ESS EARTH SCIENCESSECTOR SECTEUR DES SCIENCES
• GRACE and surface gravity trends at mid-continent North American sites are in good agreement except for Churchill and Flin Flon. The trend from surface measurements at Churchill is expected to be higher than the GRACE trend as a result of Hudson Bay outflow, which should reduce the GRACE trend and...
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| Language: | English |
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.643.4039 http://www.ngs.noaa.gov/GRAV-D/2009Workshop/Presentations/Henton_graceAG_07.pdf |
| Summary: | • GRACE and surface gravity trends at mid-continent North American sites are in good agreement except for Churchill and Flin Flon. The trend from surface measurements at Churchill is expected to be higher than the GRACE trend as a result of Hudson Bay outflow, which should reduce the GRACE trend and increase the surface gravity trend. Flin Flon is located in an area of high spatial variation in postglacial rebound [Pagiatakis and Salib, 2003]. Our GRACE processing may not yet have the spatial resolution required to resolve the trend at this site. • Absolute gravity measurements at the mid-continent sites suggest the presence of inter-annual variations that have not yet been detected by GRACE. Future comparisons using a longer data set should indicate the spatial scale of the associated mass anomaly and the possible relationship to groundwater. • Seasonal gravity variations observed by surface gravity measurements on southern Vancouver Island and by GRACE have similar amplitudes. The surface gravity, being more representative of the west coast rainforest climate, tends to rise sooner at the beginning of the wet season than the GRACE gravity which includes part of the drier continental interior. • Seasonal variations observed at the Canadian Absolute Gravity Site (CAGS), Cantley, Quebec are similar in phase but significantly larger than those observed by GRACE. Both the surface gravimeter and GRACE broadly follow the variations in a collocated well. The correlation is not perfect as both gravity systems respond to snow in the winter which is not reflected in the well levels until it melts. A higher seasonal range in water mass than average might be expected for a hilltop site such as CAGS. |
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