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Icebase: A proposed suborbital survey to map geothermal heat flux under an ice sheet

Icebase: A proposed suborbital survey to map geothermal heat flux under an ice sheet. Michael Purucker. SGT at Planetary Geodynamics Lab, Goddard Space Flight Center/NASA, Greenbelt, USA.

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Icebase: A proposed suborbital survey to map geothermal heat flux under an ice sheet

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  1. Icebase: A proposed suborbital survey to map geothermal heat flux under an ice sheet Michael Purucker SGT at Planetary Geodynamics Lab, Goddard Space Flight Center/NASA, Greenbelt, USA Team members include: Connerney, Blakely, Bracken, Nowicki, Le, Sabaka, Bonalsky, Kuang, Ravat, Ritz, Bouligand, Vaughan, Gaina, McEnroe, Tyler, Nelson + Danish team

  2. Outline • Motivation: Magnetic fields as ‘tracers’ of processes active in the lithosphere of a planet or moon. Rheology, tectonics, subduction, igneous processes and impact (Earth, Moon, Mars, Mercury) • Primary science goal: map geothermal heat flux under an ice sheet. • Relevance: response of ice sheet to climate forcing, search for oldest ice. • Isolating the geothermal heat flux: • Unmodeled external fields • Induced vs remanent magnetism • Varying magnetic susceptibility and thickness • Magnetizations below Moho • Heat production within the crust, mantle, thermal conductivity • Designing the survey and instrument suite. Why Global Hawk? • What else could the survey accomplish? Taipei: 19 Nov 2012

  3. Focus and Physics This talk will examine Earth’s magnetic field complex, concentrating on fields of internal origin. Taipei: 19 Nov 2012 NASA

  4. Planetary magnetic power spectra Purucker, 2012 Taipei: 19 Nov 2012

  5. The Earth: a satellite view of its magnetic lithosphere Maus et al., 2010 Taipei: 19 Nov 2012

  6. Integrated satellite and ground views of Earth’s magnetic lithosphere WDMAM Taipei: 19 Nov 2012

  7. Earth: rheology Purucker and Whaler, in preparation Taipei: 19 Nov 2012

  8. Why sub-orbital? • Sub-orbital missions at altitudes comparable to crustal thickness ‘image’ the upper and lower crust with comparable sensitivity. In contrast, aeromagnetic surveys are overwhelmingly dominated by the upper crust, and satellite surveys are unable to distinguish between the upper and lower crust. • Sub-orbital missions at higher, mesospheric (80-90 km) altitudes, ‘image’ a poorly understood region important for an understanding of space climate, and it’s impact on atmospheric climate. Taipei: 19 Nov 2012

  9. Why the Global Hawk? Taipei: 19 Nov 2012

  10. Survey and Instrument suite • 12 km flight line separations, 200 km tie lines, base stations, compensation maneuvers • Vector & total field magnetometers, dual frequency GPS, star camera • Team: GSFC, USGS, DTU, Grenoble, Trondheim Taipei: 19 Nov 2012

  11. Isolating the geothermal heat flux • Starting point: 3SMAC starting thermal and compositional model. • 3SMAC modified in an iterative fashion with magnetic observations until the magnetic field predicted by the model matches the observed magnetic field to some Delta. • Thermal model: 1-D, heat conducttion, steady state, constant thermal conductivity, simple model for radioactive heat production in the crust. • Input: CHAMP high degree crustal field solution (Deg 120) • Validation: Western North America, India, Australia, High Antarctic heat flux corresponds to active volcanism • Other processes in action: • Unmodeled external fields • Induced vsremanent magnetism • Varying magnetic susceptibility and thickness • Magnetizations below Moho • Heat production within the crust, mantle, thermal conductivity Taipei: 19 Nov 2012

  12. Heat flux map: Antarctica Purucker and Fox Maule, 2010 Taipei: 19 Nov 2012

  13. Heat flux map-Greenland Taipei: 19 Nov 2012

  14. Basal boundary condition Taipei: 19 Nov 2012 Hagdorn et al.,2006

  15. What else could the survey accomplish-1? • Mapping of time variable magnetic fields associated with oceanic, core, crustal, ionospheric, and magnetospheric sources through the use of exact repeat surveys under Swarm. Taipei: 19 Nov 2012

  16. Motional Induction Serpent, 2009 Magnetic field range produced by ocean flow estimated from monthly averages (Jan-Dec, 2001). Taipei: 19 Nov 2012

  17. What else could the survey accomplish-2? • In areas where heat flux can not be isolated, the magnetic maps could be used for • Tectonics • Igneous processes • Identification of impacts • Resource assessment Taipei: 19 Nov 2012

  18. Earth: subduction-1 Purucker and Clark, 2011 Serpent, 2009 Taipei: 19 Nov 2012

  19. Earth: subduction-2 Serpent, 2009 Purucker and Clark, 2011 Taipei: 19 Nov 2012

  20. Earth: igneous processes Western Australia Purucker and Whaler, 2006 Taipei: 19 Nov 2012

  21. Earth: impact 2013 IAGA Mtg On outer ring Spray et al. 2004 Purucker and Whaler, 2006 Taipei: 19 Nov 2012

  22. Basin development Siberia Purucker and Whaler, 2006 Potsdam: 12 Dec 2011

  23. Summary • A knowledge of magnetic fields at suborbital (20 km) altitudes would help answer questions about the lithosphere, and specifically heat flux under ice sheets. It is also expected to add to our knowledge of the global hydrologic cycle, and the processes producing time-variable magnetic fields of core, crustal, ionospheric, and magnetospheric sources. Taipei: 19 Nov 2012

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