Ocean glider observations of iceberg‐enhanced biological production in the northwestern Weddell Sea

Louise C Biddle,Andrew F Thompson,Adrian Jenkins,Jan Kaiser,Karen J Heywood

doi:10.1002/2014gl062850

Abstract

AbstractIcebergs affect local biological production around Antarctica. We used an ocean glider to observe the effects of a large iceberg that was advected by the Antarctic Slope Current along the continental slope in the northwestern Weddell Sea in early 2012. The high‐resolution glider data reveal a pronounced effect of the iceberg on ocean properties, with oxygen concentrations of (13 ± 4) μmol kg−1 higher than levels in surrounding waters, which are most likely due to positive net community production. This response was confined to three areas of water in the direct vicinity of the iceberg track, each no larger than 2 km2. Our findings suggest that icebergs have an impact on Antarctic production presumably through local micronutrient injections, on a scale smaller than typical satellite observations of biological production in the Southern Ocean.

Highlights

Almost half of the mass loss from Antarctica is attributed to iceberg calving [Depoorter et al, 2013]
Our findings suggest that icebergs have an impact on Antarctic production presumably through local micronutrient injections, on a scale smaller than typical satellite observations of biological production in the Southern Ocean
Ocean gliders deployed in the northwestern Weddell Sea observed lower temperature and salinity and increased dissolved oxygen, CDOM and backscatter at depths between 5 and 15 m following the passage of a large iceberg

Summary

Introduction

Almost half of the mass loss from Antarctica is attributed to iceberg calving [Depoorter et al, 2013]. There are in situ observations of delivery of Fe by icebergs with the potential to enhance productivity [Martin et al, 1990; Raiswell et al, 2008; Lancelot et al, 2009; Smith et al, 2007], but these observations are inconsistent with the apparent decrease in chlorophyll a concentrations observed by Schwarz and Schodlok [2009]. One of the methods of mixing proposed by Schwarz and Schodlok [2009] to enhance productivity (or dilute chlorophyll a) is caused by basal and sidewall melting of the iceberg. We present evidence of enhanced biological production in surface waters affected by the iceberg and describe how small-scale patchiness is an underestimated feature of Southern Ocean production

Data Collection

Results and Discussion

Conclusion