cc: plao@geo.vu.nl date: Fri, 2 Feb 2001 14:24:57 +0000 from: Tim Osborn subject: FWD: RE: SOAP to: k.briffa@uea.ac.uk 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 completion?! Tim >===== Original Message From Orson van de Plassche ===== Tim, 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). Some questions. 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. Orson