scholarly journals Airborne-radar and ice-core observations of annual snow accumulation over Thwaites Glacier, West Antarctica confirm the spatiotemporal variability of global and regional atmospheric models

2013 ◽  
Vol 40 (14) ◽  
pp. 3649-3654 ◽  
Author(s):  
B. Medley ◽  
I. Joughin ◽  
S. B. Das ◽  
E. J. Steig ◽  
H. Conway ◽  
...  
Keyword(s):  
Ice Core ◽  
Snow Accumulation ◽  
Spatiotemporal Variability ◽  
Airborne Radar ◽  
West Antarctica ◽  
Atmospheric Models

scholarly journals A 2700-year annual timescale and accumulation history for an ice core from Roosevelt Island, West Antarctica

2017 ◽  
Author(s):  
Mai Winstrup ◽  
Paul Vallelonga ◽  
Helle A. Kjær ◽  
Tyler J. Fudge ◽  
James E. Lee ◽  
...  
Keyword(s):  
Accumulation Rate ◽  
Ice Core ◽  
Early Period ◽  
Volcanic Eruptions ◽  
Snow Accumulation ◽  
Atmospheric Methane ◽  
Accumulation Rates ◽  
West Antarctica ◽  
Ross Ice Shelf ◽  
Accumulation History

Abstract. We present a 2700-year annually resolved timescale for the Roosevelt Island Climate Evolution (RICE) ice core, and reconstruct a past snow accumulation history for the coastal sector of the Ross Ice Shelf in West Antarctica. The timescale was constructed by identifying annual layers in multiple ice-core impurity records, employing both manual and automated counting approaches, and constitutes the top part of the Roosevelt Island Ice Core Chronology 2017 (RICE17). The maritime setting of Roosevelt Island results in high sulfate influx from sea salts and marine biogenic emissions, which prohibits a routine detection of volcanic eruptions in the ice-core records. This led to the use of non-traditional chronological techniques for validating the timescale: RICE was synchronized to the WAIS Divide ice core, on the WD2014 timescale, using volcanic attribution based on direct measurements of ice-core acidity, as well as records of globally-synchronous, centennial-scale variability in atmospheric methane concentrations. The RICE accumulation history suggests stable values of 0.25 m water equivalent (w.e.) per year until around 1260 CE. Uncertainties in the correction for ice flow thinning of annual layers with depth do not allow a firm conclusion about long-term trends in accumulation rates during this early period but from 1260 CE to the present, accumulation rate trends have been consistently negative. The decrease in accumulation rates has been increasingly rapid over the last centuries, with the decrease since 1950 CE being more than 7 times greater than the average over the last 300 years. The current accumulation rate of 0.22 ± 0.06 m w.e. yr−1 (average since 1950 CE, ±1σ) is 1.49 standard deviations (86th percentile) below the mean of 50-year average accumulation rates observed over the last 2700 years.

scholarly journals A low-cost autonomous rover for polar science

2019 ◽  
Author(s):  
Andrew O. Hoffman ◽  
Hans Christian Steen-Larsen ◽  
Knut Christianson ◽  
Christine Hvidberg
Keyword(s):  
Modular Design ◽  
Low Cost ◽  
Digital Elevation Models ◽  
Ice Core ◽  
Snow Accumulation ◽  
Spatiotemporal Variability ◽  
Dual Frequency ◽  
Ice Stream ◽  
Digital Elevation ◽  
Software Instrumentation

Abstract. We present the developmental considerations, design, and deployment of an autonomous modular terrestrial rover for ice-sheet exploration that is inexpensive, easy to construct, and allows for instrumentation customization. Total construction cost for this rover is less than $3000, approximately one tenth the cost of existing platforms, and it can be built using facilities frequently available at academic institutions (machine shop, 3D printer, open-source hardware and software). Instrumentation deployed on this rover can be customized; the rover presented in this study was equipped with a dual-frequency GPS receiver and a digital SLR camera for constructing digital elevation models using structure-from motion (SfM) photogrammetry. We deployed this prototype rover on the Northeast Greenland Ice Stream to map local variations in snow accumulation and surface topography. The rover conducted four autonomous missions based out of the East Greenland Ice Core Project (EGRIP) camp during July 2017, measuring surface elevation transects across the hazardous ice-stream shear margins. During these missions, the rover proved capable of driving over 20 km on a single charge with a drawbar pull of 25°N, sufficient to tow commercial ground-penetrating radars. The rover also acquired photographs that were subsequently used to construct digital elevation models of a site monitored for spatiotemporal variability in snow accumulation, demonstrating adequate stability for high-resolution imaging applications. Due to its low cost, low-power requirements, and simple modular design, mass deployments of this rover design are practicable. Furthermore, operation of the rover in hazardous areas circumvents substantial expense and risk to personnel associated with conventional, crewed deployments. Thus, this rover is an investigatory platform that enables direct exploration of polar environments considered too hazardous for conventional field expeditions.

