Carbon time series in the Norwegian sea

Depth profiles of carbon parameters were obtained monthly from 1991 to 1994 as the first time series from the weathership station M located in the Norwegian Sea at 66 degrees N 2 degrees E. CO2 was extracted from acidified seawater by a flushing procedure, with nitrogen as the carrier gas. The pure CO2 gas was measured using a manometric technique, and the gas was further used for C-13 and C-14 measurements. The precision of the dissolved inorganic carbon (DIC) was better than +/-6 parts per thousand. Satisfactory agreement was obtained with standard seawater from Scripps Institution of Oceanography. The partial pressure of CO2 (pCO(2)) was measured in the atmosphere and surface water, beginning in October 1991. The most visible seasonal variation in DIG, C-13 and pCO(2) was due to the plankton bloom in the upper 50-100 m. Typical values for surface water in the winter were: 2.140 +/- 0.012 mmol kg(-1) for DIG, 1.00 +/- 0.04 parts per thousand for delta(13)C and 357 +/- 15 mu atm for pCO(2), and the corresponding values in the summer were as low as 2.04 mmol kg(-1), greater than 2,1 parts per thousand,, and as low as 270-300 mu atm. The values for deep water are more constant during the year, with DIC values of about 2.17 +/- 0.01 mmol kg(-1), and delta(13)C values between 0.97 and 1,14 parts per thousand,. A simple one-dimensional biological model was applied in order to investigate possible short-term variability in DIC caused by the phytoplankton growth and depth variations of the wind-mixed layer. The simulated seasonal pattern was in reasonable agreement with the observed data, but there were significant temporal variations with shorter time interval than the monthly measurements. As a supplement to the measurements at station M, some representative profiles of DIG, delta(13)C, Delta(14)C, salinity and temperature from other locations in the Nordic Seas and the North Atlantic Ocean are also presented. The results are also compared with some data obtained (Delta(14)C) by the TTO expedition in 1981 and the GEOSECS expedition in 1972. The carbon profiles reflect the stable deep water in the Greenland and Norwegian Basins, and the relatively young bottom water just south of Iceland. (C) 1998 Elsevier Science Ltd. All rights reserved.