Physical Oceanography Seminar 5/29/24: Mizuki Komatsu, Hokkaido University

Wednesday, May 29, 12:30 PM to 01:30 PM PDT

Presenter: Mizuki Komatsu, Hokkaido University

Title: Mapping of sea-ice melting and net freshwater flux by sea-ice growth/melt in the Southern Ocean

Location: 123 Marine Science Building

Time: 12:30 PM

Zoom Link: https://washington.zoom.us/j/97753827276

Abstract: Sea-ice in the Southern Ocean plays a crucial role in transporting and redistributing freshwater/salt and heat via freezing, melting, and transport. Changes in northward freshwater transport by sea-ice and its melt are suggested to change the intermediate water and stratification, which could affect the carbon budget with a global impact. However, very few observational studies have estimated the ice-melt amount because of the complexity of the melting processes. Here, we estimate the ice-melt amount from the salinity deficit caused by the ice-melt, using 25,000 spring hydrographic data over the Southern Ocean. The spatial distribution of ice-melt reflects the northward advection of coastal thick ice and its melting via the three cyclonic gyres. The total freshwater flux by sea-ice melt is calculated to be 17010Gt/yr, which is six times larger than that of the total glacial melt (2900Gt/yr). Combined with the estimation of sea-ice production, we further estimated the net freshwater flux of sea-ice in the Southern Ocean for the first time on an observational basis. It shows large latitudinal variations: larger negative values at higher latitudes, with a change in sign at 62°S, suggesting its dominant role in the Southern Ocean.