The Arctic Water Cycle

1. The Arctic Water Cycle The Arctic Water Cycle Emma Sage Rebecca Hale Biogeochemistry 2 March 2005 Emma Rebecca Hale 1 March 2005 Photograph © Michael Hambrey

2. The Game Plan • Global and Arctic Water Cycles • Ice Sheets • Primary controls on the water cycle – global and Arctic • Field Methods and Modeling: how we figure it all out • “In nature there are neither rewards nor punishments, there are consequences.” – Robert Green Ingersoll • Discussion

3. The Global Water Cycle

4. The Global Water Cycle • Global and Arctic Water Cycles The Arctic Water Cycle

5. Arctic Ice Sheets Arctic Rivers and Watersheds

6. Arctic Ice Sheets

7. What Drives the Water Cycle? • Precipitation  solar radiation, Hadley cells, wind patterns, all those good things we talked about with Laura and Julie. • Ice  wind! air temperature, ocean temperature, ocean currents, pressure oscillations • Ocean currents  salinity, river discharge, temperature • River discharge  temperature, arctic ice/glaciers, human modifications

8. Some Really Cool Big Patterns • Arctic Oscillation – atmospheric pressure see-saw between upper and middle northern (~45N) latitudes • North Atlantic Oscillation – related to the AO, similar seesaw of pressure between Iceland and subtropical Atlantic • Debate whether these are part of the same mode or whether they are different. • Time scales of these are debatable –paleoclimate studies show that neither seem to have had set schedules in the past, but they change about every 10 to 40 years • Right now both are in positive phases

9. Arctic Ice Sheets • Positive AO • Low pressure over arctic • NegativeAO • High pressure over arctic Arctic Oscillation - some effects -

13. Pacific Decadal Oscillation – major source of variability in sea surface temperature lasting 20-30 years. • Since 1990s has begun to go back into cool phase. Warm phase Cool phase

14. These Pressure and Temperature Oscillations… • Control currents of air  positive AO creates strong wind current circling the Arctic • Effects on ice • affect the heating and cooling of the ocean and therefore… • Thermohaline Circulation! • Circulation of ocean water based on temperature (thermo) and salinity (haline) • Temperature and salinity determine density of sea water and cause sinking and upwelling

15. Arctic Ice Sheets

17. Atlantic Thermohaline Circulation Arctic Ice Sheets

18. Changes in the Arctic Cycle • AO and NAO have been in long positive cycles • caused by increases in GHG? • Surface air temperatures are increasing  accelerate water cycle • Increase in freshwater discharge to Arctic • Increase in cloud cover • Ice thinning • Changes in precipitation Spring Cloud Fraction of Arctic Seas (from www.arctic.noaa.gov)

19. Research Questions • Atlantic hydrologic sensitivity parameter (HSP) • Determines how thermohaline circulation will change as freshwater discharge increases • Freshwater discharge (Eurasian) expected to increase 18-70% in response to 1.4-5.8°C SAT increase • Arctic ice – what’s causing changes in thickness and extent? • How are the AO/NAO and greenhouse gases related? • How will ocean currents change? Three modes of ocean currents discussed by Taylor (1999)

20. Experimental Methods and Modeling

21. Our Questions for You! • We want you to speculate some effects of the following scenarios. Be creative: effects on ocean/wind currents, migration patterns, Arctic ice, economics, human society, etc. • Global warming causes almost total melting of the Arctic ice sheet • Greenhouse gases push AO into permanent positive phase • Global temperatures increase and cause two-fold increase in freshwater discharge to Arctic Ocean