Fonseca et al. 2009; Losada et al. 2009), a relation that was statistically pointed out in Polo et al. (2008a). These results remark the increasing importance of the TAV on the global climate and on the observed change, from the late 70's, in the global teleconnections. Although some studies point out the seasonal dependence of the leading modes of precipitation variability over Europe (Zveryaev, 2006), in this work, a gridded monthly terrestrial gauge

  1. Inconsistent Range Shifts within Species Highlight Idiosyncratic Responses to Climate Warming

    PubMed Central

    Gibson-Reinemer, Daniel K.; Rahel, Frank J.

    2015-01-01

    Climate in part determines species’ distributions, and species’ distributions are shifting in response to climate change. Strong correlations between the magnitude of temperature changes and the extent of range shifts point to warming temperatures as the single most influential factor causing shifts in species’ distributions species. However, other abiotic and biotic factors may alter or even reverse these patterns. The importance of temperature relative to these other factors can be evaluated by examining range shifts of the same species in different geographic areas. When the same species experience warming in different geographic areas, the extent to which they show range shifts that are similar in direction and magnitude is a measure of temperature’s importance. We analyzed published studies to identify species that have documented range shifts in separate areas. For 273 species of plants, birds, mammals, and marine invertebrates with range shifts measured in multiple geographic areas, 42-50% show inconsistency in the direction of their range shifts, despite experiencing similar warming trends. Inconsistency of within-species range shifts highlights how biotic interactions and local, non-thermal abiotic conditions may often supersede the direct physiological effects of temperature. Assemblages show consistent responses to climate change, but this predictability does not appear to extend to species considered individually. PMID:26162013

  2. Facilitating climate-change-induced range shifts across continental land-use barriers.

    PubMed

    Robillard, Cassandra M; Coristine, Laura E; Soares, Rosana N; Kerr, Jeremy T

    2015-12-01

    Climate changes impose requirements for many species to shift their ranges to remain within environmentally tolerable areas, but near-continuous regions of intense human land use stretching across continental extents diminish dispersal prospects for many species. We reviewed the impact of habitat loss and fragmentation on species' abilities to track changing climates and existing plans to facilitate species dispersal in response to climate change through regions of intensive land uses, drawing on examples from North America and elsewhere. We identified an emerging analytical framework that accounts for variation in species' dispersal capacities relative to both the pace of climate change and habitat availability. Habitat loss and fragmentation hinder climate change tracking, particularly for specialists, by impeding both propagule dispersal and population growth. This framework can be used to identify prospective modern-era climatic refugia, where the pace of climate change has been slower than surrounding areas, that are defined relative to individual species' needs. The framework also underscores the importance of identifying and managing dispersal pathways or corridors through semi-continental land use barriers that can benefit many species simultaneously. These emerging strategies to facilitate range shifts must account for uncertainties around population adaptation to local environmental conditions. Accounting for uncertainties in climate change and dispersal capabilities among species and expanding biological monitoring programs within an adaptive management paradigm are vital strategies that will improve species' capacities to track rapidly shifting climatic conditions across landscapes dominated by intensive human land use. PMID:26193759

  3. Facilitating climate-change-induced range shifts across continental land-use barriers.

    PubMed

    Robillard, Cassandra M; Coristine, Laura E; Soares, Rosana N; Kerr, Jeremy T

    2015-12-01

    Climate changes impose requirements for many species to shift their ranges to remain within environmentally tolerable areas, but near-continuous regions of intense human land use stretching across continental extents diminish dispersal prospects for many species. We reviewed the impact of habitat loss and fragmentation on species' abilities to track changing climates and existing plans to facilitate species dispersal in response to climate change through regions of intensive land uses, drawing on examples from North America and elsewhere. We identified an emerging analytical framework that accounts for variation in species' dispersal capacities relative to both the pace of climate change and habitat availability. Habitat loss and fragmentation hinder climate change tracking, particularly for specialists, by impeding both propagule dispersal and population growth. This framework can be used to identify prospective modern-era climatic refugia, where the pace of climate change has been slower than surrounding areas, that are defined relative to individual species' needs. The framework also underscores the importance of identifying and managing dispersal pathways or corridors through semi-continental land use barriers that can benefit many species simultaneously. These emerging strategies to facilitate range shifts must account for uncertainties around population adaptation to local environmental conditions. Accounting for uncertainties in climate change and dispersal capabilities among species and expanding biological monitoring programs within an adaptive management paradigm are vital strategies that will improve species' capacities to track rapidly shifting climatic conditions across landscapes dominated by intensive human land use.

  4. How will biotic interactions influence climate change-induced range shifts?

    PubMed

    HilleRisLambers, Janneke; Harsch, Melanie A; Ettinger, Ailene K; Ford, Kevin R; Theobald, Elinore J

    2013-09-01

    Biotic interactions present a challenge in determining whether species distributions will track climate change. Interactions with competitors, consumers, mutualists, and facilitators can strongly influence local species distributions, but few studies assess how and whether these interactions will impede or accelerate climate change-induced range shifts. In this paper, we explore how ecologists might move forward on this question. We first outline the conditions under which biotic interactions can result in range shifts that proceed faster or slower than climate velocity and result in ecological surprises. Next, we use our own work to demonstrate that experimental studies documenting the strength of biotic interactions across large environmental gradients are a critical first step for understanding whether they will influence climate change-induced range shifts. Further progress could be made by integrating results from these studies into modeling frameworks to predict how or generalize when biotic interactions mediate how changing climates influence range shifts. Finally, we argue that many more case studies like those described here are needed to explore the importance of biotic interactions during climate change-induced range shifts.

  5. North by north-west: climate change and directions of density shifts in birds.

    PubMed

    Lehikoinen, Aleksi; Virkkala, Raimo

    2016-03-01

    There is increasing evidence that climate change shifts species distributions towards poles and mountain tops. However, most studies are based on presence-absence data, and either abundance or the observation effort has rarely been measured. In addition, hardly any studies have investigated the direction of shifts and factors affecting them. Here, we show using count data on a 1000 km south-north gradient in Finland, that between 1970-1989 and 2000-2012, 128 bird species shifted their densities, on average, 37 km towards the north north-east. The species-specific directions of the shifts in density were significantly explained by migration behaviour and habitat type. Although the temperatures have also moved on average towards the north north-east (186 km), the species-specific directions of the shifts in density and temperature did not correlate due to high variation in density shifts. Findings highlight that climate change is unlikely the only driver of the direction of species density shifts, but species-specific characteristics and human land-use practices are also influencing the direction. Furthermore, the alarming results show that former climatic conditions in the north-west corner of Finland have already moved out of the country. This highlights the need for an international approach in research and conservation actions to mitigate the impacts of climate change. PMID:26691578

  6. Parasite zoonoses and climate change: molecular tools for tracking shifting boundaries.

    PubMed

    Polley, Lydden; Thompson, R C Andrew

    2009-06-01

    For human, domestic animal and wildlife health, key effects of directional climate change include the risk of the altered occurrence of infectious diseases. Many parasite zoonoses have high potential for vulnerability to the new climate, in part because their free-living life-cycle stages and ectothermic hosts are directly exposed to climatic conditions. For these zoonoses, climate change can shift boundaries for ecosystem components and processes integral to parasite transmission and persistence, and these shifts can impact host health. Vulnerable boundaries include those for spatial distributions, host-parasite assemblages, demographic rates, life-cycle phenologies, associations within ecosystems, virulence, and patterns of infection and disease. This review describes these boundary shifts and how molecular techniques can be applied to defining the new boundaries.

  7. Locomotion in response to shifting climate zones: not so fast.

    PubMed

    Feder, Martin E; Garland, Theodore; Marden, James H; Zera, Anthony J

    2010-01-01

    Although a species' locomotor capacity is suggestive of its ability to escape global climate change, such a suggestion is not necessarily straightforward. Species vary substantially in locomotor capacity, both ontogenetically and within/among populations, and much of this variation has a genetic basis. Accordingly, locomotor capacity can and does evolve rapidly, as selection experiments demonstrate. Importantly, even though this evolution of locomotor capacity may be rapid enough to escape changing climate, genetic correlations among traits (often due to pleiotropy) are such that successful or rapid dispersers are often limited in colonization or reproductive ability, which may be viewed as a trade-off. The nuanced assessment of this variation and evolution is reviewed for well-studied models: salmon, flying versus flightless insects, rodents undergoing experimental evolution, and metapopulations of butterflies. This work reveals how integration of physiology with population biology and functional genomics can be especially informative.

  8. Locomotion in response to shifting climate zones: not so fast.

    PubMed

    Feder, Martin E; Garland, Theodore; Marden, James H; Zera, Anthony J

    2010-01-01

    Although a species' locomotor capacity is suggestive of its ability to escape global climate change, such a suggestion is not necessarily straightforward. Species vary substantially in locomotor capacity, both ontogenetically and within/among populations, and much of this variation has a genetic basis. Accordingly, locomotor capacity can and does evolve rapidly, as selection experiments demonstrate. Importantly, even though this evolution of locomotor capacity may be rapid enough to escape changing climate, genetic correlations among traits (often due to pleiotropy) are such that successful or rapid dispersers are often limited in colonization or reproductive ability, which may be viewed as a trade-off. The nuanced assessment of this variation and evolution is reviewed for well-studied models: salmon, flying versus flightless insects, rodents undergoing experimental evolution, and metapopulations of butterflies. This work reveals how integration of physiology with population biology and functional genomics can be especially informative. PMID:20148672

  9. Influence of climate regime shift on the interdecadal change in tropical cyclone activity over the Pacific Basin during the middle to late 1990s

    NASA Astrophysics Data System (ADS)

    Hong, Chi-Cherng; Wu, Yi-Kai; Li, Tim

    2016-01-01

    In this study, a new interpretation is proposed for the abrupt decrease in tropical cyclone (TC) activity in the western North Pacific (WNP) after the late 1990s. We hypothesize that this abrupt change constitutes a part of the phenomenon of interdecadal change in TC activity in the Pacific Basin, including the WNP, western South Pacific (WSP), and eastern North Pacific. Our analysis revealed that the climate-regime shift (CRS) in the Pacific during the middle to late 1990s resulted in a La Niña-like mean state, which was responsible for the interdecadal change in TC activity in the late 1990s. Analyses of the TC genesis potential index and numerical experiments revealed that the decline in TC activity in both the WNP and WSP was primarily attributable to the increase of vertical wind shear in the central Pacific due to the La Niña-like associated cold sea surface temperature (SST). Conversely, the La Niña-like associated warm SST in the western Pacific produced anomalous vertical transport of water vapor, increasing moisture levels in the mid-troposphere and TC activity in the western WNP. Furthermore, the CRS modified the mean TC genesis position and shifted the steering flow to the west, resulting in the increased frequency of TC landfalls in Taiwan, southeastern China, and northern Australia after the late 1990s.

  10. Influence of climate regime shift on the interdecadal change in tropical cyclone activity over the Pacific Basin during the middle to late 1990s

    NASA Astrophysics Data System (ADS)

    Hong, Chi-Cherng; Wu, Yi-Kai; Li, Tim

    2016-10-01

    In this study, a new interpretation is proposed for the abrupt decrease in tropical cyclone (TC) activity in the western North Pacific (WNP) after the late 1990s. We hypothesize that this abrupt change constitutes a part of the phenomenon of interdecadal change in TC activity in the Pacific Basin, including the WNP, western South Pacific (WSP), and eastern North Pacific. Our analysis revealed that the climate-regime shift (CRS) in the Pacific during the middle to late 1990s resulted in a La Niña-like mean state, which was responsible for the interdecadal change in TC activity in the late 1990s. Analyses of the TC genesis potential index and numerical experiments revealed that the decline in TC activity in both the WNP and WSP was primarily attributable to the increase of vertical wind shear in the central Pacific due to the La Niña-like associated cold sea surface temperature (SST). Conversely, the La Niña-like associated warm SST in the western Pacific produced anomalous vertical transport of water vapor, increasing moisture levels in the mid-troposphere and TC activity in the western WNP. Furthermore, the CRS modified the mean TC genesis position and shifted the steering flow to the west, resulting in the increased frequency of TC landfalls in Taiwan, southeastern China, and northern Australia after the late 1990s.

  11. Climate Warming and Seasonal Precipitation Change Interact to Limit Species Distribution Shifts across Western North America.

    PubMed

    Harsch, Melanie A; HilleRisLambers, Janneke

    2016-01-01

    Using an extensive network of occurrence records for 293 plant species collected over the past 40 years across a climatically diverse geographic section of western North America, we find that plant species distributions were just as likely to shift upwards (i.e., towards higher elevations) as downward (i.e., towards lower elevations)-despite consistent warming across the study area. Although there was no clear directional response to climate warming across the entire study area, there was significant region- to region- variation in responses (i.e. from as many as 73% to as few as 32% of species shifting upward). To understand the factors that might be controlling region-specific distributional shifts of plant species, we explored the relationship between the direction of change in distribution limits and the nature of recent climate change. We found that the direction that distribution limits shifted was explained by an interaction between the rate of change in local summer temperatures and seasonal precipitation. Specifically, species were more likely to shift upward at their upper elevational limit when minimum temperatures increased and snowfall was unchanging or declined at slower rates (<0.5 mm/year). This suggests that both low temperature and water availability limit upward shifts at upper elevation limits. By contrast, species were more likely to shift upwards at their lower elevation limit when maximum temperatures increased, but also shifted upwards under conditions of cooling temperatures when precipitation decreased. This suggests increased water stress may drive upward shifts at lower elevation limits. Our results suggest that species' elevational distribution shifts are not predictable by climate warming alone but depend on the interaction between seasonal temperature and precipitation change. PMID:27447834

  12. Climate Warming and Seasonal Precipitation Change Interact to Limit Species Distribution Shifts across Western North America

    PubMed Central

    Harsch, Melanie A.; HilleRisLambers, Janneke

    2016-01-01

    Using an extensive network of occurrence records for 293 plant species collected over the past 40 years across a climatically diverse geographic section of western North America, we find that plant species distributions were just as likely to shift upwards (i.e., towards higher elevations) as downward (i.e., towards lower elevations)–despite consistent warming across the study area. Although there was no clear directional response to climate warming across the entire study area, there was significant region- to region- variation in responses (i.e. from as many as 73% to as few as 32% of species shifting upward). To understand the factors that might be controlling region-specific distributional shifts of plant species, we explored the relationship between the direction of change in distribution limits and the nature of recent climate change. We found that the direction that distribution limits shifted was explained by an interaction between the rate of change in local summer temperatures and seasonal precipitation. Specifically, species were more likely to shift upward at their upper elevational limit when minimum temperatures increased and snowfall was unchanging or declined at slower rates (<0.5 mm/year). This suggests that both low temperature and water availability limit upward shifts at upper elevation limits. By contrast, species were more likely to shift upwards at their lower elevation limit when maximum temperatures increased, but also shifted upwards under conditions of cooling temperatures when precipitation decreased. This suggests increased water stress may drive upward shifts at lower elevation limits. Our results suggest that species’ elevational distribution shifts are not predictable by climate warming alone but depend on the interaction between seasonal temperature and precipitation change. PMID:27447834

  13. Climate Warming and Seasonal Precipitation Change Interact to Limit Species Distribution Shifts across Western North America.

    PubMed

    Harsch, Melanie A; HilleRisLambers, Janneke

    2016-01-01

    Using an extensive network of occurrence records for 293 plant species collected over the past 40 years across a climatically diverse geographic section of western North America, we find that plant species distributions were just as likely to shift upwards (i.e., towards higher elevations) as downward (i.e., towards lower elevations)-despite consistent warming across the study area. Although there was no clear directional response to climate warming across the entire study area, there was significant region- to region- variation in responses (i.e. from as many as 73% to as few as 32% of species shifting upward). To understand the factors that might be controlling region-specific distributional shifts of plant species, we explored the relationship between the direction of change in distribution limits and the nature of recent climate change. We found that the direction that distribution limits shifted was explained by an interaction between the rate of change in local summer temperatures and seasonal precipitation. Specifically, species were more likely to shift upward at their upper elevational limit when minimum temperatures increased and snowfall was unchanging or declined at slower rates (<0.5 mm/year). This suggests that both low temperature and water availability limit upward shifts at upper elevation limits. By contrast, species were more likely to shift upwards at their lower elevation limit when maximum temperatures increased, but also shifted upwards under conditions of cooling temperatures when precipitation decreased. This suggests increased water stress may drive upward shifts at lower elevation limits. Our results suggest that species' elevational distribution shifts are not predictable by climate warming alone but depend on the interaction between seasonal temperature and precipitation change.

  14. Disentangling climate change effects on species interactions: effects of temperature, phenological shifts, and body size.

    PubMed

    Rudolf, Volker H W; Singh, Manasvini

    2013-11-01

    Climate-mediated shifts in species' phenologies are expected to alter species interactions, but predicting the consequences of this is difficult because phenological shifts may be driven by different climate factors that may or may not be correlated. Temperature could be an important factor determining effects of phenological shifts by altering species' growth rates and thereby the relative size ratios of interacting species. We tested this hypothesis by independently manipulating temperature and the relative hatching phenologies of two competing amphibian species. Relative shifts in hatching time generally altered the strength of competition, but the presence and magnitude of this effect was temperature dependent and joint effects of temperature and hatching phenology were non-additive. Species that hatched relatively early or late performed significantly better or worse, respectively, but only at higher temperatures and not at lower temperatures. As a consequence, climate-mediated shifts in hatching phenology or temperature resulted in stronger or weaker effects than expected when both factors acted in concert. Furthermore, consequences of phenological shifts were asymmetric; arriving relatively early had disproportional stronger (or weaker) effects than arriving relatively late, and this varied with species identity. However, consistent with recent theory, these seemingly idiosyncratic effects of phenological shifts could be explained by species-specific differences in growth rates across temperatures and concordant shifts in relative body size of interacting species. Our results emphasize the need to account for environmental conditions when predicting the effects of phenological shifts, and suggest that shifts in size-structured interactions can mediate the impact of climate change on natural communities.

  15. Shifts in phenology due to global climate change: the need for a yardstick.

    PubMed

    Visser, Marcel E; Both, Christiaan

    2005-12-22

    Climate change has led to shifts in phenology in many species distributed widely across taxonomic groups. It is, however, unclear how we should interpret these shifts without some sort of a yardstick: a measure that will reflect how much a species should be shifting to match the change in its environment caused by climate change. Here, we assume that the shift in the phenology of a species' food abundance is, by a first approximation, an appropriate yardstick. We review the few examples that are available, ranging from birds to marine plankton. In almost all of these examples, the phenology of the focal species shifts either too little (five out of 11) or too much (three out of 11) compared to the yardstick. Thus, many species are becoming mistimed due to climate change. We urge researchers with long-term datasets on phenology to link their data with those that may serve as a yardstick, because documentation of the incidence of climate change-induced mistiming is crucial in assessing the impact of global climate change on the natural world. PMID:16321776

  16. Competitive and demographic leverage points of community shifts under climate warming.

    PubMed

    Sorte, Cascade J B; White, J Wilson

    2013-07-01

    Accelerating rates of climate change and a paucity of whole-community studies of climate impacts limit our ability to forecast shifts in ecosystem structure and dynamics, particularly because climate change can lead to idiosyncratic responses via both demographic effects and altered species interactions. We used a multispecies model to predict which processes and species' responses are likely to drive shifts in the composition of a space-limited benthic marine community. Our model was parametrized from experimental manipulations of the community. Model simulations indicated shifts in species dominance patterns as temperatures increase, with projected shifts in composition primarily owing to the temperature dependence of growth, mortality and competition for three critical species. By contrast, warming impacts on two other species (rendering them weaker competitors for space) and recruitment rates of all species were of lesser importance in determining projected community changes. Our analysis reveals the importance of temperature-dependent competitive interactions for predicting effects of changing climate on such communities. Furthermore, by identifying processes and species that could disproportionately leverage shifts in community composition, our results contribute to a mechanistic understanding of climate change impacts, thereby allowing more insightful predictions of future biodiversity patterns.

  17. Competitive and demographic leverage points of community shifts under climate warming

    PubMed Central

    Sorte, Cascade J. B.; White, J. Wilson

    2013-01-01

    Accelerating rates of climate change and a paucity of whole-community studies of climate impacts limit our ability to forecast shifts in ecosystem structure and dynamics, particularly because climate change can lead to idiosyncratic responses via both demographic effects and altered species interactions. We used a multispecies model to predict which processes and species' responses are likely to drive shifts in the composition of a space-limited benthic marine community. Our model was parametrized from experimental manipulations of the community. Model simulations indicated shifts in species dominance patterns as temperatures increase, with projected shifts in composition primarily owing to the temperature dependence of growth, mortality and competition for three critical species. By contrast, warming impacts on two other species (rendering them weaker competitors for space) and recruitment rates of all species were of lesser importance in determining projected community changes. Our analysis reveals the importance of temperature-dependent competitive interactions for predicting effects of changing climate on such communities. Furthermore, by identifying processes and species that could disproportionately leverage shifts in community composition, our results contribute to a mechanistic understanding of climate change impacts, thereby allowing more insightful predictions of future biodiversity patterns. PMID:23658199

  18. Anthropogenic climate change drives shift and shuffle in North Atlantic phytoplankton communities.

    PubMed

    Barton, Andrew D; Irwin, Andrew J; Finkel, Zoe V; Stock, Charles A

    2016-03-15

    Anthropogenic climate change has shifted the biogeography and phenology of many terrestrial and marine species. Marine phytoplankton communities appear sensitive to climate change, yet understanding of how individual species may respond to anthropogenic climate change remains limited. Here, using historical environmental and phytoplankton observations, we characterize the realized ecological niches for 87 North Atlantic diatom and dinoflagellate taxa and project changes in species biogeography between mean historical (1951-2000) and future (2051-2100) ocean conditions. We find that the central positions of the core range of 74% of taxa shift poleward at a median rate of 12.9 km per decade (km⋅dec(-1)), and 90% of taxa shift eastward at a median rate of 42.7 km⋅dec(-1) The poleward shift is faster than previously reported for marine taxa, and the predominance of longitudinal shifts is driven by dynamic changes in multiple environmental drivers, rather than a strictly poleward, temperature-driven redistribution of ocean habitats. A century of climate change significantly shuffles community composition by a basin-wide median value of 16%, compared with seasonal variations of 46%. The North Atlantic phytoplankton community appears poised for marked shift and shuffle, which may have broad effects on food webs and biogeochemical cycles. PMID:26903635

  19. Anthropogenic climate change drives shift and shuffle in North Atlantic phytoplankton communities

    PubMed Central

    Barton, Andrew D.; Finkel, Zoe V.; Stock, Charles A.

    2016-01-01

    Anthropogenic climate change has shifted the biogeography and phenology of many terrestrial and marine species. Marine phytoplankton communities appear sensitive to climate change, yet understanding of how individual species may respond to anthropogenic climate change remains limited. Here, using historical environmental and phytoplankton observations, we characterize the realized ecological niches for 87 North Atlantic diatom and dinoflagellate taxa and project changes in species biogeography between mean historical (1951–2000) and future (2051–2100) ocean conditions. We find that the central positions of the core range of 74% of taxa shift poleward at a median rate of 12.9 km per decade (km⋅dec−1), and 90% of taxa shift eastward at a median rate of 42.7 km⋅dec−1. The poleward shift is faster than previously reported for marine taxa, and the predominance of longitudinal shifts is driven by dynamic changes in multiple environmental drivers, rather than a strictly poleward, temperature-driven redistribution of ocean habitats. A century of climate change significantly shuffles community composition by a basin-wide median value of 16%, compared with seasonal variations of 46%. The North Atlantic phytoplankton community appears poised for marked shift and shuffle, which may have broad effects on food webs and biogeochemical cycles. PMID:26903635

  20. Anthropogenic climate change drives shift and shuffle in North Atlantic phytoplankton communities.

    PubMed

    Barton, Andrew D; Irwin, Andrew J; Finkel, Zoe V; Stock, Charles A

    2016-03-15

    Anthropogenic climate change has shifted the biogeography and phenology of many terrestrial and marine species. Marine phytoplankton communities appear sensitive to climate change, yet understanding of how individual species may respond to anthropogenic climate change remains limited. Here, using historical environmental and phytoplankton observations, we characterize the realized ecological niches for 87 North Atlantic diatom and dinoflagellate taxa and project changes in species biogeography between mean historical (1951-2000) and future (2051-2100) ocean conditions. We find that the central positions of the core range of 74% of taxa shift poleward at a median rate of 12.9 km per decade (km⋅dec(-1)), and 90% of taxa shift eastward at a median rate of 42.7 km⋅dec(-1) The poleward shift is faster than previously reported for marine taxa, and the predominance of longitudinal shifts is driven by dynamic changes in multiple environmental drivers, rather than a strictly poleward, temperature-driven redistribution of ocean habitats. A century of climate change significantly shuffles community composition by a basin-wide median value of 16%, compared with seasonal variations of 46%. The North Atlantic phytoplankton community appears poised for marked shift and shuffle, which may have broad effects on food webs and biogeochemical cycles.

  1. Influence of Climate-induced Vegetation Shifts on Future Land Use and Associated Land Carbon Fluxes

    NASA Astrophysics Data System (ADS)

    Kicklighter, D. W.; Cai, Y.; Zhuang, Q.; PArfenova, E.; Sokolov, A. P.; Melillo, J. M.; Reilly, J. M.

    2011-12-01

    Land ecosystems will be under a variety of pressures in the 21st century that will affect both their structure and function. Climate change and land-use change are likely to be the major pressures. Climate change will lead to changes in disturbance regimes such as fire and changes in the distribution of plant and animal species. Land-use changes, driven by population growth, resource consumption and a broad set of economic considerations, will interact with climate-driven changes to reshape the earth's landscape. Northern Eurasia is a region where these changes could be dramatic. Here we present results of an integrated assessment analysis for the region that examines the consequences of concurrent pressures on land ecosystems associated with climate and land-use changes. Preliminary results indicate that climate-induced vegetation shifts allow a larger increase in area (an additional 55-60%) used for food crop production in northern Eurasia by the middle of the 21st century than is projected when vegetation shifts are not considered. In addition, the area of pastures in the region increases by 15-17% and the area of managed forests increases by 6-215% with vegetation shifts whereas these areas decrease by 3-5% and 51-68%, respectively, over this same time period when no vegetation shifts are considered. Consideration of climate-induced vegetation shifts triples the estimated loss of terrestrial carbon under a no policy scenario and causes the region to become a carbon source rather than a carbon sink under a climate policy scenario. Thus, consideration of vegetation shifts should be included in future assessments of environmental change on terrestrial carbon budgets.

  2. Reassessing regime shifts in the North Pacific: incremental climate change and commercial fishing are necessary for explaining decadal-scale biological variability.

    PubMed

    Litzow, Michael A; Mueter, Franz J; Hobday, Alistair J

    2014-01-01

    In areas of the North Pacific that are largely free of overfishing, climate regime shifts - abrupt changes in modes of low-frequency climate variability - are seen as the dominant drivers of decadal-scale ecological variability. We assessed the ability of leading modes of climate variability [Pacific Decadal Oscillation (PDO), North Pacific Gyre Oscillation (NPGO), Arctic Oscillation (AO), Pacific-North American Pattern (PNA), North Pacific Index (NPI), El Niño-Southern Oscillation (ENSO)] to explain decadal-scale (1965-2008) patterns of climatic and biological variability across two North Pacific ecosystems (Gulf of Alaska and Bering Sea). Our response variables were the first principle component (PC1) of four regional climate parameters [sea surface temperature (SST), sea level pressure (SLP), freshwater input, ice cover], and PCs 1-2 of 36 biological time series [production or abundance for populations of salmon (Oncorhynchus spp.), groundfish, herring (Clupea pallasii), shrimp, and jellyfish]. We found that the climate modes alone could not explain ecological variability in the study region. Both linear models (for climate PC1) and generalized additive models (for biology PC1-2) invoking only the climate modes produced residuals with significant temporal trends, indicating that the models failed to capture coherent patterns of ecological variability. However, when the residual climate trend and a time series of commercial fishery catches were used as additional candidate variables, resulting models of biology PC1-2 satisfied assumptions of independent residuals and out-performed models constructed from the climate modes alone in terms of predictive power. As measured by effect size and Akaike weights, the residual climate trend was the most important variable for explaining biology PC1 variability, and commercial catch the most important variable for biology PC2. Patterns of climate sensitivity and exploitation history for taxa strongly associated with biology

  3. Reassessing regime shifts in the North Pacific: incremental climate change and commercial fishing are necessary for explaining decadal-scale biological variability.

    PubMed

    Litzow, Michael A; Mueter, Franz J; Hobday, Alistair J

    2014-01-01

    In areas of the North Pacific that are largely free of overfishing, climate regime shifts - abrupt changes in modes of low-frequency climate variability - are seen as the dominant drivers of decadal-scale ecological variability. We assessed the ability of leading modes of climate variability [Pacific Decadal Oscillation (PDO), North Pacific Gyre Oscillation (NPGO), Arctic Oscillation (AO), Pacific-North American Pattern (PNA), North Pacific Index (NPI), El Niño-Southern Oscillation (ENSO)] to explain decadal-scale (1965-2008) patterns of climatic and biological variability across two North Pacific ecosystems (Gulf of Alaska and Bering Sea). Our response variables were the first principle component (PC1) of four regional climate parameters [sea surface temperature (SST), sea level pressure (SLP), freshwater input, ice cover], and PCs 1-2 of 36 biological time series [production or abundance for populations of salmon (Oncorhynchus spp.), groundfish, herring (Clupea pallasii), shrimp, and jellyfish]. We found that the climate modes alone could not explain ecological variability in the study region. Both linear models (for climate PC1) and generalized additive models (for biology PC1-2) invoking only the climate modes produced residuals with significant temporal trends, indicating that the models failed to capture coherent patterns of ecological variability. However, when the residual climate trend and a time series of commercial fishery catches were used as additional candidate variables, resulting models of biology PC1-2 satisfied assumptions of independent residuals and out-performed models constructed from the climate modes alone in terms of predictive power. As measured by effect size and Akaike weights, the residual climate trend was the most important variable for explaining biology PC1 variability, and commercial catch the most important variable for biology PC2. Patterns of climate sensitivity and exploitation history for taxa strongly associated with biology

  4. From Restoration To Resilience Ecology: Rapid Ecosystem Shifts Are Triggered By Interactions Of Landscape Fire And Climate Change

    NASA Astrophysics Data System (ADS)

    Falk, D. A.

    2013-12-01

    Many studies predict changes in species distributions in response to changing climate. Both modeling and empirical studies suggest that such changes due to climate alone are likely to be expressed at multi-annual to decadal time scales. In contrast, severe large-scale disturbances can reorganize ecosystems on much shorter time scales of days to months. To understand these dynamics, we are studying the impacts of multiple successive fires and post-fire succession in southwestern North America, which are leaving large areas of landscape with nearly total tree mortality. We posit that it is the combination of climate change and severe disturbance that is most likely to trigger abrupt ecosystem transitions into novel configurations, rather than either factor acting separately. These new configurations can be resilient in their new state, and resistant to return to pre-disturbance conditions. Such abrupt transitions are predicted to become more common under conditions of altered future climate and amplified disturbance regimes: climate provides the envelope within which these dynamics occur, but disturbance provides the trigger for abrupt system reorganization. At larger scales we have compiled the largest-ever data set for historical fire regimes in western North America to understand how climate variation has regulated disturbance regimes historically. We explore the implications of rapid ecosystem responses for design and practice of ecological restoration in a rapidly changing world, and the emergence of resilience ecology as a new paradigm in the evolution of restoration ecology.

  5. Comment on "Changes in climatic water balance drive downhill shifts in plant species' optimum elevations"

    USGS Publications Warehouse

    Stephenson, Nathan L.; Das, Adrian J.

    2011-01-01

    Crimmins et al. (Reports, 21 January 2011, p. 324) attributed an apparent downward elevational shift of California plant species to a precipitation-induced decline in climatic water deficit. We show that the authors miscalculated deficit, that the apparent decline in species' elevations is likely a consequence of geographic biases, and that unlike temperature changes, precipitation changes should not be expected to cause coordinated directional shifts in species' elevations.

  6. Predicting climate-driven regime shifts versus rebound potential in coral reefs.

    PubMed

    Graham, Nicholas A J; Jennings, Simon; MacNeil, M Aaron; Mouillot, David; Wilson, Shaun K

    2015-02-01

    Climate-induced coral bleaching is among the greatest current threats to coral reefs, causing widespread loss of live coral cover. Conditions under which reefs bounce back from bleaching events or shift from coral to algal dominance are unknown, making it difficult to predict and plan for differing reef responses under climate change. Here we document and predict long-term reef responses to a major climate-induced coral bleaching event that caused unprecedented region-wide mortality of Indo-Pacific corals. Following loss of >90% live coral cover, 12 of 21 reefs recovered towards pre-disturbance live coral states, while nine reefs underwent regime shifts to fleshy macroalgae. Functional diversity of associated reef fish communities shifted substantially following bleaching, returning towards pre-disturbance structure on recovering reefs, while becoming progressively altered on regime shifting reefs. We identified threshold values for a range of factors that accurately predicted ecosystem response to the bleaching event. Recovery was favoured when reefs were structurally complex and in deeper water, when density of juvenile corals and herbivorous fishes was relatively high and when nutrient loads were low. Whether reefs were inside no-take marine reserves had no bearing on ecosystem trajectory. Although conditions governing regime shift or recovery dynamics were diverse, pre-disturbance quantification of simple factors such as structural complexity and water depth accurately predicted ecosystem trajectories. These findings foreshadow the likely divergent but predictable outcomes for reef ecosystems in response to climate change, thus guiding improved management and adaptation.

  7. Evidence for Pacific Climate Regime Shifts as Preserved in a Southeast Alaska Ice Core

    NASA Astrophysics Data System (ADS)

    Porter, S. E.; Mosley-Thompson, E. S.; Thompson, L. G.

    2012-12-01

    Climate modes emanating from the Pacific sector have far-reaching effects across the globe. The El Niño/Southern Oscillation (ENSO) reflects anomalies in the sea surface temperature and pressure fields over the tropical Pacific, but climate implications from these anomalies extend to monsoon regions of Asia to North America and even Europe. The Pacific Decadal Oscillation (PDO) explains sea surface temperature anomalies in the North Pacific sector and influences the long-term behavior of the ENSO cycle as well as the storm track over North America expressed as the Pacific/North American Pattern (PNA). The impacts of both climate change and drastically reduced Arctic sea ice cover on these teleconnection patterns are poorly understood, and with little knowledge about their past behavior, predicting the changes in these climate modes is extremely difficult. An ice core from the col between Mt. Bona and Mt. Churchill in southeast Alaska provides an opportunity to examine the PDO prior to both the start of instrumental records and the more recent effects of anthropogenic climate change. The Bona-Churchill records of isotopic, dust, and chemical composition are compared to nearby meteorological station and 20th century reanalysis data to evaluate their strength as climate recorders. Climate indices such as the PDO and PNA, along with indices created to describe the strength and position of the Aleutian Low and Siberian High, are incorporated into the analysis to determine if proxy relationships are altered under different climate regimes. Satellite records of sea ice extent within the Sea of Okhotsk and the Bering Sea, when compared to the Bona-Churchill data, show a distinct change in behavior in the mid-1990s possibly in response to the temporary negative shift in the PDO. This behavioral shift is explored and placed into a broader climate context to determine whether similar events have occurred in the past or if this shift is unique to a rapidly warming Arctic.

  8. Demographic compensation and tipping points in climate-induced range shifts.

    PubMed

    Doak, Daniel F; Morris, William F

    2010-10-21

    To persist, species are expected to shift their geographical ranges polewards or to higher elevations as the Earth's climate warms. However, although many species' ranges have shifted in historical times, many others have not, or have shifted only at the high-latitude or high-elevation limits, leading to range expansions rather than contractions. Given these idiosyncratic responses to climate warming, and their varied implications for species' vulnerability to climate change, a critical task is to understand why some species have not shifted their ranges, particularly at the equatorial or low-elevation limits, and whether such resilience will last as warming continues. Here we show that compensatory changes in demographic rates are buffering southern populations of two North American tundra plants against the negative effects of a warming climate, slowing their northward range shifts, but that this buffering is unlikely to continue indefinitely. Southern populations of both species showed lower survival and recruitment but higher growth of individual plants, possibly owing to longer, warmer growing seasons. Because of these and other compensatory changes, the population growth rates of southern populations are not at present lower than those of northern ones. However, continued warming may yet prove detrimental, as most demographic rates that improved in moderately warmer years declined in the warmest years, with the potential to drive future population declines. Our results emphasize the need for long-term, range-wide measurement of all population processes to detect demographic compensation and to identify nonlinear responses that may lead to sudden range shifts as climatic tipping points are exceeded.

  9. Drought-induced shift of a forest–woodland ecotone: Rapid landscape response to climate variation

    PubMed Central

    Allen, Craig D.; Breshears, David D.

    1998-01-01

    In coming decades, global climate changes are expected to produce large shifts in vegetation distributions at unprecedented rates. These shifts are expected to be most rapid and extreme at ecotones, the boundaries between ecosystems, particularly those in semiarid landscapes. However, current models do not adequately provide for such rapid effects—particularly those caused by mortality—largely because of the lack of data from field studies. Here we report the most rapid landscape-scale shift of a woody ecotone ever documented: in northern New Mexico in the 1950s, the ecotone between semiarid ponderosa pine forest and piñon–juniper woodland shifted extensively (2 km or more) and rapidly (<5 years) through mortality of ponderosa pines in response to a severe drought. This shift has persisted for 40 years. Forest patches within the shift zone became much more fragmented, and soil erosion greatly accelerated. The rapidity and the complex dynamics of the persistent shift point to the need to represent more accurately these dynamics, especially the mortality factor, in assessments of the effects of climate change. PMID:9843976

  10. Drought-induced shift of a forest-woodland ecotone: Rapid landscape response to climate variation

    USGS Publications Warehouse

    Allen, C.D.; Breshears, D.D.

