K. C. Jezek

1
Some Proposed IGOS Science Objectives and
Observational Requirements for Terrestrial Ice
Sheets
Quickscat Images from D. Long
K. C. Jezek Byrd Polar Research Center
.
2
Glaciers and Ice Sheets Grand Challenges

• Understand the polar ice sheets sufficiently to
  predict their response to global climate change
  and their contribution global sea level rise

• What is the mass balance of the polar ice
  sheets?
• How will the mass balance change in the future?
  
• How do changes in the cryosphere affect human
  activity?

3
Mass Balance

• Ice sheet mass balance is described
• by the mass continuity equation

Altimeters
Act/Pass. Microwave
InSAR
No spaceborne technique available
Evaluations of the left and right hand sides of
the equation will yield a far more complete result
4
Ice Dynamics and Prediction
Force Balance Equations
No Sat. Cover
Satellite Altimetry
Basal Drag, Inferred at best
Terms related to gradients in ice velocity
(InSAR) and temperature integrated over thickness
Understanding dynamics coupled with the
continuity equations yields predictions on future
changes in mass balance
5
An IGOS Goal

• Extend local observations of ice sheet physical
  properties to realize a continent wide
  understanding of ice dynamics, mass balance and
  the interaction of the ice sheets with other
  global systems

6
IGOS and 07 IPY Snapshots From Space
Goal Advance polar science by providing a
benchmark data set of continental scale
geophysical products
Objective Develop and execute an international
plan for coordinated spaceborne observations of
the polar regions and polar processes
Balance Velocity (Wu and Jezek, 2005)
Rignot and Thomas (2002)
Approach Concentrate resources on science
questions best addressed by a 'snapshot' approach
and/or which benefit from creation of a single,
integrated data set
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Measurement Objectives
Petermann Gl.
1962 DISP (Zhou and Jezek,2002)

• Objectives geared to establishing benchmark
  measurements of properties and processes
• Ice Sheet Change Detection Studies
  Hi-resolution image maps of the polar ice sheets
  (optical and microwave)
• Ice Sheet Mass Balance Accumulation rate fields
  from passive and active microwave surface
  velocity from SAR and feature retracking
• Ice Sheet Dynamics Stress and strain rate
  fields from altimetric surface topography and SAR
  velocity surface temperature fields from medium
  resolution THIR
• Ice-Sheet Ocean Interactions Fresh water fluxes
  from ice shelves from SAR velocity and ice
  thickness supplemented from altimeters
  (isostasy) Relationships to sea ice
  concentration and extent from passive microwave.

Annual Accumulation In Central Greenland from
SMMR (Bolzan and Jezek, 1999)
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Ice Sheets
AMM-1

• Key Measurements
• Map ice sheet geography
• (coastlines, grounding lines)
• Measure surface topography
• and changes in topography
• Measure the surface and
• internal temperature
• Measure the surface and basal accumulation rate
  and changes in accumulation rate patterns
• Measure the surface velocity field and changes in
  velocity field patterns
• Map the internal velocity field
• Map internal structures (bottom crevasses, buried
  moraine bands, brine infiltration layers)
• Map the basal topography of Antarctica and
  Greenland
• Determine basal boundary conditions from radar
  reflectivity

Liu and Jezek, 2004
9
Ice thickness and Basal ConditionsAn Unresolved
Problem

• Measure ice thickness to an
• accuracy of 10 m
• Measurements every 1 km
• Measure ice thickness
• ranging from 100 m to 5 km
• Measure radar reflectivity
• from basal interfaces (relative 0.5 dB)

Measure internal layers to about 20 m elevation
accuracy Pole to pole observations ice divides
to ice terminus One time only measurement of ice
thickness Repeat every 5-10 years for changes in
basal properties NEW TECHNOLOGY REQUIRED
10
IGOS and Approaches for Acquiring Data

• Dedicated, customized data acquisition periods
  outside the scope of an existing mission profile
  (e.g. SAR mapping)
• Procurement of large, customized data set from
  vendors (e.g. Quickbird images)

