Creation of a Heat and Salt Flux Dataset Associated with Sea Ice Production and Melting in the Sea of Okhotsk

Abstract

Sea ice formation, its transport, and its melting cause the redistribution of heat and salt, which plays an important role in the climate and biogeochemical systems. In the Sea of Okhotsk, a heat and salt flux dataset is created in which such sea ice processes are included, with a spatial resolution of ;12.5 km. The dataset is based on a heat budget analysis using ice concentration, thickness, and drift speed from satellite observations and the ECMWF Interim Re-Analysis (ERA-Interim) data. The salt flux calculation considers both salt supplied to the ocean from sea ice production and freshwater supplied when the ice melts. This dataset will be useful for the validation and boundary conditions of modeling studies. The spatial distribution of the annual fluxes shows a distinct contrast between north and south: significant ocean cooling with salt supply is shown in the northern coastal polynya region, while ocean heating with freshwater supply is shown in the south. This contrast suggests a transport of freshwater and negative heat by ice advection. The annual fluxes also show ocean cooling with freshwater supply in the Kashevarov Bank (KB) region and the central and eastern Sea of Okhotsk, suggesting the effect of warm water advection. In the ice melt season, relatively prominent ice melting is shown in the coastal polynya region, probably due to large solar heating of the upper ocean. This indicates that the polynya works as a ''meltwater factory'' in spring, contrasting with its role as an ''ice factory'' in winter. In the coastal polynya region, the spatial distribution of phytoplankton bloom roughly corresponds with the ice melt region.

Circumpolar Mapping of Antarctic Coastal Polynyas and Landfast Sea Ice: Relationship and Variability

“…These results suggest that thin ice thickness of less than about 0.2 m can be estimated from the R. In situ measurements have shown that ice thickness in Antarctic coastal polynyas is generally less than about 0.2 m (Jeffries and Adolphs 1997;Tamura et al 2006). In this study, ice thickness of #0.2 m is estimated from polarization ratio (PR) of TBs, as in previous studies (Tamura et al 2007;Nihashi et al 2009;Iwamoto et al 2013Iwamoto et al , 2014. PR is defined by PR 5 (TB V 2 TB H )/(TB V 1 TB H ) and linearly transformed from R using the equation PR 5 (R 2 1)/(R 1 1).…”

Causes of the Multidecadal-Scale Warming of the Intermediate Water in the Okhotsk Sea and Western Subarctic North Pacific

“…, which is somewhat smaller than the observed estimate of sea ice production rate of 6.5 3 10 11 m 3 yr 21 (Nihashi et al 2012).…”

“…To validate the simulated sea ice production, we used ice production estimated by a heat budget analysis using ice concentration, thickness, and drift speed from satellite observation, and Interim ECMWF Re-Analysis (ERAInterim) data (Nihashi et al 2012) (available from 2003 to 2009 with a spatial resolution of 12.5 km). In their study, ice production rate per unit area (V i ) in the Okhotsk coastal polynyas is calculated by V i 5 Q/r i L f , where Q is daily heat loss from the sea surface to the atmosphere, r i (5920 kg m…”

“…For the observational data, the freshwater flux related to sea ice melting is calculated with some assumptions (e.g., constant ice thickness of 0.34 m is made for all melting ice; for details, see Nihashi et al 2012). The simulated freshwater fluxes related to ice production (or melting) are calculated from the input of freshwater from ocean to sea ice (or from sea ice to ocean).…”

“…A large amount of sea ice within the Okhotsk Sea is produced along the northwestern coastal polynyas by severe wintertime winds blowing from the Eurasian continent (Martin et al 1998;Ohshima et al 2003;Nihashi et al 2009;Kawaguchi et al 2010), and the brine rejection associated with sea ice production leads to vertical convection of up to 27.0s u [s u is defined as potential density 2 1000 (kg m 23 ); thus, the density of seawater 1027.0 kg m 23 means 27.0s u ], resulting in the formation of cold, oxygen-rich, dense shelf water (DSW) (Kitani 1973;Gladyshev et al 2000;Shcherbina et al 2003;Nakamura et al 2006;Matsuda et al 2009). DSW is transported southward by the cyclonic ocean circulation in the Okhotsk Sea Fukamachi et al 2004), and it then mixes with the warm, saline water originating from the North Pacific.…”