    1998-01-01

    In coming decades, global climate changes are expected to produce large shifts in vegetation distributions at unprecedented rates. These shifts are expected to be most rapid and extreme at ecotones, the boundaries between ecosystems, particularly those in semiarid landscapes. However, current models do not adequately provide for such rapid effects - particularly those caused by mortality - largely because of the lack of data from field studies. Here we report the most rapid landscape-scale shift of a woody ecotone ever documented: in northern New Mexico in the 1950s, the ecotone between semiarid ponderosa pine forest and pinon-juniper woodland shifted extensively (2 km or more) and rapidly (<5 years) through mortality of ponderosa pines in response to a severe drought. This shift has persisted for 40 years. Forest patches within the shift zone became much more fragmented, and soil erosion greatly accelerated. The rapidity and the complex dynamics of the persistent shift point to the need to represent more accurately these dynamics, especially the mortality factor, in assessments of the effects of climate change.

  11. Projected wetland densities under climate change: Habitat loss but little geographic shift in conservation strategy

    USGS Publications Warehouse

    Sofaer, Helen; Skagen, Susan; Barsugli, Joseph J.; Rashford, Benjamin S.; Reese, Gordon; Hoeting, Jennifer A.; Wood, Andrew W.; Noon, Barry R.

    2016-01-01

    Climate change poses major challenges for conservation and management because it alters the area, quality, and spatial distribution of habitat for natural populations. To assess species’ vulnerability to climate change and target ongoing conservation investments, researchers and managers often consider the effects of projected changes in climate and land use on future habitat availability and quality and the uncertainty associated with these projections. Here, we draw on tools from hydrology and climate science to project the impact of climate change on the density of wetlands in the Prairie Pothole Region of the USA, a critical area for breeding waterfowl and other wetland-dependent species. We evaluate the potential for a trade-off in the value of conservation investments under current and future climatic conditions and consider the joint effects of climate and land use. We use an integrated set of hydrological and climatological projections that provide physically based measures of water balance under historical and projected future climatic conditions. In addition, we use historical projections derived from ten general circulation models (GCMs) as a baseline from which to assess climate change impacts, rather than historical climate data. This method isolates the impact of greenhouse gas emissions and ensures that modeling errors are incorporated into the baseline rather than attributed to climate change. Our work shows that, on average, densities of wetlands (here defined as wetland basins holding water) are projected to decline across the U.S. Prairie Pothole Region, but that GCMs differ in both the magnitude and the direction of projected impacts. However, we found little evidence for a shift in the locations expected to provide the highest wetland densities under current vs. projected climatic conditions. This result was robust to the inclusion of projected changes in land use under climate change. We suggest that targeting conservation towards wetland

  12. Potential Influence of Climate-Induced Vegetation Shifts on Future Land Use and Associated Land Carbon Fluxes in Northern Eurasia

    NASA Astrophysics Data System (ADS)

    Kicklighter, D. W.; Cai, Y.; Zhuang, Q.; Parfenova, E. I.; Paltsev, S.; Sokolov, A. P.; Melillo, J. M.; Reilly, J. M.; Tchebakova, N. M.; Lu, X.

    2014-12-01

    Climate change will alter ecosystem metabolism and may lead to a redistribution of vegetation and changes in fire regimes in Northern Eurasia over the 21st century. Land management decisions will interact with these climate-driven changes to reshape the region's landscape. Here we present an assessment of the potential consequences of climate change on land use and associated land carbon sink activity for Northern Eurasia in the context of climate-induced vegetation shifts. Under a 'business-as-usual' scenario, climate-induced vegetation shifts allow expansion of areas devoted to food crop production (15%) and pastures (39%) over the 21st century. Under a climate stabilization scenario, climate-induced vegetation shifts permit expansion of areas devoted to cellulosic biofuel production (25%) and pastures (21%), but reduce the expansion of areas devoted to food crop production by 10%. In both climate scenarios, vegetation shifts further reduce the areas devoted to timber production by 6-8% over this same time period. Fire associated with climate-induced vegetation shifts causes the region to become more of a carbon source than if no vegetation shifts occur. Consideration of the interactions between climate-induced vegetation shifts and human activities through a modeling framework has provided clues to how humans may be able to adapt to a changing world and identified the tradeoffs, including unintended consequences, associated with proposed climate/energy policies.

  13. Pregnancy Complications: Placental Abruption

    MedlinePlus

    ... page It's been added to your dashboard . The placenta attaches to the wall of the uterus (womb) ... abruption is a serious condition in which the placenta separates from the wall of the uterus before ...

  14. Projected shifts in Coffea arabica suitability among major global producing regions due to climate change.

    PubMed

    Ovalle-Rivera, Oriana; Läderach, Peter; Bunn, Christian; Obersteiner, Michael; Schroth, Götz

    2015-01-01

    Regional studies have shown that climate change will affect climatic suitability for Arabica coffee (Coffea arabica) within current regions of production. Increases in temperature and changes in precipitation patterns will decrease yield, reduce quality and increase pest and disease pressure. This is the first global study on the impact of climate change on suitability to grow Arabica coffee. We modeled the global distribution of Arabica coffee under changes in climatic suitability by 2050s as projected by 21 global circulation models. The results suggest decreased areas suitable for Arabica coffee in Mesoamerica at lower altitudes. In South America close to the equator higher elevations could benefit, but higher latitudes lose suitability. Coffee regions in Ethiopia and Kenya are projected to become more suitable but those in India and Vietnam to become less suitable. Globally, we predict decreases in climatic suitability at lower altitudes and high latitudes, which may shift production among the major regions that produce Arabica coffee. PMID:25875230

  15. Projected Shifts in Coffea arabica Suitability among Major Global Producing Regions Due to Climate Change

    PubMed Central

    Ovalle-Rivera, Oriana; Läderach, Peter; Bunn, Christian; Obersteiner, Michael; Schroth, Götz

    2015-01-01

    Regional studies have shown that climate change will affect climatic suitability for Arabica coffee (Coffea arabica) within current regions of production. Increases in temperature and changes in precipitation patterns will decrease yield, reduce quality and increase pest and disease pressure. This is the first global study on the impact of climate change on suitability to grow Arabica coffee. We modeled the global distribution of Arabica coffee under changes in climatic suitability by 2050s as projected by 21 global circulation models. The results suggest decreased areas suitable for Arabica coffee in Mesoamerica at lower altitudes. In South America close to the equator higher elevations could benefit, but higher latitudes lose suitability. Coffee regions in Ethiopia and Kenya are projected to become more suitable but those in India and Vietnam to become less suitable. Globally, we predict decreases in climatic suitability at lower altitudes and high latitudes, which may shift production among the major regions that produce Arabica coffee. PMID:25875230

  16. Projected shifts in Coffea arabica suitability among major global producing regions due to climate change.

    PubMed

    Ovalle-Rivera, Oriana; Läderach, Peter; Bunn, Christian; Obersteiner, Michael; Schroth, Götz

    2015-01-01

    Regional studies have shown that climate change will affect climatic suitability for Arabica coffee (Coffea arabica) within current regions of production. Increases in temperature and changes in precipitation patterns will decrease yield, reduce quality and increase pest and disease pressure. This is the first global study on the impact of climate change on suitability to grow Arabica coffee. We modeled the global distribution of Arabica coffee under changes in climatic suitability by 2050s as projected by 21 global circulation models. The results suggest decreased areas suitable for Arabica coffee in Mesoamerica at lower altitudes. In South America close to the equator higher elevations could benefit, but higher latitudes lose suitability. Coffee regions in Ethiopia and Kenya are projected to become more suitable but those in India and Vietnam to become less suitable. Globally, we predict decreases in climatic suitability at lower altitudes and high latitudes, which may shift production among the major regions that produce Arabica coffee.

  17. Neanderthal and Anatomically Modern Human interaction with Abrupt Late Pleistocene Environments - the data is finally good enough to talk about climate change!

    NASA Astrophysics Data System (ADS)

    Blockley, Simon; Schreve, Danielle

    2015-04-01

    The timing and nature of the appearance of Anatomically Modern Humans (AMH) in Europe, their interaction with, and eventual morphological replacement of Neanderthals (despite some shared genetic heritage) has been a matter of intense debate within archaeology for a generation. This period, often termed the Middle to Upper Palaeolithic transition occurs in the latter part of Marine Isotope Stage Three and in recent decades archaeological interest has been complemented by the input of palaeoclimate scientists, over the role of abrupt climate change in this process. This was due to the recognition from ice core and marine proxy archives, in particular, of periods if intense cooling, correlated to the marine record of Heinrich ice rafted debris layers from the Atlantic. As a result of these collaborations between the archaeological and palaeoenvironmental communities various drivers have been proposed for the Middle to Upper Palaeolithic Transition that include: (1) resource competition between two species occupying similar niches; (2) the impact of repeated cycles of Heinrich event cooling, leading to the decline and eventual disappearance of the Neanderthal populations, leaving a new region open for AMH exploitation; and (3) catastrophic impacts of large volcanic eruptions on Neanderthal populations. Attempts to address the above hypotheses have been dogged by the chronological precision available for a number of key archives. The accuracy of many of the radiocarbon ages that underpin the chronology for both Neanderthal and AMH archaeological sites has been questioned1. This has been exacerbated by uncertainties over the influence of variability in the radiocarbon marine reservoir effect on marine palaeoclimate records and a marine dominated radiocarbon calibration curve. Additionally, the counting uncertainties of the master Greenland palaeoclimate archives are also large by this time, meaning palaeoclimate interpretation can be equivocal. However, several research

  18. Climatic regime shifts and their impacts on marine ecosystem and fisheries resources in Korean waters

    NASA Astrophysics Data System (ADS)

    Zhang, Chang Ik; Lee, Jae Bong; Kim, Suam; Oh, Jai-Ho

    2000-10-01

    There were climatic regime shifts over the North Pacific in 1976 and 1988 which affected the dynamics of the marine ecosystem and fisheries resources in Korean waters. Precipitation in Korean waters showed a decadal scale climatic jump, especially of Ullungdo Island, reflecting the regime shift that occurred in the North Pacific. The variation was also detected in East Asian atmospheric systems. The Aleutian Low and North Pacific High Pressure Systems showed substantial changes in 1976 and around 1987-89. 1976 was an unusually warm year for Korea; mean sea surface temperature (SST) was higher than ‘normal’ and was accompanied by a northward shift in the thermal front. Post 1976, the volume transport of the Kuroshio Current increased and higher seawater and air temperatures persisted until 1988. Other shifts occurred after 1976 such as an increase in mixed layer depth (MLD) and biological changes in the ecosystem of Korean waters including decreases in spring primary production and an increase in autumn primary production. Primary production increased again after 1988, and was followed by a significant increase in zooplankton biomass after 1991. The 1976 regime shift was manifested by a decreased biomass and production of saury, but an increase in biomass and production of sardine and filefish in Korean waters. After 1988, recruitment, biomass, and production of sardine collapsed while those of mackerel substantially increased. Based on these observations, hypotheses on the relationship between the climate-driven oceanic changes and changes in fisheries resources were developed and are discussed.

  19. Future changes in climatic water balance determine potential for transformational shifts in Australian fire regimes

    NASA Astrophysics Data System (ADS)

    Boer, Matthias M.; Bowman, David M. J. S.; Murphy, Brett P.; Cary, Geoffrey J.; Cochrane, Mark A.; Fensham, Roderick J.; Krawchuk, Meg A.; Price, Owen F.; Resco De Dios, Víctor; Williams, Richard J.; Bradstock, Ross A.

    2016-06-01

    Most studies of climate change effects on fire regimes assume a gradual reorganization of pyrogeographic patterns and have not considered the potential for transformational changes in the climate-vegetation-fire relationships underlying continental-scale fire regimes. Here, we model current fire activity levels in Australia as a function of mean annual actual evapotranspiration (E) and potential evapotranspiration (E 0), as proxies for fuel productivity and fuel drying potential. We distinguish two domains in E,{E}0 space according to the dominant constraint on fire activity being either fuel productivity (PL-type fire) or fuel dryness (DL-type fire) and show that the affinity to these domains is related to fuel type. We propose to assess the potential for transformational shifts in fire type from the difference in the affinity to either domain under a baseline climate and projected future climate. Under the projected climate changes potential for a transformational shift from DL- to PL-type fire was predicted for mesic savanna woodland in the north and for eucalypt forests in coastal areas of the south–west and along the Continental Divide in the south–east of the continent. Potential for a shift from PL- to DL-type fire was predicted for a narrow zone of eucalypt savanna woodland in the north–east.

  20. Future changes in climatic water balance determine potential for transformational shifts in Australian fire regimes

    NASA Astrophysics Data System (ADS)

    Boer, Matthias M.; Bowman, David M. J. S.; Murphy, Brett P.; Cary, Geoffrey J.; Cochrane, Mark A.; Fensham, Roderick J.; Krawchuk, Meg A.; Price, Owen F.; Resco De Dios, Víctor; Williams, Richard J.; Bradstock, Ross A.

    2016-06-01

    Most studies of climate change effects on fire regimes assume a gradual reorganization of pyrogeographic patterns and have not considered the potential for transformational changes in the climate-vegetation-fire relationships underlying continental-scale fire regimes. Here, we model current fire activity levels in Australia as a function of mean annual actual evapotranspiration (E) and potential evapotranspiration (E 0), as proxies for fuel productivity and fuel drying potential. We distinguish two domains in E,{E}0 space according to the dominant constraint on fire activity being either fuel productivity (PL-type fire) or fuel dryness (DL-type fire) and show that the affinity to these domains is related to fuel type. We propose to assess the potential for transformational shifts in fire type from the difference in the affinity to either domain under a baseline climate and projected future climate. Under the projected climate changes potential for a transformational shift from DL- to PL-type fire was predicted for mesic savanna woodland in the north and for eucalypt forests in coastal areas of the south-west and along the Continental Divide in the south-east of the continent. Potential for a shift from PL- to DL-type fire was predicted for a narrow zone of eucalypt savanna woodland in the north-east.

  1. Demand Shifting with Thermal Mass in Large Commercial Buildings in a California Hot Climate Zone

    SciTech Connect

    Xu, Peng; Yin, Rongxin; Brown, Carrie; Kim, DongEun

    2009-06-01

    The potential for using building thermal mass for load shifting and peak energy demand reduction has been demonstrated in a number of simulation, laboratory, and field studies. Previous Lawrence Berkeley National Laboratory research has demonstrated that the approach is very effective in cool and moderately warm climate conditions (California Climate Zones 2-4). However, this method had not been tested in hotter climate zones. This project studied the potential of pre-cooling the building early in the morning and increasing temperature setpoints during peak hours to reduce cooling-related demand in two typical office buildings in hotter California climates ? one in Visalia (CEC Climate Zone 13) and the other in San Bernardino (CEC Climate Zone 10). The conclusion of the work to date is that pre-cooling in hotter climates has similar potential to that seen previously in cool and moderate climates. All other factors being equal, results to date indicate that pre-cooling increases the depth (kW) and duration (kWh) of the possible demand shed of a given building. The effectiveness of night pre-cooling in typical office building under hot weather conditions is very limited. However, night pre-cooling is helpful for office buildings with an undersized HVAC system. Further work is required to duplicate the tests in other typical buildings and in other hot climate zones and prove that pre-cooling is truly effective.

  2. Regime Shift in an Exploited Fish Community Related to Natural Climate Oscillations.

    PubMed

    Auber, Arnaud; Travers-Trolet, Morgane; Villanueva, Maria Ching; Ernande, Bruno

    2015-01-01

    Identifying the various drivers of marine ecosystem regime shifts and disentangling their respective influence are critical tasks for understanding biodiversity dynamics and properly managing exploited living resources such as marine fish communities. Unfortunately, the mechanisms and forcing factors underlying regime shifts in marine fish communities are still largely unknown although climate forcing and anthropogenic pressures such as fishing have been suggested as key determinants. Based on a 24-year-long time-series of scientific surveys monitoring 55 fish and cephalopods species, we report here a rapid and persistent structural change in the exploited fish community of the eastern English Channel from strong to moderate dominance of small-bodied forage fish species with low temperature preferendum that occurred in the mid-1990s. This shift was related to a concomitant warming of the North Atlantic Ocean as attested by a switch of the Atlantic Multidecadal Oscillation from a cold to a warm phase. Interestingly, observed changes in the fish community structure were opposite to those classically induced by exploitation as larger fish species of higher trophic level increased in abundance. Despite not playing a direct role in the regime shift, fishing still appeared as a forcing factor affecting community structure. Moreover, although related to climate, the regime shift may have been facilitated by strong historic exploitation that certainly primed the system by favoring the large dominance of small-bodied fish species that are particularly sensitive to climatic variations. These results emphasize that particular attention should be paid to multidecadal natural climate variability and its interactions with both fishing and climate warming when aiming at sustainable exploitation and ecosystem conservation.

  3. Regime Shift in an Exploited Fish Community Related to Natural Climate Oscillations

    PubMed Central

    Auber, Arnaud; Travers-Trolet, Morgane; Villanueva, Maria Ching; Ernande, Bruno

    2015-01-01

    Identifying the various drivers of marine ecosystem regime shifts and disentangling their respective influence are critical tasks for understanding biodiversity dynamics and properly managing exploited living resources such as marine fish communities. Unfortunately, the mechanisms and forcing factors underlying regime shifts in marine fish communities are still largely unknown although climate forcing and anthropogenic pressures such as fishing have been suggested as key determinants. Based on a 24-year-long time-series of scientific surveys monitoring 55 fish and cephalopods species, we report here a rapid and persistent structural change in the exploited fish community of the eastern English Channel from strong to moderate dominance of small-bodied forage fish species with low temperature preferendum that occurred in the mid-1990s. This shift was related to a concomitant warming of the North Atlantic Ocean as attested by a switch of the Atlantic Multidecadal Oscillation from a cold to a warm phase. Interestingly, observed changes in the fish community structure were opposite to those classically induced by exploitation as larger fish species of higher trophic level increased in abundance. Despite not playing a direct role in the regime shift, fishing still appeared as a forcing factor affecting community structure. Moreover, although related to climate, the regime shift may have been facilitated by strong historic exploitation that certainly primed the system by favoring the large dominance of small-bodied fish species that are particularly sensitive to climatic variations. These results emphasize that particular attention should be paid to multidecadal natural climate variability and its interactions with both fishing and climate warming when aiming at sustainable exploitation and ecosystem conservation. PMID:26132268

  4. Regime Shift in an Exploited Fish Community Related to Natural Climate Oscillations.

    PubMed

    Auber, Arnaud; Travers-Trolet, Morgane; Villanueva, Maria Ching; Ernande, Bruno

    2015-01-01

    Identifying the various drivers of marine ecosystem regime shifts and disentangling their respective influence are critical tasks for understanding biodiversity dynamics and properly managing exploited living resources such as marine fish communities. Unfortunately, the mechanisms and forcing factors underlying regime shifts in marine fish communities are still largely unknown although climate forcing and anthropogenic pressures such as fishing have been suggested as key determinants. Based on a 24-year-long time-series of scientific surveys monitoring 55 fish and cephalopods species, we report here a rapid and persistent structural change in the exploited fish community of the eastern English Channel from strong to moderate dominance of small-bodied forage fish species with low temperature preferendum that occurred in the mid-1990s. This shift was related to a concomitant warming of the North Atlantic Ocean as attested by a switch of the Atlantic Multidecadal Oscillation from a cold to a warm phase. Interestingly, observed changes in the fish community structure were opposite to those classically induced by exploitation as larger fish species of higher trophic level increased in abundance. Despite not playing a direct role in the regime shift, fishing still appeared as a forcing factor affecting community structure. Moreover, although related to climate, the regime shift may have been facilitated by strong historic exploitation that certainly primed the system by favoring the large dominance of small-bodied fish species that are particularly sensitive to climatic variations. These results emphasize that particular attention should be paid to multidecadal natural climate variability and its interactions with both fishing and climate warming when aiming at sustainable exploitation and ecosystem conservation. PMID:26132268

  5. The abrupt onset of the modern South Asian Monsoon winds.

    PubMed

    Betzler, Christian; Eberli, Gregor P; Kroon, Dick; Wright, James D; Swart, Peter K; Nath, Bejugam Nagender; Alvarez-Zarikian, Carlos A; Alonso-García, Montserrat; Bialik, Or M; Blättler, Clara L; Guo, Junhua Adam; Haffen, Sébastien; Horozal, Senay; Inoue, Mayuri; Jovane, Luigi; Lanci, Luca; Laya, Juan Carlos; Mee, Anna Ling Hui; Lüdmann, Thomas; Nakakuni, Masatoshi; Niino, Kaoru; Petruny, Loren M; Pratiwi, Santi D; Reijmer, John J G; Reolid, Jesús; Slagle, Angela L; Sloss, Craig R; Su, Xiang; Yao, Zhengquan; Young, Jeremy R

    2016-07-20

    The South Asian Monson (SAM) is one of the most intense climatic elements yet its initiation and variations are not well established. Dating the deposits of SAM wind-driven currents in IODP cores from the Maldives yields an age of 12. 9 Ma indicating an abrupt SAM onset, over a short period of 300 kyrs. This coincided with the Indian Ocean Oxygen Minimum Zone expansion as revealed by geochemical tracers and the onset of upwelling reflected by the sediment's content of particulate organic matter. A weaker 'proto-monsoon' existed between 12.9 and 25 Ma, as mirrored by the sedimentary signature of dust influx. Abrupt SAM initiation favors a strong influence of climate in addition to the tectonic control, and we propose that the post Miocene Climate Optimum cooling, together with increased continentalization and establishment of the bipolar ocean circulation, i.e. the beginning of the modern world, shifted the monsoon over a threshold towards the modern system.

  6. The abrupt onset of the modern South Asian Monsoon winds

    NASA Astrophysics Data System (ADS)

    Betzler, Christian; Eberli, Gregor P.; Kroon, Dick; Wright, James D.; Swart, Peter K.; Nath, Bejugam Nagender; Alvarez-Zarikian, Carlos A.; Alonso-García, Montserrat; Bialik, Or M.; Blättler, Clara L.; Guo, Junhua Adam; Haffen, Sébastien; Horozal, Senay; Inoue, Mayuri; Jovane, Luigi; Lanci, Luca; Laya, Juan Carlos; Mee, Anna Ling Hui; Lüdmann, Thomas; Nakakuni, Masatoshi; Niino, Kaoru; Petruny, Loren M.; Pratiwi, Santi D.; Reijmer, John J. G.; Reolid, Jesús; Slagle, Angela L.; Sloss, Craig R.; Su, Xiang; Yao, Zhengquan; Young, Jeremy R.

    2016-07-01

    The South Asian Monson (SAM) is one of the most intense climatic elements yet its initiation and variations are not well established. Dating the deposits of SAM wind-driven currents in IODP cores from the Maldives yields an age of 12. 9 Ma indicating an abrupt SAM onset, over a short period of 300 kyrs. This coincided with the Indian Ocean Oxygen Minimum Zone expansion as revealed by geochemical tracers and the onset of upwelling reflected by the sediment’s content of particulate organic matter. A weaker ‘proto-monsoon’ existed between 12.9 and 25 Ma, as mirrored by the sedimentary signature of dust influx. Abrupt SAM initiation favors a strong influence of climate in addition to the tectonic control, and we propose that the post Miocene Climate Optimum cooling, together with increased continentalization and establishment of the bipolar ocean circulation, i.e. the beginning of the modern world, shifted the monsoon over a threshold towards the modern system.

  7. The abrupt onset of the modern South Asian Monsoon winds

    PubMed Central

    Betzler, Christian; Eberli, Gregor P.; Kroon, Dick; Wright, James D.; Swart, Peter K.; Nath, Bejugam Nagender; Alvarez-Zarikian, Carlos A.; Alonso-García, Montserrat; Bialik, Or M.; Blättler, Clara L.; Guo, Junhua Adam; Haffen, Sébastien; Horozal, Senay; Inoue, Mayuri; Jovane, Luigi; Lanci, Luca; Laya, Juan Carlos; Mee, Anna Ling Hui; Lüdmann, Thomas; Nakakuni, Masatoshi; Niino, Kaoru; Petruny, Loren M.; Pratiwi, Santi D.; Reijmer, John J. G.; Reolid, Jesús; Slagle, Angela L.; Sloss, Craig R.; Su, Xiang; Yao, Zhengquan; Young, Jeremy R.

    2016-01-01

    The South Asian Monson (SAM) is one of the most intense climatic elements yet its initiation and variations are not well established. Dating the deposits of SAM wind-driven currents in IODP cores from the Maldives yields an age of 12. 9 Ma indicating an abrupt SAM onset, over a short period of 300 kyrs. This coincided with the Indian Ocean Oxygen Minimum Zone expansion as revealed by geochemical tracers and the onset of upwelling reflected by the sediment’s content of particulate organic matter. A weaker ‘proto-monsoon’ existed between 12.9 and 25 Ma, as mirrored by the sedimentary signature of dust influx. Abrupt SAM initiation favors a strong influence of climate in addition to the tectonic control, and we propose that the post Miocene Climate Optimum cooling, together with increased continentalization and establishment of the bipolar ocean circulation, i.e. the beginning of the modern world, shifted the monsoon over a threshold towards the modern system. PMID:27436574

  8. The abrupt onset of the modern South Asian Monsoon winds.

    PubMed

    Betzler, Christian; Eberli, Gregor P; Kroon, Dick; Wright, James D; Swart, Peter K; Nath, Bejugam Nagender; Alvarez-Zarikian, Carlos A; Alonso-García, Montserrat; Bialik, Or M; Blättler, Clara L; Guo, Junhua Adam; Haffen, Sébastien; Horozal, Senay; Inoue, Mayuri; Jovane, Luigi; Lanci, Luca; Laya, Juan Carlos; Mee, Anna Ling Hui; Lüdmann, Thomas; Nakakuni, Masatoshi; Niino, Kaoru; Petruny, Loren M; Pratiwi, Santi D; Reijmer, John J G; Reolid, Jesús; Slagle, Angela L; Sloss, Craig R; Su, Xiang; Yao, Zhengquan; Young, Jeremy R

    2016-01-01

    The South Asian Monson (SAM) is one of the most intense climatic elements yet its initiation and variations are not well established. Dating the deposits of SAM wind-driven currents in IODP cores from the Maldives yields an age of 12. 9 Ma indicating an abrupt SAM onset, over a short period of 300 kyrs. This coincided with the Indian Ocean Oxygen Minimum Zone expansion as revealed by geochemical tracers and the onset of upwelling reflected by the sediment's content of particulate organic matter. A weaker 'proto-monsoon' existed between 12.9 and 25 Ma, as mirrored by the sedimentary signature of dust influx. Abrupt SAM initiation favors a strong influence of climate in addition to the tectonic control, and we propose that the post Miocene Climate Optimum cooling, together with increased continentalization and establishment of the bipolar ocean circulation, i.e. the beginning of the modern world, shifted the monsoon over a threshold towards the modern system. PMID:27436574

  9. On the influence of poleward jet shift on shortwave cloud feedback in global climate models

    NASA Astrophysics Data System (ADS)

    Wall, Casey J.; Hartmann, Dennis L.

    2015-12-01

    Experiments designed to separate the effect of atmospheric warming from the effect of shifts of the eddy-driven jet on shortwave (SW) cloud feedback are performed with three global climate models (GCMs). In each model a warming simulation produces a robust SW cloud feedback dipole, with a negative (positive) feedback in the high-latitudes (subtropics). The cloud brightening in high-latitudes that characterizes warming simulations is not produced by jet shifts alone in any of the models, but is highly sensitive to perturbations of freezing temperature seen by the cloud microphysics scheme, indicating that thermodynamic mechanisms involving the phase of cloud condensate dominate the SW feedback at high-latitudes. In one of the models a poleward jet shift causes significant cloud dimming throughout the midlatitudes, but in two models it does not. Differences in cloud response to jet shifts in two of the models are attributed to differences in the shallow convection parameterizations.

  10. Relevance of Palynological Data for Reconstruction of Abrupt Climatic Change in the Neotropics Region, Based on Marine Sediments from the Cariaco Basin, Caribbean Sea

    NASA Astrophysics Data System (ADS)

    Delusina, I.

    2007-05-01

    Pollen analyses from a deep marine core from the anoxic Cariaco Basin, off the coast of Venezuela, encompass the Late Glacial/Bolling-Allerod transition, through the Younger Dryas and into the beginning of the Preboreal. The unique pollen assemblages indicate significant differences, as well as some basic similarities, with pollen results from continental cross-sections and lacustrine deposits of Neotropical regions. Interpretation of the pollen data from these marine sediments must address the specific challenge of distinguishing the climatic signal from preservation patterns in the marine environment. Because the Cariaco Basin acts as a natural sediment trap for rapidly accumulating sediments of marine and terrestrial origin, it provides an opportunity to compare both signals. The pollen assemblages in the basin mirror the complex altitudinal zonation of the coastal vegetation as well as its dynamics in the marine environment which went through the oxic-anoxic transition. Correlation of the pollen data with percentage of sediment lightness, oxygen isotopes, and titanium/iron concentrations in other Cariaco basin cores, as well as a comparison with vascular plant data, shows that the pollen signal is related to climatic events, rather than to a simple preservation pattern. However, an increase in pollen productivity might not be indicative of climate conditions, but of increased discharge of terrigenous material from the continent. The relative constancy in the pollen list and the gradual change in the percentage of counted palynomorphs and the diversity of pollen assemblages speaks to altitudinal reconstruction of vegetation. Thus, the Montana rain forest predominated over deciduous Montana forest or Paramo elements during Bolling-Allerod time, but didn't replace them. At the end of the Late Glacial and in the middle of Younger Dryas time, seasonally dry forest prevailed. At the end of a Heinrich Event (ca 15,500 cal B.P.), the largest shift in vegetation

  11. Climate change, phenological shifts, eco-evolutionary responses and population viability: toward a unifying predictive approach.

    PubMed

    Jenouvrier, Stéphanie; Visser, Marcel E

    2011-11-01

    The debate on emission targets of greenhouse gasses designed to limit global climate change has to take into account the ecological consequences. One of the clearest ecological consequences is shifts in phenology. Linking these shifts to changes in population viability under various greenhouse gasses emission scenarios requires a unifying framework. We propose a box-in-a-box modeling approach that couples population models to phenological change. This approach unifies population modeling with both ecological responses to climate change as well as evolutionary processes. We advocate a mechanistic embedded correlative approach, where the link from genes to population is established using a periodic matrix population model. This periodic model has several major advantages: (1) it can include complex seasonal behaviors allowing an easy link with phenological shifts; (2) it provides the structure of the population at each phase, including the distribution of genotypes and phenotypes, allowing a link with evolutionary processes; and (3) it can incorporate the effect of climate at different time periods. We believe that the way climatologists have approached the problem, using atmosphere-ocean coupled circulation models in which components are gradually included and linked to each other, can provide a valuable example to ecologists. We hope that ecologists will take up this challenge and that our preliminary modeling framework will stimulate research toward a unifying predictive model of the ecological consequences of climate change.

  12. Climate change, phenological shifts, eco-evolutionary responses and population viability: toward a unifying predictive approach.

    PubMed

    Jenouvrier, Stéphanie; Visser, Marcel E

    2011-11-01

    The debate on emission targets of greenhouse gasses designed to limit global climate change has to take into account the ecological consequences. One of the clearest ecological consequences is shifts in phenology. Linking these shifts to changes in population viability under various greenhouse gasses emission scenarios requires a unifying framework. We propose a box-in-a-box modeling approach that couples population models to phenological change. This approach unifies population modeling with both ecological responses to climate change as well as evolutionary processes. We advocate a mechanistic embedded correlative approach, where the link from genes to population is established using a periodic matrix population model. This periodic model has several major advantages: (1) it can include complex seasonal behaviors allowing an easy link with phenological shifts; (2) it provides the structure of the population at each phase, including the distribution of genotypes and phenotypes, allowing a link with evolutionary processes; and (3) it can incorporate the effect of climate at different time periods. We believe that the way climatologists have approached the problem, using atmosphere-ocean coupled circulation models in which components are gradually included and linked to each other, can provide a valuable example to ecologists. We hope that ecologists will take up this challenge and that our preliminary modeling framework will stimulate research toward a unifying predictive model of the ecological consequences of climate change. PMID:21710282

  13. A New Tool for Exploring Climate Change Induced Range Shifts of Conifer Species in China

    PubMed Central

    Kou, Xiaojun; Li, Qin; Beierkuhnlein, Carl; Zhao, Yiheng; Liu, Shirong

    2014-01-01

    It is inevitable that tree species will undergo considerable range shifts in response to anthropogenic induced climate change, even in the near future. Species Distribution Models (SDMs) are valuable tools in exploring general temporal trends and spatial patterns of potential range shifts. Understanding projections to future climate for tree species will facilitate policy making in forestry. Comparative studies for a large number of tree species require the availability of suitable and standardized indices. A crucial limitation when deriving such indices is the threshold problem in defining ranges, which has made interspecies comparison problematic until now. Here we propose a set of threshold-free indices, which measure range explosion (I), overlapping (O), and range center movement in three dimensions (Dx, Dy, Dz), based on fuzzy set theory (Fuzzy Set based Potential Range Shift Index, F-PRS Index). A graphical tool (PRS_Chart) was developed to visualize these indices. This technique was then applied to 46 Pinaceae species that are widely distributed and partly common in China. The spatial patterns of the modeling results were then statistically tested for significance. Results showed that range overlap was generally low; no trends in range size changes and longitudinal movements could be found, but northward and poleward movement trends were highly significant. Although range shifts seemed to exhibit huge interspecies variation, they were very consistent for certain climate change scenarios. Comparing the IPCC scenarios, we found that scenario A1B would lead to a larger extent of range shifts (less overlapping and more latitudinal movement) than the A2 and the B1 scenarios. It is expected that the newly developed standardized indices and the respective graphical tool will facilitate studies on PRS's for other tree species groups that are important in forestry as well, and thus support climate adaptive forest management. PMID:25268604

  14. Climate change and fishing: a century of shifting distribution in North Sea cod.

    PubMed

    Engelhard, Georg H; Righton, David A; Pinnegar, John K

    2014-08-01

    Globally, spatial distributions of fish stocks are shifting but although the role of climate change in range shifts is increasingly appreciated, little remains known of the likely additional impact that high levels of fishing pressure might have on distribution. For North Sea cod, we show for the first time and in great spatial detail how the stock has shifted its distribution over the past 100 years. We digitized extensive historical fisheries data from paper charts in UK government archives and combined these with contemporary data to a time-series spanning 1913-2012 (excluding both World Wars). New analysis of old data revealed that the current distribution pattern of cod - mostly in the deeper, northern- and north-easternmost parts of the North Sea - is almost opposite to that during most of the Twentieth Century - mainly concentrated in the west, off England and Scotland. Statistical analysis revealed that the deepening, northward shift is likely attributable to warming; however, the eastward shift is best explained by fishing pressure, suggestive of significant depletion of the stock from its previous stronghold, off the coasts of England and Scotland. These spatial patterns were confirmed for the most recent 3 1/2 decades by data from fisheries-independent surveys, which go back to the 1970s. Our results demonstrate the fundamental importance of both climate change and fishing pressure for our understanding of changing distributions of commercially exploited fish.

  15. A 2400-year record of abrupt climate change from Almalou Crate Lake in NW Iran: Investigating the potential influence of solar variability on the climate of West Asia during late Holocene

    NASA Astrophysics Data System (ADS)

    Sharifi, A.; Pourmand, A.; Canuel, E. A.; Naderi Beni, A.; Lahijani, H. A.

    2013-12-01

    The Mediterranean climate of northwest Iran is influenced by mid-latitude Westerlies and the winter expansion of the Siberian Anticyclone. Given the significance of this region in development of human civilizations, high-resolution reconstructions of abrupt climate change are of particular interest during the Holocene. Almalou Crater Lake sustains the growth of plants inside the crater of a dormant volcanic cone on the eastern flank of the Sahand volcanic district in NW Iran. At an elevation of 2491 m.a.s.l., the crater is exclusively fed by rainfall during the spring and fall and snowfall during the winter. Preservation of organic matter within the crater can potentially record changes in atmospheric deposition and paleo-environmental conditions over this region. To reconstruct changes in atmospheric aeolian input, we present a high-resolution (sub-decadal) multi-proxy record of climate variability during the last 2400 years from a 3-m peat core recovered from the crater peat bog. Radiocarbon dates of eight samples along the core show a nearly constant rate of accumulation (7.7 mm yr-1, R2=0.98) since 2404×25 cal yr BP. Downcore X-ray fluorescence measurements of selected conservative lithogenic elements (e.g., Al, Si, and Ti) as well as redox-sensitive elements (e.g., Fe and Rb) at 10 mm intervals reveal several periods of elevated abundances related to enhanced atmospheric dust deposition. The co-variations between relative abundances of conservative and redox-sensitive elements as a function of time show significant agreement and attest to the ombrotrophic nature of the entire record. Intervals of enhanced dust deposition inferred from XRF data reveal three short episodes (~ 150-y) at 450-600, 1150-1300, and 1400-1550 cal yr BP, and one prolonged period (500 y) of dust accumulation from 1600 to 2070 cal yr BP. These intervals of high atmospheric dust coincide with historical records of drought and famine in Iran since 2000 BP. Wavelet analysis conducted on the

  16. 300,000 Years of Asian Monsoon History from Caves: Piecing Together the Patterns, Triggers, and Feedbacks of Abrupt and Orbital-Scale Climate Change

    NASA Astrophysics Data System (ADS)

    Edwards, R.; Cheng, H.; Wang, Y.; Yuan, D.; An, Z.; Kelly, M. J.; Dykoski, C. A.; Wang, X.

