Oceanography The Official Magazine of
The Oceanography Society
Volume 25 Issue 03

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Volume 25, No. 3
Pages 38 - 39


SIDEBAR • Islands of Ice: Influence of Free-Drifting Antarctic Icebergs on Pelagic Marine Ecosystems

By Maria Vernet , Kenneth L. Smith Jr. , Adrián O. Cefarelli , John J. Helly, Ronald S. Kaufmann, Hai Lin, David G. Long , Alison E. Murray , Bruce H. Robison, Henry A. Ruhl, Timothy J. Shaw , Alana D. Sherman, Janet Sprintall , Gordon R. Stephenson Jr. , Keith M. Stuart, and Benjamin S. Twining  
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Regional warming around West Antarctica, including the Antarctic Peninsula, is related to the retreat of glaciers that has resulted in significant ice mass loss in recent decades (De Angelis and Skvarca, 2003). Large icebergs (> 18.5 km long) originating from ice shelves in the Ross and Weddell Seas (Scambos et al., 2000) are attributed primarily to major loss events in these regions. Once free, icebergs become entrained in the counterclockwise Antarctic Coastal Current (Figure 1), eventually entering a strong northward flow in the Northwest Weddell Sea. We examined free-drifting icebergs in the Atlantic sector of the Southern Ocean in December 2005, aboard ARSV Laurence M. Gould, and in June 2008 and March/April 2009, aboard RVIB Nathaniel B. Palmer. Prior to these studies, little information was available about the effects of icebergs on the pelagic realm. On these cruises, we investigated the “iceberg ecosystem” (Smith et al., 2007; Smith, 2011) to assess the degree to which icebergs are (1) hotspots of biological activity across multiple trophic levels, and (2) focal points for enhanced export of organic carbon to the deep sea. An important focus of this work was to examine the fundamental mechanisms by which icebergs affect the pelagic ecosystem, including physical disruption and effects on the availability of critical nutrients (e.g., iron, nitrate).


Vernet, M., K.L. Smith Jr., A.O. Cefarelli, J.J. Helly, R.S. Kaufmann, H. Lin, D.G. Long, A.E. Murray, B.H. Robison, H.A. Ruhl, T.J. Shaw, A.D. Sherman, J. Sprintall, G.R. Stephenson Jr., K.M. Stuart, and B.S. Twining. 2012. Islands of ice: Influence of free-drifting Antarctic icebergs on pelagic marine ecosystems. Oceanography 25(3):38–39, https://doi.org/10.5670/oceanog.2012.72.


De Angelis, H.D., and P. Skvarca. 2003. Glacier surge after ice shelf collapse. Science 299:1,560–1,562, https://doi.org/10.1126/science.1077987.

Scambos, T.A., C. Hulbe, M. Fahnestock, and J. Bohlander. 2000. The link between climate warming and break-up of ice shelves in the Antarctic Peninsula. Journal of Glaciolology 46:516–530, https://doi.org/10.3189/172756500781833043.

Smith, K.L. Jr., B.H. Robison, J.J. Helly, R.S. Kaufmann, H.A. Ruhl, T.J. Shaw, B.S. Twining, and M. Vernet. 2007. Free-drifting icebergs: Hot spots of chemical and biological enrichment in the Weddell Sea. Science 317:478–482, https://doi.org/10.1126/science.1142834.

Smith, K.L. Jr. 2011. Free-drifting icebergs in the Southern Ocean: An overview. Deep Sea Research Part II 58:1,277–1,284, https://doi.org/10.1016/j.dsr2.2010.11.003.

Stuart, K.M., and D.G. Long. 2011. Tracking large tabular icebergs using the SeaWinds Ku-band microwave scatterometer. Deep-Sea Research Part II 58:1,285–1,300, https://doi.org/10.1016/j.dsr2.2010.11.004.

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