Arctic could become 'ice-free' within a decade

The Arctic could see summer days with practically no sea ice as early as the next couple of years, according to a new study out of the University of Colorado Boulder.

The findings, published March 5 in the journal Nature Reviews Earth & Environment, suggest that the first ice-free day in the Arctic could occur over 10 years earlier than previous projections, which focused on when the region would be ice-free for a month or more. The trend remains consistent under all future emission scenarios.

By mid-century, the Arctic is likely to see an entire month without floating ice during September, when the region's sea ice coverage is at its minimum. At the end of the century, the ice-free season could last several months a year, depending on future emissions scenarios. For example, under a high-emissions, or business-as-usual, scenario, the planet's northernmost region could become consistently ice-free even in some winter months.

For scientists, an ice-free Arctic doesn't mean there would be zero ice in the water.

Instead, researchers say the Arctic is ice-free when the ocean has less than 1 million square kilometers (386,000 square miles) of ice. The threshold represents less than 20% of what the region's seasonal minimum ice cover was in the 1980s. In recent years, the Arctic Ocean had around 3.3 million square kilometers of sea ice area at its minimum in September.

Alexandra Jahn, associate professor of atmospheric and oceanic sciences and fellow at CU Boulder's Institute of Arctic and Alpine Research, set out to analyze existing literature on sea ice projections. She and her collaborators also analyzed sea ice coverage data from computational climate models to assess how the Arctic might change daily in the future.

They found that the first day when sea ice coverage dips below the 1-square-kilometer threshold would occur on average four years earlier than the monthly averages, but could occur up to 18 years earlier.

"When it comes to communicating what scientists expect to happen in the Arctic, it is important to predict when we might observe the first ice-free conditions in the Arctic, which will show up in the daily satellite data," Jahn said.

The team projected the Arctic Ocean could become ice-free for the first time on a late August or early September day between the 2020s to 2030s under all emissions scenarios.

Jahn said greenhouse gas emissions are the main contributors to sea ice loss. A decrease in snow and ice cover increases the amount of heat from sunlight absorbed by the ocean, exacerbating ice melt and warming in the Arctic.

Sea ice declines have significant impacts on Arctic animals that rely on sea ice for survival, including seals and polar bears. In addition, as the ocean warms up, researchers are concerned that non-native fish could move into the Arctic Ocean. The impact of these invasive species on local ecosystems remains unclear.

Sea ice loss also poses a risk to the communities living near the coastal region. Sea ice plays a significant role in buffering the impacts of ocean waves on the coastal land, Jahn said. As sea ice retreats, ocean waves would get bigger, causing coastal erosion.

While an ice-free Arctic is inevitable, Jahn said future emissions levels will still determine how often the conditions occur. Under an intermediate emissions scenario, a path the current society is on, the Arctic might become ice-free only during late summer and early fall from August to October. But under the highest emissions scenario, the Arctic could be ice-free for up to nine months by late this century.

"This would transform the Arctic into a completely different environment, from a white summer Arctic to a blue Arctic. So even if ice-free conditions are unavoidable, we still need to keep our emissions as low as possible to avoid prolonged ice-free conditions," Jahn said.

The good news: Arctic sea ice is resilient and can return quickly if the atmosphere cools down.

Read more at Science Daily

Frequent marine heatwaves in the Arctic Ocean will be the norm

Marine heatwaves will become a regular occurrence in the Arctic in the near future and are a product of higher anthropogenic greenhouse-gas emissions -- as shown in a study just released by Dr. Armineh Barkhordarian from Universität Hamburg's Cluster of Excellence for climate research CLICCS.

Since 2007, conditions in the Arctic have shifted, as confirmed by data recently published in the journal Nature Communications Earth & Environment. Between 2007 and 2021, the marginal zones of the Arctic Ocean experienced 11 marine heatwaves, producing an average temperature rise of 2.2 degrees Celsius above seasonal norm and lasting an average of 37 days.

Since 2015, there have been Arctic marine heatwaves every year.

The most powerful heatwave to date in the Arctic Ocean was in 2020; it continued for 103 days, with peak temperatures intensity that were four degrees Celsius over the long-term average.

The probability of such a heatwave occurring without the influence of anthropogenic greenhouse gases is less than one percent, as calculated by Barkhordarian's team at the Cluster of Excellence CLICCS.

By doing so, they have narrowed down the number of plausible climate scenarios in the Arctic.

According to the study, annual marine heatwaves will be the norm.

The Arctic entered a new phase

In the study, Barkhordarian also proves for the first time that heatwaves are produced when sea ice melts early and rapidly after the winter.

When this happens, considerable heat energy can accumulate in the water by the time maximum solar radiation is reached in July.