    2007-12-01

    We present a continuous 300,000-year record of the oxygen isotopic composition of cave calcite from stalagmites from Hulu, Dongge, and Shanbao Caves, in southeastern China. In its present state, the record is substantially improved in resolution (oxygen isotope resolution of a few to several decades) and range over published results. The record is, in essence, a history of the oxygen isotopic composition of meteoric precipitation through time, which, in turn, is related to monsoonal precipitation in the region. The chronology is established with precise uranium-thorium ages. The monsoon is dominated by orbital-scale variability throughout, and millennial-scale variability during glacial periods. At orbital scales, the monsoon follows northern summer insolation with no discernable phase shift, supporting a direct link between seasonal heating and the monsoon. At millennial scales, the last glacial record correlates strikingly with that observed in Greenland, with Chinese correlatives to all 25 Greenland interstadial events, and broadly similar millennial-scale sequences observed and established for the penultimate and antepenultimate glacial periods. The monsoon exhibits remarkable relationships with the ice core atmospheric gas record. A tie to the oxygen isotopic composition of atmospheric oxygen supports the idea that shifts in the monsoon and low latitude hydrology change the Dole Effect, likely through a combination of changing terrestrial productivity and changes in the average isotopic composition of waters used by land plants. A close tie to methane confirms links among atmospheric methane, the low latitude hydrologic cycle, and the extent of low-latitude wetlands. We are able to correlate features in the monsoon record to ice core, marine, and other cave records, thereby establishing, for key periods, the timing and sequence of events recorded around the globe in different surface environments. Correlation strategies include the methane-monsoon relationship

  17. Response of the Arabian Sea to global warming and associated regional climate shift.

    PubMed

    Kumar, S Prasanna; Roshin, Raj P; Narvekar, Jayu; Kumar, P K Dinesh; Vivekanandan, E

    2009-12-01

    The response of the Arabian Sea to global warming is the disruption in the natural decadal cycle in the sea surface temperature (SST) after 1995, followed by a secular warming. The Arabian Sea is experiencing a regional climate-shift after 1995, which is accompanied by a five fold increase in the occurrence of "most intense cyclones". Signatures of this climate-shift are also perceptible over the adjacent landmass of India as: (1) progressively warmer winters, and (2) decreased decadal monsoon rainfall. The warmer winters are associated with a 16-fold decrease in the decadal wheat production after 1995, while the decreased decadal rainfall was accompanied by a decline of vegetation cover and increased occurrence of heat spells. We propose that in addition to the oceanic thermal inertia, the upwelling-driven cooling provided a mechanism that offset the CO(2)-driven SST increase in the Arabian Sea until 1995.

  18. Soil Carbon Stocks in a Shifting Ecosystem; Climate Induced Migration of Mangroves into Salt Marsh

    NASA Astrophysics Data System (ADS)

    Simpson, L.; Osborne, T.; Feller, I. C.

    2015-12-01

    Across the globe, coastal wetland vegetation distributions are changing in response to climate change. The increase in global average surface temperature has already caused shifts in the structure and distribution of many ecological communities. In parts of the southeastern United States, increased winter temperatures have resulted in the poleward range expansion of mangroves at the expense of salt marsh habitat. Our work aims to document carbon storage in the salt marsh - mangrove ecotone and any potential changes in this reservoir that may ensue due to the shifting range of this habitat. Differences in SOM and C stocks along a latitudinal gradient on the east coast of Florida will be presented. The gradient studied spans 342 km and includes pure mangrove habitat, the salt marsh - mangrove ecotone, and pure salt marsh habitat.This latitudinal gradient gives us an exceptional opportunity to document and investigate ecosystem soil C modifications as mangroves transgress into salt marsh habitat due to climatic change.

  19. Modelling climate change effects on benthos: Distributional shifts in the North Sea from 2001 to 2099

    NASA Astrophysics Data System (ADS)

    Weinert, Michael; Mathis, Moritz; Kröncke, Ingrid; Neumann, Hermann; Pohlmann, Thomas; Reiss, Henning

    2016-06-01

    In the marine realm, climate change can affect a variety of physico-chemical properties with wide-ranging biological effects, but the knowledge of how climate change affects benthic distributions is limited and mainly restricted to coastal environments. To project the response of benthic species of a shelf sea (North Sea) to the expected climate change, the distributions of 75 marine benthic species were modelled and the spatial changes in distribution were projected for 2099 based on modelled bottom temperature and salinity changes using the IPCC scenario A1B. Mean bottom temperature was projected to increase between 0.15 and 5.4 °C, while mean bottom salinity was projected to moderately increase by 1.7. The spatial changes in species distribution were modelled with Maxent and the direction and extent of these changes were assessed. The results showed a latitudinal northward shift for 64% of the species (maximum 109 km; brittle star Ophiothrix fragilis) and a southward shift for 36% (maximum 101 km; hermit crab Pagurus prideaux and the associated cloak anemone Adamsia carciniopados; 105 km). The relatively low rates of distributional shifts compared to fish or plankton species were probably influenced by the regional topography. The environmental gradients in the central North Sea along the 50 m depth contour might act as a 'barrier', possibly resulting in a compression of distribution range and hampering further shifts to the north. For 49 species this resulted in a habitat loss up to 100%, while only 11 species could benefit from the warming in terms of habitat gain. Particularly the benthic communities of the southern North Sea, where the strongest temperature increase was projected, would be strongly affected by the distributional changes, since key species showed northward shifts and high rates of habitat loss, with potential ramifications for the functioning of the ecosystem.

  20. Is there evidence for a shift in fish growth and recruitment success linked to climate change?

    PubMed

    Nunn, A D; Frear, P A; Lee, M; Cowx, I G

    2010-11-01

    This study investigated whether a putative shift in climate regime in the North Atlantic in the 1990s coincided with changes in the growth and recruitment of roach Rutilus rutilus in the north-east of England. The relationships between R. rutilus growth and recruitment and the environment were significantly different before and after the putative shift in climate regime. Water temperature, river discharge, growth, recruitment success and the Gulf Stream Index co-varied until the late 1990s, indicating a gradual progression between periods of warm-and-dry and cold-and-wet summers. Since the late 1990s, there has been an increased prevalence of warm-and-wet summers, and recruitment success has oscillated between extremes on an almost annual basis. The north wall (northern boundary) of the Gulf Stream has been undergoing a displacement south since the late 1990s, and the speed and amplitude of the change appears to support the hypothesis that there was a regime shift in the climate of the North Atlantic Ocean. It is possible that a continued displacement south of the north wall of the Gulf Stream will lead to further increases in river discharge, reductions in water temperature and reduced fish growth and recruitment success in the long term.

  1. The tropicalization of temperate marine ecosystems: climate-mediated changes in herbivory and community phase shifts.

    PubMed

    Vergés, Adriana; Steinberg, Peter D; Hay, Mark E; Poore, Alistair G B; Campbell, Alexandra H; Ballesteros, Enric; Heck, Kenneth L; Booth, David J; Coleman, Melinda A; Feary, David A; Figueira, Will; Langlois, Tim; Marzinelli, Ezequiel M; Mizerek, Toni; Mumby, Peter J; Nakamura, Yohei; Roughan, Moninya; van Sebille, Erik; Gupta, Alex Sen; Smale, Dan A; Tomas, Fiona; Wernberg, Thomas; Wilson, Shaun K

    2014-08-22

    Climate-driven changes in biotic interactions can profoundly alter ecological communities, particularly when they impact foundation species. In marine systems, changes in herbivory and the consequent loss of dominant habitat forming species can result in dramatic community phase shifts, such as from coral to macroalgal dominance when tropical fish herbivory decreases, and from algal forests to 'barrens' when temperate urchin grazing increases. Here, we propose a novel phase-shift away from macroalgal dominance caused by tropical herbivores extending their range into temperate regions. We argue that this phase shift is facilitated by poleward-flowing boundary currents that are creating ocean warming hotspots around the globe, enabling the range expansion of tropical species and increasing their grazing rates in temperate areas. Overgrazing of temperate macroalgae by tropical herbivorous fishes has already occurred in Japan and the Mediterranean. Emerging evidence suggests similar phenomena are occurring in other temperate regions, with increasing occurrence of tropical fishes on temperate reefs. PMID:25009065

  2. The tropicalization of temperate marine ecosystems: climate-mediated changes in herbivory and community phase shifts

    PubMed Central

    Vergés, Adriana; Steinberg, Peter D.; Hay, Mark E.; Poore, Alistair G. B.; Campbell, Alexandra H.; Ballesteros, Enric; Heck, Kenneth L.; Booth, David J.; Coleman, Melinda A.; Feary, David A.; Figueira, Will; Langlois, Tim; Marzinelli, Ezequiel M.; Mizerek, Toni; Mumby, Peter J.; Nakamura, Yohei; Roughan, Moninya; van Sebille, Erik; Gupta, Alex Sen; Smale, Dan A.; Tomas, Fiona; Wernberg, Thomas; Wilson, Shaun K.

    2014-01-01

    Climate-driven changes in biotic interactions can profoundly alter ecological communities, particularly when they impact foundation species. In marine systems, changes in herbivory and the consequent loss of dominant habitat forming species can result in dramatic community phase shifts, such as from coral to macroalgal dominance when tropical fish herbivory decreases, and from algal forests to ‘barrens’ when temperate urchin grazing increases. Here, we propose a novel phase-shift away from macroalgal dominance caused by tropical herbivores extending their range into temperate regions. We argue that this phase shift is facilitated by poleward-flowing boundary currents that are creating ocean warming hotspots around the globe, enabling the range expansion of tropical species and increasing their grazing rates in temperate areas. Overgrazing of temperate macroalgae by tropical herbivorous fishes has already occurred in Japan and the Mediterranean. Emerging evidence suggests similar phenomena are occurring in other temperate regions, with increasing occurrence of tropical fishes on temperate reefs. PMID:25009065

  3. The tropicalization of temperate marine ecosystems: climate-mediated changes in herbivory and community phase shifts.

    PubMed

    Vergés, Adriana; Steinberg, Peter D; Hay, Mark E; Poore, Alistair G B; Campbell, Alexandra H; Ballesteros, Enric; Heck, Kenneth L; Booth, David J; Coleman, Melinda A; Feary, David A; Figueira, Will; Langlois, Tim; Marzinelli, Ezequiel M; Mizerek, Toni; Mumby, Peter J; Nakamura, Yohei; Roughan, Moninya; van Sebille, Erik; Gupta, Alex Sen; Smale, Dan A; Tomas, Fiona; Wernberg, Thomas; Wilson, Shaun K

    2014-08-22

    Climate-driven changes in biotic interactions can profoundly alter ecological communities, particularly when they impact foundation species. In marine systems, changes in herbivory and the consequent loss of dominant habitat forming species can result in dramatic community phase shifts, such as from coral to macroalgal dominance when tropical fish herbivory decreases, and from algal forests to 'barrens' when temperate urchin grazing increases. Here, we propose a novel phase-shift away from macroalgal dominance caused by tropical herbivores extending their range into temperate regions. We argue that this phase shift is facilitated by poleward-flowing boundary currents that are creating ocean warming hotspots around the globe, enabling the range expansion of tropical species and increasing their grazing rates in temperate areas. Overgrazing of temperate macroalgae by tropical herbivorous fishes has already occurred in Japan and the Mediterranean. Emerging evidence suggests similar phenomena are occurring in other temperate regions, with increasing occurrence of tropical fishes on temperate reefs.

  4. Rapid climate driven shifts in wintering distributions of three common waterbird species.

    PubMed

    Lehikoinen, Aleksi; Jaatinen, Kim; Vähätalo, Anssi V; Clausen, Preben; Crowe, Olivia; Deceuninck, Bernard; Hearn, Richard; Holt, Chas A; Hornman, Menno; Keller, Verena; Nilsson, Leif; Langendoen, Tom; Tománková, Irena; Wahl, Johannes; Fox, Anthony D

    2013-07-01

    Climate change is predicted to cause changes in species distributions and several studies report margin range shifts in some species. However, the reported changes rarely concern a species' entire distribution and are not always linked to climate change. Here, we demonstrate strong north-eastwards shifts in the centres of gravity of the entire wintering range of three common waterbird species along the North-West Europe flyway during the past three decades. These shifts correlate with an increase of 3.8 °C in early winter temperature in the north-eastern part of the wintering areas, where bird abundance increased exponentially, corresponding with decreases in abundance at the south-western margin of the wintering ranges. This confirms the need to re-evaluate conservation site safeguard networks and associated biodiversity monitoring along the flyway, as new important wintering areas are established further north and east, and highlights the general urgency of conservation planning in a changing world. Range shifts in wintering waterbirds may also affect hunting pressure, which may alter bag sizes and lead to population-level consequences. PMID:23509023

  5. Shorebird migration in the face of climate change: potential shifts in migration phenology and resource availability

    USGS Publications Warehouse

    Stutzman, Ryan J.; Fontaine, Joseph J

    2015-01-01

    Changes in temperature and seasonality resulting from climate change are heterogeneous, potentially altering important sources of natural selection acting on species phenology. Some species have apparently adapted to climate change but the ability of most species to adapt remains unknown. The life history strategies of migratory animals are dictated by seasonal factors, which makes these species particularly vulnerable to heterogeneous changes in climate and phenology. Here, we examine the phenology of migratory shorebirds, their habitats, and primary food resources, and we hypothesize how climate change may affect migrants through predicted changes in phenology. Daily abundance of shorebirds at stopover sites was correlated with local phenology and peaked immediately prior to peaks in invertebrate food resources. A close relationship between migrant and invertebrate phenology indicates that shorebirds may be vulnerable to changes in seasonality driven by climate change. It is possible that shifts in migrant and invertebrate phenology will be congruent in magnitude and direction, but because migration phenology is dependent on a suite of ecological factors, any response is likely to occur at a larger temporal scale and may lag behind the response of invertebrate food resources. The resulting lack of sufficient access to food at stopover habitats may cause migrants to extend migration and have cascading effects throughout their life cycle. If the heterogeneous nature of climate change results in uneven changes in phenology between migrants and their prey, it may threaten the long-term viability of migratory populations

  6. Mid-Pliocene shifts in ocean overturning circulation and the onset of Quaternary-style climates*

    NASA Astrophysics Data System (ADS)

    Sarnthein, M.; Prange, M.; Schmittner, A.; Schneider, B.; Weinelt, M.

    2009-01-01

    A major tipping point of Earth's history occurred during the mid-Pliocene: the onset of major Northern Hemisphere Glaciation (NHG) and pronounced, Quaternary-style cycles of glacial-to-interglacial climates, that contrast with more uniform climates over most of the preceding Cenozoic, that and continue until today. The severe deterioration of climate occurred in three steps between 3.2 Ma (warm MIS K3) and 2.7 Ma (glacial MIS G6/4). Various models and paleoceanographic records (intercalibrated using orbital age control) suggest clear linkages between the onset of NHG and three steps in the final closure of the Central American Seaways (CAS), deduced from rising salinity differences between Caribbean and East Pacific. Each closing event led to enhanced North Atlantic meridional overturning circulation and strengthened the poleward transport of salt and heat (warmings of +2-3°C). Also, the closing resulted in a slight rise in the poleward atmospheric moisture transport to northwestern Eurasia, which led to enhanced precipitation and fluvial run-off, lower sea surface salinity (SSS), and increased sea-ice cover in the Arctic Ocean, hence promoting albedo and the build-up of continental ice sheets. Most important, the closing of CAS led to greater steric height of the North Pacific and thus doubled the low-saline Arctic Throughflow from the Bering Strait to the East Greenland Current (EGC). Accordingly, Labrador Sea IODP Site 1307 displays an abrupt but irreversible EGC cooling of 6°C and freshening by ~1 psu from 3.16-3.00 Ma, right after the first but still reversible attempt of closing the CAS.

  7. Mid-Pliocene shifts in ocean overturning circulation and the onset of Quaternary-style climates

    NASA Astrophysics Data System (ADS)

    Sarnthein, M.; Bartoli, G.; Prange, M.; Schmittner, A.; Schneider, B.; Weinelt, M.; Andersen, N.; Garbe-Schönberg, D.

    2009-06-01

    A major tipping point of Earth's history occurred during the mid-Pliocene: the onset of major Northern-Hemisphere Glaciation (NHG) and of pronounced, Quaternary-style cycles of glacial-to-interglacial climates, that contrast with more uniform climates over most of the preceding Cenozoic and continue until today (Zachos et al., 2001). The severe deterioration of climate occurred in three steps between 3.2 Ma (warm MIS K3) and 2.7 Ma (glacial MIS G6/4) (Lisiecki and Raymo, 2005). Various models (sensu Driscoll and Haug, 1998) and paleoceanographic records (intercalibrated using orbital age control) suggest clear linkages between the onset of NHG and the three steps in the final closure of the Central American Seaways (CAS), deduced from rising salinity differences between Caribbean and the East Pacific. Each closing event led to an enhanced North Atlantic meridional overturning circulation and this strengthened the poleward transport of salt and heat (warmings of +2-3°C) (Bartoli et al., 2005). Also, the closing resulted in a slight rise in the poleward atmospheric moisture transport to northwestern Eurasia (Lunt et al., 2007), which probably led to an enhanced precipitation and fluvial run-off, lower sea surface salinity (SSS), and an increased sea-ice cover in the Arctic Ocean, hence promoting albedo and the build-up of continental ice sheets. Most important, new evidence shows that the closing of the CAS led to greater steric height of the North Pacific and thus doubled the low-saline Arctic Throughflow from the Bering Strait to the East Greenland Current (EGC). Accordingly, Labrador Sea IODP Site 1307 displays an abrupt but irreversible EGC cooling of 6°C and freshening by ~2 psu from 3.25/3.16-3.00 Ma, right after the first but still reversible attempt of closing the CAS.

  8. Overfishing reduces resilience of kelp beds to climate-driven catastrophic phase shift.

    PubMed

    Ling, S D; Johnson, C R; Frusher, S D; Ridgway, K R

    2009-12-29

    A key consideration in assessing impacts of climate change is the possibility of synergistic effects with other human-induced stressors. In the ocean realm, climate change and overfishing pose two of the greatest challenges to the structure and functioning of marine ecosystems. In eastern Tasmania, temperate coastal waters are warming at approximately four times the global ocean warming average, representing the fastest rate of warming in the Southern Hemisphere. This has driven range extension of the ecologically important long-spined sea urchin (Centrostephanus rodgersii), which has now commenced catastrophic overgrazing of productive Tasmanian kelp beds leading to loss of biodiversity and important rocky reef ecosystem services. Coincident with the overgrazing is heavy fishing of reef-based predators including the spiny lobster Jasus edwardsii. By conducting experiments inside and outside Marine Protected Areas we show that fishing, by removing large predatory lobsters, has reduced the resilience of kelp beds against the climate-driven threat of the sea urchin and thus increased risk of catastrophic shift to widespread sea urchin barrens. This shows that interactions between multiple human-induced stressors can exacerbate nonlinear responses of ecosystems to climate change and limit the adaptive capacity of these systems. Management actions focused on reducing the risk of catastrophic phase shift in ecosystems are particularly urgent in the face of ongoing warming and unprecedented levels of predator removal from the world's oceans. PMID:20018706

  9. Overfishing reduces resilience of kelp beds to climate-driven catastrophic phase shift

    PubMed Central

    Ling, S. D.; Johnson, C. R.; Frusher, S. D.; Ridgway, K. R.

    2009-01-01

    A key consideration in assessing impacts of climate change is the possibility of synergistic effects with other human-induced stressors. In the ocean realm, climate change and overfishing pose two of the greatest challenges to the structure and functioning of marine ecosystems. In eastern Tasmania, temperate coastal waters are warming at approximately four times the global ocean warming average, representing the fastest rate of warming in the Southern Hemisphere. This has driven range extension of the ecologically important long-spined sea urchin (Centrostephanus rodgersii), which has now commenced catastrophic overgrazing of productive Tasmanian kelp beds leading to loss of biodiversity and important rocky reef ecosystem services. Coincident with the overgrazing is heavy fishing of reef-based predators including the spiny lobster Jasus edwardsii. By conducting experiments inside and outside Marine Protected Areas we show that fishing, by removing large predatory lobsters, has reduced the resilience of kelp beds against the climate-driven threat of the sea urchin and thus increased risk of catastrophic shift to widespread sea urchin barrens. This shows that interactions between multiple human-induced stressors can exacerbate nonlinear responses of ecosystems to climate change and limit the adaptive capacity of these systems. Management actions focused on reducing the risk of catastrophic phase shift in ecosystems are particularly urgent in the face of ongoing warming and unprecedented levels of predator removal from the world's oceans. PMID:20018706

  10. Overfishing reduces resilience of kelp beds to climate-driven catastrophic phase shift.

    PubMed

    Ling, S D; Johnson, C R; Frusher, S D; Ridgway, K R

    2009-12-29

    A key consideration in assessing impacts of climate change is the possibility of synergistic effects with other human-induced stressors. In the ocean realm, climate change and overfishing pose two of the greatest challenges to the structure and functioning of marine ecosystems. In eastern Tasmania, temperate coastal waters are warming at approximately four times the global ocean warming average, representing the fastest rate of warming in the Southern Hemisphere. This has driven range extension of the ecologically important long-spined sea urchin (Centrostephanus rodgersii), which has now commenced catastrophic overgrazing of productive Tasmanian kelp beds leading to loss of biodiversity and important rocky reef ecosystem services. Coincident with the overgrazing is heavy fishing of reef-based predators including the spiny lobster Jasus edwardsii. By conducting experiments inside and outside Marine Protected Areas we show that fishing, by removing large predatory lobsters, has reduced the resilience of kelp beds against the climate-driven threat of the sea urchin and thus increased risk of catastrophic shift to widespread sea urchin barrens. This shows that interactions between multiple human-induced stressors can exacerbate nonlinear responses of ecosystems to climate change and limit the adaptive capacity of these systems. Management actions focused on reducing the risk of catastrophic phase shift in ecosystems are particularly urgent in the face of ongoing warming and unprecedented levels of predator removal from the world's oceans.

  11. Shifts in the climate space of temperate cyprinid fishes due to climate change are coupled with altered body sizes and growth rates.

    PubMed

    Ruiz-Navarro, Ana; Gillingham, Phillipa K; Britton, J Robert

    2016-09-01

    Predictions of species responses to climate change often focus on distribution shifts, although responses can also include shifts in body sizes and population demographics. Here, shifts in the distributional ranges ('climate space'), body sizes (as maximum theoretical body sizes, L∞) and growth rates (as rate at which L∞ is reached, K) were predicted for five fishes of the Cyprinidae family in a temperate region over eight climate change projections. Great Britain was the model area, and the model species were Rutilus rutilus, Leuciscus leuciscus, Squalius cephalus, Gobio gobio and Abramis brama. Ensemble models predicted that the species' climate spaces would shift in all modelled projections, with the most drastic changes occurring under high emissions; all range centroids shifted in a north-westerly direction. Predicted climate space expanded for R. rutilus and A. brama, contracted for S. cephalus, and for L. leuciscus and G. gobio, expanded under low-emission scenarios but contracted under high emissions, suggesting the presence of some climate-distribution thresholds. For R. rutilus, A. brama, S. cephalus and G. gobio, shifts in their climate space were coupled with predicted shifts to significantly smaller maximum body sizes and/or faster growth rates, aligning strongly to aspects of temperature-body size theory. These predicted shifts in L∞ and K had considerable consequences for size-at-age per species, suggesting substantial alterations in population age structures and abundances. Thus, when predicting climate change outcomes for species, outputs that couple shifts in climate space with altered body sizes and growth rates provide considerable insights into the population and community consequences, especially for species that cannot easily track their thermal niches.

  12. Climate and vegetational regime shifts in the late Paleozoic ice age earth.

    PubMed

    DiMichele, W A; Montañez, I P; Poulsen, C J; Tabor, N J

    2009-03-01

    The late Paleozoic earth experienced alternation between glacial and non-glacial climates at multiple temporal scales, accompanied by atmospheric CO2 fluctuations and global warming intervals, often attended by significant vegetational changes in equatorial latitudes of Pangaea. We assess the nature of climate-vegetation interaction during two time intervals: middle-late Pennsylvanian transition and Pennsylvanian-Permian transition, each marked by tropical warming and drying. In case study 1, there is a catastrophic intra-biomic reorganization of dominance and diversity in wetland, evergreen vegetation growing under humid climates. This represents a threshold-type change, possibly a regime shift to an alternative stable state. Case study 2 is an inter-biome dominance change in western and central Pangaea from humid wetland and seasonally dry to semi-arid vegetation. Shifts between these vegetation types had been occurring in Euramerican portions of the equatorial region throughout the late middle and late Pennsylvanian, the drier vegetation reaching persistent dominance by Early Permian. The oscillatory transition between humid and seasonally dry vegetation appears to demonstrate a threshold-like behavior but probably not repeated transitions between alternative stable states. Rather, changes in dominance in lowland equatorial regions were driven by long-term, repetitive climatic oscillations, occurring with increasing intensity, within overall shift to seasonal dryness through time. In neither case study are there clear biotic or abiotic warning signs of looming changes in vegetational composition or geographic distribution, nor is it clear that there are specific, absolute values or rates of environmental change in temperature, rainfall distribution and amount, or atmospheric composition, approach to which might indicate proximity to a terrestrial biotic-change threshold.

  13. Ecosystem management mitigates climate change induced vegetation shifts in West Africa

    NASA Astrophysics Data System (ADS)

    Scheiter, S.; Savadogo, P.

    2013-12-01

    Savannas serve as benefit to livelihood for many people in the tropics and sub-tropics and welfare of people strongly depends on goods and services that savanna ecosystems provide, such as food production, livestock production, fuel wool, species richness and climate stabilization. Yet, the flow of these ecosystem services is strongly influenced by climate change and land use. Due to the large proportion of the Earth's land surface covered by savannas, changes in the dynamics and structure of savanna vegetation may not only influence the conditions for the local population, but may also have strong impacts on the climate system and global biogeochemical cycles. In this study, we use a dynamic vegetation model, the aDGVM, to explore how climate and land use interact to influence vegetation dynamics and the distribution of west African savannas under ambient and future environmental conditions. More specifically, we investigate fire management, wood cutting and grazing, land use activities often applied in savannas. We show that under future conditions and in the absence of land use, large savanna areas could shift towards a more wood dominated vegetation state due to CO2 fertilization effects, increases in water use efficiency and decreases in fire activity. However, land use has the potential to maintain desired vegetation states that ensure the flux of important ecosystem services even under future conditions. The model projects that ecosystem management can compensate climate change impacts on vegetation and delay or avoid critical biome shifts. This study highlights the impacts of land use and management on vegetation dynamics and the future distribution of savannas and the necessity to include land use into assessments of the future vegetation state.

  14. Climate change drives a shift in peatland ecosystem plant community: implications for ecosystem function and stability.

    PubMed

    Dieleman, Catherine M; Branfireun, Brian A; McLaughlin, James W; Lindo, Zoë

    2015-01-01

    The composition of a peatland plant community has considerable effect on a range of ecosystem functions. Peatland plant community structure is predicted to change under future climate change, making the quantification of the direction and magnitude of this change a research priority. We subjected intact, replicated vegetated poor fen peat monoliths to elevated temperatures, increased atmospheric carbon dioxide (CO2 ), and two water table levels in a factorial design to determine the individual and synergistic effects of climate change factors on the poor fen plant community composition. We identify three indicators of a regime shift occurring in our experimental poor fen system under climate change: nonlinear decline of Sphagnum at temperatures 8 °C above ambient conditions, concomitant increases in Carex spp. at temperatures 4 °C above ambient conditions suggesting a weakening of Sphagnum feedbacks on peat accumulation, and increased variance of the plant community composition and pore water pH through time. A temperature increase of +4 °C appeared to be a threshold for increased vascular plant abundance; however the magnitude of change was species dependent. Elevated temperature combined with elevated CO2 had a synergistic effect on large graminoid species abundance, with a 15 times increase as compared to control conditions. Community analyses suggested that the balance between dominant plant species was tipped from Sphagnum to a graminoid-dominated system by the combination of climate change factors. Our findings indicate that changes in peatland plant community composition are likely under future climate change conditions, with a demonstrated shift toward a dominance of graminoid species in poor fens.

  15. The Uncontrolled Economic Engine of the Developing Economies, Speeding up the Climate Shift

    NASA Astrophysics Data System (ADS)

    Khan, K. M.; Khan, M. A.

    2014-12-01

    As we progress into the 21st century, the world faces challenges of truly global nature bearing implications on the whole world in one way or another. The global economic engine has shifted from the western world (Developed Economies) to the eastern world (Developing Economies) which has brought about tremendous change in the climate related variables in this part of the world. As uncontrolled carbon emissions grow in the developing economies, the phenomenon of global warming and climate shifts become more and more prevalent. While this economic activity provides income for millions of households, it is contributing generously to the rapid degradation of the environment. Developing economies as it has been seen do not employ or abide by stringent regulations regarding emissions which result in uncontrolled emissions. In this particular scenario, it is a tedious task to convince governments in the developing economies to implement regulations regarding emissions because businesses in these economies deem such regulations to be economically unviable. The other side of the problem is that these uncontrolled emission are causing evident climate shifts which has had adverse impacts on the agricultural societies where shifting climates are leading to reduced agricultural output and productivity. Consequently the lives of millions associated directly or indirectly with agriculture are affected and on a more global level, the agricultural produce is decreasing which increases the chances of famine in parts of the world. The situation could have devastating impacts on the global economy and environmental standards and therefore needs to be addressed on emergency basis. The first step towards betterment could be the introduction of the carbon trading economy in the developing economies which would incentivize emission reduction and become more attractive and in the process sustaining minimum possible damage to the environment. Though carbon trading is a formidable first step

  16. Contingencies and compounded rare perturbations dictate sudden distributional shifts during periods of gradual climate change

    PubMed Central

    Harley, Christopher D. G.; Paine, Robert T.

    2009-01-01

    Ecological responses to climate change may occur gradually with changing conditions, or they may occur rapidly once some threshold or “tipping point” has been reached. Here, we use a high-resolution, 30-year data set on the upper vertical limit of a high intertidal alga to demonstrate that distributional shifts in this species do not keep pace with gradual trends in air temperature or sea level, but rather occur in sudden, discrete steps. These steps occur when unusually warm air temperatures are associated with unusually calm seas and are contingent in the sense that neither atmospheric nor sea conditions by themselves were sufficient to generate the underlying physiological challenge. Shifts in the upper limit did not correlate with large environmental perturbations such as El Niños; rather, they appeared to be associated with stochastic departures from otherwise gradual environmental trends. Our results exemplify the view that multiple environmental factors should be considered when attempting to understand ecological responses to climate change. Furthermore, punctuated responses such as those we have identified urge caution when attempting to infer causal mechanisms and project future distributional shifts using data of limited temporal resolution or scope. PMID:19541649

  17. Eluding catastrophic shifts

    PubMed Central

    Villa Martín, Paula; Bonachela, Juan A.; Levin, Simon A.; Muñoz, Miguel A.

    2015-01-01

    Transitions between regimes with radically different properties are ubiquitous in nature. Such transitions can occur either smoothly or in an abrupt and catastrophic fashion. Important examples of the latter can be found in ecology, climate sciences, and economics, to name a few, where regime shifts have catastrophic consequences that are mostly irreversible (e.g., desertification, coral reef collapses, and market crashes). Predicting and preventing these abrupt transitions remains a challenging and important task. Usually, simple deterministic equations are used to model and rationalize these complex situations. However, stochastic effects might have a profound effect. Here we use 1D and 2D spatially explicit models to show that intrinsic (demographic) stochasticity can alter deterministic predictions dramatically, especially in the presence of other realistic features such as limited mobility or spatial heterogeneity. In particular, these ingredients can alter the possibility of catastrophic shifts by giving rise to much smoother and easily reversible continuous ones. The ideas presented here can help further understand catastrophic shifts and contribute to the discussion about the possibility of preventing such shifts to minimize their disruptive ecological, economic, and societal consequences. PMID:25825772

  18. Eluding catastrophic shifts.

    PubMed

    Villa Martín, Paula; Bonachela, Juan A; Levin, Simon A; Muñoz, Miguel A

    2015-04-14

    Transitions between regimes with radically different properties are ubiquitous in nature. Such transitions can occur either smoothly or in an abrupt and catastrophic fashion. Important examples of the latter can be found in ecology, climate sciences, and economics, to name a few, where regime shifts have catastrophic consequences that are mostly irreversible (e.g., desertification, coral reef collapses, and market crashes). Predicting and preventing these abrupt transitions remains a challenging and important task. Usually, simple deterministic equations are used to model and rationalize these complex situations. However, stochastic effects might have a profound effect. Here we use 1D and 2D spatially explicit models to show that intrinsic (demographic) stochasticity can alter deterministic predictions dramatically, especially in the presence of other realistic features such as limited mobility or spatial heterogeneity. In particular, these ingredients can alter the possibility of catastrophic shifts by giving rise to much smoother and easily reversible continuous ones. The ideas presented here can help further understand catastrophic shifts and contribute to the discussion about the possibility of preventing such shifts to minimize their disruptive ecological, economic, and societal consequences.

  19. Climate warming affects biological invasions by shifting interactions of plants and herbivores.

    PubMed

    Lu, Xinmin; Siemann, Evan; Shao, Xu; Wei, Hui; Ding, Jianqing

    2013-08-01

    Plants and herbivorous insects can each be dramatically affected by temperature. Climate warming may impact plant invasion success directly but also indirectly through changes in their natural enemies. To date, however, there are no tests of how climate warming shifts the interactions among invasive plants and their natural enemies to affect invasion success. Field surveys covering the full latitudinal range of invasive Alternanthera philoxeroides in China showed that a beetle introduced for biocontrol was rare or absent at higher latitudes. In contrast, plant cover and mass increased with latitude. In a 2-year field experiment near the northern limit of beetle distribution, we found the beetle sustained populations across years under elevated temperature, dramatically decreasing A. philoxeroides growth, but it failed to overwinter in ambient temperature. Together, these results suggest that warming will allow the natural enemy to expand its range, potentially benefiting biocontrol in regions that are currently too cold for the natural enemy. However, the invader may also expand its range further north in response to warming. In such cases where plants tolerate cold better than their natural enemies, the geographical gap between plant and herbivorous insect ranges may not disappear but will shift to higher latitudes, leading to a new zone of enemy release. Therefore, warming will not only affect plant invasions directly but also drive either enemy release or increase that will result in contrasting effects on invasive plants. The findings are also critical for future management of invasive species under climate change.

  20. Which way will the circulation shift in a changing climate? Possible nonlinearity of extratropical cloud feedbacks

    NASA Astrophysics Data System (ADS)

    Tandon, Neil F.; Cane, Mark A.

    2016-08-01

    In a suite of idealized experiments with the Community Atmospheric Model version 3 coupled to a slab ocean, we show that the atmospheric circulation response to CO2 increase is sensitive to extratropical cloud feedback that is potentially nonlinear. Doubling CO2 produces a poleward shift of the Southern Hemisphere (SH) midlatitude jet that is driven primarily by cloud shortwave feedback and modulated by ice albedo feedback, in agreement with earlier studies. More surprisingly, for CO2 increases smaller than ~25 %, the SH jet shifts equatorward. Nonlinearities are also apparent in the Northern Hemisphere, but with less zonal symmetry. Baroclinic instability theory and climate feedback analysis suggest that as the CO2 forcing amplitude is reduced, there is a transition from a regime in which cloud and circulation changes are largely decoupled to a regime in which they are highly coupled. In the dynamically coupled regime, there is an apparent cancellation between cloud feedback due to warming and cloud feedback due to the shifting jet, and this allows the ice albedo feedback to dominate in the high latitudes. The extent to which dynamical coupling effects exceed thermodynamic forcing effects is strongly influenced by cloud microphysics: an alternate model configuration with slightly increased cloud liquid (LIQ) produces poleward jet shifts regardless of the amplitude of CO2 forcing. Altering the cloud microphysics also produces substantial spread in the circulation response to CO2 doubling: the LIQ configuration produces a poleward SH jet shift approximately twice that produced under the default configuration. Analysis of large ensembles of the Canadian Earth System Model version 2 demonstrates that nonlinear, cloud-coupled jet shifts are also possible in comprehensive models. We still expect a poleward trend in SH jet latitude for timescales on which CO2 increases by more than ~25 %. But on shorter timescales, our results give good reason to expect significant

  1. Northward shifts of the distributions of Spanish reptiles in association with climate change.

    PubMed

    Moreno-Rueda, Gregorio; Pleguezuelos, Juan M; Pizarro, Manuel; Montori, Albert

    2012-04-01

    It is predicted that climate change will drive extinctions of some reptiles and that the number of these extinctions will depend on whether reptiles are able to change their distribution. Whether the latitudinal distribution of reptiles may change in response to increases in temperature is unknown. We used data on reptile distributions collected during the 20th century to analyze whether changes in the distributions of reptiles in Spain are associated with increases in temperature. We controlled for biases in sampling effort and found a mean, statistically significant, northward shift of the northern extent of reptile distributions of about 15.2 km from 1940-1975 to 1991-2005. The southern extent of the distributions did not change significantly. Thus, our results suggest that the latitudinal distributions of reptiles may be changing in response to climate change.

  2. Shifts in comparative advantages for maize, oat and wheat cropping under climate change in Europe.

    PubMed

    Elsgaard, L; Børgesen, C D; Olesen, J E; Siebert, S; Ewert, F; Peltonen-Sainio, P; Rötter, R P; Skjelvåg, A O

    2012-01-01

    Climate change is anticipated to affect European agriculture, including the risk of emerging or re-emerging feed and food hazards. Indirectly, climate change may influence such hazards (e.g. the occurrence of mycotoxins) due to geographic shifts in the distribution of major cereal cropping systems and the consequences this may have for crop rotations. This paper analyses the impact of climate on cropping shares of maize, oat and wheat on a 50-km square grid across Europe (45-65°N) and provides model-based estimates of the changes in cropping shares in response to changes in temperature and precipitation as projected for the time period around 2040 by two regional climate models (RCM) with a moderate and a strong climate change signal, respectively. The projected cropping shares are based on the output from the two RCMs and on algorithms derived for the relation between meteorological data and observed cropping shares of maize, oat and wheat. The observed cropping shares show a south-to-north gradient, where maize had its maximum at 45-55°N, oat had its maximum at 55-65°N, and wheat was more evenly distributed along the latitudes in Europe. Under the projected climate changes, there was a general increase in maize cropping shares, whereas for oat no areas showed distinct increases. For wheat, the projected changes indicated a tendency towards higher cropping shares in the northern parts and lower cropping shares in the southern parts of the study area. The present modelling approach represents a simplification of factors determining the distribution of cereal crops, and also some uncertainties in the data basis were apparent. A promising way of future model improvement could be through a systematic analysis and inclusion of other variables, such as key soil properties and socio-economic conditions, influencing the comparative advantages of specific crops. PMID:22827234

  3. Climate and health impacts of the shift from traditional solid cookstove fuels to modern energy sources

    NASA Astrophysics Data System (ADS)

    Lacey, F.; Henze, D. K.; Martin, R.; Lee, C. J.; van Donkelaar, A.; Reed, L.

