Experts describe a Pacific‑Arctic regime shift: less ice, more open water and altered circulation reshaping gray whale habitat

Kate Stafford summarized physical and biological changes in the Pacific Arctic (Bering and Chukchi Seas), telling the Marine Mammal Commission that the region has lost multi‑year ice and now more commonly experiences annual ice with earlier retreat and thinner coverage. She said the Chukchi Sea is shallow (≈50 m on average) and that the Alaska coastal current has strengthened, bringing warmer, fresher, nutrient‑poor water onto shelves.

"There is no more multi‑year ice," Stafford said, stressing rapid change in seasonal ice conditions and the consequences for communities and marine mammals. She cited maps and time series showing sea‑ice extent declines and a reported >50% reduction in sea‑ice surface area metrics compared with late‑twentieth‑century baselines. Stafford and colleagues pointed to increased inflow through Bering Strait (presented as +50% in the talk) and to elevated bottom‑water temperatures that can thin ice from below.

Biologically, Stafford described evidence for a regional regime shift (circa 2017–2019) that includes higher spring and summer chlorophyll, increases in pelagic productivity, and a potential movement from benthic‑dominated to more pelagic food webs. That change, she said, creates the possibility of larger zooplankton and forage fish increasing in some areas even as benthic amphipod prey used by gray whales declines in historic hot spots. "We are potentially going to be bringing new zooplankton, bigger zooplankton, potentially more forage fish," she said, while cautioning that extreme seasonality and nutrient fluxes that historically supported benthic productivity remain important.

Why it matters: the spatial reconfiguration of productivity and prey types affects where and how gray whales can feed and has knock‑on effects for subsistence communities, shipping, and other marine uses. Stafford emphasized the need for continued coordinated observations across the DBO lines and closer involvement with coastal communities to track rapid changes.