| 1. |
- Bergstrand, Sten, 1971, et al.
(författare)
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BIFROST: Noise properties of GPS time series
- 2007
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Ingår i: in "Dynamic Planet: Monitoring and Understanding a Dynamic Planet with Geodetic and Oceanographic Tools", IAG Symposium, Cairns, Australia, 22-26 August, 2005, Series: International Association of Geodesy Symposia , Vol. 130, Tregoning, Paul; Rizos, Chris (Eds.), Springer. - 9783540493495 ; 130, s. 123-130
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Konferensbidrag (refereegranskat)
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| 2. |
- Hill, Emma M., et al.
(författare)
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Combination of geodetic observations and models for glacial isostatic adjustment fields in Fennoscandia
- 2010
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Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 115:B07
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate a new technique for using geodetic data to update a priori predictionsfor Glacial Isostatic Adjustment (GIA) in the Fennoscandia region. Global PositioningSystem (GPS), tide gauge, and Gravity Recovery and Climate Experiment (GRACE)gravity rates are assimilated into our model. The technique allows us to investigate theindividual contributions from these data sets to the output GIA model in a self‐consistentmanner. Another benefit of the technique is that we are able to estimate uncertaintiesfor the output model. These are reduced with each data set assimilated. Any uncertaintiesin the GPS reference frame are absorbed by reference frame adjustments that are estimatedas part of the assimilation. Our updated model shows a spatial pattern and magnitudeof peak uplift that is consistent with previous models, but our location of peak upliftis slightly to the east of many of these. We also simultaneously estimate a spatiallyaveraged rate of local sea level rise. This regional rate (∼1.5 mm/yr) is consistent forall solutions, regardless of which data sets are assimilated or the magnitude of a priori GPSreference frame constraints. However, this is only the case if a uniform regional gravityrate, probably representing errors in, or unmodeled contributions to, the low‐degreeharmonic terms from GRACE, is also estimated for the assimilated GRACE data. Ourestimated sea level rate is consistent with estimates obtained using a more traditionalapproach of direct “correction” using collocated GPS and tide gauge sites.
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| 3. |
- Kierulf, Halfdan Pascal, et al.
(författare)
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A GNSS velocity field for geophysical applications in Fennoscandia
- 2021
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Ingår i: Journal of Geodynamics. - : Elsevier BV. - 0264-3707. ; 146
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Tidskriftsartikel (refereegranskat)abstract
- In Fennoscandia, tectonics, Glacial Isostatic Adjustment (GIA), and climatic changes cause ongoing crustal deformation of some millimetres per year, both vertically and horizontally. These displacements of the Earth can be measured to a high degree of precision using a Global Navigation Satellite System (GNSS). Since about three decades, this is the major goal of the Baseline Inferences for Fennoscandian Rebound, Sea-level, and Tectonics (BIFROST) project. We present a new velocity field for an extended BIFROST GNSS network in the ITRF2008 reference frame making use of the GNSS processing package GPS Analysis Software of MIT (GAMIT). Compared to earlier publications, we have almost doubled the number of stations in our analysis and increased the observation time span, thereby avoiding the early years of the network with many instrument changes. We also provide modelled vertical deformation rates from contributing processes, i.e. elastic deformation due to global atmospheric and non-tidal ocean loading, ice mass and hydrological changes as well as GIA. These values for the vertical component can be used for removal of these contributions so that the residual uplift signal can be further analysed, e.g., in the context of local or regional deformation processes or large-scale but low-magnitude geodynamics. The velocity field has an uplift maximum of 10.3 mm/yr in northern Sweden west of the Gulf of Bothnia and subsidence exceeding 1 mm/yr in northern Central Europe. The horizontal velocity field is dominated by plate motion of more than 20.0 mm/yr from south-west to north-east. The elastic uplift signal sums up to 0.7–0.8 mm/yr for most stations in Northern Europe. Hence, the maximum uplift related to the past glaciation is ca. 9.6 mm/yr. The residual uplift signal after removal of the elastic and GIA contribution may point to possible improvements of the GIA model, but may also indicate regional tectonic and erosional processes as well as local deformation effects. We show an example of such residual signal discussing potential areas of interest for further studies.
