The Impact of Climate Change on Polar Regions

Warmer temperatures in the Arctic and Antarctic are causing environmental changes that affect the regions’ plants, animals, and people. These unique ecosystems, with plants and animals found nowhere else, are falling victim to some of the earliest and most severe impacts of climate change. In some cases, these changes are creating feedback loops that are intensifying climate change in the polar regions and around the globe.

Arctic & Antarctic: An Overview

Both Antarctica and the Arctic are very cold, with lots of snow and ice, and surprisingly very dry. Because they receive so little precipitation, both are classified as deserts. The most significant difference between the geography of the two polar regions is that the North Pole is located in the middle of the Arctic Ocean while the South Pole is on the Antarctic continent. At just over five million square miles, Antarctica is the planet’s fifth-largest continent after Asia, Africa, and North and South America. It is the coldest, windiest, and driest continent on Earth. Most of the plant and animal species on the continent inhabit the Antarctic Peninsula, which stretches north toward South America. The peninsula has more temperate conditions than the rest of the continent; some of its land is even ice-free during the summer months (November through March).

The Antarctic ice sheet, the largest reservoir of fresh water in the world, is about one mile thick on average and up to three miles thick in some places. It covers about 98 percent of the continent and its presence helps keep the region cold throughout the year. The low annual variability in temperature restricts the region’s biodiversity, making it habitable for relatively few terrestrial plant and animal species.

Five species of penguins breed in Antarctica and a variety of seabirds are also found there. Marine mammals, including whales and seals, populate the Antarctic seas as do fish, squid, and krill. While no trees or shrubs grow in Antarctica, some low-growing flowering plants do manage to grow there as well as mosses, lichens, and fungi that have adapted to low temperatures.

The Arctic comprises the entire region north of the Arctic Circle, which includes Greenland and the northern portions of Canada, Alaska, Russia, Norway, Sweden, Finland, and Iceland. Sea ice forms a frozen environment centered at the North Pole and extending to the surrounding land masses during the winter.

Temperatures are higher during the Arctic summer than they are in Antarctica, allowing a greater variety of plant and animal species to flourish. “It’s a much more dynamic environment,” says Glen MacDonald, a professor of geography, ecology, and evolutionary biology at the University of California, Los Angeles and director of the UCLA Institute of the Environment and Sustainability. Along with a great variety of birds and marine mammals found in the Arctic, notable animal species on land include the polar bear, Arctic fox, musk ox, caribou, and reindeer.

Ice: A Climate Indicator

All polar ice is not the same. Though it is all frozen water, polar ice is formed in several ways. The ice on land in Greenland and Antarctica was formed from annual layers of snow that were compacted into ice over thousands of years. This glacial ice flows downhill under the force of gravity, and as it reaches a coastline, it can flow outward over the water to form ice shelves. Large chunks of ice that break off of these floating masses are icebergs.

Sea ice forms when the surface of the ocean freezes in winter months. Some of the ice melts again during the warmer summer months. In the Arctic, the central core of the vast sea ice mass is centered at the North Pole and never melts away completely—it remains frozen throughout the year. But the sea ice farther away from the central core is susceptible to annual freezing and melting. Likewise, in Antarctica, much of the sea ice that forms annually also melts each summer.

“The extent of sea ice in the Arctic is a bellwether of global climate, whereas the amount of sea ice that forms around Antarctica is more a result of regional conditions,” says LuAnn Dahlman, an educator at the National Oceanic and Atmospheric Administration’s (NOAA) Climate Program Office. In fact, formation of sea ice around Antarctica each winter is aided in part by the Antarctic Circumpolar Current, which helps isolate the continent from warmer water that moves south from the Equator.

Warming Trend

Using ships’ logs, explorers’ diaries, and satellite data, scientists have compiled temperature records for the polar regions and documented the extent and thickness of the floating sea ice. Scientists have also collected ice and soil cores, which document past climate conditions dating back hundreds of thousands of years. Using modern measurement techniques and historical data, scientists have identified an unmistakable warming trend.

Since the 1950s the Arctic region has warmed more than other parts of Earth’s surface, and it is predicted that this trend will continue. Because the Arctic region is showing early and dramatic warming, it has been called the “canary in the coalmine” for climate change. “In terms of temperature, it tends to react faster and more strongly to changes in climate—and we are seeing that now,” MacDonald says. The average temperature of the Arctic has risen nearly three degrees Fahrenheit over the past century—about twice as much as the global average. Furthermore, climate records indicate that the Arctic is warmer now than it has been in over 2,000 years. Meanwhile, a warming trend around the Antarctic Peninsula has resulted in an increase in the average winter temperature of nine degrees Fahrenheit.