    2015-12-01

    Globally, 2.8 million people use solid fuels for meal preparation. As regions in which solid fuel cooking is prevalent become more industrialized, this number will decrease leading to commensurate changes in greenhouse gas, aerosol and aerosol precursor emissions from the residential sector. Here we explore the impacts of this shift from traditional solid fuel use to equivalent energy sources from modern power generation on climate change and exposure to ambient air pollution. We use sensitivities calculated with the GEOS-Chem adjoint model, which allows us to estimate the climate and health impacts due to changes in atmospheric composition from grid-scale shifts in energy usage. Various scenarios for alternative energy generation sources are considered. Climate impacts are reported as changes in global averaged surface temperature through the use of absolute regional temperature potentials and health impacts are reported as changes in premature deaths calculated using changes in population-weighted PM2.5 concentrations combined with integrated exposure response functions. Global model PM2.5 surface concentrations are downscaled to improve exposure estimates through application of remotely sensed aerosol optical depth measurements. Our assessment of the impacts of fuel switching allows for estimates of upper and lower bounds, for both climate and health impacts, at the global and national scale. Baseline calculations using these methods estimate impacts of approximately 0.22 K warming and 217,000 premature deaths caused by changes in ambient air quality due to present day cookstove emissions which represents the base case for these comparisons. Overall, the results of this study provide important information to both individual country's governments and non-governmental organizations that are targeting energy infrastructure improvements.

  4. A Holocene record of climate-driven shifts in coastal carbon sequestration

    USGS Publications Warehouse

    Mitra, Siddhartha; Zimmerman, A.R.; Hunsinger, G.B.; Willard, D.; Dunn, J.C.

    2009-01-01

    A sediment core collected in the mesohaline portion of Chesapeake Bay was found to contain periods of increased delivery of refractory black carbon (BC) and polycyclic aromatic hydrocarbons (PAHs). The BC was most likely produced by biomass combustion during four centennialscale dry periods as indicated by the Palmer Drought Severity Index (PDSI), beginning in the late Medieval Warm Period of 1100 CE. In contrast, wetter periods were associated with increased non-BC organic matter influx into the bay, likely due to greater runoff and associated nutrient delivery. In addition, an overall increase in both BC and non-BC organic matter deposition during the past millennium may reflect a shift in climate regime. The finding that carbon sequestration in the coastal zone responds to climate fluctuations at both centennial and millennial scales through fire occurrence and nutrient delivery has implications for past and future climate predictions. Drought-induced fires may lead, on longer timescales, to greater carbon sequestration and, therefore, represent a negative climate feedback. Copyright 2009 by the American Geophysical Union.

  5. Evidence of a shift in the cyclicity of Antarctic seabird dynamics linked to climate

    PubMed Central

    Jenouvrier, Stéphanie; Weimerskirch, Henri; Barbraud, Christophe; Park, Young-Hyang; Cazelles, Bernard

    2005-01-01

    Ecosystems and populations are known to be influenced not only by long-term climatic trends, but also by other short-term climatic modes, such as interannual and decadal-scale variabilities. Because interactions between climatic forcing, biotic and abiotic components of ecosystems are subtle and complex, analysis of long-term series of both biological and physical factors is essential to understanding these interactions. Here, we apply a wavelet analysis simultaneously to long-term datasets on the environment and on the populations and breeding success of three Antarctic seabirds (southern fulmar, snow petrel, emperor penguin) breeding in Terre Adélie, to study the effects of climate fluctuations on Antarctic marine ecosystems. We show that over the past 40 years, populations and demographic parameters of the three species fluctuate with a periodicity of 3–5 years that was also detected in sea-ice extent and the Southern Oscillation Index. Although the major periodicity of these interannual fluctuations is not common to different species and environmental variables, their cyclic characteristics reveal a significant change since 1980. Moreover, sliding-correlation analysis highlighted the relationships between environmental variables and the demography of the three species, with important change of correlation occurring between the end of the 1970s and the beginning of the 1980s. These results suggest that a regime shift has probably occurred during this period, significantly affecting the Antarctic ecosystem, but with contrasted effects on the three species. PMID:16024342

  6. Climate Influence on Shifts in the Deep Canyon Ecocline, 1977 - 2007

    NASA Astrophysics Data System (ADS)

    Kelly, A.; Goulden, M.

    2007-12-01

    The Deep Canyon Transect in the Santa Rosa Mountains of Southern California spans 2560 m in elevation and four major plant communities: desert scrub, Sonoran pinyon-juniper woodland, montane chaparral, and mixed conifer forest. The plant species distributions of the Deep Canyon Transect were compared from 1977 to 2007 and the causes of change were examined. We hypothesized plant species distributions to move upwards in elevation in response to climate warming and increasing climate variability. In 1977, Jan Zabriskie surveyed plant species coverage along a 400 m isocontour every 122 m in elevation along the transect. Following Zabriskie, I resurveyed these sites in 2006 -- 2007 and compared species coverage. The set of the ten most widespread species spans all elevations, plant communities, and functional types of Deep Canyon. The mean elevation increase for these ten species is 64.7 m, within a two-tailed 95% CI of 30.9 -- 98.5 m. From 1977 -- 2006, the Deep Canyon Transect experienced a significant increase in mean annual temperature of 0.5 -- 0.8° C. Variability in annual precipitation has also doubled over that time. Climate warming and increasing climate variability has been the primary driver of upward plant species shifts in Deep Canyon.

  7. Evidence of a shift in the cyclicity of Antarctic seabird dynamics linked to climate.

    PubMed

    Jenouvrier, Stéphanie; Weimerskirch, Henri; Barbraud, Christophe; Park, Young-Hyang; Cazelles, Bernard

    2005-05-01

    Ecosystems and populations are known to be influenced not only by long-term climatic trends, but also by other short-term climatic modes, such as interannual and decadal-scale variabilities. Because interactions between climatic forcing, biotic and abiotic components of ecosystems are subtle and complex, analysis of long-term series of both biological and physical factors is essential to understanding these interactions. Here, we apply a wavelet analysis simultaneously to long-term datasets on the environment and on the populations and breeding success of three Antarctic seabirds (southern fulmar, snow petrel, emperor penguin) breeding in Terre Adélie, to study the effects of climate fluctuations on Antarctic marine ecosystems. We show that over the past 40 years, populations and demographic parameters of the three species fluctuate with a periodicity of 3-5 years that was also detected in sea-ice extent and the Southern Oscillation Index. Although the major periodicity of these interannual fluctuations is not common to different species and environmental variables, their cyclic characteristics reveal a significant change since 1980. Moreover, sliding-correlation analysis highlighted the relationships between environmental variables and the demography of the three species, with important change of correlation occurring between the end of the 1970s and the beginning of the 1980s. These results suggest that a regime shift has probably occurred during this period, significantly affecting the Antarctic ecosystem, but with contrasted effects on the three species. PMID:16024342

  8. Evidence of a shift in the cyclicity of Antarctic seabird dynamics linked to climate.

    PubMed

    Jenouvrier, Stéphanie; Weimerskirch, Henri; Barbraud, Christophe; Park, Young-Hyang; Cazelles, Bernard

    2005-05-01

    Ecosystems and populations are known to be influenced not only by long-term climatic trends, but also by other short-term climatic modes, such as interannual and decadal-scale variabilities. Because interactions between climatic forcing, biotic and abiotic components of ecosystems are subtle and complex, analysis of long-term series of both biological and physical factors is essential to understanding these interactions. Here, we apply a wavelet analysis simultaneously to long-term datasets on the environment and on the populations and breeding success of three Antarctic seabirds (southern fulmar, snow petrel, emperor penguin) breeding in Terre Adélie, to study the effects of climate fluctuations on Antarctic marine ecosystems. We show that over the past 40 years, populations and demographic parameters of the three species fluctuate with a periodicity of 3-5 years that was also detected in sea-ice extent and the Southern Oscillation Index. Although the major periodicity of these interannual fluctuations is not common to different species and environmental variables, their cyclic characteristics reveal a significant change since 1980. Moreover, sliding-correlation analysis highlighted the relationships between environmental variables and the demography of the three species, with important change of correlation occurring between the end of the 1970s and the beginning of the 1980s. These results suggest that a regime shift has probably occurred during this period, significantly affecting the Antarctic ecosystem, but with contrasted effects on the three species.

  9. Early Stages Of Biome Shift in Boreal Alaska: Climate Sensitivity of Tree Growth and Accelerated Tree Mortality

    NASA Astrophysics Data System (ADS)

    Juday, G. P.; Grant, T.; Alix, C. M.; Spencer, D. L.; Beck, P. S.

    2012-12-01

    The boreal forest region of Alaska is characterized by a major east-west climate gradient, in addition to a widely appreciated north-south gradient. Low elevations of the eastern and central Interior experience warm summer temperatures and low annual precipitation, while coastal western Alaska has cool summer temperatures and greater precipitation. In the Interior the four dominant tree species of white and black spruce, aspen, and Alaska birch on low elevation sites nearly all register a strong negative radial growth relationship to summer temperatures, concentrated in May and July. Precipitation, particularly in late winter and midsummer, plays a supplemental role as a positive factor in growth. Floodplain white spruce along the Yukon and Kuskokwim Rivers transition from negative temperature response to positive response in western Alaska near the tree limit. Populations of white spruce on treeline sites display both negative growth response to July temperature and positive response to spring temperatures, with the negative response dominant in the east and the positive response dominant in the west. Across boreal Alaska summer temperatures increased abruptly in 1974, and have remained at historically high levels since. Correspondingly, climatic favorability for radial growth of Interior trees on most low elevation sites has been at extreme low levels particularly in the 21st century. Satellite-based NDVI coverage confirms that forest growth reduction is widespread in boreal Alaska since the 1980s. Defoliating and wood boring insects have reached outbreak population levels across most of boreal Alaska, partly from release of direct temperature control on the insects and partly from increased tree host susceptibility. Major outbreak species include aspen leaf miner, spruce engraver beetle, and spruce budworm. About a dozen tall willow species have been subjected to widespread attack by willow leaf blotch miner, and a new disease and defoliating insect have spread

  10. Influence of Climate-induced Vegetation Shifts on Future Land Use and Associated Land Carbon Fluxes in Northern Eurasia

    NASA Astrophysics Data System (ADS)

    Kicklighter, D. W.; Cai, Y.; Zhuang, Q.; Parfenova, E. I.; Sokolov, A. P.; Melillo, J. M.; Reilly, J. M.

    2012-04-01

    Land ecosystems in northern Eurasia will be under a variety of pressures in the 21st century that will affect both their structure and function. Climate change and land-use change are likely to be the major pressures. Climate change will lead to changes in disturbance regimes such as fire and changes in the distribution of plant and animal species. Land-use changes, driven by population growth, resource consumption and a broad set of economic considerations, will interact with climate-driven changes to reshape the earth's landscape. Here we present results of an integrated assessment analysis for the region that examines the consequences of concurrent pressures on land ecosystems associated with climate and land-use changes. Preliminary results indicate that climate-induced vegetation shifts allow more areas in northern Eurasia to be used for food crop production (an additional 23%) and pastures (an additional 38%), but limits the additional area to be used as managed forests (38% less) by the end of the 21st century than is projected when vegetation shifts are not considered and no climate policy is implemented. In contrast, under a climate policy, climate-induced vegetation shifts had little influence on food production, but allow more area to be used for cellulosic biofuel production (an additional 23%), and less additional area to be used for pasture (50% less) and managed forests (28% less) over this same time period. Fire associated with climate-induced vegetation shifts causes the region to become a carbon source over the 21st century whereas the region is projected to be a carbon sink if no vegetation shifts are assumed to occur. Thus, consideration of vegetation shifts should be included in future assessments of environmental change on terrestrial carbon budgets in this region.

  11. Risk and contributing factors of ecosystem shifts over naturally vegetated land under climate change in China.

    PubMed

    Yin, Yuanyuan; Tang, Qiuhong; Wang, Lixin; Liu, Xingcai

    2016-01-01

    Identifying the areas at risk of ecosystem transformation and the main contributing factors to the risk is essential to assist ecological adaptation to climate change. We assessed the risk of ecosystem shifts in China using the projections of four global gridded vegetation models (GGVMs) and an aggregate metric. The results show that half of naturally vegetated land surface could be under moderate or severe risk at the end of the 21(st) century under the middle and high emission scenarios. The areas with high risk are the Tibetan Plateau region and an area extended northeastward from the Tibetan Plateau to northeast China. With the three major factors considered, the change in carbon stocks is the main contributing factor to the high risk of ecosystem shifts. The change in carbon fluxes is another important contributing factor under the high emission scenario. The change in water fluxes is a less dominant factor except for the Tibetan Plateau region under the high emission scenario. Although there is considerable uncertainty in the risk assessment, the geographic patterns of the risk are generally consistent across different scenarios. The results could help develop regional strategies for ecosystem conservation to cope with climate change. PMID:26867481

  12. Risk and contributing factors of ecosystem shifts over naturally vegetated land under climate change in China

    PubMed Central

    Yin, Yuanyuan; Tang, Qiuhong; Wang, Lixin; Liu, Xingcai

    2016-01-01

    Identifying the areas at risk of ecosystem transformation and the main contributing factors to the risk is essential to assist ecological adaptation to climate change. We assessed the risk of ecosystem shifts in China using the projections of four global gridded vegetation models (GGVMs) and an aggregate metric. The results show that half of naturally vegetated land surface could be under moderate or severe risk at the end of the 21st century under the middle and high emission scenarios. The areas with high risk are the Tibetan Plateau region and an area extended northeastward from the Tibetan Plateau to northeast China. With the three major factors considered, the change in carbon stocks is the main contributing factor to the high risk of ecosystem shifts. The change in carbon fluxes is another important contributing factor under the high emission scenario. The change in water fluxes is a less dominant factor except for the Tibetan Plateau region under the high emission scenario. Although there is considerable uncertainty in the risk assessment, the geographic patterns of the risk are generally consistent across different scenarios. The results could help develop regional strategies for ecosystem conservation to cope with climate change. PMID:26867481

  13. Cross-scale assessment of potential habitat shifts in a rapidly changing climate

    USGS Publications Warehouse

    Jarnevich, Catherine S.; Holcombe, Tracy R.; Bella, Elizabeth S.; Carlson, Matthew L.; Graziano, Gino; Lamb, Melinda; Seefeldt, Steven S.; Morisette, Jeffrey T.

    2014-01-01

    We assessed the ability of climatic, environmental, and anthropogenic variables to predict areas of high-risk for plant invasion and consider the relative importance and contribution of these predictor variables by considering two spatial scales in a region of rapidly changing climate. We created predictive distribution models, using Maxent, for three highly invasive plant species (Canada thistle, white sweetclover, and reed canarygrass) in Alaska at both a regional scale and a local scale. Regional scale models encompassed southern coastal Alaska and were developed from topographic and climatic data at a 2 km (1.2 mi) spatial resolution. Models were applied to future climate (2030). Local scale models were spatially nested within the regional area; these models incorporated physiographic and anthropogenic variables at a 30 m (98.4 ft) resolution. Regional and local models performed well (AUC values > 0.7), with the exception of one species at each spatial scale. Regional models predict an increase in area of suitable habitat for all species by 2030 with a general shift to higher elevation areas; however, the distribution of each species was driven by different climate and topographical variables. In contrast local models indicate that distance to right-of-ways and elevation are associated with habitat suitability for all three species at this spatial level. Combining results from regional models, capturing long-term distribution, and local models, capturing near-term establishment and distribution, offers a new and effective tool for highlighting at-risk areas and provides insight on how variables acting at different scales contribute to suitability predictions. The combinations also provides easy comparison, highlighting agreement between the two scales, where long-term distribution factors predict suitability while near-term do not and vice versa.

  14. Understanding Abrupt, Natural Climate Variability Post-Industrial Revolution from the Subtropical Eastern Pacific: A Novel High Resolution Alkenone-derived Sea Surface Temperature Record

    NASA Astrophysics Data System (ADS)

    Kelly, C. S.; O'Mara, N. A.; Herbert, T.; Abella-Gutiérrez, J. L.; Herguera, J. C.

    2015-12-01

    Despite the ocean's importance in global biogeochemical feedbacks and heat storage, there is still a paucity of decadally-resolved sea surface temperature (SST) records to complement lacustrine and dendrological records of recent paleoclimate. Natural climate variability on multidecadal timescales is dominated by internal ocean circulation dynamics and feedbacks, and it is therefore imperative to employ marine proxies to reconstruct high resolution climate change. The timescales of this ocean-induced natural climate variability can be broken down into a few characteristic climate modes. Pressing questions about these modes include their stationarity in frequency and amplitude over time, in addition to the hypothesis that anthropogenic climate change has altered their behavior in comparison to natural variability. To pursue these questions, we must discern and analyze suitable climate archives in regions where modes of interest dominate modern climate variability. The region of Baja California, Mexico exhibits exceptional teleconnection to the El Niño Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO). Local, dramatic effects of ENSO and PDO on the marine biology and economy underline the importance of regional paleoclimate records from the Baja peninsula. Here, we present a high-resolution alkenone-derived SST reconstruction from the Industrial Revolution through the year 2000 by analysis of laminated box and Kasten sediment cores at Site PCM 00-78 (25.18°N, 112.66°W) in the subtropical eastern Pacific at a depth of 540 meters. Our SST record corresponds with NOAA extended reconstructed sea surface temperature, providing a robust basis for organic geochemical marine climatic reconstructions on timescales usually accessible only through speleothems, coral density bands, tree rings, and the like. Accordingly, based on this comparison to the historical data we expect our SST record may provide a more robust record of inter and multidecadal

  15. Effects of Interannual Climate Variability in Secondary Forests and Crops Under Traditional and Alternative Shifting Cultivation

    NASA Astrophysics Data System (ADS)

    Sa, T. D.; Guild, L. S.; Carvalho, C. J.; Potter, C. S.; Wickel, A. J.; Brienza, S.; Kato, M. A.; Kato, O.

    2002-12-01

    Regenerating forests play an important role in long-term carbon sequestration and sustainable landuse as they act as potentially important carbon and nutrient sinks during the shifting agriculture fallow period. The long-term functioning of secondary forests (capoeira) is increasingly threatened by a shortening fallow period during shifting cultivation due to demographic pressures and associated increased vulnerability to severe climatic events. Declining productivity and functioning of fallow forests of shifting cultivation combined with progressive loss of nutrients by successive burning and cropping activities has resulted in declining agricultural productivity. In addition to the effects of intense land use practices, droughts associated with El Ni¤o events are becoming more frequent and severe in moist tropical forests and negative effects on capoeira productivity could be considerable. In Igarape-Acu (near Belem, Para), we hypothesize that experimental alternative landuse/clearing practices (mulching and fallow vegetation improvement by planting with fast-growing leguminous tree species) may make capoeira and crops more resilient to the effects of agricultural pressures and drought through 1) increased biomass, soil organic matter and associated increase in soil water storage, and nutrient retention and 2) greater rooting depth of trees planted for fallow improvement. This experimental practice (mechanized chop-and-mulch with fallow improvement) has resulted in increased soil moisture during the cropping phase, reduced loss of nutrients and organic matter, and higher rates of secondary-forest biomass accumulation. We present preliminary data on water relations during the dry season of 2001 in capoeira and crops for both traditional slash-and-burn and alternative chop-and-mulch practices. These data will be used to test IKONOS data for the detection of moisture status differences. The principal goal of the research is to determine the extent to which capoeira

  16. Version 5 of Forecasts; Forecasts of Climate-Associated Shifts in Tree Species

    NASA Astrophysics Data System (ADS)

    Hargrove, W. W.; Kumar, J.; Potter, K. M.; Hoffman, F. M.

    2014-12-01

    Version 5 of the ForeCASTS tree range shift atlas (www.geobabble.org/~hnw/global/treeranges5/climate_change/atlas.html) now predicts global shifts in the suitable ranges of 335 tree species (essentially all woody species measured in Forest Inventory Analysis (FIA)) under forecasts from the Parallel Climate Model, and the Hadley Model, each under future climatic scenarios A1 and B1, each at two future dates (2050 and 2100). Version 5 includes more Global Biodiversity Information Facility (GBIF) occurrence points, uses improved heuristics for occurrence training, and recovers occurrence points that fall in water. A multivariate clustering procedure was used to quantitatively delineate 30 thousand environmentally homogeneous ecoregions across present and 8 potential future global locations at once, using global maps of 17 environmental characteristics describing temperature, precipitation, soils, topography and solar insolation. Occurrence of each tree species on FIA plots and in GBIF samples was used to identify a subset of suitable ecoregions from the full set of 30 thousand. This subset of suitable ecoregions was compared to the known current present range of the tree species. Predicted present ranges correspond well with existing ranges for all but a few of the 335 tree species. The subset of suitable ecoregions can then be tracked into the future to determine whether the suitable home range remains the same, moves, grows, shrinks, or disappears under each model/scenario combination. A quantitative niche breadth analysis allows sorting of the 17 environmental variables from the narrowest, most important, to the broadest, least restrictive environmental factors limiting each tree species. Potential tree richness maps were produced, along with a quantitative potential tree endemism map for present and future CONUS. Using a new empirical imputation method which associates sparse measurements of dependent variables with particular clustered combinations of the

  17. Abrupt climate variability since the last deglaciation based on a high-resolution, multi-proxy peat record from NW Iran: The hand that rocked the Cradle of Civilization?

    NASA Astrophysics Data System (ADS)

    Sharifi, Arash; Pourmand, Ali; Canuel, Elizabeth A.; Ferer-Tyler, Erin; Peterson, Larry C.; Aichner, Bernhard; Feakins, Sarah J.; Daryaee, Touraj; Djamali, Morteza; Beni, Abdolmajid Naderi; Lahijani, Hamid A. K.; Swart, Peter K.

    2015-09-01

    We present a high-resolution (sub-decadal to centennial), multi-proxy reconstruction of aeolian input and changes in palaeohydrological conditions based on a 13000 Yr record from Neor Lake's peripheral peat in NW Iran. Variations in relative abundances of refractory (Al, Zr, Ti, and Si), redox sensitive (Fe) and mobile (K and Rb) elements, total organic carbon (TOC), δ13CTOC, compound-specific leaf wax hydrogen isotopes (δD), carbon accumulation rates and dust fluxes presented here fill a large gap in the existing terrestrial paleoclimate records from the interior of West Asia. Our results suggest that a transition occurred from dry and dusty conditions during the Younger Dryas (YD) to a relatively wetter period with higher carbon accumulation rates and low aeolian input during the early Holocene (9000-6000 Yr BP). This period was followed by relatively drier and dustier conditions during middle to late Holocene, which is consistent with orbital changes in insolation that affected much of the northern hemisphere. Numerous episodes of high aeolian input spanning a few decades to millennia are prevalent during the middle to late Holocene. Wavelet analysis of variations in Ti abundances as a proxy for aeolian input revealed notable periodicities at 230, 320, and 470 years with significant periodicities centered around 820, 1550, and 3110 years over the last 13000 years. Comparison with palaeoclimate archives from West Asia, the North Atlantic and African lakes point to a teleconnection between North Atlantic climate and the interior of West Asia during the last glacial termination and the Holocene epoch. We further assess the potential role of abrupt climate change on early human societies by comparing our record of palaeoclimate variability with historical, geological and archaeological archives from this region. The terrestrial record from this study confirms previous evidence from marine sediments of the Arabian Sea that suggested climate change influenced the

  18. Responses of leaf traits to climatic gradients: adaptive variation versus compositional shifts

    NASA Astrophysics Data System (ADS)

    Meng, T.-T.; Wang, H.; Harrison, S. P.; Prentice, I. C.; Ni, J.; Wang, G.

    2015-09-01

    , but Parea increased with temperature. Although the adaptive nature of many of these trait-climate relationships is understood qualitatively, a key challenge for modelling is to predict them quantitatively. Models must take into account that community-level responses to climatic gradients can be influenced by shifts in PFT composition, such as the replacement of deciduous by evergreen trees, which may run either parallel or counter to trait variation within PFTs. The importance of PFT shifts varies among traits, being important for biophysical traits but less so for physiological and chemical traits. Finally, models should take account of the diversity of trait values that is found in all sites and PFTs, representing the "pool" of variation that is locally available for the natural adaptation of ecosystem function to environmental change.

  19. Shifts in Climate Foster Exceptional Opportunities for Species Radiation: The Case of South African Geraniums

    PubMed Central

    Martínez-Cabrera, Hugo I.; Peres-Neto, Pedro R.

    2013-01-01

    Climate change is often assumed to be a major driver of biodiversity loss. However, it can also set the stage for novel diversification in lineages with the evolutionary ability to colonize new environments. Here we tested if the extraordinary evolutionary success of the genus Pelargonium was related to the ability of its species to capitalize on the climate niche variation produced by the historical changes in southern Africa. We evaluated the relationship between rates of climate niche evolution and diversification rates in the main Pelargonium lineages and disentangled the roles of deep and recent historical events in the modification of species niches. Pelargonium clades exhibiting higher ecological differentiation along summer precipitation (SPP) gradients also experienced higher diversification rates. Faster rates of niche differentiation in spatially structured variables, along with lower levels of niche overlap among closely related species, suggest recent modification in species niches (e.g. dispersal or range shift) and niche lability. We suggest that highly structured SPP gradients established during the aridification process within southern Africa, in concert with niche lability and low niche overlap, contributed to species divergence. These factors are likely to be responsible for the extensive diversification of other lineages in this diversity hot spot. PMID:24358250

  20. Compounded effects of climate change and habitat alteration shift patterns of butterfly diversity.

    PubMed

    Forister, Matthew L; McCall, Andrew C; Sanders, Nathan J; Fordyce, James A; Thorne, James H; O'Brien, Joshua; Waetjen, David P; Shapiro, Arthur M

    2010-02-01

    Climate change and habitat destruction have been linked to global declines in vertebrate biodiversity, including mammals, amphibians, birds, and fishes. However, invertebrates make up the vast majority of global species richness, and the combined effects of climate change and land use on invertebrates remain poorly understood. Here we present 35 years of data on 159 species of butterflies from 10 sites along an elevational gradient spanning 0-2,775 m in a biodiversity hotspot, the Sierra Nevada Mountains of Northern California. Species richness has declined at half of the sites, with the most severe reductions at the lowest elevations, where habitat destruction is greatest. At higher elevations, we observed clear upward shifts in the elevational ranges of species, consistent with the influence of global warming. Taken together, these long-term data reveal the interacting negative effects of human-induced changes on both the climate and habitat available to butterfly species in California. Furthermore, the decline of ruderal, disturbance-associated species indicates that the traditional focus of conservation efforts on more specialized and less dispersive species should be broadened to include entire faunas when estimating and predicting the effects of pervasive stressors.

  1. Shifts in climate foster exceptional opportunities for species radiation: the case of South african geraniums.

    PubMed

    Martínez-Cabrera, Hugo I; Peres-Neto, Pedro R

    2013-01-01

    Climate change is often assumed to be a major driver of biodiversity loss. However, it can also set the stage for novel diversification in lineages with the evolutionary ability to colonize new environments. Here we tested if the extraordinary evolutionary success of the genus Pelargonium was related to the ability of its species to capitalize on the climate niche variation produced by the historical changes in southern Africa. We evaluated the relationship between rates of climate niche evolution and diversification rates in the main Pelargonium lineages and disentangled the roles of deep and recent historical events in the modification of species niches. Pelargonium clades exhibiting higher ecological differentiation along summer precipitation (SPP) gradients also experienced higher diversification rates. Faster rates of niche differentiation in spatially structured variables, along with lower levels of niche overlap among closely related species, suggest recent modification in species niches (e.g. dispersal or range shift) and niche lability. We suggest that highly structured SPP gradients established during the aridification process within southern Africa, in concert with niche lability and low niche overlap, contributed to species divergence. These factors are likely to be responsible for the extensive diversification of other lineages in this diversity hot spot. PMID:24358250

  2. Northern Peatland Shifts Under Changing Climate and Their Impact on Permafrost

    NASA Astrophysics Data System (ADS)

    Shur, Y.; Jorgenson, T.; Kanevskiy, M. Z.

    2014-12-01

    Formation of peatlands depends primarily on climate and its interactions with hydrology, soil thermal regimes, plant composition, and nutrients. A water balance with precipitation exceeding evaporation is necessary for their formation. The rate of peat accumulation also greatly depends on thermal resources. The prominent impact of the water balance and temperature on peatland formation is evident in the West Siberia Lowland. The rate of peat accumulation steadily increases from arctic tundra to moss tundra, to forest tundra, to northern taiga, and to southern taiga. This increase is a result in increase in air temperature and length of the growing season because all of these zones have water balance favorable for peat formation. Further to south, evaporation prevails over precipitation and peat formation occurs only in isolated areas. Climate change will redefine geographical distribution of climatic and vegetation zones. It is predicted that in arctic and subarctic regions the difference between precipitation and evaporation will increase and as a result these regions will remain favorable to peat accumulation. With increase of thermal resources, the rate of peat accumulation will also increase. The Alaska Arctic Coastal Plain is of a special interest because it has thousands of shallow lakes, which due to warming climate would shift from open waterbodies to peatlands through shoreline paludification and infilling. The accumulation of organic matter will likely turn open water into shore fens and bogs, and eventually to peat plateaus, as is occurring in many boreal landscapes. Expected impact on permafrost in arctic and subarctic regions will include rise of the permafrost table, thickening of the ice-rich intermediate layer with ataxitic (suspended) cryostructure, and replacement of frost boils with earth hummocks. In the contemporary continuous permafrost zone, permafrost formed as climate-driven will be transformed into climate-driven ecosystem protected

  3. Heat waves connect abrupt polar climate changes during the past 67ka: evidence from sediment core GeoB3912-1

    NASA Astrophysics Data System (ADS)

    Yang, X.; Rial, J. A.

    2014-12-01

    According to the hypothesis of polar synchronization, climate variations of Earth's poles are connected with a persistent phase lock of π/2 throughout the last glacial period. However, it is not clear yet how the Earth's two poles communicate with each other, the Thermohaline circulation (THC) being a possible candidate for signal carrier. Here we present a possible way of climate variation propagation through the Atlantic Ocean - likely in the form of heat or thermal wave (Cattaneo's solution) - based on lagged correlation between an organic carbon climate proxy record from the tropical Atlantic and the south-north polar temperature gradient. We further demonstrate that the speed of such propagation is frequency dependent, of which the wave of the longest period travels the fastest at the speed of ~32 km/year consistent with the estimated speed of the THC. The observed speed - frequency relationship can be successfully modeled as resulting from a propagating dispersive thermal wave initiated by the polar temperature gradient maximum. We show that such heat wave propagation is a potential mechanism to couple and synchronize the polar climates during the last glacial period and to force the occurrence of Heinrich events. To summarize, the polar temperature gradient anomalies are consequence of the π/2 phase lock between the polar climates, which is caused by polar synchronization maintained by the coupling, which is, as the data suggest, in the form of thermal waves. The spikes in organic carbon and the Fe/Ca ratio records in the core GeoB3912-1 can be thought of as snapshots of the passage of strong meteorological wavefronts through the equatorial region. The results strongly suggest that each peak in the organic carbon recorded a half-hemisphere-delayed passage of a wave-like disturbance through the equator carrying the south-north temperature gradient maxima. And each of these occurs within timing error of the Heinrich events H0-H6.

  4. Mountain Climates on the Move: Implications for Past and Future Vegetation Shifts in the Northeastern United States

    NASA Astrophysics Data System (ADS)

    Wason, J. W., III; Dovciak, M.; Bevilacqua, E.

    2015-12-01

    Climate change in the northeastern United States is expected to shift climatic (temperature) envelopes for spruce-fir forests upslope and northward decreasing their area in the region by 2100. Coarse scale landscape models however, may not incorporate heterogeneity in climatic conditions in mountains that can create climatic refugia for species in high-elevation spruce-fir forests. To determine spatial and temporal trends in climate of mountain spruce-fir forests we measured microclimate at 98 forest plots in 2012 and 2013 on 12 mountains in New York, Vermont, New Hampshire, and Maine. By linking regional climate trends with our spatial climate data we calculated elevational shifts in temperature envelopes during the last 50 years. Additionally we linked our spatial dataset to a range of future climate conditions for 2100 based on Representative Concentration Pathways (1 to 5°C warming). We hypothesized that climates have already changed to an extent that spruce-fir forests should begin to respond and that future climate conditions may shift suitable habitat for spruce-fir forests beyond their current range. We found that regional climate change over the last 50 years has resulted in warming of 0.66 and 1.62°C for average annual daily maximum (Tmax) and minimum (Tmin) temperatures in the region. When linked to our spatial microclimate model, this warming results in a 100 (Tmax) and 312m (Tmin) upslope shift in temperature envelopes. Future climate projections suggest that by 2100 Tmax may shift upslope between 152 and 758m for the 1 and 5°C scenarios respectively, while Tmin may shift upslope between 192 and 962m. Spruce-fir forests typically occupy an elevation range of ~500m suggesting that the climate experienced in these forests 50 years ago may not be found within their elevation range by 2100. These results are discussed in the context of responses of tree populations and growth rates observed along the elevation gradients of northeastern United States.

  5. The potential macroalgae habitat shifts in an Antarctic Peninsula fjord due to climate change

    NASA Astrophysics Data System (ADS)

    Jerosch, Kerstin; Scharf, Frauke; Deregibus, Dolores; Campana, Gabriela; Zacher, Katharina; Hass, Christian; Quartino, Liliana; Abele, Doris

    2016-04-01

    The Western Antarctic Peninsula (WAP) region is one of the most rapidly warming on earth since the last 50 yr. The WAP glaciers currently contribute one third of the melt water to global sea level rise. Climate warming is supposed to induce important changes in polar ecosystems, from microbial communities to apex predators' levels. Macroalgae are the main biomass producers in Potter Cove located at King George Island, the biggest island of the South Shetland Arc. They are sensitive to climate change factors such as suspended particulate matter (SPM). Macroalgae presence and absence data were used to test SDMs suitability and, simultaneously, to assess the environmental response of macroalgae as well as to model four scenarios of distribution shifts by varying SPM conditions due to climate change. Species distribution models (SDM) predict species occurrence based on statistical relationships with environmental conditions. The R-package 'biomod2' which includes 10 different SDM techniques and 10 different evaluation methods was used in this study. According to the averaged evaluation scores of Relative Operating Characteristics (ROC) and True scale statistics (TSS) by models, those methods based on a multitude of decision trees such as Random Forest and Classification Tree Analysis, reached the highest predictive power followed by generalized boosted models (GBM) and maximum-entropy approaches (Maxent). The final ensemble model (EM) used 135 of 200 calculated models (TSS > 0.7) and identified hard substrate and SPM as the most influencing parameters followed by distance to glacier, total organic carbon (TOC), bathymetry and slope. The modeled current status of macroalgae distribution results in only 18.25% of earlier estimated areas populated by macroalgae in Potter Cove. The climate change scenarios show an invasive reaction of the macroalgae in case of less SPM and a retreat of the macroalgae in case of higher assumed SPM values.

  6. Mechanisms Controlling Species Responses to Climate Change: Thermal Tolerances and Shifting Range Limits. (Invited)

    NASA Astrophysics Data System (ADS)

    Sage, R. F.; Bykova, O.; Coiner, H.

    2010-12-01

    One of the main effects of anthropogenic climate change will be widespread shifts in species distribution, with the common assumption that they will migrate to higher elevation and latitude. While this assumption is supported by migration patterns following climate warming in the past 20,000 years, it has not been rigorously evaluated in terms of physiological mechanism, despite the implication that migration in response to climate warming is controlled by some form of thermal adaptation. We have been evaluating the degree to which species range limits are controlled by physiological patterns of thermal tolerance in bioinvaders of North America. Bioinvaders presumably have few biotic controls over their distribution and thus are more likely to fully exploit their thermal niche. In cheatgrass (Bromus tectorum), the minimum lethal temperature in winter is -32C, which corresponds to the mean winter minimum temperature at its northern range limit. In red brome (Bromus rubens), the minimum lethal temperature is also near -32C, which is well below the minimum winter temperature near -20C that corresponds to its northern distribution limit. In kudzu (Pueraria lobata), the minimum lethal temperature is near -20C, which corresponds to the midwinter minimum at its northern distribution limit; however, overwintering kudzu tissues are insulated by soil and snow cover, and thus do not experience lethal temperatures at kudzu's northern range limit. These results demonstrate that some invasive species can exploit the potential range defined by their low temperature tolerance and thus can be predicted by mechanistic models to migrate to higher latitudes with moderation of winter cold. The distribution of other invaders such as kudzu and red brome are not controlled by tolerance of midwinter cold. Developing mechanistic models of their distributions, and how these might change with climate warming, will require extensive physiological study.

  7. Multiple abrupt climate changes in the western hemisphere during the past 50,000 years, and their implications concerning the response of vegetation to changing atmospheric chemistry

    SciTech Connect

    Jacobson, G.L. Jr.; Grimm, E.C.

    1995-06-01

    Independent evidence spanning the last 50,000 years from ice cores, ocean sediments, and detailed glacial-geologic investigations implies multiple. large warm/cool oscillations with a frequency of ca. 3000 years through much of the Western Hemisphere. Paleoecological studies at sites in North America and the west coast of South America reveal major, synchronous changes in vegetation corresponding to many of these high-frequency changes in climate. Sequences on both sides of the equator culminate in substantial warming at 14 ka BP and a brief cooling at ca. 11 ka BP just prior to the final onset of Holocene warming. The high-frequency climate oscillations are not explained by {open_quotes}Milankovitch{close_quotes} cycles in solar insolation or by changes in thermohaline ocean circulation. Rather, these changes in climate and the attendant synchronous, broad-scale responses of vegetation indicate a global atmospheric forcing. However, that forcing is apparently also distinct from changing concentrations of atmospheric CO2 (as represented in the Vostok ice-core data). High-resolution CO2 data, such as that from the new Greenland ice cores, will be required before critical assessments of plant-physiological responses to past atmospheric changes can be carried out.

  8. The role of plant functional trade-offs for biodiversity changes and biome shifts under scenarios of global climatic change

    NASA Astrophysics Data System (ADS)

    Reu, B.; Zaehle, S.; Proulx, R.; Bohn, K.; Kleidon, A.; Pavlick, R.; Schmidtlein, S.

