scholarly journals Multiproxy paleoceanographic study from the western Barents Sea reveals dramatic Younger Dryas onset followed by oscillatory warming trend

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Magdalena Łącka ◽  
Danuta Michalska ◽  
Joanna Pawłowska ◽  
Natalia Szymańska ◽  
Witold Szczuciński ◽  
...  
Keyword(s):  
Barents Sea ◽  
Younger Dryas ◽  
Warming Trend ◽  
Sharp Reduction ◽  
Gravity Core ◽  
Proxy Data ◽  
Cool Period ◽  
Anoxic Conditions ◽  
Reducing Conditions ◽  
The Last Glacial

Abstract The Younger Dryas (YD) is recognized as a cool period that began and ended abruptly during a time of general warming at the end of the last glacial. New multi-proxy data from a sediment gravity core from Storfjordrenna (western Barents Sea, 253 m water depth) reveals that the onset of the YD occurred as a single short-lived dramatic environment deterioration, whereas the subsequent warming was oscillatory. The water masses in the western Barents Sea were likely strongly stratified at the onset of the YD, possibly due to runoff of meltwater combined with perennial sea-ice cover, the latter may last up to several decades without any brake-up. Consequently, anoxic conditions prevailed at the bottom of Storfjordrenna, leading to a sharp reduction of benthic biota and the appearance of vivianite microconcretions which formation is favoured by reducing conditions. While the anoxic conditions in Storfjordrenna were transient, the unfavorable conditions for benthic foraminifera lasted for c. 1300 years. We suggest that the Pre-Boreal Oscillation, just after the onset of the Holocene, may have been a continuation of the oscillatory warming trend during the YD.

scholarly journals Climate of the last glacial maximum: sensitivity studies and model-data comparison with the LOVECLIM coupled model

2006 ◽  
Vol 2 (6) ◽  
pp. 1105-1153 ◽  
Author(s):  
D. M. Roche ◽  
T. M. Dokken ◽  
H. Goosse ◽  
H. Renssen ◽  
S. L. Weber
Keyword(s):  
Last Glacial Maximum ◽  
Glacial Maximum ◽  
Future Climate Change ◽  
Oceanic Circulation ◽  
Coupled Models ◽  
Proxy Data ◽  
Last Glacial ◽  
The Last Glacial Maximum ◽  
Last Glacial Maximum Climate ◽  
The Last Glacial

Abstract. The Last Glacial Maximum climate is one of the classic benchmarks used both to test the ability of coupled models to simulate climates different from that ot the present-day and to better understand the possible range of mechanisms that could be involved in future climate change. It also bears the advantage of being one of the most well documented periods with respect to palaeoclimatic records, allowing a thorough data-model comparison. We present here an ensemble of Last Glacial Maximum climate simulations obtained with the Earth System model LOVECLIM, including coupled dynamic atmosphere, ocean and vegetation components. The climate obtained using standard parameter values is then compared to available proxy data for the surface ocean, vegetation, oceanic circulation and atmospheric conditions. Interestingly, the oceanic circulation obtained resembles that of the present-day, but with increased overturning rates. As this result is in contradiction with the "classic" palaeoceanographic view, we ran a range of sensitivity experiments to explore the response of the model and the possibilities for other oceanic circulation states. After a critical review of our LGM state with respect to available proxy data, we conclude that the balance between water masses obtained is consistent with the available data although the specific characteristics (temperature, salinity) are not in full agreement. The consistency of the simulated state is further reinforced by the fact that the mean surface climate obtained is shown to be generally in agreement with the most recent reconstructions of vegetation and sea surface temperatures, even at regional scales.

scholarly journals PETROFYZIKÁLNÍ CHARAKTERISTIKA SPRAŠE A FOSILNÍ PŮDY V HLINÍKU U LITOVLE

