Validation of the Antarctic Snow Accumulation and Ice Discharge basal stress boundary of the southeastern region of the Ross Ice Shelf, Antarctica

An ice shelf is a floating ice sheet, attached to land where ice is grounded along the coastline. Nourished both by surface snow accumulation and by glaciers and ice sheets flowing off the land, ice shelves can reach a considerable thickness, varying from up to 1 300 m when the ice starts to float to 200 m or less at the seaward edge (known as the ice front). Nearly all the world's ice shelves are found in Antarctica, where they cover an area of about one and a half million square kilometres. The two largest are the Ross Ice Shelf and the Filchner-Ronne ice shelf, each with an area of about half a million square kilometres. Smaller ice shelves fringe other parts of the Antarctic coastline.

Download Full-text

Evaluation of the AMPS Boundary Layer Simulations on the Ross Ice Shelf, Antarctica, with Unmanned Aircraft Observations

Journal of Applied Meteorology and Climatology ◽

10.1175/jamc-d-16-0339.1 ◽

2017 ◽

Vol 56 (8) ◽

pp. 2239-2258 ◽

Cited By ~ 6

Author(s):

Jonathan D. Wille ◽

David H. Bromwich ◽

John J. Cassano ◽

Melissa A. Nigro ◽

Marian E. Mateling ◽

...

Keyword(s):

Boundary Layer ◽

Wind Speed ◽

Relative Humidity ◽

High Wind ◽

Ice Shelf ◽

High Wind Speed ◽

Near Surface ◽

Ross Ice Shelf ◽

Low Cloud ◽

The Antarctic

AbstractAccurately predicting moisture and stability in the Antarctic planetary boundary layer (PBL) is essential for low-cloud forecasts, especially when Antarctic forecasters often use relative humidity as a proxy for cloud cover. These forecasters typically rely on the Antarctic Mesoscale Prediction System (AMPS) Polar Weather Research and Forecasting (Polar WRF) Model for high-resolution forecasts. To complement the PBL observations from the 30-m Alexander Tall Tower! (ATT) on the Ross Ice Shelf as discussed in a recent paper by Wille and coworkers, a field campaign was conducted at the ATT site from 13 to 26 January 2014 using Small Unmanned Meteorological Observer (SUMO) aerial systems to collect PBL data. The 3-km-resolution AMPS forecast output is combined with the global European Centre for Medium-Range Weather Forecasts interim reanalysis (ERAI), SUMO flights, and ATT data to describe atmospheric conditions on the Ross Ice Shelf. The SUMO comparison showed that AMPS had an average 2–3 m s−1 high wind speed bias from the near surface to 600 m, which led to excessive mechanical mixing and reduced stability in the PBL. As discussed in previous Polar WRF studies, the Mellor–Yamada–Janjić PBL scheme is likely responsible for the high wind speed bias. The SUMO comparison also showed a near-surface 10–15-percentage-point dry relative humidity bias in AMPS that increased to a 25–30-percentage-point deficit from 200 to 400 m above the surface. A large dry bias at these critical heights for aircraft operations implies poor AMPS low-cloud forecasts. The ERAI showed that the katabatic flow from the Transantarctic Mountains is unrealistically dry in AMPS.

Download Full-text

Surface melt magnitude retrieval over Ross Ice Shelf, Antarctica using coupled MODIS near-IR and thermal satellite measurements

The Cryosphere Discussions ◽

10.5194/tcd-3-1069-2009 ◽

2009 ◽

Vol 3 (3) ◽

pp. 1069-1107 ◽

Cited By ~ 1

Author(s):

D. J. Lampkin ◽

C. C. Karmosky

Keyword(s):

