Characterizing Marine Heatwaves in the Kerguelen Plateau Region

Zimeng Su,Stuart Corney,Gabriela S Pilo,Mao Mori,Philippe Ziegler,Neil J Holbrook

doi:10.3389/fmars.2020.531297

Abstract

Marine heatwaves (MHWs) are prolonged extreme oceanic warm water events. Globally, the frequency and intensity of MHWs have been increasing in recent years, and it is expected that this trend is reflected in the Kerguelen Plateau region. MHWs can negatively impact the structure of marine biodiversity, marine ecosystems, and commercial fisheries. Considering that the KP is a hot-spot for marine biodiversity, characterizing MHWs and their drivers for this region is important, but has not been performed. Here, we characterize MHWs in the KP region between January 1994 and December 2016 using a combination of remotely sensed observations and output from a publicly available model hindcast simulation. We describe a strong MHW event that starts during the 2011/2012 austral summer and persists through winter, dissipating in late 2012. During the winter months, the anomalous temperature signal deepens from the surface to a depth of at least 150 m. We show that downwelling-favorable winds occur in the region during these months. At the end of 2012, as the MHW dissipates, upwelling-favorable winds prevail. We also show that the ocean temperature on the KP is significantly correlated with key modes of climate variability. Over the KP, temperature at both the ocean surface and at a depth of 150 m correlates significantly with the Indian Ocean Dipole. To the south of the KP, temperature variations are significantly correlated with the El Niño Southern Oscillation, and to both the north and south of the KP, with the Southern Annular Mode. These results suggest there may be potential predictability in ocean temperatures, and their extremes, in the KP region. Strong MHWs, like the event in 2012, may be detrimental to the unique ecosystem of this region, including economically relevant species, such as the Patagonian Toothfish.

Highlights

The Kerguelen Plateau (KP) is the largest submarine plateau in the Southern Ocean, acting as the largest topographic barrier to the eastward flowing Antarctic Circumpolar Current (ACC; van Wijk et al, 2010)
We find that OFAM is systematically warmer than observations over our study region
We show that strong Marine heatwaves (MHWs) can occur in the KP region and that a significant MHW occurred in the region during 2012

Summary

Introduction

The Kerguelen Plateau (KP) is the largest submarine plateau in the Southern Ocean, acting as the largest topographic barrier to the eastward flowing Antarctic Circumpolar Current (ACC; van Wijk et al, 2010). MHWs in the Kerguelen Plateau biological productivity. This productivity is triggered by iron supply resulting from the interaction between the Antarctic Circumpolar Current and the local bathymetry (Quéguiner et al, 2011; Cavagna et al, 2015). The KP is home to a number of exploited fish species, most notably Patagonian toothfish (Dissostichus eleginoides) which has been targeted since the 1990s and supports two economically-important fisheries (Duhamel et al, 2011). The Patagonian toothfish is a demersal fish found on the continental margins of the sub-Antarctic islands of the Southern Ocean. Adult toothfish are usually found at depths ranging from 500 m to over 3,500 m, can weigh up to 200 kg, reach 2 m in length and live in excess of 40 years (Collins et al, 2010)

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