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. Taipei: 19 Nov 2012Outline 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?

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

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

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

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

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

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 vs remanent 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 Taipei: 19 Nov 2012 Purucker and Fox Maule, 2010

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

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 Taipei: 19 Nov 2012 Purucker and Clark, 2011 Serpent, 2009

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

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

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

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

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