2018 ◽  
Vol 25 (1-2) ◽  
Author(s):  
Daniel Šimíček ◽  
Vendula Krulová
Keyword(s):  
Magnetic Susceptibility ◽  
Geochemical Data ◽  
Total Thickness ◽  
Soil Horizons ◽  
Proxy Data ◽  
The Czech Republic ◽  
Loess Deposit ◽  
Paleoclimatic Proxy ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Loess-paleosol sequences are an important source of terrestrial paleoclimatic proxy-data. Quaternary loess and loess loam cover the most of surface of the Upper Moravian Basin. Samples from loess-paleosol sequence in vicinity of Litovel town were studied using magnetic susceptibility, spectrophotometry and laser granulometry. Obtained petrophysical data were compared with detailed lithological description of section and geochemical characteristics determined by ED-XRF method. The results contribute to interpretation of paleoclimate in the Upper Moravian Basin during the last glacial.Section with total thickness of about 5 m is formed by loess in its upper part. This layer covers several soil horizons. It is most probably youngest loess deposit formed during the last glacial maximum. Petrophysical and geochemical data and comparison with nearby sites indicate relatively humid cold tundra conditions with bush-steppe vegetation during deposition of loess. Lithological features, position below youngest loess deposit and petrophysical and geochemical data allow interpretation of soil horizons as PK I. Low values of magnetic susceptibility indicate formation of soil in arctic interstadial conditions with higher humidity compared to interstadial average. Values of magnetic susceptibility of PK I are equal or even lower than in overlaying loess which doesn´t correspond with usual behaviour of magnetic susceptibility in loess-paleosol sequences in the Czech Republic. It could be explained by formation of soil horizons in cold interstadial climate (low production of oxi/hydroxide of Fe) supplemented by increased humidity and hence, intensive illimerization process (clay migration and Fe-minerals depletion).

scholarly journals Timing and structure of the Younger Dryas event and its underlying climate dynamics

2020 ◽  
Vol 117 (38) ◽  
pp. 23408-23417
Author(s):  
Hai Cheng ◽  
Haiwei Zhang ◽  
Christoph Spötl ◽  
Jonathan Baker ◽  
Ashish Sinha ◽  
...  
Keyword(s):  
Southern Hemisphere ◽  
North Atlantic ◽  
Time Scale ◽  
Asian Monsoon ◽  
Younger Dryas ◽  
Tropical Pacific ◽  
Last Glacial ◽  
The North ◽  
The North Atlantic ◽  
The Last Glacial

The Younger Dryas (YD), arguably the most widely studied millennial-scale extreme climate event, was characterized by diverse hydroclimate shifts globally and severe cooling at high northern latitudes that abruptly punctuated the warming trend from the last glacial to the present interglacial. To date, a precise understanding of its trigger, propagation, and termination remains elusive. Here, we present speleothem oxygen-isotope data that, in concert with other proxy records, allow us to quantify the timing of the YD onset and termination at an unprecedented subcentennial temporal precision across the North Atlantic, Asian Monsoon-Westerlies, and South American Monsoon regions. Our analysis suggests that the onsets of YD in the North Atlantic (12,870 ± 30 B.P.) and the Asian Monsoon-Westerlies region are essentially synchronous within a few decades and lead the onset in Antarctica, implying a north-to-south climate signal propagation via both atmospheric (decadal-time scale) and oceanic (centennial-time scale) processes, similar to the Dansgaard–Oeschger events during the last glacial period. In contrast, the YD termination may have started first in Antarctica at ∼11,900 B.P., or perhaps even earlier in the western tropical Pacific, followed by the North Atlantic between ∼11,700 ± 40 and 11,610 ± 40 B.P. These observations suggest that the initial YD termination might have originated in the Southern Hemisphere and/or the tropical Pacific, indicating a Southern Hemisphere/tropics to North Atlantic–Asian Monsoon-Westerlies directionality of climatic recovery.

scholarly journals Revisions and Extension of the Hohenheim Oak and Pine Chronologies: New Evidence About the Timing of the Younger Dryas/Preboreal Transition

Radiocarbon ◽  
1998 ◽  
Vol 40 (3) ◽  
pp. 1107-1116 ◽  
Author(s):  
Marco Spurk ◽  
Michael Friedrich ◽  
Jutta Hofmann ◽  
Sabine Remmele ◽  
Burkhard Frenzel ◽  
...  
Keyword(s):  
Calibration Curve ◽  
Younger Dryas ◽  
Ice Cores ◽  
Early Holocene ◽  
Proxy Data ◽  
The Past ◽  
Varve Chronology ◽  
New Evidence ◽  
Radiocarbon Calibration

