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

Abstract

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.

Intercomparison of Surface Heat Transfer Near the Arctic Marginal Ice Zone for Multiple Reanalyses: A Case Study of September 2009

“…Reanalyses data are sometimes used to calculate the surface heat budgets over polynyas to estimate ice production in polar/ sub-polar oceans (e.g., Ohshima et al 2006). In particular, the near-surface air temperature and wind fields, which are difficult to observe using satellites or with in-situ measurements, are key parameters for estimating turbulent heat fluxes.…”

Identification of biophysical regions in the south-western part of the Okhotsk Sea by satellite imagery classification

“…Position and weakening of Aleutian Low influences the variability of sea ice extent in the Okhotsk Sea. Variability in heat flux in autumn and winter also influences the initial sea ice production apart from local atmospheric and climatic condition such as the southward advection of sea ice by ESC and prevailing northward winds (Cavalieri and Parkinson, 1987;Ohshima et al, 2006). Advection of SWC is dependent on the transport of the Tsushima Warm Current.…”

Four-dimensional variational ocean reanalysis: a 30-year high-resolution dataset in the western North Pacific (FORA-WNP30)

“…Subsequently, the sea ice extent starts decreasing, and most of the sea ice disappears by June. The sea ice extent in the Okhotsk Sea shows large interannual variability (Ohshima et al 2006). In Fig.…”

“…Their variations accompany energetic variabilities in the associated mesoscale features such as eddies and meanders. Another prominent feature in this region is the existence of low-frequency variability on interannual to decadal time scales (e.g., Qiu 2003;Ohshima et al 2006;Taguchi et al 2007;Na et al 2012;Usui et al 2013;Kuroda et al 2015), which has a strong connection with changes in atmospheric forcing. Accumulated evidence shows that the low-frequency variability is accompanied by modulation of the mesoscale variability.…”