Emperor penguins suffer unprecedented breeding failure amid Antarctic sea ice loss

Emperor penguin colonies suffered unprecedented breeding failure in areas of Antarctica where there was a total loss of sea ice last year.

Researchers from the British Antarctic Survey said there is a high probability that no chicks survived from four of the five known emperor penguin colonies in the central and eastern Bellingshausen Sea.

They studied satellite images showing that sea ice was lost at their breeding sites well before chicks would have been able to develop waterproof feathers.

The study supports dire predictions that more than 90 per cent of emperor penguin colonies will be quasi-extinct by the end of the century, based on current trends of global warming.

Dr Peter Fretwell, lead author of the study published in Communications Earth & Environment, said: “We have never seen emperor penguins fail to breed, at this scale, in a single season. The loss of sea ice in this region during the Antarctic summer made it very unlikely that displaced chicks would survive.

“We know that emperor penguins are highly vulnerable in a warming climate - and current scientific evidence suggests that extreme sea ice loss events like this will become more frequent and widespread."

Emperor penguins require stable sea ice firmly attached to the shore - known as ‘land-fast’ ice - from April to January.

After arriving at their chosen breeding site, they lay eggs in the Antarctic winter from May to June and the eggs hatch after 65 days. Chicks do not fledge, however, until the summer - between December and January.

At the start of December 2022, the Antarctic sea ice extent matched the all-time low set in 2021 and the central and eastern Bellingshausen Sea region saw the biggest loss. Lying west of the Antarctic Peninsula, this region witnessed 100 per cent loss of sea ice in November 2022 and it did not start to re-form until late April 2023.

Antarctica has recorded four years with the lowest sea ice extents in the 45-year satellite record since 2016 - with the two lowest years in 2021-22 and 2022-23.

Thirty per cent of the 62 known emperor penguin colonies in Antarctica were affected by partial or total sea ice loss between 2018 and 2022.

Climate models suggest a longer-term decline in sea ice extent.

While emperor penguins have been known to respond to sea ice loss by moving to more stable sites the following year, but this strategy will not work if the sea ice habitat across an entire region is affected.

Dr Caroline Holmes, a polar climate scientist at Madingley Road-based BAS, said: “Right now, in August 2023, the sea ice extent in Antarctica is still far below all previous records for this time of year. In this period where oceans are freezing up, we’re seeing areas that are still, remarkably, largely ice-free.

“Year-to-year changes in sea ice extent are linked to natural atmospheric patterns such as El Niño-Southern Oscillation, the strength of the southern hemisphere jet stream, and regional low-pressure systems.

“We’ll need years of targeted observations and modelling to know precisely how much the current conditions are being influenced by these phenomena and by natural ocean variability. However, the recent years of tumbling sea ice records and warming of the subsurface Southern Ocean point strongly to human-induced global warming exacerbating these extremes."

On August 20, 2023, the sea ice extent was 2.2 million square km lower than the median between 1981 and 2022. The missing area is larger than the size of Greenland, or around 10 times the size of the United Kingdom.

Unlike most vertebrate species in decline, climate change is considered the only major factor influencing the long-term population change in emperor penguins, which have never been subject to large-scale hunting, habitat loss, overfishing or other local anthropogenic interactions in the modern era.

Recent forecasts have suggested that if present rates of warming persist, more than 90 per cent of colonies will be quasi-extinct by the end of this century - meaning the population may be doomed to extinction.

The scientists studied five penguin colonies discovered in the last 14 years using satellite imagery - Rothschild Island, Verdi Inlet, Smyley Island, Bryan Peninsula and Pfrogner Point. They are known to return to the same location each year to breed and the only previous instance of breeding failure seen was at Bryan Peninsula in 2010.

Images from the European Commission’s Copernicus Sentinel-2 satellite mission, which has continuously monitored the area in Antarctica since 2018, were used by the team,

The brown stains of birds’ guano stands out clearly against the white ice and snow in satellite imagery.

Dr Jeremy Wilkinson, a sea ice physicist at BAS, said: “This paper dramatically reveals the connection between sea ice loss and ecosystem annihilation. Climate change is melting sea ice at an alarming rate.

“It is likely to be absent from the Arctic in the 2030s - and in the Antarctic, the four lowest sea ice extents recorded have been since 2016.

“It is another warning sign for humanity that we cannot continue down this path, politicians must act to minimise the impact of climate change. There is no time left.”