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Article Type:
Research Article

Arctic Ocean Water Mass Transformation in S–T Coordinates

Per Pemberton Department of Meteorology, Stockholm University, Stockholm, and Oceanographic Research Unit, Swedish Meteorological and Hydrological Institute, Gothenburg, Sweden

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Johan Nilsson Department of Meteorology, Stockholm University, Stockholm, Sweden

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Magnus Hieronymus Institute for Coastal Research, Helmholtz Zentrum Geesthacht, Geesthacht, Germany

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H. E. Markus Meier Department of Meteorology, Stockholm University, Stockholm, and Oceanographic Research Unit, Swedish Meteorological and Hydrological Institute, Norrköping, Sweden

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Print Publication:
01 Apr 2015
DOI:
https://doi.org/10.1175/JPO-D-14-0197.1
Page(s):
1025–1050
Restricted access

Abstract

In this paper, water mass transformations in the Arctic Ocean are studied using a recently developed salinity–temperature (S–T) framework. The framework allows the water mass transformations to be succinctly quantified by computing the surface and internal diffusive fluxes in S–T coordinates. This study shows how the method can be applied to a specific oceanic region, in this case the Arctic Ocean, by including the advective exchange of water masses across the boundaries of the region. Based on a simulation with a global ocean circulation model, the authors examine the importance of various parameterized mixing processes and surface fluxes for the transformation of water across isohaline and isothermal surfaces in the Arctic Ocean. The model-based results reveal a broadly realistic Arctic Ocean where the inflowing Atlantic and Pacific waters are primarily cooled and freshened before exiting back to the North Atlantic. In the model, the water mass transformation in the T direction is primarily accomplished by the surface heat flux. However, the surface freshwater flux plays a minor role in the transformation of water toward lower salinities, which is mainly driven by a downgradient mixing of salt in the interior ocean. Near the freezing line, the seasonal melt and growth of sea ice influences the transformation pattern.

Denotes Open Access content.

Corresponding author address: Per Pemberton, Department of Meteorology, Stockholm University, SE-106 91 Stockholm, Sweden. E-mail: per.pemberton@smhi.se

Abstract

In this paper, water mass transformations in the Arctic Ocean are studied using a recently developed salinity–temperature (S–T) framework. The framework allows the water mass transformations to be succinctly quantified by computing the surface and internal diffusive fluxes in S–T coordinates. This study shows how the method can be applied to a specific oceanic region, in this case the Arctic Ocean, by including the advective exchange of water masses across the boundaries of the region. Based on a simulation with a global ocean circulation model, the authors examine the importance of various parameterized mixing processes and surface fluxes for the transformation of water across isohaline and isothermal surfaces in the Arctic Ocean. The model-based results reveal a broadly realistic Arctic Ocean where the inflowing Atlantic and Pacific waters are primarily cooled and freshened before exiting back to the North Atlantic. In the model, the water mass transformation in the T direction is primarily accomplished by the surface heat flux. However, the surface freshwater flux plays a minor role in the transformation of water toward lower salinities, which is mainly driven by a downgradient mixing of salt in the interior ocean. Near the freezing line, the seasonal melt and growth of sea ice influences the transformation pattern.

Denotes Open Access content.

Corresponding author address: Per Pemberton, Department of Meteorology, Stockholm University, SE-106 91 Stockholm, Sweden. E-mail: per.pemberton@smhi.se
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