Timescale-dependent responses of hydrological changes from global closed basins since the last glacial maximum

2021 ◽  
pp. 030913332110519
Author(s):  
Xinzhong Zhang ◽  
Yu Li ◽  
Qin Han ◽  
Yuxin Zhang
Keyword(s):  
Last Glacial Maximum ◽  
Glacial Maximum ◽  
Ice Age ◽  
Last Glacial ◽  
Future Global Warming ◽  
Precipitation Seasonality ◽  
Cold Events ◽  
Closed Basins ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Water shortage has plagued the social development and human well-being of global closed basins. However, the hydroclimate research on different time scales in these regions remains inadequate at a global scale. In this paper, the hydrological responses from global closed basins to millennial-scale and centennial-scale cold/warm events since the Last Glacial Maximum were explored. Closed-basin lake records indicate that the westerlies-dominated closed basins are generally wetter during cold events than the corresponding warm ones on the millennial and centennial scales. In contrast, the monsoon-influenced closed basins prevail wetter climates during warm events. According to the hydroclimate simulations, precipitation seasonality plays a significant role in causing above spatial–temporal patterns. There is more winter rainfall in westerlies-dominated closed basins during cold events in the Last Glacial Maximum and Little Ice Age and more summer rainfall in monsoon-influenced closed basins during warm events in the mid-Holocene and Medieval Climate Anomaly. Under modern and future global warming, the hydroclimate changes in global closed basins show more regional differentiation, resulting in wetter mid-latitude Asian and low-latitude African closed basins but drier southwest North American and Australian closed basins.

Reconstructions of the past distribution of Testudo graeca mitochondrial lineages in the Middle East and Transcaucasia support multiple refugia since the Last Glacial Maximum

2021 ◽  
pp. 10-17
Author(s):  
Oguz Turkozan
Keyword(s):  
Middle East ◽  
Last Glacial Maximum ◽  
Glacial Maximum ◽  
Testudo Graeca ◽  
Last Glacial ◽  
The Past ◽  
Precipitation Seasonality ◽  
Multiple Refugia ◽  
The Last Glacial Maximum ◽  
The Last Glacial

A cycle of glacial and interglacial periods in the Quaternary caused species’ ranges to expand and contract in response to climatic and environmental changes. During interglacial periods, many species expanded their distribution ranges from refugia into higher elevations and latitudes. In the present work, we projected the responses of the five lineages of Testudo graeca in the Middle East and Transcaucasia as the climate shifted from the Last Glacial Maximum (LGM, Mid – Holocene), to the present. Under the past LGM and Mid-Holocene bioclimatic conditions, models predicted relatively more suitable habitats for some of the lineages. The most significant bioclimatic variables in predicting the present and past potential distribution of clades are the precipitation of the warmest quarter for T. g. armeniaca (95.8 %), precipitation seasonality for T. g. buxtoni (85.0 %), minimum temperature of the coldest month for T. g. ibera (75.4 %), precipitation of the coldest quarter for T. g. terrestris (34.1 %), and the mean temperature of the driest quarter for T. g. zarudyni (88.8 %). Since the LGM, we hypothesise that the ranges of lineages have either expanded (T. g. ibera), contracted (T. g. zarudnyi) or remained stable (T. g. terrestris), and for other two taxa (T. g. armeniaca and T. g. buxtoni) the pattern remains unclear. Our analysis predicts multiple refugia for Testudo during the LGM and supports previous hypotheses about high lineage richness in Anatolia resulting from secondary contact.

scholarly journals Constant wind regimes during the Last Glacial Maximum and early Holocene: evidence from Little Llangothlin Lagoon, New England Tablelands, eastern Australia

2016 ◽  
Vol 12 (7) ◽  
pp. 1435-1444 ◽  
Author(s):  
James Shulmeister ◽  
Justine Kemp ◽  
Kathryn E. Fitzsimmons ◽  
Allen Gontz
Keyword(s):  
Last Glacial Maximum ◽  
High Elevation ◽  
Glacial Maximum ◽  
Early Holocene ◽  
Luminescence Dating ◽  
Ice Age ◽  
Last Glacial ◽  
Eastern Australia ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Abstract. Here we present the results of a multi-proxy investigation – integrating geomorphology, ground-penetrating radar, and luminescence dating – of a high-elevation lunette and beach berm in northern New South Wales, eastern Australia. The lunette occurs on the eastern shore of Little Llangothlin Lagoon and provides evidence for a lake high stand combined with persistent westerly winds at the Last Glacial Maximum (LGM – centring on 21.5 ka) and during the early Holocene (ca. 9 and 6 ka). The reconstructed atmospheric circulation is similar to the present-day conditions, and we infer no significant changes in circulation at those times, as compared to the present day. Our results suggest that the Southern Hemisphere westerlies were minimally displaced in this sector of Australasia during the latter part of the last ice age. Our observations also support evidence for a more positive water balance at the LGM and early Holocene in this part of the Australian sub-tropics.

