Late Winter First-Year Ice Floe Thickness Variability, Seawater Flooding and Snow Ice Formation in the Amundsen and Ross Seas

2013 ◽  
pp. 69-87 ◽  
Author(s):  
M. O. Jeffries ◽  
S. Li ◽  
R. A. JañA ◽  
H. R. Krouse ◽  
B. Hurst-Cushing
Keyword(s):  
Ice Formation ◽  
Late Winter ◽  
First Year ◽  
Thickness Variability

Snow-ice accretion and snow-cover depletion on Antarctic first-year sea-ice floes

2001 ◽  
Vol 33 ◽  
pp. 51-60 ◽  
Author(s):  
Martin O. Jeffries ◽  
H. Roy Krouse ◽  
Barbara Hurst-Cushing ◽  
Ted Maksym
Keyword(s):  
Snow Cover ◽  
Ice Cover ◽  
Snow Accumulation ◽  
Ice Formation ◽  
Ice Thickness ◽  
Late Winter ◽  
First Year ◽  
Frazil Ice ◽  
Ice Floes ◽  
Autumn And Winter

AbstractBetween austral late winter 1993 and austral autumn 1998, during five cruises aboard the research vessel Nathaniel B. Palmer, almost 300 m of core was obtained from first-year ice floes in the Ross, Amundsen and Bellingshausen Seas. Analysis of the texture, stratigraphy and stable-isotopic composition of the ice was used to assess the magnitude of the role of flooding and snow-ice formation at the base of the snowpack in the thickening of the ice cover and the thinning of the snow cover. Snow ice occurred in all ice-thickness categories and made a significant contribution to the total ice mass (12−36%) in both autumn and winter. Although the amount of snow ice was often exceeded by the amount of frazil ice and congelation ice, the thickness of individual layers of each ice type indicated that snow ice often made a greater contribution to the thermodynamic thickening of the ice cover than the other ice types. The larger quantities of frazil ice and congelation ice were primarily the result of dynamic thickening. Flooding and snow-ice formation reduced the snow cover to 42−70% of the total snow accumulation depending on time and location. On the basis of this information, ship-based snow-depth estimates were adjusted to estimate the total snow accumulation on different ice-thickness categories.

Prophylactic Vitamin D Dosage after Infancy

PEDIATRICS ◽  
1963 ◽  
Vol 32 (2) ◽  
pp. 308-308
Author(s):  
HARRY BAKWIN
Keyword(s):  
Vitamin D ◽  
American Academy ◽  
Children And Adolescents ◽  
Late Winter ◽  
First Year ◽  
Bellevue Hospital ◽  
American Academy Of Pediatrics ◽  
Prophylactic Dose ◽  
Nutrition Committee

In the report of the Nutrition Committee, American Academy of Pediatrics on the "Prophylactic Requirement and the Toxicity of Vitamin D" (Pediatrics, 31:512) the same prophylactic dose of vitamin D is recommended for children and adolescents as for infants. This seems to me unrealistic. Before the introduction of widespread vitamin D prophylaxis, all the babies over 3 or 4 months on the infant's ward at Bellevue Hospital had rickets during the late winter and spring. The only variation was in degree. Rickets was never seen after the first year or two except for an occasional case of "renal rickets" and "coeliac rickets."

scholarly journals Predicting Melt Pond Fraction on Landfast Snow Covered First Year Sea Ice from Winter C-Band SAR Backscatter Utilizing Linear, Polarimetric and Texture Parameters

2018 ◽  
Vol 10 (10) ◽  
pp. 1603 ◽  
Author(s):  
Saroat Ramjan ◽  
Torsten Geldsetzer ◽  
Randall Scharien ◽  
John Yackel
Keyword(s):  
Sea Ice ◽  
Regression Models ◽  
Incidence Angle ◽  
Early Summer ◽  
Aerial Photographs ◽  
Late Winter ◽  
First Year ◽  
Melt Pond ◽  
Texture Parameters ◽  
Snow Thickness