scholarly journals The Ross Sea Dipole – temperature, snow accumulation and sea ice variability in the Ross Sea region, Antarctica, over the past 2700 years

2018 ◽  
Vol 14 (2) ◽  
pp. 193-214 ◽  
Author(s):  
Nancy A. N. Bertler ◽  
Howard Conway ◽  
Dorthe Dahl-Jensen ◽  
Daniel B. Emanuelsson ◽  
Mai Winstrup ◽  
...  
Keyword(s):  
Sea Ice ◽  
Ross Sea ◽  
Ice Core ◽  
Ice Cores ◽  
Snow Accumulation ◽  
Ice Age ◽  
West Antarctica ◽  
Isotopic Enrichment ◽  
The Past ◽  
Western Ross Sea

Abstract. High-resolution, well-dated climate archives provide an opportunity to investigate the dynamic interactions of climate patterns relevant for future projections. Here, we present data from a new, annually dated ice core record from the eastern Ross Sea, named the Roosevelt Island Climate Evolution (RICE) ice core. Comparison of this record with climate reanalysis data for the 1979–2012 interval shows that RICE reliably captures temperature and snow precipitation variability in the region. Trends over the past 2700 years in RICE are shown to be distinct from those in West Antarctica and the western Ross Sea captured by other ice cores. For most of this interval, the eastern Ross Sea was warming (or showing isotopic enrichment for other reasons), with increased snow accumulation and perhaps decreased sea ice concentration. However, West Antarctica cooled and the western Ross Sea showed no significant isotope temperature trend. This pattern here is referred to as the Ross Sea Dipole. Notably, during the Little Ice Age, West Antarctica and the western Ross Sea experienced colder than average temperatures, while the eastern Ross Sea underwent a period of warming or increased isotopic enrichment. From the 17th century onwards, this dipole relationship changed. All three regions show current warming, with snow accumulation declining in West Antarctica and the eastern Ross Sea but increasing in the western Ross Sea. We interpret this pattern as reflecting an increase in sea ice in the eastern Ross Sea with perhaps the establishment of a modern Roosevelt Island polynya as a local moisture source for RICE.

scholarly journals A 2700-year annual timescale and accumulation history for an ice core from Roosevelt Island, West Antarctica

2019 ◽  
Vol 15 (2) ◽  
pp. 751-779 ◽  
Author(s):  
Mai Winstrup ◽  
Paul Vallelonga ◽  
Helle A. Kjær ◽  
Tyler J. Fudge ◽  
James E. Lee ◽  
...  
Keyword(s):  
Sea Ice ◽  
Accumulation Rate ◽  
Ice Core ◽  
Snow Accumulation ◽  
Accumulation Rates ◽  
West Antarctica ◽  
Sea Ice Extent ◽  
Amundsen Sea ◽  
The Core ◽  
Accumulation History

