The University of Southampton
University of Southampton Institutional Repository
Warning ePrints Soton is experiencing an issue with some file downloads not being available. We are working hard to fix this. Please bear with us.

Shelf‐break upwelling and productivity over the North Kenya Banks: The importance of large‐scale ocean dynamics

Shelf‐break upwelling and productivity over the North Kenya Banks: The importance of large‐scale ocean dynamics
Shelf‐break upwelling and productivity over the North Kenya Banks: The importance of large‐scale ocean dynamics
The North Kenya Banks (NKBs) have recently emerged as a new frontier for food security and could become an economically important fishery for Kenya with improved resources providing better accessibility. Little research has been done on the mechanisms supporting high fish productivity over the NKBs with information on annual and interannual environmental variability lacking. Here we use a high‐resolution, global, biogeochemical ocean model with remote sensing observations to demonstrate that the ocean circulation exerts an important control on the productivity over the NKBs. During the Northeast Monsoon, which occurs from December to February, upwelling occurs along the Kenyan coast, which is topographically enhanced over the NKBs. Additionally, enhanced upwelling events, associated with widespread cool temperatures, elevated chlorophyll, nutrients, primary production, and phytoplankton biomass, can occur over this region. Eight such modeled events, characterized by primary production exceeding 1.3 g C/m−2/day, were found to occur during January or February from 1993–2015. Even though the upwelling is always rooted to the NKBs, the position, spatial extent, and intensity of the upwelling exhibit considerable interannual variability. The confluence zone between the Somali Current and East African Coastal Current (referred to as the Somali‐Zanzibar Confluence Zone) forms during the Northeast Monsoon and is highly variable. We present evidence that when the Somali‐Zanzibar Confluence Zone is positioned further south, it acts to enhance shelf‐edge upwelling and productivity over the NKBs. These findings provide the first indication of the environmental controls that need to be considered when developing plans for the sustainable exploitation of the NKB fishery.
Indian Ocean, currents, fisheries, modeling, productivity, upwelling
2169-9275
Jacobs, Z. L.
3b55fc85-c85e-442e-949c-8a71850a66e8
Jebri, F.
d728e63e-2037-4e8b-bf90-38e374a7414a
Raitsos, D. E.
624a491c-804a-4704-83ac-b7e8adcc0ce1
Popova, E.
3ea572bd-f37d-4777-894b-b0d86f735820
Srokosz, M.
f1701d3e-01b3-43d0-8993-9fd523032a79
Painter, S.C.
29e32f35-4ee8-4654-b305-4dbe5a312295
Nencioli, F.
5a4ef2fb-0ea3-4328-9404-8c029ec28750
Roberts, M.
8841b432-f080-4b49-a9f4-1a1fbaed1a81
Kamau, J.
8c144442-8059-43d7-ad87-fe9bc8898f73
Palmer, M.
d2e60e81-5d6e-4ddb-a243-602537286080
Wihsgott, J.
42b736f5-c608-4269-b6aa-561e31ec8eba
Jacobs, Z. L.
3b55fc85-c85e-442e-949c-8a71850a66e8
Jebri, F.
d728e63e-2037-4e8b-bf90-38e374a7414a
Raitsos, D. E.
624a491c-804a-4704-83ac-b7e8adcc0ce1
Popova, E.
3ea572bd-f37d-4777-894b-b0d86f735820
Srokosz, M.
f1701d3e-01b3-43d0-8993-9fd523032a79
Painter, S.C.
29e32f35-4ee8-4654-b305-4dbe5a312295
Nencioli, F.
5a4ef2fb-0ea3-4328-9404-8c029ec28750
Roberts, M.
8841b432-f080-4b49-a9f4-1a1fbaed1a81
Kamau, J.
8c144442-8059-43d7-ad87-fe9bc8898f73
Palmer, M.
d2e60e81-5d6e-4ddb-a243-602537286080
Wihsgott, J.
42b736f5-c608-4269-b6aa-561e31ec8eba

Jacobs, Z. L., Jebri, F., Raitsos, D. E., Popova, E., Srokosz, M., Painter, S.C., Nencioli, F., Roberts, M., Kamau, J., Palmer, M. and Wihsgott, J. (2020) Shelf‐break upwelling and productivity over the North Kenya Banks: The importance of large‐scale ocean dynamics. Journal of Geophysical Research: Oceans, 125 (1), [e2019JC015519]. (doi:10.1029/2019JC015519).

Record type: Article

Abstract

The North Kenya Banks (NKBs) have recently emerged as a new frontier for food security and could become an economically important fishery for Kenya with improved resources providing better accessibility. Little research has been done on the mechanisms supporting high fish productivity over the NKBs with information on annual and interannual environmental variability lacking. Here we use a high‐resolution, global, biogeochemical ocean model with remote sensing observations to demonstrate that the ocean circulation exerts an important control on the productivity over the NKBs. During the Northeast Monsoon, which occurs from December to February, upwelling occurs along the Kenyan coast, which is topographically enhanced over the NKBs. Additionally, enhanced upwelling events, associated with widespread cool temperatures, elevated chlorophyll, nutrients, primary production, and phytoplankton biomass, can occur over this region. Eight such modeled events, characterized by primary production exceeding 1.3 g C/m−2/day, were found to occur during January or February from 1993–2015. Even though the upwelling is always rooted to the NKBs, the position, spatial extent, and intensity of the upwelling exhibit considerable interannual variability. The confluence zone between the Somali Current and East African Coastal Current (referred to as the Somali‐Zanzibar Confluence Zone) forms during the Northeast Monsoon and is highly variable. We present evidence that when the Somali‐Zanzibar Confluence Zone is positioned further south, it acts to enhance shelf‐edge upwelling and productivity over the NKBs. These findings provide the first indication of the environmental controls that need to be considered when developing plans for the sustainable exploitation of the NKB fishery.

Text
Jacobs_et_al-2020-Journal_of_Geophysical_Research__Oceans - Version of Record
Available under License Creative Commons Attribution.
Download (14MB)

More information

Accepted/In Press date: 9 January 2020
e-pub ahead of print date: 10 January 2020
Keywords: Indian Ocean, currents, fisheries, modeling, productivity, upwelling

Identifiers

Local EPrints ID: 437954
URI: http://eprints.soton.ac.uk/id/eprint/437954
ISSN: 2169-9275
PURE UUID: 3b2e77bd-133b-40f5-b74d-afeb635de55d

Catalogue record

Date deposited: 24 Feb 2020 17:31
Last modified: 25 Nov 2021 23:54

Export record

Altmetrics

Contributors

Author: Z. L. Jacobs
Author: F. Jebri
Author: D. E. Raitsos
Author: E. Popova
Author: M. Srokosz
Author: S.C. Painter
Author: F. Nencioli
Author: M. Roberts
Author: J. Kamau
Author: M. Palmer
Author: J. Wihsgott

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of http://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×