Early-summer melt pond fraction is predicted using late-winter C-band backscatter of snow-covered first-year sea ice. Aerial photographs were acquired during an early-summer 2012 field campaign in Resolute Passage, Nunavut, Canada, on smooth first-year sea ice to estimate the melt pond fraction. RADARSAT-2 Synthetic Aperture Radar (SAR) data were acquired over the study area in late winter prior to melt onset. Correlations between the melt pond fractions and late-winter linear and polarimetric SAR parameters and texture measures derived from the SAR parameters are utilized to develop multivariate regression models that predict melt pond fractions. The results demonstrate substantial capability of the regression models to predict melt pond fractions for all SAR incidence angle ranges. The combination of the most significant linear, polarimetric and texture parameters provide the best model at far-range incidence angles, with an R 2 of 0.62 and a pond fraction RMSE of 0.09. Near- and mid- range incidence angle models provide R 2 values of 0.57 and 0.61, respectively, with an RMSE of 0.11. The strength of the regression models improves when SAR parameters are combined with texture parameters. These predictions also serve as a proxy to estimate snow thickness distributions during late winter as higher pond fractions evolve from thinner snow cover.

scholarly journals Snow Thickness Estimation on First-Year Sea Ice from Late Winter Spaceborne Scatterometer Backscatter Variance

2019 ◽  
Vol 11 (4) ◽  
pp. 417 ◽  
Author(s):  
John Yackel ◽  
Torsten Geldsetzer ◽  
Mallik Mahmud ◽  
Vishnu Nandan ◽  
Stephen Howell ◽  
...  
Keyword(s):  
Sea Ice ◽  
Snow Cover ◽  
Winter Season ◽  
Late Winter ◽  
First Year ◽  
Snow Layer ◽  
Independent Case ◽  
Brine Volume ◽  
Snow Thickness

Ku- and C-band spaceborne scatterometer sigma nought (σ°) backscatter data of snow covered landfast first-year sea ice from the Canadian Arctic Archipelago are acquired during the winter season with coincident in situ snow-thickness observations. Our objective is to describe a methodological framework for estimating relative snow thickness on first-year sea ice based on the variance in σ° from daily time series ASCAT and QuikSCAT scatterometer measurements during the late winter season prior to melt onset. We first describe our theoretical basis for this approach, including assumptions and conditions under which the method is ideally suited and then present observational evidence from four independent case studies to support our hypothesis. Results suggest that the approach can provide a relative measure of snow thickness prior to σ° detected melt onset at both Ku- and C-band frequencies. We observe that, during the late winter season, a thinner snow cover displays a larger variance in daily σ° compared to a thicker snow cover on first-year sea ice. This is because for a given increase in air temperature, a thinner snow cover manifests a larger increase in basal snow layer brine volume owing to its higher thermal conductivity, a larger increase in the dielectric constant and a larger increase in σ° at both Ku- and C bands. The approach does not apply when snow thickness distributions on first-year sea ice being compared are statistically similar, indicating that similar late winter σ° variances likely indicate regions of similar snow thickness.

scholarly journals An intercomparison between AMSR-E snow-depth and satellite C- and Ku-band radar backscatter data for Antarctic sea ice

2011 ◽  
Vol 52 (57) ◽  
pp. 279-290 ◽  
Author(s):  
Stefan Kern ◽  
Burcu Ozsoy-Cicek ◽  
Sascha Willmes ◽  
Marcel Nicolaus ◽  
Christian Haas ◽  
...  
Keyword(s):  
Sea Ice ◽  
Snow Depth ◽  
Weddell Sea ◽  
Late Winter ◽  
First Year ◽  
Radar Backscatter ◽  
Antarctic Sea Ice ◽  
Ridged Ice ◽  
Ice Fraction ◽  
Ku Band

AbstractAdvanced Microwave Scanning Radiometer (AMSR-E) snow-depth data for Antarctic sea ice are compared with ship-based visual observations of snow depth, ice type and ridged-ice fraction, and with satellite C-band and Ku-band radar backscatter observations for two ship cruises into the Weddell Sea (ISPOL 2004–05,WWOS 2006) and one cruise into the Bellingshausen Sea (SIMBA 2007) during late winter/spring. Most (>75%) AMSR-E and ship-based snow-depth observations agree within 0.2 m during WWOS and SIMBA. Remaining observations indicate substantial underestimations of snow depths by AMSR-E data. These underestimations tend to increase with the ridged-ice fraction for WWOS and SIMBA. In areas with large snow depths, a combination of relatively stable low C-band radar backscatter and variable Ku-band radar backscatter is associated with undeformed first-year ice and may indicate snow metamorphism at this time of year during SIMBA. In areas with small snow depths, a combination of relatively stable low Ku-band radar backscatter, high C-band radar backscatter and low C-band radar backscatter standard deviations is associated with rough first-year ice during SIMBA. This information can help to better understand causes of the observed AMSR-E snow-depth bias during late-winter/spring conditions with decreasing average snow depth and to delineate areas where this bias occurs.