"In 2007, a new phase began in the Arctic," says Barkhordarian, an expert on climate statistics.

"There is less and less of the thicker, several-year-old ice, while the percentage of thin, seasonal ice is consistently increasing." However, the thin ice is less durable and melts more quickly, allowing incoming solar radiation to warm the water's surface.

Officially, it is considered to be a marine heatwave when temperatures at the water's surface are higher than 95 percent of the values from the past 30 years for at least five consecutive days.

"Not just the constant loss of sea ice but also warmer waters can have dramatic negative effects on the Arctic ecosystem," says Barkhordarian.

Food chains could collapse, fish stocks could be reduced, and overall biodiversity could decline.

Read more at Science Daily

Arctic cold snap transforms into a blessing

A recent cold spell plunged the nation of Korea into a deep freeze, resulting in the closure of 247 national parks, the cancellation of 14 domestic flights, and the scrapping of 107 cruise ship voyages. While the cold snap brought relief by significantly reducing the prevalence of particulate matter obscuring our surroundings, a recent study indicates that, besides diminishing particulate matter, it is significantly contributing to the heightened uptake of carbon dioxide by the East Sea.

According to research conducted by a team of researchers including Professor Kitack Lee from the Division of Environmental Science & Engineering at Pohang University of Science and Technology (POSTECH), and Professor Tongsup Lee and So-Yun Kim from the Department of Oceanography at Pusan National University, the cold atmosphere in the Arctic is influencing the absorption of carbon dioxide by the East Sea.

The research findings were published in Geophysical Research Letters, an international journal by the American Geophysical Union (AGU).

The research team investigated the correlation between the East Sea's surface-deep circulation and its carbon dioxide absorption capacity, drawing insights from observations in 1992, 1999, 2007, and 2019.

During the initial period (1992-1999), the ocean absorbed 20 million tons of carbon dioxide annually.

In the subsequent period (1999-2007), this amount decreased to under 10 million tons per year.

However, in the final period (2007-2019), the carbon dioxide uptake surged to 30 million tons per year.

The team observed that the internal circulation along the East Coast within the East Sea was influenced by the Arctic cold wave.

Cold air from the Arctic infiltrates the East Sea, causing the surface water, laden with carbon dioxide, to become denser.

This process induces vertical ventilation as the water descends into the middle and deep ocean layers.

Consequently, the intensified descent of cold air from the Arctic strengthens the internal circulation, leading to a heightened uptake of carbon dioxide in the East Sea.

Professor Kitack Lee who led the research remarked, " The oceans represent an immense reservoir of carbon dioxide and offer a secure and sustainable avenue for mitigating atmospheric carbon dioxide levels." He further stated, "It is crucial to anticipate the global ocean's capacity for carbon removal as we navigate future climate changes and identify suitable methods to leverage this potential."

In a related development, the team's earlier research uncovered the mechanism through which the ocean absorbs carbon dioxide.

Approximately half of the carbon dioxide generated by human activities remains in the atmosphere with the other half entering marine and terrestrial ecosystems.

With a carbon content 400,000 times greater than that of the atmosphere, the oceans present vast and promising potential for storing carbon dioxide.

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Unprecedented look at what influences sea ice motion in the Arctic

A new study led by researchers at Brown offers fresh insights into the forces above and beneath the ocean surface that influence how sea ice moves and disperses in the Arctic Ocean, which is warming at over twice the rate of the global average.

The in-depth analysis reveals how local tidal currents strongly affect the movement of the ice along its journey and provides an unprecedented look at how the makeup of the seafloor is causing some of the most abrupt changes.

Data from the study can be applied to improve complex computer simulations used for forecasting Arctic sea ice conditions, and in the long-term, the results may help clarify how climate change is altering the Arctic and inform future climate predictions.

"The ice is clearly feeling the influence of the bottom of the ocean," said Daniel Watkins, a postdoctoral researcher at Brown and lead author of the new study published in Geophysical Research Letters. "The landscape at the ocean floor, like canyons and continental shelves, affects tides and other ocean currents. And as it drifts, the sea ice passes over many different undersea features. We see sharp changes in the dynamics of the sea ice as soon as it gets to those undersea features."

Using data from largest ever drifting sea-ice buoy array, along with 20 years of satellite images, the researchers examined sea ice motion as it drifted from the Arctic Ocean through a deep-water passage called the Fram Strait and eventually into the Greenland Sea. The analysis revealed the seafloor's impact on some of the most abrupt changes affecting the sea ice, like dramatic gains in speed or motions that force the ice to pack in close together or even break apart.

"What we see with this dataset is a transition from the central Arctic, where the ice is mostly moving as a whole and following wind patterns, to areas where we're seeing much stronger impacts of ocean currents," Watkins said.

