By Rex Graham
For now, the scientific poop on the krill- and fish-eating bird is good, even if a few local colonies have died out where the most sea ice has disappeared.
Based on satellite images of fresh guano-discolored coastal areas of Antarctica, there are an estimated 3,790,000 breeding pairs of Adélie Penguins, a 53 percent increase over 20 years. That’s according to a study published July 9, 2014, in The Auk, Ornithological Advances.
Adelie Penguins thriving
The penguins build nests of pebbles, and each pair usually incubates two eggs. However, if each of the breeding pairs found in the new survey has only one chick, there are more Adélie Penguins in Antarctica than people in Greece. Individual colonies can include as few as 94 breeding pairs to more than 250,000. Birding cruises to
The new census found 251 total breeding colonies in Antarctica, including:
• 41 previously un-surveyed colonies.
• 17 previously unknown colonies, 11 of which may be recent colonizations.
• 13 previous colonies not found, including eight that have apparently gone extinct. (Adélie Penguins occur only where sea ice is present for at least part of the year.)
Antarctic Peninsula ice shortage
The study confirmed earlier studies that penguin colonies have declined on the tip of the Antarctic Peninsula, a place on the earth immediately south of South America that has seen the most significant climate change. The persistence of sea ice has decreased and the peninsula’s giant ice shelves are collapsing. The ice shelves form where glaciers flow into the sea. When ice shelves break free or melt, upstream glaciers accelerate toward the ocean.
Adélie Penguins live on and around sea ice, but breed on ground swept free of snow. They feed on krill and Antarctic Silverfish that live on the underside of sea ice. Losses of Adélie Penguins on the peninsula and a few other coastal spots have been more than offset by gains in the more frigid windswept East Antarctica (south of New Zealand and Australia). Adélie and Emperor Penguins breed closer to the South Pole that all but a few species of petrels and the South Polar Skua.
Frigid winds help penguins
Wind conditions along the coast of Antarctica, particularly in East Antarctica’s Ross Sea area, have been favorable for Adélies for millennia. The winds may have been boosted by a massive ozone hole larger than the area of the United States. Acceleration of surface winds help to create sea ice near the shore and push it out to sea in an ice-making conveyor belt. The result is more open water immediately near shore that allows penguin parents to move to and from breeding colonies more efficiently.
However, experts on ozone depletion above Antarctica say the expanding sea ice in East Antarctica may also be due, at least in part, to natural variability. “When you run a detailed climate model for 1,000 years, you do find times when for 20 to 30 years or even a bit more, the variability of the Antarctic ocean is such that you get a slight expansion in sea ice,” Susan Solomon, Professor of Atmospheric Chemistry and Climate Science at the Massachusetts Institute of Technology, said in an email. “Since we can’t be sure of the reasons for Antarctic sea ice’s current behavior, it’s very hard to say what might happen in the future, as the ozone hole heals.”
A hop ahead of climate change
Indeed, scientists say the short-term future prospects for the highly social Adélie Penguins are promising. However, for a continent already experiencing rapid climate change, alteration of its sea ice patterns, and melting of its massive ice shelves, the long-term outlook for its penguins is far from certain.
“The Adélie Penguin is an excellent bellwether of climate change and Southern Ocean fisheries,” said Heather Lynch, Assistant Professor of ecology at Stony Brook University in New York and lead author of the study in The Auk. “We have a much more nuanced understanding now of how climate change may be affecting these birds. In some cases, climate change may actually increase their populations, particularly in areas along the Ross Sea where we have glacial retreat that leaves them more space on which to breed.”
Flip side of Antarctic exploitation
Human exploitation of the Southern Ocean also has benefited Adélie Penguins by removing competitors for krill and silverfish, creating an ongoing surplus for penguins. Antarctic fur seals were removed in the 19th century, filter-feeding whales in the mid-20th century.
“The whales eat the same food as the penguins – especially silverfish and krill,” said David Ainley, a co-author of an Adélie Penguin population study published March 2014 in PLoS ONE. “Fewer whales means more penguins and vice versa.”
Ainley, an ecologist at the Los Gatos, Calif.-based H. T. Harvey & Associates Ecological Consultants, said more baleen whales around the Antarctic Peninsula – and previously fewer in the Ross Sea area –partially explain the respective decline and increase of penguins in those areas during the 1970s and 1980s.
Whales, which compete with penguins for krill and fish, have recovered in the ultra-productive Ross Sea region, but Ainley said penguins may be florishing anyway because of more sea ice. Humpback Whales and other whale species have only recently begun to recover in the Antarctic Peninsula region and elsewhere around Antarctica, he said.
Another penguin food competitor, the 6-foot-long Antarctic Toothfish, which is marketed as Chilean sea bass, has become a favorite target of commercial fishing. Fewer toothfish typically means more penguins.
Even bigger forces may also be affecting Adélie Penguins. In fact, studies have shown that large-scale ecological variation, with oscillations in penguin numbers, is the norm in Antarctica. The PLoS ONE study reported that a good year for Adélie Penguins is usually followed by a decline the next, and vice versa.
Census by satellite
Michelle LaRue, a research associate in the College of Science and Engineering at the University of Minnesota, said the 53 percent higher number of breeding pairs may actually not represent a long-term trend for Adélie Penguins. The seemingly high counts could be a one-time anomaly due to better reporting.
The newest census, the first truly comprehensive one, was made possible with better satellite imaging. The imagery enabled LaRue to distinguish the fresh pink-stained areas from the slightly different colors of older guano. (Gentoo Penguins can be difficult to distinguish from Adélies in satellite images; the two species congregate in mixed colonies in the peninsula region. Field surveys are used in conjunction with the images to better estimate Adélie numbers.)
