ATM S 111, Global Warming: Understanding the Forecast

1. ATM S 111, Global Warming: Understanding the Forecast Dargan M. W. Frierson Department of Atmospheric Sciences Day 8: 04/22/2010

2. The Oceans (RG p. 106-127) From sticks to satellites: measuring sea level Monitoring the ocean below the surface Balancing the sea level budget How high the sea? Climate change and El Niño Will the Atlantic turn cold on Britain Living in a changing sea Coral reefs at risk ocean acidification

3. 20th Century Sea Level Rise 20th century sea level rise was 12-22 mm/decade on average red = “reconstructed” from tide gauges and other sources blue = tide gauges black = satellite altimetry

4. Mean Sea Level - The average height of the ocean at a given location What controls it? Thermal expansion of the ocean The exchange of seawater/ice with lake/soil water or land ice Tides Ocean currents Atmospheric winds Tsunamis The first two vary with global warming

5. From sticks to satellites: measuring sea level Tide gauges are measuring sticks or sometimes floats in wells Always coastal Few long records

6. From sticks to satellites: measuring sea level TOPEX-Poseidon Radar Altimetry Instruments emits a short radar flash and measures the time-of-flight of its reflection from earth. 1,000 times per second. Measures sea level and ice sheet height

7. Sea level rise from TOPEX-Poseidon Radar Altimetry Each 10 day measurement has an accuracy of 3-4 mm

8. No more enigma Balancing the Sea Level Rise Budget • IPCC 2007 Figure 5.21. 1961 to 2003 (blue) 1993 to 2003 (brown) ~60% ~25% ~15%

9. Monitoring the ocean Many instruments are used to measure ocean heat content

10. Argo floats StephenRiser, UW Oceanography

11. Monitoring the ocean heat content Argo floats, since ~2000 measure to 2000m depth

12. Monitoring the ocean heat content Expendable Bathyermographs (XBT) About 70 Voluntary ships toss them overboard 14,000 each year (they are cheap, even these figures are ugly) measure down to 1500 m, in use since 1962

13. Ocean Heat Content Observations in black with uncertainty shaded grey Models are colored lines - span the observations 1950 1960 1970 1980 1990 2000 Domingues et al 2008

14. What will sea level be by the end of the 21st century? 200-500 mm for 3 intermediate scenarios But had no increase in dynamical thinning from Greenland and Antarctica! Criticized by James Hansen FAQ 5.1, Figure 1

15. More recent estimates: 0.5 to 1.4 m by considering past SLR to past warming dependence and used IPCC estimate of future warming, Rahmstorf 2007 http://www.sciencemag.org/cgi/content/abstract/315/5810/368 Accelerated but plausible dynamic thinning could give 0.8-2 m Pfeffer et al 2008 http://www.sciencemag.org/cgi/content/abstract/321/5894/1340

16. The very latest on Greenland from the GRACE superstar GRACE - Gravity Recovery and Climate Experiments Greenland contributed 0.5 mm/yr to SLR between 2000-2008 or 237 Gt/yr loss more than 2X the IPCC 2007 estimate for 1993-2003 van den Broeke et al 2009 D=dynamic loss (+ = loss), SMB = accumulation - ablation

17. The very latest on Antarctica from the GRACE superstar 2002-2009 Antarctica losing ice - despite increased snowfall cause - dynamic thinning http://grace.jpl.nasa.gov/news/index.cfm?FuseAction=ShowNews&NewsID=33 192 +/- 92 Gt/yr from 1996-2006 according to Rignot et al 2008

18. Frequency of storm surge passing a given threshold is likely to be as serious as mean sea level rise

23. “The Day After Tomorrow” had it wrong: a disintegrating floating ice shelf is sea level neutral. The cooling that ensued should have caused sea level to drop!

24. Gulf Stream transports heat it is mostly wind driven (not subject to stopping) North America Gulf Stream Colors show Temperature AVHRR satellite

25. Thermohaline circulation driven by buoyancy differences also moves heat

26. Atlantic circulation Red branches carry heat northward When water loses enough heat it tends to sink Weaken this circulation would cool England and Norway Global warming is expected to weaken the portion that is buoyancy driven as the water would not lose as much heat.

27. Coral reefs at risk

28. Coral reefs at risk

29. Coral reefs at risk Coral bleaching

30. Coral reefs at risk Coral bleaching

31. Another risk to coral: ocean acidification

32. When CO2 dissolves in water, carbonic acid is produced via the reaction: CO2 (aq) + H2O <-> H2CO3 This carbonic acid is like sparkling water. Chemistry of ocean acidification Coral reefs at risk Coral bleaching What happens when you open a can of sparkling water? CO2 comes out of the water. The opposite is happening on Earth today. So CO2 is going into the ocean. And this acidifies the ocean…

33. Chemistry of ocean acidification Coral reefs at risk Coral bleaching When CO2 dissolves in water, carbonic acid is produced via the reaction: CO2 (aq) + H2O <-> H2CO3 Acid dissociate into ions, including hydrogen ion H2CO3 <-> H++ HCO3- The increase in the hydrogen ion concentration causes an increase in acidity, since acidity is defined by the pH scale, where pH = -log [H+] (so as hydrogen increases, the pH decreases).  This log scale means that for every unit decrease on the pH scale, the hydrogen ion concentration has increased 10-fold. so far the hydrogen ion concentration has increased by 30%

34. Chemistry of ocean acidification Coral reefs at risk Coral bleaching When CO2 dissolves in water, carbonic acid is produced via the reaction: CO2 (aq) + H2O <-> H2CO3 Acid dissociate into ions, including hydrogen ion H2CO3 <-> H++ HCO3- H+ reacts with carbonate ion as in H++ CO32-<-> HCO3-

35. In your stomach or in the ocean, the chemistry is the same Coral reefs at risk Coral bleaching The source of the carbonate ionsCO32- is calcium carbonate CaCO3 Just as the Tums dissolve, creatures with shells dissolve… such as phytoplankton, which are responsible for 1/3 of all photosynthesis on the planet and feed the marine food web.

36. Coral reefs at risk Ocean Acidification Coral bleaching pH Pre-industrial (1700s) 8.18 Recent past (1990s) 8.10 2050 (2×CO2 = 560 ppm) 7.95 2100 (IS92a) 7.82

37. Harmful algal blooms (HABs)