New Scientist recently published an interesting article discussing the importance of weather for fisheries. Specifically, it examines some of the ways in which weather and climatic phenomena affect the stocks of individual species and the balance of species within an ecosystem. Important mechanisms through which effects are transmitted include changed ocean temperatures and the aggravated mixing of nutrient-rich deep waters and sunlight-rich surface waters. Where they are persistent, such upwellings produce some of the world’s most fertile marine habitats, such as those off the west coast of Africa.
When it comes to the ocean in general, humanity is in the midst of an overlapping series of massive experiments: bumping the temperature and acidity by emitting CO2, altering salinity by melting ice, aggressively fishing for creatures of all kinds, dumping plastics into the oceans, and so forth. Given the scale of these actions, the unknown linkages between them, and our poor level of overall knowledge about the chemistry and biology of the oceans, it would be surprising if all this did not produce major unexpected changes in the biological makeup of the seas within the next half-century or so.
Nature Geoscience
Published online: 25 January 2009 | doi:10.1038/ngeo420
Long-term ocean oxygen depletion in response to carbon dioxide emissions from fossil fuels
Gary Shaffer, Steffen Malskær Olsen & Jens Olaf Pepke Pedersen
Ongoing global warming could persist far into the future, because natural processes require decades to hundreds of thousands of years to remove carbon dioxide from fossil-fuel burning from the atmosphere. Future warming may have large global impacts including ocean oxygen depletion and associated adverse effects on marine life, such as more frequent mortality events, but long, comprehensive simulations of these impacts are currently not available. Here we project global change over the next 100,000 years using a low-resolution Earth system model, and find severe, long-term ocean oxygen depletion, as well as a great expansion of ocean oxygen-minimum zones for scenarios with high emissions or high climate sensitivity. We find that climate feedbacks within the Earth system amplify the strength and duration of global warming, ocean heating and oxygen depletion. Decreased oxygen solubility from surface-layer warming accounts for most of the enhanced oxygen depletion in the upper 500 m of the ocean. Possible weakening of ocean overturning and convection lead to further oxygen depletion, also in the deep ocean. We conclude that substantial reductions in fossil-fuel use over the next few generations are needed if extensive ocean oxygen depletion for thousands of years is to be avoided.
What I took from the fisheries article is that we could set quotas that would bear a sensible relation to the number of a type of fish likely to exist that year (due to storms bringing nutrients to the surface) but which might vary a lot from the last few years. That might be common knowledge amongst folks who know more about fish, but it seemed pretty cool to me & helped to clarify why we get these stupid arguments between government saying ‘fish stocks are declining, we should catch less’ and fishermen saying ‘we found tons of fish on x year, contrary to your projections, so the fish are fine’ – now I understand why both positions might be right & what we should do about that.
Of course the intellectual problem of deciding upon an appropriate quota seems secondary to the political problem of actually setting and enforcing that quota (thereby displeasing the fishing industry and public opinion), but better science still strikes me as a good thing.