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Observed changes in the Arctic Freshwater Outflow in Fram Strait
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  • Theodoros Karpouzoglou,
  • Laura de Steur,
  • Lars Henrik Smedsrud,
  • Hiroshi Sumata
Theodoros Karpouzoglou
Norwegian Polar Institute

Corresponding Author:[email protected]

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Laura de Steur
Norwegian Polar Institute
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Lars Henrik Smedsrud
University of Bergen, Norway
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Hiroshi Sumata
Norwegian Polar Institute
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Abstract

We present year-round estimates of liquid freshwater transport (FWT) in the East Greenland Current (EGC) in the western Fram Strait from mooring observations since 2015. Novel data from additional instruments deployed in recent years are used to correct earlier estimates when instrument coverage was lower. The updated FWT time series (reference salinity 34.9) show that the increased export between 2010 and 2015 has not continued, and that FWT has decreased to pre-2009 levels. Salt transport independent of a reference salinity is shown not to be sensitive to salinity changes. Between 2015-2019, the FWT in the Polar Water decreased to an average of 56.9 (±4.5) mSV, 15% less than the 2003-2019 long-term mean, however, high FWT events occurred in 2017. The overall decrease is related with a slowdown of the EGC, partly attributed to a decrease of the baroclinic component, due to salinification of the halocline waters (26.5 < σθ < 27.7 kg/m3) which counterbalanced the freshening of the surface layer (σθ < 26.5 kg/m3). Our results show changes in the Polar Water between 2003-2019: Salinity stratification increased as the salinity difference between 155 and 55 m increased by 0.63 psu , the Polar Water layer became thinner by 46 m and the Polar-Atlantic front moved abruptly west in June 2015. All processes point to an “Atlantification” of the western Fram Strait and reduced Polar outflow. Including the novel data sets decreased the uncertainty of the FWT to an average of 8% after 2015, as opposed to 17% in earlier estimates.