scholarly journals Interdecadal Pacific Oscillation Drives Enhanced Greenland Surface Temperature Variability During the Last Glacial Maximum

2020 ◽  
Vol 47 (23) ◽  
Author(s):  
Zhaoyang Song ◽  
Mojib Latif ◽  
Wonsun Park ◽  
Yuming Zhang
Keyword(s):  
Surface Temperature ◽  
Last Glacial Maximum ◽  
Temperature Variability ◽  
Glacial Maximum ◽  
Interdecadal Pacific Oscillation ◽  
Last Glacial ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Enhanced multidecadal Greenland surface temperature variability during the Last Glacial Maximum linked to the Interdecadal Pacific Oscillation

2020 ◽  
Author(s):  
Zhaoyang Song ◽  
Mojib Latif ◽  
Wonsun Park ◽  
Yuming Zhang
Keyword(s):  
Sea Ice ◽  
Boundary Conditions ◽  
Surface Temperature ◽  
Last Glacial Maximum ◽  
Temperature Variability ◽  
Interdecadal Pacific Oscillation ◽  
Atmospheric Teleconnection ◽  
Last Glacial ◽  
The Last Glacial Maximum ◽  
The Last Glacial

<p>Stable oxygen isotope records from northern Greenland suggest that the local multidecadal surface-temperature variability exhibited a large reduction from the last glaciation to the Holocene. The origin of the reduced variability is thought to be perturbations in the mean atmospheric circulation due to Northern Hemisphere ice sheet variability. We reassess the factors driving the large multidecadal Greenland surface temperature (T<sub>2m</sub>) variability during the Last Glacial Maximum. The Kiel Climate Model has been integrated under preindustrial and glacial boundary conditions. We find that both atmospheric teleconnections from the Interdecadal Pacific Oscillation (IPO) and North Atlantic/Arctic sea ice variations strongly intensify under glacial boundary conditions, driving enhanced surface wind and in turn heat flux variability over Greenland. Additional simulations that restore the Pacific sea-surface temperature (SST) to its climatology confirm the important role of the IPO.</p><p>To investigate the relative contributions of atmospheric teleconnection from the IPO and sea-ice on the Greenland T<sub>2m</sub>, we force the atmospheric component of the coupled model in stand-alone mode by SSTs and sea ice concentrations simulated in coupled mode. The influence of atmospheric teleconnection is three times larger than that of sea ice. We conclude that the enhanced multidecadal Greenland surface-temperature variability during the LGM can largely be attributed to stronger atmospheric teleconnection from the IPO.</p>

scholarly journals What was the surface temperature in central Antarctica during the last glacial maximum?

2004 ◽  
Vol 218 (3-4) ◽  
pp. 379-388 ◽  
Author(s):  
Thomas Blunier ◽  
Jakob Schwander ◽  
Jérôme Chappellaz ◽  
Frédéric Parrenin ◽  
Jean Marc Barnola
Keyword(s):  
Surface Temperature ◽  
Last Glacial Maximum ◽  
Glacial Maximum ◽  
Last Glacial ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Reconstruction of sea-surface temperature, salinity, and sea-ice cover in the northern North Atlantic during the last glacial maximum based on dinocyst assemblages

2000 ◽  
Vol 37 (5) ◽  
pp. 725-750 ◽  
Author(s):  
Anne de Vernal ◽  
Claude Hillaire-Marcel ◽  
Jean-Louis Turon ◽  
Jens Matthiessen
Keyword(s):  
Sea Ice ◽  
Surface Temperature ◽  
Last Glacial Maximum ◽  
North Atlantic ◽  
Ice Cover ◽  
Glacial Maximum ◽  
Sea Surface ◽  
Last Glacial ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Past sea-surface conditions over the northern North Atlantic during the last glacial maximum were examined from the study of 61 deep-sea cores. The last glacial maximum time slice studied here corresponds to an interval between Heinrich layers H2 and H1, and spanning about 20-16 ka on a 14C time scale. Transfer functions based on dinocyst assemblages were used to reconstruct sea-surface temperature, salinity, and sea-ice cover. The results illustrate extensive sea-ice cover along the eastern Canadian margins and sea-ice spreading, only during winter, over most of the northern North Atlantic. On the whole, much colder winter prevailed, despite relatively mild conditions in August (10-15°C at most offshore sites), thus suggesting a larger seasonal contrast of temperatures than today. Lower salinity than at present is reconstructed, especially along the eastern Canadian and Scandinavian margins, likely because of meltwater supply from the surrounding ice sheets. These reconstructions contrast with those established by CLIMAP on the basis of planktonic foraminifera. These differences are discussed with reference to the stratigraphical frame of the last glacial maximum, which was not the coldest phase of the last glacial stage. The respective significance of dinocyst and foraminifer records is also examined in terms of the thermohaline characteristics of surface waters and the vertical structure of upper water masses, which was apparently much more stratified than at present in the northern North Atlantic, thus preventing deep-water formation.

