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1

Microwave Signatures of Snow on Sea Ice: Modeling  

Microsoft Academic Search

Accurate knowledge of snow-depth distribution over sea ice is critical for polar climate studies. Current snow-depth-over-sea-ice retrieval algorithms do not sufficiently account for variations in snow and ice physical properties that can affect the accuracy of retrievals. For this reason, airborne microwave observations were coordinated with ground-based measurements of snow depth and snow properties in the vicinity of Barrow, AK,

Dylan C. Powell; Thorsten Markus; Donald J. Cavalieri; Albin J. Gasiewski; Marian Klein; James A. Maslanik; Julienne C. Stroeve; Mathew Sturm

2006-01-01

2

Antarctic sea ice thickness and snow-to-ice conversion from atmospheric reanalysis and passive microwave snow depth  

Microsoft Academic Search

Passive microwave snow depth, ice concentration, and ice motion estimates are combined with snowfall from the European Centre for Medium-Range Weather Forecasting (ECMWF) reanalysis (ERA-40) from 1979–2001 to estimate the prevalence of snow-to-ice conversion (snow-ice formation) on level sea ice in the Antarctic for April–October. Snow ice is ubiquitous in all regions throughout the growth season. Calculated snow-ice thicknesses fall

Ted Maksym; Thorsten Markus

2008-01-01

3

A First Assessment of IceBridge Snow and Ice Thickness Data Over Arctic Sea Ice  

Microsoft Academic Search

We present a first assessment of airborne laser and radar altimeter data over snow-covered sea ice, gathered during the National Aeronautics and Space Administration Operation IceBridge Mission. We describe a new technique designed to process radar echograms from the University of Kansas snow radar to estimate snow depth. We combine IceBridge laser altimetry with radar-derived snow depths to determine sea

Sinéad Louise Farrell; Nathan Kurtz; Laurence N. Connor; Bruce C. Elder; Carlton Leuschen; Thorsten Markus; David C. McAdoo; Ben Panzer; Jacqueline Richter-Menge; John G. Sonntag

2012-01-01

4

Radar surveys of snow depth over Arctic sea ice during Operation IceBridge (Invited)  

Microsoft Academic Search

TThe transfer of heat through the pack ice is regulated by ice thickness and by the thickness of the snow blanket. Since snow is an effective barrier to heat transfer, the large-scale spatial distribution of snow depth and its small-scale variability associated with sea ice topography must be considered for evaluating regional energy balance. Because of the importance of snow

R. Kwok; C. Leuschen; B. Panzer; A. Patel; N. T. Kurtz; T. Markus; B. Holt; P. S. Gogineni

2010-01-01

5

East Antarctic Sea Ice: Albedo, Thickness Distribution, and Snow Cover  

Microsoft Academic Search

Characteristics of springtime sea ice off East Antarctica were investigated during a cruise of the Australian National Antarctic Research Expedition in October through December 1988. The fractional coverage of the ocean surface, the ice thickness, and the snow cover thickness for each of several ice types were estimated hourly for the region near the ship. These observations were carried out

Ian Allison; Richard E. Brandt; Stephen G. Warren

1993-01-01

6

Large-scale surveys of snow depth on Arctic sea ice from Operation IceBridge  

Microsoft Academic Search

We show the first results of a large-scale survey of snow depth on Arctic sea ice from NASA's Operation IceBridge snow radar system for the 2009 season and compare the data to climatological snow depth values established over the 1954-1991 time period. For multiyear ice, the mean radar derived snow depth is 33.1 cm and the corresponding mean climatological snow

Nathan T. Kurtz; Sinead L. Farrell

2011-01-01

7

Climate Records of Snow, Glaciers and Sea Ice  

NASA Astrophysics Data System (ADS)

Cryospheric data can be used to study global climate change. For example, various environmental factors contribute to changes in annual and interannual snow cover, glacier terminus movement and anomalies of sea ice extent. Archiving and making the data easily accessible is important. At the National Snow and Ice Data Center (NSIDC), three data sets in particular exhibit characteristics that allow for understanding global climate change. Users can analyze glacier retreat from historical glacier photographs, study changes in sea ice by reviewing historical ice charts, and review changes in the annual autumn snow cover onset and last day of snow cover in the Northern Hemisphere. By including a temporal component, the Timing and Statistics of Autumn and Spring Annual Snow Cover for the Northern Hemisphere data set is useful for analyzing statistics of snow cover timing and their relation to other environmental phenomena, for example, vegetation growth dynamics. The Online Glacier Photograph Database, which contains approximately 3,000 images, provides online search and order options for photographs that were previously in risk of deterioration. The Arctic Sea Ice Charts, 1953-1986: W. Dehn Collection data set includes ice charts of the Canadian and Alaskan Arctic Ocean that can be browsed by region and date range. Previously, these ice charts were archived in analog format and in need of long-term preservation. The NOAA Climate Database Modernization Program (CDMP) supported the digitization of both the historical photographs and the sea ice charts. By evaluating these data sets, users will have the opportunity to better interpret climatic change related to snow cover, sea ice and glacier retreat.

Ballagh, L.; Dye, D.; Howard, A.; Fetterer, F.

2005-12-01

8

Evaluation of snow\\/ice albedo parameterizations and their impacts on sea ice simulations  

Microsoft Academic Search

Climate models use a variety of snow\\/ice albedo parameterizations for the ice covered ocean. In this study, we applied in situ measurements (surface temperature, snow depth and ice thickness) obtained from the Surface Heat Budget of the Arctic Ocean (SHEBA) as input values to four different snow\\/ice albedo parameterizations (representing the spectrum of parameterizations used in stand-alone sea ice models,

Jiping Liu; Zhanhai Zhang; Jun Inoue; Radley M. Horton

2007-01-01

9

Large-scale surveys of snow depth on Arctic sea ice from Operation IceBridge  

NASA Astrophysics Data System (ADS)

We show the first results of a large-scale survey of snow depth on Arctic sea ice from NASA's Operation IceBridge snow radar system for the 2009 season and compare the data to climatological snow depth values established over the 1954-1991 time period. For multiyear ice, the mean radar derived snow depth is 33.1 cm and the corresponding mean climatological snow depth is 33.4 cm. The small mean difference suggests consistency between contemporary estimates of snow depth with the historical climatology for the multiyear ice region of the Arctic. A 16.5 cm mean difference (climatology minus radar) is observed for first year ice areas suggesting that the increasingly seasonal sea ice cover of the Arctic Ocean has led to an overall loss of snow as the region has transitioned away from a dominantly multiyear ice cover.

Kurtz, Nathan T.; Farrell, Sinead L.

2011-10-01

10

Wideband radar for airborne measurements of snow thickness on sea ice  

Microsoft Academic Search

Ocean-ice-atmosphere interactions are modulated by snow cover on the sea ice due to the low thermal conductivity and high reflectivity of snow. Current sea ice models use climatological data to simulate a snow cover on the sea ice. Snow cover is also the main source of error in deriving sea ice thickness from freeboard height measurements made by satellite-borne radar

B. Panzer; C. Leuschen; W. Blake; R. Crowe; A. Patel; P. S. Gogineni; T. Markus

2010-01-01

11

The effect of snow on Antarctic sea ice simulations in a coupled atmosphere-sea ice model  

Microsoft Academic Search

The effect of a snow cover on sea ice accretion and ablation is estimated based on the ‘zero-layer’ version sea ice model\\u000a of Semtner, and is examined using a coupled atmosphere-sea ice model including feedbacks and ice dynamics effects. When snow\\u000a is disregarded in the coupled model the averaged Antarctic sea ice becomes thicker. When only half of the snowfall

X. Wu; W. F. Budd; V. I. Lytle; R. A. Massom

1999-01-01

12

The Influence of Platelet Ice and Snow on Antarctic Land-fast Sea Ice  

NASA Astrophysics Data System (ADS)

Sea ice fastened to coasts, icebergs and ice shelves is of crucial importance for climate- and ecosystems. Near Antarctic ice shelves, this land-fast sea ice exhibits two unique characteristics that distinguish it from most other sea ice: a sub-ice layer of ice platelets and a highly stratified and thick snow cover. Ice platelets are flat, plate-like ice crystals forming and growing in a layer of super-cooled water which originates from ice shelf cavities. During growth, heat is lost to the super-cooled ocean rather than conducted to the atmosphere. The crystals accumulate beneath the solid sea-ice cover, forming a layer of loose platelets and eventually becoming incorporated into the sea-ice fabric as platelet ice. Considering the fact that the amount of platelet ice contributes between 10 and 60% to the mass of the land-fast sea ice around Antarctica, very little is known about its spatial and temporal variability. A thick and partly multi-year snow cover develops on top of the Antarctic fast ice, ultimately altering the sea-ice surface and affecting the sea-ice thermodynamics and mass balance. It typically leads to snow-ice formation, surface flooding, and the development of superimposed ice from snow melt water. In order to investigate the role of platelet ice and snow for Antarctic fast ice, we have initiated a regular observation program on the land-fast sea ice of Atka Bay as part of the international Antarctic Fast Ice Network (AFIN). We performed manual measurements of sea-ice and snow thicknesses from June to December 2010 and 2011. Additionally, a mass balance buoy and an automatic weather station were deployed in 2011 and ice cores were taken. Our measurements will reveal insight into the spatial and temporal variability of sea-ice and snow thickness distributions on Atka Bay fast ice. First results show that sea-ice thickness is lowest in the eastern part of the Bay, where a thick snow cover leads to extensive surface flooding. In the West, dynamic conditions lead to high thickness and high local variability. Ice platelets were observed regularly in the boreholes, but measurement techniques have to be improved to assess the thickness of the platelet layer.

Hoppmann, M.; Nicolaus, M.

2011-12-01

13

Radar surveys of snow depth over Arctic sea ice during Operation IceBridge (Invited)  

NASA Astrophysics Data System (ADS)

TThe transfer of heat through the pack ice is regulated by ice thickness and by the thickness of the snow blanket. Since snow is an effective barrier to heat transfer, the large-scale spatial distribution of snow depth and its small-scale variability associated with sea ice topography must be considered for evaluating regional energy balance. Because of the importance of snow depth in sea-ice mass balance and in the surface heat and energy budget, remote determination of snow depth at almost any spatial scale has long been desired. Even though radars have demonstrated a capability to simultaneously resolve the air-snow and snow-ice interfaces in the past, they have not been employed to provide large-scale mapping of snow depth over sea ice. During the early spring of 2009, an ultra-wideband radar with vertical resolution of about 5 cm was deployed as part of Operation IceBridge to obtain several trans-Arctic surveys of the snow cover. This radar provided sufficient penetration and range resolution for delineation of the air-snow and the snow-ice interfaces, especially over largely undeformed ice. Here, we discuss the phenomenology of the scattering from different types of surfaces, our preliminary estimates of Arctic sea ice snow depth and its distribution from the IceBridge surveys. The results are extremely promising and suggest that Operation IceBridge should be able to provide a geophysically rich and useful record for understanding the snow depth distribution of the Arctic Ocean and potentially the Southern Ocean in the coming years.

Kwok, R.; Leuschen, C.; Panzer, B.; Patel, A.; Kurtz, N. T.; Markus, T.; Holt, B.; Gogineni, P. S.

2010-12-01

14

Evolution of Snow Over Sea-Ice during SHEBA using the SNTHERM Snow Model  

NASA Astrophysics Data System (ADS)

Snow processes over sea-ice are currently represented with a simple one-layer snow model in the Meteorological Service of Canada (MSC) operational forecasting systems. Although fully coupled with a multi- layer sea-ice model, the snow scheme does not represent detailed processes like snow densification, vertical profiles of density and temperature, liquid water in the snow, among others. Previous studies have shown that the widely accepted SNTHERM snow model predicts reasonably well the behavior of snow during cold periods. But this scheme has not been implemented yet in operational systems. To more realistically describe snowpack and sea ice dynamics, while preserving reasonable computing efficiency, SNTHERM has been included in MSC's physics package and coupled with the multi-layer sea-ice model. This coupled system is evaluated with forcings and validated data obtained from the Surface Heat Budget of the Arctic Ocean (SHEBA) field campaign conducted in 1997. Results with SNTHERM are compared with those obtained using MSC's current operational system; they provide an interesting framework for exploring the ice-snow interactions in the Arctic.

Chung, Y.; Bélair, S.; Mailhot, J.

2007-12-01

15

Snow on Arctic sea ice: Updating the climatology and assessing its impact on ice ablation  

NASA Astrophysics Data System (ADS)

The Arctic sea-ice cover is undergoing a major transformation with perennial ice extent decreasing at a rate of more than 8% per decade since 1979 and onset of seasonal ice formation delayed over much of the Arctic shelf seas. In this presentation we will (1) discuss the role of snow and its variability in summer surface ice melt, and (2) examine whether any significant changes are detectable in the depth or characteristics of the snow cover on Arctic sea ice based on measurements compiled for the time period from the 1960s onward. The importance of snow as a thermal insulator that constrains conductive heat flux and hence ice growth is well recognized. Less understood is its role in controlling surface melt and evolution of ice albedo. Studies of the evolution of melting landfast and drifting sea ice indicate that snow depth is a key variable that drives the initial evolution of surface melt ponds during summer. The latter in turn controls ice albedo over much of the melt season. Studies of ice melt indicate three primary controlling mechanisms, i.e. the role of snow in retarding ice surface warming, concealing surface melt water accumulation and in governing the formation of superimposed ice which in turn is critical to retention of melt water at the ice surface. Long-term studies at Barrow, Alaska suggest that through these mechanisms snow-depth variations are responsible for significant interannual variability in ponding and ice albedo. Based on field studies in the Alaskan Arctic and analysis of snow depth data compiled from icebreaker cruises, drifting stations and Russian "Sever" aircraft landings, snow depth patterns in the Arctic are examined, in particular in comparison with the climatology derived by Warren et al. (1999) from Russian drifting stations. Regional and temporal variations are discussed in the context of sea ice and precipitation changes as well as their potential impact on ice ablation patterns.

Eicken, H.; Harbeck, J. P.; Perovich, D. K.

2007-12-01

16

The effect of a new snow and sea ice albedo scheme on regional climate model simulations  

Microsoft Academic Search

The HIRHAM snow and sea ice albedo scheme and several other existing snow and sea ice albedo parameterizations forced with observed input parameters are compared with observed albedo. For snow on land in non-forested areas, the original linear temperature-dependent snow albedo is suggested to be replaced with a polynomial temperature-dependent scheme. For sea ice albedo none of the evaluated schemes

Morten Køltzow

2007-01-01

17

Tools for Accessing and Manipulating MODIS Snow & Sea Ice Products at the National Snow and Ice Data Center  

NASA Astrophysics Data System (ADS)

Snow and sea ice cover are some of the more important spatial features of the Earth's surface that can be readily measured from space. Moderate Resolution Imaging Spectroradiometer (MODIS) instruments onboard NASA's Terra and Aqua spacecraft collect spectral data that are used to routinely produce snow cover and sea ice products. With higher spatial and spectral resolution, the MODIS snow and ice products (including snow albedo and sea ice surface temperature) improve upon a long history of global coverage satellite-derived products that have been produced from polar-orbiting satellites since the early 1970s. Fully automated, quality controlled, daily global maps of snow cover and sea ice extent, produced at 500m, 1000m, and 0.05° spatial resolutions by the MODIS Land Team, are available from the National Snow and Ice Data Center (NSIDC) Distributed Active Archive Center (DAAC). The product suite will be further enhanced beginning mid-2005 with the inclusion of fractional snow cover in the daily product, addition of a daily snow product in a polar projection, and production of monthly climate modeling grid products for both snow and sea ice. Several tools are now available to streamline data acquisition and processing for users. Automated access to current data can be obtained through ingest subscriptions, data pool cache scripting, and a machine-to-machine gateway. Users can select data with targeted interfaces and the EOS Data Gateway, both with online reduced-resolution images to allow users to identify usable data prior to ordering. Integrated data manipulation tools provide subsetting, gridding, and resampling of images prior to downloading, minimizing the burden of data management by users. Collectively, the suite enables users to efficiently manage the large quantity of MODIS data available for regional and global studies.

Kaminski, M.; Khalsa, S.; Haran, T.; Wolfe, J.

2004-12-01

18

State of the Arctic and Antarctic sea ice covers from Operation IceBridge snow and ice thickness observations  

NASA Astrophysics Data System (ADS)

Sea ice observations from the suite of airborne instruments aboard the Operation IceBridge mission are currently being utilized to provide a unique look at the state of the Arctic and Antarctic sea ice covers. Presently, work on the production and validation of freeboard, snow depth, and sea ice thickness data products is being done with the goal of distributing these products to the broader scientific community for analysis. We first present a description of the techniques being used for the retrieval of specific sea ice parameters and discuss the results of in-situ validation studies which allow us to establish uncertainties and error sources in the methods. Results of an analysis of the snow and sea ice thickness data sets will also be presented. The comparison of IceBridge snow radar results with historical snow climatological data shows interesting similarities and differences which are found to be important for the use of present day snow depth on sea ice data sets. Comparisons with previous estimates of sea ice thickness from the 2003-2008 ICESat measurements also give insight into the current state and future trends of the global sea ice cover.

Kurtz, N. T.; Farrell, S. L.; Harbeck, J. P.; Koenig, L.; Onana, V.; Sonntag, J. G.; Studinger, M.

2011-12-01

19

Evaluation of snow/ice albedo parameterizations and their impacts on sea ice simulations  

NASA Astrophysics Data System (ADS)

Climate models use a variety of snow/ice albedo parameterizations for the ice covered ocean. In this study, we applied in situ measurements (surface temperature, snow depth and ice thickness) obtained from the Surface Heat Budget of the Arctic Ocean (SHEBA) as input values to four different snow/ice albedo parameterizations (representing the spectrum of parameterizations used in stand-alone sea ice models, numerical weather prediction and regional climate models of the Arctic Basin, and coupled global climate models), and evaluated the parameterized albedos against the SHEBA observed albedo. Results show that these parameterizations give very different representations of surface albedo. The impacts of systematic biases in the input values on the parameterized albedos were also assessed. To further understand how sea ice processes are influenced by differences in the albedo parameterizations, we examined baseline sea ice characteristics and responses of sea ice to an external perturbation for the simulations of the albedo parameterizations using a stand-alone basin-scale dynamic/thermodynamic sea ice model. Results show that an albedo treatment of sufficient complexity can produce more realistic basin-scale ice distributions, and likely more realistic ice responses as climate warms.

Liu, Jiping; Zhang, Zhanhai; Inoue, Jun; Horton, Radley M.

2007-01-01

20

Summer and Fall Sea Ice Processes in the Amundsen Sea: Bottom melting, surface flooding and snow ice formation  

NASA Astrophysics Data System (ADS)

Two ice mass balance buoys were deployed on the Amundsen Sea, Antarctica, ice pack near January 1, 2011. Below freezing air and snow temperatures and sea ice and seawater temperatures at the freezing point at this time indicated that summer melt had not yet commenced. Over the next two months, however, while snow depths changed by less than 0.1m, ice thickness decreased, from bottom melting, by 0.9-1.0m. As snow temperature records did not show temperatures ever reaching the melting point, no surface melt was recorded during the summer period and the small snow depth changes were presumed to occur by consolidation or wind scouring. Water temperatures above the freezing point caused the observed bottom melting from mid January to late February. During the ice loss periods, progressive flooding by sea water at the base of the snow pack was recorded by temperature sensors, showing an increase in the depth of flooded snow pack of 0.4m by the end of the summer period in late February. We hypothesize that progressive flooding of the surface snow pack gives a mechanism for nutrient replenishment in these upper layers, and continuous high algal growth can therefore occur in the flooded snow layer during summer. An underice radiometer recorded light transmission through the ice and snow at selective wavelengths sensitive to chlorophyll. These radiometric results will be presented to examine this algal growth hypothesis. This flooded layer then refroze from the top down into snow ice as air temperatures dropped during March and April, showing that the layer had refrozen as snow ice on the top surface of the ice. Refreezing of the flooded layer gives an ice growth mechanism at the end of summer of 0.2 m to 0.4m of new ice growth over the majority of the ice pack. The snow ice growth in areas covered with pack ice gives salt fluxes commensurate with new ice growth in the autumn expansion of the ice edge over open water. These high salt fluxes therefore represent a marked contrast to the lower values of salt flux under the Arctic summer ice pack where salt fluxes are only associated with new ice forming in fall over a smaller percentage of the area than the widespread snow ice growth in the Antarctic pack ice zone.

Ackley, S. F.; Perovich, D. K.; Weissling, B.; Elder, B. C.

2011-12-01

21

The role of declining Arctic sea ice in recent decreasing terrestrial Arctic snow depths  

NASA Astrophysics Data System (ADS)

The dramatic decline in Arctic sea ice cover is anticipated to influence atmospheric temperatures and circulation patterns. These changes will affect the terrestrial climate beyond the boundary of the Arctic, consequently modulating terrestrial snow cover. Therefore, an improved understanding of the relationship between Arctic sea ice and snow depth over the terrestrial Arctic is warranted. We examined responses of snow depth to the declining Arctic sea ice extent in September, during the period of 1979-2006. The major reason for a focus on snow depth, rather than snow cover, is because its variability has a climatic memory that impacts hydrothermal processes during the following summer season. Analyses of combined data sets of satellite measurements of sea ice extent and snow depth, simulated by a land surface model (CHANGE), suggested that an anomalously larger snow depth over northeastern Siberia during autumn and winter was significantly correlated to the declining September Arctic sea ice extent, which has resulted in cooling temperatures, along with an increase in precipitation. Meanwhile, the reduction of Arctic sea ice has amplified warming temperatures in North America, which has readily offset the input of precipitation to snow cover, consequently further decreasing snow depth. However, a part of the Canadian Arctic recorded an increase in snow depth driven locally by the diminishing September Arctic sea ice extent. Decreasing snow depth at the hemispheric scale, outside the northernmost regions (i.e., northeastern Siberia and Canadian Arctic), indicated that Arctic amplification related to the diminishing Arctic sea ice has already impacted the terrestrial Arctic snow depth. The strong reduction in Arctic sea ice anticipated in the future also suggests a potential long-range impact on Arctic snow cover. Moreover, the snow depth during the early snow season tends to contribute to the warming of soil temperatures in the following summer, at least in the northernmost regions.

Park, Hotaek; Walsh, John E.; Kim, Yongwon; Nakai, Taro; Ohata, Tetsuo

2013-06-01

22

Properties of sea ice and overlying snow in the Southern Sea of Okhotsk  

Microsoft Academic Search

The general properties of sea ice and overlying snow in the southern Sea of Okhotsk were examined during early February of\\u000a 2003 to 2005 with the P\\/V “Soya”. Thin section analysis of crystal structure revealed that frazil ice (48% of total core length)\\u000a was more prevalent than columnar ice (39%) and that stratigraphic layering was prominent with a mean layer

Takenobu Toyota; Shinya Takatsuji; Kazutaka Tateyama; Kazuhiro Naoki; Kay I. Ohshima

2007-01-01

23

A tentative climatology of the snow load on Arctic sea ice based on satellite  

Microsoft Academic Search

Having a firm grasp of the sea ice extent carries over to the understanding of poleward energy transport, atmospheric heat exchange and high-latitude ocean dynamics at large. One reason to investigate the snow load is the insulation against exchange of heat. Another, regarding the intrinsic value of remote sensing, is that snow constitutes the greatest unknown in sea ice altimetry.

T. M. Schroeder; L. T. Pedersen; R. T. Tonboe

2007-01-01

24

Wideband radar for airborne measurements of snow thickness on sea ice  

NASA Astrophysics Data System (ADS)

Ocean-ice-atmosphere interactions are modulated by snow cover on the sea ice due to the low thermal conductivity and high reflectivity of snow. Current sea ice models use climatological data to simulate a snow cover on the sea ice. Snow cover is also the main source of error in deriving sea ice thickness from freeboard height measurements made by satellite-borne radar and laser altimeters. To improve sea ice models, and, ultimately, global climate models accurate knowledge of snow thickness of sea ice over a large area, with fine spatial resolution is desired. The Center for Remote Sensing of Ice Sheets at the University of Kansas has developed a wideband, frequency-modulated, continuous-wave (FMCW) radar for measuring snow thickness on sea ice from a fast-moving, long-range aircraft. The wideband radar, referred to as the Snow Radar, has been successfully deployed on multiple NASA Operation IceBridge missions. Basic waveform parameters of the Snow Radar are a 2.0 to 6.5 GHz bandwidth with a 250-us pulse length. However, with the FMCW radar architecture intermediate frequencies in the range of 31-62 MHz are digitized. The Snow Radar was designed to operate from a nominal altitude of 1500 ft above ground level, but can withstand +/- 500 ft of altitude variation without tweaking the nominal waveform parameters. Vertical resolution of the Snow Radar in snow, assuming a density of 0.3 g/cm3 and after application of a fast-time Hann window, is approximately 5.25 cm. We will discuss radar hardware, performance specifications, signal processing, measurements attained and provide preliminary results from the 2009-2010 Operation IceBridge missions. Representative Snow Radar processing output from 04/02/09 Thule to Fairbanks flight

Panzer, B.; Leuschen, C.; Blake, W.; Crowe, R.; Patel, A.; Gogineni, P. S.; Markus, T.

2010-12-01

25

On the sensitivity of large scale sea-ice models to snow thermal conductivity  

NASA Astrophysics Data System (ADS)

In both hemispheres, the sea-ice snow cover is a key element in the local climate system and particularly in the processes driving the sea-ice thickness evolution. Because of its high reflectance and thermal insulating properties, the snow pack inhibits or delays the sea-ice summer surface melt. In winter however, snow acts as a blanket that curtails the heat loss from the sea ice to the atmosphere and therefore reduces the basal growth rate. Among the snow thermo-physical properties, snow thermal conductivity is known to be one of the most important with regard to the sea-ice-related thermodynamical processes. In the literature, both model and observational studies parameterize the snow thermal conductivity as a function of density and several different relationships are used. For the purpose of large scale modelling, one issue is then to have the snow density correctly represented while, for computational cost reasons, a comprehensive snow scheme can generally not be used in such models. Since it is known by observationalists that one of the key atmospheric parameters that affect snow thermal conductivity and density is the wind speed, one way to get around the problem is to try to have a realistic representation of the snow density profiles on the sea-ice directly using observations or simple wind speed depending parameterizations. In this study, we analyze the importance of the snow density profile and thermal conductivity in the thermodynamic-dynamic Louvain-la-Neuve Sea-Ice Model (LIM3), which is part of the ocean modelling platform NEMO (Nucleus for European Modelling of the Ocean, IPSL, Paris). In order to do this, a new snow thermodynamic scheme was developed and implemented into LIM3. This scheme is multilayer with varying snow thermo-physical properties. For memory and computational cost reasons, it includes only 3 layers but the vertical grid is refined in thermodynamic routines. Although snow density is time- and space-dependent in the model, it is not a prognostic variable. The shape of the density profile is either prescribed as a function of snow and ice thicknesses and based on snow pit observations, or parameterized as a function of seasonally averaged wind speeds. LIM3 exhibits a large sensitivity to the different tested formulations in both the Arctic, due to considerable changes in the sea-ice bottom growth and melting rates and therefore significant total sea-ice volume changes between the various runs ; and the Antarctic, because of strong ice-ocean feedbacks impacting on the sea-ice volume and extent of the whole Southern Ocean.

Lecomte, O.; Fichefet, T.; Vancoppenolle, M.; Massonnet, F.

2012-04-01

26

Modelling the influence of snow accumulation and snow-ice formation on the seasonal cycle of the Antarctic sea-ice cover  

Microsoft Academic Search

Recent observational and numerical studies of the maritime snow cover in the Antarctic suggest that snow on top of sea ice\\u000a plays a major role in shaping the seasonal growth and decay of the ice pack in the Southern Ocean. Here, we make a quantitative\\u000a assessment of the importance of snow accumulation in controlling the seasonal cycle of the ice

T. Fichefet; M. A. Morales Maqueda

1999-01-01

27

On the representation of snow in large scale sea-ice models  

NASA Astrophysics Data System (ADS)

In both hemispheres, the sea-ice snow cover is a key element in the local climate system and particularly in the processes driving the sea-ice thickness evolution. Because of its high reflectance and thermal insulating properties, the snow pack inhibits or delays the sea-ice summer surface melt. In winter however, snow acts as a blanket that curtails the heat loss from the sea ice to the atmosphere and therefore reduces the basal growth rate. Among the processes controlling the snow state on sea ice, snowfall, wind and temperature changes are probably the most important. Despite its high horizontal heterogeneity, due to the transport by wind and the underlying sea-ice thickness distribution, the snow cover is vertically stratified. Each layer carries a signature of past weather events, for relatively recent snow, and metamorphic pathways that older snow may have been through. In a simplified model, this snow stratigraphy can be represented by its vertical density profi[|#12#|]le, while the other snow properties are assumed to be computationable from density. In this study, we analyze the importance of the snow density profi[|#12#|]le in both one-dimensional and full versions of the thermodynamic-dynamic Louvain-la-Neuve Sea-Ice Model (LIM3), which is part of the ocean modelling platform NEMO (Nucleus for European Modelling of the Ocean, IPSL, Paris). In order to do this, a new snow thermodynamic scheme was developed and implemented into LIM3. This scheme is multilayer with varying snow thermo-physical properties. For memory and computational cost reasons, it includes only 3 layers but the vertical grid is refi[|#12#|]ned in thermodynamic routines. Although snow density is time- and space-dependent in the model, it is not a prognostic variable. The shape of the density pro[|#12#|]file is prescribed as a function of snow and ice thicknesses, based on snow pit observations. Several typical profi[|#12#|]les are tested in the model and results are presented by comparison with the model's standard version and sea-ice extent satellite observations.

Lecomte, O.; Fichefet, T.; Vancoppenolle, M.; Massonnet, F.

2011-12-01

28

Elevated mercury measured in snow and frost flowers near Arctic sea ice leads  

Microsoft Academic Search

Elevated mercury concentrations have been reported in arctic coastal snow far from emission sources. The mercury is deposited during mercury depletion events (MDEs), a set of photochemical atmospheric reactions involving reactive halogens. The highest mercury concentrations are clustered near the coast, leading to speculation that sea ice or sea ice leads play a role in MDEs. The nature of this

T. A. Douglas; M. Sturm; W. R. Simpson; S. Brooks; S. E. Lindberg; D. K. Perovich

2005-01-01

29

Vertical profiles of bromoform in snow, sea ice, and seawater in the Canadian Arctic  

NASA Astrophysics Data System (ADS)

Bromoform (CHBr3) was measured in vertical profiles from the snow surface through the snowpack, sea ice, and water column to the seafloor at Resolute Bay, Canada, in the spring of 1992. Elevated concentrations of bromoform were observed in both the ice (32-266 ng L-1 by liquid water volume) and seawater (˜20 ng L-1) at the ice-water interface, associated with bromoform emission from ice microalgae. A surprising finding was a second horizon of high bromoform concentrations (336-367 ng L-1) in sea ice at the snow-ice interface. Chlorophyll and salinity were also elevated in this upper ice layer, although chlorophyll was much lower than in the basal ice microalgal layer. We speculate that this upper bromoform-enriched layer may have originated from scavenging of the surface water layer by frazil ice during initial ice formation in the preceding autumn. Equally unexpected was the occurrence of yet higher bromoform concentrations in snowpack immediately overlying the sea ice (492-1260 ng L-1), declining in concentration (by about a factor of 2 or more) toward the snow surface. Snow of very recent origin, however, contained as little as 2 orders of magnitude less bromoform than the older snowpack. Possible origins for elevated bromoform in the snowpack include diffusion out of the bromoform-enriched upper ice layer and gradual concentration of bromoform out of the atmosphere by adsorption on to ice crystals. These are considered in turn. In one scenario, photolysis of bromoform from snow is considered, which might help account for atmospheric bromine-ozone chemistry. The possible contributions from snow, sea ice, and seawater to atmospheric bromoform levels during both the winter and spring are also considered, and it is concluded that surface seawater presents the most significant reservoir for atmospheric bromoform.

Sturges, William T.; Cota, Glenn F.; Buckley, Paul T.

1997-11-01

30

On the representation of snow in large scale sea ice models  

NASA Astrophysics Data System (ADS)

An assessment of the performance of a state-of-the-art large-scale coupled sea ice -ocean model, including a new snow multi-layer thermodynamic scheme, in simulating the sea ice thickness and extent over the past three decades in both hemispheres, is performed. Four simulations from the model are compared against each other and against submarine, airborne and satellite observations. Each simulation uses a separate formulation for snow apparent thermal conductivity and density. In the first experiment, the snow density profile is prescribed from observations and the thermal conductivity is constant and equal to 0.31 W m-1 K-1, a typical value for such models. Formulations (2) and (3) are typical power-law relationships linking thermal conductivity directly to density (prescribed as in simulation (1)). Parameterization (4) is newly developed and consists of a set of two linear equations relating the snow thermal conductivity and density to the mean seasonal wind speed. We show that the first simulation leads to an overestimation of the sea ice thickness due to overestimated snow thermal conductivity, particularly in the Northern Hemisphere. Formulation (2) leads to a realistic simulation of the Arctic sea ice mean state while (3) provides the minimum deviations with respect to sea ice extent and thickness observations in the Southern Ocean. Parameterization (4), accounting for the snow packing process in a simple way, is the most promising formulation. In particular, this formulation improves the simulated large-scale snow depth probability density functions. The intercomparison of all simulations suggests that the sea ice model is more sensitive to the snow representation in the Arctic than it is in the Southern Ocean, where both the simulated sea ice mean state and variability seem to be dominantly driven by the ocean.

Lecomte, Olivier; Fichefet, Thierry; Vancoppenolle, Martin; Domine, Florent; Massonnet, François; Mathiot, Pierre; Morin, Samuel; Barriat, Pierre-Yves

2013-04-01

31

The role of snow on microwave emission and scattering over first-year sea ice  

Microsoft Academic Search

Investigates the geophysical and thermodynamic effects of snow on sea ice in defining the electromagnetic (EM) interaction within the microwave portion of the spectrum. The authors combine observational evidence of both the physical and thermodynamic characteristics of snow with direct measurements of scattering and emission at a variety of frequencies. They explain their observational results using various “state-of-the-art” forward scattering

David G. Barber; A. K. Fung; Thomas C. Grenfell; Son V. Nghiem; Robert G. Onstott; V. I. Lytle; Donald K. Perovich; Anthony J. Gow

1998-01-01

32

The effects of additional black carbon on the albedo of Arctic sea ice: variation with sea ice type and snow cover  

NASA Astrophysics Data System (ADS)

The response of the albedo of bare sea ice and snow-covered sea ice to the addition of black carbon is calculated. Visible light absorption and light-scattering cross-sections are derived for a typical first-year and multi-year sea ice with both "dry" and "wet" snow types. The cross-sections are derived using data from a 1970s field study that recorded both reflectivity and light penetration in Arctic sea ice and snow overlying sea ice. The variation of absorption cross-section over the visible wavelengths suggests black carbon is the dominating light-absorbing impurity. The response of first-year and multi-year sea ice albedo to increasing black carbon, from 1 to 1024 ng g-1, in a top 5 cm layer of a 155 cm-thick sea ice was calculated using a radiative-transfer model. The albedo of the first-year sea ice is more sensitive to additional loadings of black carbon than the multi-year sea ice. An addition of 8 ng g-1 of black carbon causes a decrease to 98.7% of the original albedo for first-year sea ice compared to a decrease to 99.7% for the albedo of multi-year sea ice, at a wavelength of 500 nm. The albedo of sea ice is surprisingly unresponsive to additional black carbon up to 100 ng g-1 . Snow layers on sea ice may mitigate the effects of black carbon in sea ice. Wet and dry snow layers of 0.5, 1, 2, 5 and 10 cm depth were added onto the sea ice surface. The albedo of the snow surface was calculated whilst the black carbon in the underlying sea ice was increased. A layer of snow 0.5 cm thick greatly diminishes the effect of black carbon in sea ice on the surface albedo. The albedo of a 2-5 cm snow layer (less than the e-folding depth of snow) is still influenced by the underlying sea ice, but the effect of additional black carbon in the sea ice is masked.

Marks, A. A.; King, M. D.

2013-07-01

33

An Evaluation of MODIS Snow Cover and Sea Ice Extent Products at the NSIDC DAAC  

NASA Astrophysics Data System (ADS)

With the launch of the MODIS instrument on NASA's Earth Observing System (EOS) Terra satellite a new era of cryospheric monitoring from space began. For the first time daily, global maps of snow cover and sea ice extent are being produced in a fully automated fashion from space-borne measurements in optical wavelengths. The capabilities and limitations of the MODIS instrument for measuring snow cover and sea ice extent will be highlighted in several case studies in which the MODIS products are compared with other available operational analyses based on both optical and passive microwave measurements. The 1-km resolution MODIS sea ice product, as determined from both solar reflective and terrestrial emissive bands, will be compared to sea ice concentration based on passive microwave measurements. The 500-m MODIS snow cover product will be compared both to analyses based exclusively on passive microwave as well as to NOAA operational analyses based on multiple satellite sensors.

Khalsa, S. S.; Scharfen, G. R.; McLean, B.; Wolfe, J. D.

2001-12-01

34

Thermal conductivity and heat transfer through the snow on the ice of the Beaufort Sea  

Microsoft Academic Search

Eighty-nine point measurements of the thermal conductivity (ks) of the snow on the sea ice of the Beaufort Sea were made using a heated needle probe. Average values ranged from 0.078 W m-1 K-1 for new snow to 0.290 W m-1 K-1 for an ubiquitous wind slab. ks increased with increasing density, consistent with published equations, but could also be

Matthew Sturm; Donald K. Perovich; Jon Holmgren

2002-01-01

35

Impact of snow and sea-ice variations on global climate change  

SciTech Connect

Recent work with a coupled energy balance climate-sea ice model has shown that sea ice has a large impact on the energy fluxes between the ocean and the atmosphere and thus on climate, especially in the polar regions. In this study the impact of the addition of snowfall on sea ice and its effect on climate is examined. The results show that the addition of snow introduces three major competing effects. The first effect is that the snow acts as an insulator, keeping the ice warm and thus thin. This would seem to produce a warming effect on the climate. The second is that snow has a lower volumetric specific heat than ice causing it to cool during the winter and warm during the summer more rapidly than ice. The third is that snow has a higher albedo than ice. This causes a reduction in the absorbed solar energy by the entire earth-atmosphere system and thus a cooling of the climate. The results described here indicate that the albedo effect is dominant, so that the addition of snow cools the climate.

