Observations of snowdrift over Antarctic snow and blue-ice surfaces

AbstractVertical profiles of snowdrift density and concurrent meteorological data were measured over Antarctic snow and blue ice during a 1 month field experiment in austral summer 1997/98. It is found that drift densities and transport rates over blue ice are significantly smaller than over snow, which can be attributed mainly to the limited availability of snow particles at the blue-ice surface. Hence, over blue ice, near-surface drift densities and vertical gradients in drift density are relatively small. Over blue ice, snowdrift can occur in very weak winds, presumably because of the smoothness of the surface. Over snow, in contrast, drift occurs only in much stronger winds, such that the shear stress applied by the flow can overcome the cohesive interparticle bonds.

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Near-surface internal melting: a substantial mass loss on Antarctic Dry Valley glaciers

Journal of Glaciology ◽

10.3189/2014jog13j095 ◽

2014 ◽

Vol 60 (220) ◽

pp. 361-374 ◽

Cited By ~ 20

Author(s):

Matthew J. Hoffman ◽

Andrew G. Fountain ◽

Glen E. Liston

Keyword(s):

Meteorological Data ◽

Primary Source ◽

Balance Model ◽

Weathering Crust ◽

Field Observations ◽

Dry Valleys ◽

Near Surface ◽

Ice Surface ◽

Dry Valley ◽

Glacier Ablation

AbstractThe McMurdo Dry Valleys, southern Victoria Land, East Antarctica, are a polar desert, and melt from glacial ice is the primary source of water to streams, lakes and associated ecosystems. Previous work found that to adequately model glacier ablation and subsurface ice temperatures with a surface energy-balance model required including the transmission of solar radiation into the ice. Here we investigate the contribution of subsurface melt to the mass balance of (and runoff from) Dry Valley glaciers by including a drainage process in the model and applying the model to three glacier sites using 13 years of hourly meteorological data. Model results for the smooth glacier surfaces common to many glaciers in the Dry Valleys showed that sublimation was typically the largest component of surface lowering, with rare episodes of surface melting, consistent with anecdotal field observations. Results also showed extensive internal melting 5–15 cm below the ice surface, the drainage of which accounted for ~50% of summer ablation. This is consistent with field observations of subsurface streams and formation of a weathering crust. We identify an annual cycle of weathering crust formation in summer and its removal during the 10 months of winter sublimation.

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A measurement system for vertical seawater profiles close to the air/sea interface

10.5194/os-2017-7 ◽

2017 ◽

Author(s):

Richard P. Sims ◽

Ute Schuster ◽

Andrew J. Watson ◽

Ming Xi Yang ◽

Frances E. Hopkins ◽

...

Keyword(s):

Carbon Dioxide ◽

System Response ◽

Vertical Profiles ◽

Near Surface ◽

Wind Speeds ◽

Small Frame ◽

System Response Time ◽

Wave Heights ◽

Gas Measurements ◽

Vertical Gradients

Abstract. This paper describes a Near Surface Ocean Profiler, which has been designed to precisely measure vertical gradients in the top 10 m of the ocean. Variations in the depth of seawater collection are minimised when using the profiler compared to conventional CTD/rosette deployments. The profiler consists of a remotely operated winch mounted on a tethered yet free floating buoy, which is used to raise and lower a small frame housing sensors and inlet tubing. Seawater at the inlet depth is pumped back to the ship for analysis. The profiler can be used to make continuous vertical profiles or to target a series of discrete depths. The profiler has been successfully deployed during wind speeds up to 10 m s−1 and significant wave heights up to 2 m. We demonstrate the potential of the profiler by presenting measured vertical profiles of the trace gases carbon dioxide and dimethylsulfide. Trace gas measurements use an efficient microporous membrane equilibrator to minimise the system response time. The example profiles show vertical gradients in the upper 5 m for temperature, carbon dioxide and dimethylsulfide of 0.15 °C, 4 μatm and 0.4 nM respectively.

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A measurement system for vertical seawater profiles close to the air–sea interface

Ocean Science ◽

10.5194/os-13-649-2017 ◽

2017 ◽

Vol 13 (5) ◽

pp. 649-660 ◽

Cited By ~ 4

Author(s):

Richard P. Sims ◽

Ute Schuster ◽

Andrew J. Watson ◽

Ming Xi Yang ◽

Frances E. Hopkins ◽

...