Oak and pine samples housed at the Institute of Botany, University of Hohenheim, are the backbone of the early Holocene part of the radiocarbon calibration curve, published in 1993 (Becker 1993; Kromer and Becker 1993; Stuiver and Becker 1993; Vogel et al. 1993). Since then the chronologies have been revised. The revisions include 1) the discovery of 41 missing years in the oak chronology and 2) a shift of 54 yr for the oldest part back into the past. The oak chronology was also extended with new samples as far back as 10,429 BP (8480 BC). In addition, the formerly tentatively dated pine chronology (Becker 1993) has been rebuilt and shifted to an earlier date. It is now positioned by 14C matching at 11,871-9900 BP (9922–7951 BC) with an uncertainty of ±20 yr (Kromer and Spurk 1998). With these new chronologies the 14C calibration curve can now be corrected, eliminating the discrepancy in the dating of the Younger Dryas/Preboreal transition between the proxy data of the GRIP and GISP ice cores (Johnsen et al. 1992; Taylor et al. 1993), the varve chronology of Lake Gościąż (Goslar et al. 1995) and the pine chronology (Becker, Kromer and Trimborn 1991).

Methane hydrate mobilization by ice stream erosion during the last glacial

2020 ◽  
Author(s):  
Pavel Serov ◽  
Henry Patton ◽  
Malin Waage ◽  
Calvin Shackleton ◽  
Jurgen Mienert ◽  
...  
Keyword(s):  
Gas Hydrate ◽  
Methane Hydrate ◽  
Barents Sea ◽  
Ice Sheet ◽  
Permafrost Degradation ◽  
Last Glacial ◽  
The Barents Sea ◽  
Ice Stream ◽  
Geophysical Imaging ◽  
The Last Glacial

<p>During the past ~2.6 Ma, some 30 glaciations have caused episodic high pressure and low temperature conditions and forced growth and decay of extensive subglacial methane hydrate accumulations globally. Research on Arctic methane release has primarily focused on warm, interglacial episodes when hydrates became unstable across territories either abandoned by former ice sheets or affected by permafrost degradation. Here we present a new mechanism – the subglacial erosion of gas hydrate-bearing sediments – that actively mobilizes methane in hydrate and dissolved form and delivers it to the ice sheet margin. We investigate this mechanism using geophysical imaging and ice sheet/gas hydrate modeling focused on a study site in Storfjordrenna, that hosted large ice stream draining the Barents Sea ice sheet. During the last glacial, we find that this ice stream overrode an extensive cluster of conduits that supplied a continuous methane flux from a deep, thermogenic source and delivered it to the subglacial environment. Our analysis reveals that 15,000 to 44,000 m<sup>3</sup> of gas hydrates were subglacially eroded from the 17 km<sup>2</sup> study site and transported to the shelf-edge. Given the abundance of natural gas reservoirs across the Barents Sea and marine-based glaciated petroleum provinces elsewhere, we propose that this mechanism had the potential to mobilize a substantial flux of subglacial methane throughout multiple Quaternary glacial episodes.</p>

scholarly journals A new global reconstruction of temperature changes at the Last Glacial Maximum

2013 ◽  
Vol 9 (1) ◽  
pp. 367-376 ◽  
Author(s):  
J. D. Annan ◽  
J. C. Hargreaves
Keyword(s):  
Last Glacial Maximum ◽  
Climate Models ◽  
State Of The Art ◽  
Glacial Maximum ◽  
Proxy Data ◽  
Temperature Changes ◽  
Last Glacial ◽  
The Last Glacial Maximum ◽  
Global Mean ◽  
The Last Glacial

