A warming Arctic can stretch the polar vortex, a high-altitude air ribbon, one says. The “wobble” can disrupt the jet stream, causing extreme cold in the East.

Pedestrians walked the snow-covered streets of Jersey City, N.J., during last month’s winter storm. Some scientists say there is a link between a warming planet and the recent frigid temperatures. Credit…Aristide Economopoulos for The New York Times

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Global Warming Acceleration: Impact on Sea Ice

02 April 2025
James Hansen, Joe Kelly, Pushker Kharecha

Abstract. Global warming has accelerated.[2] Warming melts sea ice, but it also melts ice sheets, ice shelves, ice caps and glaciers, which affects sea ice cover. Injection of cold freshwater and icebergs into the ocean tends to increase sea ice cover during a transient period until the climate forcing stabilizes and a new climate state is approached. Sea ice melt due to the warming ocean has the upper hand over freshwater injection in both hemispheres today, and thus global sea ice cover is near a historic low (Fig. 1). Arctic sea ice has been relatively stable for the past 10-20 years while Antarctic sea ice has declined, but global warming acceleration may alter both cases. In the Arctic, warm Atlantic water is intruding under the cold Arctic surface layer and warm Pacific water is spilling over the Aleutian sill into the Arctic Basin. Paleoclimate data show that warming at depth can lead to sudden loss of sea ice near Greenland, with consequences for the Greenland ice sheet. In the Antarctic, accelerated ocean warming increases melting of ice shelves and freshwater injection, which can cause temporary growth of sea ice cover. Global climate models employed by the Intergovernmental Panel on Climate Change (IPCC) have failed to account well for the freshwater effect on sea ice cover, thus contributing to IPCC’s underestimate of climate sensitivity. Overall, accelerated global warming does not bode well for stability of the ice sheets, the ocean’s overturning circulations, and global sea level in coming decades – despite the complexity of sea ice changes and uncertainty about the growth rate of ice sheet mass loss.

Global sea ice cover is one of the three big “fast” climate feedbacks in the classical definition of equilibrium climate sensitivity (ECS), which the Charney report[3] cemented. The Charney committee’s decision to exclude the “slow” feedbacks of ice sheets and the carbon cycle in their assessment was invaluable, as it allowed focus on the crucial water vapor, cloud and ice/snow feedbacks, and their interactions, in the global climate models (GCMs) then under development. Charney realized that the excluded feedbacks may have effects on short timescales, but those could be kept in mind for later study.

Recently, we concluded that climate sensitivity is high, ECS = 4.5 ± 0.5°C (1σ) for doubled atmospheric CO₂, based on three independent analyses (glacial-interglacial climate change, 1850-2024 global warming, and Earth’s darkening during 2000-2024).[2] High ECS changes everything: it fundamentally alters expectations for continued climate change. Why? Because “fast” feedbacks are not really fast: they come into play in proportion to temperature change, not in direct response to climate forcing. Thus, climate response time is approximately proportional to climate sensitivity squared.[4] One consequence is that the “fast” feedback response to ship aerosol reduction[2] is still growing significantly after five years, which is the reason we expect 2025 global temperature to be about as high as in 2024, despite the El Nino having faded to the ENSO-neutral state. A second result is that we must simultaneously consider “fast” and “slow” feedback effects because their timescales overlap. Let’s start with sea ice.

Fig. 2. Arctic and Antarctic sea ice area (31-day running-mean of daily data) from National Snow and Ice Data Center daily sea ice extent data.[1] The most recent 15 days (shown be a dotted line) are 29-day, 27-day… 3-day, 1-day means, and are thus estimates that will be replaced as data are updated.

Sea ice cover is now near its minimum during the era of global satellite data (i.e., since 1979) in both hemispheres (Figs. 2 and 3). The warm-season minimum of Arctic sea ice decreased sharply in 2007 and even further in 2012. The 2007 decrease was associated with sustained wind anomalies that drove ice from the Arctic toward warmer water and the Fram Strait.[6],[7] The 2012 melt was enhanced by an intense cyclonic storm that mixed heat upward in a normally well-stratified summer ocean, thus melting sea ice from below.[8] As the thickness of sea ice declines, such weather anomalies melt ice more effectively.

