Abstract
This study used several model-based tools to analyse the dynamics of the Arctic Basin between 1997 and 2006 as a linked system of land-ocean-atmosphere C exchange. The analysis estimates that terrestrial areas of the Arctic Basin lost 62.9 Tg C yr-1 and that the Arctic Ocean gained 94.1 Tg C yr-1. Arctic lands and oceans were a net CO2 sink of 108.9 Tg C yr-1, which is within the range of uncertainty in estimates from atmospheric inversions. Although both lands and oceans of the Arctic were estimated to be CO2 sinks, the land sink diminished in strength because of increased fire disturbance compared to previous decades, while the ocean sink increased in strength because of increased biological pump activity associated with reduced sea ice cover. Terrestrial areas of the Arctic were a net source of 41.5 Tg CH4 yr-1 that increased by 0.6 Tg CH4 yr-1 during the decade of analysis, a magnitude that is comparable with an atmospheric inversion of CH4. Because the radiative forcing of the estimated CH4 emissions is much greater than the CO2 sink, the analysis suggests that the Arctic Basin is a substantial net source of green house gas forcing to the climate system.
Highlights
Recent studies have revealed surface air temperature increases on the average of 0.6 ◦C per decade since 1985 over land and ocean areas north of 62◦N (Polyakov et al, 2002) and 0.35 ◦C per decade from 1970 to 2000 for terrestrial regions between 50◦ and 70◦N (Serreze and Francis, 2006; Euskirchen et al, 2007)
This terrestrial sink is the result of a positive uptake of 311 Tg C yr−1 by the terrestrial component as net ecosystem production (NEP), the balance between net primary productivity (NPP; 4190 Tg C yr−1) in dissolved organic C (DOC) export (g C m−2 yr−1)
Our study indicates that between 1997 and 2006, the terrestrial regions of the Arctic were a source of carbon to the atmosphere and to the Arctic Ocean, and the Arctic Ocean was sequestering carbon from both the atmosphere and the land with the overall ocean sink greater than the land source by approximately 30 Tg C yr−1
Summary
Recent studies have revealed surface air temperature increases on the average of 0.6 ◦C per decade since 1985 over land and ocean areas north of 62◦N (Polyakov et al, 2002) and 0.35 ◦C per decade from 1970 to 2000 for terrestrial regions between 50◦ and 70◦N (Serreze and Francis, 2006; Euskirchen et al, 2007). The recent warming in northern high latitudes is affecting a broad spectrum of physical, ecological and human/cultural systems in this region (Serreze et al, 2000; Chapin et al, 2005; Hinzman et al, 2005; Serreze and Francis, 2006; Post et al, 2009) Some of these changes may be irreversible on century time scales, and have the potential to cause rapid changes in the earth system (Curry et al, 1996; Chapin et al, 2000; McGuire et al, 2006; Lenton et al, 2008). Bottom-up studies estimate (1) that the land sink of the Arctic is between 0.3 and 0.6 Pg C yr−1 in the Tellus 62B (2010), 5
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