scholarly journals Last glacial maximum hydro-climate and cyclone characteristics in the Levant: a regional modelling perspective

2021 ◽  
Author(s):  
Patrick Ludwig ◽  
Assaf Hochman
Keyword(s):  
Last Glacial Maximum ◽  
Water Availability ◽  
Hydrological Cycle ◽  
Low Frequency ◽  
Weather Type ◽  
Glacial Maximum ◽  
Driving Mechanism ◽  
Last Glacial ◽  
Additional Water ◽  
Type Classification

Abstract Proxy-based hydro-climatic reconstructions over the Levant suggest enhanced water availability during the Last Glacial Maximum (LGM) compared to present-day conditions. To date, the governing hypothesis is that additional water availability may be directly linked to increased Cyprus Low frequency and intensity over the region. However, this paradigm has not been tested in a modelling framework. With this aim, we analyzed results from a weather type classification algorithm and regional climate simulations. The weather type classification is applied to ERA5 Reanalysis data for present-day (1979-2018) and two PMIP3/PMIP4 pre-industrial and LGM model runs. Dynamical downscaling of the two models with the regional WRF model shows that the present hydro-climate can largely be reproduced. Our simulations suggest that both evaporation and precipitation were lower in the LGM compared to pre-industrial conditions, and that their relative changes can thus most likely explain the additional water availability during that time. Indeed, evaporation in the eastern Mediterranean is reduced to a higher degree (~-33%) as compared to precipitation (~-20%) during the LGM. Particularly, lower evaporation during LGM summer may have sustained the year-round wetter conditions in the Levant. In addition, we find significant changes in Cyprus Low characteristics for the LGM. The simulated daily precipitation associated with Cyprus Lows is significantly lower than pre-industrial values (reduction of 26 - 29%), whereas the wind intensity is stronger (increase of 7 - 8%). Finally, a significant increase in Cyprus Low frequency during LGM winter is likely (+22%). Indeed, our findings are in line with a plethora of proxy-based reconstructions, and provide a reinterpretation of the driving mechanism of water availability, i.e., strong changes in evaporation rather than precipitation. This study places projected hydro-climatic drying of the Levant in a long timescale perspective. As such, it improves our understanding of the physical processes influencing the hydrological cycle in this vulnerable region, situated on the border between sub-tropical and mid-latitude climatic zones.

A 3000-yr Annually Laminated Stalagmite Record of the Last Glacial Maximum from Hulu Cave, China

2015 ◽  
Vol 83 (2) ◽  
pp. 360-369 ◽  
Author(s):  
Fucai Duan ◽  
Jiangying Wu ◽  
Yongjin Wang ◽  
R. Lawrence Edwards ◽  
Hai Cheng ◽  
...  
Keyword(s):  
Last Glacial Maximum ◽  
Ocean Circulation ◽  
Hydrological Cycle ◽  
Glacial Maximum ◽  
Solar Cycles ◽  
Last Glacial ◽  
The North ◽  
Annual Layer ◽  
The Last Glacial Maximum ◽  
The Last Glacial

A high-resolution, annual layer-counted and 230Th-dated multi-proxy record is constructed from a stalagmite in Hulu Cave, China. These proxies, including δ18O, annual layer thickness (ALT), gray level (GL) and Sr/Ca, cover a time span of ~ 3000 yr from 21 to 24 ka. The physical proxies (ALT and GL) and the geochemical index (Sr/Ca), all primarily reflecting karst hydrological processes, vary in concert and their coherence is supported by wavelet analyses. Variations in the δ18O data agree with fluctuations in the ALT and Sr/Ca records on multi-decadal to centennial scales, suggesting that the Hulu δ18O signal is strongly associated with varying local rainfall amounts on short timescales. A monsoon failure event at ~ 22.2 ka correlates with a decrease in tropical rainfall, a reduction in global CH 4 and an ice-rafted event in the North Atlantic. This correlation highlights roles of the Asian monsoon and tropical hydrological cycle in modulating global CH 4, because the high-latitude emission was inhibited during the Last Glacial Maximum (LGM). Spectral analysis of the δ18O record displays peaks at periodicities of 139, 59, 53, 43, 30, 23 and 19"15 yr. The absence of typical centennial solar cycles may be related to muted changes in ocean circulation during the LGM.