Abstract. Some recent compilations of proxy data both on land and ocean (MARGO Project Members, 2009; Bartlein et al., 2011; Shakun et al., 2012), have provided a new opportunity for an improved assessment of the overall climatic state of the Last Glacial Maximum. In this paper, we combine these proxy data with the ensemble of structurally diverse state of the art climate models which participated in the PMIP2 project (Braconnot et al., 2007) to generate a spatially complete reconstruction of surface air (and sea surface) temperatures. We test a variety of approaches, and show that multiple linear regression performs well for this application. Our reconstruction is significantly different to and more accurate than previous approaches and we obtain an estimated global mean cooling of 4.0 ± 0.8 °C (95% CI).

scholarly journals An improved land biosphere module for use in reduced complexity Earth System Models with application to the last glacial termination

2017 ◽  
Author(s):  
Roland Eichinger ◽  
Gary Shaffer ◽  
Nelson Albarrán ◽  
Maisa Rojas ◽  
Fabrice Lambert
Keyword(s):  
Carbon Cycling ◽  
Climatic Conditions ◽  
Cold Climate ◽  
Earth System ◽  
Proxy Data ◽  
Last Glacial ◽  
Transition Functions ◽  
Vegetation Zones ◽  
Reduced Complexity ◽  
The Last Glacial

Abstract. Interactions between the land biosphere and the atmosphere play an important role for the Earth's carbon cycle and thus should be considered in studies of global carbon cycling and climate. Simple approaches are a useful first step in this direction but may not be applicable for certain climatic conditions. To improve the ability of the reduced-complexity Danish Center for Earth System Science (DCESS) Earth System Model DCESS to address cold climate conditions, we reformulated the model's land biosphere module by extending it to include three dynamically varying vegetation zones as well as a permafrost component. The vegetation zones are formulated by emulating the behavior of a complex land biosphere model. We show that with the new module, the size and timing of carbon exchanges between atmosphere and land are represented more realistically in cooling and warming experiments. In particular, we use the new module to address carbon cycling and climate change across the last glacial transition. Within the constraints provided by various proxy data records, we tune the DCESS model to a Last Glacial Maximum state and then conduct transient sensitivity experiments across the transition under the application of explicit transition functions for high latitude ocean exchange, atmospheric dust, and the land ice sheet extent. We compare simulated time evolutions of global mean temperature, pCO2, atmospheric and oceanic carbon isotopes as well as ocean dissolved oxygen concentrations with proxy data records. In this way we estimate the importance of different processes across the transition with emphasis on the role of land biosphere variations.

Late Pleistocene environments of the Bighorn Basin, Wyoming-Montana, USA

2020 ◽  
pp. 1-14
Author(s):  
Thomas A. Minckley ◽  
Mark Clementz ◽  
Marcel Kornfeld ◽  
Mary Lou Larson ◽  
Judson B. Finley
Keyword(s):  
Late Pleistocene ◽  
Environmental Changes ◽  
Isotope Analysis ◽  
Younger Dryas ◽  
Ecological Change ◽  
Bighorn Basin ◽  
Bulk Organic Matter ◽  
Intermontane Basins ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Abstract Limited numbers of high-resolution records predate the Last Glacial Maximum (LGM) making it difficult to quantify the impacts of environmental changes prior to peak glaciation. We examined sediments from Last Canyon Cave in the Pryor Mountains of Montana and Wyoming to construct a >45 ka environmental record from pollen and stable isotope analysis. Artemisia pollen was hyper-abundant at the beginning of the record. Carbon isotope values of bulk organic matter (>40 ka) showed little variation (-25.3 ± 0.4‰) and were consistent with a arid C3 environment, similar to today. After 40 cal ka BP, Artemisia pollen decreased as herbaceous taxa increased toward the LGM. A significant decrease in δ13C values from 40–30 cal ka BP (~1.0‰) established a new baseline (-26.6 ± 0.2‰), suggesting cooler, seasonally wetter conditions prior to the LGM. These conditions persisted until variation in δ13C values increased significantly with post-glacial warming, marked by two spikes in values at 14.4 (-25.2‰) and 13.5 cal ka BP (-25.4‰) before δ13C values dropped to their lowest values (-26.9 ± 0.2‰) at the onset of the Younger Dryas (12.8 ka). These results provide insights into late Pleistocene conditions and ecological change in arid intermontane basins of the Rocky Mountains.

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