Distributions of mixed layer properties in North Pacific water mass formation areas: comparison of Argo floats and World Ocean Atlas 2001

F. M. Bingham (1) , T. Suga (2)

1 University of North Carolina Wilmington
2 Tohoku University [Sendai]

Winter mixed layer characteristics in the North Pacific Ocean are examined and compared between Argo floats in 2004 and 2005 and the World Ocean Atlas 2001 (WOA01) climatology for a series of named water masses, North Pacific Tropical Water (NPTW), Eastern Subtropical Mode Water (ESTMW), North Pacific Subtropical Mode Water (NPSTMW), Light Central Mode Water (LCMW) and Dense Central Mode Water (DCMW). The WOA01 is found to be in good agreement with the Argo data in terms of water mass volumes, average temperature-salinity (T-S) properties, and outcrop areas. The exception to this conclusion is for the central mode waters, especially DCMW, whose outcropping is shown to be much more intermittent than is apparent in the WOA01 and whose T-S properties vary from what is shown in the WOA01. Distributions of mixed layer T-S properties measured by floats are examined within the outcropping areas defined by the WOA01 and show some shifting of T-S characteristics within the confines of the named water masses. In 2005, all the water masses were warmer than climatology on average, with DCMW being highest at about 1°C. Similar results were found for the 2004 Argo data except ESTMW and DCMW which were slightly cooler than climatology. Differences between float data and climatology were examined for the entire North Pacific in order to put the above results into context. This analysis showed the winter North Pacific mixed layer to be warmer and fresher than climatology in both 2004 and 2005, with magnitudes of about 0.3?0.4°C and 0.06?0.07. This warming and freshening was apparent throughout a large area of the tropics and northeastern North Pacific, but in the mode water formation areas the trends were less clear.

Domaines: Océan, Atmosphère

F. M. Bingham, T. Suga. Distributions of mixed layer properties in North Pacific water mass formation areas: comparison of Argo floats and World Ocean Atlas 2001. Ocean Science Discussions, 2006, 3 (1), pp.1-24. ⟨hal-00298369⟩