Impacts of Climate Change

In the Arctic, rising temperatures are decreasing both the area covered by and the thickness of sea ice. Satellite data collected since 1979 show a decline in the amount of sea ice in winter as well as summer. In 2009 alone the amount of Arctic sea ice that was lost, compared to the historic average, was roughly the size of the state of Alaska. The loss of sea ice in the Arctic over the past several decades is one of the most dramatic indicators of climate change, scientists say.

The polar ice caps help regulate Earth’s climate by reflecting a certain amount of sunlight back into space. Snow and ice are said to have a high “albedo” because they reflect sunlight. In contrast, the land and ocean have low albedo; they are much darker and absorb solar energy. As Arctic ice disappears, more of the darker surface is exposed, absorbing more solar energy. The lower albedo leads to additional warming. This melts more ice and exposes even more of the darker surface, creating a feedback loop that accelerates climate change.

Another source of concern is the thawing of frozen Arctic soils, which contain undecomposed dead vegetation. When soils warm, the decomposition process can begin. “As we warm the Arctic, the soils will warm, and the carbon which they’ve stored for thousands of years will be released into the atmosphere, and that will then increase the greenhouse effect,” MacDonald says.

Scientists are also conducting research into changing weather patterns that may arise from sea ice loss. As more of the ocean is warmed by sunlight, the changing balance may affect the circulation patterns of air above the water.

In Antarctica sea ice levels have hovered around the thirty-year average. However, Dahlman points out that the collapse of ice shelves on the continent in recent years is an issue of great concern. As temperatures rise and ice shelves break up, ice flows off the continent at a faster rate, directly affecting sea level rise.

Sea Level Rise

Sea level rise is caused by melting of continental glaciers, including the ice sheets on Greenland and Antarctica, and by the expansion of warming seawater. This is posing a threat to human populations around the world. MacDonald estimates that if warming continues at its current rate, sea levels may rise anywhere from thirty inches to three feet by the end of this century. Other experts place the range anywhere from three to six feet, with the possibility of higher levels depending upon what happens to the ices sheets on Greenland and the Antarctic Peninsula. Human settlements in low-lying coastal areas around the world will be threatened with by flooding and erosion, and vital infrastructure like ports, airports, and major coastal cities will also be affected.

Impacts on Arctic Animal Species

Scientists have limited knowledge of how global warming will impact animal species in the Arctic. However, research indicates that changing climate conditions are already having measureable effects.

For thousands of years, areas in the Arctic over the continental shelf, where the water is relatively shallow, have been covered by ice for at least part of the year. “As the ice retreats, species that depend on that combination of shallow water and ice will have to adapt to new conditions, migrate to new areas, or perish,” Dahlman says. Important commercial fisheries, such as king crabs, may be affected, she adds. Polar bears are also dependent on sea ice as a platform from which to hunt seals. Studies confirm that polar bear populations have seen a measurable decline over the past few decades.

Warmer ocean temperatures are also causing population explosions or “blooms” of sea jellies. When warm water currents bring high volumes of plankton into Arctic seas, sea jellies drift along with the food source. Their presence affects fisheries because the jellies feed on larval fish and clog fishermen’s nets.

Arctic fox populations are facing pressures, particularly in the Scandinavian portion of their range. Here climate change is affecting the habitat of lemmings and voles, the foxes’ primary food source. The Arctic fox also faces increased competition from the red fox, which is more acclimated to the warmer forest environment. As predators, Arctic foxes are reliant on the stability of the food chain, which is currently vulnerable to disturbance by climate change impacts.

Conversely, warming temperatures and the extension of the forest boundary further north would improve conditions for spruce trees. This would allow forest species such as the grizzly bear and others to move north, MacDonald says. “I suppose there are winners and losers, but the losers in some ways could include some of the really wonderful iconographic animals and plants that typify this very interesting biome—the Arctic tundra,” he says.

Case Study: Penguins of the Antarctic Peninsula

Rosi Dagit, senior research scientist for the Oceanites Antarctic Site Inventory project, has been tracking penguin populations in the Antarctic Peninsula region for eighteen years. She says that while penguins in that area spend most of their time during the winter months dispersed and out to sea, in November they begin to return to land to find their nests. “There are literally hundreds of thousands of Adélies and Chinstraps, and they all lay their eggs within a week or two,” according to Dagit.

