"The global mean sea level (GMSL) we
estimate is an average over the oceans (limited by the satellite inclination to ± 66 degrees latitude),"
[66 degrees roughly Arctic to Antarctic circles]
Tempered and further explained from Page 2 ...
"The groundtrack of these satellites repeats every 10 days, providing near-global (±66°latitude) maps of sea level change with this temporal sampling. When averaged globally, these maps provide 10-day
estimates of global mean sea level with an accuracy of roughly 4-5 mm [5]. Over the last 13 years, observations of changes in these
estimates have shown a rise in global mean sea level of 3.2 ± 0.4 mm/year"
found here...
earth.esa.int/workshops/venice06/participants/1092/paper_venice06.pdfalso page 2...
"Long-term changes in global mean sea level can be caused by a variety of different phenomena, but the major contributions arise from changes in ocean temperature (thermal expansion), changes in the amount of water stored in mountain glaciers, and changes in the volume of ice in Greenland and Antarctica.
Our knowledge of the magnitude of each of these contributions varies considerably. In addition, we have much better knowledge of these contributions during
the satellite era than over the last century."
and from page 3, glaciers...
"In situ observations of the mountain glaciers are
sparse – only a small fraction of the world’s glaciers are actively monitored. However, when observations of these glaciers are
extrapolated globally, they show a contribution to sea level change of 0.4 mm/year over the four decades, and 0.9 mm/year during the satellite era [19], although the
errors on these estimates could be quite large."
"Greenland and Antarctica
Perhaps the least is known about the contributions to sea level change from Greenland and Antarctica ice melt. Even during the satellite era,
the sea level contributions from Greenland and Antarctica are uncertain, in particular because measurements do not provide complete coverage of the ice sheets."
page 5...
"Satellite
measurements show that the rate of sea level rise has
increased when compared to 20th century tide gauge
measurements, though it
is unknown if this increase in
the rate will be maintained. About half of the current
rise is due to thermal expansion, leaving a large fraction
to be explained by the melting of mountain glaciers and
polar ice."
"
Unfortunately, direct satellite observations of the polar
ice sheets are in disagreement, and thus future efforts
should be focused on improving mass balance of the
polar ice sheets, especially since Greenland and
Antarctica represent the large source of potential future
sea level change (7 and 60 meters respectively),
as well
as the anthropogenic land water component, at present
virtually unknown."
from pdf...
" Satellite Measurements of Sea Level Change:
Where Have We Been and Where Are We Going "
earth.esa.int/workshops/venice06/participants/1092/paper_venice06.pdf"Impact of self-attraction and loading on the annual cycle in sea level"
"The SAL effects cause annual amplitudes at tide gauges (modeled here with a global average of ~9 mm)
to vary from less than 2 mm to more than 18 mm. We find a variance reduction (global average of 3 to 4%) after removing the modeled time series from a global set of tide gauges. We conclude that SAL effects are
significant in places (e.g., the south central Pacific and coastal regions in Southeast Asia and west central Africa) and should be considered when interpreting these data sets and using them to constrain ocean circulation models."
sealevel.colorado.edu/content/impact-self-attraction-and-loading-annual-cycle-sea-level-0So significant in places and not in others.
"We do calibrate the altimeter sea level measurements against a network tide gauges to discover and monitor drift in the satellite (and sometimes tide gauge) measurements.
This is discussed further in the tide gauge discussion."
sealevel.colorado.edu/content/why-gmsl-different-local-tide-gauge-measurements"Tide Gauge Sea Level"
"Although the global network of tide gauges comprises of
a poorly distributed sea level measurement system, it offers the only source of historical, precise, long-term sea level data. Major conclusions from tide gauge data have been that global sea level has risen approximately 10-25 cm during the past century." [4-10 inches]
sealevel.colorado.edu/content/tide-gauge-sea-levelCalibration.
"Ideally, one would want to include all of the available tide gauges in the calibration. A number of gauges, however, have a significant lag in reporting of records and are not available for the Jason calibration. On the other hand, some others do not extend backward through most of the T/P mission. We have restricted the ~100 available gauges to a set of 64 near real-time stations that span the majority of both the T/P and Jason missions, and will therefore provide a relatively consistent calibration for both."
sealevel.colorado.edu/content/calibration-----------
"CU Sea Level Research Group
University of Colorado"
"Since 1993, measurements from the TOPEX and Jason series of satellite radar altimeters have allowed
estimates of global mean sea level. These measurements are continuously calibrated against a network of tide gauges. When seasonal and other variations are subtracted, they allow
estimation of the global mean sea level rate. As
new data, models and corrections become available, we continuously revise these
estimates (about every two months) to improve their quality."
sealevel.colorado.edu/"do you believe the o.3mm/year quoted error on sea-level change measurements or not, since that is where we started?"
Ummm?
map of World...
www.worldpress.org/map.cfm(Credits University of Colorado at Boulder for graph)
Late mod: Hi-light
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