Ledley, T.S.

1992-03-01

36

The effect of snow on the thermodynamic evolution of the sea-ice cover at SHEBA  

NASA Astrophysics Data System (ADS)

A multi-layer sigma-coordinate thermodynamic snow and sea-ice model, combined with a careful heat and mass balance at the SHEBA site are used to assess errors in the model and/or inconsistencies in the SHEBA data. This model-data analysis reveals that the snow depth derived from observed precipitation (assuming a constant density of 150 kg/m3), is too low when compared to in-situ measurements or snow thickness derived from an analysis of internal temperature profiles. Moreover, the snow thermal conductivity inferred from changes in temperature gradient at the snow-ice interface are much higher than in-situ measurements or values commonly used in general circulation model. When correcting for those factors, simulation results are in very good agreement with measured ice and snow internal temperature profile and ice thickness evolution at SHEBA. These results supports the use of a brine pocket parameterization scheme included in the present model -- results without brine pocket parameterization yields basal growth in winter larger by 8cm (15%). Results also show that the ocean heat fluxes (Focn) derived from observed ice melt/growth and internal temperature at the ice base are very consistent from one mass balance site to another. The simulated basal ice evolution however cannot be sensitive to the detailed of the Focn reconstruction (e.g. assumed salinity of newly formed ice), provided the same assumption are made in the model.

Tremblay, B.; Huwald, H.; Blatter, H.

2004-05-01

37

Snow depth and sea ice thickness from 2009 and 2010 IceBridge ATM data in the Weddell Sea and the Bellingshausen Seas in Antarctica  

NASA Astrophysics Data System (ADS)

IceBridge airborne measurements are intended to fill the gap in data on the elevations of the ice sheets and the sea ice covers, caused by the interval between the demise of ICESat 1's laser altimetry in 2009 and the launch of ICESat2 approximately in 2016. IceBridge LiDAR elevation measurements from aircraft are intended to provide a means of obtaining estimates of sea ice thickness and roughness with widespread application to sea ice modeling and effects of ongoing climate change. The IceBridge's Advanced Topographic Mapper (ATM) georeferenced L1B data provides elevations relative to a geoid at nominal spot size of 1-2m spaced at 5m intervals (at nadir) along track over a track swath width of 150m to 300m. Thus, in order to derive sea ice thickness and freeboard using the ATM L1B data, a local sea level reference must be established. The IceBridge's Digital Mapping System (DMS) is a digital camera that acquires high resolution natural color and panchromatic imagery from low and medium altitude. The DMS images are used to manually identify leads (open water or thin ice), where the ATM L1B elevations can be used as local sea level references. Then, the identified local sea level references are used to validate our algorithms to automatically determine the local sea level reference using the same ATM L1B data. Finally, we use the algorithm to determine the local sea level reference and thus derive the snow depth and sea ice thickness for all ATM L1B data over the Weddell Sea and the Bellingshausen-Amundsen Seas in two IceBridge missions to Antarctica in 2009 and 2010 based on an empirical relationship between snow depth and sea ice freeboard in this region.

Wang, X.; Xie, H.; Ackley, S. F.

2011-12-01

38

Snow and sea ice thickness measurements from Operation IceBridge: bridging the past, present, and future  

NASA Astrophysics Data System (ADS)

Airborne measurements collected during NASA's Operation IceBridge have provided a rich new data set to characterize the properties and changes occurring to the Arctic and Antarctic sea ice covers. As of this writing, one Antarctic and two Arctic IceBridge campaigns have been completed. The suite of instruments aboard the IceBridge aircraft include digital photography, laser and radar altimeters, and an FMCW radar which are capable of providing measurements of sea ice freeboard, snow depth, and thickness. We will first review the methods used to obtain sea ice properties from these instruments. We will also provide an evaluation of the quality of the results through comparison with nearly coincident in-situ data collected in the Lincoln Sea in 2009. A comparison of the airborne and in-situ data shows good agreement which is very promising for the continued use of IceBridge data in studying the sea ice cover. These results are also important for quantifying the uncertainties in the IceBridge data set. We will then provide a preliminary assessment of snow and sea ice thickness over the IceBridge campaigns, and discuss the challenge of placing these results into the context of past results from the ICESat mission.

Kurtz, N. T.; Farrell, S. L.; Markus, T.; McAdoo, D. C.

2010-12-01

39

A tentative climatology of the snow load on Arctic sea ice based on satellite  

NASA Astrophysics Data System (ADS)

Having a firm grasp of the sea ice extent carries over to the understanding of poleward energy transport, atmospheric heat exchange and high-latitude ocean dynamics at large. One reason to investigate the snow load is the insulation against exchange of heat. Another, regarding the intrinsic value of remote sensing, is that snow constitutes the greatest unknown in sea ice altimetry. The properties of snow can modify how deeply into the snow-ice system the altimeter signal penetrates. While Cryosat views to the ice surface, Icesat views to the snow surface. The freeboard cannot be measured and converted to ice thickness properly without compensation for the thickness and density of the snow cover. To identify the satellite channels with most information on the scenery, we made the standard assumption that the inversion of measured brightness temperature to physical parameters is sufficiently linear to converge for Gauss-Newtonian iteration. An optimal estimation scheme has been adopted and the information content in the averaging kernel matrix scrutinized for the parameters at stake. The a priori covariance and initial guess on parameters was computed by feeding the snow-ice model Memls with ERA40 atmospheric reanalysis over a range of locations, winters, and type of ice as having grown from either scratch (first-year) or not (multiyear). Each of the currently flown passive sounders under consideration, the Advanced Microwave Scanning Radiometer (AMSR), the Advanced Microwave Sounding Unit (AMSU), and the Microwave Humidity Sounder (MHS), is modelled with a measurement error taken as the sum of sensitivity and accuracy prior to launch. Covariance between the channels has been neglected. Simulation of the actual measurement discretizes the snow pack into ten numerical layers to resolve the steep temperature gradient and applies the model Rttov to represent the air column. Snow is taken to be fresh and dry, a valid assumption until melt sets in, and the density of multi-year ice is imposed a fixed decrease above the waterline. The correlation length in ice that governs scattering shifts from water content (brine) to air bubbles after the first year. The optimal set of satellite channels has been chosen, in part, by minimizing the number of platforms involved and the jumps in frequency between them. These channels provide the basis on which we intend to retrieve a snow climatology that spans the past few years. Construction requires iteration against the assumption that either type of ice alone was covering the surface pixel and then engagement with a lookup table to meet with the brightness temperature observed. Comparison of the seasonal and regional variability is made to reanalysis and in situ measurement.

Schroeder, T. M.; Pedersen, L. T.; Tonboe, R. T.

2007-12-01

40

Estimation of snow water equivalent using microwave radiometry over Arctic first-year sea ice  

NASA Astrophysics Data System (ADS)

The magnitude and spatial distribution of snow on sea ice are both integral components of the ocean-sea-ice-atmosphere system. Although there exists a number of algorithms to estimate the snow water equivalent (SWE) on terrestrial surfaces, to date there is no precise method to estimate SWE on sea ice. Physical snow properties and in situ microwave radiometry at 19, 37 and 85 GHz, V and H polarization were collected for a 10-day period over 20 first-year sea ice sites.We present and compare the in situ physical, electrical and microwave emission properties of snow over smooth Arctic first-year sea ice for 19 of the 20 sites sampled. Physical processes creating the observed vertical patterns in the physical and electrical properties are discussed. An algorithm is then developed from the relationship between the SWE and the brightness temperature measured at 37 GHz (55°) H polarization and the air temperature. The multiple regression between these variables is able to account for over 90% of the variability in the measured SWE. This algorithm is validated with a small in situ data set collected during the 1999 field experiment. We then compare our data against the NASA snow thickness algorithm, designed as part of the NASA Earth Enterprise Program. The results indicated a lack of agreement between the NASA algorithm and the algorithm developed here. This lack of agreement is attributed to differences in scale between the Special Sensor Microwave/Imager and surface radiometers and to differences in the Antarctic versus Arctic snow physical and electrical properties. Copyright

Barber, D. G.; Iacozza, J.; Walker, A. E.

2003-12-01

41

A theory for the scalar roughness and the scalar transfer coefficients over snow and sea ice  

Microsoft Academic Search

Although the bulk aerodynamic transfer coefficients for sensible (CH) and latent (CE) heat over snow and sea ice surfaces are necessary for accurately modeling the surface energy budget, they have been measured rarely. This paper, therefore, presents a theoretical model that predicts neutral-stability values of CH and CE as functions of the wind speed and a surface roughness parameter. The

Edgar L. Andreas

1987-01-01

42

Brine-Wetted Snow on the Surface of Sea Ice: A Potentially Vast and Overlooked Microbial Habitat  

NASA Astrophysics Data System (ADS)

On the hemispheric scale, snow on the surface of sea ice significantly impacts the exchange of mass and energy across the ocean-ice-atmosphere interface. The snow cover over Arctic sea ice plays a central role in Arctic photochemistry, including atmospheric depletion events at the onset of spring, and in ecosystem support, by determining the availability of photosynthetically active radiation for algal primary production at the bottom of the ice. Among the non-uniformities of snow relevant to its larger-scale roles is salt content. When snow is deposited on the surface of new sea ice, brine expelled onto the ice surface during ice formation wicks into the snow by capillary action, forming a brine-wetted or saline snow layer at the ice-snow interface. A typical salinity for this basal snow layer in the Arctic (measured on a 3-cm depth interval of melted snow) is about 20 (ppt by optical salinometer), with maxima approaching 30 ppt, thus higher than the salinity of melted surface sea ice (< 12 ppt). Although the physical-chemical properties of this brine-wetted layer have been examined in recent years, and the (assumed) air-derived microbial content of overlying low-salinity snow is known to be low in winter, basal saline snow is essentially unexplored as a microbial habitat. As part of an NSF-supported project on frost flowers, we investigated snow overlying coastal sea ice off Barrow, Alaska, in February 2010 (since snow buries frost flowers). Sterile (ethanol-rinsed) tools were used to open snow pits 60 cm wide, record temperature by thermoprobe at 3-cm depth intervals, and collect samples from newly exposed snow walls for salinity (3-cm intervals) and biological measurements (6-cm intervals). The latter included counts of bacterial abundance by epifluorescence microscopy and assays of extracellular polysaccharide substances (EPS). We also sampled snow on a larger scale to extract sufficient DNA to analyze microbial community composition (ongoing work), as well as underlying sea ice for comparative purposes. Results indicated presence of an areally extensive saline snow layer (salinities of 18.5-30.9 ppt) that was enriched in bacteria (0.28-1.5 x 10E4 bacteria/ml) and EPS (0.07-0.22 mg glucose equivalents/L) relative to overlying low-salinity snow (0.3-9 ppt; 2-9 x 10E2 bacteria/ml; 0.021-0.11 mg glucose equivalents/L). Analysis of content and distribution of salts, bacteria and EPS throughout the snow and underlying sea ice indicated sea-ice brines as the source of these materials in snow. Although marine bacteria appeared to have moved upwards into snow in sync with brine, EPS was subject to different transport or production and degradation pathways, perhaps connected to a detected sensitivity of bacteria in upper sea ice brines to osmotic shock. The possible passive and dynamic roles of bacteria and their exudates in these brine-wetted snows in influencing the physical-chemical properties of snow over sea ice, including later season physical and biological impacts as the snow melts and infiltrates the ice below, await further study.

Deming, J. W.; Ewert, M.; Bowman, J. S.; Colangelo-Lillis, J.; Carpenter, S. D.

2010-12-01

43

Spatial Variation of, and Correlations Among, Snow Surface Albedo and Physical Parameters of Summer Snow Cover on Sea Ice in the Ross Sea, Antarctica  

NASA Astrophysics Data System (ADS)

All-wave albedo and spectral albedo of snow on sea ice were measured in the Ross Sea during a cruise in January-February, 1999. Concurrent measurements of physical parameters of the snow cover such as composite snow grain size, single snow grain size, snow mass density, snow surface temperature, and snow stratification were carried out. Snow particles in each 3 cm deep sample (volume 100 cm-3) were described in terms of shape and general appearance using standardized terms, i.e., facets, striates, meltclusters, chains of grains, etc., and the relative proportion of each particle type with average radius were determined. Most of the snow samples had undergone some metamorphosis. As a consequence, the particles were divided into two categories: the overall centimeter-order size of the larger, composite grains such as meltclusters, and the millimeter-order size of the grains (single grains) that made up the meltclusters. Based on these in situ measurements, three statistically average grain size models (equal grain number model, size distribution integrated average model and effective radius model) are used for the relation analyses between albedo and snow grain size for the two categories (composite grain and single grain). Correlations between albedo and snow physical parameters show that summer snow albedo is more sensitive to the snow cluster grain size than the single snow grain size for the top 9 cm of the snow cover. The strongest correlation is observed for the top 3 cm of snow. Coefficients and significance of correlation between albedo and composite grain size decrease with snow depth. Correlation analyses between albedo and composite grain number density show that in the top 9 cm of the snow cover, albedo is strongly correlated with the composite grain number density: the larger the number density of composite grains of the snow surface layer, the higher the albedo. This correlation decreases with depth. The same analyses for the single grain size and single grain number density show that there is no significant correlation between albedo and single grain size or between albedo and single grain number density. From the correlation analyses between albedo, snow surface temperature and composite grain size, it is found that the lower the surface temperature and the smaller the surface composite grain size, the higher the albedo. Spatial variation analyses of snow albedo and physical parameters show that in the Ross Sea pack ice there are notable latitudinal variations in albedo and physical snow parameters. As the ship moved southward through the pack ice: the snow surface temperature decreased; albedo was higher; the snow mass density was higher; the snow composite grain size decreased; and the number density of composite grains increased. All-wave albedo in visible and near infrared were lower at ice edges than at central pack ice due to larger grain size and lower number density.

Zhou, X.; Li, S.; Morris, K.

2001-12-01

44

Geostatistical Characterization of Snow-Depth Structures on Sea Ice Near Point Barrow, Alaska—A Contribution to the AMSR-Ice03 Field Validation Campaign  

Microsoft Academic Search

The objective of this paper is to characterize spatial properties of snow-depth structures and their role as indicators of sea-ice properties and sea-ice-morphogenetic processes, and to provide quantitative measures of sea-ice properties that may be utilized in analyses of passive-microwave data. Snow-depth data collected near Point Barrow, Alaska, as part of the AMSRIce03 Field Validation Campaign for Advanced Microwave Scanning

Ute C. Herzfeld; James A. Maslanik; Matthew Sturm

2006-01-01

45

Climate response of fossil fuel and biofuel soot, accounting for soot's feedback to snow and sea ice albedo and emissivity  

Microsoft Academic Search

The first three-dimensional global model in which time-dependent spectral albedos and emissivities over snow and sea ice are predicted with a radiative transfer solution, rather than prescribed, is applied to study the climate response of fossil fuel plus biofuel black carbon plus organic matter (ff+bf BC+OM) when BC absorption in snow and sea ice is accounted for. The model treats

Mark Z. Jacobson

2004-01-01

46

East Antarctic Sea Ice: Albedo, Thickness Distribution, and Snow Cover  

Microsoft Academic Search

types were estimated hourly for the region near the ship. These observations were carried out continuously during the 4 weeks the ship was in the ice. Thin and young ice types were prevalent throughout the region, and the observations show a systematic increase in the total area-weighted pack ice thickness (including open water area) from only 0.2 m within 50

Ian Allison; Richard E. Brandt; Stephen G. Warren

1993-01-01

47

Evolution of first-year and second-year snow properties on sea ice in the Weddell Sea during spring-summer transition  

Microsoft Academic Search

Observations of snow properties, superimposed ice, and atmospheric heat fluxes have been performed on first-year and second-year sea ice in the western Weddell Sea, Antarctica. Snow in this region is particular as it does usually survive summer ablation. Measurements were performed during Ice Station Polarstern (ISPOL), a 5-week drift station of the German icebreaker RV Polarstern. Net heat flux to

Marcel Nicolaus; Christian Haas; Sascha Willmes

2009-01-01

48

Arctic report card: Sea ice and snow reached record lows in 2012  

NASA Astrophysics Data System (ADS)

Despite air temperatures that were not abnormally high, the Arctic set new record lows for snow cover and sea ice extent in 2012. Studies detailing these records are included in the 2012 update of NOAA's Arctic Report Card, which was released 5 December at a press conference at the AGU Fall Meeting. This is the sixth annual update of the report card, which covers a wide variety of indicators about the Arctic, including the atmosphere, sea ice, glaciers and terrestrial snow cover, and marine and terrestrial ecosystems. Among the records noted is extensive melting of the Greenland ice sheet. “I've studied Greenland for 20 years now—I've devoted my career to it—and 2012 was an astonishing year,” said Jason Box of the Byrd Polar Research Center at Ohio State University. He noted that the duration of the melting season in 2012 was the longest in the recent record, there were record high areas and volumes of ice lost, and surface melting was documented at the highest elevations of the ice sheet.

Balcerak, Ernie

2012-12-01

49

Evolution of first-year and second-year snow properties on sea ice in the Weddell Sea during spring-summer transition  

NASA Astrophysics Data System (ADS)

Observations of snow properties, superimposed ice, and atmospheric heat fluxes have been performed on first-year and second-year sea ice in the western Weddell Sea, Antarctica. Snow in this region is particular as it does usually survive summer ablation. Measurements were performed during Ice Station Polarstern (ISPOL), a 5-week drift station of the German icebreaker RV Polarstern. Net heat flux to the snowpack was 8 W m-2, causing only 0.1 to 0.2 m of thinning of both snow cover types, thinner first-year and thicker second-year snow. Snow thinning was dominated by compaction and evaporation, whereas melt was of minor importance and occurred only internally at or close to the surface. Characteristic differences between snow on first-year and second-year ice were found in snow thickness, temperature, and stratigraphy. Snow on second-year ice was thicker, colder, denser, and more layered than on first-year ice. Metamorphism and ablation, and thus mass balance, were similar between both regimes, because they depend more on surface heat fluxes and less on underground properties. Ice freeboard was mostly negative, but flooding occurred mainly on first-year ice. Snow and ice interface temperature did not reach the melting point during the observation period. Nevertheless, formation of discontinuous superimposed ice was observed. Color tracer experiments suggest considerable meltwater percolation within the snow, despite below-melting temperatures of lower layers. Strong meridional gradients of snow and sea-ice properties were found in this region. They suggest similar gradients in atmospheric and oceanographic conditions and implicate their importance for melt processes and the location of the summer ice edge.

Nicolaus, Marcel; Haas, Christian; Willmes, Sascha

2009-09-01

50

Sea ice and snow cover characteristics during the winter–spring transition in the Bellingshausen Sea: An overview of SIMBA 2007  

Microsoft Academic Search

The Sea Ice Mass Balance in the Antarctic (SIMBA) experiment was conducted from the RVIB N.B. Palmer in September and October 2007 in the Bellingshausen Sea in an area recently experiencing considerable changes in both climate and sea ice cover. Snow and ice properties were observed at 3 short-term stations and a 27-day drift station (Ice Station Belgica, ISB) during

M. J. Lewis; J. L. Tison; B. Weissling; B. Delille; S. F. Ackley; F. Brabant; H. Xie

2011-01-01

51

Protective Coverings for Ice and Snow.  

National Technical Information Service (NTIS)

Summer deterioration of snow and ice surfaces due to high solar radiation and near-melting temperatures hampers the year-round use of natural ice islands and smooth sea-ice areas in the Arctic Ocean, and permanent snow and ice areas in the Antarctic. Sawd...

N. S. Stehle

1966-01-01

52

In Situ Thickness Observations of Sea Ice and Snow in the Fram Strait  

Microsoft Academic Search

The Fram Strait, at the end of the transpolar drift is the main gateway for multiyear sea ice exiting the Arctic Basin. Knowledge about sea ice in the Fram Strait gives information on the general state of high-arctic sea ice. In particular, sea ice mass balance can be derived from knowing ice concentration, extent and thickness. Since 2003, we regularly

S. Gerland; C. Haas; H. Goodwin; M. Nicolaus; A. Nicolaus; E. Hansen; A. H. Renner

2007-01-01

53

Bacterial and extracellular polysaccharide content of brine-wetted snow over Arctic winter first-year sea ice  

NASA Astrophysics Data System (ADS)

During freeze-up and consolidation, sea ice rejects to its surface brine of marine origin that is incorporated into overlying snow. To evaluate the transport of biological components in brines from ice to snow, vertical profiles of temperature, salinity, bacterial abundance, and extracellular polysaccharide substances (EPS) were obtained through snow and first-year sea ice (Barrow, AK) in consecutive winters (2010, 2011). Snow profiles showed strong interannual variation, with 2010 presenting higher values and wider ranges in salinity (0.3-30.9, practical salinity), bacterial abundance (2.8 × 102-1.5 × 104 cells mL- 1), and particulate EPS (pEPS, 0.04-0.23 glucose equivalents (glu-eq) mg L- 1) than 2011 (0-11.9, 2.7 × 103-4.2 × 103 cells mL- 1 and 0.04-0.09 glu-eq mg L- 1, respectively). Surface ice also differed interannually, with 2010 presenting again higher salinity (19.4, n = 1), bacterial abundance (5.4 × 104-9.6 × 104 cells mL- 1) and pEPS (0.13-0.51 glu-eq mg L- 1) than 2011 (7.7-11.9, 1.7 × 104-2.2 × 104 cells mL- 1, and 0.01-0.09 glu-eq mg L- 1, respectively). Transport of bacteria and pEPS from sea-ice brines into snow was evident in 2010 but not 2011, a year with more extreme winter conditions of colder temperature, thinner snow, and stronger wind. By size fraction, the smallest EPS (< 0.1 µm) dominated (> 80%) total EPS in both ice and snow; the > 3 µm fraction of EPS in snow appeared to have an atmospheric source. Evaluation of membrane integrity by Live/Dead stain revealed a high percentage (85%) of live bacteria in saline snow, identifying this vast environment as a previously unrecognized microbial habitat.

Ewert, M.; Carpenter, S. D.; Colangelo-Lillis, J.; Deming, J. W.

2013-02-01

54

The seasonal cycle of snow cover, sea ice and surface albedo  

Microsoft Academic Search

The paper examines satellite data used to construct mean snow cover caps for the Northern Hemisphere. The zonally averaged snow cover from these maps is used to calculate the seasonal cycle of zonally averaged surface albedo. The effects of meltwater on the surface, solar zenith angle, and cloudiness are parameterized and included in the calculations of snow and ice albedo.

Alan Robock

1980-01-01

55

Snow and Ice Data Discovery and Access  

NSDL National Science Digital Library

The National Snow and Ice Data Center has produced numerous resources for exploring snow and ice through data, images, and visualization. This site includes access to data sets, image banks, web-based map servers and Google Earth KML files. Topics include glaciers, sea ice, climate change, and polar research.

Center, National S.

56

An AeroCom assessment of black carbon in Arctic snow and sea ice  

NASA Astrophysics Data System (ADS)

Though many global aerosols models prognose surface deposition, only a few models have been used to directly simulate the radiative effect from black carbon (BC) deposition to snow and sea-ice. Here, we apply aerosol deposition fields from 25 models contributing to two phases of the Aerosol Comparisons between Observations and Models (AeroCom) project to simulate and evaluate within-snow BC concentrations and radiative effect in the Arctic. We accomplish this by driving the offline land and sea-ice components of the Community Earth System Model with different deposition fields and meteorological conditions from 2004-2009, during which an extensive field campaign of BC measurements in Arctic snow occurred. We find that models generally underestimate BC concentrations in snow in northern Russia and Norway, while overestimating BC amounts elsewhere in the Arctic. Although simulated BC distributions in snow are poorly correlated with measurements, mean values are reasonable. The multi-model mean (range) bias in BC concentrations, sampled over the same grid cells, snow depths, and months of measurements, are -4.4 (-13.2 to +10.7) ng g-1 for an earlier Phase of AeroCom models (Phase I), and +4.1 (-13.0 to +21.4) ng g-1 for a more recent Phase of AeroCom models (Phase II), compared to the observational mean of 19.2 ng g-1. Factors determining model BC concentrations in Arctic snow include Arctic BC emissions, transport of extra-Arctic aerosols, precipitation, deposition efficiency of aerosols within the Arctic, and meltwater removal of particles in snow. Sensitivity studies show that the model-measurement evaluation is only weakly affected by meltwater scavenging efficiency because most measurements were conducted in non-melting snow. The Arctic (60-90° N) atmospheric residence time for BC in Phase II models ranges from 3.7 to 23.2 days, implying large inter-model variation in local BC deposition efficiency. Combined with the fact that most Arctic BC deposition originates from extra-Arctic emissions, these results suggest that aerosol removal processes are a leading source of variation in model performance. The multi-model mean (full range) of Arctic radiative effect from BC in snow is 0.15 (0.07-0.25) W m-2 and 0.18 (0.06-0.28) W m-2 in Phase I and Phase II models, respectively. After correcting for model biases relative to observed BC concentrations in different regions of the Arctic, we obtain a multi-model mean Arctic radiative effect of 0.17 W m-2 for the combined AeroCom ensembles. Finally, there is a high correlation between modeled BC concentrations sampled over the observational sites and the Arctic as a whole, indicating that the field campaign provided a reasonable sample of the Arctic.

Jiao, C.; Flanner, M. G.; Balkanski, Y.; Bauer, S. E.; Bellouin, N.; Berntsen, T. K.; Bian, H.; Carslaw, K. S.; Chin, M.; De Luca, N.; Diehl, T.; Ghan, S. J.; Iversen, T.; Kirkevåg, A.; Koch, D.; Liu, X.; Mann, G. W.; Penner, J. E.; Pitari, G.; Schulz, M.; Seland, Ø.; Skeie, R. B.; Steenrod, S. D.; Stier, P.; Takemura, T.; Tsigaridis, K.; van Noije, T.; Yun, Y.; Zhang, K.

2013-10-01

57

Derivation and Validation of Snow Depth over Arctic Sea Ice by Integrating Snow Radar, Airborne Topographic Mapper, and In-Situ Measurement Data from the Greenland 2009 IceBridge Campaign  

NASA Astrophysics Data System (ADS)

Using NASA's Operation IceBridge airborne data, this paper examines the derivation of snow depth on sea ice using measurements from two instruments, the Snow Radar and Atmospheric Topographic Mapper (ATM), taken off the northern coast of Greenland in April 2009. In-situ measurements of sea ice thickness, freeboard and snow depth obtained at the GreenArc ice camp are used as comparison points to the estimates made where possible. We also present range estimation and geolocation methodology for the Snow Radar data and analyze possible sources of error within these estimates. The Snow Radar is an ultra-wideband (2 - 6.5 GHz) Frequency Modulated Continuous-Wave (FMCW) radar that penetrates the snow layer and is able to discern both the snow-ice (SI) and the snow-air (SA) interfaces. The detected radar backscatter signature contains peaks in the return where the boundaries occur, with the SI interface having a stronger power return than the SA boundary. Level 1B data of radar echo strength range profiles are used to generate estimates of the distance from the radar antenna to the SI and SA interfaces. Aircraft position and attitude data are then used to georeference the radar range data as height estimates above the WGS-84 ellipsoid. The ATM is a conically scanning LIDAR that measures the range from the aircraft to the Earth's surface. Because the laser does not penetrate the snow or ice surface, the surface is interpreted to be the SA interface or the ice-air (IA) interface in the case of bare ice. Level 1B ATM data of WGS-84 referenced elevations are used in the comparison. Validation of the ATM-provided elevations and calibration of the Snow Radar-derived elevations were performed using data collected over GPS surveyed areas of the Thule air force base in Greenland. ATM surface height elevations will be shown to agree with the GPS surveyed area to within 10 cm. Initial calibrations of the radar estimated heights with the GPS surveyed area show an offset of approximately 1 m. When the radar measurements are corrected for the estimated offset and compared to the ATM measurements over bare ice, the two will be shown to be in very good agreement. This paper will then show how the collocated Snow Radar and ATM measurements are used to derive estimates of snow depth over sea ice, which are also compared where possible with the snow depth measurements.

Johnson, M. P.; Perkovic, D.; Panzer, B.; Holt, B.; Leuschen, C.

2011-12-01

58

Thermal conductivity and heat transfer through the snow on the ice of the Beaufort Sea  

Microsoft Academic Search

snowpack was 0.14 W m? 1 K? 1. In contrast, ks inferred from ice growth and temperature gradients in the snow was 0.33 W m? 1 K? 1. The mismatch arises in part because the second estimate is based on measurements from an aggregate scale that includes enhanced heat flow due to two- and three-dimensional snow and ice geometry. A

Matthew Sturm; Donald K. Perovich; Jon Holmgren

2000-01-01

59

Applications of MODIS Snow and Ice Products  

NASA Astrophysics Data System (ADS)

For nearly seven years, daily global estimates of snow cover and sea ice extent have been produced using data from the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard NASA's Terra spacecraft. Data from a second MODIS, launched on the Aqua satellite in 2002, added observations from a local time of day 3 hours later than Terra. These datasets are providing new opportunities for global cryospheric monitoring. The products include snow cover, fractional snow cover, snow albedo, and sea ice extent. They are available on a daily or 8-day composite basis and at nominal 500 m (sinusoidal) or 0.05 degree (climate modeling grid) spatial resolution. In this paper we summarize the advantages of the MODIS snow and ice products over other available operational analyses and highlight several applications that are currently using the MODIS products. Improvements to hydrological modeling in several different regions of the world have been realized through the application of MODIS snow cover data. Sea ice monitoring and the identification of melt ponds has been improved. Also, MODIS snow cover and sea ice data are showing potential to improve numerical models of land surface processes and weather forecasting. The MODIS snow cover products are providing supplementary products for sensor fusion efforts with passive microwave and radar retrievals to improve, for example, estimates of snow water equivalent. Efforts to produce a global mapping of perennial land ice will also be highlighted.

Khalsa, S. S.; Painter, T. H.; McAllister, M.; Duerr, R.

2006-12-01

60

Recent progress in snow and ice research  

SciTech Connect

A review of snow and ice research in 1987-1990 is presented, focusing on the effects of layers in seasonal snow covers, ice mechanics on fresh water and sea ice, and remote sensig of polar ice sheets. These topics provide useful examples of general needs in snow and ice research applicable to most areas, such as better representation in models of detailed processes, controlled laboratory experiments to quantify processes, and field studies to provide the appropriate context for interpretation of processes from remote sensing.

Richter-menge, J.A.; Colbeck, S.C.; Jezek, K.C. (USAF, Geophysics Laboratory, Hanscom AFB, MA (United States))

1991-01-01

61

Remote Sensing of Sea Ice.  

National Technical Information Service (NTIS)

We are studying fully polarimetric scattering of electromagnetic waves from snow and sea ice with a three-layer random medium model which can account for snow covered sea ice. The snow layer is modeled as an isotropic random medium characterized by a scal...

J. A. Kong R. T. Shin M. Borgeaud S. V. Nghiem

1989-01-01

62

Studying Snow and Ice Changes  

NSDL National Science Digital Library

Scientists have recently been reporting that the average temperature of the Earth has been rising, usually referred to as 'global warming'. What is the evidence for this change? One piece of evidence could come from patterns of snow (on land) and ice (either sea ice floating on the oceans or glaciers on land) on the Earth - if the snow and ice are disappearing, it would indicate rising average temperatures. This exercise is meant to examine the pattern of snow and ice on the Earth to determine what trends are visible. Students will create maps that show the average of a year's worth of snow and ice data for the entire Earth, by using MY NASA DATA's 'Define Variable' procedure. This will be done for 2 years, 1994 and 2004. Then they will use the 'Compare Two' capability to find the difference between the 2 average maps (i.e., subtract the 1994 value from the 2004 value in all corresponding locations on the map), to see how the averages have changed in all locations between the 2 years.

63

Winter snow cover on the sea ice of the Arctic Ocean at the Surface Heat Budget of the Arctic Ocean (SHEBA): Temporal evolution and spatial variability  

Microsoft Academic Search

The evolution and spatial distribution of the snow cover on the sea ice of the Arctic Ocean was observed during the Surface Heat Budget of the Arctic Ocean (SHEBA) project. The snow cover built up in October and November, reached near maximum depth by mid-December, then remained relatively unchanged until snowmelt. Ten layers were deposited, the result of a similar

Matthew Sturm; Jon Holmgren; Don K. Perovich

2002-01-01

64

Diversity and characterization of mercury-resistant bacteria in snow, freshwater and sea-ice brine from the High Arctic.  

PubMed

It is well-established that atmospheric deposition transports mercury from lower latitudes to the Arctic. The role of bacteria in the dynamics of the deposited mercury, however, is unknown. We characterized mercury-resistant bacteria from High Arctic snow, freshwater and sea-ice brine. Bacterial densities were 9.4 × 10(5), 5 × 10(5) and 0.9-3.1 × 10(3) cells mL(-1) in freshwater, brine and snow, respectively. Highest cultivability was observed in snow (11.9%), followed by freshwater (0.3%) and brine (0.03%). In snow, the mercury-resistant bacteria accounted for up to 31% of the culturable bacteria, but <2% in freshwater and brine. The resistant bacteria belonged to the Alpha-, Beta- and Gammaproteobacteria, Firmicutes, Actinobacteria, and Bacteriodetes. Resistance levels of most isolates were not temperature dependent. Of the resistant isolates, 25% reduced Hg(II) to Hg(0). No relation between resistance level, ability to reduce Hg(II) and phylogenetic group was observed. An estimation of the potential bacterial reduction of Hg(II) in snow suggested that it was important in the deeper snow layers where light attenuation inhibited photoreduction. Thus, by reducing Hg(II) to Hg(0), mercury-resistant bacteria may limit the supply of substrate for methylation processes and, hence, contribute to lowering the risk that methylmercury is being incorporated into the Arctic food chains. PMID:21166687

Møller, Annette K; Barkay, Tamar; Abu Al-Soud, Waleed; Sørensen, Søren J; Skov, Henrik; Kroer, Niels

2010-12-17

65

The influence of sea ice on Antarctic ice core sulfur chemistry and on the future evolution of Arctic snow depth: Investigations using global models  

NASA Astrophysics Data System (ADS)

Observational studies have examined the relationship between methanesulfonic acid (MSA) measured in Antarctic ice cores and sea ice extent measured by satellites with the aim of producing a proxy for past sea ice extent. MSA is an oxidation product of dimethylsulfide (DMS) and is potentially linked to sea ice based on observations of very high surface seawater DMS in the sea ice zone. Using a global chemical transport model, we present the first modeling study that specifically examines this relationship on interannual and on glacial-interglacial time scales. On interannual time scales, the model shows no robust relationship between MSA deposited in Antarctica and sea ice extent. We show that lifetimes of MSA and DMS are longer in the high latitudes than in the global mean, interannual variability of sea ice is small (<25%) as a fraction of sea ice area, and sea ice determines only a fraction of the variability (<30%) of DMS emissions from the ocean surface. A potentially larger fraction of the variability in DMS emissions is determined by surface wind speed (up to 46%) via the parameterization for ocean-to-atmosphere gas exchange. Furthermore, we find that a significant fraction (up to 74%) of MSA deposited in Antarctica originates from north of 60°S, north of the seasonal sea ice zone. We then examine the deposition of MSA and non-sea-salt sulfate (nss SO2-4 ) on glacial-interglacial time scales. Ice core observations on the East Antarctic Plateau suggest that MSA increases much more than nss SO2-4 during the last glacial maximum (LGM) compared to the modern period. It has been suggested that high MSA during the LGM is indicative of higher primary productivity and DMS emissions in the LGM compared to the modern day. Studies have also shown that MSA is subject to post-depositional volatilization, especially during the modern period. Using the same chemical transport model driven by meteorology from a global climate model, we examine the sensitivity of MSA and nss SO2-4 deposition to differences between the modern and LGM climates, including sea ice extent, sea surface temperatures, oxidant concentrations, and meteorological conditions. We are unable to find a mechanism whereby MSA deposition fluxes are higher than nss SO2-4 deposition fluxes on the East Antarctic Plateau in the LGM compared the modern period. We conclude that the observed differences between MSA and nss SO2-4 on glacial-interglacial time scales are due to post-depositional processes that affect the ice core MSA concentrations. We can not rule out the possibility of increased DMS emissions in the LGM compared to the modern day. If oceanic DMS production and ocean-to-air fluxes in the sea ice zone are significantly enhanced by the presence of sea ice as indicated by observations, we suggest that the potentially larger amplitude of the seasonal cycle in sea ice extent in the LGM implies a more important role for sea ice in modulating the sulfur cycle during the LGM compared to the modern period. We then shift our focus to study the evolution of snow depth on sea ice in global climate model simulations of the 20th and 21st centuries from the Coupled Model Intercomparison Project 5 (CMIP5). Two competing processes, decreasing sea ice extent and increasing precipitation, will affect snow accumulation on sea ice in the future, and it is not known a priori which will dominate. The decline in Arctic sea ice extent is a well-studied problem in future scenarios of climate change. Moisture convergence into the Arctic is also expected to increase in a warmer world, which may result in increasing snowfall rates. We show that the accumulated snow depth on sea ice in the spring declines as a result of decreased ice extent in the early autumn, in spite of increased winter snowfall rates. The ringed seal (Phoca hispida ) depends on accumulated snow in the spring to build subnivean birth lairs, and provides one of the motivations for this study. Using an empirical threshold of 20 cm of snow depth on level sea ice for ringed seal lair success, we estimate a declin

Hezel, Paul J.

