Commission 3 Earth rotation and Geodynamics Véronique Dehant

Sub-commissions 1.Earth Tides: Chair: Gerhard Jentzsch 2.Crustal Deformation: Chair: Markku Poutanen 3.Geophysical Fluids: Chair: Richard Gross

Subcommission 3.1. Earth Tides Website exist and has been transferred from Japan to Jena and updated; still checking national representative and affiliations. Most important activity: preparation of the Earth tide meeting in Ottawa in August ; the new ET sub- commission Vice president, S. Patiatakis, is LOC chair. –Names of sessions –Names of conveners –Proceeding publication Hsu Houtse’s 70 th anniversary in Wuhan, opened China, especially toward Europe. Talk given by President of ET SC.

Subcommission 3.2. Crustal Deformation Markku Poutanen gave me an update of their objectives (particular objectives in the frame of the general objectives presented in the Travaux and in the website). He noted in his report that these objectives are very close to those of IGGOS. They don’t have a website. Markku Poutanen will send me some additional information to put on the web soon.

Subcommission 3.2. Crustal Deformation SC 3.2. comprises sub-entities corresponding either to different regions or different important topics involved in the field. These sub-entities are dealing with main scientific objectives and in parallel follow the new developments in technology and instruments. It is planed to establish new WGs according to the needs. Close contacts between Wegener (L. Bastos) and SC 3.2. the Directing Board members are involved in the Scientific program Committee of the 12 th GA of Wegener project (Tangier, Marocco, September 21-23, 2004). President of SC 3.2. is chairman of the NGOS (Nordic Geodetic Observing System) that will follow guidelines and principles of IGGOS.

Subcommission 3.3. Geophysical Fluids Workshops – Chandler Wobble Workshop “Forcing of Polar Motion in the Chandler Frequency Band: A Contribution to Understanding Interannual Climate Variations” April 21–23, 2004, Hotel Parc Belle-Vue, Luxembourg Approximately 40 people participated

Subcommission 3.3. Geophysical Fluids Conference sessions (1) – 2003 Fall Meeting of the American Geophysical Union (December 7–10, 2003, San Francisco, CA) Session G02: Satellite Measurements of Temporal Gravity Variations Session G07: Reference Frame Definition and Modeling and Influence of Geophysical Fluids Session G08: Effect of Atmosphere and Ocean on Geodesy and Geodynamics: Observation and Modeling Session G13: Seasonal Signals in Space Geodetic Solutions – 1st General Assembly of the European Geosciences Union ( April 24–30, 2004, Nice, France) Session G1: Global Water Cycle from Geodesy Session G2: Time Varying Gravity: Observations and Interpretation Session G5: Earth Rotation and Polar Motion Session G7: Reference Frame Definition, Influence of Geophysical Fluids, and Combination of Space Geodesy Techniques Session G9: Results of Recently Launched Missions: CHAMP, ENVISAT, ICESAT, JASON-1, and GRACE Session G10: Seasonal signals in Space Geodetic Solutions

Subcommission 3.3. Geophysical Fluids Conference sessions (2) – 2004 Spring Meeting of the American Geophysical Union (May 17–21, 2004, Montreal, Canada) Session U08: Time-Variable Gravity: Observation, Modeling, and Interpretation Session G03: Observations of Glacial Isostatic Adjustment and Contemporary Ice-Ocean-Mantle Mass Redistribution Session G05: Causes and Consequences of Variations in Earth Rotation on Seismic to Millennial Time Scales

Subcommission 3.3. Geophysical Fluids Future activities – Continue to convene sessions at future conferences (AGU, EGU…) – Propose joint session with IAPSO for the 2005 General Assembly of the IAG – Are thinking to create a WG for examining all the questions related to the excitation of CW. No website but I will put the information given by R. Gross on our website

Commission Project: GGP Present activities – Continue to monitoring of gravity – Some stations have experienced some failure but currently in good shape or in transition phase – New stations – Inclusion of earthquake data from SC gravimeter in database.

Program activities 1.Participation in particular meetings related to geodynamics and Earth rotation. See SC activities. 2.Participation in the IAG Project Integrated Global Geodetic Observing System (IGGOS). Descartes Prize money dedicated to a project related to IGGOS. 3.Linking Commission 3 with its sister commission of the IAU. Preparation of NRO movies Outside of the proposed activities: A lot of press interviews related to Descartes Prize and publicity for IAG € on ROB account; Call for Proposals; Advisory Board has selected the projects for the next decimal of nutation, for the geophysical fluids (IERS), for IGGOS.