    2010-10-01

    The global geographic distribution of biodiversity and biomes is determined by species-specific physiological tolerances to climatic constraints. Current models implement empirical bioclimatic relationships to predict present-day vegetation patterns and to forecast biodiversity changes and biome shifts under climatic change. In this paper, we consider plant functional trade-offs and their interactions with climatic changes to forecast and explain biodiversity changes and biome shifts. The Jena Diversity model (JeDi) simulates plant survival according to essential plant functional trade-offs, including eco-physiological processes such as water uptake, photosynthesis, allocation, reproduction and phenology. We apply JeDi to quantify biodiversity changes and biome shifts between present-day and a range of possible future climates from two scenarios (A2 and B1) and seven global climate models using metrics of plant functional richness and functional identity. Our results show (i) a significant biodiversity loss in the tropics, (ii) an increase in biodiversity at mid and high latitudes, and (iii) a poleward shift of biomes. While these results are consistent with the findings of empirical approaches, we are able to explain them in terms of the plant functional trade-offs involved in the allocation, metabolic and reproduction strategies of plants. We conclude that general aspects of plant physiological tolerances can be derived from plant functional trade-offs, which may provide a useful process- and trait-based alternative to bioclimatic relationships in order to address questions about the causes of biodiversity changes and biome shifts.

  9. Compositional shifts in Costa Rican forests due to climate-driven species migrations.

    PubMed

    Feeley, Kenneth J; Hurtado, Johanna; Saatchi, Sassan; Silman, Miles R; Clark, David B

    2013-11-01

    Species are predicted to shift their distributions upslope or poleward in response to global warming. This prediction is supported by a growing number of studies documenting species migrations in temperate systems but remains poorly tested for tropical species, and especially for tropical plant species. We analyzed changes in tree species composition in a network of 10 annually censused 1-ha plots spanning an altitudinal gradient of 70-2800 m elevation in Costa Rica. Specifically, we combined plot data with herbarium records (accessed through GBIF) to test if the plots' community temperature scores (CTS, average thermal mean of constituent species weighted by basal area) have increased over the past decade as is predicted by climate-driven species migrations. In addition, we quantified the contributions of stem growth, recruitment, and mortality to the observed patterns. Supporting our a priori hypothesis of upward species migrations, we found that there have been consistent directional shifts in the composition of the plots, such that the relative abundance of lowland species, and hence CTS, increased in 90% of plots. The rate of the observed compositional shifts corresponds to a mean thermal migration rate (TMR) of 0.0065 °C yr(-1) (95% CI = 0.0005-0.0132 °C yr(-1) ). While the overall TMR is slower than predicted based on concurrent regional warming of 0.0167 °C yr(-1) , migrations were on pace with warming in 4 of the 10 plots. The observed shifts in composition were driven primarily by mortality events (i.e., the disproportionate death of highland vs. lowland species), suggesting that individuals of many tropical tree species will not be able to tolerate future warming and thus their persistence in the face of climate change will depend on successful migrations. Unfortunately, in Costa Rica and elsewhere, land area inevitably decreases at higher elevations; hence, even species that are able to migrate successfully will face heightened risks of

  10. A stratigraphic framework for naming and robust correlation of abrupt climatic changes during the last glacial period based on three synchronized Greenland ice core records

    NASA Astrophysics Data System (ADS)

    Rasmussen, Sune O.

    2014-05-01

    Due to their outstanding resolution and well-constrained chronologies, Greenland ice core records have long been used as a master record of past climatic changes during 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 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. This is based on a combination of isotope ratios (δ18O, reflecting mainly local temperature) and calcium concentrations (reflecting mainly atmospheric dust loading). 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. This is a key step aimed at promoting unambiguous comparison and correlation between different proxy records, as well as a more secure basis for investigating the dynamics and fundamental causes of these climatic perturbations. The work presented is under review for publication in Quaternary Science Reviews. Author team: S

  11. Surface water input from snowmelt and rain throughfall in western juniper: potential impacts of climate change and shifts in semi-arid vegetation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Shifts in both climate and land cover can both potentially impact above ground hydrological processes. In the western U.S., both climatic shifts from snow to rain-dominated precipitation and land cover shifts of pinyon and juniper species in grass and shrub-dominated landscapes alter interception, ...

  12. Long-term changes in the fish community structure from the Tsushima warm current region of the Japan/East Sea with an emphasis on the impacts of fishing and climate regime shift over the last four decades

    NASA Astrophysics Data System (ADS)

    Tian, Yongjun; Kidokoro, Hideaki; Watanabe, Tatsuro

    2006-02-01

    climatic regime shifts in the North Pacific. These results strongly suggest that the structure of the fish community in the Japan/East Sea was largely affected by climatic and oceanic regime shifts rather than by fishing. There is no evidence showing “fishing down food webs” in the Japan/East Sea. However, in addition to the impacts of abrupt shifts that occurred in the late 1980s, the large predatory and demersal fishes seem to be facing stronger fishing pressure with the collapse of the Japanese sardine.

  13. Non Stationary And Non Gaussian Character Of ENSO: The Role Of Climate Shifts And Nonlinearities

    NASA Astrophysics Data System (ADS)

    Boucharel, J.; Dewitte, B.; Garel, B.; Du Penhoat, Y.

    2008-12-01

    ENSO is the dominant climate mode of variability in the Pacific, having socio-economical impacts on surrounding regions. ENSO exhibits a significant modulation at decadal to interdecadal timescales which is associated to changes of its characteristics (onset, amplitude, frequency, propagation, and predictability). Among these characteristics, some of them are generally ignored in ENSO studies, such as its asymmetry and the deviation of its statistics from those of the Gaussian distribution. These properties could be related to the ability of the current generation of coupled models to predict ENSO and its modulation. Here, the non-Gaussian nature and asymmetry of ENSO is diagnosed from in situ data and the outputs of a variety of models (from intermediate complexity models to full physics coupled general circulation models) using robust statistical tools. In particular alpha-stable laws are used as theoretical background material to quantify the non-Gaussian character of ENSO time series. It is shown that the Alpha-stable character of ENSO may result from the presence of climate shifts inducing non stationnarity in the time series. Also, cool (warm) periods are associated with ENSO statistics having a larger (weaker) tendency towards Gaussianity and a weaker (larger) asymmetry. This supports the hypothesis of ENSO being rectified by changes in mean state through non-linear processes. The relationship between change in mean state and non-linearity is investigated both in the Zebiak and Cane model and the IPCC models, which indicate that the propensity of a model to reproduce extreme events is related to its tendency to emphasize the non-linear interaction between mean state and ENSO variability. More particularly, high statistical moments i.e. high order nonlinearities seem to be involved in the feedback between extreme events occurrence and mean state shift triggering through inverse energy cascade, emphasizing the ENSO multifractal nature.

  14. Shift of grey seal subspecies boundaries in response to climate, culling and conservation.

    PubMed

    Fietz, Katharina; Galatius, Anders; Teilmann, Jonas; Dietz, Rune; Frie, Anne Kristine; Klimova, Anastasia; Palsbøll, Per J; Jensen, Lasse F; Graves, Jeff A; Hoffman, Joseph I; Olsen, Morten Tange

    2016-09-01

    Identifying the processes that drive changes in the abundance and distribution of natural populations is a central theme in ecology and evolution. Many species of marine mammals have experienced dramatic changes in abundance and distribution due to climatic fluctuations and anthropogenic impacts. However, thanks to conservation efforts, some of these species have shown remarkable population recovery and are now recolonizing their former ranges. Here, we use zooarchaeological, demographic and genetic data to examine processes of colonization, local extinction and recolonization of the two northern European grey seal subspecies inhabiting the Baltic Sea and North Sea. The zooarchaeological and genetic data suggest that the two subspecies diverged shortly after the formation of the Baltic Sea approximately 4200 years bp, probably through a gradual shift to different breeding habitats and phenologies. By comparing genetic data from 19th century pre-extinction material with that from seals currently recolonizing their past range, we observed a marked spatiotemporal shift in subspecies boundaries, with increasing encroachment of North Sea seals on areas previously occupied by the Baltic Sea subspecies. Further, both demographic and genetic data indicate that the two subspecies have begun to overlap geographically and are hybridizing in a narrow contact zone. Our findings provide new insights into the processes of colonization, extinction and recolonization and have important implications for the management of grey seals across northern Europe. PMID:27616353

  15. Phase shifts, herbivory, and the resilience of coral reefs to climate change.

    PubMed

    Hughes, Terence P; Rodrigues, Maria J; Bellwood, David R; Ceccarelli, Daniela; Hoegh-Guldberg, Ove; McCook, Laurence; Moltschaniwskyj, Natalie; Pratchett, Morgan S; Steneck, Robert S; Willis, Bette

    2007-02-20

    Many coral reefs worldwide have undergone phase shifts to alternate, degraded assemblages because of the combined effects of over-fishing, declining water quality, and the direct and indirect impacts of climate change. Here, we experimentally manipulated the density of large herbivorous fishes to test their influence on the resilience of coral assemblages in the aftermath of regional-scale bleaching in 1998, the largest coral mortality event recorded to date. The experiment was undertaken on the Great Barrier Reef, within a no-fishing reserve where coral abundances and diversity had been sharply reduced by bleaching. In control areas, where fishes were abundant, algal abundance remained low, whereas coral cover almost doubled (to 20%) over a 3 year period, primarily because of recruitment of species that had been locally extirpated by bleaching. In contrast, exclusion of large herbivorous fishes caused a dramatic explosion of macroalgae, which suppressed the fecundity, recruitment, and survival of corals. Consequently, management of fish stocks is a key component in preventing phase shifts and managing reef resilience. Importantly, local stewardship of fishing effort is a tractable goal for conservation of reefs, and this local action can also provide some insurance against larger-scale disturbances such as mass bleaching, which are impractical to manage directly.

  16. Climate-Induced Range Shifts and Possible Hybridisation Consequences in Insects

    PubMed Central

    Sánchez-Guillén, Rosa Ana; Muñoz, Jesús; Rodríguez-Tapia, Gerardo; Feria Arroyo, T. Patricia; Córdoba-Aguilar, Alex

    2013-01-01

    Many ectotherms have altered their geographic ranges in response to rising global temperatures. Current range shifts will likely increase the sympatry and hybridisation between recently diverged species. Here we predict future sympatric distributions and risk of hybridisation in seven Mediterranean ischnurid damselfly species (I. elegans, I. fountaineae, I. genei, I. graellsii, I. pumilio, I. saharensis and I. senegalensis). We used a maximum entropy modelling technique to predict future potential distribution under four different Global Circulation Models and a realistic emissions scenario of climate change. We carried out a comprehensive data compilation of reproductive isolation (habitat, temporal, sexual, mechanical and gametic) between the seven studied species. Combining the potential distribution and data of reproductive isolation at different instances (habitat, temporal, sexual, mechanical and gametic), we infer the risk of hybridisation in these insects. Our findings showed that all but I. graellsii will decrease in distributional extent and all species except I. senegalensis are predicted to have northern range shifts. Models of potential distribution predicted an increase of the likely overlapping ranges for 12 species combinations, out of a total of 42 combinations, 10 of which currently overlap. Moreover, the lack of complete reproductive isolation and the patterns of hybridisation detected between closely related ischnurids, could lead to local extinctions of native species if the hybrids or the introgressed colonising species become more successful. PMID:24260411

  17. Catastrophic ecosystem shifts in dry tropical forest: evidence, mechanisms and implications for climate change

    NASA Astrophysics Data System (ADS)

    Lawrence, D.; D'Odorico, P.; Runyan, C.; Diekmann, L.; DeLonge, M. S.; Das, R.; Eaton, J.; Vandecar, K.; Schmook, B.

    2015-12-01

    Tropical dry forests have long been used by humans. Has it been sustainable? Not in the southern Yucatan. Biomass accumulation declines with each cycle of shifting cultivation with implications for both internal recycling of nutrients and external inputs of nutrients. We detail the evidence for a decline in P inputs from biomass burning (aboveground biomass, litter, and coarse woody debris), an increase in leaching losses from deep soils, and a decline in atmospheric inputs of new P from Saharan dust following the transition from mature to secondary forest. Canopy trapping of dust is critical to maintaining P balance in this system. Effective trapping is diminished by changes in the structure of secondary forest--loss of height, leaf area and basal area. Experimental studies show that it is atmospheric transport of dust, not microbial shedding or leaching from live tissues, that explains the difference between throughfall P and P in bulk deposition. Because of net losses in P, uptake of carbon during regrowth is slower with each cycle of shifting cultivation. As much of the tropics has moved beyond a mature forest frontier, the decline in carbon sequestration is likely widespread over both dry and wet forests. The terrestrial carbon sink in the tropics may be declining. The capacity to sequester carbon through afforestation, reforestation and restoration has certainly diminished over time, limiting the effectiveness of such efforts to help mitigate climate change.

  18. Climate warming shifts carbon allocation from stemwood to roots in calcium-depleted spruce forests

    NASA Astrophysics Data System (ADS)

    Lapenis, Andrei; Lawrence, Gregory; Buyantuev, Alexander

    2015-04-01

    Increased greening of northern forests, measured by the Normalized Difference Vegetation Index (NDVI), has been presented as evidence that a warmer climate has increased both net primary productivity (NPP) and the carbon sink in boreal forests. However, higher production and greener canopies may accompany changes in carbon allocation that favor foliage or fine roots over less decomposable woody biomass. Furthermore, tree core data throughout mid- and northern latitudes have revealed a divergence problem (DP), a weakening in tree ring responses to warming over the past half century that is receiving increasing attention, but remains poorly understood. Often, the same sites exhibit trend inconsistency phenomenon (TIP), namely positive, or no trends in growing season NDVI where negative trends in tree ring indexes are observed. Here we studied growth of two Norway spruce (Picea abies) stands in western Russia that exhibited both the DP and TIP but were subject to soil acidification and calcium depletion of differing timing and severity. Our results link the decline in radial growth starting in 1980 to a shift in carbon allocation from wood to roots driven by a combination of two factors: (a) soil acidification that depleted calcium and impaired root function and (b) earlier onset of the growing season that further taxed the root system. The latter change in phenology appears to act as a trigger at both sites to push trees into nutrient limitation as the demand for Ca increased with the longer growing season, thereby causing the shift in carbon allocation.

  19. Climate change and glacier retreat drive shifts in an Antarctic benthic ecosystem.

    PubMed

    Sahade, Ricardo; Lagger, Cristian; Torre, Luciana; Momo, Fernando; Monien, Patrick; Schloss, Irene; Barnes, David K A; Servetto, Natalia; Tarantelli, Soledad; Tatián, Marcos; Zamboni, Nadia; Abele, Doris

    2015-11-01

    The Antarctic Peninsula (AP) is one of the three places on Earth that registered the most intense warming in the last 50 years, almost five times the global mean. This warming has strongly affected the cryosphere, causing the largest ice-shelf collapses ever observed and the retreat of 87% of glaciers. Ecosystem responses, although increasingly predicted, have been mainly reported for pelagic systems. However, and despite most Antarctic species being benthic, responses in the Antarctic benthos have been detected in only a few species, and major effects at assemblage level are unknown. This is probably due to the scarcity of baselines against which to assess change. We performed repeat surveys of coastal benthos in 1994, 1998, and 2010, analyzing community structure and environmental variables at King George Island, Antarctica. We report a marked shift in an Antarctic benthic community that can be linked to ongoing climate change. However, rather than temperature as the primary factor, we highlight the resulting increased sediment runoff, triggered by glacier retreat, as the potential causal factor. The sudden shift from a "filter feeders-ascidian domination" to a "mixed assemblage" suggests that thresholds (for example, of tolerable sedimentation) and alternative equilibrium states, depending on the reversibility of the changes, could be possible traits of this ecosystem. Sedimentation processes will be increasing under the current scenario of glacier retreat, and attention needs to be paid to its effects along the AP. PMID:26702429

  20. Holocene peatland shifts in vegetation, carbon, and climate at Imnavait, Alaska

    NASA Astrophysics Data System (ADS)

    Peteet, D. M.; Nichols, J. E.; Ouni, S.; Pavia, F.; Pearl, Y.

    2012-12-01

    The Imnavait Creek basin (68 40'N, 149 20'W; elevation 875-945 m) in the foothills of the Brooks Range, AK has been well studied in terms of modern vegetational communities, hydrology, and soils. But paleoclimate and paleovegetation reconstructions are limited. We retrieved a 2-m peatland core to examine the macrofossil/biomarker/carbon sequestration history throughout the Holocene and late-glacial. AMS 14C dates of the macrofossil remains will allow us to calculate carbon sequestration rates. The Holocene history (the top meter) records marked shifts in vascular plant as well as bryophyte history. A tri-partite sequence is apparent, with Andromeda/Sphagnum remains abundant in the early Holocene. The absence of bryophytes and the presence of Eriophorum and Carex achenes characterize the mid-Holocene. Andromeda and Betula nana with Sphagnum remains are abundant in the upper 30 cm of the core. Hydrogen isotope ratios of leaf wax alkanes record higher effective moisture in the early and late Holocene, suggesting more evaporative loss in the mid-Holocene which is characterized by Eriophorum. We compare our results with previously observed palynological shifts from lakes in the region and place this Arctic paleorecord in a larger perspective of peatland histories in a N-S transect covering nearly 10 degrees of latitude across Alaska. This tripartite pattern of effective moisture appears to be the same throughout the Alaskan transect, suggesting strong climatic control.

  1. Climate change and glacier retreat drive shifts in an Antarctic benthic ecosystem.

    PubMed

    Sahade, Ricardo; Lagger, Cristian; Torre, Luciana; Momo, Fernando; Monien, Patrick; Schloss, Irene; Barnes, David K A; Servetto, Natalia; Tarantelli, Soledad; Tatián, Marcos; Zamboni, Nadia; Abele, Doris

    2015-11-01

    The Antarctic Peninsula (AP) is one of the three places on Earth that registered the most intense warming in the last 50 years, almost five times the global mean. This warming has strongly affected the cryosphere, causing the largest ice-shelf collapses ever observed and the retreat of 87% of glaciers. Ecosystem responses, although increasingly predicted, have been mainly reported for pelagic systems. However, and despite most Antarctic species being benthic, responses in the Antarctic benthos have been detected in only a few species, and major effects at assemblage level are unknown. This is probably due to the scarcity of baselines against which to assess change. We performed repeat surveys of coastal benthos in 1994, 1998, and 2010, analyzing community structure and environmental variables at King George Island, Antarctica. We report a marked shift in an Antarctic benthic community that can be linked to ongoing climate change. However, rather than temperature as the primary factor, we highlight the resulting increased sediment runoff, triggered by glacier retreat, as the potential causal factor. The sudden shift from a "filter feeders-ascidian domination" to a "mixed assemblage" suggests that thresholds (for example, of tolerable sedimentation) and alternative equilibrium states, depending on the reversibility of the changes, could be possible traits of this ecosystem. Sedimentation processes will be increasing under the current scenario of glacier retreat, and attention needs to be paid to its effects along the AP.

  2. Climate change and glacier retreat drive shifts in an Antarctic benthic ecosystem

    PubMed Central

    Sahade, Ricardo; Lagger, Cristian; Torre, Luciana; Momo, Fernando; Monien, Patrick; Schloss, Irene; Barnes, David K. A.; Servetto, Natalia; Tarantelli, Soledad; Tatián, Marcos; Zamboni, Nadia; Abele, Doris

    2015-01-01

    The Antarctic Peninsula (AP) is one of the three places on Earth that registered the most intense warming in the last 50 years, almost five times the global mean. This warming has strongly affected the cryosphere, causing the largest ice-shelf collapses ever observed and the retreat of 87% of glaciers. Ecosystem responses, although increasingly predicted, have been mainly reported for pelagic systems. However, and despite most Antarctic species being benthic, responses in the Antarctic benthos have been detected in only a few species, and major effects at assemblage level are unknown. This is probably due to the scarcity of baselines against which to assess change. We performed repeat surveys of coastal benthos in 1994, 1998, and 2010, analyzing community structure and environmental variables at King George Island, Antarctica. We report a marked shift in an Antarctic benthic community that can be linked to ongoing climate change. However, rather than temperature as the primary factor, we highlight the resulting increased sediment runoff, triggered by glacier retreat, as the potential causal factor. The sudden shift from a “filter feeders–ascidian domination” to a “mixed assemblage” suggests that thresholds (for example, of tolerable sedimentation) and alternative equilibrium states, depending on the reversibility of the changes, could be possible traits of this ecosystem. Sedimentation processes will be increasing under the current scenario of glacier retreat, and attention needs to be paid to its effects along the AP. PMID:26702429

  3. Climate warming shifts carbon allocation from stemwood to roots in calcium-depleted spruce forests

    USGS Publications Warehouse

    Lapenis, Andrei Gennady; Lawrence, Gregory B.; Heim, Alexander; Zheng, Chengyang; Shortle, Walter

    2013-01-01

    Increased greening of northern forests, measured by the Normalized Difference Vegetation Index (NDVI), has been presented as evidence that a warmer climate has increased both net primary productivity (NPP) and the carbon sink in boreal forests. However, higher production and greener canopies may accompany changes in carbon allocation that favor foliage or fine roots over less decomposable woody biomass. Furthermore, tree core data throughout mid- and northern latitudes have revealed a divergence problem (DP), a weakening in tree ring responses to warming over the past half century that is receiving increasing attention, but remains poorly understood. Often, the same sites exhibit trend inconsistency phenomenon (TIP), namely positive, or no trends in growing season NDVI where negative trends in tree ring indexes are observed. Here we studied growth of two Norway spruce (Picea abies) stands in western Russia that exhibited both the DP and TIP but were subject to soil acidification and calcium depletion of differing timing and severity. Our results link the decline in radial growth starting in 1980 to a shift in carbon allocation from wood to roots driven by a combination of two factors: (a) soil acidification that depleted calcium and impaired root function and (b) earlier onset of the growing season that further taxed the root system. The latter change in phenology appears to act as a trigger at both sites to push trees into nutrient limitation as the demand for Ca increased with the longer growing season, thereby causing the shift in carbon allocation.

  4. Effects of climate change on mountain ecosystems -- Upward shifting of alpine plants

    SciTech Connect

    Pauli, H.; Gottfried, M.; Grabherr, G.

    1996-09-01

    Ecosystems at high latitudes and altitudes are particularly sensitive to climate change. As an effect of global warming, upward shifting of plant species in high mountain systems was predicted for the near future. In consequence the habitats of the alpine and nival vegetation could be restricted drastically, which might result in extinctions, particular of summit floras. Evidence of upward movement of vascular plants in high mountains was recently empirically determined in the European Alps. In 1992 and 1993, data on the flora of 30 high summits were collected. A comparison of the recent investigations with historical records from the same peaks indicated a distinct increase of species richness at 70% of the summits. A stagnation or a slight decrease of species richness was recorded at 9 summits, but one of them showed an increase in species abundance. The change of species richness is correlated with the geomorphological situation, whereas no significant difference could be found by comparing siliceous and carbonate summits. Approximate moving rates for common alpine plants were calculated to be between 0 and 4 meters per decade. This evidence of upward shifting of high mountain plants may already be a measurable result of global warming since the 19th century.

  5. Simulating the Interacting Effects of Intraspecific Variation, Disturbance, and Competition on Climate-Driven Range Shifts in Trees.

    PubMed

    Moran, Emily V; Ormond, Rhys A

    2015-01-01

    Climate change is expected to favor shifts in plant distributions; some such shifts are already being observed along elevation gradients. However, the rate of such shifts may be limited by their ability to reach newly suitable areas and by competition from resident species. The degree of local adaptation and genetic variation may also play a role in the interaction between migrants and residents by affecting relative fitness. We used a simulation model to explore the interacting effects of dispersal, fecundity, disturbance, and genetic variation on range-edge dynamics between a pair of demographically similar tree species. Ideal climate for an individual is determined by genotype. The simulated landscape undergoes an 80-year period of climate change in which climate bands shift upslope; subsequently, climate is held constant for 300 years. The presence of a high-elevation competitor caused a significant lag in the range shift of the low-elevation species relative to competition-free scenarios. Increases in fecundity and dispersal distance both helped to speed up the replacement of the high-elevation species by the low-elevation species at their range boundary. While some disturbance scenarios facilitated this transition, frequent canopy disturbance inhibited colonization by removing reproductive adults and led to range contractions in both species. Differences between dispersal scenarios were more pronounced when disturbance was frequent (15 vs. 25 year return interval) and dispersal was limited. When the high-elevation species lacked genetic variation, its range was more-easily invaded by the low-elevation species, while a similar lack of variation in the low-elevation species inhibited colonization-but only when this lack of variation decreased the fitness of the affected species near the range boundary. Our model results support the importance of measuring and including dispersal/fecundity, disturbance type and frequency, and genetic variation when assessing the

  6. Simulating the Interacting Effects of Intraspecific Variation, Disturbance, and Competition on Climate-Driven Range Shifts in Trees

    PubMed Central

    2015-01-01

    Climate change is expected to favor shifts in plant distributions; some such shifts are already being observed along elevation gradients. However, the rate of such shifts may be limited by their ability to reach newly suitable areas and by competition from resident species. The degree of local adaptation and genetic variation may also play a role in the interaction between migrants and residents by affecting relative fitness. We used a simulation model to explore the interacting effects of dispersal, fecundity, disturbance, and genetic variation on range-edge dynamics between a pair of demographically similar tree species. Ideal climate for an individual is determined by genotype. The simulated landscape undergoes an 80-year period of climate change in which climate bands shift upslope; subsequently, climate is held constant for 300 years. The presence of a high-elevation competitor caused a significant lag in the range shift of the low-elevation species relative to competition-free scenarios. Increases in fecundity and dispersal distance both helped to speed up the replacement of the high-elevation species by the low-elevation species at their range boundary. While some disturbance scenarios facilitated this transition, frequent canopy disturbance inhibited colonization by removing reproductive adults and led to range contractions in both species. Differences between dispersal scenarios were more pronounced when disturbance was frequent (15 vs. 25 year return interval) and dispersal was limited. When the high-elevation species lacked genetic variation, its range was more-easily invaded by the low-elevation species, while a similar lack of variation in the low-elevation species inhibited colonization—but only when this lack of variation decreased the fitness of the affected species near the range boundary. Our model results support the importance of measuring and including dispersal/fecundity, disturbance type and frequency, and genetic variation when assessing

  7. Simulating the Interacting Effects of Intraspecific Variation, Disturbance, and Competition on Climate-Driven Range Shifts in Trees.

    PubMed

    Moran, Emily V; Ormond, Rhys A

    2015-01-01

    Climate change is expected to favor shifts in plant distributions; some such shifts are already being observed along elevation gradients. However, the rate of such shifts may be limited by their ability to reach newly suitable areas and by competition from resident species. The degree of local adaptation and genetic variation may also play a role in the interaction between migrants and residents by affecting relative fitness. We used a simulation model to explore the interacting effects of dispersal, fecundity, disturbance, and genetic variation on range-edge dynamics between a pair of demographically similar tree species. Ideal climate for an individual is determined by genotype. The simulated landscape undergoes an 80-year period of climate change in which climate bands shift upslope; subsequently, climate is held constant for 300 years. The presence of a high-elevation competitor caused a significant lag in the range shift of the low-elevation species relative to competition-free scenarios. Increases in fecundity and dispersal distance both helped to speed up the replacement of the high-elevation species by the low-elevation species at their range boundary. While some disturbance scenarios facilitated this transition, frequent canopy disturbance inhibited colonization by removing reproductive adults and led to range contractions in both species. Differences between dispersal scenarios were more pronounced when disturbance was frequent (15 vs. 25 year return interval) and dispersal was limited. When the high-elevation species lacked genetic variation, its range was more-easily invaded by the low-elevation species, while a similar lack of variation in the low-elevation species inhibited colonization-but only when this lack of variation decreased the fitness of the affected species near the range boundary. Our model results support the importance of measuring and including dispersal/fecundity, disturbance type and frequency, and genetic variation when assessing the

  8. Simulated lake phytoplankton composition shifts toward cyanobacteria dominance in a future warmer climate.

    PubMed

    Markensten, Hampus; Moore, Karen; Persson, Irina

    2010-04-01

    The climate is expected to become warmer and wetter in many temperate regions and is expected to affect the water quality in lakes and reservoirs. In this paper, we investigate the impacts of a regional climate scenario on lake productivity using three models in sequence and quantify the response in biomass of three phytoplankton groups. We used a watershed model (GWLF), a physical lake model (PROBE), and a phytoplankton model (PROTBAS) for simulations of a large (61 km2), shallow (mean depth 3.4 m), wind-exposed lake basin with a short water retention time (1 month) at the western end of Lake Mälaren, Sweden. The results suggest that a future scenario with increased warming leads to a longer growing season for phytoplankton, slightly increased levels of total biomass, and a distinct shift in phytoplankton groups to favor nitrogen-fixing cyanobacteria at the expense of diatoms in this lake basin. The changes in the timing of nutrient export from the catchment are the primary cause of cyanobacteria dominance over diatoms, and elevated lake temperatures are responsible for the increase in total phytoplankton biomass.

  9. Climate change, shifting seasons, and the ecohydrology of Devils Hole, Death Valley National Park

    NASA Astrophysics Data System (ADS)

    Hausner, M. B.; Wilson, K. P.; Gaines, D. B.; Suarez, F. I.; Tyler, S. W.

    2011-12-01

    Devils Hole, a water-filled fracture in the carbonate aquifer of the Death Valley Regional Flow System, comprises an ecosystem that can serve as a bellwether of climate change. This 50 square meter pool of unknown depth is home to the only extant population of the endangered Devils Hole pupfish (Cyprinodon diabolis). A shallow shelf in the system provides the most suitable habitat for spawning, and the past pupfish population counts have been correlated to the water level in the system. Recently, however, population declines unrelated to water level have been observed. The 33° C waters of Devils Hole are near the upper threshold for most Cyprinodon species, and the shallow shelf experiences the greatest diurnal and seasonal temperature variability. The extremely limited habitat, small population (the spring, 2011 population survey counted approximately 100 individuals), and precarious nature of populations near survival thresholds combine to make the system exceptionally susceptible to the impacts of climate change. A hydrodynamic model of the shallow shelf was developed to simulate thermal convection in response to a number of energy fluxes, including climatic drivers such as air temperature and solar radiation. Simulations of current conditions demonstrate seasonal and diurnal changes in the temperature of the water and the substrate in which adult pupfish spawn, eggs hatch, and larvae develop. The simulated convection patterns also influence the oxygen dynamics, nutrient cycling, and the food web of the ecosystem. Simulations of future conditions using a delta change methodology point towards changes in the seasonal cycles, which may limit or shift the reproductive season of the species.

  10. Shifting ranges and conservation challenges for lemurs in the face of climate change

    PubMed Central

    Brown, Jason L; Yoder, Anne D

    2015-01-01

    Geospatial modeling is one of the most powerful tools available to conservation biologists for estimating current species ranges of Earth's biodiversity. Now, with the advantage of predictive climate models, these methods can be deployed for understanding future impacts on threatened biota. Here, we employ predictive modeling under a conservative estimate of future climate change to examine impacts on the future abundance and geographic distributions of Malagasy lemurs. Using distribution data from the primary literature, we employed ensemble species distribution models and geospatial analyses to predict future changes in species distributions. Current species distribution models (SDMs) were created within the BIOMOD2 framework that capitalizes on ten widely used modeling techniques. Future and current SDMs were then subtracted from each other, and areas of contraction, expansion, and stability were calculated. Model overprediction is a common issue associated Malagasy taxa. Accordingly, we introduce novel methods for incorporating biological data on dispersal potential to better inform the selection of pseudo-absence points. This study predicts that 60% of the 57 species examined will experience a considerable range of reductions in the next seventy years entirely due to future climate change. Of these species, range sizes are predicted to decrease by an average of 59.6%. Nine lemur species (16%) are predicted to expand their ranges, and 13 species (22.8%) distribution sizes were predicted to be stable through time. Species ranges will experience severe shifts, typically contractions, and for the majority of lemur species, geographic distributions will be considerably altered. We identify three areas in dire need of protection, concluding that strategically managed forest corridors must be a key component of lemur and other biodiversity conservation strategies. This recommendation is all the more urgent given that the results presented here do not take into

  11. An abrupt weakening of the subpolar gyre as trigger of Little Ice Age-type episodes

    NASA Astrophysics Data System (ADS)

    Moreno-Chamarro, Eduardo; Zanchettin, Davide; Lohmann, Katja; Jungclaus, Johann H.

    2016-04-01

    We investigate the mechanism of a decadal-scale weakening shift in the strength of the subpolar gyre (SPG) that is found in one among three last millennium simulations with a state-of-the-art Earth system model. The SPG shift triggers multicentennial anomalies in the North Atlantic climate driven by long-lasting internal feedbacks relating anomalous oceanic and atmospheric circulation, sea ice extent, and upper-ocean salinity in the Labrador Sea. Yet changes throughout or after the shift are not associated with a persistent weakening of the Atlantic Meridional Overturning Circulation or shifts in the North Atlantic Oscillation. The anomalous climate state of the North Atlantic simulated after the shift agrees well with climate reconstructions from within the area, which describe a transition between a stronger and weaker SPG during the relatively warm medieval climate and the cold Little Ice Age respectively. However, model and data differ in the timing of the onset. The simulated SPG shift is caused by a rapid increase in the freshwater export from the Arctic and associated freshening in the upper Labrador Sea. Such freshwater anomaly relates to prominent thickening of the Arctic sea ice, following the cluster of relatively small-magnitude volcanic eruptions by 1600 CE. Sensitivity experiments without volcanic forcing can nonetheless produce similar abrupt events; a necessary causal link between the volcanic cluster and the SPG shift can therefore be excluded. Instead, preconditioning by internal variability explains discrepancies in the timing between the simulated SPG shift and the reconstructed estimates for the Little Ice Age onset.

  12. The role of plant functional trade-offs for biodiversity changes and biome shifts under scenarios of global climatic change

    NASA Astrophysics Data System (ADS)

    Reu, B.; Zaehle, S.; Proulx, R.; Bohn, K.; Kleidon, A.; Pavlick, R.; Schmidtlein, S.

    2011-05-01

    The global geographic distribution of biodiversity and biomes is determined by species-specific physiological tolerances to climatic constraints. Current vegetation models employ empirical bioclimatic relationships to predict present-day vegetation patterns and to forecast biodiversity changes and biome shifts under climatic change. In this paper, we consider trade-offs in plant functioning and their responses under climatic changes to forecast and explain changes in plant functional richness and shifts in biome geographic distributions. The Jena Diversity model (JeDi) simulates plant survival according to essential plant functional trade-offs, including ecophysiological processes such as water uptake, photosynthesis, allocation, reproduction and phenology. We use JeDi to quantify changes in plant functional richness and biome shifts between present-day and a range of possible future climates from two SRES emission scenarios (A2 and B1) and seven global climate models using metrics of plant functional richness and functional identity. Our results show (i) a significant loss of plant functional richness in the tropics, (ii) an increase in plant functional richness at mid and high latitudes, and (iii) a pole-ward shift of biomes. While these results are consistent with the findings of empirical approaches, we are able to explain them in terms of the plant functional trade-offs involved in the allocation, metabolic and reproduction strategies of plants. We conclude that general aspects of plant physiological tolerances can be derived from functional trade-offs, which may provide a useful process- and trait-based alternative to bioclimatic relationships. Such a mechanistic approach may be particularly relevant when addressing vegetation responses to climatic changes that encounter novel combinations of climate parameters that do not exist under contemporary climate.

  13. Hunting and gathering silicon data to tackle climate forecasting

    NASA Astrophysics Data System (ADS)

    Dittert, Nicolas; Leynaert, Aude; Ragueneau, Olivier; Heinze, Christoph

    The frequent, large, and often extremely abrupt shifts in global climate in the past occurred in lockstep across the globe. This seems to tell us that Earth's climate system has several distinct modes of operation that are linked in subtle yet dramatic ways.Does this finding about past climates have any implication for future climate? Will greenhouse warming continue, or will it slow or cease? And when would that be?

  14. Fifty-Year Record of Glacier Change Reveals Shifting Climate in the Pacific Northwest and Alaska, USA

    USGS Publications Warehouse

    ,

    2009-01-01

    Fifty years of U.S. Geological Survey (USGS) research on glacier change shows recent dramatic shrinkage of glaciers in three climatic regions of the United States. These long periods of record provide clues to the climate shifts that may be driving glacier change. The USGS Benchmark Glacier Program began in 1957 as a result of research efforts during the International Geophysical Year (Meier and others, 1971). Annual data collection occurs at three glaciers that represent three climatic regions in the United States: South Cascade Glacier in the Cascade Mountains of Washington State; Wolverine Glacier on the Kenai Peninsula near Anchorage, Alaska; and Gulkana Glacier in the interior of Alaska (fig. 1).

  15. Projected climate regime shift under future global warming from multi-model, multi-scenario CMIP5 simulations

    NASA Astrophysics Data System (ADS)

    Feng, Song; Hu, Qi; Huang, Wei; Ho, Chang-Hoi; Li, Ruopu; Tang, Zhenghong

    2014-01-01

    This study examined shifts in climate regimes over the global land area using the Köppen-Trewartha (K-T) climate classification by analyzing observations during 1900-2010, and simulations during 1900-2100 from twenty global climate models participating in Phase 5 of the Coupled Model Inter-comparison Project (CMIP5). Under the Intergovernmental Panel on Climate Change Representative Concentration Pathways 8.5 (RCP8.5) scenario, the models projected a 3°-10 °C warming in annual temperature over the global land area by the end of the twenty-first century, with strong (moderate) warming in the high (middle) latitudes of the Northern Hemisphere and weaker warming in the tropics and the Southern Hemisphere. The projected changes in precipitation vary considerably in space and present greater uncertainties among the models. Overall, the models are consistent in projecting increasing precipitation over the high-latitude of the Northern Hemisphere, and reduced precipitation in the Mediterranean, southwestern North America, northern and southern Africa and Australia. Based on the projected changes in temperature and precipitation, the K-T climate types would shift toward warmer and drier climate types from the current climate distribution. Regions of temperate, tropical and dry climate types are projected to expand, while regions of polar, sub-polar and subtropical climate types are projected to contract. The magnitudes of the projected changes are stronger in the RCP8.5 scenario than the low emission scenario RCP4.5. On average, the climate types in 31.4% and 46.3% of the global land area are projected to change by the end of the twenty-first century under RCP4.5 and RCP8.5 scenarios, respectively. Further analysis suggests that changes in precipitation played a slightly more important role in causing shifts of climate type during the twentieth century. However, the projected changes in temperature play an increasingly important role and dominate shifts in climate type

  16. Early indicators of change: divergent climate envelopes between tree life stages imply range shifts in the western United States

    USGS Publications Warehouse

    Bell, David M.; Bradford, John B.; Lauenroth, William K.

