Son assistant prof is now on board the German research vessel Polarstern, conducting research. Updates from the cruise will be posted weekly!

 

 

 PS149 “CONTRAST” Completes Sea-Ice Observations（Updated: 8/29）

“Using the icebreaker Polarstern, the Alfred Wegener Institute’s PS149 “CONTRAST” expedition concluded all sea-ice observations on 27 August 2025. To mark the milestone, the team held a small celebration on the ice. The ocean team wrapped up its program at 16:30 the same day with a final fishing-rod CTD cast. Over roughly 40 days, Specially Appointed Assistant Professor EunYae Son (Uehiro Oceanography) collected under-ice turbulent heat-flux measurements along with ocean current, salinity, and temperature data. The dataset will be carefully analyzed after returning to Japan to advance discussions on ocean-to-multiyear-sea-ice heat transfer in the Greenland region during summer. ”

Completion of oceanographic observations, with the Uehiro Laboratory for Oceanography banner.

　

Rescue on the Ice: Polarstern Seizes Weather Break to Recover Lost Instruments（Updated: 8/22）

“An unusual shift in sea-ice drift created a narrow recovery window for scientific instruments deployed at “Station 1” in the central Arctic. Beginning on August 18, a northward-moving Arctic low altered the prevailing eastward drift to a westward flow that persisted for the past two to three days. As a result, equipment initially expected to be carried deeper into the Russian Exclusive Economic Zone (EEZ) instead moved toward—and eventually into—the Norwegian EEZ, improving the prospects for retrieval. Responding to the opportunity, the icebreaker Polarstern altered course to the east to intercept the drifting payloads. Each unit had been mounted on flotation and paired with a GPS tracker, allowing teams to navigate through the floes and close in on the sites. Although several GPS transmitters temporarily went silent during the operation, all instruments were ultimately located and recovered safely. The recovery combined precise drift forecasting with hands-on deck work using a hydraulic deck crane and basket, enabling researchers to reach equipment embedded among moving floes. The operation secured high-value assets—including a camera buoy—and preserved continuous records from the recent observation period. ”

※You can view the current location of the Polarstern on the website of the Alfred Wegener Institute (AWI) in Germany.

https://follow-polarstern.awi.de/?lang=en

A researcher rides the basket—nicknamed the “Mummy Chair”—on a hydraulic deck crane to retrieve a camera buoy from the sea ice.

 

New Observations on Seasonal Sea Ice near the Russian EEZ during Arctic Expedition （Updated: 8/15）

“As the first observation ice floe, a seasonal ice floe named Ice Floe 1, drifted into the interior of the Russian Exclusive Economic Zone (EEZ), a new observational site was established on another seasonal ice floe located near the Russian EEZ boundary. Unfortunately, the instruments deployed during the initial visit to Ice Floe 1 are expected to be difficult to recover unless the floe drifts out of the EEZ. At the new seasonal ice site, Team Ocean conducted routine operations, including MSS (Microstructure Sonde, Sea & Sun), CTD (SBE911+, Sea-Bird Electronics), and water sampling. In addition, surface observations of temperature, salinity, and currents were carried out using Otter, an underwater vehicle operated by the Alfred Wegener Institute for near-surface surveys.”

　Underwater vehicle, Otter, that measures temperature and velocity

 

Completion of the Second Sea Ice Observation Cycle and Progress on Equipment Retrieval （Updated: 8/8）

“Team ocean has completed the retrieval of data and redeployment of instruments installed during the first visit. At each station, observations were carried out using the ocean turbulence measurement instrument MSS (MicroStructure Sonde, Sea and Sun) and the fishing-rod CTD (Sea and Sun). Currently, the sea ice has entered the melt phase, with a thickness reduction of approximately 10–50 cm compared to the first visit.
In particular, the first station, consisting of first-year ice, showed the highest melt rate.
Footage from cameras installed for real-time sea ice monitoring confirmed that most of the ice at Station 1 has melted. At present, Polarstern is sailing toward the position of the GPS buoy deployed alongside other instruments, with the aim of recovering equipment from the first station.”

 

Sea Ice Observation during the Arctic Expedition — Airborne Surveys Using EM-Bird （Updated: 8/4)）

“During this expedition, sea ice observations were conducted not only through helicopter-based Sea Ice Surveys but also by utilizing aircraft dispatched from the Arctic research camp “Station Nord,” located in Greenland. The EM-Bird used in these surveys is an instrument that continuously measures sea ice thickness based on the principle of electromagnetic induction (EM). Typically, the EM-Bird is suspended on a cable approximately 10–20 meters long beneath a helicopter and flown over the survey area. The device is equipped with a transmitter coil and a receiver coil, which enable the indirect measurement of ice thickness by exploiting the differences in electrical conductivity between sea ice and seawater. This method allows for efficient and highly accurate mapping of sea ice thickness over a wide area.” 

 

Initial Observations of Sea Ice with Varying Properties Completed （Updated: 7/25）

“The first observation at Station 3 has been completed. With this, the first round of observations for sea ice with different physical properties has been finalized. Team Ocean deployed equipment such as the eddy covariance system, acoustic Doppler current profiler, and mini moorings at the ice-ocean interface at Station 3. The data from these instruments will be retrieved during the second visit, after which the instruments will be redeployed at the same location for continued sampling until the third visit.”

  　　　　　　　　　Apparatus deployed at Station 3

　　

Second Multiyear Ice Station: Instrument Deployment and Initial Observations （Updated: 7/17）

“Observation at the second sea ice station has begun. Unlike the first station, the second one is located on multiyear sea ice, which is estimated to be more than three years old. The ocean team of the CONTRAST expedition deployed four mini mooring systems and turbulence observation instruments—Acoustic Doppler Current Profilers (Signature1000, Nortek)—on the ice. Each mooring is equipped with four temperature sensors (RBR Solo, RBR Global) and one conductivity-temperature-depth (CTD) sensor (MicroCAT, Sea-Bird Scientific). In addition, an iAOOS system (photo), an autonomous CTD profiler with an 800-meter-long observational wire, was installed.”

 

The First Ice Camp of Station1 Begins Amidst a Polar Bear Encounter （Updated: 7/14）

“The first ice camp of Station1 commenced on seasonal sea ice at 83.45°N, 20.53°E, near Svalbard. On the morning of the first day, a polar bear appeared on the ice where the research vessel Polarstern was anchored. Due to safety concerns, morning observations were canceled. However, operations resumed in the afternoon under careful monitoring. Dr. Son, a member of Uehiro laboratory of oceanography, was able to safely install the equipment later that day.”

 

Son project asst prof departs for sea ice research around Greenland （Updated: 7/4）

“On July 2nd, the German research vessel Polarstern, operated by the Alfred Wegener Institute, finally set sail from a fjord near Tromsø, Norway. Carrying 49 researchers, the vessel is heading to the Arctic to establish ice camps on three different types of sea ice, each representing a different age, near Greenland. Among the researchers on board are three scientists from the Graduate School of Fisheries Sciences at Hokkaido University, including Eun Yae Son from the Uehiro Laboratory for Oceanography.”