scholarly journals The Ronne polynya of 1997/98: observations of air-ice-ocean interaction

2001 ◽  
Vol 33 ◽  
pp. 425-429 ◽  
Author(s):  
S. F. Ackley ◽  
C. A. Geiger ◽  
J. C. King ◽  
E. C. Hunke ◽  
J. Comiso
Keyword(s):  
Solar Radiation ◽  
Sea Ice ◽  
Satellite Imagery ◽  
Southern Oscillation ◽  
Open Water ◽  
Weddell Sea ◽  
Ice Formation ◽  
Late Winter ◽  
Wind Fields ◽  
Ice Shelf

AbstractThe Ronne polynya formed in the Weddell Sea, Antarctica, during the period November 1997−February 1998 to an extent not seen previously in the 25 years of all-weather satellite observations. The vessel HMS Endurance traversed the polynya region and took sea-ice, physical oceanographic and meteorological measurements during January and early February 1998. These observations, together with satellite imagery and weather records, were analyzed to determine the causes of the anomalous condition observed and to provide comparisons for numerical modeling experiments. The polynya area, analyzed from satellite imagery, showed a linear, nearly constant, increase with time from mid-November 1997 through February 1998. It had a maximum open-water area of 3 × 105 km2 and extended 500 km north of the Ronne Ice Shelf (at 76° S) to 70° S. The ice and snow structure of floes at the northern edge of the polynya showed the ice there had formed in the previous mid- to late winter (October 1997 or earlier) and had been advected there either from the eastern Weddell Sea or from the front of the Ronne Ice Shelf. Analyses of the wind fields showed anomalous spring-summer wind fields in the polynya year, with a strong southerly to southwesterly component compared to the mean easterly winds typical of summer conditions. These southerly wind conditions, in both magnitude and direction, therefore account for the drift of ice northward. The predominant summer easterly winds usually fill the southern Weddell Sea with ice from the east, and the high-albedo surfaces reflect the solar radiation, preventing warming of the surface ocean waters and consequent sea-ice melt. Instead, high incident solar radiation from November 1997 to February 1998 was absorbed by the open water, rather than being reflected, thereby both melting ice and preventing ice formation, and thereby sustaining the polynya. We conclude that open-water-albedo feedback is necessary to allow the observed polynya formation, since similar drift conditions prevail in winter (arising from southerly winds also) and usually result in extensive new ice formation in front of the Ronne Ice Shelf. The strong southerly winds therefore have quite opposing seasonal effects, leading to high ice production in winter as usually found, and extensive open water if they occur in spring and summer, as seen in this atypical event in 1997/98. In this case, the atypical southerly winds may be associated with an El Niño-Southern Oscillation (ENSO)-induced atmospheric circulation pattern.

A Subice Suction Corer for Sampling Epontic Ice Algae

1988 ◽  
Vol 45 (3) ◽  
pp. 562-568 ◽  
Author(s):  
Harold E. Welch ◽  
Martin A. Bergmann ◽  
John K. Jorgenson ◽  
William Burton
Keyword(s):  
Sea Ice ◽  
Quantitative Assessment ◽  
Early Spring ◽  
Late Winter ◽  
First Year ◽  
Ice Algae ◽  
Sources Of Error

Standard SIPRE coring was compared with a new Subice Suction Corer and cores taken by diver for the quantitative assessment of epontic (subice) algae on first-year congelation sea ice at Resolute, N.W.T., Canada (≈75°N). The diver cores were probably most accurate but were slow and costly. SIPRE coring was as good as other techniques in late winter and early spring but gave progressively poorer (under) estimates as the season progressed, with up to 90% of the ice algae being lost from SIPRE cores by June. The Subice Suction Corer was fast, easy to operate, cheap, and gave results comparable with samples obtained by diving. Sources of error are discussed.

scholarly journals Textural characteristics of sea ice and the major mechanisms of ice growth in the Weddell Sea

1991 ◽  
Vol 15 ◽  
pp. 210-215 ◽  
Author(s):  
M. A. Lange ◽  
H. Eicken
Keyword(s):  
Sea Ice ◽  
Formation Process ◽  
Large Fraction ◽  
Large Degree ◽  
Weddell Sea ◽  
The Arctic ◽  
Ice Formation ◽  
First Year ◽  
Ice Edge ◽  
The Antarctic

We report on studies of sea-ice texture conducted during a number of expeditions into the Weddell Sea. Sea ice in the Antarctic is dominated by granular ice of frazil origin in floes of all ages, in contrast to ice in the Arctic, which consists predominantly of columnar ice of congelation origin. The large fraction of granular ice in first-year sea ice is a result of the dominant ice-formation process in the advancing ice edge, the pancake cycle. The dominance of granular over columnar ice in second- and/or multi-year ice is a result of the large degree of deformational activity in the Southern Ocean.