    2014-01-01

    Our results indicated that climate-induced contractions and shifts in seedling distribution in response to recent change are already under way and are particularly severe in montane tree species. While adult trees may persist for hundreds of years without significant regeneration, tree species ranges will eventually contract where tree regeneration fails.

  17. Shifting species interactions in terrestrial dryland ecosystems under altered water availability and climate change

    USGS Publications Warehouse

    McCluney, Kevin E.; Belnap, Jayne; Collins, Scott L.; González, Angélica L.; Hagen, Elizabeth M.; Holland, J. Nathaniel; Kotler, Burt P.; Maestre, Fernando T.; Smith, Stanley D.; Wolf, Blair O.

    2012-01-01

    Species interactions play key roles in linking the responses of populations, communities, and ecosystems to environmental change. For instance, species interactions are an important determinant of the complexity of changes in trophic biomass with variation in resources. Water resources are a major driver of terrestrial ecology and climate change is expected to greatly alter the distribution of this critical resource. While previous studies have documented strong effects of global environmental change on species interactions in general, responses can vary from region to region. Dryland ecosystems occupy more than one-third of the Earth's land mass, are greatly affected by changes in water availability, and are predicted to be hotspots of climate change. Thus, it is imperative to understand the effects of environmental change on these globally significant ecosystems. Here, we review studies of the responses of population-level plant-plant, plant-herbivore, and predator-prey interactions to changes in water availability in dryland environments in order to develop new hypotheses and predictions to guide future research. To help explain patterns of interaction outcomes, we developed a conceptual model that views interaction outcomes as shifting between (1) competition and facilitation (plant-plant), (2) herbivory, neutralism, or mutualism (plant-herbivore), or (3) neutralism and predation (predator-prey), as water availability crosses physiological, behavioural, or population-density thresholds. We link our conceptual model to hypothetical scenarios of current and future water availability to make testable predictions about the influence of changes in water availability on species interactions. We also examine potential implications of our conceptual model for the relative importance of top-down effects and the linearity of patterns of change in trophic biomass with changes in water availability. Finally, we highlight key research needs and some possible broader impacts

  18. Shifting species interactions in terrestrial dryland ecosystems under altered water availability and climate change.

    PubMed

    McCluney, Kevin E; Belnap, Jayne; Collins, Scott L; González, Angélica L; Hagen, Elizabeth M; Nathaniel Holland, J; Kotler, Burt P; Maestre, Fernando T; Smith, Stanley D; Wolf, Blair O

    2012-08-01

    Species interactions play key roles in linking the responses of populations, communities, and ecosystems to environmental change. For instance, species interactions are an important determinant of the complexity of changes in trophic biomass with variation in resources. Water resources are a major driver of terrestrial ecology and climate change is expected to greatly alter the distribution of this critical resource. While previous studies have documented strong effects of global environmental change on species interactions in general, responses can vary from region to region. Dryland ecosystems occupy more than one-third of the Earth's land mass, are greatly affected by changes in water availability, and are predicted to be hotspots of climate change. Thus, it is imperative to understand the effects of environmental change on these globally significant ecosystems. Here, we review studies of the responses of population-level plant-plant, plant-herbivore, and predator-prey interactions to changes in water availability in dryland environments in order to develop new hypotheses and predictions to guide future research. To help explain patterns of interaction outcomes, we developed a conceptual model that views interaction outcomes as shifting between (1) competition and facilitation (plant-plant), (2) herbivory, neutralism, or mutualism (plant-herbivore), or (3) neutralism and predation (predator-prey), as water availability crosses physiological, behavioural, or population-density thresholds. We link our conceptual model to hypothetical scenarios of current and future water availability to make testable predictions about the influence of changes in water availability on species interactions. We also examine potential implications of our conceptual model for the relative importance of top-down effects and the linearity of patterns of change in trophic biomass with changes in water availability. Finally, we highlight key research needs and some possible broader impacts

  19. Non Gaussian and Non stationary characters of ENSO: the role of climate shifts and nonlinearities

    NASA Astrophysics Data System (ADS)

    Boucharel, J.; Dewitte, B.; Garel, B.; Du Penhoat, Y.

    2009-04-01

    ENSO is the dominant climate mode of variability in the Pacific, having socio-economical impacts on surrounding regions. ENSO exhibits a significant modulation at decadal to multidecadal timescales which is associated to changes of its characteristics (onset, amplitude, frequency, propagation, and predictability). Among these characteristics, some of them are generally ignored in ENSO studies, such as its asymmetry and the deviation of its statistics from those of the Gaussian distribution. These properties could be related to the ability of the current generation of coupled models to predict ENSO and its modulation. Here, the non-Gaussian nature and asymmetry of ENSO is diagnosed from in situ data and a variety of models (from intermediate complexity models to full physics coupled general circulation models) using robust statistical tools. In particular α-stable laws are used as theoretical background material to quantify the non-Gaussian character of ENSO time series. It is shown that the α-stable character of ENSO may result from the presence of climate shifts inducing non stationnarity in the time series. Also, cool (warm) periods are associated with ENSO statistics having a larger (weaker) tendency towards Gaussianity and a weaker (larger) asymmetry. This supports the hypothesis of ENSO being rectified by changes in mean state through non-linear processes. The relationship between change in mean state and non-linearity is investigated both in the Zebiak and Cane model and the IPCC models, which indicate that the propensity of a model to reproduce extreme events is related to its tendency to emphasize the non-linear interaction between mean state and ENSO variability. More particularly, high statistical moments i.e high order nonlinearities seem to be involved in the feedback between extreme events occurrence and mean state shit triggering through energy cascade, emphasizing the ENSO multifractal nature.

  20. Mid- to Late Holocene Climate Shift in the Southern Gulf of California and Tropical Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Perez-Cruz, L. L.; Fucugauchi, J. U.; Velasco, V.; Rodriguez, A.; Choumiline, K.

    2014-12-01

    A multiproxy record has been acquired from a gravity core (DIPAL-I K47) taken in La Paz Basin, an area which is situated in the southwestern sector of the Gulf of California at the junction to the Tropical Pacific Ocean. The high-resolution data sets, from XRF, TOC, magnetic susceptibility and hysteresis measurements, were used to track climatic changes in the tropical climate system at sub-centennial time scales over the past 7.3 cal kyr BP. The paleoprecipitation record shows variation trends, with a shift during the mid- to late Holocene, characterized by changes from high to low humidity. Pluvial, biogenic and eolian input, marked by variations in Ti, Si, Fe, K, Ca, Zr/Ti, Ca/Ti and magnetic susceptibility, shows trend changes between 7-5 cal kyr, 5-4.5 cal kyr, 4.5-3.5 cal kyr and 2.15-1.4 kyr. Drought events are recognized from 3.7 to 3.4, 2.8 to 1.8 cal kyr BP, and between 1.4 and 1.2 cal kyr BP. The southern Gulf is well suited for documenting the climatic and precipitation changes in the tropical Pacific Ocean associated with ITCZ latitudinal migration, PDO, ENSO events and the North American monsoon. Analysis of sourcing, transport and deposition of sediments is used for reconstructing the changing ocean-atmosphere circulation patterns, particularly sensitive to paleoprecipitation. The Bay receives sediments mainly from the surrounding volcanic ranges of the peninsular Baja California. There are no rivers in the peninsula and sediments are related to pluvial input trough ephemeral creeks along the steep cliff ranges and narrow shelf. Biogenic sediments are associated with productivity and oceanographic conditions through upwellings and mesoscale gyres. Eolian sediments are transported into the basin from the peninsula and continent, including transport of fine dust from the northern desert of Sonora-Mojave and arid terrains in the peninsula. It is important to highlight that a common 1800 yr solar variation spectral periodicity has been captured

  1. Watershed sulfur biogeochemistry: shift from atmospheric deposition dominance to climatic regulation.

    PubMed

    Mitchell, Myron J; Likens, Gene E

    2011-06-15

    North American atmospheric S emissions peaked in the early 1970s followed by a dramatic decrease that resulted in marked declines in sulfate (SO₄²⁻)) concentrations in precipitation and many surface waters. These changes in S biogeochemistry have important implications with respect to the mobilization of toxic (Al(n⁺), H⁺) and nutrient (Ca²⁺, Mg²⁺, K⁺) cations and the acidification of watersheds. We used the continuous long-term record for watersheds 1, 3, 5, and 6 (37-44 years from 1965 through 2008) of SO₄²⁻ concentrations and fluxes at Hubbard Brook Experimental Forest in New Hampshire (U.S.) for evaluating S budgets. Analysis revealed that the annual discrepancies in the watershed S budgets (SO₄²⁻ flux in drainage waters minus total atmospheric S deposition) have become significantly (p < 0.001) more negative, indicating the increasing importance of the release of S from internal sources with time. Watershed wetness, as a function of log₁₀ annual water flux, was highly significant (p < 0.001) and explained 57% (n = 157) of the annual variation for the combined results from watersheds 1, 3, 5, and 6. The biogeochemical control of annual SO₄²⁻ export in streamwater of forested watersheds has shifted from atmospheric S deposition to climatic factors by affecting soil moisture.

  2. Predicting competitive shifts and responses to climate change based on latitudinal distributions of species assemblages.

    PubMed

    Lord, Joshua; Whitlatch, Robert

    2015-05-01

    Many terrestrial plant and marine benthic communities involve intense competition for space as a means to survive and reproduce. Superior competitors can dominate other species numerically with high reproductive rates, indirectly with high growth rates that facilitate space acquisition, or directly with competitive overgrowth. To assess how climate change could affect competitive interactions, we examined latitudinal patterns in growth rates and overgrowth competition via field surveys and experiments with marine epibenthic communities. Epibenthic fouling communities are dominated by invasive tunicates, bryozoans, and other species that grow on docks, boats, and other artificial structures. Fouling communities are space limited, so growth rate and overgrowth competition play an important role in shaping abundance patterns. We experimentally assessed temperature-dependent growth rates of several tunicates and bryozoans in eight regions spanning the U.S. east and west coasts. Several species displayed positive growth responses to warmer temperature in the northern portions of their latitudinal ranges, and vice versa. We used photo surveys of floating docks in at least 16 harbors in each region to compare communities and overgrowth competition. There was a strong correlation across species and regions between growth rate and competitive ability, indicating that growth plays an important role in competitive outcomes. Because growth rates are typically temperature dependent for organisms that compete for space, including terrestrial plants, fungi, algae, bacteria, and sessile benthic organisms, global warming could affect competitive outcomes. Our results suggest that these competitive shifts can be predicted by species' relative growth rates and latitudinal ranges.

  3. Predicting competitive shifts and responses to climate change based on latitudinal distributions of species assemblages.

    PubMed

    Lord, Joshua; Whitlatch, Robert

    2015-05-01

    Many terrestrial plant and marine benthic communities involve intense competition for space as a means to survive and reproduce. Superior competitors can dominate other species numerically with high reproductive rates, indirectly with high growth rates that facilitate space acquisition, or directly with competitive overgrowth. To assess how climate change could affect competitive interactions, we examined latitudinal patterns in growth rates and overgrowth competition via field surveys and experiments with marine epibenthic communities. Epibenthic fouling communities are dominated by invasive tunicates, bryozoans, and other species that grow on docks, boats, and other artificial structures. Fouling communities are space limited, so growth rate and overgrowth competition play an important role in shaping abundance patterns. We experimentally assessed temperature-dependent growth rates of several tunicates and bryozoans in eight regions spanning the U.S. east and west coasts. Several species displayed positive growth responses to warmer temperature in the northern portions of their latitudinal ranges, and vice versa. We used photo surveys of floating docks in at least 16 harbors in each region to compare communities and overgrowth competition. There was a strong correlation across species and regions between growth rate and competitive ability, indicating that growth plays an important role in competitive outcomes. Because growth rates are typically temperature dependent for organisms that compete for space, including terrestrial plants, fungi, algae, bacteria, and sessile benthic organisms, global warming could affect competitive outcomes. Our results suggest that these competitive shifts can be predicted by species' relative growth rates and latitudinal ranges. PMID:26236840

  4. Climate Shifts and Plant-Community Transformations Affect Nitrogen Cycling in Semi-Arid Rangelands

    NASA Astrophysics Data System (ADS)

    Huber, D. P.; Hardenbrook, S.; Lohse, K. A.; Germino, M. J.; Reinhardt, K.

    2011-12-01

    Semi-arid rangelands are being impacted by climate shifts and plant-community transformations. However, little is known about how these ecosystems will respond to long-term changes in amount and seasonality of precipitation, or how shifts in vegetation modulate the response of plant-soil processes. Semi-arid rangelands are typically characterized by resource islands (perennial shrubs) and contrasting "interplant" (IP) spaces or patch types which may increase the complexity of ecosystem response to climate change. We used an established long-term ecohydrologic experiment (Est. 1993) located in southeastern Idaho to evaluate ecosystem response to changing precipitation seasonality and magnitude. The experiment consists of 3 replicated blocks of 2 vegetation types (a diverse sagebrush steppe assemblage or monoculture of exotic crested wheatgrass, CWG) and 3 irrigation treatments. We hypothesized that increased precipitation will enhance storage of soil organic matter (SOM) due to greater detrital inputs. Rates of nitrogen (N) mineralization and decomposition were also expected to increase relative to ambient treatments. Additionally, we expected that change from native sagebrush to CWG would reduce N availability due to differences in detrital C:N ratios and biomass partitioning. Preliminary results show increased precipitation enhanced carbon pools in native vegetation plots, with SOM in ambient, fall/spring, and summer precipitation treatments of 2.27, 2.73, and 2.71% respectively, and average plot cover of 29, 48, and 40% respectively. Under shrubs, available N increased with increased precipitation (3.5, 4.6, and 5.6 μg-N g-1 soil) although N-cycling rates remained constant. Conversely, IP patches experienced a steady increase in both net N mineralization and nitrification between ambient, fall/spring, and summer precipitation treatments. The IP patches experienced lower absolute values but similar trends in SOM and available N. Crested wheatgrass plots showed

  5. Pathogen-Host Associations and Predicted Range Shifts of Human Monkeypox in Response to Climate Change in Central Africa

    PubMed Central

    Thomassen, Henri A.; Fuller, Trevon; Asefi-Najafabady, Salvi; Shiplacoff, Julia A. G.; Mulembakani, Prime M.; Blumberg, Seth; Johnston, Sara C.; Kisalu, Neville K.; Kinkela, Timothée L.; Fair, Joseph N.; Wolfe, Nathan D.; Shongo, Robert L.; LeBreton, Matthew; Meyer, Hermann; Wright, Linda L.; Muyembe, Jean-Jacques; Buermann, Wolfgang; Okitolonda, Emile; Hensley, Lisa E.; Lloyd-Smith, James O.; Smith, Thomas B.; Rimoin, Anne W.

    2013-01-01

    Climate change is predicted to result in changes in the geographic ranges and local prevalence of infectious diseases, either through direct effects on the pathogen, or indirectly through range shifts in vector and reservoir species. To better understand the occurrence of monkeypox virus (MPXV), an emerging Orthopoxvirus in humans, under contemporary and future climate conditions, we used ecological niche modeling techniques in conjunction with climate and remote-sensing variables. We first created spatially explicit probability distributions of its candidate reservoir species in Africa's Congo Basin. Reservoir species distributions were subsequently used to model current and projected future distributions of human monkeypox (MPX). Results indicate that forest clearing and climate are significant driving factors of the transmission of MPX from wildlife to humans under current climate conditions. Models under contemporary climate conditions performed well, as indicated by high values for the area under the receiver operator curve (AUC), and tests on spatially randomly and non-randomly omitted test data. Future projections were made on IPCC 4th Assessment climate change scenarios for 2050 and 2080, ranging from more conservative to more aggressive, and representing the potential variation within which range shifts can be expected to occur. Future projections showed range shifts into regions where MPX has not been recorded previously. Increased suitability for MPX was predicted in eastern Democratic Republic of Congo. Models developed here are useful for identifying areas where environmental conditions may become more suitable for human MPX; targeting candidate reservoir species for future screening efforts; and prioritizing regions for future MPX surveillance efforts. PMID:23935820

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

    PubMed

    Nunes, Flavia; Norris, Richard D

    2006-01-01

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

  7. Survival and Hsp70 Gene Expression in Plutella xylostella and Its Larval Parasitoid Diadegma insulare Varied between Slowly Ramping and Abrupt Extreme Temperature Regimes

    PubMed Central

    Bahar, Md Habibullah; Hegedus, Dwayne; Soroka, Juliana; Coutu, Cathy; Bekkaoui, Diana; Dosdall, Lloyd

    2013-01-01

    Background In nature, insects have evolved behavioural and physiological adaptations to cope with short term exposure to extreme temperatures. Extreme heat events may increase as a result of climate change; this in turn will affect insect population dynamics. We examined the effect of abrupt and ecologically relevant gradual exposure to high temperatures on the survival and hsp70 gene expression in diamondback moth (DBM) adults and the parasitoid Diadegmainsulare, as well as in parasitized and non-parasitized DBM larvae. Principal Findings Tolerance to high temperatures in DBM adults was higher than in D. insulare adults. There was no difference in the survival of DBM adults between abrupt and ramped increases from 25 to 38°C; however, at 40°C survival was higher when the temperature increased gradually. In contrast, more D. insulare adults survived when the temperature was ramped rather than shifted abruptly to both 38 and 40°C. There was no heat stress effect of up to 40°C on the survival of either parasitized or non-parasitized DBM larvae. In adults of both species, more hsp70 expression was observed when temperatures increased abruptly to 38°C compared to ramping. In contrast, at 40°C significantly more expression was found in insects exposed to the ramping rather than the abrupt regime. Hsp70 expression level was in agreement with adult survival data and appears to be a good indicator of stress levels. In parasitized and non-parasitized larvae, hsp70 expression was significantly higher after abrupt shifts compared to ramping at both temperatures. Conclusions/Significance Hsp70 gene expression was responsive to extreme temperatures in both DBM and D. insulare, which may underlie the ability of these insects to survive in extreme temperatures. Survival and hsp70 expression upon abrupt changes are distinctly different from those after ramping indicating that experimental protocol must be considered before extrapolating laboratory results to natural field

  8. Linking soil chemistry, treeline shifts and climate change: scenario modeling using an experimental approach

    NASA Astrophysics Data System (ADS)

    Mavris, Christian; Furrer, Gerhard; Anderson, Susanne; Blum, Alex; Wells, Aaron; Dahms, Dennis; Egli, Markus

    2014-05-01

    Climate change and global warming have a strong influence on the landscape development. As cold areas become warmer, both flora and fauna must adapt to new conditions (a). It is widely accepted that climate changes deeply influence the treeline shifts. In addition to that, wildfires, plant diseases and insect infestation (i.e. mountain pine beetle) can promote a selective replacement of plants, inhibiting some and favoring others, thus modifying the ecosystem in diverse ways. There is little knowledge on the behavior of soil chemistry when such changes occur. Will elemental availability become a crucial factor as a function of climate changes? The Sinks Canyon and Stough Basin - SE flank of the Wind River Range, Wyoming, USA - offer an ideal case study. Conceptually, the areas were divided into three main subsets: tundra, forest and a subarid environment. All soils were developed on granitoid moraines (b, c). From each subset, a liquid topsoil extract was produced and mixed with the solid subsoil samples in batch reactors at 50 °C. The batch experiments were carried out over 1800 h, and the progress of the dissolution was regularly monitored by analyzing liquid aliquots using IC and ICP-OES. The nutrients were mostly released within the first hours of the experiment. Silicon and Al were continuously released into the solution, while some alkali elements - i.e. Na - showed a more complex trend. Organic acids (acetic, citric) and other ligands produced during biodegradation played an active role in mineral dissolution and nutrient release. The mineral colloids detected in the extract (X-ray diffraction) can significantly control surface reactions (adsorption/desorption) and contributed to specific cationic concentrations. The experimental set up was then compared to a computed dissolution model using SerialSTEADYQL software (d, e). Decoding the mechanisms driving mineral weathering is the key to understand the main geochemical aspects of adaptation during climate

  9. Dynamical regime shifts in the North Atlantic climate variability during the last 2 ka as revealed by terrestrial proxies

    NASA Astrophysics Data System (ADS)

    Franke, Jasper G.; Donner, Reik V.

    2016-04-01

    The climate during the last two millennia is in general considered to be exceptionally stable compared to prior times. Nevertheless, there have been different episodes of distinguishable climate dynamics, most prominently the Medieval Climate Anomaly (MCA) and the Little Ice Age (LIA). In this study, we test a set of terrestrial paleoclimate records from Northern Europe for indications of temporary time-reversal asymmetry implying that during the thus identified periods of time, the data cannot be described by a linear Gaussian process and thus exhibit marked (possibly nonlinear) dynamics. Our analysis reveals that the onsets of both the MCA and the LIA are characterized by such complex dynamics indicating possible dynamical regime shifts in the regional climate system. Furthermore, the end of the Roman Warm Period as well as the 1.4k event are accompanied by similar signatures of time-reversal asymmetry.

  10. Contributions of cultivar shift, management practice and climate change to maize yield in North China Plain in 1981-2009

    NASA Astrophysics Data System (ADS)

    Xiao, Dengpan; Tao, Fulu

    2016-07-01

    The impact of climate change on crop yield is compounded by cultivar shifts and agronomic management practices. To determine the relative contributions of climate change, cultivar shift, and management practice to changes in maize ( Zea mays L.) yield in the past three decades, detailed field data for 1981-2009 from four representative experimental stations in North China Plain (NCP) were analyzed via model simulation. The four representative experimental stations are geographically and climatologically different, represent the typical cropping system in the study area, and have more complete weather/crop records for the period of 1981-2009. The results showed that while the shift from traditional to modern cultivar increased yield by 23.9-40.3 %, new fertilizer management increased yield by 3.3-8.6 %. However, the trends in climate variables for 1981-2009 reduced maize yield by 15-30 % in the study area. Among the main climate variables, solar radiation had the largest effect on maize yield, followed by temperature and then precipitation. While a significant decline in solar radiation in 1981-2009 (maybe due to air pollution) reduced yield by 12-24 %, a significant increase in temperature reduced yield by 3-9 %. In contrast, a non-significant increase in precipitation during the maize growth period increased yield by 0.9-3 % at three of the four investigated stations. However, a decline in precipitation reduced yield by 3 % in the remaining station. The study revealed that although the shift from traditional to modern cultivars and agronomic management practices contributed most to the increase in maize yield, the negative impact of climate change was large enough to offset 46-67 % of the trend in the observed yields in the past three decades in NCP. The reduction in solar radiation, especially in the most critical period of maize growth, limited the process of photosynthesis and thereby further reduced maize yield.

  11. Murres, capelin and ocean climate: Inter-annual associations across a decadal shift

    USGS Publications Warehouse

    Regular, P.M.; Shuhood, F.; Power, T.; Montevecchi, W.A.; Robertson, G.J.; Ballam, D.; Piatt, J.F.; Nakashima, B.

    2009-01-01

    To ensure energy demands for reproduction are met, it is essential that marine birds breed during periods of peak food availability. We examined associations of the breeding chronology of common murres (Uria aalge) with the timing of the inshore arrival of their primary prey, capelin (Mallotus villosus) from 1980 to 2006 across a period of pervasive change in the Northwest Atlantic ecosystem. We also assessed the influence of ocean temperature and the North Atlantic Oscillation (NAO; an index of winter climate and oceanography) on these interactions. We found a lagged linear relationship between variations in murre breeding chronology and the timing of capelin arrival in the previous year. On a decadal level, we found a non-linear threshold relationship between ocean temperature and the timing of capelin arrival and murre breeding. Centennially anomalous cold water temperatures in 1991 generated a marked shift in the timing of capelin spawning inshore and murre breeding, delaying both by more than 2 weeks. By the mid-1990s, ocean temperatures returned to pre-perturbation levels, whereas the temporal breeding responses of capelin and murres were delayed for a decade or more. Oceanographic conditions (temperature, NAO) were poor predictors of the timing of capelin arrival inshore in the current year compared to the previous one. Our findings suggest that knowledge of the timing of capelin availability in the previous year provides a robust cue for the long-lived murres, allowing them to achieve temporal overlap between breeding and peak capelin availability. ?? Springer Science+Business Media B.V. 2008.

  12. RESTORING COASTAL ECOSYSTEMS: ABRUPT CLIMATE CHANGE

    EPA Science Inventory

    Consensus exists that U.S. coastal ecosystems are severely degraded due to a variety of human-factors requiring large financial expenditures to restore and manage. Yet, even as controversy surrounds human factors in ecosystem degradation in the Gulf of Mexico, Chesapeake Bay, an...

  13. Abrupt Climate Change Research Act of 2009

    THOMAS, 111th Congress

    Sen. Collins, Susan M. [R-ME

    2009-09-14

    09/14/2009 Read twice and referred to the Committee on Commerce, Science, and Transportation. (text of measure as introduced: CR S9330) (All Actions) Tracker: This bill has the status IntroducedHere are the steps for Status of Legislation:

  14. Plausibility Reappraisals and Shifts in Middle School Students' Climate Change Conceptions

    ERIC Educational Resources Information Center

    Lombardi, Doug; Sinatra, Gale M.; Nussbaum, E. Michael

    2013-01-01

    Plausibility is a central but under-examined topic in conceptual change research. Climate change is an important socio-scientific topic; however, many view human-induced climate change as implausible. When learning about climate change, students need to make plausibility judgments but they may not be sufficiently critical or reflective. The…

  15. Recent Shifts in Shoreline Orientation along a Cuspate Coast Potentially Linked to Climate Change, North Carolina Outer Banks, USA (Invited)

    NASA Astrophysics Data System (ADS)

    Moore, L. J.; Brenner, O.; McNamara, D.; Murray, A. B.

    2009-12-01

    Recent modeling (e.g., Ashton and Murray, 2006a) and observations (Ashton and Murray 2006b) suggest that sandy coastlines self-organize into large-scale plan-view shapes that depend sensitively on the regional wave climate. Subsequent modeling (Slott et al., 2007) shows that even moderate changes in wave climate, likely to arise as storm behaviors shift, may cause coastlines to change shape rapidly. Such large-scale shape changes involve greatly accentuated rates of local erosion and highly variable erosion/accretion rates. A recent analysis of wave records from the Southeastern U.S. (Komar and Allen, 2007) indicates that wave climates have already been changing over the past three decades; the heights of waves attributable to tropical storms have been increasing, changing the angular distribution of wave influences. Changes in coastline shape resulting from changes in the regional wave climate identified by Komar and Allen (2007) will likely be difficult to detect along most coastlines due to short-term variability in shoreline position and limits to the resolution at which shoreline changes can be measured over a 30-year time period. However, adjustments in coastline shape are likely to occur most quickly, and therefore to be most pronounced, on cuspate shorelines along and adjacent to cape tips because rapid changes in shoreline orientation make these locations particularly sensitive to deep-water wave approach angles. To test for the presence of detectable climate-change related shifts in coastline shape along a cuspate shoreline we conduct an historical (1852 - 1974) and recent (1974 - 2004) shoreline change analysis for Cape Hatteras and Cape Lookout, North Carolina. Results indicate a recent shift in shoreline-change patterns, with trends toward more-erosional/less-accretional shoreline response and more-accretional/less-erosional response in roughly consistent locations (relative to cape tips) on the flanks of both capes. These changes in shoreline response

  16. Climate change-related regime shifts have altered spatial synchrony of plankton dynamics in the North Sea.

    PubMed

    Defriez, Emma J; Sheppard, Lawrence W; Reid, Philip C; Reuman, Daniel C

    2016-06-01

    During the 1980s, the North Sea plankton community underwent a well-documented ecosystem regime shift, including both spatial changes (northward species range shifts) and temporal changes (increases in the total abundances of warmer water species). This regime shift has been attributed to climate change. Plankton provide a link between climate and higher trophic-level organisms, which can forage on large spatial and temporal scales. It is therefore important to understand not only whether climate change affects purely spatial or temporal aspects of plankton dynamics, but also whether it affects spatiotemporal aspects such as metapopulation synchrony. If plankton synchrony is altered, higher trophic-level feeding patterns may be modified. A second motivation for investigating changes in synchrony is that the possibility of such alterations has been examined for few organisms, in spite of the fact that synchrony is ubiquitous and of major importance in ecology. This study uses correlation coefficients and spectral analysis to investigate whether synchrony changed between the periods 1959-1980 and 1989-2010. Twenty-three plankton taxa, sea surface temperature (SST), and wind speed were examined. Results revealed that synchrony in SST and plankton was altered. Changes were idiosyncratic, and were not explained by changes in abundance. Changes in the synchrony of Calanus helgolandicus and Para-pseudocalanus spp appeared to be driven by changes in SST synchrony. This study is one of few to document alterations of synchrony and climate-change impacts on synchrony. We discuss why climate-change impacts on synchrony may well be more common and consequential than previously recognized. PMID:26810148

  17. Climate change-related regime shifts have altered spatial synchrony of plankton dynamics in the North Sea.

    PubMed

    Defriez, Emma J; Sheppard, Lawrence W; Reid, Philip C; Reuman, Daniel C

    2016-06-01

    During the 1980s, the North Sea plankton community underwent a well-documented ecosystem regime shift, including both spatial changes (northward species range shifts) and temporal changes (increases in the total abundances of warmer water species). This regime shift has been attributed to climate change. Plankton provide a link between climate and higher trophic-level organisms, which can forage on large spatial and temporal scales. It is therefore important to understand not only whether climate change affects purely spatial or temporal aspects of plankton dynamics, but also whether it affects spatiotemporal aspects such as metapopulation synchrony. If plankton synchrony is altered, higher trophic-level feeding patterns may be modified. A second motivation for investigating changes in synchrony is that the possibility of such alterations has been examined for few organisms, in spite of the fact that synchrony is ubiquitous and of major importance in ecology. This study uses correlation coefficients and spectral analysis to investigate whether synchrony changed between the periods 1959-1980 and 1989-2010. Twenty-three plankton taxa, sea surface temperature (SST), and wind speed were examined. Results revealed that synchrony in SST and plankton was altered. Changes were idiosyncratic, and were not explained by changes in abundance. Changes in the synchrony of Calanus helgolandicus and Para-pseudocalanus spp appeared to be driven by changes in SST synchrony. This study is one of few to document alterations of synchrony and climate-change impacts on synchrony. We discuss why climate-change impacts on synchrony may well be more common and consequential than previously recognized.

  18. The potential for climate-driven bathymetric range shifts: sustained temperature and pressure exposures on a marine ectotherm, Palaemonetes varians

    PubMed Central

    Morris, J. P.; Thatje, S.; Cottin, D.; Oliphant, A.; Brown, A.; Shillito, B.; Ravaux, J.; Hauton, C.

    2015-01-01

    Range shifts are of great importance as a response for species facing climate change. In the light of current ocean-surface warming, many studies have focused on the capacity of marine ectotherms to shift their ranges latitudinally. Bathymetric range shifts offer an important alternative, and may be the sole option for species already at high latitudes or those within enclosed seas; yet relevant data are scant. Hydrostatic pressure (HP) and temperature have wide ranging effects on physiology, importantly acting in synergy thermodynamically, and therefore represent key environmental constraints to bathymetric migration. We present data on transcriptional regulation in a shallow-water marine crustacean (Palaemonetes varians) at atmospheric and high HP following 168-h exposures at three temperatures across the organisms’ thermal scope, to establish the potential physiological limit to bathymetric migration by neritic fauna. We observe changes in gene expression indicative of cellular macromolecular damage, disturbances in metabolic pathways and a lack of acclimation after prolonged exposure to high HP. Importantly, these effects are ameliorated (less deleterious) at higher temperatures, and exacerbated at lower temperatures. These data, alongside previously published behavioural and heat-shock analyses, have important implications for our understanding of the potential for climate-driven bathymetric range shifts PMID:26716003

  19. A holistic view of marine regime shifts

    PubMed Central

    Conversi, Alessandra; Dakos, Vasilis; Gårdmark, Anna; Ling, Scott; Folke, Carl; Mumby, Peter J.; Greene, Charles; Edwards, Martin; Blenckner, Thorsten; Casini, Michele; Pershing, Andrew; Möllmann, Christian

    2015-01-01

    Understanding marine regime shifts is important not only for ecology but also for developing marine management that assures the provision of ecosystem services to humanity. While regime shift theory is well developed, there is still no common understanding on drivers, mechanisms and characteristic of abrupt changes in real marine ecosystems. Based on contributions to the present theme issue, we highlight some general issues that need to be overcome for developing a more comprehensive understanding of marine ecosystem regime shifts. We find a great divide between benthic reef and pelagic ocean systems in how regime shift theory is linked to observed abrupt changes. Furthermore, we suggest that the long-lasting discussion on the prevalence of top-down trophic or bottom-up physical drivers in inducing regime shifts may be overcome by taking into consideration the synergistic interactions of multiple stressors, and the special characteristics of different ecosystem types. We present a framework for the holistic investigation of marine regime shifts that considers multiple exogenous drivers that interact with endogenous mechanisms to cause abrupt, catastrophic change. This framework takes into account the time-delayed synergies of these stressors, which erode the resilience of the ecosystem and eventually enable the crossing of ecological thresholds. Finally, considering that increased pressures in the marine environment are predicted by the current climate change assessments, in order to avoid major losses of ecosystem services, we suggest that marine management approaches should incorporate knowledge on environmental thresholds and develop tools that consider regime shift dynamics and characteristics. This grand challenge can only be achieved through a holistic view of marine ecosystem dynamics as evidenced by this theme issue.

  20. On the generality of a climate-mediated shift in the distribution of the American pika (Ochotona princeps).

    PubMed

    Erb, Liesl P; Ray, Chris; Guralnick, Robert

    2011-09-01

    Alpine species are among those most threatened by climatic shifts due to their physiological and geographic constraints. The American pika (Ochotona princeps), a small mammal found in mountainous, rocky habitats throughout much of western North America, has experienced recent population extirpations in the Great Basin linked to climatic drivers. It remains unclear whether these patterns of climate-related loss extend to other portions of the species' range. We investigated the distribution of the American pika and the climatic processes shaping this distribution within the Southern Rocky Mountain region. Results from a survey of 69 sites historically occupied by pikas indicate that only four populations have been extirpated within this region over the past few decades. Despite relatively few extirpations, low annual precipitation is implicated as a limiting factor for pika persistence in the Southern Rockies. Extirpations occurred only at sites that were consistently dry over the last century. While there was no climate change signal in our results, these data provide valuable insight into the potential future effects of climate change on O. princeps throughout its range.

  1. Climate and Pest-Driven Geographic Shifts in Global Coffee Production: Implications for Forest Cover, Biodiversity and Carbon Storage.

    PubMed

    Magrach, Ainhoa; Ghazoul, Jaboury

    2015-01-01

    Coffee is highly sensitive to temperature and rainfall, making its cultivation vulnerable to geographic shifts in response to a changing climate. This could lead to the establishment of coffee plantations in new areas and potential conflicts with other land covers including natural forest, with consequent implications for biodiversity and ecosystem services. We project areas suitable for future coffee cultivation based on several climate scenarios and expected responses of the coffee berry borer, a principle pest of coffee crops. We show that the global climatically-suitable area will suffer marked shifts from some current major centres of cultivation. Most areas will be suited to Robusta coffee, demand for which could be met without incurring forest encroachment. The cultivation of Arabica, which represents 70% of consumed coffee, can also be accommodated in the future, but only by incurring some natural forest loss. This has corresponding implications for carbon storage, and is likely to affect areas currently designated as priority areas for biodiversity. Where Arabica coffee does encroach on natural forests, we project average local losses of 35% of threatened vertebrate species. The interaction of climate and coffee berry borer greatly influences projected outcomes.

  2. Repeated climate-linked host shifts have promoted diversification in a temperate clade of leaf-mining flies.

    PubMed

    Winkler, Isaac S; Mitter, Charles; Scheffer, Sonja J

    2009-10-27

    A central but little-tested prediction of "escape and radiation" coevolution is that colonization of novel, chemically defended host plant clades accelerates insect herbivore diversification. That theory, in turn, exemplifies one side of a broader debate about the relative influence on clade dynamics of intrinsic (biotic) vs. extrinsic (physical-environmental) forces. Here, we use a fossil-calibrated molecular chronogram to compare the effects of a major biotic factor (repeated shift to a chemically divergent host plant clade) and a major abiotic factor (global climate change) on the macroevolutionary dynamics of a large Cenozoic radiation of phytophagous insects, the leaf-mining fly genus Phytomyza (Diptera: Agromyzidae). We find one of the first statistically supported examples of consistently elevated net diversification accompanying shift to new plant clades. In contrast, we detect no significant direct effect on diversification of major global climate events in the early and late Oligocene. The broader paleoclimatic context strongly suggests, however, that climate change has at times had a strong indirect influence through its effect on the biotic environment. Repeated rapid Miocene radiation of these flies on temperate herbaceous asterids closely corresponds to the dramatic, climate-driven expansion of seasonal, open habitats. PMID:19805134

  3. Climate and Pest-Driven Geographic Shifts in Global Coffee Production: Implications for Forest Cover, Biodiversity and Carbon Storage

    PubMed Central

    Magrach, Ainhoa; Ghazoul, Jaboury

    2015-01-01

    Coffee is highly sensitive to temperature and rainfall, making its cultivation vulnerable to geographic shifts in response to a changing climate. This could lead to the establishment of coffee plantations in new areas and potential conflicts with other land covers including natural forest, with consequent implications for biodiversity and ecosystem services. We project areas suitable for future coffee cultivation based on several climate scenarios and expected responses of the coffee berry borer, a principle pest of coffee crops. We show that the global climatically-suitable area will suffer marked shifts from some current major centres of cultivation. Most areas will be suited to Robusta coffee, demand for which could be met without incurring forest encroachment. The cultivation of Arabica, which represents 70% of consumed coffee, can also be accommodated in the future, but only by incurring some natural forest loss. This has corresponding implications for carbon storage, and is likely to affect areas currently designated as priority areas for biodiversity. Where Arabica coffee does encroach on natural forests, we project average local losses of 35% of threatened vertebrate species. The interaction of climate and coffee berry borer greatly influences projected outcomes. PMID:26177201

  4. Bias in streamflow projections due to climate-induced shifts in catchment response

    NASA Astrophysics Data System (ADS)

    Saft, Margarita; Peel, Murray C.; Western, Andrew W.; Perraud, Jean-Michel; Zhang, Lu

    2016-02-01

    Demand for quantitative assessments of likely climate change impact on runoff is increasing and conceptual rainfall-runoff models are essential tools for this task. However, the capacity of these models to extrapolate under changing climatic conditions is questionable. A number of studies have found that model predictive skill decreases with changed climatic conditions, especially when predicting drier climates. We found that model skill only declines under certain circumstances, in particular, when a catchment's rainfall-runoff processes change due to changed climatic drivers. In catchments where the rainfall-runoff relationship changed significantly in response to prolonged dry conditions, runoff was consistently overestimated. In contrast, modeled runoff was unbiased in catchments where the rainfall-runoff relationship remained unchanged during the dry period. These conclusions were not model dependent. Our results suggest that current projections of runoff under climate change may provide overly optimistic assessments of future water availability in some regions expecting rainfall reductions.