Abstract. We present a 2700-year annually resolved chronology and snow accumulation history for the Roosevelt Island Climate Evolution (RICE) ice core, Ross Ice Shelf, West Antarctica. The core adds information on past accumulation changes in an otherwise poorly constrained sector of Antarctica. The timescale was constructed by identifying annual cycles in high-resolution impurity records, and it constitutes the top part of the Roosevelt Island Ice Core Chronology 2017 (RICE17). Validation by volcanic and methane matching to the WD2014 chronology from the WAIS Divide ice core shows that the two timescales are in excellent agreement. In a companion paper, gas matching to WAIS Divide is used to extend the timescale for the deeper part of the core in which annual layers cannot be identified. Based on the annually resolved timescale, we produced a record of past snow accumulation at Roosevelt Island. The accumulation history shows that Roosevelt Island experienced slightly increasing accumulation rates between 700 BCE and 1300 CE, with an average accumulation of 0.25±0.02 m water equivalent (w.e.) per year. Since 1300 CE, trends in the accumulation rate have been consistently negative, with an acceleration in the rate of decline after the mid-17th century. The current accumulation rate at Roosevelt Island is 0.210±0.002 m w.e. yr−1 (average since 1965 CE, ±2σ), and it is rapidly declining with a trend corresponding to 0.8 mm yr−2. The decline observed since the mid-1960s is 8 times faster than the long-term decreasing trend taking place over the previous centuries, with decadal mean accumulation rates consistently being below average. Previous research has shown a strong link between Roosevelt Island accumulation rates and the location and intensity of the Amundsen Sea Low, which has a significant impact on regional sea-ice extent. The decrease in accumulation rates at Roosevelt Island may therefore be explained in terms of a recent strengthening of the ASL and the expansion of sea ice in the eastern Ross Sea. The start of the rapid decrease in RICE accumulation rates observed in 1965 CE may thus mark the onset of significant increases in regional sea-ice extent.

scholarly journals A low-cost autonomous rover for polar science

2019 ◽  
Vol 8 (1) ◽  
pp. 149-159 ◽  
Author(s):  
Andrew O. Hoffman ◽  
Hans Christian Steen-Larsen ◽  
Knut Christianson ◽  
Christine Hvidberg
Keyword(s):  
Modular Design ◽  
Low Cost ◽  
Digital Elevation Models ◽  
Ice Core ◽  
Snow Accumulation ◽  
Spatiotemporal Variability ◽  
Dual Frequency ◽  
Ice Stream ◽  
Digital Elevation ◽  
Software Instrumentation

Abstract. We present the developmental considerations, design, and deployment of an autonomous modular terrestrial rover for ice-sheet exploration that is inexpensive, easy to construct, and allows for instrumentation customization. The total construction cost for this rover is less than USD 3000, approximately one-tenth the cost of existing platforms, and it can be built using facilities frequently available at academic institutions (machine shop, 3-D printer, open-source hardware and software). Instrumentation deployed on this rover can be customized; the rover presented in this study was equipped with a dual-frequency GPS receiver and a digital SLR camera for constructing digital elevation models using structure-from-motion (SfM) photogrammetry. We deployed this prototype rover on the Northeast Greenland Ice Stream to map local variations in snow accumulation and surface topography. The rover conducted four autonomous missions based out of the East Greenland Ice-Core Project (EastGRIP) camp during July 2017, measuring surface elevation transects across the hazardous ice-stream shear margins. During these missions, the rover proved capable of driving over 20 km on a single charge with a drawbar pull of 250 N, sufficient to tow instrumentation of up to 100 kg. The rover also acquired photographs that were subsequently used to construct digital elevation models of a site monitored for spatiotemporal variability in snow accumulation, demonstrating adequate stability for high-resolution imaging applications. Due to its low cost, low-power requirements, and simple modular design, mass deployments of this rover design are practicable. Operation of the rover in hazardous areas circumvents the substantial expense and risk to personnel associated with conventional, crewed deployments. Thus, this rover is an investigatory platform that enables direct exploration of polar environments considered too hazardous for conventional field expeditions.

scholarly journals The Ross Sea Dipole – Temperature, Snow Accumulation and Sea Ice Variability in the Ross Sea Region, Antarctica, over the Past 2,700 Years

2017 ◽  
Author(s):  
Nancy A. N. Bertler ◽  
Howard Conway ◽  
Dorthe Dahl-Jensen ◽  
Daniel B. Emanuelsson ◽  
Mai Winstrup ◽  
...  
Keyword(s):  
Sea Ice ◽  
Ross Sea ◽  
Ice Core ◽  
Reanalysis Data ◽  
Snow Accumulation ◽  
West Antarctica ◽  
Dynamic Interactions ◽  
Sea Ice Extent ◽  
The Past ◽  
Western Ross Sea

