Predictions of Deformation and Gravity Change Caused by Recent Melting of the Vatnajökull Ice Cap, Iceland

Climate is a fundamental and independent variable of human existence. Given that 50 percent of the Earth’s surface and much of its population exist between 30oN and 30oS, paleoenvironmental research in the Earth’s tropical regions is vital to our understanding of the world’s current and past climate change. Most of the solar energy that drives the climate system is absorbed in these regions. Paleoclimate records reveal that tropical processes, such as variations in the El Niño-Southern Oscillation (ENSO), have affected the climate over much of the planet. Climatic variations, particularly in precipitation and temperature, play a critical role in the adaptations of agrarian cultures located in zones of environmental sensitivity, such as those of the coastal deserts, highlands, and altiplano of the Andean region. Paleoclimate records from the Quelccaya ice cap (5670 masl) in highland Peru that extend back ~1800 years show good correlation between precipitation and the rise and fall of pre-Hispanic civilizations in western Peru and Bolivia. Sediment cores extracted from Lake Titicaca provide independent evidence of this correspondence with particular reference to the history of the pre-Hispanic Tiwanaku state centered in the Andean altiplano. Here we explore, in particular, the impacts of climate change on the development and ultimate dissolution of this altiplano state.

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Forty-three years of absolute gravity observations of the Fennoscandian postglacial rebound in Finland

Journal of Geodesy ◽

10.1007/s00190-020-01470-9 ◽

2021 ◽

Vol 95 (2) ◽

Author(s):

Mirjam Bilker-Koivula ◽

Jaakko Mäkinen ◽

Hannu Ruotsalainen ◽

Jyri Näränen ◽

Timo Saari

Keyword(s):

Gravity Data ◽

Gravity Change ◽

Global Navigation Satellite Systems ◽

Absolute Gravity ◽

Data Sets ◽

Postglacial Rebound ◽

Land Uplift ◽

Satellite Systems ◽

Gravity Measurements ◽

Global Navigation Satellite

AbstractPostglacial rebound in Fennoscandia causes striking trends in gravity measurements of the area. We present time series of absolute gravity data collected between 1976 and 2019 on 12 stations in Finland with different types of instruments. First, we determine the trends at each station and analyse the effect of the instrument types. We estimate, for example, an offset of 6.8 μgal for the JILAg-5 instrument with respect to the FG5-type instruments. Applying the offsets in the trend analysis strengthens the trends being in good agreement with the NKG2016LU_gdot model of gravity change. Trends of seven stations were found robust and were used to analyse the stabilization of the trends in time and to determine the relationship between gravity change rates and land uplift rates as measured with global navigation satellite systems (GNSS) as well as from the NKG2016LU_abs land uplift model. Trends calculated from combined and offset-corrected measurements of JILAg-5- and FG5-type instruments stabilized in 15 to 20 years and at some stations even faster. The trends of FG5-type instrument data alone stabilized generally within 10 years. The ratio between gravity change rates and vertical rates from different data sets yields values between − 0.206 ± 0.017 and − 0.227 ± 0.024 µGal/mm and axis intercept values between 0.248 ± 0.089 and 0.335 ± 0.136 µGal/yr. These values are larger than previous estimates for Fennoscandia.

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Ice-Breaking Fleets of the United States and Canada: Assessing the Current State of Affairs and Future Plans

Sustainability ◽

10.3390/su13020703 ◽

2021 ◽

Vol 13 (2) ◽

pp. 703

Author(s):

Megan Drewniak ◽

Dimitrios Dalaklis ◽

Anastasia Christodoulou ◽

Rebecca Sheehan

Keyword(s):

United States ◽

The United States ◽

Maritime Transportation ◽

The Arctic ◽

Polar Ice ◽

Northwest Passage ◽

Ice Cap ◽

Ice Coverage ◽

Current State ◽

State Of Affairs

In recent years, a continuous decline of ice-coverage in the Arctic has been recorded, but these high latitudes are still dominated by earth’s polar ice cap. Therefore, safe and sustainable shipping operations in this still frozen region have as a precondition the availability of ice-breaking support. The analysis in hand provides an assessment of the United States’ and Canada’s polar ice-breaking program with the purpose of examining to what extent these countries’ relevant resources are able to meet the facilitated growth of industrial interests in the High North. This assessment will specifically focus on the maritime transportation sector along the Northwest Passage and consists of four main sections. The first provides a very brief description of the main Arctic passages. The second section specifically explores the current situation of the Northwest Passage, including the relevant navigational challenges, lack of infrastructure, available routes that may be used for transit, potential choke points, and current state of vessel activity along these routes. The third one examines the economic viability of the Northwest Passage compared to that of the Panama Canal; the fourth and final section is investigating the current and future capabilities of the United States’ and Canada’s ice-breaking fleet. Unfortunately, both countries were found to be lacking the necessary assets with ice-breaking capabilities and will need to accelerate their efforts in order to effectively respond to the growing needs of the Arctic. The total number of available ice-breaking assets is impacting negatively the level of support by the marine transportation system of both the United States and Canada; these two countries are facing the possibility to be unable to effectively meet the expected future needs because of the lengthy acquisition and production process required for new ice-breaking fleets.