  5. A Sediment Record of Abrupt Lake Level Change in West-Central Minnesota

    NASA Astrophysics Data System (ADS)

    Mueller, S. B.; Triplett, L. D.; Myrbo, A.; Clotts, R. A.; Russell, J. M.; Shapley, M. D.

    2001-12-01

    Records of historical events preserved in lacustrine sediments are valuable for testing the conceptual models used in paleolimnology. The effects of climatic forcing and internal hydrologic dynamics are typically commingled in the geochemical signatures in sediments. However, Campbell Lake, Becker County, Minnesota, provides a record of abrupt lake-level drop unrelated to climate: in 1915 ditching reduced the lake surface area from 250 to 40 hectares and its average depth from three meters to one meter. We use sediment cores to assess the lake's response to this documented forcing, within the context of natural long-term variability. Existing paleoclimate studies from lakes in the region, as well as the historical record of anthropogenic impact to the lake, also make Campbell Lake a natural site to evaluate models of carbon and sulfur storage and carbon and oxygen stable isotope response to hydrologic changes. Loss-on-ignition and 210Pb chronology show only a slight increase in sedimentation rate following the drainage event, rather than the expected sharp increase due to reworking of littoral sediments. There is a dramatic rise in sedimentation rate around 1960, which may be indirectly related to the 1915 decrease in lake depth. The top 30 cm of sediment contains abundant carbonate stem casts from charophyte algae, indicating a shift to the lake's modern condition of aquatic macrophyte dominance. The time lag between lake-level drop and its manifestation in the sediments suggests that abrupt forcing events may not always be immediately reflected in the paleorecord.

  6. Future climate change is predicted to shift long-term persistence zones in the cold-temperate kelp Laminaria hyperborea.

    PubMed

    Assis, Jorge; Lucas, Ana Vaz; Bárbara, Ignacio; Serrão, Ester Álvares

    2016-02-01

    Global climate change is shifting species distributions worldwide. At rear edges (warmer, low latitude range margins), the consequences of small variations in environmental conditions can be magnified, producing large negative effects on species ranges. A major outcome of shifts in distributions that only recently received attention is the potential to reduce the levels of intra-specific diversity and consequently the global evolutionary and adaptive capacity of species to face novel disturbances. This is particularly important for low dispersal marine species, such as kelps, that generally retain high and unique genetic diversity at rear ranges resulting from long-term persistence, while ranges shifts during climatic glacial/interglacial cycles. Using ecological niche modelling, we (1) infer the major environmental forces shaping the distribution of a cold-temperate kelp, Laminaria hyperborea (Gunnerus) Foslie, and we (2) predict the effect of past climate changes in shaping regions of long-term persistence (i.e., climatic refugia), where this species might hypothetically harbour higher genetic diversity given the absence of bottlenecks and local extinctions over the long term. We further (3) assessed the consequences of future climate for the fate of L. hyperborea using different scenarios of greenhouse gas emissions (RCP 2.6 and RCP 8.5). Results show NW Iberia, SW Ireland and W English Channel, Faroe Islands and S Iceland, as regions where L. hyperborea may have persisted during past climate extremes until present day. All predictions for the future showed expansions to northern territories coupled with the significant loss of suitable habitats at low latitude range margins, where long-term persistence was inferred (e.g., NW Iberia). This pattern was particularly evident in the most agressive scenario of climate change (RCP 8.5), likely driving major biodiversity loss, changes in ecosystem functioning and the impoverishment of the global gene pool of L

  7. Future climate change is predicted to shift long-term persistence zones in the cold-temperate kelp Laminaria hyperborea.

    PubMed

    Assis, Jorge; Lucas, Ana Vaz; Bárbara, Ignacio; Serrão, Ester Álvares

    2016-02-01

    Global climate change is shifting species distributions worldwide. At rear edges (warmer, low latitude range margins), the consequences of small variations in environmental conditions can be magnified, producing large negative effects on species ranges. A major outcome of shifts in distributions that only recently received attention is the potential to reduce the levels of intra-specific diversity and consequently the global evolutionary and adaptive capacity of species to face novel disturbances. This is particularly important for low dispersal marine species, such as kelps, that generally retain high and unique genetic diversity at rear ranges resulting from long-term persistence, while ranges shifts during climatic glacial/interglacial cycles. Using ecological niche modelling, we (1) infer the major environmental forces shaping the distribution of a cold-temperate kelp, Laminaria hyperborea (Gunnerus) Foslie, and we (2) predict the effect of past climate changes in shaping regions of long-term persistence (i.e., climatic refugia), where this species might hypothetically harbour higher genetic diversity given the absence of bottlenecks and local extinctions over the long term. We further (3) assessed the consequences of future climate for the fate of L. hyperborea using different scenarios of greenhouse gas emissions (RCP 2.6 and RCP 8.5). Results show NW Iberia, SW Ireland and W English Channel, Faroe Islands and S Iceland, as regions where L. hyperborea may have persisted during past climate extremes until present day. All predictions for the future showed expansions to northern territories coupled with the significant loss of suitable habitats at low latitude range margins, where long-term persistence was inferred (e.g., NW Iberia). This pattern was particularly evident in the most agressive scenario of climate change (RCP 8.5), likely driving major biodiversity loss, changes in ecosystem functioning and the impoverishment of the global gene pool of L

  8. Climate-Induced Elevational Range Shifts and Increase in Plant Species Richness in a Himalayan Biodiversity Epicentre

    PubMed Central

    Telwala, Yasmeen; Brook, Barry W.; Manish, Kumar; Pandit, Maharaj K.

    2013-01-01

    Global average temperature increase during the last century has induced species geographic range shifts and extinctions. Montane floras, in particular, are highly sensitive to climate change and mountains serve as suitable observation sites for tracing climate-induced biological response. The Himalaya constitute an important global biodiversity hotspot, yet studies on species’ response to climate change from this region are lacking. Here we use historical (1849–50) and the recent (2007–2010) data on temperature and endemic species’ elevational ranges to perform a correlative study in the two alpine valleys of Sikkim. We show that the ongoing warming in the alpine Sikkim Himalaya has transformed the plant assemblages. This study lends support to the hypothesis that changing climate is causing species distribution changes. We provide first evidence of warmer winters in the region compared to the last two centuries, with mean temperatures of the warmest and the coldest months may have increased by 0.76±0.25°C and 3.65±2°C, respectively. Warming-driven geographical range shifts were recorded in 87% of 124 endemic plant species studied in the region; upper range extensions of species have resulted in increased species richness in the upper alpine zone, compared to the 19th century. We recorded a shift of 23–998 m in species’ upper elevation limit and a mean upward displacement rate of 27.53±22.04 m/decade in the present study. We infer that the present-day plant assemblages and community structure in the Himalaya is substantially different from the last century and is, therefore, in a state of flux under the impact of warming. The continued trend of warming is likely to result in ongoing elevational range contractions and eventually, species extinctions, particularly at mountaintops. PMID:23437322

  9. Climate-induced elevational range shifts and increase in plant species richness in a Himalayan biodiversity epicentre.

    PubMed

    Telwala, Yasmeen; Brook, Barry W; Manish, Kumar; Pandit, Maharaj K

    2013-01-01

    Global average temperature increase during the last century has induced species geographic range shifts and extinctions. Montane floras, in particular, are highly sensitive to climate change and mountains serve as suitable observation sites for tracing climate-induced biological response. The Himalaya constitute an important global biodiversity hotspot, yet studies on species' response to climate change from this region are lacking. Here we use historical (1849-50) and the recent (2007-2010) data on temperature and endemic species' elevational ranges to perform a correlative study in the two alpine valleys of Sikkim. We show that the ongoing warming in the alpine Sikkim Himalaya has transformed the plant assemblages. This study lends support to the hypothesis that changing climate is causing species distribution changes. We provide first evidence of warmer winters in the region compared to the last two centuries, with mean temperatures of the warmest and the coldest months may have increased by 0.76±0.25°C and 3.65±2°C, respectively. Warming-driven geographical range shifts were recorded in 87% of 124 endemic plant species studied in the region; upper range extensions of species have resulted in increased species richness in the upper alpine zone, compared to the 19(th) century. We recorded a shift of 23-998 m in species' upper elevation limit and a mean upward displacement rate of 27.53±22.04 m/decade in the present study. We infer that the present-day plant assemblages and community structure in the Himalaya is substantially different from the last century and is, therefore, in a state of flux under the impact of warming. The continued trend of warming is likely to result in ongoing elevational range contractions and eventually, species extinctions, particularly at mountaintops.

  10. Embracing Uncertainty: A Case Study Examination of How Climate Change is Shifting Water Utility Planning

    NASA Astrophysics Data System (ADS)

    Kaatz, L.

    2015-12-01

    Climate change has emerged as one of the greatest challenges facing water utilities' planning for the future, adding a new source and level of complexity that is forcing many agencies to re-examine their decision-making processes. A significant barrier for many agencies is figuring out how to consider highly uncertain climate information and move away from deterministic thinking to make climate-informed decisions. To provide water professionals with practical and relevant information, the Water Utility Climate Alliance teamed up with the American Water Works Association, in coordination with the Water Research Foundation and Association of Metropolitan Water Agencies, to develop a white paper sharing insights into how and why water agencies are modifying planning and decision-making processes. The 13 case studies presented illustrate the variety of ways in which utilities are incorporating climate change into planning, from immediate operational decisions, to capital planning and asset management, to long-term supply planning.

  11. Water Resources and Supply Adaptation: A paradigm Shifting for Future Climate?

    EPA Science Inventory

    Climate change adds another layer of complexity in planning, engineering and management of water resources and urban water infrastructures. Yet our current practice is confined to the traditional approach that evaluates developmental scenarios and their sustainability mostly by a...

  12. Shifts in Köppen-Geiger climate zones over southern Africa in relation to key global temperature goals

    NASA Astrophysics Data System (ADS)

    Engelbrecht, Christien J.; Engelbrecht, Francois A.

    2016-01-01

    Potential changes in Köppen-Geiger climate zones over southern Africa (Africa south of 22 °S) under future climate change are investigated using an ensemble of high-resolution projections of a regional climate model. The projections are performed under the A2 scenario of the Special Report on Emission Scenarios (SRES), and changes are presented for those times in the future when the increase in global average surface temperature reaches thresholds of 1, 2, and 3 °C, relative to the present-day baseline climatology. Widespread shifts in climate regimes are projected, of which the southern and eastern expansion of the hot desert and hot steppe zones is the most prominent. From occupying 33.1 and 19.4 % of southern Africa under present-day climate, these regions are projected to occupy between 47.3 and 59.7 % (hot desert zone) and 24.9 and 29.9 % (hot steppe zone) of the region in a future world where the global temperature has increased by 3 °C. The cold desert and cold steppe zones are projected to decrease correspondingly. The temperate regions of eastern South Africa, the Cape south coast, and winter rainfall region of the southwestern Cape are also projected to contract. An expansion of the hot steppe zone into the cold steppe and temperate zones may favor the intrusion of trees (and therefore the savanna biome) into the most pristine grasslands of southern Africa. However, the correlative climate-vegetation approach of using projected changes in Köppen-Geiger zones to infer future vegetation patterns is of limited value in the savanna complex of southern Africa, where complex feedbacks occur between carbon dioxide (CO2) concentrations, trees, C4 grasses, fire, and climate. The present-day temperate Cape Fynbos regime may come under increasing pressure as the encompassing temperate zone is invaded mainly from the east by the hot steppe climate regime under climate change, with the incidence of Fynbos fires also becoming more likely in a generally warmer and

  13. Subtask 7.3 - The Socioeconomic Impact of Climate Shifts in the Northern Great Plains

    SciTech Connect

    Jaroslav Solc; Tera Buckley; Troy Simonsen

    2007-12-31

    The Energy & Environmental Research Center (EERC) evaluated the water demand response/vulnerability to climate change factors of regional economic sectors in the northern Great Plains. Regardless of the cause of climatic trends currently observed, the research focused on practical evaluation of climate change impact, using water availability as a primary factor controlling long-term regional economic sustainability. Project results suggest that the Upper Missouri, Red River, and Upper Mississippi Watersheds exhibit analogous response to climate change, i.e., extended drought influences water availability in the entire region. The modified trend suggests that the next period for which the Red River Basin can expect a high probability of below normal precipitation will occur before 2050. Agriculture is the most sensitive economic sector in the region; however, analyses confirmed relative adaptability to changing conditions. The price of agricultural commodities is not a good indicator of the economic impact of climate change because production and price do not correlate and are subject to frequent and irregular government intervention. Project results confirm that high water demand in the primary economic sectors makes the regional economy extremely vulnerable to climatic extremes, with a similar response over the entire region. Without conservation-based water management policies, long-term periods of drought will limit socioeconomic development in the region and may threaten even the sustainability of current conditions.

  14. Indigenous Food Systems and Climate Change: Impacts of Climatic Shifts on the Production and Processing of Native and Traditional Crops in the Bolivian Andes

    PubMed Central

    Keleman Saxena, Alder; Cadima Fuentes, Ximena; Gonzales Herbas, Rhimer; Humphries, Debbie L.

    2016-01-01

    Inhabitants of the high-mountain Andes have already begun to experience changes in the timing, severity, and patterning of annual weather cycles. These changes have important implications for agriculture, for human health, and for the conservation of biodiversity in the region. This paper examines the implications of climate-driven changes for native and traditional crops in the municipality of Colomi, Cochabamba, Bolivia. Data were collected between 2012 and 2014 via mixed methods, qualitative fieldwork, including participatory workshops with female farmers and food preparers, semi-structured interviews with local agronomists, and participant observation. Drawing from this data, the paper describes (a) the observed impacts of changing weather patterns on agricultural production in the municipality of Colomi, Bolivia and (b) the role of local environmental resources and conditions, including clean running water, temperature, and humidity, in the household processing techniques used to conserve and sometimes detoxify native crop and animal species, including potato (Solanum sp.), oca (Oxalis tuberosa), tarwi (Lupinus mutabilis), papalisa (Ullucus tuberosus), and charke (llama or sheep jerky). Analysis suggests that the effects of climatic changes on agriculture go beyond reductions in yield, also influencing how farmers make choices about the timing of planting, soil management, and the use and spatial distribution of particular crop varieties. Furthermore, household processing techniques to preserve and detoxify native foods rely on key environmental and climatic resources, which may be vulnerable to climatic shifts. Although these findings are drawn from a single case study, we suggest that Colomi agriculture characterizes larger patterns in what might be termed, “indigenous food systems.” Such systems are underrepresented in aggregate models of the impacts of climate change on world agriculture and may be under different, more direct, and more immediate

  15. Indigenous Food Systems and Climate Change: Impacts of Climatic Shifts on the Production and Processing of Native and Traditional Crops in the Bolivian Andes.

    PubMed

    Keleman Saxena, Alder; Cadima Fuentes, Ximena; Gonzales Herbas, Rhimer; Humphries, Debbie L

    2016-01-01

    Inhabitants of the high-mountain Andes have already begun to experience changes in the timing, severity, and patterning of annual weather cycles. These changes have important implications for agriculture, for human health, and for the conservation of biodiversity in the region. This paper examines the implications of climate-driven changes for native and traditional crops in the municipality of Colomi, Cochabamba, Bolivia. Data were collected between 2012 and 2014 via mixed methods, qualitative fieldwork, including participatory workshops with female farmers and food preparers, semi-structured interviews with local agronomists, and participant observation. Drawing from this data, the paper describes (a) the observed impacts of changing weather patterns on agricultural production in the municipality of Colomi, Bolivia and (b) the role of local environmental resources and conditions, including clean running water, temperature, and humidity, in the household processing techniques used to conserve and sometimes detoxify native crop and animal species, including potato (Solanum sp.), oca (Oxalis tuberosa), tarwi (Lupinus mutabilis), papalisa (Ullucus tuberosus), and charke (llama or sheep jerky). Analysis suggests that the effects of climatic changes on agriculture go beyond reductions in yield, also influencing how farmers make choices about the timing of planting, soil management, and the use and spatial distribution of particular crop varieties. Furthermore, household processing techniques to preserve and detoxify native foods rely on key environmental and climatic resources, which may be vulnerable to climatic shifts. Although these findings are drawn from a single case study, we suggest that Colomi agriculture characterizes larger patterns in what might be termed, "indigenous food systems." Such systems are underrepresented in aggregate models of the impacts of climate change on world agriculture and may be under different, more direct, and more immediate threat

  16. Indigenous Food Systems and Climate Change: Impacts of Climatic Shifts on the Production and Processing of Native and Traditional Crops in the Bolivian Andes.

    PubMed

    Keleman Saxena, Alder; Cadima Fuentes, Ximena; Gonzales Herbas, Rhimer; Humphries, Debbie L

    2016-01-01

    Inhabitants of the high-mountain Andes have already begun to experience changes in the timing, severity, and patterning of annual weather cycles. These changes have important implications for agriculture, for human health, and for the conservation of biodiversity in the region. This paper examines the implications of climate-driven changes for native and traditional crops in the municipality of Colomi, Cochabamba, Bolivia. Data were collected between 2012 and 2014 via mixed methods, qualitative fieldwork, including participatory workshops with female farmers and food preparers, semi-structured interviews with local agronomists, and participant observation. Drawing from this data, the paper describes (a) the observed impacts of changing weather patterns on agricultural production in the municipality of Colomi, Bolivia and (b) the role of local environmental resources and conditions, including clean running water, temperature, and humidity, in the household processing techniques used to conserve and sometimes detoxify native crop and animal species, including potato (Solanum sp.), oca (Oxalis tuberosa), tarwi (Lupinus mutabilis), papalisa (Ullucus tuberosus), and charke (llama or sheep jerky). Analysis suggests that the effects of climatic changes on agriculture go beyond reductions in yield, also influencing how farmers make choices about the timing of planting, soil management, and the use and spatial distribution of particular crop varieties. Furthermore, household processing techniques to preserve and detoxify native foods rely on key environmental and climatic resources, which may be vulnerable to climatic shifts. Although these findings are drawn from a single case study, we suggest that Colomi agriculture characterizes larger patterns in what might be termed, "indigenous food systems." Such systems are underrepresented in aggregate models of the impacts of climate change on world agriculture and may be under different, more direct, and more immediate threat

  17. Simulating phenological shifts in French temperate forests under two climatic change scenarios and four driving global circulation models.

    PubMed

    Lebourgeois, François; Pierrat, Jean-Claude; Perez, Vincent; Piedallu, Christian; Cecchini, Sébastien; Ulrich, Erwin

    2010-09-01

    After modeling the large-scale climate response patterns of leaf unfolding, leaf coloring and growing season length of evergreen and deciduous French temperate trees, we predicted the effects of eight future climate scenarios on phenological events. We used the ground observations from 103 temperate forests (10 species and 3,708 trees) from the French Renecofor Network and for the period 1997-2006. We applied RandomForest algorithms to predict phenological events from climatic and ecological variables. With the resulting models, we drew maps of phenological events throughout France under present climate and under two climatic change scenarios (A2, B2) and four global circulation models (HadCM3, CGCM2, CSIRO2 and PCM). We compared current observations and predicted values for the periods 2041-2070 and 2071-2100. On average, spring development of oaks precedes that of beech, which precedes that of conifers. Annual cycles in budburst and leaf coloring are highly correlated with January, March-April and October-November weather conditions through temperature, global solar radiation or potential evapotranspiration depending on species. At the end of the twenty-first century, each model predicts earlier budburst (mean: 7 days) and later leaf coloring (mean: 13 days) leading to an average increase in the growing season of about 20 days (for oaks and beech stands). The A2-HadCM3 hypothesis leads to an increase of up to 30 days in many areas. As a consequence of higher predicted warming during autumn than during winter or spring, shifts in leaf coloring dates appear greater than trends in leaf unfolding. At a regional scale, highly differing climatic response patterns were observed.

  18. Climate-change-related shifts in annual phenology of a temperate snake during the last 20 years

    NASA Astrophysics Data System (ADS)

    Rugiero, Lorenzo; Milana, Giuliano; Petrozzi, Fabio; Capula, Massimo; Luiselli, Luca

    2013-08-01

    Global warming is thought to be a far-reaching threat to biodiversity, and is supposed to influence several aspects of the ecology of animals. Global warming should influence especially the ectotherm vertebrates, which depend directly from the external thermal conditions for their activities and performances. Here, we analyze the changes in phenology which have occurred in the last 20 years in a marked population of vipers, Vipera aspis, and we try to relate these changes with the intervening climatic changes. We analyzed three metrics of viper's annual phenology: (i) annual onset of above-ground activity (hereby AOA); (ii) annual onset of feeding period (AOF); (iii) annual onset of the hibernation (AOH). The annual variations of these three phenological metrics were correlated to five variables of climatic data: (1) mean annual air temperature, (2) mean February air temperature, (3) mean July air temperature, (4) yearly number of rainy days, and (5) yearly number of days with rainstorm. We observed a statistically significant reduction of AOA values from >28 days between 1987 and 1997, to approximately 20 days from 1998 to 2011, with a similar statistical trend also found for AOF values. The number of days of delay in entering hibernation increased significantly since 1998. Three sets of relationships between climatic variables and metrics of viper phenology were statistically significant, i.e. the correlation (i) between annual mean temperature and AOA (negative), (ii) between annual mean temperature and AOF (negative), and (iii) between annual mean temperature and AOH (positive). The percent of field days (between 20th February and 20th March) with no viper observed also decreased significantly over the years. Our study showed that three different traits of the annual phenology of a Mediterranean snake are shifting in the 20+ years of monitoring, and that there is correlational evidence that these shifts are linked to intervening climate change.

  19. Genetic Adaptation to Climate in White Spruce Involves Small to Moderate Allele Frequency Shifts in Functionally Diverse Genes

    PubMed Central

    Hornoy, Benjamin; Pavy, Nathalie; Gérardi, Sébastien; Beaulieu, Jean; Bousquet, Jean

    2015-01-01

    Understanding the genetic basis of adaptation to climate is of paramount importance for preserving and managing genetic diversity in plants in a context of climate change. Yet, this objective has been addressed mainly in short-lived model species. Thus, expanding knowledge to nonmodel species with contrasting life histories, such as forest trees, appears necessary. To uncover the genetic basis of adaptation to climate in the widely distributed boreal conifer white spruce (Picea glauca), an environmental association study was conducted using 11,085 single nucleotide polymorphisms representing 7,819 genes, that is, approximately a quarter of the transcriptome. Linear and quadratic regressions controlling for isolation-by-distance, and the Random Forest algorithm, identified several dozen genes putatively under selection, among which 43 showed strongest signals along temperature and precipitation gradients. Most of them were related to temperature. Small to moderate shifts in allele frequencies were observed. Genes involved encompassed a wide variety of functions and processes, some of them being likely important for plant survival under biotic and abiotic environmental stresses according to expression data. Literature mining and sequence comparison also highlighted conserved sequences and functions with angiosperm homologs. Our results are consistent with theoretical predictions that local adaptation involves genes with small frequency shifts when selection is recent and gene flow among populations is high. Accordingly, genetic adaptation to climate in P. glauca appears to be complex, involving many independent and interacting gene functions, biochemical pathways, and processes. From an applied perspective, these results shall lead to specific functional/association studies in conifers and to the development of markers useful for the conservation of genetic resources. PMID:26560341

  20. Forecasting range expansion into ecological traps: climate-mediated shifts in sea turtle nesting beaches and human development.

    PubMed

    Pike, David A

    2013-10-01

    Some species are adapting to changing environments by expanding their geographic ranges. Understanding whether range shifts will be accompanied by increased exposure to other threats is crucial to predicting when and where new populations could successfully establish. If species overlap to a greater extent with human development under climate change, this could form ecological traps which are attractive to dispersing individuals, but the use of which substantially reduces fitness. Until recently, the core nesting range for the Critically Endangered Kemp's ridley sea turtle (Lepidochelys kempii) was ca. 1000 km of sparsely populated coastline in Tamaulipas, Mexico. Over the past twenty-five years, this species has expanded its range into populated areas of coastal Florida (>1500 km outside the historical range), where nesting now occurs annually. Suitable Kemp's ridley nesting habitat has persisted for at least 140 000 years in the western Gulf of Mexico, and climate change models predict further nesting range expansion into the eastern Gulf of Mexico and northern Atlantic Ocean. Range expansion is 6-12% more likely to occur along uninhabited stretches of coastline than are current nesting beaches, suggesting that novel nesting areas will not be associated with high levels of anthropogenic disturbance. Although the high breeding-site fidelity of some migratory species could limit adaptation to climate change, rapid population recovery following effective conservation measures may enhance opportunities for range expansion. Anticipating the interactive effects of past or contemporary conservation measures, climate change, and future human activities will help focus long-term conservation strategies.

  1. Combining Population Structure with Historic Abitoic Processes to Better Understand Species and Community Range Shifts in Response to Climate Change

    NASA Astrophysics Data System (ADS)

    Graham, N. M.

    2015-12-01

    The evolution and speciation of plants is directly tied to the environment as the constrained stages of dispersal creates strong genetic differentiation among populations. This can result in differing genetic patterns between nuclear and chloroplast loci, where genes are inherited differently and dispersed via separate vectors. By developing distribution models based on genetic patterns found within a species, it is possible to begin understanding the influence of historic geomorphic and/or climatic processes on population evolution. If genetic patterns of the current range correlate with specific patterns of climate variability within the Pleistocene, it is possible that future shifts in species distribution in response to climate change can be more accurately modelled due to the historic signature that is found within inherited genes. Preliminary genetic analyses of Linanthus dichotomus, an annual herb distributed across California, suggests that the current taxonomic treatment does not accurately depict how this species is evolving. Genetic patterns of chloroplast genes suggest that populations are more correlated with biogeography than what the current nomenclature states. Additionally, chloroplast and nuclear genes show discrepancies in the dispersal across the landscape, suggesting pollinator driven gene flow overcoming seed dispersal boundaries. By comparing discrepancies between pollinator and seed induced gene flow we may be able to gain insight into historical pollinator communities within the Pleistocene. This information can then be applied to projected climate models to more accurately understand how species and/or communities will respond to a changing environment.

  2. Surveillance tools and strategies for animal diseases in a shifting climate context.

    PubMed

    Salman, Mo D

    2013-12-01

    Animal disease surveillance is watching an animal population closely to determine if a specific disease or a group of diseases makes an incursion so that a prior plan of action can be implemented. The purpose of this paper is to review existing tools and techniques for an animal disease-surveillance system that can incorporate the monitoring of climate factors and related data to enhance understanding of disease epidemiology. In recent decades, there has been interest in building information systems by combining various data sources for different purposes. Within the field of animal health, there have only been limited attempts at the integration of surveillance data with relevant climate conditions. Statistical techniques for data integration, however, have been explored and used by several disciplines. Clearly the application of available techniques for linking climate data with surveillance systems should be explored with the aim of facilitating prevention, mitigation, and adaptation responses in the surveillance setting around climate change and animal disease risks. Drawing on this wider body of work, three of the available techniques that can be utilized in the analysis of surveillance data with the available climate data sets are reviewed.

  3. Climate change and physical disturbance cause similar community shifts in biological soil crusts

    USGS Publications Warehouse

    Ferrenberg, Scott; Reed, Sasha C.; Belnap, Jayne

    2015-01-01

    Biological soil crusts (biocrusts)—communities of mosses, lichens, cyanobacteria, and heterotrophs living at the soil surface—are fundamental components of drylands worldwide, and destruction of biocrusts dramatically alters biogeochemical processes, hydrology, surface energy balance, and vegetation cover. While there has been long-standing concern over impacts of 5 physical disturbances on biocrusts (e.g., trampling by livestock, damage from vehicles), there is also increasing concern over the potential for climate change to alter biocrust community structure. Using long-term data from the Colorado Plateau, USA, we examined the effects of 10 years of experimental warming and altered precipitation (in full-factorial design) on biocrust communities, and compared the effects of altered climate with those of long-term physical 10 disturbance (>10 years of replicated human trampling). Surprisingly, altered climate and physical disturbance treatments had similar effects on biocrust community structure. Warming, altered precipitation frequency [an increase of small (1.2 mm) summer rainfall events], and physical disturbance from trampling all promoted early successional community states marked by dramatic declines in moss cover and increased cyanobacteria cover, with more variable effects 15 on lichens. While the pace of community change varied significantly among treatments, our results suggest that multiple aspects of climate change will affect biocrusts to the same degree as physical disturbance. This is particularly disconcerting in the context of warming, as temperatures for drylands are projected to increase beyond those imposed by the climate treatments used in our study.

  4. Predicting ecosystem shifts requires new approaches that integrate the effects of climate change across entire systems

    PubMed Central

    Russell, Bayden D.; Harley, Christopher D. G.; Wernberg, Thomas; Mieszkowska, Nova; Widdicombe, Stephen; Hall-Spencer, Jason M.; Connell, Sean D.

    2012-01-01

    Most studies that forecast the ecological consequences of climate change target a single species and a single life stage. Depending on climatic impacts on other life stages and on interacting species, however, the results from simple experiments may not translate into accurate predictions of future ecological change. Research needs to move beyond simple experimental studies and environmental envelope projections for single species towards identifying where ecosystem change is likely to occur and the drivers for this change. For this to happen, we advocate research directions that (i) identify the critical species within the target ecosystem, and the life stage(s) most susceptible to changing conditions and (ii) the key interactions between these species and components of their broader ecosystem. A combined approach using macroecology, experimentally derived data and modelling that incorporates energy budgets in life cycle models may identify critical abiotic conditions that disproportionately alter important ecological processes under forecasted climates. PMID:21900317

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

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

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

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

    PubMed

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

    2015-09-25

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

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

    PubMed

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

    2015-09-25

    Antarctic ice-core data reveal that the atmosphere experienced abrupt centennial increases in CO2 concentration during the last deglaciation (~18 thousand to 11 thousand years ago). Establishing the role of ocean circulation in these changes requires high-resolution, accurately dated marine records. Here, we report radiocarbon data from uranium-thorium-dated deep-sea corals in the Equatorial Atlantic and Drake Passage over the past 25,000 years. Two major deglacial radiocarbon shifts occurred in phase with centennial atmospheric CO2 rises at 14.8 thousand and 11.7 thousand years ago. We interpret these radiocarbon-enriched signals to represent two short-lived (less than 500 years) "overshoot" events, with Atlantic meridional overturning stronger than that of the modern era. These results provide compelling evidence for a close coupling of ocean circulation and centennial climate events during the last deglaciation. PMID:26404835

  8. Projected Shifts in Köppen Climate Zones over China and Their Temporal Evolution in CMIP5 Multi-Model Simulations

    NASA Astrophysics Data System (ADS)

    Wu, Q.; Chan, D.; Jiang, G.; Dai, X.

    2014-12-01

    This study uses CMIP5 multi-model ensemble projections to calculate Köppen-Geiger climate classifications and changes in China from 1990 to 2100. The projected climate types would shift toward warmer climate types from current climate distribution, changes are characterized by pronounced retreat of alpine (ET) climate type on the Tibetan Plateau, disappearance of sub-polar continental winter dry (Dwc) over Northeast China, expansion of temperate (C-type) climate over eastern China. Projected climate shifts are time-dependent. Large climate shifts are already detected in transition regions (7.5% of total land area) around 2010, including rapid replacement of mixed forest (Dwb) by deciduous forest (Dwa) over Northeast China and strong shrinkage of ET on the Tibetan Plateau, weak northward expansion of subtropical winter-dry (Cwa) over eastern China and contract of oceanic climate (Cwb) in Southwest China. Reduction of Dwb in Northeast China and ET on the Tibetan Plateau accelerates substantially during 2010-2030 under all scenarios. Half of the total area occupied by ET in 1990 is projected to be redistributed by 2040. Under the RCP 8.5 scenario, Dwc over Northeast China disappears by 2040-2050, ET on the Tibetan Plateaus disappears by 2070, shift of subtropical humid (Cfa) climate to Cwa over large parts of southeastern China occurs after 2050 due to decreasing wintertime precipitation, and the coverage of C-type climate increases about 7.6% by 2090. Under the RCP2.6, 4.5, 6 and 8.5 emissions pathways, climate types in 22.8%, 39.0%, 46.4% and 52.6% of China's land area change by 2100, primarily following simulated warming changes.

  9. Climate change and physical disturbance cause similar community shifts in biological soil crusts.

    PubMed

    Ferrenberg, Scott; Reed, Sasha C; Belnap, Jayne

    2015-09-29

    Biological soil crusts (biocrusts)—communities of mosses, lichens, cyanobacteria, and heterotrophs living at the soil surface—are fundamental components of drylands worldwide, and destruction of biocrusts dramatically alters biogeochemical processes, hydrology, surface energy balance, and vegetation cover. Although there has been long-standing concern over impacts of physical disturbances on biocrusts (e.g., trampling by livestock, damage from vehicles), there is increasing concern over the potential for climate change to alter biocrust community structure. Using long-term data from the Colorado Plateau, we examined the effects of 10 y of experimental warming and altered precipitation (in full-factorial design) on biocrust communities and compared the effects of altered climate with those of long-term physical disturbance (>10 y of replicated human trampling). Surprisingly, altered climate and physical disturbance treatments had similar effects on biocrust community structure. Warming, altered precipitation frequency [an increase of small (1.2 mm) summer rainfall events], and physical disturbance from trampling all promoted early successional community states marked by dramatic declines in moss cover and increases in cyanobacteria cover, with more variable effects on lichens. Although the pace of community change varied significantly among treatments, our results suggest that multiple aspects of climate change will affect biocrusts to the same degree as physical disturbance. This is particularly disconcerting in the context of warming, as temperatures for drylands are projected to increase beyond those imposed as treatments in our study.

  10. PREDICTING CLIMATE-INDUCED GEOGRAPHIC RANGE SHIFTS FOR MAMMALS IN THE WESTERN HEMISPHERE

    EPA Science Inventory

    In order to manage wildlife and conserve biodiversity, it is critical that we understand the potential impacts of climate change on species distributions. I used six different modeling approaches to predict the future distributions of 100 mammal species in the western hemisphere...

  11. Predicted habitat shifts of Pacific top predators in a changing climate

    NASA Astrophysics Data System (ADS)

    Hazen, Elliott L.; Jorgensen, Salvador; Rykaczewski, Ryan R.; Bograd, Steven J.; Foley, David G.; Jonsen, Ian D.; Shaffer, Scott A.; Dunne, John P.; Costa, Daniel P.; Crowder, Larry B.; Block, Barbara A.

    2013-03-01

    To manage marine ecosystems proactively, it is important to identify species at risk and habitats critical for conservation. Climate change scenarios have predicted an average sea surface temperature (SST) rise of 1-6°C by 2100 (refs , ), which could affect the distribution and habitat of many marine species. Here we examine top predator distribution and diversity in the light of climate change using a database of 4,300 electronic tags deployed on 23 marine species from the Tagging of Pacific Predators project, and output from a global climate model to 2100. On the basis of models of observed species distribution as a function of SST, chlorophyll a and bathymetry, we project changes in species-specific core habitat and basin-scale patterns of biodiversity. We predict up to a 35% change in core habitat for some species, significant differences in rates and patterns of habitat change across guilds, and a substantial northward displacement of biodiversity across the North Pacific. For already stressed species, increased migration times and loss of pelagic habitat could exacerbate population declines or inhibit recovery. The impending effects of climate change stress the urgency of adaptively managing ecosystems facing multiple threats.

  12. Climate change and physical disturbance cause similar community shifts in biological soil crusts.

    PubMed

    Ferrenberg, Scott; Reed, Sasha C; Belnap, Jayne

    2015-09-29

    Biological soil crusts (biocrusts)—communities of mosses, lichens, cyanobacteria, and heterotrophs living at the soil surface—are fundamental components of drylands worldwide, and destruction of biocrusts dramatically alters biogeochemical processes, hydrology, surface energy balance, and vegetation cover. Although there has been long-standing concern over impacts of physical disturbances on biocrusts (e.g., trampling by livestock, damage from vehicles), there is increasing concern over the potential for climate change to alter biocrust community structure. Using long-term data from the Colorado Plateau, we examined the effects of 10 y of experimental warming and altered precipitation (in full-factorial design) on biocrust communities and compared the effects of altered climate with those of long-term physical disturbance (>10 y of replicated human trampling). Surprisingly, altered climate and physical disturbance treatments had similar effects on biocrust community structure. Warming, altered precipitation frequency [an increase of small (1.2 mm) summer rainfall events], and physical disturbance from trampling all promoted early successional community states marked by dramatic declines in moss cover and increases in cyanobacteria cover, with more variable effects on lichens. Although the pace of community change varied significantly among treatments, our results suggest that multiple aspects of climate change will affect biocrusts to the same degree as physical disturbance. This is particularly disconcerting in the context of warming, as temperatures for drylands are projected to increase beyond those imposed as treatments in our study. PMID:26371310

  13. Sensitivity of Vadose Zone Water Fluxes to Climate Shifts in Arid Settings

    SciTech Connect

    Pfletschinger, H.; Prömmel, K.; Schüth, C.; Herbst, M.; Engelhardt, I.

    2014-01-01

    Vadose zone water fluxes in arid settings are investigated regarding their sensitivity to hydraulic soil parameters and meteorological data. The study is based on the inverse modeling of highly defined soil column experiments and subsequent scenario modeling comparing different climate projections for a defined arid region. In arid regions, groundwater resources are prone to depletion due to excessive water use and little recharge potential. Especially in sand dune areas, groundwater recharge is highly dependent on vadose zone properties and corresponding water fluxes. Nevertheless, vadose zone water fluxes under arid conditions are hard to determine owing to, among other reasons, deep vadose zones with generally low fluxes and only sporadic high infiltration events. In this study, we present an inverse model of infiltration experiments accounting for variable saturated nonisothermal water fluxes to estimate effective hydraulic and thermal parameters of dune sands. A subsequent scenario modeling links the results of the inverse model with projections of a global climate model until 2100. The scenario modeling clearly showed the high dependency of groundwater recharge on precipitation amounts and intensities, whereas temperature increases are only of minor importance for deep infiltration. However, simulated precipitation rates are still affected by high uncertainties in the response to the hydrological input data of the climate model. Thus, higher certainty in the prediction of precipitation pattern is a major future goal for climate modeling to constrain future groundwater management strategies in arid regions.

