As I wrote in the Introduction, the objective of our expedition is to witness the entire life cycle of the phytoplankton and to understand why and how they have bloomed beneath the ice. This requires that we reach ice thick enough and still snow covered such that no light has penetrated it and no plankton has yet bloomed—which is why we’ve come north so early in the year. However, satellite imagery is showing that the melt back has already begun. So now we’re heading north at flank speed, hoping we’re not too late. Sea-ice cover typically recedes to its annual minimum extent in September. On 5 September 1980, sea ice covered 7.5 million square kilometers, an area nearly equal to that of the contiguous United States. Sixty-two percent of that coverage consisted of resilient “old” ice that had survived the summer melt back for two or more years (Jefferies, et al. 2013). Back then, all seemed normal and unchanging in the north. With the exception of military planners, fledging oil producers, and transient scientists, few people gave much thought to the Arctic. But big changes were, quite literally, in the air. By 16 September 2012, the minimum coverage had diminished to 3.4 million square kilometers, 55% less than in 1980, the lowest since the advent of satellite observations in 1979. Further, 58% of the coverage consisted of thin single-year ice. “The minimum extent of sea ice is currently declining by an average of 91,600 km2, roughly equivalent to the area of Maine….Indeed, the six years from 2007 through 2012 have seen the lowest ice extents in the satellite record,” wrote Martin Jefferies, et al. in Physics Today, Oct., 2012. This, then, was no temporal anomaly attributable to natural variation. To a real extent, the identity of the oceanic Arctic is sea ice; every organism from phytoplankton to polar bears evolved within the context of the seasonal wax and wane of ice. Yet now, in most of the Arctic Ocean, the ice is vanishing, and that which remains consists mainly of thin, single-year ice. As every sensate citizen knows by now, Earth’s climate is changing due to anthropogenically produced global warming. Climate is, of course, an enormously complex system, and despite assiduous efforts by scientists from myriad disciplines, it remains only partially understood. However, the fundamental physics is easy to grasp: Carbon dioxide (CO2) is a heat-trapping gas, and the more of it we dump in the atmosphere, the more we alter the climate. The Swedish scientist Svante Arrhenius pointed this out as early as 1896. He wasn’t thinking about global warming, but about the causes of ice ages, hypothesizing that if the quantity of atmospheric CO2 changed, for example, because of a spate of volcanic eruptions spewing vast quantities of CO2, then temperatures would raise. Conversely, he contended, if volcanic activity ceased and oceans and soil absorbed residual CO2, then the climate would cool perhaps enough to engender an ice age. But in Arrhenius’s time, when the world’s population hovered around one billion, and technology seemed capable of solving, not causing, problems, no one imagined that humans could alter Earth’s climate. In 1980, Syukuro Manabe, at NOAA’s Geophysical Fluid Dynamics Lab, developed an early global circulation model into which he fed four times the contemporary concentration of CO2 to test Earth’s atmospheric sensitivity. Results suggested an asymmetrical warming in the Artic compared to the lower latitudes and an attendant precipitous decline in sea-ice extent and thickness. It wasn’t reality, only a model, but it was prescient. However, the actual increase in CO2, it later turned out, was only 15% of the 331 parts per million Manabe had modeled. Yet the decline in Arctic sea ice was even more profound than his model had predicted. Why? As always in climate matters, there are multiple, braided factors and feedbacks, but, in the Arctic, among the most influential and easiest to grasp is the straightforward difference between light and dark. Light things, like ice, reflect the sun’s radiation back into the atmosphere. Dark things, like oceans, absorb and store heat. As air and sea temperature rise and more ice melts, more dark ocean is exposed, causing more heating, which in turn causes more ice melt. This has come to be known as “Arctic amplification.” The feedbacks can and likely will roll on until the Arctic Ocean is ice-free in summer. Yesterday, we encountered our first ice in the Bering Strait right on the edge of the Arctic Circle at 66° N. This morning, at 69°46’ N, we saw large patches of consolidated pack ice separated by open water, called leads. The bridge has been pouring on the power, over 14 knots, to make time in the leads. Now, late afternoon, Healy lurches, jerks, and scrapes her way through well-consolidated pack; there’s no sound like that of a big icebreaker making way through a frozen sea. Some of the ice looks quite thick as Healy breaks and upends it, but it’s all first-year ice. There is no longer any multi-year ice in the Chukchi Sea, and that matters significantly for our purposes, as we’ll see in the next days. So what will we find when we reach our farthest north, up around 72° N? Is the ice thick enough to prohibit light penetration or has light somehow already found its way into the water below, initiating photosynthesis? Are under-ice plankton blooms the new normal in these waters? And what will happen to Arctic ice in near and long term? Will it really disappear in summer? Will the storied Northwest Passage become an unimpeded trade route with all the economic advantages and ecological dangers? At the conclusion of this cruise, we’ll know a bit more about the evolving ecological conditions in the Chukchi Sea; and other scientific expeditions, some working on land and at sea even as we speak, will add other pieces to the Arctic puzzle. But as Yogi Berra put it in his inimical fashion, “Predictions are hard, especially about the future.” I owe thanks to Martin Jefferies, Harold Loeng, James Overland, Donald Perovich, and to Spencer Weart’s brilliant book The Discovery of Global Warming. Leave a Reply Cancel Reply Your email address will not be published. Name* Email* Website Comment Notify me of follow-up comments by email. Notify me of new posts by email.