ERS SAR
Bolzan and Jezek, 2000
Fahnestock and others, 1993

• Specialized processing of routinely acquired data
  (e.g. accelerated processing of passive microwave
  products for incorporation into integrated data
  set)

Accumulation from SSMI
11
The Particular Problem of SAR and IGOS
RAMP and RGPS are illustrations of issues that
IGOS might face in terms of resource allocation
and data volumes Involved multiple flight
agencies Utilized spacecraft and ground
segment capabilities for defined period of time
Required international cooperation Required
coordination of flight operations and science
requirements Other examples of international,
large scale programs include Boreal Forest
Mapping, Amazon Rain Forest Mapping, and these
may offer valuable lessons.
12
Historical PerspectiveEuropean Remote Sensing
Satellites -1/2

• Program for International Polar Oceans
  Research(PIPOR)
• ERS-1/2 coverage of the Arctic Ocean
• for sea ice and polar ocean studies
• Collaboration established by NASA
• investment in ASF, conceived to extend
• the reach of ERS coverage to the
• north pole.
• Later extended to include coverage
• over Southern ocean via McMurdo
• Ground Station
• Tandem mission provided interferometry
• data for ice sheet velocity measurements.

13
Radarsat -1

• NASA and the CSA conducted negotiations in the
  early 1980s for use of Radarsat-1
• Negotiations provided access to science data
  (e.g. ADRO, Arctic Snapshot), data to the Joint
  Ice Center and provision for two, complete
  mappings
• of Antarctica
• In exchange, NASA launched Radarsat-1
• Radarsat Geophysical Processor System
• Arctic Snapshot obtained continuously
• since 1996.
• 3-day sampling of sea ice motion and
• deformation along with derived properties

14
Radarsat-1

• 1997, first Antarctic Mapping Mission (map and
  InSAR)
• 2000, modified InSAR mission to measure surface
  velocity
• 2004 InSAR
• acquisitions to acquire
• data over scientifically
• interesting areas.

15
Project Lessons

• Working relationships between PIPOR, ESA and
  NASA resulted in 8 minutes of SAR data per day
  becoming 30-40 minutes per day. Mutual desire
  to use the satellite and the early limitation of
  direct downlink meant that NASA through ASF was
  well positioned to acquire vastly more data than
  were originally anticipated.

• RAMP and RGPS showed that a formal agreement
  established early in a mission plan resulted in
  voluminous data acquisitions.
• RAMP and RGPS required extended and detailed
  interactions by the science community (PI) with
  the flight agencies to accomplish the goals.
• Role of commercial groups in the data path and
  unrestricted use of science data remains a
  discussion point.

16
Strategic Lessons

• Cryospheric science has benefited from
• pre-arranged agreements, polar ground
• stations, data management facilities.
• Flight agencies and the science community
• have devised strategies for acquiring large
• volumes of SAR data through international
• partners
• Successful arrangements required that flight
• agencies, such as NASA, enter into
  negotiations with partner flight agencies early
  in the project
• Science community must be intimately involved in
  all aspects of the planning and execution of
  large campaigns
• The role of the commercial sector is still being
  defined

17
Outstanding Issues for IGOS

• Existing Archives and Data Systems
• Overall pretty good for polar regions. Issues
  associated with timely data access, cost AND data
  and metadata from past and current in situ
  measurements.
• Encourage more access to digital data via
  pointing tools such as GCMD
• SAR Time series
• Planned SAR systems such as Radarsat-2 and
  TerraSAR X could begin to build time series of
  observations BUT No approved SAR missions beyond
  2011!
• SAR Velocity Control
• SAR velocity data are being controlled using in
  situ data from multiple epochs. This will
  eventually make velocity comparisons difficult.
• Role of commercial data vendors in IGOS

18

• IGOS and IPY '07 are important next steps that
  can
• build on a strong legacy of polar science
• establish an essential benchmark for gauging
  changes in polar systems
• further our understanding of how polar
  processes are intertwined with those of the rest
  of the globe

