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The vertical transport of surface water and carbon into ocean's interior, known as subduction, is one of the main mechanisms through which the ocean influences Earth's climate. New instrumental approaches have shown the occurrence of localized and intermittent subduction episodes associated with small-scale ocean circulation features. These studies also revealed the importance of such events for the export of organic matter, the so-called eddy-pump. However, the transient and localized nature of episodic subduction hindered its large-scale evaluation to date. In this work, we present an approach to detect subduction events at the scale of the Southern Ocean using measurements collected by biogeochemical autonomous floats (BGCArgo). We show how subduction events can be automatically identified as anomalies of spiciness and Apparent Oxygen Utilization (AOU) below the mixed layer. Using this methodology over more than 4,000 profiles, we detected 40 subduction events unevenly distributed across the Sothern Ocean. Events were more likely found in hot spots of eddy kinetic energy (EKE), downstream major bathymetric features. Moreover, the bio-optical measurements provided by BGCArgo allowed measuring the amount of Particulate Organic Carbon (POC) being subducted and assessing the contribution of these events to the total downward carbon flux at 100 m (EP100). We estimated that the eddy-pump represents less than 19% to the EP100 in the Southern Ocean, although we observed particularly strong events able to locally duplicate the EP100. This approach provides a novel perspective on where episodic subduction occurs that will be naturally improved as BGCArgo observations continue to increase.

Item Type:	Refereed Article
Keywords:	biogeochemical Argo floats, Southern Ocean, biological carbon pump, submesoscale
Research Division:	Earth Sciences
Research Group:	Oceanography
Research Field:	Oceanography not elsewhere classified
Objective Division:	Environmental Management
Objective Group:	Marine systems and management
Objective Field:	Oceanic processes (excl. in the Antarctic and Southern Ocean)
UTAS Author:	Llort, J (Dr Joan Llort Jordi)
UTAS Author:	Moreau, S (Dr Sebastien Moreau)
UTAS Author:	Lenton, A (Dr Andrew Lenton)
UTAS Author:	Strutton, PG (Professor Peter Strutton)
ID Code:	124576
Year Published:	2018
Web of Science® Times Cited:	48
Deposited By:	Oceans and Cryosphere
Deposited On:	2018-02-27
Last Modified:	2019-04-26
Downloads:	191 View Download Statistics