Understanding an ice stream in Greenland at the EastGRIP camp: An international-multidisciplinary effort and knowledge transfer among scientists

The East Greenland Ice-core Project (EastGRIP) aims to retrieve a 2650m long ice core by drilling through the Northeast Greenland Ice Stream (NEGIS). Scientists from a variety of physical sciences and engineers hope to gain new knowledge on ice stream dynamics and about the past climate. The project has many partners from all around the world, who contribute to the science, logistics and economics of the project. Most of the data is processed and analysed in the field. As there is limited capacity in the field camp, scientists and technical staff are encouraged to learn different working techniques to support their project partners. The community also invites scientists, who work on theoretical aspects on the ice stream to communicate the perspective on the procedures and challenges of data collection in the field. And so it happens that earth system modellers learn how to drill an ice core or non-scientific staff helps with the preparation of the ice core samples. Also, the project partners are motivated to bring together scientists at early stages in their careers to gain fieldwork experience. Once each season the field camp also welcomes high school students and teachers as a part of a joint science and education programme

Crystal fabric orientation of the NEGIS ice stream

IASC Workshop on the dynamics and mass budget of Arctic glacier

Complex basal conditions influence flow at the onset of the Northeast Greenland Ice Stream

The onset and high upstream ice surface velocities of the North East Greenland Ice Stream (NEGIS) are not yet well reproducible in ice sheet models. A major uncertainty remains the understanding of basal sliding and a parameterization of basal conditions. In this study, we assess the slow-flowing part of the NEGIS in a systematic analysis of the basal conditions and investigate the increased ice flow. We analyze the spectral basal roughness in correlation with basal return power from an airborne radar survey with AWIs ultra-wideband radar system in 2018 and compare our results with current ice flow geometry and ice surface flow. We observe a roughness anisotropy where the ice stream widens, indicating a change from a smooth and soft bed to a harder bedrock as well as the evolution of elongated subglacial landforms. In addition, at the upstream part of the NEGIS we find a clear zoning of the bedrock return power, indicating an increased water content at the base of the ice stream. At the downstream part, we observe an increased bedrock return power throughout the entire width of the ice stream and outside its margins, indicating enhanced melting and the distribution of basal water beyond the shear zones

Towards interpretation of the radio-stratigraphy of Antarctic ice shelves from modeling and observations: A case study for the Roi Baudouin Ice Shelf, East Antarctica

Ice shelves surrounding the Antarctic perimeter buttress ice flow from the continent towards the ocean, and their disintegration leads to an increase in ice discharge and sea level rise. The evolution and integrity of ice shelves is governed by surface accumulation, basal melting, and ice dynamics. We find history of these processes imprinted in the ice-shelf stratigraphy, which is mapped using isochrones imaged with radar. As an observational archive, the radar obtained stratigraphy combined with ice flow modeling has high potential to assist model calibration and reduce uncertainties in projections for the ice-sheet evolution. In this study we use a simplistic and observationally driven ice-dynamic forward model to predict the ice-shelf stratigraphy. We validate this approach with the full Stokes ice-flow model Elmer/Ice, and present a test-case for the Roi Baudouin Ice Shelf (East Antarctica) - where our model predictions agree well with radar obtained observations. The presented method enables us to investigate whether ice shelves are in steady-state, as well as to map spatial variations of how much of the ice-shelf volume is determined by its local surface mass balance. In the case of Roi Baudouin, we find the ice-shelf volume in the western part to be dominated by ice inflowing from the ice sheet, while the eastern part of the ice shelf is dominated by ice locally accumulated on the shelf. Such analysis serves as a metric for the susceptibility of ice shelves to climate change. We further apply our approach to other ice shelves in Antarctica

Fold and strain analysis of the large NE Greenland Ice Stream

The >500 km long and tens of kilometres wide North-East Greenland Ice Stream (NEGIS) is the largest ice stream in the Greenland Ice Sheet (GrIS). Satellite data show that flow inside the ice stream is significantly faster than adjacent to it and that NEGIS is bound by shear boundaries that are a few kilometres wide. The ice stream drains a large area of the GrIS. As the genesis of NEGIS is unclear, it remains uncertain how it may react to global climate change

Trained immunity or tolerance : opposing functional programs induced in human monocytes after engagement of various pattern recognition receptors

Article Accepted Date: 29 January 2014. ACKNOWLEDGMENTS D.C.I. received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreement HEALTH-2010-260338 (“Fungi in the setting of inflammation, allergy and autoimmune diseases: translating basic science into clinical practices” [ALLFUN]) (awarded to M.G.N.). M.G.N. and J.Q. were supported by a Vici grant of the Netherlands Organization of Scientific Research (awarded to M.G.N.). This work was supported, in part, by National Institutes of Health grant GM53522 to D.L.W. N.A.R.G. was supported by the Wellcome Trust.Peer reviewedPublisher PD

Predicting the steady-state isochronal stratigraphy of ice shelves using observations and modeling

Ice shelves surrounding the Antarctic perimeter moderate ice discharge towards the ocean through buttressing. Ice-shelf evolution and integrity depend on the local surface accumulation, basal melting and on the spatially variable ice-shelf viscosity. These components of ice-shelf mass balance are often poorly constrained by observations and introduce uncertainties in ice-sheet projections. Isochronal radar stratigraphy is an observational archive for the atmospheric, oceanographic and ice-flow history of ice shelves. Here, we predict the stratigraphy of locally accumulated ice on ice shelves with a kinematic forward model for a given atmospheric and oceanographic scenario. This delineates the boundary between local meteoric ice (LMI) and continental meteoric ice (CMI). A large LMI to CMI ratio hereby marks ice shelves whose buttressing strength is more sensitive to changes in atmospheric precipitation patterns. A mismatch between the steady-state predictions of the kinematic forward model and observations from radar can highlight inconsistencies in the atmospheric and oceanographic input data or be an indicator for a transient ice-shelf history not accounted for in the model. We discuss pitfalls in numerical diffusion when calculating the age field and validate the kinematic model with the full Stokes ice-flow model Elmer/Ice. The Roi Baudouin Ice Shelf (East Antarctica) serves as a test case for this approach. There, we find a significant east–west gradient in the LMI / CMI ratio. The steady-state predictions concur with observations on larger spatial scales (>10 km), but deviations on smaller scales are significant, e.g., because local surface accumulation patterns near the grounding zone are underestimated in Antarctic-wide estimates. Future studies can use these mismatches to optimize the input data or to pinpoint transient signatures in the ice-shelf history using the ever growing archive of radar observations of internal ice stratigraphy