§ Research Projects » Icebergs

Collaborative Research: Free-drifting icebergs as proliferating dispersion sites of iron enrichment, organic carbon production and export in the Southern Ocean (1 July 2007 - 30 June 2010). Principal Investigator: K. L. Smith Jr. (Monterrey Bay Aquarium Research Institute), co-Principal investigators: B.H. Robison (Monterrey Bay Aquarium Research Institute); John Helly (University of California San Diego); Ronald S. Kaufmann (University of San Diego); Timothy J. Shaw (University of South Carolina); Benjamin S. Twining (University of South Carolina); Alison Murray (Desert Research Institute); David Long (Bringham Young University)

INTELLECTUAL MERIT: Atmospheric warming has been associated with retreating glaciers, disintegrating ice shelves, and the increasing prevalence of icebergs in the Southern Ocean over the last decade. The scarcity of information about the impact of free-drifting icebergs on the pelagic ecosystem prompted our preliminary study in 2005 of two icebergs in the NW Weddell Sea, an area of high iceberg concentration. This study showed significant delivery of terrestrial material accompanied by significant enhancement of phytoplankton and zooplankton/micronekton abundance, and primary production surrounding the icebergs. Based on these initial results, we hypothesize that nutrient enrichment by free-drifting icebergs will increase primary production and sedimentation of organic carbon, thus increasing the draw-down and sequestration of CO₂ in the Southern Ocean and impacting the global carbon cycle.

Four critical questions are posed to resolve the importance of free-drifting icebergs on natural fertilization, pelagic community response, and organic carbon export.

1. 1) What is the relationship between the physical dynamics of free-drifting icebergs and the Fe and nutrient distributions of the surrounding water column?
2. 2) What is the relationship between Fe and nutrient distributions associated with free-drifting icebergs and the organic carbon dynamics of the ice-attached and surrounding pelagic communities (microbes, zooplankton, micronekton)?
3. 3) What is the relationship between organic carbon dynamics of the iceattached and surrounding pelagic communities and the export flux of particulate organic carbon from the mixed layer?
4. 4) What is the estimated combined impact of the population of free-drifting icebergs in the Weddell Sea on natural enrichment, carbon production and particulate carbon export from the mixed layer?

An interdisciplinary approach is proposed, consisting of seven components, each with a particular disciplinary focus that is defined by the recognized expertise of nine investigators from six institutions.

1. 1) Iceberg structure and dynamics (J. Helly, D. Long).
2. 2) Trace element, nutrient and radionuclide distributions (T. Shaw, B. Twining).
3. 3) Organic carbon dynamics mediated by microbial communities (M. Vernet, A. Murray).
4. 4) Organic carbon dynamics mediated by iceberg-attached communities (B. Robison, M. Vernet).
5. 5) Organic carbon dynamics mediated by zooplankton/micronekton (R. Kaufmann, B. Robison).
6. 6) Particulate organic carbon export fluxes (K. Smith, T. Shaw).
7. 7) Enrichment, carbon production and particulate export synthesis (all 9 P.I.s).

BROADER IMPACTS: The increased prevalence of free-drifting icebergs in the Southern Ocean should have a pronounced enrichment effect on the surrounding pelagic community. Enhanced primary production accompanied by increased draw-down and sequestration of CO₂ associated with icebergs will impact the global carbon cycle. Results from this iceberg project will be incorporated into the Antarctic Research division of the Ocean Exploration Center (OEC) as part of the SIOExplorer: Digital Library Project. The OEC allows users to access content, which is classified to one of four levels: entry (grade K-6), student (grade 6-12), college, and research. Graduate students, undergraduates, teachers, and volunteers are important participants in the proposed field and laboratory work. For the K-12 level, we will take a professional writer of children's books on our cruises to produce a non-fiction account of the expedition and a daily interactive website.

Project Links:

• MBARI Antarctic Expedition 2009 Website