“The increase in Adélies is very likely due to better technology to detect their presence and also probably better ice conditions in East Antarctica – a little of both,” LaRue said. “Our census is most definitely a snapshot and can be used as a baseline for future work.”
Perfect penguin conditions
The Southern Ocean is an incredibly productive source of ocean biomass, accounting for up to 10 percent of global ocean production. The Ross Sea, the area seeing the most significant increase in Adélie Penguin numbers, is the most productive. It accounts for an estimated 28 percent of Southern Ocean productivity, making it a popular destination for birding cruises.
Continent-wide, melting ice shelves “fertilize” the ocean by releasing iron-containing debris that has accumulated from long-distances during previous millennia. Iron is an essential nutrient that is always in limited supply in the waters off Antarctica. The injection of iron supercharges the bottom of the food web: plankton.
Accelerating ice melt
In turn, krill and silverfish feed on the plankton. Penguins, seals, seabirds along with other top predators eat the krill and silverfish.
The accelerated melting of iron-rich Antarctic ice fosters plankton blooms that sequester atmospheric CO2 in additional biomass. Most of it falls as sediment to the ocean floor.
If Adélie Penguins are bellwethers of Antarctic climate change, they also are intimately connected to Southern Ocean biomass productivity, commercial fishing, climatic changes and other factors.
For now, more food and sea ice in East Antarctica has most benefited the ice-obligate penguins. However, changes in sea ice is the norm. An inevitable decline land the accelerating reduction of ice shelves will likely impact penguins.
On satellite images, LaRue and Lynch estimated colony size based on the typical density of penguins and the area of guano stain, which appears as a bright pink or light gray rocky or sandy terrain.
The huge patches of pink amount to indirect evidence that penguins are finding ample prey. After molting, two-month-old juveniles go to sea to migrate with their parents and peers. Adults pause after the breeding season to rest, molt and ride on top of sea ice, out of range of the jaws of Leopard Seals, their chief predators.
Ice sheet breakup
Climatic and ocean-circulation phenomena interact in complex ways at the margins of the earth’s huge ice sheets in Greenland and Antarctica. Experts had predicted that melting of Greenland’s ice sheets would be offset by more snowfall in Antarctica, due to warmer conditions there. However, that hasn’t happened. The interior of Antarctica has actually cooled, possibly because less ozone means slightly more heat can escape into space.
For the coastal edge of Antarctica and its ice sheets, the situation is different. In fact, ice sheets in both Greenland and Antarctica are melting at accelerating rates, raising the global sea level by 0.2 millimeter per year over a 20-year period beginning in 1992.
“There is strong evidence that the Arctic change is due mainly to global warming, and its Northern Hemisphere polar amplification,” MIT’s Solomon said.
However, decades-long oscillations in ocean temperatures may play the lead role in the Antarctic. The warmer-cooler oscillations repeat about every 50 or 60 years, and Antarctica is currently under the influence of a warm phase of the oscillation.
“Yes, climate change is important — not necessarily global warming,” Ainley said in an email. “The reasons behind the Antarctic temperature increases are complex, so much so that one can search far and wide in journalism and not find an attempt at explanation.”
Sea-level ‘wild cards’
Yet, scientists themselves don’t agree on the various factors affecting the earth’s prodigious ice shelves. Computerized climate models are being improved to more accurately predict how oceans will interact with the ice sheets of Antarctica and Greenland. Researchers need to understand key details and trends incorporated into those models to make more reliable predictions of future sea levels.
“Until that time, Greenland and Antarctica will remain the ‘wild cards’ in sea-level projections,” top atmospheric and ocean scientists wrote in a 2012 review in Science.
Another wild card in Antarctica’s climate is the amount of ozone in the stratosphere above the continent. A hole in that layer grew to the size of North America by 2000. It was caused by CFC (chlorofluorocarbon) compounds once used as refrigerants and spray-can propellants that chemically degrade ozone in the presence of light.
Polar vortex redux
During the dark of winter, a vast whirling eddy of extremely cold air called the polar vortex emits heat from earth into space. The ozone layer slows that heat loss and the ozone hole enhances it. When sunlight returns in the spring, the vortex warms and dissipates. Any change in the ozone layer icould be critical because of its effect on the vortex, but exactly how is not fully understood.
The polar vortex remains at roughly -112°F or colder from mid-May through mid-October. The cold air swirls at over 100 mph. It is self-contained: it doesn’t mix with warmer air to the north, thereby locking Antarctica and all of its interior ice in a permanent deep freeze.
Ozone hole repair kit
Because of the hole in the ozone layer, the frigid vortex persists one to two weeks longer than normal, which may be responsible in contributing to more sea ice. But that’s about to slowly change.
Thanks to implementation of the Montreal Protocol and its revisions, production of ozone-destroying CFCs was supposed to have been phased out and stopped. However, up to 20 percent of the CFCs currently in use in the United States, Europe and other countries were purchased after the treaty was ratified by 196 countries and the European Union. Even those nations can import CFCs on the black market. In some U.S. ports, the smuggling of CFCs is second in value to the smuggling of narcotics.
The overall impact of the treaty has been significant. By about 2006, CFC levels in the atmosphere leveled off, and have since edged lower, and the ozone hole has begun to slowly shrinkage. Climate projections now indicate that the ozone layer will return to 1980 levels between 2050 and 2070. The eventual effect on penguins is not known.
The continual rise in global greenhouse gases also is expected to warm Antarctica. If that eventual warming occurs, the size and location of sea ice will change, profoundly influencing the fate of penguins.
“While Antarctic penguins are doing fine at the present, all is not well as climate change and fishery extractions begin to change the ecosystem,” Ainley said. “A few decades from now, if sea ice retreats as predicted, penguins will be decreasing almost everywhere as well.”