Arctic conditions may become critical for polar bears by end of 21st century

This is a photo of an Arctic polar bear. Shifts in the timing and duration of ice cover, especially the possible lengthening of ice-free periods, may impact polar bears under projected warming before the end of the 21st century, according to a study published Nov. 26, 2014 in the open-access journal PLOS ONE by Stephen Hamilton from University of Alberta and colleagues. Credit: Andrew Derocher; CC-BY

Shifts in the timing and duration of ice cover, especially the possible lengthening of ice-free periods, may impact polar bears under projected warming before the end of the 21st century, according to a study published November 26, 2014 in the open-access journal PLOS ONE by Stephen Hamilton from University of Alberta and colleagues.

Sea ice across the Arctic is declining and altering physical characteristics of marine ecosystems, and polar bears are vulnerable to these changes in sea ice conditions. The authors of this study used sea ice projections for the Canadian Arctic Archipelago from 2006-2100 and metrics developed from polar bear energetics modeling to gain insight into the conservation challenges for polar bears facing habitat loss.

Shifts away from multiyear ice to annual ice cover throughout the region, as well as lengthening ice-free periods, may become critical for polar bears before the end of the 21st century with projected warming. Each polar bear population in the Archipelago may undergo 2-5 months of ice-free conditions, where no such conditions exist presently. Under business-as-usual climate projections, polar bears may face starvation and reproductive failure across the entire Archipelago by the year 2100. "We predict that nearly one-tenth of the world's polar bear habitat, as much as one-quarter of their global population, may undergo significant habitat loss under business-as-usual climate projections," said Stephen Hamilton.

Source: PLOS

Sampling rivers for genes rather than organisms

Conventional methods used to inventory macroinvertebrates are extremely time-consuming. Credit: Image courtesy of EAWAG: Swiss Federal Institute of Aquatic Science and Technology

Effective environmental management depends on a detailed knowledge of the distribution of species. But taxonomists are in short supply, and some species can be difficult to identify, even for experts. Eawag, in collaboration with Canton Zurich, is now pursuing a new approach for species identification, requiring no more than samples of DNA shed into the environment.

If amphipods are detected in a river, are they a threatened species, or organisms indicating good water quality? Or perhaps the first arrivals of an invasive species? Conservation and environmental management call for a detailed knowledge of species. But experts capable of identifying species under the microscope on the basis of morphological characteristics are increasingly rare. Alternative methods for water monitoring would therefore be welcome. Biologists at Eawag are now pursuing a new approach for the detection of species, involving the use of environmental DNA (eDNA). Because organisms continuously release genetic material into the environment in the form of faeces, hair or skin cells, water samples collected from a river or lake contain innumerable fragments of DNA. As long as the relevant genetic code is known, these DNA segments can be assigned to particular species, using the latest molecular biological techniques and global databases.

Cantonal authorities interested
In cooperation with the Canton Zurich Office of Waste, Water, Energy and Air (AWEL), the researchers investigated whether this method is suitable for the detection of macroinvertebrates: organisms such as mayflies, amphipods, mussels or snails are important bioindicators, used in the assessment of water quality and ecotoxicity. Water samples were collected from 14 lake and river habitats in Canton Zurich for eDNA analysis, and macroinvertebrate species collected by kicknet sampling were also determined in the conventional manner.

While the two methods did not always deliver the same results, five of the six target species were reliably detected by both methods. Especially for organisms occurring in small populations, the eDNA method appears to be more sensitive. With this approach, the rare mayfly Baetis buceratus was additionally detected at two sites where no Baetis specimens where found by kicknet sampling. According to project leader Florian Altermatt, the new method may also be suitable for the detection of invasive species at an early stage of colonization. In the US and France, it is already being tested for invasive carp species.

Long-term goal: routine monitoring of biodiversity
The eDNA method offers additional advantages. As eDNA is ubiquitous in freshwater throughout the year, the findings reflect the situation of an entire catchment, and surveillance is less time-critical. By contrast, kicknet sampling merely provides a snapshot, and for many species it can only be carried out at certain stages of the life cycle and certain times of the year. For eDNA analysis, organisms do not have to be removed from a river or lake and -- in principle -- hundreds of species can be detected at the same time. This means that continuous monitoring of freshwater biodiversity could one day become possible, just as chemical parameters are routinely monitored today.

This, however, is still a long way off: apart from the need for further refinements, the method is still costly and time-consuming. The cantons currently lack the necessary infrastructure and expertise. But Altermatt believes it will not take too long for technical standards to be established, permitting efficient operation: "eDNA analysis will then cost a few hundred Swiss francs and will be cheaper than conventional surveys." However, the new method will not wholly replace the conventional approach. Altermatt argues that the benefits of both approaches should be exploited. In addition, taxonomists will remain indispensable for validation and calibration of the new procedures.

