Lora Koenig

• PhD Geophysics
• Researcher at University of Colorado Boulder

perennial storage of water in a firn aquifer was discovered in southeast Greenland in 2011. We present the first in situ measurements of the aquifer, including densities and temperatures. Water was present at depths between ~12 and 37 m and amounted to 18.7 ± 0.9 kg in the extracted core. The water filled the firn to capacity at ~35 m. Measurements...

Current trends show a rise in Arctic surface and air temperatures, including over the Greenland ice sheet where rising temperatures will contribute to increased sea-level rise through increased melt. We aim to establish the uncertainties in using satellite-derived surface temperature for measuring Arctic surface temperature, as satellite data are i...

A focus group’s executive committee asks whether the number of accolades given to women reflects the demographics of scientists within the field, from students to senior researchers.

Increased surface melt over the Greenland Ice Sheet (GrIS) is now estimated to account for half or more of the ice sheet's total mass loss. Here, we show that some meltwater is stored, over winter, in buried supraglacial lakes. We use airborne radar from Operation IceBridge between 2009 and 2012 to detect buried supraglacial lakes, and we find that...

We present measurements of the density, hydraulic conductivity, and specific discharge of a widespread firn aquifer in Antarctica, within the Wilkins Ice Shelf. At the field site, the aquifer is 16.2 m thick, starting at 13.4 m from the snow surface and transitioning from water-saturated firn to ice at 29.6 m. Hydraulic conductivity derived from sl...

Plain Language Summary The density of snow (and firn–high‐density compacted snow) on the Greenland ice sheet is an important parameter because it is used to convert changes in ice sheet thickness measured from satellite and airborne instruments into changes in mass, which is key to estimating the ice sheet contribution to sea level change. The simu...

We apply the Magnetic Resonance Sounding (MRS) method to investigate a firn aquifer in the southeast region of the Greenland ice sheet. Our study aims to delineate and estimate the volume of recently discovered water stored within the firn (compacted snow) that remains liquid throughout the year. We develop and test successfully a methodology for j...

The surface snow density of glaciers and ice sheets is of fundamental importance in converting volume to mass in both altimetry and surface mass balance studies, yet it is often poorly constrained. Site-specific surface snow densities are typically derived from empirical relations based on temperature and wind speed. These parameterizations commonl...

Recent observations of the Greenland ice sheet show an increase of the area affected by progressive melt of snow and ice, thus resulting in production of the additional meltwater. In 2011, an important storage of meltwater in the firn has been observed in the S-E Greenland. This water does not freeze during the wintertime and forms a perennial firn...

Within the lower percolation zone of the southeastern Greenland ice sheet, meltwater has accumulated within the firn pore space, forming extensive firn aquifers. Previously it was unclear if these aquifers stored or facilitated meltwater runoff. Following mixing of a saline solution into boreholes within the aquifer, we observe that specific conduc...

Some regions of the Greenland ice sheet, where snow accumulation and melt rates are high, currently retain substantial volumes of liquid water within the firn pore space throughout the year. These firn aquifers, found between ~10 and 30 m below the snow surface, may significantly affect sea level rise by storing or draining surface meltwater. The h...

In spring of 2011, a perennial storage of water was observed in the firn of the southeastern Greenland Ice Sheet (GrIS), a region of both high snow accumulation and high melt. This aquifer is created through percolation of surface meltwater downward through the firn, saturating the pore space above the ice-firn transition. The aquifer may play a si...

Runoff has recently become the main source of mass loss from the Greenland Ice Sheet and is an important contributor to global sea level rise. Linking runoff to surface meltwater production is complex, as meltwater can be retained within the firn by refreezing or perennial liquid water storage. To constrain these uncertainties, the outputs of two o...

We document the existence of widespread firn aquifers in an elevation range of ~1200-2000 m, in the high snow-accumulation regions of the Greenland ice sheet. We use NASA Operation IceBridge (OIB) accumulation radar data from five campaigns (2010-2014) to estimate a firn-aquifer total extent of 21,900 km2. We investigate two locations in Southeast...

Contemporary climate warming over the Arctic is accelerating mass loss from the Greenland Ice Sheet through increasing surface melt, emphasizing the need to closely monitor its surface mass balance in order to improve sea-level rise predictions. Snow accumulation is the largest component of the ice sheet's surface mass balance, but in situ observat...

