The Bay of Biscay climatology is the synthesis of all the in situ data collected in the bay of Biscay area as far as 15°W, in the 20th century and mainly by IFREMER, SHOM, and WDCA. It shows temperature and salinity monthly information through the whole water column with a 1/10 degree resolution. The resulting atlas was produced by an optimal analysis which can reflect different scales: shelf and abyssal plain. A fine scale on the coast reveals all the local effects, including plume and upwelling, and a large scale on the shelf where a slower signal is obtained due to the large scale circulation