Arctic freshwater fluxes: sources, tracer budgets and inconsistencies
The net rate of freshwater input to the Arctic Ocean has been calculated in the past by two methods: directly, as the sum of precipitation, evaporation and runoff, an approach hindered by sparsity of measurements, and by the ice and ocean budget method, where the net surface freshwater flux within a...
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ftsouthampton:oai:eprints.soton.ac.uk:433703 2023-08-27T04:06:38+02:00 Arctic freshwater fluxes: sources, tracer budgets and inconsistencies Forryan, Alexander Bacon, Sheldon Tsubouchi, Takamasa Torres-Valdés, Sinhué Garabato, Alberto C.Naveira 2019-08 text https://eprints.soton.ac.uk/433703/ https://eprints.soton.ac.uk/433703/1/tc_13_2111_2019.pdf en English eng https://eprints.soton.ac.uk/433703/1/tc_13_2111_2019.pdf Forryan, Alexander, Bacon, Sheldon, Tsubouchi, Takamasa, Torres-Valdés, Sinhué and Garabato, Alberto C.Naveira (2019) Arctic freshwater fluxes: sources, tracer budgets and inconsistencies. Cryosphere, 13 (8), 2111-2131. (doi:10.5194/tc-13-2111-2019 <http://dx.doi.org/10.5194/tc-13-2111-2019>). cc_by_4 Article PeerReviewed 2019 ftsouthampton https://doi.org/10.5194/tc-13-2111-2019 2023-08-03T22:24:06Z The net rate of freshwater input to the Arctic Ocean has been calculated in the past by two methods: directly, as the sum of precipitation, evaporation and runoff, an approach hindered by sparsity of measurements, and by the ice and ocean budget method, where the net surface freshwater flux within a defined boundary is calculated from the rate of dilution of salinity, comparing ocean inflows with ice and ocean outflows. Here a third method is introduced, the geochemical method, as a modification of the budget method. A standard approach uses geochemical tracers (salinity, oxygen isotopes, inorganic nutrients) to compute "source fractions" that quantify a water parcel's constituent proportions of seawater, freshwater of meteoric origin, and either sea ice melt or brine (from the freezing-out of sea ice). The geochemical method combines the source fractions with the boundary velocity field of the budget method to quantify the net flux derived from each source. Here it is shown that the geochemical method generates an Arctic Ocean surface freshwater flux, which is also the meteoric source flux, of 200±44 mSv (1 Sv = 10^6 m^3 s^-1), statistically indistinguishable from the budget method's 187±44 mSv, so that two different approaches to surface freshwater flux calculation are reconciled. The freshwater export rate of sea ice (40±14 mSv) is similar to the brine export flux, due to the "freshwater deficit" left by the freezing-out of sea ice (60±50 mSv). Inorganic nutrients are used to define Atlantic and Pacific seawater categories, and the results show significant non-conservation, whereby Atlantic seawater is effectively "converted" into Pacific seawater. This is hypothesized to be a consequence of denitrification within the Arctic Ocean, a process likely becoming more important with seasonal sea ice retreat. While inorganic nutrients may now be delivering ambiguous results on seawater origins, they may prove useful to quantify the Arctic Ocean's net denitrification rate. End point degeneracy is also discussed: ... Article in Journal/Newspaper Arctic Arctic Arctic Ocean Sea ice University of Southampton: e-Prints Soton Arctic Arctic Ocean Pacific The Cryosphere 13 8 2111 2131 |
institution |
Open Polar |
collection |
University of Southampton: e-Prints Soton |
op_collection_id |
ftsouthampton |
language |
English |
description |
