The effect of surface flooding on the physical-biogeochemical dynamics of a warm-core eddy off southeast Australia

Baird, ME; Suthers, IM; Griffin, DA; Hollings, B; Pattiaratchi, C; Everett, JD; Roughan, M; Oubelkheir, K; Doblin, M

The effect of surface flooding on the physical-biogeochemical dynamics of a warm-core eddy off southeast Australia

Baird, ME

Suthers, IM Griffin, DA Hollings, B Pattiaratchi, C Everett, JD

Roughan, M Oubelkheir, K

Doblin, M

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Publication Type:: Journal Article
Citation:: Deep-Sea Research Part II: Topical Studies in Oceanography, 2011, 58 (5), pp. 592 - 605
Issue Date:: 2011-03-01

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Field	Value	Language
dc.contributor.author	Baird, ME https://orcid.org/0000-0003-4955-2298	en_US
dc.contributor.author	Suthers, IM	en_US
dc.contributor.author	Griffin, DA	en_US
dc.contributor.author	Hollings, B	en_US
dc.contributor.author	Pattiaratchi, C	en_US
dc.contributor.author	Everett, JD https://orcid.org/0000-0002-6681-8054	en_US
dc.contributor.author	Roughan, M	en_US
dc.contributor.author	Oubelkheir, K https://orcid.org/0000-0002-6515-3791	en_US
dc.contributor.author	Doblin, M https://orcid.org/0000-0001-8750-3433	en_US
dc.date.issued	2011-03-01	en_US
dc.identifier.citation	Deep-Sea Research Part II: Topical Studies in Oceanography, 2011, 58 (5), pp. 592 - 605	en_US
dc.identifier.issn	0967-0645	en_US
dc.identifier.uri	http://hdl.handle.net/10453/14736
dc.description.abstract	Warm-core eddies (WCEs) formed from the East Australian Current (EAC) play an important role in the heat, mass and biogeochemical budgets of the western Tasman Sea. The development and separation of an EAC WCE during July-December 2008 was observed using remotely sensed temperature, ocean colour and sea-level elevation, three Argo floats, a shipboard CTD, a shelf mooring array and a 15-day deployment of a Slocum glider. The eddy formed from an EAC meander during the first half of 2008 and in late August had a ~275m deep surface mixed layer. In the two months before separation in early December, fresher and warmer EAC water flooded the top of the eddy, submerging the winter mixed layer. The rate of vertical transport due to submergence was estimated to be between 1 and 6Sv, at the time accounting for a significant fraction of the mean southward flow of the EAC. The core of the eddy had a surface chlorophyll a concentration of <0.4mgm-3 throughout the observations. A 20-40m thick pycnocline formed at the interface of the flooding surface waters and the submerged layer. Chlorophyll a concentration in the pycnocline ranged from 0.5 to 2mgm-3, with depth-integrated concentration ranging between 25 and 75mgm-2. The development of a sub-surface maximum suggests that flooding increased light levels in the pycnocline. Elevated levels of coloured dissolved organic matter in the submerged layer correspond to oxygen depletion, suggesting respiration of organic matter. A comparison is made with observations from WCEs in 1978 and 1997 in which, unusually, surface flooding did not occur, but solar heating stratified the top 50m. In the two eddies with surface capping, surface chlorophyll a concentrations were an order of magnitude higher than the 2008 flooded eddy, but depth-integrated chlorophyll a was similar. These findings suggest that EAC WCEs with relatively shallow surface flooding contain more phytoplankton biomass than surface images would suggest, with the vertical position of the chlorophyll a maximum depending on whether, and to what depth, the winter surface mixed layer is submerged. © 2010 Elsevier Ltd.	en_US
dc.relation.ispartof	Deep-Sea Research Part II: Topical Studies in Oceanography	en_US
dc.relation.isbasedon	10.1016/j.dsr2.2010.10.002	en_US
dc.subject.classification	Oceanography	en_US
dc.title	The effect of surface flooding on the physical-biogeochemical dynamics of a warm-core eddy off southeast Australia	en_US
dc.type	Journal Article
utslib.citation.volume	5	en_US
utslib.citation.volume	58	en_US
utslib.for	0402 Geochemistry	en_US
utslib.for	0405 Oceanography	en_US
utslib.for	0602 Ecology	en_US
pubs.embargo.period	Not known	en_US
pubs.organisational-group	/University of Technology Sydney
pubs.organisational-group	/University of Technology Sydney/Faculty of Science
pubs.organisational-group	/University of Technology Sydney/Strength - C3 - Climate Change Cluster
utslib.copyright.status	open_access
pubs.issue	5	en_US
pubs.publication-status	Published	en_US
pubs.volume	58	en_US

Abstract:

Warm-core eddies (WCEs) formed from the East Australian Current (EAC) play an important role in the heat, mass and biogeochemical budgets of the western Tasman Sea. The development and separation of an EAC WCE during July-December 2008 was observed using remotely sensed temperature, ocean colour and sea-level elevation, three Argo floats, a shipboard CTD, a shelf mooring array and a 15-day deployment of a Slocum glider. The eddy formed from an EAC meander during the first half of 2008 and in late August had a ~275m deep surface mixed layer. In the two months before separation in early December, fresher and warmer EAC water flooded the top of the eddy, submerging the winter mixed layer. The rate of vertical transport due to submergence was estimated to be between 1 and 6Sv, at the time accounting for a significant fraction of the mean southward flow of the EAC. The core of the eddy had a surface chlorophyll a concentration of <0.4mgm-3 throughout the observations. A 20-40m thick pycnocline formed at the interface of the flooding surface waters and the submerged layer. Chlorophyll a concentration in the pycnocline ranged from 0.5 to 2mgm-3, with depth-integrated concentration ranging between 25 and 75mgm-2. The development of a sub-surface maximum suggests that flooding increased light levels in the pycnocline. Elevated levels of coloured dissolved organic matter in the submerged layer correspond to oxygen depletion, suggesting respiration of organic matter. A comparison is made with observations from WCEs in 1978 and 1997 in which, unusually, surface flooding did not occur, but solar heating stratified the top 50m. In the two eddies with surface capping, surface chlorophyll a concentrations were an order of magnitude higher than the 2008 flooded eddy, but depth-integrated chlorophyll a was similar. These findings suggest that EAC WCEs with relatively shallow surface flooding contain more phytoplankton biomass than surface images would suggest, with the vertical position of the chlorophyll a maximum depending on whether, and to what depth, the winter surface mixed layer is submerged. © 2010 Elsevier Ltd.

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