Coherent variability of the Norwegian Atlantic Slope Current derived from TOPEX/ERS altimeter data

Abstract

This study deals with large‐scale variability of the Norwegian Atlantic Current (NwAC) transporting warm and saline Atlantic water toward the Arctic Ocean. We concentrate on the eastern branch of the NwAC, the Norwegian Atlantic Slope Current (NwASC), an about 3500 km long, nearly barotropic shelf edge current. Comparison of variations of cross‐slope sea level gradient based on the CLS TOPEX/ERS altimeter data and the NwASC from direct current measurements 1995–2002 in the Svinøy section at about 63°N shows significant coherence for periods of 1 to 12 months. Motivated by this the analysis is extended to the entire NwASC using the local cross‐slope sea level gradient from the altimeter data as a proxy. The leading NwASC mode represents along‐slope current variations of similar sign from the Irish‐Scottish shelf to the Fram Strait that can be interpreted as a quasi‐steady, direct response to the large‐scale wind field.