date: Fri, 2 Feb 2001 14:24:57 +0000
from: Tim Osborn <T.OsbornatXYZxyz.ac.uk>
subject: FWD: RE: SOAP
Keith - I can't really reply to this while I'm away. Can you? If not then
please remind me when I'm back on Tuesday! Hope the proposal is moving towards
>===== Original Message From Orson van de Plassche <plaoatXYZxyz.vu.nl> =====
To avoid the sea-level part being perceived too much as an easily removable
tag-on to the project, I am trying to integrate it a bit into the climate
body of the proposal by formulating one or more hypotheses. But I find the
situation confusing (hopefully a sign that there is fertile climate-ocean
ground out there that needs further consideration).
The long-term temperature trend for the NH (past 1000 yr) is characterised
by gradual overall cooling until shortly after AD 1900, when temperature
takes off (TAR IPCC). Many long (>100 yr) North Atlantic tide-gauge records
show a 'sudden' increase in the rate of relative MSL rise shortly after AD
1900 too. If this observation is correct, why is sea level able to respond
so rapidly? Should it not have a lag time of some 15 years? How rigorously
has this link for the 20th century been tested? Why is it that NH mean
temp. stabilizes or begins to fall around AD 1945 and almost all tide-gauge
records along the US east coast show an end to relative MSL rise shortly
before AD 1950? Is the Gulfstream a rapidly responding system which
influences sea-surface topography? What is the regional variability in
average MSL rise during the past century? Are models able to deal with this
question? Or do they 'simply' compute a global average?
Given the long-term average temp. trend for the NH, why did glacier melting
begin, on average, (much) earlier than shortly after AD 1900?
The mean NH temperature record does not show evidence for a MWP or a LIA.
Sea-level studies from the US NE coast suggest MWP- and LIA-related mean
high water variations. How accurate are those reconstructions? Or are they
valid only for part fo the North Atlantic region?
I suppose I am trying to define an existing problem in (palaeo)climate
research to which the study of sea-level variations (which is still wide
open in terms of available records for the past 500 years) might make some
contribution. The question of regional differences may be a useful hookup
for a bit of sea-level in the project.
workin' on it.