The question before us yesterday was: Given the cost and massive concerted effort required, why study the Agulhas Current? As I watched the team deploy another mooring to measure the current, a black-browed albatross with those beautiful chevron-shaped, high aspect wings effortlessly wheeled and soared on the wind, and I wondered if we would ask of ornithologists, why study sea birds? Would we ask that of scientists studying wolves or polyps or pelagic fish? Probably not. Is that because biology is so much more accessible than physics, or that we can see animals, but not ocean currents, with the naked eye?
Who’s to say whether it’s more “important” to understand the ways and means of an ocean current than, say, those of sea birds, and by what criteria? However, there remains this significant difference between the two in what we might call context and causality: Plants and animals always exist within the context of a particular ecosystem, and when local climate conditions change, resident organisms are forced to adapt or die out. To oversimplify only slightly, the ocean and its colleague, the atmosphere, can cause climate change.
The top few meters of the oceans contain more heat energy than the entire atmosphere. Because all currents are linked within each ocean basin and because they “communicate” between all oceans, currents transport that heat energy around the globe, spreading it more evenly than would otherwise be so—and thereby moderating tropical and high-latitude extremes. But that doesn’t mean that they will continue to do so. Therefore, most oceanographic expeditions today carry at least a climatic subtext. How will the coupled ocean-atmosphere system respond to the carbon dioxide we’ve been dumping into the atmosphere since the dawn of the Industrial Revolution? We know that CO2 is a greenhouse gas; we know that its quantity has been steadily increasing; and we know that the world is warming as a result. Will the ocean protect us from ourselves by continuing to absorb nearly half of that CO2, or will it reach a saturation point and begin outgassing CO2 into the atmosphere? Will a complex series of feedbacks kick in and trip rapid climate change? We’d like to know these things for their potential usefulness to policy makers, but scientists—in the business of understanding and explaining how nature works—would still be studying the ocean, its internal dynamics and their relationship to external systems, even if there were no climate emergency in the offing.
Lisa published a fascinating paper in the Journal Nature (28 April 2011) that focused in part on the role of those rings spinning off from the Agulhas Retroflection around the Cape of Good Hope into the South Atlantic, thus linking the Atlantic and Indian Oceans. This, the Agulhas leakage, has been largely overlooked in most climate models, but we’re likely to hear more about it in the future. In a warming world, Lisa points out, the leakage is likely to increase in volume, delivering more warm, salty water into the Atlantic, where it can act as a “positive feedback” increasing the heat transport, thus exacerbating global warming.
However, while we’re talking about these world-shaping physical forces, it’s worth recognizing that we—humankind—have become a geophysical force in our own right. The same fossil fuels that have contributed so much to our technological advancement and quality of life are now reshaping the world to our disadvantage. And so, despite our power, we find ourselves in a similar position to that of any other organism constrained in a changing ecosystem and forced to adapt. The only difference is that our ecosystem is global in scope.
