Stations In Iceland Research Articles

Monitoring of Icelandic plate movement with GNSS method and GPS signal jamming effects in Iceland

Abstract Jamming is electromagnetic radiation or reflection that impairs the function of electronic instruments and equipment or communication tools. Intentionally disrupting or interfering with GPS signals, which are used for positioning, navigation, and timing, known as “GPS jamming”, is accomplished using a radio frequency emitting device. On January 8, 2022 (the day of a NATO exercise), it was investigated how GPS signal jamming affected the position accuracy at three IGS points in Iceland. The obtained coordinate differences between kinematic processing and static processing reached values of about 0.5–10 meters for the MAYV, and HOFN stations in this study. In addition to GPS signal jamming effect in Iceland, horizontal and vertical velocity fields of the three IGS stations in Iceland covering a twenty-two year period (2000–2022) in this study. According to the obtained results, a motion of about 2cm–2.5cm per year (horizontal) and 0.1cm–2.1cm per year (vertical) was computed at the three IGS stations (HOFN, REYK, and MAYV) located in Iceland.

Analysis of observed rapid increases in surface wind speed

A database of 21 million hourly observations from 200 weather stations in Iceland within the period from January 1993 until March 2017 is explored to assess rapid increases of wind speed. In the summer, strong winds are more frequent in the afternoon than at night, while rapid increases in wind speed are slightly more frequent at night. Westerly winds have a relatively high frequency of rapid increases in wind speed, while easterly winds have a relatively low frequency of rapid increases in wind speed. This can be explained by the form and tracks of cyclones. Rapid increases in wind speed are particularly frequent in northern Iceland. They occur in winds blowing from the central highlands and typically in stably stratified air masses. Analysis of winds at individual stations reveals a large impact of topography and that the wind direction distribution for strong wind events may be quite different from the wind direction distribution for rapid increases in wind speed. However, a simple and general connection between the height and distance to nearby mountains and the frequency of rapid increases in wind speed has not been found. At stations with a high frequency of rapid increases in wind speed, downslope flow is a very important contributor, while gap and corner winds are not.

Persistence of observed air temperatures in Iceland

A large data set from 40 weather stations in Iceland is explored for persistence in monthly mean temperatures. There are great seasonal and regional variations in the persistence. Extremely high values of correlation (r > 0.8) of temperatures with subsequent months are found. These values are higher than reported elsewhere in the scientific literature. The highest values are found in coastal regions in the summer, while in the early winter there is overall little correlation. In general, there are two distinct maxima in the temperature correlations, one in late winter/early spring and one in the summer. In most seasons, there is greater correlation at the coast than inland. The high correlations are linked to snow melt, persistence in sea surface temperatures, weak winds and strong static stability. Remarkably low correlations reveal a negative feedback process: A warm May leads to less snow in inland regions, which favours a cold sea breeze in coastal regions in June. In regions of high correlation, the persistence is indeed useful for subseasonal forecasting of mean temperatures in late winter/spring and summer.

Orkan opens two hydrogen refueling stations in Iceland

Icelandic filling station operator Orkan has opened two hydrogen refueling stations, in the capital Reykjavik and in Reykjanesbær, near Keflavík International Airport, with a third station expected to open at the beginning of 2019.

Meteorological effects of the solar eclipse of 20 March 2015: analysis of UK Met Office automatic weather station data and comparison with automatic weather station data from the Faroes and Iceland.

Here, we analyse high-frequency (1 min) surface air temperature, mean sea-level pressure (MSLP), wind speed and direction and cloud-cover data acquired during the solar eclipse of 20 March 2015 from 76 UK Met Office weather stations, and compare the results with those from 30 weather stations in the Faroe Islands and 148 stations in Iceland. There was a statistically significant mean UK temperature drop of 0.83±0.63°C, which occurred over 39 min on average, and the minimum temperature lagged the peak of the eclipse by about 10 min. For a subset of 14 (16) relatively clear (cloudy) stations, the mean temperature drop was 0.91±0.78 (0.31±0.40)°C but the mean temperature drops for relatively calm and windy stations were almost identical. Mean wind speed dropped significantly by 9% on average during the first half of the eclipse. There was no discernible effect of the eclipse on the wind-direction or MSLP time series, and therefore we can discount any localized eclipse cyclone effect over Britain during this event. Similar changes in air temperature and wind speed are observed for Iceland, where conditions were generally clearer, but here too there was no evidence of an eclipse cyclone; in the Faroes, there was a much more muted meteorological signature.This article is part of the themed issue ‘Atmospheric effects of solar eclipses stimulated by the 2015 UK eclipse’.

