Arctic sea ice
Arctic Sea Ice News and Analysis
Read scientific analysis on Arctic sea ice conditions. We provide an update during the first week of each month, or more frequently as conditions warrant.
A mostly ho-hum January
Sea ice extent for January 2020 tracked well below average, with the monthly average ranking as ninth lowest in the satellite record. While air temperatures were above average across much of the Arctic Ocean, it was colder than average over the northern Barents Sea, Alaska, the eastern Canadian Arctic Archipelago, and Greenland.
Overview of conditions
Arctic sea ice extent for January 2020 was 13.65 million square kilometers (5.27 million square miles), placing it ninth in the satellite record. This was 770,000 square kilometers (297,000 square miles) below the 1981 to 2010 January average and 570,000 square kilometers (220,000 square miles) above the record low mark for January set in 2018. At the end of January, ice extent was below average over parts of the Bering Sea, the Sea of Okhotsk, and the East Greenland Sea. The near average extent in the Barents Sea contrasts with recent years, which were characterized by well below average extent in this area.
Climate Change: Arctic sea ice summer minimum
Through 2018, the downward trend for the summer minimum in September was 12.8 percent per decade relative to the 1981–2010 average. (The trend is updated each year as part of NOAA's Arctic Report Card, which is released in mid-December.) Summer ice declines have been especially rapid since the start of the twenty-first century.
Sea ice is in equilibrium with the water around it, so it doesn't raise sea levels when it melts. But it is disastrous for polar bears and other ocean life, and it allows the Arctic ocean to absorb more light during the summer, in a positive feedback loop.
Greenland ice sheet
Greenland's ice sheet just lost 11 billion tons of ice — in one day
Greenland's ice sheet melting seven times faster than in 1990s
Greenland has lost 3.8 trillion tonnes of ice since 1992, and the rate of ice loss has risen from 33bn tonnes a year in the 1990s to 254bn tonnes a year in the past decade. Greenland’s ice contributes directly to sea level rises as it melts because it rests on a large land mass, unlike the floating sea ice that makes up much of the of the Arctic ice cap.
Boreal forests
The Rapid and Startling Decline Of World’s Vast Boreal Forests
Scientists are becoming increasingly concerned about the fate of the huge boreal forest that spans from Scandinavia to northern Canada. Unprecedented warming in the region is jeopardizing the future of a critical ecosystem that makes up nearly a third of the earth’s forest cover.
Permafrost
Rapid Permafrost Collapse Is Underway, Disintegrating Landscapes And Our Predictions
Scientists have long fretted that climate change - which has heated Arctic and subarctic regions at double the global rate - will release planet-warming CO2 and methane that has remained safely locked inside Earth's frozen landscapes for millennia.
It was assumed this process would be gradual, leaving humanity time to draw down carbon emissions enough to prevent permafrost thaw from tipping into a self-perpetuating vicious circle of ice melt and global warming.
But a study published on Monday in Nature Geoscience says projections of how much carbon would be released by this kind of slow-and-steady thawing overlook a less well-known process whereby certain types of icy terrain disintegrate suddenly - sometimes within days.
Atlantic Meridional Overturning Circulation
Atlantic meridional overturning circulation
The Atlantic meridional overturning circulation (AMOC) is the zonally-integrated component of surface and deep currents in the Atlantic Ocean. It is characterized by a northward flow of warm, salty water in the upper layers of the Atlantic, and a southward flow of colder, deep waters that are part of the thermohaline circulation. These "limbs" are linked by regions of overturning in the Nordic and Labrador Seas and the Southern Ocean. The AMOC is an important component of the Earth's climate system, and is a result of both atmospheric and thermohaline drivers.
AMOC has undergone exceptional weakening in the last 150 years compared to the previous 1500 years,[10] as well as a weakening of around 15% since the mid-twentieth century.[11] Direct observations of the strength of the AMOC have only been available since 2004 from the in situ mooring array at 26°N in the Atlantic.[12] While climate models predict a weakening of AMOC under global warming scenarios, the magnitude of observed and reconstructed weakening is out of step with model predictions. Observed decline in the period 2004–2014 was a factor of 10 higher than that predicted by climate models participating in Phase 5 of the Coupled Model Intercomparison Project (CMIP5).[13][14] While observations of Labrador Sea outflow showed no negative trend from 1997–2009, this period is likely an atypical and weakened state.[15] As well as an underestimation of the magnitude of decline, grain size analysis has revealed a discrepancy in the modelled timing of AMOC decline after the Little Ice Age.[10]
Amazon rainforest
The Amazon Rainforest Is About To Cross An Irreversible Threshold That Will Turn It Into A Savanna, Top Scientists Say
Leading rainforest scientists Thomas Lovejoy and Carlos Nobre warned in an editorial published Thursday that deforestation in the world's largest rainforest has led the Amazon to the brink of an irreversible process called "dieback."
That scenario would turn the Amazon into an African-savanna-type landscape. The tropical trees — and the fauna they support — would disappear, releasing up to 140 billion tons of stored carbon into the atmosphere, causing an uptick in already rising global temperatures.
