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Volume 7, issue 2
Ocean Sci., 7, 185-202, 2011
https://doi.org/10.5194/os-7-185-2011
© Author(s) 2011. This work is distributed under
the Creative Commons Attribution 3.0 License.

Special issue: Synoptic Antarctic Shelf-Slope Interactions (SASSI)

Ocean Sci., 7, 185-202, 2011
https://doi.org/10.5194/os-7-185-2011
© Author(s) 2011. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 11 Mar 2011

Research article | 11 Mar 2011

Upper ocean stratification and sea ice growth rates during the summer-fall transition, as revealed by Elephant seal foraging in the Adélie Depression, East Antarctica

G. D. Williams1,2, M. Hindell3, M.-N. Houssais1, T. Tamura2, and I. C. Field4 G. D. Williams et al.
  • 1LOCEAN, Univerity of Pierre and Marie Curie, UMR 7159, Jussieu 75252 PARIS Cedex 05, France
  • 2ACE CRC Private Bag 80 Hobart TAS 7001, Australia
  • 3Institute for Marine and Antarctic Studies, University of Tasmania, Private Bag 129, Hobart TAS 7001, Australia
  • 4Graduate School of the Environment, Macquarie University, North Ryde NSW, 2109 Australia

Abstract. Southern elephant seals (Mirounga leonina), fitted with Conductivity-Temperature-Depth sensors at Macquarie Island in January 2005 and 2010, collected unique oceanographic observations of the Adélie and George V Land continental shelf (140–148° E) during the summer-fall transition (late February through April). This is a key region of dense shelf water formation from enhanced sea ice growth/brine rejection in the local coastal polynyas. In 2005, two seals occupied the continental shelf break near the grounded icebergs at the northern end of the Mertz Glacier Tongue for several weeks from the end of February. One of the seals migrated west to the Dibble Ice Tongue, apparently utilising the Antarctic Slope Front current near the continental shelf break. In 2010, immediately after that year's calving of the Mertz Glacier Tongue, two seals migrated to the same region but penetrated much further southwest across the Adélie Depression and sampled the Commonwealth Bay polynya from March through April. Here we present observations of the regional oceanography during the summer-fall transition, in particular (i) the zonal distribution of modified Circumpolar Deep Water exchange across the shelf break, (ii) the upper ocean stratification across the Adélie Depression, including alongside iceberg C-28 that calved from the Mertz Glacier and (iii) the convective overturning of the deep remnant seasonal mixed layer in Commonwealth Bay from sea ice growth. Heat and freshwater budgets to 200–300 m are used to estimate the ocean heat content (400→50 MJ m−2), flux (50–200 W m−2 loss) and sea ice growth rates (maximum of 7.5–12.5 cm day−1). Mean seal-derived sea ice growth rates were within the range of satellite-derived estimates from 1992–2007 using ERA-Interim data. We speculate that the continuous foraging by the seals within Commonwealth Bay during the summer/fall transition was due to favorable feeding conditions resulting from the convective overturning of the deep seasonal mixed layer and chlorophyll maximum that is a reported feature of this location.

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