The impact of melt water discharge from the Greenland ice sheet on the Atlantic nutrient supply to the Northwest European Shelf
Projected future shoaling of the wintertime mixed layer in the Northeast (NE) Atlantic has been shown to induce a regime shift in the main nutrient supply pathway from the Atlantic to the Northwest European Shelf (NWES) near the end of the 21st century. While reduced winter convection leads to a sub...
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ftcopernicus:oai:publications.copernicus.org:osd79977 2023-05-15T16:28:39+02:00 The impact of melt water discharge from the Greenland ice sheet on the Atlantic nutrient supply to the Northwest European Shelf Mathis, Moritz Mikolajewicz, Uwe 2019-09-17 application/pdf https://doi.org/10.5194/os-2019-100 https://www.ocean-sci-discuss.net/os-2019-100/ eng eng doi:10.5194/os-2019-100 https://www.ocean-sci-discuss.net/os-2019-100/ eISSN: 1812-0792 Text 2019 ftcopernicus https://doi.org/10.5194/os-2019-100 2019-12-24T09:48:31Z Projected future shoaling of the wintertime mixed layer in the Northeast (NE) Atlantic has been shown to induce a regime shift in the main nutrient supply pathway from the Atlantic to the Northwest European Shelf (NWES) near the end of the 21st century. While reduced winter convection leads to a substantial decrease in the vertical nutrient supply and biological productivity in the open ocean, vertical mixing processes at the shelf break maintain a connection to the subpycnocline nutrient pool and thus productivity on the shelf. Here we investigate how meltwater discharge from the Greenland ice sheet (GIS) not yet taken into account impacts the mixed layer shoaling and the regime shift in terms of spatial distribution and temporal variability. To this end we have downscaled sensitivity experiments by a global earth system model for various GIS melting rates with a regionally coupled ocean-atmosphere climate system model. The model results indicate that increasing GIS meltwater discharge leads to a general intensification of the regime shift. Atlantic subpycnocline water masses mixed up at the shelf break become richer in nutrients and thus limit the projected nutrient decline on the shelf. Moreover, the stronger vertical nutrient gradient through the pycnocline results in an enhanced interannual variability of on-shelf nutrient fluxes which, however, do not significantly increase variations in nutrient concentrations and primary production on the shelf. Moreover, due to the impact of the GIS meltwater discharge on the NE Atlantic mixed layer depth, the regime shift becomes initiated earlier in the century by about 1–2 decades, depending on the discharge rate. The effect on the onset timing, though, is found to be strongly damped by the weakening of the Atlantic meridional overturning circulation. A GIS melting rate that is even 10 times higher than expected for emission scenario RCP8.5 would lead to an onset of the regime shift not until the 2070s. Text Greenland Ice Sheet Copernicus Publications: E-Journals Greenland |
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Open Polar |
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Copernicus Publications: E-Journals |
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ftcopernicus |
language |
English |
description |
Projected future shoaling of the wintertime mixed layer in the Northeast (NE) Atlantic has been shown to induce a regime shift in the main nutrient supply pathway from the Atlantic to the Northwest European Shelf (NWES) near the end of the 21st century. While reduced winter convection leads to a substantial decrease in the vertical nutrient supply and biological productivity in the open ocean, vertical mixing processes at the shelf break maintain a connection to the subpycnocline nutrient pool and thus productivity on the shelf. Here we investigate how meltwater discharge from the Greenland ice sheet (GIS) not yet taken into account impacts the mixed layer shoaling and the regime shift in terms of spatial distribution and temporal variability. To this end we have downscaled sensitivity experiments by a global earth system model for various GIS melting rates with a regionally coupled ocean-atmosphere climate system model. The model results indicate that increasing GIS meltwater discharge leads to a general intensification of the regime shift. Atlantic subpycnocline water masses mixed up at the shelf break become richer in nutrients and thus limit the projected nutrient decline on the shelf. Moreover, the stronger vertical nutrient gradient through the pycnocline results in an enhanced interannual variability of on-shelf nutrient fluxes which, however, do not significantly increase variations in nutrient concentrations and primary production on the shelf. Moreover, due to the impact of the GIS meltwater discharge on the NE Atlantic mixed layer depth, the regime shift becomes initiated earlier in the century by about 1–2 decades, depending on the discharge rate. The effect on the onset timing, though, is found to be strongly damped by the weakening of the Atlantic meridional overturning circulation. A GIS melting rate that is even 10 times higher than expected for emission scenario RCP8.5 would lead to an onset of the regime shift not until the 2070s. |
format |
Text |
author |
Mathis, Moritz Mikolajewicz, Uwe |
spellingShingle |
Mathis, Moritz Mikolajewicz, Uwe The impact of melt water discharge from the Greenland ice sheet on the Atlantic nutrient supply to the Northwest European Shelf |
author_facet |
Mathis, Moritz Mikolajewicz, Uwe |
author_sort |
Mathis, Moritz |
title |
The impact of melt water discharge from the Greenland ice sheet on the Atlantic nutrient supply to the Northwest European Shelf |
title_short |
The impact of melt water discharge from the Greenland ice sheet on the Atlantic nutrient supply to the Northwest European Shelf |
title_full |
The impact of melt water discharge from the Greenland ice sheet on the Atlantic nutrient supply to the Northwest European Shelf |
title_fullStr |
The impact of melt water discharge from the Greenland ice sheet on the Atlantic nutrient supply to the Northwest European Shelf |
title_full_unstemmed |
The impact of melt water discharge from the Greenland ice sheet on the Atlantic nutrient supply to the Northwest European Shelf |
title_sort |
impact of melt water discharge from the greenland ice sheet on the atlantic nutrient supply to the northwest european shelf |
publishDate |
2019 |
url |
https://doi.org/10.5194/os-2019-100 https://www.ocean-sci-discuss.net/os-2019-100/ |
geographic |
Greenland |
geographic_facet |
Greenland |
genre |
Greenland Ice Sheet |
genre_facet |
Greenland Ice Sheet |
op_source |
eISSN: 1812-0792 |
op_relation |
doi:10.5194/os-2019-100 https://www.ocean-sci-discuss.net/os-2019-100/ |
op_doi |
https://doi.org/10.5194/os-2019-100 |
_version_ |
1766018321094803456 |