In a 2026 study published in Communications Earth & Environment, scientists have analyzed marine sediment cores (NPAL04, BASICC 1, and BASICC 43) from the northern Barents Sea to reconstruct historical sea-ice conditions and marine productivity.

Using highly branched isoprenoid (HBI) diatom biomarkers—specifically HBI III and HBI IV as well as EZ₂₅ sea surface temperature (SST) proxy—the researchers mapped ocean temperatures across recent centuries.

As illustrated in the study’s multi-core comparison, the EZ₂₅ SST records (shown in yellow) indicate that sea surface temperatures in the Barents Sea were warmer during the 1700s than they were in the 2000s.

Alongside these temperature trends, the researchers examined historical sea-ice coverage using spring sea ice (SpSIC) reconstructions and the sea-ice biomarker IP₂₅ (shown in blue). These proxy records demonstrate that reduced sea-ice conditions are not exclusive to the modern era.

Across the Barents Sea cores, spring sea-ice presence was just as low—or even lower—than 2000s levels during several distinct historical intervals, including the 1700s, the 1800s, and the mid-twentieth century from the 1930s to the 1950s.

Image Source: Pieńkowski et al., 2026