1. Cryosphere (Too Frozen Water)

2. TOPICS How ice forms What controls ice dynamics & importance Interaction of sea and continental ice with atmosphere over different time scales

3. IMPORTANCE OF CRYOSPHERE To climate system –  Change in sea ice & snow cover changes albedo & temperatures  Change in glacial ice changes sea level  Melting permafrost releases methane  Sea-ice formation changes salinity and affects density, bottom- water formation & deep-ocean circulation To biosphere -  Challenge of living on frozen ground  Meltwater source and reservoir of freshwater

4. Components of Cryosphere Continental ice sheets & ice shelves Mountain glaciers Sea ice River and lake ice Snow cover Permafrost

5. Time scales relevant to the cryosphere

6. 87% of ice is in Antarctica 10% Greenland 2.5% ice shelves (mostly Antarctic) If all ice melted sea levels would go up by about 65 meters (213 ft)

7. Phase Diagram - Water Triple Point Critical Point Ice grows by deposition from gas to solid (snowflake) Ice grows by deposition from water to ice (graupel) Ice grows by agglomeration (ice crystals join Together)

8. Dendrite: Common six sided ice crystal / snow flake. Influences interaction with climate system

9. The shape of ice crystals cause ice to be less dense than liquid water This causes ice to float with about 9% of the ice volume above water (91% below). a.k.a. - the tip of the iceberg.

10. Snow Cover Essential for water resources in the western US Roughly 75% of the Western US fresh water comes from snow pack.

11. NA snow cover – February 2002 High albedo – large number of reflecting surfaces return radiation to space (80-90%) What is the effect on regional energy balances?

12. January or February have most NH snow cover. 10 x more than in summer

13. Aside from Antarctica the SH has very little snow cover

15. Figure 1. History of global mean surface air temperature, from NASA

17. Permafrost

19. NH permafrost likely to decrease 20-35% by 2050

21. Carbon balance in the tundra

22. Methane possibly released from permafrost?

23. Methane change Since 2005

26. Feedback Arctic warming faster than rest of planet  snow and ice-albedo feedback Positive feedback Permafrost Melting Methane release Temperature

27. Methane Clathrate Hydrates

28. River and Lakes Spring Thaw

29. Most rivers are thawing earlier and freezing later.

30. GLACIERS AND ICE SHEETS Glaciers begin when snow accumulation is greater than snow melt

31. Glacier Formation Pressure Sintering – with increasing density snow is compacted and crystals fuse together

32. Density Differences New snow – 50-70 kg/m 3 Firn – 400-800 kg/m 3 Glacial Ice – 850-900 kg/m 3  Low permeability  Flows under own weight

33. Types of Glaciers Alpine or Mountain  Small  Confined to mountainous valleys Continental  Large  Unconfined by topography

34. Glacier Flow Plastic Deformation – Flow due to high pressure Basal Sliding – glacier slides over the bed due to presence of liquid water or unconsolidated material

35. Ice flow speed increases with distance above ground - flow at base equals zeor, ice frozen to the bed Side view

36. Top view: Ice flow increases with distance from valley walls. Friction at the sides reduces flow

37. Basal melt (or unconsolidated material) can provide a lubricant to increase total ice flow

38. Ice flow increases with increasing tilt of the mountain

39. Air bubbles trapped in ice can reveal atmospheric composition in the past (up to about 800,000 yrs) For long term climate reconstruction – take cores from part of ice cap not moving

40. Accumulation: Snow persists through summer &builds up Ablation: Melt, sublimation, loss from wind, loss from flow Equilibrium line: Accumulation = Ablation

42. When accumulation is greater than ablation in a certain zone the ice sheet : a)Grows b)Shrinks c)Stays the same size Sublimation or calving

43. When accumulation is greater than ablation in a certain zone the ice sheet : a)Grows b)Shrinks c)Stays the same size Sublimation or calving

44. Alpine Glaciers Milk Lake glacier 1988 Milk Lake 2009

45. Glaciers around the world are in retreat

46. Greenland Ice Sheet (Land Ice)

47. From GRACE See The State of the Greenland Ice Sheet and The State of the Greenland Ice Sheet Gravity Recovery And Climate Experiment Right: Mass change distribution (2002-2009) across the ice sheet as determined by GRACE observations.

48. 2010 was an exceptional year for Greenland’s ice cap. Melting started early and stretched later in the year than usual. Little snow fell to replenish the losses. By the end of the season, much of southern Greenland had set a new record, with melting that lasted 50 days longer than average.

49. West Antarctic Ice Sheet (Land Ice) East Antarctica is Now Losing Ice

50. 350 Gt – 1 mm sea level rise Both Antarctica and Greenland have been losing ice over the past 8 years.

51. Sea Ice What happens to the water level when the ice melts? a. Overflows b. Goes down c. Stays the same

52. Sea Ice What happens to the water level when the ice melts? a. Overflows b. Goes down c. Stays the same

53. Sea Ice Importance  Ice-albedo feedback  Bottom water formation  Changes affect polar ocean climate  These effects dominate high-latitude response to increasing atmospheric CO 2 levels in cgolbal climate models

54. Formation of Sea Ice When temps reach -1.8 °C Thickens when new ice freezes onto the bottom of the ice pack (~1 m every winter) At high latitudes persists during summer Permanent thickness  ~5 m in Arctic  ~0 m very little survives summer

56. Seasonal Ice Cover range Northern Hemisphere  Doubles  Summer ice extent decreasing drastically Southern Hemisphere  5 fold increase

57. From: http://earthobservatory.nasa.gov/Features/WorldOfChange/sea_ice.ph0phttp://earthobservatory.nasa.gov/Features/WorldOfChange/sea_ice.ph0p The yellow outline on each image shows the median sea ice extent observed by satellite sensors in September and March from 1979 through 2000.

58. Sept 2011

59. From: http://earthobservatory.nasa.gov/Features/WorldOfChange/sea_ice_south.phphttp://earthobservatory.nasa.gov/Features/WorldOfChange/sea_ice_south.php

63. http://nsidc.org/arcticseaicenews/2011/020211.html

64. Sea ice moves In a constant state of motion Moves faster than land ice 2 features of circulation: Transpolar Drift (ice lasts 5 yr) Beaufort Sea Gyre (ice lasts longer) Sea Ice Drift in the Arctic

65. Ice Floes Ice moved by wind and currents  Form pressure ridges, leads and polynii Always small amount of open water (even in winter)  Importance  Open water allows for production of ice Release salt to upper ocean, increasing density  Impacts Arctic energy budget Positive ice-albedo feedback Heat loss (100x that of ice) from water to atmosphere

66. Ice-Atmosphere Interactions Ice cover modifies atmospheric & oceanic circulation Formation of NADW (drives thermohaline circulation) Ice-albedo feedback