Spring is arriving earlier, but how much earlier? The answer depends on where on Earth you find yourself, according to a study led by the University of California, Davis.

Spring is springing earlier at northern latitudes, such as in Greenland, than it is at lower latitudes [Credit: Eric Post/UC Davis]

The study, published in Nature’s online journal Scientific Reports, found that for every 10 degrees north from the equator you move, spring arrives about four days earlier than it did a decade ago. This northward increase in the rate of springtime advance is roughly three times greater than what previous studies have indicated.

For example, at southern to mid latitudes such as Los Angeles, New Orleans or Dallas, the study suggests spring might be arriving a mere one day earlier than it did a decade ago. Farther north, in Seattle, Chicago or Washington D.C., it might be arriving four days earlier. And if you live in the Arctic, it might be arriving as much as 16 days earlier.

“This study verifies observations that have been circulating in the scientific community and popular reports for years,” said lead author Eric Post, a fellow of the John Muir Institute and polar ecologist in the UC Davis Department of Wildlife, Fish and Conservation Biology. “Yes, spring is arriving earlier, and the Arctic is experiencing greater advances of spring than lower latitudes. What our study adds is that we connect such differences to more rapid springtime warming at higher latitudes.”

Cottongrass blows in the Greenland wind [Credit: Eric Post/UC Davis]

Accelerated spring 
                                         
The study is the most comprehensive analysis to date of springtime advance, or phenology, as you move north with latitude. Such signs include birds migrating, flowers blooming, amphibians calling and the emergence of leaves.

The researchers analyzed 743 previously published estimates of the rate of springtime advance from studies spanning 86 years across the Northern Hemisphere, as well as rates of springtime warming over the same range of years and latitude. Even after accounting for differences in the length, time and location of those previous studies, the relationship between earlier springs and higher latitudes was strong.

A nest holding the eggs of northern wheatears rests on branches in Greenland. These birds are long-distance migrants, overwintering in sub-Saharan Africa and breeding in the Arctic. With earlier springs happening faster at higher but not lower latitudes, the birds may find themselves "late for dinner" if the insects they flew north to feast upon have already emerged [Credit: Eric Post/UC Davis]

Unknowns for birds, migratory species

Springtime provides important biological cues for many plant and animal species, and it is unclear how an accelerated spring could play out for these species across the planet.

The study notes that impacts to migratory birds are a potential concern. Many birds move from tropical zones to higher latitudes, such as the Arctic, to breed.

“Whatever cues they’re relying on to move northward for spring might not be reliable predictors of food availability once they get there if the onset of spring at these higher latitudes is amplified by future warming,” Post said. “The springtime emergence of the plants and insects they’ll eat when they arrive is happening faster than the changes at the lower latitudes those birds are departing from.”

Author: Kat Kerlin | Source: UC Davis [March 02, 2018]

Hundreds of methane flares observed offshore Western Svalbard in the Arctic are caused by a process that started at the end of the last ice age, according to the study. The methane release happens because the gas is freed from melting hydrates - an icy substance found below the ocean floor, containing methane in a cage of frozen water.

Gas hydrates are formed under cold temperature and high pressure conditions beneath the ocean floor. They contain large amounts of greenhouse gas methane [Credit: CAGE]

Ocean water warming was previously thought to be the cause of the hydrate melt in this particular area. But the study in Nature Communications suggests otherwise.

"Our investigations show that uplift of the sea floor in this region, caused by the melting of the ice masses since the end of the last ice age, is probably the reason for the dissolution of methane hydrate." says first author of the study Professor Klaus Wallmann at GEOMAR.

Leaking methane for 8000 years

Methane hydrate forms in cold temperatures and under high pressure - conditions that can be found at the bottom of the ocean.

When the Earth's crust naturally rebounds as ice sheets begin to shrink, the seafloor changes position. That and a subsequent shallowing of the water column above can cause he hydrates to destabilise and dissolve. Through a combination of sediment cores analyses and ice-sheet modelling, the study shows that this area has probably been steadily leaking methane from hydrates for 8000 years.

Ice sheet reconstruction

An important part of the study is the reconstruction of the Eurasian ice sheet that once covered the area. It was developed by scientists at CAGE - Centre for Arctic Gas Hydrate Environment and Climate, and shows that seafloor off Western Svalbard was covered by a large ice sheet during the last glaciation.

The load of ice in the area during the last glacial maximum would have added significant pressure to the crust below. Depression of the crust in the area off Western Svalbard was caused by the heavy load of the ice [Credit: Henry Patton/CAGE]

As that ice sheet retreated, some 20,000 years ago, the sea floor started bouncing back. The process is called isostatic rebound: the rise of land masses that were depressed by the huge weight of ice sheets.

