Premium
Summertime Atmospheric Boundary Layer Gradients of O 2 and CO 2 over the Southern Ocean
Author(s) -
Morgan Eric J.,
Stephens Britton B.,
Long Matthew C.,
Keeling Ralph F.,
Bent Jonathan D.,
McKain Kathryn,
Sweeney Colm,
HoeckerMartínez Martín S.,
Kort Eric A.
Publication year - 2019
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1029/2019jd031479
Subject(s) - trace gas , atmospheric sciences , planetary boundary layer , boundary layer , mixed layer , flux (metallurgy) , environmental science , geology , climatology , oceanography , chemistry , physics , organic chemistry , thermodynamics
We present airborne observations of the vertical gradient of atmospheric oxygen ( δ (O 2 /N 2 )) and carbon dioxide (CO 2 ) through the atmospheric boundary layer (BL) over the Drake Passage region of the Southern Ocean, during the O 2 /N 2 Ratio and CO 2 Airborne Southern Ocean Study, from 15 January to 29 February 2016. Gradients were predominately anticorrelated, with excesses of δ (O 2 /N 2 ) and depletions of CO 2 found within the boundary layer, relative to a mean reference height of 1.7 km. Through analysis of the molar ratio of the gradients (GR), the behavior of other trace gases measured in situ, and modeling experiments with the Community Earth System Model, we found that the main driver of gradients was air‐sea exchange of O 2 and CO 2 driven by biological processes, more so than solubility effects. An exception to this was in the eastern Drake Passage, where positive GRs were occasionally observed, likely due to the dominance of thermal forcing on the air‐sea flux of both species. GRs were more spatially consistent than the magnitudes of the gradients, suggesting that GRs can provide integrated process constraints over broad spatial scales. Based on the model simulation within a domain bounded by 45°S, 75°S, 100°W, and 45°W, we show that the sampling density of the campaign was such that the observed mean GR (± standard error), −4.0± 0.8 mol O 2 per mol CO 2 , was a reasonable proxy for both the mean GR and the mean molar ratio of air‐sea fluxes of O 2 and CO 2 during the O 2 /N 2 Ratio and CO 2 Airborne Southern Ocean Study.