Vertical eddy diffusivity in the subsurface pycnocline across the Pacific

Abstract In the stratified ocean, vertical eddy diffusivity in the subsurface pycnocline plays a major role in new production through transporting nutrients upwards from the darker/nutrient-rich layer. In order to evaluate the diffusivity that was less available in the subsurface layers where indire...

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Published in:Journal of Oceanography
Main Authors: Itoh, S., Kaneko, H., Kouketsu, S., Okunishi, T., Tsutsumi, E., Ogawa, H., Yasuda, I.
Other Authors: Japan Society for the Promotion of Science
Format: Article in Journal/Newspaper
Language:English
Published: Springer Science and Business Media LLC 2021
Subjects:
Online Access:http://dx.doi.org/10.1007/s10872-020-00589-9
https://link.springer.com/content/pdf/10.1007/s10872-020-00589-9.pdf
https://link.springer.com/article/10.1007/s10872-020-00589-9/fulltext.html
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spelling crspringernat:10.1007/s10872-020-00589-9 2023-05-15T18:28:36+02:00 Vertical eddy diffusivity in the subsurface pycnocline across the Pacific Itoh, S. Kaneko, H. Kouketsu, S. Okunishi, T. Tsutsumi, E. Ogawa, H. Yasuda, I. Japan Society for the Promotion of Science 2021 http://dx.doi.org/10.1007/s10872-020-00589-9 https://link.springer.com/content/pdf/10.1007/s10872-020-00589-9.pdf https://link.springer.com/article/10.1007/s10872-020-00589-9/fulltext.html en eng Springer Science and Business Media LLC https://creativecommons.org/licenses/by/4.0 https://creativecommons.org/licenses/by/4.0 CC-BY Journal of Oceanography volume 77, issue 2, page 185-197 ISSN 0916-8370 1573-868X Oceanography journal-article 2021 crspringernat https://doi.org/10.1007/s10872-020-00589-9 2022-01-04T08:16:23Z Abstract In the stratified ocean, vertical eddy diffusivity in the subsurface pycnocline plays a major role in new production through transporting nutrients upwards from the darker/nutrient-rich layer. In order to evaluate the diffusivity that was less available in the subsurface layers where indirect estimations are difficult, we conducted direct microstructure measurements in the upper 300 m of the open Pacific during summer, from 40°S to 50°N along 170°W and from 137°E to 120°W across the subtropical North Pacific (21°30′N–23°N). The subsurface pycnocline in the mid- and low-latitude regions was occupied primarily by the Subtropical Underwaters characterized by high salinity, and the Subtropical Mode Waters appeared with an increasing depth and latitude. In the North Pacific, low-salinity subarctic water with shallow seasonal pycnocline was observed in the high-latitude region. The base level of the diffusivity was 0.14–0.47 × 10 –5 m 2 s –1 , while elevations up to 0.51–13 × 10 –5 m 2 s –1 were observed at the equator where the Equatorial Undercurrents formed the strong shear in the subsurface layer, and in areas high internal tide energy such as the Hawaiian Ridge. The effect of wind on the diffusivity was less clear, probably because the wind energy is generally low during summer. The shear-to-strain ratio showed dome-shaped profiles with respect to latitude and an increasing trend from west to east in the subtropical North Pacific. The geographical distributions of the diffusivity presented in this study will contribute to better understanding biogeochemical cycles in the stratified upper ocean through improving estimations of the material transport. Article in Journal/Newspaper Subarctic Springer Nature (via Crossref) Pacific Journal of Oceanography 77 2 185 197
institution Open Polar
collection Springer Nature (via Crossref)
op_collection_id crspringernat
language English
topic Oceanography
spellingShingle Oceanography
Itoh, S.
Kaneko, H.
Kouketsu, S.
Okunishi, T.
Tsutsumi, E.
Ogawa, H.
Yasuda, I.
Vertical eddy diffusivity in the subsurface pycnocline across the Pacific
topic_facet Oceanography
description Abstract In the stratified ocean, vertical eddy diffusivity in the subsurface pycnocline plays a major role in new production through transporting nutrients upwards from the darker/nutrient-rich layer. In order to evaluate the diffusivity that was less available in the subsurface layers where indirect estimations are difficult, we conducted direct microstructure measurements in the upper 300 m of the open Pacific during summer, from 40°S to 50°N along 170°W and from 137°E to 120°W across the subtropical North Pacific (21°30′N–23°N). The subsurface pycnocline in the mid- and low-latitude regions was occupied primarily by the Subtropical Underwaters characterized by high salinity, and the Subtropical Mode Waters appeared with an increasing depth and latitude. In the North Pacific, low-salinity subarctic water with shallow seasonal pycnocline was observed in the high-latitude region. The base level of the diffusivity was 0.14–0.47 × 10 –5 m 2 s –1 , while elevations up to 0.51–13 × 10 –5 m 2 s –1 were observed at the equator where the Equatorial Undercurrents formed the strong shear in the subsurface layer, and in areas high internal tide energy such as the Hawaiian Ridge. The effect of wind on the diffusivity was less clear, probably because the wind energy is generally low during summer. The shear-to-strain ratio showed dome-shaped profiles with respect to latitude and an increasing trend from west to east in the subtropical North Pacific. The geographical distributions of the diffusivity presented in this study will contribute to better understanding biogeochemical cycles in the stratified upper ocean through improving estimations of the material transport.
author2 Japan Society for the Promotion of Science
format Article in Journal/Newspaper
author Itoh, S.
Kaneko, H.
Kouketsu, S.
Okunishi, T.
Tsutsumi, E.
Ogawa, H.
Yasuda, I.
author_facet Itoh, S.
Kaneko, H.
Kouketsu, S.
Okunishi, T.
Tsutsumi, E.
Ogawa, H.
Yasuda, I.
author_sort Itoh, S.
title Vertical eddy diffusivity in the subsurface pycnocline across the Pacific
title_short Vertical eddy diffusivity in the subsurface pycnocline across the Pacific
title_full Vertical eddy diffusivity in the subsurface pycnocline across the Pacific
title_fullStr Vertical eddy diffusivity in the subsurface pycnocline across the Pacific
title_full_unstemmed Vertical eddy diffusivity in the subsurface pycnocline across the Pacific
title_sort vertical eddy diffusivity in the subsurface pycnocline across the pacific
publisher Springer Science and Business Media LLC
publishDate 2021
url http://dx.doi.org/10.1007/s10872-020-00589-9
https://link.springer.com/content/pdf/10.1007/s10872-020-00589-9.pdf
https://link.springer.com/article/10.1007/s10872-020-00589-9/fulltext.html
geographic Pacific
geographic_facet Pacific
genre Subarctic
genre_facet Subarctic
op_source Journal of Oceanography
volume 77, issue 2, page 185-197
ISSN 0916-8370 1573-868X
op_rights https://creativecommons.org/licenses/by/4.0
https://creativecommons.org/licenses/by/4.0
op_rightsnorm CC-BY
op_doi https://doi.org/10.1007/s10872-020-00589-9
container_title Journal of Oceanography
container_volume 77
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container_start_page 185
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