The uplift of the crust is a very slow process that is still happening and affecting the environment. Instead of abrupt release of methane which is evident in other parts of the Arctic, the hydrate melt in ocean floor off Western Svalbard caused slow and steady seeps that are ongoing.

"This study illustrates the colossal influence that the ice sheets that once covered Eurasia had on their surrounding environment" says co-author Henry Patton, researcher at CAGE. Another example according to Patton is the uplift in the Baltic, which is still observable today, though the pace of rebound has now slowed significantly to less than a centimetre per year.

Anthropogenic influence open for discussion

The scientists behind the study suggest that warming of the oceans due to recent anthropogenic climate change is not to blame for the methane seeps off Western Svalbard.

"But gas hydrates are still widespread elsewhere beneath the Barents Sea and across the Arctic. How these reservoirs respond to any future changes in ocean bottom-water temperatures, natural or anthropogenic, is still a topic very much open for discussion." says Patton.

One of the other conclusions from the study is that the impact of future seabed methane fluxes may be underestimated. Hydrates should be seen as a seal blocking the flux of methane from underlying reservoirs, and not the total source of gas in themselves.

Source: CAGE - Center for Arctic Gas Hydrate, Climate and Environment [February 07, 2018]

A new study finds polar bears in the wild have higher metabolic rates than previously thought, and as climate change alters their environment a growing number of bears are unable to catch enough prey to meet their energy needs.

Adult female polar bear on the sea ice wearing a GPS satellite video-camera collar. GPS video-camera collars were applied to solitary adult female polar bears for 8 to 12 days in April, 2014-2016. These collars enabled researchers to understand the movements, behaviors, and foraging success of polar bears on the sea ice [Credit: Anthony Pagano, USGS]

The study, published in Science, reveals the physiological mechanisms behind observed declines in polar bear populations, said first author Anthony Pagano, a Ph.D. candidate at UC Santa Cruz.

"We've been documenting declines in polar bear survival rates, body condition, and population numbers over the past decade," he said. "This study identifies the mechanisms that are driving those declines by looking at the actual energy needs of polar bears and how often they're able to catch seals."

Pagano, who is also a wildlife biologist with the U.S. Geological Survey (USGS), conducted the study as part of his Ph.D. thesis research at UC Santa Cruz, where he has been working with coauthors Terrie Williams and Daniel Costa, both professors of ecology and evolutionary biology.

The researchers monitored the behavior, hunting success, and metabolic rates of adult female polar bears without cubs as they hunted for prey on the sea ice of the Beaufort Sea in the spring. High-tech collars on the bears recorded video, locations, and activity levels over a period of eight to 11 days, while metabolic tracers enabled the team to determine how much energy the bears expended.

The field metabolic rates they measured averaged more than 50 percent higher than previous studies had predicted. Five of the nine bears in the study lost body mass, meaning they weren't catching enough fat-rich marine mammal prey to meet their energy demands.

"This was at the start of the period from April through July when polar bears catch most of their prey and put on most of the body fat they need to sustain them throughout the year," Pagano said.

Polar bear still-hunting at a seal hole on the sea ice of the southern Beaufort Sea [Credit: Mike Lockhart, USGS]

Climate change is having dramatic effects on the Arctic sea ice, forcing polar bears to move greater distances and making it harder for them to catch prey. In the Beaufort Sea, sea ice starts to retreat away from the continental shelf in July, and most of the bears move north on the ice as it retreats. As the Arctic warms and more sea ice melts, the bears are having to move much greater distances than previously. This causes them to expend more energy during the summer, when they are fasting until the ice returns to the continental shelf in the fall.

In other areas, such as Hudson Bay, most bears move onto land when the sea ice retreats. There, Arctic warming means the sea ice is breaking up earlier in the summer and returning later in the fall, forcing bears to spend more time on land.

"Either way, it's an issue of how much fat they can put on before the ice starts to break up, and then how much energy are they having to expend," Pagano said.

Previous studies had tried to estimate polar bear metabolic rates and energy expenditures based on some assumptions about their behavior and physiology. For example, since polar bears are primarily "sit and wait" hunters, it was thought this would minimize their energy expenditure during hunting. Researchers also speculated that polar bears could lower their metabolic rate to save energy if they were not successful catching seals, Pagano said.

"We found that polar bears actually have much higher energy demands than predicted. They need to be catching a lot of seals," he said.

In the spring, polar bears are mostly preying on recently weaned ringed seals, which are more susceptible to being caught than adult seals. By the fall, the young seals are older and wiser, and polar bears are not able to catch as many. "It's thought that bears might catch a couple per month in the fall, compared to five to 10 per month in the spring and early summer," Pagano said.

