Separating the natural and anthropogenic air‐sea flux of CO2: The Indian Ocean

Timothy M Hall,Francois W Primeau

doi:10.1029/2004gl020589

Abstract

We estimate the natural and anthropogenic components of the air‐sea flux of CO2 in the Indian Ocean. The increase in atmospheric CO2 driven by human activity has caused the air‐sea CO2 disequilibrium, and consequently the flux, to increase significantly over the industrial era. We estimate the flux in the year 1780 to be approximately 0.2 Gt/yr, increasing by 0.26 Gt/yr to 0.5 Gt/yr in 2000. The estimate of the natural (preindustrial) flux is highly sensitive to uncertainties in modern‐day CO2 disequilibrium measurements. By contrast, the estimate of the anthropogenic flux is only weakly sensitive to these measurements.

Highlights

The majority of the Antarctic ice sheet drains to the ocean through floating ice shelves (Barkov, 1985), most of which are contained in embayments or run aground against ice rises, ice rumples or islands
Even though Cochran and Bell (2012) measured a maximum gravity anomaly associated with Bawden ice rise, this ice rise is not represented in the bathymetry data set used by the ocean circulation model
The analytical theory for the creep deformation of a floating ice shelf was extended using continuum damage mechanics to account for the softening influence of fractures on longitudinal deformation

Summary

Introduction

The majority of the Antarctic ice sheet drains to the ocean through floating ice shelves (Barkov, 1985), most of which are contained in embayments or run aground against ice rises, ice rumples or islands. Ice shelves play a major role in modulating the mass balance and contribution to sea level rise of the Antarctic ice sheet. This influence was brought into sharp focus following the collapse of the Larsen B ice shelf in 2002, after which the tributary glaciers that fed the shelf accelerated three- to eightfold (Rignot et al, 2004; Scambos et al, 2004) with sustained dynamic thinning and retreat ongoing (Rott et al, 2011).

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Conclusion