66

Projected decline in spring snow depth on Arctic sea ice caused by progressively later autumn open ocean freeze-up this century  

NASA Astrophysics Data System (ADS)

We present the first analysis of snow depth on Arctic sea ice in the Coupled Model Intercomparison Project 5 (CMIP5) because of its importance for sea ice thermodynamics and ringed seal (Phoca hispida) habitat. Snow depths in April on Arctic sea ice decrease over the 21st century in RCP2.6, RCP4.5, and RCP8.5 scenarios. The chief cause is loss of sea ice area in autumn and, to a lesser extent, winter. By the end of the 21st century in the RCP8.5 scenario, snowfall accumulation is delayed by about three months compared to the late 20th century in the multi-model mean. Mean April snow depth north of 70°N declines from about 28 cm to 16 cm. Precipitation increases as expected in a warmer climate, but much of this increase in the Arctic occurs as rainfall. The seasonality of snowfall rate grows, with increasing rates in winter and decreasing rates in summer and autumn, but the cumulative snowfall from September to April does not change. Ringed seals depend on spring snow cover on Arctic sea ice to create subnivean birth lairs. The area with snow depths above 20 cm — a threshold needed for ringed seals to build snow caves — declines by 70%.

Hezel, P. J.; Zhang, X.; Bitz, C. M.; Kelly, B. P.; Massonnet, F.

2012-09-01

67

Snow and sea ice thickness measurements from Operation IceBridge: bridging the past, present, and future  

Microsoft Academic Search

Airborne measurements collected during NASA's Operation IceBridge have provided a rich new data set to characterize the properties and changes occurring to the Arctic and Antarctic sea ice covers. As of this writing, one Antarctic and two Arctic IceBridge campaigns have been completed. The suite of instruments aboard the IceBridge aircraft include digital photography, laser and radar altimeters, and an

N. T. Kurtz; S. L. Farrell; T. Markus; D. C. McAdoo

2010-01-01

68

Snow depth determination on Arctic sea-ice using a combination of laser altimetry and radar the CryoVex 2006 experiment  

NASA Astrophysics Data System (ADS)

In spring 2006 a major pre-launch campaign of CryoSat-2 was carried out in the Arctic Ocean North of Greenland and Canada. The aim was to validate the airborne radar and laser instrumentation planned for the CryoSat mission. The radar which was used was the ESA 13 GHz coherent ASIRAS radar. In situ snow depths, snow physics and sea ice depth / freeboard were measured at two sites on the sea ice north of the Canadian Forces Station Alert, Ellesmere Island (82°30' N 62°19' W). Site 1 was on multiyear fast ice (MYI), approximately 5 km from the coast line. Site 2 was approximately 10 km north of Alert, on first-year ice (FYI). Data was acquired through a combination of airborne laser and radar altimetry using a Twin-Otter aircraft. By combining laser altimetry with radar waves it is possible to distinguish the sea ice surface from the snow surface and in this manner determine the snow thickness. The results show good agreement between in situ and airborne measured data. Snow cover on sea ice is an effective insulator that regulates the exchange of energy and momentum between ocean and atmosphere. The knowledge of distribution and variability of snow depth is therefore vital to our understanding of the overall heat exchange in the Arctic region. Observing climatic parameters in the Arctic region is challenged by extreme weather together with logistic constrain which demands unconventional equipment and methods to gain data. The possibility to measure snow depth from aircraft will provide an opportunity to cover huge areas and still produce a fine-scale dataset and in addition provide data for converting satellite-measured sea ice-freeboard heights to ice thickness.

Hanson, S.; Hvidegaard, S. M.; Skorup, H.; Forsberg, R.; Wilkinson, J.; Jaapala, J.; Haas, C.

2006-12-01

69

Sea Ice  

NSDL National Science Digital Library

In this resource, students will discover that there are notable differences between sea ice and fresh-water ice, such as density. In on segment, students learn that the first sign of freezing on the sea is an oily appearance of the water caused by the formation of needle-like crystals. The site explains the relationship between growth and the rate at which heat flows from the water and that the ice pack can alter its shape and dimension due to the movement of winds, currents, thermal expansion, and contraction of the ice. Types of ice described here include new ice, nilas, young ice, first-year ice, and old ice while the forms of ice covered include pancake ice, brash ice, ice cake, floe, and fast ice. The site also explains the meteorological and oceanographic factors that control the amount and movement of ice.

70

Observing the snow and ice properties in the Arctic coastal waters of the Canadian Beaufort Sea with helicopter-borne Ground-Penetrating Radar, Laser and Electromagnetic sensors  

NASA Astrophysics Data System (ADS)

A helicopter-borne Ground-Penetrating-Radar (GPR) has been providing in real-time snow depths and ice thicknesses of low saline ice and complemented the Electromagnetic-Laser and Video-Laser data sets to explain the winter and summer ice and snow properties found in the Canadian Beaufort Sea. In the shallow inshore delta areas where river runoff dilutes the oceanic water such as the Mackenzie Delta, the GPR and EM together can determine in winter the floating, grounded ice conditions from the ice frozen to the bottom where the EM on its own only indicates areas where the ice is attached to the frozen mud layer. In these low saline areas the GPR can measure both the snow depth and ice thickness and provide an estimate of the freshwater river plume layer trapped inshore behind the lad-fast shear zone. Overlain this survey data of 2010 on SAR imagery provides a means to validate the ice signature seen in satellite imagery. During the summer of 2009, the helicopter-borne sensors have observed the break-up of the Arctic pack ice by long period ocean surface waves generated in open water region north of the Bering Strait. The waves penetrating the Beaufort Sea pack ice up to 300km, breaking up the pack ice into less than 100m floes. All data and reports of the helicopter survey and publications are available http://www.mar.dfo-mpo.gc.ca/science/ocean/seaice/public.html and associated FTP site.

Prinsenberg, S.

2011-12-01

71

Creep of Snow and Ice.  

National Technical Information Service (NTIS)

Constant load creep tests in uniaxial unconfined compression were performed on samples of sintered snow and bubbly polycrystalline ice. Nominal axial stresses were in the range 0.1 to 1.0 kgf/sq cm for snow, and 0.5 to 20 kgf/sq cm for ice. The range of t...

M. Mellor J. H. Smith

1966-01-01

72

Development of a one-dimensional electro-thermophysical model of the snow sea-ice system: Arctic climate processes and microwave remote sensing applications  

Microsoft Academic Search

Snow covered sea ice plays a crucial role in the earth's climate. This includes polar biology, local, regional and world weather and ocean circulations as well as indigenous people's way of life. Recent research has indicated significant climate change in the polar regions, especially the Canadian arctic. Polar climate processes are also among the most poorly misrepresented within global circulation

John Michael Hanesiak

2001-01-01

73

Observations of geophysical and dielectric properties and ground penetrating radar signatures for discrimination of snow, sea ice and freshwater ice thickness  

Microsoft Academic Search

Separate snow and ice thickness at the same location are important parameters in determining the flux of heat and light between the atmosphere and ocean in Arctic marine environments, but physical sampling requires a great deal of effort to yield few results spatially and temporally. Here, ground penetrating radar (GPR) at 250 MHz and 1 GHz reliably measured snow, river ice and

R. J. Galley; M. Trachtenberg; A. Langlois; D. G. Barber; L. Shafai

2009-01-01

74

Search for Ice and Snow  

NSDL National Science Digital Library

Using an Earth image database (Space Shuttle images), students try to find places on Earth where there is ice and snow. In some arid areas, water can come from snow and ice found on nearby high mountains or at extreme latitudes. In this activity, students can express ideas about where there is ice on the Earth and why. They also can find Web images of Earth and download them to determine ways to distinguish areas of ice/snow from clouds or other white features on the images of Earth. In addition, students can use world maps to mark places where they find ice, putting in place names and/or coordinates where possible.

75

Comparison of AMSR-E derived Antarctic snow-ice interface temperatures with previous surface observations  

Microsoft Academic Search

The AMSR-E Sea Ice Temperature (L3 25 km) data product derived from passive microwave emissions at 6.9 GHz is available from the National Snow and Ice Data Center. The Sea Ice Temperature data represents the temperature at the surface of the sea ice, or the temperature corresponding to the snow-ice interface. Antarctic sea ice images from 2005 were obtained at

M. Lewis; S. F. Ackley; H. Xie; B. Cicek

2006-01-01

76

Students Measure Changes in Ice and Snow  

NSDL National Science Digital Library

This short video features the Alaska Lake Ice and Snow Observatory Network (ALISON project), a citizen science program in which 4th and 5th graders help scientists study the relationship between climate change and lake ice and snow conditions.

Alaska, Fairbanks K.; Domain, Teachers'

77

CO2 climate sensitivity and snow-sea-ice albedo parameterization in an atmospheric GCM coupled to a mixed-layer ocean model  

Microsoft Academic Search

The snow-sea-ice albedo parameterization in an atmospheric general circulation model (GCM), coupled to a simple mixed-layer ocean and run with an annual cycle of solar forcing, is altered from a version of the same model described by Washington and Meehl (1984). The model with the revised formulation is run to equilibrium for 1 × CO2 and 2 × CO2 experiments.

Gerald A. Meehl; Warren M. Washington

1990-01-01

78

Snow Ice Crystals  

NSDL National Science Digital Library

This article from Physics Today by Yoshinori Furukawa and John S. Wettlaufer and John S. Wettlaufer describes how ice crystals form on the earth. The resource includes graphics depicting how different shapes of ice crystals are formed.

Furukawa, Y.; Wettlaufer, John S., 1963-

2010-03-12

79

Spatial distribution and radiative effects of soot in the snow and sea ice during the SHEBA experiment  

Microsoft Academic Search

Soot observations around the periphery of the Arctic Ocean indicate snowpack concentrations ranging from about 1 to more than 200 ng carbon\\/g snow (ngC\\/g), with typical values being near 40-50 ngC\\/g. Values of this magnitude would significantly affect not only the albedo and transmissivity of the ice cover but also surface melt rates and internal heat storage in the ice.

Thomas C. Grenfell; Bonnie Light; Matthew Sturm

2002-01-01

80

Diversity and Vertical Distribution of Microbial Eukaryotes in the Snow, Sea Ice and Seawater Near the North Pole at the End of the Polar Night  

PubMed Central

Our knowledge about the microorganisms living in the high Arctic Ocean is still rudimentary compared to other oceans mostly because of logistical challenges imposed by its inhospitable climate and the presence of a multi-year ice cap. We have used 18S rRNA gene libraries to study the diversity of microbial eukaryotes in the upper part of the water column (0–170?m depth), the sea ice (0–1.5?m depth) and the overlying snow from samples collected in the vicinity of the North Pole (N88°35?, E015°59) at the very end of the long polar night. We detected very diverse eukaryotes belonging to Alveolata, Fungi, Amoebozoa, Viridiplantae, Metazoa, Rhizaria, Heterokonta, and Telonemia. Different alveolates (dinoflagellates and Marine Alveolate Groups I and II species) were the most abundant and diverse in gene libraries from water and sea ice, representing 80% of the total number of clones and operational taxonomic units. Only contaminants and/or species from continental ecosystems were detected in snow, suggesting wind- and animal- or human-mediated cosmopolitan dispersal of some taxa. By contrast, sea ice and seawater samples harbored a larger and more similar inter-sample protist diversity as compared with snow. The North Pole was found to harbor distinctive eukaryotic communities along the vertical gradient with an unparalleled diversity of core dinoflagellates, largely dominant in libraries from the water column, as compared to other oceanic locations. In contrast, phototrophic organisms typical of Arctic sea ice and plankton, such as diatoms and prasinophytes, were very rare in our samples. This was most likely due to a decrease of their populations after several months of polar night darkness and to the presence of rich populations of diverse grazers. Whereas strict phototrophs were scarce, we identified a variety of likely mixotrophic taxa, which supports the idea that mixotrophy may be important for the survival of diverse protists through the long polar night.

Bachy, Charles; Lopez-Garcia, Purificacion; Vereshchaka, Alexander; Moreira, David

2011-01-01

81

Important Changes in Microwave Scattering Properties of Young Snow-Covered Sea Ice as Indicated from Dielectric Modelling.  

National Technical Information Service (NTIS)

Winter measurements of the properties of young snow-covered fast ice are input into a mixture model to calculate the complex dielectric constant. Large changes in the electromagnetic properties of the medium occur over the 46 day period of measurements. T...

M. R. Drinkwater

1988-01-01

82

Sea ice-albedo climate feedback mechanism  

Microsoft Academic Search

The sea ice-albedo feedback mechanism over the Arctic Ocean multiyear sea ice is investigated by conducting a series of experiments using several one-dimensional models of the coupled sea ice-atmosphere system. In its simplest form, ice-albedo feedback is thought to be associated with a decrease in the areal cover of snow and ice and a corresponding increase in the surface temperature,

J. L. Schramm; J. A. Curry; Elizabeth E. Ebert

1995-01-01

83

Sea Ice-Albedo Climate Feedback Mechanism  

Microsoft Academic Search

The sea ice-albedo feedback mechanism over the Arctic Ocean multiyear sea ice is investigated by conducting a series of experiments using several one-dimensional models of the coupled sea ice-atmosphere system. In its simplest form, ice-albedo feedback is thought to be associated with a decrease in the areal cover of snow and ice and a corresponding increase in the surface temperature,

Judith A. Curry; Julie L. Schramm; Elizabeth E. Ebert

1995-01-01

84

Applications of SHEBA\\/FIRE data to evaluation of snow\\/ice albedo parameterizations  

Microsoft Academic Search

Climate models use a wide variety of parameterizations for surface albedos of the ice-covered ocean. These range from simple broadband albedo parameterizations that distinguish among snow-covered and bare ice to more sophisticated parameterizations that include dependence on ice and snow depth, solar zenith angle, and spectral resolution. Several sophisticated parameterizations have also been developed for thermodynamic sea ice models that

J. A. Curry; J. L. Schramm; D. K. Perovich; J. O. Pinto

2001-01-01

85

A global coupled sea ice–ocean model  

Microsoft Academic Search

A new sea ice model, GELATO, was developed at Centre National de Recherches Météorologiques (CNRM) and coupled with OPA global ocean model. The sea ice model includes elastic–viscous–plastic rheology, redistribution of ice floes of different thicknesses, and it also takes into account leads, snow cover and snow ice formation. Climatologies of atmospheric surface parameters are used to perform a 20-year

D. Salas Mélia

2002-01-01

86

Sea ice-albedo climate feedback mechanism  

SciTech Connect

The sea ice-albedo feedback mechanism over the Arctic Ocean multiyear sea ice is investigated by conducting a series of experiments using several one-dimensional models of the coupled sea ice-atmosphere system. In its simplest form, ice-albedo feedback is thought to be associated with a decrease in the areal cover of snow and ice and a corresponding increase in the surface temperature, further decreasing the area cover of snow and ice. It is shown that the sea ice-albedo feedback can operate even in multiyear pack ice, without the disappearance of this ice, associated with internal processes occurring within the multiyear ice pack (e.g., duration of the snow cover, ice thickness, ice distribution, lead fraction, and melt pond characteristics). The strength of the ice-albedo feedback mechanism is compared for several different thermodynamic sea ice models: a new model that includes ice thickness distribution., the Ebert and Curry model, the Mayjut and Untersteiner model, and the Semtner level-3 and level-0 models. The climate forcing is chosen to be a perturbation of the surface heat flux, and cloud and water vapor feedbacks are inoperative so that the effects of the sea ice-albedo feedback mechanism can be isolated. The inclusion of melt ponds significantly strengthens the ice-albedo feedback, while the ice thickness distribution decreases the strength of the modeled sea ice-albedo feedback. It is emphasized that accurately modeling present-day sea ice thickness is not adequate for a sea ice parameterization; the correct physical processes must be included so that the sea ice parameterization yields correct sensitivities to external forcing. 22 refs., 6 figs., 1 tab.

Schramm, J.L.; Curry, J.A. [Univ. of Colorado, Boulder, CO (United States); Ebert, E.E. [Bureau of Meterology Research Center, Melbourne (Australia)

1995-02-01

87

An eight-year (1987-1994) time series of rainfall, clouds, water vapor, snow cover, and sea ice derived from SSM/I measurements  

SciTech Connect

The Special Microwave Sensor/Imager (SSM/I), first placed into operation in July 1987, has been making measurements of earth-emitted radiation for over eight years. These data are used to estimate both atmospheric and surface hydrological parameters and to generate a time series of global monthly mean products averaged to a 1{degrees} lat x 1{degrees} long grid. Specifically, this includes monthly estimates of rainfall and its frequency, cloud liquid water and cloud frequency, water vapor, snow cover frequency, and sea ice frequency. This study uses seasonal mean values to demonstrate the spatial and temporal distributions of the hydrological variables. Examples of interannual variability such as the 1993 flooding in the Mississippi Valley and the 1992-93 snow coverage changes over the United States are used to demonstrate the utility of these data for regional application. 28 refs., 16 figs., 4 tabs.

Ferraro, R.R.; Weng, F.; Grody, N.C. [Satellite Research Lab., Camp Springs, MD (United States)] [and others

1996-05-01

88

Snow and Ice Products from the Aqua, Terra, and ICESat Satellites at the National Snow and Ice Data Center  

NASA Astrophysics Data System (ADS)

The National Snow and Ice Data Center (NSIDC) at the University of Colorado, Boulder - one of eight NASA Distributed Active Archive Centers (DAACs) - archives and distributes several products from sensors on the suite of NASA Earth Observing System (EOS) satellites. These include the sun-synchronous polar-orbiting Aqua (launched 4 May 2002) and Terra (launched 18 December 1999) platforms and the Ice, Cloud, and land Elevation Satellite (ICESat) (launched 12 January 2003). The Advanced Microwave Scanning Radiometer-EOS (AMSR-E) is a multi-channel passive microwave radiometer on Aqua (http://nsidc.org/daac/amsr/). AMSR-E Level 3 snow products are produced in EASE-Grid format for both the Northern and Southern Hemisphere and are available as daily, 5-day, and monthly fields. Daily AMSR-E Level 3 sea ice products are produced on a polar stereographic projection at gridded spatial resolutions of 6.25 km, 12.5 km and 25 km. Since April 2004, these products have been available for public distribution from NSIDC. The Moderate-resolution Imaging Spectroradiometer (MODIS) on Terra and Aqua is a 36-channel visible/infrared sensor that produces a consistent long-term time series of fully-automated, quality-controlled data. Level 2 swath products are available for both snow cover and sea ice. Daily and 8-day Level 3 gridded snow cover products are available with estimates of snow extent and albedo at 500m resolution, along with daily Level 3 gridded sea ice products with estimates for sea ice extent and ice surface temperature at 1 km resolution. These products are currently available from NSIDC (http://nsidc.org/daac/modis/). The Geoscience Laser Altimeter System (GLAS) is the sole instrument on ICESat. The standard GLAS Level 2 ice sheet altimetry product contains the ice sheet elevation and elevation distribution calculated from algorithms fine-tuned for ice sheet returns. The standard GLAS Level 2 sea ice altimetry product contains the sea ice freeboard and sea ice roughness calculated from algorithms fine-tuned for sea ice returns. Both products also include the laser footprint geolocation, reflectance, and the geodetic, instrument, and atmospheric corrections used to correct the range measurements. An 8-day sample of these products has been available to the public (http://nsidc.org/daac/glas/) since October 2003. Improved versions, covering additional dates, have continued to be released since March 2004. In addition to the standard snow and ice products distributed by the data center, NSIDC scientists are also developing a variety of experimental products. One such product combines snow extent data from MODIS visible bands with snow water equivalent data from AMSR-E to improve snow cover estimates. Another product under investigation at NSIDC is a sea ice motion product derived from AMSR-E brightness temperature fields using cross-correlation feature matching techniques. These EOS sensors substantially enhance our ability to observe the cryosphere. GLAS represent an entirely new type of sensor for the cryosphere, while AMSR-E and MODIS offer significant improvements over the previous generation of sensors. The products from these sensors are a valuable resource for the investigation of regional and global climate issues and should yield new insights into the cryospheric system.

Meier, W. N.; Marquis, M.; Kaminski, M.; Armstrong, R.; Brodzik, M.

2004-05-01

89

Search for Ice and Snow  

NSDL National Science Digital Library

This resource is part of the Science Education Gateway (SEGway) project, funded by NASA, which is a national consortium of scientists, museums, and educators working together to bring the latest science to students, teachers, and the general public. Students pretend that they are on the Earth task force for drought prevention and, using an Earth Image database (Space Shuttle images), try to find places on Earth where there is ice and snow. For some communities water is not a problem, but some areas in the world are arid or prone to droughts. Students learn that water sources are crucial for people living in these regions. A teacher's section provides goals, objectives, materials, and teaching strategies.

Gould, Alan

90

A new sea ice albedo scheme including melt ponds for ECHAM5 general circulation model  

Microsoft Academic Search

Today we experience an accelerated melting of sea ice in the Arctic which global circulation models are inadequate to predict. We believe one of the reasons is the shortcomings in the sea ice albedo schemes for these models. This paper investigates a physically based sea ice albedo scheme for ECHAM5 GCM, which separates between snow-covered sea ice, bare sea ice,

Christina A. Pedersen; Erich Roeckner; Mikael Lüthje; Jan-Gunnar Winther

2009-01-01

91

The Seasonal Evolution of Sea Ice Floe Size Distribution  

Microsoft Academic Search

The Arctic sea ice cover undergoes large changes over an annual cycle. In winter and spring the ice cover consists of large, snow-covered plate-like ice floes, with very little open water. By the end of summer the snow cover is gone and the large floes have broken into a complex mosaic of smaller, rounded floes surrounded by a lace of

D. K. Perovich; G. A. Maykut; K. F. Jones

2004-01-01

92

A New Climate State: Arctic Sea Ice 2012  

NSDL National Science Digital Library

This video contains a visualization and explanation of the Arctic sea ice and how it has changed over the 25 years. In September 2012, the National Snow and Ice Data Center recorded the lowest extent of Arctic sea ice. The video discusses the climate importance of ice thickness and reflective properties.

Sinclair, Peter; Media, The Y.

93

Sea Ice and Polar Climate in the NCAR CSM  

Microsoft Academic Search

The Climate System Model (CSM) consists of atmosphere, ocean, land, and sea-ice components linked by a flux coupler, which computes fluxes of energy and momentum between components. The sea-ice component consists of a thermodynamic formulation for ice, snow, and leads within the ice pack, and ice dynamics using the cavitating-fluid ice rheology, which allows for the compressive strength of ice

John W. Weatherly; Bruce P. Briegleb; William G. Large; James A. Maslanik

1998-01-01

94

Sea ice and polar climate in the NCAR CSM  

Microsoft Academic Search

The Climate System Model (CSM) consists of atmosphere, ocean, land, and sea-ice components linked by a flux coupler, which computes fluxes of energy and momentum between components. The sea-ice component consists of a thermodynamic formulation for ice, snow, and leads within the ice pack, and ice dynamics using the cavitating-fluid ice rheology, which allows for the compressive strength of ice

J. W. Weatherly; B. P. Briegleb; W. G. Large; J. A. Maslanik

1998-01-01

95

Obtaining and Using the MODIS Snow and Ice Products for Land Surface Research  

NASA Astrophysics Data System (ADS)

Snow and sea ice cover are some of the more important spatial features of the Earth's surface that can be readily measured from space. Moderate Resolution Imaging Spectroradiometer (MODIS) instruments onboard NASA's Terra and Aqua spacecraft collect spectral data that are used to routinely produce snow cover and sea ice products. With higher spatial and spectral resolution, the MODIS snow and ice products (including snow albedo and sea ice surface temperature) improve upon a long history of global coverage satellite-derived products that have been produced from polar-orbiting satellites since the early 1970s. Fully automated, quality controlled, daily global maps of snow cover and sea ice extent, produced at 500m, 1000m, and 0.05° spatial resolutions by the MODIS Land Team, are available from the National Snow and Ice Data Center (NSIDC) Distributed Active Archive Center (DAAC). MODIS snow and ice products from the Terra satellite have been produced since 2000; most of these products have been validated over a wide range of locations and time periods. Production of comparable snow and ice products using Aqua data will begin during the next few months after final testing of an algorithm that uses a slightly different set of spectral bands. Recent work to improve the performance and utility of the products includes: subsetting, gridding, and resampling tools; an easy-access Data Pool of recent and popular data holdings; reduced-resolution browse data available through the ordering systems; and plans for new products including a snow albedo product as well as a sea ice product on a climate modeling grid. Through examples of current MODIS data usage, we describe the characteristics and state of validation of the MODIS snow and ice products, their accessibility from the NSIDC DAAC, and current user support and tools.

Kaminski, M.; Khalsa, S. S.; McLean, B.; Scharfen, G. R.; Wolfe, J.; Hall, D. K.

2003-12-01

96

Accessing and Utilizing the MODIS Snow and Ice Products at the NSIDC DAAC for Cryospheric Research  

NASA Astrophysics Data System (ADS)

The Moderate Resolution Imaging Spectroradiometer (MODIS) is the key instrument for snow and ice studies supported by the Terra satellite. The spectral and spatial resolutions of MODIS represent a considerable improvement in capability for global cryospheric monitoring over comparable existing systems. The MODIS snow and ice products augment the existing record of satellite-derived snow cover and sea ice products that began about 30 years ago. The MODIS snow products are archived and distributed by the National Snow and Ice Data Center (NSIDC) as part of its NASA Earth Observing System Distributed Active Archive Center (DAAC). Level 2 swath format and level 3 gridded snow extent data, collected since September 2000, are available through the EOS Data Gateway (EDG). This poster describes and illustrates the steps involved in accessing the MODIS snow products via the EDG, displaying them with NSIDC-provided MODIS tools, and includes some simple image analysis and scientific interpretation.

McLean, B.; Scharfen, G. R.; Khalsa, S. S.; Wolfe, J. D.

2001-12-01

97

Amundsen Sea ice production and transport  

NASA Astrophysics Data System (ADS)

Drift and variability of sea ice in the Amundsen Sea are investigated with ice buoys deployed in March 2000 and a coupled ice-ocean model. The Bremerhaven Regional Ice Ocean Simulations (BRIOS) model results are compared with in situ ocean, atmosphere, and sea ice measurements; satellite observations; and 8-19 months of buoy drift data. We identify a zone of coastal westward drift and a band of faster eastward drift, separated by a broad transition region characterized by variable ice motions. The model represents drift events at scales approaching its resolution but is limited at smaller scales and by deficiencies in the National Centers for Environmental Prediction forcing. Two thirds of the modeled ice production in the southern Amundsen moves westward near the coast, its transport modulated by meridional wind strength, damping sea ice formation in the eastern Ross Sea. Half of the ice exported from the Ross moves eastward into the northern Amundsen Sea, a net sea ice sink that also receives more than one third of the ice generated to its south. A low rate of exchange occurs with the Bellingshausen Sea, which must have a more independent ice regime. Snow ice formation resulting from high precipitation accounts for one quarter of the ice volume in the Amundsen Sea, aiding the formation of thick ice in a region with generally divergent ice drift. Freshwater extraction by sea ice formation is roughly balanced by precipitation and ice shelf melting, but a positive trend in the surface flux is consistent with an Amundsen source for reported freshening in the Ross Sea.

Assmann, Karen M.; Hellmer, Hartmut H.; Jacobs, Stanley S.

2005-12-01

98

Snow and ice facies variability and ice layer formation on Canadian Arctic ice caps, 1999–2005  

Microsoft Academic Search

Time series of enhanced resolution data from the SeaWinds scatterometer aboard QuikScat were used to map the distribution of snow and ice surface facies and ice layer formation in the percolation zone on ice caps in the Queen Elizabeth Islands during the period 1999–2005. Iterative Self-Organizing Data Analysis classification of the mean postfreeze-up biweekly average ?0 signal for the 7-year

Gabriel J. Wolken; Martin Sharp; Libo Wang

2009-01-01

99

FORMATION, GROWTH, AND DECAY OF SEA-ICE IN THE CANADIAN ARCTIC ARCHIPELAGO  

Microsoft Academic Search

of sea-ice with air temperatures, and its rate of accretion with air temperatures and snow depths. Investigations usually indicate that air temperature, snow depth, and initial ice thickness are the most important data required to predict the thickening of the ice sheet. Most formulas derived empirically (Bydin 1933, Lebedev 1938) express the vertical growth of sea-ice as: where: I =

Michael A. Bilello

100

Quantification of ikaite in Antarctic sea ice  

NASA Astrophysics Data System (ADS)

Calcium carbonate precipitation in sea ice can increase pCO2 during precipitation in winter and decrease pCO2 during dissolution in spring. CaCO3 precipitation in sea ice is thought to potentially drive significant CO2 uptake by the ocean. However, little is known about the quantitative spatial and temporal distribution of CaCO3 within sea ice. This is the first quantitative study of hydrous calcium carbonate, as ikaite, in sea ice and discusses its potential significance for the carbon cycle in polar oceans. Ice cores and brine samples were collected from pack and land fast sea ice between September and December 2007 during an expedition in the East Antarctic and another off Terre Adélie, Antarctica. Samples were analysed for CaCO3, Salinity, DOC, DON, Phosphate, and total alkalinity. A relationship between the measured parameters and CaCO3 precipitation could not be observed. We found calcium carbonate, as ikaite, mostly in the top layer of sea ice with values up to 126 mg ikaite per liter melted sea ice. This potentially represents a contribution between 0.12 and 9 Tg C to the annual carbon flux in polar oceans. The horizontal distribution of ikaite in sea ice was heterogenous. We also found the precipitate in the snow on top of the sea ice.

Fischer, M.; Thomas, D. N.; Krell, A.; Nehrke, G.; Göttlicher, J.; Norman, L.; Riaux-Gobin, C.; Dieckmann, G. S.

2012-02-01

101

Operation IceBridge: Sea Ice Interlude  

NASA Video Gallery

Sea ice comes in an array of shapes and sizes and has its own ephemeral beauty. Operation IceBridge studies sea ice at both poles, and also runs across interesting formations en route to other targets.

Holly Zell

2012-11-05

102

Monitoring Snow on ice as Critical Habitat for Ringed Seals  

NASA Astrophysics Data System (ADS)

Ringed seals are the primary prey of polar bears, and they are found in all seasonally ice covered seas of the northern hemisphere as well as in several freshwater lakes. The presence of snow covered sea ice is essential for successful ringed seal reproduction. Ringed seals abrade holes in the ice allowing them to surface and breathe under the snow cover. Where snow accumulates to sufficient depths, ringed seals excavate subnivean lairs above breathing holes. They rest, give birth, and nurse their young in those lairs. Temperatures within the lairs remain within a few degrees of freezing, well within the zone of thermal neutrality for newborn ringed seals, even at ambient temperatures of -30° C. High rates of seal mortality have been recorded when early snow melt caused lairs to collapse exposing newborn seals to predators and to subsequent extreme cold events. As melt onset dates come earlier in the Arctic Ocean, ringed seal populations (and the polar bears that depend upon them) will be increasingly challenged. We determined dates of lair abandonment by ringed seals fitted with radio transmitters in the Beaufort Sea (n = 60). We compared abandonment dates to melt onset dates measured in the field, as well as estimated dates derived from active (Ku-band backscatter) and passive (SSM/I) microwave satellite imagery. Date of snow melt significantly improved models of environmental influences on the timing of lair abandonment. We used an algorithm based on multi-channel means and variances of passive microwave data to detect melt onset dates. Those melt onset dates predicted the date of lair abandonment ± 3 days (r 2 = 0.982, p = 0.001). The predictive power of passive microwave proxies combined with their historical record suggest they could serve to monitor critical changes to ringed seal habitat.

Kelly, B. P.; Moran, J.; Douglas, D. C.; Nghiem, S. V.

2007-12-01

103

Water, Ice, and Snow: Unit Outlines  

NSDL National Science Digital Library

This article assembles free resources from the Water, Ice, and Snow issue of the Beyond Penguins and Polar Bears cyberzine into a unit outline based on the 5E learning cycle framework. Outlines are provided for Grades K-2 and 3-5.

Fries-Gaither, Jessica

104

Sea Ice Rheology  

NASA Astrophysics Data System (ADS)

The polar oceans of Earth are covered by sea ice. On timescales much greater than a day, the motion and deformation of the sea ice cover (i.e., its dynamics) are primarily determined by atmospheric and oceanic tractions on its upper and lower surfaces and by internal ice forces that arise within the ice cover owing to its deformation. This review discusses the relationship between the internal ice forces and the deformation of the ice cover, focusing on representations suitable for inclusion within global climate models. I first draw attention to theories that treat the sea ice cover as an isotropic continuum and then to the recent development of anisotropic models that deal with the presence of oriented weaknesses in the ice cover, known as leads.

Feltham, Daniel L.

2008-01-01

105

Airborne Measurement of Sea-Ice Thickness  

NASA Astrophysics Data System (ADS)

The Naval Research Laboratory (NRL) is planning a major program of measurement and modeling of sea-ice thickness in the Arctic. The program will include in-situ, airborne and satellite measurements as well as development of coupled models of ocean, atmosphere and sea-ice. The authors' primary responsibility in this program will be the airborne measurement segment of the program utilizing the freeboard method for estimation of ice thickness (e.g. Hvidegaard and Forsberg, 2002). Essentially, the in-situ measurements of ice and snow thickness will be used to cal/val the airborne methodology, which will then be used to cal/val techniques of snow and ice-thickness extraction from satellite measurements. For the airborne program we plan to fly 10 and 18 GHz short-pulse (~3nsec) radar altimeters and a scanning LiDAR altimeter as well as optical or thermal camera systems. The goal is measurement of free-board at leads in the ice, and snow-thickness by the differential penetration of the three altimeter systems to estimate ice thickness. All altimeters will have full wave-form recording for the analysis of mixed and spread returns. The optical/thermal instruments will be used to help differentiate leads from the ice. We plan to coordinate the NRL airborne field program with Navy ICEX submarine and ice-island programs as well as other opportunities for ground-truth and airborne programs of NASA (ICEBRIDGE) and ESA (CRYOSAT-2).

Gardner, Joan; Brozena, John

2010-05-01

106

Antarctica: Sea Ice  

NSDL National Science Digital Library

This video segment, adapted from a NOVA broadcast, shows how sea ice forms in the Southern Ocean around Antarctica and how its seasonal fluctuation dramatically changes the continent. The segment, two minutes thirty-five seconds in length, includes rare footage of the destruction of the British ship 'Endurance', trapped and crushed by sea ice in 1914.

2010-09-30

107

Antarctica: Sea Ice  

NSDL National Science Digital Library

This video segment, adapted from a NOVA broadcast, shows how sea ice forms in the Southern Ocean around Antarctica and how its seasonal fluctuation dramatically changes the continent. The segment, two minutes thirty-five seconds in length, includes rare footage of the destruction of the British ship 'Endurance', trapped and crushed by sea ice in 1914.

108

Arctic Sea Ice  

Microsoft Academic Search

Of all the recent observed changes in the Arctic environment, the reduction of sea ice cover stands out most prominantly. Several independent analysis have established a trend in Arctic ice extent of -3% per decade from the late 1970s to the late 1990s, with a more pronounced trend in summer. The overall downward trend in ice cover is characterized by

J. C. Stroeve; F. Fetterer; K. Knowles; W. Meier; M. Serreze; T. Arbetter

2004-01-01

109

Modelling of melt ponds on a sea ice floe  

NASA Astrophysics Data System (ADS)

During winter the ocean surface at the poles freezes over to form sea ice. Sea ice floats on the ocean surface and has a matrix structure caused by the rejection of salts during freezing. In the summer sea ice melts at its surface creating melt ponds. An accurate estimate of the fraction of the upper sea-ice surface covered in melt ponds during the summer melt season is essential for a realistic estimate of the albedo for global climate models. We present a sea ice model that simulates the two-dimensional (areal) evolution of melt ponds on an Arctic sea-ice surface. Water transport across and through the sea-ice surface is described by the major hydraulic processes believed to be present. Thermodynamic processes are modelled using heat flux equations. Lateral and vertical melt water transport is described by Darcy's Law. The model simulates a section of a sea ice floe where edge effects such as the presence of leads are neglected. The model consists of a grid of cells, each of which can be in one of four possible configurations: snow covered ice; bare ice; melt pond covered ice or open water. A cluster of adjacent cells containing melt water may be considered to have formed a melt pond. The model is initialised with ice topographies that represent either first-year or multi-year sea ice, these are reconstructed from ice thickness data using standard statistical methods; in this way characteristic examples of both first-year ice and multi-year ice can be constructed. The roughness of the ice and snow surfaces were altered and the sensitivity of the model to the initial data was tested. First-year ice and multi-year ice simulations agreed with observed differences in individual pond size and depth. Sensitivity studies showed that pond fraction is most sensitive to mean initial snow depth in first-year ice simulations and reduction of ice permeability all cases.

Scott, F.; Feltham, D.

2009-04-01

110

Modeling of radiation transport in coupled atmosphere-snow-ice-ocean systems  

Microsoft Academic Search

A radiative transfer model for coupled atmosphere-snow-ice-ocean systems (CASIO-DISORT) is used to develop accurate and efficient tools for computing the bidirectional reflectance distribution function (BRDF) of sea ice for a wide range of situations occurring in nature. These tools include a method to generate sea ice inherent optical properties (IOPs: single-scattering albedo, extinction optical depth, and scattering asymmetry parameter) for

K. Stamnes; B. Hamre; J. J. Stamnes; G. Ryzhikov; M. Biryulina; R. Mahoney; B. Hauss; A. Sei

2011-01-01

111

Trend analysis of Arctic sea ice extent  

NASA Astrophysics Data System (ADS)

The extent of Arctic sea ice is a fundamental parameter of Arctic climate variability. In the context of climate change, the area covered by ice in the Arctic is a particularly useful indicator of recent changes in the Arctic environment. Climate models are in near universal agreement that Arctic sea ice extent will decline through the 21st century as a consequence of global warming and many studies predict a ice free Arctic as soon as 2012. Time series of satellite passive microwave observations allow to assess the temporal changes in the extent of Arctic sea ice. Much of the analysis of the ice extent time series, as in most climate studies from observational data, have been focussed on the computation of deterministic linear trends by ordinary least squares. However, many different processes, including deterministic, unit root and long-range dependent processes can engender trend like features in a time series. Several parametric tests have been developed, mainly in econometrics, to discriminate between stationarity (no trend), deterministic trend and stochastic trends. Here, these tests are applied in the trend analysis of the sea ice extent time series available at National Snow and Ice Data Center. The parametric stationary tests, Augmented Dickey-Fuller (ADF), Phillips-Perron (PP) and the KPSS, do not support an overall deterministic trend in the time series of Arctic sea ice extent. Therefore, alternative parametrizations such as long-range dependence should be considered for characterising long-term Arctic sea ice variability.

