Morphological dynamics of an englacial channel

Despite an interest in the hydraulic functioning of supraglacial and englacial channels over the last 4 decades, the processes and forms of such ice-bounded streams have remained poorly documented. Recent glaciological research has demonstrated the potential significance of so-called "cut-and-closure" streams, where englacial or subglacial flow paths are created from the long-term incision of supraglacial channels. These flow paths are reported to exhibit step-pool morphology, comprising knickpoints and/or knickzones, exaggerated in dimensions in comparison to supraglacial channels. However, little is known of the development of such channels' morphology. Here, we examine the spatial organisation of step pools and the upstream migration of steps, many of which form knickzones, with repeated surveys over a 10-year period in an englacial conduit in cold-based Austre Brøggerbreen, Svalbard. The observations show upstream step recession to be the dominant process for channel evolution. This is paralleled by an increase in average step height and conduit gradient over time. Characteristic channel-reach types and step-riser forms are consistently observed in each of the morphological surveys reported. We suggest that the formation of steps has a hydrodynamic origin, where step-pool geometry is more efficient for energy dissipation than meanders. The englacial channel system is one in rapid transition towards a quasi-equilibrium form within a decadal timescale. The evolution and recession of knickzones reported here result in the formation of a 37 m deep moulin shaft, suggesting that over time an incising supraglacial channel may evolve towards an englacial channel form exhibiting a stable end-point characterised by a singular vertical descent, which potentially can reach the glacier bed. This challenges the prevailing notions that crevasses or hydrofractures are needed to form deep moulins. Our observations highlight the need to further examine the adjustment processes in cut-and-closure channels to better understand their coupling to supraglacial meltwater sources and potential significance in cold-based glacier hydrology and ice dynamics

Decomposing Debt Growth

High debt growth can increase the risk of instability in the financial system. In monitoring financial stability it is therefore important to closely monitor debt accumulation. Norges Bank uses Statistics Norway’s credit indicators and various sources of microdata in its analyses of debt growth. Microdata sources comprise financial reporting, household income statistics and enterprises' annual financial reporting. In this commentary, we examine how this information can be used to shed light on risks posed by debt growth.publishedVersio

Decomposing Debt Growth

High debt growth can increase the risk of instability in the financial system. In monitoring financial stability it is therefore important to closely monitor debt accumulation. Norges Bank uses Statistics Norway’s credit indicators and various sources of microdata in its analyses of debt growth. Microdata sources comprise financial reporting, household income statistics and enterprises' annual financial reporting. In this commentary, we examine how this information can be used to shed light on risks posed by debt growth

Dekomponering av gjeldsveksten

Sterk vekst i gjeld kan øke risikoen for ustabilitet i det finansielle systemet. I overvåkingen av den finansielle stabiliteten er det derfor viktig å følge gjeldsveksten nøye. Norges Bank benytter Statistisk sentralbyrås kredittindikatorer og ulike mikrodatakilder i analyser av gjeldsutviklingen. Mikrodatakildene består av bankenes regnskapsrapportering, inntektsstatistikk for husholdninger, samt foretakenes årsregnskaper. I denne artikkelen ser vi på hvordan vi kan bruke disse opplysningene til å belyse risikoen knyttet til gjeldsveksten.publishedVersio

Dekomponering av gjeldsveksten

Sterk vekst i gjeld kan øke risikoen for ustabilitet i det finansielle systemet. I overvåkingen av den finansielle stabiliteten er det derfor viktig å følge gjeldsveksten nøye. Norges Bank benytter Statistisk sentralbyrås kredittindikatorer og ulike mikrodatakilder i analyser av gjeldsutviklingen. Mikrodatakildene består av bankenes regnskapsrapportering, inntektsstatistikk for husholdninger, samt foretakenes årsregnskaper. I denne artikkelen ser vi på hvordan vi kan bruke disse opplysningene til å belyse risikoen knyttet til gjeldsveksten

Gyrobehandling av Ømmervatn, Mjåvatn og Fustvatn. Matematisk modellering

Hensikten med denne rapporten var å bedre grunnlaget for en vellykket behandling av Ømmervatn, Mjåvatn og Fustvatn med rotenon (CFT-Legumin). Behandlingen ble simulert ved en matematisk modell. I simuleringene oppnådde vi en tilfredsstillende jevn fordeling av dosert rotenon innen hver av innsjøene. I modellen ble det ble dosert i striper med 100 meters mellomrom, og fra overflate til bunn. Oktober er valgt for tidspunkt for behandlingen ut fra hensiktsmessig temperatur på vannet med hensyn til bestandighet av rotenon og vertikale blandingsforhold

Mass balance and changes of surface slope, crevasse and flow pattern of Erikbreen, northern Spitsbergen: an application of a geographical information system (GIS)

The polythcrmal valley glacier Erikbreen (79°40?N 12°30?E), northern Spitsbergen, was investigated in 1970 and 1990 using digital photogrammetry and digital elevation model (DEM) techniques. The bottom topography was derived from radio-echo soundings. Based on the DEM, mass balance and changes of surface slope, crevasse and flow pattern were evaluated, and internal ice deformation velocities were calculated. Calculations of the total mass balance show that Erikbreen has not been in equilibrium for the last 20 years. The average surface lowering was 0.38 m/a and the volume had decreased by 5% to 6% from 1970 to 1990 or on the average by 3.5 × 10?1 water. The glacier surface subsided over the whole glacier area except in minor areas with northfacing slopes in the accumulation area. The surface slope and the crevasse pattern, however, did not change significantly during the 20-year-period, except in areas below 100 ma.s.l

Ice-marginal sediment delivery to the surface of a High-Arctic glacier: Austre Brøggerbreen, Svalbard

The definitive version is found at: http://onlinelibrary.wiley.com/ Copyright Wiley-BlackwellEnhanced delivery of water-saturated, ice-marginal sediments to the glacier surface is a response to glacier thinning that has the potential to increase both levels of sediment transfer through the glacier hydrological system and total basin sediment yields. Preliminary observations made during summer 2007 at Austre Br circle divide ggerbreen, Svalbard, confirm that ice-marginal debris flows in the upper reaches of the glacier are actively delivering sediments to the glacier surface, which may then be flushed into the glacier's hydrological system. During a four-day observation period, several stochastic pulses in water turbidity were observed at a single portal where solely supra- and englacial drainage emerge at the glacier margin. The erratic suspended sediment fluxes were hypothesized to originate from ice-marginal sources. Quantitative analysis of continuous turbidity and discharge data confirm that discharge is not driving these turbidity pulses and, combined with observational data, that the most likely origin is the delivery of water-saturated sediments to the glacier surface from ice-marginal, debris flows with subsequent transfer to the portal via the glacial drainage system. These observations illustrate the potential importance of the paraglacial component to the overall sediment cascade of deglaciating basins and highlight the need for careful interpretation of turbidity records, where stochastic pulses in turbidity may be attributed to sources and processes other than ice-marginal sediment inputs.Peer reviewe