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dominated by strong seasonality in sea ice and water temperatures. Extremely warm conditions from 2017 into 2019 -including loss of ice cover across portions of the region in all three winters -were a marked change even from other recent warm years. Biological indicators suggest th is state change could alter ecosystem structure and function. Here we report observations of ke y physical drivers, biological responses, and consequences for humans, including subsisten ce hunting, commercial fishing, and industrial shipping. We consider whether observed state changes are indicative of future norms, whether an ecosystem transformation is alread y underway, and if so, whether shifts are synchronously functional and system-wide, or reveal a slower cascade of changes from the physical environment through the food web to huma n society. Understanding of this observed process of ecosystem reorganization may shed light on transformations occurring elsewhere.The highly productive northern Bering and Chukchi marine shelf ecosystem has long been

An array of autonomous hydrophones moored in the eastern tropical Pacific was monitored for one year to examine the occurrence of whale calls in this region. Six hydrophones which recorded from 0-40 Hz were placed at 8 degrees N, 0 degree, and 8 degrees S along longitudes 95 degrees W and 110 degrees W. Seven types of sounds believed to be produced by large whales were detected. These sound types were categorized as either moan-type (4) or pulse-type (3) calls. Three of the moan-type calls, and probably the fourth, may be attributed to blue whales. The source(s) of the remaining calls is unknown. All of the call types studied showed seasonal and geographical variation. There appeared to be segregation between northern and southern hemispheres, such that call types were recorded primarily on the northern hydrophones in the northern winter and others recorded primarily on the southern hemisphere hydrophones in the southern winter. More calls and more call types were recorded on the eastern hydrophones than on the western hydrophones.