The Arctic is the fastest warming part of the globe and it has long been understood that sea ice in the region plays an important role in the planet's climate. For instance, the ice acts like a reflective surface deflecting how much sunlight is absorbed by the Earth. As it disappears, more sunlight is absorbed, leading to a warmer planet. Many scientists also expect that as Arctic ice vanishes, weather across the Northern Hemisphere will be impacted, producing periods of bitter cold, punishing heat waves and disastrous floods.

With the study, the researchers wanted to delve deeper into the changes happening in this critically important part of the Earth. Much of the data for the study was gathered during the largest polar expedition in history -- the Multidisciplinary drifting Observatory for the Study of Arctic Climate.

Comprehensive research reveals sudden increases in ice speed

During the expedition, teams of researchers took turns spending a year drifting with the sea ice aboard a massive German icebreaker in the Arctic Ocean. Watkins was there for two weeks in October 2019 to help install a network of autonomous sensors around the base camp. While there, Watkins coordinated helicopter flights to remote patches of sea ice, worked with analysts to find suitable sites for instruments and buoys and deployed them on the ice.

Throughout the year-long expedition, a total of 214 buoys were deployed, including 51 during Watkins' tenure on the expedition. The study is based on GPS data transmitted from a set of 108 of the buoys that drifted from the central Arctic through the Fram Strait and into the Greenland Sea.

The major focus was on what are known as marginal ice zones in the Greenland Sea and Fram Strait, which is the transition zone between the open, ice-free ocean and the pack ice of the central arctic.

As part of their analysis, the group also analyzed satellite measurements taken from 2003 to 2020 to put the data the buoys gathered over the year adrift into historical context. The satellite data helped confirm sharp changes in ice velocity and ice motion that could only be explained by the seafloor's influence on the sea ice.

For instance, looking at the data from an area northeast of Svalbard, Norway, the researchers noticed the speed of the ice suddenly increased even though the wind hadn't changed. That meant the ice was getting pushed by the ocean currents, so the team delved deeper to find where this happens and how. They found that the sea ice speeds up where the Transpolar Drift Stream, one of the Arctic's Ocean major currents, ends and the fast-moving East Greenland Current, which forms due to a combination of the Earth's rotation and the edge of the continental shelf on the seafloor, begins. The analysis shows how the sea ice responds to different ocean currents and that the sea floor plays a role.

"In the beginning of this journey, there was almost no difference in the drift speed across the whole set of buoys," Watkins said. "Then there's essentially one day where the wind died down and the ice ran into the that boundary current and it just took off. It was like a one-day-to-the-next change in what was pushing the ice."

As next steps, the researchers plan to work with model developers to help implement the data from the study into forecasts of how the ice will move and where it will end up. They also plan to further develop an ice floe tracking tool to track the motion of individual pieces of ice. The tool would help researchers see details of ice motion that are invisible to standard approaches.

"We're hoping to understand the changing ice physics in a warming Arctic and use it to help make our models of those physics better," Watkins said.

Read more at Science Daily

Legacy industrial contamination in the Arctic permafrost

Many of us picture the Arctic as largely untouched wilderness. But that has long-since ceased to be true for all of the continent. It is also home to oilfields and pipelines, mines and various other industrial activities. The corresponding facilities were built on a foundation once considered to be particularly stable and reliable: permafrost. This unique type of soil, which can be found in large expanses of the Northern Hemisphere, only thaws at the surface in summer. The remainder, extending up to hundreds of metres down, remains frozen year-round.

Accordingly, permafrost has not only been viewed as a solid platform for buildings and infrastructure. "Traditionally, it's also been considered a natural barrier that prevents the spread of pollutants," explains Moritz Langer from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI). "Consequently, industrial waste from defunct or active facilities was often simply left on-site, instead of investing the considerable effort and expense needed to remove it." As a result of the industrial expansion during the cold war, over the decades this led to micro-dumps full of toxic sludge from oil and gas exploration, stockpiles of mining debris, abandoned military installations, and lakes in which pollutants were intentionally poured. "In many cases, the assumption was that the permafrost would reliably and permanently seal off these toxic substances, which meant there was no need for costly disposal efforts," says Guido Grosse, who heads the AWI's Permafrost Research Section. "Today, this industrial legacy still lies buried in the permafrost or on its surface. The substances involved range from toxic diesel fuel to heavy metals and even radioactive waste."

But as climate change progresses, this "sleeping giant" could soon become an acute threat: since the permafrost regions are warming between twice as fast and four times as fast as the rest of the world, the frozen soil is increasingly thawing. When this happens, it changes the hydrology of the region in question, and the permafrost no longer provides an effective barrier. As a result, contaminants that have accumulated in the Arctic over decades can be released, spreading across larger regions.

