Where is the NW Corner of Stable North America Jeff Freymueller and Chris Larsen Geophysical Institute, Univ.of Alaska Stephane Mazzotti, GSC

Is There Any Stable North America on Preceding Slide? Siberia east of Cherskiy Range appears to lie on North American plate But most of Alaska and Northern Cordillera in Canada is (geologically) mobile relative to stable North America Strong time-dependent signal from large earthquakes Rapid uplift from regional ice loss

NOAM NOAM

Blue: no ocean loading model Red: ocean loading corrected

GPS uplift rates 76 sites, 5 years of campaign measurements Peak uplift rates 30-32 mm/yr Average  = 1.8 mm/yr Max  = 4 mm/yr

Greatly Uplifted

~5000 km to “stable” region defined geodetically A Long Lever Arm! ~2500 Fairbanks to Seattle ~5000 km to “stable” region defined geodetically

Work to Date Initial comparison of UAF and PGC solutions. Are there sites that geodesy tells us are stable? Investigation of error sources/noise sources in out existing time series Ocean tidal loading mismodeling is probably the dominant error source

Ocean Tidal Loading Tidal range in Gulf of Alaska extremely large Comparison done on 6 months of data With and without ocean tidal loading modeling Load model computed using SPOTL, based on TPXO.2 + CSR3.0 Dominant peak is at 14 day period, aliased tidal loading

Initial Conclusions Don’t forget far NW sites as part of frame definition Bilibino (BILI) Barrow? (SG27) Non-secular components are particularly strong in north country