Journal of Oceanography, 57,
451-460., 2001
Winter Oceanographic Conditions in the Southwestern Part of the Okhotsk Sea and
Their Relation to Sea Ice
K. I. Ohshima, G. Mizuta, M. Itoh, Y. Fukamachi, T. Watanabe, Y. Nabae, K.
Suehiro, and M. Wakatsuchi
In the southwestern part of the Okhotsk Sea,
oceanographic and sea-ice observations on board the icebreaker Soya were
carried out in February 1997. A mixed layer of uniform temperature nearly at the
freezing point extending down to a depth of about 300 m was observed. This is
much deeper than has previously been reported. It is suggested that this deep
mixed layer originated from the north (off East Sakhalin), being advected along
the shelf slope via the East Sakhalin Current, accompanied with the thick
first-year ice (average thickness 0.6 m). This vertically uniform winter water,
through mixing with the surrounding water, makes the surface water more saline
(losing a characteristic of East Sakhalin Current Water) and the water in the
100-300 m depth zone less saline, colder, and richer in oxygen (a characteristic
of the intermediate Okhotsk Sea water). The oceanographic structure and a heat
budget analysis suggest that new ice zone, which often appears at ice edges, can
be formed through preconditioning of thick ice advection and subsequent cooling
by the latent heat release due to its melting.