the Creative Commons Attribution 3.0 License. Ocean Science Observations of new western Mediterranean deep water formation using Argo floats 2004–2006

Abstract. The deep convection that occurs in the western basin of the Mediterranean Sea was investigated using Argo float data over two consecutive winters in 2004–2005 and 2005–2006. The results showed deep mixed layers reach-ing 2000 m in surprising locations, namely the eastern Cata-lan subbasin (39.785 ◦ N, 4.845 ◦ E) and the western Ligurian subbasin (43.392 ◦ N, 7.765 ◦ E). Subsequently, new deep wa-ter was formed in March of 2005 and 2006 with θ=12.89– 12.92◦C, S=38.48–38.49 and σθ=29.113 kg m−3. The deep water produced in the Ligurian subbasin during 2006 was more saline, warmer and denser than any historical obser-vations of western Mediterranean deep water. The results show S, θ and σθ in the western Mediterranean deep wa-ter are higher than 1990s values, with a salinity increase of 1.5×10−3 yr−1, a temperature increase of 3.6×10−3 ◦C yr−1 and a density increase of 4.0×10−4 kg m−3 yr−1 apparent from a dataset of western Mediterranean deep water prop-erties spanning 1955–2006.