USGS researchers have been studying polar bears in the Beaufort Sea area since the 1980s. Their most recent population estimate indicates the polar bear population has declined by about 40 percent over the past decade. It has been difficult, however, for researchers to study the fundamental biology and behavior of polar bears in this very remote and harsh environment, Pagano said.

"We now have the technology to learn how they are moving on the ice, their activity patterns, and their energy needs, so we can better understand the implications of these changes we are seeing in the sea ice," he said.

Author: Tim Stephens | Source: University of California - Santa Cruz [February 01, 2018]

A new Canadian study has found that carbon released by some ponds in the High Arctic could potentially be a hidden source of greenhouse gas emissions.

Researcher Gillian Thiel records water samples taken from a pond in the High Arctic near the Cape Bounty Arctic Watershed Observatory [Credit: Melissa Lafreniere]

The study looked at how dissolved organic carbon (DOC) stored in Arctic permafrost - which is thawing at an accelerated rate due to climate change - is being released into Arctic watersheds as a result of physical disturbances that relocate nutrients across the landscape. For the first-time researchers were able to determine that the chemical composition of carbon in these ponds is vastly different than in rivers in the High Arctic.

"These ponds in the High Arctic seem to be hotspots for DOC degradation," says Myrna Simpson, Professor of Environmental Science at U of T Scarborough and co-author of the research.

"Very little consideration has been given to what's happening with DOC in these ponds that are all over the Arctic, and it could potentially be a source of CO2 emissions released into the atmosphere with these disturbances."

DOC is everywhere - it can be found in lakes, oceans and in soil. It's essentially decomposed plant or animal material that can dissolve by coming into contact with water. In the High Arctic DOC becomes mobile by entering watersheds, which is happening at an accelerated rate due to rapid permafrost thaw and the resulting change to the physical landscape.

"The rapid thawing results in what's called active layer detachments," explains Simpson. "Think of these disturbances as landslides where soil and water gets all mixed up."

When the DOC settles into ponds it can be biodegraded by microbes more easily than in rivers, which means more carbon can get released into the atmosphere. While past studies have explored how active layer detachments have stimulated microbial activity in Arctic soil, this is the first to look mostly at water sources including ponds.

"We didn't measure how much carbon was being released because we didn't expect to find this," says Simpson. "This is one of the novel findings of the study - that these ponds could play an important role in the global carbon cycle."

What's more, Simpson notes, the Arctic permafrost stores a lot of carbon because it generally remains frozen, locked into place for a long time. With rapid thawing of the permafrost, that's changing. In fact, using radiocarbon dating, the researchers found DOC more than 5,000 years old that was being degraded.

Sampling of the water sources for the study was done by Queen's University researchers Associate Professor Melissa Lafrenière and Professor Scott Lamoureux out of the Cape Bounty Arctic Watershed Observatory near Melville Island in Nunavut.

An important next step for the research will be to see how widespread the phenomenon is, for example if it happens in all Arctic ponds. But as Lafrenière points out, it's also important to understand the underlying mechanisms driving the difference between DOC in ponds versus rivers.

"We need to do some mass balance studies to figure out the mass of carbon in these bodies of water. This includes how much carbon is present, and what are the main inputs and outputs controlling how much carbon is in the water," she says.

In order to do that, they will need to measure not only the amount of carbon in the water but also the different forms of carbon including DOC, dissolved inorganic carbon, particulate organic carbon, gaseous CO2 and methane.

Future lab and field experiments will be designed to figure out the processes responsible for gains or losses of carbon from these ponds, and also the process behind transforming carbon from one form to another, adds Lafrenière.

Analysis of the DOC for the study was carried out in three different labs across Canada in order for researchers to use a host of sophisticated measurements. Professor Yves Gélinas from Concordia University and Professor André Simpson from U of T Scarborough lent their expertise to the study. Data was also collected and compiled by Dr. Jun-Jian Wang, a former postdoctoral fellow in Professor Myrna Simpson's lab, now an Assistant Professor at the Southern University of Science and Technology in China.

The research is published in the journal Environmental Science and Technology.

Author: Don Campbell | Source: University of Toronto [February 01, 2018]

Archaeologists are a little like forensic investigators: They scour the remains of past societies, looking for clues in pottery, tools and bones about how people lived, and how they died.