Dagit says she has seen some seabird populations decline across the entire Antarctic Peninsula region. The changing temperatures seem to be resulting in changes in phytoplankton availability. This impact travels up the food chain, affecting the birds’ ability to find food, she explains. Climate change has had a measurable impact on penguin chick viability. “The hypothesis is that with the increase in sea temperature, the sea ice along the Antarctic Peninsula is not forming the way it used to and the storm tracks are coming at a different point in time,” she explains. Heavy snowfall in December can cause breeding failures, and not all the birds are able to re-establish a second set of eggs. It also pushes the timing back so that chicks are too small to survive by the time fall comes, and the adults abandon them to molt and prepare for the winter. When it gets really warm in January, February, and March, the penguin chicks get overheated because they are too well insulated for the moisture-loaded storms that bring rain instead of snow. Chicks that get rained on get wet and can become hypothermic and die.

Over the past few years Dagit has noticed another climate change-related threat to penguin populations in the Antarctic Peninsula region. Not only have warmer temperatures impacted their ability to reproduce, but also the Gentoo penguin, a species better adapted to a more temperate climate, has been out-competing Adélie and Chinstrap penguins.

This is verified by data originally collected at the turn of the twentieth century by French explorer Jean Baptiste Charcot and the team of scientists he brought with him to Petermann Island. Between 1908 and 1909 Adélies outnumbered Gentoos at Petermann Island by the hundreds. “Now the numbers are completely reversed,” Dagit says. “In addition, the Gentoos have been successfully nesting at several different island groups even further south, so they’re spreading,” she says.

Impacts on Humans

While Antarctica has never had a permanent population, only serving as a temporary residence to scientific parties and tourists, the Arctic has been home to indigenous peoples for many thousands of years. Today, it is home to more than four million people.

The stability of structures, roads, and other infrastructure in the Arctic relies on permafrost—soils that remain frozen throughout the year. In some places the permafrost has begun to thaw, making the surface unstable. In addition, people use the sea ice and ice on land for transportation in the Arctic. Major industries could be affected, including mining, oil and gas exploration, and other industries served by ice road truckers.

A decline in animal populations resulting from warming temperatures would also affect humans in the Arctic who rely on caribou and seals and other marine mammals as a source of food. “There would be decreases in the availability or the timing of availability of these resources,” MacDonald says.

However, global warming and the break-up of ice cover may make some human activities easier. Loss of sea ice will lead to open navigable ocean, making it easier for ships to bring supplies in or ship out naturally derived resources, such as natural gas and petroleum. Tourist activity has already taken advantage. In summer 2007 tourists sailed through the Northwest Passage for the first time in history.

Predictions for the Future

When asked what the Arctic and Antarctic regions could look like ten to fifty years from now, Dagit, Dahlman, and MacDonald agree that significant impacts will continue to be felt. “Fifty years into the future, I expect that we’ll have more ice shelves breaking up around Antarctica, ultimately increasing the rate of ice flowing off the land,” Dahlman says.

MacDonald also predicts that the amount of Arctic sea ice will be considerably reduced, leading to increased shipping activity across the Arctic Ocean. While he does not believe the open tundra will ever completely disappear, he thinks continued warming trends will cause the forest to move north and encroach on the tundra, negatively impacting animals adapted to this habitat. Warming temperatures may also introduce new diseases in Arctic animal species. Bird, mammal, and insect populations may be impacted by changes in vegetation, such as the time of year when plants flower.

Dagit sees a future in which Antarctic species and their habitats have shifted significantly. “The Gentoos are taking over [on the Antarctic Peninsula],” she says. “We’re going to see a total shift in species composition and diversity because these penguins are going to be much more successful and able to keep reproducing. They’ll displace Adélies and Chinstraps, and those species are not going to be able to compete as effectively, both for food and for nests.”

However, uncertainties remain. “We’re probably still at a very early stage in understanding how natural climate variability might play out in the Arctic on top of projected greenhouse gas-induced warming,” MacDonald says. Although measurable changes are taking place in both polar regions that scientists have been able to trace to human activity, the very nature of these regions, isolated and characterized by extreme conditions, makes looking into the future a complex prospect. “It’s still an environment with a lot of mysteries,” MacDonald says. “It’s vast and sparsely populated, and it’s a tough environment to work in. It’s also having some of the most amplified changes in climate, and it makes us realize how much we have yet to learn about our planet.”