In addition, thawing permafrost becomes more and more unstable, which can lead to further contamination. When the ground collapses, it can damage pipelines, chemical stockpiles and depots. Just how real this risk already is can be seen in a major incident from May 2020 near the industrial city Norilsk in northern Siberia: a destabilized storage tank released 17,000 metric tons of diesel, which polluted the surrounding rivers, lakes and tundra. According to Langer: "Incidents like this could easily become more frequent in the future."

In order to more accurately assess such risks, he and an international team of experts from Germany, the Netherlands and Norway took a closer look at industrial activities in the High North. To do so, they first analysed freely available data from the portal OpenStreetMap and from the Atlas of Population, Society and Economy in the Arctic. According to these sources, the Arctic permafrost regions contain ca. 4,500 industrial sites that either store or use potentially hazardous substances.

"But this alone didn't tell us what types of facilities they were, or how badly they could potentially pollute the environment," says Langer. More detailed information on contaminated sites is currently only available for North America, where roughly 40 percent of the global permafrost lies. The data from Canada and Alaska showed that, using the location and type of facility, it should be possible to accurately estimate where hazardous substances were most likely to be found.

For Alaska, the Contaminated Sites Program also offers insights into the respective types of contaminants. For example, roughly half of the contaminations listed can be attributed to fuels like diesel, kerosene and petrol. Mercury, lead and arsenic are also in the top 20 documented environmental pollutants. And the problem isn't limited to the legacy of past decades: although the number of newly registered contaminated sites in the northernmost state of the USA declined from ca. 90 in 1992 to 38 in 2019, the number of affected sites continues to rise.

There are no comparable databases for Siberia's extensive permafrost regions. "As such, our only option there was to analyse reports on environmental problems that were published in the Russian media or other freely accessible sources between 2000 and 2020," says Langer. "But the somewhat sparse information available indicates that industrial facilities and contaminated sites are also closely linked in Russia's permafrost regions."

Using computer models, the team calculated the occurrence of contaminated sites for the Arctic as a whole. According to the results, the 4,500 industrial facilities in the permafrost regions have most likely produced between 13,000 and 20,000 contaminated sites. 3,500 to 5,200 of them are located in regions where the permafrost is still stable, but will start to thaw before the end of the century. "But without more extensive data, these findings should be considered a rather conservative estimate," Langer emphasises. "The true scale of the problem could be even greater."

Making matters worse, the interest in pursuing commercial activities in the Arctic continues to grow. As a result, more and more industrial facilities are being constructed, which could also release toxic substances into nearby ecosystems. Further, this is happening at a time when removing such environmental hazards is getting harder and harder -- after all, doing so often requires vehicles and heavy gear, which can hardly be used on vulnerable tundra soils that are increasingly affected by thaw.

Read more at Science Daily

Arctic climate modelling too conservative

Climate models used by the UN's IPCC and others to project climate change are not accurately reflecting what the Arctic's future will be. Researchers at the University of Gothenburg argue that the rate of warming will be much faster than projected.

Due to the Arctic´s sea ice cover and its harsh climate, relatively few observations are made in that part of world. This means that the climate models used for projecting the future of the Arctic have not been calibrated to the same extent there as in other parts of the world.

Two recent scientific studies involving researchers from the University of Gothenburg compared the results of the climate models with actual observations. They concluded that the warming of the Arctic Ocean will proceed at a much faster rate than projected by the climate models.

Climate models underestimate the consequences

"These climate models underestimate the consequences of climate change. In reality, the relatively warm waters in the Arctic regions are even warmer, and closer to the sea ice. Consequently, we believe that the Arctic sea ice will melt away faster than projected," explains Céline Heuzé, climatologist at the University of Gothenburg and lead author of one of the studies.

Warm water flows into the Arctic Ocean via Fram Strait between Greenland and Svalbard. However, the volume of water in these ocean currents and its temperature in the climate models are too low, which is one of the reasons why the climate models' projections will not be accurate. Even the stratification of the Arctic Ocean is incorrect. The researchers argue that since roughly half of the models project an increase and the other half a decrease in stratification, the consequences of global warming cannot be estimated accurately.

Acquiring hard data in the Arctic must be prioritised

"This is a serious situation. If governments and organisations all over the world are going to rely on these climate models, they must be improved. Which is why research and data acquisition in the Arctic ocean must be prioritised. At present, we cannot provide a useful prediction of how quickly the Arctic sea ice is melting," Céline Heuzé explains.

The Arctic is an important region for projecting what the future intensity of global warming will be. Its sea ice contributes an albedo effect -- a white surface that reflects sunlight away from the planet. If the ice were to disappear, more solar radiation would reach the Earth.