For the Greenland Ice Sheet (GrIS), large-scale melt area has increased in recent years and is detectable via remote sensing, but its relation to runoff is not known. Historical, modeled melt area and runoff from Modern-Era Retrospective Analysis for Research and Applications (MERRA-Replay), the Interim Re-Analysis of the European Centre for Medium...

Contemporary climate warming over the Arctic is accelerating mass loss from the Greenland Ice Sheet (GrIS) through increasing surface melt, emphasizing the need to closely monitor surface mass balance (SMB) in order to improve sea-level rise predictions. Here, we quantify accumulation rates, the largest component of GrIS SMB, at a higher spatial re...

Surface snow accumulation over East Antarctica is an important climate indicator but a difficult parameter to constrain. Surface mass ablation prevails over persistent wind-scour zones as the near-surface katabatic winds accelerate over steep ice surface topography, sublimate and redistribute snow. Here we quantify ablation rates and downwind redep...

Surface albedo is a key variable controlling solar radiation absorbed at the Greenland Ice Sheet (GrIS) surface and, thus, meltwater production. Recent decline in surface albedo over the GrIS has been linked to enhanced snow grain metamorphic rates, earlier snowmelt, and amplified melt–albedo feedback from atmospheric warming. However, the importan...

The mean, trend and variability of net snow accumulation in firn cores are often used to validate model output, develop remote-sensing algorithms and quantify ice-sheet surface mass balance. Thus, accurately defining uncertainties associated with these in situ measurements is critical. In this study, we apply statistical simulation methods to quant...

Snow accumulation over an ice sheet is the sole mass input, making it a primary measurement for understanding the past, present, and future mass balance. Near-surface frequency-modulated continuous-wave (FMCW) radars image isochronous firn layers recording accumulation histories. The Semiautomated Multilayer Picking Algorithm (SAMPA) was designed a...

Earth's sea level fluctuations are predominantly determined by the amount of ice contained in the Antarctica and Greenland ice sheets. Spaceborne active and passive microwave remote sensing have received the most attention, due to their responsiveness from snow and firn properties related to accumulation rates, and their ability to operate independ...

Passive and active observations at L band (frequency ~1.4 GHz) from the Aquarius/SAC-D mission offer new capabilities to study the polar regions. Due to the lack of polar-gridded products, however, applications over the cryosphere have been limited. We present three weekly polar-gridded products of Aquarius data to improve our understanding of L-ba...

Following the development and availability of Aquarius weekly polar-gridded products, this study presents the spatial and temporal radiometer and scatterometer observations at L band (frequency ~1.4 GHz) over the cryosphere including the Greenland and Antarctic ice sheets, sea ice in both hemispheres, and over sub-Arctic land for monitoring the soi...

Mass loss from the Greenland ice sheet contributes significantly to present sea level rise. High meltwater runoff is responsible for half of Greenland's mass loss. Surface melt has been spreading and intensifying in Greenland, with the highest ever surface area melt and runoff recorded in 2012. However, how surface melt water reaches the ocean, and...

moderate-resolution imaging spectroradiometer (MODIS) ice-surface temperature (IST) of the Greenland ice sheet shows a positive trend and two major melt events from 2000 to present. IST increased by ~0.55 ± 0.44°C/decade, with the greatest increase (~0.95 ± 0.44°C/decade) found in northwestern Greenland where coastal temperatures and mass loss are...

Observations of snow accumulation rates from five new firn cores show a negative trend that is statistically significant over the past several decades across the central West Antarctic ice sheet (WAIS). A negative temporal trend in accumulation rates is unexpected in light of rising surface temperatures as well as model simulations predicting highe...

Surface mass balance (SMB) over ice sheets and snow on sea ice (SOSI) are important components of the cryosphere. Large knowledge gaps remain in scientists’ abilities to monitor SMB and SOSI, including insufficient measurements and difficulties with satellite retrievals. On ice sheets, snow accumulation is the sole mass gain to SMB, and meltwater r...

The detection of leads, or cracks, in sea ice is critical for the derivation of sea-ice freeboard from altimetric measurements of sea-ice elevation. We present an approach for lead detection in sea ice using high-resolution visible imagery from airborne platforms. We develop a new algorithm, i.e., the sea-ice lead detection algorithm using minimal...

