Evolution of the deep Atlantic water masses since the last glacial maximum based on a transient run of NCAR-CCSM3

Author(s)

Marson, Juliana M. ; Mysak, Lawrence A. ; Mata, Mauricio M. ; Wainer, Ilana

• Document type: Journal article
• Source: Climate Dynamics; v. 47, n. 3-4, p. 865-877, AUG 2016.
• Web of Science Citations: 0

Abstract

During the last deglaciation (from approximately 21 to 11 thousand years ago), the high latitudes of the Atlantic Ocean underwent major changes. Besides the continuous warming, the polar and subpolar ocean surface received a large amount of meltwater from the retracting ice sheets. These changes in temperature and salinity affected deep waters, such as the Antarctic Bottom Water (AABW) and the North Atlantic Deep Water (NADW), which are formed in the Southern Ocean and in the northern North Atlantic, respectively. In this study, we present the evolution of the physical properties and distribution of the AABW and the NADW since the last glacial maximum using the results of a transient simulation with NCAR-CCSM3. In this particular model scenario with a schematic freshwater forcing, we find that modern NADW, with its characteristic salinity maximum at depth, was absent in the beginning of the deglaciation, while its intermediate version-Glacial North Atlantic Intermediate Water (GNAIW)-was being formed. GNAIW was a cold and relatively fresh water mass that dominated intermediate depths between 60 and 20 degrees N. At this time, most of the deep and abyssal Atlantic basin was dominated by AABW. Within the onset of the Bolling-Allerod period, at nearly 15 thousand years ago (ka), GNAIW expanded southwards when the simulated Meridional Overturning Circulation overshoots. The transition between GNAIW and NADW ocurred after that, when AABW was fresh enough to allow NADW to sink deeper in the water column. When the NADW appears (similar to 11 ka), AABW retracts and is constrained to lie near the bottom. (AU)

• FAPESP's process: 11/02047-9 - Meltwater pulses in the Last Glacial Maximum transition: impacts on physical and dynamical structure of Southern Ocean
• Grantee: Juliana Marini Marson
• Support type: Scholarships in Brazil - Doctorate