FAQ: Climate Change in the Polar Regions

Image
PC: European Space Agency
Larsen Ice Shelf, part of the Antarctic Peninsula. PC: European Space Agency

How is climate change affecting polar regions?

Climate change is amplified in the polar regions. The northern and southern reaches of the planet are warming faster than any area on Earth, with the Arctic ocean and air temperatures rising twice as much as elsewhere. The Greenland and Antarctic ice sheets are both losing net mass to the ocean, mostly through increased melting from the atmosphere and the ocean. Scientists are increasingly alarmed at the changes these regions face and will continue to face due to climate change.

One major concern is that of declining sea ice in the Arctic and Antarctic. During the winter months in each hemisphere, the polar regions gain sea ice as seawater freezes. That total amount has been shrinking steadily in recent decades. Sea ice is critical habitat for a variety of animals, including polar bears, seals, and penguins. In addition to having effects on wildlife, declining sea ice accelerates the rate of ocean warming. Sea ice reflects sunlight, providing a buffer to the effects of warmer temperatures. When sea ice is lost and the darker ocean surface is exposed, more warmth is absorbed by the sea, exacerbating the effects of climate change. This is known as the ice-albedo feedback.

 

How is the Arctic changing?

Surface temperatures in the Arctic Ocean are warming more rapidly than anywhere else on the planet. The Arctic ice cap is composed mainly of sea ice, and not ice on land. Sea ice fluctuates with the seasons, expanding in the fall and winter and shrinking in the spring and summer. In September of each year, Arctic sea ice is at its minimum. Based on data over the past 40 years, September sea ice is declining at a rate of almost 13 percent per decade. In 2012, scientists recorded the lowest Arctic sea ice minimum on record, when the ice cap shrank to 1.32 million square miles. 

Researchers are also concerned about the Greenland Ice Sheet, the region’s main expanse of land ice. This ice sheet has lost over 5,000 gigatons of ice over the last four decades. This has led to 14 millimeters of sea-level rise, and the freshwater and sediments that have flowed into the ocean have disrupted local climate and ecosystems. If the entire Greenland Ice Sheet were to melt, scientists estimate that global sea levels would rise about 7 meters (23 feet). 

 

How is Antarctica changing?

Long-term changes in the Southern Ocean are contributing to ongoing Antarctic ice loss. The West Antarctic Peninsula is another fast-warming area of the planet, and is home to many iconic Antarctic animals including penguins, seals, and whales. Changes to the surrounding ocean, including warmer waters and more freshwater from melting ice, are affecting ecosystems (see more below). 

The Antarctic Ice Sheet is losing mass due to warmer air and water temperatures. In many areas where Antarctic land ice meets the ocean, large floating ice shelves form, areas particularly vulnerable to ocean melting. Warm ocean currents flowing under ice shelves are driving increasing melt. Scripps researchers have found that geologic formations that allow water to flow below ice shelves are responsible for differing melt rates of the Ross Ice Shelf, Antarctica’s largest. 

This remote area greatly influences climate and ecosystem health for the rest of the planet. Studies show that although the Southern Ocean comprises only about 30 percent of the world’s ocean area, it accounts for half the ocean’s uptake of human-made carbon from the atmosphere and the majority of its uptake of heat. Upwelling – the process by which colder water from the depths circulates to the surface – in the Southern Ocean delivers nutrients to temperate and tropical areas that are critical to ocean ecosystems around the world. Furthermore, the impacts of ocean acidification, due to an increasing amount of ocean CO2 absorption, are projected to be most severe in the Southern Ocean, with ecosystem tipping points being reached in a few decades.

Video URL

 

How do scientists at Scripps study the polar regions? 

Scripps researchers use a variety of on-site and remote tools and methods to study changes to the polar regions. One of the most comprehensive ways to obtain a large-scale view of the polar regions is through satellites. The Ice, Cloud, and land Elevation Satellites (ICESat and ICESat-2) use laser altimetry measurements to determine changes in elevations of glaciers and ice sheets, as well as sea-ice thickness distribution. Scripps glaciologist Helen Amanda Fricker was part of NASA’s Science Definition Team for the launch of ICESat-2 in 2018. These measurements have provided important information on the response of Earth's frozen surfaces to changes in atmosphere and ocean conditions.

