I collected all the Greenland and Arctic talks at AGU 2014 that had an attached pdf poster. Less than 1 in 10 offered anything beyond an abstract; whole poster sessions went by without a single poster posted! Worse, the .php formatting prevented advance google search from seeing the abstracts or finding the ePoster attachments; some talks had an attached graphic not listed anywhere.
This is about the lamest excuse for a scientific meeting I have ever come across, unless it be AGU 2013.https://agu.confex.com/data/handout/agu/fm14/Paper_28053_handout_1869_0.pdf
# Greenland # Saturated Crevasses along Shear Margins of Jakobshavn # A Ring # "temporal increase in lateral drag seems to indicate long-‐term stress loading of the shear margins as the ice stream response to down stream mass perturbaAons at the terminus. Differences in transects indicate that regions where water-‐filled crevasses are found the magnitude of lateral drag is less and the rate of drag increase is smaller than regions without water. Given this, preliminary results suggest that water-‐filled crevasses are weakening the shear margins and likely resulAng in enhanced stress loading in other parts of the shear margins that are devoid of water."https://agu.confex.com/data/handout/agu/fm14/Paper_10527_handout_506_0.pdf
# Greenland # Perched Ice Layers In Shallow Firn Inhibit Percolation And Enhance Runoff # MJ MacFerrin # "mapping: some regions have formed multi-annual ice layers several meters thick in the top 20 meters of firn. When such layers grow thick enough to be impermeable, they prevent water from percolating to depth and cause surface runof. thick refrozen ice layers in the top 20 meters of firn in Greenland’s lower accumulation zone. • When thick enough, these perched layers become impervious to further melt and quickly migrate the runoff line inland, even when pore space still exists below that could otherwise absorb water. If warming continues, these layers are expected to grow inland. Radar enables us to map and monitor these massive perched ice layershttps://agu.confex.com/data/handout/agu/fm14/Paper_24929_handout_1496_0.pdf
# Greenland # Firn and percolation in high elevation supra-glacial lakes # Peña Howat # "assessment of percolation in accumulation zone of western Greenland after the intense melt episodes of 2010 and 2012. Concentrations of ice has increased dramatically over the firn of the GIS, limiting the buffering capacity of the firn and facilitating meltwater transport and retention as ponds. The area covered by percolation features has expanded more than twice in 10 years, and melt intensity above 2000 m in 2012 was found to be an order of magnitude greater than at the end of the 20th Century... abrupt densification due to percolation processes a larger factor in altimetry–derived studies."https://agu.confex.com/data/handout/agu/fm14/Paper_8948_handout_2231_0.pdf
# Greenland # Disko Bay icebergs # J Scheick # "algorithm to delineate and extract quantitative information (location, geometry) about icebergs in optical satellite imagery. Future work will improve the cloud mask apply the algorithm to a long time series of Landsat images (1994-present), map changes in iceberg distributions with time (do export pathways remain constant or change depending on iceberg size?)"https://agu.confex.com/data/handout/agu/fm14/Paper_11555_handout_734_0.pdf
# Greenland # Rapid drainage of supraglacial lakes # S Adhikari # "Some Greenland Ice Sheet supraglacial lakes drain rapidly within the timescale of a few hours. The vertical discharge of water during these events may find a pre-existing film of water potentially within a system of linked cavities. Here, we present a model for subglacial flooding in these circumstances."https://agu.confex.com/data/handout/agu/fm14/Paper_17159_handout_1223_0.pdf
# Greenland # Snow/firn density distribution on Devon Ice Cap, Canadian Arctic from airborne radar reflectometry # A Rutishauser # "Scattering and reflectivity distributions demonstrate the potential of using RES data to characterize the near-surface snow/firn properties. We hypothesize that the scattering values indicate a pseudo dry snow zone above ~1800 m asl, and the transition between the SI and glacier ice zone at ~1300 m asl. From the reflectivity values, we estimate the winter snow pack thicknesses, showing highest snow accumulation (~70-120 cm) in the southeast sector of DIC. The derived RSR dataset might help understanding the complex nature of the internal layering pattern. Especially the distribution of refrozen ice lenses/layers might explain complex internal layers resulting from a distorted snow/firn deposition pattern."https://agu.confex.com/data/handout/agu/fm14/Paper_17824_handout_1269_0.pdf
# Greenland # High frequency seismic waves recorded by the greenland ice sheet monitoring network (glisn) during the drainage of a supraglacial lake # EJ Orantes # "Supraglacial lake drainage is a major source of subglacial water under the Greenland Ice Sheet, impacting the ice dynamics at different temporal and spatial scales. Previous studies have shown that fast drainage of a supraglacial lake can produce high frequency seismic waves that are detected by local seismometers; however, little work has been done on the regional detection of such waves. Here we present the results of a study focusing on seismic data and their potential linkage to the drainage of a supraglacial lake (Lake Ponting) in the Paakitsoq region of the West Greenland ice sheet. The corrected seismograms show similar waveforms for arrivals on a single line supporting the idea that each line represents a traveling wave. The velocities derived from the trendlines are too low for the waves to be traveling through either the rock or the solid ice. Our current hypothesis is that they are traveling in a low-velocity channel of till underneath the ice. This would be consistent with the low attenuation required for the propagation of high frequency energy over regional distances."https://agu.confex.com/data/handout/agu/fm14/Paper_19489_handout_1454_0.pdf
# Greenland # Modeling of subaqueous melting in Petermann fjord, northwestern Greenland using an ocean general circulation model # C Cai # "Petermann Glacier drains approximate 6.1% (73,927k m2 of total 1,209,280 km2) of Greenland Ice Sheet. Basal melting of the floating tongue of Petermann Glacier is by far the largest process of mass ablation. Melting of the floating tongue is controlled by the buoyancy of the melt water plume, the pressure dependence of the melting point of sea ice, and the mixing of warm subsurface water with fresh buoyant subglacial discharge. In prior simulations of this melting process, the role of subglacial discharge has been neglected because in the Antarctic surface runoff is negligible; this is however not true in Greenland. In this work, we simulate the melting process of the ice shelf by MITgcm) at high resolution including outflow. We use varying oceanic thermal forcing and new bathymetry from Operation IceBridge.