Overview of results from continuous GPS observations in Iceland from 1995 to 2010

Iceland is a natural laboratory for a variety of processes associated with crustal deformation, such as earthquakes, magmatic events, tectonic plate motions, and glacial load changes. Continuous GPS (CGPS) measurements started in Iceland in 1995, and since then data from the network have helped to shed light on many different active deformation processes. The number of CGPS sites in Iceland tripled during 2006–2008, as a result of an international collaborative effort coordinated by Icelandic scientists. By early 2010 the number of CGPS stations in Iceland had reached 64, located primarily around and within the North-American–Eurasian plate boundary zone. Since its initiation, the CGPS network has played an important role in monitoring volcanoes and seismogenic areas, most notably during the 2009–2010 Eyjafjallajökull volcano unrest. Plate spreading of up to 2 cm per year usually dominates the horizontal motion observed at the CGPS sites, while uplift is observed at many of the stations due to recent retreat of the Icelandic ice caps. Co-seismic and post-seismic deformation of the largest earthquakes in 2000 and 2008 in the South Iceland Seismic Zone were captured by the network, and high-rate (1 Hz) CGPS observations helped to identify two magnitude 6 mainshocks in 2008 that were separated in time by only 2–3 seconds. The CGPS network has thus enabled us to monitor deformation occurring over days to months caused by migration of magma or fluids, post-seismic transients, rapid deformation caused by earthquakes and eruptions, as well as the long term plate spreading signal.

A new day-to-day pressure variability index as a proxy of Icelandic storminess and complement to the North Atlantic Oscillation index 18232005

As unknown instrument index errors might affect the accuracy of the early parts of the long-term baseline North Atlantic Oscillation (NAO) indices, it is of interest to find alternative means for an assessment of the behavior of the NAO. Our novel day-to-day pressure variability index (dp) introduced in this paper shows interesting secular variability that is in some sense a 'measure' of the proximity of the Atlantic storm track to Iceland and thus also an independent measure of the activity of the NAO. Like the NAO indices, dp is significantly negatively (positively) correlated with temperature in western Greenland (north-west Europe). There is a significant correlation between the dp index and average wind speed at the Icelandic stations (for the time of available wind records). This correlation becomes especially prominent at multi-year time scales, but is also evident at the scale of individual months. There is no evidence of a global warming signal in this storminess proxy.

Current plate movements across the Mid‐Atlantic Ridge determined from 5 years of continuous GPS measurements in Iceland

We analyze data spanning up to 5 years from 18 continuous GPS stations in Iceland, computing daily positions of the stations with three different high‐level geodetic processing software packages. We observe large‐scale crustal deformation due to plate spreading across Iceland. The observed plate divergence between the North American and the Eurasian plates is in general agreement with existing models of plate motion. Spreading is taken up within a ∼100–150 km wide plate boundary zone that runs through the island. Of the two parallel branches of the plate boundary in south Iceland, the eastern volcanic zone is currently taking up the majority of the spreading and little is left for the western volcanic zone. The plate boundary deformation field has been locally and temporarily affected in south Iceland by two Mw = 6.5 earthquakes in June 2000, inflation at Katla volcano during 2000 to 2004, and an eruption of Hekla volcano in February 2000. All stations with significant vertical velocities are moving up relative to the reference station REYK, with the highest velocity exceeding 20 mm/yr in the center of the island.

Seismic structure of Iceland from Rayleigh wave inversions and geodynamic implications

Abstract We have constrained the shear-wave structure of crust and upper mantle beneath Iceland by analyzing fundamental mode Rayleigh waves recorded at the ICEMELT and HOTSPOT seismic stations in Iceland. The crust varies in thickness from 20 to 28 km in western and northern Iceland and from 26 to 34 km in eastern Iceland. The thickest crust of 34–40 km lies in central Iceland, roughly 100 km west to the current location of the Iceland hotspot. The crust at the hotspot is ∼32 km thick and is underlain by low shear-wave velocities of 4.0–4.1 km/s in the uppermost mantle, indicating that the Moho at the hotspot is probably a weak discontinuity. This low velocity anomaly beneath the hotspot could be associated with partial melting and hot temperature. The lithosphere in Iceland is confined above 60 km and a low velocity zone (LVZ) is imaged at depths of 60 to 120 km. Shear wave velocity in the LVZ is up to 10% lower than a global reference model, indicating the influence of the Mid-Atlantic Ridge and the hotspot in Iceland. The lowest velocities in the LVZ are found beneath the rift zones, suggesting that plume material is channeled along the Mid-Atlantic Ridge. At depths of 100 to 200 km, low velocity anomalies appear at the Tjornes fracture zone to the north of Iceland and beneath the western volcanic zone in southwestern Iceland. Interestingly, a relatively fast anomaly is imaged beneath the hotspot with its center at ∼135 km depth, which could be due to radial anisotropy associated with the strong upwelling within the plume stem or an Mg-enriched mantle residual caused by the extensive extraction of melts.