Fig. 3. Arctic and Antarctic sea ice area, with the solid curves being the 365-day running-mean of National Snow and Ice Data Center daily sea ice extent data[1] and the squares being annual results.

Sea ice volume is an important diagnostic because reduction of ice volume is a freshwater injection onto the ocean that can affect ocean circulation. Sea ice volume change is more difficult to measure than area change. Remarkably, changes of the ice “freeboard” (the height of the ice surface above sea level) can be detected by satellite, but measurement accuracy is limited, especially for Antarctic sea ice, which is less thick than Arctic sea ice. Sea ice volume estimates for the entire ocean (Fig. 4) are based on ice-ocean data assimilation models constrained by available observations. The difference between results from two data assimilation models for Arctic sea (Fig. 4, left) is one measure of uncertainty in sea ice volume changes. [PIOMAS (Pan-Arctic Ice-Ocean Modeling and Assimilation System) and GIOMAS (Global Ice-Ocean Modeling and Assimilation System) employ different ocean and sea ice models.[10]] The PIOMAS data set is preferred for the Arctic because it has been more extensively validated and used.[11]

Fig. 4. Sea ice volume: solid curves are 12-month running-mean of PIOMAS and 365-day running-mean of GIOMAS data, both from the Polar Science Center of the University of Washington.[5]

The volume of Arctic sea ice declined of the order of 10,000 cubic kilometers in the 40 years 1980-2020, thus about 250 km³/year, a freshwater injection rate comparable to the annual mass loss rate of the Greenland ice sheet. This decrease of Arctic sea ice volume over the past several decades provides a substantial term to the total freshwater injection that affects stability of the Atlantic Overturning Meridional Circulation (AMOC), as discussed in the Supplementary Material of our recent paper.[2] Total freshwater injection from all sources is now large enough to affect ocean temperature, salinity, and overturning ocean circulations, as shown, for example, in observed zonal-mean ocean temperature change (Fig. 5A)[12] and in our climate simulations.[13] However, increase of freshwater injection is absent or underestimated in models employed by the Intergovernmental Panel on Climate Change (IPCC), as shown by the absence of cooling in their climate model simulations (Fig. 5B,C) and underestimates of the freshening of polar surface waters.

Fig. 5. (A) Observed zonal-mean 2001-2020 ocean temperature relative to 1981-2000, (B) ensemble mean of CMIP6 for that period, and (C) CMIP6 result for 2081-2100 (from Fig. 1, Shu et al., 2022).[10]

Climate sensitivity. Failure of IPCC models to capture the cooling from freshwater injection affects IPCC’s best estimate for equilibrium climate sensitivity (ECS) because IPCC relies heavily on comparison of climate simulations for 1850-present with observed global warming. Models that fail to capture the freshwater effect – which causes a delay of polar warming and reduced global warming – require unrealistically low ECS in order to avoid global warming that exceeds observations. However, this effect on estimated ECS is exceeded by the aerosol effect described next.

Aerosols are the main reason for IPCC’s underestimate of climate sensitivity. IPCC’s estimate of aerosol climate forcing (Fig. 3 of ref. 2) is nearly linear in global sulfur emissions (Fig. SM1 of ref. 2). With the IPCC aerosol forcing, an ECS of about 3°C for doubled CO₂ is required to yield close agreement with observed global warming over the past century. However, the impact of aerosols on clouds (which is most of the aerosol forcing) is highly nonlinear; we conclude in paper 2 that global aerosol forcing increased (became more negative) by about 0.5 W/m² during the period 1970-2005 as a result of human-made aerosols being spread more globally into more pristine air, including over the ocean. Aerosols thus reduced the net human-made (greenhouse gas plus aerosols) climate forcing, and as a result a higher climate sensitivity (4.5°C ± 0.5°C for doubled CO₂) is required to match observed global warming. This high climate sensitivity is also best able to simulate the strong warming in the past two years, and it is the main reason that we expect little if any cooling in the annual mean 2025 global temperature.