The shape of the ice shelf cavity influences the ice shelf melt rate, especially in summer. ith the OIB-derived bathymetry, the melt rate is 34% higher in summer compared to winter. Between the 1990s and the 2010s, runoff increased by 20% and ice shelf melting should have increased by 16%. Between the 1990s and the 2010s, ocean temperature warmed by 0.5-0.9 C, the melt rate should have increased by 7%~20% . Taken together, these numbers may explain the recent break up of Petermann ice tongue, which is indicative of ice thinning. We will pursue this work in 3-D to include the assymetry in the bathymetry of Petermann Fjord.
# Greenland # Predicting the stability of ice sheets with crevasses: a numerical experiment # Y Ma # "Iceberg calving accounts for ~50% of the mass lost from the Greenland Ice Sheet. Increased calving rates can lead to rapid sea level rise. Calving is not well parameterized in numerical ice sheet models. Water plays a negative role in the growth of crevasses and thus calving events, by both creating a more negative largest principle stress field and slowing down both the thinning process and flow speed of the glacier. The depth of a crevasse is inversly related to water depth but calving rate can be directly related to flow speed. The same buttressing effect applies to ice shelves, melange, etc. When water is absent, surface crevasses may reach the bed."https://agu.confex.com/data/handout/agu/fm14/Paper_24717_handout_1434_0.pdf
# Greenland # Improving estimates of cloud radiative forcing over Greenland # W Wang # "Larger uncertainty in SW, especially in Shelf and Coastal areas. Positive (warm the surface). Negative (cool the surface): Shelf Average total forcing over both Inland: ~28 W/m2 ≈ 0.89 m snowmelt (liquid water) from May to Aug Low Clouds: liquid-only clouds High Clouds: mixed and ice clouds. Surface Ratidation Fluxes > Cloud Radiative Forcing because CRF bias is partially reduced when clear-sky fluxes are removed from the all-sky fluxes. No dataset is outstanding in all fluxes: CERES does a fairly good job in CRF. In Inland areas (warming area), low clouds warm the surface better than high clouds."https://agu.confex.com/data/handout/agu/fm14/Paper_26038_handout_952_0.pdf
# Greenland # Thermo-mechanically coupled modeling of high elevation regions of the Greenland Ice Sheet # A Sommers # "Thermo-mechanical simulations were conducted on 54 flowlines in western and southeastern Greenland (shown on map) from the main divide past the 2,000 m elevation PARCA stake location. The mean absolute velocity difference between modeled and observed surface velocity at each PARCA stake is 21 m/a. Geothermal heat flux To examine the sensitivity of model results to the magnitude of prescribed geothermal heat flux, simulations were conducted with the geothermal heat flux increased or decreased. Surface velocity decreases in cases with lower geothermal heat flux (colder ice, lower viscosity). Quite surprisingly, surface velocity also decreases as the geothermal heat flux is increased for stake locations with temperate bed. The driving mechanism for this behavior may be that when the viscosity very near the bed is decreased, higher advection rates of cold ice from upstream result, producing colder temperatures and thus smaller velocity gradients in the slightly higher locations in the ice column. Bedrock elevation To examine the influence of uncertainty in bedrock elevation, the prescribed data (Bamber et al., 2013) were perturbed by adding Gaussian white noise (with standard deviation of 125 m) and smoothing using a moving average function to generate ‘similar but different’ bed profiles. Importance of thermo-mechanical coupling A substantial underestimation of surface velocities results from isothermal calculations (assuming ice temperature -5°C) with no enhancement to the flow law parameter for Wisconsin ice. The isothermal model tends to overpredict surface velocity when the enhancement factor is included."https://agu.confex.com/agu/fm14/meetingapp.cgi#Paper/21416
# Greenland # Isochronal Ice Sheet Model: a new approach to tracer transport by explicitly tracing accumulation layers # A Born # "The long, high-resolution and largely undisturbed depositional record of polar ice sheets is one of the greatest resources in paleoclimate research. The vertical profile of isotopic and other geochemical tracers provides a full history of depositional and dynamical variations. Numerical simulations of this archive could afford great advances both in the interpretation of these tracers as well as to help improve ice sheet models themselves, as show successful implementations in oceanography and atmospheric dynamics. However, due to the slow advection velocities, tracer modeling in ice sheets is particularly prone to numerical diffusion, thwarting efforts that employ straightforward solutions. Previous attemps to circumvent this issue follow conceptually and computationally extensive approaches that augment traditional Eulerian models of ice flow with a semi-Lagrangian tracer scheme. Here, we propose a new vertical discretization for ice sheet models that eliminates numerical diffusion entirely. Vertical motion through the model mesh is avoided by mimicking the real-world ice flow as a thinning of underlying layers (see figure). A new layer is added to the surface at equidistant time intervals (isochronally). Therefore, each layer is uniquely identified with an age. Horizontal motion follows the shallow ice approximation using an implicit numerical scheme. Vertical diffusion of heat which is physically desirable is also solved implicitly. A simulation of a two-dimensional section through the Greenland ice sheet will be discussed."