Annual cycle of air‐sea CO2 exchange in an Arctic Polynya Region. Issue 2 (9th May 2013)

• Record Type: Journal Article
• Authors: Else, B. G. T.; Papakyriakou, T. N.; Asplin, M. G.; Barber, D. G.; Galley, R. J.; Miller, L. A.; Mucci, A.
• Is Part Of: Global biogeochemical cycles. Volume 27:Issue 2(2013)
• Page Start: 388
• Page End: 398
• Publication Date: 2013-05-09
• Subjects: Biogeochemical cycles -- Periodicals; Electronic journals; 577.1405
• DOI: 10.1002/gbc.20016
• Languages: English
• ISSNs: 0886-6236

Abstract

<abstract abstract-type="main"> <title>Abstract</title> <p>[1] During the Canadian International Polar Year projects in the Cape Bathurst polynya region, we measured a near–complete annual cycle of sea surface CO<sub>2</sub> (<italic>p</italic>CO<sub>2<italic>sw</italic></sub>), atmospheric CO<sub>2</sub> (<italic>p</italic>CO<sub>2<italic>atm</italic></sub>), sea surface temperature (SST), salinity (S), and wind speed (<italic>U</italic>). In this paper, we combine these data with ancillary measurements of sea ice concentration (<italic>C</italic><sub><italic>i</italic></sub>) to estimate the mean annual (September 2007–September 2008) air–sea CO<sub>2</sub> exchange for the region. For the non–freezing seasons the exchange was calculated using a standard bulk aerodynamic approach, whereas during the freezing seasons we extrapolated eddy covariance measurements of CO<sub>2</sub> exchange. Our results show that in 2007–08 the region served as a net sink of atmospheric CO<sub>2</sub> at a mean rate of ‐10.1 ± 6.5 mmol m<sup>− 2</sup> d<sup>− 1</sup>. The strongest calculated uptake rate occurred in the fall when wind velocities were highest, <italic>p</italic>CO<sub>2<italic>sw</italic></sub> was significantly lower than <italic>p</italic>CO<sub>2<italic>atm</italic></sub>, and ice was beginning to form. Atmospheric CO<sub>2</sub> uptake was calculated to occur (at lower rates) throughout the rest of the year, except for a brief period of outgassing during late July. Using archival <italic>U</italic>, <italic>C</italic><sub><italic>i</italic></sub>, and <italic>p</italic>CO<sub>2<italic>sw</italic></sub> data for the region, we found that winds in 2007–08 were 25–35 % stronger than the decadal mean and were predominately easterly, which appears to have induced a relatively late freeze–up (by ∼ 3 weeks relative to mean conditions) and an early polynya opening (by ∼ 4 weeks). In turn, these conditions may have given rise to a higher CO<sub>2</sub> uptake than normal. Estimated winter CO<sub>2</sub> exchange through leads and small polynya openings made up more than 50% of the total CO<sub>2</sub> uptake, consistent with recent observations of enhanced CO<sub>2</sub> exchange associated with open water components of the winter icescape. Our calculations for the Cape Bathurst polynya region are consistent with past studies that estimated the total winter CO<sub>2</sub> uptake in Arctic coastal polynyas to be on the order of 10<sup>12</sup> g C yr<sup>− 1</sup>.</p> </abstract>