Simulated response of the mid-Holocene Atlantic meridional overturning circulation in ECHAM6-FESOM/MPIOM


Contact
xiaoxu.shi [ at ] awi.de

Abstract

Changes of the Atlantic meridional overturning circulation (AMOC) in the mid-Holocene compared to the preindustrial state are explored in different coupled climate models. Using time-slice integrations by a newly developed global finite-element model ECHAM6-FESOM with unstructured mesh and high resolution, our simulations show an enhanced mid-Holocene AMOC, accompanied by an increase in the ocean salinity over regions of deep water formation. We identify two different processes affecting the AMOC: (1) a more positive phase of North Atlantic Oscillation (NAO) increased water density over the Labrador Sea through anomalous net evaporation and surface heat loss; (2) a decreased import of sea ice from the Arctic causes a freshwater reduction in the northern North Atlantic Ocean. Using the coupled model ECHAM6-MPIOM in T63GR15 and T31GR30 grids, we find that the simulated AMOC has significant discrepancy with different model resolutions. In detail, stronger-than-present mid-Holocene AMOC is revealed by simulations with the T63GR15 grid, which resembles the result of ECHAM6-FESOM, while a decline of the mid-Holocene AMOC is simulated by the low resolution model with the T31GR30 grid. Such discrepancy can be attributed to different changes in Labrador Sea density which is mainly affected by (1) NAO-induced net precipitation and deep water convection, (2) freshwater transport from the Arctic Ocean, and (3) the strength of AMOC itself. Finally, we analyzed available coupled climate models showing a diversity of responses of AMOC to mid-Holocene forcings, most of which reveal positive AMOC changes related to northern high latitudes salinification.



Item Type
Article
Authors
Divisions
Primary Division
Programs
Primary Topic
Peer revision
ISI/Scopus peer-reviewed
Publication Status
Published
Eprint ID
42755
DOI 10.1002/2015JC011584

Cite as
Shi, X. and Lohmann, G. (2016): Simulated response of the mid-Holocene Atlantic meridional overturning circulation in ECHAM6-FESOM/MPIOM , Journal of Geophysical Research: Oceans, 121 (8), pp. 6444-6469 . doi: 10.1002/2015JC011584


Download
[img]
Preview
PDF
Shi_et_al-2016-Journal_of_Geophysical_Research__Oceans.pdf

Download (12MB) | Preview
Cite this document as:

Share


Citation

Research Platforms

Campaigns


Actions
Edit Item Edit Item