Unraveling the Mystery of the Stark Contrast between Bouvet and Heard Islands in the Subantarctic - Implications for Seasonal Sea Ice Modeling and Forecasting
Abstract
Located in the Subantarctic, Bouvet and Heard are two remote and desolated volcanic islands about a thousand miles away from the closest Antarctic coast line. Despite such similarities, environmental conditions on the two islands are in a stark contrast. Bouvet Island is shrouded under a thick glacier year-round and surrounded by seasonal sea ice every year, in contrast to a green vegetation cover on Heard Island where sea ice never reaches its vicinity. Here, observations from radar backscatter data acquired by the QuikSCAT satellite together with sea ice products from the U.S. National Ice Center, sea surface temperature (SST) data from the Multi-sensor Ultra-high Resolution product, bathymetry data from the General Bathymetric Chart of the Oceans, and output from the Global Ocean Forecast System (GOFS) are used to unravel the mystery of the environmental contrast between the two islands. The results reveal that Bouvet Island is located on the cold side in the south the southern Antarctic Circumpolar Current front (sACCf) with a cold-water mass that can support a rough and thick sea ice cover in the Frontal Ice Zone (FIZ) while imposing a cold climatic condition that sustains the glacial cover on the island. In contrast, Heard Island is located on the warm side in the north of the sACCf with a warm-water mass that prevents sea ice formation while imposing a warm climatic condition that allows a green vegetation cover on the island. Our data animation shows how sea ice evolves and reaches Bouvet Island, and how the FIZ is restricted to the south of Heard Island. In both cases, the water mass distribution across the sACCf is dictated by the bathymetry, which has a pronounced underwater feature near Bouvet Island lying at the southern end of the Mid-Atlantic Ridge, while the Fawn Trough bisects the submerged Kerguelen Plateau and guides the sACCf to the south of Heard Island. GOFS is used to study the impact of the seafloor features on the regional circulation. With implications beyond the local regions, the contrast between the two islands illustrates the role of bathymetry, a geological factor, in controlling the water masses that in turns impact sea ice cover on the ocean and land cover on the islands. As such, the bathymetry serves as the system memory enabling the predictability in modeling and forecasting sea ice in the Southern Ocean.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.C31D1571N
- Keywords:
-
- 0750 Sea ice;
- CRYOSPHEREDE: 0766 Thermodynamics;
- CRYOSPHEREDE: 0770 Properties;
- CRYOSPHEREDE: 0774 Dynamics;
- CRYOSPHERE