As in previous months, climate change and its effects on the poles dominated the month’s news. Scientists continue to analyze records of past climates, study the global climate system, use computer modeling to predict possible effects, and consider how humans can mitigate and adapt to a changing climate.

Earth’s oceans play an important role in the climate system, taking up about one-third of human-released carbon dioxide gas. This happens as planktonic algae increase in the spring and summer, using nutrients and carbon dioxide to grow. When the algae die, some sink, taking the carbon with it. Scientists exposed plankton communities to various temperatures, and found that at higher temperatures, bacteria consumed more of the algae before they could die and sink. As a result, the carbon dioxide was released back into the water and caused less of the gas to be taken in from the atmosphere in the first place. While more data is needed, scientists wonder if climate change may thus weaken the oceans’ “biological carbon pump.”

The Indigenous People’s Global Summit on Climate Change met in Anchorage, Alaska this month to discuss how traditional knowledge might be in addressing and adapting to climate change. The Summit called for world governments to fully include Indigenous People in any climate change regime adopted at the December UN climate change conference in Copenhagen. Just 800 kilometers to the east of Anchorage is Newtok, an Alaskan village that is being forced to relocate as a result of home and infrastructure damage caused by intensifying river flow and melting permafrost. Five other Alaskan Inuit settlements are similarly threatened. It is believed that global climate change will disproportionately affect Indigenous People around the world, many of whose lifestyles contribute little to the global carbon footprint.

A warming Arctic is making it harder for reindeer herds to find food and navigate. Satellite-based snow maps provided by an IPY project are helping herders in Norway make decisions about winter pasture quality and migration routes.

A team of NASA researchers has spent the last month on an airborne campaign over Greenland to assess ice sheet and glacial health. The mission uses lasers and radars to record ice sheet and glacier thickness. Scientists have flown this mission nearly every spring since 1991. Data from recent years indicates a net loss of ice from Greenland.

The latest Arctic sea ice data shows the continuation of the decade-long trend of shrinking sea ice extent. The winter of 2008-2009 was the fifth lowest maximum extent on record. The six lowest maximum events have occurred in the past six years. In addition, younger, thinner ice that is more susceptible to summer melt is replacing older, thicker ice. Scientists now estimate that an ice-free summer Arctic Ocean may be possible in 30 years, as opposed to previous estimates of 90 years. However, the threat of global warming can still be greatly diminished if nations cut greenhouse gas emissions by 70 percent this century. This prediction was generated using supercomputer simulations of “business as usual” and dramatic cuts in emissions beginning in about a decade. Scientists from the National Corporation for Atmospheric Research say that while the cuts would not avoid significant warming during this century, they would help partially avoid massive losses of Arctic sea ice and permafrost as well as sea level rise.

While the majority of conversation about climate change revolves around greenhouse gases, new research suggests that tiny airborne particles called aerosols are also to blame for Arctic warming. Aerosols include black carbon (small, soot-like particles) and sulfates, which are produced from the burning of fossil fuels, biofuels, and biomass. Sulfates have a net cooling effect on climate because they scatter solar radiation. However, international laws passed over the last three decades have reduced sulfate emissions by 50 percent – improving air quality but also decreasing cooling. On the other hand, black carbon, which absorbs solar radiation and thus increases warming, has steadily increased due to increasing emissions from Asia. According to the cited climate model, the impact of aerosols in the Arctic may be just as great as that of greenhouse gases. These results suggest that climate change is quite a complex problem and may have important implications for policymakers.

In addition to aerosols and greenhouse gases, fire may also be an important player in climate change. According to a new study, intentional deforestation fires alone contribute up to one-fifth of the human-caused increase in emissions of carbon dioxide. The researchers call more the Intergovernmental Panel on Climate Change (IPCC) to consider fire in their assessments of global climate change.  Wildfires, which have also increased, influence climate as well.

While Arctic sea ice is rapidly declining, Antarctic sea ice has actually increased by a small amount over the past 30 years. The reason why? Changing weather patterns caused by the ozone hole. The hole has strengthened surface winds around Antarctica, created more intense storms in the Southern Ocean, and increased the flow of cold air over the Ross Sea, leading to greater ice formation. However, scientists expect that this unexpected result is temporary, and that when the ozone levels recover (around the end of the 21st century), there will be less Antarctic sea ice as a result of climate change.

The ice bridge supporting the Wilkins ice shelf in Antarctica broke off in early April, after a year of disintegration. Radar satellite images have allowed scientists to track the ice shelf’s break up. In late April a piece of ice the size of New York City broke into icebergs - the first icebergs were released from the destabilized ice shelf. The Antarctic Peninsula is one of the most rapidly warming places on Earth.

Dust from Patagonian glaciers, trapped in Antarctic ice and accessed via ice cores, may help scientists better understand past glacier activity and climate change. Changes in dust levels can be correlated with advancing and retreating glaciers in Chile and Argentina. Scientists hope the findings will help predict environmental changes in the future.

News from the polar regions in April also included several interesting biological discoveries. Researchers have found a fossil skeleton of a carnivorous animal considered to be a “missing link” in the evolution of seals, sea lions, and walruses. Discovered in Nunavut, Canada, the species provides evidence of the transition from terrestrial to aquatic animals.

Antarctic researchers have long speculated that “Blood Falls,” a red, frozen, waterfall-like feature at the edge of Taylor Glacier, was caused by rust (iron oxide). New research reveals that a reservoir of briny liquid deep beneath the glacier supports microbes that have lived there – in isolation – for millions of years. The hardy organisms survive in a cold, dark, and oxygen-less environment by breathing iron leached from bedrock.

Mating preferences in many animals can be explained by physical characteristics. For example, female auklets (a northern seabird) prefer males with larger crests. But why? Biologists have discovered that males with large crests have lower levels of stress hormones than those with shorter crests. Lower stress hormone levels mean that the birds are better able to cope with the stresses associated with reproduction (finding food, competing for mates and nest sites, and helping rear chicks). The crest size may thus be an outward sign of physiological “fitness.”

One of the International Polar Year’s many legacies is a network of databases on Antarctic marine biodiversity. The network allows scientists and conservationists to access information about newly discovered species as well as their collection history. While the project began as a Belgian initiative, hundreds of scientists around the world joined forces to create the web-based tool.

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