Hot mantle transition zone beneath Iceland and the adjacent Mid‐Atlantic Ridge inferred from P‐to‐S conversions at the 410‐ and 660‐km discontinuities

P‐to‐S conversions from the two primary discontinuities near 410 and 660 km depth (P410s and P660s phases) are evident in particle motions and receiver functions of teleseismic body waves recorded by broadband seismic stations in Iceland. The average arrival times of P410s and P660s are later by 7.0±0.5 s (standard error) and 4.7±0.2 s, respectively, than predicted by the iasp91 Earth model. Differential P660s–P410s travel times indicate that the upper mantle transition zone between the 410‐ and 660‐km discontinuities is 23±9 km thinner than in the iasp91 model. From estimates for the Clapeyron slopes of the phase transitions associated with these discontinuities, this lesser transition zone thickness is consistent with temperatures 180±70 K hotter than normal. We interpret this result as evidence for upwelling mantle flow at 400–700 km depth beneath Iceland and the adjacent Mid‐Atlantic Ridge.

Estimation of Geomagnetic Conjugate Points Using Pc5 Geomagnetic Pulsation.

We have attempted to estimate geomagnetic conjugate points using Pc5 geomagnetic pulsation data. The Pc5 pulsation data were obtained simultaneously at three coordinated stations in Iceland and at three stations in Antarctica, including Syowa Station, for the months of March and May in 1988. In this analysis, it was principally assumed that Pc5 pulsations have a form of odd mode standing oscillations of the geomagnetic field line with linear phase shifts among the stations in the horizontal plane. Conjugate points were calculated uniquely. The statistical result showed that conjugate points of Syowa Station estimated from the Pc5 events were concentrated around the conjugate points in Iceland calculated from the magnetic field model of Tsyganenko (1987) within the range of 66°-68° in latitude, and 70°-76° in longitude, i.e., less than 1/5 wave length.

On the standing wave mode of giant pulsations

Both odd‐mode and even‐mode standing wave structures have been proposed for giant pulsations. Unless a conclusion is drawn on the field‐aligned mode structure, little progress can be made in understanding the excitation mechanism of giant pulsations. In order to determine the standing wave mode, we have made a systematic survey of magnetic field data from the AMPTE CCE spacecraft and from ground stations located near the geomagnetic foot point of CCE. We selected time intervals when CCE was close to the magnetic equator and also magnetically close to Syowa and stations in Iceland, and when either transverse or compressional Pc 4 waves were observed at CCE. Magnetograms from the ground stations were then examined to determine if there was a giant pulsation in a given time interval. One giant pulsation was associated with a compressional wave, while no giant pulsation was observed in association with transverse wave events. The CCE magnetic field record for the giant pulsation exhibited a remarkable similarity to a giant pulsation observed from the ATS 6 geostationary satellite near the magnetic equator (Hillebrand et al., 1982). In agreement with Hillebrand et al., we conclude that the compressional nature of the giant pulsation is due to an odd‐mode standing wave structure. This conclusion places a strong constraint on the generation mechanism of giant pulsations. In particular, if giant pulsations are excited through the drift bounce resonance of ions with standing Alfvén waves, ω ‐ mωd = ±Nωb, where ω is the wave frequency, m is the azimuthal wave number, ωd is the ion drift frequency, N is an integer, and ωb is the ion bounce frequency, then the resonance must occur at an even N.

Probable Maximum Precipitation in Iceland – Station Values –

The meteorological stations in Iceland are rather few compared to the size of the country, and their service time is short compared to other developed countries. Investigations of individual 24-hour station PMP values computed by the Hershfield and NERC methods show trends that are important for the application of PMP values in engineering design. The results fall into two series, one with high PMP values and the other with lower values. The low values originate from station groups situated in areas with mildly sloping terrain and here the results compare fully with what should be expected from experience from other countries. The other series shows results that do not compare as well with previously published results. Their general characteristics is that PMP values calculated hy the Hershfield method are of the order 80% higher than the corresponding results obtained by the NERC method. The results of this high series do not check against results obtained from meteorological models. It is noteworthy, that all the stations of the low series belong to station groups where the terrain is gently sloping, i.e. average terrain slopes less than 1.4%, while in the high series all the stations belong to station groups where the terrain slopes steeply from a highland plateau down to sea level. It is concluded that the generalized estimates of PMP values needed in engineering design could be obtained.