Source:  EAWAG: Swiss Federal Institute of Aquatic Science and Technology

Satellites measure increase of Sun's energy absorbed in the Arctic

The Arctic Ocean is absorbing more of the sun's energy in recent years as white, reflective sea ice melts and darker ocean waters are exposed. The increased darker surface area during the Arctic summer is responsible for a 5 percent increase in absorbed solar radiation since 2000.
Credit: NASA Goddard's Scientific Visualization Studio/Lori Perkins

NASA satellite instruments have observed a marked increase in solar radiation absorbed in the Arctic since the year 2000 -- a trend that aligns with the steady decrease in Arctic sea ice during the same period.

While sea ice is mostly white and reflects the sun's rays, ocean water is dark and absorbs the sun's energy at a higher rate. A decline in the region's albedo -- its reflectivity, in effect -- has been a key concern among scientists since the summer Arctic sea ice cover began shrinking in recent decades. As more of the sun's energy is absorbed by the climate system, it enhances ongoing warming in the region, which is more pronounced than anywhere else on the planet.

Since the year 2000, the rate of absorbed solar radiation in the Arctic in June, July and August has increased by five percent, said Norman Loeb, of NASA's Langley Research Center, Hampton, Virginia. The measurement is made by NASA's Clouds and the Earth's Radiant Energy System (CERES) instruments, which fly on multiple satellites.

While a five percent increase may not seem like much, consider that the rate globally has remained essentially flat during that same time. No other region on Earth shows a trend of potential long-term change.

When averaged over the entire Arctic Ocean, the increase in the rate of absorbed solar radiation is about 10 Watts per square meter. This is equivalent to an extra 10-watt light bulb shining continuously over every 10.76 square feet of Arctic Ocean for the entire summer.

Regionally, the increase is even greater, Loeb said. Areas such as the Beaufort Sea, which has experienced the some of the most pronounced decreases in sea-ice coverage, show a 50 watts per square meter increase in the rate of absorbed solar radiation.

"Advances in our understanding of Arctic climate change and the underlying processes that influence it will depend critically upon high quality observations like these from CERES," Loeb said.

As a region, the Arctic is showing more dramatic signs of climate change than any other spot on the planet. These include a warming of air temperatures at a rate two to three times greater than the rest of the planet and the loss of September sea ice extent at a rate of 13 percent per decade.

While these CERES measurements could ultimately become another of those signs of dramatic climate change, right now scientists say they have obtained the bare minimum of a data record needed to discern what's happening over the long term.

Getting data beyond 15 years will allow scientists to better assess if recent trend falls outside the realm of natural variability, said Jennifer Kay, an atmospheric scientist at the Cooperative Institute for Research and Environmental Science at the University of Colorado.

"We need long time series to detect climate change signals over the internal variability. For example, observed sea ice loss over the last 30 years cannot be explained by natural variability alone." Kay said. "Fifteen years is long, but climate is often defined as the average over 30 years -- so we are only half-way there with the CERES observations."

Kay and colleagues have also analyzed satellite observations of Arctic clouds during this same 15-year period. Kay's research shows summer cloud amounts and vertical structure are not being affected by summer sea ice loss. While surprising, the observations show that the bright sea ice surface is not automatically replaced by bright clouds. Indeed, sea ice loss, not clouds, explain the increases in absorbed solar radiation measured by CERES.

Increasing absorbed solar radiation is causing multiple changes in the sea ice cover, said Walt Meier, a sea ice scientist from NASA's Goddard Space Flight Center, Greenbelt, Maryland. Two of those changes include the timing of the beginning of the melt season each year and the loss of older, thicker sea ice.

The onset of the melt season in the high Arctic is now on average seven days earlier than it was in 1982, Meier said. Earlier melting can lead to increased solar radiation absorption. This is one step in a potential feedback cycle of warming leading to melting, melting leading to increased solar radiation absorption, and increased absorption leading to enhanced warming.

Since 2000, the Arctic has lost 1.4 million square kilometers (541,000 square miles) of older ice that is more than 3 meters thick, which during winter has essentially been replaced by ice that is less than 2 meters thick, according to data provided by Mark Tschudi at the University of Colorado. Once again, Meier said, this trend is a step in a feedback cycle.

"Having younger and thus thinner ice during winter makes the system more vulnerable to ice loss during the summer melt season," Meier said.

CERES instruments are currently flying on the Terra, Aqua and Suomi-NPP satellites. The Terra satellite launched Dec. 18, 1999, and CERES first started collecting Arctic data in 2000 so 2015 will mark 15 continuous years of CERES measurements over the Arctic.

The instruments include three radiometers -- one measuring solar radiation reflected by Earth (shortwave), one measuring thermal infrared radiation emitted by Earth (longwave), and one measuring all outgoing radiation, whether emitted or reflected.

Source:  NASA/Goddard Space Flight Center