Read more at Science Daily

On a warming planet, these Arctic geese rapidly found (and shared) a new migratory route

As the planet warms, animals that breed in the Arctic are at particular risk. But a new study reported in Current Biology on March 1 offers some encouraging news: in an apparent reaction to pressures along their former migratory route, a population of Arctic geese has rapidly adjusted, forming a new migration route and breeding location almost 1,000 kilometers from their original stomping grounds.

What's more, it appears the new route has caught on with other geese and even birds of other species via cultural transmission (social learning). As such, the new population already has grown to as many as 4,000 individuals.

"It is extremely fascinating to witness such rapid evolution of new breeding grounds and migratory route by a bird species that is regarded as being very traditional in its behavior and site use," said Jesper Madsen of Aarhus University in Denmark. "It gives some hope for 'ecological rescue' at times of very radical environmental changes due to climate change and, more broadly, global change."

"We observe a new distinct population of birds in the making in real time," he added. "This is very rare to observe. The speed of the development is astonishing."

Madsen's team has been studying Norway's Svalbard population of pink-footed geese for more than 35 years. They've kept tabs on their population size and demographic variables, using a systematic marking and resighting program. About 20 years ago, they started getting reports of geese turning up on migration in Sweden and Finland, which were confirmed as members of the Svalbard population.

To learn more, Madsen went to Oulu, Finland, in the spring of 2018 and 2019 with his goose-catching team from Denmark as well as Dutch and Finnish partners. Their hope was to catch and tag some pink-footed geese with GPS tags. They wanted to know where these geese were going, and they got an unexpected answer.

"It was a real surprise to see that half of the marked individuals in Oulu migrated northeast to Novaya Zemlya in north Russia," Madsen says. "From the tagging information we could not only follow their new path but also got indications that females were breeding there. This site is around 1,000 kilometers east of the Svalbard breeding grounds.

"It was also cool to observe that geese from the traditional flyway have turned up on the new route and seemed to have switched. Hence, social learning and following individuals from the new route has been an important phenomenon, which also explains how this development could be so fast."

With their new report, they've now documented an abrupt formation of a new migration route and population for the Arctic geese over the course of 10 to 15 years. The population has grown over time due to successful breeding and high survival rates combined with continued immigration of geese from the old route to the new one.

Their ability to live in Novaya Zemlya has apparently been aided by warming in the area, they say. While the new population is not genetically or demographically isolated yet, they note that it already now qualifies as a separate population.

The new route does have some disadvantages, Madsen says. For instance, it's longer. But they suspect the benefits of the new route and grounds outweigh any downsides. The findings in geese show the importance of social learning on a changing planet, Madsen notes, especially in social animals including birds but perhaps also hoofed ungulates, wolves, and whales.

"At this time, when climate change and other human activities threaten many species, not least the Arctic ones, social learning can be a behavior that can provide advantages to avoid some negative impacts, at least in the short term," Madsen says.

The researchers say they hope one day to observe the geese in their new breeding grounds in Russia. For now, they'll keep an eye on the future development of the new population using GPS-tracking devices and remote sensing of the new environment.

Read more at Science Daily

Caribou have been using same Arctic calving grounds for 3,000 years

Caribou have been using the same Arctic calving grounds for more than 3,000 years, according to a new study by the University of Cincinnati.

Female caribou shed their antlers within days of giving birth, leaving behind a record of their annual travels across Alaska and Canada's Yukon that persists on the cold tundra for hundreds or even thousands of years. Researchers recovered antlers that have sat undisturbed on the arctic tundra since the Bronze Age.

"To walk around the landscape and pick up something that's 3,000 years old is truly amazing," said Joshua Miller, an assistant professor of geosciences at the University of Cincinnati.

He has been leading summer expeditions to the Arctic National Wildlife Refuge since 2010, using rafts to navigate remote rivers to search for caribou antlers exposed on the tundra.

"We think about having to dig down into the soil to find that kind of ecological history, but on the Coastal Plain, the vegetation grows extremely slowly," Miller said. "Bones dropped by animals that lived dozens or even hundreds of generations in the past can provide really meaningful information."

The study demonstrates how important the area is for an animal that native Alaskans and Candians still depend on for sustenance, even as energy companies seek to exploit oil and gas resources in this protected area.

The Biden Administration in 2021 suspended drilling leases in the Arctic National Wildlife Refuge, the largest tract of undeveloped wilderness in the United States.

"We know this region of the Arctic National Wildlife Refuge has been an important area for caribou for millennia," Miller said. "That should give us pause on how we think about those landscapes."

The study was published in the journal Frontiers in Ecology and Evolution.

Barren ground caribou undertake nature's longest overland migration, traveling as far as 800 miles each year to reach their spring calving grounds in the Arctic National Wildlife Refuge and Canada's Ivvavik National Park. The largest herd in this area, named for the Porcupine River, numbers in the hundreds of thousands of animals.