Silva, M. E.; Barbosa, S. M.; Antunes, Luís; Rocha, Conceição

2009-04-01

112

Soot climate forcing via snow and ice albedos.  

PubMed

Plausible estimates for the effect of soot on snow and ice albedos (1.5% in the Arctic and 3% in Northern Hemisphere land areas) yield a climate forcing of +0.3 W/m(2) in the Northern Hemisphere. The "efficacy" of this forcing is approximately 2, i.e., for a given forcing it is twice as effective as CO(2) in altering global surface air temperature. This indirect soot forcing may have contributed to global warming of the past century, including the trend toward early springs in the Northern Hemisphere, thinning Arctic sea ice, and melting land ice and permafrost. If, as we suggest, melting ice and sea level rise define the level of dangerous anthropogenic interference with the climate system, then reducing soot emissions, thus restoring snow albedos to pristine high values, would have the double benefit of reducing global warming and raising the global temperature level at which dangerous anthropogenic interference occurs. However, soot contributions to climate change do not alter the conclusion that anthropogenic greenhouse gases have been the main cause of recent global warming and will be the predominant climate forcing in the future. PMID:14699053

Hansen, James; Nazarenko, Larissa

2003-12-29

113

Soot climate forcing via snow and ice albedos  

PubMed Central

Plausible estimates for the effect of soot on snow and ice albedos (1.5% in the Arctic and 3% in Northern Hemisphere land areas) yield a climate forcing of +0.3 W/m2 in the Northern Hemisphere. The “efficacy” of this forcing is ?2, i.e., for a given forcing it is twice as effective as CO2 in altering global surface air temperature. This indirect soot forcing may have contributed to global warming of the past century, including the trend toward early springs in the Northern Hemisphere, thinning Arctic sea ice, and melting land ice and permafrost. If, as we suggest, melting ice and sea level rise define the level of dangerous anthropogenic interference with the climate system, then reducing soot emissions, thus restoring snow albedos to pristine high values, would have the double benefit of reducing global warming and raising the global temperature level at which dangerous anthropogenic interference occurs. However, soot contributions to climate change do not alter the conclusion that anthropogenic greenhouse gases have been the main cause of recent global warming and will be the predominant climate forcing in the future.

Hansen, James; Nazarenko, Larissa

2004-01-01

114

Sea Ice Index Monitors Polar Ice Extent  

Microsoft Academic Search

In September 2002, Arctic sea ice extent reached a minimum unprecedented in 24 years of satellite passive microwave observations, and almost certainly unmatched in 50 years of charting Arctic ice. Again, in September 2003, ice retreated to an unusually low extent, almost equaling the previous year's minimum. The Sea Ice Index (http:\\/\\/nsidc.org\\/data\\/seaice_index\\/), an easy-to-use source of information on sea ice

Florence Fetterer; Kenneth Knowles

2004-01-01

115

HAS ARCTIC SEA ICE RAPIDLY THINNED?  

Microsoft Academic Search

ABSTRACT Reports based on submarine,sonar data have suggested Arctic sea ice has thinned nearly by half in recent decades. Such rapid thinning is a concern for detection of global change and for Arctic regional impacts. Including atmospheric time series, ocean currents and river runoff into an ocean?ice?snow model show that the inferred rapid thinning was unlikely. The problem,stems from undersampling.

Greg Holloway; Tessa Sou

2001-01-01

116

Albedo of the ice covered Weddell and Bellingshausen Seas  

NASA Astrophysics Data System (ADS)

This study investigates the surface albedo of the sea ice areas adjacent to the Antarctic Peninsula during the austral summer. Aircraft measurements of the surface albedo, which were conducted in the sea ice areas of the Weddell and Bellingshausen Seas show significant differences between these two regions. The averaged surface albedo varied between 0.13 and 0.81. The ice cover of the Bellingshausen Sea consisted mainly of first year ice and the sea surface showed an averaged sea ice albedo of ?i = 0.64 ± 0.2 (± standard deviation). The mean sea ice albedo of the pack ice area in the western Weddell Sea was ?i = 0.75 ± 0.05. In the southern Weddell Sea, where new, young sea ice prevailed, a mean albedo value of ?i = 0.38 ± 0.08 was observed. Relatively warm open water and thin, newly formed ice had the lowest albedo values, whereas relatively cold and snow covered pack ice had the highest albedo values. All sea ice areas consisted of a mixture of a large range of different sea ice types. An investigation of commonly used parameterizations of albedo as a function of surface temperature in the Weddell and Bellingshausen Sea ice areas showed that the albedo parameterizations do not work well for areas with new, young ice.

Weiss, A. I.; King, J. C.; Lachlan-Cope, T. A.; Ladkin, R. S.

2012-04-01

117

Arctic Sea Ice Maximum 2011  

NASA Video Gallery

AMSR-E Arctic Sea Ice: September 2010 to March 2011: Scientists tracking the annual maximum extent of Arctic sea ice said that 2011 was among the lowest ice extents measured since satellites began collecting the data in 1979.

Holly Zell

2011-03-29

118

The role of sea ice in structuring Antarctic ecosystems  

Microsoft Academic Search

This paper focusses on the links between growth, persistence and decay of sea ice and the structure of Antarctic marine ecosystems on different spatial and temporal scales. Sea-ice growth may divide an oceanic ecosystem into two dissimilar compartments: (1) the water column, with primary production controlled by the reduction of irradiative fluxes due to the snow-laden sea-ice cover and thermo-haline

Hajo Eicken

1992-01-01

119

Airborne electromagnetic measurements of sea ice thickness: methods and applications  

Microsoft Academic Search

Alfred Wegener Institute operates two helicopter-borne electromagnetic (EM) sounding devices dedicated to the measurement of sea ice thickness. With the method, level total (ice plus snow) thickness can be determined with an accuracy of ±0.1 m. However, due to the footprint of the method and due to the porosity of unconsolidated ridge keels, deformed ice thickness can be strongly underestimated.

Christian Haas; Sibylle Goebell; Stefan Hendricks; Torge Martin; Andreas Pfaffling; Carola von Saldern

120

Sea Ice Index Monitors Polar Ice Extent  

NASA Astrophysics Data System (ADS)

In September 2002, Arctic sea ice extent reached a minimum unprecedented in 24 years of satellite passive microwave observations, and almost certainly unmatched in 50 years of charting Arctic ice. Again, in September 2003, ice retreated to an unusually low extent, almost equaling the previous year's minimum. The Sea Ice Index (http://nsidc.org/data/seaice_index/), an easy-to-use source of information on sea ice trends and anomalies, assists in observing these minima. The Sea Ice Index is intended for both researchers and the scientifically inclined general public.

Fetterer, Florence; Knowles, Kenneth

2004-04-01

121

All About Sea Ice  

NSDL National Science Digital Library

This comprehensive site is an introduction to sea ice: what it is, how it forms, how it is studied, how it affected historical expedition in the polar regions, and what role it plays in the global climate. The site contains a glossary of sea ice terms and references to additional information, which all serve as an excellent introduction. Data are also available from various collection methods for student interpretation.

122

All About Sea Ice  

NSDL National Science Digital Library

This comprehensive site is an introduction to sea ice: what it is, how it forms, how it is studied, how it affected historical expedition in the polar regions, and what role it plays in the global climate. The site contains a glossary of sea ice terms and references to additional information, which all serve as an excellent introduction. Data are also available from various collection methods for student interpretation.

2011-07-15

123

Arctic Sea Ice  

NASA Astrophysics Data System (ADS)

Of all the recent observed changes in the Arctic environment, the reduction of sea ice cover stands out most prominantly. Several independent analysis have established a trend in Arctic ice extent of -3% per decade from the late 1970s to the late 1990s, with a more pronounced trend in summer. The overall downward trend in ice cover is characterized by strong interannual variability, with a low September ice extent in one year typically followed by recovery the next September. Having two extreme minimum years, such as what was observed in 2002 and 2003 is unusual. 2004 marks the third year in a row of substantially below normal sea ice cover in the Arctic. Early summer 2004 appeared unusual in terms of ice extent, with May a record low for the satellite period (1979-present) and June also exhibiting below normal ice extent. August 2004 extent is below that of 2003 and large reductions in ice cover are observed once again off the coasts of Siberia and Alaska and the Greenland Sea. Neither the 2002 or 2003 anomaly appeared to be strongly linked to the positive phase of the Arctic Oscillation (AO) during the preceding winter. Similarly, the AO was negative during winter 2003/2004. In the previous AO framework of Rigor et al (2002), a positive winter AO implied preconditioning of the ice cover to extensive summer decay. In this hypothesis, the AO does not explain all aspects of the recent decline in Arctic ice cover, such as the extreme minima of 2002, 2003 and 2004. New analysis by Rigor and Wallace (2004) suggest that the very positive AO state from 1989-1995 can explain the recent sea ice minima in terms of changes in the Arctic surface wind field associated with the previous high AO state. However, it is also reasonable to expect that a general decrease in ice thickness accompanying warming would manifest itself as greater sensitivity of the ice pack to wind forcings and albedo feedbacks. The decrease in multiyear ice and attendant changes in ice thickness distribution could in turn precondition the Arctic ice cover to further reductions in the subsequent summer(s) regardless if the summer temperatures were anomalously warm. The NSIDC Sea Ice Index (http://nsidc.org/data/seaice_index/) can be used to view trends and anomalies from 1979 on.

Stroeve, J. C.; Fetterer, F.; Knowles, K.; Meier, W.; Serreze, M.; Arbetter, T.

2004-12-01

124

Sensitivity of a global sea ice model to the treatment of ice thermodynamics and dynamics  

NASA Astrophysics Data System (ADS)

The sensitivity of a global thermodynamic-dynamic sea ice model coupled to a one-dimensional upper ocean model to degradations of the model physics is investigated. The thermodynamic component of the sea ice model takes into consideration the presence of snow on top of sea ice, the storage of sensible and latent heat inside the snow-ice system, the influence of the subgrid-scale snow and ice thickness distributions on sea ice thermodynamics, the transformation of snow into snow ice when snow depth increases to the point where the snow-ice interface sinks below the waterline, and the existence of leads and polynyas (areas of open water) within the ice cover. Ice dynamics is treated basically as by Hibler [1979]. Regarding the upper ocean model, it is made up of an integral mixed layer model and of a diffusive model of the pycnocline. Advection of heat and salt by oceanic currents is implicitly accounted for by restoring the temperatures and salinities of the water column to annual mean data. It is very important to note that a single set of parameter values is employed to simultaneously simulate the Arctic and Antarctic ice regimes. A control run carried out with the model demonstrates that it does reasonably well in simulating the seasonal waxing and waning of both ice packs. The sensitivity study focuses on physical processes pertaining to (1) the vertical growth and decay of sea ice (thermal inertia of snow and ice, heat conduction, and snow cover), (2) the lateral growth and decay of sea ice (leads and polynyas), and (3) the sea ice dynamics (ice motion and shear strength). A total of nine sensitivity experiments have been performed. Each experiment consisted of removing a particular parameterization from the control run computer code. It appears that the thermal inertia of the snow-ice system is negligible in the Antarctic but not in the Arctic, where the total heat content of sea ice is chiefly dictated by internal storage of latent heat in brine pockets, sensible heat storage being of very minor consequence. It is also found that the inclusion of a prognostic snow layer and of a scheme of snow ice formation is important for sea ice modeling in the southern hemisphere. Furthermore, our results suggest that the thermodynamic effect of the subgrid-scale snow and ice thickness distributions, the existence of open water areas within the ice cover, and the ice motion play a crucial role in determining the seasonal behavior of both ice packs. The ice shear strength seems to be of lesser importance, although it has a nonnegligible effect in both hemispheres. We can therefore conclude that all these processes should be represented in global climate models.

Fichefet, T.; Maqueda, M. A. Morales

1997-01-01

125

Sea ice microbial communities (SIMCO)  

Microsoft Academic Search

Sea ice microbial communities (SIMCO) grow luxuriantly within several microhabitats of sea ice, indicating that the microorganisms comprising these communities are well adapted to the physicochemical gradients which characterize sea ice. We used SIMCO obtained from the bottom of congelation ice in McMurdo Sound, Antarctica, to test the hypothesis that low temperature limits microbial productivity in polar oceans and also

Steven T. Kottmeier; Cornelius W. Sullivan

1988-01-01

126

Melting Ice Rising Seas  

NSDL National Science Digital Library

This NASA video presents animations, photos and footage of melting polar ice as a result of climate change, the resulting sea-level rise, and selected consequences of that rise. Excellent animations, interviews with scientists, and clear step-by-step explanations provide a solid introduction to one facet of sea level rise and its consequences.

Noaa

127

Sea Ice 2000 - 2008  

NSDL National Science Digital Library

This site features a video that illustrates both seasonal patterns and long-term changes in sea ice distribution across the Arctic Ocean. It draws data from two satellite instruments that measure emitted microwave radiation, which helps distinguish open ocean from ice. It shows that during the winter months, a layer of ice forms across vast expanses of the Arctic Ocean and each summer, more than half of that ice vanishes. Students discover that this natural cycle of freezing and thawing is influenced both by seasonal temperature variations and long-term climate change and that scientists are using satellite images to measure the distribution of Arctic sea ice in order to gain a better understanding of how it is linked to Earth's climate system.

128

Level-ice melt ponds in the Los Alamos sea ice model, CICE  

NASA Astrophysics Data System (ADS)

A new meltpond parameterization has been developed for the CICE sea ice model, taking advantage of the level ice tracer available in the model. The ponds evolve according to physically based process descriptions, assuming a depth-area ratio for changes in pond volume. A novel aspect of the new scheme is that the ponds are carried as tracers on the level ice area of each thickness category, thus limiting their spatial extent based on the simulated sea ice topography. This limiting is meant to approximate the horizontal drainage of melt water into depressions in ice floes. Simulated melt pond processes include collection of liquid melt water and rain into ponds, drainage through permeable sea ice or over the edges of floes, infiltration of snow by pond water, and refreezing of ponds. Furthermore, snow that falls on top of ponds whose top surface has refrozen blocks radiation from penetrating into the ponds and sea ice below.

Hunke, Elizabeth C.; Hebert, David A.; Lecomte, Olivier

2013-11-01

129

Sea ice properties in the Bohai Sea measured by MODIS-Aqua: 1. Satellite algorithm development  

NASA Astrophysics Data System (ADS)

Based on the fact that sea ice reflectance drops significantly in the shortwave infrared (SWIR) wavelengths, black pixel assumption is assessed for three SWIR bands for the Moderate Resolution Imaging Spectroradiometer (MODIS)-at 1240, 1640, and 2130 nm—over the sea ice in the Bohai Sea in order to carry out atmospheric correction for deriving sea ice reflectance spectra. For the SWIR 1240 nm band, there is usually a small (but non-negligible) reflectance contribution over sea ice. Although there is a slight sea ice reflectance contribution at the MODIS 1640 nm band over sporadic land-fast or hummock ice, the black pixel assumption is generally valid with the MODIS bands 1640 and 2130 nm in the Bohai Sea. Thus, the SWIR-based atmospheric correction algorithm using MODIS bands at 1640 and 2130 nm can be conducted to derive sea ice optical properties in the region. Based on spectral features of the sea ice reflectance, a regionally optimized ice-detection algorithm is proposed. This regional algorithm shows considerable improvements in detecting sea ice over the Bohai Sea region, compared with a previous MODIS global sea ice detection algorithm. The sea ice coverage as identified in the new algorithm matches very well with the sea ice coverage from both the MODIS true color image and the imagery from the Interactive Multisensor Snow and Ice Mapping System (IMS).

Shi, Wei; Wang, Menghua

2012-07-01

130

Antarctic ice sheet and sea ice regional albedo and temperature change, 1981–2000, from AVHRR Polar Pathfinder data  

Microsoft Academic Search

Spring–summer (November, December, January) ice sheet and sea ice regional surface albedo, surface temperature, sea ice concentration and sea ice extent averages and trends from 1981 to 2000 have been calculated for the Antarctic area. In this research the AVHRR Polar Pathfinder 5-km EASE-Grid Composites and the combined SMMR and SSMI data sets from the National Snow and Ice Data

Vesa Laine

2008-01-01

131

Epidemic of fractures during period of snow and ice  

Microsoft Academic Search

During four days of snow and ice in which more than 70% of pavements in the Cardiff area were covered by slippery hard snow and ice the number of patients who attended the accident and emergency department at this hospital with fractured bones increased 2.85 times as compared with those who attended during four control days with comparable hours of

Z A Rális

1981-01-01

132

Crystal structure, stable isotopes (delta O-18), and development of sea ice in the Ross, Amundsen, and Bellingshausen seas, Antarctica  

NASA Astrophysics Data System (ADS)

The crystal structure and oxygen isotopic composition of ice cores obtained from floes at the end of summer in the eastern Ross Sea, the Amundsen Sea, and the western Bellingshausen Sea were investigated to determine the ice growth processes and conditions that contribute to sea ice development in the eastern Pacific sector of the southern ocean. The isotope data indicate that a moderate amount of snow contributes to the development of the sea ice. However, even the combined use of isotopes and crystal structure analysis does not unambiguously explain the means by which all of the snow is entrained in the ice. Nevertheless, it seems clear that much of the snow is contained in granular snow-ice that results from seawater flooding of floes and the base of the snow cover. The snow cover in the Ross-Amundsen region was as much as 2 m deep and supported by 7- to 8-m-thick floes primarily composed of frazil ice. In the Bellingshausen region the snow cover and the floes were thinner than in the Ross-Amundsen region. The Bellingshausen cores were composed primarily of multiple layers of frazil and congelation ice. In addition, in both regions there were numerous tipped or inclined blocks of congelation ice and layers of rafted nilas in the cores. The data indicate that the sea ice develops by multiple mechanisms in a turbulent environment.

Jeffries, Martin O.; Shaw, Raymond A.; Morris, Kim; Veazey, Alice L.; Krouse, H. Roy

1994-01-01

133

Rapid switch-like sea ice growth and land ice–sea ice hysteresis  

Microsoft Academic Search

Rapid and extensive growth of sea ice cover was suggested to play a major role in the sea ice switch mechanism for the glacial cycles as well as on shorter millennial scales [Gildor and Tziperman, 2000]. This mechanism also predicts a hysteresis between sea ice and land ice, such that land ice grows when sea ice cover is small and

Roiy Sayag; Eli Tziperman; Michael Ghil

2004-01-01

134

Airborne Spectral Measurements of Surface-Atmosphere Anisotropy for Arctic Sea Ice and Tundra.  

National Technical Information Service (NTIS)

Angular distributions of spectral reflectance for four common arctic surfaces: snow-covered sea ice, melt-season sea ice, snow-covered tundra, and tundra shortly after snowmelt were measured using an aircraft based, high angular resolution (1-degree) mult...

G. T. Arnold S. C. Tsay M. D. King J. Y. Li P. F. Soulen

1999-01-01

135

Sea-ice thickness distribution of the Bellingshausen Sea from surface measurements and ICESat altimetry  

Microsoft Academic Search

Although sea-ice extent in the Bellingshausen-Amundsen (BA) seas sector of the Antarctic has shown significant decline over several decades, there is not enough data to draw any conclusion on sea-ice thickness and its change for the BA sector, or for the entire Southern Ocean. This paper presents our results of snow and ice thickness distributions from the SIMBA 2007 experiment

H. Xie; S. F. Ackley; D. Yi; H. J. Zwally; P. Wagner; B. Weissling; M. Lewis; K. Ye

2011-01-01

136

MMAB Sea Ice Analysis Page  

NSDL National Science Digital Library

This is the sea ice analysis page of the Marine Modeling and Analysis Branch (MMAB) of the National Oceanic and Atmospheric Administration (NOAA). Users can access images of sea ice extent that can be animated to show the previous 30 days activity. Images are available for the entire globe, the Northern Hemisphere (Alsaka, Sea of Okhotsk, and Sea of Japan), and the Southern Hemisphere (Weddell Polynya Watch, Ross Sea and Amery Basin). Information on sea ice modelling and forecasts is also accessible.

137

Modeling brine and nutrient dynamics in Antarctic sea ice: The case of dissolved silica  

Microsoft Academic Search

Sea ice ecosystems are characterized by microalgae living in brine inclusions. The growth rate of ice algae depends on light and nutrient supply. Here, the interactions between nutrients and brine dynamics under the influence of algae are investigated using a one-dimensional model. The model includes snow and ice thermodynamics with brine physics and an idealized sea ice biological component, characterized

Martin Vancoppenolle; Hugues Goosse; Anne de Montety; Thierry Fichefet; Bruno Tremblay; Jean-Louis Tison

2010-01-01

138

Variability of light transmission through Arctic land-fast sea ice during spring  

NASA Astrophysics Data System (ADS)

The amount of solar radiation transmitted through Arctic sea ice is determined by the thickness and physical properties of snow and sea ice. Light transmittance is highly variable in space and time since thickness and physical properties of snow and sea ice are highly heterogeneous on variable time and length scales. We present field measurements of under-ice irradiance along repeated (March, May, June 2010) transects under un-deformed land-fast sea ice at Barrow, Alaska. The objective was to quantify seasonal evolution and spatial variability of light transmittance through snow and sea ice. Along with optical measurements, snow depth, sea ice thickness, and freeboard were recorded, and ice cores were analyzed for Chlorophyll a and particulate matter. Our results show that snow cover variability prior to onset of snow melt may cause as much spatial variability of relative light transmittance as the contrast of ponded and white ice during summer. In both instances, a spatial variability of up to three times above and below the mean was measured. In addition, we found a thirtyfold increase of light transmittance as a result of partial snowmelt. Hence, the seasonal evolution of transmittance through sea ice exceeded the spatial variability. Nevertheless, more comprehensive under-ice radiation measurements are needed for a more generalized and large-scale understanding of the under-ice energy budget for physical, biological, and geochemical applications.

Nicolaus, M.; Petrich, C.; Hudson, S. R.; Granskog, M. A.

2012-10-01

139

Melting Sea Ice  

NSDL National Science Digital Library

This activity uses a mix of multimedia resources and hands-on activities to support a storyline of investigation into melting sea ice. The lesson begins with a group viewing of a video designed to get students to consider both the local and global effects of climate change. The class then divides into small groups for inquiry activities on related topics followed by a presentation of the findings to the entire class. A final class discussion reveals a more complex understanding of both the local and global impacts of melting sea ice.

Domain, Wgbh E.

140

Atmospheric mercury over sea ice during the OASIS-2009 campaign  

NASA Astrophysics Data System (ADS)

Measurements of gaseous elemental mercury (GEM), reactive gaseous mercury (RGM) and particulate mercury (PHg) were collected on sea ice near open leads in the Beaufort Sea near Barrow, Alaska in March 2009 as part of the Ocean-Atmosphere-Sea Ice-Snowpack (OASIS) International Polar Year Program. These results represent the first atmospheric mercury speciation measurements collected on the sea ice. Concentrations of PHg over the sea ice averaged 393.5 pg m-3 (range 47.1-900.1 pg m-3) during the two week long study. RGM concentrations averaged 30.1 pg m-3 (range 3.5-105.4 pg m-3). The mean GEM concentration of 0.59 ng m-3 during the entire study (range 0.01-1.51 ng m-3) was depleted compared to annual Arctic ambient boundary layer concentrations. It was shown that when ozone (O3) and bromine oxide (BrO) chemistry are active there is a~linear relationship between GEM, PHg and O3 but there was no correlation between RGM and O3. There was a linear relationship between RGM and BrO and our results suggest that the origin and age of air masses play a role in determining this relationship. These results were the first direct measurements of these atmospheric components over the sea ice. For the first time, GEM was measured simultaneously over the tundra and the sea ice. The results show a significant difference in the magnitude of the emission of GEM from the two locations where significantly higher emission occurs over the tundra. Elevated chloride levels in snow over sea ice are believed to be the cause of lower GEM emissions over the sea ice because chloride has been shown to suppress photoreduction processes of Hg(II) to Hg(0) (GEM) in snow. These results are important because while GEM is emitted after depletion events on snow inland, less GEM is emitted over sea ice. Since the snow pack on sea ice retains more mercury than inland snow current models of the Arctic mercury cycle, which are based predominantly on land based measurements, may greatly underestimate atmospheric deposition fluxes. Land based measurements of atmospheric mercury deposition may also underestimate the impacts of sea ice changes on the mercury cycle in the Arctic. The findings reported in this study improve the current understanding of mercury cycling in the changing Arctic. The predicted changes in sea ice conditions and a~more saline snow pack in the Arctic could lead to even greater retention of atmospherically deposited mercury in the future. This could severely impact the amount of mercury entering the Arctic Ocean and coastal ecosystems.

Steffen, A.; Bottenheim, J.; Cole, A.; Douglas, T. A.; Ebinghaus, R.; Friess, U.; Netcheva, S.; Nghiem, S.; Sihler, H.; Staebler, R.

2013-03-01

141

The interactive multisensor snow and ice mapping system  

NASA Astrophysics Data System (ADS)

The interactive multisensor snow and ice mapping system (IMS) was developed to give snow and ice analysts the tools, on one platform, to inspect visually the imagery and mapped data from various sensor sources to determine the presence of snow and ice and to depict snow- and ice-covered areas on a map on a daily basis, in one hour or less. Snow and ice analysts in the National Environmental Satellite, Data, and Information Service have been creating weekly maps showing the extent of snow cover for the Northern Hemisphere since 1966 using visible imagery from polar-orbiting and geostationary satellites and surface observations as data sources. The current process is mostly manual and time-consuming, taking up to 10 hours to produce a map during the snow season. Where cloud cover precludes an unobstructed view of an area during the entire week, the analysis from the previous week is carried forward. Each week the analyst draws a new map by hand, then digitizes the extent of snow and ice cover using an 89×89 line grid overlaid on a stereographic map of the Northern Hemisphere. The hand-drawn map is photocopied and distributed and the digitized map is saved to a file for use in National Weather Service numerical models and for archival storage. IMS was designed and built to replace and improve this process by producing a more accurate and timely product.

Ramsay, Bruce H.

1998-07-01

142

Recent increase in snow-melt area in the Greenland Ice sheet as an indicator of the effect of reduced surface albedo by snow impurities  

NASA Astrophysics Data System (ADS)

Recent rapid decline of cryosphere including mountain glaciers, sea ice, and seasonal snow cover tends to be associated with global warming. However, positive feedback is likely to operate between the cryosphere and air temperature, and then it may not be so simple to decide the cause-and-effect relation between them. The theory of heat budget for snow surface tells us that sensible heat transfer from the air to the snow by atmospheric warming by 1°C is about 10 W/m2, which is comparable with heat supply introduced by reduction of the snow surface albedo by only 0.02. Since snow impurities such as black carbon and soil- origin dusts have been accumulated every year on the snow surface in snow-melting season, it is very important to examine whether the snow-melting on the ice sheets, mountain glaciers, and sea ice is caused by global warming or by accumulated snow impurities originated from atmospheric pollutants. In this paper we analyze the dataset of snow-melt area in the Greenland ice sheet for the years 1979 - 2007 (available from the National Snow and Ice Data Center), which is reduced empirically from the satellite micro-wave observations by SMMR and SMM/I. It has been found that, seasonally, the snow-melt area extends most significantly from the second half of June to the first half of July when the sun is highest and sunshine duration is longest, while it doesn't extend any more from the second half of July to the first half of August when the air temperature is highest. This fact may imply that sensible heat required for snow-melting comes from the solar radiation rather than from the atmosphere. As for the interannual variation of snow-melt area, on the other hand, we have found that the growth rate of snow-melt area gradually increases from July, to August, and to the first half of September as the impurities come out to and accumulated at the snow surface. However, the growth rate is almost zero in June and the second half of September when fresh snow of high albedo covers the surface. This fact may imply that the combined operation of solar radiation and snow impurities is responsible for the recent global decline of cryosphere. Discussion about other research works will be given in the presentation in order to support the above idea.

Rikiishi, K.

2008-12-01

143

Applied Sea Ice Research  

NASA Astrophysics Data System (ADS)

In the late 1960s oil and gas development became an issue in the northern coastal areas of Alaska and Canada. More lately this has also become an issue in the Euroasian Arctic with the Barents and Kara Seas as example on where offshore hydrocarbon production now is being planned. In such waters the key questions prior to a development are related to water depths at the site and in case of ice, how frequent and what type of ice features will be met. Especially the ice conditions and knowledge about them are very decisive for the field development solutions to be chosen. The paper will highlight examples on development solutions where the ice conditions have played a paramount role in the field development plans. An example is the consequences of iceberg threaten in an area and the effect sudden changes in ice drift directions may have on the exploration and drilling solutions chosen. The paper will also discuss how to derive design ice actions values for such waters including scaling from nature to model ice basins.

Løset, S.

2009-04-01

144

Mapping Antarctic sea ice thickness distribution from above and below  

NASA Astrophysics Data System (ADS)

Understanding of Antarctic sea ice processes, both small and large scale, have been hampered by our inability to reliably monitor ice thickness distribution from space, primarily due to the confounding role of its snow cover. This is highlighted by a large discrepancy between recent ice thickness estimates from ICESat and ship-based observations. We present a first look at results from a recent British Antarctic Survey led expedition, ICEBell, to map selected sea ice floes close to the Antarctic Peninsula coast in the Weddell and Bellingshausen Seas in November, 2010. This combined, for the first time, three-dimensional ice draft measurements from an autonomous underwater vehicle, coincident with detailed in situ mapping, and airborne lidar mapping of the surface topography to comprehensively map sea ice floes in detail. These measurements were made near-contemporaneously and nearly collocated with two NASA IceBridge flights which will both place our measurements within a broader regional context and provide some validation of the IceBridge measurements. Several process studies were also undertaken - ice mass balance buoys deployed to investigate sea ice melt processes and investigations of remote sensing signatures of the ice. Ice was generally very heavily deformed, with drafts of surveyed floes averaging over three meters, much of it under deep snow cover. I will discuss how these data might be used to move beyond simple mass balance relationships and use spatial morphological information to develop improved relationships between snow and ice thickness distributions, and hence, improved algorithms for determining Antarctic sea ice thickness from space.

Maksym, T. L.; Wilkinson, J.; Singh, H.; Lewis, M.; Hochheim, K.; Wagner, T.

2011-12-01

145

Sea ice and polar climate in the NCAR CSM  

SciTech Connect

The Climate System Model (CSM) consists of atmosphere, ocean, land, and sea-ice components linked by a flux coupler, which computes fluxes of energy and momentum between components. The sea-ice component consists of a thermodynamic formulation for ice, snow, and leads within the ice pack, and ice dynamics using the cavitating-fluid ice rheology, which allows for the compressive strength of ice but ignores shear viscosity. The results of a 300-yr climate simulation are presented, with the focus on sea ice and the atmospheric forcing over sea ice in the polar regions. The atmospheric model results are compared to analyses from the European Centre for Medium-Range Weather Forecasts and other observational sources. The sea-ice concentrations and velocities are compared to satellite observational data. The atmospheric sea level pressure (SLP) in CSM exhibits a high in the central Arctic displaced poleward from the observed Beaufort high. The Southern Hemisphere SLP over sea ice is generally 5 mb lower than observed. Air temperatures over sea ice in both hemispheres exhibit cold biases of 2--4 K. The precipitation-minus-evaporation fields in both hemispheres are greatly improved over those from earlier versions of the atmospheric GCM.

Weatherly, J.W.; Briegleb, B.P.; Large, W.G. [National Center for Atmospheric Research, Boulder, CO (United States). Climate and Global Dynamics Div.; Maslanik, J.A. [Univ. of Colorado, Boulder, CO (United States)

1998-06-01

146

Bibliography on Snow, Ice and Permafrost with Abstracts. Volume XVIII.  

National Technical Information Service (NTIS)

The Bibliography provides current and comprehensive coverage on scientific information, both basic and applied, about living and operating in the polar regions and cold areas where snow, ice and permafrost exist. Each entry includes an informative abstrac...

1964-01-01

147

Sea Level: Ice Volume Changes  

NSDL National Science Digital Library

In this exercise, students observe simulations of melting sea ice and a melting continental ice sheet in order to investigate the relationship between the melting of the ice and the water level in the tank. The water tanks simulate the world oceans. In the first example, the ice is floating in water. This would be an example of icebergs or Arctic ice floating on the ocean. In the second example the ice lies on a wood structure. The structure simulates a continent. The block of ice on top of the structure simulates ice grounded on top of a continent. This would be an example of ice sheets in Greenland and Antarctica.

148

The rates of sea salt sulfatization in the atmosphere and surface snow of inland Antarctica  

NASA Astrophysics Data System (ADS)

Most of the aerosol particles present in the surface snow and ice of inland Antarctica come from primary sea salt (sodium chloride) and marine biological activity (methansulfonic and sulfuric acids). Melted water from surface snow, firn, and Holocene ice contains mainly sodium, chloride, and sulfate ions. Although it is well known that sea salt aerosols react rapidly with sulfuric acid, a process known as sulfatization, it is not known when this process takes place. In this research we undertake to measure the proportion of sea salt aerosols that undergo sulfatization in the atmosphere and surface snow, as opposed to deeper ice, in order to understand the suitability of sea salt aerosols as a proxy for past climates in deep ice cores. We directly measure the sulfatization rates in recently fallen snow (0-4 m in depth) collected at the Dome Fuji station, using X-ray dispersion spectroscopy to determine the constituent elements of soluble particles and computing the molar ratios of sodium chloride and sodium sulfate. We estimate that about 90% of the initial sea salt aerosols sulfatize as they are taken up by precipitation over Dome Fuji or in the snowpack within one year after being deposited on the ice sheet.

Iizuka, Yoshinori; Tsuchimoto, Akira; Hoshina, Yu; Sakurai, Toshimitsu; Hansson, Margareta; Karlin, TorbjöRn; Fujita, Koji; Nakazawa, Fumio; Motoyama, Hideaki; Fujita, Shuji

2012-02-01

149

Total inorganic carbon in sea ice  

NASA Astrophysics Data System (ADS)

The method proposed for determining the total inorganic carbon (TC) concentrations in sea ice (Arctic region, North Pole-35 expedition) based on the measurement of the total alkalinity (TA) and the pH in the melt waters without the CO2 exchange with the atmosphere is considered. It is shown that the TC/Sal and TA/TC values through the entire ice section remain similar to these parameters in the subice water. The surface snow and the uppermost ice layers are characterized by elevated TA/TC values, which indicate the reaction Ca2+ + 2HCO{3/-} = ?CaCO3 + ?CO2 + H2O. The release of CO2 to the atmosphere due to the decomposition of calcium hydrocarbonate is as high as ˜20 mmol/m2. The meltwater of the examined ice is undersaturated with CO2, which may result in a sink of atmospheric CO2 (˜30 mmol/m2).

Nedashkovsky, A. P.; Shvetsova, M. G.

2010-12-01

150

Arctic Sea ice at a new low  

NASA Astrophysics Data System (ADS)

On 26 August, Arctic sea ice cover dipped to 4.1 million square kilometers, 70,000 square kilometers below the 2007 mark, which was previously the lowest extent of ice cover in the satellite record, according to an analysis of satellite data by scientists with NASA and the National Snow and Ice Data Center (NSIDC) of the University of Colorado, Boulder. “By itself it's just a number, and occasionally records are going to get set. But in the context of what's happened in the last several years and throughout the satellite record, it's an indication that the Arctic sea ice cover is fundamentally changing,” said NSIDC scientist Walt Meier. “The persistent loss of perennial ice cover—ice that survives the melt season—led to this year's record summertime retreat. Unlike 2007, temperatures were not unusually warm in the Arctic this summer,” said Joey Comiso, senior research scientist at NASA's Goddard Space Flight Center, in Greenbelt, Md. The six lowest ice extents in the satellite record have occurred in the last 6 years, according to NSIDC.

Showstack, Randy

2012-09-01

151

Seasonal and decadal expansions of the snow-melt area in the Greenland ice sheet and its possible relation with the decrease in snow surface albedo  

NASA Astrophysics Data System (ADS)

Rapid decline of the entire cryosphere in recent years is generally considered to be caused by global warming. However, estimates of the heat budget at the snow surface lead to the conclusion that the sensible heat transfer from air to snow by the air temperature rise by 1 K is only about 10 W/m2. Consequently, it seems uncertain whether or not this amount of heat addition is large enough to cause the simultaneous decline of ice sheets, mountain glaciers, sea ice, and seasonal snow cover all over the world. In this paper we have analyzed the dataset of snow-melt area in the Greenland ice sheet for the years 1979 - 2007 (available from the National Snow and Ice Data Center). The melt-area is estimated empirically from the satellite micro-wave observations by SMMR and SMM/I. It has been found that the seasonal expansion of snow-melt area is more significant during the periods when the sun is higher and sunshine duration is longer rather than during the periods when the air temperature is higher. On the other hand, the decadal growth rate of snow-melt area shows maximum values in the first half of September when the snow surface is covered with accumulated snow impurities, and minimum values in June and the second half of September when the surface is covered with clean or newly fallen snow. We have then analyzed the dataset of clear-sky surface albedo over the Greenland for the years 1981 - 2005 (available from the National Snow and Ice Data Center). The albedo values are estimated from visible imageries by making corrections for the effects of water vapor, cloud, and angles between the zenith and sun and satellite. Similar trends have been found in terms of the seasonal expansion and the decadal growth rate for the snow surface albedo. These facts imply that the snow-melting in the Greenland ice sheet may be caused by the decrease in snow surface albedo (or by the increase in snow impurities) rather than the air temperature rise.

Rikiishi, K.

