Research Highlights
Placement of Sea-ice drifting buoys in the Bering Sea in February 2007
Linkages between freshwater discharges, sea-ice conditions and primary productivity and climate changes in the sub arctic marginal seas and Arctic Ocean
Snow Cover and Sea Ice Group
Prof. Hiroyuki Enomoto, Kitami Institute of Technology
[May 25, 2007]
We carried the buoys from Bethel to the Emmonak, a village at the estuary of Yukon River. The Bering Sea was freezing over.
Increase of river inflow into Arctic Sea is reported in recent years. River inflow prompts the growth of sea-ice by supplying freshwater and reducing salinity concentration. Meanwhile, heat of river water suppresses growth of sea-ice. The relationship between rivers and sea-ice growth has not been fully described because of these opposite influence of river inflow.
On the other hand, materials from land transferred by rivers are important factors affecting the arctic marine ecosystem. Flux and material transportation of a river are related to the fluctuation of precipitation on land in the short term, and also related to the melting of glacier and permafrost in the long term. The complicated linkage between these phenomena has an effect on the marine ecosystem.
In February 2007, we placed drifting buoys on the fast sea-ice in 20km offing of the estuary of the Yukon River. The purpose of this project is to study the variability and relationship of great rivers, sea-ice, and marine ecosystem.
The points of buoys and water sampling near the estuary of the Yukon River.
MODIS image in winter and the observation site (red rectangle).
(Date: March 04, 2007, Courtesy of Geophysical Inst., Univ. of Alaska.)
The drifting buoy for observation of sea-ice. The location of the buoy is measured by GPS and the data are sent via global communication satellites.
Placement of a buoy on the frozen Bering Sea.
Preparation for the placement
Observation on an ice-covered sea area is generally difficult and we didn’t know how to approach the estuary of the Yukon in winter season. But fortunately, Alaskan people kindly supported us and we could settle the buoys.
Staff of Yukon Delta NWR (National Wildlife Refuge) of USFW (U.S. Fish and Wildlife Service) in Bethel, a city in the Western Alaska near the Bearing Sea, provided information on how to access the Yukon River in winter and on the transportation by air. They also provided a stepping point of the air transport and arranged accommodation in Bethel and a place to set up the observation equipment.
We departed Bethel by a small plane to Emmonak, a village 20km inland from the estuary of the Yukon River.
After going down on the frozen Yukon River by snowmobile from Emmonak to the estuary, we went farther 20km offshore on the fast ice and found thin, young sea ice. We placed the first buoy there, and moving 20km northward, we put two more buoys separately to build up the observation grid.
The buoys detect the time of melt and fragmentation of fast ice, and collect data of the motion of sea-ice, i.e., convergence, divergence, rotation, and deformation. We will compare the information with satellite data by MODIS and AMSR-E.
State-of-the-art technology and human experience
In this project, the locations of drifting buoys are sent via global communication satellites of ORBCOMM Inc. State-of-the-art technology of satellite data and analytical method helps us to investigate the nature of sea-ice.
This time we reaffirmed that local people’s interest and understanding in the project was necessary to execute the observation. When we arrived at Emmonak, we went straight to the representative of the village to explain the plan. We joined a community meeting to obtain understanding and cooperation from the people. We also visited schools to introduce our project to teachers and students.
People in the village have large interest in the change of sea-ice and asked us what happened around the village. They are also very familiar with IPY (International Polar Year). They hope that they contribute to the observation of global change and the results will be announced worldwide.
Without their experienced help, we could not have placed the buoys, running around 100km on the frozen Bering Sea by snowmobile all the day. A local fisherman guiding us usually uses satellite images via Internet, checking sea-ice condition, such as cracks and overhead flooding and comparing his experience with them. He also told us his observation of the recent change of sea-ice.
Even after setting drifting buoys, people in Bethel and Emmonak are sending us continuous information about the movement of the buoys, changes of sea-ice, channels, and water color around the estuary. In the end of April 2007, water around the Yukon delta turns brown. Snowmelt appears to spread around the coastal area.
We hope that successful observation will provide the useful results from the buoys and satellite observations to the people at the Yukon River.
"Linkages between freshwater discharges, sea-ice conditions and primary productivity and climate changes in the sub arctic marginal seas and Arctic Ocean" is continuing in 2007. (PI: Sei-ichi Saitoh)
