—by Jiaxu Zhang, UW CICOES & NOAA PMEL

Arrival in Kotzebue

We arrived in Kotzebue, Alaska, on May 15, 2025, after a smooth transit flight from Anchorage. The Twin Otter was packed with instruments and, by late afternoon, we were already in the air again, performing calibration and collecting the first sample data over Kobuk Lake.

The next day, under calm skies, we carried out our first full mapping survey—flying low at 500 feet for the LATIS LIDAR and later climbing to 7,000 feet for the Pika-L hyperspectral camera. From above, the lake appeared frozen and bright, but subtle cracks and dark patches hinted that breakup would begin soon.

Watching the instruments record the data felt like seeing spring arrive in real time.

We came to Kotzebue to study how the lake ice evolves each year and how the timing of spring breakup affects the community. A rural Alaska Native village tucked against the Chukchi Sea on Alaska’s west coast, Kotzebue has few roads leading away from it. It has no connections to the state’s highways; residents instead rely on off-road transportation: ATVs in the summer and, in the winter, snowmobiles. When Kobuk Lake is frozen over, residents use snowmobiles to traverse it to reach subsistence fishing camps. But in recent years, as breakup has become increasingly unpredictable, residents have had a tougher go of it getting to those camps.

Combining measurements with observations

Our goal was to combine airborne measurements with observations from local community members to better understand and model these changes.

Flying low over the beautiful white landscape was humbling. From above, the ice looked smooth, but the LIDAR revealed subtle ridges and pressure lines invisible to the eye. In some places, the surface darkened where river water flowed under the ice—a process nicknamed the “tea-bag effect,” when tannin-rich meltwater from tundra and wetlands spreads across the surface like brown ink. These areas absorb more sunlight, accelerating melt and signaling where the first open water will form.

Not every day allowed flying. Fog and low clouds often grounded us for hours, sometimes for days. During those times, we checked instruments, reviewed flight tracks, visited the radio station, and shared updates with the environmental office. I liked those small moments: explaining our work, hearing stories, and feeling part of the community.

One moment that has stayed with me came through our local collaborator, Alex Whiting, who was in regular contact with Kotzebue Elder Bobby Schaeffer. After one flight, we showed Alex our aerial map of a long ice ridge crossing the lake. He later told us that Bobby had recognized it immediately—it’s a feature he has seen every spring since childhood, marking a weak point in the ice that usually opens first. Hearing about that connection gave new meaning to our data. It reminded me that every line on a map represents a place people know personally.

When the flights ended, we had mapped Kobuk Lake four times, deployed four buoys over the open ocean farther south, and collected hours of hyperspectral imagery. But what stayed with me most was not just the data, it was also the teamwork, the patience in the cold, and the generosity of people in Kotzebue who shared their knowledge and hospitality.

As we took off for the last time, the lake below looked different: the cracks wider, the snow thinner, a darker color spreading from the inlet. The Arctic summer was coming.