Sensitivity of isotopes in the hydrological cycle to simulated vs. reconstructed Last Glacial Maximum surface conditions

2020 ◽  
Author(s):  
André Paul ◽  
Martin Werner ◽  
Alexandre Cauquoin ◽  
Javier García-Pintado ◽  
Ute Merkel ◽  
...  
Keyword(s):  
Sea Ice ◽  
Last Glacial Maximum ◽  
General Circulation ◽  
Hydrological Cycle ◽  
Ocean Surface ◽  
Glacial Maximum ◽  
Water Isotopes ◽  
Last Glacial ◽  
Direct Model ◽  
The Impact

<p><span>The evaluation of a specific component of a comprehensive climate model is often hindered by biases in the coupled system, in simulations of </span><span>the </span><span>present as well as </span><span>of </span><span>past climate conditions. To assess different implementations of water isotopes </span><span>as part of</span><span> the hydrological cycle, we carried out atmosphere-only runs using different atmospheric general circulation models (</span><span>AGCMs, here: CAM and ECHAM</span><span>) but the same pre-industrial and Last Glacial Maximum </span><span>(</span><span>LGM, ~</span><span>19,000 to ~23,000 a before present)</span><span> boundary conditions, especially </span><span>with respect to </span><span>the monthly </span><span>sea-surface temperature (SST) and sea-ice fraction </span><span>fields</span><span>. For the LGM, we used a new global climatology of the ocean surface during the Last Glacial Maximum mapped on a regular grid (GLOMAP), which is an extension of the Glacial Atlantic Ocean Mapping (GLAMAP) reconstruction of the Atlantic SST based on the results of the Multiproxy Approach for the Reconstruction of the Glacial Ocean Surface (MARGO) project and several recent estimates of the LGM sea-ice extent. This way, we can, on the one hand, avoid the propagation of the SST bias in coupled climate models. </span><span>O</span><span>n the other hand, </span><span>by comparing to fully-coupled simulations,</span><span> we can isolate the impact of the ocean feedback on the simulated distributions of water isotopes over land, ice and ocean. To analyze the results, we calculated the anomal</span><span>ies</span><span> between the LGM and pre-industrial climate states and compared the</span><span>m</span><span> between the different models and to data. It turned out that </span><span>the </span><span>model response was affected by the amount of global cooling as well as the structure of the SST anomalies. T</span><span>he patterns in the simulated isotopic composition of precipitation for the LGM tended to follow the patterns in the SST boundary condition; a more zonal structure in the SST led to a more zonal response. Our results show the advantage of using water isotopes as a diagnostic tool for an AGCM th</span><span>r</span><span>ough direct model-data comparison.</span></p>

Last Glacial Maximum to Early Holocene Wind Strength in the Mid-latitudes of the Southern Hemisphere from Aeolian Dust in the Tasman Sea

1999 ◽  
Vol 52 (3) ◽  
pp. 343-349 ◽  
Author(s):  
Paul P. Hesse ◽  
Grant H. McTainsh
Keyword(s):  
Southern Hemisphere ◽  
Last Glacial Maximum ◽  
Hydrological Cycle ◽  
Glacial Maximum ◽  
Early Holocene ◽  
Last Glacial ◽  
Zonal Winds ◽  
Tasman Sea ◽  
Westerly Winds ◽  
Sand Movement

Dust transported by Southern Hemisphere mid-latitude westerly winds from Australia and deposited in the Tasman Sea shows no evidence for stronger winds during the last glacial maximum (LGM), compared to the Holocene. Features of the particle-size distributions of the dust do, however, indicate enhanced dry deposition of dust in the LGM changing to rainfall scavenging during deglaciation and the early Holocene as climate ameliorated. From these results it appears that activation of desert dunefields over 40% of Australia during the LGM was the result of a reduction in stabilizing vegetation and more frequent episodes of sand movement rather than of increased wind strength. The LGM climate of inland Australia must have been considerably more stressful for plants as a result of lower precipitation and/or carbon dioxide stress to achieve the implied levels of surface destabilization. Enhanced atmospheric dust loads in the Southern Hemisphere and deposition over Antarctica were most likely the result of greatly expanded source areas in the mid-latitude southern continents and a weaker hydrological cycle rather than greater entrainment or more efficient transport by stronger winds. During the LGM wind strength appears to have varied regionally, and predominantly in high latitudes, rather than uniformly for all zonal winds.

