Marine biogeochemical responses to the North Atlantic Oscillation in a coupled climate model.

Patara, Lavinia , Visbeck, Martin , Masina, Simona, Krahmann, Gerd and Vichi, Marcello (2011) Marine biogeochemical responses to the North Atlantic Oscillation in a coupled climate model. Open Access Journal of Geophysical Research: Oceans, 116 (C7). C07023. DOI 10.1029/2010JC006785.

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Abstract

In this study a coupled ocean-atmosphere model containing interactive marine biogeochemistry is used to analyze interannual, lagged, and decadal marine biogeochemical responses to the North Atlantic Oscillation (NAO), the dominant mode of North Atlantic atmospheric variability. The coupled model adequately reproduces present-day climatologies and NAO atmospheric variability. It is shown that marine biogeochemical responses to the NAO are governed by different mechanisms according to the time scale considered. On interannual time scales, local changes in vertical mixing, caused by modifications in air-sea heat, freshwater, and momentum fluxes, are most relevant in influencing phytoplankton growth through light and nutrient limitation mechanisms. At subpolar latitudes, deeper mixing occurring during positive NAO winters causes a slight decrease in late winter chlorophyll concentration due to light limitation and a 10%–20% increase in spring chlorophyll concentration due to higher nutrient availability. The lagged response of physical and biogeochemical properties to a high NAO winter shows some memory in the following 2 years. In particular, subsurface nutrient anomalies generated by local changes in mixing near the American coast are advected along the North Atlantic Current, where they are suggested to affect downstream chlorophyll concentration with 1 year lag. On decadal time scales, local and remote mechanisms act contemporaneously in shaping the decadal biogeochemical response to the NAO. The slow circulation adjustment, in response to NAO wind stress curl anomalies, causes a basin redistribution of heat, freshwater, and biogeochemical properties which, in turn, modifies the spatial structure of the subpolar chlorophyll bloom.

Document Type: Article
Keywords: Oceanography; Biogeochemistry; Deep winter mixing increases annual subpolar chlorophyll and its seasonality; Changes in subsurface nutrients have lagged effects on downstream chlorophyll; Altered ocean circulation affects the decadal biogeochemical response to the NAO
Research affiliation: OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-TM Theory and Modeling
OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-PO Physical Oceanography
OceanRep > The Future Ocean - Cluster of Excellence
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1029/2010JC006785
ISSN: 2169-9275
Projects: Future Ocean, VECTOR
Date Deposited: 25 Aug 2011 13:04
Last Modified: 19 Jan 2018 11:41
URI: http://oceanrep.geomar.de/id/eprint/12045

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