Free-drifting icebergs as sources of iron to the Weddell Sea

Hai Lin; Sara Rauschenberg; Cole R. Hexel; Timothy J. Shaw; Benjamin S. Twining

doi:10.1016/j.dsr2.2010.11.020

Free-drifting icebergs as sources of iron to the Weddell Sea

Hai Lin, Sara Rauschenberg, Cole R. Hexel, Timothy J. Shaw, Benjamin S. Twining

Research output: Contribution to journal › Article › peer-review

90 Scopus citations

Abstract

In recent years glaciers on the Antarctic Peninsula have retreated, resulting in loss of mass from ice shelves and increased supply of icebergs to the Southern Ocean. Free-drifting icebergs may serve as an important source of Fe to surrounding waters. We measured concentrations of dissolved Fe and Fe content of suspended particulate material (via flow injection-chemiluminescence and ICP-MS, respectively) in the waters surrounding several icebergs during cruises to the Scotia and Weddell Seas in June 2008 and March 2009. Surface dissolved Fe (DFe) concentrations varied from 0.58 to 2.92. nM and were elevated up to 60% at some stations <1. km from the nearest iceberg. The highest surface DFe concentrations were associated with low salinity waters, regardless of distance to the iceberg. Depth profiles revealed surface enrichment at most stations >10. km from the icebergs, indicating general Fe enrichment in the lower-salinity surface layer. However surface DFe within 1. km of the iceberg was similar to that measured at depths below the draft of the iceberg, a feature that may result from upwelling of circumpolar deep water caused by basal melting at the face of the iceberg. Iron concentrations in ice collected following calving events were highly variable (4-600. nM) but were elevated above concentrations in seawater. Particulate Fe (normalized to particulate P) in suspended particulate material was up to 20-fold higher within 0.6. km of two large tabular icebergs, but no enrichment was observed at two smaller icebergs. Iron:phosphorus ratios of suspended particulate material were also higher in deeper (40. m) waters compared to shallow (ca. 15. m) waters at the iceberg face. Iron release appeared to be episodic, producing a spatially heterogeneous environment around icebergs. This source term may increase in coming years as Antarctic ice shelves degrade further, potentially impacting the ecology and biogeochemistry of low-Fe waters of the Southern Ocean.

Original language	English
Pages (from-to)	1392-1406
Number of pages	15
Journal	Deep-Sea Research Part II: Topical Studies in Oceanography
Volume	58
Issue number	11-12
DOIs	https://doi.org/10.1016/j.dsr2.2010.11.020
State	Published - Jun 2011
Externally published	Yes

Funding

We thank the captain and crew of the RVIB Nathaniel B. Palmer and the staff from Raytheon Polar Services for their professional assistance throughout two cruises (NBP08-06 and NBP09-02). We are also grateful to B. Robison, R. Sherlock, K. Reisenbichler, B. Hobson, C. Dawe, for providing ROV sampling around icebergs. The manuscript benefited from discussions with Gordon Stephenson and Maria Vernet regarding the influence of iceberg melting on salinity anomalies in surface waters, and was significantly improved by the comments of two anonymous reviewers. Mike Handley at the University of Maine assisted with the ICP-MS analysis of particulate samples. This project was supported by NSF grant ANT-0636319 to TJS and BST.

Funders	Funder number
National Science Foundation	ANT-0636319

Keywords

Antarctica
Climate change
Dissolved fe
Flow injection analysis
Southern ocean

UN SDGs

This output contributes to the following UN Sustainable Development Goals (SDGs)

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10.1016/j.dsr2.2010.11.020

Cite this

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title = "Free-drifting icebergs as sources of iron to the Weddell Sea",

abstract = "In recent years glaciers on the Antarctic Peninsula have retreated, resulting in loss of mass from ice shelves and increased supply of icebergs to the Southern Ocean. Free-drifting icebergs may serve as an important source of Fe to surrounding waters. We measured concentrations of dissolved Fe and Fe content of suspended particulate material (via flow injection-chemiluminescence and ICP-MS, respectively) in the waters surrounding several icebergs during cruises to the Scotia and Weddell Seas in June 2008 and March 2009. Surface dissolved Fe (DFe) concentrations varied from 0.58 to 2.92. nM and were elevated up to 60% at some stations <1. km from the nearest iceberg. The highest surface DFe concentrations were associated with low salinity waters, regardless of distance to the iceberg. Depth profiles revealed surface enrichment at most stations >10. km from the icebergs, indicating general Fe enrichment in the lower-salinity surface layer. However surface DFe within 1. km of the iceberg was similar to that measured at depths below the draft of the iceberg, a feature that may result from upwelling of circumpolar deep water caused by basal melting at the face of the iceberg. Iron concentrations in ice collected following calving events were highly variable (4-600. nM) but were elevated above concentrations in seawater. Particulate Fe (normalized to particulate P) in suspended particulate material was up to 20-fold higher within 0.6. km of two large tabular icebergs, but no enrichment was observed at two smaller icebergs. Iron:phosphorus ratios of suspended particulate material were also higher in deeper (40. m) waters compared to shallow (ca. 15. m) waters at the iceberg face. Iron release appeared to be episodic, producing a spatially heterogeneous environment around icebergs. This source term may increase in coming years as Antarctic ice shelves degrade further, potentially impacting the ecology and biogeochemistry of low-Fe waters of the Southern Ocean.",

