Monitoring Climate Change



There is overwhelming evidence that the land and ocean environments of the Antarctic are being altered owing to climate change. In fact, the South Shetland Islands and the surrounding ocean exhibit some of the most dynamic changes on the planet. Over the last 50 years annual mean air temperature in this area has increased by approximately 2.5 degrees Centigrade (~ 5 degrees Fahrenheit). The figure to the right shows that mean surface land temperature has increased accordingly - as much as .25 degrees Centigrade in some areas, especially the Western Antarctic Peninsula.

Right: Land temperature increase has been more rapid in Antarctica than other regions of the world. Photo credit: Dave Shindell, NASA-GISS.

The changes in air temperature and corresponding surface temperature have caused “permanent” ice shelves - some the size of the state of Rhode Island - to crumble, permanently modifying the Antarctic environments in these areas.

Right: On March 5, 2002, the northern piece of the Larsen B ice shelf on the Antarctic Peninsula, which was the size of Rhode Island, fell from the continent due to warming temperatures in that area. Photo credit: NASA-GISS.

NOAA’s Antarctic Ecosystem Research Division ( AERD) is the cornerstone of NOAA’s mission to understand the ecological consequences of climate change in the Antarctic. Over the last 25 years AERD scientists have conducted annual studies during the breeding season of penguins, seals, finfish, and their principal prey, Antarctic krill.

Our studies have shown that, historically, sea ice played a critical role in the relative success of krill reproduction by providing a food source (sea-ice algae and microbial communities) for larval and juvenile krill. In years with a large amount of ice, food resources for these vulnerable stages of krill are high and survival is high. Krill predators also do well following winters with large amounts of ice.

NOAA’s research will help to develop rational and responsive conservation measures to ensure that the Antarctic ecosystems are protected; changes in climate forcing are integrated with other environmental data to create recommendations for sustainable management actions while providing the opportunity to commercially harvest krill.

Warming Oceans

One of the most dramatic effects of the warming of the oceans and atmosphere is the decline in the extent and duration of annual sea ice critical to many species including krill, penguins, seals and whales.

Right top: Sea ice extent, as indicated by blue, is shown to decrease in cycles. Krill are numerous when sea ice extends northward; in years with little sea ice, the less-beneficial salp dominates the waters. Figure: Reiss, unpublished.

Over the last 20 years, the AERD has observed that the decline in sea-ice extent and duration has resulted in not only a decline in krill, but also fundamental changes to the mechanisms governing the environment around the South Shetland Islands. As annual sea ice extent and duration decline and ice is less prevalent each decade, the productivity of the ecosystem becomes controlled by other atmospheric forcing affecting the temperature and currents in the ocean and the amount of nutrients in the water.

Right bottom: Average krill density has decline dramatically in recent years, which has been correlated with the loss of sea ice and warming oceans, among other factors. Figure: Atkinson et. al, 2004.

Climate Cycles

Surprisingly, one of the principal drivers of the environment in the Antarctic is the El Niño-Southern Oscillation (ENSO), which is traditionally known to affect environments at mid-latitudes. For example, the anchovy and sardine populations off South America and California are widely known to be influenced by ENSO. However, in the South Shetland Islands, the El Niño-Southern Oscillation can cause the productivity of the marine environment to vary greatly within and among years. ENSO interacts with the local atmospheric and marine climate to create complicated patterns that scientists are just beginning to unravel.

Right: During warm years, increased water temperatures cause the ocean around the South Shetland Islands to form a discrete layer called the Upper Mixed Layer(UML), which traps phytoplankton and nutrients at the surface and can lead to phytoplankton blooms. During El Niño episodes water temperature decreases and the discrete UML mixes deeper, minimizing primary productivity. Figure: Reiss et. al, 2009.

Effects of climate change and the El Niño-Southern Oscillation can be tracked as they ripple up the food chain, causing predators at every level to change their behavior, their feeding, or their reproductive strategy. As ocean temperatures and nutrients change, AERD scientists monitor their effects on all components of the ecosystem, including changes in water density and current patterns, changes in abundance of Antarctic krill and other zooplankton, and changes to predator populations.

Adapting to Change

Recently, AERD scientist Dr. Christian Reiss worked with scientists at the Scripps Institution of Oceanography to show that inter-annual variability in phytoplankton production (the principal food for krill) is associated with the rising and falling water temperatures caused by ENSO. This fundamental connection between global atmospheric climate patterns and the production upon which the Antarctic ecosystem is based, shows that global climate changes will directly affect the Antarctic animals that NOAA is designated to protect.

The three different species of penguins that nest on the South Shetland Islands have been changing their ways in an effort to adapt to a changing environment. AERD scientist Dr. Wayne Trivelpiece has found that generalist gentoo penguins that are able to quickly adapt to changes are thriving; at the same time, chinstrap and Adélie penguins, specialists in either food or nesting habitat selection, are declining in number every year.

Right: Adelie penguins gather at a nesting site in the South Shetland Islands, where they spend October through March of each year caring for new young.

Antarctic fur seals populations have also undergone changes, though not as dramatic as penguin declines. Dr. Mike Goebel has shown that after three decades of population growth following re-colonization of the South Shetlands in the early 60’s, the fur seal population stabilized and has not increased in the last decade. Krill is the primary prey of fur seals during the austral summer. However, they appear to have more flexibility in diet and consume more fish than chinstrap and Adélie penguins. Their ability to exploit other non-krill prey may serve to buffer their response to changes in krill populations.

Right: Antarctic fur seals haul out at breeding sites throughout the South Shetland Islands and other areas in Antarctica during the summer breeding season.

Each of these changes is not isolated, but could cause continued fluctuation to the ecosystem in the South Shetland Islands. Because the AERD has conducted annual surveys for more than 20 years, scientists are able to detect these changes and determine if they are linked to the annual shift of the currents in the Southern Ocean, or the decadal shift of global climate.

For more information on the AERD climate change monitoring program, contract Dr. Christian Reiss at christian.reiss@noaa.gov.

Last modified: 12/24/2014