Absolute gravity observations in Norway (1993–2014) for glacial isostatic adjustment studies: The influence of gravitational loading effects on secular gravity trends

Ophaug, Vegard; Breili, Kristian; Gerlach, Christian; Gjevestad, Jon Glenn Omholt; Lysaker, D. I.; Omang, O. C. D.; Pettersen, B. R.

doi:10.1016/j.jog.2016.09.001

Cited by 10 publications

(14 citation statements)

References 42 publications

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“…When corrected for short period and seasonal variability, the time series of absolute gravity values reveals secular changes specific to each observing site in Norway (Ophaug et al, 2016). Postglacial land uplift is a viscoelastic rebound from the melting of the Fennoscandian ice sheet that began about 10 4 years ago.…”

Section: Applications Of Terrestrial Gravimetry To Geophysical Phenomenamentioning

confidence: 98%

“…The orientation of the arc was determined by astronomical observations for 1868-1888 in a dozen selected stations, which also revealed deflections of the vertical. The longitude differences between Oslo, Stockholm, and Copenhagen were determined astronomically in 1865 by telegraphic time transfer (Fearnley et al, 1890;Pettersen, 2007) and between Oslo and Bergen in 1880 (Fearnley 1884). The first tide gauges were mounted in the 1880s to provide scale zero for a leveled height system.…”

Section: Norway's First Gravity Network: 1892-1903mentioning

confidence: 99%

“…Absolute gravity data for the sites in Table 2 (column 5) are found in Breili et al (2010), Table 3, doi:10.1080/00291951.2010.481125, and in Ophaug et al (2016), supplemental data, doi:10.1016/j.jog.2016.09.001. The values in Table 2 (column 5) were derived by correcting for the height of the observing station above sea level.…”

Section: Data Availabilitymentioning

confidence: 99%

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A historical review of gravimetric observations in Norway

Pettersen

2016

Hist. Geo Space. Sci.

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Abstract. The first gravity determinations in Norway were made by Edward Sabine in 1823 with a pendulum instrument by Henry Kater. Seventy years later a Sterneck pendulum was acquired by the Norwegian Commission for the International Arc Measurements. It improved the precision and eventually reduced the bias of the absolute calibration from 85 to 15 mGal. The last pendulum observations in Norway were made in 1955 with an instrument from Cambridge University. At a precision of ±1 mGal, the purpose was to calibrate a section of the gravity line from Rome, Italy, to Hammerfest, Norway.Relative spring gravimeters were introduced in Norway in 1946 and were used to densify and expand the national gravity network. These data were used to produce regional geoids for Norway and adjacent ocean areas. Improved instrument precision allowed them to connect Norwegian and foreign fundamental stations as well. Extensive geophysical prospecting was made, as in other countries.The introduction of absolute gravimeters based on free-fall methods, especially after 2004, improved the calibration by 3 orders of magnitude and immediately revealed the secular changes of the gravity field in Norway. This was later confirmed by satellite gravimetry, which provides homogeneous data sets for global and regional gravity models.The first-ever determinations of gravity at sea were made by pendulum observations onboard the Norwegian polar vessel Fram during frozen-in conditions in the Arctic Ocean in 1893-1896. Simultaneously, an indirect method was developed at the University of Oslo for deducing gravity at sea with a hypsometer. The precision of both methods was greatly superseded by relative spring gravimeters 50 years later. They were employed extensively both at sea and on land. When GPS allowed precise positioning, relative gravimeters were mounted in airplanes to cover large areas of ocean faster than before.Gravimetry is currently being applied to study geodynamical phenomena relevant to climate change. The viscoelastic postglacial land uplift of Fennoscandia has been detected by terrestrial gravity time series as well as by satellite gravimetry. Corrections for local effects of snow load, hydrology, and ocean loading at coastal stations have been improved. The elastic adjustment of present-day melting of glaciers at Svalbard and in mainland Norway has been detected. Gravimetry is extensively employed at offshore oil facilities to monitor the subsidence of the ocean floor during oil and gas extraction.

