From November through the first part of January the AO was in a generally positive phase, which tends to bring warm conditions to the United States and Europe, and colder conditions to the Arctic. However, in the middle of the month, the AO shifted back to a negative phase. This shift helped bring cold air outbreaks over middle latitudes, notably a record cold snap throughout much of Europe.

The AO can persist in one phase from anywhere from days to months. When pressure is higher than normal over the Arctic, and lower than normal over middle latitudes, the AO is in its negative mode. When it is positive, air pressure is lower than normal over the Arctic and higher than normal over middle latitudes. Researchers look to the AO to better understand year-to-year variability in climate indicators like the Arctic sea ice cover.
The AO, which had been in its positive phase most of the winter, switched to a negative mode, bringing cold weather to Europe and changing the direction of sea ice movement on the Arctic Ocean. This may explain why sea ice extent remained lower than average in January but why sea ice extent in the Bering Sea was much greater than normal.

Using satellites to measure sea surface height from 1995 to 2010, scientists from University College London and Britain’s National Oceanography Center found that the western Arctic’s sea surface has risen by about 15 cms since 2002.

The volume of fresh water has increased by at least 8,000 cubic km, or about 10 percent of all the fresh water in the Arctic Ocean. The fresh water comes from melting ice and river run-off.

The rise could be due to strong Arctic winds increasing an ocean current called the Beaufort Gyre, making the sea surface bulge upwards.

The Beaufort Gyre is one of the least understood bodies of water on the planet. It is a slowly swirling body of ice and water north of Alaska, about 10 times bigger than Lake Michigan in the United States.

Some scientists believe the natural rhythms of the gyre could be affected by global warming which could have serious implications for the ocean’s circulation and rising sea levels.

Climate models have suggested that wind blowing on the surface of the sea has formed a raised dome in the middle of the Beaufort Gyre, but there have been few in-depth studies to confirm this.

If the wind changes direction, which happened between the mid-1980s to mid-1990s, the pool of fresh water could spill out into the rest of the Arctic Ocean and even into the north Atlantic Ocean, the study said.

This could cool Europe by slowing down an ocean current coming from the Gulf Stream, which keeps Europe relatively mild compared with countries at similar latitudes.

“Our findings suggest that a reversal of the wind could result in the release of this fresh water to the rest of the Arctic Ocean and even beyond,” said Katharine Giles at UCL’s Center for Polar Observation and Modelling and lead author of the study, published in the journal Nature Geoscience.

Of course, a Norwegian team led by Roald Amundsen reached the pole first. And Scott and his team never returned home, dying of starvation and exposure on the return journey. Alongside their bodies, however, were several pounds of their precious geological samples and scientific notebooks which, even while approaching death through exhaustion, Scott and his men continued to take with them.

Those samples and data are an enduring legacy of the Terra Nova expedition.

The expedition was the ambitious scientific endeavour of its time, and it was the largest ever research mission to the pole – comprising 12 scientists including two biologists, three geologists and a meteorologist.

The team collected specimens from 2,109 different animals. Of these, 401 were new to science. They also collected rock samples, penguin eggs and plant fossils.

One of the most important discoveries was a fossilised fern-like plant which was known to grow in India, Africa, New Zealand and Australia. It suggested that the climate 250 million years ago had been mild enough for trees to grow.

More intriguingly, the discovery, along with other evidence gathered by Scott’s team, was a hint that India, Africa, New Zealand, Australia and Antarctica had in the distant past all been part of one “supercontinent”. Researchers now call this landmass Gondwanaland.

It was around this time that the idea of continental drift was first put forward, independently, by the German scientist, Alfred Wegener. Scott’s team also collected the first thorough set of weather data for the Antarctic, which has served as a baseline to track changes in weather patterns ever since.

The team also travelled for three weeks to study an Emperor penguin colony come on to land and lay their eggs. The team took some of the eggs – which contained embryos – believing that they would shed more light on a possible link between birds and dinosaurs.

In the end, the eggs were of little use in this regard, but the efforts the men went to and the risks they took under the most extreme circumstances epitomise a spirit of heroic scientific investigation that arguably has not been matched since.

Concentrations of the main gases blamed for global warming reached record levels in 2010 and will linger in the atmosphere for decades even if the world stopped pumping out emissions today, according to the U.N.’s weather agency.

An ice age is a period when there is a long-term reduction in the earth’s surface and atmospheric temperature, which leads to the growth of ice sheets and glaciers.

There have been at least five ice ages on earth. During ice ages there are cycles of glaciation with ice sheets both advancing and retreating.

Officially, the earth has been in an interglacial, or warmer period, for the last 10,000 to 15,000 years, and estimates vary on how long such periods last.

“(Analysis) suggests that the end of the current interglacial (period) would occur within the next 1,500 years, if atmospheric CO2 concentrations do not exceed (around) 240 parts per million by volume (ppmv),” the study said.

However, the current carbon dioxide concentration is of 390 ppmv, and at that level an increase in the volume of ice sheets would not be possible, it added.

The study based on variations in the earth’s orbit and rock samples was conducted by academics at Cambridge University, University College London, the University of Florida and Norway’s University of Bergen.

The causes of ice ages are not fully understood but concentrations of methane and carbon dioxide in the atmosphere, changes in the earth’s orbit around the sun, and the movement of tectonic plates are all thought to contribute.

The world is forecast to grow hotter as greenhouse gases continue to rise, increasing threats such as extreme weather events and sea level rise.

