Study reveals strong links between Antarctic climate, food web

July 07, 2014

A long-term study of the links between climate and marine life along the rapidly warming West Antarctic Peninsula reveals how changes in physical factors such as wind speed and sea-ice cover send ripples up the food chain, with impacts on everything from single-celled algae to penguins.

The study, published in today's issue of Nature Communications, is authored by Dr. Grace Saba, an alumna of William & Mary's Virginia Institute of Marine Science (now at Rutgers University); VIMS professor Deborah Steinberg; Dr. Vincent Saba, a VIMS alumnus now at NOAA's National Marine Fisheries Service; and colleagues with the Polar Oceans Research Group, Lamont-Doherty Earth Observatory, Woods Hole Oceanographic Institution, and the University of Colorado at Boulder.

The authors are members of the Palmer Long-Term Ecological Research program (PAL-LTER), which conducts annual shipboard surveys along the western side of the Antarctic Peninsula, including the coastal ocean near Palmer Station--one of the three U.S. research stations in Antarctica. Program scientists began studying the fast-changing region in 1990.

Steinberg, one of the Palmer program's lead scientists since 2008, says the current study provides one of the few instances where marine researchers have a dataset of sufficient length and detail to reveal how climate signals can reverberate through a polar food web.

"That's the importance of long-term ecosystem monitoring," says Steinberg. "It provides the data needed to separate a signal from the noise, and to determine how plants and animals interact with both their physical environment and each other. That knowledge is critical as climate warming continues to impact this polar ocean ecosystem." The West Antarctic Peninsula is one of the fastest warming regions on Earth, with annual winter temperatures increasing by 11°F during the last 50 years.

The team's research shows that populations of photosynthetic algae--the tiny drifting plants that support the polar food web--peak every four to six years in the waters along the West Antarctic Peninsula. These blooms correlate with a negative phase of the "Southern Annular Mode," or SAM, a seesaw shift in atmospheric pressure between mid-latitudes and Antarctica.

In winter during a negative phase of SAM, cold southerly winds blow across the Peninsula, increasing the extent of winter ice. From spring into summer, winds are significantly reduced, delaying ice retreat.

"The combination of a windy winter with heavy sea ice followed by a calm spring favors the development and persistence of a stable water column in the summer along the West Antarctic Peninsula," says Saba. This stable, or stratified water column, with a layer of fresher, less-dense ice-melt floating atop a saltier layer below, encourages phytoplankton growth, likely by keeping the tiny plants nearer the sunlit surface and in proximity to the iron-rich glacial meltwater they need to thrive.

Moving up the food chain, the team's sampling reveals that the area's periodic, climate-driven phytoplankton blooms are a key to krill "recruitment"--the addition of new, young individuals into the krill population. Adélie penguins and other top predators in the Antarctic food web rely on a robust population of krill prey for their own health and reproductive success.

"When climate conditions--a negative SAM and stable water column--lead to peaks in the abundance of phytoplankton and krill, Adélie penguins don't have to go far to forage," explains Saba. "But when SAM is positive, warm northwesterly winds blow over the Peninsula region, bringing less sea ice and a less-stable water column--factors that discourage the large blooms of phytoplankton on which krill rely. Penguins then have to forage further, and thus end up delivering less food to their chicks. That can decrease their reproductive success."

Ongoing work by Palmer scientists shows that the population of Adélie penguins near Palmer Station has fallen 85% since 1974. Though the researchers stop short of attributing this decline solely to a climate-related shortage of krill, they do express concern for the future given that climate models project an increase in the occurrence of positive SAM episodes during the coming century.

"Projections from global climate models under 'business-as-usual' emission scenarios up to the year 2100 suggest a further increase in temperature and in the occurrence of positive-SAM conditions," says Saba. "If even one positive SAM episode lasted longer than the krill lifespan--4 or 6 years with decreased phytoplankton abundance and krill recruitment--it could be catastrophic to the krill population."

In addition to Adélie penguins, krill are the main food source for Antarctic fur seals, macaroni and gentoo penguins, and albatross. They also feed baleen whales such as humpbacks.
-end-


Virginia Institute of Marine Science

Related Sea Ice Articles from Brightsurf:

2020 Arctic sea ice minimum at second lowest on record
NASA and the National Snow and Ice Data Center (NSIDC) at the University of Colorado Boulder shows that the 2020 minimum extent, which was likely reached on Sept.

Sea ice triggered the Little Ice Age, finds a new study
A new study finds a trigger for the Little Ice Age that cooled Europe from the 1300s through mid-1800s, and supports surprising model results suggesting that under the right conditions sudden climate changes can occur spontaneously, without external forcing.

How much will polar ice sheets add to sea level rise?
Over 99% of terrestrial ice is bound up in the ice sheets covering Antarctic and Greenland.

A snapshot of melting Arctic sea ice during the summer of 2018
A study appearing July 29 in the journal Heliyon details the changes that occurred in the Arctic in September of 2018, a year when nearly 10 million kilometers of sea ice were lost throughout the summer.

Antarctic penguins happier with less sea ice
Researchers have been surprised to find that Adélie penguins in Antarctica prefer reduced sea-ice conditions, not just a little bit, but a lot.

Seasonal sea ice changes hold clues to controlling CO2 levels, ancient ice shows
New research has shed light on the role sea ice plays in managing atmospheric carbon dioxide levels.

Artificial intelligence could revolutionize sea ice warnings
Today, large resources are used to provide vessels in the polar seas with warnings about the spread of sea ice.

Antarctic sea ice loss explained in new study
Scientists have discovered that the summer sea ice in the Weddell Sea sector of Antarctica has decreased by one million square kilometres -- an area twice the size of Spain -- in the last five years, with implications for the marine ecosystem.

Antarctic sea-ice models improve for the next IPCC report
All the new coupled climate models project that the area of sea ice around Antarctica will decline by 2100, but the amount of loss varies considerably between the emissions scenarios.

Earth's glacial cycles enhanced by Antarctic sea-ice
A 784,000 year climate simulation suggests that Southern Ocean sea ice significantly reduces deep ocean ventilation to the atmosphere during glacial periods by reducing both atmospheric exposure of surface waters and vertical mixing of deep ocean waters; in a global carbon cycle model, these effects led to a 40 ppm reduction in atmospheric CO2 during glacial periods relative to pre-industrial level, suggesting how sea ice can drive carbon sequestration early within a glacial cycle.

Read More: Sea Ice News and Sea Ice Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.