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Technical and procedural comparison of two different cryoballoon ablation systems in patients with atrial fibrillation

Journal of Interventional Cardiac Electrophysiology ◽

10.1007/s10840-021-01035-6 ◽

2021 ◽

Author(s):

Sven Knecht ◽

Christian Sticherling ◽

Laurent Roten ◽

Patrick Badertscher ◽

Laurève Chollet ◽

...

Keyword(s):

Atrial Fibrillation ◽

Left Atrial Volume ◽

Median Number ◽

Volume Index ◽

Group Differences ◽

Cryoballoon Ablation ◽

Left Atrial Volume Index ◽

Ice Cap ◽

Total Procedure Time ◽

Catheter Design

Abstract Purpose The aim was to report procedural and technical differences of a novel cryoballoon (NCB) ablation catheter for pulmonary vein isolation (PVI) compared to the standard cryoballoon (SCB) catheter. Methods Consecutive patients with atrial fibrillation (AF) undergoing PVI using the NCB and the SCB were included. Procedural parameters, technical differences, acute efficacy, and safety are reported. Results Eighty patients (age 66 ± 10 years, ejection fraction 57 ± 10%, left atrial volume index 40 ± 6 ml/m2) were studied. With the NCB, 156 of 158 PVs (99%) were isolated compared to isolation of 159 of 159 PVs (100%) with the SCB. The median number of freezes in the NCB and the SCB group was 6 (IQR 5–8) and 5 (IQR 4–7), respectively (p = 0.051), with 73% and 71% of the PVs isolated with a single freeze, respectively. Nadir temperature and temperature at isolation were − 59 ± 6 °C and − 45 ± 17 °C in the NCB group and − 46 ± 7 °C and − 32 ± 23 °C in the SCB group, respectively (both p < 0.001) with no difference in time to isolation (TTI). Procedural differences were observed for the total procedure time (84 ± 29 min in the NCB group and 65 ± 17 min in the SCB group, p = 0.003). There was a peri-procedural stroke in one patient in the NCB group. Differences in catheter design were observed that may account for the differences in temperature recordings and ice cap formation. Conclusions Acute efficacy and TTI were similar with the NCB compared to the SCB. Measured temperatures were lower with the NCB, most likely due to differences in catheter design.

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Ice thickness and volume of the Renland Ice Cap, East Greenland

Journal of Glaciology ◽

10.1017/jog.2021.11 ◽

2021 ◽

pp. 1-13

Author(s):

Iben Koldtoft ◽

Aslak Grinsted ◽

Bo M. Vinther ◽

Christine S. Hvidberg

Keyword(s):

Surface Topography ◽

Climate Model ◽

Thickness Distribution ◽

High Elevation ◽

Surface Velocity ◽

Ice Thickness ◽

Model Parameters ◽

East Greenland ◽

Ice Volume ◽

Ice Cap

Abstract To assess the amount of ice volume stored in glaciers or ice caps, a method to estimate ice thickness distribution is required for glaciers where no direct observations are available. In this study, we use an existing inverse method to estimate the bedrock topography and ice thickness of the Renland Ice Cap, East Greenland, using satellite-based observations of the surface topography. The inverse approach involves a procedure in which an ice dynamical model is used to build-up an ice cap in steady state with climate forcing from a regional climate model, and the bedrock is iteratively adjusted until the modelled and observed surface topography match. We validate our model results against information from airborne radar data and satellite observed surface velocity, and we find that the inferred ice thickness and thereby the stored total volume of the ice cap is sensitive to the assumed ice softness and basal slipperiness. The best basal model parameters for the Renland Ice Cap are determined and the best estimated total ice volume of 384 km3 is found. The Renland Ice Cap is particularly interesting because of its location at a high elevation plateau and hence assumed low sensitivity to climate change.