scholarly journals A model-data comparison of the Last Glacial Maximum surface temperature changes

2018 ◽  
Author(s):  
Akil Hossain ◽  
Xu Zhang ◽  
Gerrit Lohmann
Keyword(s):  
Surface Temperature ◽  
Last Glacial Maximum ◽  
Planktonic Foraminifera ◽  
Ice Sheet ◽  
Glacial Maximum ◽  
Model Data ◽  
Last Glacial ◽  
Proxy Records ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Abstract. Over the Last Glacial Maximum (LGM, ~ 21 ka BP), the presence of vast Northern Hemisphere ice-sheets caused abrupt changes in surface topography and background climatic state. While the ice-sheet extent is well known, several conflicting ice-sheet topography reconstructions suggest that there is uncertainty in this boundary condition. The terrestrial and sea surface temperature (SST) of the LGM as simulated with six different Laurentide Ice Sheet (LIS) reconstructions in a fully coupled Earth System Model (COSMOS) have been compared with the subfossil pollen and plant macrofossil based and marine temperature proxies reconstruction. The terrestrial reconstruction shows a similar pattern and in good agreement with model data. The SST proxy dataset comprises a global compilation of planktonic foraminifera, diatoms, radiolarian, dinocyst, alkenones and planktonic foraminifera Mg / Ca-derived SST estimates. Significant mismatches between modeled and reconstructed SST have been observed. Among the six LIS reconstructions, Tarasov’s LIS reconstruction shows the highest correlation with reconstructed terrestrial and SST. In the case of radiolarian, Mg / Ca, diatoms and foraminifera show a positive correlation while dinocyst and alkenones show very low and negative correlation with the model. Dinocyst-based SST records are much warmer than reconstructed by other proxies as well as Pre-industrial (PI) temperature. However, there are large discrepancies between model temperatures and temperature recorded by different proxies. Eight different PMIP3 models also compared with temperature proxies reconstruction which show mismatches with the proxy records might be due to misinterpreted and/or biased proxy records. Therefore, it has been speculated that considering different habitat depths and growing seasons of the planktonic organisms used for SST reconstruction could provide a better agreement of proxy data with model results on a regional scale. Moreover, it can reduce model-data misfits. It is found that shifting in the habitat depth and living season can remove parts of the observed model-data mismatches in SST anomalies.

scholarly journals An ice sheet model of reduced complexity for paleoclimate studies

2015 ◽  
Vol 6 (2) ◽  
pp. 1395-1443
Author(s):  
B. Neff ◽  
A. Born ◽  
T. F. Stocker
Keyword(s):  
Surface Temperature ◽  
Last Glacial Maximum ◽  
Computational Efficiency ◽  
Ice Sheet ◽  
Glacial Maximum ◽  
Last Glacial ◽  
Ice Volume ◽  
Reduced Complexity ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Abstract. IceBern2D is a vertically integrated ice sheet model to investigate the ice distribution on long timescales under different climatic conditions. It is forced by simulated fields of surface temperature and precipitation of the last glacial maximum and present day climate from a comprehensive climate model. This constant forcing is adjusted to changes in ice elevation. Bedrock sinking and sea level are a function of ice volume. Due to its reduced complexity and computational efficiency, the model is well-suited for extensive sensitivity studies and ensemble simulations on extensive temporal and spatial scales. It shows good quantitative agreement with standardized benchmarks on an artificial domain (EISMINT). Present day and last glacial maximum ice distributions on the Northern Hemisphere are also simulated with good agreement. Glacial ice volume in Eurasia is underestimated due to the lack of ice shelves in our model. The efficiency of the model is utilized by running an ensemble of 400 simulations with perturbed model parameters and two different estimates of the climate at the last glacial maximum. The sensitivity to the imposed climate boundary conditions and the positive degree day factor β, i.e., the surface mass balance, outweighs the influence of parameters that disturb the flow of ice. This justifies the use of simplified dynamics as a means to achieve computational efficiency for simulations that cover several glacial cycles. The sensitivity of the model to changes in surface temperature is illustrated as a hysteresis based on 5 million year long simulations.

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