Intensive mixing along an island chain controls oceanic biogeochemical cycles
The subarctic Pacific is a high-nutrient low-chlorophyll (HNLC) region in which phytoplankton growth is broadly limited by iron (Fe) availability. However, even with Fe limitation, the western subarctic Pacific (WSP) has significant phytoplankton growth and greater seasonal variability in lower trop...
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fthokunivhus:oai:eprints.lib.hokudai.ac.jp:2115/54810 2023-05-15T16:55:52+02:00 Intensive mixing along an island chain controls oceanic biogeochemical cycles Nishioka, Jun Nakatsuka, Takeshi Watanabe, Yutaka W. Yasuda, Ichiro Kuma, Kenshi Ogawa, Hiroshi Ebuchi, Naoto Scherbinin, Alexey Volkov, Yuri N. Shiraiwa, Takayuki Wakatsuchi, Masaaki http://hdl.handle.net/2115/54810 https://doi.org/10.1002/gbc.20088 eng eng Amer geophysical union http://hdl.handle.net/2115/54810 Global biogeochemical cycles, 27(3): 920-929 http://dx.doi.org/10.1002/gbc.20088 iron islands chain mixing biogeochemical cycle subarctic North Pacific IPY-GEOTRACES 452 article fthokunivhus https://doi.org/10.1002/gbc.20088 2022-11-18T01:02:57Z The subarctic Pacific is a high-nutrient low-chlorophyll (HNLC) region in which phytoplankton growth is broadly limited by iron (Fe) availability. However, even with Fe limitation, the western subarctic Pacific (WSP) has significant phytoplankton growth and greater seasonal variability in lower trophic levels than the eastern subarctic Pacific. Therefore, differences in Fe supply must explain the west-to-east decrease in seasonal phytoplankton growth. The Fe flux to the euphotic zone in the WSP occurs at a moderate value, in that it is significantly higher than its value on the eastern side, yet it is not sufficient enough to cause widespread macronutrient depletion, that is, HNLC status is maintained. Although we recognize several Fe supply processes in the WSP, the mechanisms that account for this moderate value of Fe supply have not previously been explained. Here we demonstrate the pivotal role of tidal mixing in the Kuril Islands chain (KIC) for determining the moderate value. A basin-scale meridional Fe section shows that Fe derived from sediments in the Sea of Okhotsk is discharged through the KIC into the intermediate water masses (similar to 800m) of the western North Pacific. The redistribution of this Fe-rich intermediate water by intensive mixing as it crosses the KIC is the predominant process determining the ratio of micronutrient (Fe) to macronutrients (e.g., nitrate) in subsurface waters. This ratio can quantitatively explain the differences in surface macronutrient consumption between the western and eastern subarctic, as well as the general formation and biogeochemistry of HNLC waters of the subarctic North Pacific. Copyright 2013 American Geophysical Union. Article in Journal/Newspaper IPY Subarctic Hokkaido University Collection of Scholarly and Academic Papers (HUSCAP) Okhotsk Pacific Iron Islands ENVELOPE(-113.408,-113.408,61.661,61.661) Global Biogeochemical Cycles 27 3 920 929 |
institution |
Open Polar |
collection |
Hokkaido University Collection of Scholarly and Academic Papers (HUSCAP) |
op_collection_id |
fthokunivhus |
language |
English |
topic |
iron islands chain mixing biogeochemical cycle subarctic North Pacific IPY-GEOTRACES 452 |
spellingShingle |
iron islands chain mixing biogeochemical cycle subarctic North Pacific IPY-GEOTRACES 452 Nishioka, Jun Nakatsuka, Takeshi Watanabe, Yutaka W. Yasuda, Ichiro Kuma, Kenshi Ogawa, Hiroshi Ebuchi, Naoto Scherbinin, Alexey Volkov, Yuri N. Shiraiwa, Takayuki Wakatsuchi, Masaaki Intensive mixing along an island chain controls oceanic biogeochemical cycles |
