Biogeosciences www.biogeosciences.net 1726-4170 1726-4189 5 2 2008 10.5194/bg-5-549-2008 http://www.biogeosciences.net/5/549/2008/ http://www.biogeosciences.net/5/549/2008/bg-5-549-2008.html http://www.biogeosciences.net/5/549/2008/bg-5-549-2008.pdf 549 560 2008-04-10 Inorganic carbon time series at Ocean Weather Station M in the Norwegian Sea I. Skjelvan ingunn.skjelvan@gfi.uib.no E. Falck F. Rey S. B. Kringstad Bjerknes Centre for Climate Research, University of Bergen, Norway Geophysical Institute, University of Bergen, Norway Institute of Marine Research, Bergen, Norway Dissolved inorganic carbon (CT) has been collected at Ocean Weather Station M (OWSM) in the Norwegian Sea since 2001. Seasonal variations in (CT) are confined to the upper 50 m, where the biology is active, and below this layer no clear seasonal signal is seen. From winter to summer the surface (CT) concentration typical drop from 2140 to about 2040 μmol kg−1, while a deep water (CT) concentration of about 2163 μmol kg−1 is measured throughout the year. Observations show an annual increase in salinity normalized carbon concentration (nCT) of 1.3±0.7 μmol kg−1 yr−1 in the surface layer, which is equivalent to a pCO2 increase of 2.6±1.2 μatm yr−1, i.e. larger than the atmospheric increase in this area (2.1±0.2 μatm yr-1). Observations also show an annual increase in the deep water nCT of 0.57±0.24 μmol kg−1 yr−1, of which about 15% is due to inflow of old Arctic water with larger amounts of remineralised matter. The remaining part has an anthropogenic origin and sources for this might be Greenland Sea surface water, Iceland Sea surface water, and/or recirculated Atlantic Water. By using an extended multi linear regression method (eMLR) it is verified that anthropogenic carbon has entered the whole water column at OWSM. Alvarez, M., Rios, A. F., and Perez, F. F.: Transports and budgets of total inorganic carbon in the subpolar and temperate North Atlantic, Global Biogeochem. Cy., 17, 1002, doi:10.1029/2002GB001881, 2003. Anderson, L. G., Chierici, M., Fogelqvist, E., and Johannessen, T.: Flux of anthropogenic carbon into the deep Greenland Sea, J. Geophys. Res., 105(C6), 14 339–14 345, 2000. Anderson, L. G. and Olsen, A.: Air-sea flux of anthropogenic carbon dioxide in the North Atlantic, Geophys. Res. Lett., 29, 1835, doi:10.1029/2002GL014820, 2002. Blindheim, J. and Rey, F.: Water-mass formation and distribution in the Nordic Seas during the 1990s, ICES J. Mar. Sci., 61, 846–863, 2004. Blindheim, J. and Østerhus, S.: The Nordic Seas, Main Oceanographic Features, in: The Nordic Seas – An integrated perspective, AGU Geophysical Monograph, 158, dited by: H. Drange, T. Dokken, T. Furevik, R. Gerdes, and W. Berger, 11–37, 2005. Brewer, P. G.: Direct observation of the oceanic CO2 increase, Geophys. Res. Lett, 5, 997–1000, 1978. Brewer, P. G., Glover, D. M., Goyet, C., and Shafer, D. K.: The pH of the North Atlantic Ocean: Improvements to the global model for sound absorption in seawater, J. Geophys. Res., 100, 8761–8776, 1995. Chen, C.-T. A. and Millero, F. J.: Gradual increase of oceanic CO2, Nature, 277, 205–206, 1979. Chen, C.