"Today, we stand exactly in a moment of destiny," Lovejoy and Nobre wrote in the editorial, which was published in the journal Science Advances. Both scientists have studied the Amazon for decades. "The tipping point is here, it is now."
Warm-water corals
Saving the World's Coral Reefs
What Do Coral Reefs Need to Survive?
Sunlight: Corals need to grow in shallow water where sunlight can reach them. Corals depend on the zooxanthellae (algae) that grow inside of them for oxygen and other things, and since these algae needs sunlight to survive, corals also need sunlight to survive. Corals rarely develop in water deeper than 165 feet (50 meters).
Clear water: Corals need clear water that lets sunlight through; they don’t thrive well when the water is opaque. Sediment and plankton can cloud water, which decreases the amount of sunlight that reaches the zooxanthellae.
Warm water temperature: Reef-building corals require warm water conditions to survive. Different corals living in different regions can withstand various temperature fluctuations. However, corals generally live in water temperatures of 68–90° F or 20–32° C.
Clean water: Corals are sensitive to pollution and sediments. Sediment can create cloudy water and be deposited on corals, blocking out the sun and harming the polyps. Wastewater discharged into the ocean near the reef can contain too many nutrients that cause seaweeds to overgrow the reef.
Saltwater: Corals need saltwater to survive and require a certain balance in the ratio of salt to water. This is why corals don’t live in areas where rivers drain fresh water into the ocean (“estuaries”).
Warm-water coral reefs and climate change
Warm-water coral reefs are celebrated for their spectacular diversity (estimates exceed 3 million species).
Coral reefs are highly dynamic ecosystems that are regularly exposed to natural perturbations. Human activities have increased the range, intensity, and frequency of disturbance to reefs. Threats such as overfishing and pollution are being compounded by climate change, notably warming and ocean acidification. Elevated temperatures are driving increasingly frequent bleaching events that can lead to the loss of both coral cover and reef structural complexity. There remains considerable variability in the distribution of threats and in the ability of reefs to survive or recover from such disturbances. Without significant emissions reductions, however, the future of coral reefs is increasingly bleak.
Parts of East Antarctica
Sustained levels of moderate warming could melt the East Antarctic Ice Sheet
New research on marine sediment layers from Antarctica indicates that the East Antarctic Ice Sheet (EAIS) retreated during extended warm periods in the past, when temperatures were like those predicted for this century.
The most extreme changes in the ice sheet occurred during two interglacial periods 125,000 and 400,000 years ago, when global sea levels were between six and 13 metres higher than they are today.
Ice loss from the EAIS likely made a significant contribution to those higher sea levels in the past.
Dr. Wilson said: "What we have learned is that even modest warming of just two degrees, if sustained for a couple of thousand years, is enough to cause the ice sheet in East Antarctica to retreat in some of its low-lying areas.
So, not an all-at-once starting tomorrow catastrophe, but still a significant amount of melting. Maybe another millimeter a year of sea-level rise, to start out.
West Antarctic Ice Sheet
Four decades of Antarctic Ice Sheet mass balance from 1979–2017
We evaluate the state of the mass balance of the Antarctic Ice Sheet over the last four decades using a comprehensive, precise satellite record and output products from a regional atmospheric climate model to document its impact on sea-level rise. The mass loss is dominated by enhanced glacier flow in areas closest to warm, salty, subsurface circumpolar deep water, including East Antarctica, which has been a major contributor over the entire period. The same sectors are likely to dominate sea-level rise from Antarctica in decades to come as enhanced polar westerlies push more circumpolar deep water toward the glaciers.
We use updated drainage inventory, ice thickness, and ice velocity data to calculate the grounding line ice discharge of 176 basins draining the Antarctic Ice Sheet from 1979 to 2017. We compare the results with a surface mass balance model to deduce the ice sheet mass balance. The total mass loss increased from 40 ± 9 Gt/y in 1979–1990 to 50 ± 14 Gt/y in 1989–2000, 166 ± 18 Gt/y in 1999–2009, and 252 ± 26 Gt/y in 2009–2017. In 2009–2017, the mass loss was dominated by the Amundsen/Bellingshausen Sea sectors, in West Antarctica (159 ± 8 Gt/y), Wilkes Land, in East Antarctica (51 ± 13 Gt/y), and West and Northeast Peninsula (42 ± 5 Gt/y). The contribution to sea-level rise from Antarctica averaged 3.6 ± 0.5 mm per decade with a cumulative 14.0 ± 2.0 mm since 1979, including 6.9 ± 0.6 mm from West Antarctica, 4.4 ± 0.9 mm from East Antarctica, and 2.5 ± 0.4 mm from the Peninsula (i.e., East Antarctica is a major participant in the mass loss). During the entire period, the mass loss concentrated in areas closest to warm, salty, subsurface, circumpolar deep water (CDW), that is, consistent with enhanced polar westerlies pushing CDW toward Antarctica to melt its floating ice shelves, destabilize the glaciers, and raise sea level.
This is where we came in.