Movement of the Ward Hunt Ice Shelf, Ellesmere Island, N.W.T., Canada

AbstractThe movement at a marginal location on the Ward Hunt Ice Shelf, northern Ellesmere Island, was determined by repeated survey measurements with theodolite and geodimeter. The purpose and duration of the field work, and reduction of the observational data are described, and the resulting mean ice velocity of 0.53 m year-1 is discussed. Strain-rates of a 1 km by 1 km deformation figure are determined. The parameters n and B of Glen’s power flow law are determined by using the equations given by Nye and Weertman. The results are compared with experimental data. Computed ice stresses show that the “ridge-and-trough" structure on the ice shelf surface is not originated by internal ice forces. The elevations of all survey markers have been determined from vertical-angle measurements, and the peculiarities of atmospheric refraction in near-surface layers are discussed.

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The 520-Year Temperature Record of a 100 M Core from the Ronne Ice Shelf, Antarctica

Annals of Glaciology ◽

10.3189/s0260305500008326 ◽

1990 ◽

Vol 14 ◽

pp. 90-93 ◽

Cited By ~ 1

Author(s):

W. Graf ◽

O. Reinwarth ◽

H. Moser

Keyword(s):

Ice Core ◽

Middle Part ◽

Temperature Record ◽

Ice Shelf ◽

Surface Layers ◽

Near Surface ◽

The Core ◽

Drilling Site ◽

Local Variability ◽

10 M Firn Temperature

Evidence for climatic changes during the last 520 years was inferred from 18O content of a 100 m ice core from the Ronne Ice Shelf, Antarctica. The core was stratigraphically dated using seasonal variations of l8O content. The mean 18O content of the annual layers calculated on the basis of this dating decreases with depth z according to δ18O (‰) = −27.3 - 0.049z (m) and reflects first of all the decrease of the 18O content of the near-surface layers in the catchment area of the core from the drilling site 250 km to the south. This effect was corrected by assuming a linear decrease of the 18O content of the near-surface layers with increasing distance from the drilling site. Corrected δ18O values show a large scatter from year-to-year due to the local variability. The smoothed isotopic record displays variations in different time scales, which are caused most probably by climatological induced temperature variations. The gradient of 18O content with the 10 m firn temperature of 1.15‰/K found in the middle part of the Filchner-Ronne Ice Shelf was used to transfer the 18O series to a temperature record.

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Surface accumulation on Foundation Ice Stream, Antarctica

Annals of Glaciology ◽

10.3189/172756499781820987 ◽

1999 ◽

Vol 29 ◽

pp. 23-28 ◽

Cited By ~ 16

Author(s):

Wolfgang Graf ◽

Oskar Reinwarth ◽

Hans Oerter ◽

Christoph Mayer ◽

Astrid Lambrecht

Keyword(s):

Accumulation Rate ◽

Regional Distribution ◽

Accumulation Rates ◽

Ice Shelf ◽

Surface Layers ◽

Climatic Trend ◽

Near Surface ◽

Ice Stream ◽

Grounding Line ◽

Inland Ice

AbstractThis paper presents new data, derived from an analysis of 16 firn cores, on the distribution of the accumulation rate and 18O content of near-surface layers in the eastern part of the Ronne Ice Shelf, Antarctica. The firn cores were drilled along the traverse route of the Filchner-V-Campaign in 1995. The traverse followed an ice flowline of the Foundation Ice Stream and reached the margin of the inland ice, an area which has not yet been investigated. On the ice shelf the accumulation rates decrease with distance from the coast. Ascending to the inland ice the accumulation rates again reach almost coastal values. This regional distribution is in agreement with the temperature gradient along the traverse. The 18 content of the near-surface layers is closely related to the 10 m firn temperature. They strongly decrease from the grounding line towards the inland ice. At the southernmost site at 1100 ma.s.l, the mean δ18O value of the firn decreases to –40‰. Ice with that isotopic signature was found in cores from the central part of the Ronne Ice Shelf just above the marine ice layer, indicating that it originates from this area. All ice deposited as snow further south was melted beneath the ice shelf after passing the grounding-line area. The time series of accumulation rate and 18O content reveal no climatic trend during the last 30-50 years.

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Accumulation and Ice-Core Studies on Filchner-Ronne Ice Shelf, Antarctica

Annals of Glaciology ◽

10.1017/s0260305500006273 ◽

1988 ◽

Vol 11 ◽

pp. 23-31 ◽

Cited By ~ 16

Author(s):

W. Graf

Keyword(s):

Flow Model ◽

Accumulation Rate ◽

Ice Core ◽

Ice Shelf ◽

Surface Layers ◽

Ice Flow ◽

Measuring Point ◽

Near Surface ◽

Ice Edge ◽

Drilling Site

Accumulation rates in the eastern part of Ronne Ice Shelf were determined by isotopic stratigraphy (18O). The samples were taken from snow-pits dug during the Filchner I and II operations in 1984 and 1986. In general, the accumulation rate decreases towards the south; the greatest decrease, from 21.3 to 13.3 g cm−2 a−1, was observed between Filchner Station and measuring point 341, sited 270 km up-stream of the ice edge. The δ18O values of the near-surface layers vary between −25 and -29‰. The 18O content in the more southerly part is progressively depleted in the direction of Möllereisstrom, paralleling a decrease in the accumulation rate. Near the ice edge the 18O content decreases to the west. A 100 m ice core drilled in 1984 at point 340, 220 km from the ice edge, probably goes back to A.D. 1460; it has been dated by isotopic stratigraphy. The accumulation rate up-stream of the drilling site was deduced from the sequence of annual layers, using a simple ice-flow model. The accumulation shows strong variations over the last 200 years, which may be caused in part by local variations in the accumulation on Ronne Ice Shelf.

