Originally published on March 30th, 2014 at generalcirculation.blogspot.com
The disappearance of Malaysian Airlines Flight 370 is deeply unsettling to me. Not only is it a tragedy of loss and uncertainty for the friends and families of those on board, but it's also a disconcerting reminder of how very big the Earth is.
The search for the flight has mainly focused over the South Indian Ocean, where it's been stymied by treacherous weather and unpredictable currents that could take debris in any direction. It's a part of the world that we rarely think about, but the recent search efforts have been a reminder to me that it's actually tremendously important.
The South Indian Ocean is part of what climate scientists think of as the "Southern Ocean"--a vast stretch of the world's water that wraps all the way around Antarctica without any land to get in its way.
One side effect of the absence of land, is "infinite fetch."
Aside from being the name of my future rock band and an excellent compliment on someone's looks, "infinite fetch" refers to the fact that, because there's no land in the way, the winds above the Southern Ocean have a fetch (what oceanographers call the distance over which winds blow in a roughly constant direction) that's essentially an infinite loop. The longer the fetch, the bigger the waves and the stronger the storms. Hence, the unpleasant MH370 search conditions.
Image courtesy of William Putnam and Arlindo da Silva, NASA/Goddard Space Flight Center. A model simulation shows the flow of particle air pollution over the Southern Ocean.
On Tuesday, though, I was reminded of another way in which the Southern Ocean is a climate science box of chocolates. Dr. Daniel Sigman, Princeton Geosciences Professor and winner of a 2009 MacArthur "genius" grant, led a dinner discussion featuring some of his lab's work that was recently published in Science magazine.
The work confirms a fascinating feedback loop that is thought to have helped the last ice age take hold.
The Southern Ocean is full of phytoplankton, little ocean organisms that (among other things) turn carbon dioxide into oxygen. The phytoplankton need iron in order to grow, which there's relatively little of in the Southern Ocean, though there are tons of the other nutrients phytoplankton need. If lots of iron were to miraculously appear, the phytoplankton could grow rapidly and turn more carbon dioxide into oxygen.
Here's the feedback loop that Dr. Sigman's lab has confirmed: Step 1: Cooling from the start of the ice age dried out the southern continents, leading to more dust. Step 2: That dust, which was filled with iron from the soil, blew over the Southern Ocean and settled on it. Step 3: The extra iron in all that dust led to a big bloom in phytoplankton growth. Step 4: As the phytoplankton grew, they turned huge amounts of carbon dioxide into oxygen. Step 5: Because carbon dioxide is a greenhouse gas, less of it meant that the planet got cooler. Step 6: That cooling led to more drying in the southern continents, and we're back to Step 1!
In the image above, from a model simulation of modern-day atmospheric pollution flows around Antarctica, you can see big plumes of dust (the red/orange stuff) coming off of South America. Imagine this multiplied several times over and you get an idea of what was going on during the ice age.
The theory Sigman's group confirmed was first theorized in the early 1990s, and has spawned lots of speculation about how deliberate iron fertilization could be used to engineer storage of carbon dioxide in the ocean. Even though I'm not an oceanographer, "geoengineering"schemes like iron fertilization open up a whole vat of interesting (and troubling) environmental policy questions, so I dug into the topic a bit for a class a few semesters back.
Iron fertilization is controversial, and possibly dangerous and ineffective. In order for the carbon dioxide to actually get stored, the phytoplankton have to sink below the mixed layer of water at the surface when they die, which only happens 10% of the time. The phytoplankton blooms can also be toxic and cause changes farther up the food chain. Then there's all the carbon dioxide that would be emitted in mining the iron and getting it out to where the phytoplankton are (check out this report for more).
Nonetheless, a random Californian businessman, Russ George, apparently tried doing it single-handedly off the coast of Alaska in 2012, which raises lots of interesting governance questions. How should we approach deliberate ecological manipulation? How do we monitor attempted iron fertilization (George's fertilization scheme was only identified in satellite imagery after he announced its completion)? And should we even consider trying to solve one environmental problem by potentially creating another?
The Earth is so very big, and I have so many questions.