Summary
Captain Ashley McKinley holding the first aerial
surveying camera used in Antarctica. It was
mounted in the aircraft Floyd Bennett during
Byrds historic flight to the pole in 1929.
(Photo from The Ohio State University Archives)
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Preliminary Requirements
20
Ice Sheet Requirements
Parameter accuracy (absolute) Acccuarcy Relative Spatial Resolution Temporal Resolution Comments
ice margin 500 km 250 m 1 km 5 yr
grounding line 1 km 250 m 1 km 5 yr
surface accumulatoin 10 (for low accumulation about 2 cm/yr we 10 10 km (1 km selected areas) 5-20 yr resolution (200-500 yr data for trends at selected sites) (seaonal at selected sites Useful to reassess the accuracy of current techniques
Basal melt 10 (binary accepatble) 10 10 km (1 km selected sites) 5 yr Knowning where melt is occuring is useful as a binary parameter
surface elevation 50 cm 10 cm 200 m 5 yr for ice dynamics modeling and image rectification
21
surface elevation change 10 cm 5 cm 1 km annually multidecadal records needed for trend
snow/firn density lt 10 10 100 km (1 km selected sites) (10 cm vertically) 20 )yr (annually at selected sites needed to intepret elevation change and for analysis of some remote sensing data
Snow Grain Size and shape 0.25 mm 0.1 mm 100 km (10 cm vertical) 20 yr
Surface Temperature 1 degree C 0.5 degree C 10 km annually
Internal Temperature 0.1 degree C 0.05 degree Selected sites 5 yr
Gravity field 1 mgal (0.01 mgal selected sites) 0.5 mgal 25 km annually Changes in mass, ice sheet reconstruction
22
Surface Velocity field (3d) 10 (1 m/yr) 1 m/yr (5 cm/yr vertical) 1 km (500 m selected) Annually (seasonally at selected sites)
Internal Velocity field 10 (0.5 m/yr) 0.5 m/y Selected sites 10 yrs
Ice thickness 10 m 5 m 1 km (250 m selected) Once for grounded ice (assuming continous elevation data available)
Iceberg calving rate 10 10 1 km annually
Location of Crevasse fields 10 10 1 km 20 yr
Location of Shear margins 10 10 500 m 20 yr
Surface melt patterns 1 km 500 m 1 km Annually Onset date, freeze date, extent
23
PRELIMINARY SET OF PRODUCT OBJECTIVES FOR
IPY.   Image Map/Mosaic Products
Preliminary Set of Map Products
 
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Preliminary Derived Products List
25
Back Up View Graphs

26
RAMP as a Model
RADARSAT-1, CSA

• RAMP is one illustration of how
• project could be organized.
• Involved multiple flight agencies
• Utilized spacecraft and ground
• segment capabilities for defined period of
  time
• Required international cooperation
• Required coordination of flight operations and
  science requirements
• Other examples of international, large scale
  programs include Boreal Forest Mapping, Amazon
  Rain Forest Mapping, and these may offer valuable
  lessons.

27
AMM-2 Acquisition Phase Organization
Mission Planning
ASF Mission Planning and Conflict Resolution
CSA Mission Planning
GSFC WFF WS
JPL Mission Plan
JPL/OSU Replanning Team
TDRSS/DOMSAT
ASF Science Tool Development
28
IPY Approach
Aqua, NASA
ALOS, NASDA
Cryosat, ESA
29
Some Practicalities

• access time and coverage
• repeat cycle (modified and coordinated with
  other instruments)
• imaging/data collection modes (e.g. beam
  combinations)
• scheduling (e.g. contemporaneous SAR and
  optical mapping)

RAMP Acquisitions, JPL

• orbit maintenance (minimize disruptions during
  coordinated acquisition activities)
• duty cycle (intense observations during an IPY
  window)
• coordinated/optimized mission planning - develop
  mission planning and mission monitoring tools

MODIS, 2002
Larsen Ice Shelf