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Presented by Dave McAdoo

Arctic Sea Ice Freeboard Measurements from Satellite Altimetry . Presented by Dave McAdoo. Objective, Science, and Benefit. Requirements/Objective Research area: Document and understand changes in climate forcings and feedbacks, thereby reducing uncertainty in climate projections

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Presented by Dave McAdoo

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  1. Arctic Sea Ice Freeboard Measurements from Satellite Altimetry Presented by Dave McAdoo

  2. Objective, Science, and Benefit • Requirements/Objective • Research area: Document and understand changes in climate forcings and feedbacks, thereby reducing uncertainty in climate projections • Priority research activity: Monitor changes in the Arctic and impacts on ecosystems • Science • At what volumetric rate is loss of Arctic sea ice occurring and how accurately can we track sea ice thickness changes using altimetry? • What is the role of observed sea ice flux in climate system? • Benefits • New, refined sea ice volume constraints on climate models. • Near-real-time tracking of thick, multi-year sea ice in support • of NSPD-66 and Commerce Transportation and Goal #8. • Improved oceanographic and geodetic constraints for Arctic Ocean circulation modelling. 2

  3. Challenges and Path Forward • Science Challenges -Deriving precise (to ~3-5 cm), detailed (to ~ 10 km) sea ice freeboard and thickness estimates from complex satellite altimeter data sets • Next Steps -Publish analyses of CBSIT (2009) data sets -Prepare for and conduct BESIE 2011 - Beaufort Sea Ice Camp as advisors to NASA’s OIB Airborne Campaigns in Antarctic and Arctic -Validate, analyze and exploit sea ice data from ESA’s CryoSat-2 (as ESA Data AO and Cal-val investigators). Process the complex returns from its advanced altimeter for ice freeboard -Prepare for ICESat-2 as members of the Science Definition Team • Transition Path -Multi-year ice tracking and thickness products for the NIC, as well as climate models. CryoSat-2 3

  4. Motivation: Diminishing Arctic Sea Ice Extent From passive microwave satellite data Sep 2007: Minimum Sea Ice Extent for 30 yrs NSIDC Sep Anomalies 1979-2009 Projected Sep Ice Extent (5-model Average) 2010-2030 2040-2060 2070-2090 Total: 4.3 million sq. km ACIA 4

  5. Satellite Altimetry (laser and radar) over Sea Ice . . RADAR LASER RADAR LASER Snow Thickness SNOW Ice Freeboard SEA ICE Sea Ice Thickness Satellite Altimetry WATER Altimeters provide basin-scale freeboard and sea surface height data over the Arctic Ocean 5

  6. Ice - Open Water Discrimination: Detecting Leads Satellite Laser Altimetry (ICESat) Leads Ice Floes Highly specular reflections from leads Difficult to distinguish leads from ice floes Several methods for determining SSH (e.g. Kwok et al. 2007; Zwally et al., 2008 ; Farrell et al., 2009) Satellite Radar Altimetry (Envisat & ERS) . . Specular Echo (Leads) Diffuse Echo (Ice Floes) Provides unambiguous detections of leads for sea surface height measurements Large footprint means returns from “mixed” surfaces (distorted echoes) have to be discarded (e.g. Peacock & Laxon, 2004) 6

  7. Change in Arctic Sea Ice Freeboard from ICESat 2003 – 2008 2003 2008 2003 2008 Fall (Oct-Nov) Winter (Feb-Mar) Seasonal mean removed to create anomaly 7

  8. Validating Satellite Altimeter Data over Sea Ice • In-situ measurements on ice • Airborne surveys above ice • NOAA Validation Experiments • (all joint with NASA; airborne & in situ) • LaRA–FASIT (2002) Fram Strait • AAA (2006) - Beaufort Sea • Canada Basin Sea Ice Thickness • (CBSIT, April 2009) • BESIE (2011) 8

  9. CBSIT Experiment: April 2009 Component of NASA’s Operation Ice Bridge (OIB) . . • Envisat Under-flight • April 21 2009 • Canada Basin • Near 2006 survey line • Thick MY ice to FY ice • Ice Camp Over-flight • April 25 2009 • GreenArc Ice Camp • Thick, Old MY ice • Nares Strait For details see: Connor et al. poster, “Airborne & in situ validation of aatellite altimetry measurements over sea ice” 9

  10. GreenArc Ice Camp Over-flight (CBSIT 2009) . . • In Situ Measurements: • EM-31 Ice thickness profiling • Snow depth • Snow pits • Drill holes for calibrations Courtesy J. Yungel, NASA 10

  11. Challenges and Path Forward • Science Challenges -Deriving precise (to ~3-5 cm), detailed (to ~ 10 km) sea ice freeboard and thickness estimates from complex satellite altimeter data sets • Next Steps -Publish analyses of CBSIT (2009) data sets -Prepare for and conduct BESIE 2011 - Beaufort Sea Ice Camp as advisors to NASA’s OIB Airborne Campaigns in Antarctic and Arctic -Validate, analyze and exploit sea ice data from ESA’s CryoSat-2 (as ESA Data AO and Cal-val investigators). Process the complex returns from its advanced altimeter for ice freeboard -Prepare for ICESat-2 as members of the Science Definition Team • Transition Path -Multi-year ice tracking and thickness products for the NIC, as well as climate models. CryoSat-2 11

  12. Extra Slides

  13. Arctic Airborne Altimetry AAA: 2006 Envisat and ICESat Validation over Sea Ice Along Envisat/RA-2 track - AB AAA Experiment flight path in the Canada Basin Std dev = 0.08m  Envisat vs ATM Lead elevs (using lead detection algorithm) From Connor et al., RSE, 2009 13

  14. Principle of Satellite Altimetry Measuring the third / vertical dimension Measuring Surface Elevation (h): R = ct / 2 R = range measured by satellite altimeter c = speed of light t = round-trip travel time h = H – R h = sea surface heightrelative to reference ellipsoid H = satellite altitude above reference ellipsoid 14

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