Arctic sea ice loss

Effects & Impacts: Arctic sea ice loss

Baffin Bay Greenland image: Sonny Whitelaw

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Summary

[The] complete loss of Arctic sea ice in summer is now inevitable, even with the very lowest emissions pathways that peak temperatures at 1.6°C. This finding is a terminal diagnosis for that ecosystem and its essential role reflecting sunlight as the “Earth’s refrigerator,” something sea ice scientists have been warning for decades would come with continued high emissions. No one seems to have listened. – State of the Cryosphere Report 2022

The Arctic Ocean is semi-enclosed, surrounded almost entirely by land—Eurasia, North America, Greenland and some smaller islands. The land keeps most of the sea ice penned up, making it less mobile than sea ice that forms around Antarctica.
Sea ice is not the same as icebergs, which come from glaciers.
Sea ice grows throughout the autumn and winter and then melts throughout the spring and summer; it has declined 95% in the past 33 years.
The world’s oceans have absorbed around 93% of global warming to date with the Arctic warming 4 times faster than the global average (over the Barents Sea as much as 7 times faster) in part because the positive albedo effect of ice is rapidly diminishing, triggering feedback effects. This is known as ‘Polar Amplification’.

The planetary cooling effect of sea ice has reduced by 14% since the 1980s – Duspayev et al, 2024

Recent research indicates the Arctic is now undergoing abrupt climate change, and that climate models underestimated this in part due to a giant and growing ‘blob’ of warm water (see the MOSAiC Expedition).
A reduction in the formation of sea ice doesn’t raise sea levels, however it does trigger cascading feedback effects including but not limited to:

- Changing the world’s two largest ocean currents, with global implications.
- Melting permafrost and methane clathrates, which are releasing large volumes of the greenhouse gases carbon dioxide and methane into the atmosphere
- Changing global weather patterns: temperature differences between the poles and tropics is a key part of how global weather works. As the poles are warming 2-4 times faster than elsewhere, the temperature difference is declining. The polar jetstreams are now ‘wobbling’; instead of super-cold Arctic and hot tropical air kept in place at the poles and equator, they’re moving into temperate areas, causing weather extremes globally in 2022, 2023, 2024, and 2025.
- Phenological changes in phytoplankton, which is the base of the food chain, and loss of habitat for iconic species such as polar bears and godwits (which migrate to New Zealand) are now underway.

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Home > Climate wiki > Effects > Arctic sea ice loss

Summary

The Arctic Ocean is semi-enclosed, surrounded almost entirely by land—Eurasia, North America, Greenland and some smaller islands. The land keeps most of the sea ice penned up, making it less mobile than sea ice that forms around Antarctica.
Sea ice is not the same as icebergs, which come from glaciers.
Sea ice grows throughout the autumn and winter and then melts throughout the spring and summer; it has declined 95% in the past 33 years.
The world’s oceans have absorbed around 93% of global warming to date with the Arctic warming 4 times faster than the global average (over the Barents Sea as much as 7 times faster) in part because the positive albedo effect of ice is rapidly diminishing, triggering feedback effects. This is known as ‘Polar Amplification’.
Recent research indicates the Arctic is now undergoing abrupt climate change, and that climate models underestimated this in part due to a giant and growing ‘blob’ of warm water (see the MOSAiC Expedition).
A reduction in the formation of sea ice doesn’t raise sea levels, however it does trigger cascading feedback effects including but not limited to:

- Changing the world’s two largest ocean currents, with global implications.
- Melting permafrost and methane clathrates, which are releasing large volumes of the greenhouse gases carbon dioxide and methane into the atmosphere
- Changing global weather patterns: temperature differences between the poles and tropics is a key part of how global weather works. As the poles are warming 2-4 times faster than elsewhere, the temperature difference is declining. The polar jetstreams are now ‘wobbling’; instead of super-cold Arctic and hot tropical air kept in place at the poles and equator, they’re moving into temperate areas, causing weather extremes globally in 2022 and again in 2023.
- Phenological changes in phytoplankton, which is the base of the food chain, and loss of habitat for iconic species such as polar bears and godwits (which migrate to New Zealand) are now underway.