Northern-sourced water dominated the Atlantic Ocean during the Last Glacial Maximum

Geology ◽  
2020 ◽  
Vol 48 (8) ◽  
pp. 826-829 ◽  
Author(s):  
F. Pöppelmeier ◽  
P. Blaser ◽  
M. Gutjahr ◽  
S.L. Jaccard ◽  
M. Frank ◽  
...  
Keyword(s):  
Last Glacial Maximum ◽  
Water Mass ◽  
Stable Carbon Isotope ◽  
Glacial Maximum ◽  
Meridional Overturning Circulation ◽  
Ice Age ◽  
Δ13c Values ◽  
Last Glacial ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Abstract Increased carbon sequestration in the ocean subsurface is commonly assumed to have been one of the main causes responsible for lower glacial atmospheric CO2 concentrations. Remineralized carbon must have been stored away from the atmosphere for thousands of years, yet the water mass structure accommodating such increased carbon storage continues to be debated. Here, we present new sediment-derived bottom-water neodymium isotope records that allow fingerprinting of water masses and provide a more complete picture of the Atlantic Meridional Overturning Circulation geometry during the Last Glacial Maximum. These results suggest that the vertical and meridional structure of the Atlantic water mass distribution only experienced minor changes since the last ice age. In particular, we find no compelling evidence supporting glacial southern-sourced water substantially expanding to shallower depths and farther into the Northern Hemisphere than today, which had been previously inferred from stable carbon isotope (δ13C) reconstructions. We argue that depleted δ13C values observed in the deep Northwest Atlantic do not necessarily indicate the presence of southern-sourced water. Instead, these values may represent a northern-sourced water mass with lower than modern preformed δ13C values that were further modified downstream by increased sequestration of remineralized carbon, facilitated by a more sluggish glacial deep circulation, corroborating previous evidence.

Northern Sourced Water dominated the Atlantic Ocean during the Last Glacial Maximum

2020 ◽  
Author(s):  
Frerk Pöppelmeier ◽  
Patrick Blaser ◽  
Marcus Gutjahr ◽  
Samuel Jaccard ◽  
Martin Frank ◽  
...  
Keyword(s):  
Carbon Storage ◽  
Last Glacial Maximum ◽  
Water Mass ◽  
Stable Carbon Isotope ◽  
Deep Ocean ◽  
Glacial Maximum ◽  
Ice Age ◽  
Last Glacial ◽  
The Last Glacial Maximum ◽  
The Last Glacial

<p>Increased carbon sequestration in the ocean subsurface is commonly assumed to have been one of the main causes responsible for lower glacial atmospheric CO<sub>2</sub> concentrations. This carbon must have been stored away from the atmosphere for thousands of years, yet the water mass structure accommodating such increased carbon storage continues to be debated. Here we present new sediment derived bottom water neodymium isotope data that allow fingerprinting of water masses and their mixtures and provide a more complete picture of the Atlantic overturning circulation geometry during the Last Glacial Maximums. These results suggest that the vertical and meridional structure of the Atlantic deep water mass distribution only experienced minor changes since the last ice age. In particular, we find no compelling evidence supporting glacial southern sourced water substantially expanding to shallower depths and farther into the northern hemisphere than today, which has been inferred from stable carbon isotope reconstructions. We argue that depleted δ<sup>13</sup>C values observed in the deep Northwest Atlantic do not necessarily indicate the presence of southern sourced water. Instead, these values may represent a northern sourced water mass with lower than modern preformed δ<sup>13</sup>C values that were further modified downstream by increased sequestration of remineralized carbon, facilitated by a more sluggish glacial deep circulation. If proven to be correct, the glacial water mass structure inferred from Nd isotopes has profound implications on our understanding of the deep ocean carbon storage during the Last Glacial Maximum.</p>

scholarly journals Ice-age ice-sheet rheology: constraints from the Last Glacial Maximum form of the Laurentide ice sheet

2000 ◽  
Vol 30 ◽  
pp. 163-176 ◽  
Author(s):  
W. Richard Peltier ◽  
David L. Goldsby ◽  
David L. Kohlstedt ◽  
Lev Tarasov
Keyword(s):  
Last Glacial Maximum ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Glacial Maximum ◽  
Ice Age ◽  
Laurentide Ice Sheet ◽  
Last Glacial ◽  
Flow Law ◽  
The Last Glacial Maximum ◽  
The Last Glacial

AbstractState-of-the-art thermomechanical models of the modern Greenland ice sheet and the ancient Laurentide ice sheet that covered Canada at the Last Glacial Maximum (LGM) are not able to explain simultaneously the observed forms of these cryospheric structures when the same, anisotropy-enhanced, version of the conventional Glen flow law is employed to describe their rheology. The LGM Laurentide ice sheet, predicted to develop in response to orbital climate forcing, is such that the ratio of its thickness to its horizontal extent is extremely large compared to the aspect ratio inferred on the basis of surface-geomorphological and solid-earth-geophysical constraints. We show that if the Glen flow law representation of the rheology is replaced with a new rheology based upon very high quality laboratory measurements of the stress-strain-rate relation then the aspect ratios of both the modern Greenland ice sheet and the Laurentide ice sheet, that existed at the LGM, are simultaneously explained with little or no retuning of the flow law.