2009-04-01

152

Improved simulation of feedbacks between atmosphere and sea ice over the Arctic Ocean in a coupled regional climate model  

Microsoft Academic Search

Modeling sea ice in a realistic manner is still a great challenge, in particular with respect to the minimum ice extent at the end of the summer. Modified descriptions of ice growth, snow and ice albedo, and snow cover on ice have been incorporated into the coupled regional atmosphere–ocean–ice model HIRHAM–NAOSIM, and a series of sensitivity experiments has been performed

W. Dorn; K. Dethloff; A. Rinke

2009-01-01

153

Sea ice dynamics influence halogen deposition to Svalbard  

NASA Astrophysics Data System (ADS)

Sea ice is an important parameter in the climate system and its changes impact upon the polar albedo and the atmospheric and oceanic circulation. Iodine (I) and bromine (Br) have been measured in a shallow ice core drilled at the summit of the Holtedahlfonna glacier (Northwest Spitsbergen, Svalbard). Changing I concentrations can be linked to the spring maximum sea ice extension. Bromine enrichment, indexed to the Br/Na sea water mass ratio, appears to be influenced by changes in the seasonal sea ice area. I is emitted from marine biota and so the retreat of spring sea ice coincides with enlargement of the open ocean surface which enhances marine primary production and consequent I emission. The observed Br enrichment can be explained by greater Br emissions during the Br explosion that have been observed to occur above first year sea ice during the early springtime. In this work we present the first comparison between halogens in surface snow and Arctic sea ice extension. Although further investigation is required to characterize potential depositional and post-depositional processes, these preliminary findings suggest that I and Br can be linked to variability in the spring maximum sea ice extension and seasonal sea ice surface area.

Spolaor, A.; Gabrieli, J.; Martma, T.; Kohler, J.; Björkman, M.; Isaksson, E.; Varin, C.; Vallelonga, P.; Plane, J. M. C.; Barbante, C.

2013-03-01

154

Abundance and composition of the sea-ice meiofauna in off-shore pack ice of the Beaufort Gyre in summer 2002 and 2003  

Microsoft Academic Search

We studied the abundance, biomass and potential ingestion rates of meiofauna in multi-year sea ice (MYI) of the Beaufort Gyre during two icebreaker expeditions in summers 2002 and 2003. Ice cores were taken at a total of ten stations and analyzed for ice temperature, salinity, chlorophyll a (Chl a), and ice meiofauna abundances. In 2002, ice was free of snow

Rolf R. Gradinger; Klaus Meiners; Gerry Plumley; Qing Zhang; Bodil A. Bluhm

2005-01-01

155

Cladoceran zooplankton abundance under clear and snow-covered ice  

USGS Publications Warehouse

We described the distribution of cladoceran zooplankton under the ice in a natural, glacial lake. Local light availability apparently altered the spatial distribution of cladocerans. Light levels measured under snow-covered areas (0.178 lux) were an order of magnitude less than those measured at the same depth under clear ice (1.750 lux). Cladoceran density under snow-covered areas was significantly higher (Bosmina spp.=3.34/L; Daphnia spp.=0.61/L) than cladoceran abundance under clear ice (Bosmina spp.=0.91/L; Daphnia spp.=0.19/L).

DeBates, T. J.; Chipps, S. R.; Ward, M. C.; Werlin, K. B.; Lorenzen, P. B.

2003-01-01

156

Snow and ice volume on Mount Spurr Volcano, Alaska, 1981  

USGS Publications Warehouse

Mount Spurr (3,374 meters altitude) is an active volcano 130 kilometers west of Anchorage, Alaska, with an extensive covering of seasonal and perennial snow, and glaciers. Knowledge of the volume and distribution of snow and ice on a volcano aids in assessing hydrologic hazards such as floods, mudflows, and debris flows. In July 1981, ice thickness was measured at 68 locations on the five main glaciers of Mount Spurr: 64 of these measurements were made using a portable 1.7 megahertz monopulse ice-radar system, and 4 measurements were made using the helicopter altimeter where the glacier bed was exposed by ice avalanching. The distribution of snow and ice derived from these measurements is depicted on contour maps and in tables compiled by altitude and by drainage basins. Basal shear stresses at 20 percent of the measured locations ranged from 200 to 350 kilopascals, which is significantly higher than the 50 to 150 kilopascals commonly referred to in the literature as the 'normal' range for glaciers. Basal shear stresses higher than 'normal' have also been found on steep glaciers on volcanoes in the Cascade Range in the western United States. The area of perennial snow and ice coverage on Mount Spurr was 360 square kilometers in 1981, with an average thickness of 190?50 meters. Seasonal snow increases the volume about 1 percent and increases the area about 30 percent with a maximum in May or June. Runoff from Mount Spurr feeds the Chakachatna River and the Chichantna River (a tributary of the Beluga River). The Chakachatna River drainage contains 14 cubic kilometers of snow and ice and the Chichantna River drainage contains 53 cubic kilometers. The snow and ice volume on the mountain was 67?17 cubic kilometers, approximately 350 times more snow and ice than was on Mount St. Helens before its May 18, 1980, eruption, and 15 times more snow and ice than on Mount Rainier, the most glacierized of the measured volcanoes in the Cascade Range. On the basis of these relative quantities, hazard-producing glaciovolcanic phenomena at Mount Spurr could be significantly greater than similar phenomena at Cascade Volcanoes.

March, Rod S.; Mayo, Lawrence R.; Trabant, Dennis C.

1997-01-01

157

Physical, structural, and isotopic characteristics and growth processes of fast sea ice in Lützow-Holm Bay, Antarctica  

NASA Astrophysics Data System (ADS)

A sea-ice/ocean study was conducted off Queen Maud Land and Enderby Land, Antarctica, from 1990 to 1991 by the Japanese Antarctic Research Expedition. Observations of multiyear land fast sea ice were made in Lützow-Holm Bay over a period of 2 years to determine the snow and ice characteristics and ice growth processes. The snow depth in the bay reached large values of 1.0 to 1.5 m during the winter season at offshore locations. From the analysis of ice thickness measurements, it is confirmed that the fast ice with deep snow cover grew little in winter but substantially thickened during the summer months. On the basis of ice core structure, salinity, and stable isotopic composition, we conclude that the summer growth was caused by upward growth at the top of the ice to which snow ice and superimposed ice formation contribute. These processes were the primary contributors to sea-ice growth and characteristics only where the snow accumulation was large. In areas of low snow accumulation, there was no surface growth. Superimposed ice formation on sea ice in Antarctica has not been reported previously. Evidence for snow cover melting, which is a prerequisite for superimposed ice formation, was also found.

Kawamura, T.; Ohshima, K. I.; Takizawa, T.; Ushio, S.

1997-02-01

158

Sea Ice Thickness Variability in Fram Strait  

NASA Astrophysics Data System (ADS)

On this poster, we show results from airborne electromagnetic (EM) sea ice thickness measurements demonstrating the temporal and spatial complexity of the ice thickness distribution in Fram Strait between Greenland and Svalbard. Knowledge about the spatial and temporal sea ice thickness distribution in the Arctic Ocean is necessary to assess the state of the sea-ice cover, and to understand relevant processes and changes. Since 2003, the Norwegian Polar Institute (NPI) has been conducting systematic in situ monitoring of sea ice thickness in the western Fram Strait, using both ground and airborne techniques. Fram Strait is a key region for large-scale ice dynamics in the Arctic. It represents the main export route for sea ice from the Arctic and the only deep strait connecting the interior Arctic Ocean and the rest of the world oceans. The ice thickness distribution in this region is the result of a combination of dynamic and thermodynamic sea ice processes. Transects for airborne EM observations were flown by NPI in spring 2005, 2008, and late summer 2010, and by the Alfred Wegener Institute in spring 2009. The regional ice thickness distributions are supplemented with ground measurements including snow thickness observations taken on ice stations during ship expeditions in spring 2005, 2007, and 2008 and annually in late summer from 2003 to 2011. From all these observations, we can show the differing characteristics of the thickness distributions in spring (2005, 2008, 2009) and late summer (2010) when the ice thickness is at its annual maximum (end of the freezing period) and minimum (end of the melting period), respectively. The ice thickness distribution can also vary spatially over short distances in north-south direction. Features such as the East Greenland Polynya, which varies in size for a given time from year to year, contribute to the spatial and temporal variability on the Greenlandic Shelf. In spring 2005, a gradient is visible across Fram Strait from thinner pack ice at the eastern ice edge towards thicker pack ice on the Greenland shelf in the western part of Fram Strait with thick multiyear ice. The spring modal thickness ranged from about 2 m to 3.5 m. In contrast, the spatial variability of the modal thickness in 2008 is larger than observed in the previous campaigns with a wider range of modal ice thicknesses, predominantly due to thinner ice than in 2005. Finally, during late summer 2010 modal thicknesses in the central and eastern part of Fram Strait ranged from about 1 to 2 m. At the same time distributions were in general narrower than observed in previous years, showing a decrease of the fraction of thick pressure ridges. Thick ice was measured only in the westernmost part of Fram Strait. These observations are in agreement with a reported trend towards a generally larger amount of first-year ice versus multiyear ice in the Arctic.

Gerland, S.; Renner, A.; Haas, C.; Nicolaus, M.; Granskog, M.; Hansen, E.; Hendricks, S.; Hudson, S. R.; Beckers, J.; Goodwin, H.

2011-12-01

159

The Future of Arctic Sea Ice  

NASA Astrophysics Data System (ADS)

Arctic sea ice is a key indicator of the state of global climate because of both its sensitivity to warming and its role in amplifying climate change. Accelerated melting of the perennial sea ice cover has occurred since the late 1990s, which is important to the pan-Arctic region, through effects on atmospheric and oceanic circulations, the Greenland ice sheet, snow cover, permafrost, and vegetation. Such changes could have significant ramifications for global sea level, the ocean thermohaline circulation, native coastal communities, and commercial activities, as well as effects on the global surface energy and moisture budgets, atmospheric and oceanic circulations, and geosphere-biosphere feedbacks. However, a system-level understanding of critical Arctic processes and feedbacks is still lacking. To better understand the past and present states and estimate future trajectories of Arctic sea ice and climate, we argue that it is critical to advance hierarchical regional climate modeling and coordinate it with the design of an integrated Arctic observing system to constrain models.

Maslowski, Wieslaw; Clement Kinney, Jaclyn; Higgins, Matthew; Roberts, Andrew

2012-05-01

160

Modelling the Areal Evolution of Arctic Melt Ponds on Sea Ice  

NASA Astrophysics Data System (ADS)

During winter the ocean surface at the poles freezes over to form sea ice. Sea ice floats on the ocean surface and has a matrix structure caused by the rejection of salts during freezing. In the summer sea ice melts at its surface creating melt ponds. An accurate estimate of the fraction of the upper sea-ice surface covered in melt ponds during the summer melt season is essential for a realistic estimate of the albedo for global climate models. We present a sea ice model that simulates the two-dimensional (areal) evolution of melt ponds on an Arctic sea-ice surface. Water transport across and through the sea-ice surface is described by the major hydraulic processes believed to be present. Thermodynamic processes are modelled using heat flux equations. Lateral and vertical melt water transport is described by Darcy's Law. The model simulates a section of a sea ice floe where edge effects such as the presence of leads are neglected. The model consists of a grid of cells, each of which can be in one of four possible configurations: snow covered ice; bare ice; melt pond covered ice or open water. A cluster of adjacent cells containing melt water may be considered to have formed a melt pond. The model is initialised with ice topographies that represent either first-year or multi-year sea ice, these are reconstructed from ice thickness data using standard statistical methods; in this way characteristic examples of both first-year ice and multi-year ice can be constructed. The roughness of the ice and snow surfaces were altered and the sensitivity of the model to the initial data was tested. First-year ice and multi-year ice simulations agreed with observed differences in individual pond size and depth. Sensitivity studies showed that pond fraction is most sensitive to mean initial snow depth in first-year ice simulations and reduction of ice permeability all cases.

Feltham, D. L.; Scott, F.

2009-12-01

161

Kindergarten Explorations with Snow, Ice, and Water  

ERIC Educational Resources Information Center

Using winter snow, kindergarten students can explore the properties of water. Students demonstrate melting, freezing, expansion, and evaporation through a number of activities involving a paper cup and a scoop of snow. Procedures and student reactions are described in detail by the teacher-author. (MA)

Carroll, Martha A.

1978-01-01

162

Feature Identification Exerecises: Clouds, Snow, and Ice Using MODIS  

NSDL National Science Digital Library

The Feature Identification Exercises: Clouds, Snow, and Ice Using MODIS module consists of four exercises where users identify surface features, distinguish clouds from snow on the ground, and determine cloud phase using multispectral analysis. The module also includes an overview of multispectral techniques available on many operational and research polar-orbiting satellites. A page with links to real-time polar-orbiting data and information is also included.

Spangler, Tim

2003-01-01

163

Drifting snow climate of the Antarctic and Greenland ice sheets  

NASA Astrophysics Data System (ADS)

This study presents the drifting snow climate of the Earth's ice sheets, Antarctica and Greenland. For that purpose we use a regional atmospheric climate model, RACMO2. We included a routine that is able to calculate the drifting snow fluxes and accounts for the interaction between drifting snow on the one hand and the atmosphere and snow surface on the other. RACMO2 is run at 27 km resolution for Antarctica, and 11 km resolution for Greenland, and forced at its lateral boundaries by ECMWF reanalyses (32 years for Antarctica and 52 years for Greenland). Because direct evaluation for drifting snow is challenging due to sparseness of observational data, we focussed the model evaluation on the ability of RACMO2 to represent near-surface wind climate, temperature, surface mass balance, the extent of ablation areas and remote-sensed drifting snow frequency. We show that RACMO2 is very well able to represent the present-day near-surface climate of Antarctica and Greenland. Drifting snow occurs 20-80% of the time on Antarctica, depending on the local wind climate. Highest frequencies are found in the coastal areas, where drifting snow sublimation (SUds) removes up to 150 mm water equivalent of snow, whereas the high-elevation areas experience little or no SUds. Drifting snow erosion (ER­ds) can be negative (deposition) or positive (erosion), and varies generally between -50 and 50 mm in regions where the wind field convergences and diverges, respectively. Integrated over the ice sheet, SUds removes around 165 Gt of snow, which is equivalent to ~6% of the precipitated snow. The impact of ER­ds on the Antarctic ice sheet SMB is negligible . We found several feedbacks between SUds and the atmosphere. SUds moistens the near-surface atmosphere, limiting its own potential, but also enhancing precipitation in some coastal areas. By removing mass from the snow surface, drifting snow processes increase the top snow layer density, increasing the threshold wind speed for further drifting snow. Since the impacts of drifting snow are included, we are able to quantify all contributors to the Antarctic SMB. The SMB equals 2479 +/- 147 Gt/yr, and is largely determined by snowfall. It varies from <50 mm/yr on the East Antarctic Plateau to more than 2000 mm/yr in coastal West Antarctica and the Antarctic Peninsula. Mass is primarly removed by SUds, because all meltwater produced refreezes in the snowpack, and surface sublimation equals only ~30% of SUds. The influence of model resolution on the resulting impact of drifting snow on the East Antarctic SMB is small, although locally ERds is much more significant due to the better representation of small-scale topography and related wind gradients. The impact of drifting snow on the Greenland ice sheet SMB is generally less significant than on Antarctica, due to lower wind speeds, more melt that increases the snow density, and warmer temperatures. SUds equals 24 Gt/yr, equivalent to ~3% of the precipitation, and is only a winter phenomenon on Greenland. Ablation on Greenland is primarly governed by meltwater runoff in summer.

Lenaerts, J. T. M.

2013-02-01

164

Coupling snow densification and melt-water retention in a large-scale ice sheet model  

Microsoft Academic Search

The physics of snow and how the annual snow changes during a melting season is important for the surface mass balance of the Greenland Ice Sheet. Densification when meltwater is present will generally go much faster than the dry snow densification due to percolation and refreezing of meltwater in the snow-pack and it needs to be considered in ice sheet

R. S. Fausto; A. P. Ahlstrøm; S. J. Johsen

2008-01-01

165

Mercury deposition to snow and ice provides a link between the lower atmosphere and the cryosphere in northern Alaska  

NASA Astrophysics Data System (ADS)

We investigated a wide range of snow and ice forms as potential scavengers of atmospheric mercury during mercury depletion events (MDEs). Our work was part of a large campaign near Barrow, Alaska in the spring of 2005 (LEADEX-2005). Gaseous and reactive phase mercury, ozone and halogen oxide measurements were made at numerous locations along the Arctic Ocean Coast as part of the campaign and allowed us to identify when MDEs were occurring. Results from previous work implicated sea ice leads and the near shore coastal snow pack as locations where elevated mercury concentrations in frost flowers (75-185 ng/L) and surface hoar (~900 ng/L) were likely. In LEADEX-2005 the previous work was expanded by sampling snow along transects away from the lead edge and from daily sampling of diamond dust and surface snow at a site located 6 kilometers inland from the lead. Vapor condensate was also collected on chilled sample bottles hoisted above the lead on a 2 m2 kite and from a 2-m high pole. We also sampled surface hoar, rime ice, wind slab, fresh snow and blowing snow near the leads. Diamond dust was collected in glass trays and rime was scraped from the leading edge of an unmanned aerial vehicle wing. Nilas and frost flowers of varying ages were collected from a boat in open water at the lead. Elevated mercury concentrations were measured in virtually every type of vapor deposited snow or ice form, including some samples that yielded concentrations well over 1000 ng/L. Our results suggest that deposition of mercury to snow and ice during MDEs is controlled by four processes: 1) scavenging during crystallization or snow fall, 2) impaction of mercury laden aerosols onto crystalline surfaces, 3) sublimation of snow and ice, and 4) condensation driven by temperature gradients. We believe these four factors combine to control elevated mercury concentrations where the lower atmosphere and cryosphere meet.

Douglas, T. A.; Sturm, M.; Simpson, W. R.; Alvarez-Aviles, L.; Blum, J. D.; Perovich, D. K.; Keeler, G. J.; Lammers, A.; Biswas, A.

2005-12-01

166

Ice and Snow Feedbacks and the Latitudinal and Seasonal Distribution of Climate Sensitivity.  

NASA Astrophysics Data System (ADS)

A new parameterization of snow and ice area and albedo as functions of surface temperature is presented based on recent satellite observations of snow and ice extent. This parameterization is incorporated into a seasonal energy-balance climate model. Experiments are conducted with the model to determine the effects of this parameterization change on the latitudinal and seasonal distribution of model sensitivity to external forcings of climate change, such as solar constant variations and changes in the atmospheric carbon dioxide amount.The sea ice-thermal inertia feedback is found to be the determining factor in this sensitivity pattern, producing enhanced sensitivity in the polar regions in the winter and decreased sensitivity in the polar regions in the summer. The albedo feedbacks (snow-area and snow/ice-meltwater) are weak and produce a small amount of additional sensitivity, but do not change the pattern. The response pattern is the same as that found by Manabe and Stouffer (1980) with a general circulation model. The enhanced sensitivity in the summer found by Ramanathan et al. (1979) is shown to be due to a surface albedo feedback parameterization which does not allow the thermal inertia to change. The sensitivity of an annual average version of the model is approximately the same as that of the seasonal model.

Robock, Alan

1983-04-01

167

Uncertainties in Arctic sea ice thickness and volume: new estimates and implications for trends  

NASA Astrophysics Data System (ADS)

Sea ice volume has been found to decrease in the last decades, evoked by changes in sea ice area and thickness. Estimates of sea ice area and thickness rely on a number of geophysical parameters which introduce large uncertainties. To quantify these uncertainties we use freeboard retrievals from ICESat and investigate different assumptions on snow depth, sea ice density and area. We find that uncertainties in ice area are of minor importance for the estimates of sea ice volume during the cold season in the Arctic basin. The choice of mean ice density used when converting sea ice freeboard into thickness mainly influences the resulting mean sea ice thickness, while snow depth on top of the ice is the main driver for the year-to-year variability, particularly in late winter. The absolute uncertainty in the mean sea ice thickness is 0.28 m in February/March and 0.21 m in October/November. The uncertainty in snow depth contributes up to 70% of the total uncertainty and the ice density 30-35%, with higher values in October/November. We find large uncertainties in the total sea ice volume and trend. The mean total sea ice volume is 10 120 ± 1278 km3 in October/November and 13 254 ± 1858 km3 in February/March for the time period 2005-2007. Based on these uncertainties we obtain trends in sea ice volume of -1445 ± 531 km^3 a-1 in October/November and -875 ± 257 km3 a-1 in February/March over the ICESat period (2003-2008). Our results indicate that, taking into account the uncertainties, the decline in sea ice volume in the Arctic between the ICESat (2003-2008) and CryoSat-2 (2010-2012) periods may have been less dramatic than reported in previous studies.

Zygmuntowska, M.; Rampal, P.; Ivanova, N.; Smedsrud, L. H.

2013-10-01

168

Amundsen Sea ice production and transport  

Microsoft Academic Search

Drift and variability of sea ice in the Amundsen Sea are investigated with ice buoys deployed in March 2000 and a coupled ice-ocean model. The Bremerhaven Regional Ice Ocean Simulations (BRIOS) model results are compared with in situ ocean, atmosphere, and sea ice measurements; satellite observations; and 8–19 months of buoy drift data. We identify a zone of coastal westward

Karen M. Assmann; Hartmut H. Hellmer; Stanley S. Jacobs

2005-01-01

169

Improvements and Comparisons of Shortwave Radiation Physics in a Sea Ice Model  

NASA Astrophysics Data System (ADS)

Shortwave radiation physics in CICE4.0 is improved and evaluated. First, we improved surface albedo parameterization that depends on large-scale variables (named SHCE). The improvements include expanding the spectrum from two to four bands, distinguishing direct and diffuse, considering different albedo for wet and dry snow, and effects of sea ice and snow thickness on albedo, especially incorporating explicit melt pond and its impacts on albedo. Compared to CICE4.0, improved simulations are found in the following aspects: 1) sea ice concentration in the central Arctic is increased, especially in the East Siberia Sea, 2) sea ice thickness gradient from the Canadian Archipelago and Greenland Sea to East Siberia Sea is more like observations, 3) snow and ice albedo is increased in the central Arctic Ocean and closer to the observation. Also, the impacts of different albedo parameterization schemes (SHCE vs. Delta-Eddington which is based on the optical property) on sea ice simulations are examined. The results show that SHCE gives slightly better simulation, as the simulated albedo of Delta-Eddington is much lower than the observations, and sea ice concentration in the East Siberia Sea is less than the observations. Furthermore, the two different albedo scheme show different response to global warming. Second, we improved penetration of solar radiation in snow and sea ice. The improvements include expanding the spectrum bands and distinguishing extinction coefficients as a function of spectral bands and surface properties. Compared to CICE4.0, sea ice is reduced in the Arctic marginal sea ice zone and becomes thinner in the central Arctic Ocean, especially in the East Siberia Sea. This is mainly due to more absorbed shortwave in the inner ice and penetrated radiation into the mixed layer beneath the ice, which increases the basal ice melt.

Song, Mirong; Liu, Jiping

2013-04-01

170

Towards a satellite-based sea ice climate data record  

NASA Astrophysics Data System (ADS)

Sea ice plays an important role in the Earth's climate through its influence on the surface albedo, heat and moisture transfer between the ocean and the atmosphere, and the thermohaline circulation. Satellite data reveal that since 1979, summer Arctic sea ice has, overall, been declining at a rate of almost 8%/decade, with recent summers (beginning in 2002) being particularly low. The receding sea ice is having an effect on wildlife and indigenous peoples in the Arctic, and concern exists that these effects may become increasingly severe. Thus, a long-term, ongoing climate data record of sea ice is crucial for tracking the changes in sea ice and for assessing the significance of long-term trends. Since the advent of passive microwave satellite instruments in the early 1970s, sea ice has been one of the most consistently monitored climate parameters. There is now a 27+ year record of sea ice extent and concentration from multi-channel passive microwave radiometers that has undergone inter-sensor calibration and other quality controls to ensure consistency throughout the record. Several algorithms have been developed over the years to retrieve sea ice extent and concentration and two of the most commonly used algorithms, the NASA Team and Bootstrap, have been applied to the entire SMMR-SSM/I record to obtain a consistent time series. These algorithms were developed at NASA Goddard Space Flight Center and are archived at the National Snow and Ice Data Center. However, the complex surface properties of sea ice affect the microwave signature, and algorithms can yield ambiguous results; no single algorithm has been found to work uniformly well under all sea ice conditions. Thus there are ongoing efforts to further refine the algorithms and the time series. One approach is to develop data fusion methods to optimally combine sea ice fields from two or more algorithms. Another approach is to take advantage of the improved capabilities of JAXA's AMSR-E sensor on NASA's Aqua satellite to provide improved parameters and additional insights into deficiencies in the SMMR-SSM/I products. Finally, other fertile sources of sea ice information are operational sea ice charts, such as those produced at the U.S. National Ice Center (NIC). There is a 23-year (1972-1994) record of sea ice available from the NIC ice charts and an update is in progress. These charts have already been used to evaluate passive microwave retrievals and to extend the SMMR-SSM/I time series back to late 1972, when a proof-of-concept single-channel ESMR radiometer began operation.

Meier, W. N.; Fetterer, F.; Stroeve, J.; Cavalieri, D.; Parkinson, C.; Comiso, J.; Weaver, R.

2005-12-01

171

The Sea Ice Board Game  

NSDL National Science Digital Library

The National Science Foundation-funded Arctic Climate Modeling Program (ACMP) provides "curriculum resource-based professional development" materials that combine current science information with practical classroom instruction embedded with "best practice" techniques for teaching science to diverse students. The Sea Ice Board Game, described here, is one of 183 ACMP hands-on lessons designed to help students around the nation understand weather and climate. In addition, the game illuminates 14 of the most common types of sea ice and introduces the four stages of the sea ice cycle (formation, growth, deformation, and disintegration).

Bertram, Kathryn B.

2008-10-01

172

Tracer studies of pathways and rates of meltwater transport through Arctic summer sea ice  

Microsoft Academic Search

(1) At the Surface Heat Budget of the Arctic Ocean (SHEBA) program's field site in the northern Chukchi Sea, snow and ice meltwater flow was found to have a strong impact on the heat and mass balance of sea ice during the summer of 1998. Pathways and rates of meltwater transport were derived from tracer studies (H2 18 O, 7Be,

H. Eicken; H. R. Krouse; D. Kadko; D. K. Perovich

2000-01-01

173

Tracer studies of pathways and rates of meltwater transport through Arctic summer sea ice  

Microsoft Academic Search

At the Surface Heat Budget of the Arctic Ocean (SHEBA) program's field site in the northern Chukchi Sea, snow and ice meltwater flow was found to have a strong impact on the heat and mass balance of sea ice during the summer of 1998. Pathways and rates of meltwater transport were derived from tracer studies (H218O, 7Be, and release of

H. Eicken; H. R. Krouse; D. Kadko; D. K. Perovich

2002-01-01

174

External Resource: March of the Polar Bears: Global Change, Sea Ice, and Wildlife Migration  

NSDL National Science Digital Library

Learners/students will use NASA satellite data to study changes in temperature and snow-ice coverage in the South Beaufort Sea, Alaska, correlate with USGS ground tracking of polar bears, and relate this to global change, sea ice changes, and polar bear m

1900-01-01

175

March of the Polar Bears: Global Change, Sea Ice, and Wildlife Migration  

NSDL National Science Digital Library

In this activity students use NASA satellite data to study changes in temperature and snow-ice coverage in the South Beaufort Sea, Alaska. They will then correlate the data with USGS ground tracking of polar bears and relate their findings to global change, sea ice changes, and polar bear migration and survival.

Bhat, Venugopal; Plans, Nasa -.

176

March of the Polar Bears: Global Change, Sea Ice, and Wildlife Migration  

NSDL National Science Digital Library

Students will use NASA satellite data to study temperature and snow-ice coverage in the South Beaufort Sea, Alaska. The data can be used to correlate with USGS ground tracking of polar bears, and to relate this to global change, sea ice changes, and polar bear migration. The data can be used to draw conclusions surrounding any migration patterns in the region.

177

Polar bear and walrus response to the rapid decline in Arctic sea ice  

USGS Publications Warehouse

The Arctic is warming faster than other regions of the world due to positive climate feedbacks associated with loss of snow and ice. One highly visible consequence has been a rapid decline in Arctic sea ice over the past 3 decades - a decline projected to continue and result in ice-free summers likely as soon as 2030. The polar bear (Ursus maritimus) and the Pacific walrus (Odobenus rosmarus divergens) are dependent on sea ice over the continental shelves of the Arctic Ocean's marginal seas. The continental shelves are shallow regions with high biological productivity, supporting abundant marine life within the water column and on the sea floor. Polar bears use sea ice as a platform for hunting ice seals; walruses use sea ice as a resting platform between dives to forage for clams and other bottom-dwelling invertebrates. How have sea ice changes affected polar bears and walruses? How will anticipated changes affect them in the future?

Oakley, K.; Whalen, M.; Douglas, D.; Udevitz, M.; Atwood, T.; Jay, C.

2012-01-01

178

Antarctic Sea ice--a habitat for extremophiles.  

PubMed

The pack ice of Earth's polar oceans appears to be frozen white desert, devoid of life. However, beneath the snow lies a unique habitat for a group of bacteria and microscopic plants and animals that are encased in an ice matrix at low temperatures and light levels, with the only liquid being pockets of concentrated brines. Survival in these conditions requires a complex suite of physiological and metabolic adaptations, but sea-ice organisms thrive in the ice, and their prolific growth ensures they play a fundamental role in polar ecosystems. Apart from their ecological importance, the bacterial and algae species found in sea ice have become the focus for novel biotechnology, as well as being considered proxies for possible life forms on ice-covered extraterrestrial bodies. PMID:11809961

Thomas, D N; Dieckmann, G S

2002-01-25

179

Incorporation of sulfur dioxide into snow and depositing ice  

SciTech Connect

Depth profiles of S(IV) and S(VI) in snow exposed to 20-140 ppbv SO/sub 2/ for 6 to 12 hours were determined in 48 laboratory experiments. Surface deposition velocity (V/sub d/) averaged 0.06 cm s/sup -1/. Well-metamorphosed snow, longer run times, higher SO/sub 2/ concentrations and colder snow were associated with lower values of V/sub d/, and vice versa. Melting followed by draining increased v/sub d/ greatly (0.14 cm s/sup -1/). Any effect of ozone on SO/sub 2/ v/sub d/ was undetectable. Most sulfur in the snow was a S(VI), even without added ozone, indicating the presence of other oxidants, especially in new snow. The deposition of SO/sub 2/ into a snowpack is modeled as an aqueous system, where the liquid water is considered to be present on snow grain surfaces. Gas transport into the snow, air-water partitioning,and aqueous-phase reactions are explicitly considered. Experiments were also conducted on the incorporation of SO/sub 2/ into ice depositing from the vapor at -7 and -15/sup 0/C. Remarkably, SO/sub 2/ is captured in deposited ice at concentrations comparable to Henry's Law equilibrium with water at 0/sup 0/C. Ozone and HCHO appear to inhibit, not enhance, SO/sub 2/ capture. An aqueous-film model accounting for the capture of SO/sub 2/ by depositing ice was developed.

Valdez, M.P.

1987-01-01

180

Synoptic Observation of Sea Ice.  

National Technical Information Service (NTIS)

In order to keep navigation safe and to prevent marine accidents, prompt reports of sea ice, which contain maps of ice made from the observation data by ships, airplanes, satellites, etc. are published. In this experiment, whether MOS-1 (Marine Observatio...

T. Hattori H. Ura S. Sato

1990-01-01

181

The NRL 2011 Airborne Sea-Ice Thickness Campaign  

NASA Astrophysics Data System (ADS)

In March of 2011, the US Naval Research Laboratory (NRL) performed a study focused on the estimation of sea-ice thickness from airborne radar, laser and photogrammetric sensors. The study was funded by ONR to take advantage of the Navy's ICEX2011 ice-camp /submarine exercise, and to serve as a lead-in year for NRL's five year basic research program on the measurement and modeling of sea-ice scheduled to take place from 2012-2017. Researchers from the Army Cold Regions Research and Engineering Laboratory (CRREL) and NRL worked with the Navy Arctic Submarine Lab (ASL) to emplace a 9 km-long ground-truth line near the ice-camp (see Richter-Menge et al., this session) along which ice and snow thickness were directly measured. Additionally, US Navy submarines collected ice draft measurements under the groundtruth line. Repeat passes directly over the ground-truth line were flown and a grid surrounding the line was also flown to collect altimeter, LiDAR and Photogrammetry data. Five CRYOSAT-2 satellite tracks were underflown, as well, coincident with satellite passage. Estimates of sea ice thickness are calculated assuming local hydrostatic balance, and require the densities of water, ice and snow, snow depth, and freeboard (defined as the elevation of sea ice, plus accumulated snow, above local sea level). Snow thickness is estimated from the difference between LiDAR and radar altimeter profiles, the latter of which is assumed to penetrate any snow cover. The concepts we used to estimate ice thickness are similar to those employed in NASA ICEBRIDGE sea-ice thickness estimation. Airborne sensors used for our experiment were a Reigl Q-560 scanning topographic LiDAR, a pulse-limited (2 nS), 10 GHz radar altimeter and an Applanix DSS-439 digital photogrammetric camera (for lead identification). Flights were conducted on a Twin Otter aircraft from Pt. Barrow, AK, and averaged ~ 5 hours in duration. It is challenging to directly compare results from the swath LiDAR with the pulse-limited radar altimeter that has a footprint that varies from a few meters to a few tens of meters depending on altitude and roughness of the reflective surface. Intercalibration of the two instruments was accomplished at leads in the ice and by multiple over-flights of four radar corner-cubes set ~ 2 m above the snow along the ground-truth line. Direct comparison of successive flights of the ground-truth line to flights done in a grid pattern over and adjacent to the line was complicated by the ~ 20-30 m drift of the ice-floe between successive flight-lines. This rapid ice movement required the laser and radar data be translated into an ice-fixed, rather than a geographic reference frame. This was facilitated by geodetic GPS receiver measurements at the ice-camp and Pt. Barrow. The NRL data set, in combination with the ground-truth line and submarine upward-looking sonar data, will aid in understanding the error budgets of our systems, the ICEBRIDGE airborne measurements (also flown over the ground-truth line), and the CRYOSAT-2 data over a wide range of ice types.

Brozena, J. M.; Gardner, J. M.; Liang, R.; Ball, D.; Richter-Menge, J.

2011-12-01

182

Impact of subgrid-scale ice thickness distribution on heat flux on and through sea ice  

NASA Astrophysics Data System (ADS)

We evaluate the impact of subgrid-scale ice thickness distribution on the heat flux on and through sea ice in a numerical model. An ice-ocean coupled model with a subgrid-scale ice thickness distribution scheme, COCO4.5, is used. The number of the thickness categories is 15. The model is forced by an atmospheric climatology based on the CORE (Common Ocean Reference Experiment) normal year forcing to simulate the present state of the sea ice and ocean. The modeled climatology reproduces the ice cover reasonably well with a realistic ice thickness distribution. The heat flux on and through the sea ice is established using the grid-representative sea-ice and snow-on-ice thickness calculated by some different methods from the results of the identical simulation. When the grid-representative thickness is calculated as a weighted arithmetic mean of the subgrid-scale ice thickness distribution, the conductive heat flux through the ice and snow is underestimated compared with that actually driving the model. The bias is larger in the Arctic basin (approximately 50% underestimation) compared with that in the Southern Ocean (approximately 20%). This underestimation becomes smaller in magnitude when a weighted harmonic mean is employed as the grid-representative thickness. The ratio of the weighted harmonic mean thickness to the weighted arithmetic mean thickness, cm, is smaller in the Arctic basin compared with that in the Southern Ocean. The smaller cm in the Arctic basin corresponds to the larger heat flux bias there. The flux underestimation also becomes smaller when the conductive heat flux is calculated using the weighted arithmetic mean thickness multiplied by cm. The heat flux is also established with using the subgrid-scale ice thickness distribution rearranged to smaller number of the categories than the original. The result shows that the flux bias decreases with an increase in the number of categories. We also perform a sensitivity experiment in which the model is forced by the biased heat flux identified using the arithmetic mean of the ice thickness. A significant decrease in ice volume is found, notably in the Arctic Ocean. These results suggest that sea-ice models without an ice thickness distribution scheme underestimate the conductive heat flux through ice, and thereby the resultant sea-ice thickness, because the ice thickness from these models typically corresponds to the weighted arithmetic mean thickness.

Komuro, Yoshiki; Suzuki, Tatsuo

2013-04-01

183

Remote sensing of sea ice: advances during the DAMOCLES project  

NASA Astrophysics Data System (ADS)

In the Arctic, global warming is particularly pronounced so that we need to monitor its development continuously. On the other hand, the vast and hostile conditions make in situ observation difficult, so that available satellite observations should be exploited in the best possible way to extract geophysical information. Here, we give a résumé of the sea ice remote sensing efforts of the EU project DAMOCLES (Developing Arctic Modeling and Observing Capabilities for Long-term Environmental Studies). The monthly variation of the microwave emissivity of first-year and multiyear sea ice has been derived for the frequencies of the microwave imagers like AMSR-E and sounding frequencies of AMSU, and has been used to develop an optimal estimation method to retrieve sea ice and atmospheric parameters simultaneously. A sea ice microwave emissivity model has been used together with a thermodynamic model to establish relations between the emisivities at 6 GHz and 50 GHz. At the latter frequency, the emissivity is needed for assimilation into atmospheric circulation models, but more difficult to observe directly. A method to determine the effective size of the snow grains from observations in the visible range (MODIS) is developed and applied. The bidirectional reflectivity distribution function (BRDF) of snow, which is an essential input parameter to the retrieval, has been measured in situ on Svalbard during the DAMOCLES campaign, and a BRDF model assuming aspherical particles is developed. Sea ice drift and deformation is derived from satellite observations with the scatterometer ASCAT (62.5 km grid spacing), with visible AVHRR observations (20 km), with the synthetic aperture radar sensor ASAR (10 km), and a multi-sensor product (62.5 km) with improved angular resolution (Continuous Maximum Cross Correlation, CMCC method) is presented. CMCC is also used to derive the sea ice deformation, important for formation of sea ice leads (diverging deformation) and pressure ridges (converging). The indirect determination of sea ice thickness from altimeter freeboard data requires knowledge of the ice density and snow load on sea ice. The relation between freeboard and ice thickness is investigated based on the airborne Sever expeditions conducted between 1928 and 1993.

