Recent geological–geomorphological processes on the east Arctic shelf: Results of the expedition of the icebreaker Oden in 2014     

L. I. Lobkovsky  S. L. Nikiforov  R. A. Ananiev  A. V. Khortov  I. P. Semiletov  M. Jakobsson  N. N. Dmitrievskiy 《Oceanology》2015,55(6):926-929

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Performance results of HESP physical model     

Anantha Chanumolu  Sivarani Thirupathi  Damien Jones  Sunetra Giridhar  Deon Grobler  Robert Jakobsson 《Experimental Astronomy》2017,43(1):39-58

As a continuation to the published work on model based calibration technique with HESP(Hanle Echelle Spectrograph) as a case study, in this paper we present the performance results of the technique. We also describe how the open parameters were chosen in the model for optimization, the glass data accuracy and handling the discrepancies. It is observed through simulations that the discrepancies in glass data can be identified but not quantifiable. So having an accurate glass data is important which is possible to obtain from the glass manufacturers. The model’s performance in various aspects is presented using the ThAr calibration frames from HESP during its pre-shipment tests. Accuracy of model predictions and its wave length calibration comparison with conventional empirical fitting, the behaviour of open parameters in optimization, model’s ability to track instrumental drifts in the spectrum and the double fibres performance were discussed. It is observed that the optimized model is able to predict to a high accuracy the drifts in the spectrum from environmental fluctuations. It is also observed that the pattern in the spectral drifts across the 2D spectrum which vary from image to image is predictable with the optimized model. We will also discuss the possible science cases where the model can contribute.  相似文献   

Management of summer-spawning herring off Iceland   总被引：1，自引：0，他引：1  

Jakobsson  J.; Stefansson  G. 《ICES Journal of Marine Science》1999,56(6):827-833

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The PT phase relations of a primary oceanite from the Reykjanes peninsula,Iceland     

Sven Maaløe  Sveinn P Jakobsson 《Lithos》1980,13(3):237-246

The field relationships and petrographic features of the oceanites of the Reykjanes peninsula suggest that they might have originated as primary magmas. The principal phase relationships of primary liquids formed by the partial melting of lherzolites are defined. The phase relations obtained for oceanite RE78 between 0 and 30 kbar at dry conditions suggest that the oceanite originated as a primary magma at 25 kbar and 1580°C, and erupted at a temperature near 1300°C.  相似文献   

Long range forecasts of Northern Hemisphere 500 mb height fields by ARIMA modesl     

Dr. Thor Jakobsson 《Meteorology and Atmospheric Physics》1979,28(2-3):149-158

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Mantle melting in equilibrium with an Iron–Wüstite–Graphite buffered COH-fluid     

Sigurdur Jakobsson  John R. Holloway 《Contributions to Mineralogy and Petrology》2009,157(2):283-284

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The extreme, red afterglow of GRB 060923A: distance or dust?     

N. R. Tanvir  A. J. Levan  E. Rol  R. L. C. Starling  J. Gorosabel  R. S. Priddey  D. Malesani  P. Jakobsson  P. T. O'Brien  A. O. Jaunsen  J. Hjorth  J. P. U. Fynbo  A. Melandri  A. Gomboc  B. Milvang-Jensen  A. S. Fruchter  M. Jarvis  C. A. C. Fernandes  T. Wold 《Monthly notices of the Royal Astronomical Society》2008,388(4):1743-1750

Gamma-ray bursts (GRBs) are powerful probes of the early Universe, but locating and identifying very distant GRBs remain challenging. We report here the discovery of the K -band afterglow of Swift GRB 060923A, imaged within the first hour post-burst, and the faintest so far found. It was not detected in any bluer bands to deep limits, making it a candidate very high- z burst  ( z ≳ 11)  . However, our later-time optical imaging and spectroscopy reveal a faint galaxy coincident with the GRB position which, if it is the host, implies a more moderate redshift (most likely   z ≲ 2.8  ) and therefore that dust is the likely cause of the very red-afterglow colour. This being the case, it is one of the few instances so far found of a GRB afterglow with high-dust extinction.  相似文献   

Estimating ventilation time scales using overturning stream functions     

Bijoy Thompson  Jonas Nycander  Johan Nilsson  Martin Jakobsson  Kristofer Döös 《Ocean Dynamics》2014,64(6):797-807

