Saturday, September 24, 2016

Every Single Part of the Arctic is Becoming worse for Polar Bears

The bears are actually doing fine but no one asked them of course.  Our arctic warm spell is now ten years old.   It took tens years for the 1998 heat surge to knock back the ice to reach the 2007 low.  it then largely stabilized with more and more multi year ice disappearing but the sea other wise covered with last winters ice in most locates.  2012 had a burst of unusual wind activity that pushed a lot of ice out into Davis Strait among other things.

 Meanwhile the ice is having a significant low this year that does match the second lowest low in 2007.

 During the past decade the seal population has exploded to the millions and this has fed an increasing bear population.


Every single part of the Arctic is becoming worse for polar bears

By Chelsea Harvey September 14 at 11:23 AM 

A polar bear dries off after taking a 2014 swim in the Chukchi Sea in Alaska. (AP Photo/U.S. Geological Survey, Brian 

Battaile) As climate change continues to heat up the Arctic, there’s rarely good news these days for the polar bears who call it home. And now, a broad new study charting nearly four decades of changes in Arctic sea ice has again underscored the animal’s plight.

The study, just out in the journal The Cryosphere, finds that in every Arctic region where polar bears live, there’s been a decline in the total number of ice-covered days the bears have at their disposal. That’s a serious problem because polar bears use sea ice as their prime hunting grounds, waiting near the edge and snatching up seals as the marine mammals surface for air.

Previous research has already suggested that as less ice is available, polar bears are forced to spend more time on land, where they have to scavenge or hunt smaller prey to survive. As this behavior becomes more frequent, scientists worry the bears could become malnourished or even starve. 

Earlier this week, reports of polar bears stalking a Russian research outpost drove this point home again.

A group of hungry polar bears are circling Russian scientists at a remote weather outpost in the Arctic. (Jenny Starrs/The Washington Post) While there’s great concern about the future of the species, there’s some debate about how the bears are faring now. Scientists estimate there are currently about 25,000 bears in all, divided into 19 subpopulations throughout the Arctic. For the new study, the researchers decided to investigate sea ice trends in each of these subpopulation regions. 

The researchers relied on satellite data from 1979 through 2014. Every year, for each of the 19 regions, they calculated the date sea ice began to melt in the spring; the date it began to refreeze in the fall; the amount of sea ice present during the summer months (when the ice concentration is typically at its lowest); and the total number of ice-covered days per year.

They found that in 17 out of the 19 subpopulation regions, there are significant trends toward earlier sea ice retreat in the spring, generally by about three-to-nine days per decade. And in 16 of the regions, there were significant trends toward a later fall sea ice advance, again by about three-to-nine days per decade. These trends were slightly more pronounced in some regions, such as the Barents Sea off the northern coasts of Norway and Russia, and the central Arctic Basin.

An earlier spring melt was associated with a later fall freeze pretty much every time — and the researchers have attributed this pattern to a special kind of climate feedback system. 

“Sunlight bounces off ice, but it’s absorbed by water,” explained Harry Stern, a mathematician and sea ice researcher at the University of Washington and one of the study’s two authors. So when sea ice melts, it opens up large swaths of water where sunlight can be absorbed and heat can be trapped. The earlier the ice melts, the more heat goes into the ocean. In the fall, when temperatures start to drop again, all of this heat has to be released before the sea ice can refreeze. But if there’s more heat stored in the water than usual, the process takes longer and the freeze is delayed.

Overall, the researchers found that the length of time between spring sea ice retreat and fall sea ice advance has increased by between three and nine weeks since 1979. The biggest single increase of any polar bear subpopulation region was in the Barents Sea, where the interval lengthened by a whopping 17 weeks. 

Additionally, the researchers found the concentrations of summer sea ice is declining by anywhere from one to nine percent per decade in most regions. And the total number of ice-covered days per year has also significantly declined in every subpopulation region, generally by between seven and 19 days per decade. Again, these trends were slightly larger in the Barents Sea. 

The study’s results are already being used by conservationists, said Kristin Laidre, a principal scientist and polar bear expert at the University of Washington’s Polar Science Center and the study’s other author. The International Union for the Conservation of Nature (IUCN) has incorporated the sea ice data into its Red List assessment of polar bears (which is part of a global assessment of the endangered or threatened status of wildlife all over the world) and into its public status information on the 19 subpopulations. 

As for the future of the bears’ habitat, most projections suggest things are looking pretty grim. 

Models have predicted that we could be seeing ice-free Arctic summers by mid-century.

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In that light, the new study “highlights the clear changes we’re seeing around the globe, especially in the Arctic,” Laidre said, adding that she hopes the results might influence high-level decision-making about climate policy and greenhouse gas emissions moving forward. 

Assuming the sea ice trends are irreversible, though — at least in the short term — she said the results could also be used to “compare and contrast subpopulations of polar bears across the Arctic and identify areas where we might expect to see more negative changes occurring.” 

In this way, increased knowledge of sea ice trends in each of the subpopulation regions could help inform management decisions and future conservation effort. As for the bears themselves, continued monitoring will be necessary to find out how they respond to the ongoing ice losses. 

For the time being, nine of the populations don’t have enough data for scientists to make an assessment of how they’re doing, while three are known to be declining, six are considered stable and just one is growing. How these patterns change in the future remains to be seen. But given the bears’ dependence on the sea ice, the researchers have concluded in their paper that “climate warming poses the single more important threat to their persistence.”
Arctic sea ice appears to have reached its seasonal minimum extent for 2016 on September 10. A relatively rapid loss of sea ice in the first ten days of September has pushed the ice extent to a statistical tie with 2007 for the second lowest in the satellite record. September’

Please note that this is a preliminary announcement. Changing winds or late-season melt could still reduce the Arctic ice extent, as happened in 2005 and 2010. NSIDC scientists will release a full analysis of the Arctic melt season, and discuss the Antarctic winter sea ice growth, in early October. 

