Ocean Science www.ocean-sci.net 1812-0784 1812-0792 5 3 2009 10.5194/os-5-247-2009 http://www.ocean-sci.net/5/247/2009/ http://www.ocean-sci.net/5/247/2009/os-5-247-2009.html http://www.ocean-sci.net/5/247/2009/os-5-247-2009.pdf 247 257 2009-07-14 Role of cabbeling in water densification in the Greenland Basin Y. Kasajima yoshie.kasajima@gfi.uib.no T. Johannessen Geophysical Institute, University of Bergen, Allégaten 70, 5007 Bergen, Norway Bjerkrnes Centre for Climate Research, Allégaten 55, 5007 Bergen, Norway The effects of cabbeling mixing on water mass modification in the Greenland Sea were explored by hydrographic observations across the Greenland Basin in summer 2006. The neutral surface was chosen as a reference frame, and the strength of cabbeling mixing was quantified by the dianeutral velocity magnitude. Active cabbeling spots were detected with the criterion of the velocity magnitude >1 m/day, and four active cabbeling areas were identified; the west of Bear Island (SB), the Arctic Frontal Zone (AFZ), the central Greenland Sea (CG) and the western Greenland Sea (WG). The most vigorous cabbeling mixing was found at SB, where warm North Atlantic Water (NAW) mixed with cold water from the Barents Sea, inducing a maximum velocity of 7.5 m/day and a maximum density gain of 4.7×10^−3 kg/m³. At AFZ and CG, the mixing took place between NAW, modified NAW and Arctic Intermediate Water (AIW), and the density gain at these fronts were 1.5×10^−3 kg/m³ (AFZ) and 1.3×10^−3 kg/m³ (CG). In the western Greenland Sea, the active cabbeling spots were widely separated and mixing appeared to be rather weak, with a maximum velocity of 2.5 m/day. The mixing source waters at WG were modified NAW, AIW and even denser water, and the density gain in this area was 0.4×10^−3 kg/m³. The deepest mixing produced water whose density is equivalent to that of the dense water of the basin, indicating that cabbeling in the western Greenland Sea contributed directly to basin-scale water densification. The water mass modification rate was the highest at AFZ (about 8.0 Sv), suggesting that cabbeling may play an important role in water transformation in the Greenland Basin. % vor jede Referenz Akitomo, K.: Open-ocean deep convection due to thermobaricity 1. Scaling argument, J. Geophys., Res. 104(C3), 5225–5234, 1999. % vor jede Referenz Bönisch, G., Blindheim, J., Bullister, J., Schlosser, P., and Wallace, D.: Long-term trends of temperature, salinity, density and transient tracers in the central Greenland Sea, J. Geophys. Res., 102, 18553–18571, 1997. % vor jede Referenz Budéus, G., Schneider, W., and Krause, G. : Winter convective events and bottom water warming in the Greenland Sea, J. Geophys. Res., 103(C9), 18513–18527, 1998. % vor jede Referenz Clarke, R., Swift, J., Reid, J., and Kolterman, K. : The formation of Greenland Sea Deep Water: Double Diffusion or deep convection?, Deep-Sea Res., 37, 1385–1424, 1990. % vor jede Referenz Cottier, F. R. and Venables, E. J.: On the double-diffusive and cabbeling environment of the Arctic Front, West Spitsbergen, Polar Res., 26, 152–159, 2007. % vor jede Referenz Garrett, C. and Horne, E.: Frontal circulation due to cabbeling and Double diffusion, J. Geophys. Res., 83(C9), 4651–4656, 1978. % vor jede Referenz Gill, A. E. : Atmosphere-ocean dynamics, Academic Press, 1982. % vor jede Referenz Gordon, A. L., Georgi, D. T., and Taylor, H. W. : Antarctic polar front zone in the western Scotia Sea, J. Phys. Oceanogr., 7, 309–328, 1977. % vor jede Referenz Hansen, B. and Østerhus, S.: North Atlantic-Nordic Seas exchanges, Prog. Oceanogr., 45, 109–208, 2000. % vor jede Referenz Horne, E. P. W.: Interleaving at the subsurface front in the slope water off Nova Scotia, J. Geophys. Res., 83(C7), 3659–3671, 1978. % vor jede Referenz