Atlantic waters inflow north of Svalbard: Insights from IAOOS observations and Mercator Ocean global operational system during N-ICE2015

Abstract

As part of the N‐ICE2015 campaign, IAOOS (Ice Atmosphere Ocean Observing System) platforms gathered intensive winter data at the entrance of Atlantic Water (AW) inflow to the Arctic Ocean north of Svalbard. These data are used to examine the performance of the 1/12° resolution Mercator Ocean global operational ice/ocean model in the marginal ice zone north of Svalbard. Modeled sea‐ice extent, ocean heat fluxes, mixed layer depths and AW mass characteristics are in good agreement with observations. Model outputs are then used to put the observations in a larger spatial and temporal context. Model outputs show that AW pathways over and around the Yermak Plateau differ in winter from summer. In winter, the large AW volume transport of the West Spitsbergen Current (WSC) (∼4 Sv) proceeds to the North East through 3 branches: the Svalbard Branch (∼0.5 Sv) along the northern shelf break of Svalbard, the Yermak Branch (∼1.1 Sv) along the western slope of the Yermak Plateau and the Yermak Pass Branch (∼2.0 Sv) through a pass in the Yermak Plateau at 80.8°N. In summer, the AW transport in the WSC is smaller (∼2 Sv) and there is no transport through the Yermak Pass. Although only eddy‐permitting in the area, the model suggests an important mesoscale activity throughout the AW flow. The large differences in ice extent between winters 2015 and 2016 follow very distinct atmospheric and oceanic conditions in the preceding summer and autumn seasons. Convection‐induced upward heat fluxes maintained the area free of ice in winter 2016.

Atmosphere‐Ice‐Ocean‐Ecosystem Processes in a Thinner Arctic Sea Ice Regime: The Norwegian Young Sea ICE (N‐ICE2015) Expedition

“…Using profiling buoys, Koenig et al () suggest a contribution of warm AW inflow through the Yermak pass, a 700 m deep passage over the YP. Numerical operational model outputs support these interpretations of warm water pathways (Koenig et al, ).…”

“…The observations of hydrography, ocean currents and mixing in the water column, together with under‐ice boundary layer measurements provided unique data sets and new insights in a region with scarce prior observations, especially in winter (Koenig et al, ; Meyer et al, ; Peterson et al, ). Episodic events during storms were found to be important for heat, salt, and nutrient fluxes (Fer et al, ; Koenig et al, ; Meyer et al, ; Peterson et al, ; Randelhoff et al, ).…”

“…Largest ocean heat fluxes exceeded 300 W m −2 when drifting over AW during storms, resulting in rapid ice melt (Meyer et al, ; Peterson et al, ; Provost et al, ). A combination of observations and modeling (Koenig et al, ; Meyer et al, ) added to our understanding of the AW pathways in the Yermak Plateau (YP) area.…”

Winter to summer oceanographic observations in the Arctic Ocean north of Svalbard

“…[] show that the Svalbard Branch is stronger in winter (N‐ICE2015 observations) and spring than in summer and autumn [ Cokelet et al ., , observations]. Similar seasonal variability of the Svalbard Branch is presented in Koenig et al [].…”

New Hydrographic Measurements of the Upper Arctic Western Eurasian Basin in 2017 Reveal Fresher Mixed Layer and Shallower Warm Layer Than 2005–2012 Climatology

“…In most of the Arctic Ocean, the strongly stratified halocline prevents the heat of the warm Atlantic Water (AW) from reaching the surface. One notable exception is the western Nansen Basin, where the weaker halocline allows vertical ventilation of the AW up to the surface (Carmack et al, ; Koenig et al, ; Onarheim et al, ). However, the Arctic Ocean has undergone a substantial weakening of the stratification at the base of the mixed layer (Polyakov et al, ; Toole et al, ).…”