Two additional – independent and consistent – evaluations of climate sensitivity are provided by (1) comparison of paleoclimate equilibrium states,[14] and (2) inference of large amplifying cloud feedback based on accurate monitoring of Earth’s radiation balance.[2]

Summary implications. High climate sensitivity (including the implied corollary that human-made aerosols have partly offset greenhouse gas warming) changes everything. Most important: it makes it much more difficult to avoid passing the “point-of-no-return” – shutdown of the Atlantic Meridional Overturning Circulation (AMOC) and, in turn, sea level rise of several meters.

AMOC shutdown occurs when the density of the upper ocean in the regions of deepwater formation in the North Atlantic becomes sufficiently light relative to deeper ocean layers, i.e., light enough to prevent the winter sinking of surface water that drives the global ocean conveyor. Accelerated warming has three effects that increase the likelihood of AMOC shutdown and the speed with which shutdown can occur: (1) accelerated global warming limits mixing of the warmed surface water with deeper, colder, layers, (2) greater warming increases precipitation, adding freshwater to the surface layer; and (3) greater warming increases ice melt and thus increases freshwater injection onto the North Atlantic.

AMOC shutdown is the “point-of-no-return” because it requires centuries for the ocean circulation to recover from shutdown and, in the meantime, transport of heat from the Southern Hemisphere into the North Atlantic is greatly reduced. Resulting increase of ocean temperature in the Southern Hemisphere practically locks in demise of the West Antarctic ice sheet, with sea level rise of several meters.

Evaluation of how close the world is to AMOC shutdown is extremely difficult. IPCC’s approach – relying almost entirely on global climate models – is fraught with uncertainty and errors, as suggested by a paper[15] concluding that AMOC would not shut down even with 5°C global warming and by the IPCC AR6[16] conclusion that AMOC shutdown is low probability.

More reliable analysis, we argue, requires comparable emphasis on information obtained from (1) paleoclimate, (2) global climate models, and (3) ongoing observations of climate change and climate processes. That is the approach that we will follow at Climate Science, Awareness and Solutions (CSAS) and we appreciate support that allows us to continue to pursue that research. We plan to make available and continually update a broad array of the most essential data, e.g., the sea ice graphs are here.[17] However, timely results in support of policy needs are dependent on continuation and enhancement of crucial observations. We draw attention especially to:

(1) the global ARGO float program[18] of several thousand deep-diving autonomous floats, which needs to be continued and expanded with more capable floats in the polar regions that can assess changes near vulnerable ice shelves and in the sub-sea-ice ocean. The United States National Oceanic and Atmospheric Administration (NOAA) has provided a large fraction of these floats, but it is unclear whether they can be counted on to continue and to enhance the observations. It is important for more nations to step up their contributions to the program.

(2) the global Earth radiation budget measurements presently obtained by CERES[19] instruments nearing their end-of-life. It is not clear that NASA has adequate plans for continuation of the measurements. In any case, it would be very useful if the European Union and/or China carried out measurements with a quality comparable to the high-precision NASA data and made the data freely available.