  14. Climate change and physical disturbance cause similar community shifts in biological soil crusts

    PubMed Central

    Ferrenberg, Scott; Reed, Sasha C.; Belnap, Jayne

    2015-01-01

    Biological soil crusts (biocrusts)—communities of mosses, lichens, cyanobacteria, and heterotrophs living at the soil surface—are fundamental components of drylands worldwide, and destruction of biocrusts dramatically alters biogeochemical processes, hydrology, surface energy balance, and vegetation cover. Although there has been long-standing concern over impacts of physical disturbances on biocrusts (e.g., trampling by livestock, damage from vehicles), there is increasing concern over the potential for climate change to alter biocrust community structure. Using long-term data from the Colorado Plateau, we examined the effects of 10 y of experimental warming and altered precipitation (in full-factorial design) on biocrust communities and compared the effects of altered climate with those of long-term physical disturbance (>10 y of replicated human trampling). Surprisingly, altered climate and physical disturbance treatments had similar effects on biocrust community structure. Warming, altered precipitation frequency [an increase of small (1.2 mm) summer rainfall events], and physical disturbance from trampling all promoted early successional community states marked by dramatic declines in moss cover and increases in cyanobacteria cover, with more variable effects on lichens. Although the pace of community change varied significantly among treatments, our results suggest that multiple aspects of climate change will affect biocrusts to the same degree as physical disturbance. This is particularly disconcerting in the context of warming, as temperatures for drylands are projected to increase beyond those imposed as treatments in our study. PMID:26371310

  15. Climate change and decadal shifts in the phenology of larval fishes in the California Current ecosystem

    PubMed Central

    Asch, Rebecca G.

    2015-01-01

    Climate change has prompted an earlier arrival of spring in numerous ecosystems. It is uncertain whether such changes are occurring in Eastern Boundary Current Upwelling ecosystems, because these regions are subject to natural decadal climate variability, and regional climate models predict seasonal delays in upwelling. To answer this question, the phenology of 43 species of larval fishes was investigated between 1951 and 2008 off southern California. Ordination of the fish community showed earlier phenological progression in more recent years. Thirty-nine percent of seasonal peaks in larval abundance occurred earlier in the year, whereas 18% were delayed. The species whose phenology became earlier were characterized by an offshore, pelagic distribution, whereas species with delayed phenology were more likely to reside in coastal, demersal habitats. Phenological changes were more closely associated with a trend toward earlier warming of surface waters rather than decadal climate cycles, such as the Pacific Decadal Oscillation and North Pacific Gyre Oscillation. Species with long-term advances and delays in phenology reacted similarly to warming at the interannual time scale as demonstrated by responses to the El Niño Southern Oscillation. The trend toward earlier spawning was correlated with changes in sea surface temperature (SST) and mesozooplankton displacement volume, but not coastal upwelling. SST and upwelling were correlated with delays in fish phenology. For species with 20th century advances in phenology, future projections indicate that current trends will continue unabated. The fate of species with delayed phenology is less clear due to differences between Intergovernmental Panel on Climate Change models in projected upwelling trends. PMID:26159416

  16. Climate change and decadal shifts in the phenology of larval fishes in the California Current ecosystem.

    PubMed

    Asch, Rebecca G

    2015-07-28

    Climate change has prompted an earlier arrival of spring in numerous ecosystems. It is uncertain whether such changes are occurring in Eastern Boundary Current Upwelling ecosystems, because these regions are subject to natural decadal climate variability, and regional climate models predict seasonal delays in upwelling. To answer this question, the phenology of 43 species of larval fishes was investigated between 1951 and 2008 off southern California. Ordination of the fish community showed earlier phenological progression in more recent years. Thirty-nine percent of seasonal peaks in larval abundance occurred earlier in the year, whereas 18% were delayed. The species whose phenology became earlier were characterized by an offshore, pelagic distribution, whereas species with delayed phenology were more likely to reside in coastal, demersal habitats. Phenological changes were more closely associated with a trend toward earlier warming of surface waters rather than decadal climate cycles, such as the Pacific Decadal Oscillation and North Pacific Gyre Oscillation. Species with long-term advances and delays in phenology reacted similarly to warming at the interannual time scale as demonstrated by responses to the El Niño Southern Oscillation. The trend toward earlier spawning was correlated with changes in sea surface temperature (SST) and mesozooplankton displacement volume, but not coastal upwelling. SST and upwelling were correlated with delays in fish phenology. For species with 20th century advances in phenology, future projections indicate that current trends will continue unabated. The fate of species with delayed phenology is less clear due to differences between Intergovernmental Panel on Climate Change models in projected upwelling trends.

  17. Climate change and decadal shifts in the phenology of larval fishes in the California Current ecosystem.

    PubMed

    Asch, Rebecca G

    2015-07-28

    Climate change has prompted an earlier arrival of spring in numerous ecosystems. It is uncertain whether such changes are occurring in Eastern Boundary Current Upwelling ecosystems, because these regions are subject to natural decadal climate variability, and regional climate models predict seasonal delays in upwelling. To answer this question, the phenology of 43 species of larval fishes was investigated between 1951 and 2008 off southern California. Ordination of the fish community showed earlier phenological progression in more recent years. Thirty-nine percent of seasonal peaks in larval abundance occurred earlier in the year, whereas 18% were delayed. The species whose phenology became earlier were characterized by an offshore, pelagic distribution, whereas species with delayed phenology were more likely to reside in coastal, demersal habitats. Phenological changes were more closely associated with a trend toward earlier warming of surface waters rather than decadal climate cycles, such as the Pacific Decadal Oscillation and North Pacific Gyre Oscillation. Species with long-term advances and delays in phenology reacted similarly to warming at the interannual time scale as demonstrated by responses to the El Niño Southern Oscillation. The trend toward earlier spawning was correlated with changes in sea surface temperature (SST) and mesozooplankton displacement volume, but not coastal upwelling. SST and upwelling were correlated with delays in fish phenology. For species with 20th century advances in phenology, future projections indicate that current trends will continue unabated. The fate of species with delayed phenology is less clear due to differences between Intergovernmental Panel on Climate Change models in projected upwelling trends. PMID:26159416

  18. Predicted altitudinal shifts and reduced spatial distribution of Leishmania infantum vector species under climate change scenarios in Colombia.

    PubMed

    González, Camila; Paz, Andrea; Ferro, Cristina

    2014-01-01

    Visceral leishmaniasis (VL) is caused by the trypanosomatid parasite Leishmania infantum (=Leishmania chagasi), and is epidemiologically relevant due to its wide geographic distribution, the number of annual cases reported and the increase in its co-infection with HIV. Two vector species have been incriminated in the Americas: Lutzomyia longipalpis and Lutzomyia evansi. In Colombia, L. longipalpis is distributed along the Magdalena River Valley while L. evansi is only found in the northern part of the Country. Regarding the epidemiology of the disease, in Colombia the incidence of VL has decreased over the last few years without any intervention being implemented. Additionally, changes in transmission cycles have been reported with urban transmission occurring in the Caribbean Coast. In Europe and North America climate change seems to be driving a latitudinal shift of leishmaniasis transmission. Here, we explored the spatial distribution of the two known vector species of L. infantum in Colombia and projected its future distribution into climate change scenarios to establish the expansion potential of the disease. An updated database including L. longipalpis and L. evansi collection records from Colombia was compiled. Ecological niche models were performed for each species using the Maxent software and 13 Worldclim bioclimatic coverages. Projections were made for the pessimistic CSIRO A2 scenario, which predicts the higher increase in temperature due to non-emission reduction, and the optimistic Hadley B2 Scenario predicting the minimum increase in temperature. The database contained 23 records for L. evansi and 39 records for L. longipalpis, distributed along the Magdalena River Valley and the Caribbean Coast, where the potential distribution areas of both species were also predicted by Maxent. Climate change projections showed a general overall reduction in the spatial distribution of the two vector species, promoting a shift in altitudinal distribution for L

  19. Predicted altitudinal shifts and reduced spatial distribution of Leishmania infantum vector species under climate change scenarios in Colombia.

    PubMed

    González, Camila; Paz, Andrea; Ferro, Cristina

    2014-01-01

    Visceral leishmaniasis (VL) is caused by the trypanosomatid parasite Leishmania infantum (=Leishmania chagasi), and is epidemiologically relevant due to its wide geographic distribution, the number of annual cases reported and the increase in its co-infection with HIV. Two vector species have been incriminated in the Americas: Lutzomyia longipalpis and Lutzomyia evansi. In Colombia, L. longipalpis is distributed along the Magdalena River Valley while L. evansi is only found in the northern part of the Country. Regarding the epidemiology of the disease, in Colombia the incidence of VL has decreased over the last few years without any intervention being implemented. Additionally, changes in transmission cycles have been reported with urban transmission occurring in the Caribbean Coast. In Europe and North America climate change seems to be driving a latitudinal shift of leishmaniasis transmission. Here, we explored the spatial distribution of the two known vector species of L. infantum in Colombia and projected its future distribution into climate change scenarios to establish the expansion potential of the disease. An updated database including L. longipalpis and L. evansi collection records from Colombia was compiled. Ecological niche models were performed for each species using the Maxent software and 13 Worldclim bioclimatic coverages. Projections were made for the pessimistic CSIRO A2 scenario, which predicts the higher increase in temperature due to non-emission reduction, and the optimistic Hadley B2 Scenario predicting the minimum increase in temperature. The database contained 23 records for L. evansi and 39 records for L. longipalpis, distributed along the Magdalena River Valley and the Caribbean Coast, where the potential distribution areas of both species were also predicted by Maxent. Climate change projections showed a general overall reduction in the spatial distribution of the two vector species, promoting a shift in altitudinal distribution for L

  20. Effects of Interannual Climate Variability on Water Availability and Productivity in Capoeira and Crops Under Traditional and Alternative Shifting Cultivation

    NASA Technical Reports Server (NTRS)

    Guild, Liane S.; Sa, Tatiana D. A.; Carvalho, Claudio J. R.; Potter, Christopher S.; Wickel, Albert J.; Brienza, Silvio, Jr.; Kato, Maria doSocorro A.; Kato, Osvaldo; Brass, James (Technical Monitor)

    2002-01-01

    Regenerating forests play an important role in long-term carbon sequestration and sustainable landuse as they act as potentially important carbon and nutrient sinks during the shifting agriculture fallow period. The long-term functioning of capoeira. is increasingly threatened by a shortening fallow period during shifting cultivation due to demographic pressures and associated increased vulnerability to severe climatic events. Declining productivity and functioning of fallow forests of shifting cultivation combined with progressive loss of nutrients by successive burning and cropping activities has resulted in declining agricultural productivity. In addition to the effects of intense land use practices, droughts associated with El Nino events are becoming more frequent and severe in moist tropical forests and negative effects on capoeira productivity could be considerable. In Igarape-Acu (near Belem, Para), we hypothesize that experimental alternative landuse/clearing practices (mulching and fallow vegetation improvement by planting with fast-growing leguminous tree species) may make capoeira and agriculture more resilient to the effects of agricultural pressures and drought through (1) increased biomass, soil organic matter and associated increase in soil water storage, and nutrient retention and (2) greater rooting depth of trees planted for fallow improvement. This experimental practice (moto mechanized chop-and-mulch with fallow improvement) has resulted increased soil moisture during the cropping phase, reduced loss of nutrients and organic matter, and higher rates of secondary-forest biomass accumulation. We present preliminary data on water relations during the dry season of 2001 in capoeira and crops for both traditional slash-and-burn and alternative chop-and-mulch practices. These data will be used to test IKONOS data for the detection of moisture status differences. The principal goal of the research is to determine the extent to which capoeira and

  1. Abrupt decadal-to-centennial hydroclimate changes in the Mediterranean region since the mid-Holocene

    NASA Astrophysics Data System (ADS)

    Hu, Hsun-Ming; Shen, Chuan-Chou; Jiang, Xiuyang; Wang, Yongjin; Mii, Horng-Sheng; Michel, Véronique

    2016-04-01

    A series of severe drought events in the Mediterranean region over the past two decades has posed a threat on both human society and biosystem. Holocene hydrological dynamics can offer valuable clues for understanding future climate and making proper adaption strategy. Here, we present a decadal-resolved stalagmite record documenting various hydroclimatic fluctuations in the north central Mediterranean region since the middle Holocene. The stalagmite δ18O sequence shows dramatic instability, characterized by abrupt shifts between dry and wet conditions <50 years. The timing of regional culture demises, such as the Hittite Kingdom, Mycenaean Greece, Akkadian Empire, Egyptian Old Kingdom, and Uruk, occurred during the drought events, suggesting an important role of climate impact on human civilization. The unstable hydroclimate evolution is related to transferred North Atlantic Oscillation states. Rate of rapid transfer of precipitation patterns, which can be pin-pointed by our good chronology, improves the prediction to future climate changes in North Atlantic region. We also found that a strong correlation between this stalagmite δ18O and sea surface temperatures especially in Pacific Ocean. This agreement suggests a distant interregional climate teleconnection.

  2. A phenological shift in the time of recruitment of the shipworm, Teredo navalis L., mirrors marine climate change.

    PubMed

    Appelqvist, Christin; Havenhand, Jonathan N

    2016-06-01

    For many species, seasonal changes in key environmental variables such as food availability, light, and temperature drive the timing ("phenology") of major life-history events. Extensive evidence from terrestrial, freshwater, and marine habitats shows that global warming is changing the timings of many biological events; however, few of these studies have investigated the effects of climate change on the phenology of larval recruitment in marine invertebrates. Here, we studied temperature-related phenological shifts in the breeding season of the shipworm Teredo navalis (Mollusca, Bivalvia). We compared data for the recruitment period of T. navalis along the Swedish west coast during 2004-2006 with similar data from 1971-1973, and related differences in recruitment timing to changes in sea surface temperature over the same period. We found no significant shift in the timing of onset of recruitment over this ~30-year time span, but the end of recruitment was an average of 26 days later in recent years, leading to significantly longer recruitment periods. These changes correlated strongly with increased sea surface temperatures and coincided with published thermal tolerances for reproduction in T. navalis. Our findings are broadly comparable with other reports of phenological shifts in marine species, and suggest that warmer sea surface temperatures are increasing the likelihood of successful subannual reproduction and intensifying recruitment of T. navalis in this region.

  3. A phenological shift in the time of recruitment of the shipworm, Teredo navalis L., mirrors marine climate change.

    PubMed

    Appelqvist, Christin; Havenhand, Jonathan N

    2016-06-01

    For many species, seasonal changes in key environmental variables such as food availability, light, and temperature drive the timing ("phenology") of major life-history events. Extensive evidence from terrestrial, freshwater, and marine habitats shows that global warming is changing the timings of many biological events; however, few of these studies have investigated the effects of climate change on the phenology of larval recruitment in marine invertebrates. Here, we studied temperature-related phenological shifts in the breeding season of the shipworm Teredo navalis (Mollusca, Bivalvia). We compared data for the recruitment period of T. navalis along the Swedish west coast during 2004-2006 with similar data from 1971-1973, and related differences in recruitment timing to changes in sea surface temperature over the same period. We found no significant shift in the timing of onset of recruitment over this ~30-year time span, but the end of recruitment was an average of 26 days later in recent years, leading to significantly longer recruitment periods. These changes correlated strongly with increased sea surface temperatures and coincided with published thermal tolerances for reproduction in T. navalis. Our findings are broadly comparable with other reports of phenological shifts in marine species, and suggest that warmer sea surface temperatures are increasing the likelihood of successful subannual reproduction and intensifying recruitment of T. navalis in this region. PMID:27516852

  4. Global vegetation model diversity and the risks of climate-driven ecosystem shifts

    SciTech Connect

    Bond-Lamberty, Benjamin

    2013-11-08

    Climate change is modifying global biogeochemical cycles, and is expected to exert increasingly large effects in the future. How these changes will in turn affect and interact with the structure and function of particular ecosystems is unclear, however, both because of scientific uncertainties and the very diversity of global vegetation models in use. Writing in Environmental Research Letters, Warszawski et al. (1) aggregate results from a group of models, across a range of emissions scenarios and climate data, to investigate these risks. Although the models frequently disagree about which specific regions are at risk, they consistently predict a greater chance of ecosystem restructuring with more warming; this risk roughly doubles between 2 and 3 °C increases in global mean temperature. The innovative work of Warszawski et al. represents an important first step towards fully consistent multi-model, multi-scenario assessments of the future risks to global ecosystems.

  5. Shifts in deep-sea community structure linked to climate and food supply.

    PubMed

    Ruhl, Henry A; Smith, Kenneth L

    2004-07-23

    A major change in the community structure of the dominant epibenthic megafauna was observed at 4100 meters depth in the northeast Pacific and was synchronous to a major El Niño/La Niña event that occurred between 1997 and 1999. Photographic abundance estimates of epibenthic megafauna from 1989 to 2002 show that two taxa decreased in abundance after 1998 by 2 to 3 orders of magnitude, whereas several other species increased in abundance by 1 to 2 orders of magnitude. These faunal changes are correlated to climate fluctuations dominated by El Niño/La Niña. Megafauna even in remote marine areas appear to be affected by contemporary climatic fluctuations. Such faunal changes highlight the importance of an adequate temporal perspective in describing biodiversity, ecology, and anthropogenic impacts in deep-sea communities. PMID:15273392

  6. Climate change implications of shifting forest management strategy in a boreal forest ecosystem of Norway.

    PubMed

    Bright, Ryan M; Antón-Fernández, Clara; Astrup, Rasmus; Cherubini, Francesco; Kvalevåg, Maria; Strømman, Anders H

    2014-02-01

    Empirical models alongside remotely sensed and station measured meteorological observations are employed to investigate both the local and global direct climate change impacts of alternative forest management strategies within a boreal ecosystem of eastern Norway. Stand-level analysis is firstly executed to attribute differences in daily, seasonal, and annual mean surface temperatures to differences in surface intrinsic biophysical properties across conifer, deciduous, and clear-cut sites. Relative to a conifer site, a slight local cooling of −0.13 °C at a deciduous site and −0.25 °C at a clear-cut site were observed over a 6-year period, which were mostly attributed to a higher albedo throughout the year. When monthly mean albedo trajectories over the entire managed forest landscape were taken into consideration, we found that strategies promoting natural regeneration of coniferous sites with native deciduous species led to substantial global direct climate cooling benefits relative to those maintaining current silviculture regimes – despite predicted long-term regional warming feedbacks and a reduced albedo in spring and autumn months. The magnitude and duration of the cooling benefit depended largely on whether management strategies jointly promoted an enhanced material supply over business-as-usual levels. Expressed in terms of an equivalent CO2 emission pulse at the start of the simulation, the net climate response at the end of the 21st century spanned −8 to −159 Tg-CO2-eq., depending on whether near-term harvest levels increased or followed current trends, respectively. This magnitude equates to approximately −20 to −300% of Norway's annual domestic (production) emission impact. Our analysis supports the assertion that a carbon-only focus in the design and implementation of forest management policy in boreal and other climatically similar regions can be counterproductive – and at best – suboptimal if boreal forests are to be used as a

  7. Tropically-driven climate shifts in southwestern Europe during MIS 19, a low eccentricity interglacial

    NASA Astrophysics Data System (ADS)

    Sánchez Goñi, M. F.; Rodrigues, T.; Hodell, D. A.; Polanco-Martínez, J. M.; Alonso-García, M.; Hernández-Almeida, I.; Desprat, S.; Ferretti, P.

    2016-08-01

    The relative roles of high- versus low-latitude forcing of millennial-scale climate variability are still not well understood. Here we present terrestrial-marine climate profiles from the southwestern Iberian margin, a region particularly affected by precession, that show millennial climate oscillations related to a nonlinear response to the Earth's precession cycle during Marine Isotope Stage (MIS) 19. MIS 19 has been considered the best analogue to our present interglacial from an astronomical point of view due to the reduced eccentricity centred at 785 ka. In our records, seven millennial-scale forest contractions punctuated MIS 19 superimposed to two orbitally-driven Mediterranean forest expansions. In contrast to our present interglacial, we evidence for the first time low latitude-driven 5000-yr cycles of drying and cooling in the western Mediterranean region, along with warmth in the subtropical gyre related to the fourth harmonic of precession. These cycles indicate repeated intensification of North Atlantic meridional moisture transport that along with decrease in boreal summer insolation triggered ice growth and may have contributed to the glacial inception, at ∼774 ka. The freshwater fluxes during MIS 19ab amplified the cooling events in the North Atlantic promoting further cooling and leading to MIS 18 glaciation. The discrepancy between the dominant cyclicity observed during MIS 1, 2500-yr, and that of MIS 19, 5000-yr, challenges the similar duration of the Holocene and MIS 19c interglacials under natural boundary conditions.

  8. Climate change on the Tibetan Plateau in response to shifting atmospheric circulation since the LGM

    PubMed Central

    Zhu, Liping; Lü, Xinmiao; Wang, Junbo; Peng, Ping; Kasper, Thomas; Daut, Gerhard; Haberzettl, Torsten; Frenzel, Peter; Li, Quan; Yang, Ruimin; Schwalb, Antje; Mäusbacher, Roland

    2015-01-01

    The Tibetan Plateau (TP) is primarily influenced by the northern hemispheric middle latitude Westerlies and the Indian summer monsoon (ISM). The extent, long-distance effects and potential long-term changes of these two atmospheric circulations are not yet fully understood. Here, we analyse modern airborne pollen in a transition zone of seasonally alternating dominance of the Westerlies and the ISM to develop a pollen discrimination index (PDI) that allows us to distinguish between the intensities of the two circulation systems. This index is applied to interpret a continuous lacustrine sedimentary record from Lake Nam Co covering the past 24 cal kyr BP to investigate long-term variations in the atmospheric circulation systems. Climatic variations on the central TP widely correspond to those of the North Atlantic (NA) realm, but are controlled through different mechanisms resulting from the changing climatic conditions since the Last Glacial Maximum (LGM). During the LGM, until 16.5 cal kyr BP, the TP was dominated by the Westerlies. After 16.5 cal kyr BP, the climatic conditions were mainly controlled by the ISM. From 11.6 to 9 cal kyr BP, the TP was exposed to enhanced solar radiation at the low latitudes, resulting in greater water availability. PMID:26294226

  9. The effects of phenotypic plasticity and local adaptation on forecasts of species range shifts under climate change.

    PubMed

    Valladares, Fernando; Matesanz, Silvia; Guilhaumon, François; Araújo, Miguel B; Balaguer, Luis; Benito-Garzón, Marta; Cornwell, Will; Gianoli, Ernesto; van Kleunen, Mark; Naya, Daniel E; Nicotra, Adrienne B; Poorter, Hendrik; Zavala, Miguel A

    2014-11-01

    Species are the unit of analysis in many global change and conservation biology studies; however, species are not uniform entities but are composed of different, sometimes locally adapted, populations differing in plasticity. We examined how intraspecific variation in thermal niches and phenotypic plasticity will affect species distributions in a warming climate. We first developed a conceptual model linking plasticity and niche breadth, providing five alternative intraspecific scenarios that are consistent with existing literature. Secondly, we used ecological niche-modeling techniques to quantify the impact of each intraspecific scenario on the distribution of a virtual species across a geographically realistic setting. Finally, we performed an analogous modeling exercise using real data on the climatic niches of different tree provenances. We show that when population differentiation is accounted for and dispersal is restricted, forecasts of species range shifts under climate change are even more pessimistic than those using the conventional assumption of homogeneously high plasticity across a species' range. Suitable population-level data are not available for most species so identifying general patterns of population differentiation could fill this gap. However, the literature review revealed contrasting patterns among species, urging greater levels of integration among empirical, modeling and theoretical research on intraspecific phenotypic variation. PMID:25205436

  10. The effects of phenotypic plasticity and local adaptation on forecasts of species range shifts under climate change.

    PubMed

    Valladares, Fernando; Matesanz, Silvia; Guilhaumon, François; Araújo, Miguel B; Balaguer, Luis; Benito-Garzón, Marta; Cornwell, Will; Gianoli, Ernesto; van Kleunen, Mark; Naya, Daniel E; Nicotra, Adrienne B; Poorter, Hendrik; Zavala, Miguel A

    2014-11-01

    Species are the unit of analysis in many global change and conservation biology studies; however, species are not uniform entities but are composed of different, sometimes locally adapted, populations differing in plasticity. We examined how intraspecific variation in thermal niches and phenotypic plasticity will affect species distributions in a warming climate. We first developed a conceptual model linking plasticity and niche breadth, providing five alternative intraspecific scenarios that are consistent with existing literature. Secondly, we used ecological niche-modeling techniques to quantify the impact of each intraspecific scenario on the distribution of a virtual species across a geographically realistic setting. Finally, we performed an analogous modeling exercise using real data on the climatic niches of different tree provenances. We show that when population differentiation is accounted for and dispersal is restricted, forecasts of species range shifts under climate change are even more pessimistic than those using the conventional assumption of homogeneously high plasticity across a species' range. Suitable population-level data are not available for most species so identifying general patterns of population differentiation could fill this gap. However, the literature review revealed contrasting patterns among species, urging greater levels of integration among empirical, modeling and theoretical research on intraspecific phenotypic variation.

  11. Towards Greenland Glaciation: cumulative or abrupt transition?

    NASA Astrophysics Data System (ADS)

    Tan, Ning; Dumas, Christophe; Ladant, Jean-Baptiste; Ramstein, Gilles; Contoux, Camille

    2016-04-01

    During the mid-Pliocene warming period (3-3.3 Ma BP), global annual mean temperature is warmer by 2-3 degree than pre-industrial. Greenland ice sheet volume is supposed to be a 50% reduction compared to nowadays [Haywood et al. 2010]. Around 2.7-2.6 Ma BP, just ~ 500 kyr after the warming peak of mid-Pliocene, there is already full Greenland Glaciation [Lunt et al. 2008]. How does Greenland ice sheet evolve from a half size to a glaciation level during 3 Ma - 2.5 Ma? Data show that there is a decreasing trend of atmospheric CO2 concentration from 3 Ma to 2.5 Ma [Seki et al.2010; Bartoli et al. 2011; Martinez et al. 2015]. However, a recent study [Contoux et al. 2015] suggests that a lowering of CO2 is not sufficient to initiate a perennial glaciation on Greenland and must be combined to low summer insolation, to preserve the ice sheet during insolation maximum, suggesting a cumulative process. In order to diagnose whether the ice sheet build-up is an abrupt event or a cumulative process, we carry on, for the first time, a transient simulation of climate and ice sheet evolutions from 3 Ma to 2.5 Ma. This strategy enables to investigate waxing and waning of the ice sheet during several orbital cycles. To reach this goal, we use a tri-dimensional interpolation method designed by Ladant et al. (2014) which combines the evolution of CO2 concentration, orbital parameters and Greenland ice sheet sizes in an off-line way by interpolating snapshots simulations. Thanks to this new method, we can build a transient like simulation through asynchronous coupling between GCM and ice sheet model. With this method, we may consistently answer the question of the build-up of Greenland: abrupt or cumulative process.

  12. Projected shifts in Köppen climate zones over China and their temporal evolution in CMIP5 multi-model simulations

    NASA Astrophysics Data System (ADS)

    Chan, Duo; Wu, Qigang; Jiang, Guixiang; Dai, Xianglin

    2016-03-01

    Previous studies have examined the projected climate types in China by 2100. This study identified the emergence time of climate shifts at a 1◦ scale over China from 1990 to 2100 and investigated the temporal evolution of Köppen-Geiger climate classifications computed from CMIP5 multi-model outputs. Climate shifts were detected in transition regions (7%-8% of China's land area) by 2010, including rapid replacement of mixed forest (Dwb) by deciduous forest (Dwa) over Northeast China, strong shrinkage of alpine climate type (ET) on the Tibetan Plateau, weak northward expansion of subtropical winterdry climate (Cwa) over Southeast China, and contraction of oceanic climate (Cwb) in Southwest China. Under all future RCP (Representative Concentration Pathway) scenarios, the reduction of Dwb in Northeast China and ET on the Tibetan Plateau was projected to accelerate substantially during 2010-30, and half of the total area occupied by ET in 1990 was projected to be redistributed by 2040. Under the most severe scenario (RCP8.5), sub-polar continental winter dry climate over Northeast China would disappear by 2040-50, ET on the Tibetan Plateau would disappear by 2070, and the climate types in 35.9% and 50.8% of China's land area would change by 2050 and 2100, respectively. The results presented in this paper indicate imperative impacts of anthropogenic climate change on China's ecoregions in future decades.

  13. Climate regime shifts in paleoclimate time series from the Yucatán Peninsula: from the Preclassic to Classic period

    NASA Astrophysics Data System (ADS)

    Polanco Martínez, Josue M.; Medina-Elizalde, Martin; Burns, Stephen J.; Jiang, Xiuyang; Shen, Chuan-Chou

    2015-04-01

    It has been widely accepted by the paleoclimate and archaeology communities that extreme climate events (especially droughts) and past climate change played an important role in the cultural changes that occurred in at least some parts of the Maya Lowlands, from the Pre-Classic (2000 BC to 250 AD) to Post-Classic periods (1000 to 1521 AD) [1, 2]. In particular, a large number of studies suggest that the decline of the Maya civilization in the Terminal Classic Period was greatly influenced by prolonged severe drought events that probably triggered significant societal disruptions [1, 3, 4, 5]. Going further on these issues, the aim of this work is to detect climate regime shifts in several paleoclimate time series from the Yucatán Peninsula (México) that have been used as rainfall proxies [3, 5, 6, 7]. In order to extract information from the paleoclimate data studied, we have used a change point method [8] as implemented in the R package strucchange, as well as the RAMFIT method [9]. The preliminary results show for all the records analysed a prominent regime shift between 400 to 200 BCE (from a noticeable increase to a remarkable fall in precipitation), which is strongest in the recently obtained stalagmite (Itzamna) delta18-O precipitation record [7]. References [1] Gunn, J. D., Matheny, R. T., Folan, W. J., 2002. Climate-change studies in the Maya area. Ancient Mesoamerica, 13(01), 79-84. [2] Yaeger, J., Hodell, D. A., 2008. The collapse of Maya civilization: assessing the interaction of culture, climate, and environment. El Niño, Catastrophism, and Culture Change in Ancient America, 197-251. [3] Hodell, D. A., Curtis, J. H., Brenner, M., 1995. Possible role of climate in the collapse of Classic Maya civilization. Nature, 375(6530), 391-394. [4] Aimers, J., Hodell, D., 2011. Societal collapse: Drought and the Maya. Nature 479(7371), 44-45 (2011). [5] Medina-Elizalde, M., Rohling, E. J., 2012. Collapse of Classic Maya civilization related to modest reduction

  14. Climate-driven regime shifts in the biological communities of arctic lakes

    PubMed Central

    Smol, John P.; Wolfe, Alexander P.; Birks, H. John B.; Douglas, Marianne S. V.; Jones, Vivienne J.; Korhola, Atte; Pienitz, Reinhard; Rühland, Kathleen; Sorvari, Sanna; Antoniades, Dermot; Brooks, Stephen J.; Fallu, Marie-Andrée; Hughes, Mike; Keatley, Bronwyn E.; Laing, Tamsin E.; Michelutti, Neal; Nazarova, Larisa; Nyman, Marjut; Paterson, Andrew M.; Perren, Bianca; Quinlan, Roberto; Rautio, Milla; Saulnier-Talbot, Émilie; Siitonen, Susanna; Solovieva, Nadia; Weckström, Jan

    2005-01-01

    Fifty-five paleolimnological records from lakes in the circumpolar Arctic reveal widespread species changes and ecological reorganizations in algae and invertebrate communities since approximately anno Domini 1850. The remoteness of these sites, coupled with the ecological characteristics of taxa involved, indicate that changes are primarily driven by climate warming through lengthening of the summer growing season and related limnological changes. The widespread distribution and similar character of these changes indicate that the opportunity to study arctic ecosystems unaffected by human influences may have disappeared. PMID:15738395

  15. Coherent late-Holocene climate-driven shifts in the structure of three Rocky Mountain lakes

    USGS Publications Warehouse

    Stone, Jeffery R.; Saros, Jasmine E.; Pederson, Gregory T.

    2016-01-01

    Large-scale atmospheric pressure centers, such as the Aleutian and Icelandic Low, have a demonstrated relationship with physical lake characteristics in contemporary monitoring studies, but the responses to these phenomena are rarely observed in lake records. We observe coherent changes in the stratification patterns of three deep (>30 m) lakes inferred from fossil diatom assemblages as a response to shifts in the location and intensity of the Aleutian Low and compare these changes with similar long-term changes observed in the δ18O record from the Yukon. Specifically, these records indicate that between 3.2 and 1.4 ka, the Aleutian Low shifted westward, resulting in an increased frequency of storm tracks across the Pacific Northwest during winter and spring. This change in atmospheric circulation ultimately produced deeper mixing in the upper waters of these three lake systems. Enhanced stratification between 4.5 and 3.3 ka and from 1.3 ka to present suggests a strengthened Aleutian Low and more meridional circulation.

  16. Climate Change and Eutrophication Induced Shifts in Northern Summer Plankton Communities

    PubMed Central

    Suikkanen, Sanna; Pulina, Silvia; Engström-Öst, Jonna; Lehtiniemi, Maiju; Lehtinen, Sirpa; Brutemark, Andreas

    2013-01-01

    Marine ecosystems are undergoing substantial changes due to human-induced pressures. Analysis of long-term data series is a valuable tool for understanding naturally and anthropogenically induced changes in plankton communities. In the present study, seasonal monitoring data were collected in three sub-basins of the northern Baltic Sea between 1979 and 2011 and statistically analysed for trends and interactions between surface water hydrography, inorganic nutrient concentrations and phyto- and zooplankton community composition. The most conspicuous hydrographic change was a significant increase in late summer surface water temperatures over the study period. In addition, salinity decreased and dissolved inorganic nutrient concentrations increased in some basins. Based on redundancy analysis (RDA), warming was the key environmental factor explaining the observed changes in plankton communities: the general increase in total phytoplankton biomass, Cyanophyceae, Prymnesiophyceae and Chrysophyceae, and decrease in Cryptophyceae throughout the study area, as well as increase in rotifers and decrease in total zooplankton, cladoceran and copepod abundances in some basins. We conclude that the plankton communities in the Baltic Sea have shifted towards a food web structure with smaller sized organisms, leading to decreased energy available for grazing zooplankton and planktivorous fish. The shift is most probably due to complex interactions between warming, eutrophication and increased top-down pressure due to overexploitation of resources, and the resulting trophic cascades. PMID:23776676

  17. Climate change and eutrophication induced shifts in northern summer plankton communities.

    PubMed

    Suikkanen, Sanna; Pulina, Silvia; Engström-Öst, Jonna; Lehtiniemi, Maiju; Lehtinen, Sirpa; Brutemark, Andreas

    2013-01-01

    Marine ecosystems are undergoing substantial changes due to human-induced pressures. Analysis of long-term data series is a valuable tool for understanding naturally and anthropogenically induced changes in plankton communities. In the present study, seasonal monitoring data were collected in three sub-basins of the northern Baltic Sea between 1979 and 2011 and statistically analysed for trends and interactions between surface water hydrography, inorganic nutrient concentrations and phyto- and zooplankton community composition. The most conspicuous hydrographic change was a significant increase in late summer surface water temperatures over the study period. In addition, salinity decreased and dissolved inorganic nutrient concentrations increased in some basins. Based on redundancy analysis (RDA), warming was the key environmental factor explaining the observed changes in plankton communities: the general increase in total phytoplankton biomass, Cyanophyceae, Prymnesiophyceae and Chrysophyceae, and decrease in Cryptophyceae throughout the study area, as well as increase in rotifers and decrease in total zooplankton, cladoceran and copepod abundances in some basins. We conclude that the plankton communities in the Baltic Sea have shifted towards a food web structure with smaller sized organisms, leading to decreased energy available for grazing zooplankton and planktivorous fish. The shift is most probably due to complex interactions between warming, eutrophication and increased top-down pressure due to overexploitation of resources, and the resulting trophic cascades. PMID:23776676

  18. Optimal forcing of ENSO either side of the 1970's climate shift and its implications for predictability

    NASA Astrophysics Data System (ADS)

    Aiken, Christopher M.; Santoso, Agus; McGregor, Shayne; England, Matthew H.

    2015-07-01

    Inverse methods are used to investigate changes in the precursors to El Niño Southern Oscillation (ENSO) events since the so-called 1970's climate shift, associated with a change in the phase of the Interdecadal Pacific Oscillation (IPO). Linear Inverse Models (LIMs) constructed from tropical sea surface temperature, thermocline depth and zonal wind stress anomalies from each of the periods 1959-1978 and 1979-1998, are able to reproduce the major observed characteristics of ENSO, including its amplitude, frequency and time evolution. Each LIM possesses low-frequency and biennial ENSO modes, the former being both the least damped and the mode responsible for strongest pseudoresonance, as quantified via calculation of the resolvent norm. Because these modes are damped, ENSO variability is sustained in the stochastically forced LIMs by transiently growing perturbations, and predictability is determined by the character of the transiently growing subspace of perturbations. The optimal linear precursor over any given lead time is equivalent to the optimal perturbation of the LIM, that represents the most rapidly growing linear perturbation over that timescale. In both periods linear ENSO growth occurs through one of two trajectories associated with the 7 and 15 month optimal perturbations. The structure of these two optimal perturbations change significantly between the two periods, and their ability to predict ENSO degrades dramatically when applied to the alternate period. This suggests that ENSO precursors changed following the 1970s climate shift over both 7 and 15 month time-scales. In particular, while prior to the climate shift the heat content of the equatorial Pacific alone is a skillful ENSO predictor on 7 month lead times, afterwards Indian and south Atlantic sea surface temperature anomalies are inferred to have become important. Optimal ENSO growth over 15 months also contains a significant extra-Pacific contribution, and it is possible to skillfully

  19. Varied response of western Pacific hydrology to climate forcings over the last glacial period.