Climate Witness: David Ainley, Antarctica
For the past 12 southern summers, with my colleagues, I’ve been engaged in a study funded by the National Science Foundation to understand why Adélie penguins have been increasing in number in the Ross Sea, and why small colonies have been growing much more rapidly than the large ones.
Owing to global warming and the ozone hole (which is still growing), a weather system called the Southern Annular Mode has been stuck in its current mode since the mid-1970s. As a result, since the 1970s, the Antarctic Peninsula region has been blasted by warm winds sucked from South America.
Meanwhile, the Ross Sea region has experienced the opposite: winds blowing north from the Antarctic continent. The result is that the ice season is growing in length in the Ross Sea region, but the opposite trends are occurring in the Antarctic Peninsula region, which is warming faster than just about anywhere else on the planet.
Weather used to be predictable
When I first visited the penguins of Ross Island in the late 1960s and early 1970s, the weather was very predictable. Generally, winds were fairly calm in spring, with infrequent blasts of hurricane force winds. Thus, the sea was generally largely ice covered for most of spring.
By late December, with the coming of summer warmth, the ice would mostly be gone. Actually, in those years, the Ross Island Adélie penguin colonies were slowly decreasing a few percentage points per year. This was because extensive sea ice forces the penguins to do a lot of walking, rather than quickly swimming, and less of the food that adults collect goes toward producing their eggs and offspring.
The weather shifts
In the mid-1970s, winds began to increase in strength and persistence, and winter temperatures changed from about -26 (average annual temperature) to -23 C. The sea ice became thinner, since the wind didn’t allow it enough time to thicken and it disintegrated more easily once the warmer summer temperatures arrived.
Coastal waters became all or partly ice-free earlier in the summer, although with the stronger winds more ice was blown off shore, where it remained longer (lengthening sea ice season). This favoured penguins because they now could swim more than walk.
As a result Adélie penguin colonies in the Ross Sea, where about 38% of the world population nests, began to increase in size. Meanwhile, I made a few trips to the Antarctic Peninsula between 1987 and 1992, and saw first hand how even then glaciers and sea ice were disappearing, and so were Adélie penguins.
Global warming (and the ozone hole) has changed the Antarctic weather. Actually there has been no net change in the amount of sea ice that forms around Antarctica, and likely there is still no net change in the total number of Adélie penguins in the Antarctic.
The shape of things to come for penguins and people
What is happening is that these penguins have given up in some regions but taken advantage of better conditions in others. This is kind of what humans are going to have to be doing, as droughts become more severe in some areas while it rains more in others and as sea level begins to rise dramatically as polar ice caps begin to melt rapidly.
That’s pretty abstract, though, until the time comes when these changes force you or a friend to move house.
In fact, snow fields are disappearing and so are some of the glaciers around the southern Ross Sea. This is dramatically illustrated at nearby Beaufort Island, where rapidly decreasing snow fields are providing more nesting space for the penguins.
That colony, therefore, has been growing rapidly and so now the young penguins that were raised there can find plenty of space to make their own nests rather than having to move to a roomier colony.
Melting glaciers are flooding nesting areas
During this past year, the warming summer temperatures had dramatic results around Ross Island. In particular, I noticed that the ice cap that rests upon Mt Bird has become severely degraded.
Moreover, on warm, cloudless days, with lots of sun beating down, great torrents of water have begun to flow off the glacier and run down through the penguin colonies. Penguins are suddenly finding themselves and their nests inundated by raging torrents.
It’s rather unsettling to see them searching for rocks to raise their nests higher and higher to keep their eggs from floating away. Actually, pretty disgusting, knowing that it’s we humans who have made their lives even more complex and tenuous.
So, for now the penguins in the southern Ross Sea are holding their own, but they have to jump through more hoops, faster and faster, as they are being confronted with situations they’ve never experienced before.
David and his colleagues have completed an educational DVD about penguins and climate change and it is available for cost of shipping at: www.penguinscience.com. There are also sections of the website that discuss the complex subject of Antarctic penguins and climate change.
Scientific reviewReviewed by: Dr. Andres Barbosa Alcon, Departamento de Ecologia Funcional y Evolutiva, Estacion Experimental de Zonas Aridas, CSIC, Spain
The scenario described by David Ainley is highly consistent with the observations published about changes in the climate, the ice and the penguins in Antarctica. It is worth to mention that most of the observations carried out in Ross Sea on this topic have been recorded and published by David himself and collaborators in high-ranked scientific journals.
Such observations also coincide with data published by Italian researchers in the same area. Moreover, the description on the changes in Adelie penguin populations caused by changes in the ice is in agreement with observations made by French researchers at Point Geologie and published in relevant scientific journals. This place is located 1502 km Eastern of the Ross Sea.
On the other hand, the description about the situation of Adelie penguins on the Antarctic Peninsula coincides with observations made by other researchers from the United States at Palmer Archipelago, a place located at half distance along the Antarctic Peninsula.
In this place a clear causal relationship has been established between the variability in ice cover, krill abundance (the main prey of penguins, seals and whales) and penguin foraging. These data together with those indicating a reduction in the populations of Adelie penguins in the area allows one to establish a clear mechanism explaining the effect of climate change on Adelie penguin populations.Reduction of populations of this species and other close relative such as chinstrap and gentoo has been reported in South Shetlands an archipielago located further north.
My conclusion is that the observations reported by David Ainley are highly consistent with peer-reviewed literature on the effects of climate change on penguins in Antarctica.
- Wilson, P.R., Ainley, D.G., Nur, N, Jacobs, S.S., Barton, K.J., Ballard, G., Comiso, J.C. 2001. Adelie penguin population change in the pacific sector of Antarctica: relation to sea-ice extent and the Antarctic Circumpolar Current. Marine Ecology Progress Series 213: 301-309
- Jenouvrier, S., Barbraud, C., Weimerskirch, H. 2006. Sea ice affects the population dynamics of Adelie penguins in Terre Adelie. Polar Biology 29: 413-423.
- Olmastroni, S., Pezzo, F., Volpi, V., Focardi, S. 2004. Effects of weather and sea-ice on the reproductive performance of the adelie penguin at Edmonson Point, Ross Sea. CCAMLR Science 11: 99-109.
- Frase, W., Hofmann, E.E. 2003. A predator’s perspective on causal links between climate change, physical forcing and ecosystem response. Marine Ecology Progress Series 265: 1-15.
All articles are subject to scientific review by a member of the Climate Witness Science Advisory Panel.