Distributions of surface water CO2 and air-sea flux of CO2 in coastal regions of the Canadian Beaufort Sea in late summer

• Main Authors: Murata, A., Shimada, K., Nishino, S., Itoh, M.
• Format: Text
• Language: English
• Published: 2018
• Subjects: Arctic; Arctic Ocean; Beaufort Sea
• Online Access: https://doi.org/10.5194/bgd-5-5093-2008; https://www.biogeosciences-discuss.net/bgd-2008-0180/

To quantify the air-sea flux of CO 2 in a high-latitude coastal region, we conducted shipboard observations of atmospheric and surface water partial pressures of CO 2 ( p CO 2 ) and total dissolved inorganic carbon (TCO 2 ) in the Canadian Beaufort Sea (150° W–127° W; 69° N–73° N) in late summer 2000 and 2002. Surface water p CO 2 was lower than atmospheric p CO 2 (2000, 361.0 μatm; 2002, 364.7 μatm), and ranged from 250 to 344 μatm. Accordingly, Δ p CO 2 , which is the driving force of the air-sea exchange of CO 2 and is calculated from differences in p CO 2 between the sea surface and the overlying air, was generally negative (potential sink for atmospheric CO 2 ), although positive Δ p CO 2 values (source) were also found locally. Distributions of surface water p CO 2 , as well as those of Δ p CO 2 and CO 2 flux, were controlled mainly by water mixing related to river discharge. The air-sea fluxes of CO 2 were −15.0 and −16.8 mmol m −2 d −1 on average in 2000 and 2002, respectively, implying that the area acted as a moderate sink for atmospheric CO 2 . The air-to-sea net CO 2 flux in an extended area of the western Arctic Ocean (411 000 km 2 ) during the ice-free season (=100 days) was calculated as 10.2±7.7 mmol m −2 d −1 , equivalent to a regional CO 2 sink of 5.0±3.8 Tg C. The estimated buffer factor was 1.5, indicating that the area is a high-capacity CO 2 sink. These CO 2 flux estimates will need to be revised because they probably include a bias due to the vertical gradients of physical and chemical properties characteristic in the region, which have not yet been adequately considered.