Heygster, G.; Alexandrov, V.; Dybkjær, G.; Girard-Ardhuin, F.; von Hoyningen-Huene, W.; Katsev, I. L.; Kokhanovsky, A.; Lavergne, T.; Malinka, A. V.; Melsheimer, C.; Toudal Pedersen, L.; Prikhach, A. S.; Saldo, R.; Tonboe, R.; Wiebe, H.; Zege, E. P.

2012-01-01

184

Polar Sea Ice Processes  

NSDL National Science Digital Library

The goal of this NASA Earth Science Enterprise-funded project is to increase the use of satellite data in high school and college science classrooms by developing classroom materials linked to guided inquiry computer exercises. This Polar Sea Ice Processes module is one of four Studying Earth's Environment from Space (SEES) modules. Each module consists of three sections: Class Resources, Computer Lab Resources and a Glossary and Acronym List. Class Resources is an electronic lecture viewable by a Web browser. Computer Lab Resources contains an instructor's guide, data and software. The instructor's guide contains exercises for using the data and software. The public domain software, a version of NIH-Image for the Macintosh that was modified by NASA Goddard Space Flight Center especially for SEES, is for data display, analysis and tutorial of satellite data. The software will also work on Windows machines with a Mac emulator. Image2000, a cross-platform Java version of the software, is expected to be available by the end of the year 2000. Each module section can stand-alone (e.g. you don't have to use the Class Resources in order to complete the Computer Lab Resources). Students and instructors may continue their own scientific discovery by accessing archived and current data from various NASA Earth Science data centers.

Smith, Elizabeth; Alfultus, Michael

2000-06-01

185

BERING SEA ICE DYNAMICS AND PRIMARY PRODUCTION  

Microsoft Academic Search

Sea ice communities in multi-year ice can accumulate a high algal biomass and develop a complex food web, and most higher trophic level biota of the regions north of 70 to 80° depend on this for food. Further to the south, even within the seasonal sea ice zone, processes associated with the sea ice influence the biological regimes in important

Vera ALEXANDER; Susan M. HENRICHS; H. J. NIEBAUER

1996-01-01

186

Floe formation in Arctic sea ice  

Microsoft Academic Search

The ice pack covering northern seas is composed of a mixture of thick ridged and rafted ice, undeformed ice, and open water. Ice motions determined from satellite remote sensing data show that deformation of the pack takes place along the boundary of large floes. Eulerian continuum sea ice models can simulate this behavior to a degree by capturing the localization

Mark A. Hopkins; Alan S. Thorndike

2006-01-01

187

Five New Data Sets from the National Snow and Ice Data Center  

NSDL National Science Digital Library

The site includes data from Radarsat Antarctic Mapping Project Digital Elevation Model (RAMP DEM); State of the Cryosphere; Previously Classified Imagery of the Arctic Ocean; the Historical Soviet Daily Snow Depth (HSDSD) Version Two; and a Summary of Ice-Motion Mapping Using Passive Microwave Data (.pdf). The RAMP DEM data are available in ARC/INFO, binary, and ASCII text formats. The State of the Cryosphere page features photographic and satellite images of sea ice thickness, snow cover, etc. The SHEBA (Surface Heat Balance of the Arctic) project provides the previously classified imagery of the Arctic Ocean. The new version of the HSDSD contains data spanning from 1881 to 1995, improved data quality control, an HTML interface, and a Java tool for data browsing and extraction (ASCII). Note: Data come in a variety of formats and may require special software to read.

188

Geophysical Aspects of Sea-ice Nomenclatures  

NSDL National Science Digital Library

This reference discusses the evolution of nomenclature for sea ice, originally developed for polar travel, and how it is seen from a geophysical perspective, particularly ocean-ice-atmosphere interaction or remote sensing. The site includes links to a number of student papers on sea-ice geophysics that provide background and material for discussion on the geophysical aspects of sea-ice nomenclatures. There is also a link to a pictorial glossary of sea ice terms and evolution.

2010-12-29

189

Perennial snow and ice volumes on Iliamna Volcano, Alaska, estimated with ice radar and volume modeling  

USGS Publications Warehouse

The volume of four of the largest glaciers on Iliamna Volcano was estimated using the volume model developed for evaluating glacier volumes on Redoubt Volcano. The volume model is controlled by simulated valley cross sections that are constructed by fitting third-order polynomials to the shape of the valley walls exposed above the glacier surface. Critical cross sections were field checked by sounding with ice-penetrating radar during July 1998. The estimated volumes of perennial snow and glacier ice for Tuxedni, Lateral, Red, and Umbrella Glaciers are 8.6, 0.85, 4.7, and 0.60 cubic kilometers respectively. The estimated volume of snow and ice on the upper 1,000 meters of the volcano is about 1 cubic kilometer. The volume estimates are thought to have errors of no more than ?25 percent. The volumes estimated for the four largest glaciers are more than three times the total volume of snow and ice on Mount Rainier and about 82 times the total volume of snow and ice that was on Mount St. Helens before its May 18, 1980 eruption. Volcanoes mantled by substantial snow and ice covers have produced the largest and most catastrophic lahars and floods. Therefore, it is prudent to expect that, during an eruptive episode, flooding and lahars threaten all of the drainages heading on Iliamna Volcano. On the other hand, debris avalanches can happen any time. Fortunately, their influence is generally limited to the area within a few kilometers of the summit.

Trabant, Dennis C.

1999-01-01

190

Ice dynamics in the central Greenland Sea  

Microsoft Academic Search

Until recently a tongue-shaped sea ice feature formed over the central Greenland Sea each winter. This tongue, known to generations of Norwegian sealers as “Odden,” sometimes protrudes several hundred kilometres in a northeast direction from the main East Greenland ice edge. Owing to the high wave energy in the Greenland Sea in winter, the formation of sea ice is restricted

J. P. Wilkinson

2006-01-01

191

Comparison of the MASIE with Other Sea Ice Extent Products  

NASA Astrophysics Data System (ADS)

The Multisensor Analyzed Sea Ice Extent (MASIE) has been made available to the public via the National Snow and Ice Data Center (NSIDC) since 2010, with daily data covering from January 2006 on. The MASIE is based on NOAA ice and snow cover analysis utilizing nearly 30 data sources to generate an integrated daily ice cover. While the resolution of the imagery sources ranges from 100m resolution synthetic aperture radar (SAR) to coarse 48km passive microwave (PM) data, the MASIE analysis attempts to synthesize the data sources into a 4km identification of sea-ice covered areas over the Northern Hemisphere. The MASIE differs from other ice extent data sources in three key ways. First, MASIE applies multiple data sources ranging from point sources and models to imagery acquired through a wide range in the electromagnetic spectrum. Second, MASIE has a moderate resolution so it is able to account relatively well for the ice extent in smaller bays, straits, coastlines, and along the marginal ice zone, particularly when compared to passive microwave sources. And third, MASIE relies on expert identification of the ice and manual assimilation of the multiple data sources rather than on a given automated algorithm. This study compares the MASIE with other sea extent products to understand their similarities and try to explain their differences. We analyze temporal and spatial behavior between ice extents from different products over the Northern Hemisphere, as well as within selected regions of interest. This comparison will help users in the interpretation of popular ice cover products and their applications in weather forecasting, ocean and ice modeling, safe navigation, and climate monitoring.

Helfrich, S.; Jackson, B. M.; Clemente-Colon, P.; Fetterer, F. M.; Savoie, M.

2011-12-01

192

Accessing the MODIS snow and ice products at the NSIDC DAAC  

Microsoft Academic Search

The Moderate Resolution Imaging Spectroradiometer (MODIS) is the key instrument for snow and ice studies supported by the Terra satellite, launched in December 1999. The spectral and spatial resolutions of MODIS represent a considerable improvement in capability for global cryospheric monitoring over comparable existing systems. The MODIS snow and ice products augment the existing record of satellite-derived snow cover and

Greg R. Scharfen; Dorothy K. Hall; Siri Jodha Singh Khalsa; J. D. Wolfe; M. C. Marquis; G. A. Rigg; B. McLean

2000-01-01

193

Does sea ice influence Greenland ice sheet surface-melt?  

Microsoft Academic Search

Recent decreases in Arctic sea ice and increases in Greenland ice sheet surface-melt may have global impacts, but the interactions between these two processes are unknown. Using microwave satellite data, we explore the spatial and temporal covariance of sea ice extent and ice sheet surface-melt around Greenland from 1979 to 2007. Significant covariance is discovered in several loci in the

Asa K Rennermalm; Laurence C Smith; Julienne C Stroeve; Vena W Chu

2009-01-01

194

Estimation of Antarctic sea ice properties using surface and space borne data  

NASA Astrophysics Data System (ADS)

Sea ice is a fundamental component of the Earth's systems that cannot be ignored in the large scale environmental predictions of future climate conditions. Sea ice is a complex material and has major influences on global climate with its large maximum extent and seasonal change. In this research, remote sensing validation based on comparisons with surface based data has been done for quantitative monitoring of the ice properties. Various satellite products consisting of passive microwave, active microwave, and high resolution visible imagery were used and compared with in-situ measurements collected during scientific Antarctic cruises, conducted during International Polar Year (IPY) 2007--2008. This data used to provide a quantifiable method for observing sea ice, from all regions of the Antarctic sea ice zone to develop relationships that test existing remote sensing algorithms, evaluate alternative algorithms and provide error estimates on sea ice thickness derived from existing algorithms. Chapter 2 presents the comparison of ice extent/ice edge data from the NIC and the AMSR-E (Advanced Microwave Scanning Radiometer-Earth Observing System) passive microwave products using the Antarctic Sea Ice Process and Climate (ASPeCt) ship observations from the Oden expedition in December 2006 as ground truth to verify the two products during Antarctic summer. Ice edge location comparison has also been made between the two data sets, ship ice observations and NIC daily ice edge products. NIC analyses rely more heavily on high resolution satellite imagery such as active radar and visible imagery when visibility (clouds) allows. From these comparisons, a quantitative estimate of the differences in summer ice extent between the two remotely obtained products, AMSR-E and NIC ice edge, over the larger West Antarctic sea ice zone, has been obtained. Chapter 3 evaluates the comparison of ASPeCt ship based observations (conducted during Sea Ice Mass Balance in the Antarctic (SIMBA) 2007 Antarctic cruise) with coincident satellite active and passive microwave data. We combined visual ship-based observations of sea-ice and snow properties during SIMBA with coincident active and passive microwave satellite data with the aims to (a) derive typical radar backscatter ranges for observed sea-ice types and ice type mixtures, (b) improve our knowledge about the radar backscatter of different ice types in the Bellingshausen Sea at early-middle spring, (c) interpret AMSR-E snow depth over these ice types, and (d) identify the potential of the investigated active microwave signatures for a synergy with AMSR-E data to eventually improve the snow depth retrieval. Chapter 4 presents the validation of remote sensing measurements of ice extent and concentration with ASPeCt ship-based ice observations, conducted during the SIMBA and the Sea Ice Physics and Ecosystem eXperiment (SIPEX) International Polar Year (IPY) cruises (Sept--Oct 2007). First, the total sea ice cover around the entire continent was determined for 2007--2008 from Advanced Microwave Scanning Radiometer-Earth Observing System (AMSR-E) passive microwave and National Ice Center (NIC) charts. Second, Antarctic Sea Ice Processes and Climate (ASPeCt) ship observations from the SIMBA and SIPEX expeditions in the austral end of winter--beginning of spring 2007 are used as ground truth to verify the AMSR-E sea ice concentration product provided by both the Enhanced NASA Team Algorithm (NT2) and Bootstrap Basic Algorithm (BBA). Chapter 5 presents supplemental analysis related to the baseline thickness of Antarctic sea ice on a circumpolar basis from field measurements. In this part, our objectives were (1) Develop statistical relationships between surface elevation (snow freeboard), ice elevation (ice freeboard) and mean sea ice thickness using previous and newly obtained Antarctic sea ice profiles and examine these relationships for any consistent regional trends, (2) Derive sea ice thickness from profile elevations, using buoyancy equation, to determine error estimates compared to measured thic

Ozsoy Cicek, Burcu

195

Significant Reduction in Arctic Perennial Sea Ice  

Microsoft Academic Search

Increasing temperature in summer can further decrease Arctic sea ice extent and ice thickness by stronger melting. Here, we examine a different mechanism, ice export by strong or persistent wind forcing, which can cause an anomalous decrease in perennial ice extent. An excessive perennial ice export may result in an effective thinning of the ice cover consisting less of thicker

S. V. Nghiem; Y. Chao; G. Neumann; P. Li; D. K. Perovich; P. Clemente-Colon

2006-01-01

196

Snow  

NSDL National Science Digital Library

Snow can be one of the most destructive forces in nature but also one of the most fun to learn about. An article from Associated Press writer Lourdes Navarro, featured in the Minneapolis Star Tribune, describes the avalanche in the Hindu Kush Mountains in Afghanistan. Avalanche.org's Web site offers visitors up-to-date avalanche information for the western US and one area in the east, as well as accident statistics and additional links. The NOVA site Avalanche has a Snow Sense link that gives practical advice on maximizing your safety in avalanche terrain and even rescue techniques. For those interested in data related to snow, ice, glaciers, and more, the National Snow and Ice Data Center (NSIDC) compiles and distributes such records to the public in this extensive site. The Alaska Climate Research Center, which is funded by the State of Alaska, contains a weather web cam, a link to Alaskan climatology, and even long term climatological records. The next site, from DiscoverySchool.com, is a lesson plan geared for students in the 6-8 grade called Avalanche. The activity involves learning the necessary conditions that create an avalanche, such as lack of friction. More lesson plans from snowschool.com include snow melting and snow density lesson plans, geared for students between the grades of 2-6. The final site Snow Crystals, created by California Institute of Technology Physics Professor Kenneth G. Libbrecht, is a terrific site dedicated to snow crystals and snowflakes, showing "how these remarkably complex and beautiful structures appear, quite literally, out of thin air." The site is definitely worth a look for anyone interested in snow and snowflakes.

Brieske, Joel A.

2002-01-01

197

Radar Images of the Earth: Snow, Ice, and Glaciers  

NSDL National Science Digital Library

This site features links to fourteen NASA radar images of the world's snow, ice, and glaciers, including brief descriptions of the respective processes and settings involved. The images were created with the Spaceborne Imaging Radar-C and X-Band Synthetic Aperture Radar (SIR-C/X-SAR) as part of NASA's Mission to Planet Earth. The radar illuminates Earth with microwaves allowing detailed observations at any time, regardless of weather or sunlight conditions.

198

Ice Tank Experiments Highlight Changes in Sea Ice Types  

NASA Astrophysics Data System (ADS)

With the current and likely continuing reduction of summer sea ice extent in the Arctic Ocean, the predominant mechanism of sea ice formation in the Arctic is likely to change in the future. Although substantial new ice formation occurred under preexisting ice in the past, the fraction of sea ice formation in open water likely will increase significantly. In open water, sea ice formation starts with the development of small ice crystals, called frazil ice, which are suspended in the water column [World Meteorological Organization, 1985]. Under quiescent conditions, these crystals accumulate at the surface to form an unbroken ice sheet known in its early stage as nilas. Under turbulent conditions, caused by wind and waves, frazil ice continues to grow and forms into a thick, soupy mixture called grease ice. Eventually the frazil ice will coalesce into small, rounded pieces known as pancake ice, which finally consolidate into an ice sheet with the return of calm conditions. This frazil/pancake/ice sheet cycle is currently frequently observed in the Antarctic [Lange et al., 1989]. The cycle normally occurs in regions that have a significant stretch of open water, because this allows for the formation of larger waves and hence increased turbulence. Given the increase of such open water in the Arctic Ocean caused by retreating summer sea ice, the frazil/pancake/ice sheet cycle may also become the dominant ice formation process during freezeup in the Arctic.

Wilkinson, Jeremy P.; DeCarolis, Giacomo; Ehlert, Iris; Notz, Dirk; Evers, Karl-Ulrich; Jochmann, Peter; Gerland, Sebastian; Nicolaus, Marcel; Hughes, Nick; Kern, Stefan; de la Rosa, Sara; Smedsrud, Lars; Sakai, Shigeki; Shen, Hayley; Wadhams, Peter

2009-03-01

199

Community-based sea ice thickness observatories in the Arctic  

NASA Astrophysics Data System (ADS)

The thickness of sea ice is a fundamental diagnostic variable for assessing the state of the ice cover. At the scale of the Arctic Basin, the ice thickness distribution determines the volume of the ice pack and its susceptibility to a warming climate as well as affecting the exchange of heat between the ocean and atmosphere. At the local scale, it dictates where and when it is safe to travel on the ice or through the water. Measuring the thickness of sea ice is challenging both technically and logistically and any measurement program strikes a balance between cost and coverage accordingly. Accurately measuring the thickness of large areas of sea ice generally requires airplanes, ice breakers or submarines and electromagnetic or acoustic devices. In this study, we use one of the least technical methods combined with support from remote communities to establish a set of sea ice observation stations in Barrow (Alaska), Clyde River (Baffin Island, Nunavut) and Qaanaaq (northwest Greenland). We employ hunters from these communities, who are experts in traveling and working on the ice, and train them to deploy ice observation stations and take measurements. Each station consists of snow stakes and hot-wire ice thickness gauges and the local observers take measurements on a weekly basis. Involvement of the community is fundamental to the success of these measurement programs and ensures the data collected are relevant to the local use of the sea ice. Community elders and hunters chose the station locations according to where they hunt and travel and to be representative of local variability. As partners in research, the scientists and local hunters are able to share and synthesize their knowledge; the scientific community gains a better understanding of the extraordinary depth of traditional knowledge and the communities improve their understanding of global changes and ability to adapt. Here we present data from observation stations near Clyde River and Qaanaaq. At Clyde River, in comparison with measurements taken by the Canadian Ice Service during the period 1959-93, the sea ice in 2006-07 was below but within one standard deviation of the mean thickness. Combined with local air temperature measurements from nearby meteorological stations, we calculated approximate surface energy balances that indicate the ocean heat flux is significantly greater at Qaanaaq than Clyde River, despite otherwise being similar environments for sea ice. Findings such as this are important in understanding the specific ways in which sea ice is changing in different locales and are vital for community planning for the near future.

Gearheard, S.; Mahoney, A. R.; Huntington, H.; Oshima, T.; Qillaq, T.; Barry, R. G.

2007-12-01

200

Epidemic of fractures during period of snow and ice.  

PubMed

During four days of snow and ice in which more than 70% of pavements in the Cardiff area were covered by slippery hard snow and ice the number of patients who attended the accident and emergency department at this hospital with fractured bones increased 2.85 times as compared with those who attended during four control days with comparable hours of sunshine and four control calendar days a year later. Fractures of the arm were increased 3.7 times and of the forearm and wrist 7.3 times. For a town population of one million people who may walk on untreated slippery and icy pavements this means that on average in a single day 74 more people than usual sustain a fracture unnecessarily. This traumatic epidemic has all the characteristics of a "major accident" and should be treated as such, since mobilisation of additional facilities, staff, and reserves might be necessary. Snow and ice injuries, however, differ from injuries sustained in a major accident in one important point: they may be predicted and prevented. The mass media should warn the population about the oncoming hazards and give practical advice on safer walking on slippery surfaces. The most important aspect of prevention, however, is instant cleaning of pavements around buildings, shops, and houses, especially in town centres and other areas busy with pedestrians. PMID:6781587

Rális, Z A

1981-02-21

201

Measured Black Carbon Deposition on the Sierra Nevada Snow Pack and Implication for Snow Pack Retreat  

Microsoft Academic Search

Modeling studies show that the darkening of snow and ice by black carbon deposition is a major factor for the rapid disappearance of arctic sea ice, mountain glaciers and snow packs. This study provides one of the first direct measurements for the efficient removal of black carbon from the atmosphere by snow and its subsequent deposition to the snow packs

O. L. Hadley; C. E. Corrigan; T. W. Kirchstetter; S. S. Cliff; V. Ramanathan

2010-01-01

202

Measured black carbon deposition on the Sierra Nevada snow pack and implication for snow pack retreat  

Microsoft Academic Search

Modeling studies show that the darkening of snow and ice by black carbon (BC) deposition is a major factor for the rapid disappearance of arctic sea ice, mountain glaciers and snow packs. This study provides one of the first direct measurements for the efficient removal of black carbon from the atmosphere by snow and its subsequent deposition on the snow

O. L. Hadley; C. E. Corrigan; T. W. Kirchstetter; S. S. Cliff; V. Ramanathan

2010-01-01

203

Interactions of wind-transported snow with a rift in the Ross Ice Shelf, Antarctica  

Microsoft Academic Search

Rifts in ice shelves accumulate a mélange of snow and firn from above and marine ice from below, material that has been postulated to negatively influence iceberg calving. From measurements and modeling we show that a 100 m wide rift near the front of the Ross Ice Shelf captures all wind-transported snow traveling in saltation and a substantial fraction of

Katherine C. Leonard; L.-Bruno Tremblay; Douglas R. MacAyeal; Stanley S. Jacobs

2008-01-01

204

Help, I don’t know which sea ice algorithm to use?!: Developing an authoritative sea ice climate data record  

NASA Astrophysics Data System (ADS)

The declining Arctic sea ice is one of the most dramatic indicators of climate change and is being recognized as a key factor in future climate impacts on biology, human activities, and global climate change. As such, the audience for sea ice data is expanding well beyond the sea ice community. The most comprehensive sea ice data are from a series of satellite-borne passive microwave sensors. They provide a near-complete daily timeseries of sea ice concentration and extent since late-1978. However, there are many complicating issues in using such data, particularly for novice users. First, there is not one single, definitive algorithm, but several. And even for a given algorithm, different processing and quality-control methods may be used, depending on the source. Second, for all algorithms, there are uncertainties in any retrieved value. In general, these limitations are well-known: low spatial-resolution results in an imprecise ice edge determination and lack of small-scale detail (e.g., lead detection) within the ice pack; surface melt depresses concentration values during summer; thin ice is underestimated in some algorithms; some algorithms are sensitive to physical surface temperature; other surface features (e.g., snow) can influence retrieved data. While general error estimates are available for concentration values, currently the products do not carry grid-cell level or even granule level data quality information. Finally, metadata and data provenance information are limited, both of which are essential for future reprocessing. Here we describe the progress to date toward development of sea ice concentration products and outline the future steps needed to complete a sea ice climate data record.

Meier, W.; Stroeve, J.; Duerr, R. E.; Fetterer, F. M.

2009-12-01

205

Recent State of Arctic Sea Ice  

Microsoft Academic Search

We present the recent state of Arctic sea ice including observations from 2008 in a context of a multi-decadal perspective. A new record has been set in the reduction of Arctic perennial sea ice extent this winter. As of 1 March 2008, the extent of perennial sea ice was reduced by one million km2 compared to that at the same

S. V. Nghiem; I. G. Rigor; P. Clemente-Colón; D. K. Perovich; J. A. Richter-Menge; Y. Chao; G. Neumann; M. Ortmeyer

2008-01-01

206

Arctic Sea Ice Extent Plummets in 2007  

Microsoft Academic Search

Arctic sea ice declined rapidly to unprecedented low extents in the summer of 2007, raising concern that the Arctic may be on the verge of a fundamental transition toward a seasonal ice cover. Arctic sea ice extent typically attains a seasonal maximum in March and minimum in September. Over the course of the modern satellite record (1979 to present), sea

Julienne Stroeve; Mark Serreze; Sheldon Drobot; Shari Gearheard; Marika Holland; James Maslanik; Walt Meier; Ted Scambos

2008-01-01

207

Investigations of newly formed sea ice in the Cape Bathurst polynya: 2. Microwave emission  

NASA Astrophysics Data System (ADS)

This study examines the role of newly formed sea ice geophysical state on microwave emission. Coincident with sea ice geophysical sampling, ship-based passive microwave emission data (dual-polarized at 19, 37 and 85 GHz) were collected in the Cape Bathurst Polynya during 18 October and 13 November 2003. Using polarization ratios (PRs), we found that bare thin ice was separable from snow-covered ice. Thin snow (equal to 0.02-0.13 m) thickness is significantly correlated with the spectral gradient ratios GRV(85,19) (R2 = 0.55, P-value <0.05) and GRV(85,37) (R2 = 0.66, P-value < 0.05), but not with GRV(37,19) (R2 = 0.19, P-value > 0.2). The relationship between atmospherically corrected R37 and bare ice thickness showed an exponential relationship very comparable to that reported by [2004], which is ascribed to the reduction of bare ice surface salinity based on both observational and modeling studies. However, the relationship quickly becomes invalid for even thin snow covered ice, due to significant impact of thin wet (liquid water fraction ˜0.02-0.04) snow on microwave emission. Our results suggest that the sea ice algorithms NASA Team and NASA Team 2 could underestimate total ice concentration over thin bare ice by 35% on average, while both algorithms underestimate the total ice concentration by 20% over snow-covered ice. Using PR(85) sea ice could be delineated from open water using a properly adjusted threshold value accounting for cloud or fog effects, possibly with the exception of dark nilas and/or bare consolidated pancakes.

Hwang, Byong Jun; Ehn, Jens K.; Barber, David G.; Galley, Ryan; Grenfell, Thomas C.

2007-05-01

208

Loss of sea ice in the Arctic.  

PubMed

The Arctic sea ice cover is in decline. The areal extent of the ice cover has been decreasing for the past few decades at an accelerating rate. Evidence also points to a decrease in sea ice thickness and a reduction in the amount of thicker perennial sea ice. A general global warming trend has made the ice cover more vulnerable to natural fluctuations in atmospheric and oceanic forcing. The observed reduction in Arctic sea ice is a consequence of both thermodynamic and dynamic processes, including such factors as preconditioning of the ice cover, overall warming trends, changes in cloud coverage, shifts in atmospheric circulation patterns, increased export of older ice out of the Arctic, advection of ocean heat from the Pacific and North Atlantic, enhanced solar heating of the ocean, and the ice-albedo feedback. The diminishing Arctic sea ice is creating social, political, economic, and ecological challenges. PMID:21141043

Perovich, Donald K; Richter-Menge, Jacqueline A

2009-01-01

209

Theoretical estimates of light reflection and transmission by spatially complex and temporally varying sea ice covers  

SciTech Connect

The reflection, absorption, and transmission of light at visible and near-infrared wavelengths by snow and ice covers is important for a number of geophysical problems. The focus of this paper is on the reflection and transmission of light by spatially inhomogeneous and temporally varying sea ice covers. This is investigated using a two-stream, multilayer radiative transfer model in the wavelength region from 400 to 1,000 nm. The model is computationally simple and utilizes the available experimental data on the optical properties of sea ice. The ice cover is characterized as a layered medium composed of selections from nine distinct snow and ice types. Three case studies are presented illustrating values of spectral albedo, transmittance, and transmitted photosynthetically active radiation (PAR) for (1) a spatially inhomogeneous ice cover, (2) a uniform ice cover as it undergoes a melt cycle, and (3) a temporally changing spatially variable ice cover. Results indicate that small-scale horizontal variations in snow depth and ice thickness can cause light transmission to change over 3 orders of magnitude. Dramatic changes in light reflection and transmission are predicted in the early part of the melt season as the ice cover evolves from an opaque, snow-covered medium to translucent bare or ponded ice.

Perovich, D.K. (Army Cold Regions Research and Engineering Lab., Hanover, NH (United States))

1990-06-15

210

Sensitivity of passive microwave snow depth retrievals to weather effects and snow evolution  

Microsoft Academic Search

Snow fall and snow accumulation are key climate parameters due to the snow's high albedo, its thermal insulation, and its importance to the global water cycle. Satellite passive microwave radiometers currently provide the only means for the retrieval of snow depth and\\/or snow water equivalent (SWE) over land as well as over sea ice from space. All algorithms make use

Thorsten Markus; Dylan C. Powell; James R. Wang

2006-01-01

211

Antarctic sea ice variability using NASA team algorithm data  

NASA Astrophysics Data System (ADS)

Sea ice is an important, highly variable feature of the Earth's surface, both reflecting and influencing climatic conditions. Sea ice covers approximately 7 percent of the world oceans, significantly reduces the amount of solar radiation absorbed at the Earth's surface, greatly restricts the transfer of heat from the ocean to the atmosphere in winter, and influences global atmospheric and oceanic circulation. In this paper, monthly through interannual variability of the sea ice between 0 and 120W is analysed for the 22-year period 1979 through 2000. The monthly Polar Gridded Sea Ice Concentrations data set derived from the Nimbus-7 Scanning Multichannel Microwave Radiometer (SMMR) and the Defense Meteorological Satellite Program's (DMSP) DMSP-F8, F11 and F13, Special Sensor Microwave/Imager (SSM/I) generated by NASA team algorithm were used. This data were acquired from the National Snow and Ice Data Center (NSIDC) and are gridded on the SSM/I polar stereographic grid (25 x 25 km) provided in two-byte integer format. Principal Components Analysis in T-Mode was performed on pre-processed sea ice data (anomalies from which have been removed continent and perennial open water), in order to investigate which are the main space patterns, when do they present and how they are coupled to different atmospheric variables. This analysis provide 12 patterns (6 in direct mode and 6 in inverse mode) that represent the most important spatial features that dominate sea ice variability in the Weddell, Amudsen and Bellinghausen Seas. These 12 patterns, or their combinations, describe completely the behavior of the 264 month means sea ice concentration anomalies of the record we used of the selected Antarctic region.

Barreira, S.; Compagnucci, R.

212

EOS Science Poster Series: ICE- Global Ice and Snow  

NSDL National Science Digital Library

This poster, one in a four-part series, highlights recent images from select NASA Earth Science spacecraft and showcases related research results. The back gives a brief overview of the science and missions behind NASA's study of ICE.

2007-08-01

213

Theoretical estimates of light reflection and transmission by spatially complex and temporally varying sea ice covers  

Microsoft Academic Search

The reflection, absorption, and transmission of light at visible and near-infrared wavelengths by snow and ice covers is important for a number of geophysical problems. The focus of this paper is on the reflection and transmission of light by spatially inhomogeneous and temporally varying sea ice covers. This is investigated using a two-stream, multilayer radiative transfer model in the wavelength

Donald K. Perovich

1990-01-01

214

Sea ice and iceberg dynamic interaction  

NASA Astrophysics Data System (ADS)

A model of iceberg motion has been implemented in the Los Alamos sea ice model (CICE). Individual bergs are tracked under the influence of winds, currents, sea surface tilt, Coriolis, and sea ice forcing. In turn, sea ice is affected by the presence of icebergs, primarily as obstacles that cause the sea ice to ridge on the upstream side or create open water on the downstream side of the bergs. Open water formed near icebergs due to sea ice ridging and blocking of sea ice advection increases level and ridged ice downstream of the bergs through increased frazil ice formation. Resulting anomalies in sea ice area and thickness (compared with a simulation without icebergs) are transported with the sea ice flow, expanding over time. Although local changes in the sea ice distribution may be important for smaller-scale studies, these anomalies are small compared with the total volume of sea ice and their effect on climate-scale variables appears to be insignificant.

Hunke, Elizabeth C.; Comeau, Darin

2011-05-01

215

The Sea Ice Board Game  

ERIC Educational Resources Information Center

The National Science Foundation-funded Arctic Climate Modeling Program (ACMP) provides "curriculum resource-based professional development" materials that combine current science information with practical classroom instruction embedded with "best practice" techniques for teaching science to diverse students. The Sea Ice Board Game, described…

Bertram, Kathryn Berry

2008-01-01

216

An investigation of the small ice cap instability in the Southern Hemisphere with a coupled atmosphere-sea ice-ocean-terrestrial ice model  

Microsoft Academic Search

A simple climate model has been developed to investigate the existence of the small ice cap instability in the Southern Hemisphere.\\u000a The model consists of four coupled components: an atmospheric energy balance model, a thermodynamic snow-sea ice model, an\\u000a oceanic mixed layer model and a terrestrial ice model. Results from a series of experiments involving different degrees of\\u000a coupling in

M. A. Morales Maqueda; A. J. Willmott; J. L. Bamber; M. S. Darby

1998-01-01

217

The East Antarctic sea ice zone: Ice characteristics and drift  

Microsoft Academic Search

Results from studies of the surface energy balance and the ocean structure in the presence of fast ice near Mawson on the Antarctic coast are used to illustrate the important ways in which sea ice interacts with the ocean and atmosphere. Away from the coast, ship and drifting buoy observations are used to characterize the E Antarctic sea ice zone

Ian Allison

1989-01-01

218

Modelling past sea ice changes  

NASA Astrophysics Data System (ADS)

A dominant characteristic of the available simulations of past sea ice changes is the strong link between the model results for modern and past climates. Nearly all the models have similar extent for pre-industrial conditions and for the mid-Holocene. The models with the largest extent at Last Glacial Maximum (LGM) are also characterized by large pre-industrial values. As a consequence, the causes of model biases and of the spread of model responses identified for present-day conditions appear relevant when simulating the past sea ice changes. Nevertheless, the models that display a relatively realistic sea-ice cover for present-day conditions often display contrasted response for some past periods. The difference appears particularly large for the LGM in the Southern Ocean and for the summer ice extent in the Arctic for the early Holocene (and to a smaller extent for the mid-Holocene). Those periods are thus key ones to evaluate model behaviour and model physics in conditions different from those of the last decades. Paleoclimate modelling is also an invaluable tool to test hypotheses that could explain the signal recorded by proxies and thus to improve our understanding of climate dynamics. Model analyses have been focused on specific processes, such as the role of atmospheric and ocean heat transport in sea ice changes or the relative magnitude of the model response to different forcings. The studies devoted to the early Holocene provide an interesting example in this framework as both radiative forcing and freshwater discharge from the ice sheets were very different compared to now. This is thus a good target to identify the dominant processes ruling the system behaviour and to evaluate the way models represent them.

Goosse, H.; Roche, D. M.; Mairesse, A.; Berger, M.

2013-11-01

219

Northern Alaskan land surface response to reduced Arctic sea ice extent  

NASA Astrophysics Data System (ADS)

With Arctic sea ice extent at near-record lows, an improved understanding of the relationship between sea ice and the land surface is warranted. We examine the land surface response to changing sea ice by first conducting a simulation using the Community Atmospheric Model version 3.1 with end of the twenty-first century sea ice extent. This future atmospheric response is then used to force the Weather and Research Forecasting Model version 3.1 to examine the terrestrial land surface response at high resolution over the North Slope of Alaska. Similar control simulations with twentieth century sea ice projections are also performed, and in both simulations only sea ice extent is altered. In the future sea ice extent experiment, atmospheric temperature increases significantly due to increases in latent and sensible heat flux, particularly in the winter season. Precipitation and snow pack increase significantly, and the increased snow pack contributes to warmer soil temperatures for most seasons by insulating the land surface. In the summer, however, soil temperatures are reduced due to increased albedo. Despite warmer near-surface atmospheric temperatures, it is found that spring melt is delayed throughout much of the North Slope due to the increased snow pack, and the growing season length is shortened.

Higgins, Matthew E.; Cassano, John J.

2012-05-01

220

Operational Products Archived at the National Snow and Ice Data Center  

NASA Astrophysics Data System (ADS)

Sea ice charts for shipping interests from the Navy/NOAA/Coast Guard National Ice Center are often laboriously produced by manually interpreting and synthesizing data from many sources, both satellite and in situ. They are generally more accurate than similar products from single sources. Upward looking sonar data from U.S. Navy submarines operating in the Arctic provides information on ice thickness. Similarly extensive data were available from no other source prior to the recently established reliability of ice thickness estimates from polar orbiting instruments like the Geoscience Laser Altimeter System (GLAS). Snow Data Assimilation System (SNODAS) products from the NOAA NWS National Operational Hydrologic Remote Sensing Center give researchers the best possible estimates of snow cover and associated variables to support hydrologic modeling and analysis for the continental U.S. These and other snow and ice data products are produced by the U.S. Navy, the NOAA National Weather Service, and other agency entities to serve users who have an operational need: to get a ship safely to its destination, for example, or to predict stream flow. NOAA supports work at NSIDC with data from operational sources that can be used for climate research and change detection. We make these products available to a new user base, by archiving operational data, making data available online, providing documentation, and fielding questions from researchers about the data. These data demand special consideration: often they are advantageous because they are available on a schedule in near real time, but their use in climate studies is problematic since many are produced with regard for ‘best now’ and without regard for time series consistency. As arctic climate changes rapidly, operational and semi-operational products have an expanding science support role to play.

Fetterer, F. M.; Ballagh, L.; Gergely, K.; Kovarik, J.; Wallace, A.; Windnagel, A.

2009-12-01

221

State of the Cryosphere: An overview of the status of snow and ice as indicators of climate change  

NSDL National Science Digital Library

Climatologists know that the measure of the world's ice, in all its many dimensions and forms, is a measure of current conditions as well as of those frozen over time. These pages present a summary of cryospheric and related indicators of global climate trends including: temperature change over the past century, trends in hemispheric snow extent, trends in hemispheric sea ice extent, glacier melt, and changes in sea level. Also included is a snapshot of current permafrost conditions. Links to current news releases and journal articles, a glossary, and reference list are also provided.

222

Creating Arctic Sea Ice Protected Areas?  

NASA Astrophysics Data System (ADS)

As Arctic sea ice retreats and the Northwest Passage and Northern Sea Route open, the Arctic will experience more extensive human activity than it has ever encountered before. New development will put pressure on a system already struggling to adapt to a changing environment. In this analysis, locations are identified within the Arctic that could be protected from resource extraction, transportation and other development in order to create refuges and protect remnants of sea ice habitat, as the Arctic transitions to ice-free summer conditions. Arctic sea ice forms largely along the Siberian and Alaskan coasts and is advected across the North Pole towards Fram Strait, the Canadian Archipelago and the Barents Sea. In addition to the future loss of ice itself, contaminants entrained in sea ice in one part of the ocean can affect other regions as the ice drifts. Using observations and models of sea ice origins, trajectories and ages, we track sea ice from its origins towards marginal ice zones, mapping pathways and termination locations. Critical sea ice source areas and collection regions are identified with the goal of aiding in the protection of the remaining Arctic sea ice habitat for as long as possible.