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Implications of postseismic gravity change following the great 2004 Sumatra-Andaman earthquake from the regional harmonic analysis of GRACE intersatellite tracking data

Journal of Geophysical Research Atmospheres ◽

10.1029/2008jb005705 ◽

2008 ◽

Vol 113 (B11) ◽

Cited By ~ 59

Author(s):

Shin-Chan Han ◽

Jeanne Sauber ◽

Scott B. Luthcke ◽

Chen Ji ◽

Fred F. Pollitz

Keyword(s):

Harmonic Analysis ◽

Gravity Change ◽

Tracking Data ◽

Andaman Earthquake

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Provenance of basaltic tephra from Vatnajökull subglacial volcanoes, Iceland, as determined by major- and trace-element analyses

The Holocene ◽

10.1177/0959683611400456 ◽

2011 ◽

Vol 21 (7) ◽

pp. 1037-1048 ◽

Cited By ~ 62

Author(s):

Bergrún Arna Óladóttir ◽

Olgeir Sigmarsson ◽

Gudrún Larsen ◽

Jean-Luc Devidal

Keyword(s):

Trace Element ◽

Inductively Coupled Plasma ◽

Major Element ◽

Element Composition ◽

Major Element Composition ◽

Volcanic System ◽

The Holocene ◽

Inductively Coupled ◽

Ice Cap ◽

The North

The Holocene eruption history of subglacial volcanoes in Iceland is largely recorded by their tephra deposits. The numerous basaltic tephra offer the possibility to make the tephrochronology in the North Atlantic area more detailed and, therefore, more useful as a tool not only in volcanology but also in environmental and archaeological studies. The source of a tephra is established by mapping its distribution or inferred via compositional fingerprinting, mainly based on major-element analyses. In order to improve the provenance determinations for basaltic tephra produced at Grímsvötn, Bárdarbunga and Kverkfjöll volcanic systems in Iceland, 921 samples from soil profiles around the Vatnajökull ice-cap were analysed for major-element concentrations by electron probe microanalysis. These samples are shown to represent 747 primary tephra units. The tephra erupted within each of these volcanic system has similar chemical characteristics. The major-element results fall into three distinctive compositional groups, all of which show regular decrease of MgO with increasing K2O concentrations. The new analyses presented here considerably improve the compositional distinction between products of the three volcanic systems. Nevertheless, slight overlap of the compositional groups for each system still remains. In situ trace-element analyses by laser-ablation-inductively-coupled-plasma-mass-spectrometry were applied for better provenance identification for those tephra having similar major-element composition. Three trace-element ratios, Rb/Y, La/Yb and Sr/Th, proved particularly useful. Significantly higher La/Yb distinguishes the Grímsvötn basalts from those of Bárdarbunga and Rb/Y values differentiate the basalts of Grímsvötn and Kverkfjöll. Additionally, the products of Bárdarbunga, Grímsvötn and Kverkfjöll form distinct compositional fields on a Sr/Th versus Th plot. Taken together, the combined use of major- and trace-element analyses in delineating the provenance of basaltic tephra having similar major-element composition significantly improves the Holocene tephra record as well as the potential for correlations with tephra from outside Iceland.

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Site information and initial results from deep ice drilling on Law Dome, Antarctica

Journal of Glaciology ◽

10.3189/s0022143000002768 ◽

1997 ◽

Vol 43 (143) ◽

pp. 3-10 ◽

Cited By ~ 10

Author(s):

V.I. Morgan ◽

C.W. Wookey ◽

J. Li ◽

T.D. van Ommen ◽

W. Skinner ◽

...

Keyword(s):

Ice Core ◽

Ice Sheet ◽

High Accumulation ◽

Ice Flow ◽

Ice Cap ◽

Basal Ice ◽

Inland Ice ◽

The Last Glacial Maximum ◽

Initial Results ◽

The Last Glacial

AbstractThe aim of deep ice drilling on Law Dome, Antarctica, has been to exploit the special characteristics of Law Dome summit, i.e. low temperature and high accumulation near an ice divide, to obtain a high-resolution ice core for climatic/environmental studies of the Holocene and the Last Glacial Maximum (LGM). Drilling was completed in February 1993, when basal ice containing small fragments of rock was reached at a depth of 1196 m. Accurate ice dating, obtained by counting annual layers revealed by fine-detail δ18О, peroxide and electrical-conductivity measurements, is continuous down to 399 m, corresponding to a date of AD 1304. Sulphate concentration measurements, made around depths where conductivity tracing indicates volcanic fallout, allow confirmation of the dating (for Agung in 1963 and Tambora in 1815) or estimates of the eruption date from the ice dating (for the Kuwae, Vanuatu, eruption ~1457). The lower part of the core is dated by extrapolating the layer-counting using a simple model of the ice flow. At the LGM, ice-fabric measurements show a large decrease (250 to 14 mm2) in crystal size and a narrow maximum in c-axis vertically. The main zone of strong single-pole fabrics however, is located higher up in a broad zone around 900 m. Oxygen-isotope (δ18O) measurements show Holocene ice down to 1113 m, the LGM at 1133 m and warm (δ18O) about the same as Holocene) ice near the base of the ice sheet. The LGM/Holocene δ18O shift of 7.0‰, only ~1‰ larger than for Vostok, indicates that Law Dome remained an independent ice cap and was not overridden by the inland ice sheet in the Glacial.

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