Abstract. High-resolution, well-dated climate archives provide an opportunity to investigate the dynamic interactions of climate patterns relevant for future projections. Here, we present data from a new, annually-dated ice core record from the eastern Ross Sea. Comparison of the Roosevelt Island Climate Evolution (RICE) ice core records with climate reanalysis data for the 1979–2012 calibration period shows that RICE records reliably capture temperature and snow precipitation variability of the region. RICE is compared with data from West Antarctica (West Antarctic Ice Sheet Divide Ice Core) and the western (Talos Dome) and eastern (Siple Dome) Ross Sea. For most of the past 2,700 years, the eastern Ross Sea was warming with perhaps increased snow accumulation and decreased sea ice extent. However, West Antarctica cooled whereas the western Ross Sea showed no significant temperature trend. From the 17th Century onwards, this relationship changes. All three regions now show signs of warming, with snow accumulation declining in West Antarctica and the eastern Ross Sea, but increasing in the western Ross Sea. Analysis of decadal to centennial-scale climate variability superimposed on the longer term trend reveal that periods characterised by opposing temperature trends between the Eastern and Western Ross Sea have occurred since the 3rd Century but are masked by longer-term trends. This pattern here is referred to as the Ross Sea Dipole, caused by a sensitive response of the region to dynamic interactions of the Southern Annual Mode and tropical forcings.

scholarly journals The Amundsen Sea Low: Variability, Change, and Impact on Antarctic Climate

2016 ◽  
Vol 97 (1) ◽  
pp. 111-121 ◽  
Author(s):  
M. N. Raphael ◽  
G. J. Marshall ◽  
J. Turner ◽  
R. L. Fogt ◽  
D. Schneider ◽  
...  
Keyword(s):  
Sea Ice ◽  
Climate Model ◽  
Ross Sea ◽  
Ice Core ◽  
Meridional Wind ◽  
West Antarctica ◽  
Sea Ice Extent ◽  
Amundsen Sea ◽  
West Antarctic ◽  
Climate Model Simulations

Abstract The Amundsen Sea low (ASL) is a climatological low pressure center that exerts considerable influence on the climate of West Antarctica. Its potential to explain important recent changes in Antarctic climate, for example, in temperature and sea ice extent, means that it has become the focus of an increasing number of studies. Here, the authors summarize the current understanding of the ASL, using reanalysis datasets to analyze recent variability and trends, as well as ice-core chemistry and climate model projections, to examine past and future changes in the ASL, respectively. The ASL has deepened in recent decades, affecting the climate through its influence on the regional meridional wind field, which controls the advection of moisture and heat into the continent. Deepening of the ASL in spring is consistent with observed West Antarctic warming and greater sea ice extent in the Ross Sea. Climate model simulations for recent decades indicate that this deepening is mediated by tropical variability while climate model projections through the twenty-first century suggest that the ASL will deepen in some seasons in response to greenhouse gas concentration increases.

scholarly journals Spatial and temporal variability in isotope composition of recent snow in the vicinity of Vostok station, Antarctica: implications for ice-core record interpretation

2002 ◽  
Vol 35 ◽  
pp. 181-186 ◽  
Author(s):  
Alexey A. Ekaykin ◽  
Vladimir Ya. Lipenkov ◽  
Narcisse I. Barkov ◽  
Jean Robert Petit ◽  
Valerie Masson-Delmotte
Keyword(s):  
Isotope Composition ◽  
Ice Core ◽  
Snow Accumulation ◽  
Spatial And Temporal Variability ◽  
Weak Correlation ◽  
Ice Core Record ◽  
Vostok Station ◽  
The Mean ◽  
Mean Annual Air Temperature ◽  
Snow Samples

AbstractContinuous, detailed isotope (δD and δ18O) profiles were obtained from eight snow pits dug in the vicinity of Vostok station, Antarctica, during the period 1984– 2000. In addition, snow samples taken along the 1km long accumulation-stake profile were measured to determine spatial variability in isotope composition of recent snow. the stacked δD time series spanning the last 55 years shows only weak correlation with the mean annual air temperature recorded at Vostok station. Significant oscillations of both snow accumulation and snow isotope composition with the periods 2.5, 5, 20 and, possibly, ~102 years observed at single points are interpreted in terms of drift of snow-accumulation waves of various scales on the surface of the ice sheet.