Scientists also use permanent and mobile GPS sensors to monitor changes to the surface of the polar regions. These sensors relay data on the height of glaciers, ice sheets, and ice shelves as they change. 

An array of ocean floats are also used to monitor changes to the oceans in the polar regions.  The Argo global network of ocean observing floats has instruments deployed throughout the world’s oceans, including in the polar regions. The floats are designed to spend time at the surface as well as dive to depth to collect information on the chemistry and biology of the oceans, and have the ability to collect measurements under ice – a feature that has drastically improved with the advancement of technology since the early days of the Argo program. Data collected by the more than 4,000 Argo floats has greatly increased our understanding of how the oceans are changing. 

The Southern Ocean Carbon and Climate Observations and Modeling project (SOCCOM) is a multi-institutional project that studies the Southern Ocean’s effects on climate, in particular by deploying Argo equipped with biogeochemical sensors. The data from these floats allows researchers to better understand the currents and carbon systems of the Southern Ocean, in order to make more informed projections about the future of the Earth’s climate and chemistry.  

Many scientists from the Scripps Polar Center travel to the polar regions to conduct research. Physical oceanographer Fiamma Straneo deploys and retrieves sensors around glaciers and ice shelves in the Arctic to study how meltwater affects global climate. Jen MacKinnon, also a physical oceanographer, uses research buoys to study how seawater circulates in the Arctic, and how these physical processes affect sea ice cover. Jeff Severinghaus specializes in studying ice cores, traveling to the poles to drill into ice that has been compacted for many thousands of years. From these cores he analyzes gases trapped in bubbles to determine what Earth’s climate looked like in the past million years. 

 

What are the biological impacts of changes in the poles?

Polar marine ecosystems are particularly sensitive to climate change because small temperature differences can have large effects on the extent and thickness of sea ice. Animals that rely on sea ice, including seals and polar bears, are experiencing habitat loss, forcing them out of breeding and hunting grounds. At the base of the food chain, however, are phytoplankton and other microscopic marine organisms. These organisms are food for krill and fish that in turn supply larger animals with prey. Researchers have documented declining krill populations in areas of the Antarctic, which has affected species like Adelie penguins. Scripps researchers are working to understand how changing temperatures and salinity in the polar regions affect the organisms at the base of the food chain. 

One such example is the Fjord Phyto Citizen Science Project at Scripps, which matches a scientist with tourist cruises to the Antarctic. Travelers get hands-on experience in marine ecology, assisting with data collection on the phytoplankton communities so scientists can better understand how changes in the area are affecting the local wildlife and food webs. 

 

How does warming of the polar regions contribute to sea-level rise?

A large portion of the Earth’s freshwater is frozen in ice sheets in the polar regions. These large expanses of ice cover great land masses. Where they meet the sea they form large platforms of floating ice called ice shelves. Although ice shelf loss itself does not directly contribute to sea-level rise because ice shelves are already floating, ice shelves act as buffers to help slow the slide of ice sheets from land into the ocean. When they become smaller this effect is weakened. If the West Antarctic Ice Sheet were to completely melt into the ocean, it would raise sea levels worldwide by around 3.3 meters (10 feet). Although that amount of melt is unlikely in the coming decades, even four inches of sea-level rise can double the frequency of flooding on the U.S. West Coast. 

Under worst-case scenarios, if the Greenland Ice Sheet melted scientists estimate that sea levels would rise about 7 meters (23 feet). If the Antarctic Ice Sheet melted, global sea levels would jump up a staggering 60 meters (200 feet). Currently, the Greenland Ice Sheet is losing an average of 234 billion tons of ice each year, with researchers predicting 3-5 inches of sea level rise by 2100 if conditions remain the same. In the Southern Hemisphere, Antarctica is losing an average of 252 billion tons of ice per year. Sea level has been higher in the past; the last time global average air temperatures were similar to what they are today, sea level was between six and nine meters (19.6 to 29.5 feet) higher than it is today.