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The 520-Year Temperature Record of a 100 M Core from the Ronne Ice Shelf, Antarctica

Annals of Glaciology ◽

10.1017/s0260305500008326 ◽

1990 ◽

Vol 14 ◽

pp. 90-93 ◽

Cited By ~ 8

Author(s):

W. Graf ◽

O. Reinwarth ◽

H. Moser

Keyword(s):

Ice Core ◽

Middle Part ◽

Temperature Record ◽

Ice Shelf ◽

Surface Layers ◽

Near Surface ◽

The Core ◽

Drilling Site ◽

Local Variability ◽

10 M Firn Temperature

Evidence for climatic changes during the last 520 years was inferred from 18O content of a 100 m ice core from the Ronne Ice Shelf, Antarctica. The core was stratigraphically dated using seasonal variations of l8O content. The mean 18O content of the annual layers calculated on the basis of this dating decreases with depth z according to δ18O (‰) = −27.3 - 0.049z (m) and reflects first of all the decrease of the 18O content of the near-surface layers in the catchment area of the core from the drilling site 250 km to the south. This effect was corrected by assuming a linear decrease of the 18O content of the near-surface layers with increasing distance from the drilling site. Corrected δ18O values show a large scatter from year-to-year due to the local variability. The smoothed isotopic record displays variations in different time scales, which are caused most probably by climatological induced temperature variations. The gradient of 18O content with the 10 m firn temperature of 1.15‰/K found in the middle part of the Filchner-Ronne Ice Shelf was used to transfer the 18O series to a temperature record.

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Accumulation and Ice-Core Studies on Filchner-Ronne Ice Shelf, Antarctica

Annals of Glaciology ◽

10.3189/s0260305500006273 ◽

1988 ◽

Vol 11 ◽

pp. 23-31 ◽

Cited By ~ 3

Author(s):

W. Graf ◽

H. Moser ◽

H. Oerter ◽

O. Reinwarth ◽

W. Stichler

Keyword(s):

Flow Model ◽

Accumulation Rate ◽

Ice Core ◽

Ice Shelf ◽

Surface Layers ◽

Ice Flow ◽

Measuring Point ◽

Near Surface ◽

Ice Edge ◽

Drilling Site

Accumulation rates in the eastern part of Ronne Ice Shelf were determined by isotopic stratigraphy (18O). The samples were taken from snow-pits dug during the Filchner I and II operations in 1984 and 1986. In general, the accumulation rate decreases towards the south; the greatest decrease, from 21.3 to 13.3 g cm−2 a−1, was observed between Filchner Station and measuring point 341, sited 270 km up-stream of the ice edge. The δ18O values of the near-surface layers vary between −25 and -29‰. The 18O content in the more southerly part is progressively depleted in the direction of Möllereisstrom, paralleling a decrease in the accumulation rate. Near the ice edge the 18O content decreases to the west. A 100 m ice core drilled in 1984 at point 340, 220 km from the ice edge, probably goes back to A.D. 1460; it has been dated by isotopic stratigraphy.The accumulation rate up-stream of the drilling site was deduced from the sequence of annual layers, using a simple ice-flow model. The accumulation shows strong variations over the last 200 years, which may be caused in part by local variations in the accumulation on Ronne Ice Shelf.

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Investigation of inhomogeneous structures of near-surface-layers in ion-implanted silicon

Thin Solid Films ◽

10.1016/s0040-6090(97)01082-1 ◽

1998 ◽

Vol 319 (1-2) ◽

pp. 39-43 ◽

Cited By ~ 1

Author(s):

Z Swiatek ◽

J.T Bonarski ◽

R Ciach ◽

Z.T Kuznicki ◽

I.M Fodchuk ◽

...

Keyword(s):

Surface Layers ◽

Near Surface ◽

Ion Implanted

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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.

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Important factors in the tracking of tropical cyclones in operational models

Journal of Applied Meteorology and Climatology ◽

10.1175/jamc-d-20-0175.1 ◽

2021 ◽

Author(s):

Timothy Marchok

Keyword(s):

Geophysical Fluid Dynamics Laboratory ◽

Surface Layers ◽

Individual Parameter ◽

Near Surface ◽

Parameter Configuration ◽

Multiple Variables ◽

The Mean ◽

Tropical Cyclone Center ◽

Multiple Configurations ◽

Better Than

AbstractMultiple configurations of the Geophysical Fluid Dynamics Laboratory vortex tracker are tested to determine a setup that produces the best representation of a model forecast tropical cyclone center fix for the purpose of providing track guidance with the highest degree of accuracy and availability. Details of the tracking algorithms are provided, including descriptions of both the Barnes analysis used for center-fixing most variables and a separate scheme used for center-fixing wind circulation. The tracker is tested by running multiple configurations on all storms from the 2015-2017 hurricane seasons in the Atlantic and eastern Pacific Basins using forecasts from two operational National Weather Service models, the Global Forecast System (GFS) and the Hurricane Weather Research and Forecast (HWRF) model. A configuration that tracks only 850 mb geopotential height has the smallest forecast track errors of any configuration based on an individual parameter. However, a configuration composed of the mean of eleven parameters outperforms any of the configurations that are based on individual parameters. Configurations composed of subsets of the eleven parameters and including both mass and momentum variables provide results comparable to or better than the full 11-parameter configuration. In particular, a subset configuration with thickness variables excluded generally outperforms the 11-parameter mean, while one composed of variables from only the 850 mb and near-surface layers performs nearly as well as the 11-parameter mean. Tracker configurations composed of multiple variables are more reliable in providing guidance through the end of a forecast period than are tracker configurations based on individual parameters.

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