Understanding Sea Level Variations: Reference Frame,
Data Analysis, and Modeling
Motivation
Different estimates of global raise of mean sea level varies in the range of
0.5-3.0 mm/yr. The reason of this wide range of estimates is a difficulty in
defining with respect to what the sea
level is rising. Sea level guages have vertical motions due to crust
deformation at the same or even higher rate. The orbit of altimetry satellites
may have secular drift of the same order of magnitude, the microwave altimeter
may have drifts in excess of 1 cm/yr. The idea is to develop an integrated
system of various space geodesy techniques in order to define the reference
for the sea level changes in a consistent way.
Goals of the project
To understand the sea level variations is a complex interdisciplinary
scientific challenge that has important implications for humankind
living on this restless Earth. Caused by a myriad of climatic and
geophysical processes, the sea level varies from place to place
on a wide range of temporal scale. This project has the following goals:
- To develop a comprehensive methodology for implementing and maintaining
a uniform terrestrial reference frame (TRF) based on all space
geodetic observations, from which the sea level variations can be
precisely defined and calculated: Measuring the sea level variations
continuously and globally using today's various high-precision
techniques, and being able to interpret the data quantitatively,
demand a uniform definition of the TRF. This has not been doable
until recent years as we understand better the inter-relationship of
the (space) geodetic measurements. We intend to bring together
Global Positioning System (GPS), Satellite Laser Ranging (SLR), Very
Long Baseline Interferometry (VLBI) and and DORIS network observations
and develop an empirical methodology to implement an integrated,
uniform terrestrial reference frame (TRF) centered at the same
geocenter. Precise sea level variations will be computed and analyzed
with respect to this reference frame. A primary data source is
microwave altimetry with orbits determined from SLR, DORIS and GPS.
New laser altimeter measurements will also be solved in this TRF.
Tide gauges will be used to calibrate and tie the altimetry over time
and across missions. The computation of the highest precision orbits
for the altimeters and the successful calibration of altimetry with
tide gauges depends on reference frame unification.
-
To analyze the above observational data and data/models of global
geophysical fluids towards a comprehensive understanding of the
relative sea level variations along the world's coasts, and the anatomy
and budget of the absolute sea level variations: Tide gauges will be
employed as source data for inferring coastal vertical motion of the
solid Earth for various geophysical investigations, although a full
understanding and modeling of vertical motions of the solid Earth are
beyond the scientific scope of this proposal. Global sea level change
will consequently be better determined and understood, especially at
longer than interannual periods. We will study mass flow and steric
effects in the oceans, and the water exchange with other components of
Earth system (atmosphere, cryosphere, land hydrology). Extensive use
will be made of (i) the observations in (1) above; and (ii) the output
of global water-budget models. Variations in ocean mass distribution
will be examined to study their contributions in low-degree
time-variable gravity signals derived from SLR, using in particular
ocean general circulation model output, including those assimilating
altimetric and in situ data types.
Role of Leonid Petrov in this project is to develop integrated algorithms for
data analysis of VLBI and satellite measurements, incorporate them in software
Geodyn, test them and investigate results of data analysis.
Back to Leonid Petrov's Home Page.
Last update: 20-MAY-2004 19:19:06