Estimation of Surface Heat Flux Based on Rawinsonde Observation in the Southwestern Part of the Sea of Okhotsk under Ice-covered Condition.

We examine the interannual variability of the sea ice area in the Sea of Okhotsk in terms of surface heat flux, using highly resolved flux data with the ice concentration taken into account. On the northwest and east Sakhalin shelves, where the initial ice formation occurs, the onset of ice formation is simply determined by the local heat flux in fall (October-November); the degree to which the ocean is cooled by the atmosphere. Consequently, this heat flux mostly determines the interannual variability of sea ice area in the Okhotsk Sea in the initial stage. The air temperature anomaly is the main cause of the heat flux anomaly in fall. The fall heat flux has persistently affected the ice area anomaly, particularly until mid-January. In the later sea ice season, the relationship between the ice area and heat flux is obscured, particularly after mid-January, by the heat insulating effect of sea ice. The ice area variabilities in the southern and northeast regions are correlated with the local heat flux in the months preceding ice appearance, but not strongly. Our analysis suggests that the heat flux does not determine to what extent the ice advances finally in the Okhotsk Sea. Typical heat flux distributions in heavy and light ice years are also presented from our heat flux data: the heat loss center is located in the central Okhotsk Sea in light ice years, and moves to the eastern Okhotsk Sea near the Kuril Straits in heavy ice years.

Section: Introductionmentioning

confidence: 99%

Interannual Variability of Sea Ice Area in the Sea of Okhotsk: Importance of Surface Heat Flux in Fall

Ohshima

Nihashi

Hashiya

et al. 2006

“…Iwamoto et al (2001) and Inoue et al (2001) estimated the surface heat flux based on Rawinsonde observations in the southern part of the sea under ice-covered conditions. Inoue (2001) directly measured the turbulent heat flux over the sea ice region off Sakhalin Island by aircraft using the eddy correlation methods.…”

Section: Introductionmentioning

confidence: 99%

Surface Heat Budget of the Sea of Okhotsk during 1987-2001 and the Role of Sea Ice on it

Ohshima

Watanabe

Nihashi

2003

The surface heat flux over the Sea of Okhotsk has been calculated from 1987 to 2001 by bulk parameterizations using ECMWF, ISCCP, and GISST data, corrected by COADS data. Sea ice concentration and ice type are incorporated by using an SSM/I open water and thin-ice algorithm to better represent the sea ice conditions. The mean seasonal variation of the net heat flux, averaged over the entire Okhotsk Sea, ranges from a summer maximum of 158 W m À2 in June (a positive value indicates that the sea or sea ice gains heat form the air), to a winter minimum of À219 W m À2 in December. The seasonal geographic distribution of the net heat flux is determined mostly by turbulent (sensible and latent) heat flux. Because of the heat insulating effect of sea ice, the turbulent heat flux and accordingly the net heat flux has the largest variation in winter, particularly in the north region, reflecting the yearly difference of sea ice extent. The geographic distribution of the annual net heat flux shows a distinct contrast, significant cooling of the ocean in the north and net heating of the ocean in the south. This contrast is a result of heat transport by both sea ice and the southward East Sakhalin Current; sea ice formed by obtaining negative latent heat in the north is transported to the south, then it releases the negative latent heat by melting. The annual net heat budget is estimated to be À22 W m À2 averaged over the entire sea. The Okhotsk Sea loses heat to the atmosphere on an annual basis, although at least the order of 20 W m À2 error exists in the estimation. A trial was performed to estimate sea ice production using the heat budget calculation. The results suggest that most of the production occurs in open water and thin ice areas. The highest production area is located over the northwest shelf, within 100 km of the coast.

“…To estimate Q R , the one-dimensional radiative model Streamer (Key 1999) is used, which is the same method as described by Iwamoto et al (2001). The Streamer is a radiative transfer model, containing the effects of cloud, realistic incoming solar radiation at the specific location and time, and albedos associated with various surface conditions.…”

Section: Estimation Of the Turbulent Heat Fluxmentioning

confidence: 99%

“…(8) among ice concentration, temperature difference and wind velocity. For example, Iwamoto et al (2001) pointed out the importance of contribution of the ice concentration to F total , while Inoue et al (2001) emphasized the contribution of the temperature of the air mass.…”

Section: Comparisons Of the Bulk Heat Transfer Coefficientmentioning

confidence: 99%

See 1 more Smart Citation

Characteristics of Heat Transfer over the Ice Covered Sea of Okhotsk during Cold-air Outbreaks

Inoue

Ono

Tachibana³

et al. 2003

Self Cite

Heat transfer coefficients, and relative importance of factors affecting surface turbulent heat flux in sea-ice covered ocean, were investigated using data obtained by rawinsonde observations over, and around, the southwestern region of the Sea of Okhotsk from Jan. to Feb. in 1998Feb. in , 1999Feb. in and 2000. The range of the fluxes estimated by an atmospheric heat budget analysis was large, associated with the ice concentration and synoptic situation. The turbulent heat fluxes from the open water surrounded by the sea ice are always positive (upward). However, the heat flux through sea-ice surface tends to be negative (downward) over sea-ice area associated with the relationship between the air and ice-surface temperature. Using the obtained turbulent heat fluxes and a bulk formula, relationships of turbulent heat fluxes with ice concentrations and atmospheric parameters were investigated, and a representative value of the bulk heat transfer coefficient was obtained. The estimated conditional bulk heat transfer coefficient (1:33 Â 10 À3 ) in the Sea of Okhotsk shows a smaller value than that in the Arctic region, reflecting the difference of the ice conditions, and thermal conditions in the boundary layer. Through an idea of the insulating coefficient, which measures degrees of the insulating effect of sea ice on the heat transfer, we explained that the sea ice works as a more effective insulator in weaker cold-air outbreaks. From a regression analysis, we found that the primary contribution to the amount of turbulent heat flux is the ice concentration, and second is the air temperature in the boundary layer.