1. International Symposium on Radioglaciology 9/09/2013 Nicholas Holschuh, Sridhar Anandakrishnan, Knut Christianson

2. Introduction Stacking Refraction Objectives of RES Conclusions R. Pattern Historic Objectives Determine the depth to (and geometry of) the basal reflector Describe the internal structure of the ice sheets using the internal reflecting horizons (IRHs) Modern Objectives Use return powers from basal reflectors to determine dielectric properties of the ice-bed interface Analyze the spectral quality of reflectors to uniquely identify layers through space

3. Introduction Stacking Refraction Motivation Conclusions R. Pattern

4. Introduction Stacking Refraction Motivation Conclusions R. Pattern  The brightest reflectors are sometimes traceable through the lossy region  …but at other times, are completely lost in the noise…

5. Introduction Stacking Refraction Motivation Conclusions R. Pattern What is the source of the data loss? - Affects deeper reflectors more than shallow ones - Appears to be related to reflector slope - More prevalent in the High Frequency Airborne Data

6. Introduction Stacking Refraction Motivation Conclusions R. Pattern

7. Introduction Stacking Refraction Motivation Conclusions R. Pattern

8. Introduction Stacking Refraction Motivation Conclusions R. Pattern

9. Introduction Stacking Refraction Assumptions - Specularity Conclusions R. Pattern Internal Reflectors: Specular (Obey the Law of Reflection) Basal Reflectors: Diffuse Reflection Coefficient Reflection Coefficient + Angular Distribution

10. Refraction Stacking Introduction Beam Focusing Conclusions R. Pattern Ground Survey Airborne Survey n = 1 + 0.851 ρ

11. Refraction Stacking Introduction Beam Focusing Conclusions R. Pattern Ground SurveyAirborne Survey Refraction Limits: Ground Survey – 49º Airborne Survey – 34º

12. Conclusions Refraction Stacking Introduction R. Pattern Stacking Component Traces Superimposed Components Stacked Trace (Normalized) Ideal Stack (Normalized)

13. Conclusions Refraction Stacking Introduction R. Pattern Stacking Component Traces Superimposed Components Stacked Trace (Normalized) Ideal Stack (Normalized) Stacking Controls 1)Radar Frequency 2)Reflector Dip 3)Stacking Distance

14. Conclusions Refraction Stacking – 1m Posting Interval Introduction R. Pattern Stacking

15. Conclusions Refraction Stacking – 1m Posting Interval Introduction R. Pattern Stacking 0.863

16. Conclusions Refraction Stacking – 10m Posting Interval Introduction R. Pattern Stacking 0.018

17. Conclusions Refraction Stacking – 10m Posting Interval Introduction R. Pattern Stacking 0.202

18. Conclusions Refraction Stacking – 20m Posting Interval Introduction R. Pattern Stacking 0.009

19. Conclusions Refraction Stacking – 10m Posting Interval Introduction R. Pattern Stacking 0.00090.00210.01790.01950.04681 0.00260.02240.02950.03020.08211 0.01180.02520.03020.04790.09851 0.02250.04050.07090.09850.20271 0.94620.96190.97680.98910.9971

20. Conclusions Refraction Stacking Amplitude Loss Introduction R. Pattern Stacking

21. Refraction Radiation Pattern Introduction Conclusions R. Pattern Describes the angular distribution of the gain for a given radar antenna (Typically optimized for Nadir)

22. Stacking Refraction Radiation Pattern Introduction Conclusions R. Pattern

23. Stacking Refraction Caveats - Specularity Introduction R. Pattern Conclusions Offsets 0 – 1400m (100m) TransmitterReceiver

24. Stacking Refraction Conclusions Introduction R. Pattern Conclusions  Areas of intense deformation (and therefore glaciological interest) are prone to internal data loss  Amplitude loss due to reflector geometry should be corrected for if dipping beds are used in amplitude analysis.  Loss is ultimately a function of radar design and data collection methods. Choosing appropriate radars (frequency), platform, and stacking distances can minimize data loss.

25. Nicholas Holschuh – ndh147@psu.edu Advisors: Sridhar Anandakrishnan Richard Alley Collaborator:Knut Christianson Questions? This material is based upon work supported by the National Science Foundation Graduate Research Fellowship Program under Grant No. DGE1255832. We would like to acknowledge the use of data products from CReSIS generated with support from NSF grant ANT-0424589 and NASA grant NNX10AT68G. Stacking Refraction Introduction R. Pattern Conclusions