Geological Survey of Denmark and Greenland

About: Geological Survey of Denmark and Greenland is a facility organization based out in Copenhagen, Denmark. It is known for research contribution in the topics: Greenland ice sheet & Ice sheet. The organization has 844 authors who have published 3152 publications receiving 104706 citations. The organization is also known as: Danmarks og Grønlands Geologiske Undersøgelse.

Neogene evolution of the Atlantic continental margin of NW Europe (Lofoten Islands to SW Ireland): anything but passive

Abstract: A regional stratigraphic framework for the Neogene succession along and across the NW European margin is presented, based on a regional seismic and sample database. The stratigraphy provides constraints on the timing and nature of the mid- to late Cenozoic differential tectonic movements that have drivenmajor changes in sediment supply, oceanographic circulation and climate (culminating in continental glaciation). The overall context for Neogene deposition on the margin was established in the mid-Cenozoic, when rapid, km-scale differential subsidence (sagging) created the present-day deep-water basins. The Neogene is subdivided into lower (Miocene–lower Pliocene) and upper (lower Pliocene–Holocene) intervals. The lower Neogene contains evidence of early to mid-Miocene compressive tectonism, including inversion anticlines and multiple unconformities that record uplift and erosion of basin margins, as well as changes in deep-water currents. These movements culminated in a major expansion of contourite drifts in the mid-Miocene, argued to reflect enhanced deep-water exchange across the Wyville-Thomson Ridge Complex, via the Faroe Conduit. The distribution and amplitude of the intra-Miocene movements are consistent with deformation and basin margin flexure in response to enhanced intra-plate compressive stresses during a local plate reorganization (transfer of the Jan Mayen Ridge from Greenland to Europe). The upper Neogene records a seaward tilting (

Transcription dynamics of the functional tfdA gene during MCPA herbicide degradation by Cupriavidus necator AEO106 (pRO101) in agricultural soil

Abstract: A modified protocol for simultaneous extraction of RNA and DNA, followed by real-time polymerase chain reaction quantification, was used to investigate tfdA gene expression during in situ degradation of the herbicide MCPA (4-chloro-2-methylphenoxy-acetic acid) in soil. tfdA encodes an alpha-ketoglutarate-dependent dioxygenase catalysing the first step in the degradation pathway of MCPA and 2,4-D (2,4-dichlorophenoxy-acetic acid). A linear recovery of tfdA mRNA over three orders of magnitude was shown, and the tfdA mRNA level was normalized using the tfdA mRNA/DNA ratio. The density of active cells required for tfdA mRNA detection was 10(5) cells g(-1) soil. Natural soil microcosms inoculated with Cupriavidus necator (formerly Ralstonia eutropha) AEO106 (pRO101) cells were amended with four different MCPA concentrations (2, 20, 50 and 150 mg kg(-1)). Mineralization rates were estimated by quantification of 14CO2 emission from degradation of 14C-MCPA. tfdA mRNA was detected 1 h after amendment at all four concentrations. In soils amended with 2 and 20 mg kg(-1), the mRNA/DNA ratio for tfdA demonstrated a sharp transient maximum of tfdA expression from no to full expression within 3 and 6 h respectively, followed by a decline and complete loss of expression after 19 and 43 h. A more complex pattern of tfdA expression was observed for the higher 50 and 150 mg kg(-1) amendments; this coincided with growth of C. necator AEO106 (pRO101) in the system. Repeated amendment with MCPA after 2 weeks in the 20 mg kg(-1) scenario revealed a sharp increase of tfdA mRNA, and absence of a mineralization lag phase. For all amendments, tfdA mRNA was detectable only during active mineralization, and thus revealed a direct correlation between tfdA mRNA presence and microbial degrader activity. The present study demonstrates that direct analysis of functional gene expression dynamics by quantification of mRNA can indeed be made in natural soil.

A decade (2002–2012) of supraglacial lake volume estimates across Russell Glacier, West Greenland

Abstract: Supraglacial lakes represent an ephemeral storage buffer for meltwater runoff and lead to significant, yet short-lived, episodes of ice-flow acceleration by decanting large meltwater and energy fluxes into the ice sheet's hydrological system. Here, a methodology for calculating lake volume is used to quantify storage and drainage across Russell Glacier, West Greenland, between 2002 and 2012. Using 502 MODIS scenes, water volume at ~200 seasonally occurring lakes was derived using a depth–reflectance relationship, which was independently calibrated and field validated against lake bathymetry. The inland expansion of lakes is strongly correlated with air temperature: during the record melt years of 2010 and 2012, lakes formed and drained earlier, attaining their maximum volume 38 and 20 days earlier than the 11 yr mean, as well as occupying a greater area and forming at higher elevations (> 1800 m) than previously. Despite occupying under 2% of the study area, lakes delay the transmission of up to 7–13% of the bulk meltwater discharged. Although the results are subject to an observational bias caused by periods of cloud cover, we estimate that across Russell Glacier, 28% of supraglacial lakes drain rapidly (< 4 days). Clustering of such events in space and time suggests a synoptic trigger mechanism. Further, we find no evidence to support a unifying critical size or depth-dependent drainage threshold.

Late Quaternary development of the southern sector of the Greenland Ice Sheet, with particular reference to the Qassimiut lobe

Abstract: The evolution of the southern Greenland Ice Sheet is interpreted from a synthesis of geological data and palaeoclimatic information provided by the ice-sheet cores. At the Last Glacial Maximum the ice margin would have been at the shelf break and the ice sheet was fringed by shelf ice. Virtually all of the present ice-free land was glaciated. The initial ice retreat was controlled by eustatic sea level rise and was mainly by calving. When temperatures increased, melt ablation led to further ice-margin retreat and areas at the outer coast and mountain tops were deglaciated. Retreat was interrupted by a readvance during the Neria stade that may correlate with the Younger Dryas cooling. The abrupt temperature rise at the Younger Dryas—Holocene transition led to a fast retreat of the ice margin, and after ˜9 ka BP the ice sheet was smaller than at present. Expansion of the ice cover began in the Late Holocene, with a maximum generally during the Little Ice Age. The greatest changes in ice cover occurred in lowland areas, i.e. in the region of the Qassimiut lobe. The date of the historical maximum advance shows considerable spatial variability and varies between AD 1600 and the present. Local anomalous readvances are seen at possibly 7–8 ka and at c. 2 ka BP. A marked relative sea level rise is seen in the Late Holocene; this is believed to reflect a direct glacio-isostatic response to increasing ice load.

Greenland Ice Sheet surface melt amplified by snowline migration and bare ice exposure.

Abstract: Greenland Ice Sheet mass loss has recently increased because of enhanced surface melt and runoff. Since melt is critically modulated by surface albedo, understanding the processes and feedbacks that alter albedo is a prerequisite for accurately forecasting mass loss. Using satellite imagery, we demonstrate the importance of Greenland's seasonally fluctuating snowline, which reduces ice sheet albedo and enhances melt by exposing dark bare ice. From 2001 to 2017, this process drove 53% of net shortwave radiation variability in the ablation zone and amplified ice sheet melt five times more than hydrological and biological processes that darken bare ice itself. In a warmer climate, snowline fluctuations will exert an even greater control on melt due to flatter ice sheet topography at higher elevations. Current climate models, however, inaccurately predict snowline elevations during high melt years, portending an unforeseen uncertainty in forecasts of Greenland's runoff contribution to global sea level rise.