A simple method for estimating ventilation time scales from overturning stream functions is proposed. The stream function may be computed using either geometric coordinates or a generalized vertical coordinate, such as potential density (salinity in our study). The method is tested with a three-dimensional circulation model describing an idealized semi-enclosed ocean basin ventilated through a narrow strait over a sill, and the result is compared to age estimates obtained from a passive numerical age tracer. The best result is obtained when using the stream function in salinity coordinates. In this case, the reservoir-averaged advection time obtained from the overturning stream function in salinity coordinates agrees rather well with the mean age of the age tracer, and the corresponding maximum ages agree very well.  相似文献   

Melt inclusion constraints on volatile systematics and degassing history of the 2014–2015 Holuhraun eruption,Iceland     

E.?BaliEmail authorView author&#;s OrcID profile  M.?E.?Hartley  S.?A.?Halldórsson  G.?H.?Gudfinnsson  S.?Jakobsson 《Contributions to Mineralogy and Petrology》2018,173(2):9

The mass of volatiles emitted during volcanic eruptions is often estimated by comparing the volatile contents of undegassed melt inclusions, trapped in crystals at an early stage of magmatic evolution, with that of the degassed matrix glass. Here we present detailed characterisation of magmatic volatiles (H₂O, CO₂, S, Fl and Cl) of crystal-hosted melt and fluid inclusions from the 2014–2015 Holuhraun eruption of the Bárðarbunga volcanic system, Iceland. Based on the ratios of magmatic volatiles to similarly incompatible trace elements, the undegassed primary volatile contents of the Holuhraun parental melt are estimated at 1500–1700 ppm CO₂, 0.13–0.16 wt% H₂O, 60–80 ppm Cl, 130–240 ppm F and 500–800 ppm S. High-density fluid inclusions indicate onset of crystallisation at pressures?≥?0.4 GPa (~?12 km depth) promoting deep degassing of CO₂. Prior to the onset of degassing, the melt CO₂ content may have reached 3000–4000 ppm, with the total magmatic CO₂ budget estimated at  23–55 Mt. SO₂ release commenced at 0.12 GPa (~?3.6 km depth), eventually leading to entrapment of SO₂ vapour in low-density fluid inclusions. We calculate the syn-eruptive volatile release as 22.2 Mt of magmatic H₂O, 5.9–7.7 Mt CO₂, and 11.3 Mt of SO₂ over the course of the eruption; F and Cl release were insignificant. Melt inclusion constraints on syn-eruptive volatile release are similar to estimates made during in situ field monitoring, with the exception of H₂O, where field measurements may be heavily biased by the incorporation of meteoric water.  相似文献   

Multiple re‐advances of a Lake Vättern outlet glacier during Fennoscandian Ice Sheet retreat,south‐central Sweden          下载免费PDF全文

Sarah L. Greenwood  Matt O'Regan  Henrik Swärd  Tom Flodén  Roman Ananyev  Denis Chernykh  Martin Jakobsson 《Boreas: An International Journal of Quaternary Research》2015,44(4):619-637

Lake Vättern represents a critical region geographically and dynamically in the deglaciation of the Fennoscandian Ice Sheet. The outlet glacier that occupied the basin and its behaviour during ice‐sheet retreat were key to the development and drainage of the Baltic Ice Lake, dammed just west of the basin, yet its geometry, extent, thickness, margin dynamics, timing and sensitivity to regional retreat forcing are rather poorly known. The submerged sediment archives of Lake Vättern represent a missing component of the regional Swedish deglaciation history. Newly collected geophysical data, including high‐resolution multibeam bathymetry of the lake floor and seismic reflection profiles of southern Lake Vättern, are used here together with a unique 74‐m sediment record recently acquired by drill coring, and with onshore LiDAR‐based geomorphological analysis, to investigate the deglacial environments and dynamics in the basin and its terrestrial environs. Five stratigraphical units comprise a thick subglacial package attributed to the last glacial period (and probably earlier), and an overlying >120‐m deglacial sequence. Three distinct retreat–re‐advance episodes occurred in southern Lake Vättern between the initial deglaciation and the Younger Dryas. In the most recent of these, ice overrode proglacial lake sediments and re‐advanced from north of Visingsö to the southern reaches of the lake, where ice up to 400 m thick encroached on land in a lobate fashion, moulding crag‐and‐tail lineations and depositing till above earlier glacifluvial sediments. This event precedes the Younger Dryas, which our data reveal was probably restricted to north‐central sectors of the basin. These dynamics, and their position within the regional retreat chronology, indicate a highly active ice margin during deglaciation, with retreat rates on average 175 m a^?1. The pronounced topography of the Vättern basin and its deep proglacial‐dammed lake are likely to have encouraged the dynamic behaviour of this major Fennoscandian outlet glacier.  相似文献