1 / 15

Permafrost Stability in dry Environments: Antarctica & Mars

Permafrost Stability in dry Environments: Antarctica & Mars. 16 Nov 2004 Madison Wisconsin Chris McKay NASA Ames Research Center cmckay@mail.arc.nasa.gov. The Dry Valleys Largest ice-free region in Antarctica Temperatures: -20 o C average +10 o C maximum

wgaskin
Download Presentation

Permafrost Stability in dry Environments: Antarctica & Mars

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Permafrost Stability in dry Environments: Antarctica & Mars 16 Nov 2004 Madison Wisconsin Chris McKay NASA Ames Research Center cmckay@mail.arc.nasa.gov

  2. The Dry Valleys • Largest ice-free region in Antarctica • Temperatures: -20oC average +10oC maximum • 1-2 cm equivalent H2O as snow • Pressure well above triple point of H2O

  3. Lake Vanda and the Onyx River in the Antarctic dry valleys

  4. Linnaeous Terrace, Antarctica Beacon Sandstone Rocks 1500 m elevation Tair < 0oC

  5. Algae and lichens living is a rock “greenhouse” • Temperatures 15oC warmer than the air • Moisture from snowmelt held in pore spaces • Shielded from UV 1 cm

  6. Dry and ice-cemented permafrost at Linnaeous Terrace Temp = -23.3 oC RH = 62% Frost Point= -26 ±1.0oC Air 0 x -18.7oC Active zone 12 cm x -21.1oC Dry permafrost x -21.6oC 25 cm Ice-rich permafrost x -22.3oC

  7. Net Vapor Flux from Ice-cemented Permafrost F = [D/] dn/dz D = 2x10-5 m2 s-1, diffusion coefficient  = 0.41, porosity  = 1.5 - 2.0, tortuosity n = water vapor density z = depth

  8. Net Vapor Flux from Ice-cemented Permafrost F = 0.4 to 0.6 mm/yr = 400 to 600 m/Myr Very old (over 1 Myr) ice-cemented ground Has lost hundreds of meters by ablation Is sealed under very compact soils Is recharged by episodic snowmelt

  9. Mars has extensive dry and ice-rich permafrost

  10. Mars is cold now and it was cold then • Evidence of very low erosion, post Noachian: < 10-9 m/yr, compare to dry valleys 10-6 m/yr • Sporadic distribution of valley features • Unweathered basaltic surface minerals • Climate modelers have difficulty getting mean surface temperatures above 0oC. • No massive surface carbonates detectable by remote sensing.

  11. Odyssey GRS has found near surface water ice polewards of 60o latitude in both hemispheres.

  12. Where is ancient ice? X From:Smith & McKay, PSS 2004; data from Acuna et al, 1999; Barlow, 1997

  13. Limits on long term dormancy • kT: Thermal decay: ~e-E/kTracemization of amino acidsdegradation of organic material • eV: Radiation:background radiation U,Th, K ~0.2rad/yrlethal dose: 2 Mrad for most bugs; 10 Myr 20 Mrad for Deinococcus radiodurans; 100 Myr

  14. Depths below about 1000 m do not feel the obliquity warming ( 1Myr period) Damping depth vs. period

  15. this slide intentionally not left blank

More Related