[1] Sea ice extent is defined by NSIDC (National Snow and Ice Data Center) as the ocean area with sea ice concentration exceeding 15%. NSIDC Artic Sea Ice News and Analysis and daily updates of sea ice extent for the Arctic and Antarctic are available from NSIDC.
[2] JE Hansen, P Kharecha, M Sato et al., Global warming has accelerated: are the United Nations and the public well-informed? Environment: Science and Policy for Sustainable Development, 67(1), 6–44, 2025, https://doi.org/10.1080/00139157.2025.2434494
[3] J Charney et al., Carbon Dioxide and Climate: A Scientific Assessment. (Washington: National Academy of Sciences Press, 1979)
[4] J Hansen, G Russell, A Lacis et al. Climate response times: dependence on climate sensitivity and ocean mixing. Science 229, 857-9, 1985
[5] Polar Science Center. Data. Applied Physics Laboratory, University of Washington. (last accessed 31 March 2025), https://psc.apl.uw.edu/data/
[6] J Zhang, RW Lindsay, A Schweiger, I. Rigor, What drove the dramatic retreat of Arctic sea ice during summer 2007?, Geophys Res Lett, 35, doi:10.1029/2008GL034005
[7] RW Lindsay, J Zhang, A. Schweiger et al, Arctic sea ice retreat in 2007 following thinning trend, J Clim 22, 165-76, 2009
[8] J Zhang, R Lindsay, A. Schweiger, M Steele, The impact of an intense cyclone on 2012 Arctic sea ice retreat, Geophys Res Lett 40, 720-6, 2013
[9] J Zhang, DA Rothrock, Modeling global sea ice with a thickness and enthalpy distribution model in generalized curvilinear coordinates, Mon. Wea. Rev., 131(5), 681-97, 2003
[10] S Liao, H Luo, J Wang et al., An evaluation of Antarctic sea-ice thickness from the Global Ice-Ocean Modeling and Assimilation System based on in situ and satellite observations, The Cryosphere, 16, 1807-19, 2022
[11] J Zhang, private communication, 27 March 2025
[12] Q Shu, Q Wang, M Arthum et al., “Arctic Ocean amplification in a warming climate in CMIP6 models,” Sci. Adv. 8, eabn9755, 2022
[13] J Hansen, M Sato, P Hearty et al., “Ice melt, sea level rise and superstorms: evidence from paleoclimate data, climate modeling, and modern observations that 2 C global warming is highly dangerous,” Atmos Chem Phys 16, 3761-812, 2015. See also the Supplementary Material of reference 2
[14] JE Hansen, M Sato, L Simons et al., “Global warming in the pipeline,” Oxford Open Clim. Chan. 3 (1) (2023): doi.org/10.1093/oxfclm/kgad008
[15] P Bakker, A Schmittner, JTM Lenaerts et al., Fate of the Atlantic Meridional Overturning Circulation: strong decline under continued warming and Greenland melting. Geophy Res Lett; 43, 12252-60, 2016
[16] IPCC. Climate Change 2021: The Physical Science Basis [Masson-Delmotte V, Zhai P, Pirani A et al. (eds)]. Cambridge and New York: Cambridge University Press, 2021
[17] Various data sets are being revised and updated, to be made available at https://www.columbia.edu/~jeh1/Data
[18] K. von Schuckmann, L Cheng, ND Palmer et al., “Heat stored in the Earth system: where does the energy go?” Earth System Science Data 12, 2013-41, 2020
[19] NG Loeb, GC Johnson, TJ Thorsen et al., “Satellite and ocean data reveal marked increase in Earth’s heating rate,” Geophys Res Lett 48, 2021: e2021GL093047

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Norwegian polymath and polar explorer Fridtjof Nansen was no stranger to “impossible” challenges. He led many expeditions to the Arctic, including the first to cross the entire frozen expanse of the Greenland interior, in 1888. Later, he was awarded the Nobel Peace Prize for his humanitarian work in the wake of World War I, providing aid to thousands of refugees, prisoners of war, and victims of the famine in Russia. Nansen’s achievements prove that an “impossible” task is often simply something that’s never been done before. If we have the patience and tenacity to conquer even the most difficult goals, what was previously unimaginable suddenly comes into the realm of possibility.

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Nearly 20 feet below the ground of a field of open tundra in the nation’s northernmost community, an icy world gives a picture of the ancient past and the future of this part of the Arctic.

Embedded in the walls of a tunnel is frozen peat, its features perfectly preserved from 10,000 years ago.

“It’s quite fresh, and it keeps the shape of the moss,” said Go Iwahana, a University of Alaska Fairbanks scientist who descended down a metal ladder to reach a low, 10-meter (32-foot) long tunnel built into the permafrost in the 1960s.

Sloshing below the floor are mobile pools of super-salty and bacteria-packed brine, the remnants of an ancient lagoon that dates back at least 40,000 years and is completely cut off from the Arctic Ocean.

