<?xml version="1.0" encoding="UTF-8"?><xml><records><record><source-app name="Biblio" version="6.x">Drupal-Biblio</source-app><ref-type>47</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Cazenave, A.</style></author><author><style face="normal" font="default" size="100%">Chambers, D.</style></author><author><style face="normal" font="default" size="100%">Cipollini, P.</style></author><author><style face="normal" font="default" size="100%">Fu, L.</style></author><author><style face="normal" font="default" size="100%">Hurrell, J. W.</style></author><author><style face="normal" font="default" size="100%">Merrifield, M. A.</style></author><author><style face="normal" font="default" size="100%">R. S. Nerem</style></author><author><style face="normal" font="default" size="100%">Plag, H. P.</style></author><author><style face="normal" font="default" size="100%">Shum, C. K.</style></author><author><style face="normal" font="default" size="100%">Willis, J. K.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">The Challenge for Measuring Sea Level Rise and Regional and Global Trends</style></title><secondary-title><style face="normal" font="default" size="100%">OCEANOBS2009</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">gia</style></keyword><keyword><style  face="normal" font="default" size="100%">grace</style></keyword><keyword><style  face="normal" font="default" size="100%">processing</style></keyword><keyword><style  face="normal" font="default" size="100%">sea_level</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2010</style></year><pub-dates><date><style  face="normal" font="default" size="100%">10/2010</style></date></pub-dates></dates><urls><web-urls><url><style face="normal" font="default" size="100%">https://abstracts.congrex.com/scripts/jmevent/abstracts/FCXNL-09A02b-1877091-1-Cazenave_Plenary_SeaLevelRise.pdf</style></url></web-urls></urls><publisher><style face="normal" font="default" size="100%">ESA</style></publisher><pub-location><style face="normal" font="default" size="100%">Venice</style></pub-location><abstract><style face="normal" font="default" size="100%">This Plenary Paper on sea level is based on several
Community White Papers submitted to
OceanObs09. Considerable progress has been
realized during the past decade in measuring sea
level change globally and regionally, and in
understanding the climate-related causes of
observed changes. We first review current
knowledge about sea level change, globally and
regionally. We summarize recent results from the
2007 IPCC 4th Assessment Report (AR4), as well as
post-IPCC results relevant to sea level observations,
causes and projections. New challenges are
identified for the coming decade in terms of
observations, modelling and impact studies. From
these challenges, a number of recommendations
emerge, which are listed below:
a) An accurate (at the &lt;0.3 mm/yr level
uncertainty), multi-decade-long sea level record by
altimeter satellites of the T/P- Jason class is
essential, as is continued funding of the altimeter
science team to provide leadership. To meet the
goal of 0.3 mm/yr or better in sea level rate
accuracy, the global geodetic infrastructure needs to
be maintained on the long-term; the Terrestrial
Reference Frame must be accurate and stable at the
1 mm and 0.5 mm/yr level; radiometers required for
the correction of radar path delays must also be
stable (or calibrated) at 0.1 mm/year. A network of
tide gauges with precise positioning (GPS, or moregeneral, GNSS) should be maintained with an
emphasis on long record lengths and global spatial
coverage (e.g., the GLOSS Core Network plus
additional stations with especially long record
lengths).
b) Continuity of GRACE-type space gravimetry
observations is critically needed. No other data
exist to measure ocean mass changes directly. To
avoid an undesirable gap in data record, a GRACE
Stop-Gap mission should be undertaken by space
agencies to continue the geophysical time series of
the current GRACE mission. Meanwhile, new
concept for improving precision and resolution
need to be developed..
c) Improved accuracy for the Glacial Isostatic
Adjustment (GIA) forward modelling that are
needed to provide corrections for GRACE, tide
gauges and satellite altimetry observations over
ocean, land and ice-sheets should be made
available. Specifically, the GIA community should
be encouraged to perform intercomparison studies
of GIA modelling, similar to what has been done
for coupled climate model outputs. The goal should
be to produce a global, spatially varying,
community wide best-estimate of GIA and its
uncertainty that is appropriate for application to
global sea level studies.
d) Long-term maintenance of the Argo network in
its optimal configuration is imperative for
measuring ocean temperature and salinity;
development of a shipboard CTD measurement
program for absolute calibration of other in situ
hydrographic data is critical to maintain the fidelity
of other networks; reanalyses of historical
temperature and salinity is strongly recommended;
development of new methods/systems to estimate
deep changes in ocean heat content and thermal
expansion is needed.
e) High priority should be given to the development
of integrated, multidisciplinary studies of presentday
and last century sea level changes (global and
regional), accounting for the various factors
(climate change, ocean/atmosphere forcing, land
hydrology change—both natural and
anthropogenic, solid Earth processes, etc.) that act
on a large variety of spatio-temporal scales.
Improvement and validation of 2-dimensional past
sea level reconstructions is also important, as well
as development of attribution studies for
global/regional sea level variations using ocean
reanalyses.
f) Inter comparison of sea level projections from
climate models need to be developed to assess
uncertainty. Projections need to include regional
and decadal variability. Development and inclusion
of realistic ice sheet dynamics in coupled climate
models is a key issue for projecting sea level
change, as the potential contribution from ice sheets
like Greenland and Antarctica is much larger than
any other source.
Finally, as local (relative) sea level rise is among
the major threats of future global warming, it is
both of primary importance and urgence to:
g) develop multidisciplinary studies to understand
and discriminate causes of current sea level changes
in some key coastal regions, integrating the various
factors that are important at local scales (climate
component, oceanographic processes, sediment
supply, ground subsidence, anthropogenic forcing,
etc.)
h) implement additional in situ observing systems
in vulnerable coastal areas, in particular, tide
gauges co-located with GNSS stations for
measuring (mainly vertical) ground motions,
i) improve current altimetry-based sea level
observations in coastal zones and continue to
develop SWOT (Surface Water and Ocean
Topography) satellite mission, a wide-swath
altimeter, for accurate future monitoring of local
sea level changes at the land-sea interface. SWOT
is able to measure sea surface height in the presence
of sea ice and is thus able to provide information on
ocean circulation near ice shelves for studying the
process of the breakup of ice shelves that buttress
ice sheets.
j) for decision support, provide reliable local sea
level forecasts on time scales of decades. Improved
sea level (global and regional) projections at
centennial time scales are also desired.
This long list of recommendations results from the
interdisciplinary nature of sea level studies.
Recommendations a, b and d rely on the continuity
of observing systems and are directed towards
space agencies and international organizations. No
priority can be given as satellite altimetry, space
gravimetry and Argo are all complementary and
critically needed to observe and understand sea
level. Recommendations c, e and f concern the sea
level community itself and ask for better
organisation and closer collaboration between data
analysists and modellers. Finally, recommendations
g to j call for better understanding of coastal
impacts and call for wider collaboration between
Earth science researchers.</style></abstract></record></records></xml>