Climate change in Antarctica

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Antarctic Skin Temperature Trends between 1981 and 2007, based on thermal infrared observations made by a series of NOAA satellite sensors. Skin temperature trends do not necessarily reflect air temperature trends.

Climate change in Antarctica is resulting in rising temperatures and increasing snowmelt and ice loss.[1] A summary study in 2018 incorporating calculations and data from many other studies estimated that total ice loss in Antarctica due to climate change was 43 gigatons per year on average during the period from 1992 to 2002 but has accelerated to an average of 220 gigatons per year during the five years from 2012 to 2017.[2]

Some of Antarctica has been warming up; particularly strong warming has been noted on the Antarctic Peninsula. A study by Eric Steig published in 2009 noted for the first time that the continent-wide average surface temperature trend of Antarctica was slightly positive from 1957 to 2006.[3] Over the second half of the 20th century, the Antarctic Peninsula was the fastest-warming place on Earth, closely followed by West Antarctica, but these trends weakened in the early 21st-century.[4] Conversely, the South Pole in East Antarctica barely warmed last century, but in the last three decades the temperature increase there has been more than three times greater than the global average.[5] In February 2020, the continent recorded its highest temperature of 18.3 °C (64.9 °F), which was a degree higher than the previous record of 17.5 °C (63.5 °F) in March 2015.[6]

There is some evidence that surface warming in Antarctica is due to human greenhouse gas emissions,[7] but this is difficult to determine due to internal variability.[8] A main component of climate variability in Antarctica is the Southern Annular Mode, which showed strengthened winds around Antarctica in summer of the later decades of the 20th century, associated with cooler temperatures over the continent. The trend was at a scale unprecedented over the last 600 years; the most dominant driver of this mode of variability is likely the depletion of ozone above the continent.[9]

In 2002, the Antarctic Peninsula's Larsen-B ice shelf collapsed.[10] Between 28 February and 8 March 2008, about 570 km2 (220 sq mi) of ice from the Wilkins Ice Shelf on the southwest part of the peninsula collapsed, putting the remaining 15,000 km2 (5,800 sq mi) of the ice shelf at risk. The ice was being held back by a "thread" of ice about 6 km (4 mi) wide,[11][12] prior to its collapse on 5 April 2009.[13][14]

Impacts on the natural environment[]

The continent-wide average surface temperature trend of Antarctica is positive and significant at >0.05 °C/decade since 1957.[15][16] The West Antarctic ice sheet has warmed by more than 0.1 °C/decade in the last 50 years, with most of the warming occurring in winter and spring. This is somewhat offset by cooling in East Antarctica during the fall. This effect is restricted to the 1980s and 1990s.[17][18][15]

Research published in 2009 found that overall the continent had become warmer since the 1950s, a finding consistent with the influence of man-made climate change:

"We can't pin it down, but it certainly is consistent with the influence of greenhouse gases from fossil fuels", said NASA scientist Drew Shindell, another study co-author. Some of the effects also could be natural variability, he said.[19]

2000s[]

September 20, 2007 NASA map showing previously un-melted snowmelt

The British Antarctic Survey, which has undertaken the majority of Britain's scientific research in the area, had the following positions in 2006:[20]

  • Ice, especially sea once, increases the sensitivity of polar regions to warming , by introducing a strong positive feedbacks loop.
  • Melting of continental Antarctic ice could contribute to global sea-level rise.
  • Climate models predict more snowfall than ice melting during the next 50 years, but the models are not good enough for them to be confident about the prediction.
  • Antarctica seems to be both warming around the edges and cooling at the center at the same time. Thus it is not possible to say whether it is warming or cooling overall.
  • There is no evidence for a decline in the overall Antarctic sea ice extent.[21]
  • The central and southern parts of the west coast of the Antarctic Peninsula have warmed by about 2.4 °C. The cause is not known.
  • Changes have occurred in the upper atmosphere over Antarctica.

The area of strongest cooling appears at the South Pole, and the region of strongest warming lies along the Antarctic Peninsula. A possible explanation is that loss of UV-absorbing ozone may have cooled the stratosphere and strengthened the polar vortex, a pattern of spinning winds around the South Pole. The vortex acts like an atmospheric barrier, preventing warmer, coastal air from moving into the continent's interior. A stronger polar vortex might explain the cooling trend in the interior of Antarctica. [1]

Ice mass loss since 2002, as measured by NASA's GRACE and GRACE Follow-On satellite projects, was 149 billion metric tons per year. (Time between projects caused gap in data.)[22]

In their latest study (September 20, 2007) NASA researchers have confirmed that Antarctic snow is melting farther inland from the coast over time, melting at higher altitudes than ever and increasingly melting on Antarctica's largest ice shelf.[23]

There is also evidence for widespread glacier retreat around the Antarctic Peninsula.[24]

2010s[]

