The distinguishing of the Ob and Yenisei waters in the desalinated lenses of the Kara Sea in 1993 and 2007

In 1993 and 2007 when the expeditions of the Shirshov Institute of Oceanology were performed in the Kara Sea, a significant part of its aquatic area was occupied by lenses of desalinated water. The fresh-water is supplied by the runoff of the Ob and Yenisei rivers, as well as by meltwaters. The report considers the features of the freshwater chemical transformation in the sea. It is shown that the contribution of meltwaters is small in the highly desalinated lenses (with salinity below 15‰) and the freshwater is supplied by the riverine runoff. It is also shown that, under definite conditions, it is possible to determine the relative shares of the Ob and Yenisei waters using the chemical parameters (the silicon and alkalinity). The data of 1993 when two lenses as such were found in the sea were confirmed; at that, the waters of the Yenisei and Ob rivers were prevailing in the western and northeastern lenses, respectively. In 2007, one lens was found in the treated area of the sea. It is shown that the chemical characteristics of the freshwater in the lens appeared to be sufficiently different from those of the Ob river but similar to the Yenisei river’s characteristics according to the data of 1993. A map of the Ob’s and the Yenisei’s water spreading over the sea’s aquatic area is presented.