Meteorological Data ◽

Temporal Variations ◽

Katabatic Wind ◽

Ice Shelf ◽

Water Fraction ◽

Ross Ice Shelf ◽

Near Ir ◽

Coarse Spatial Resolution ◽

Surface Melt ◽

The Antarctic

Abstract. Surface melt has been increasing over recent years, especially over the Antarctic Peninsula, contributing to disintegration of shelves such as Larsen. Unfortunately, we are not realistically able to quantify surface snowmelt from ground-based methods because there is sparse coverage of automatic weather stations. Satellite based assessments of melt from passive microwave systems are limited in that they only provide an indication of melt occurrence and have coarse spatial resolution. An algorithm was developed to retrieve surface melt magnitude using coupled near-IR/thermal surface measurements from MODIS were calibrated by estimates of liquid water fraction (LWF) in the upper 1 cm of the firn derived from a one-dimensional physical snowmelt model (SNTHERM89). For the modeling phase of this study, SNTHERM89 was forced by hourly meteorological data from automatic weather station data at reference sites spanning a range of melt conditions across the Ross Ice Shelf during a relatively intense melt season (2002). Effective melt magnitude or LWF<eff> were derived for satellite composite periods covering the Antarctic summer months at a 4 km resolution over the entire Ross Ice Shelf, ranging from 0–0.5% LWF<eff> in early December to areas along the coast with as much as 1% LWF<eff> during the time of peak surface melt. Spatial and temporal variations in the magnitude of surface melt are related to both katabatic wind strength and advection during onshore flow.

Download Full-text

Enhanced Moisture Delivery into Victoria Land, East Antarctica During the Early Last Interglacial: Implications for West Antarctic Ice Sheet Stability

10.5194/cp-2021-7 ◽

2021 ◽

Author(s):

Yuzhen Yan ◽

Nicole E. Spaulding ◽

Michael L. Bender ◽

Edward J. Brook ◽

John A. Higgins ◽

...

Keyword(s):

Accumulation Rate ◽

Ice Cores ◽

Snow Accumulation ◽

East Antarctica ◽

Ice Age ◽

Accumulation Rates ◽

Last Interglacial ◽

Ice Shelf ◽

Ross Ice Shelf ◽

Victoria Land

Abstract. The S27 ice core, drilled in the Allan Hills Blue Ice Area of East Antarctica, is located in Southern Victoria Land ~80 km away from the present-day northern edge of the Ross Ice Shelf. Here, we utilize the reconstructed accumulation rate of S27 covering the Last Interglacial (LIG) period between 129 and 116 thousand years before present (ka) to infer moisture transport into the region. The accumulation rate is based on the ice age-gas age differences calculated from the ice chronology, which is constrained by the stable water isotopes of the ice, and an improved gas chronology based on measurements of oxygen isotopes of O2 in the trapped gases. The peak accumulation rate in S27 occurred at 128.2 ka, near the peak LIG warming in Antarctica. Even the most conservative estimate yields a six-fold increase in the accumulation rate in the LIG, whereas other Antarctic ice cores are typically characterized by a glacial-interglacial difference of a factor of two to three. While part of the increase in S27 accumulation rates must originate from changes in the large-scale atmospheric circulation, additional mechanisms are needed to explain the large changes. We hypothesize that the exceptionally high snow accumulation recorded in S27 reflects open-ocean conditions in the Ross Sea, created by reduced sea ice extent and increased polynya size, and perhaps by a southward retreat of the Ross Ice Shelf relative to its present-day position near the onset of LIG. The proposed ice shelf retreat would also be compatible with a sea-level high stand around 129 ka significantly sourced from West Antarctica. The peak in S27 accumulation rates is transient, suggesting that if the Ross Ice Shelf had indeed retreated during the early LIG, it would have re-advanced by 125 ka.

