Arctic had the hottest summer on record in 2023 – 12/12/2023 – Environment

The Arctic had the hottest summer (which occurs between July and August in the Northern Hemisphere) on record in 2023, with an average temperature of 6.4°C. The index was half a degree above the previous record, set in 2016, according to the Arctic Report, from the United States Oceanic and Atmospheric Agency (Noaa, its acronym in English), released this Tuesday (12).

Coming at the end of the hottest year on record, the 18th edition of the annual report shows a continuation — and, in some cases, an acceleration — of trends that are reshaping the polar region as the planet warms due to climate change driven by climate change. man. These trends include less sea ice, more rain and warmer sea surface temperatures.

“By no means is this normal,” said Paul Overduin, a geoscientist at the Alfred Wegener Helmholtz Institute for Polar and Marine Research in Germany who contributed to the report.

“It’s not just summer itself that’s changing. Spring is coming earlier, fall is coming later, so summer is kind of taking over, and the Arctic is losing its winter at some point in the future. And The question is: what will it do and what will it look like?”

Already the loss of near-surface ice in permafrost (permanently frozen ground) is triggering landslides and sinkholes that are dumping material into Arctic rivers, lakes and seas.

“There are places where you look at the landscape — the Canadian Arctic Archipelago, for example, or also in western Siberia — where it looks like the surface of the Earth has a disease,” Overduin said. “The whole landscape is in motion. That’s just in the last five years.”

NOAA tracks eight different “vital signs” for Arctic health in the report. Among this year’s main discoveries are:

In addition to the hottest summer on record, the Arctic had the sixth warmest year since the time series began in 1900, with an average surface air temperature of -6.9°C, 0.7°C warmer than the 1991-2020 average.

Since 1940, average annual temperatures have increased by 0.25°C per decade. Higher temperatures on land could warm large rivers that flow into Arctic seas, raising these surface temperatures and melting sea ice.

Sea ice coverage continues to decrease — which means the planet’s reflective shield is also decreasing. This year’s sea ice extent was the sixth lowest since satellite records began in 1979. The 17 lowest sea ice extents in the Arctic have occurred in the last 17 years.

Arctic sea surface temperatures in August were 5°C to 7°C warmer than the 1991-2020 average values ​​in the Barents, Kara, Laptev and Beaufort Seas, while unusually cold temperatures were observed in the Bay of Baffin, the Greenland Sea and parts of the Chukotka Sea.

The Arctic is getting greener. The tundra green cover rate was the third highest in 24 years of satellite records. As sea ice melts earlier in the spring, the warmer exposed water creates a more moderate maritime climate in coastal areas. This leads to the growth of more biomass — including shrubs and small trees — on land that was mostly covered in lichen.

This has secondary effects that are not yet fully understood, said Uma Bhatt, a professor of atmospheric sciences at the University of Alaska Fairbanks who contributed to the report. This could affect the food chain and indigenous communities that depend on animals like caribou, which feed on lichen.

Much of the Arctic is seeing a rise in seaweed, with the largest phytoplankton blooms occurring in the Eurasian Arctic and Barents Sea, linked to warmer temperatures. Harmful algal blooms are an emerging threat to human and ecosystem health, the report states.

Snow cover in North America reached a negative record in May, but overall snow accumulation was above average across the continent and Eurasia during the winter of 2022-2023. Snow could help mitigate mass loss from the Greenland ice sheet.

Despite this above-average snow accumulation, the Greenland ice sheet continued to lose mass. The highest point on the ice sheet recorded a temperature above freezing on June 26 — only the fifth time in 34 years of records that this has happened. If this layer were to melt completely, scientists estimate that global sea levels would rise by about 7.4 meters.

The Arctic continues to get wetter, with pan-Arctic precipitation expected to be the sixth highest on record in 2023. But northern Canada has had an unusually dry summer, contributing to record wildfire conditions already worsened by the long-term warming trend . By the end of October, 4.61 million hectares of forest had burned in high-latitude North America, releasing devastating levels of greenhouse gases.

Anomalies within long-term warming trends, such as the cold sea temperatures observed in some locations, are the inevitable result of the interaction and rapid change of complex systems.

While these anomalies can have serious local consequences, from freak storms to swings in fish populations, the report notes that the prevailing trend of a warming Arctic is contributing to “high-impact” events like this summer’s record-breaking wildfires in Canada. , through cascading environmental effects.

The report also highlights the role of indigenous communities in mitigating the harmful impacts of climate change, as well as areas where further research is urgently needed.

Among them is underwater permafrost: permafrost that began on land but was covered by rising sea levels about 18,000 years ago. Some scientists believe it may play a significant role in carbon sequestration, due both to the amount of methane frozen in it and its role as a barrier that prevents the release of greenhouse gases from beneath the seafloor, but there are many unanswered questions. response.

By highlighting these unknowns, the report also emphasizes irrefutable facts.

“[O Ártico] It’s getting warmer, it’s getting wetter, sea ice is getting smaller,” Bhatt said. “We’re seeing the consequences of human impact on all of our vital variables.”