In:
Journal of Geophysical Research: Oceans, American Geophysical Union (AGU), Vol. 106, No. C12 ( 2001-12-15), p. 31197-31215
Abstract:
A coupled, one‐dimensional ecosystem/carbon flux model is used to simulate the seasonal and interannual variability of phytoplankton, nutrients, TCO 2 , O 2 , and p CO 2 at ocean weather station Papa (OWS P at 50°N, 145°W). The 23‐year interannual simulation (1958–1980) is validated with available data and analyzed to extend seasonal and interannual variations beyond the limited observational records. The seasonal cycles of p CO 2 and sea‐air CO 2 flux are controlled by a combination of thermodynamics, winds, and biological uptake. There is ingassing of CO 2 during the fall‐winter months when SSTs are colder and wind forcing is vigorous, while there is a much smaller ingassing of CO 2 during the summer when sea surface temperatures are warmer and wind speeds are reduced. Biological production plays a major role in maintaining the air‐sea equilibrium. An abiotic simulation showed that OWS P would be a source of atmospheric CO 2 (1.41 mol C m −2 yr −1 ) if the biological sink of CO 2 were removed. The peak net community production in summer compensates for the increased temperature effect on p CO 2 , which prevents large outgassing in summer. Oxygen anomalies relative to the temperature‐determined saturation value show that there is a seasonal cycle of air‐sea flux, with ingassing in winter and outgassing in summer. The net surface oxygen flux is positive (0.8 mol m −2 yr −1 ), indicating that OWS P is a source of oxygen to the atmosphere. The average primary production is 167 g C m −2 yr −1 . The 1960–1980 (1958 and 1959 spin‐up years removed) mean carbon flux is −1.8 mol C m −2 yr −1 , indicating that the ocean at OWS P is a sink of atmospheric carbon. The sea‐air CO 2 flux ranges from −1.2 to −2.3 mol C m −2 yr −1 during the 21‐year simulation period. This finding emphasizes the need for long‐term observations to accurately determine carbon flux budgets. A series of sensitivity experiments indicate that the seasonal variability and overall (21 years) mean of TCO 2 , p CO 2 , Δ p CO 2 , and air‐sea CO 2 flux are strongly dependent on the gas transfer formulation adopted, the total alkalinity near the surface, and the bottom (350 m) value adopted for TCO 2 . The secular atmospheric p CO 2 upward trend is manifested in the TCO 2 concentration within the upper 100 m by an increase of 15 mmol m −3 in 20 years, consistent with observations at other locations [ Winn et al. , 1998; Bates , 2001].
Type of Medium:
Online Resource
ISSN:
0148-0227
DOI:
10.1029/2000JC000343
Language:
English
Publisher:
American Geophysical Union (AGU)
Publication Date:
2001
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