Climate change and the ocean. Climate change and the ocean. Change in ocean currents. Change in ocean currents. Global conveyor belt

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1 Climate change and the ocean Climate change and the ocean Avg Pacific and Indian Hurricane intensification, loss of coral reefs Atlantic Ocean Mean concentration of anthropogenic carbon as of 1994 in μmol/kg Global conveyor belt 1

2 Could less sea ice formation + melting Greenland ice sheet stop thermohaline circulation? Reorganize the subpolar gyre? YoungerDryas analogy 12,800 years ago Abrupt cooling in N. America & Europe Massive (9500 km 3 ) freshwater discharge to the N. Atlantic Source: LamontDoherty EO Multimodel mean sea ice concentration (%) Modified from Flato et al. (2004). Complete shutdown not expected Models of º C temperature increase project: 3540% decrease in thermohaline circulation Recovery between Red arrows of m/s/decade indicate slowing subpolar gyre from Source: NASA,

3 Corals & climate change Coral polyps 50% loss expected by 2030 Functional extinction by 2050 Thousands of individual but genetically identical polyps Class Anthozoa Subclass: Hermatypic (hard) coral reef building Mutualistic relationship with unicellular algae Algae provide carbs from photosynthesis Corals provide safety, CO 2, nitrogenous wastes Subclass: Ahermatypic (soft) coral: nonreef building Lack zooxanthellae Tropic or polar waters Coral Reef Alliance Red sea finger Photo: Paul Kay Hermatypic coral Energy Symbiotic algae (80%) Colony shares algae and nutrients Consumption of plankton, small fish Stinging cells on tentacles Hermatypic coral Asexual reproduction Sexual reproduction by broadcast spawn Gemmation budding Egg packets Division 3

4 Coral reef ecosystem Metropolis of the sea Support the lives of 25% of marine species 4,000 species fish 7,000 coral species Distribution of all benthic organisms Coral species are 240 million years old (hominids: 5 million years old) Coral reefs existing today began growing 50 million years ago Majority are 5,000 and 10,000 years old Distribution of all benthic organisms Coral: anthropogenic threats Sewage Too many nutrients, too many algae Human interference Tourism Destructive fishing practices Coastal development Coral mining Distribution of coral reefs Coral: threats from climate change Coral: threats from climate change 1. Change in water temperature (1º enough) Projected 5ºF increase in sea surface temp. by 2100 Global or isolated events Corals expel algae (coral bleaching) when stressed Increased chance for survival if conditions return to normal J Hoogesteger 4

5 Coral: threats from climate change 1. Change in water temperature (1º enough) Coral: threats from climate change 2. Change in ph (ocean acidification) Dropped 0.02 per decade Concern over rate of change Source: Pearson and Palmer 1. Ocean gets more acidic ph = log [H + ] (increase H +, decrease ph) 2. Less carbonate available for shelled organisms Surface ocean: CaCO 3 supersaturated 2. Less carbonate available for shelled organisms 3. CaCO 3 begins dissolving shallower decrease by m since 1700 s CaCO 3 dissolves 5

6 Affect on marine life Form weaker skeletons due to less carbonate (CO 3 ) Dissolution of skeleton 3. CaCO 3 begins dissolving shallower decrease by m since 1700 s Major planktonic calcifiers Coccolithophore Foraminifera Pteropod Major benthic calcifiers a) Algae (some) d) Coral e) Coral f) Bryozoan g) Molluscs h) Echinoderms i) Crustacean Hurricane intensification Water above 79ºF Low vertical wind shear High humidity Hurricane intensification Hurricanes fueled by warm water Hurricane intensification Source: Union Concerned Scientists Source: NOAA 6

7 Hurricane intensification 1. Thermal expansion 2. Melting land ice Source: Union Concerned Scientists 1. Thermal expansion 2. Melting land ice population potentially displaced by current sealevel trends, 2050 Extreme = >1 million High = 1 million to 50,000 Medium = 50,000 to 5,000 7