Seasonal and diurnal dependence of Pc 3‐5 magnetic pulsation power at geomagnetically conjugate stations in the auroral zones

Seasonal and diurnal variations of Pc 3–5 magnetic pulsation powers have been examined using 2 years of magnetic data from geomagnetically conjugate stations, Syowa in Antarctica and Husafell and Tjörnes in Iceland. The magnetic pulsation powers are found to be relatively higher at the winter hemisphere station than at the summer station. The pulsations observed during equinox show a diurnal dependence, i.e., that the power density is higher in the geomagnetic morning at the stations in Iceland than at Syowa, and this relationship is reversed in the afternoon. The power density ratio of Pc 3 pulsations between the conjugate stations, which is associated with the seasons and with local time, is higher than that of Pc 5. These characteristics can be attributed to the effects of sunlight in the ionosphere, i.e., Pc 3–5 pulsations are shielded when the waves propagate from the magnetosphere to the ground through the sunlit ionosphere.

CNA pulsations accompanying hydromagnetic waves at conjugate stations

The coherency and phase relation between the CNA pulsations and Pc 3–5 magnetic pulsations observed at the Syowa Station in the Antarctica and its conjugate three stations in Iceland are examined. It is confirmed that the H-component of the magnetic pulsations tends to correlate more with the CNA pulsations rather than the D-component of magnetic pulsations. There is a relative phase difference between the magnetic pulsations and CNA pulsations which shows a linear relationship vs the pulsation frequency. This phase difference suggests that the particle modulation of the CNA pulsations by the hydromagnetic waves occurs near the equatorial region in the magnetosphere. Furthermore, a suitable conjugate location is determined by the relative phase difference between the CNA pulsations at the Syowa Station and the three stations in Iceland.

Teleseismic P-wave Delay Time in Iceland

Summary An evaluation is made of relative teleseismic P-wave delays between stations in Iceland and EKA (Scotland), KIR (Sweden) and KTG (Greenland). A detailed analysis of possible sources of error including the use of array data to detect the onset of events, shows there is a delay of at least 1 s associated with the upper mantle beneath Iceland. The delay does not appear to vary with distance or azimuth, and shows little variations over Iceland itself. Large teleseismic P-wave delays have been observed in Iceland both as residuals from travel-time determinations (Clearly & Hales 1966; Herrin & Taggart 1968; Lilwall & Douglas 1970) and by Tryggvason’s special determination at Reykjavik (Tryggvason 1964). The Icelandic crust has an anomalously high velocity (Bath 1960) so this delay has been associated with an anomalous upper mantle beneath Iceland. Its determination is therefore important in the study of the mantle beneath Iceland in particular and the mid-Atlantic ridge in general. Tryggvason (1964) has compared delays and structures at Reykjavik and Kiruna (Sweden), and concluded that the Icelandic delay was consistent with a vertical extension of the anomalous 7.4 layer observed by the refraction work of Bath (1960), to a depth of about 240 km. Three possible sources of error in these studies may, however, be cited: (a) Most earthquakes recorded at teleseismic distances are from a single seismic region (the island areas of the North Pacific) so that delays at source might give an apparent station delay. (b) Errors in travel-time tables can give apparent delays. Tryggvason’s estimate is relative to J & B tables which are known to be in error over the region of interest (Cleary & Hales 1966; Herrin et al. 1968). (c) It has been suggested (Stefansson 1967) that the Icelandic delay arises from a consistently late reading of the records-the onsets being lost in the high background noise of Iceland. The present paper seeks to establish the presence of a delay due to anomalous mantle beneath Iceland, using an improved analysis of the data from a wider range of stations, with improved travel-time tables (Herrin et al. 1968), and incorporating array processing to improve the observation of onsets. The method employed here attempts to separate from the gross travel-time residual the relative delay between pairs of stations caused by the different crust and upper mantle beneath each station. Relative delays are measured between Akureyi (AKU) and a temporary array station at Hveravellir in Iceland, Eskdalemuir

Whaling from shore stations in Iceland, 1883–1968

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Meteorological stations in Iceland

Meteorological stations in Iceland

Upper Mantle Structure Along the Axis of the Mid-Atlantic Ridge near Iceland

Apparent velocity measurements of P arrivals from Mid-Atlantic Ridge earthquakes across pairs of stations in Iceland and Greenland have been made using bulletin data. They define both the vertical and horizontal extent of the low velocity anomalous mantle zone between 50° and 70° N.