1] Glacierized change in the Himalayas affects river-discharge, hydro-energy and agricultural production, and Glacial Lake Outburst Flood potential, but its quantification and extent of impacts remains highly uncertain. Here we present conservative, comprehensive and quantitative pre-dictions for glacier area and meltwater flux changes in Bhutan, m...

The authors have developed a climate-quality data record of the clear-sky surface temperature of the Greenland Ice Sheet using the Moderate-Resolution Imaging Spectroradiometer (MODIS) ice-surface temperature (IST) algorithm. Daily and monthly quality-controlled MODIS ISTs of the Greenland Ice Sheet beginning on 1 March 2000 and continuing through...

Five snowpit and shallow (less than 20 m) firn cores were collected along a transect across the West Antarctic Ice Sheet (WAIS) divide. Sub-annually resolved accumulation-rate records were developed by combining density, isotope and electrical conductivity datasets from each location. These new records overlap with and extend previous records in th...

Enhanced melting of the Greenland Ice Sheet has been documented in recent literature along with surface-temperature increases measured using infrared satellite data since 1981. Using a recently-developed climate-quality data record, 11- and 12-year trends in the clear-sky ice-surface temperature (IST) of the Greenland Ice Sheet have been studied us...

Regional patterns in glacier changes are often cited as evidence of patterns in climate change. However, the response of a glacier to climate change is intimately tied to that glacier's sensitivity to the imposed changes. Therefore, regional patterns in glacier sensitivity will give rise to regional patterns in glacier response, even in the absence...

A liquid water layer was discovered below the surface of the southeast Greenland ice sheet at depths of 10 and 25 m. The melt layer was observed 30 April, 2011, prior to any seasonal melting. The discovery was made during firn core drilling to measure snow accumulation rates. The extent and depth is mapped with surface-based radar and from NASA Ope...

Sea ice observations from the suite of airborne instruments aboard the Operation IceBridge mission are currently being utilized to provide a unique look at the state of the Arctic and Antarctic sea ice covers. Presently, work on the production and validation of freeboard, snow depth, and sea ice thickness data products is being done with the goal o...

In 2009, the NASA satellite laser altimeter mission ICESat (Ice, Cloud and Land Elevation Satellite), which was launched in 2003, ceased to operate. To bridge the gap in polar laser observations between ICESat and its replacement ICESat-2, which is not scheduled for launch until 2015, Operation IceBridge, a six-year NASA airborne mission, was initi...

In October 2009, NASA's Ice, Cloud, and land Elevation Satellite (ICESat) stopped collecting science data. However, noting the progressive degradation of ICESat's Geoscience Laser Altimeter System (GLAS), NASA had begun the previous year to plan a series of instrumented aircraft missions to fill the impending gap in satellite observations due to th...

Operation IceBridge, a six-year NASA mission, is the largest airborne survey of Earth's polar ice ever flown. Data collected during IceBridge will help scientists bridge the gap in polar observations between NASA's Ice, Cloud and Land Elevation Satellite (ICESat), in orbit from 2003 to 2009, and ICESat-2, planned for launch in late 2015, making Ice...

During the Boreal winter of 2008-09 snow surface and air temperature were measured at Summit, Greenland using small (~1.5 cm), easily deployable thermochron sensors. Thermochron temperatures had an accuracy of ±0.3 °C and were on average within 0.1 °C of an adjacent NOAA instrument. Snow surface temperatures were measured, by thermochrons, at two l...

The relationship between time series of physical surface temperature and microwave brightness temperature of polar firn depends both on the physical properties of the firn and the surface temperature history. In perennially dry firn this relationship is well characterized by a timescale, referred to as the extinction-diffusion time, which is the ra...

This research investigates the utility of passive microwave remote sensing instruments to accurately determine snow water equivalent (SWE) over large spatial extents. Three existing Special Sensor Microwave Imager (SSM/I) snow water equivalent algorithms produced by Chang, Tait and Goodison were evaluated for their ability to determine snow water e...

A method is presented for calculating longitudinal glacier strain rates directly from the wrapped phase of an interferometric synthetic aperture radar (InSAR) interferogram assuming the ice flow path is known. This technique enables strain rates to be calculated for scenes lacking any velocity control points or areas within a scene where the phase...