Non-surface mass balance of glaciers in Iceland

Publisher's version (útgefin grein)Non-surface mass balance is non-negligible for glaciers in Iceland. Several Icelandic glaciers are in the neo-volcanic zone where a combination of geothermal activity, volcanic eruptions and geothermal heat flux much higher than the global average lead to basal melting close to 150 mm w.e. a−1 for the Mýrdalsjökull ice cap and 75 mm w.e. a−1 for the largest ice cap, Vatnajökull. Energy dissipation in the flow of water and ice is also rather large for the high-precipitation, temperate glaciers of Iceland resulting in internal and basal melting of 20–150 mm w.e. a−1. The total non-surface melting of glaciers in Iceland in 1995–2019 was 45–375 mm w.e. a−1 on average for the main ice caps, and was largest for Mýrdalsjökull, the south side of Vatnajökull and Eyjafjallajökull. Geothermal melting, volcanic eruptions and the energy dissipation in the flow of water and ice, as well as calving, all contribute, and thus these components should be considered in mass-balance studies. For comparison, the average mass balance of glaciers in Iceland since 1995 is −500 to −1500 mm w.e. a−1. The non-surface mass balance corresponds to a total runoff contribution of 2.1 km3 a−1 of water from Iceland.Financial support for lidar mapping of glaciers in Iceland in 2008–2012 was provided by the Icelandic Research Fund (163391-052), the Landsvirkjun (National Power Company of Iceland) Research Fund, the Icelandic Road Administration, the Reykjavík Energy Environmental and Energy Research Fund, the National Land Survey of Iceland, the Klima- og Luftgruppen (KoL) research fund of the Nordic Council of Ministers, and the Vatnajökull National Park. The acquisition of the Hofsjökull 2013 DEM was funded by AlpS GmbH and the University of Innsbruck. The acquisition of the Langjökull 2013 DEM was funded by NERC grant IG 13/12 and the DEM was provided by Ian Willis at the Scott Polar Research Institute. The work on estimating geothermal and volcanic power is based on funding from many sources, including the Research Fund of the University of Iceland, ISAVIA (the Icelandic Aviation Service), the Icelandic Road Administration and Landsvirkjun; logistical support has been provided by the Iceland Glaciological Society.Peer Reviewe

Multi-messenger Observations of a Binary Neutron Star Merger

On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of ∼ 1.7 {{s}} with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg2 at a luminosity distance of {40}-8+8 Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 {M}ȯ . An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at ∼ 40 {{Mpc}}) less than 11 hours after the merger by the One-Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ∼10 days. Following early non-detections, X-ray and radio emission were discovered at the transient’s position ∼ 9 and ∼ 16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC 4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta.</p

Bílastæðalausn fyrir Seðlabanka Íslands

Í þessari skýrslu er yfirlit yfir lokaverkefni fyrir Háskólann í Reykjavík sem unnið var í samstarfi við Seðlabanka Íslands. Bílakjallari höfuðstöðva Seðlabankans er of lítill miðað við fjölda starfsmanna svo þörf hefur myndast að koma skipulagi á hann. Verkefnið er því að útbúa hugbúnað sem á að leysa þessa þörf. Markmiðið er því að koma upp kerfi á innra neti bankans sem heldur utan um bílastæðamál í kjallara höfuðstöðvanna. Kerfið verður notað af starfsmönnum bankans og þarf það því að vera notendavænt og auðvelt í notkun. Í þessari skýrslu er farið nánar yfir verkskipulag og verkáætlun fyrir þróun kerfisins. Einnig er farið í greiningu og hönnun kerfisins auk áhættugreiningar og framvinduyfirlits