Fig. 1: Arctic sea ice declined between 1988-2025 from 15 million km2 to 12.8 million km2.

Fig. 2: Arctic sea ice 1979 – December 2025 (Image: Zack Labe)

Sea ice versus icebergs
Icebergs: are made of that has broken off a glacier or ice shelf and floats out to sea or into lakes.

Sea ice: forms when ocean water freezes over autumn and winter. Although sea ice is made from salty seawater, there isn’t much room for salt molecules to be trapped in the close-knit structure of ice, so the salt molecules are rejected into a dense, briny solution that drops into deeper water. This plays a crucial role in driving the world’s two largest ocean currents.

State of the Cryosphere Report 2025

Summary: Arctic Sea Ice

Polar sea ice is essential for maintaining a livable global climate, with global risks from its decline ranging from disruption of weather and ocean currents; to accelerated Greenland and Antarctic melt and associated sea-level rise; to extinction of ice-dependent species at the base of the food chain for humans and many polar and marine mammals. Sea ice coverage at both poles has declined by 40–60% since satellite measurements began in 1979, with nearly all Antarctic sea ice decline occurring precipitously since 2016. While most attention is given to the September sea ice minimum in the Arctic, this loss has occurred year-round, in all months of the year including sea ice maximums, when the ice reaches its largest extent. A record-low maximum occurred in the Arctic in March 2025, and Antarctica’s record-low maximum was set in September 2023. Global sea-ice coverage, combining both poles, reached a record all-time low in February 2025.

Sea ice has declined not only in extent, but in thickness. Much of the Arctic Ocean used to be covered in thick, multi-year ice that was 4–7 years old. Such “old” ice has virtually disappeared, with even two or three-year-old ice comprising under 10% of today’s sea-ice coverage. Antarctic sea ice plays an essential role in several ways, including formation of Antarctic Bottom Water: the densest water mass on the planet, driving the entire global ocean “conveyor belt.” A 40% decline in sea ice in the Weddell Sea has reduced the production of Antarctic Bottom Water in this region by almost a third.

Future sea ice survival is extremely sensitive to current and future human emissions of greenhouse gases. If governments course-correct to 2025 NDCs consistent with 1.5°C of warming or below at 2100, sea ice may slowly begin to recover in the 2070s and beyond. At least one ice-free Arctic summer event seems increasingly likely however before 2050, and the summer ice-free period would increase with additional warming. NDCs that result in global mean temperatures of 2°C or above would lead to ice-free conditions in the Arctic every summer, with high-risk and unpredictable global impacts. Loss of Antarctic sea ice and associated ice shelves is less certain, but holds even greater long-term and non-reversible risks because the sea ice and ice shelves are essential to protecting Antarctica’s ice sheet, and holding sea-level rise to adaptable levels in coming decades and centuries.

More information

Explainer: Polar Amplification
Arctic or Polar Amplification are terms used to describe why the poles are warming far faster than the rest of the planet. There are several reasons for this:

The Albedo Effect: Click the next ‘Explainer’ tab for details.

Ozone-depleting substances (this is a new area of research: see here for how this is happening).

Air pressure differences between the tropics and the poles may also be a factor: warmer (and therefore denser, higher pressure) air tends to travel from the tropics to the cooler (lower pressure less dense air) poles (see 5-min. Video 1 here). However, weather systems are stalling as the jet stream wobbles; see the ‘Explainer’ tab below. While this allows cold arctic air to move further south for longer periods, it also allows warmer tropical air to invade polar latitudes. A very small rise in temperatures for long periods is leading to dramatic melting across Greenland, Antarctica, and Arctic sea ice.

Climate system feedbacks have also changed ocean currents as well as the weather associated with them.

Explainer: The Albedo Effect

Clean ice and snow have a very high albedo, that is, they reflect up to 90% of solar radiation back into space. The ocean is much darker, so it has a very low albedo, reflecting only about 6% of the incoming solar radiation and absorbing the other 94%, warming it much faster than the snow and ice.

As more ice forms, the water is cooler, leading to more ice forming, and so on, in a feedback effect.