Keyword(s):

Carbon Dioxide ◽

System Response ◽

Vertical Profiles ◽

Near Surface ◽

Wind Speeds ◽

Small Frame ◽

System Response Time ◽

Wave Heights ◽

Gas Measurements ◽

Vertical Gradients

Abstract. This paper describes a near-surface ocean profiler, which has been designed to precisely measure vertical gradients in the top 10 m of the ocean. Variations in the depth of seawater collection are minimized when using the profiler compared to conventional CTD/rosette deployments. The profiler consists of a remotely operated winch mounted on a tethered yet free-floating buoy, which is used to raise and lower a small frame housing sensors and inlet tubing. Seawater at the inlet depth is pumped back to the ship for analysis. The profiler can be used to make continuous vertical profiles or to target a series of discrete depths. The profiler has been successfully deployed during wind speeds up to 10 m s−1 and significant wave heights up to 2 m. We demonstrate the potential of the profiler by presenting measured vertical profiles of the trace gases carbon dioxide and dimethylsulfide. Trace gas measurements use an efficient microporous membrane equilibrator to minimize the system response time. The example profiles show vertical gradients in the upper 5 m for temperature, carbon dioxide and dimethylsulfide of 0.15 °C, 4 µatm and 0.4 nM respectively.

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An Assessment of ERA5 Reanalysis for Antarctic Near-Surface Air Temperature

Atmosphere ◽

10.3390/atmos12020217 ◽

2021 ◽

Vol 12 (2) ◽

pp. 217

Author(s):

Jiangping Zhu ◽

Aihong Xie ◽

Xiang Qin ◽

Yetang Wang ◽

Bing Xu ◽

...

Keyword(s):

Linear Relationship ◽

Antarctic Peninsula ◽

Austral Summer ◽

Correlation Coefficients ◽

East Antarctica ◽

West Antarctica ◽

Austral Spring ◽

Reanalysis Dataset ◽

Near Surface ◽

The Antarctic

The European Center for Medium-Range Weather Forecasts (ECMWF) released its latest reanalysis dataset named ERA5 in 2017. To assess the performance of ERA5 in Antarctica, we compare the near-surface temperature data from ERA5 and ERA-Interim with the measured data from 41 weather stations. ERA5 has a strong linear relationship with monthly observations, and the statistical significant correlation coefficients (p < 0.05) are higher than 0.95 at all stations selected. The performance of ERA5 shows regional differences, and the correlations are high in West Antarctica and low in East Antarctica. Compared with ERA5, ERA-Interim has a slightly higher linear relationship with observations in the Antarctic Peninsula. ERA5 agrees well with the temperature observations in austral spring, with significant correlation coefficients higher than 0.90 and bias lower than 0.70 °C. The temperature trend from ERA5 is consistent with that from observations, in which a cooling trend dominates East Antarctica and West Antarctica, while a warming trend exists in the Antarctic Peninsula except during austral summer. Generally, ERA5 can effectively represent the temperature changes in Antarctica and its three subregions. Although ERA5 has bias, ERA5 can play an important role as a powerful tool to explore the climate change in Antarctica with sparse in situ observations.

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Physical properties and spatial distribution of the sea ice surface layer (SSL/snow) during the autumn phase of the MOSAiC expedition

10.5194/egusphere-egu21-1467 ◽

2021 ◽

Author(s):

Ruzica Dadic ◽

Martin Schneebeli ◽

Henna-Reeta Hannula ◽

Amy Macfarlane ◽

Roberta Pirazzini

Keyword(s):

Surface Layer ◽

Spatial Distribution ◽

Sea Ice ◽

Physical Properties ◽

Surface Scattering ◽

Climate Feedback ◽

Energy Fluxes ◽

Scattering Layer ◽

Near Surface ◽

Ice Surface

<p>Snow cover dominates the thermal and optical properties of sea ice and the energy fluxes between the ocean and the atmosphere, yet data on the physical properties of snow and its effects on sea ice are limited. This lack of data leads to two significant problems: 1) significant biases in model representations of the sea ice cover and the processes that drive it, and 2) large uncertainties in how sea ice influences the global energy budget and the coupling of climate feedback. The &#160;MOSAiC research initiative enabled the most extensive data collection of snow and surface scattering layer (SSL) properties over sea ice to date. During leg 5 of the MOSAiC expedition, we collected multi-scale (microscale to 100-m scale) measurements of the surface layer (snow/SSL) over first year ice (FYI) and MYI on a daily basis. The ultimate goal of our measurements is to determine the spatial distribution of physical properties of the surface layer. During leg 5 of the MOSAiC expedition, that surface layer changed from the &#160;surface scattering layer (SSL), &#160; characteristic for the melt season, to an early autumn snow pack. Here, &#160;we will present data showing both a) the physical properties and the spatial distribution of the SSL during the late melt season and b) the transition of the sea ice surface from the SSL to the fresh autumn snowpack. The structural properties of this transition period are poorly documented, and this season is critical &#160;for the initialization of sea ice and snow models. Furthermore, these data are crucial to interpret simultaneous observations of surface energy fluxes, surface optical and remote sensing data (microwave signals in particular), near-surface biochemical activity, and to understand the sea ice &#160;processes that occur as the sea ice transitions from melting to freezing.</p>

