Presented by Dave McAdoo

Center for Satellite Applications and Research (STAR) Review 09 – 11 March 2010

Image:

MODIS Land Group,

NASA GSFC

March 2000


Image:

MODIS Land Group,

NASA GSFC

March 2000

Presented byDave McAdoo

Arctic Sea Ice Freeboard Measurements from Satellite

Altimetry

Center for Satellite Applications and Research (STAR) Review09 – 11 March 2010

Center for Satellite Applications and Research (STAR) Review09 – 11 March 2010 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

ecosystemsScience • 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.



CryoSat-2

• 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.

3

Challenges and Path Forward



From passive microwave satellite data

Sep 2007: Minimum Sea Ice Extent for 30 yrs NSIDC

Total: 4.3 million sq. km

Motivation: Diminishing Arctic Sea Ice Extent

Sep Anomalies 1979-2009

Projected Sep Ice Extent (5-model Average)2010-2030 2040-2060 2070-2090

ACIA



.

.

5

SNOW

SEA ICE

WATER

RA

DA

R

LAS

ER

Ice Freeboard

Satellite Altimetry (laser and radar) over Sea Ice

Sea Ice Thickness

Altimeters provide basin-scale freeboard and sea surface height data over the Arctic Ocean

Snow Thickness

RA

DA

R

LAS

ER

Satellite Altimetry



.

.6

Ice - Open Water Discrimination: Detecting Leads

Specular Echo (Leads) Diffuse Echo (Ice Floes)

Satellite Radar Altimetry (Envisat & ERS)

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)

Satellite Laser Altimetry (ICESat)

Leads Ice FloesHighly 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)



Seasonal mean removed to create anomaly

Change in Arctic Sea Ice Freeboard from ICESat 2003 – 2008

2003 2008 2003 2008

Fall (Oct-Nov) Winter (Feb-Mar)



Validating Satellite Altimeter Dataover 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)



.

.9

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

Component of NASA’s Operation Ice Bridge (OIB) CBSIT Experiment: April 2009

For details see: Connor et al. poster, “Airborne & in situ validation of aatellite altimetry measurements over sea ice”



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.10

In Situ Measurements:

• EM-31 Ice thickness profiling

• Snow depth

• Snow pits

• Drill holes for calibrations

Courtesy J. Yungel, NASA

GreenArc Ice Camp Over-flight (CBSIT 2009)



CryoSat-2

• 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.

11

Challenges and Path Forward


Image:

MODIS Land Group,

NASA GSFC

March 2000


Image:

MODIS Land Group,

NASA GSFC

March 2000

Extra Slides



Envisat and ICESat Validation over Sea Ice

AAA Experiment flight path in the Canada Basin

From Connor et al., RSE, 2009

Arctic Airborne Altimetry AAA: 2006 Along Envisat/RA-2 track - AB

Std dev = 0.08m

Envisat vs ATM Lead elevs(using lead detection algorithm)



Principle of Satellite AltimetryMeasuring 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

Presented by Dave McAdoo

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