[] TL: CLIMATE CHANGE & OCEANS SO: INTERNATIONAL OCEANS NEWSLETTER Greenpeace International (GP) DT: October 26, 1993 Keywords: environment oceans fisheries greenpeace gp ocean dumping algae coral marine mammals / OUT OF THE FRYING PAN, INTO THE FIRE: Climate change and the oceans Erwin Jackson and Lyn Goldsworthy The threat of human-induced climate change is real, and in the years to come is likely to radically alter ocean ecosystems. Changes in ocean circulation, the enhancement or suppression upwellings, and the loss of important habitat such as coastal wetlands can be expected. However, considering all the threats faced by marine ecosystems, it would be easy to take the view that climate change was not an immediate problem and would require little action at least in the short term. Overfishing, coastal habitat destruction and toxic pollution would all appear more urgent. Nevertheless, if policy makers interested in the future sustainablity of the oceans ignore climate change they may find themselves stepping out of an overfishing frying pan and into the climate change fire. Changes in ocean circulation: Modelling experiments reviewed by the Intergovernmental Panel on Climate Change (IPCC) suggest that climate change will result in an increase in sea surface temperature of between 0.2 and 2.5 degrees Celsius by 2030. Ocean warming will be most severe in the surface layer, which will result in less vertical mixing between the surface layer and the nutrient-rich deep ocean. Experiments from four major models also show that maximum warming will occur in the polar regions, and that rainfall could increase especially along the eastern fringes of the continents. Changes in climate may result in a dramatic change of large-scale ocean circulation and upwellings. Recent work by Manabe and Stouffer, published in the British Journal Nature, suggests that within 50 years the oceanic conveyor belt may begin to slow. This is mainly in response to a freshwater cap forming in the North Atlantic and thus inhibiting bottom water formation. Manabe and Stouffer also suggest that if we allow carbon dioxide to quadruple in the atmosphere the oceanic conveyer belt may grind to a virtual halt with catastrophic consequences to the ocean's ecosystems and the Earth's climate. The IPCC submits that these changes in the deep water and surface water mixing may have a significant impact on ocean productivity. Palaeoecological studies reviewed by the IPCC confirm that in the warm periods between ice ages, ocean productivity was reduced in response to changes in oceanic upwellings. In contrast, an increase in the temperature gradient between the quickly warming land masses and the slower warming oceans may cause an increase in along-shore winds. This increase would result in the intensification of coastal upwellings. The IPCC concludes that both processes may be active in the warming world, but the dominance of one will depend on the proximity to land (eg eastern boundary current regimes) or open ocean (North Pacific Equatorial Counter-Current). They warn that these changes may have "profound impacts" on fisheries. Impacts of changing currents and nutrient availability: 45 per cent of the primary production of the ocean is produced in the polar regions and the upwelling zones. The expected decrease in oceanic upwellings will lead to a global decrease in the primary productivity of the world's oceans. This may be further exacerbated in some regions by the increased frequency and intensity of drought and decreased rainfall (resulting from climate change). In some regions this would lead to the reduction of nutrient input from the landmasses. The decrease in upwellings and increase in vertical stratification will result in the reduction of nutrients being injected from rich deep water into surface water layers. This has an obvious consequence of diminishing nutrient supply to the open ocean, leading to a loss of phytoplankton productivity. An increase in temperature could also be expected to increase photosynthesis in phytoplankton, which would in turn lead to a faster turnover of nutrients, thus exhausting the already reduced nutrient supply. However, the intensification of coastal upwellings, as well as, for example, increased run-off from land masses in some areas (as climate change intensifies regional rainfall) could result in increased nutrient supply in coastal waters. The destruction of coastal habitats such as mangrove communities by climate change could temporarily also increase the input of nutrients. Dramatic increases in nutrient supply may result in detrimental changes in ecosystem structure; algal blooms, which are exacerbated by warmer temperatures, may be one consequence of this ecosystem imbalance. Some algae produce toxins: the mass death of dolphins in the Carolinas in 1988 has been linked to such alankton bloom" killed salmon off Sweden and threatened Norway's salmon mariculture industry. Impacts of sea level rise: Thermal expansion of the warming oceans will result in global sea level rise, estimated at around 20-40mm per decade. The IPCC classifies this as the most important effect to impact on coastal communities and associated marine ecosystems. Over two-thirds of all commercial fish species rely on wetlands for at least one part of their life cycle. Currently, there is no evidence to suggest that such wetlands can adapt to rapidly changing oceans, and they may well be drowned even with the very small sea level rises predicted by IPCC. Conclusion: Climate change has emerged as one of the world's most pressing problems. It is a problem that must be addressed if we are to ensure the future viability of society. While policy-makers continue to procrastinate, ocean habitats are being dangerously stressed from overfishing, pollution and loss of habitat -- and greenhouse gases continue to build up in the atmosphere.