9:30 AM - 9:45 AM
[MIS10-03] Melting area of coastal-origin sea ice and its relationship with material transport and biological productivity in the Southern Ocean
Keywords:sea ice, particle tracking experiment, coastal polynya, material transport, phytoplankton bloom, ice melting
The Southern Ocean is the area of the largest primary production. Prominent phytoplankton bloom generally occurs just after sea-ice melt. In addition to the enhancement of stratification due to freshwater input by ice melting, micro-nutrients (iron) released from sea ice is considered as the cause of the bloom. The origin of the micro-nutrients (iron) in the sea ice likely originates from the coastal areas, where bottom sediment or Ice Shelf Water can be incorporated into sea ice. However, few investigations have been made for the transport and melting area of coastal-origin sea ice. Such investigations also provide the basic information for the heat and freshwater transport by sea ice as well as the material transport. To elucidate the transport and melting area of sea ice produced in the coastal polynyas, we made the particle-tracking experiments of coastal-origin sea ice and identified the areas of ice melting.
We focused on sea ice produced in the Cape Darley polynya (CDP: 68-70°E, 67-68°S), because the CDP has the second largest sea-ice production and we have the information of sea-ice drift from several mooring observations with Acoustic Doppler Profilers. Sea ice production was calculated based on the heat budget calculation using thin-ice thickness data from the AMSR algorithm (Nakata et al. 2021). The particles were placed at every time step with the number of deployed particles being proportional to the amount of sea ice production and were tracked using the ice drift data. The ice drift velocities primarily used were calculated from the AMSR data (Kimura et al. 2013). However, the ice drift velocity near the coast cannot be obtained accurately from the satellite AMSR data because of the contamination of the land data. Therefore, we also used ice drift data estimated from the wind using the wind factor and turning angle, obtained from the mooring data, assuming a free drift. These two kinds of drift data were merged within 200 km from the coast with a larger weight of the estimation by the wind closer to the coast. In this study, an ice particle is considered to melt when the ice concentration at the particle position was continuously less than 50% for 5 days.
To examine the average melting position of coastal-origin sea ice, we counted the total number of melted particles (sea ice) for the simulation results from 2003-2009 and 2013-2019. Sea ice produced in the CDP melts mostly over the continental slope regions between 10-70°E. When compared with the spatial distribution of chlorophyll-a concentration for each ice-melt month, the melting areas of coastal-origin sea ice tend to show high chlorophyll-a concentration. This suggests that the melting of coastal-origin sea ice is a key factor of the spring phytoplankton bloom. We carried out the particle tracking experiments for sea ice originating from all the Antarctic coastal polynyas. Then we provided the mapping of melting areas of these coastal-origin sea ice, which gives the basic information to evaluate the role of the coastal-origin sea ice in material transport and phytoplankton bloom.
We focused on sea ice produced in the Cape Darley polynya (CDP: 68-70°E, 67-68°S), because the CDP has the second largest sea-ice production and we have the information of sea-ice drift from several mooring observations with Acoustic Doppler Profilers. Sea ice production was calculated based on the heat budget calculation using thin-ice thickness data from the AMSR algorithm (Nakata et al. 2021). The particles were placed at every time step with the number of deployed particles being proportional to the amount of sea ice production and were tracked using the ice drift data. The ice drift velocities primarily used were calculated from the AMSR data (Kimura et al. 2013). However, the ice drift velocity near the coast cannot be obtained accurately from the satellite AMSR data because of the contamination of the land data. Therefore, we also used ice drift data estimated from the wind using the wind factor and turning angle, obtained from the mooring data, assuming a free drift. These two kinds of drift data were merged within 200 km from the coast with a larger weight of the estimation by the wind closer to the coast. In this study, an ice particle is considered to melt when the ice concentration at the particle position was continuously less than 50% for 5 days.
To examine the average melting position of coastal-origin sea ice, we counted the total number of melted particles (sea ice) for the simulation results from 2003-2009 and 2013-2019. Sea ice produced in the CDP melts mostly over the continental slope regions between 10-70°E. When compared with the spatial distribution of chlorophyll-a concentration for each ice-melt month, the melting areas of coastal-origin sea ice tend to show high chlorophyll-a concentration. This suggests that the melting of coastal-origin sea ice is a key factor of the spring phytoplankton bloom. We carried out the particle tracking experiments for sea ice originating from all the Antarctic coastal polynyas. Then we provided the mapping of melting areas of these coastal-origin sea ice, which gives the basic information to evaluate the role of the coastal-origin sea ice in material transport and phytoplankton bloom.