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Subtropical contribution to sub‐Antarctic mode waters

Subtropical contribution to sub‐Antarctic mode waters
Subtropical contribution to sub‐Antarctic mode waters
Sub-Antarctic Mode Waters (SAMW) form to the north of the Antarctic Circumpolar Current (ACC) through deep winter mixing. SAMW connect the atmosphere with the oceanic pycnocline, transferring heat and carbon into the ocean interior and supplying nutrients to the northern ocean basins. The processes controlling SAMW ventilation and properties remain poorly understood. Here, we investigate the significance and origin of a ubiquitous feature of SAMW formation regions: The seasonal build-up of a subsurface salinity maximum. With biogeochemical Argo floats, we show that this feature influences SAMW mixed-layer dynamics, and that its formation is associated with a decline in preformed nutrients comparable to biological drawdown in surface waters (∼0.15 mol m−2 y−1). Our analysis reveals that these features are driven by advection of warm, salty, nutrient-poor waters of subtropical origin along the ACC. This influx represents a leading-order term in the SAMW physical and biogeochemical budgets, and can impact large-scale nutrient distributions.
Southern Ocean, Sub-Antartic Mode Water, biogeochemical Argo float, mixed layer, preformed nutrients, subtropical gyre
0094-8276
Fernández Castro, Bieito
8017e93c-d5ee-4bba-b443-9c72ca512d61
Mazloff, Matthew
420716bf-9145-441a-b600-0233215ed6c6
Williams, Richard G.
2155309e-1c07-4365-b46a-04baeb2fb63c
Naveira Garabato, Alberto C.
97c0e923-f076-4b38-b89b-938e11cea7a6
Fernández Castro, Bieito
8017e93c-d5ee-4bba-b443-9c72ca512d61
Mazloff, Matthew
420716bf-9145-441a-b600-0233215ed6c6
Williams, Richard G.
2155309e-1c07-4365-b46a-04baeb2fb63c
Naveira Garabato, Alberto C.
97c0e923-f076-4b38-b89b-938e11cea7a6

Fernández Castro, Bieito, Mazloff, Matthew, Williams, Richard G. and Naveira Garabato, Alberto C. (2022) Subtropical contribution to sub‐Antarctic mode waters. Geophysical Research Letters, 49 (11). (doi:10.1029/2021GL097560).

Record type: Article

Abstract

Sub-Antarctic Mode Waters (SAMW) form to the north of the Antarctic Circumpolar Current (ACC) through deep winter mixing. SAMW connect the atmosphere with the oceanic pycnocline, transferring heat and carbon into the ocean interior and supplying nutrients to the northern ocean basins. The processes controlling SAMW ventilation and properties remain poorly understood. Here, we investigate the significance and origin of a ubiquitous feature of SAMW formation regions: The seasonal build-up of a subsurface salinity maximum. With biogeochemical Argo floats, we show that this feature influences SAMW mixed-layer dynamics, and that its formation is associated with a decline in preformed nutrients comparable to biological drawdown in surface waters (∼0.15 mol m−2 y−1). Our analysis reveals that these features are driven by advection of warm, salty, nutrient-poor waters of subtropical origin along the ACC. This influx represents a leading-order term in the SAMW physical and biogeochemical budgets, and can impact large-scale nutrient distributions.

Text
Geophysical Research Letters - 2022 - Fern ndez Castro - Subtropical Contribution to Sub‐Antarctic Mode Waters - Version of Record
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More information

Accepted/In Press date: 20 May 2022
e-pub ahead of print date: 27 May 2022
Published date: 16 June 2022
Keywords: Southern Ocean, Sub-Antartic Mode Water, biogeochemical Argo float, mixed layer, preformed nutrients, subtropical gyre

Identifiers

Local EPrints ID: 458190
URI: http://eprints.soton.ac.uk/id/eprint/458190
ISSN: 0094-8276
PURE UUID: 563de21d-32aa-4423-8a04-005c423ce0c0
ORCID for Bieito Fernández Castro: ORCID iD orcid.org/0000-0001-7797-854X
ORCID for Alberto C. Naveira Garabato: ORCID iD orcid.org/0000-0001-6071-605X

Catalogue record

Date deposited: 30 Jun 2022 16:43
Last modified: 27 Jan 2023 02:39

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Contributors

Author: Matthew Mazloff
Author: Richard G. Williams

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