18 December 2009

Dust’s Importance to Climate Change

Posted by Michael McFadden

Image from NASA/SeaWiFSI’m going to start master’s research soon, and one of my options is to work on dust. I tell people about the project, and inevitably I get quizzical looks and raised eyebrows–“Dust? Really?” But dust is a key part of marine fertilization processes. Dust fluxes, especially over oceans (as seen in the NASA image to the right), provide iron and other micronutrients that phytoplankton need, and changes in dust flux are often tied to marine primary productivity—which mean that dust flux is also intimately related to carbon dioxide drawdown from the atmosphere.

A series of atmospheric science posters about dust were presented this morning. Matthew Johnson, of the University of North Carolina, modeled potential iron inputs to the Southern Ocean; he asked whether anthropogenic factors might be changing the amounts of biologically-available iron—what can the phytoplankton use, and have we changed that available fraction? Becky Alexander, of the University of Washington, Seattle, wanted to know whether atmospheric absorption of sulfates was acidifying dust (which would change the chemical nature of the dust floating out over the ocean, potentially changing its bioavailability). Akori Ito, of the Research Institute for Global Change, asked the question more directly: are anthropogenically-induced pollutants being processed to become more bioavailable?

It’s really easy to focus on carbon dioxide and the six major greenhouse gases as the main atmospheric components of climate change, but these modelers are looking at some of the less obvious ways atmospheric aerosols and the atmosphere-marine barrier work to influence climate.

So—what’s the next step? The modelers have generated really interesting predictions of how the atmospheric dissemination system works. Are there people out there who are now connecting the dots to the biologic response? Have phytoplankton assemblages responded to changes in the acidity of dust flux, or to the changes in bioavailable iron? For that matter, do the models correspond to observed changes in dust? There’s a million questions, but I think there’s a lot to be learned about ocean’s control on climate responses, as mediated through dust—maybe I’ll get to learn more next year!

–Ale Borunda, Columbia University Earth and Environmental Sciences Journalism Graduate Student