Prospects for Improving Mediterranean Grasslands in Lebanon through Seeding, Fertilization and Protection from Grazing

1992 ◽  
Vol 28 (4) ◽  
pp. 461-472 ◽  
Author(s):  
Ahmed E. Osman ◽  
Phil S. Cocks
Keyword(s):  
Land Surface ◽  
Subterranean Clover ◽  
Phosphate Fertilizer ◽  
Late Winter ◽  
First Year ◽  
Legume Seeds ◽  
Natural Grasslands ◽  
Annual Grasses ◽  
Medicago Rigidula ◽  
Exotic Legumes

SUMMARYGrassland productivity was studied for four years near Terbol, Lebanon. In the first year pasture availability and plant numbers were monitored along transects, and in the following three years the effects of sowing four Mediterranean annual legumes (three cultivars of subterranean clover and a local ecotype of Medicago rigidula) and top-dressing with super-phosphate were studied. The results indicated that natural grasslands were dominated by annual grasses (Aegilops, Hordeum, Bromur, Lolium and Poa). Legume density was low, which resulted in poor legume productivity, especially in winter. Exotic legumes only resulted in a slight improvement in pasture productivity even when phosphate fertilizer was added. However, partial protection from grazing (for one or two months in late winter and spring) more than doubled the number of legume seeds in the seed bank compared with full protection and open grazing. The build up of seeds in the soil is an essential step towards the improvement of productivity in these degraded pastures, which form a large part of the land surface in Lebanon and on which small ruminant production largely depends.

Management of highly fecund ewe types and their lambs for 8-monthly lambing. 1. Effect of lamb weaning age on ewe reproductive activity in spring

1992 ◽  
Vol 32 (4) ◽  
pp. 421 ◽  
Author(s):  
NM Fogarty ◽  
DG Hall ◽  
ST Dawe ◽  
W Atkinson ◽  
C Allan
Keyword(s):  
Post Partum ◽  
Reproductive Activity ◽  
Ovulation Rate ◽  
Late Winter ◽  
First Year ◽  
Weaning Age ◽  
Second Year

The spring reproductive activity of ewes following a late winter lambing, and varying duration of suckling or lamb weaning age of 6-13 weeks, was investigated in 321 Booroola Merino x Dorset (BD) and 543 Trangie Fertility Merino x Dorset (TD) ewe records over 2 years and 238 Border Leicester x Merino (BLM) ewes in the second year. The ewes were joined about 12 weeks post-partum in November for 6 weeks, following lambing in July-August to conform to an %-monthly lambing regime. In the first year, ewes were run with vasectomised rams and oestrus, ovulation rate, and interval to first observed oestrus were determined under a simulated joining regime. In the second year entire rams were joined in spring following July-August lambing and oestrus, pregnancy, fetal number, lambs born per ewe joined and lambing interval were analysed. Amongst ewes rearing lambs, longer suckling significantly increased the interval to first oestrus and the lambing interval (P<0.01), but had no effect on the percentage of ewes expressing oestrus, percentage of pregnant ewes or lambs born. Significantly fewer ewes that lambed but failed to rear any lambs (LL), than ewes rearing lambs expressed oestrus, ovulated and became pregnant. This resulted in considerably lower lambing rates for LL ewes (95.8 v 137.2% lambs born, P<0.01). Reproductive activity was not greatly affected by ewe liveweight or liveweight gain during joining. BD and TD ewes had hgher pregnancy and lambing rates and a shorter lambing interval than BLM ewes. Ovulation rate and fetal number increased with the number of lambs being reared (0.20 � 0.08 and 0.11 � 0.04 per lamb, P<0.05). The results show that high pregnancy and lambing rates can be achieved from natural joining in the spring following late winter lambings within an 8-monthly lambing regime, when lambs are weaned prior to joining.

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