Overview of conditions 

Figure 1. Arctic sea ice extent for September 10, 2016 was 4.14 million square kilometers (1.60 million square miles). The orange line shows the 1981 to 2010 median extent for that day. The black cross indicates the geographic North Pole. Sea Ice Index data. About the data

Credit: National Snow and Ice Data Center

On September 10, Arctic sea ice extent stood at 4.14 million square kilometers (1.60 million square miles). This appears to have been the lowest extent of the year and is tied with 2007 as the second lowest extent on record. This year’s minimum extent is 750,000 square kilometers (290,000 square miles) above the record low set in 2012 and is well below the two standard deviation range for the 37-year satellite record. Satellite data show extensive areas of open water in the Beaufort and Chukchi seas, and in the Laptev and East Siberian seas. 

During the first ten days of September, the Arctic lost ice at a faster than average rate. Ice extent lost 34,100 square kilometers (13,200 square miles) per day compared to the 1981 to 2010 long-term average of 21,000 square kilometers (8,100 square miles) per day. The early September rate of decline also greatly exceeded the rate observed for the same period in 2012 (19,000 square kilometers, or 7,340 square miles, per day). Recent ice loss has been most pronounced in the Chukchi Sea. This may relate to the impact of two strong cyclones that passed through the region during August. 

Satellite passive microwave data and images from the Moderate Resolution Imaging Spectroradiometer (MODIS) suggest that the southern Northwest Passage routes are still open. While the passive microwave data show that the Northern Sea route is open, MODIS data reveal a narrow band of scattered sea ice blocking the passage near the Taymyr Peninsula.
Conditions in context

Figure 2a. The graph shows Arctic sea ice extent as of September 12, 2016, along with daily ice extent data for four other record low years. 2016 is shown in blue, 2015 in green, 2012 in orange, 2011 in brown, and 2007 in purple. The 1981 to 2010 average is in dark gray. The gray area around the average line shows the two standard deviation range of the data. Sea Ice Index data.

Credit: National Snow and Ice Data Center

Figure 2b. This plot shows Arctic air temperature anomalies at the 925 hPa level in degrees Celsius and sea level pressure anomalies for two periods: July 1 to August 31, and September 1 through September 11. Yellows and reds indicate higher than average temperatures and pressure; blues and purples indicate lower than average temperatures and pressure.

Weather in early September was warm along the Siberian coast (up to 9 degrees Celsius or 16 degrees Fahrenheit above average), with high pressure over the same region and strong winds across the central Arctic. However, as discussed in previous posts, weather over the Arctic Ocean this past summer has been generally stormy, cool, and cloudy—conditions that previous studies have shown to generally limit the rate of summer ice loss. That September ice extent nevertheless fell to second lowest in the satellite record is hence surprising. Averaged for July through August, air temperatures at the 925 hPa level (about 2,500 feet above sea level) were 0.5 to 2 degrees Celsius (1 to 4 degrees Fahrenheit) below the 1981 to 2010 long-term average over much of the central Arctic Ocean, and near average to slightly higher than average near the North American and easternmost Siberian coasts. Reflecting the stormy conditions, sea level pressures were much lower than average in the central Arctic during these months. 

Why did extent fall to a tie for second lowest with 2007? The 2016 Arctic melt season started with a record low maximum extent in March, and sea ice was measured at record low monthly extents well into June. Computer models of ice thickness, and maps of sea ice age both indicated a much thinner ice pack at the end of winter. Statistically, there is little relationship between May and September sea ice extents after removing the long-term trend, indicating the strong role of summer weather patterns in controlling sea ice loss. However, the initial ice thickness may play a significant role. As noted in our mid-August post, the upper ocean was quite warm this summer and ocean-driven melting is important during late summer. The science community will be examining these issues in more detail in coming months. 

Ice loss primarily in the northern Chukchi Sea 

Figure 4. This figure compares Arctic sea ice extent for September 1 (orange) and September 10 
(blue), with overlap areas in purple. 

Credit: National Snow and Ice Data Center

The late season ice loss appears to have been greatest in an extended area of patchy ice reaching from the eastern Beaufort Sea to the northern Chukchi Sea. This is in the area influenced by the two strong cyclones discussed in our August posts—the strong winds appear to have compacted the ice cover and may have led to an upward mixing of warm ocean water.
Second opinion 

Figure 5. This graph compares Arctic sea ice extent trends from August 15 to September 10 for the years 2007 (F-17), 2012 (F-17), and 2016 (F-17 and F-18). The NSIDC Sea Ice Index currently uses data from the F-18 satellite.

Credit: W. Meier, NASA GSFC, NSIDC

The Defense Meteorological Satellite Program (DMSP) F-17 satellite, which NSIDC ceased to use in May as its primary source for sea ice extent due to erratic data, has since re-stabilized and is providing more consistent day-to-day readings. While NSIDC will continue to use the DMSP F-18 satellite for data processing, it is instructive to examine the F-17 record. Early September extent from the F-17 record is slightly higher than from F-18. Both sensors indicate that the minimum extent for 2016 is slightly lower than the 2007 minimum, which was 4.15 million square kilometers (1.60 million square miles) and reached on September 18. However, the measurement accuracy is about ±25,000 square kilometers (±9,600 square miles) for a five-day trailing average daily extent measurement. This means that at the present levels, 2016 is a statistical tie for second lowest sea ice extent.

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