By Kelly

http://www.news.nationalgeographic.com/news/2009/09/pacific-garbage-patch-pictures/

After reading Evan‘s post on the Tsunami Debris that is now littering the North Pacific I starting thinking about signal to noise ratios. I’ve been sitting here for days looking at data from the laser ablation ICP-MS thinking about signal to noise ratios so now I see them everywhere. If the Japanese government is offering to help clean up the debris, how do they plan to distinguish the signal (tsunami debris) from the noise (the flotilla of garbage already present). And so today’s post is dedicated not to spectral analysis, but to the Great Pacific Garbage Patch, and how I learned to love ocean circulation.

So to answer my own question straight off the bat, I discovered that the difference is  likely to be a matter of size. While the Great Pacific Garbage Patch is a colourful name it conjures images of a garbage dump full of household rubbish and the odd white good. In fact there are no refrigerators floating around the Pacific (at least not to my knowledge), but there is an awful lot of plastic confetti so to speak. Plastic that is in the process of being broken down by sunlight and the action of waves, that is retained in discrete patches (yes plural, the Japanese and the Americans have one each), by the action of the prevailing currents within the North Pacific Gyre (see cartoon below). Thank-you ocean circulation, for sweeping up our mess.

The concentration of these small plastic particles has increased within these patches by almost 100-fold in the past few decades. There are reports that these patches are the “size of Texas!”, however these claims are very hard to quantify, so should be taken with a grain of garbage. What is more certain is that there are serious implications for marine life, some good, others not so. Fish that come to surface waters to feed (known as diel vertigal migration) are consuming what is believed to be 24,000 tonnes of plastic waste per year! This still leaves plenty of  habitat for insects, such as sea skaters, that have been found using the debris as substrate to lay their eggs. What a world.

There have been a number of posts on the blogosphere surrounding research published this year ( the paper is open access) . In fact one of the lead authors regularly appears on the excellent Deep Sea News blog (see here and here). While the size, concentration and implications of these garbage patches may be under debate, I don’t think any one can argue it wise to ignore the fact that our open oceans are accumulating garbage. But further, the origin and nature of the debris doesn’t matter either; household goods drawn out to sea by a tsunami or decades of careless waste disposal, it just shouldn’t be there.

I have seen several excellent talks by Professor Will Steffan from the ANU’s Climate Change Institute on the “Anthropocene“, the period of time that will be evident within the geological record to show the imprint of man. Or will future geologists say, the plastic man.

For more information NOAA has an excellent ‘Marine Debris’ site,  found here, or have a look around Deep Sea News.