Higher Methane Emissions in Regions of Sea Ice Retreat

Abstract:

Arctic sea ice has seen a tremendous decline in recent decades, concurrently leading to higher temperatures across the high latitudes. Although increasingly strong evidence exists for this link between sea ice and temperature, the extra step of linking sea ice retreat – through these climatic changes – to a change in greenhouse-gas exchange is much less obvious. Recently, however, it has been suggested that methane emissions have increased as sea ice declined (Parmentier et al., 2013), leading to concerns that sea ice decline has led to a perturbation of the terrestrial component of the Arctic greenhouse gas balance.

This initial analysis, however, compared average methane emissions of the Arctic Region with anomalies in the average sea ice extent for the entire summer, which evens out regional and temporal differences. The pattern of year-to-year fluctuations in sea ice extent varies from region to region and the impact on methane emissions – through temperature – is therefore expected to vary spatially, too. Our goal is thus to elucidate to what degree a correlation between methane emissions and sea ice exists in areas of high retreat compared to areas that have seen less sea ice decline. In addition, the impact of sea ice retreat on methane emissions is investigated throughout the melt season to identify those periods in which the teleconnection between sea ice and methane emissions is most pronounced.

To this purpose, the output from three regional methane models (LPJ-GUESS WhyMe, Peatland-VU and TEM6) has been compared to independent observations of sea ice extent, and subjected to a rigorous spatial and temporal analysis. A similar response to sea ice retreat among these models will increase our confidence that teleconnections between methane emissions and sea ice decline exist within the Arctic.

References: 

Parmentier, F. J. W., Christensen, T. R., Sørensen, L. L., Rysgaard, S., McGuire, A. D., Miller, P. A., & Walker, D. A. (2013). The impact of lower sea-ice extent on Arctic greenhouse-gas exchange. Nature Climate Change, 3, 195–202. doi:10.1038/nclimate1784