Within the soil, though, the modern world is making its mark. Iwahana, crawling around along the low tunnel, sent probes 1.5 to 2 meters down boreholes to see how the modern world has made its mark. “Three,” he called out after reading a thermometer.

The soil here has warmed over the past decade from minus-6 degrees Celsius to minus-3 , or from 21.6 degrees to 26.6 degrees Fahrenheit, said Iwahana, who works at UAF’s International Arctic Research Center.

“That’s a lot,” he said.

Findings at the tunnel are consistent with those elsewhere on the North Slope. As air temperatures rise, the soils as deep as 20 meters below the surface are warming at a rate of up to 4 degrees Celsius per decade, according to long-term measurements by UAF scientists.

For Utqiagvik, the North Slope’s biggest community and home to nearly half of the North Slope Borough’s residents, the unrelenting warming means trouble.

The most obvious is seen at the places where ice-rich permafrost is closest to the surface: the coastline at Utqiagvik’s downtown core, where a bluff has cleaved dangerously close to the edge of houses. Beneath one abandoned house is a gaping hole where the bluff has completely eroded away. Another house, owned by Doreen Fogg-Leavitt’s mother-in-law, is teetering on the edge.

“I remember 20 years ago, when her backyard to the edge was a good 30 feet, 40 feet. Now it’s about three,” said Fogg-Leavitt, natural resources manager for the Inupiat Community of the Arctic Slope, the local tribal government.

The North Slope has some of the fastest erosion measured in the nation, according to the U.S. Geological Survey, and rates have accelerated. The coastline is losing as much as 9.5 meters a month, according to findings by Williams College researchers presented in mid-December at the annual conference of the American Geophysical Union.

The long-term warming of frozen soil that Iwahana and his UAF colleagues are measuring in the tunnel is just one of the factors that work in combination to erode the coastline.

Another is sea ice loss. More open water – persisting this year into late November – means more opportunities throughout the year for waves to hit the beach and make contact with permafrost bluffs. That causes “niche-erosion block collapse,” said Tom Ravens, a University of Alaska Anchorage civil engineering professor.

There are more subtle factors, too, which Ravens listed at a permafrost workshop held in Anchorage in November. A change in precipitation patterns from snow to rain sends heat from the surface into the soil. The ocean water, aside from bringing soils in contact with heat, also contains salt, another thaw factor. Long-term thawing is causing vast stretches of land to sink, pulling down the coastline along with the rest of the landscape. Measured sinking across the North Slope from 2017 to 2022 averaged 3 centimeters to 5.8 centimeters, depending on location, according to UAF research to be presented at this month’s AGU annual meeting.

Sophisticated revetment to replace sand-filled bags and sand piles

At Utqiagvik, erosion is especially worrisome because of the large size of the community – about 4,500 people – and the large concentration of important infrastructure, including buildings, roads, utilities and, right next to the beach, a landfill.

The North Slope Borough in recent years has piled up masses of sand-filled Supersacks, delivered by barge each summer, to keep the sea’s water away from the most vulnerable resources. Beyond the walls of Supersacks, the borough uses heavy equipment to pile up beach sand into a makeshift barrier.

A more durable fix is on the way.

The U.S. Army Corps of Engineers is putting the final touches on the design for five miles of what’s known as a “revetment” to protect the shoreline. It is a massive project that has been several years in the planning and is expected to take at least six years to complete, said Bruce Sexauer, chief of civil works project management for the Corps of Engineers’ Alaska district.

In the past, Utiqagvik has been able to do a little mix of “managed retreat,” moving some buildings and property away from the disappearing shoreline. But the region is fairly flat, and those options are largely exhausted.

“Now they are at a place where the important infrastructure is right up next to the edge. Their water supply and sewage lagoon are right up against the edge,” Sexauer said. The revetment project is seen as the most practical long-term solution, and Utqiagvik’s position as a service and business hub gives all North Slope communities a stake in it.

“If Utqiagvik suddenly had a catastrophic issue, that would have an effect on the other communities in the area,” Sexauer said.

The full cost of the revetment project is yet to be determined. The 2022 Disaster Relief Supplemental Appropriations Act included a provision that puts $364.3 million into the project.