The net rate of freshwater input to the Arctic Ocean has been calculated in the past by two methods: directly, as the sum of precipitation, evaporation and runoff, an approach hindered by sparsity of measurements, and by the ice and ocean budget method, where the net surface freshwater flux within a defined boundary is calculated from the rate of dilution of salinity, comparing ocean inflows with ice and ocean outflows. Here a third method is introduced, the geochemical method, as a modification of the budget method. A standard approach uses geochemical tracers (salinity, oxygen isotopes, inorganic nutrients) to compute "source fractions" that quantify a water parcel's constituent proportions of seawater, freshwater of meteoric origin, and either sea ice melt or brine (from the freezing-out of sea ice). The geochemical method combines the source fractions with the boundary velocity field of the budget method to quantify the net flux derived from each source. Here it is shown that the geochemical method generates an Arctic Ocean surface freshwater flux, which is also the meteoric source flux, of 200±44 mSv (1 Sv = 10^6 m^3 s^-1), statistically indistinguishable from the budget method's 187±44 mSv, so that two different approaches to surface freshwater flux calculation are reconciled. The freshwater export rate of sea ice (40±14 mSv) is similar to the brine export flux, due to the "freshwater deficit" left by the freezing-out of sea ice (60±50 mSv). Inorganic nutrients are used to define Atlantic and Pacific seawater categories, and the results show significant non-conservation, whereby Atlantic seawater is effectively "converted" into Pacific seawater. This is hypothesized to be a consequence of denitrification within the Arctic Ocean, a process likely becoming more important with seasonal sea ice retreat. While inorganic nutrients may now be delivering ambiguous results on seawater origins, they may prove useful to quantify the Arctic Ocean's net denitrification rate. End point degeneracy is also discussed: ... |
format |
Article in Journal/Newspaper |
author |
Forryan, Alexander Bacon, Sheldon Tsubouchi, Takamasa Torres-Valdés, Sinhué Garabato, Alberto C.Naveira |
spellingShingle |
Forryan, Alexander Bacon, Sheldon Tsubouchi, Takamasa Torres-Valdés, Sinhué Garabato, Alberto C.Naveira Arctic freshwater fluxes: sources, tracer budgets and inconsistencies |
author_facet |
Forryan, Alexander Bacon, Sheldon Tsubouchi, Takamasa Torres-Valdés, Sinhué Garabato, Alberto C.Naveira |
author_sort |
Forryan, Alexander |
title |
Arctic freshwater fluxes: sources, tracer budgets and inconsistencies |
title_short |
Arctic freshwater fluxes: sources, tracer budgets and inconsistencies |
title_full |
Arctic freshwater fluxes: sources, tracer budgets and inconsistencies |
title_fullStr |
Arctic freshwater fluxes: sources, tracer budgets and inconsistencies |
title_full_unstemmed |
Arctic freshwater fluxes: sources, tracer budgets and inconsistencies |
title_sort |
arctic freshwater fluxes: sources, tracer budgets and inconsistencies |
publishDate |
2019 |
url |
https://eprints.soton.ac.uk/433703/ https://eprints.soton.ac.uk/433703/1/tc_13_2111_2019.pdf |
geographic |
Arctic Arctic Ocean Pacific |
geographic_facet |
Arctic Arctic Ocean Pacific |
genre |
Arctic Arctic Arctic Ocean Sea ice |
genre_facet |
Arctic Arctic Arctic Ocean Sea ice |
op_relation |
https://eprints.soton.ac.uk/433703/1/tc_13_2111_2019.pdf Forryan, Alexander, Bacon, Sheldon, Tsubouchi, Takamasa, Torres-Valdés, Sinhué and Garabato, Alberto C.Naveira (2019) Arctic freshwater fluxes: sources, tracer budgets and inconsistencies. Cryosphere, 13 (8), 2111-2131. (doi:10.5194/tc-13-2111-2019 <http://dx.doi.org/10.5194/tc-13-2111-2019>). |
op_rights |
cc_by_4 |
op_doi |
https://doi.org/10.5194/tc-13-2111-2019 |
container_title |
The Cryosphere |
container_volume |
13 |
container_issue |
8 |
container_start_page |
2111 |
op_container_end_page |
2131 |
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1775347489777385472 |