Climatically sensitive transfer of iron to maritime Antarctic ecosystems by surface runoff

Andy Hodson,Aga Nowak,Gonçalo Vieira,David Pearce,Peter Convey,Marie Sabacka,Francisco Navarro,Anne Jungblut,María Luisa Ávila-Jiménez

doi:10.1038/ncomms14499

Abstract

Iron supplied by glacial weathering results in pronounced hotspots of biological production in an otherwise iron-limited Southern Ocean Ecosystem. However, glacial iron inputs are thought to be dominated by icebergs. Here we show that surface runoff from three island groups of the maritime Antarctic exports more filterable (<0.45 μm) iron (6–81 kg km−2 a−1) than icebergs (0.0–1.2 kg km−2 a−1). Glacier-fed streams also export more acid-soluble iron (27.0–18,500 kg km−2 a−1) associated with suspended sediment than icebergs (0–241 kg km−2 a−1). Significant fluxes of filterable and sediment-derived iron (1–10 Gg a−1 and 100–1,000 Gg a−1, respectively) are therefore likely to be delivered by runoff from the Antarctic continent. Although estuarine removal processes will greatly reduce their availability to coastal ecosystems, our results clearly indicate that riverine iron fluxes need to be accounted for as the volume of Antarctic melt increases in response to 21st century climate change.

Highlights

Iron supplied by glacial weathering results in pronounced hotspots of biological production in an otherwise iron-limited Southern Ocean Ecosystem
Characterizing the iron geochemistry of maritime Antarctic runoff, including both Antarctic and sub-Antarctic islands, could significantly change our understanding of glacier-ocean ecosystem interactions. The glaciers on these islands are experiencing an earlier and faster response to warming than the large ice masses upon the Antarctic Peninsula and continent; representing a basis to understand the future contribution of Antarctic continent melting to the iron budget of the Southern Ocean following projected climate trends[14]
Our results represent a multi-site inventory of Antarctic data and allow us to quantify the potential for iron fertilization by runoff in an area where it arguably matter most: the ironlimited Southern Ocean

Summary

Introduction

Temporal and spatial changes in iron transport by snowmelt-dominated runoff are described, showing that the riverine iron flux delivered to coastal waters in the Antarctic Peninsula region is extremely sensitive to climate warming. This is because both the meltwater volume and its iron concentration increase with temperature, resulting in marked increases in the meltwater iron flux, especially in areas where the rate of melting is currently low and dominated by snowmelt. More attention needs to be given the fate of iron delivered to coastal waters by a climate-sensitive Antarctic meltwater flux

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Conclusion