SSTs

Sea Surface Temperatures (SSTs)

The Potential Link Between Sea Surface Temperatures and Flooding What are High SSTs? • Historically what has been the temperature • • How has it increased/ trends in warming? o (from epa.gov/climatechange) “sea surface temperature increased over the 20th century and continues to rise. From 1901 through 2012, temps rose at an average rate of .13 degrees F per decade. o “have been higher during the past three decades than at any other time since observations began.” o “increases in sst have largely occurred over two key periods: between 1910 and 1940 and from about 1960 to the present. SST appear to have cooled between 1880 and 1910” o What are causes of SSTs? • Anthropogenic • Earth’s oceans are warming as a direct result of increased concentrations of atmospheric carbon dioxide and other greenhouse gases that increase air temperatures. • Natural • “Oceans have the ability to release or attain heat from the atmosphere and this exchange of heat is a driving force of atmospheric circulation. Evaporation rates are expected to increase with climate change, resulting in increases in atmospheric water vapor. Water vapor is a much more potent greenhouse gas than carbon dioxide; thus, increased water vapor concentrations contribute to greater downward longwave radiation fluxes that increase the amount of heat retained in the atmosphere. • • Cycle of increased water vapor to stimulate increased global warming and thus continued production of water vapor, leading to a “runaway greenhouse effect” • • Water vapor clouds at high altitudes absorb and re-radiate long-wave radiation, which causes warming by augmenting the greenhouse effect, but low altitude clouds reflect incoming solar radiation which leads to cooling • • Do not know which effect will have greatest impact, but evidence suggests it will lead to an increase in warming which will cause upper ocean temperatures to increase at a faster rate • “Dominant atmospheric factors driving ocean temperature include wind speed, air temperature, cloudiness, and humidity; dominant oceanic factors include heat transport by currents and vertical mixing. Fluctuations in sea surface temperatures vary with the seasons.” (11) • Feedback loops • • Relationship between ocean-atmosphere heat exchanges and global weather and climate patterns • • “In the case of thermal expansion, given an equal mass, the total volume of ocean waters decrease when ocean temperatures drop and expand when temperatures increase” 12 • • Positive Feedback: warming of sea surface temperatures à increased ice melting and evaporation à increased humidity creates more intense storms à more extreme precipitation and wind events. Some areas because of increased evaporation will experience intense surface drying increasing the risk of flooding when intense storms occur. • Effects of SSTs on Coral? • Coral Bleaching • Increase in Severity of Storms • http://water.usgs.gov/nrp/proj.bib/Publications/2008/mccabe_wolock_2008.pdf o Increase flooding of Nutrients  Effects on Coral reef o Increase in Sediment Overload  Effects on Coral Reef Recovery/Treatment Options • Can High SSTs be reversed • Can effects on Coral be mitigated Sources • Russ and McCook. 1999, Potential effects of a cyclone on benthic algae production and yield to grazers on the great barrier reef. Journal of Experimental Marine Biology and Ecology.235:237-244 • Oceanographic Processes of Coral Reefs: Physical and Biological links in the Great Barrier Reef by Eric Wolanski • http://www.epa.gov/climatechange/science/indicators/oceans/sea-surface-temp.html • McCabe and Wolock.2007. Joint Variability of Global Runoff and Global Sea Surface Temperatures. Journal of Hydrometerology. 9: 816-824