Lack of Antarctic sea ice causes catastrophic breeding failure for emperor penguins
Emperor penguin colonies skilled unprecedented breeding failure in a area of Antarctica the place there was complete sea ice loss in 2022. The invention helps predictions that over 90% of emperor penguin colonies can be quasi-extinct by the top of the century, primarily based on present world warming traits.
In a brand new examine revealed at this time in Communications Earth & Atmosphere, researchers from British Antarctic Survey mentioned the excessive chance that no chicks had survived from 4 of the 5 identified emperor penguin colonies within the central and japanese Bellingshausen Sea. The scientists examined satellite tv for pc pictures that confirmed the lack of sea ice at breeding websites, properly earlier than chicks would have developed waterproof feathers.
Emperor penguins are depending on steady sea ice that’s firmly hooked up to the shore (‘land-fast’ ice) for almost all of the 12 months, from April via to January. As soon as they arrive at their chosen breeding website, penguins lay eggs in Antarctic winter from Might to June. Eggs hatch after 65 days, however chicks don’t fledge till summer time, between December and January.
At the start of December 2022, the Antarctic sea ice extent had matched the earlier all-time low set in 2021. Probably the most excessive loss was seen within the central and japanese Bellingshausen Sea area, west of the Antarctic Peninsula the place there was a 100% lack of sea ice in November 2022.
Lead creator of the examine, Dr Peter Fretwell, stated:
“We have now by no means seen emperor penguins fail to breed, at this scale, in a single season. The lack of sea ice on this area throughout the Antarctic summer time made it not possible that displaced chicks would survive.
We all know that emperor penguins are extremely weak in a warming local weather — and present scientific proof means that excessive sea ice loss occasions like this can develop into extra frequent and widespread.
Since 2016, Antarctica has seen the 4 years with the bottom sea ice extents within the 45-year satellite tv for pc report, with the 2 lowest years in 2021/22 and 2022/23. Between 2018 and 2022, 30% of the 62 identified emperor penguin colonies in Antarctica have been affected by partial or complete sea ice loss. Though it’s tough to instantly hyperlink particular excessive seasons to local weather change, a longer-term decline in sea ice extent is anticipated from the present era of local weather fashions.
Understanding emperor penguin colonies
Emperor penguins have beforehand responded to incidents of sea ice loss by transferring to extra steady websites the next 12 months. Nevertheless, scientists say that this technique will not work if sea ice habitat throughout a complete area is affected.
Emperor penguin populations have by no means been topic to massive scale searching, habitat loss, overfishing or different native anthropogenic interactions within the fashionable period. Unusually for a vertebrate species, local weather change is taken into account the one main issue influencing their long-term inhabitants change. Latest efforts to foretell emperor penguin inhabitants traits from forecasts of sea ice loss have painted a bleak image, exhibiting that if current charges of warming persist, over 90% of colonies can be quasi-extinct by the top of this century.
The 5 colonies of penguins studied have been all found within the final 14 years utilizing satellite tv for pc imagery — Rothschild Island, Verdi Inlet, Smyley Island, Bryan Peninsula and Pfrogner Level. All 5 colonies had been proven to return to the identical location every year to breed, with just one earlier occasion of breeding failure at Bryan Peninsula in 2010.
Scientists now routinely use satellite tv for pc imagery to find and monitor emperor penguin colonies, because the brown stains of the birds’ guano stands out clearly towards the stark white of ice and snow. The group used pictures from the European Fee’s Copernicus Sentinel-2 satellite tv for pc mission, which has constantly monitored the realm in Antarctica since 2018.
The affect of Antarctic sea ice loss
Over the previous seven years, sea ice round Antarctica has decreased considerably. By the top of December 2022, sea ice extent was the bottom skilled within the 45-year satellite tv for pc report. Within the Bellingshausen Sea, the house of the penguin colonies on this examine, sea ice did not begin to re-form till late April 2023.
Since then, the deviation from the norm has intensified: as of 20 August 2023 the ocean ice extent was 2.2 million km2 decrease than the 1981-2022 median (17.9 million km2) considerably surpassing the report winter low on 20 August 2022 of 17.1 million km2. This lacking space is bigger than the dimensions of Greenland, or round ten occasions the dimensions of the UK.
Dr Caroline Holmes, a polar local weather scientist at BAS, stated:
“Proper now, in August 2023, the ocean ice extent in Antarctica continues to be far beneath all earlier data for this time of 12 months. On this interval the place oceans are freezing up, we’re seeing areas which might be nonetheless, remarkably, largely ice-free.
12 months-to-year modifications in sea ice extent are linked to pure atmospheric patterns corresponding to El Niño-Southern Oscillation, the power of the southern hemisphere jet stream, and regional low-pressure techniques.
We’ll want years of focused observations and modelling to know exactly how a lot the present circumstances are being influenced by these phenomena and by pure ocean variability. Nevertheless, the latest years of tumbling sea ice data and warming of the subsurface Southern Ocean level strongly to human-induced world warming exacerbating these extremes.”
Local weather fashions present a decline in Antarctic sea ice each below current and forecast human carbon dioxide emissions.
Dr Jeremy Wilkinson, a sea ice physicist at BAS, commented:
“This paper dramatically reveals the connection between sea ice loss and ecosystem annihilation. Local weather change is melting sea ice at an alarming fee. It’s more likely to be absent from the Arctic within the 2030s — and within the Antarctic, the 4 lowest sea ice extents recorded have been since 2016.
It’s one other warning signal for humanity that we can’t proceed down this path, politicians should act to minimise the affect of local weather change. There isn’t a time left.”
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