Lagrangian sampling of the northward route of the Atlantic Water and its spreading in the Nordic Seas
Inga Koszalka, Joseph Henry LaCasce, Cecilie Mauritzen, Heinrik Soiland
University of Oslo, Institute for Geosciences
(Abstract received 08/17/2009 for session A)
ABSTRACT
Lagrangian techniques provide an unique insight into structure of the oceanic circulation and its variability. In this study we focus on the route of the Norwegian Atlantic Current (NwAC) towards the Arctic as well as spreading of the Atlantic Water in the Nordic Seas with help of surface drifters and subsurface RAFOS floats. Surface drifters dataset consists of 118 drifters drogued at 15m depth and deployed along the path of the Norwegian Atlantic Current during 6 fields campaigns (June 2007 – October 2008) within the POLEWARD project. These data were integrated with historical drifters released in the Nordic Seas region in 1990-2008 and available through the Global Drifter Program database (http://www.aoml.noaa.gov/phod/dac/gdp.html). RAFOS float data embraces 45 instruments deployed in the southern Norwegian Sea in July-October 2004: 23 floating at 200m depth and 22 floating at 800m depth (Søiland et. al. 2008, Rossby et. al. 2009). The goal of the study is to describe the circulation within NwAC, Lofoten and Norwegian basins from the Lagrangian viewpoint, and better understand the fates of fluid parcels transported from the southern part of the Nordic Seas northward towards the Arctic. For this purpose, the drifter and float data are analyzed with respect to the following aspects:
(1) Lagrangian pathways of fluid parcels from drifters and floats deployed in the Nordic Seas
(2) Exchange of the surface drifters from the NwAC into Norwegian Coastal Current, the Norwegian and Lofoten basins
(3) Characterisation of the velocity signal in the Lagrangian instruments floating at different depths with focus on
topographic steering quantified by means of the sensitivity of oceanic float dispersion to f/H (potential vorticity) contours (LaCasce, 2000).We compare information provided by instruments floating at different depths and assess the value of such comparative study.
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