Surface mass loading Conclusions discussion recommandations

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					(a) Pre-earthquake and (b) post-earthquake Advanced Spaceborne Thermal Emission and Reflection
Radiometer (ASTER) images of North Sentinel Island. The image shows sea -level lowering caused
by the great Aceh-Andaman earthquake of 2004 (Mw ~ 9.2). Here the emergence of the coral reef surrounding the
island is very clear in the image. Co-seismic, tidally corrected, uplift is 1-2 meters. Frame (c) shows pre-
earthquake and (d) post-earthquake ASTER images of a small island off the northwest coast of Rutland Island, 38
km east of North Sentinel Island, showing submergence of the coral reef surrounding the island. Frames (a) and
(b) are about 50 km from the rupture on the underthrusting Sunda Trench. (Adapted from Meltzer et al., 2005).
        Surface Mass Loading – Conclusions

1. Uncertainties in mantle viscosity and Late-Pleistocene ice
   mass histories have a significant impact on estimates of
   global sea level rise from tide gauge observations

2. Differences between current models of Antarctic and
   Greenland deglaciation histories are considerable and will
   influence interpretations of altimetry and time variable
   gravity data

3. Fingerprinting of sea level data (e.g., for polar ice melt
   signatures) offers promise of understanding mass
   balances given enhanced relative sea level (RSL) data sets

4. Improved constraints on RSL variations should be made in
   all parts of the world. These RSL data provide important
   feedback into all models of ice mass change and sea level
   mass change
          Surface Mass Loading – Discussion

1. Improve constraints on the fingerprints associated with
   thermosteric effects and recent ice mass flux
2. Determine what other data sets can be invoked to limit the
   range of possible melting geometries, or to expand the range
   from the simple scenarios considered to date
3. How can the uncertainty in the GIA signal, which is still
   significant, be best parameterized within the fingerprint
4. What is the correct way to incorporate polar wander
   variations in the (relative) sea level predictions?
5. What are the important sources of noise, and which
   processes (e.g., terrestrial hydrological redistributions) need
   to be included in an expanded regression analysis?
6. In regard to tide gauge records, what is the appropriate
   balance to strike between retaining information and culling
   the data set to avoid systematic sources of error, and how
   might this data set be combined with others (e.g., GRACE
   and GOCE gravity) in an extended fingerprint analysis
   Surface Mass Loading – Recommendations 1: Data

For offering the community better GIA constraints we need:

1. Continuous GPS networks as dense as feasible in the way this
   was done with the BIFROST project

2. Follow-on GRACE gravity mission for continuity of the gravity
   data sets and for observing temporal variations at higher

3. Follow-on JASON mission with higher latitude coverage for ocean
   surfaces, notably for fingerprinting, and a dedicated altimetry
   mission (ICESAT follow-on, CRYOSAT) for ice mass surfaces

4. Continuity of tide gauges and network densification in the
   southern hemisphere

5. Extension of the relative sea level data sets from geological and
   archaeological indicators
Surface Mass Loading – Recommendations 2: Modelling
Concerning modelling efforts:

1. Truly 3D earth modelling that incorporates more realistic lateral
   variations in (possibly non-linear) rheologies and lithosphere for
   regional applications when there is a clear necessity for it (Occam’s

2. A more reliable prediction is needed of GIA-induced True Polar Wander

3. Ice sheet models that are internally dynamically consistent and that are
   consistent with all known geological, ice-core, sedimentary-core,
   trimline and other data

4. Non-ice sheet related surface forcings (tectonic, co- and postseismic,
   sedimentary, hydrological, changes in ocean currents, etc.)

5. Standardisation for practical purposes with clear instructions on how
   to use them (e.g. valid for global applications but not for regional ones)

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