The Grim Reaper of the Arctic Ocean
28 February 2019
Canadian ocean scientist EDDY CARMACK wonders if it’s time to face the possibility of mass extinction in our northern oceans.
Bad news on the doorstep
I couldn’t take one more step.
—Don McLean, from “American Pie,” 1971
WHAT IS THIS “bad news on the doorstep” stuff? Isolated, the lyrics from Don McLean’s timeless song lamenting the death of American musician Buddy Holly have a different meaning today.
The “bad news on the doorstep” now revolves around the existential risk of climate change. And the Arctic—a harbinger of what may befall the rest of the world—is sending the loudest message of all.
It’s common knowledge that sea ice loss is the leading signal of global warming, and that iconic Arctic animals, such as polar bears and walruses, are acutely stressed. Most researchers recognize that changes in the Arctic are severely affecting mid-latitude weather. But are we fully aware of another impending signal of global change? We are talking about progressive extinction in our oceans, whereby one by one—like the lights of a city going out—individual taxa die off in a process called extirpation that creeps across the planet like an environmental Grim Reaper.
Arctic air temperatures are rising at twice the global rate. So if the bad news climate models foretell potential 6°C to 8°C degree increases in air temperatures by the end of our century, should we expect the Arctic to warm by 12°C to 16°C? Will sea water temperatures reflect this change? This is a scary thought. But one thing to appreciate is the fact that by warming more quickly, the Arctic marine system is offering us a glimpse of the future. By daring to look, might we discover a means of coping with the greatest threat ever faced by our species?
LOOKING AT THE PAST TO UNDERSTAND THE FUTURE
New studies from deep-time geology validate important insights.1 It is thought that life first developed in shallow waters where the right ingredients are brought together. Ironically, it is these same shallow waters that now may be most threatened by mass extinction. Geological and climate modelling studies are showing that the Arctic Ocean lies at the centre of the action, as past extinctions appear to have been most severe in the high latitudes.2 We can now match the projections of climate models for the next few decades to climatic events covering the past 50 million years.3
Fast forward to the present and ask: Why is the Arctic Ocean front and centre? Although it comprises less than 3% of the world’s surface area, it holds a quarter of the world’s shallow continental shelves and a third of its coastlines. As a result, it contains a disproportionate amount of rapidly warming real estate where multicellular life began and is now threatened.
COMING TO GRIPS WITH A NONLINEAR FUTURE
When we think of global warming, we tend to think in terms of linear increases—in other words, 2°C of warming means 2°C warmer. But we are entering a non-linear future, literally. The physical and chemical processes that affect the climate system and life on Earth are extraordinarily complex, so they are captured by parameterizations that mimic the laws of nature. These rate-governing equations are generally non-linear: the density of sea water, the capacity of the atmosphere to carry moisture, the rates of microbial utilization of oxygen and more are all governed by either exponential functions or power laws. Oxygen concentrations in the world’s oceans have already decreased by 2% over the past 50 years, with the Arctic Ocean identified as a region of concern.4 Non-linear systems are subject to surprise, as our Arctic marine system is now demonstrating.
Organisms have evolved the physiological mechanisms they need to live where they do. For example, marine species require thermal, pH and oxygen limits to thrive.5 When these are exceeded too rapidly to allow adaptation, species either move or die. Rising water temperatures are already testing the physiological limits of ecologically and culturally invaluable species such as the circumpolar Arctic cod and Arctic char6, 7; loss of these critical species would reverberate upward through the entire food web.
But extirpation will not occur uniformly or predictably. The consequences of change will spread along different pathways. Consider the Canadian Arctic archipelago, a vast continental shelf and mix of islands and waterways fed by an uncountable number of lakes and rivers and ultimately connecting water masses derived from the Pacific, Atlantic and Arctic oceans.8 This complex geography means signals of warming and chemical change can attack from all directions—even from below, where vast amounts of methane locked in frozen ground await release.9 The dominant variables defining the windows of life are few—temperature, oxygen, pH, salinity, carbon, nutrients and available light—and all are undergoing significant perturbations now. Where do we start? How can we best make decisions about the vulnerability of thousands of species that comprise the complex and distinctive food webs in coastal sites around the Arctic?
Setting up a community-based coastal observatory is one idea, and easy enough to do. But Indigenous People living close to the land must play the key role here, because they know the land and can identify the local species that are most important to their way of life, and thus determine what to study first. This is the experiment we must launch.
Where we end is another matter. The above story spells out a worst-case scenario. It remains to be seen whether or not we heed the news on the doorstep and—in deference to the words of Don McLean—dare take the next step.
EDDY CARMACK is a senior research scientist emeritus for Fisheries and Oceans Canada at the Institute of Ocean Sciences in Sidney, B.C. He has participated in more than 90 field investigations in high-latitude waters.
1. H. Fischer et al., Nature Geosci., 11 (2018)
2. J. Penn et al., Science 362, 1327 (2018)
3. K.D. Burke et al., PNAS, 115, 52 (2018)
4. S. Schmidtko et al., Nature, 543, 335 (2017)
5. H. O Pörtner, & Farrell, A. P. Science 322 (2008)
6. H.E. Drost et al., J. Exper. Biol. 0 (2016)
7. M.J. Gilbert, & Tierney, K.B. Funct. Ecol., 32(3) (2018)
8. E.C. Carmack et al., Ambio (2012)
9. J.F. Dean et al., Rev. Geophys., 56, 207-250 (2018)