It is a Boulder thing...
Zurich, Canberra, Grenoble, Hamburg, Vancouver, Vienna and now Boulder. No, not a list of major battles, at least not of the martial kind. These are the locations of recent Assemblies of the International Union of Geodesy and Geophysics. Every four years the great and the good, and more important the young and scientifically vigorous, gather in their thousands: geophysicists, geodesists, vulcanologists, meteorologists, seismologists, hydrologists and, of course, the physical oceanographers. This year the IUGG met in Boulder Colorado in July. Except the physical oceanographers, who decided to meet in Hawaii in August instead.
Some of our sea level community made it to Boulder. For the rest of you, here are some personal impressions.
The main symposium for sea level addicts, organised under the collective banners of IAPSO, IAHS (the hydrologists), IAG (the geodesists) and the Commission on the Lithosphere, dealt with "Sea Level and Ice Changes as Geophysical Indicators". Held in the University of Colorado campus Planetarium, some 22 speakers covered topics from the way in which climate warming may affect sea level regionally and globally, to observations of green icebergs in Antarctica. After the session, participants repaired to the poster displays in the basketball stadium! Here, amid copious supplies of free beer, the interaction continued. Overall, the symposium attracted 80 to 100 people, well above the average for meetings at the IUGG, and clear evidence of a strong scientific activity which cuts across the traditional IUGG Association boundaries.
The papers from the symposium will be published in a special edition of Global and Planetary Change, so keep checking at your local library, but not just yet. Here are a few controversial points from the talks, to stimulate further scientific argument.
H-P Plag suggests that the phase and amplitudes of the annual sea level cycle (Sa) changed post 1950. Global ocean-atmosphere models of responses to doubling atmospheric CO2 are still some way from giving regional estimates of sea level change, but are improving rapidly. Peltier now gives the rate of sea level rise globally as 2.4 +/- 0.9 mm per year, after ice load corrections. Dyurgerov and Meier have recalculated the mass balance of glaciers on a yearly basis, and find that the contribution of glaciers to sea level rise increases at the end of the 1980s. Gornitz has revisited the problem of estimating the influences of ground water abstraction and other anthropogenic activities on water balance, and finds the effects of reservoirs has been substantially underestimated. Wahr and Dickey have both examined changes in gravity and geopotential as indicators of mass balance and mass distribution. For more information, read the Special Edition when it appears.
Elsewhere, there was much of interest for the sea level enthusiast: studies of earth rotation can now reveal small changes due to tidal, meteorological, and seasonal redistribution of sea water mass. Even for tides the movement of mass vertically away from the axis of rotation is much more important in changing the rate of rotation than the transfer of momentum to and from tidal currents. Several sessions on position fixing showed how benchmarks can now be geocentrically located to 10mm or better, with careful use of GPS and VLBI.
Few delegates expressed concern that the physical oceanographers had moved their tents elsewhere. If they want to go to Hawaii, that's up to them, was the general view. I disagree. The discussions on earth rotation and on climate variability would both have been much more productive if physical oceanographers had been there to contribute.
The next IUGG Assembly will probably be in England in 1999. I hope that all the IUGG Associations will be there. And that sea level studies will be as prominent as ever.