Reconstructing Antarctic snow accumulation using nitrogen isotopes of nitrate

2021 ◽  
Author(s):  
Pete D. Akers ◽  
Joël Savarino ◽  
Nicolas Caillon ◽  
Mark Curran ◽  
Tas Van Ommen
Keyword(s):  
Nitrogen Isotopes ◽  
Full Range ◽  
Ice Core ◽  
Ice Cores ◽  
Snow Accumulation ◽  
East Antarctica ◽  
Accumulation Rates ◽  
Sea Levels ◽  
Antarctic Snow ◽  
Parallel Reconstruction

<p>Precise Antarctic snow accumulation estimates are needed to understand past and future changes in global sea levels, but standard reconstructions using water isotopes suffer from competing isotopic effects external to accumulation. We present here an alternative accumulation proxy based on the post-depositional photolytic fractionation of nitrogen isotopes (d<sup>15</sup>N) in nitrate. On the high plateau of East Antarctica, sunlight penetrating the uppermost snow layers converts snow-borne nitrate into nitrogen oxide gas that can be lost to the atmosphere. This nitrate loss favors <sup>14</sup>NO<sub>3</sub><sup>-</sup> over <sup>15</sup>NO<sub>3</sub><sup>-</sup>, and thus the d<sup>15</sup>N of nitrate remaining in the snow will steadily increase until the nitrate is eventually buried beneath the reach of light. Because the duration of time until burial is dependent upon the rate of net snow accumulation, sites with lower accumulation rates have a longer burial wait and thus higher d<sup>15</sup>N values. A linear relationship (r<sup>2</sup> = 0.86) between d<sup>15</sup>N and net accumulation<sup>-1</sup> is calculated from over 120 samples representing 105 sites spanning East Antarctica. These sites largely encompass the full range of snow accumulation rates observed in East Antarctica, from 25 kg m-<sup>2</sup> yr<sup>-1</sup> at deep interior sites to >400 kg m-<sup>2</sup> yr<sup>-1</sup> at near coastal sites. We apply this relationship as a transfer function to an Aurora Basin ice core to produce a 700-year record of accumulation changes. Our nitrate-based estimate compares very well with a parallel reconstruction for Aurora Basin that uses volcanic horizons and ice-penetrating radar. Continued improvements to our database may enable precise independent estimates of millennial-scale accumulation changes using deep ice cores such as EPICA Dome C and Beyond EPICA-Oldest Ice.</p>

scholarly journals Observationally constrained surface mass balance of Larsen C ice shelf, Antarctica

2017 ◽  
Vol 11 (6) ◽  
pp. 2411-2426 ◽  
Author(s):  
Peter Kuipers Munneke ◽  
Daniel McGrath ◽  
Brooke Medley ◽  
Adrian Luckman ◽  
Suzanne Bevan ◽  
...  
Keyword(s):  
Mass Balance ◽  
Climate Model ◽  
Regional Climate ◽  
Snow Accumulation ◽  
Airborne Radar ◽  
Surface Mass Balance ◽  
Spatial And Temporal Patterns ◽  
Ice Shelf ◽  
The West ◽  
Surface Mass

Abstract. The surface mass balance (SMB) of the Larsen C ice shelf (LCIS), Antarctica, is poorly constrained due to a dearth of in situ observations. Combining several geophysical techniques, we reconstruct spatial and temporal patterns of SMB over the LCIS. Continuous time series of snow height (2.5–6 years) at five locations allow for multi-year estimates of seasonal and annual SMB over the LCIS. There is high interannual variability in SMB as well as spatial variability: in the north, SMB is 0.40 ± 0.06 to 0.41 ± 0.04 m w.e. year−1, while farther south, SMB is up to 0.50 ± 0.05 m w.e. year−1. This difference between north and south is corroborated by winter snow accumulation derived from an airborne radar survey from 2009, which showed an average snow thickness of 0.34 m w.e. north of 66° S, and 0.40 m w.e. south of 68° S. Analysis of ground-penetrating radar from several field campaigns allows for a longer-term perspective of spatial variations in SMB: a particularly strong and coherent reflection horizon below 25–44 m of water-equivalent ice and firn is observed in radargrams collected across the shelf. We propose that this horizon was formed synchronously across the ice shelf. Combining snow height observations, ground and airborne radar, and SMB output from a regional climate model yields a gridded estimate of SMB over the LCIS. It confirms that SMB increases from north to south, overprinted by a gradient of increasing SMB to the west, modulated in the west by föhn-induced sublimation. Previous observations show a strong decrease in firn air content toward the west, which we attribute to spatial patterns of melt, refreezing, and densification rather than SMB.

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