Download Full-text

The Equilibrium State of the Eastern Half of the Ross Ice Shelf

Journal of Glaciology ◽

10.3189/s0022143000020906 ◽

1978 ◽

Vol 20 (84) ◽

pp. 509-518 ◽

Cited By ~ 1

Author(s):

Robert H. Thomas ◽

Charles R. Bentley

Keyword(s):

Indirect Evidence ◽

Melting Rate ◽

Snow Accumulation ◽

Surface Strain ◽

The South ◽

Ice Shelf ◽

Ross Ice Shelf ◽

Average Value ◽

West Antarctic ◽

Flow Band

AbstractMeasurements of ice thickness, velocity, snow accumulation rates, and surface strain-rates are used to examine the state of equilibrium of three flow bands of the Ross Ice Shelf. The analysis gives the rate of thickening of the ice shelf in terms of the basal freezing rate, which is unknown. However, indirect evidence suggests that the basal flux ranges from a small value of freezing in the south to a melting rate of about one meter of ice per year at the ice front. If these values are correct then the flow band in the south-east corner of the ice shelf appears to be thickening at an average value of (34 ± 15) cm of ice per year. Persistent thickening at this rate must lead to grounding of large areas of the ice shelf. This would restrict drainage from West Antarctic ice streams which feed this part of the ice shelf and these would tend to thicken and advance their grounding lines into the ice shelf. Further north, near the RISP bore-hole site, the ice shelf is probably in equilibrium. The largest flow band is to the south and east of Roosevelt Island, and this also may be in equilibrium if there is significant bottom melting from ice shelf that is more than 100 km from the ice front.

Download Full-text

The Equilibrium State of the Eastern Half of the Ross Ice Shelf

Journal of Glaciology ◽

10.1017/s0022143000020906 ◽

1978 ◽

Vol 20 (84) ◽

pp. 509-518 ◽

Cited By ~ 51

Author(s):

Robert H. Thomas ◽

Charles R. Bentley

Keyword(s):

Indirect Evidence ◽

Melting Rate ◽

Snow Accumulation ◽

Surface Strain ◽

The South ◽

Ice Shelf ◽

Ross Ice Shelf ◽

Average Value ◽

West Antarctic ◽

Flow Band

AbstractMeasurements of ice thickness, velocity, snow accumulation rates, and surface strain-rates are used to examine the state of equilibrium of three flow bands of the Ross Ice Shelf. The analysis gives the rate of thickening of the ice shelf in terms of the basal freezing rate, which is unknown. However, indirect evidence suggests that the basal flux ranges from a small value of freezing in the south to a melting rate of about one meter of ice per year at the ice front. If these values are correct then the flow band in the south-east corner of the ice shelf appears to be thickening at an average value of (34 ± 15) cm of ice per year. Persistent thickening at this rate must lead to grounding of large areas of the ice shelf. This would restrict drainage from West Antarctic ice streams which feed this part of the ice shelf and these would tend to thicken and advance their grounding lines into the ice shelf. Further north, near the RISP bore-hole site, the ice shelf is probably in equilibrium. The largest flow band is to the south and east of Roosevelt Island, and this also may be in equilibrium if there is significant bottom melting from ice shelf that is more than 100 km from the ice front.

Download Full-text

Two decades of Antarctic coastal-change revealed by satellite imagery and deep learning

10.5194/egusphere-egu21-5344 ◽

2021 ◽

Author(s):

Celia A. Baumhoer ◽

Andreas Dietz ◽

Mariel Dirscherl ◽

Claudia Kuenzer

Keyword(s):

Deep Learning ◽

Ice Sheet ◽

Continuous Mapping ◽

Coastal Change ◽

Ice Shelf ◽

Antarctic Ice Sheet ◽

Ice Shelves ◽

Ross Ice Shelf ◽

Wilkes Land ◽

The Antarctic

Antarctica&#8217;s coastline is constantly changing by moving glacier and ice shelf fronts. The extent of glaciers and ice shelves influences the ice discharge and sea level contribution of the Antarctic Ice Sheet. Therefore, it is crucial to assess where ice shelf areas with strong buttressing forces are lost. So far, those changes have not been assessed for entire Antarctica within comparable time frames.We present a framework for circum-Antarctic coastline extraction based on a U-Net architecture. Antarctic coastal-change is calculated by using a deep learning derived coastline for the year 2018 in combination with earlier manual derived coastlines of 1997 and 2009. For the first time, this allows to compare circum-Antarctic changes in glacier and ice shelf front position for the last two decades. We found that the Antarctic Ice Sheet area decreased by -29,618&#177;1,193 km2 in extent between 1997-2008 and gained an area of 7,108&#177;1,029km2 between 2009 and 2018. Retreat dominated for the Antarctic Peninsula and West Antarctica and advance for the East Antarctic Ice Sheet over the entire investigation period. The only exception in East Antarctica was Wilkes Land experiencing simultaneous calving front retreat of several glaciers between 2009-2018. Biggest tabular iceberg calving events occurred at Ronne and Ross Ice Shelf within their natural calving cycle between 1997-2008. Future work includes the continuous mapping of Antarctica&#8217;s coastal-change on a more frequent temporal scale. &#160;