Jansen, E. and Opheim, V. (Eds.): European Subpolar Ocean Program (ESOP-II), The thermohaline circulation in the Greenland Sea-Final scientific report, contract MAS3-CT95-0015, Eur. Union, Brussels, 1999. % vor jede Referenz Karstensen, J., Schlosser, P., Wallace, D. W. R., Bullister, J. L., and Blindeheim, J.: Water mass transformation in the Greenland Sea during the 1990s, J. Geophys. Res., 110, C07002, doi:10.1029/2004JC002510, 2005. % vor jede Referenz Loeng, H.: Features of the physical oceanographi conditions of the Barents, Sea. Polar Res., 10(1), 5–18, 1990. % vor jede Referenz Marsh, R.: Cabbeling due to isopycnal mixing in isopycnic coordinate models, J. Phys. Oceanogr., 30, 1757–1775, 2000. % vor jede Referenz McDougall, T. J.: Thermobaricity, cabbeling and water mass conversion, J. Geophys. Res., 92(C5), 5448–5464, 1987a. % vor jede Referenz McDougall, T. J.: Neutral surface, J. Phys. Oceanogr., 17, 1950–1964, 1987b. % vor jede Referenz McDougall, T. J.: The relative roles of diapycnal and isopycnal mixing on subsurface water mass conversion, J. Phys. Oceanogr., 14, 1577–1589, 1984. % vor jede Referenz Messias, M.-J., Watson, A. T., Johannessen, T., Oliver, K. I. C., Olsson, K. A., Fogelqvist, E., Olafsson, J., Bacaon, S., Balle, J., Balle, N., Bergman, N., Budéus, G., Danielsen, M., Gascard, J.-C., Jeansson, E., Olafsdottir, S. R., Simonsen, K., Tauhua, T., Van Scoy, K., and Ledwell, J. R.: The Greenland Sea Tracer Experiment 1996–2002: horizontal mixing and transport of Greenland Sea Intermediate Water, Prog. Oceanogr., 78(1), 85–105, doi:10.1016/j.pocean.2007.06.005, 2007. % vor jede Referenz Munk, W. H. and Wunch, C.: Abyssal Recipes II: energetics of tidal and wind mixing, Deep-Sea Res., 45, 1977–2010, 1998. % vor jede Referenz Omar, A., Johannessen, T., Kaltin, S., and Olsen, A.: Anthropogenic increase of oceanic $p$CO₂ in the Barents Sea surface water, J. Geophys. Res., 108(C12), 388, doi:10.1029/2002JC001628, 2003. % vor jede Referenz Skogseth, R., Smedrud, L. H., Nilsen, F., and Fer, I. : Observations of hydrography and downflow of brine-enriched shelf water in the Storfjorden polynya, Svalbard, J. Geophys. Res., 113, C08049, doi:10.1029/2007JC004452, 2008. % vor jede Referenz Sundfjord, A., Fer, I., Kasajima, Y., and Svendsen, H. : Observations of turbulent mixing and hydrography in the marginal ice zone of the Barents Sea, J. Geophys. Res., 112, C05008, doi:101029/2006JC003524, 2007. % vor jede Referenz Swift, J. H. and Aagaard, K. : Seasonal transitions and water mass formation in the Iceland and Greenland seas, Deep-Sea Res., 28A(10), 1107–1129, 1981. % vor jede Referenz Talley, L. and Yun, J. Y.: Role of cabbeling and double diffusion in setting the density of the North Pacific intermediate water salinity minimum, J. Phys. Oceanogr., 31, 1538–1549, 2001. % vor jede Referenz van Aken, H., Budéus, G., and Hahnel, M.: The anatomy of the Arctic Frontal Zone in the Greenland Sea, J. Geophys. Res., 100(C8), 15999–16014, 1995. % vor jede Referenz van Aken, H. M., Quadfasel, D., and Warpakowski, A.: The Arctic front in the Greenland Sea during February 1989: Hydrographyc and biological observations, J. Geophys. Res., 96, 4739–4750, 1991. % vor jede Referenz Walin, G.: On the relation between sea-surface heat flow and thermal circulation in the ocean, Tellus, 34, 187–195, 1982. % vor jede Referenz Whitehead, J. A.: Topographic control of oceanic flows in deep passage and straits, Rev. Geophys., 36(3), 423–440, 1998. % vor jede Referenz You, Y.: Dianeutral mixing in the thermocline of the Indian Ocean, Deep-Sea Res. Pt. I, 43, 291–320, 1996. % vor jede Referenz You, Y.: Dianeutral mixing, transformation and transformation and transport of Antarctic Intermediate Water in the South Atlantic Ocean, Deep-Sea Res. Pt. II, 46, 393–435, 1999.