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| 4. |
- Lidberg, Martin, 1964, et al.
(författare)
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A new GPS derived velocity field of the postglacial adjustment in Fennoscandia, and its implications for the maintenance of the European geodetic reference frame
- 2006
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Ingår i: In: Report of the Symposium of the IAG Sub commission for Europe (EUREF) held in Vienna, 1-4 June 2005, J.A. Torres and H. Hornik (eds.), Mitteilungen des Bundesamtes für Kartographie und Geodäsie, Band 38, EUREF Publication No. 15, Verlag des Bundesamtes für Kartographie und Geodäsie, Frankfurt am Main.. - 1436-3445. - 3898887995 ; :38 /15, s. 102-107
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 5. |
- Lidberg, Martin, 1964, et al.
(författare)
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An improved and extended GPS-derived 3D velocity field of the glacial isostatic
- 2007
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Ingår i: Journal of Geodesy. - : Springer Science and Business Media LLC. - 0949-7714 .- 1432-1394. ; 81:3, s. 213-230
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Tidskriftsartikel (refereegranskat)abstract
- We present a new GPS-derived 3D velocity field for the Fennoscandia glacial isostatic adjustment (GIA) area. This new solution is based upon 3,000 days of continuous GPS observations obtained from the permanent networks in Fennoscandia. The period encompasses a prolongated phase of stable observation conditions after the northern autumn of 1996. Several significant improvements have led to smaller uncertainties and lower systematic errors in the new solutions compared to our previous results. The GPS satellite elevation cut-off angle was lowered to 10°, we fixed ambiguities to integers where possible, and only a few hardware changes occurred over the entire network. The GAMIT/GLOBK software package was used for the GPS analysis and reference frame realization. Our new results confirmed earlier findings of maximum discrepancies between GIA models and observations in northern Finland. The reason may be related to overestimated ice-sheet thickness and glaciation period in the north. In general, the new solutions are more coherent in the velocity field, as some of the perturbations are now avoided. We compared GPS-derived GIA rates with sea-level rates from tide-gauge observations, repeated precise leveling, and with GIA model computations, which showed consistency. © Springer-Verlag 2006.
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| 6. |
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| 7. |
- Lidberg, Martin, 1964, et al.
(författare)
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Geodetic reference frames in the presence of crustal deformations - with focus on Nordic conditions
- 2008
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Ingår i: Report on the symposium of the IAG sub commission for Europe (EUREF), Riga, June 14-17, 2006, eds. J.A. Torres, H. Hornik, EUREF publication no. 16, Mitteilungen des Bundesamtes für Kartographie und Geodäsie, Frankfurt am Main 2008. - 1436-3445. - 3898888452 ; 40, s. 189-198
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 8. |
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| 9. |
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| 10. |
- Lidberg, Martin, 1964, et al.
(författare)
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Recent results based on continuous GPS observations of the GIA process in Fennoscandia from BIFROST
- 2010
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Ingår i: Journal of Geodynamics. - : Elsevier BV. - 0264-3707. ; 50:1, s. 8-18
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Tidskriftsartikel (refereegranskat)abstract
- We present the latest 3D velocity field of the Fennoscandian glacial isostatic adjustment (GIA) processfrom BIFROST. It is derived from more than 4800 days (13 years) of data at more than 80 permanentGPS sites. We use the GAMIT/GLOBK and the GIPSY/OASIS II software packages for GPS analysis andcompare the results. The solution has an internal accuracy at the level of 0.2 mm/year (1 sigma) forhorizontal velocities at the best sites.Wealso present a revised GIA prediction model. At the best sites, theoptimal model agrees with the observations to within 0.4 mm/year. However, the model systematicallyoverpredicts the magnitude of horizontal rates in the north. We discuss limitations in computed andpresented GNSS station velocities, where especially possible instability over time causing non-linearpattern in vertical time series are considered. In extension, preliminary results from an investigationapplying revised analysis strategies on a sparse subset of the database are presented, indicating possibleimprovements for the future.
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