Researchers reported on December 21, 2012 in Nature Geoscience that from 1958 to 2010, the average temperature at the mile-high Byrd Station rose by 2.4 degrees Celsius, with warming fastest in its winter and spring. The spot which is in the heart of the West Antarctic Ice Sheet is one of the fastest-warming places on Earth.[25][26][27]

A study of the Antarctic Peninsula, a small subregion of Lesser Antarctica, published in 2017 found that the temperature trends at the northern tip of the Peninsula, the north-east region of the Peninsula, and the South Shetland Islands "shifted from a warming trend of 0.32 °C/decade during 1979–1997 to a cooling trend of -0.47 °C/decade during 1999–2014" but that this variation was absent from the south-west region of the Peninsula.[28]

In 2015, the temperature showed changes but in a stable manner and the only months that have drastic change in that year are August and September. It also did show that the temperature was very stable throughout the year.[29][30][31][32]

A 2018 systematic review of all previous studies and data by the Ice Sheet Mass Balance Inter-comparison Exercise (IMBIE) found that Antarctica lost 2720 ± 1390 gigatons of ice during the period from 1992 to 2017, enough to contribute 7.6 millimeters to sea level rise once all detached icebergs melt. Most ice losses occurred in West Antarctica and the Antarctic Peninsula. The overall loss has substantially accelerated since the 2012 IMBIE assessment: an average loss of 43 gigatons per year during the first ten years, 1992 to 2002, rose to an average of 220 gigatons per year in the last 5 years. East Antarctica appears to have experienced a net gain of a relatively small amount of ice during the 25-years although uncertainty is greater due to subsidence of the underlying bedrock.[2]

Through his ongoing study, climate scientist, Nick Golledge, has estimated that Antarctic ice sheets will continue to melt and will have a profound effect on global climate.[33]According to Golledge's analysis, by the year 2100, 25 centimeters of water will have been added to the world's ocean, as water temperature continues to rise.[34]

2020s[]

Scientists confirm the first active leak of sea-bed methane in Antarctica and report that "the rate of microbial succession may have an unrealized impact on greenhouse gas emission from marine methane reservoirs".[35][36]

From 1989–2018, the South Pole experienced a record high statistically significant warming of 0.61 ± 0.34 °C per decade, more than three times the global average.[37] However, this warming lies within the upper bounds of the simulated range of natural variability, leading researchers to conclude that extreme decadal variability has masked anthropogenic warming across interior Antarctica during the twenty-first century.[37]

On 1 July 2021, the United Nations' World Meteorological Organization confirmed that a record high temperature of 18.3 °C (64.9 °F) had been recorded in Antarctica at the Esperanza Base.[38]

Future impacts of climate change[]

Antarctic Ice Shelf loss visualized

Even if global temperature rise is limited to the Paris Agreement's stated temperature goals of capping global mean temperature increases to 1.5-2°C above pre-industrial levels, there is still concern that West Antarctic ice-sheet instability may be already irreversible.[39] If a similar trajectory, still under the global temperature limit goals, persists, the East Antarctic Ice Sheet may also be at risk of permanent destabilization.[40] It has been shown using physics-based computer modeling that even with a 2°C reduction in global mean temperatures Antarctic ice loss could continue at the same rate as it did in the first two decades of the 21st century.[41]

The continued effects of climate change is likely to be felt by animal populations as well. Adélie penguins, a species of penguin found only along the coast of Antartica, may see nearly one-third of their current population threatened by 2060 with unmitigated climate change.[42] Emperor penguin populations may be at a similar risk, with 80% of populations being at risk of extinction by 2100 with no mitigation. With Paris Agreement temperature goals in place, however, that number may decline to 19% under the 2°C goal or 31% under the 1.5° goal.[43] Warming ocean temperatures have also reduced the amount of krill and copepods in the ocean surrounding Antartica, which has led to the inability of baleen whales to recover from pre-whaling levels. Without a reversal in temperature increases, baleen whales are likely to be forced to adapt their migratory patterns or face local extinction.[44]

Finally, the development of Antarctica for the purposes of industry, tourism, or an increase in research facilities may put direct pressure on the continent and threaten its status as largely untouched land.[45]

See also[]

References[]