-T. A., Jones, E. P. and Lin, K.: Wintertime total carbon dioxide measurements in the Norwegian and Greenland Sea, Deep Sea Res., 37, 1455–1473, 1990. Dale, T., Rey, F., and Heimdal, B.: Seasonal development of phytoplankton at a high latitude oceanic site, Sarsia, 84, 419–435, 1999. DOE: Handbook of methods for the analysis of the various parameters of the carbon dioxide system in sea water, ver. 2, edited by: A. G. Dickson and C. Goyet, ORNL/CDIAC-74, 1994. Falck, E. and Anderson, L. G.: The dynamics of the carbon cycle in the surface water of the Norwegian Sea, Mar. Chem., 94, 43–53, 2005. Friis, K., Körtzinger, A., Pätsch, J., and Wallace, D. W. R.: On the temporal increase of anthropogenic CO2 in the subpolar North Atlantic, Deep-Sea Res. Pt. I, 52, 681–698, 2005. Gislefoss, J. S., Nydal, R., Slagstad, D., Sonninen, E., and Holmén, K.: Carbon time series in the Norwegian Sea, Deep-Sea Res. Pt. I, 45, 433–460, 1998. Goyet, C, Coatanoan, C., Eischeid, G., Amaoka, T., Okuda, K., Healy, R., and Tsunogai, S.: Spatial variation of total CO2 and total alkalinity in the northern Indian Ocean: A novel approach for the quantification of anthropogenic CO2 in seawater, J. Mar. Res., 57, 135–163, 1999. Gruber, N., Sarmiento, J. L., and Stocker, T. F.: An improved method for detecting anthropogenic CO2 in the oceans, Global Biogeochem. Cy., 10, 809–837, 1996. Johnson, K. M., Wills, K. D., Butler, D. B., Johnson, W. K., and Wong, C. S.: Coulometric total carbon dioxide analysis for marine studies, Mar. Chem., 44, 167–187, 1993. Jónsson, S.: The sources of fresh water in the Iceland Sea and the mechanisms governing its interannual variability, ICES Marine Science Symposia, 195, 62–67, 1992. Kara, A. B., Rochford, P. A., and Hurlburt, H. E.: An optimal definition for ocean mixed layer depth, J. Geophys. Res., 105, 16 803–16 821, 2000. Lewis, E. and Wallace, D. W. R.: Program Developed for CO2 System Calculations, ORNL/CDIAC-105, Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, US Department of Energy, Oak Ridge, Tennessee, 1998. Mosby, H.: Water, salt and heat balance of the North Polar Sea and of the Norwegian Sea, Geophysica Norvegica, 24, 289–313, 1962. Nilsen, J. E. Ø. and Falck, E.: Variations of Mixed Layer Properties in the Norwegian Sea for the period 1948–1999, Prog. Oceanogr., 70, 58–90, 2006. Olsen, A., Omar, A. M., Bellerby, R. G. J., Johannessen, T., Ninnemann, U., Brown, K. R., Olsson, K. A., Olafsson, J., Nondal, G., Kivimäe, C., Kringstad, S., Neill, C., and Olafsdottir, S.: Magnitude and Origin of the Anthropogenic CO2 Increase and $^13$C Suess Effect in the Nordic Seas Since 1981, Global Biogeochem. Cy., 20, GB3027, doi:10.1029/2005GB002669, 2006. Omar, A. and Olsen, A.: Reconstructing the time history of the air-sea CO2 disequilibrium and its rate of change in eastern subpolar North Atlantic, 1972–1989, Geophys. Res. Lett., 33, L04602, doi:10.1029/2005GL025425, 2006. Orvik, K. A., Skagseth, Ø., and Mork, M.: Atlantic Inflow to the Nordic Seas: current structure and volume fluxes from moored current meters, VM-ADCP and SeaSOAR-CTD observations, 1995–99, Deep-Sea Res. Pt. I, 48, 937–957, 2001. Redfield, A. C., Ketchum, B. H., and Richards, F. A.: The influence of organisms on the composition of seawater, in: The Sea, edited by: M. N. Hill and J. Wiley, New York, 26–77, 1963. Rey, F.: Phytoplankton: The grass of the sea, in: The Norwegian Sea Ecosystem, ed. H.R. Skjoldal, Tapir, Trondheim, Norway, 93–132, 2004. Ronski, S. and Budéus, G.: Time series of winter convection in the Greenland