Pfirman, S.; Hoff, K.; Temblay, B.; Fowler, C.

2008-12-01

223

Arctic sea ice as a granular plastic  

Microsoft Academic Search

An important consideration in understanding sea ice mechanics is the integration of observed sea ice behavior on a floe neighborhood scale (1-10 km) into ice dynamics on a regional scale O(50km). We investigate sea ice kinematics from October 1993 through April 1994 using relative motions from 13 drifting buoys with Global Positioning System navigation in a 20-km array centered on

James E. Overland; S. Lyn McNutt; Sigrid Salo; Joanne Groves; Shusun Li

1998-01-01

224

Automated mapping of Earth's annual minimum exposed snow and ice with MODIS  

NASA Astrophysics Data System (ADS)

Global snow and ice have been diminishing during the Anthropocene but we still lack a complete mapping of annual minimum exposed snow and ice with a consistent, repeatable algorithm. The Global Land Ice Measurements from Space (GLIMS) project has compiled digital glacier outlines and related metadata for the majority of the world's glaciers but inconsistency among product algorithms and time periods represented precludes the production of a consistently derived global data set. Here we present the MODIS Persistent Ice (MODICE) algorithm that leverages the time series of fractional snow and ice cover from the MODIS Snow Covered Area and Grain size (MODSCAG) algorithm. The end product of MODICE is a consistently derived map of annual minimum exposed snow and ice. Comparisons of MODICE with GLIMS glacier outlines derived from SPOT, ASTER, and Landsat Thematic Mapper show strong agreement with the higher resolution outlines subject to uncertainties with spatial resolution, deep mountain shadows, and GLIMS interpretation errors.

Painter, Thomas H.; Brodzik, Mary J.; Racoviteanu, Adina; Armstrong, Richard

2012-10-01

225

Mapping radiation transfer through sea ice using a remotely operated vehicle (ROV)  

NASA Astrophysics Data System (ADS)

Light (solar short-wave radiation) transmission into and through sea ice is of high importance for various processes in Polar Regions. The amount of energy transferred through the ice determines formation and melt of sea ice and finally contributes to warming of the uppermost ocean. At the same time the amount and distribution of light, as the primary source of energy, is of critical importance for sea-ice associated organisms and bio-geochemical processes. However, our current understanding of these processes and their interdisciplinary interactions is still sparse. The main reason is that the under-ice environment is difficult to access and measurements require large logistical and instrumental efforts. Particularly, it was not possible to map light conditions under sea ice over larger areas. Here we present a detailed methodical description of operating spectral radiometers on a remotely operated vehicle (ROV) in the Central Arctic under sea ice. This new measurement concept resulted in a~most comprehensive data set of spectral radiance and irradiance under and above sea ice, complemented through various additional in-situ measurements of sea-ice, snow, and surface properties. Finally, such data sets allow quantifying the spatial variability of light under sea ice, especially highlighting differences between ponded and white ice as well as different ice types.

Nicolaus, M.; Katlein, C.

2012-09-01

226

Metamorphism of snow and ice sintering observed by time lapse cine-photom icrography  

Microsoft Academic Search

Metamorphism of snow crystals and grains was observed under an alternating temperature gradient by using time lapse cine-photomicrography. Original forms of the snow crystals were destroyed by vapour transfer due to the alternating temperature gradient, but in high density snows, ice bondings between grains were accelerated by the vapour transfer. The following conspicuous phenomena were observed during the sintering processes:

Daisuke Kuroiwa

227

Sea Ice Characteristics from the West Antarctic ODEN Cruise Compared to Satellite Analyses  

NASA Astrophysics Data System (ADS)

In this study, AMSR-E's (The Advanced Microwave Scanning Radiometer - Earth Observing System) geophysical product for ice concentration and ice edge location was compared to ice observations made aboard ship in the Antarctic pack ice during ODEN expedition (Swedish icebreaker) sponsored by United States National Science Foundation (NSF) as of the first collaborative activities of the International Polar Year (IPY) 2007 - 2008. Ice observations consist of ASPECT (Antarctic Sea Ice Process and Climate) protocol that provides a standardized and quantifiable method for observing sea ice that is now accepted as the international standard. Estimates of ice concentration, ice type with its thickness, floe size, and snow type with it is thicknesses are conducted along with meteorological observations. Observations involved making half an hour observations from the ship's bridge within a radius of approximately 1 km of the ship. Our observations made along 67° 53 S latitude and 102° 97 W longitude and along 73° 52 S latitude and 178° 54 E longitude in December 2006. Different ice types and temperature conditions were encountered during the observations. Sea ice concentration varied between 10% and 90%. During the expedition the minimum and maximum ice thickness varied between 10 cm and 3m. The results from the observations analyzed using a GIS platform and provided detailed data for comparison with satellite products. AMSR-E microwave remote sensing data contains brightness temperatures (TBs) at 6.9 GHz, 10.7 GHz, 18.7 GHz, 23.8 GHz, 36.5 GHz, and 89.0 GHz. and uses various algorithms to estimate the snow depth, sea ice concentration, and sea ice temperature. The study region for the comparison includes the West Antarctic sea ice zone which is particularly interesting since the sea ice of the area is highly sensitive to global climate change.

Ozsoy-Cicek, B.; Xie, H.; Ackley, S.

2007-12-01

228

Sea Ice Lead Distribution from High Resolution Airborne Imagery  

NASA Astrophysics Data System (ADS)

NASA's Operation IceBridge Mission provides continuity of the sea ice thickness time series, between the now complete ICESat mission and the planned ICESat-2 mission, by utilizing airborne laser and radar altimetry measurements to improve estimates of snow and ice thickness. An essential step in deriving sea ice freeboard (and hence thickness) from altimetry measurements of sea ice elevation is the determination of local sea level. Discrimination of leads along-track is therefore critical for deriving the elevation of open water within leads and defining sea surface height. Here we provide an assessment of the lead mapping capabilities of the Digital Mapping System (DMS), a nadir-looking, high-resolution digital camera mounted on IceBridge aircraft. For a nominal aircraft operating-altitude around 500 m, the resolution of the DMS imagery is approximately 0.1 m. A novel lead detection algorithm was applied to DMS digital photography for unambiguous detection of leads within the sea ice pack and classification of lead type. The data were used to generate statistics on lead distribution and spacing, lead width, and areal coverage. We compare results from the Arctic multi-year ice pack with data gathered over the mainly seasonal ice pack of the Southern Ocean. We find that areal coverage of Antarctic leads is about 5 % and three times higher than in the Arctic (1.5 %). Both dynamic and thermodynamic modeling of the sea ice pack relies on knowledge of lead distribution to effectively model ice motion and interactions between the ocean and atmosphere. We describe the potential contribution our results can make towards the improvement of coupled ice-ocean numerical models. We discuss the application of lead discrimination for freeboard retrieval from satellite altimetry (e.g. CryoSat-2 and ICESat-2) and the use of lead distribution statistics for assessing sampling geometries employed by current airborne and future satellite laser altimeters to map the complex sea ice environment, including the multi-beam photon-counting approach proposed for ICESat-2.

Farrell, S. L.; Kurtz, N. T.; Onana, V.; Harbeck, J. P.; Duncan, K.

2011-12-01

229

Brine-ecosystem interactions in sea ice  

NASA Astrophysics Data System (ADS)

Microalgae grow in brine inclusions in sea ice. Previous sea ice-ecosystem models neglect brine-microalgae interactions, prescribing the location of the microbial communities. In this study, a sea ice model with explicit brine dynamics coupled to a simple nutrient-phytoplankton (N-P) module (diatoms and dissolved silicates) is introduced. The model predicts bottom and surface microalgal populations. In fall, brine convection in cooling ice supplies nutrients, which favors microalgal growth. In early summer, the vertical brine density profile in warmer ice stabilizes, nutrient supply shuts off, which prevents further biomass building. Sensitivity tests in an idealized Antarctic pack ice configuration suggest that mode of microalgal transport within brine (passive or active) induces important population differences. This study is a step toward a more realistic sea ice-ecosystem model, which is required to understand the role of sea ice and associated ecosystems in global biogeochemical cycles.

Vancoppenolle, M.; Bitz, C. M.; Fichefet, T.; Goosse, H.; Lancelot, C.; Tison, J.

2010-12-01

230

Sea ice detection with space-based LIDAR  

NASA Astrophysics Data System (ADS)

Monitoring long-term climate change in the Polar Regions relies on accurate, detailed and repeatable measurements of geophysical processes and states. These regions are among the Earth's most vulnerable ecosystems, and measurements there have shown rapid changes in the seasonality and the extent of snow and sea ice coverage. The authors have recently developed a promising new technique that uses lidar surface measurements from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) mission to infer ocean surface ice-water phase. CALIPSO's 532 nm depolarization ratio measurements of the ocean surface are uniquely capable of providing information about the ever-changing sea surface state within the Polar Regions. With the finer resolution of the CALIPSO footprint (90 m diameter, spaced 335 m apart) and its ability to acquire measurements during both daytime and nighttime orbit segments and in the presence of clouds, the CALIPSO sea ice product provides fine-scale information on mixed phase scenes and can be used to assess/validate the estimates of sea-ice concentration currently provided by passive sensors. This paper describes the fundamentals of the CALIPSO sea-ice detection and classification technique. We present retrieval results from a six-year study, which are compared to existing data sets obtained by satellite-based passive remote sensors.

Rodier, S.; Hu, Y.; Vaughan, M.

2013-09-01

231

Representativity analysis and statistical modeling of snow and ice thickness data sets from the southern polar Pacific Ocean  

NASA Astrophysics Data System (ADS)

Data sets of sea ice and snow thickness, acquired as drilling profiles and shipboard observations during three Antarctic expeditions in the Ross, Amundsen and Bellingshausen Seas are studied with respect to their statistical robustness towards "weed-out", "sectional", and "random" subsampling. For individual profiles of the drilling data the resulting subsampling errors, associated with the means and standard deviations of ice and snow thicknesses, and freeboard were generally smallest for the weed-out method, where the spacing between drilling points was increased, while the profile length was unchanged. On the "cruise" level, floe drilling data and shipboard observations (consisting of individual sets of 25 single observations) were subsampled by picking every nth floe (or observation set). Up to n = 3, subsampling errors were negligible against the inherent errors of the full data sets. The effects of subsampling depend on the measured probability density functions (PDFs) of the full data sets whose statistical properties are studied in the section 2. It was found that lognormal or gamma distributions are better statistical representations for both drilling and shipboard data than normal distributions. A simple statistical ice thickness model is presented, which explains how different ice growth and development processes influence the shape of the ice thickness PDF. Appropriate choices of the parameters, consistent with cruise dates and observational evidence of ice deformation, give good representations of the measured ice thickness PDFs for the three cruises.

Adolphs, Ute

1999-06-01

232

Multi-year Arctic Sea Ice  

NASA Video Gallery

The most visible change in the Arctic region in recent years has been the rapid decline of the perennial ice cover. The perennial ice is the portion of the sea ice floating on the surface of the ocean that survives the summer. This ice that spans multiple years represents the thickest component of the sea ice cover. This visualization shows the perennial Arctic sea ice from 1980 to 2012. The grey disk at the North Pole indicates the region where no satellite data is collected. A graph overlay shows the area's size measured in million square kilometers for each year. The '1980','2008', and '2012' data points are highlighted on the graph.

Holly Zell

2012-02-29

233

Inverse electromagnetic scattering models for sea ice  

Microsoft Academic Search

Inverse scattering algorithms for reconstructing the physical properties of sea ice from scattered electromagnetic field data are presented. The development of these algorithms has advanced the theory of remote sensing, particularly in the microwave region, and has the potential to form the basis for a new generation of techniques for recovering sea ice properties, such as ice thickness, a parameter

K. M. Goldenl; D. Borup; M. Cheney; E. Cherkaeva; M. S. Dawson; Kung-Hau Ding; A. K. Fung; D. Isaacson; S. A. Johnson; Arthur K. Jordan; Jin Au Kong; Ronald Kwok; Son V. Nghiem; Robert G. Onstott; J. Sylvester; D. P. Winebrenner; I. H. H. Zabel

1998-01-01

234

Spatial scaling of Arctic sea ice deformation  

Microsoft Academic Search

Arctic sea ice deformation arises from spatial gradients in the ice velocity field. This deformation occurs across a wide range of spatial scales, from meters to thousands of kilometers. We analyze 7 years of sea ice deformation data from the RADARSAT Geophysical Processor System (RGPS) covering the western Arctic Ocean. We find that the mean deformation rate is related to

H. L. Stern; R. W. Lindsay

2009-01-01

235

Antarctic Sea Ice in the IPY  

Microsoft Academic Search

Antarctic Sea Ice covers an area of 20 million km2 at maximum extent and therefore represents an areal coverage larger than either the Arctic ice cover or the Antarctic continent. Studies of Antarctic sea ice in the modern era were only initiated well after the IGY, with the advent of passive microwave satellite coverage in 1973, followed by the use

S. F. Ackley; D. K. Perovich; C. A. Geiger

2003-01-01

236

Thickness distribution, texture and stratigraphy, and a simple probabilistic model for dynamical thickening of sea ice in the southern Sea of Okhotsk  

NASA Astrophysics Data System (ADS)

Sea ice thickness data and sea ice samples were analyzed to examine the characteristics of the ice thickness distribution and ice texture, and to understand ice growth processes in the southern Sea of Okhotsk. Ice thickness data and samples were obtained aboard the icebreaker Soya in early February, the ice growth season. Ice thickness data, which were obtained with a video monitoring system installed on the side deck of the ship each winter from 1991 to 2000 except 1995, show that the average thickness ranges from 19 ± 7 to 55 ± 23 cm and that it matches the characteristics of a Poisson distribution. Ice structure analysis reveals that granular texture occupies about three quarters of the total ice thickness and that the ice exhibits a layered structure with unit thickness averaging 5 to 10 cm. Stratigraphy and stable isotopic composition of the ice indicate that snow ice accounts for 10% and frazil ice accounts for 64% of the total ice thickness. This suggests that dynamic ice thickening processes such as frazil ice growth and piling up are more significant than congelation growth. On the basis of these characteristics, which resemble more those of Antarctic than Arctic sea ice, we propose a conceptual model for the ice thickening process in this region. It is shown that this model can explain the shape of the ice thickness distribution well, and is analogous with the concept of the "pancake cycle" and multiple rafting of Antarctic sea ice growth and thickening.

Toyota, Takenobu; Kawamura, Toshiyuki; Ohshima, Kay I.; Shimoda, Haruhito; Wakatsuchi, Masaaki

2004-06-01

237

Studies of ice-snow melt debris flows in the western Tian Shan Mountains, China  

Microsoft Academic Search

The ice-snow melt debris flow in the west part of the Tian Shan Mountains is an important natural hazard. The sediment for the debris flows is derived from the thick Quaternary deposits which occur in the Tain Shan Mountains. Another cause of the debris flows is the ice- snow meltwater and the abundant precipitation in the western part of the

WEI WENSHOU; GAO CUNHAI

1992-01-01

238

Snow and ice perturbation during historical volcanic eruptions and the formation of lahars and floods  

Microsoft Academic Search

Historical eruptions have produced lahars and floods by perturbing snow and ice at more than 40 volcanoes worldwide. Most of these volcanoes are located at latitudes higher than 35°; those at lower latitudes reach altitudes generally above 4000 m. Volcanic events can perturb mantles of snow and ice in at least five ways: (1) scouring and melting by flowing pyroclastic

Jon J. Major; Christopher G Newhall

1989-01-01

239

Simulated climate change effects on ice and snow covers on lakes in a temperate region  

Microsoft Academic Search

A simulation model for ice and snow covers is applied to dimictic and polymictic lakes of the temperate zone to project the effects of possible climate warming on ice and snow covers. The winter cover model is associated with a deterministic, one-dimensional water temperature model. The lake parameters required as model input are surface area (AS), maximum depth (Hmax), summer

Heinz G. Stefan; Xing Fang

1997-01-01

240

Interactions between lava and snow/ice during the 2010 Fimmvörðuháls eruption, south-central Iceland  

NASA Astrophysics Data System (ADS)

The 20 March-12 April basaltic effusive eruption at Fimmvörðuháls, southern Iceland, was an important opportunity to directly observe interactions between lava and snow/ice. The eruption site has local perennial snowfields and snow covered ice, and at the time of eruption it was covered with an additional ˜1-3 m of seasonal snow. Syn-eruption observations of interactions between lava and snow/ice are grouped into four categories: (1) lava advancing directly on top of snow, (2) lava advancing on top of tephra-covered snow, (3) snow/ice melting at lava flow margins, and (4) lava flowing beneath snow. Based on syn- and post-eruption observations in 2010/11, we conclude that the features seen in the lava flow field show only limited and localized evidence for the influence of snow/ice presence during the eruption. Estimated melting rates from radiant and conductive heating at the flow fronts are too slow (on the order of 5 m/hr) to allow for complete melting of snow/ice ahead of the advancing lava flows, at least during periods of observed rapid lava advance rates (15-55 m/hr). Thus we conclude that during those periods, which largely established the aerial extent of the lava flow field, lava advanced on top of snow; that this likely was the predominant mode of lava emplacement for much of the eruption is supported by many syn-eruption field observations. Examination of the lava flows subsequent to the eruption has so far only found subtle evidence for interactions between lava and snow/ice; for example, locally lava flows have fractured and are collapsing, or have developed marginal rubble aprons from melting of snow banks that were partly covered by lava flow margins.

Edwards, B.; Magnússon, E.; Thordarson, T.; Gu?mundsson, M. T.; Höskuldsson, A.; Oddsson, B.; Haklar, J.

2012-04-01

241

Snow chemistry measurements on James Ross Island (Antarctic Peninsula) showing sea-salt aerosol modifications  

NASA Astrophysics Data System (ADS)

The fractionation of atmospheric sea-salt has been investigated by glaciochemical analysis of the sea-salt deposited on the snow covering the small ice cap of James Ross Island, Antarctic Peninsula, at an elevation of 1640 m. The data show that, generally, but not always, the sea-salt deposited at this location most likely originates directly from seawater, as is the case at lower latitudes. It is found that the original chemical composition of the sea-salt aerosol is significantly modified, in particular by the reaction of sea-salt particles in the atmosphere with acid species. A ternary diagram (sodium, chloride, sulfate) is used to enlighten the involved modification processes. The study points out the frequent formation of HCl in the regional atmosphere.

Aristarain, Alberto J.; Delmas, Robert J.

242

How Does Melting Ice Affect Sea Level?  

NSDL National Science Digital Library

In this activity, students investigate how sea levels might rise when ice sheets and ice caps melt by constructing a pair of models and seeing the effects of ice melt in two different situations. Students should use their markers to predict the increase of water in each box before the ice melts.

Dahlman, Luann; Andrill

243

An Over-Sea-Ice Seismic Reflection Survey: Offshore New Harbor, Antarctica  

Microsoft Academic Search

During the austral spring of 2008, approximately 48 km of multi-channel seismic reflection data were collected on a sea-ice platform east of New Harbor, Antarctica. The Offshore New Harbor (ONH) survey is third in a series of three successful over-sea-ice seismic reflection surveys recently conducted in McMurdo Sound, Antarctica. For rapid data acquisition, the ONH project employed a 60-channel snow

D. A. Sunwall; M. A. Speece; S. F. Pekar; G. S. Wilson; K. J. Tinto

2009-01-01

244

A review of snow and ice albedo and the development of a new physically based broadband albedo parameterization  

Microsoft Academic Search

We present a computationally simple, theoretically based parameterization for the broadband albedo of snow and ice that can accurately reproduce the theoretical broadband albedo under a wide range of snow, ice, and atmospheric conditions. Depending on its application, this parameterization requires between one and five input parameters. These parameters are specific surface area of snow\\/ice, concentration of light-absorbing carbon, solar

Alex S. Gardner; Martin J. Sharp

2010-01-01

245

Simultaneous Retrieval of Aerosol and Snow/ice Properties Using Multi- and Hyperspectral Data  

NASA Astrophysics Data System (ADS)

Retrieval of surface properties of highly reflecting targets such as snow and ice is a challenging problem due to the influence of aerosols, which vary considerably in space and time. Also, accounting for the bidirectional properties of a bright surface such as snow is very important for reliable retrievals. Here we explore the opportunities and possibilities offered by multi- and hyperspectral data, such as those provided by the MODIS, GLI, VIIRS, the Advanced Land Imager (ALI), and Hyperion sensors, to retrieve reliable aerosol and surface properties. Over snow and ice surfaces these properties include aerosol optical depth, single scattering albedo, the mean size of snow grains and ice 'particles' (inclusions), and the spectral and broadband snow/ice albedo. We emphasize the use of linearized forward radiative transfer models for the coupled snow/ice system, because it allows us to compute weighting functions (Jacobians) required in state-of-the-art nonlinear, iterative inversion schemes. By using several wavelengths with different penetration depths we may retrieve depth information about snow properties, and thereby accurate spectral albedo of snow. In particular the following question will be addressed: To what extent can multi- and hyperspectral data help improve our knowledge of snow and ice parameters that are important for understanding global climate change?

Li, W.; Eide, H.; Stamnes, K.; Spurr, R.; Aoki, T.; Hori, M.

2005-12-01

246

Photochemical Degradation of Persistent Organic Pollutants in Snow and Ice  

NASA Astrophysics Data System (ADS)

The frozen surfaces of polar regions are highly reactive. The Arctic snowpack has been shown to play an important role in processing atmospheric species such as mercury, molecular halogens, organics and ozone. Several recent studies have demonstrated photochemical transformations of anthropogenic organic contaminants in ice. Unfortunately, information on transformations of organic contaminants in snow and ice is currently limited. It is important to gain a better understanding of the photochemical processes that occur, as well as identify the products of degradation, in order to assess the possible ecosystem-wide implications of pollutant degradation (i.e. generation of products more toxic than the original pollutant). With a better grasp of the photochemical processes of anthropogenic organic pollutants, an improved understanding of their effects on the environment can be obtained. In our research, we investigated both direct and indirect photodegradation of several persistent organic pollutants of concern to the Arctic environment, including aldrin, dieldrin, PCBs and hexachlorobenzene. Reactivity in both ice and liquid samples was assessed. We found selective degradation in the samples, with some of the pollutants exhibiting greater degradation in liquid samples, while others showed greater degradation in the ice samples. The methods and results of these experiments will be discussed.

Greis, V. M.; Mahanna, K. M.; Grannas, A. M.

2005-12-01

247

A case study of a modelled episode of low Arctic sea ice  

NASA Astrophysics Data System (ADS)

Simulations of the Arctic sea ice cover over the last 32 years generated by the HadGEM1 coupled climate model are able to capture the observed long term decline in mean September ice extent. HadGEM1 is also capable of producing an episode of low September ice extent of similar magnitude to the anomalously low extent observed in 2007. Using a heat budget analysis, together with diagnostics partitioning the changes in ice and snow mass into thermodynamic and dynamic components, we analyse the factors driving the long term decline in the ice mass and extent as well as those causing the modelled low ice event. The long term decline in the mass of ice and snow in HadGEM1 is largely due to extra melting during the summer, partly at the top surface of the ice, and partly via extra heating from the ocean as it warms due to the ice retreat. The episode of low summer ice extent is largely driven by the synoptic conditions over the summer moving the ice across and out of the Arctic basin, and also due to pre-conditioning of the snow and ice which is thinner than usual in the Eastern Arctic at the start of the melt season. This case study demonstrates that although HadGEM1 does not capture the persistent dipole pressure anomaly observed during the summer of 2007, it represents broadly similar mechanisms of generating a low ice extent.

Keen, Ann B.; Hewitt, Helene T.; Ridley, Jeff K.

2013-09-01

248

Arctic Sea Ice Melt in the Summer of 2008  

NASA Astrophysics Data System (ADS)

There has been a marked decline in the summer extent of Arctic sea ice over the past few decades. To enhance our understanding of this decline, autonomous ice mass balance buoys were deployed in the sea ice cover as part of the North Pole Environmental Observatory, the Beaufort Gyre Environmental Observatory, and the Developing Arctic Modeling and Observing Capabilities for Long-term Environmental Studies Program. These buoys monitor changes in snow deposition and ablation, ice growth, and ice surface and bottom melt. Results during the summer of 2008 showed considerable spatial variability in the amount of surface and bottom melt. In the vicinity of the North Pole the amounts of surface and bottom ablation were comparable to values observed in recent years. Modest (less than 0.5 m total) amounts of melting were observed north of Greenland. Melting in the Southern Beaufort Sea was quite large, with 0.85 m of surface melt and more than 1 m of bottom melt. Reduced ice concentration in this region led to a buildup of solar heat in the upper ocean. This absorbedsolar heat was released gradually and also through abrupt episodes when peak bottom melt rates exceeded several cm per day.

Perovich, D. K.; Richter-Menge, J. A.; Elder, B. C.; Polashenski, C. M.

2008-12-01

249

Rapid reduction of Arctic perennial sea ice  

Microsoft Academic Search

The extent of Arctic perennial sea ice, the year-round ice cover, was significantly reduced between March 2005 and March 2007 by 1.08 × 106 km2, a 23% loss from 4.69 × 106 km2 to 3.61 × 106 km2, as observed by the QuikSCAT\\/SeaWinds satellite scatterometer (QSCAT). Moreover, the buoy-based Drift-Age Model (DM) provided long-term trends in Arctic sea-ice age since

S. V. Nghiem; I. G. Rigor; D. K. Perovich; P. Clemente-Colón; J. W. Weatherly; G. Neumann

2007-01-01

250

Sea ice's effect on oceanic deepwater  

NSDL National Science Digital Library

A coupled sea ice-ocean model of the Southern Ocean was used to analyze the effects of sea ice on dense, cold deepwater formation. It was found that this model can more accurately project the amount of freshwater entering the oceans from sea ice, which may help researchers better estimate ocean circulation patterns and produce more accurate climate estimates based on the ocean's salinity.

Komuro, Yoshiki; Hasumi, Hiroyasu; Agu

251

The Last Arctic Sea Ice Refuge  

NASA Astrophysics Data System (ADS)

Summer sea ice may persist along the northern flank of Canada and Greenland for decades longer than the rest of the Arctic, raising the possibility of a naturally formed refugium for ice-associated species. Observations and models indicate that some ice in this region forms locally, while some is transported to the area by winds and ocean currents. Depending on future changes in melt patterns and sea ice transport rates, both the central Arctic and Siberian shelf seas may be sources of ice to the region. An international system of monitoring and management of the sea ice refuge, along with the ice source regions, has the potential to maintain viable habitat for ice-associated species, including polar bears, for decades into the future. Issues to consider in developing a strategy include: + the likely duration and extent of summer sea ice in this region based on observations, models and paleoenvironmental information + the extent and characteristics of the “ice shed” contributing sea ice to the refuge, including its dynamics, physical and biological characteristics as well as potential for contamination from local or long-range sources + likely assemblages of ice-associated species and their habitats + potential stressors such as transportation, tourism, resource extraction, contamination + policy, governance, and development issues including management strategies that could maintain the viability of the refuge.

Pfirman, S. L.; Tremblay, B.; Newton, R.; Fowler, C.

2010-12-01

252

A Multi-Disciplinary Sea Ice Ontology  

NASA Astrophysics Data System (ADS)

Sea ice is a central element of the Arctic system and a strong indicator of high-latitude climate change. In addition to the many scientific disciplines in which sea ice is of importance, the domains of transportation, defense, natural resources and human settlements all have interests in and contribute to the body of knowledge regarding sea ice. To help advance the interdisciplinary understanding and usability of sea ice data we have developed a preliminary sea ice ontology. This effort began with a workshop in which sea ice modelers, field researchers, remote sensing scientists and operational forecasters described the facets of sea ice from the perspective of their respective disciplines. We will describe the features of this ontology and highlight some of the challenges we encountered in building it. We will also describe our plans to incorporate indigenous sea ice knowledge, map some existing sea ice data sets using the ontology, and to link the ontology to relevant marine, polar, atmospheric, and global ontologies and semantic services.

Khalsa, S. S.; Parsons, M. A.; Duerr, R. E.; Pulsifer, P. L.; McGuinness, D. L.; Fox, P. A.; McCusker, J.

2011-12-01

253

[Reflectance of sea ice in Liaodong Bay].  

PubMed

In the present study, the relationships between sea ice albedo and the bidirectional reflectance distribution in Liaodong Bay were investigated. The results indicate that: (1) sea ice albedo alpha(lambda) is closely related to the components of sea ice, the higher the particulate concentration in sea ice surface is, the lower the sea ice albedo alpha(lambda) is. On the contrary, the higher the bubble concentration in sea ice is, the higher sea ice albedo alpha(lambda) is. (2) Sea ice albedo alpha(lambda) is similar to the bidirectional reflectance factor R(f) when the probe locates at nadir. The R(f) would increase with the increase in detector zenith theta, and the correlation between R(f) and the detector azimuth would gradually increase. When the theta is located at solar zenith 63 degrees, the R(f) would reach the maximum, and the strongest correlation is also shown between the R(f) and the detector azimuth. (3) Different types of sea ice would have the different anisotropic reflectance factors. PMID:20827996

Xu, Zhan-tang; Yang, Yue-zhong; Wang, Gui-fen; Cao, Wen-xi; Kong, Xiang-peng

2010-07-01

254

CryoVEx 2011: In-situ sea ice measurements in the high Arctic Ocean for the validation of CryoSat-2 ice thickness retrievals  

NASA Astrophysics Data System (ADS)

The European Space Agency (ESA) CryoSat-2 satellite, which was launched in April 2010, is designed to measure changes in the thickness of the polar ice caps. By means of radar altimetry, CryoSat-2 performs accurate measurements of sea ice freeboard, the height of the ice surface above the water level, which is related to ice thickness via isostasy. From this, ice thickness can be estimated when assumptions are made about the density of snow and ice as well as about the thickness of snow and radar penetration into the snow. There are thus many sources of uncertainty related to the physical properties of snow and ice which may lead to significant errors in the satellite-retrieved ice thickness. Some of these uncertainties can be addressed through in-situ measurements. These were performed during CryoVEx 2011, an international project sponsored and coordinated by ESA and other funding agencies. Three sites with different ice and snow properties were studied between the coast of Ellesmere Island, Canada, and 85.5°N. These sites were visited by Twin Otter airplane landing on unprepared landing strips. At each site, corner reflectors to be used as references for airborne radar altimeter surveys were deployed and marked with drifting GPS buoys, and extensive snow and ice measurements were performed between the corner reflectors. Very high-resolution measurements were carried out in the immediate vicinity of the corner reflectors, including snow pit studies and measurements of radar penetration using a ground-based radar. Subsequently, the sites were overflown by aircraft carrying radar altimeters and ice thickness sensors. This presentation will review the validation concept implemented in the campaign and will summarize the snow and ice properties obtained at the different sites.

Haas, C.; Willatt, R. C.; Laxon, S. W.; Giles, K. A.; Beckers, J.; Hendricks, S.; Davidson, M.

2011-12-01

255

Study of the surface albedo of the ice-covered Weddell and Bellingshausen Sea  

NASA Astrophysics Data System (ADS)

Sea ice has a major influence on the energy and radiation budget of the maritime atmospheric boundary layer, because it insulates the water surface from direct contact with the atmosphere and varies the sea surface albedo. In this study we investigate the surface albedo of the sea ice zone around the Antarctic Peninsula. For this purpose, we utilize aircraft measurements of sea surface and atmospheric parameters. The data is set based on observations conducted in the West Antarctic sea ice zone in the austral summer seasons 2007 and 2008. The sea surface albedo shows significant regional differences along with the sea ice and atmospheric conditions. We observed the smallest albedo values over newly formed ice in polynyas and nilas and the largest albedo values over snow-covered pack ice. The ice-covered sea surface is often a mixture of different sea ice types or thicknesses. For characteristic sea ice covers we determined effective albedo values. In the Bellingshausen Sea the median effective albedo of first year sea ice was 0.63, in the Weddell Sea of pack ice with leads 0.78 and of new, young ice 0.41. In many models the sea surface albedo is parameterized in a relatively simplified manner by using a constant albedo value or by using a parameterization, which assumes that the sea ice albedo depends inversely only on the surface or air temperature. Such albedo-temperature parameterizations are applied in global circulation models like the UK GCM, described by Ingram (1989), in thermodynamic sea ice models, e.g. as described by Ross and Walsh (1987), or in climate models like the ECHAM 5, described by Roeckner et al. (2003). In general our data verify an inverse relation between albedo and temperature. In order to investigate how accurately such parameterization could simulate the sea surface albedo of the West Antarctic sea ice zone, and which parameterization is most appropriate for certain sea ice areas, we forced commonly-used albedo-temperature parameterizations with temperature observations. The comparison of the simulated albedo values with observations shows that large biases occur for certain sea ice regions.

Weiss, A.; King, J.; Lachlan-Cope, T.; Ladkin, R.

2009-04-01

256

Springtime atmospheric transport controls Arctic summer sea-ice extent  

NASA Astrophysics Data System (ADS)

The sea-ice extent in the Arctic has been steadily decreasing during the satellite remote sensing era, 1979 to present, with the highest rate of retreat found in September. Contributing factors causing the ice retreat are among others: changes in surface air temperature (SAT; Lindsay and Zhang, 2005), ice circulation in response to winds/pressure patterns (Overland et al., 2008) and ocean currents (Comiso et al., 2008), as well as changes in radiative fluxes (e.g. due to changes in cloud cover; Francis and Hunter, 2006; Maksimovich and Vihma, 2012) and ocean conditions. However, large interannual variability is superimposed onto the declining trend - the ice extent by the end of the summer varies by several million square kilometer between successive years (Serreze et al., 2007). But what are the processes causing the year-to-year ice variability? A comparison of years with an anomalously large September sea-ice extent (HIYs - high ice years) with years showing an anomalously small ice extent (LIYs - low ice years) reveals that the ice variability is most pronounced in the Arctic Ocean north of Siberia (which became almost entirely ice free in September of 2007 and 2012). Significant ice-concentration anomalies of up to 30% are observed for LIYs and HIYs in this area. Focusing on this area we find that the greenhouse effect associated with clouds and water-vapor in spring is crucial for the development of the sea ice during the subsequent months. In years where the end-of-summer sea-ice extent is well below normal, a significantly enhanced transport of humid air is evident during spring into the region where the ice retreat is encountered. The anomalous convergence of humidity increases the cloudiness, resulting in an enhancement of the greenhouse effect. As a result, downward longwave radiation at the surface is larger than usual. In mid May, when the ice anomaly begins to appear and the surface albedo therefore becomes anomalously low, the net shortwave radiation anomaly becomes positive. The net shortwave radiation contributes during the rest of the melting season to an enhanced energy flux towards the surface. These findings lead to the conclusion that enhanced longwave radiation associated with positive humidity and cloud anomalies during spring plays a significant role in initiating the summer ice melt, whereas shortwave-radiation anomalies act as an amplifying feedback once the melt has started. References: Lindsay, R. and J. Zhang. The thinning of Arctic Sea Ice, 19882003: Have We Passed a Tipping Point?. J. Clim. 18, 48794894 (2005). Overland, J. E., M. Wang and S. Salo. The recent Arctic warm period. Tellus 60A, 589-597 (2008). Comiso, J. C., C. L. Parkinson, R. Gersten and L. Stock. Accelerated Decline in the Arctic sea ice cover. Geophys. Res. Lett. 35, L01703 (2008). Francis, J. A. and E. Hunter. New Insight Into the Disappearing Arctic Sea Ice. EOS T. Am. Geophys. Un. 87, 509511 (2006). Maksimovich, E. and T. Vihma. The effect of heat fluxes on interannual variability in the spring onset of snow melt in the central Arctic Ocean. J. Geophys. Res. 117, C07012 (2012). Serreze, M. C., M. M. Holland and J. Stroeve. Perspectives on the Arctic's Shrinking Sea-Ice Cover. Science 315, 1533-1536 (2007).

Kapsch, Marie; Graversen, Rune; Tjernström, Michael

2013-04-01

257

Air- ice-snow interaction in the Northern Hemisphere under different stability conditions  

NASA Astrophysics Data System (ADS)

The traditional parameterizations of the atmospheric boundary layer are based on similarity theory and the coefficients of turbulent transfer, describing the atmospheric-surface interaction and the diffusion of impurities in the operational models of air pollution, weather forecasting and climate change. Major drawbacks of these parameterizations is that they are not applicable for the extreme conditions of stratification and currents over complex surfaces (such as sea ice, marginal ice zone or stormy sea). These problem could not be overcome within the framework of classical theory, i.e, by rectifying similarity functions or through the introduction of amendments to the traditional turbulent closure schemes. Lack of knowledge on the structure of the surface air layer and the exchange of momentum, heat and moisture between the rippling water surface and the atmosphere at different atmospheric stratifications is at present the major obstacle which impede proper functioning of the operational global and regional weather prediction models and expert models of climate and climate change. This is especially important for the polar regions, where in winter time the development of strong stable boundary layer in the presence of polynyas and leads usually occur. Experimental studies of atmosphere-ice-snow interaction under different stability conditions are presented. Strong stable and unstable conditions are discussed. Parametrizations of turbulent heat and gas exchange at the atmosphere ocean interface are developed. The dependence of the exchange coefficients and aerodynamic roughness on the atmospheric stratification over the snow and ice surface is experimentally confirmed. The drag coefficient is reduced with increasing stability. The behavior of the roughness parameter is simple. This result was obtained in the Arctic from the measurements over hummocked surface. The value of the roughness in the Arctic is much less than that observed over the snow in the middle and even high latitudes of the Northern Hemisphere because the stable conditions above Arctic ice field dominate. Under such conditions the air flow over the uneven surface behaves in the way it does over the even one. This happens because depressions between ridges are filled with heavier air up to the height of irreguralities. As a result, the air moves at the level of ridges without entering depressions. Increased heat and mass transfer over polynyas and leads through self-organization of turbulent convection is found. The work was sponsored by RFBR grants and funded by the Government of the Russian Federation grants.

