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Seasonal cycle of O 2 and p CO 2 in the central Labrador Sea: Atmospheric, biological, and physical implications
Author(s) -
Körtzinger A.,
Send U.,
Wallace D. W. R.,
Karstensen J.,
DeGrandpre M.
Publication year - 2008
Publication title -
global biogeochemical cycles
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.512
H-Index - 187
eISSN - 1944-9224
pISSN - 0886-6236
DOI - 10.1029/2007gb003029
Subject(s) - sink (geography) , mixed layer , environmental science , oceanography , bloom , atmospheric sciences , spring bloom , carbon cycle , phytoplankton , geology , chemistry , ecosystem , nutrient , ecology , geography , cartography , biology , organic chemistry
We present full 2004–2005 seasonal cycles of CO 2 partial pressure ( p CO 2 ) and dissolved oxygen (O 2 ) in surface waters at a time series site in the central Labrador Sea (56.5°N, 52.6°W) and use these data to calculate annual net air‐sea fluxes of CO 2 and O 2 as well as atmospheric potential oxygen (APO). The region is characterized by a net CO 2 sink (2.7 ± 0.8 mol CO 2 m −2 yr −1 ) that is mediated to a major extent by biological carbon drawdown during spring/summer. During wintertime, surface waters approach equilibrium with atmospheric CO 2 . Oxygen changes from marked undersaturation of about 6% during wintertime to strong supersaturation by up to 10% during the spring/summer bloom. Overall, the central Labrador Sea acts as an O 2 sink of 10.0 ± 3.1 mol m −2 yr −1 . The combined CO 2 and O 2 sink functions give rise to a sizable APO flux of 13.0 ± 4.0 mol m −2 yr −1 into surface waters of the central Labrador Sea. A mixed layer carbon budget yields a net community production of 4.0 ± 0.8 mol C m −2 during the 2005 productive season about one third of which appears to undergo subsurface respiration in a depth range that is reventilated during the following winter. The timing of the spring bloom is discussed and eddies from the West Greenland Current are thought to be associated with the triggering of the bloom. Finally, we use CO 2 and O 2 mixed layer dynamics during the 2005 spring bloom to evaluate a suite of prominent wind speed‐dependent parameterizations for the gas transfer coefficient. We find very good agreement with those parameterizations which yield higher transfer coefficients at wind speeds above 10 m s −1 .