Recent global temperature surge intensified by record-low planetary albedo – Science, 05 Dec. 2024

Image – Nathan Kurtz / NASA

The planetary cooling effect of sea ice loss has reduced by 14% since the 1980s.

Explainer: A giant blob of warm water

When the albedo effect creates dark water that absorbs more heat, that heat must go somewhere:

These warming surface waters are likely migrating down into the blob, which robotic temperature probes, moorings, and oceanographic surveys show is steadily warming and growing. With enough heat to melt the Arctic’s ice three to four times over, the blob could devour the ice from below if the barrier of the cold surface layers ever dissipates… Measurements from the eastern Arctic Ocean show the blob, usually found 150 meters below or deeper, has recently moved up to within 80 meters of the surface… The process, called “Atlantification [see the 2025 Arctic Report Card video below]” is already well underway in the Barents Sea, north of Norway, where fingers of warm Atlantic water have spread north and risen, melting sea ice even in winter months. The invasion shows no sign of stopping…”– Voosen, August 2020.

Explainer: World's largest ocean currents

In the Northern Hemisphere, the world’s second largest current, the Atlantic Meridional Overturning Current (AMOC) abruptly shut down when Earth warmed quickly at the end of the Last Glacial Maximum 14,500 years ago, leading to equally abrupt cooling over much of Europe (called the Younger Dryas), and an unstable climate that brought wild weather globally for several thousand years.

In the Southern Hemisphere, the Antarctic Circumpolar Current, the largest current, is also shutting down, allowing warm water eddies to reach further into Antarctica, with implications for sea level rise and changes to our weather patterns. Find out more about these currents and the links to research papers here (links to a page on this website).

Earth viewed on a Spilhaus projection showing how oceanic currents circle the globe. Warm current are red, cool are blue.

Explainer: Wobbly weather patterns - the jetstream & polar vortex

Polar regions are warming 4-7 faster than as the rest of the planet. This is changing our weather, which is strongly influenced by jetstreams including the polar vortex. Extreme hot or cold weather is often ‘stuck’ over one place for long periods. While this video largely features the Northern Hemisphere, the same mechanisms are underway in the Southern Hemisphere. Moreover, the impact on the AMOC (explained in the tab above) affects ocean currents around New Zealand.

Explainer: Phenological changes

How plants and animals change the way they behave according to temperature (Video 3). See more about ‘phenology’ on this website. A good research paper regarding the Arctic is here Gou et al; The changing nature of future Arctic marine heatwaves and its potential impacts on the ecosystem, Nature Climate Change 15 pp162-170, 2025 (Open access)

References and further reading
2025: Arctic Report Card; NOAA

2025: State of the Cryosphere Report, International Cryosphere Climate Initiative (ICCI), Stockholm, Sweden

2025: Yi et al; Future mesoscale horizontal stirring in polar oceans intensified by sea ice decline, Nature climate Change 15 pp1315-1323 (Open access)

2025: Gou et al; The changing nature of future Arctic marine heatwaves and its potential impacts on the ecosystem, Nature Climate Change 15 pp162-170 (Open access)

2025: Svensson, Dramatic Changes in the Greenland Sea, Bjerknes Centre for Climate Research, 18 March

2025: Stroeve et al; Disappearing landscapes: The Arctic at +2.7°C global warming, Science 6 February

Plain English: SciTech daily

2024: ICCI: State of the Cryosphere, Lost Ice, Global Damage, International Cryosphere Climate Initiative (ICCI), Stockholm, Sweden

2024: NOAA Arctic Report Card 2024

2024: Kim & An; Emergence of a climate oscillation in the Arctic Ocean due to global warming, Nature Climate Change 14 pp1268-1274 (open access)

2024: Duspayev et al; Earth’s Sea Ice Radiative Effect from 1980 to 2023, Geophysical Research Letters 51 | 14 (Open access)

2024: Xu et al; High-resolution modelling identifies the Bering Strait’s role in amplified Arctic warming, Nature Climate Change 14 pp615-622 03 June

2024: Strehl et al; A 70-year perspective on water-mass transformation in the Greenland Sea: From thermobaric to thermal convection, Progress in Oceanography 227 (Open access)

