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Sea Ice

Sea Ice Reflects suns waves (energy) Permanent on the poles (volume changes, but never completely melts ~ 4m thick Sea water freezes at ~2 º C not 0 º C Leaves behind salts (denser water) Wind-Driven circulation Air mass movement produces prevailing winds

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Sea Ice

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  1. Sea Ice • Reflects suns waves (energy) • Permanent on the poles (volume changes, but never completely melts • ~ 4m thick • Sea water freezes at ~2 ºC not 0 ºC • Leaves behind salts (denser water)

  2. Wind-Driven circulation Air mass movement produces prevailing winds Wind from the uneven heating of Earth’s Surface Presence of land masses influences circulation Energy & Motion of Oceans – Surface Waters

  3. Atmospheric Circulation Ocean Surface Currents

  4. Surface Currents • Driven by atmospheric circulation. Transfer heat from one place to another. Keep the upper 100 meters of the ocean well mixed.

  5. Surface Circulation – Gulf Stream Current

  6. Oceans and Climate • Q. Why is the climate in England mild even though it's at 55o N latitude?

  7. Oceans and Climate • A. The Gulf Stream current carries heat to Northern Europe. Fig. 9.14

  8. Energy & Motion of Oceans – Deep Waters • Deep water circulation not influenced by wind • Density controlled by temperature and salinity • Cold dense water sinks at poles • Migrates slowly away, hugging the sea floor • Temperature and density difference allow for different currents to develop

  9. Global Circulation Patterns • Waters cycle between the different oceans. • One cycle takes 1000 years

  10. Thermohaline Current • Evaporation as current moves north, salinity (and density) increase.

  11. Thermohaline Current • Warm water loses heat to the atmosphere, density increases.

  12. temperature Global climate change atmospheric CO2 sea level

  13. Climate Change Climate = average of weather conditions over seasons, years or decades e.g. The climate of Illinois is "humid continental" Depends on latitude, proximity to ocean, etc. Climate changes over geologic time as continents drift and as Ice Ages come and go

  14. Studying Global Change Geologic record: what happened in the past Real-time monitoring: what is happening now Mathematical models: predicting the future(also tested against the geologic record)

  15. What is a normal Earth Temperature? "Snowball" Earth Greenhouse Earth

  16. What is a normal Earth temperature? Note we are actually way below average for the last 100 million years. So why worry? 1) we were not around last time it was hot! 2) we are perturbing Earth systems much faster than most natural processes

  17. Temperatures: last 800,000 y We are in an interglacial period; still have permanent ice caps (for the moment) so technically we are still in an Ice Age.

  18. Temperatures: last 150,000 y Glacial-interglacial cycle is about 120,000 years Now look at CO2 for the same period

  19. Temperatures: last 18,000 y Glaciers retreated from upper midwest ~10,000 years ago Last ~8,000 years have had relatively stable temperatures

  20. Temperatures: last 1,000 y Vikings settled Greenland Vikings abandoned Greenland

  21. Sea temperature in Medieval times estimated ~4 ˚C warmer than today text Medieval warming period

  22. Temperatures: last 140 y Not everywhere has the same temperature trend, but on average the planet's surface is heating up

  23. CO2 in the Atmosphere Temperature during the Industrial Revolution Link between CO2 and Global Temperature ?

  24. CO2 and climate (Last 160,000 years). Clearly the "Greenhouse Effect" is very real and acts on a short timescale What about other greenhouse gases?

  25. The Greenhouse Effect • Greenhouse Gases • Carbon Dioxide (CO2) • Methane (CH4) • Nitrogen oxide (N2O) • Chlorofluorocarbons

  26. Concentrations of Greenhouse Gases – Modern Era

  27. Carbon Cycle

  28. Greenhouse gases Each greenhouse gas differs in its ability to absorb heat in the atmosphere. HFC's and PFC's are most heat-absorbent. Nitrous oxide traps ~ 270 times more heat per molecule than CO2; methane traps ~21 times more.

  29. Greenhouse gases Greenhouse gases are global in their effect upon the atmosphere. The main greenhouse gases have long residence times in the atmosphere, and therefore accumulate over time (unlike many local air pollutants) Greenhouse gases are generally well mixed in the atmosphere, so their impact is mostly independent of where they were emitted. Hence the emission of greenhouse gases should be addressed on a global (i.e., international) scale.

  30. A True Greenhouse Climate!

  31. Recent CO2 emissions The US currently emits ~ 25% of anthropogenic CO2, mostly from burning fossil fuels In 1990 the US emitted 5 billion tons of CO2 (~20 tons per person)

  32. CO2 emissions by country text

  33. Some conclusions • "Naturally occurring" climate change has occurred in the paston many timescales, and will continue in the future. Several times in the past, Earth has been hotter or colder than today • Anthropogenic activities have greatly increased (and continue to increase) the concentration of greenhouse gases in the atmosphere • In the past, high levels of CO2 (greenhouse gas) have correlated with high temperatures • So we should expect global warming to continue in the future (noticeable on a human timescale)

  34. Title text

  35. Future sea level rise (models) Expect about 0.5 m in the next century. Longer range predictions are less certain.

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