Volume and temperature transports through the main Arctic Gateways: A comparative study between an ocean reanalysis and mooring-derived data

Abstract. Oceanic transports through the Arctic gateways represent an integral part of the polar climate system, but comprehensive in-situ-based estimates of this quantity have been lacking in the past. New observation-based estimates of oceanic volume, temperature and freshwater transports have recently become available. Those estimates have been derived from moored observations in the four major gateways by applying mass and salinity constraints. We seize this opportunity to compare a recent ocean reanalysis release with those observation-based estimates. First, time series of integrated volume and temperature transports through each strait are considered. Good agreement is found for Davis Strait volume transports, but considerable disagreement of up to 1.1 Sv in Fram Strait and the Barents Sea Opening. The annual mean net volume export through the gateways is −0.03 ± 0.23 Sv in the reanalysis, weaker than the −0.15 ± 0.06 Sv derived from the observation-based estimate (uncertainties represent the monthly standard deviation). The net ocean heat transport to the Arctic Ocean is similar in the two datasets (observation-based: 153 ± 44 TW, reanalysis: 145 ± 35 TW). Discrepancies in the integrated transports are further investigated by studying cross-sections of velocity, temperature and temperature flux density. These reveal good qualitative agreement in all straits, but considerable differences in the strength of major features like the East Greenland Current and the West Spitzbergen Current. Examination of the instrumental coverage reveals that areas of discrepancy are often co-located with poorly observed regions. In conclusion, both types of data sets have their merits and are recommended to be used complementarily for climate studies in this data-sparse region. We hope that the results presented in this study can assist in planning future observational efforts and in the development of ocean reanalysis products.