The potential response of the hydrate reservoir in the South Shetland Margin, Antarctic Peninsula, to ocean warming over the 21st century

Abstract

In the South Shetland Margin (SSM), Antarctic Peninsula, a bottom-simulating reflector indicates the presence of hydrate between ca. 500 and 3000 m water depth (mwd). The cold seabed temperatures allow hydrate stability at shallower water depths. During the past five decades, the Antarctic Peninsula has been warming up faster than any other part of the Southern Hemisphere, and long-term ocean warming could affect the stability of the SSM hydrate reservoir at shallow waters. Here, we model the transient response of the SSM hydrate reservoir between 375 and 450 mwd to ocean warming for the period 1958–2100. For the period 1958–2010, seabed temperatures are given by oceanographic measurements in the area, and for 2010–2100 by two temperature scenarios represented by the observed trends for the periods 1960–2010 (0.0034°C y⁻¹) and 1980–2010 (0.023°C y⁻¹). Our results show no hydrate-sourced methane emissions for an ocean warming rate at the seabed of 0.0034 °C y⁻¹. For a rate of 0.023°C y⁻¹, emissions start in 2028 at 375 mwd and extend to 442 mwd at an average rate of about 0.91 mwd y⁻¹, releasing ca. 1.13×10³ mol y⁻¹ of methane per metre along the margin by 2100. These emissions originate from dissociation at the top of the hydrate layer, a physical process that steady-state modelling cannot represent. Our results are speculative on account of the lack of direct evidence of a shallow water hydrate reservoir, but they illustrate that the SSM is a key area to observe the effects of ocean warming-induced hydrate dissociation in the coming decades.

Keywords: Hydrate; ocean warming; methane emissions; transient modelling; South Shetland Margin; Antarctic Peninsula.

(Published: 11 December 2015)

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Citation: Polar Research 2015, 34, 27443, http://dx.doi.org/10.3402/polar.v34.27443