University of Washington researchers re-created ancient projectile points to test their effectiveness. From left to right: stone, microblade and bone tips [Credit: Janice Wood]

And just as detectives might re-create the scene of a crime, University of Washington archaeologists have re-created the weapons used by hunter-gatherers in the post-Ice Age Arctic some 14,000 years ago. Looking for clues as to how those early people advanced their own technology, researchers also considered what that might tell us about human migration, ancient climates and the fate of some animal species.

In an article published in the Journal of Archaeological Science, Janice Wood, recent UW anthropology graduate, and Ben Fitzhugh, a UW professor of anthropology, show how they reconstructed prehistoric projectiles and points from ancient sites in what is now Alaska and studied the qualities that would make for a lethal hunting weapon.

The UW team chose to study hunting weapons from the time of the earliest archaeological record in Alaska (around 10,000 to 14,000 years ago), a time that is less understood archaeologically, and when different kinds of projectile points were in use. Team members designed a pair of experiments to test the effectiveness of the different point types. By examining and testing different points in this way, the team has come to a new understanding about the technological choices people made in ancient times.

"The hunter-gatherers of 12,000 years ago were more sophisticated than we give them credit for," Fitzhugh said. "We haven't thought of hunter-gatherers in the Pleistocene as having that kind of sophistication, but they clearly did for the things that they had to manage in their daily lives, such as hunting game. They had a very comprehensive understanding of different tools, and the best tools for different prey and shot conditions."

Prior research has focused on the flight ballistics of the hunting weapons in general, and no prior study has looked specifically at the ballistics of tools used in Siberia and the Arctic regions of North America just after the Ice Age. In addition to foraging for plants and berries (when available), nomadic groups hunted caribou, reindeer and other animals for food, typically with spears or darts (thrown from atlatl boards). Without preservation of the wood shafts, these tools are mainly differentiated in the archaeological record by their stone and bone points. But it was not known how effective different kinds of points were in causing lethal injury to prey.

Nor is it known, definitively, whether different types of points were associated with only certain groups of people, or whether with the same groups used certain point types to specialize on particular kinds of game or hunting practices. It is generally accepted that different point types were developed in Africa and Eurasia and brought to Alaska before the end of the Ice Age. These included rudimentary points made of sharpened bone, antler or ivory; more intricate, flaked stone tips popularly familiar as "arrowheads"; and a composite point made of bone or antler with razor blade-like stone microblades embedded around the edges.

The three likely were invented at separate times but remained in use during the same period because each presumably had its own advantages, Wood said. Learning how they functioned informs what we know about prehistoric hunters and the repercussions of their practices.

So Wood traveled to the area around Fairbanks, Alaska, and crafted 30 projectile points, 10 of each kind. She tried to stay as true to the original materials and manufacturing processes as possible, using poplar projectiles, and birch tar as an adhesive to affix the points to the tips of the projectiles. While ancient Alaskans used atlatls (a kind of throwing board), Wood used a maple recurve bow to shoot the arrows for greater control and precision.

- For the bone tip, modeled on a 12,000-year-old ivory point from an Alaskan archaeological site, Wood used a multipurpose tool to grind a commercially purchased cow bone;

- For the stone tip, she used a hammerstone to strike obsidian into flakes, then shaped them into points modeled on those found at another site in Alaska from 13,000 years ago;

- And for the composite microblade tip -- modeled microblade technologies seen in Alaska since at least 13,000 years ago and a rare, preserved grooved antler point from a more recent Alaskan site used more than 8,000 years ago -- Wood used a saw and sandpaper to grind a caribou antler to a point. She then used the multipurpose tool to gouge out a groove around its perimeter, into which she inserted obsidian microblades.

Wood then tested how well each point could penetrate and damage two different targets: blocks of ballistic gelatin (a clear synthetic gelatin meant to mimic animal muscle tissue) and a fresh reindeer carcass, purchased from a local farm. Wood conducted her trials over seven hours on a December day, with an average outdoor temperature of minus 17 degrees Fahrenheit.

In Wood's field trial, the composite microblade points were more effective than simple stone or bone on smaller prey, showing the greatest versatility and ability to cause incapacitating damage no matter where they struck the animal's body. But the stone and bone points had their own strengths: Bone points penetrated deeply but created narrower wounds, suggesting their potential for puncturing and stunning larger prey (such as bison or mammoth); the stone points could have cut wider wounds, especially on large prey (moose or bison), resulting in a quicker kill.

Wood said the findings show that hunters during this period were sophisticated enough to recognize the best point to use, and when. Hunters worked in groups; they needed to complete successful hunts, in the least amount of time, and avoid risk to themselves.

"We have shown how each point has its own performance strengths," she said. Bone points punctured effectively, flaked stone created a greater incision, and the microblade was best for lacerated wounds. "It has to do with the animal itself; animals react differently to different wounds. And it would have been important to these nomadic hunters to bring the animal down efficiently. They were hunting for food."

