Cosmic dust reveals dynamic shifts in central Arctic sea-ice coverage over the past 30,000 years.

Arctic sea-ice loss affects biological productivity, sustenance in coastal communities, and geopolitics. Forecasting these impacts requires mechanistic understanding of how Arctic sea ice responds to climate change, but this is limited by scarce long-term records. We present continuous 30,000-year reconstructions of sea-ice coverage from the Arctic Ocean based on measurements of two isotopes, thorium-230 and extraterrestrial helium-3, whose burial ratio changes with sea-ice coverage. We found that the central Arctic was perennially covered by sea ice during the last glaciation. Sea-ice cover retreated during the deglaciation approximately 15,000 years ago, culminating in seasonal sea-ice coverage in the warm early Holocene, before ice coverage increased into the late Holocene. Sea-ice changes closely correlate with biological nutrient consumption, supporting projections of a nutrient-starved central Arctic Ocean with continued sea-ice loss. Editor's summary: Sea ice coverage in the Arctic has been declining rapidly over the past several decades because of the influence of anthropogenic warming, which is occurring faster in the Arctic region than in any other on the globe. Pavia et al. used helium-3 and thorium-230 isotopes to reconstruct the history of sea ice coverage of the central Arctic over the past 30,000 years. They concluded that this region was perennially covered during the last glaciation, had decreased coverage during the deglaciation, and became seasonally covered in the warmer-than-present early Holocene. An observed correlation with biological nutrient consumption has implications for the productivity of the region as climate warming progresses. —Jesse Smith [ABSTRACT FROM AUTHOR]