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Section: Applications Of Terrestrial Gravimetry To Geophysical Phenomenamentioning

confidence: 98%

Section: Norway's First Gravity Network: 1892-1903mentioning

confidence: 99%

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A historical review of gravimetric observations in Norway

Pettersen

2016

Hist. Geo Space. Sci.

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“…For ocean tides, Green's functions for a spherical Earth are appropriate, but the effect of elevated observation points should be taken into account [1]. We follow the methodology and use the same software as discussed in [26] who computed OTL and nontidal loading (NTL) at coastal gravity stations in Norway. With this methodology, OTL was computed by convolving the Green's function with a global ocean tide (GOT) model resampled to higher spatial resolution within a spherical distance of 1 degree from the gravity laboratory.…”

Section: The Effect Of Ocean Loadingmentioning

confidence: 99%

“…For NyÅlesund, we used a detailed coastline provided by the NPI [23] to decide whether cells in the ocean model are located on land or not. We opt to use the two GOTs FES2012 [12] and NAO99b [13] because [26] have previously demonstrated that corrections based on these models strongly reduced the long periodic residuals in measurements at AG sites along the Norwegian coast.…”

Section: The Effect Of Ocean Loadingmentioning

confidence: 99%

Research Article. A new gravity laboratory in Ny-Ålesund, Svalbard

Breili

Hougen

Lysaker

et al. 2017

Journal of Geodetic Science

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Abstract:The Norwegian Mapping Authority (NMA) has recently established a new gravity laboratory in Ny-Ålesund at Svalbard, Norway. The laboratory consists of three independent pillars and is part of the geodetic core station that is presently under construction at Brandal, approximately 1.5 km north of NMA's old station. In anticipation of future use of the new gravity laboratory, we present benchmark gravity values, gravity gradients, and final coordinates of all new pillars. Test measurements indicate a higher noise level at Brandal compared to the old station. The increased noise level is attributed to higher sensitivity to wind. We have also investigated possible consequences of moving to Brandal when it comes to the gravitational signal of present-day ice mass changes and ocean tide loading. Plausible models representing ice mass changes at the Svalbard archipelago indicate that the gravitational signal at Brandal may differ from that at the old site with a size detectable with modern gravimeters. Users of gravity data from Ny-Ålesund should, therefore, be cautious if future observations from the new observatory are used to extend the existing gravity record. Due to its lower elevation, Brandal is significantly less sensitive to gravitational ocean tide loading. In the future, Brandal will be the prime site for gravimetry in Ny-Ålesund. This ensures gravity measurements collocated with space geodetic techniques like VLBI, SLR, and GNSS.

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Geophysics From Terrestrial Time‐Variable Gravity Measurements

Camp

Viron

Watlet

et al. 2017

Reviews of Geophysics

183

105

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In a context of global change and increasing anthropic pressure on the environment, monitoring the Earth system and its evolution has become one of the key missions of geosciences. Geodesy is the geoscience that measures the geometric shape of the Earth, its orientation in space, and gravity field. Time‐variable gravity, because of its high accuracy, can be used to build an enhanced picture and understanding of the changing Earth. Ground‐based gravimetry can determine the change in gravity related to the Earth rotation fluctuation, to celestial body and Earth attractions, to the mass in the direct vicinity of the instruments, and to vertical displacement of the instrument itself on the ground. In this paper, we review the geophysical questions that can be addressed by ground gravimeters used to monitor time‐variable gravity. This is done in relation to the instrumental characteristics, noise sources, and good practices. We also discuss the next challenges to be met by ground gravimetry, the place that terrestrial gravimetry should hold in the Earth observation system, and perspectives and recommendations about the future of ground gravity instrumentation.

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Absolute gravity observations in Norway (1993–2014) for glacial isostatic adjustment studies: The influence of gravitational loading effects on secular gravity trends

Cited by 10 publications

References 42 publications

A historical review of gravimetric observations in Norway

A historical review of gravimetric observations in Norway

Research Article. A new gravity laboratory in Ny-Ålesund, Svalbard

Geophysics From Terrestrial Time‐Variable Gravity Measurements

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