Scientists have warned that global temperature rise should be limited to within 2 degrees Celsius to avoid the worst effects of climate change but delays in curbing emissions growth are putting the planet at risk.

In recent years, low sea ice extent in the summer has been linked to unusually warm autumn air temperatures, resulting from the larger areas of open water (due to ever increasing sea ice loss) that absorb more heat during the summer. This heat must escape back to the atmosphere in the autumn, before the ocean can freeze over. This escaping heat contributes to warmer-than-average conditions, which have been most apparent in October but may now be extending into November.

Average ice extent for November 2011 was 10.01 million square kilometers, 1.30 million square kilometers below the 1979 to 2000 average. This was 170,000 square kilometers above the average for November 2006, the lowest extent recorded for that month in the satellite data record.

At the end of November, ice extent remained below the 1979 to 2000 average in the Chukchi, Barents and Kara seas, and Hudson Bay was still nearly ice free. Ice extent was near average in the East Greenland and the Bering seas.

The linear rate of decline for November over the satellite record is now 53,200 square kilometers per year, or 4.7% per decade relative to the 1979 to 2000 average.

Statistics courtesy of NSIDC

Polar bears have a circumpolar distribution that is influenced by the distribution and availability of sea ice. Sea ice provides the primary platform on which polar bears travel, hunt, mate and, in some areas, den. Polar bears prey primarily on seals and to a lesser extent on other marine mammals (e.g., walrus and whales). As a result, climate-mediated changes in the availability of sea ice have the potential to significantly influence the availability of prey for bears, potentially affecting individual growth, reproduction and survival.

The world’s polar bear population is estimated to be between 20,000-25,000 bears occurring in 19 relatively discrete sub-populations around the Arctic (see below diagram).

Of the 12 sub-populations currently considered as having sufficient data to assess a population trend, only three have good trend data (western Hudson Bay, northern Beaufort and southern Beaufort).

Despite substantial research and monitoring of polar bears in some areas of the Arctic there is a general lack of knowledge in regards to how the cumulative effects of climate warming, contaminants, disease, harvest, industrial development and other human activities are likely to interact to influence the status of the world’s polar bear sub-populations. In an effort to address both the individual and cumulative effects of these stressors, the Conservation of Arctic Flora and Fauna Working Group of the Arctic Council (CAFF) has facilitated the development of a Circumpolar Polar Bear Monitoring Plan that will provide advice on approaches for the coordinated collection and synthesis of the data required to effectively manage and mitigate existing threats to polar bear conservation.

The report considers a wide range of environmental observations throughout the Arctic and is updated annually. A major conclusion of the 2011 Report is that there are now a sufficient number of years of data to indicate a shift in the Arctic Ocean system since 2006. This shifted is characterized by the persistent decline in the thickness and summer extent of the sea ice cover, and a warmer, fresher upper ocean. As a result of increased open water area, biological productivity at the base of the marine food chain has increased and sea ice-dependent marine mammals continue to lose habitat.

Sea ice and ocean observations over the past decade suggest that the Arctic Ocean climate has reached a new state, with characteristics different than those observed previously. The new ocean climate has less sea ice (both thickness and summer extent) and, as a result, a warmer and fresher upper ocean. A clockwise ocean circulation regime has dominated the Arctic Ocean for at least 14 years (1997-2011), in contrast to the typical duration of a 5-8 year pattern of circulation shifts observed from 1948-1996.

In the Bering Sea, aragonite under-saturation, i.e., ocean acidification, throughout the water column is causing seasonal calcium carbonate mineral suppression in some areas.

The September 2011 Arctic sea ice extent was the second lowest of the past 30 years. The five lowest September ice extents having occurred in the past five years, suggesting that a shift to a new sea ice state continues. The amount of older, thicker multiyear ice continues to decrease and both the Northern Sea Route and the Northwest Passage were ice-free in September.

Click here for the full report

So-called greenhouse gases may be contributing to the warming, and trends from the last several decades suggest there may soon be an ice-free Arctic in the summer, according to a study published today in the journal Nature.

The ice, which melts every summer before cold weather makes it expand again, shrank this year to its second-smallest size since 1979, covering 4.33 million square kilometers (1.67 million square miles), according to the U.S. National Snow and Ice Data Center. Although previous sea ice declines have occurred at a similar pace, they don’t match the extent of the melt, the study authors said.

“This drastic and continuous decrease we’ve been seeing from the satellites does seem to be anomalous,” Christophe Kinnard, a study author and a geographer at the Centro de Estudios Avanzados en Zonas Aridas in La Serena, Chile, said in a telephone interview. “It does point to a continuation of this trend in the future.”

The researchers used ice core records, tree ring data, lake sediment and historical evidence to reconstruct the amount of Arctic cover. The thickness and extent of sea ice have declined dramatically over the last 30 years, the researchers said.

Arctic sea ice influences the global climate, since 80 percent of the sunlight that strikes it is reflected back to space. When the ice melts in the summer, it exposes the ocean surface, which absorbs about 90 percent of the light, heating the water, according to the National Snow and Ice Data Center. That influences climate patterns.

“You increase the radiation that’s absorbed by the oceans, that’s one of the strongest climate feedback mechanisms,” Kinnard said. “The more sea ice you lose, the more energy you get in the ocean, which warms the atmosphere.”

The Catlin Arctic Survey 2010 data is now starting to be published. The 2011 data is going through the final stages of analysis. As with this study, the 2010 and 2011 data sets (from Ice Base and Explorers) are expected to provide unprecedented insight into the rates, causes of impacts of sea ice loss on the Arctic Ocean.