topic_facet |
iron islands chain mixing biogeochemical cycle subarctic North Pacific IPY-GEOTRACES 452 |
description |
The subarctic Pacific is a high-nutrient low-chlorophyll (HNLC) region in which phytoplankton growth is broadly limited by iron (Fe) availability. However, even with Fe limitation, the western subarctic Pacific (WSP) has significant phytoplankton growth and greater seasonal variability in lower trophic levels than the eastern subarctic Pacific. Therefore, differences in Fe supply must explain the west-to-east decrease in seasonal phytoplankton growth. The Fe flux to the euphotic zone in the WSP occurs at a moderate value, in that it is significantly higher than its value on the eastern side, yet it is not sufficient enough to cause widespread macronutrient depletion, that is, HNLC status is maintained. Although we recognize several Fe supply processes in the WSP, the mechanisms that account for this moderate value of Fe supply have not previously been explained. Here we demonstrate the pivotal role of tidal mixing in the Kuril Islands chain (KIC) for determining the moderate value. A basin-scale meridional Fe section shows that Fe derived from sediments in the Sea of Okhotsk is discharged through the KIC into the intermediate water masses (similar to 800m) of the western North Pacific. The redistribution of this Fe-rich intermediate water by intensive mixing as it crosses the KIC is the predominant process determining the ratio of micronutrient (Fe) to macronutrients (e.g., nitrate) in subsurface waters. This ratio can quantitatively explain the differences in surface macronutrient consumption between the western and eastern subarctic, as well as the general formation and biogeochemistry of HNLC waters of the subarctic North Pacific. Copyright 2013 American Geophysical Union. |
format |
Article in Journal/Newspaper |
author |
Nishioka, Jun Nakatsuka, Takeshi Watanabe, Yutaka W. Yasuda, Ichiro Kuma, Kenshi Ogawa, Hiroshi Ebuchi, Naoto Scherbinin, Alexey Volkov, Yuri N. Shiraiwa, Takayuki Wakatsuchi, Masaaki |
author_facet |
Nishioka, Jun Nakatsuka, Takeshi Watanabe, Yutaka W. Yasuda, Ichiro Kuma, Kenshi Ogawa, Hiroshi Ebuchi, Naoto Scherbinin, Alexey Volkov, Yuri N. Shiraiwa, Takayuki Wakatsuchi, Masaaki |
author_sort |
Nishioka, Jun |
title |
Intensive mixing along an island chain controls oceanic biogeochemical cycles |
title_short |
Intensive mixing along an island chain controls oceanic biogeochemical cycles |
title_full |
Intensive mixing along an island chain controls oceanic biogeochemical cycles |
title_fullStr |
Intensive mixing along an island chain controls oceanic biogeochemical cycles |
title_full_unstemmed |
Intensive mixing along an island chain controls oceanic biogeochemical cycles |
title_sort |
intensive mixing along an island chain controls oceanic biogeochemical cycles |
publisher |
Amer geophysical union |
url |
http://hdl.handle.net/2115/54810 https://doi.org/10.1002/gbc.20088 |
long_lat |
ENVELOPE(-113.408,-113.408,61.661,61.661) |
geographic |
Okhotsk Pacific Iron Islands |
geographic_facet |
Okhotsk Pacific Iron Islands |
genre |
IPY Subarctic |
genre_facet |
IPY Subarctic |
op_relation |
http://hdl.handle.net/2115/54810 Global biogeochemical cycles, 27(3): 920-929 http://dx.doi.org/10.1002/gbc.20088 |
op_doi |
https://doi.org/10.1002/gbc.20088 |
container_title |
Global Biogeochemical Cycles |
container_volume |
27 |
container_issue |
3 |
container_start_page |
920 |
op_container_end_page |
929 |
_version_ |
1766046911270223872 |