 

How does warming of the polar regions affect the rest of the world?

In addition to sea-level rise, climate change impacts on the polar regions can lead to drastic changes in global weather patterns. Melting ice produces water that is colder and fresher than the surrounding ocean. Depending on where this water ends up in the ocean, it can have a large effect on ocean circulation and climate around the globe. 

A study from Scripps scientists found that polar sea ice loss will account for one-fifth of the warming that is projected to happen in the tropics. The researchers found that meltwater could affect wind patterns, which are responsible for moving cold, deep ocean water to the surface. With less cold water circulating, surface temperatures will continue to warm, creating more precipitation and potentially strengthening the El Niño climate pattern that often brings intense rains to North and South America and droughts to Australia and other western Pacific countries.

Increased rates of warming in the North Atlantic could impact a key oceanic cycle, the Atlantic Meridional Overturning Circulation, or AMOC. An important part of the Earth’s climate system, the AMOC is a large system of ocean currents – including the Gulf Stream – that pulls warmer water from the tropics toward the North Atlantic where it cools, sinks into the deep ocean, and flows southward again. Eventually the water is pulled back to the surface, where it warms and completes the circulation. Because it distributes heat and energy, the AMOC plays a major role in sustaining worldwide climate patterns, and is especially important in regulating climate in northern Europe and coastal North America.

A warmer North Atlantic could significantly weaken the AMOC. The system is driven by changes in salinity and temperature; as the warm water moves north, it evaporates to become saltier and gets cooler in the northern latitudes, making it denser so it sinks. Changes in water temperature in the North Atlantic could disrupt this process. In fact, recent studies have shown that the AMOC may have started weakening over the past decade. Greater weakening could have widespread impacts on climate and weather patterns. While all of the exact consequences are still unknown, for instance, warmer water on the surface could fuel stronger hurricanes.

 

Expert Reviewers:

  • Helen Fricker, Glaciologist and Professor: Scripps Polar Center
  • Fiamma Straneo, Oceanographer and Professor: Scripps Polar Center
  • Jamin Greenbaum, Assistant Researcher: Scripps Polar Center

 

Further reading:

 

Recent Releases

 

References:

  1. Adusumilli et al.,Interannual variations in meltwater input to the Southern Ocean from Antarctic ice shelves.” https://www.nature.com/articles/s41561-020-0616-z 
  2. Smith et al., “Pervasive ice sheet mass loss reflects competing ocean and atmosphere processes.https://www.nature.com/articles/s41561-020-0616-z 
  3. England et al., “Tropical climate responses to projected Arctic and Antarctic sea-ice loss.” https://www.nature.com/articles/s41561-020-0546-9 
  4. Beer et al., “Polar Amplification Due to Enhanced Heat Flux Across the Halocline.” https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019GL086706 
  5. Kennel and Yulaeva, “Influence of Arctic sea-ice variability on Pacific trade winds.” https://www.pnas.org/content/117/6/2824 
  6. Porter et al., “Evolution of the Seasonal Surface Mixed Layer of the Ross Sea, Antarctica, Observed With Autonomous Profiling Floats.” https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018JC014683 
  7. Pistone et al., “Radiative Heating of an Ice‐Free Arctic Ocean.” https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019GL082914 
  8. Tinto et al., “Ross Ice Shelf response to climate driven by the tectonic imprint on seafloor bathymetry.” https://www.nature.com/articles/s41561-019-0370-2 
  9. Shi et al., “Evolving Relative Importance of the Southern Ocean and North Atlantic in Anthropogenic Ocean Heat Uptake.” https://journals.ametsoc.org/jcli/article/31/18/7459/92234/Evolving-Relative-Importance-of-the-Southern-Ocean