scholarly journals An Initial Intercomparison of Atmospheric and Oceanic Climatology for the ICE-5G and ICE-4G Models of LGM Paleotopography

2006 ◽  
Vol 19 (1) ◽  
pp. 3-14 ◽  
Author(s):  
F. Justino ◽  
A. Timmermann ◽  
U. Merkel ◽  
W. R. Peltier
Keyword(s):  
North America ◽  
Last Glacial Maximum ◽  
Land Surface ◽  
Hydrological Cycle ◽  
Ice Sheet ◽  
Glacial Maximum ◽  
Positive Temperature ◽  
Last Glacial ◽  
The Impact ◽  
Ice Sheet Topography

Abstract This paper investigates the impact of the new ICE-5G paleotopography dataset for Last Glacial Maximum (LGM) conditions on a coupled model simulation of the thermal and dynamical state of the glacial atmosphere and on both land surface and sea surface conditions. The study is based upon coupled climate simulations performed with the ocean–atmosphere–sea ice model of intermediate-complexity Climate de Bilt-coupled large-scale ice–ocean (ECBilt-Clio) model. Four simulations focusing on the Last Glacial Maximum [21 000 calendar years before present (BP)] have been analyzed: a first simulation (LGM-4G) that employed the original ICE-4G ice sheet topography and albedo, and a second simulation (LGM-5G) that employed the newly constructed ice sheet topography, denoted ICE-5G, and its respective albedo. Intercomparison of the results obtained in these experiments demonstrates that the LGM-5G simulation delivers significantly enhanced cooling over Canada compared to the LGM-4G simulation whereas positive temperature anomalies are simulated over southern North America and the northern Atlantic. Moreover, introduction of the ICE-5G topography is shown to lead to a deceleration of the subtropical westerlies and to the development of an intensified ridge over North America, which has a profound effect upon the hydrological cycle. Additionally, two flat ice sheet experiments were carried out to investigate the impact of the ice sheet albedo on global climate. By comparing these experiments with the full LGM simulations, it becomes evident that the climate anomalies between LGM-5G and LGM-4G are mainly driven by changes of the earth’s topography.

Global water balance and atmospheric water vapour transport at last glacial maximum: climate simulations with the Canadian Climate Centre for Modelling and Analysis atmospheric general circulation model

2000 ◽  
Vol 37 (5) ◽  
pp. 695-723 ◽  
Author(s):  
G Vettoretti ◽  
W R Peltier ◽  
N A McFarlane
Keyword(s):  
Water Vapour ◽  
Last Glacial Maximum ◽  
General Circulation ◽  
Hydrological Cycle ◽  
Ice Sheet ◽  
Atmospheric Model ◽  
Glacial Maximum ◽  
Vapour Transport ◽  
Last Glacial ◽  
Water Vapour Transport

A series of new simulations of the climate state at last glacial maximum has been performed using the Canadian second-generation atmospheric general circulation model and are described herein. The primary goal has been to assess the dynamic changes in the global water balance and water vapour transport that were characteristic of the climate state during this epoch of Earth's history. We pay special attention to comparisons of the atmospheric model simulations of last glacial maximum climate with those produced with a much simpler coupled energy balance-ice-sheet model, which has been designed to simulate the late Pleistocene cycle of glacial-interglacial ice volume variations. Our analyses, using the atmospheric model, demonstrate that the vigour of the hydrological cycle was markedly decreased under last glacial maximum conditions, as would be expected on the simplest thermodynamic grounds. The primary components of the hydrological cycle in the atmospheric model, namely precipitation and evaporation, constitute essential mechanisms that control ice-sheet mass balance. We also investigate changes in the Northern Hemisphere stationary wave patterns, as well as changes in the total and eddy moisture transport by the global circulation at last glacial maximum to illustrate the role played by the dynamics of the atmosphere in the maintenance of the Northern Hemisphere ice sheets. In particular, we find that the enhancement of the stationary wave pattern along with the convergence in atmospheric water vapour transport produces increased cooling and snow accumulation at last glacial maximum over the southeastern lobes of the Laurentide Ice Sheet. This suggests an explanation for the previously unexplained extension of these lobes deep into the New England states.

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.

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