Decadal fingerprints of freshwater discharge around Greenland in a multi-model ensemble.

Swingedouw, Didier, Rodehacke, Christian B., Behrens, Erik, Menary, Matthew, Olsen, Steffen M., Gao, Yongqi, Mikolajewicz, Uwe, Mignot, Juliette and Biastoch, Arne (2013) Decadal fingerprints of freshwater discharge around Greenland in a multi-model ensemble. Climate Dynamics, 41 (3-4). pp. 695-720. DOI 10.1007/s00382-012-1479-9.

[img] Text
art_10.1007_s00382-012-1479-9.pdf - Published Version
Restricted to Registered users only

Download (3238Kb) | Contact

Supplementary data:

Abstract

The recent increase in the rate of the Greenland ice sheet melting has raised with urgency the question of the impact of such a melting on the climate. As former model projections, based on a coarse representation of the melting, show very different sensitivity to this melting, it seems necessary to consider a multi-model ensemble to tackle this question. Here we use five coupled climate models and one ocean-only model to evaluate the impact of 0.1 Sv (1 Sv = 106 m3/s) of freshwater equally distributed around the coast of Greenland during the historical era 1965–2004. The ocean-only model helps to discriminate between oceanic and coupled responses. In this idealized framework, we find similar fingerprints in the fourth decade of hosing among the models, with a general weakening of the Atlantic Meridional Overturning Circulation (AMOC). Initially, the additional freshwater spreads along the main currents of the subpolar gyre. Part of the anomaly crosses the Atlantic eastward and enters into the Canary Current constituting a freshwater leakage tapping the subpolar gyre system. As a consequence, we show that the AMOC weakening is smaller if the leakage is larger. We argue that the magnitude of the freshwater leakage is related to the asymmetry between the subpolar-subtropical gyres in the control simulations, which may ultimately be a primary cause for the diversity of AMOC responses to the hosing in the multi-model ensemble. Another important fingerprint concerns a warming in the Nordic Seas in response to the re-emergence of Atlantic subsurface waters capped by the freshwater in the subpolar gyre. This subsurface heat anomaly reaches the Arctic where it emerges and induces a positive upper ocean salinity anomaly by introducing more Atlantic waters. We found similar climatic impacts in all the coupled ocean–atmosphere models with an atmospheric cooling of the North Atlantic except in the region around the Nordic Seas and a slight warming south of the equator in the Atlantic. This meridional gradient of temperature is associated with a southward shift of the tropical rains. The free surface models also show similar sea-level fingerprints notably with a comma-shape of high sea-level rise following the Canary Current.

Document Type: Article
Funder compliance: info:eu-repo/grantAgreement/EC/FP7/212643
Additional Information: WOS:000322619500010
Keywords: Greenland ice sheet melting; Thermohaline circulation; Oceanic gyre; Ocean–atmosphere interactions; Oceanic dynamics; Sea-level rise; AMOC North Atlantic
Research affiliation: OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-TM Theory and Modeling
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1007/s00382-012-1479-9
ISSN: 0930-7575
Projects: THOR, Future Ocean
Expeditions/Models/Experiments:
Date Deposited: 26 Nov 2012 07:17
Last Modified: 23 Sep 2019 19:00
URI: http://oceanrep.geomar.de/id/eprint/19287

Actions (login required)

View Item View Item

Document Downloads

More statistics for this item...