Declining Nutrient Concentrations in the Northeast Atlantic as a Result of a Weakening Subpolar Gyre
Between 1996 and the mid-2000s the upper waters (200-700 m) of the Rockall Trough became warmer (+0.72 C), saltier (+0.088) and reduced in nitrate and phosphate (-2.00 Micron and -0.14 Micron respectively). These changes, out-with calculated errors, can be explained by the varying influence of south...
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ftnasantrs:oai:casi.ntrs.nasa.gov:20140010833 2023-05-15T17:35:48+02:00 Declining Nutrient Concentrations in the Northeast Atlantic as a Result of a Weakening Subpolar Gyre Johnson, Clare Hakkinen, Sirpa Inall, Mark Unclassified, Unlimited, Publicly available December 2013 application/pdf http://hdl.handle.net/2060/20140010833 unknown Document ID: 20140010833 http://hdl.handle.net/2060/20140010833 Copyright, Distribution as joint owner in the copyright CASI Oceanography GSFC-E-DAA-TN11148 Deep Sea Research Part I: Oceanographic Research Papers (ISSN 0967-0637); 82; 95-107 2013 ftnasantrs 2019-07-21T00:26:50Z Between 1996 and the mid-2000s the upper waters (200-700 m) of the Rockall Trough became warmer (+0.72 C), saltier (+0.088) and reduced in nitrate and phosphate (-2.00 Micron and -0.14 Micron respectively). These changes, out-with calculated errors, can be explained by the varying influence of southern versus subpolar water masses in the basin as the Subpolar Gyre weakened and contracted. Upper water properties strongly correlate with a measure of the strength of the Subpolar Gyre (the first principal component of sea surface height over the Subpolar North Atlantic) prior to the mid-2000s. As the gyre weakens, the upper layers of the trough become warmer (r -0.85), more saline (r -0.86) and reduced in nitrate and phosphate (r +0.81 and r +0.87 respectively). Further the proportion of subpolar waters in the basin decreases from around 50% to less than 20% (r +0. 88). Since the mid-2000s the Subpolar Gyre has been particularly weak. During this period temperatures decreased slightly (-0.21 1C), salinities remained near constant (35.410 +/- 0.005) and phosphate levels low and stable (0.68 +/- 0.02 Micron). These relative lack of changes are thought to be related to the maximum proportion of southern water masses within the Rockall Trough having been reached. Thus the upper water properties are no longer controlled by changes in the relative importance of different water masses in the basin (as prior to the mid-2000s), but rather a different process. We suggest that when the gyre is particularly weak the interannual changes in upper water properties in the Rockall Trough reflect changes in the source properties of the southern water masses. Since the early-2000s the Subpolar Gyre has been weaker than observed since 1992, or modelled since 1960-1970. Hence upper waters within the Rockall Trough may be warmer, saltier and more depleted in nitrate and phosphate than at any time in the last half century. Other/Unknown Material North Atlantic Northeast Atlantic NASA Technical Reports Server (NTRS) Rockall Trough ENVELOPE(-15.036,-15.036,53.825,53.825) |
institution |
Open Polar |
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NASA Technical Reports Server (NTRS) |
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ftnasantrs |
language |
unknown |
topic |
Oceanography |
spellingShingle |
Oceanography Johnson, Clare Hakkinen, Sirpa Inall, Mark Declining Nutrient Concentrations in the Northeast Atlantic as a Result of a Weakening Subpolar Gyre |
topic_facet |
Oceanography |
description |
Between 1996 and the mid-2000s the upper waters (200-700 m) of the Rockall Trough became warmer (+0.72 C), saltier (+0.088) and reduced in nitrate and phosphate (-2.00 Micron and -0.14 Micron respectively). These changes, out-with calculated errors, can be explained by the varying influence of southern versus subpolar water masses in the basin as the Subpolar Gyre weakened and contracted. Upper water properties strongly correlate with a measure of the strength of the Subpolar Gyre (the first principal component of sea surface height over the Subpolar North Atlantic) prior to the mid-2000s. As the gyre weakens, the upper layers of the trough become warmer (r -0.85), more saline (r -0.86) and reduced in nitrate and phosphate (r +0.81 and r +0.87 respectively). Further the proportion of subpolar waters in the basin decreases from around 50% to less than 20% (r +0. 88). Since the mid-2000s the Subpolar Gyre has been particularly weak. During this period temperatures decreased slightly (-0.21 1C), salinities remained near constant (35.410 +/- 0.005) and phosphate levels low and stable (0.68 +/- 0.02 Micron). These relative lack of changes are thought to be related to the maximum proportion of southern water masses within the Rockall Trough having been reached. Thus the upper water properties are no longer controlled by changes in the relative importance of different water masses in the basin (as prior to the mid-2000s), but rather a different process. We suggest that when the gyre is particularly weak the interannual changes in upper water properties in the Rockall Trough reflect changes in the source properties of the southern water masses. Since the early-2000s the Subpolar Gyre has been weaker than observed since 1992, or modelled since 1960-1970. Hence upper waters within the Rockall Trough may be warmer, saltier and more depleted in nitrate and phosphate than at any time in the last half century. |
format |
Other/Unknown Material |
author |
Johnson, Clare Hakkinen, Sirpa Inall, Mark |
author_facet |
Johnson, Clare Hakkinen, Sirpa Inall, Mark |
author_sort |
Johnson, Clare |
title |
Declining Nutrient Concentrations in the Northeast Atlantic as a Result of a Weakening Subpolar Gyre |
title_short |
Declining Nutrient Concentrations in the Northeast Atlantic as a Result of a Weakening Subpolar Gyre |
title_full |
Declining Nutrient Concentrations in the Northeast Atlantic as a Result of a Weakening Subpolar Gyre |
title_fullStr |
Declining Nutrient Concentrations in the Northeast Atlantic as a Result of a Weakening Subpolar Gyre |
title_full_unstemmed |
Declining Nutrient Concentrations in the Northeast Atlantic as a Result of a Weakening Subpolar Gyre |
title_sort |
declining nutrient concentrations in the northeast atlantic as a result of a weakening subpolar gyre |
publishDate |
2013 |
url |
http://hdl.handle.net/2060/20140010833 |
op_coverage |
Unclassified, Unlimited, Publicly available |
long_lat |
ENVELOPE(-15.036,-15.036,53.825,53.825) |
geographic |
Rockall Trough |
geographic_facet |
Rockall Trough |
genre |
North Atlantic Northeast Atlantic |
genre_facet |
North Atlantic Northeast Atlantic |
op_source |
CASI |
op_relation |
Document ID: 20140010833 http://hdl.handle.net/2060/20140010833 |
op_rights |
Copyright, Distribution as joint owner in the copyright |
_version_ |
1766135082314104832 |