The Coherence of the Oceanic Heat Transport Through the Nordic Seas: Oceanic Heat Budget and Interannual Variability

Abstract

The Atlantic Water is the main source of heat and salt in the Arctic. Properties of the Atlantic Water inflow regionally affect sea ice extent and deep water formation rate. The Atlantic Water heat transported into the Nordic Seas has a significant impact on the local climate and is investigated here along with its inter-annual variability. We use the ARMOR3D dataset, which is a collection of 3D monthly temperature, salinity and geostrophic velocities fields, derived from in situ and satellite data on a regular grid available since 1993. We compare the heat transport across seven zonal transects in the eastern part of the Nordic seas, from Svinøy section (65°N) to the Fram Strait (78.8°N). 
 The correlations of the interannual variations of the advective heat fluxes rapidly drop from Svinøy to Jan Mayen sections and between Bear Island and Sørkapp sections. This is a result of different tendencies over the latest decades in the southern and the northern parts of the study region, as well as of a differential damping of the observed periodicities along the Atlantic Water path on its way north (the amplitude of 5–6 year oscillations drops significantly faster than that of 2–3 year oscillations). 
 A certain link between the heat fluxes and the North Atlantic Oscillation (NAO), Arctic Oscillation (AO) and East Atlantic (EA) indices is observed only for the southern sections. On the other hand, the heat fluxes at all sections show a consistent increase during the dominance of western weather type W and a decrease – of meridional weather type C. The link is explained by the variations of the wind fields, favourable for the sea-level build-up (Ekman pumping) east of the branching of the Norwegian Current for type W and an opposite tendency for type C.