Title: K. C. Jezek
1Some Proposed IGOS Science Objectives and
Observational Requirements for Terrestrial Ice
Sheets
Quickscat Images from D. Long
K. C. Jezek Byrd Polar Research Center
.
2Glaciers 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?
3Mass 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
4Ice 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
5An 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
6IGOS 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
7Measurement 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)
8Ice 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
9Ice 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
10IGOS 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
11The 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.
12Historical 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.
13Radarsat -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
14Radarsat-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.
15Project 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.
16Strategic 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
17Outstanding 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)
19Preliminary Requirements
20Ice 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
21surface 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
22Surface 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
23PRELIMINARY SET OF PRODUCT OBJECTIVES FOR
IPY. Â Image Map/Mosaic Products
Preliminary Set of Map Products
Â
24Preliminary Derived Products List
25Back Up View Graphs
26RAMP 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.
27AMM-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
28IPY Approach
Aqua, NASA
ALOS, NASDA
Cryosat, ESA
29Some 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