The Corps expects to formally seek bids this coming summer for the first phase of the project, the 0.75-mile section right at the central bluff, Sexauer said. A request for bids for the rest of the project is expected about a year later. The full project also incorporated a rebuild of Stevenson Street to raise the elevation of the oft-flooded roadway leading north of town toward Point Barrow.

Site-preparation work for the erosion-control project is expected to start in 2024, Sexauer said. 

The revetment design plan is for multiple layers of different material with varying porosity, from industrial fabric to large boulders, to preserve the ground’s cold temperatures, Sexauer said. That type of multilayer technology has proved to be successful, so far, for a much-smaller revetment at the erosion-threatened village of Shishmaref farther south in the Bering Strait region, according to Corps of Engineers’ reports.

It is important that the revetment be more than a simple rock wall, said one expert.

“Even if you build a rock revetment very strong, the permafrost below can degrade,” said Ming Xiao, a Pennsylvania State University civil engineering professor. “You can’t just build on the existing permafrost.”

Xiao is leading a project, with collaborators from UAF and Virginia Tech University, that uses a buried fiber-optic cable to measure the minute movements within the soil of Utqiagvik’s warming permafrost. The hope is that the underground vibrations, when correlated with temperature measurements, can forecast conditions in decades to come. “Then we can predict in the future, say 50 years, what the ground temperature is going to be,” he said. And that, in turn, will give information about whether the ground is too weak to support any structures atop it, he said.

The Supersacks are certainly not up to the erosion-control task, Xiao said. For one thing, he said, they are made of material that degrades when exposed to the sun’s ultraviolet light, something that is unrelenting in summer. For another, the sacks can be punctured in rough weather, “and the wave is going to pick up the Supersasck and put it into the ocean,” he said.

Below-ground threats to pipelines and cellars

Beyond the eroding shoreline, a less-visible thaw problem lies beneath the surface: threats to underground pipes for water and utilities.

About a third of Utqiagvik’s water, wastewater and electrical lines run through a protected, temperature-controlled tunnel called the “Utilidor.” Built in the oil-money heyday of the 1980s, the Utilidor was too expensive to extend beyond its initial 3 miles. That leaves most of the rest of the system with underground piping, and thaw risks lurk even 12 feet below the ground’s surface.

That danger materialized in a different North Slope community in the spring of 2021. In Point Lay, 180 miles southwest of Utqiagvik, a sudden thaw collapse in the permafrost severed a main water line, temporarily cutting off flow of water to the village clinic and to several houses. It was a particularly ill-timed event, as it came during the COVID-19 pandemic, when clean water became a critical need.

Protected as it is, the Utilidor is not impenetrable. Storms in 2015 and 2017 came close to sending water flooding into it, according to the Corps of Engineers. With waves breaking up the seasonally maintained beach berms, seawater also came close to contaminating the freshwater lagoon, the Corps reported. In October, Utqiagvik was slammed by a storm that, though not as serious as the 2015 and 2017 events, pushed saltwater from the sea again over barriers to flood Stevenson Street and enter the lower lagoon; one more breach and seawater would have hit the city’s upper-lagoon drinking water supply.

Permafrost thaw, in combination with storm flooding, is encroaching on some cultural practices, too.

Many of the community’s traditional Inupiat permafrost cellars, known as sigluaqs, have been damaged by flooding or other incursions.

That happened in 2015 to the sigluaq maintained by Fogg-Leavitt’s family. While there was no pooled water in it, the temperatures rose high enough to thaw the meat. It remained edible, she said, but the taste was compromised; the blood ran out during the thaw, meaning it was impossible to create the traditional fermented product.

The thaw threats have prompted some changes in practices, she said. “Some younger crews are using walk-in freezers exclusively,” she said. But others are passionate about keeping their sigluaqs intact and functional. To that end, ICAS is experimenting this winter with technology: installation of thermosyphons, devices that pull heat out of the ground passively. Only a few cellars are to be included in the first phase of the project, but it could be expanded in the future, she said.

