Polar Data Centre, Natural Environment Research Council, UK
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Borehole density profiles reconstructed from calibrated optical televiewer (OPTV) logs from the northern sector of Larsen C Ice Shelf, Antarctica
These are vertical density profiles of snow, firn and ice reconstructed from the vertical luminosity trace of 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. The associated borehole OPTV logs and temperature profiles are also available, as are other MIDAS datasets.
The data consists of 30 minute observations recorded by an automatic weather station (iWS 18) in Cabinet Inlet on Larsen C Ice Shelf on the Antarctic Peninsula. The iWS consists of a custom-built weather station unit, assembled at the Institute of Marine and Atmospheric research Utrecht (IMAU). There are sensors for air temperature, surface air pressure, relative humidity, as well as a gps, an acoustic snow height sensor, an ARGOS communication antenna, and three Lithium batteries that fuel the unit when solar radiation is absent. The unit is complemented by a propeller-vane Young anemometer measuring wind direction and speed. Additionally, all radiation fluxes are measured with a Kipp and Zonen CNR4 radiometer. This dataset runs from November 2014 to January 2017. Funded was provided by the NERC grant NE/L005409/1. ***** PLEASE BE ADVISED TO USE VERSION 2.0 DATA ***** The VERSION 2.0 data set (see ''Related Data Set Metadata'' link below) has an additional 10 months of measurements.
Timeseries from GPS units deployed on ice streams and the adjoining ice shelf across the Filchner-Ronne region, Antarctica, 2005-2016
This is a collection of GPS data from dual-frequency GPS units deployed on the Filchner-Ronne Ice Shelf and adjoining ice streams. Filenames contain ice stream code and, in some cases, where the ice stream code is followed by a plus or minus sign, the approximate distance in kilometres upstream from the ice stream''s grounding line, although in other cases the number is arbitrary. The naming convention has been preserved for legacy reasons. The ice streams are Evans (E & XX), Rutford (R), Institute (IIS), Talutis (T & TT) and Foundation (H) ice streams. Each GPS unit''s data are given in a netCDF4_classic file containing 4 columns: "Date number", as the number of days from January 0, 0000 in the proleptic ISO calendar; "Latitude" & "Longitude", both in decimal degrees in the WGS 1984 EPSG:4326 co-ordinate system; "height", in metres above the reference ellipsoid. The data have been collated from daily files, processed using the Bernese 5.0 software, using precise point positioning at intervals of 30 seconds. Note that data have not been corrected for inverse barometer or ocean tide loading effects. These data were collected as part of a systemic campaign to look for modulation in ice flow through ocean tidal forcing. The vertical tidal motion of floating ice shelves generates stresses which cause a change in horizontal ice velocity at periods of hours to years. These signals can travel far upstream of ice stream grounding lines and often exhibit a change in frequency from the astronomical tides that generate them. As such, they can act as a natural experiment with which we can learn about ice rheology and subglacial processes.
Stable isotope data and snow accumulation from the Dyer Plateau ice core, drilled 1989-90, Palmer Land, Antarctic Peninsula
A record of the oxygen-isotope ratios and net accumulation from an ice core drilled on Dyer Plateau in the Antarctic Peninsula is presented. This 233 m long ice core was drilled in the southern summer season of 1989/90. The isotope data covers the years 1505 to 1988. The snow accumulation data covers 1840 to 1988.
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.
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 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 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.
Output of 3D model simulating externally driven ULF waves in Earth's magnetosphere, including the effect of convection on plasmaspheric density
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.
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.