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Salinity-induced mixed and barrier layers in the southwestern tropical Atlantic Ocean off the northeast of Brazil

Ocean Science ◽

10.5194/os-7-63-2011 ◽

2011 ◽

Vol 7 (1) ◽

pp. 63-73 ◽

Cited By ~ 6

Author(s):

M. Araujo ◽

C. Limongi ◽

J. Servain ◽

M. Silva ◽

F. S. Leite ◽

...

Keyword(s):

Barrier Layer ◽

Austral Summer ◽

Late Winter ◽

Brazilian Coast ◽

Tropical Atlantic ◽

Austral Winter ◽

Surface Salinity ◽

Barrier Layer Thickness ◽

Near Surface ◽

Mixed Layers

Abstract. High-resolution hydrographic observations of temperature and salinity are used to analyze the formation and distribution of isothermal depth (ZT), mixed depth (ZM) and barrier layer thickness (BLT) in a section of the southwestern Atlantic (0°30´ N–14°00´ S; 31°24´–41°48´ W), adjacent to the northeastern Brazilian coast. Analyzed data consists of 279 CTD casts acquired during two cruises under the Brazilian REVIZEE Program. One occurred in late austral winter (August–October 1995) and another in austral summer (January–April 1997). Oceanic observations are compared to numerical modeling results obtained from the French Mercator-Coriolis Program. Results indicate that the intrusion of subtropical Salinity Maximum Waters (SMW) is the major process contributing to the seasonal barrier layer formation. These waters are brought by the South Equatorial Current (SEC), from the subtropical region, into the western tropical Atlantic boundary. During late austral winter southeastern trade winds are more intense and ITCZ precipitations induce lower surface salinity values near the equator. During this period a 5–90 m thick BLT (median = 15 m) is observed and BLT > 30 m is restricted to latitudes higher than 8° S, where the intrusion of salty waters between 8°–12.3° S creates shallow mixed layers over deep (ZT ≥ 90 m) isothermal layers. During austral summer, shallow isothermal and mixed layers prevail, when northeasterly winds are predominant and evaporation overcomes precipitation, causing saltier waters at the surface/subsurface layers. During that period observed BLT varies from 5 to 70 m and presents thicker median value of 35 m, when comparing to the winter. Furthermore, BLT ≥ 30 m is observed not only in the southernmost part of the study area, as verified during late winter, but in the latitude range 2°–14° S, where near-surface salty waters are transported westward by the SEC flow. These results indicate that the inclusion of salinity dynamics and its variability are necessary for studying mixed and barrier layer behaviors in the tropical Atlantic, where ocean-atmosphere coupling is known to be stronger.

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The composition of Europa's near-surface atmosphere

Proceedings of the International Astronomical Union ◽

10.1017/s1743921308021856 ◽

2008 ◽

Vol 4 (S251) ◽

pp. 327-328

Author(s):

Mau C. Wong ◽

Tim Cassidy ◽

Robert E. Johnson

Keyword(s):

Solar System ◽

Surface Composition ◽

Near Surface ◽

Water Ice ◽

Model Studies ◽

Surface Atmosphere ◽

Jovian Magnetosphere ◽

Ice Surface ◽

Geophysical Phenomenon ◽

Inorganic Species

AbstractThe presence of an undersurface ocean renders Europa as one of the few planetary bodies in our Solar System that has been conjectured to have possibly harbored life. Some of the organic and inorganic species present in the ocean underneath are expected to transport upwards through the relatively thin ice crust and manifest themselves as impurities of the water ice surface. For this reason, together with its unique dynamic atmosphere and geological features, Europa has attracted strong scientific interests in past decades.Europa is imbedded inside the Jovian magnetosphere, and, therefore, is constantly subjected to the immerse surrounding radiations, similar to the other three Galilean satellites. The magnetosphere-atmosphere-surface interactions form a complex system that provides a multitude of interesting geophysical phenomenon that is unique in the Solar System. The atmosphere of Europa is thought to have created by, mostly, charged particles sputtering of surface materials. Consequently, the study of Europa's atmosphere can be used as a tool to infer the surface composition. In this paper, we will discuss our recent model studies of Europa's near-surface atmosphere. In particular, the abundances and distributions of the dominant O2 and H2O species, and of other organic and inorganic minor species will be addressed.

