scholarly journals Simulated ocean circulation and sediment transport in the North Atlantic during the Last Glacial Maximum and today

1997 ◽  
Vol 12 (2) ◽  
pp. 281-305 ◽  
Author(s):  
Dan Seidov ◽  
Bernd J. Haupt
Keyword(s):  
Sediment Transport ◽  
Last Glacial Maximum ◽  
Ocean Circulation ◽  
North Atlantic ◽  
Glacial Maximum ◽  
Last Glacial ◽  
The North ◽  
The North Atlantic ◽  
The Last Glacial Maximum ◽  
The Last Glacial

A weaker Atlantic Meridional Overturning Circulation at the Last Glacial Maximum led to a greater deep ocean carbon content

2020 ◽  
Author(s):  
Laurie Menviel ◽  
Paul Spence ◽  
Luke Skinner ◽  
Kazuyo Tachikawa ◽  
Tobias Friedrich ◽  
...  
Keyword(s):  
Last Glacial Maximum ◽  
North Atlantic ◽  
Deep Ocean ◽  
Glacial Maximum ◽  
Last Glacial ◽  
The North ◽  
The North Atlantic ◽  
Ocean Carbon ◽  
The Last Glacial Maximum ◽  
The Last Glacial

<p>While paleoproxy records and modelling studies consistently suggest that North Atlantic  Deep Water (NADW) was shallower at the Last Glacial Maximum (LGM) than during pre-industrial times, its strength is still subject to debate partly due to different signals across the North Atlantic. Here, using a series of LGM experiments performed with a carbon isotopes enabled Earth system model, we show that proxy records are consistent with a shallower and weaker NADW. A significant equatorward advance of sea-ice over the Labrador Sea and the Nordic Seas shifts the NADW convection sites to the south of the Norwegian Sea. While the deep western boundary current in the Northwest Atlantic weakens with NADW, a change in density gradients strengthens the deep southward flow in the Northeast Atlantic. A shoaling and weakening of NADW further allow penetration of Antarctic Bottom Water in the North Atlantic despite its transport being reduced. This resultant globally weaker oceanic circulation leads to an increase in deep ocean carbon of ~500 GtC, thus significantly contributing to the lower LGM atmospheric CO<sub>2</sub> concentration.</p><p> </p>

scholarly journals A coupled model study of the Last Glacial Maximum: Was part of the North Atlantic relatively warm?

2001 ◽  
Vol 28 (8) ◽  
pp. 1571-1574 ◽  
Author(s):  
Chris D. Hewitt ◽  
Anthony J. Broccoli ◽  
John F. B. Mitchell ◽  
Ronald J. Stouffer
Keyword(s):  
Last Glacial Maximum ◽  
North Atlantic ◽  
Coupled Model ◽  
Glacial Maximum ◽  
Last Glacial ◽  
The North ◽  
Model Study ◽  
The North Atlantic ◽  
The Last Glacial Maximum ◽  
The Last Glacial

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.

scholarly journals Climate response to freshwater perturbations in Northern or Southern Hemispheres at the last glacial inception, the last glacial maximum and the present-day

2010 ◽  
Vol 6 (3) ◽  
pp. 1077-1110
Author(s):  
G. Philippon-Berthier ◽  
G. Ramstein ◽  
S. Charbit ◽  
C. Ritz
Keyword(s):  
Last Glacial Maximum ◽  
North Atlantic ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Last Glacial ◽  
The North ◽  
The North Atlantic ◽  
Freshwater Inputs ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Abstract. Freshwater inputs in North Atlantic due to huge surge of icebergs coming from ice sheets might be responsible for drastic regional and global abrupt climatic transitions. To quantify the sensitivity of climate system to these freshwater inputs, we use a model of intermediate complexity coupled to ice-sheet models for both Northern and Southern Hemispheres. We mimic the Dansgaard-Oeschger and Heinrich Events by forcing the model with appropriate freshwater perturbations. The originality of this study is to investigate with such a global model, the response of the coupled system to freshwater discharges for three different climate contexts, the Last Glacial Maximum (LGM), the Last Glacial Inception (LGI) and the present-day (PD) climates. We first show that in all climate contexts, the North Atlantic circulation is more sensitive to freshwater flux when ice sheets are present. Secondly, the "seesaw" mechanism occurs mostly for the North Atlantic freshwater perturbation whereas it remains very weak for the Southern Ocean freshwater release. Moreover, this seesaw is generally enhanced when ice sheets are interactive. The most striking result is that the freshwater perturbation amplifies the inception of the North American ice sheet at LGI the sea-level drop associated is significantly increased and in a much better agreement with data.

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