Sea, J. Geophys. Res., 110, C04015, doi:10.1029/2004JC002318, 2005. Rudels, B., Friederich, H. J., and Quadfasel, D.: The Arctic circumpolar boundary current, Deep-Sea Res. Pt. II, 46, 1023–1062, 1999. Rudels, B., Fahrbach, E., Meincke, J., Budéus, G., and Eriksson, P.: The East Greenland Current and its contribution to the Denmark Strait overflow, ICES J. Mar. Sci., 59, 1133–1154, 2002. Sabine, C. L., Key, R. M., Johnson, K. M., Millero, F. J., Poisson, A., Sarmiento, J. L., Wallace, D. W. R., and Winn, C. D.: Anthropogenic CO2 inventory of the Indian Ocean, Global Biogeochem. Cy., 13, 179–198, 1999. Schlosser, P., Bönisch, G., Rhein, M., and Bayer, R.: Reduction of Deepwater Formation in the Greenland Sea During the 1980s: Evidence from Tracer Data, Science, 251, 1054–1056, 1991. Skjelvan, I., Olsen, A., Anderson, L. G., Bellerby, R. G. J., Falck, E., Kasajima, Y., Kivimäe, C., Omar, A., Rey, F., Olsson, K. A., Johannessen, T., and Heinze, C.: A Review of the Inorganic Carbon Cycle of the Nordic Seas and Barents Sea, in: The Nordic Seas – An integrated perspective, AGU Geophysical Monograph, 158, edited by: H. Drange, T. Dokken, T. Furevik, R. Gerdes, and W. Berger, 157–175, 2005. Solomon, S., Qin, D., Manning, M., Alley, R. B., Berntsen, T., Bindoff, N. L., Chen, Z., Chidthaisong, A., Gregory, J. M., Hegerl, G. C., Heimann, M., Hewitson, B., Hoskins, B. J., Joos, F., Jouzel, J., Kattsov, V., Lohmann, U., Matsuno, T., Molina, M., Nicholls, N., Overpeck, J., Raga, G., Ramaswamy, V., Ren, J., Rusticucci, M. Somerville, R., Stocker, T. F., Whetton, P., Wood R. A., and Wratt, D.: Technical Summary, in: Climate Change 2007: The Physical Science Basis, Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, edited by: Solomon, S., Qin, D., Manning, M., Chen, Z., Marquis, M., Averyt, K. B., Tignor M., and Miller, H. L., Cambridge University Press, Cambridge, UK and New York, NY, USA, 2007. Swift, J. H. and Koltermann, K. P.: The origin of Norwegian Sea deep-waters, J. Geophys. Res., 93, 3563–3569, 1988. Takahashi, T., Sutherland, S. C., Sweeney, C., Poisson, A., Metzl, N., Tilbrook, B., Bates, N., Wanninkhof, R., Feely, R. A., Sabine, C., Olafsson, J., and Nojiri, Y.: Global sea-air CO2 flux based on climatological surface ocean $p$CO2, and seasonal biological and temperature effects, Deep-Sea Res. Pt. II, 49, 1601–1622, 2002. Tanhua, T. and Wallace, D. W. R.: Consistency of TTO-NAS inorganic carbon data with modern measurements, Geophys. Res. Lett., 32, L14618, doi:10.1029/2005GL023248, 2005. Tans, P. P. and Conway, T. J.: Monthly Atmospheric CO2 Mixing Ratios from the NOAA CMDL Carbon Cycle Cooperative Global Air Sampling Network, 1968-2002, in: Trends: A Compendium of Data on Global Change, Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, US Department of Energy, Oak Ridge, Tenn., U.S.A, 2005. Wallace, D. W. R.: Monitoring global ocean carbon inventories, OOSDP Background Report No. 5, Texas A&M University, College Station, Texas, USA, pp. 54, 1995. Wallace, D. W. R.: Storage and transport of excess CO2 in the oceans: The JGOFS/WOCE global CO2 Survey, in: Ocean circulation and climate: observing and modelling the global ocean, edited by: G. Siedler, J. Church, and J. Gould, 489–521, 2001. Østerhus, S. and Gammelsrød, T.: The abyss of the Nordic Seas is warming, J. Climate, 2, 3297–3304, 1999.