Han writes:
Doug Miller wrote in
:

Han wrote in news:XnsA0847BD6DC6C5ikkezelf@
207.246.207.124:

One of the scary reasons to pay attention to ocean warming is
that much is really cold (like in the 30's and low 40's in
Fahrenheit). If all that ocean water warms just a few degrees, it
will expand, and thus the level will go up. Somebody ought to have
the calculated data how much up that up is.

Not scary at all to anyone who's had an education in the physical
sciences.

Water has its maximum density of 1.00000 g/ml at 3.98 degrees C. At 5
deg C (41 deg F) its density is 0.99999 g/ml, and at 10 deg C (50 deg
F) the density is 0.99973 g/ml -- IOW, warming from 4 deg C to 10 deg
C, water will expand by a factor of (1.00000 / 0.99973) = 1.00027, or
about one-fortieth of one per cent.

Water is actually more dense at 5 deg C than at 0.

[Source for the above data is the Handbook of Chemistry and Physics]

My Handbook is upstairs. One of the very few books I took when I
retired. It is really old, though still the larger format.

OK, let's do the calculations.

First let's assume that the ocean basins don't change in volume as the
ocean warms up.

From http://ngdc.noaa.gov/mgg/global/etopo1_ocean_volumes.html
total volume: 1,335,000,000 km^3
Total surface area 361,900,000 km^2

Using your expansion factor as a very large approximation:
Total volume becomes 1,335,000,000 * 1.00027 = 1,335,360,450 or
360,450 km^3 more, which is divided over an area of 361,900,000 km^2.
That is a height of 0.000995993368 km, i.e. 99.59 cm or over 3 feet.

Your temperature rise is very large, so with a lower rise in temperature,
the rise in sea level won't be as great. But, keep in mind that this is
only the effect of warming of the whole ocean. I don't (yet) know what
the expansion will be on average, because I don't know how fast a) the
oceans will heat up, and b) how fast the oceans mix. However, we need to
add the effects of glacier and icecap melts, and we have no idea really
how the rate of melting is going to change. Overall (and there are vast
variations), that rate seems likely to increase, rather than decrease.

Of course, a couple of dozen Mt Pinatubo sized volcanic eruptions will
likely cool things down for at least a few years, let alone Krakatao-
sized ones ...

There are a number of factors that need to be considered when
thinking about the average sea level:

1) Isostatic rebound; some land surfaces in the Northern Hemisphere are still
rebounding (rising) from the last ice age. All things equal, this
results in relative lowering of sea level in such areas.

2) Subsidence due to loading (e.g. large river system deltas), all
things equal, this results in a relative rise of sea level in such
areas. Subsidence due to groundwater depletion also has local effects.

3) Thermal expansion due to heat content of the ocean. You've calculated
this above. Note that the thermal content of the ocean changes
relatively slowly as the thermohaline circulation moves water between
colder and warmer regions. The thermohaline circulation has a period
of about 1600 years (for water to make a complete cycle). The thermal
input is via thermal diffusion between the air and the water, so the
rate is governed by the difference in water and air temperatures. This
also implies that more than the top 50 feet of the ocean matters, since
the warm water sinks at the poles, moves equator-ward and upwells causing
warming at all levels to some extent.

4) Melting of land-bound ice (note that as floating ice (e.g. the Arctic)
melts, sea level is not affected) such as Greenland, the Antarctic
plateau (but not the floating sea-ice) and continental glaciers.
I'll note here that southern hemisphere ice extent hasn't changed
much at all since 1979 (if anything, it has increased), while the
northern hemisphere icecap has thinned and shrunk over the same
time period (there is no satellite data prior to 1979). There hasn't
yet been much change to Greenland (in fact, recent research has
significantly lower estimates of greenland ice loss).

5) Groundwater drawdown (since most of it ends up flowing to the ocean
via runoff or precipitation). Note that this has been calculated to
be a significant portion of the sea level rise to date, with different
studies showing different levels based on different assumptions as to
the amount of geologic water that has been withdrawn.

6) Currents caused by prevailing winds tend to cause surges in certain
areas; tidal effects thus vary (some areas have larger differences
between low and high tides than others). If the prevailing winds
change due to thermal radiation/circulation changes, then there will
be changes in the tidal response in various areas.

scott