Scientists think caribou use these areas because they have fewer predators and offer seasonal vegetation near places where they can avoid the worst of the mosquitoes.

"The mosquitoes are horrible," Miller said. "You get swarmed -- literally covered in them. They can do significant damage to a young calf."

Whatever the reason, the antlers they leave behind provide a physical record of their epic yearly travels that researchers can unlock through isotopic analysis.

Caribou antlers, like those of elk, deer and moose, are made of fast-growing bone that the animals shed each year and regrow the following year.

"It is amazing to think that the oldest of the antlers found in our study were growing approximately the same time Homer was penning 'the Iliad' and 'the Odyssey,'" study co-author Patrick Druckenmiller said.

He is director of the University of Alaska Museum and professor of the Department of Geology and Geophysics at the University of Alaska Fairbanks. Eric Wald from the U.S. Fish and Wildlife Service also co-authored the study.

The antler surveys in the vast expanse of the Arctic refuge require meticulous logistical planning, Miller said. Small planes deposit researchers and their gear deep in the interior, where they have to be watchful for grizzly and polar bears. They pilot rafts to the Beaufort Sea, conducting a grid search of suitable caribou habitat identified in advance using aerial photography.

"We search for antlers along old river terraces, walking back and forth, covering every inch of habitat to find those ancient treasures," Miller said.

While male caribou antlers span four feet and weigh more than 20 pounds, female caribou antlers are much smaller. The antlers contain nutrients such as phosphorus and calcium that are important to plants and animals.

The dropped antlers create "nutrient sinks," which could have a profound effect on the area's vegetation. Miller said the caribou's migration serves as a nutrient "conveyor belt" that might even draw caribou back to reap the benefits of this fertilizer in a reinforcement loop.

Caribou and other mammals are known to chew on dropped antlers for their valuable minerals. This could be an important dietary supplement for new caribou moms.

"We'd like to know to what degree this conveyor belt influences why caribou are going there in the first place," Miller said. The study was supported by the U.S. Fish and Wildlife Service, the National Geographic Society, the National Science Foundation, the Wildlife Society and the UC Office of Research.

Miller said the Arctic is warming faster than other parts of the globe. Parts of the Arctic that were once barren tundra are sprouting new spruce forests.

Read more at Science Daily

Arctic carbon conveyor belt discovered

Every year, the cross-shelf transport of carbon-rich particles from the Barents and Kara Seas could bind up to 3.6 million metric tons of CO2 in the Arctic deep sea for millennia. In this region alone, a previously unknown transport route uses the biological carbon pump and ocean currents to absorb atmospheric CO2 on the scale of Iceland's total annual emissions, as researchers from the Alfred Wegener Institute and partner institutes report in the current issue of the journal Nature Geoscience.

Compared to other oceans, the biological productivity of the central Arctic Ocean is limited, since sunlight is often in short supply -- either due to the Polar Night or to sea-ice cover -- and the available nutrient sources are scarce. Consequently, microalgae (phytoplankton) in the upper water layers have access to less energy than their counterparts in other waters. As such, the surprise was great when, on the expedition ARCTIC2018 in August and September 2018 on board the Russian research vessel Akademik Tryoshnikov, large quantities of particulate -- i.e., stored in plant remains -- carbon were discovered in the Nansen Basin of the central Arctic. Subsequent analyses revealed a body of water with large amounts of particulate carbon to depths of up to two kilometres, composed of bottom water from the Barents Sea. The latter is produced when sea ice forms in winter, then cold and heavy water sinks, and subsequently flows from the shallow coastal shelf down the continental slope and into the deep Artic Basin.

"Based on our measurements, we calculated that through this water-mass transport, more than 2,000 metric tons of carbon flow into the Arctic deep sea per day, the equivalent of 8,500 metric tons of atmospheric CO2. Extrapolated to the total annual amount revealed even 13.6 million metric tons of CO2, which is on the same scale as Iceland's total annual emissions," explains Dr Andreas Rogge, first author of the Nature Geoscience study and an oceanographer at the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI). This plume of carbon-rich water spans from the Barents- and Kara Sea shelf to roughly 1,000 kilometres into the Arctic Basin. In light of this newly discovered mechanism, the Barents Sea -- already known to be the most productive marginal sea in the Arctic -- would appear to effectively remove roughly 30 percent more carbon from the atmosphere than previously believed. Moreover, model-based simulations determined that the outflow manifests in seasonal pulses, since in the Arctic's coastal seas, the absorption of CO2 by phytoplankton only takes place in summer.

