COMMENT pubs.acs.org/est
Oceans: The Final Frontier ne of the first assignments I give my students in modeling class is to solve a simple problem: Calculate the mass of the oceans compared to that of the atmosphere and “living soil”. (Answer below.) Of course students discover that the mass of the ocean is huge— it's orders of magnitude greater than the atmosphere and soil. That's why it's so surprising to me that humans have begun to change drastically the open ocean. I would have guessed we first would change the atmosphere based on billions of people consuming rapaciously and emitting gobs of greenhouse gases. (And, indeed, we have changed it.) But I wouldn't have predicted that we could modify the entire ocean. For one thing, oceans are really starting to warm up. Sea surface temperatures in Figure 1 average ∼0.6 °C warmer during than 50 years ago—warmer still in the Arctic and many coastal areas. Ice is melting. Obviously soil, atmosphere, and oceans are interconnected. There’s strong evidence that rising levels of atmospheric CO2 (a weak acid) are acidifying the oceans. Best estimates would indicate that the pH has changed from about 8.179 to 8.069 (SCOR report at www.scor-int.org/OBO2009/A&O_Report.pdf). That's a 29% increase in acidity since preindustrial times plus an accelerating trend. Coral reefs and ocean fisheries are also threatened. Coral reefs suffer too many insults including acidification, warming and bleaching, pesticide runoff from intensive agricultural practices, water pollution from coastal development, and destructive fishing practices (www.coral.org/resources/about_coral_reefs/ threats_to_coral_reefs). Meanwhile, more than 90 species of ocean fish have been depleted in recent years such as bluefin tuna, cod, flounder, swordfish, blue marlin, red snapper, and several species of whales and sharks. Without more aggressive fisheries management, collapse is a real possibility (www.savethefish.org/ about_ocean_fisheries_overfishing.htm). Although the oceans are still a vast and rich resource, they are in serious jeopardy. When speaking with the general public, I no longer include predictions of climate change from general circulation models (GCM). Observational data are sobering enough! Unfortunately, the enormity of these changes in ocean and atmosphere are lost on the general public. But it's our job as scientists to keep reminding them. It should give people pause because oceans are the final frontier where we expect to observe these effects.
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Figure 1. Long-term (50 y) change in sea surface temperature (Allison, I., et al. The Copenhagen Diagnosis; The University of New South Wales Climate Change Research Centre (CCRC): Sydney, Australia, 2009; http://www.copenhagendiagnosis.org/).
’ AUTHOR INFORMATION Corresponding Author
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Answers: Mass of atmosphere = 5.25 1018 kg Mass of top 2 m soil = 3.9 1017 kg Mass of oceans = 1.40 1021 kg Source: Schnoor, J. L. Environmental Modeling; Wiley-Interscience: NY, 1996. Jerald L. Schnoor Editor
Published: February 25, 2011 r 2011 American Chemical Society
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dx.doi.org/10.1021/es200328b | Environ. Sci. Technol. 2011, 45, 1749–1749
