From May 2009 to May 2013, seven dual-frequency GPS receivers were deployed along a 120 km-long transect in the south-west of the Greenland Ice Sheet. Two additional dual-frequency GPS receivers were deployed perpendicular to longitudinal ice flow at ~14 km inland: one 5 km distant from June 2011 to May 2013, and another 2.5 km distance from May 2012 to May 2013. Each receiver recorded position observations every 10 seconds or 30 seconds (depending on configuration), enabling resolution of horizontal and vertical ice motion. Sites were powered by solar panels and operated 24 hours a day during summer but shut down in the autumn. Absolute ice displacements at each site were obtained for each summer and winter period in the absence of continuous measurements. Position measurements were kinematically corrected relative to an off-ice base station using TRACK (Chen, 1999). Daily velocities were then obtained by differencing across 24-hour periods, whilst continuous velocities were obtained through application of a sliding 6-hour differencing window. At each GPS site we also measured (1) the near-surface air temperature every 15 minutes year-round, (2) net seasonal ablation using ablation stakes, and (3) at several selected sites melt rates using sonic ranging sensors. This version 2 of the dataset updates the previously 2-day temporal resolution of the ice motion records to 1-day resolution. In other respects the dataset has not changed. Funded by NERC, the Carnegie Trust for the Universities of Scotland and The University of Edinburgh. Relevant grants: NE/F021399/1, NE/H024964/1 Studentships: NE/I52830X/1, NE/J500021/1, NE/H526794/1
This gridded dataset provides geometry (ice thickness and bedrock topography) covering the Pine Island Glacier catchment. It has been created using the principle of mass conservation, given observed fields of velocity, surface elevation change and surface mass balance, together with sparse ice thickness data measured along airborne radar flight-lines. Previous ice flow modelling studies show that gridded geometry products that use traditional interpolation techniques (e.g. Bedmap2) can result in a spurious thickening tendency near the grounding line of Pine Island Glacier. Removing the cause of this thickening signal, in order to more accurately model ice flow dynamics, has been the motivation for creating a new geometry that is consistent with the conservation of mass. This data was funded by a PhD project within the iSTAR-C programme (with NERC grant reference NE/J005738/1).
This dataset documents the trends and variability in the latitude and strength of the belt of lower-atmosphere westerly winds over the Southern Ocean, referred to as the ''westerly jet''. Time series of annual mean and seasonal diagnostics are available for the period 1979-present, specifically time series of seasonal and annual mean jet latitude and strength. The diagnostics are derived from the European Centre for Medium Range Weather Forecasts (ECMWF) ERA-Interim reanalysis (for more information see www.ecmwf.int and Dee et al. (2011)), which is an observationally-constrained reconstruction of atmospheric conditions. The broad characterisation of the westerly winds into these simple diagnostics has been found to be useful for understanding long-term climate change due to contrasting drivers of change and impacts on other aspects of the climate system. This is an index of winds around the full circumference of all longitudes at Southern Hemisphere middle latitudes. The exact latitude depends on the position of the jet at any given time, but on average the jet (the core of the westerlies) is located at approximately 52 deg S.
This dataset contains measurements of snow accumulation over an 11-month period in 2016 at six sites in the Pine Island-Thwaites Glacier catchment of West Antarctica. The sites were visited on two occasions, the first in January 2016 and the second in December 2016. The accumulation rate at each site was calculated using an average density profile, based on a compilation of six low elevation sites on Pine Island Glacier (iSTAR sites 15-19, and 22; Morris et al., 2017) that are situated nearby. The average density for the top metre based on this compilation is 419 kg m-3. Further details are provided in the associated publication.
This data set contains the ULF wave model output data required to produce the figures in the article: A. W. Degeling, I. J. Rae, C. E. J. Watt, Q. Q. Shi, R. Rankin and Q. G. Zong, "Control of ULF Wave Accessibility to the Inner Magnetosphere by the Convection of Plasma Density", J. Geophys. Res. (accepted Dec. 2017) doi:10.1002/2017JA024874 The dataset has a Matlab binary file format. It consists of a structure array "d" (with 325 elements). These elements correspond to the 2D parameter scan in driver frequency and elapsed time during plume development performed for this study. The elapsed time parameter has 25 elements, ranging 0 to 24 hours (i.e. 1 hour spacing), and the driver frequency parameter has 13 elements ranging from 1 to 7 mHz (with 0.5 mHz spacing). e.g. use "d = reshape(d,25,13);" to reshape the structure array into 2D with columns for the frequency scan and rows for the elapsed time scan. The Matlab function "make_PDP_figs.m" is used to read the data, perform the necessary post-processing operations and output the article figures. To produce all six figures, simply run the file without any input arguments.
The datasets are temperature time series from strings of thermistors, each located at a discrete depth within one of six boreholes drilled to a depth of ~100 m in the northern sector of Larsen C Ice Shelf, Antarctica. Supporting borehole information is presented by Ashmore and others (2017). These data are part of the NERC-funded MIDAS (''Impact of surface melt and ponding on ice shelf dynamics and stability'') research project, with grant references NE/L006707/1 and NE/L005409/1. Associated (near-surface) borehole temperature records, OPTV logs and density records are also available, as are other MIDAS datasets.
These are digital optical televiewer (OPTV) logs of five boreholes drilled by hot water to ~100 m depth in Larsen C Ice Shelf, Antarctica. Boreholes were drilled in austral summers of 2014 and 2015 in order to investigate the internal properties of the ice shelf, and specifically the influence of surface melting and melt pond formation on those properties. These data are part of the NERC-funded MIDAS (''Impact of surface melt and ponding on ice shelf dynamics and stability'') research project, with grant references NE/L006707/1 and NE/L005409/1. Borehole density and temperature profiles are also available, as are other MIDAS datasets.
These two files (.csv) provide independent methods of quantifying subglacial roughness in Greenland, both calculated from radio-echo sounding (or ice penetrating radar) data collected by the Operation Ice Bridge programme using CReSIS instrumentation. They are an output of the Basal Properties of Greenland (BPOG) project (http://bpog.blogs.ilrt.org/), with funding from NERC grant NE/M000869/1. Roughness here, and in the wider literature, is defined as the variation in bed elevation (in the vertical) at the ice-bed interface, over a given length-scale. These two metrics calculate/quantify this variation in different ways: one shows topographic-scale roughness, calculated from the variation in along-track topography (bed elevation measurements derived from the radar pulse); and the other shows scattering-derived roughness, calculated from quantifying characteristics of each bed-echo (the return from the radar pulse at the ice-bed interface).
This dataset represents model output from 4 simulations of Store Glacier produced using the Elmer/Ice glacier model equipped with novel 3D calving subroutines. As described in the paper associated with this dataset (Todd et al., JGR, 2018), the model is initialised with velocity observations and then forced with present day environmental forcing. The simulation covers a 5 year time period with no fixed dates. Funding was provided by the NERC grant NE/K500884/1.
The data are from a proof-of-concept study to assess the feasibility of accurately measuring ozone (O3) and hydroxyl (OH) profiles from the ground using accessible satellite TV receiver technology. The datasets include a synthesis of atmospheric model and a priori atmospheric datasets for selected polar locations, atmospheric transmittance spectra calculated for those locations, and O3 and OH profile retrieval results.