Presentation on theme: "When you hear climate change, what do you think?"— Presentation transcript:
1 When you hear climate change, what do you think? Rising temperaturesRising levels of CO2 in atmosphereRising levels of CO2 in oceansRising sea levelmelting of land icethermal expansion of water
2 Life in a hotter, higher CO2 world What role do the oceans play in climate?Exchange and transfer of heatOceans carry heat from the tropics (equator) to the poles, to maintain Earth's temperatureExchange and transfer of CO2 (and O2)What are the sources of increased CO2 in the atmosphere?DeforestationFossil fuelsCement productionOceans are main reservoirs of readily available carbon dioxide (CO2)The cold, deep water in the ocean is the main reservoir of dissolved CO2
3 Oceans and heatSolar energy is absorbed by both oceans and continents. BUT-- because the oceans cover over 70% of Earth's surface and are darker than the continents--they absorb more of the sun's energyOceans not only absorb lots of energy from the sun--they can also store lots of solar energy in the form of heatAND they can do this with very little change in temperatureHigh specific heat of water80% of heat generated by global warming is stored in the oceans
4 Atmosphere and Oceans in Motion Half of the incoming solar radiation is absorbed by the oceanEnergy is stored in the water as it is picked up by winds which blow over the ocean surfaceWhen the wind releases the water as precipitation the heat energy of the water is released into the atmosphere causing an increase in temperatureThe oceans' waters are constantly on the move
5 Global Conveyor Belt – thermohaline circulation Sunlight warms the surface of the ocean in the tropicsWind-driven surface currents carry the heat toward the polesIn the North Atlantic, the warm currents from the tropics feed the North Atlantic Current (in red on figure on next slide)As the current flows northward toward Norway and Greenland, it loses heat to the atmosphere and cools downIn winter the water near Norway and Greenland gets so cold and dense it sinks all the way to the bottom of the oceanThe cold bottom water feeds bottom currents (in blue and green on figure)Eventually, mixing brings the bottom water back to the surface in other parts of the ocean, sometime as far away as the North PacificWhen the water gets to the surface, sunlight warms the water, and the cycle starts over
6 Global Conveyor Belt – thermohaline circulation Surface processes determine density (and other properties) of waterBecause of the high specific heat of water, the oceans store heatCurrents transport heat
7 Global Carbon CycleExchange of carbon between different reservoirs (atmosphere, ocean, fossil fuels, land)Ocean is largest active reservoirMore CO2 in atmosphere, more CO2 in oceans
8 Global Carbon Cycle How much carbon is in each reservoir? Land = Most in rock/soilOcean = Most in deep oceanWhat is the residence time in each reservoir?3 yrs.Alive = 5 yrsDead = 30 yrs.Soil/rocks = 1000 yrs.Surface = 6 yrsMid-water = 100 yrs.Deep = 100,000 yrs.
9 Oceans in a High CO2 World Oceans absorb and release CO2More CO2 in the atmosphere, more CO2 in the oceansCO2 reacts with water to form an acidRefered to previously. Here present in more detail, giving the mechanism.This is what happens in a greenhouse, that you use to grow plants.Inconvenient Truth cartoon
10 What is an acid?Any chemical compound that, when dissolved in water, gives a solution with a hydrogen ion (H+) greater than in pure waterMeasured by pH scalepH = -log [H+]higher [H+] = lower pH0–6 = acid, 7 = neutral, 8–14 = alkalineEach is a power of 10 difference in acidityBorder wars - Pentagon studypH scale
11 Oceans in a High CO2 World When CO2 dissolves, it reacts with water to form a balance of chemical species: dissolved free carbon dioxide (CO2(aq)), carbonic acid (H2CO3), bicarbonate (HCO−3) and carbonate (CO2−3)The ratio of these species depends on temperature and pHDissolving CO increases [H+]Lower pH
12 What are the factors that determine how much CO2 dissolves in seawater? Solubility determined by temperatureColder water holds more CO2 than warmer waterOcean circulationAreas of convergence = downwelling = sink for CO2Old, dense waterAreas of divergence = upwelling = source of CO2More CO2 than atmosphereBiologyPhotosynthesis/respirationRecycling of matter in surface versus burial to deep ocean
13 Circulation transports dissolved CO2 Oceans are a sink for CO2Circulation transports dissolved CO2Areas of deep water formation have high CO2What happens as water gets older and makes voyage around the globe?What happens when this water surfaces?
14 Oceans in a High CO2 World Where do we see the most change in CO2?Why?
15 CO2 and “Old” Water CO2 photosynthesis CO2 + H2O organic carbon + O2 respirationCO2 + H2O organic carbon + O2euphotic zonerespirationCO2 + H2O organic carbon + O2sediments
16 Ocean Acidification in WA Waters Old, CO2 rich water Aragonite Saturation State in West Coast WatersMay-June 2007Ocean Acidification in WA WatersOld, CO2 rich water120m16
17 Effects of Ocean Acidification Impacts on organisms that build shells and plates out of calcium carbonate (CaCO3)More acidic (lower pH) = less carbonateVulnerable organisms:Bivalves (mussels, clams, oysters)Coccolithophorids (phytoplankton)Pteropods, foraminifera (zooplankton)Coral reefsCoccolithophoreBorder wars - Pentagon studyCoralsPteropod
18 Status of Ocean Acidification Slowing growth of Great Barrier Reef14% reduction in skeletal formation since 1990Experimental corrosion of calcium shellsPteropod (48 hrs) b = acid, c = normal seawaterDeformed coccolithsBorder wars - Pentagon study
19 Status of Ocean Acidification Impact on biodiversityNumber of speciesEcosystem functionImpact on marine foodwebs
20 Ocean Acidification & Marine Foodweb What will the impact of ocean acidification be on the marine foodweb?
21 What will happen to the Deadliest Catch? Benthic organismsMarine MammalsCoccolithophore bloom in the Bering SeaSalmon
22 Status of Ocean Acidification ~1/3 of fossil-fuel CO2 dissolves in oceanBetween 1751 and 1994 surface ocean pH is estimated to have decreased from approximately 8.2 to 8.1Logarithmic scale of pH; approximately a 25% increase in H+Estimated that it will drop by a further 0.3 to 0.5 units by 2100Border wars - Pentagon study
23 Global Conveyor BeltThe deep circulation shown in the picture is important for two reasons:Cold water carries carbon dioxide deep into the ocean, taking it away from the atmosphere andSurface currents that sink and feed deep currents carry much more heat toward Europe than currents that stay on the surface
24 Understanding Ocean Acidification Chemistry of oceans depends on chemistry of atmosphereMore CO2 in atmosphere = more CO2 in oceansMore CO2 in oceans = more acidic oceans (lower pH)More acidic oceans = negative impact on algae and animals with shells or skeletons made of calcium carbonate