2024: Cheng et al; Ocean heat content in 2023; Nature Communications Earth & Environment 5 pp232-234

2023: State of the Cryosphere – Two Degrees is Too High. International Cryosphere Climate Initiative (ICCI), Stockholm, Sweden (PDF)

2023: Dutta et al; Early Eocene low orography and high methane enhance Arctic warming via polar stratospheric clouds, Nature Geoscience 16, pp1027–1032 (Open access)

2023: Vermassen et al; A seasonally ice-free Arctic Ocean during the Last Interglacial, Nature Geoscience 16, pp723–729

2022: State of the Cryosphere

2022: NOAA Arctic Report Card

2022: Rantanen et al; The Arctic has warmed nearly four times faster than the globe since 1979, Nature Communications Earth and environment 3 |168

Tandon, Carbon Brief explains the research (open access)

2021: NOAA Arctic Report Card

2021: Jacobs et al; The Arctic Is Now Warming Four Times As Fast As the Rest of the Globe, AGU Fall Meeting 13-17 December

2021: Bailey et al; Arctic sea-ice loss fuels extreme European snowfall, Nature Geoscience 14 pp283–288

National Snow and Ice Data Centre (NSIDC)

(undated) Harvey et al; Equator-to-pole temperature differences and the extra-tropicalstorm track responses of the CMIP5 climate models, NCAS-Climate, Department of Meteorology, University of Reading, UK

2020: Guarono et al; Sea-ice-free Arctic during the Last Interglacial supports fast future loss, Nature Climate Change 10 pp928-932

2020: Ardyna & Arrigo; Phytoplankton dynamics in a changing Arctic Ocean, Nature Climate Change 10 pp892–903

2020: Polyakov et al; Weakening of Cold Halocline Layer Exposes Sea Ice to Oceanic Heat in the Eastern Arctic Ocean, Journal of Climate American Meteorological Society 33/18 pp8107–8123.

2020: Timmermans et al; Warming of the interior Arctic Ocean linked to sea ice losses at the basin margins, Science Advances 4/8

2020: Voosen; Growing underwater heat blob speeds demise of Arctic sea ice, Science 25 August.

2020: Skagseth et al; Reduced efficiency of the Barents Sea cooling machine, Nature Climate Change 10, pp661-666

2020: Jansen et al; Past perspectives on the present era of abrupt Arctic climate change Nature Climate Change 10, pp714–721

2020: Ouyang et al; Sea-ice loss amplifies summertime decadal CO₂ increase in the western Arctic Ocean Nature Climate Change 10, 678–684

2020: NASA Earth Observatory: Ice Bridge

2020: NASA; Mapping Snow on Arctic Ice

2020: Thomas et al; Tipping elements and amplified polar warming during the Last Interglacial, Quaternary Science Reviews 233 / 106222

2020: England et al; Tropical climate responses to projected Arctic and Antarctic sea-ice loss Nature Geoscience 13, 275–281

2019: Lade et al; Human impacts on planetary boundaries amplified by Earth system interactions, Nature Sustainability 3, pp 119–128

2019 IPCC: Special Report on the Ocean and Cryosphere in a Changing Climate

2019: NASA: 2019 Arctic Sea Ice Minimum Tied for Second Lowest On Record

2019: NOAA Richter-Menge et al; Arctic Report Card 2019

2019: National Geographic: The Arctic Is Heating Up September 2019 special issue

2019: Thackeray et al. An emergent constraint on future Arctic sea-ice albedo feedback, Nature Climate Change 9, pp972-978

2019: Cheng et al; How fast are the oceans warming? Science 363/6423 pp128-129

2018 NOAA Arctic Report Card: Executive summary

2018 IPCC: Summary for Policymakers of IPCC Special Report on Global Warming of 1.5°C approved by governments

2018: Carbon Brief Analysis; Why the IPCC 1.5C report expanded the carbon budget

2017: Jones; How the World Passed a Carbon Threshold and Why It Matters, Yale Environment 360 – Yale School of Forestry & Environmental Studies

2017: Kashiwase et al; Evidence for ice-ocean albedo feedback in the Arctic Ocean shifting to a seasonal ice zone, Nature – Scientific Reports 7, 8170