Record low 2022 Antarctic sea ice led to catastrophic breeding failure of emperor penguins

Abrupt reductions in Antarctic sea ice extent can have profound effects on ecosystems and species that depend on sea ice for reproduction and foraging. Emperor penguins (Aptenodytes forsteri) rely on stable land-fast sea ice for breeding and moulting and on the marginal ice zone for foraging. They arrive at breeding sites in late April, lay eggs from May to June, hatch after ~65 days, and chicks fledge in December–January; therefore, stable land-fast ice from April through January is essential for breeding success. The study addresses whether the record-low Antarctic sea ice of 2022 caused regional-scale breeding failure in emperor penguins, assessing the extent, timing, and ecological consequences of sea ice loss on breeding outcomes in the central and eastern Bellingshausen Sea.

Previous research has linked emperor penguin demography and breeding success to sea ice variability and loss driven by climate change, including site abandonment following long-term sea ice decline or regime shifts. Projections indicate that if current warming rates persist, many colonies could become quasi-extinct by the end of the century. Unlike many species, emperor penguins have not faced large-scale hunting or significant habitat loss, overfishing, or other local anthropogenic impacts in the modern era; climate change is considered the primary driver of long-term population change. While conservation efforts have advanced, measures have not adequately protected critical breeding habitat necessary for chick survival.

The presence and status of emperor penguin colonies were monitored primarily using ESA Copernicus Sentinel-2 imagery (2015–present) accessed via the Copernicus Open Access Hub and Sentinel Hub browser. Imagery from August through December each year was examined to provide continuous seasonal coverage. Colonies were detected visually using the presence of brown guano staining pixels arranged in colony formations; brown staining may persist briefly after abandonment until snowfall. Custom visualization emphasized bands B08+B04+B03+B02. Very High-Resolution (VHR) MAXAR WorldView-3 imagery (0.31 m) supplemented Sentinel-2 to confirm colony presence/absence, enable rough counts, and validate abandonment events at specific sites (e.g., Pfrogner Point, Rothschild Island). Additional counts were obtained from helicopter-based aerial imagery (Commandant Charcot) at Rothschild Island. Historical satellite records (Sentinel, Landsat, VHR) were used to contextualize 2018–2022 colony presence and typical sea ice timing. Sea ice extent and anomaly context referenced NSIDC and ERA5/ECMWF products. Colony fate was inferred from the timing of sea ice break-up relative to the fledging period and the disappearance of guano staining and birds in imagery.

- Antarctic sea ice extent during October–January 2022–2023 was at or below the lowest values in the 45-year satellite record, with a pronounced negative anomaly in the central and eastern Bellingshausen Sea; some areas experienced up to 100% loss of sea ice concentration in November 2022. - In this region, four of five emperor penguin colonies experienced early sea ice loss; three colonies visible in late Oct/early Nov were abandoned by early December as fast ice broke up before fledging. - Site-specific outcomes: • Verdi Inlet: Fast ice broke up between Oct 31–Nov 4, 2022; by early December no guano staining remained, indicating abandonment (prior estimate ~3000 pairs in 2021). • Smyley Island: Fast ice broke up mid-November; penguins split into two groups and some moved onto a grounded iceberg; survival of chicks on the berg is unknown. • Bryant Coast: Colony present mid-November; fast ice broke into pack by Nov 29; guano staining disappeared by Dec 2, indicating abandonment. • Pfrogner Point: Small guano staining visible in October; disappeared by Nov 8 and did not return; VHR imagery on Nov 26 confirmed abandonment; all sea ice dissipated by Dec 12. Access issues related to a ~4.5 m ice cliff and loss of a snow ramp may have contributed. • Rothschild Island: The only site with successful fledging in 2022; helicopter imagery on Nov 20 counted 820 chicks and 228 adults; fast ice persisted to Dec 17 and began breaking up Dec 30, allowing fledging; local bay geometry and icebergs likely stabilized ice. - This represents the first documented widespread regional breeding failure of emperor penguins clearly linked to large-scale contractions in sea ice extent.

The 2022 regional-scale sea ice collapse in the Bellingshausen Sea caused widespread emperor penguin breeding failures because fast ice broke up before chicks developed waterproof plumage and fledged. While colonies can sometimes relocate after local failures (e.g., Halley Bay to Dawson-Lambton in the Weddell Sea), such behavioral buffering is ineffective when habitat unsuitability occurs across a region, unless localized refugia like Rothschild Island persist. The findings demonstrate a clear linkage between negative sea ice anomalies and breeding failure and may foreshadow conditions under continued warming, where such events become more frequent and widespread, threatening population viability. Although attributing a single extreme season to anthropogenic forcing is challenging, the recent clustering of record-low Antarctic sea ice years (including 2021/22 and 2022/23) aligns with expectations from climate models of long-term decline. Regional atmospheric drivers, including the recent Triple-Dip La Niña and strongly negative Southern Annular Mode associated with deep Amundsen Sea low pressure, likely contributed to the 2022 anomaly. Understanding future land-fast sea ice dynamics and regional variability is critical for predicting emperor penguin outcomes and informing conservation planning.

Using Sentinel-2 and VHR satellite observations, the study documents a regional, largely catastrophic breeding failure of emperor penguins in the central and eastern Bellingshausen Sea in 2022, with four of five colonies losing breeding habitat before fledging; only Rothschild Island showed successful fledging due to locally stable fast ice. These results provide the first clear, region-wide linkage between large negative sea ice anomalies and emperor penguin breeding failure, offering a snapshot of potential futures under continued warming. Future work should refine predictions of land-fast sea ice responses to climate variability and change, assess the persistence and characteristics of local refugia, and integrate enhanced monitoring (satellite and aerial) to inform protection of critical breeding habitats.

- Satellite resolution (Sentinel-2) is insufficient to distinguish chicks from adults; thus, the proportion of chicks potentially surviving on grounded icebergs or small remnant ice cannot be quantified. - Guano staining may persist for days after abandonment until snowfall, introducing uncertainty in precise abandonment timing. - The exact cause of abandonment at Pfrogner Point is uncertain; access issues (ice cliff/snow ramp loss) are inferred from imagery rather than direct observation. - While the study links breeding failure to sea ice anomalies, attributing the 2022 extreme season directly to anthropogenic climate change remains uncertain. - Temporal sampling limits (cloud cover, revisit rates) may miss short-term behavioral or ice dynamics events.