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  28. ^ Oliva, M; Navarro, F; Hrbáček, F; Hernández, A; Nývltc, D (February 2017). P. Pereira, J. Ruiz-Fernández, R. Trigo. "Recent regional climate cooling on the Antarctic Peninsula and associated impacts on the cryosphere". Science of the Total Environment. 580: 210–223. Bibcode:2017ScTEn.580..210O. doi:10.1016/j.scitotenv.2016.12.030. hdl:10451/36205. PMID 27979621. Retrieved May 1, 2017. The Antarctic Peninsula (AP) is often described as a region with one of the largest warming trends on Earth since the 1950s, based on the temperature trend of 0.54 °C/decade during 1951–2011 recorded at Faraday/Vernadsky station. Accordingly, most works describing the evolution of the natural systems in the AP region cite this extreme trend as the underlying cause of their observed changes. However, a recent analysis (Turner et al., 2016) has shown that the regionally stacked temperature record for the last three decades has shifted from a warming trend of 0.32 °C/decade during 1979–1997 to a cooling trend of − 0.47 °C/decade during 1999–2014. While that study focuses on the period 1979–2014, averaging the data over the entire AP region, we here update and re-assess the spatially-distributed temperature trends and inter-decadal variability from 1950 to 2015, using data from ten stations distributed across the AP region. We show that Faraday/Vernadsky warming trend is an extreme case, circa twice those of the long-term records from other parts of the northern AP. Our results also indicate that the cooling initiated in 1998/1999 has been most significant in the N and NE of the AP and the South Shetland Islands (> 0.5 °C between the two last decades), modest in the Orkney Islands, and absent in the SW of the AP. This recent cooling has already impacted the cryosphere in the northern AP, including slow-down of glacier recession, a shift to surface mass gains of the peripheral glacier and a thinning of the active layer of permafrost in northern AP islands.
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  35. ^ Carrington, Damian (21 July 2020). "First active leak of sea-bed methane discovered in Antarctica". The Guardian. Retrieved 16 August 2020.
  36. ^ Thurber, Andrew R.; Seabrook, Sarah; Welsh, Rory M. (29 July 2020). "Riddles in the cold: Antarctic endemism and microbial succession impact methane cycling in the Southern Ocean". Proceedings of the Royal Society B: Biological Sciences. 287 (1931): 20201134. doi:10.1098/rspb.2020.1134. PMC 7423672. PMID 32693727. CC-BY icon.svg Text and images are available under a Creative Commons Attribution 4.0 International License.
  37. ^ Jump up to: a b Clem, Kyle R.; Fogt, Ryan L.; Turner, John; Lintner, Benjamin R.; et al. (August 2020). "Record warming at the South Pole during the past three decades". Nature Climate Change. 10 (8): 762–770. Bibcode:2020NatCC..10..762C. doi:10.1038/s41558-020-0815-z. S2CID 220261150.
  38. ^ "UN confirms 18.3C record heat in Antarctica". France 24. 1 July 2021.
  39. ^ Schleussner, Carl-Friedrich; Rogelj, Joeri; Schaeffer, Michiel; Lissner, Tabea; Licker, Rachel; Fischer, Erich M.; Knutti, Reto; Levermann, Anders; Frieler, Katja; Hare, William (September 2016). "Science and policy characteristics of the Paris Agreement temperature goal" (PDF). Nature Climate Change. 6 (9): 827–835. Bibcode:2016NatCC...6..827S. doi:10.1038/nclimate3096.
  40. ^ Mengel, M.; Levermann, A. (June 2014). "Ice plug prevents irreversible discharge from East Antarctica". Nature Climate Change. 4 (6): 451–455. Bibcode:2014NatCC...4..451M. doi:10.1038/nclimate2226.
  41. ^ DeConto, Robert M.; Pollard, David; Alley, Richard B.; Velicogna, Isabella; Gasson, Edward; Gomez, Natalya; Sadai, Shaina; Condron, Alan; Gilford, Daniel M.; Ashe, Erica L.; Kopp, Robert E.; Li, Dawei; Dutton, Andrea (6 May 2021). "The Paris Climate Agreement and future sea-level rise from Antarctica". Nature. 593 (7857): 83–89. Bibcode:2021Natur.593...83D. doi:10.1038/s41586-021-03427-0. PMID 33953408.
  42. ^ Cimino, Megan A.; Lynch, Heather J.; Saba, Vincent S.; Oliver, Matthew J. (June 2016). "Projected asymmetric response of Adélie penguins to Antarctic climate change". Scientific Reports. 6 (1): 28785. Bibcode:2016NatSR...628785C. doi:10.1038/srep28785. PMC 4926113. PMID 27352849.
  43. ^ Jenouvrier, Stéphanie; Holland, Marika; Iles, David; Labrousse, Sara; Landrum, Laura; Garnier, Jimmy; Caswell, Hal; Weimerskirch, Henri; LaRue, Michelle; Ji, Rubao; Barbraud, Christophe (March 2020). "The Paris Agreement objectives will likely halt future declines of emperor penguins". Global Change Biology. 26 (3): 1170–1184. Bibcode:2020GCBio..26.1170J. doi:10.1111/gcb.14864. PMID 31696584.
  44. ^ Tulloch, Vivitskaia J. D.; Plagányi, Éva E.; Brown, Christopher; Richardson, Anthony J.; Matear, Richard (April 2019). "Future recovery of baleen whales is imperiled by climate change". Global Change Biology. 25 (4): 1263–1281. Bibcode:2019GCBio..25.1263T. doi:10.1111/gcb.14573. PMC 6850638. PMID 30807685.
  45. ^ Liggett, Daniela; Frame, Bob; Gilbert, Neil; Morgan, Fraser (September 2017). "Is it all going south? Four future scenarios for Antarctica". Polar Record. 53 (5): 459–478. doi:10.1017/S0032247417000390.

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