On the flow of Atlantic water and temperature anomalies in the Nordic Seas toward the Arctic Ocean

Abstract

The climatic conditions over the Arctic Ocean are strongly influenced by the inflow of warm Atlantic water conveyed by the Norwegian Atlantic Slope Current (NwASC). Based on sea surface height (SSH) data from altimetry, we develop a simple dynamical measure of the NwASC transport to diagnose its spatio‐temporal variability. This supports a dynamical division of the NwASC into two flow regimes; the Svinøy Branch (SvB) in the southern Norwegian Sea, and the Fram Strait Branch (FSB) west of Spitsbergen. The SvB transport is well correlated with the SSH and atmospheric variability within the Nordic Seas, factors that also affect the inflow to the Barents Sea. In contrast, the FSB is influenced by regional atmospheric conditions around Svalbard and northern Barents Sea. Using a composite analysis, we further relate anomalous strong SvB flow events to temperature fluctuations along the core of Atlantic water. A warm composite anomaly is found to propagate northward, with a tendency to amplify enroute, after these events. A roughly 12 months delayed temperature signal is identified in the FSB. However, also in the Lofoten Basin interior a delayed temperature signal is found, which appears to originate from the NwASC. This study suggests that hydrographic anomalies both upstream from the North Atlantic, and locally generated in the Norwegian Sea, are important for the oceanic heat and salt transport that eventually enters into the Arctic.

Impact of North Atlantic Teleconnection Patterns on Northern European Sea Level

“…Richter et al [49] modelled the boundary current at one location (Svinøy) using the across-slope sea level gradient from tide gauges between the Norwegian west coast and the Faroe Islands and found a good correlation of 0.6. We think that the altimetric on-shelf or TG PC1 may be useful to reconstruct the variability of this boundary current, and that these binary combinations may further elucidate the drivers, which have solely been investigated in terms of the NAO (see, e.g., Skagseth et al [50], Sandø et al [51], Chafik et al [52]). Furthermore, the European shelves respond on decadal timescales to open-ocean steric height variations [11,53], which may impact the across-slope sea level gradient and hence regulate the strength of the boundary current.…”

Wind-Driven Atlantic Water Flow as a Direct Mode for Reduced Barents Sea Ice Cover

“…However, for these winds to generate ocean heat transport anomalies, they need to be part of a larger-scale atmospheric field causing an anomalous Atlantic flow through the Barents Sea (Ingvaldsen et al 2004;Skagseth et al 2011;Lien et al 2013a). A regional dependence has also been found in the strengths of the two branches of Atlantic water flow toward the Arctic through the Fram Strait (Chafik et al 2015) and the Barents Sea (Lien et al 2013a). Thus, the regional wind field over the Barents Sea area induces a mode of variability on time scales of about one month affecting changes in ocean circulation and sea ice, as well as ocean-to-air heat exchange.…”

“…The advective nature and annual time scales of these temperature anomalies enable predictability of the downstream sea ice cover (Årthun et al 2012;Onarheim et al 2015). Hence, also accounting for the regional mode of Barents Sea variability documented here and by others (Lien et al 2013a;Chafik et al 2015) might further improve the precision of seasonal-scale sea ice predictions.…”

“…5). Although the mechanism modulating Barents Sea ocean transport anomalies is forced regionally (Ingvaldsen et al 2004;Skagseth et al 2011;Lien et al 2013a;Chafik et al 2015), a positive NAO means a northward shift of the storm tracks in the Nordic seas and also an increase in the number of low pressure systems within the Nordic seas (e.g., Bader et al 2011). This may also increase the number of atmospheric cyclones that enters the Barents Sea region, generating barotropic transport anomalies.…”

“…To the northeast, the thermal gradient is oriented along the flow of Atlantic water because of heat loss to the atmosphere. Hence, a positive volume transport anomaly will cause a coherent temperature increase rather than an advectively propagating temperature anomaly (Sundby and Drinkwater 2007;Chafik et al 2015). The northeastern Barents Sea is the area where the winter sea ice extent displays the largest variability (Årthun et al 2012;Yang et al 2016).…”