This past week I attended a science speaker series in my local community. Our guest that evening was Dr. Sue Moore, a cetacean researcher with the National Oceanic and Atmospheric Administration (NOAA) who has been studying cetaceans (whales, dolphins and their relatives) and Arctic ecology for over 30 years. Dr. Moore came to speak to us about what she calls “the new normal”- massive, visible shifts in arctic oceanography and ecology that we are witnessing as a result of climate change.
According to Dr. Moore, the arctic ecosystem that she came to work in in 1981 no longer exists. The most obvious visual reason for this is the massive change in both the extent and thickness of arctic sea ice during her period of study. Dr. Moore and her colleagues have witnessed a dramatic decline in sea ice between the late 1970s and today, to the extent that we are now left with what she calls “ice refugia” in many areas, rather than an actual ice shelf- small pockets of remaining ice that become life-rafts for many marine mammals including polar bear and walrus.
We are literally “on thin ice”, according to Dr. Moore, as in addition to huge loss of the reach of the sea ice, we see a consistently downward trend in ice volume.
We also looked at data that supports that sea ice is melting earlier in the year, and forming later in the year, for a net effect of up to a month less of ice in the system compared to several decades ago. Not only do these downward trends concern polar scientists, they also are the harbinger of positive feedback loops: ice reflects heat, and its loss means more ice is absorbed into the ice-free areas of the ocean. Thinner ice also allows more heat to pass through, heating the ocean surface.
Gains in surface temperature are also translating into increased storm activity in the arctic region. The last few years have seen huge storms, including large cyclones Dr. Moore described in the Beaufort Sea in 2010 and 2012. These storms are intersecting with changes in sea ice to further extreme events in the polar region, including further weakening of already thin ice, and powerful storms that can build up larger wave heights over larger ice-free areas, to the devastation of coastal communities.
Unsurprisingly, physical and chemical changes in the form of ice extent, thickness, and storm activity is translating into large-scale ecological change in the Arctic. Dr. Moore described huge shifts that polar researchers have seen in primary productivity in large areas of the Arctic over the past few decades. Warmer temperatures and reduced ice extent and thickness are allowing for increased productivity of the plankton that form the foundation of the Arctic food web. Dr. Moore described that primary productivity is overall up about 20% over the time she has been working in the area. What is particularly fascinating about these changes is that we are not only seeing a net positive trend in productivity, but importantly, we are seeing a change in the way that productivity is being moved through the food web. Historically with thicker ice conditions, plankton that grew under the ice sheets would die and fall to the sea floor, supporting a benthic food web including tube worms and other creatures that lived on the sea floor and the benthic predators that fed in turn on them. With greater ice-free areas, the food web in many areas is shifting towards a more pelagic, or water-column, based web: more open-ocean plankton that is directly accessible by fish and baleen whales. Evidence of this shift can be seen in increasing numbers of forage fish that feed on open-ocean plankton, and by tracking the diets of bowhead whales, which are increasingly showing signs of feeding heavily on krill that are being brought further north on advective currents and being supported by the shift towards more pelagic primary productivity. Dr. Moore also described a dramatic northward shift in the feeding grounds of grey whales in recent years, which are following the northward shift in sea ice and the benthic food web that it supports and which this whale species forages on.
These changes are making for a dynamic and complex story for bowhead and gray whale populations, who may shift their ranges, or even fare better, as a result of some of these large-scale food web shifts. But it is a very different story for the animals which depend strongly on sea ice, including polar bears and walrus. Dr. Moore has seen distinct shifts in the behaviors of these species, where they can no longer depend on nearby sea ice for haul out areas, and need to swim much farther in order to find food and return back to their resting areas. In some areas, sea ice that was available 20 or 30 miles off of land is now hundreds of miles offshore, making for much farther and rarer resting areas. Dr. Moore described that while a few decades ago approximately 3/4 of polar bears would do their denning on ice, and a quarter on land; that number has shifted over time, so the majority of polar bear are now denning on land (here’s a recent USGS study that also talks about studying this shift in denning). They, and walrus, are both seen far more often on land, the walrus in huge haul-out populations that are beyond what most researchers and coastal villages are used to seeing. Dr. Moore predicts these stressors will lead over time to thinner, smaller, and fewer bears and walrus as the arctic sea ice landscape continues to diminish.
What was also compelling about Dr. Moore’s talk was her descriptions of how difficult it is for the native coastal communities of the Arctic to respond to these rapid changes. Lack of sea ice, and major shifts in feeding grounds of many of their primary food sources, are posing serious challenges to the native people of these areas. They have not seen these types of conditions in their lifetimes, or even through their oral histories. And these changes are complex: for example, the growth of some whale populations may be a benefit to local communities, but native communities also do not have the sea ice they used to have as a base for their hunting efforts, which hampers the ability to hunt for whales.
When I asked Dr. Moore whether her research and that of her colleagues were finding any receptive ears in Congress, she said that the federal agencies are working hard to communicate the results of this research, but they are not always finding active listeners that are willing to receive or work with what they have to say. The message I took home from Dr. Moore’s talk was that evidence of climate change in the Arctic is nothing we have to wait for from predictive models: it is here and now, and it is contributing to visible, rapid, and complex changes in Arctic ecology; and that the folks doing the decision making about how this story continues to play out, still aren’t getting the message. As Dr. Moore pointed out, there is nothing simple about these changes, and as with all ecosystems, resource shifts provide the advantage to some populations, and the disadvantage to others. However, the declines in sea ice thickness and extent and the upswing in violent storms and the increase in their impacts, does not speak well for the stability of sea-ice dependent animal populations or the native coastal communities that live in the path of these changes.