scholarly journals Surface geometry of the Last Glacial Maximum (LGM) in the southeastern Swiss Alps (Graubünden) and its paleoclimatological significance

1998 ◽  
Vol 48 (1) ◽  
pp. 23-37 ◽  
Author(s):  
Duri Florineth
Keyword(s):  
Last Glacial Maximum ◽  
Storm Track ◽  
Glacial Maximum ◽  
Swiss Alps ◽  
Geographical Information ◽  
Ice Age ◽  
Surface Geometry ◽  
Last Glacial ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Abstract. Using detailed field evidence provided by trimlines on former nunataks, erratic boulders and the orientations of glacial striae, the surface geometry in the accumulation area during the Last Glacial Maximum was reconstructed for the area of SE Switzerland and adjacent Italy. Collectively, the trends of trimline elevations, flowlines deduced from glacial striae and bedrock morphology along the longitudinal valleys and their tributaries indicate that the former accumulation area consisted of an ice dome with the ice divide located over the area enclosed by Schlarignia, Cinuos-chel, Livigno and Piz Bernina. It attained a minimum altitude of approximately 3000 m. Modelling the topography of the ice surface using a Geographical Information System (GIS) is consistent with these results. The paleoclimatological signal included in this surface geometry was used to draw conclusions about the main atmospheric paleocireulation patterns and to outline the principal precipitation areas for the Alps during the last glaciation. It followed from this that ice build-up was principally related to dominating precipitation by southerly circulation (foehn). The prevaleance of foehn circulation most likely reflects a southward shift of the North Atlantic polar atmospheric front and of the accompanied storm track due to the advancing margin of sea ice. There exists good agreement between these assumptions and (a) results of global circulation models for the time of the LGM; (b) estimations of basal shear stress values and flow velocities for Ice Age glaciers; and (c) interpretations of paleowind indicators.

The Biological Pump During the Last Glacial Maximum

2020 ◽  
Vol 12 (1) ◽  
pp. 559-586 ◽  
Author(s):  
Eric D. Galbraith ◽  
Luke C. Skinner
Keyword(s):  
Carbon Storage ◽  
Last Glacial Maximum ◽  
Ocean Circulation ◽  
Marine Ecosystem ◽  
Glacial Maximum ◽  
Ice Age ◽  
Natural Experiments ◽  
Last Glacial ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Much of the global cooling during ice ages arose from changes in ocean carbon storage that lowered atmospheric CO2. A slew of mechanisms, both physical and biological, have been proposed as key drivers of these changes. Here we discuss the current understanding of these mechanisms with a focus on how they altered the theoretically defined soft-tissue and biological disequilibrium carbon storage at the peak of the last ice age. Observations and models indicate a role for Antarctic sea ice through its influence on ocean circulation patterns, but other mechanisms, including changes in biological processes, must have been important as well, and may have been coordinated through links with global air temperature. Further research is required to better quantify the contributions of the various mechanisms, and there remains great potential to use the Last Glacial Maximum and the ensuing global warming as natural experiments from which to learn about climate-driven changes in the marine ecosystem.

scholarly journals Interplay between detrital and diagenetic processes since the last glacial maximum on the northwest Iberian continental shelf

2010 ◽  
Vol 73 (3) ◽  
pp. 507-520 ◽  
Author(s):  
Kais Jacob Mohamed ◽  
Daniel Rey ◽  
Belen Rubio ◽  
Federico Vilas ◽  
Thomas Frederichs
Keyword(s):  
Continental Shelf ◽  
Last Glacial Maximum ◽  
Glacial Maximum ◽  
Warm Period ◽  
Ice Age ◽  
Magnetic Minerals ◽  
Last Glacial ◽  
Textural Data ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Integrated analyses of magnetic, geochemical and textural data on six cores from the northwestern Iberian continental shelf allowed the reconstruction of the paleoenvironmental evolution of this area since the last glacial maximum (LGM). Four sedimentary units were identified, representing a succession from fluvial and subaerial settings to high and finally low-energy marine deposits subsequent to the post-LGM sea-level rise. The uppermost unit was deposited during the Holocene and its magnetic properties were controlled by the interplay between detrital input and early diagenetic reductive dissolution of magnetic minerals. Identification of a primary steady-state early diagenetic signal allowed the recognition of periods of increased detrital input, bounded by intervals of lower detrital input and intensified reductive diagenesis related to intensified upwelling in the area. These paleoenvironmental alternations are consistent with the climatic evolution of the late Holocene. During the Roman Warm Period and Medieval Warm Period, the combined effect of greater humidity and intense agricultural and mining activities led to a greater erosion and transport of detrital sediments to the shelf. In contrast, enhanced diagenetic reduction intervals, caused by upwelling intensification, were roughly coincident with the colder Dark Ages and the Little Ice Age.

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