Nonseasonal fluctuations of the Arctic Ocean mass observed by the GRACE satellites

Journal of Geophysical Research Atmospheres (Impact Factor: 3.44). 08/2013; DOI: 10.1002/2013JC009341

ABSTRACT Time variable gravity observations from the GRACE satellites reveal strong non-seasonal fluctuations of bottom pressure in the Arctic Ocean on the time scales from 2 to 6 months and a record-high bottom pressure anomaly in February of 2011. Here, we examine the nature and driving forces behind those fluctuations. We find that the non-seasonal variability of the Arctic Ocean mass is strongly coupled to wind forcing. The zonal wind pattern is correlated with a di-pole pattern of Arctic Ocean mass changes. Westerly wind intensification over the North Atlantic at about 60°N as well as over the Russian Arctic continental shelf break cause the ocean mass to decrease in the Nordic seas and in the central Arctic, and to increase over the Russian Arctic shelf. Basin-wide Arctic Ocean mass fluctuations are correlated with northward wind anomalies over the northeastern North Atlantic and Nordic seas, and over the Bering Sea. We show that positive (negative) Arctic Ocean mass anomalies are associated with anticyclonic (cyclonic) anomalies of the large-scale ocean circulation pattern. Based on ocean model simulations, we conclude that the observed non-seasonal Arctic Ocean mass variability is mostly explained by the net horizontal wind-driven transports, and the contribution of fresh water fluxes is negligible. We demonstrate that transport anomalies across both the Atlantic and Pacific gateways were equally important for generating large Arctic Ocean mass anomalies in 2011.

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    ABSTRACT: The GRACE satellites have observed coherent and nearly uniform nonseasonal fluctuations of bottom pressure throughout the Arctic Ocean and the Nordic seas. Strong correlation between the nonseasonal GRACE and satellite altimetry data is found in the Nordic and Barents seas, which suggests a possibility of using the longer altimetry records in these areas as a proxy for the nonseasonal sea level variability over the entire Arctic. This study identifies the dominant pattern of the nonseasonal atmospheric pressure variability that drives strong zonal wind anomalies over the northeastern North Atlantic associated with the nonseasonal sea level anomalies in the Nordic seas. Our results show that wind-driven northward Ekman transport anomalies in the northeastern North Atlantic may induce coherent changes of sea level across the entire Arctic Ocean.
    Geophysical Research Letters 02/2014; · 4.46 Impact Factor


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May 21, 2014