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Brief communication: Rare ambient saturation during drifting snow occurrences at a coastal location of East Antarctica

The Cryosphere ◽

10.5194/tc-13-3405-2019 ◽

2019 ◽

Vol 13 (12) ◽

pp. 3405-3412 ◽

Cited By ~ 1

Author(s):

Charles Amory ◽

Christoph Kittel

Keyword(s):

Relative Humidity ◽

Meteorological Data ◽

Ice Sheet ◽

Ambient Air ◽

East Antarctica ◽

Strong Increase ◽

Katabatic Wind ◽

Strong Wind ◽

Near Surface ◽

Drifting Snow

Abstract. Sublimation of snow particles during transport has been recognized as an important ablation process on the Antarctic ice sheet. The resulting increase in moisture content and cooling of the ambient air are thermodynamic negative feedbacks that both contribute to increase the relative humidity of the air, inhibiting further sublimation when saturation is reached. This self-limiting effect and the associated development of saturated near-surface air layers in drifting snow conditions have mainly been described through modelling studies and a few field observations. A set of meteorological data, including drifting snow mass fluxes and vertical profiles of relative humidity, collected at site D17 in coastal Adélie Land (East Antarctica) during 2013 is used to study the relationship between saturation of the near-surface atmosphere and the occurrence of drifting snow in a katabatic wind region that is among the most prone to snow transport by wind. Atmospheric moistening by the sublimation of the windborne snow particles generally results in a strong increase in relative humidity with the magnitude of drifting snow and a decrease in its vertical gradient, suggesting that windborne-snow sublimation can be an important contributor to the local near-surface moisture budget. Despite a high incidence of drifting snow at the measurement location (60.1 % of the time), saturation, when attained, is however most often limited to a thin air layer below 1 m above ground. The development of a near-surface saturated air layer up to the highest measurement level of 5.5 m is observed in only 8.2 % of the drifting snow occurrences or 6.3 % of the time and mainly occurs in strong wind speed and drift conditions. This relatively rare occurrence of ambient saturation is explained by the likely existence of moisture-removal mechanisms inherent to the katabatic and turbulent nature of the boundary-layer flow that weaken the negative feedback of windborne-snow sublimation. Such mechanisms, potentially quite active in katabatic-generated windborne-snow layers all over Antarctica, may be very important in understanding the surface mass and atmospheric moisture budgets of the ice sheet by enhancing windborne-snow sublimation.

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The role of open lead interactions in atmospheric ozone variability between Arctic coastal and inland sites

Elem Sci Anth ◽

10.12952/journal.elementa.000109 ◽

2016 ◽

Vol 4 ◽

Cited By ~ 2

Author(s):

Peter K. Peterson ◽

Kerri A. Pratt ◽

William R. Simpson ◽

Son V. Nghiem ◽

Lemuel X. Pérez Pérez ◽

...

Keyword(s):

Boundary Layer ◽

Sea Ice ◽

Ozone Depletion ◽

Surface Ozone ◽

Optical Absorption Spectroscopy ◽

Atmospheric Ozone ◽

Vertical Profiles ◽

Large Spatial Scale ◽

Near Surface ◽

Air Masses

Abstract Boundary layer atmospheric ozone depletion events (ODEs) are commonly observed across polar sea ice regions following polar sunrise. During March-April 2005 in Alaska, the coastal site of Barrow and inland site of Atqasuk experienced ODEs (O3< 10 nmol mol-1) concurrently for 31% of the observations, consistent with large spatial scale ozone depletion. However, 7% of the time ODEs were exclusively observed inland at Atqasuk. This phenomenon also occurred during one of nine flights during the BRomine, Ozone, and Mercury EXperiment (BROMEX), when atmospheric vertical profiles at both sites showed near-surface ozone depletion only at Atqasuk on 28 March 2012. Concurrent in-flight BrO measurements made using nadir scanning differential optical absorption spectroscopy (DOAS) showed the differences in ozone vertical profiles at these two sites could not be attributed to differences in locally occurring halogen chemistry. During both studies, backward air mass trajectories showed that the Barrow air masses observed had interacted with open sea ice leads, causing increased vertical mixing and recovery of ozone at Barrow and not Atqasuk, where the air masses only interacted with tundra and consolidated sea ice. These observations suggest that, while it is typical for coastal and inland sites to have similar ozone conditions, open leads may cause heterogeneity in the chemical composition of the springtime Arctic boundary layer over coastal and inland areas adjacent to sea ice regions.

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