4:45 PM - 5:00 PM
[AOS15-06] Monitoring the motion of the land-fast ice in Lützow-Holm Bay, Antarctica
During the 64th Japanese Antarctic Research Expedition (JARE), we deployed over 30 wave buoys in the Lützow-Holm Bay, Antarctica. Syowa Station is the central hub of the Japanese Antarctica observation, and its maintenance relies on the successful and timely berthing of the Ice breaker Shirase on the Syowa land-fast ice docking station. Syowa Station is located in the East Ongul Island, east of the Lützow-Holm Bay. Shirase visits Syowa Station every year, bringing cargos over 1000 tons and around 70 members of JARE.
Syowa Station is protected from the incoming swells of the screaming 60s by a vast land-fast ice, packed ice zone in the north, and the Marginal Ice Zone (MIZ). Waves that propagate under sea ice are considered to be one of the causes of a large breakup of the land-fast ice. The sea ice in the Lützow-Holm Bay grows not only because of the freezing of the sea water, but because of the icing of the snow at the surface as the sea water intrudes into the snow. The material strength of such sea ice is considered to be weak and subject to breakup as it oscillates due to the incoming waves. The cycle of sea-ice breakup and growth has been around 10 years and interestingly enough, the number of ramming maneuver of the ship synchronously changes. The knowledge of the long-term cycle of sea-ice breakup is critical for the long-term planning of Shirase operation.
The aim of our observational campaign during JARE64 is to monitor the incoming waves through the MIZ, packed ice zone (PIZ), and the land-fast ice zone, and to monitor the horizontal movement of the sea ice. Eventually, the land-fast ice may breakup and drift away from the Lützow-Holm Bay. 15 wave buoys were deployed on the land-fast ice, 8 wave buoys on the drifting ice floes, and 10 wave buoys in the water covered by blush ice between ice floes. The deployment was conducted by a helicopter and by a ship operation. A wide areal coverage of the buoys was possible only with the use of a helicopter. We have also landed on the land-fast ice of the 13 buoy locations and measured the ice thickness.
We present here, preliminary results of our observations, first regarding the horizontal movement of the land-fast ice, and second a signature of wave propagation in ice. Results are summarized in Figure 1.
During the deployments of the 15 buoys on 12/26 2022, we observed a zonal crack that divided the multi-year ice (over 3.5 m) and the first year ice in the north whose thickness gradually decreased from 2 m to 1 m towards the north. The multi-year ice survived the large sea ice loss in April 2022, and the first year ice gradually developed in the north. The crack that divides the multi-year and the first year ice likely formed in the austral summer in 2022. We have visited those buoys on 1/3 and 2/7 to measure the ice thickness. On 2/7, we observed new zonal cracks that formed after our first visit. In a month, the buoys in the south of the crack moved around 20 m horizontally while the others, particularly the ones close to the ice-berg trains in the northeast, remained stationary. Likely, the ice moved after the formation of the new ice cracks due to strong wind events. The wind affects the coastal area as well. After the strong gust event on 1/23, a large open water was created along the continental coast from the east of the Ongul Islands to the Lang Hovde glacier detaching the multi-year land-fast ice from the land.
A wave propagation through MIZ and PIZ, reaching the land-fast ice zone was observed in 2/6 and 7. Typically, when a depression passes by the north of the Lützow-Holm Bay, a strong North Easterly wind develops and a swell propagates into the bay. To monitor waves propagating in the PIZ, 6 wave buoys were deployed by the helicopter on ice floes on 2/11. Two wave buoys were deployed on ice floes from Shirase on 2/12 and 2/14. 8 other buoys are deployed in the open waters between ice floes. When a large wave event happens, these buoys are positioned to detect swell propagation from the ice free ocean into the ice-covered ocean. By the meeting, a report on more wave events is expected, with a viewpoint of detecting a precursor to the sea-ice breakup.
Figure 1: Wave buoys deployed on ice during JARE64. The yellow dots mark the wave buoys on land-fast ice, the red dots mark the ones deployed on the drift ice zone, and the blue dots marks the ones deployed from Shirase (including the ones on ice and in open water).
Syowa Station is protected from the incoming swells of the screaming 60s by a vast land-fast ice, packed ice zone in the north, and the Marginal Ice Zone (MIZ). Waves that propagate under sea ice are considered to be one of the causes of a large breakup of the land-fast ice. The sea ice in the Lützow-Holm Bay grows not only because of the freezing of the sea water, but because of the icing of the snow at the surface as the sea water intrudes into the snow. The material strength of such sea ice is considered to be weak and subject to breakup as it oscillates due to the incoming waves. The cycle of sea-ice breakup and growth has been around 10 years and interestingly enough, the number of ramming maneuver of the ship synchronously changes. The knowledge of the long-term cycle of sea-ice breakup is critical for the long-term planning of Shirase operation.
The aim of our observational campaign during JARE64 is to monitor the incoming waves through the MIZ, packed ice zone (PIZ), and the land-fast ice zone, and to monitor the horizontal movement of the sea ice. Eventually, the land-fast ice may breakup and drift away from the Lützow-Holm Bay. 15 wave buoys were deployed on the land-fast ice, 8 wave buoys on the drifting ice floes, and 10 wave buoys in the water covered by blush ice between ice floes. The deployment was conducted by a helicopter and by a ship operation. A wide areal coverage of the buoys was possible only with the use of a helicopter. We have also landed on the land-fast ice of the 13 buoy locations and measured the ice thickness.
We present here, preliminary results of our observations, first regarding the horizontal movement of the land-fast ice, and second a signature of wave propagation in ice. Results are summarized in Figure 1.
During the deployments of the 15 buoys on 12/26 2022, we observed a zonal crack that divided the multi-year ice (over 3.5 m) and the first year ice in the north whose thickness gradually decreased from 2 m to 1 m towards the north. The multi-year ice survived the large sea ice loss in April 2022, and the first year ice gradually developed in the north. The crack that divides the multi-year and the first year ice likely formed in the austral summer in 2022. We have visited those buoys on 1/3 and 2/7 to measure the ice thickness. On 2/7, we observed new zonal cracks that formed after our first visit. In a month, the buoys in the south of the crack moved around 20 m horizontally while the others, particularly the ones close to the ice-berg trains in the northeast, remained stationary. Likely, the ice moved after the formation of the new ice cracks due to strong wind events. The wind affects the coastal area as well. After the strong gust event on 1/23, a large open water was created along the continental coast from the east of the Ongul Islands to the Lang Hovde glacier detaching the multi-year land-fast ice from the land.
A wave propagation through MIZ and PIZ, reaching the land-fast ice zone was observed in 2/6 and 7. Typically, when a depression passes by the north of the Lützow-Holm Bay, a strong North Easterly wind develops and a swell propagates into the bay. To monitor waves propagating in the PIZ, 6 wave buoys were deployed by the helicopter on ice floes on 2/11. Two wave buoys were deployed on ice floes from Shirase on 2/12 and 2/14. 8 other buoys are deployed in the open waters between ice floes. When a large wave event happens, these buoys are positioned to detect swell propagation from the ice free ocean into the ice-covered ocean. By the meeting, a report on more wave events is expected, with a viewpoint of detecting a precursor to the sea-ice breakup.
Figure 1: Wave buoys deployed on ice during JARE64. The yellow dots mark the wave buoys on land-fast ice, the red dots mark the ones deployed on the drift ice zone, and the blue dots marks the ones deployed from Shirase (including the ones on ice and in open water).