Mooring observations of air-sea heat fluxes in two Subantarctic Mode Water formation regions
Mooring observations of air-sea heat fluxes in two Subantarctic Mode Water formation regions
Wintertime surface ocean heat loss is the key process driving the formation of Subantarctic Mode Water (SAMW), but there are few direct observations of heat fluxes, particularly during winter. The Ocean Observatories Initiative (OOI) Southern Ocean mooring in the southeast Pacific Ocean and the Southern Ocean Flux Station (SOFS) in the southeast Indian Ocean provide the first concurrent, multiyear time series of air-sea fluxes in the Southern Ocean from two key SAMW formation regions. In this work we compare drivers of wintertime heat loss and SAMW formation by comparing air-sea fluxes and mixed layers at these two mooring locations. A gridded Argo product and the ERA5 reanalysis product provide temporal and spatial context for the mooring observations. Turbulent ocean heat loss is on average 1.5 times larger in the southeast Indian (SOFS) than in the southeast Pacific (OOI), with stronger extreme heat flux events in the southeast Indian leading to larger cumulative winter ocean heat loss. Turbulent heat loss events in the southeast Indian (SOFS) occur in two atmospheric regimes (cold air from the south or dry air circulating via the north), while heat loss events in the southeast Pacific (OOI) occur in a single atmospheric regime (cold air from the south). On interannual time scales, wintertime anomalies in net heat flux and mixed layer depth (MLD) are often correlated at the two sites, particularly when wintertime MLDs are anomalously deep. This relationship is part of a larger basin-scale zonal dipole in heat flux and MLD anomalies present in both the Indian and Pacific basins, associated with anomalous meridional atmospheric circulation.
2757-2777
Tamsitt, Veronica
17fd51ee-936c-4633-8e9b-687e4aa4243a
Cerovečki, Ivana
c525a0d2-e7d0-4d93-91b5-0b0099674a78
Josey, Simon A.
2252ab7f-5cd2-49fd-a951-aece44553d93
Gille, Sarah T.
6685a419-8041-49eb-98e5-b54d7aef90ec
Schulz, Eric
6c59ce62-49cc-485b-84f6-7531782dcf86
1 April 2020
Tamsitt, Veronica
17fd51ee-936c-4633-8e9b-687e4aa4243a
Cerovečki, Ivana
c525a0d2-e7d0-4d93-91b5-0b0099674a78
Josey, Simon A.
2252ab7f-5cd2-49fd-a951-aece44553d93
Gille, Sarah T.
6685a419-8041-49eb-98e5-b54d7aef90ec
Schulz, Eric
6c59ce62-49cc-485b-84f6-7531782dcf86
Tamsitt, Veronica, Cerovečki, Ivana, Josey, Simon A., Gille, Sarah T. and Schulz, Eric
(2020)
Mooring observations of air-sea heat fluxes in two Subantarctic Mode Water formation regions.
Journal of Climate, 33 (7), .
(doi:10.1175/JCLI-D-19-0653.1).
Abstract
Wintertime surface ocean heat loss is the key process driving the formation of Subantarctic Mode Water (SAMW), but there are few direct observations of heat fluxes, particularly during winter. The Ocean Observatories Initiative (OOI) Southern Ocean mooring in the southeast Pacific Ocean and the Southern Ocean Flux Station (SOFS) in the southeast Indian Ocean provide the first concurrent, multiyear time series of air-sea fluxes in the Southern Ocean from two key SAMW formation regions. In this work we compare drivers of wintertime heat loss and SAMW formation by comparing air-sea fluxes and mixed layers at these two mooring locations. A gridded Argo product and the ERA5 reanalysis product provide temporal and spatial context for the mooring observations. Turbulent ocean heat loss is on average 1.5 times larger in the southeast Indian (SOFS) than in the southeast Pacific (OOI), with stronger extreme heat flux events in the southeast Indian leading to larger cumulative winter ocean heat loss. Turbulent heat loss events in the southeast Indian (SOFS) occur in two atmospheric regimes (cold air from the south or dry air circulating via the north), while heat loss events in the southeast Pacific (OOI) occur in a single atmospheric regime (cold air from the south). On interannual time scales, wintertime anomalies in net heat flux and mixed layer depth (MLD) are often correlated at the two sites, particularly when wintertime MLDs are anomalously deep. This relationship is part of a larger basin-scale zonal dipole in heat flux and MLD anomalies present in both the Indian and Pacific basins, associated with anomalous meridional atmospheric circulation.
Text
joseyy
- Accepted Manuscript
Restricted to Repository staff only
Request a copy
More information
e-pub ahead of print date: 7 January 2020
Published date: 1 April 2020
Additional Information:
Funding Information:
QNLM and CSIRO. IC was supported by the National Science Foundation (NSF) Ocean Sciences Grant NSF OCE-1658001 to Scripps Institution of Oceanography. SAJ is supported by the U.K. Natural Environment Research Council, including the ORCHESTRA Grant (NE/N018095/1). STG was supported by the U.S. National Science Foundation under Grants OCE-1658001 and PLR-1425989. OOI flux data can be obtained from the NSF Ocean Observatories Initiative Data Portal (http:// ooinet.oceanobservatories.org), and SOFS flux data can be obtained from the IMOS (Integrated Marine Observing System) Australian Ocean Data Network portal (https:// portal.aodn.org.au). The objectively mapped Argo data were provided by John Gilson, available from http:// www.argo.ucsd.edu/Gridded_fields.html. Argo data were collected and made freely available by the International Argo Program and the national programs that contribute to it (http://www.argo.ucsd.edu; http://argo.jcommops.org; http://doi.org/10.17882/42182). The Argo Program is part of the Global Ocean Observing System. The ERA5 dataset, developed by the European Centre for Medium-Range Weather Forecasts, was obtained from the Research Data Archive at the National Center for Atmospheric Research, Computational and Information Systems Laboratory. VT would like to thank Matthew England, Annie Foppert, and Steve Rintoul for helpful discussions and feedback on the manuscript. We thank Sjoerd Groeskamp, Marcel du Plessis, and two anonymous reviewers for their feedback that has improved this manuscript.
Publisher Copyright:
© 2020 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses).
Identifiers
Local EPrints ID: 437957
URI: http://eprints.soton.ac.uk/id/eprint/437957
ISSN: 0894-8755
PURE UUID: b4035917-4a95-4743-b658-58710694b901
Catalogue record
Date deposited: 24 Feb 2020 17:31
Last modified: 16 Mar 2024 06:33
Export record
Altmetrics
Contributors
Author:
Veronica Tamsitt
Author:
Ivana Cerovečki
Author:
Simon A. Josey
Author:
Sarah T. Gille
Author:
Eric Schulz
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