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 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 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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