Interactions between the Oceans and the Atmosphere And its influence on global and regional climate

Currents interact with climate and weather Wind causes surface currents which will determine the air temperature above. Surface currents help to distribute heat around the globe. Warm water gets moved away from the equator toward the poles. Cool water gets moved away from the poles toward the equator. Next we will watch a video on currents and climate.

What drives thermohaline circulation? (Deep Ocean Currents) Thermo=temperature Haline=Salt High-Latitude Cooling (latitudes near the poles) In cold regions (poles) water gets cold, which increases the density of the water, causing it to sink and begin moving the water beneath it. This drives the movement of water. The global conveyer belt. (circulation)

Causes of salinity differences: Thermohaline Circulation ocean circulation which is driven by density differences The differences in temperature come from the uneven heating of the earth’s surface. Where are we heated most intensely? Where are we heated least intensely? Causes of salinity differences: evaporation and sea ice formation increase salinity precipitation, runoff and ice-melt decrease salinity Heat sources at the ocean bottom play a minor role.

Global Conveyer Belt

What is happening in our oceans? Carbon Dioxide Acidification Carbon dioxide (CO2) and methane concentrations are higher than they have been for more than 400,000 years. Why? Human use of fossil fuels Land clearing-deforestation Ocean is the largest natural reservoir for excess Carbon Dioxide. Absorbs 1/3rd that humans add to the atmosphere The excess carbon dioxide causes the pH of the ocean to become more acidic

Consequences of CO2 in the Ocean Threatens marine organisms including corals that support oceanic biodiversity. Over the next millennium oceans are expected to absorb 90% of CO2. What will happen? Thermohaline circulation will slow down. Greenland ice sheet partially melts due to warmer Arctic temperatures. Lowering of Atlantic air temperatures, Changing of the climate in only a matter of decades on both sides of the Atlantic.

DRAMATIC CHANGES IN THE NORTH ATLANTIC—Subpolar seas bordering the North Atlantic have become noticeably less salty since the mid-1960s, especially in the last decade. This is the largest and most dramatic oceanic change ever measured in the era of modern instruments. This has resulted in a freshening of the deep ocean in the North Atlantic, which in the past disrupted the Ocean Conveyor and caused abrupt climate changes. (B. Dickson, et. al., in Nature, April 2002)