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T1 - Free-drifting icebergs as sources of iron to the Weddell Sea

AU - Lin, Hai

AU - Rauschenberg, Sara

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AU - Twining, Benjamin S.

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N2 - In recent years glaciers on the Antarctic Peninsula have retreated, resulting in loss of mass from ice shelves and increased supply of icebergs to the Southern Ocean. Free-drifting icebergs may serve as an important source of Fe to surrounding waters. We measured concentrations of dissolved Fe and Fe content of suspended particulate material (via flow injection-chemiluminescence and ICP-MS, respectively) in the waters surrounding several icebergs during cruises to the Scotia and Weddell Seas in June 2008 and March 2009. Surface dissolved Fe (DFe) concentrations varied from 0.58 to 2.92. nM and were elevated up to 60% at some stations <1. km from the nearest iceberg. The highest surface DFe concentrations were associated with low salinity waters, regardless of distance to the iceberg. Depth profiles revealed surface enrichment at most stations >10. km from the icebergs, indicating general Fe enrichment in the lower-salinity surface layer. However surface DFe within 1. km of the iceberg was similar to that measured at depths below the draft of the iceberg, a feature that may result from upwelling of circumpolar deep water caused by basal melting at the face of the iceberg. Iron concentrations in ice collected following calving events were highly variable (4-600. nM) but were elevated above concentrations in seawater. Particulate Fe (normalized to particulate P) in suspended particulate material was up to 20-fold higher within 0.6. km of two large tabular icebergs, but no enrichment was observed at two smaller icebergs. Iron:phosphorus ratios of suspended particulate material were also higher in deeper (40. m) waters compared to shallow (ca. 15. m) waters at the iceberg face. Iron release appeared to be episodic, producing a spatially heterogeneous environment around icebergs. This source term may increase in coming years as Antarctic ice shelves degrade further, potentially impacting the ecology and biogeochemistry of low-Fe waters of the Southern Ocean.

AB - In recent years glaciers on the Antarctic Peninsula have retreated, resulting in loss of mass from ice shelves and increased supply of icebergs to the Southern Ocean. Free-drifting icebergs may serve as an important source of Fe to surrounding waters. We measured concentrations of dissolved Fe and Fe content of suspended particulate material (via flow injection-chemiluminescence and ICP-MS, respectively) in the waters surrounding several icebergs during cruises to the Scotia and Weddell Seas in June 2008 and March 2009. Surface dissolved Fe (DFe) concentrations varied from 0.58 to 2.92. nM and were elevated up to 60% at some stations <1. km from the nearest iceberg. The highest surface DFe concentrations were associated with low salinity waters, regardless of distance to the iceberg. Depth profiles revealed surface enrichment at most stations >10. km from the icebergs, indicating general Fe enrichment in the lower-salinity surface layer. However surface DFe within 1. km of the iceberg was similar to that measured at depths below the draft of the iceberg, a feature that may result from upwelling of circumpolar deep water caused by basal melting at the face of the iceberg. Iron concentrations in ice collected following calving events were highly variable (4-600. nM) but were elevated above concentrations in seawater. Particulate Fe (normalized to particulate P) in suspended particulate material was up to 20-fold higher within 0.6. km of two large tabular icebergs, but no enrichment was observed at two smaller icebergs. Iron:phosphorus ratios of suspended particulate material were also higher in deeper (40. m) waters compared to shallow (ca. 15. m) waters at the iceberg face. Iron release appeared to be episodic, producing a spatially heterogeneous environment around icebergs. This source term may increase in coming years as Antarctic ice shelves degrade further, potentially impacting the ecology and biogeochemistry of low-Fe waters of the Southern Ocean.

KW - Antarctica

KW - Climate change

KW - Dissolved fe

KW - Flow injection analysis

KW - Southern ocean

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JF - Deep-Sea Research Part II: Topical Studies in Oceanography

IS - 11-12

ER -

Free-drifting icebergs as sources of iron to the Weddell Sea

Abstract

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Keywords

UN SDGs

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