scholarly journals Atlantic Ocean circulation at the Last Glacial Maximum : inferences from data and models

2012 ◽  
Author(s):  
Holly J. Dail
Keyword(s):  
Atlantic Ocean ◽  
Last Glacial Maximum ◽  
Ocean Circulation ◽  
Glacial Maximum ◽  
Last Glacial ◽  
The Last Glacial Maximum ◽  
The Last Glacial

PMIP-carbon: towards a multi-models comparison of climate-carbon interactions at the Last Glacial Maximum

2020 ◽  
Author(s):  
Nathaelle Bouttes ◽  
Ruza Ivanovic ◽  
Ayako Abe-Ouchi ◽  
Hidetaka Kobayashi ◽  
Laurie Menviel ◽  
...  
Keyword(s):  
Carbon Cycle ◽  
Carbon Isotopes ◽  
Last Glacial Maximum ◽  
Ocean Circulation ◽  
Ice Cores ◽  
Glacial Maximum ◽  
Last Glacial ◽  
Intercomparison Project ◽  
The Last Glacial Maximum ◽  
The Last Glacial

<p>More and more climate models now include the carbon cycle, but multi-models studies of climate-carbon simulations within the Climate Model Intercomparison Project (CMIP) are limited to present and future time periods. In addition, the carbon cycle is not considered in the simulations of past periods analysed within the Paleoclimate Modelling Intercomparison Project (PMIP). Yet, climate-carbon interactions are crucial to anticipate future atmospheric CO<sub>2</sub> concentrations and their impact on climate. Such interactions can change depending on the background climate, it is thus necessary to compare model results among themselves and to data for past periods with different climates such as the Last Glacial Maximum (LGM).</p><p>The Last Glacial Maximum, around 21,000 years ago, was about 4°C colder than the pre-industrial, and associated with large ice sheets on the American and Eurasian continents. It is one of the best documented periods thanks to numerous paleoclimate archives such as marine sediment cores and ice cores. Despite this period having been studied for years, no consensus on the causes of the lower atmospheric CO<sub>2</sub> concentration at the time (around 180 ppm) has been reached and models still struggle to simulate these low CO<sub>2</sub> values. The ocean, which contains around 40 times more carbon than the atmosphere, likely plays a key role, but models tend to simulate ocean circulation changes in disagreement with proxy data, such as carbon isotopes.</p><p>This new project aims at comparing, for the first time, the carbon cycle representation at the Last Glacial Maximum from general circulation models and intermediate complexity models. We will explain the protocol and present first results in terms of carbon storage in the main reservoirs (atmosphere, land and ocean) and their link to key climate variables such as temperature, sea ice and ocean circulation. The use of coupled climate-carbon models will not only allow to compare changes in the carbon cycle in models and analyse their causes, but it will also enable us to better compare to indirect data related to the carbon cycle such as carbon isotopes.</p>

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.

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.

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