Understanding transport and transformation processes within the carbon cycle is essential to creating global carbon dioxide budgets and therefore also projections for global warming. On the ocean's surface, single-celled algae absorb CO2 from the atmosphere and sink towards the deep sea when aged out. Once carbon bound in this manner reaches the deep water, it stays there until overturning currents bring the water back to the ocean's surface, which takes several thousand years in the Arctic. And if the carbon is deposited in deep-sea sediments, it can even be trapped there for millions of years, as only volcanic activity can release it. This process, also known as the biological carbon pump, can remove carbon from the atmosphere for long periods of time and represents a vital sink in our planet's carbon cycle. The process also represents a food source for the local deep sea fauna like sea stars, sponges and worms. What percentage of the carbon is actually absorbed by the ecosystem is something only further research can tell us.

Read more at Science Daily

Refreezing poles feasible and cheap, new study finds

The poles are warming several times faster than the global average, causing record smashing heatwaves that were reported earlier this year in both the Arctic and Antarctic. Melting ice and collapsing glaciers at high latitudes would accelerate sea level rise around the planet. Fortunately, refreezing the poles by reducing incoming sunlight would be both feasible and remarkably cheap, according to new research published today in IOP Publishing's Environmental Research Communications.

Scientists laid out a possible future program whereby high-flying jets would spray microscopic aerosol particles into the atmosphere at latitudes of 60 degrees north and south -- roughly Anchorage and the southern tip of Patagonia. If injected at a height of 43,000 feet (above airliner cruising altitudes), these aerosols would slowly drift poleward, slightly shading the surface beneath. "There is widespread and sensible trepidation about deploying aerosols to cool the planet," notes lead author Wake Smith, "but if the risk/benefit equation were to pay off anywhere, it would be at the poles."

Particle injections would be performed seasonally in the long days of the local spring and early summer. The same fleet of jets could service both hemispheres, ferrying to the opposite pole with the change of seasons.

Pre-existing military air-to-air refuelling tankers such as the aged KC-135 and the A330 MMRT don't have enough payload at the required altitudes, whereas newly designed high-altitude tankers would prove much more efficient. A fleet of roughly 125 such tankers could loft a payload sufficient to cool the regions poleward of 60°N/S by 2°C per year, which would return them close to their pre-industrial average temperatures. Costs are estimated at $11 billion annually -- less than one-third the cost of cooling the entire planet by the same 2°C magnitude and a tiny fraction of the cost of reaching net zero emissions.

"Game changing though this could be in a rapidly warming world, stratospheric aerosol injections merely treat a symptom of climate change but not the underlying disease. It's aspirin, not penicillin. It's not a substitute for decarbonization," says Smith.

Cooling at the poles would provide direct protection for only a small fraction of the planet, though the mid-latitudes should also experience some temperature reduction. Since less than 1% of the global human population lives in the target deployment zones, a polar deployment would entail much less direct risk to most of humanity than a global program. "Nonetheless, any intentional turning of the global thermostat would be of common interest to all of humanity and not merely the province of Arctic and Patagonian nations," adds Smith.

Read more at Science Daily

Ozone depletion over North Pole produces weather anomalies

Many people are familiar with the hole in the ozone layer over Antarctica, but what is less well known is that occasionally, the protective ozone in the stratosphere over the Arctic is destroyed as well, thinning the ozone layer there. This last happened in the spring months of 2020, and before that, in the spring of 2011.

Each time the ozone layer has been thinned out, climate researchers subsequently observed weather anomalies across the entire northern hemisphere. In central and northern Europe, Russia and especially in Siberia, those spring seasons were exceptionally warm and dry. In other areas, such as polar regions, however, wet conditions prevailed. These weather anomalies were particularly pronounced in 2020. Switzerland was also unusually warm and dry that spring.

Whether there is a causal relationship between stratospheric ozone destruction and the observed weather anomalies is a matter of debate in climate research. The polar vortex in the stratosphere, which forms in winter and decays in spring, also plays a role. Scientists who have studied the phenomenon so far have arrived at contradictory results and different conclusions.

New findings are now shedding light on the situation, thanks to doctoral student Marina Friedel and Swiss National Science Foundation Ambizione Fellow Gabriel Chiodo. Both are members of the group headed by Thomas Peter, Professor of Atmospheric Chemistry at ETH Zurich, and are collaborating with Princeton University and other institutions.

Simulations reveal correlation

To uncover a possible causal relationship, the researchers ran simulations that integrated ozone depletion into two different climate models. Most climate models consider only physical factors, not variations in stratospheric ozone levels, in part because this would require much more computing power.

But the new calculations make it clear: the cause of the weather anomalies observed in the northern hemisphere in 2011 and 2020 is mostly ozone depletion over the Arctic. The simulations the researchers ran with the two models largely coincided with observational data from those two years, as well as eight other such events that were used for comparison purposes. However, when the scientists "turned off" ozone destruction in the models, they could not reproduce those results.