Weapon use can shed light on the movement of people and animals as humans spread across the globe and how ecosystems changed before, during and after the ice ages.

"The findings of our paper have relevance to the understanding of ballistic properties affecting hunting success anywhere in the world people lived during the 99 percent of human history that falls between the invention of stone tools more than 3 million years ago in Africa and the origins of agriculture," Fitzhugh said.

It could also inform debates on whether human hunting practices directly led to the extinction of some species. The team's findings and other research show that our ancestors were thinking about effectiveness and efficiency, Wood said, which may have influenced which animals they targeted. An animal that was easier to kill may have been targeted more often, which could, along with changing climates, explain why animals such as the horse disappeared from the Arctic. A shot to the lung was lethal for early equines, Wood said, but a caribou could keep going.

"I see this line of research as looking at the capacity of the human brain to come up with innovations that ultimately changed the course of human history," she said. "This reveals the human capacity to invent in extreme circumstances, to figure out a need and a way to meet that need that made it easier to eat and minimized the risk."

Upon completion of the experiment, the bones were sterilized for future study of projectile impact marks.

Author: Kim Eckart | Source: University of Washington [January 31, 2018]

Despite the growth in knowledge about the effects of a warming Arctic on its cold-adapted species, how these changes affect animal populations is poorly understood. Research efforts have been hindered by the area's remoteness and complex logistics required to gain access.

Cold-adapted species, like the muskoxen, are feeling the heat, according to wildlife biologist Joel Berger  [Credit: Joel Berger/Colorado State University]

A new Scientific Reports study led by Joel Berger, professor in the Department of Fish, Wildlife and Conservation Biology at Colorado State University, has uncovered previously unknown effects of rain-on-snow events, winter precipitation and ice tidal surges on the Arctic's largest land mammal, the muskoxen.

The warmer climate is stressing mothers and young muskoxen, said Berger, also a senior scientist with the Wildlife Conservation Society. Rain-on-snow events occurring in the winter -- when muskoxen gestate -- and unusually dry winter conditions have also led to underdeveloped skeletal growth in juvenile muskoxen. This effect can be traced back to their pregnant mothers.

"When rain-on-snow events occur in the Arctic, due to warming temperatures, and the snow freezes again, this leads to mothers not being able to access food for adequate nutrition," said Berger. "The babies then, unfortunately, pay the price."

The smaller size observed in juvenile and young adult muskoxen is associated with poorer health and fitness, due to delayed puberty, and increased mortality, according to the research team.

Muskoxen on Wrangel Island, located in the Arctic Ocean, between the Chukchi Sea and East Siberian Sea  [Credit: Joel Berger/Colorado State University]

In addition, scientists documented a mass mortality event due to a one-time extreme ice event caused by a tidal surge. In February 2011, an historically high tidal surge resulted in at least 52 muskoxen being submerged at the northern coast of Bering Land Bridge peninsula.

Researchers also found historical records documenting deaths due to rapid freezing and thawing during winter at a range of single sites of whales -- 170 Beluga and 150 narwhals -- and sea otters along the Aleutian Islands.

"Unlike polar bears, which are on the world's stage, no one really knows about muskoxen or cares," said Berger. "They roamed with wooly mammoths but still survive. Muskoxen are feeling the heat, just as we humans are feeling the extremes of climate. These wild weather swings have massive impacts on us. Solutions are clear, but we fail to respond by changing our consumptive ways."

Measuring a muskox, tracking temperatures

The research team analyzed head size of juvenile muskoxen using digital photo data over the span of seven years and at three sites in Alaska and Russia. They also compiled winter weather data for the Alaskan sites from the closest weather stations maintained by the National Oceanic and Atmospheric Administration. Data used to calculate rain-on-snow events on Wrangel Island, located in the Arctic Ocean, between the Chukchi Sea and East Siberian Sea, were from the Federal Hydro-meteorological Service of Russia, whose records date back to 1926.

Biologist Joel Berger (left) confers with biotechnician Fred Goodhope, Jr. in Alaska  [Credit: Ellen Cheng]

Berger acknowledged the role his research plays "in a challenging political era." His collaborators include Russian scientists in Asia and the Alaskan Arctic. Berger is not only a researcher, but he also serves as a diplomat of sorts, working closely with Russian research counterparts and the government. He praised them for their active engagement and willingness to share data.

"To better understand how species like the muskoxen are responding to a changing Arctic, we must collaborate, so that we can document rare and often tragic events, and gain additional insight from local people," said Berger.

Source: Colorado State University [January 18, 2018]