Download Full-text

Estimating Ratios of Snow Accumulation in Antarctica by Chemical Methods

Journal of Glaciology ◽

10.3189/s0022143000015422 ◽

1981 ◽

Vol 27 (96) ◽

pp. 347-357

Author(s):

J. A Warburton ◽

L. G. Young

Keyword(s):

Large Scale ◽

Temporal Variations ◽

Snow Accumulation ◽

Ice Shelf ◽

Chemical Methods ◽

Sea Ice Extent ◽

Ross Ice Shelf ◽

Chemical Profiles ◽

Time Of Year ◽

Highly Correlated

AbstractSnow and firn samples from 2 and 5 m deep pits were analyzed for seven sites on the Ross Ice Shelf, Antarctica. Na, Mg, Ca, and K concentrations change with depth, the range of concentrations being approximately 10 : 1 for all four elements. The changes in concentrations for the four elements at any one site are highly correlated, suggesting that the impurities are introduced into the snow-pack simultaneously by the same mechanisms.Pronounced periodic structure of the vertical chemical profiles leads to strong correlations (γ> 0.9) of the chemical features from site to site separated by distances up to 440 km.Assuming that the observed chemical features are periodic as a function of depth due to temporal variations caused by large-scale phenomena, then the wavelength (in depth) of these features should be proportional to the accumulation. Under the assumptions, the linear regression ratio of one site to another will give the relative accumulations at these sites. The ratios of snow accumulation estimated by these chemical methods agree, within a few per cent, with the ratios for the same sites estimated by total β-activity or stratigraphic methods.It is suggested that the chemical variations with depth are caused by meteorological events which may have seasonal changes in frequency and intensity. It is also suggested that the most-favored season for the production of chemical-concentration maxima is autumn because of the documented higher frequency of precipitating storms on the Ross Ice Shelf and the minimum in sea-ice extent at that time of year.

Download Full-text

Spatial Distribution of Microparticles Within Antarctic Snow-Fall

Annals of Glaciology ◽

10.3189/s0260305500002962 ◽

1982 ◽

Vol 3 ◽

pp. 300-306 ◽

Cited By ~ 1

Author(s):

Lonnie G. Thompson ◽

Ellen Mosley Thompson

Keyword(s):

Size Distribution ◽

Snow Accumulation ◽

Distribution Data ◽

South Pole ◽

The South ◽

Near Surface ◽

Ross Ice Shelf ◽

Particle Accumulation ◽

Base Camp ◽

Antarctic Snow

The concentration and size distribution of water insoluble microparticles were measured in 2 332 snow and firn samples from (a) two sites on the Antarctic Peninsula, (b) the Byrd station strain network, West Antarctica, (c) the Q-13 and base camp sites on the Ross Ice Shelf, and (d) the South Pole and Dome C sites in East Antarctica. These near-surface microparticle studies indicate that, while the number of particles per unit volume of sample remains fairly uniform from site to site, the annual particle accumulation is greatest at locations nearest the coast and decreases rapidly with distance inland. The relationship between particle accumulation and distance from the coast is analogous to a relationship between snow accumulation and distance from the coast. Ten times more particles are deposited annually at stations within 50 km of the coast than at the South Pole and Dome C sites. The size distribution data reveal that, with the possible exception of the Q-13 site, the particulates deposited in Antarctica are well-sorted, indicating little contribution from local sources.

Download Full-text