“This is what we’re going to do to sustain our culture,” Fogg-Leavitt said. “We’ll see if it works.”

Gravesites and archaeological resources at risk

Thaw effects extend even to the dead.

That is seen at the modern cemetery, where grave markers have tilted as the ground below warmed. It is also seen at the central bluff in town, where remnants of historic homes made of sod and driftwood are crumbling away, and at more remote sites, to more remote coastal area, where sometimes-ancient artifacts and even gravesites are being lost.

Rescuing those sites has been the mission of archaeologist Anne Jensen. Now with Bryn Mawr College, Jensen lived for decades in Utqiagvik and previously worked for the Ukpeaġvik Iñupiat Corp.’s science department.

When the 800-year-old remains of a young girl were uncovered by erosion in 1994, Jensen was on the case; the girl was determined to have been a victim of starvation and numerous chronic diseases. She was named Anaiyaaq, meaning “young girl,” and her body was reburied.

When accelerating erosion was exposing gravesites at Nuvuk, an ancient settlement at Point Barrow, Jensen was also at work to rescue remains; the sites were from a cemetery area with use stretching back about 1,000 years. She has done other work at a well-known archaeological site about 18 miles down the Chukchi Sea coast called Walakpa, which was thought to be stable until about a decade ago, when a fall storm began carving off the once-frozen bluff.

The vulnerable archaeological sites are not just about culture, Jensen said. “Sites are not just culture. They are a frozen tissue archive. Everything in it is preserved.” That includes ancient DNA in both tissues and sediments, stable isotopes and other pieces of information that can be used to reconstruct past conditions, she said.

The places where Jensen has worked represent only a small fraction of the archaeological and cultural sites packed along the coastlines at Utqiagvik and elsewhere on the North Slope. Several have already been lost, such as the 100-year-old Esook Trading Post that was swallowed by the Beaufort Sea in the early 2000s. Many more are likely to wash away before anyone knows what they held, Jensen said.

“There’s not enough money on the planet. It’s either excavate them or write them off,” she said.

This story was first published by Alaska Beacon and is republished here under a Creative Commons license. You can read the original here.

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While orbiting the Earth near the Arctic Ocean at the North Pole between Russia & Canada, the Moon comes so close to the Earth that it looks as though it will collide with the Earth. The Moon completes this cycle in just 30 secs & for 5 secs it covers the Sun before disappearing immediately… one of many wonders of Nature…Enjoy!

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A solstice is an astronomical event that occurs twice each year as the Sun reaches its highest or lowest excursion relative to the celestial equator on the celestial sphere. As a result, on the day of the solstice, the Sun appears to have reached its highest or lowest annual altitude in the sky above the horizon at local solar noon. The word solstice is derived from the Latin sol(sun) and sistere (to stand still), because at the solstices, the Sun stands still in declination; that is, the seasonal movement of the Sun’s path (as seen from Earth) comes to a stop before reversing direction. The solstices, together with the equinoxes, are connected with the seasons. In many cultures the solstices mark either the beginning or the midpoint of winter and summer.

The term solstice can also be used in a broader sense, as the date (day) when this occurs. The day of the solstice is either the longest day of the year (in summer) or the shortest day of the year (in winter) for any place outside of the tropics.

The longest day of 2013 is finally here — but this year, it comes with a twist.

While the solstice in the northern hemisphere traditionally falls on June 21 — and this year it will occur on that date at 1:04 a.m. EDT — it will begin on Thursday, June 20, for parts of the western U.S., according to the website of the Clark Planetarium. The time of the solstice depends upon your position on Earth and, as a consequence, where you are in relation to the sun.

The summer solstice occurs when Earth’s axis is the most tilted toward the sun — the angle is known as “maximum axial tilt.” As a consequence of this specific orientation, the sun rises at its most northeasterly point along the horizon and also sets at its most northwesterly point in the northern hemisphere.

The solstice isn’t the only big celestial event this week. Skywatchers are gearing up for the arrival of the 2013 supermoon, which is set to peak June 22-23 and deliver the biggest, brightest moon of the year.

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