"What surprised us most from a scientific point of view is that, even though the models we were using for the simulation are utterly different, they produced similar results," says co-author Gabriel Chiodo, SNSF Ambizione Fellow at the Institute for Atmospheric and Climate Science.

The mechanism explained

The phenomenon as the researchers have now studied it begins with ozone depletion in the stratosphere. For ozone to be broken down there, temperatures in the Arctic must be very low. "Ozone destruction occurs only when it is cold enough and the polar vortex is strong in the stratosphere, about 30 to 50 kilometres above the ground," Friedel points out.

Normally, ozone absorbs UV radiation emitted by the sun, thereby warming the stratosphere and helping to break down the polar vortex in spring. But if there is less ozone, the stratosphere cools and the vortex becomes stronger. "A strong polar vortex then produces the effects observed at the Earth's surface," Chiodo says. Ozone thus plays a major role in temperature and circulation changes around the North Pole.

Greater accuracy possible for long-term forecasts

The new findings could help climate researchers make more accurate seasonal weather and climate forecasts in future. This allows for better prediction of heat and temperature changes, "which is important for agriculture," Chiodo says.

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Siberian tundra could virtually disappear by mid-millennium

Due to global warming, temperatures in the Arctic are climbing rapidly. As a result, the treeline for Siberian larch forests is steadily advancing to the north, gradually supplanting the broad expanses of tundra which are home to a unique mix of flora and fauna. Experts from the Alfred Wegener Institute have now prepared a computer simulation of how these woods could spread in the future, at the tundra's expense. Their conclusion: only consistent climate protection measures will allow roughly 30 percent of the Siberian tundra to survive to mid-millennium. In all other, less favourable scenarios, the unique habitat is projected to disappear entirely. The study was just released in the journal eLife.

The climate crisis can especially be felt in the Arctic: in the High North, the average air temperature has risen by more than two degrees Celsius over the past 50 years -- far more than anywhere else. And this trend will only continue. If ambitious greenhouse-gas reduction measures (Emissions Scenario RCP 2.6) are taken, the further warming of the Arctic through the end of the century could be limited to just below two degrees. According to model-based forecasts, if the emissions remain high (Scenario RCP 8.5), we could see a dramatic rise in the average summer temperatures in the Arctic -- by up to 14 degrees Celsius over today's norm by 2100.

"For the Arctic Ocean and the sea ice, the current and future warming will have serious consequences," says Prof Ulrike Herzschuh, Head of the Polar Terrestrial Environmental Systems Division at the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI). "But the environment on land will also change drastically. The broad expanses of tundra in Siberia and North America will be massively reduced, as the treeline, which is already slowly changing, rapidly advances northward in the near future. In the worst-case scenario, there will be virtually no tundra left by the middle of the millennium. In the course of our study, we simulated this process for the tundra in northeast Russia. The central question that concerned us was: which emissions path does humanity have to follow in order to preserve the tundra as a refuge for flora and fauna, as well its role for the cultures of indigenous peoples and their traditional ties to the environment?"

The tundra is home to a unique community of plants, roughly five percent of which are endemic, i.e., can only be found in the Arctic. Typical species include the mountain avens, Arctic poppy and prostrate shrubs like willows and birches, all of which have adapted to the harsh local conditions: brief summers and long, arduous winters. It also offers a home for rare species like reindeer, lemmings and insects like the Arctic bumblebee.

For their simulation, Ulrike Herzschuh and AWI modeller Dr Stefan Kruse employed the AWI vegetation model LAVESI. "What sets LAVESI apart is that it allows us to display the entire treeline at the level of individual trees," Kruse explains. "The model portrays the entire lifecycle of Siberian larches in the transition zone to the tundra -- from seed production and distribution, to germination, to fully grown trees. In this way, we can very realistically depict the advancing treeline in a warming climate."

The findings speak for themselves: the larch forests could spread northward at a rate of up to 30 kilometres per decade. The tundra expanses, which can't shift to colder regions due to the adjacent Arctic Ocean, would increasingly dwindle. Since trees aren't mobile and each one's seeds can only reach a limited distribution radius, initially the vegetation would significantly lag behind the warming, but then catch up to it again. In the majority of scenarios, by mid-millennium less than six percent of today's tundra would remain; saving roughly 30 percent would only be possible with the aid of ambitious greenhouse-gas reduction measures. Otherwise, Siberia's once 4,000-kilometre-long, unbroken tundra belt would shrink to two patches, 2,500 kilometres apart, on the Taimyr Peninsula to the west and Chukotka Peninsula to the east. Interestingly, even if the atmosphere cooled again in the course of the millennium, the forests would not completely release the former tundra areas.

Read more at Science Daily