Repina, Irina; Chechin, Dmitry; Artamonov, Arseny

2013-04-01

258

NOx emission from surface snow and ice over Tibetan Plateau, China  

NASA Astrophysics Data System (ADS)

Photochemical reactions on the surface of snow and ice have been proved to be an important NOx source in the polar boundary layer. The exchanges of NOx between snow and air have significant impacts on the atmospheric components and photochemical processes in the overlying boundary layer, which can increase the oxidizing capacity and may impact on the environmental records that are retrieved from ice cores. The Tibetan Plateau (TP) is the main snow-covered area in the mid-latitudes of northern hemisphere. Different from the Arctic and Antarctic, TP has strong UV radiation on the surface of snow and ice due to its high altitude and the large area of snow and glaciers. With four field measurements in July 1st Glacier, Mount Everest Area, Yulong Snow Mountain, and Tianshan NO.1 Glacier, we obtained observational evidences on the release of NOx from surface snow and ice over Tibetan Plateau. The average NOx concentration during daytime was 1-5 ppbv, this is much higher than that in Arctic and Antarctic (pptv level). Besides the photochemical reaction and transfer process within snow/ice, factors such as UV radiation intensity, temperature, snow characteristics and mountain-valley winds all affect NOx release processes from those snow covered areas. The NOx fluxes during daytime in Yulong Snow Mountain and Tianshan NO.1 Glacier were about 10-45nmol m-2 h-1, this is similar as those observed in Arctic and Antarctic (15-40 nmol m-2 h-1). The contribution of NOx emission from snow/ice over Tibetan Plateau to the atmosphere oxidizing capacity needs more research.

Wang, J.; Zhu, T.; Lin, W.; Wang, F.

2010-12-01

259

Measurement and evolution of the thickness distribution and morphology of deformed features of Antarctic sea ice  

NASA Astrophysics Data System (ADS)

Antarctic sea ice thickness data obtained from drilling on sea ice floes were examined with the goal of enhancing our capability to estimate ice thickness remotely, especially from air- or space-borne altimetry and shipboard visual observations. The state of hydrostatic equilibrium of deformed ice features and the statistical relationships between ice thickness and top surface roughness were examined. Results indicate that ice thickness may be estimated fairly reliably from surface measurements of snow elevation on length scales of ?100 m. Examination of the morphology of deformed ice features show that Antarctic pressure ridges are flatter and less massive than Arctic pressure ridges and that not all surface features (ridge sails) are associated with features underwater (ridge keels). I propose that the differences in morphology are due to differences in sampling strategies, parent ice characteristics and the magnitude and duration of driving forces. As a result of these findings, the existing methodology used to estimate ice thickness from shipboard visual observations was modified to incorporate the probability that a sail is associated with a keel underwater, and the probability that keels may be found under level surfaces. Using the improved methodology, ice thickness was estimated from ship observations data obtained during two cruises in the Ross Sea, Antarctica. The dynamic and thermodynamic processes involved in the development of the ice prior to their observation were examined employing a regional sea ice-mixed layer-pycnocline model. Both our model results and previously published ice core data indicate that thermodynamic thickening is the dominant process that determines the thickness of first year ice in the central Ross Sea, although dynamic thickening also plays a significant role. Ice core data also indicate that snow ice forms a significant proportion of the total ice mass. For ice in the northeast Ross Sea in the summer, model results and evidence from ice core and oceanographic data indicate that dynamic thickening, snow ice formation and bottom melting compete to determine the ice thickness during mid and late winter.

Tin, Tina

260

Enhanced sea ice cover characterization from new passive microwave systems  

NASA Astrophysics Data System (ADS)

The most detailed and consistent information about the large scale characteristics and temporal variability of the sea ice cover has come from satellite passive microwave data. The latter are noted for comprehensive day/night almost all weather coverages of both polar regions. In 2002, two satellite passive microwave systems were launched successful thereby ushering the advent of new and improved sea ice data sets. These new almost identical systems, call the Advanced Microwave Scanning Radiometer (AMSR), provide brightness temperature data at a wider spectral range than previous systems and a spatial resolution as high as 5 km. Better temporal coverage is also attained since one has a morning equatorial crossing while the other has an afternoon crossing. Preliminary analysis of the AMSR data show some distinct advantages over previous data including more defined and accurate characterization of the ice edge, better quantification of polynyas and divergence areas, and estimates of ice temperature and snow depth. They also provide a good baseline for the assessment of the state of the global sea ice cover. The latest results from AMSR include the detection in 2002 of the least extensive perennial ice cover in the Arctic during the satellite era, supporting a recent report of a rapidly declining perennial ice cover. This result is in good agreement with co-registered and almost coincident Special Sensor Microwave Imager (SSM/I) data providing a good justification in the use of historical microwave data, that now spans more than 24 years, for evaluating the variability and trend in the sea ice cover.

Comiso, J.

2003-04-01

261

Operationally Monitoring Sea Ice at the Canadian Ice Service  

NASA Astrophysics Data System (ADS)

The Canadian Ice Service (CIS) of the Meteorological Service of Canada promotes safe and efficient maritime operations and protects Canada's environment by providing reliable and timely information about ice and iceberg conditions in Canadian waters. Daily and seasonal charts describing the extent, type and concentration of sea ice and icebergs are provided to support navigation and other activities (e.g. oil and gas) in coastal waters. The CIS relies on a suite of spaceborne visible, infrared and microwave sensors to operationally monitor ice conditions in Canadian coastal and inland waterways. These efforts are complemented by operational sea ice models that are customized and run at the CIS. The archive of these data represent a 35 year archive of ice conditions and have proven to be a valuable dataset for historical sea ice analysis. This presentation will describe the daily integration of remote sensing observations and modelled ice conditions used to produce ice and iceberg products. A review of the decadal evolution of this process will be presented, as well as a glimpse into the future of ice and iceberg monitoring. Examples of the utility of the CIS digital sea ice archive for climate studies will also be presented.

de Abreu, R.; Flett, D.; Carrieres, T.; Falkingham, J.

2004-05-01

262

Anisotropic model for granulated sea ice dynamics  

NASA Astrophysics Data System (ADS)

A continuum model describing sea ice as a layer of granulated thick ice, consisting of many rigid, brittle floes, intersected by long and narrow regions of thinner ice, known as leads, is developed. We consider the evolution of mesoscale leads, formed under extension, whose lengths span many floes, so that the surrounding ice is treated as a granular plastic. The leads are sufficiently small with respect to basin scales of sea ice deformation that they may be modelled using a continuum approach. The model includes evolution equations for the orientational distribution of leads, their thickness and width expressed through second-rank tensors and terms requiring closures. The closing assumptions are constructed for the case of negligibly small lead ice thickness and the canonical deformation types of pure and simple shear, pure divergence and pure convergence. We present a new continuum-scale sea ice rheology that depends upon the isotropic, material rheology of sea ice, the orientational distribution of lead properties and the thick ice thickness. A new model of lead and thick ice interaction is presented that successfully describes a number of effects: (i) because of its brittle nature, thick ice does not thin under extension and (ii) the consideration of the thick sea ice as a granular material determines finite lead opening under pure shear, when granular dilation is unimportant.

Wilchinsky, Alexander V.; Feltham, Daniel L.

2006-06-01

263

Spatial and temporal variability of snow accumulation rate at East Antarctic ice sheet in 1993-2010  

NASA Astrophysics Data System (ADS)

Snow stakes along the traverse routes have been observed for long term monitoring program 'the variation of ice sheet surface mass balance' from the 1960's by the Japanese Antarctic Research Expedition in Shirase glacier drainage basin, East Antarctica. During the traverse route between coastal S16 point (69 02'S, 40 03'E, 580m a.s.l.) to inland Dome Fuji (77 22'S, 39 42'E, 3,810m a.s.l.), the snow stake observations every 2 km have been carried out from 1993. Latest stake heights were measured in January 2011 and February 2011. Yearly net snow accumulations from S16 to Dome Fuji were calculated. Heavy snow events were shown in 1998, 2004, 2005, 2008-2009 and 2010. Otherwise, in 1994, 1996, 1999, 2000, 2001, 2002 and 2006, light snow events were observed. They were different in way accumulating spatial pattern depending on places. The yearly accumulation rates were compared with seasonal change of AAO-index (SAM). As a result, yearly accumulation rate and AAO-index showed the positive correlation. We would indicate the spatial distributions of air parcel origins. So we calculate air transport by using the NITRAM trajectory model (Tomikawa and Sato, 2005) and ERA-Interim meteorological data set in 1990-2009. The time duration is 5 days and we suppose the origin of air parcel is the point of trajectory at 5 days ago. The starting points are distributed on 1 deg. x 1 deg. grids over Antarctica and its altitude is 1,300m above the surface. We indicate the spatial distributions of air parcel origins to Antarctica. If there were high ratios of sea origin atmosphere in the inland, there was much snow. It is indicated that the humid air from the sea is the main origin of snowfall. But such relations were not seen on the coast. We try to understand the cause of heavy snow and light snow event.

Motoyama, H.; Suzuki, K.; Yamanouchi, T.; Kawamura, K.

2012-04-01

264

Physical control of chlorophyll a, POC, and TPN distributions in the pack ice of the Ross Sea, Antarctica  

NASA Astrophysics Data System (ADS)

The pack ice ecosystem of the Ross Sea was investigated along a 1470-km north-south transect during the spring 1998 oceanographic program Research on Ocean-Atmosphere Variability and Ecosystem Response in the Ross Sea (ROAVERRS). Snow and sea ice thickness along the transect varied latitudinally, with thinner snow and ice at the northern ice edge and thin new ice in the vicinity of the Ross Sea polynya. Relative to springtime observations in other sea ice regions, algal chlorophyll a (Chl a) concentrations were low. In contrast, particulate organic carbon (POC), total particulate nitrogen (TPN), and POC:Chl a were all high, indicating either that the ice contained substantial amounts of detritus or nonphotosynthetic organisms, or that the algae had a high POC:Chl a ratio. The abundance of Chl a, POC, and TPN in the sea ice was related to ice age and thickness, as well as to snow depth: older ice had thinner snow cover and contained higher algal biomass while new ice in the polynya had lower biomass. Older pack ice was dominated by diatoms (particularly Fragilariopsis cylindrus) and had vertical distributions of Chl a, POC, and TPN that were related to salinity, with higher biomass at the ice-water interface. Fluorescence-based measurements of photosynthetic competence (Fv/Fm) were higher at ice-water interfaces, and photosynthesis-irradiance characteristics measured for bottom ice algae were comparable to those measured in pack ice communities of other regions. Nutrient concentrations in extracted sea ice brines showed depletion of silicate and nitrate, depletion or regeneration of phosphate and nitrite, and production of ammonium when normalized to seawater salinity; however, concentrations of dissolved inorganic nitrogen, phosphorous, and silica were typically above levels likely to limit algal growth. In areas where pack ice and snow cover were thickest, light levels could be limiting to algal photosynthesis. Enrichment of ?13C-POC in the sea ice was correlated with the accumulation of POC, suggesting that carbon sources for photosynthesis might shift in response to decreasing CO2 supply. Comparisons between new ice and underlying waters showed similar algal species dominance (Phaeocystis antarctica) implying incorporation of phytoplankton, with substantially higher POC and TPN concentrations in the ice.

Arrigo, Kevin R.; Robinson, Dale H.; Dunbar, Robert B.; Leventer, Amy R.; Lizotte, Michael P.

2003-10-01

265

Direct measurements of DMS flux from Antarctic fast sea ice to the atmosphere by a chamber technique  

NASA Astrophysics Data System (ADS)

We present the first direct measurements of dimethylsulfide (DMS) emissions from Antarctic sea ice to the atmosphere during the seasonal warming period obtained using a chamber technique. Estimated DMS fluxes measured over the snow and superimposed ice (ice formed by the freezing of snow meltwater) were from 0.1 to 0.3 ?mol m-2 d-1. The DMS fluxes measured directly over the sea-ice slush layer after removal of the snow and superimposed ice, ranged from 0.1 to 5.3 ?mol m-2 d-1, were large compared to those measured over the snow and superimposed ice. The DMS concentrations in slush water ranged from 1.0 to 103.7 nM. The DMS fluxes increased with increasing DMS concentrations in slush water. Our results indicate that the potential DMS flux measured over the slush layer occurred originally from the slush layer, and was dependent on the DMS concentrations in slush water. However, snow accumulation and the formation of superimposed ice over the slush layer significantly blocks the diffusion of DMS to the atmosphere, with the result that DMS tends to accumulate in the slush layer although the removal process of DMS by photolysis reaction can modify the DMS flux from the slush layer. Hence, the slush layer has the potential to release the DMS to the atmosphere and ocean when the snow and superimposed ice melts.

Nomura, Daiki; Koga, Seizi; Kasamatsu, Nobue; Shinagawa, Hideo; Simizu, Daisuke; Wada, Makoto; Fukuchi, Mitsuo

2012-04-01

266

Recent State of Arctic Sea Ice  

NASA Astrophysics Data System (ADS)

We present the recent state of Arctic sea ice including observations from 2008 in a context of a multi-decadal perspective. A new record has been set in the reduction of Arctic perennial sea ice extent this winter. As of 1 March 2008, the extent of perennial sea ice was reduced by one million km2 compared to that at the same time last year as observed by the NASA SeaWinds scatterometer on the QuikSCAT satellite (QSCAT). This decrease of perennial ice continues the precipitous declining trend observed in this decade. Furthermore, the perennial sea ice pattern change was deduced by buoy-based estimates with 50 years of data from drifting buoys and measurement camps to track sea ice movement around the Arctic Ocean. The combination of the satellite and surface data records confirms that the reduction of winter perennial ice extent broke the record in 2008 compared to data over the last half century. In the winter, the loss of perennial ice extent was driven by winds that compressed the ice and transported it out of the Fram Strait and Nares Strait to warmer ocean waters at lower latitudes, where the ice melted very effectively. Another historical fact is that the boundary of perennial sea ice already crossed the North Pole (NP) in February 2008, leaving the area around the NP occupied by seasonal sea ice. This is the first time, not only from the satellite data record but also in the history of sea ice charting at the National Ice Center since the 1970's, that observations indicate the seasonal ice migration into the NP area so early in winter. In the Bering Sea by 12 March 2008, the sea ice edge reached to an extent that coincided with the continental shelf break, indicating bathymetric effects on the distribution of water masses along the Aleutian North Slope, Bering Slope, Anadyr, and Kamchatka Currents that governed the pattern of sea ice formation in this region. Moreover, QSCAT observations showed that, in the 2008 winter, seasonal ice occupied the Northern Sea Route, and most of two routes of the Northwest Passage, north and south of Victoria Island, which facilitated ice retreat and the opening of waterways this summer. Most importantly, the shift from a perennial to a seasonal ice covered Arctic Ocean significantly decreases the overall surface albedo resulting in enhanced solar heat absorption in spring and summer, which further decreases the Arctic ice pack through the ice albedo feedback mechanism. In early September 2008, a major melt event occurred over a large region extending from the Beaufort Sea across the Kara Sea toward the Laptev Sea, with active melt areas encroaching in the NP vicinity. This melt event was caused by an advection of warm air from the south, which melted and pushed sea ice away at the same time. At that time, the total extent of Arctic sea ice was about 0.5 million km2 (size of Spain) larger than that at the same time last year.

Nghiem, S. V.; Rigor, I. G.; Clemente-Colón, P.; Perovich, D. K.; Richter-Menge, J. A.; Chao, Y.; Neumann, G.; Ortmeyer, M.

2008-12-01

267

Chemical properties of brackish water ice in the Bothnian Bay, the Baltic Sea  

NASA Astrophysics Data System (ADS)

The behavior of major ions, 18O, dissolved organic carbon (DOC) and trace elements was studied during the initial freezing of low-saline water (3 practical salinity units) in a freezing experiment. Samples were also collected from first-year sea ice from pack ice in the Bothnian Bay, northern Baltic Sea. During initial ice formation, the major-ion ratios in sea ice indicated variable behavior, with some ions showing relative enrichment (sulfate, calcium and magnesium), conservative behavior (sodium) or relative depletion (potassium) compared to sea water at the same salinity. DOC, iron and aluminum showed enrichment in the ice, while zinc was depleted to salinity. Lead was detected in surface snow-ice layers only, implying atmospheric accumulation. First-year sea ice, with a variable growth and thermal history, showed behavior for major ions similar to that observed in new ice. However, for trace elements the picture was much more complicated, most likely due to active secondary processes such as atmospheric supply and biological activity. Ice growth has a potential impact on the chemical budgets and cycling of some elements, especially those which are selectively rejected/retained during sea-ice formation, particularly in the shallow parts of the Bothnian Bay covered with a land-fast ice cover.

Granskog Mats, A.; Virkkunen, Kristiina; Thomas, N. David; Ehn, Jens; Kola, Harri; Martma, Tõnu

268

Geothermal energy for highway snow and ice control. Summary report  

SciTech Connect

The feasibility of using geothermal water to maintain ice and snow-free structures in the Glenwood Canyon area has been investigated. Structures incorporating this feature would be located in high hazard locations as a result of structure alignment, lack of exposure to sunlight, or a rapid change in environment (i.e. in and out of tunnels). Two technical reports have been published on the subject. The first dealt with the environment and natural resources within the canyon as well as various deicing alternatives. The second publication provided a technical evaluation of a prototype bridge deck heating system. This report provides a brief overall description of the study as well as a non-technical summary of the two published reports.

Donnelly, D.E.

1981-11-01

269

Sea ice cover in the Caspian and Aral seas from active and passive satellite microwave data  

NASA Astrophysics Data System (ADS)

Stable ice cover forms every year in the Caspian and Aral seas. Ice stays for several months and negatively affects navigation conditions, endangers constructions located on the coast and the oil rigs that have recently been installed in the shelf regions of the Northern Caspian by Russia and Kazakhstan. Ice extent varies significantly from year to year in response to changes in hydrometeorological conditions over the region and its variations may serve as an early indicator of the large-scale climate change. We studied ice cover in these two seas using data from the Topex-Poseidon satellite, operating since 1992. This platform has two nadir-looking instruments - a dual-frequency radar altimeter and a passive microwave radiometer. Five Topex-Poseidon passes covering the northern part of the Caspian sea and two passes covering the central part of the Big Aral sea, were selected, providing data for ten consecutive years with a 10 days repetitive period. The combination of both active (backscatter coefficient at 13 GHz) and passive (brightness temperature at 18 and 37 GHz) microwave measurements provides information to estimate ice concentration, roughness and height of snow cover on ice. This information on ice cover was complemented by passive microwave data from the SMMR (Scanning Multichannel Microwave Radiometer) instrument onboard the satellite NIMBUS-7 (since 1979) and the SSMI (Special Sensor Microwave Imager) instrument on board the DMSP (Defense Meteorological Satellite Program) series (since 1987). Analysis of time series of ice extent and types shows pronounced regional, seasonal and interannual variability. In the Northern Caspian sea ice cover has a maximum extent in the shallow and isolated eastern part, while in the western part presence of ice cover is reduced. Interannual variability of ice cover extent for ten selected years show a warming signal: ratio of presence of ice cover in observations in both Caspian and Aral seas is reduced (more than two times), especially during the four unusually mild winters (1998/99 to 2001/02). In the Caspian sea such dramatic reduction of ice extent affects breeding habits and living conditions of the Caspian seal - the only mammal in this sea.

Kouraev, A. V.; Papa, F.; Mognard, N. M.; Buharizin, P. I.; Cazenave, A.; Cretaux, J.-F.; Dozortseva, J.; Remy, F.

2003-04-01

270

Simulation of snow and ice melt discharge into the Gepatsch reservoir (Kaunertal/Austrian Alps)  

NASA Astrophysics Data System (ADS)

We present an enhanced method to simulate snow and ice melt discharge into an Alpine reservoir (Gepatsch reservoir, Ötztal Alps, Tyrol/Austria) by combining a process based snow model with sophisticated data assimilation techniques. Within the frame of the alpS project MUSICALS (MUltiscale Snow/ICemelt Discharge Simulation into ALpine ReservoirS), snow cover distribution is analysed based on a set of high-resolution surface elevation datasets acquired from airborne laserscan (ALS) flights over the entire catchments (approx. 580 km², 23% glacierized) contributing directly or by diversion to discharge into the Gepatsch reservoir. The resulting maps of spatially distributed snow water equivalent (SWE) are compared to SWE maps produced by the snow model AMUNDSEN, a distributed physically based energy balance model specifically designed for high mountain regions. AMUNDSEN distinguishes between different types of snow and ice (new snow, old snow, firn and glacier ice) and accounts for their distinct properties. The initial ice thickness distribution is modeled based on digital elevation models and glacier outlines from the Austrian glacier inventory. This is required to account for changing runoff generated from glacier melt under conditions of glacier retreat. Discharge generation from calculated meltwater production and precipitation is simulated in AMUNDSEN using a linear reservoir model with five parallel reservoir cascades considering the distinct storage properties of snow, firn, ice, unglacierized areas and soil. Calibration of the recession coefficients is done separately for each subcatchment. MUSICALS aims to model discharge generated by spatially differentiated snow and ice melt more realistically and to develop a robust simulation tool that is able to calculate short-, middle- and long-term forecasts of reservoir inflow based on weather predictions and climate scenarios.

Hanzer, Florian; Helfricht, Kay; Schneider, Katrin; Marke, Thomas; Kuhn, Michael; Strasser, Ulrich

2013-04-01

271

Seasonal and interannual pollen variability in snow layers of arctic ice caps  

Microsoft Academic Search

The pollen content of snow, deposited at the summit of three ice caps and a small glacier in the Canadian Arctic and at one ice cap in the Russian Arctic, was determined for periods ranging from one to 13 years. On the ice caps, boreal forest trees and low arctic shrubs account, on average, for 26% to 49% of the

Jocelyne C. Bourgeois

2000-01-01

272

High Frequency Audio Absorption in Sea Ice.  

National Technical Information Service (NTIS)

This is a preliminary report on a programme to measure acoustic absorption in sea ice in the frequency range from 25-250 kc. Artificial sea water is frozen in a tank 2 feet to the side with a pressure release mechanism. A slab of ice 2 feet x 2 feet x 1 f...

E. R. Pounder

1966-01-01

273

Variability in Arctic sea ice optical properties  

Microsoft Academic Search

The optical properties of sea ice exhibit considerable spatial, temporal, and spectral variability. During a field experiment at Barrow, Alaska, we examined the horizontal variability of spectral albedo and transmittance as well as the vertical variability of in-ice radiance. Temporal changes were monitored under cold conditions in April and during the onset of melt in June. Physical properties, including ice

Donald K. Perovich; Collin S. Roesler; W. Scott Pegau

1998-01-01

274

Brine fluxes from growing sea ice  

Microsoft Academic Search

It is well known that brine drainage from growing sea ice has a controlling influence on its mechanical, electromagnetic, biological and transport properties, and hence upon the buoyancy forcing and ecology in the polar oceans. When the ice has exceeded a critical thickness the drainage process is dominated by brine channels: liquid conduits extending through the ice. We describe a

A. J. Wells; J. S. Wettlaufer; S. A. Orszag

2011-01-01

275

The secret of the Svalbard sea ice barrier  

Microsoft Academic Search

An elongated sea ice feature called the Svalbard sea ice barrier rapidly formed over an area in the Barents Sea to the east of Svalbard posing a significant navigational hazard. The secret of this sea ice formation lies in the bottom bathymetry, which governs the distribution of cold Arctic waters masses and sea ice growth

S. V. Nghiem; M. L. Van Woert; G. Neumann

2004-01-01

276

Ridged sea ice characteristics in the Arctic from a coupled multicategory sea ice model  

NASA Astrophysics Data System (ADS)

In this study, a multicategory sea ice model with explicit ice classes for ridged and rafted ice was used to examine the evolution of deformed ice during the period 1980-2002. The results show that (1) ridged ice comprises roughly 45-60% of Arctic sea ice volume and 25-45% of the sea ice area, (2) most of the perennial ice consists of ridged ice, and (3) ridged ice exhibits a small seasonal variability. Our results also show an increase in mean ridged ice thickness of 4-6 cm yr-1 during the summer in an area north of the Canadian Archipelago and a corresponding decrease in the East Siberian Sea and Nansen Basin. At the same time, Arctic sea ice age has been observed to decline and ice drift speed to increase during the simulation period. We connect these findings with a modeled regional increase in the production rate of ridged ice. Comparison of the multicategory model and a two category reference model shows a substantially increased ice production rate due to a more frequent occurrence of leads, resulting in an ice thickness increase of up to 0.8 m. Differences in ice physics between the multicategory and reference models also affect the freshwater content. The sum of liquid and solid freshwater content in the entire Arctic Ocean is about 10% lower and net precipitation (P-E) is about 7% lower as compared to the reference model.

MâRtensson, S.; Meier, H. E. M.; Pemberton, P.; Haapala, J.

2012-04-01

277

Antarctic Sea Ice in the IPY  

NASA Astrophysics Data System (ADS)

Antarctic Sea Ice covers an area of 20 million km2 at maximum extent and therefore represents an areal coverage larger than either the Arctic ice cover or the Antarctic continent. Studies of Antarctic sea ice in the modern era were only initiated well after the IGY, with the advent of passive microwave satellite coverage in 1973, followed by the use of several countries icebreaking research vessels over the last two decades. Useful knowledge of basic ice thickness, properties and processes is being addressed by an ice observations programs and several process studies, but the scale of activity is well below that conducted for the Arctic ice cover. The absence of submarine activity in the Antarctic which has provided large scale information on the changing Arctic ice thickness distribution is particularly notable as a critical measurement in understanding climate impact. As well, only two short term drift stations (Ice Station Weddell in 1992 and Ice Station Polarstern in 2004) have or will provide limited time series information on sea ice and ocean processes compared to multiple drift stations and yearlong experiments in the Arctic, dating back to IGY. The two technologies of Autonomous Underwater Vehicles specifically designed for long-range ice operations (500km) (e.g. Autosub Under Ice) and the recently developed international icebreaking research vessel capability for the Antarctic therefore gives an opportunity for two International Polar Year programs to provide critical information for the Antartic sea ice cover commensurate with our knowledge of the Arctic. The proposed programs are: 1. A circumpolar survey of the Antarctic sea ice thickness distribution at near maximum extent using two ship-based autonomous underwater vehicles and several countries' icebreakers. 2. An International Ice Drifting Station in the Bellingshausen-Amundsen-Ross Sea using icebreakers and drifting buoys to characterize the sea ice, ocean and climate in this unknown region of Antarctic multiyear ice. These measurements will provide directly comparable measurements to those of the Arctic Ocean' ice cover as well as a year-long snapshot of ice, ocean and climate conditions useful for numerical model verification for climate change prediction. New venues for training and experience of oceanographers, climate and sea ice scientists, and numerical modelers will also be provided to examine the many future opportunites in the Antarctic.

Ackley, S. F.; Perovich, D. K.; Geiger, C. A.

2003-12-01

278

History of sea ice in the Arctic  

Microsoft Academic Search

Arctic sea-ice extent and volume are declining rapidly. Several studies project that the Arctic Ocean may become seasonally ice-free by the year 2040 or even earlier. Putting this into perspective requires information on the history of Arctic sea-ice conditions through the geologic past. This information can be provided by proxy records from the Arctic Ocean floor and from the surrounding

Leonid Polyak; Richard B. Alley; John T. Andrews; Julie Brigham-Grette; Thomas M. Cronin; Dennis A. Darby; Arthur S. Dyke; Joan J. Fitzpatrick; Svend Funder; Marika Holland; Anne E. Jennings; Gifford H. Miller; Matt O'Regan; James Savelle; Mark Serreze; Kristen St. John; James W. C. White; Eric Wolff

2010-01-01

279

Macronutrients in the Summer Sea ice of the Ross Sea  

Microsoft Academic Search

The development and production of sea ice microbial communities is often linked to limitations imposed by light, temperature and salinity. Nutrients also impose a limitation upon biomass development and production. Nutrient constraints on biomass development was readily evident in surface habitats of the pack ice of the Ross Sea during the summer of 1999. The spatial extent of nutrient depletions,

C. H. Fritsen; D. L. Garrison; D. R. Neenan; S. L. Coale; A. H. Gibson

2004-01-01

280

Satellite Detection of Smoke Aerosols Over a Snow/Ice Surface by TOMS.  

National Technical Information Service (NTIS)

The use of TOMS (Total Ozone Mapping Spectrometer) satellite data demonstrates the recently developed technique of using satellite UV radiance measurements to detect absorbing tropospheric aerosols is effective over snow/ice surfaces. Instead of the tradi...

N. C. Hsu J. R. Herman J. F. Gleason O. Torres C. J. Seftor

1998-01-01

281

Review of Climatological Influences on the Deterioration of Ice and Snow.  

National Technical Information Service (NTIS)

The climatological factors of high solar radiation and air temperature contribute to ablation and deterioration processes in ice and snow. Local environment and climate are as important as elevation and latitude in determining the importance of these fact...

N. S. Stehle

1965-01-01

282

Snow and Land Ice in the Climate System: Research Problems and Possibilities of Remote Sensing.  

National Technical Information Service (NTIS)

The significance of the main components of the cryosphere, ice sheets, seasonal snow cover and glaciers, is discussed. Interpretation of climatic data from the past as a means of improving climate modeling techniques is called for. The physical basis for ...

H. Rott

1990-01-01

283

Sea ice in the paleoclimate system: the challenge of reconstructing sea ice from proxies – an introduction  

NASA Astrophysics Data System (ADS)

Sea ice is an important component of the Earth system with complex dynamics imperfectly documented from direct observations, which are primarily limited to the last 40 years. Whereas large amplitude variations of sea ice have been recorded, especially in the Arctic, with a strikingly fast decrease in recent years partly attributed to the impact of anthropogenic climate changes, little is known about the natural variability of the sea ice cover at multi-decadal to multi-millennial time scales. Hence, there is a need to establish longer sea ice time series to document the full range of sea ice variations under natural forcings. To do this, several approaches based on biogenic or geochemical proxies have been developed from marine, ice core and coastal records. The status of the sea ice proxies has been discussed by the Sea Ice Proxy (SIP) working group endorsed by PAGES during a first workshop held at GEOTOP in Montréal. The present volume contains a set of papers addressing various sea ice proxies and their application to large scale sea ice reconstruction. Here we summarize the contents of the volume, including a table of various proxies available in marine sediments and ice cores, with their possibilities and limitations.

de Vernal, Anne; Gersonde, Rainer; Goosse, Hugues; Seidenkrantz, Marit-Solveig; Wolff, Eric W.

2013-11-01

284

An estimate of the impact of trapped melt ponds on sea ice thinning  

NASA Astrophysics Data System (ADS)

Melt ponds form on Arctic sea ice during the melting season and their presence affects the heat and mass balance of the ice cover. Towards the end of the melt season melt ponds cover up to 50% of the sea ice area decreasing the value of the surface albedo by up to 20%. The dramatic impact of melt ponds on the albedo feedback mechanism for sea ice melt has been demonstrated in previous studies. Here, we focus on the refreezing of melt ponds. As the ponds freeze from above, they gradually release latent heat that inhibits basal ice growth. The refreezing process can take up to three months. Freezing of the melt pond comes to an halt if the pond's freezing point reaches the air temperature since the Stefan condition for sea ice growth is not met anymore. Since the ice in presence of melt pond will stay thinner and flatter for longer, the areas where ponds are present are likely location for pond formation in the subsequent years. The presence of a pond trapped in the ice delays significantly the sea ice growth at locations where melt ponds form. The potential volume loss of sea ice per year in the Arctic considering a melt pond cover of 20% is up to 1000 km3 without considering the presence of snow. Within the ASBO (Arctic Synoptic Basin-wide Observations) project we have developed a model of refreezing melt ponds that uses mushy layer theory to describe the sea ice and takes account of the presence of salt in the refreezing melt pond. We use this model to investigate the rate at which melt ponds refreeze, releasing latent heat, and their impact on sea ice growth. In this work we would like to present model result with climatology input. We will give an estimate of the impact of the melt pond presence on sea ice growth in the Arctic basin.

Flocco, Daniela; Feltham, Daniel; Schroeder, David

2013-04-01

285

Development of a Seismic Snow Streamer and Use of Multi- Offset Reflection for Determining Glacier Ice Properties  

NASA Astrophysics Data System (ADS)

Glaciers and ice sheets are important to climate research due to their role in controlling worldwide weather and temperature patterns as well as their potential impact in sea level rise. Because of this, scientists are attempting to model large ice sheets and important fast flowing glaciers. These models are limited in large part to the lack of data which govern the nonlinear behavior of ice flow. Seismic data acquisition can provide high resolution data which can be used to extract information of variables like bed topography, ice temperature and preferred ice crystal orientation. But seismic data acquisition in polar environments is challenging. This is mainly due to the labor intensive process of manually hand planting geophones. In order to improve the efficiency of active source seismic reflection data acquisition in polar environments, two prototype seismic snow-streamers were constructed for this investigation and optimized for deployment in remote locations. The first snow-streamer (experimental snow-streamer) was field tested in the Jakobshavn Glacier located in central western Greenland. The experimental snow-streamer was equipped with multiple geophone configurations and two plate materials. Twenty-two variable angle records were collected using the stationary snow streamer in the center of the survey. The source consisted of 0.5 kg of explosives buried 10 m below the snow surface at 160 m intervals. The resultant data set consisted of offsets ranging from -1760 to +1600 m and the ice-bed interface as well as two internal ice layers were imaged at approximately 1.85, 1.5 and 1.7 km depth respectively. The snow-streamer data was simultaneously collected with a mirror arrangement of hand planted buried geophones in order to test for the effects of plate weight, wind noise, geophone burial and plate to snow coupling in the seismic signal. The signal analysis and the comparison of streamer vs. buried geophones showed that geophone burial can degrade the seismic signal while the wind and signal analysis revealed that the best snow-streamer configuration was a combination of aluminum plates with vertical geophones. Using these results a second 480m full scale snow-streamer was tested in the Thwaites Glacier Antarctica. The snow-streamer data was simultaneously collected with a mirrored arrangement of surface planted and buried geophones. The trace by trace comparison revealed higher signal to noise in the data collected using the snow-streamer when compared to the surface planted and buried geophones. The full scale snow-streamer was easy to maneuver, very light and could be pulled in speeds up to 15 km/h. The use of the snow-streamer proved to be an efficient data acquisition tool, yielding high quality data. Therefore the use of snow-streamers can represent a significant improvement in the efficiency of seismic data acquisition in polar environments opening the possibility of determining important ice column properties for areas of interest. An important parameter affecting glacier flow is preferred ice crystal orientation. Seismic waves in ice travel up to 5% faster along the c-axis than when travelling perpendicular to it. Therefore, reflected seismic wave slowness (inverse of the velocity) variability as a function of angle of incidence can be used to detect anisotropy in ice crystal orientation. By combining the multi-offset seismic reflection data set acquired with the experimental snow-streamer and a 2D seismic reflection profile simultaneously collected for the same location, we investigated the presence of preferred ice crystal orientation for the area of study on the Jakobshavn Glacier. The combination of both data sets allowed the approximation of the average ray velocity as a function of angle of incidence. Given that the seismic velocity varies as a function of ice crystal orientation, we can use an existing model to relate the variation of seismic velocity as a function of offset to estimate the mean ice crystal orientation for the bed and imaged internal layers in terms of a conical c-axes distributi

Velez Gonzalez, Jose A.

286

Climatic and environmental records from Altai glaciers, Siberia, recovered from ice-cores and snow samples  

Microsoft Academic Search

A depth\\/accumulation scale for the Altai glaciers, Siberia, established based on delta18O and deltaD firn-ice cores analysis. In sequences of annual layers in the firn-ice cores recovered in 2001 and 2002, the mean annual snow accumulation was found to be 800 mm at 4115 m of the Belukha Snow-Firn Plateau. The transfer function was developed using the seasonality of accumulation

V. B. Aizen; E. M. Aizen; K. J. Kreutz; K. Fujita; D. Cecil; S. A. Nikitin

2002-01-01

287

Arctic sea-ice ridges—Safe heavens for sea-ice fauna during periods of extreme ice melt?  

NASA Astrophysics Data System (ADS)

The abundances and distribution of metazoan within-ice meiofauna (13 stations) and under-ice fauna (12 stations) were investigated in level sea ice and sea-ice ridges in the Chukchi/Beaufort Seas and Canada Basin in June/July 2005 using a combination of ice coring and SCUBA diving. Ice meiofauna abundance was estimated based on live counts in the bottom 30 cm of level sea ice based on triplicate ice core sampling at each location, and in individual ice chunks from ridges at four locations. Under-ice amphipods were counted in situ in replicate ( N=24-65 per station) 0.25 m 2 quadrats using SCUBA to a maximum water depth of 12 m. In level sea ice, the most abundant ice meiofauna groups were Turbellaria (46%), Nematoda (35%), and Harpacticoida (19%), with overall low abundances per station that ranged from 0.0 to 10.9 ind l -1 (median 0.8 ind l -1). In level ice, low ice algal pigment concentrations (<0.1-15.8 ?g Chl a l -1), low brine salinities (1.8-21.7) and flushing from the melting sea ice likely explain the low ice meiofauna concentrations. Higher abundances of Turbellaria, Nematoda and Harpacticoida also were observed in pressure ridges (0-200 ind l -1, median 40 ind l -1), although values were highly variable and only medians of Turbellaria were significantly higher in ridge ice than in level ice. Median abundances of under-ice amphipods at all ice types (level ice, various ice ridge structures) ranged from 8 to 114 ind m -2 per station and mainly consisted of Apherusa glacialis (87%), Onisimus spp. (7%) and Gammarus wilkitzkii (6%). Highest amphipod abundances were observed in pressure ridges at depths >3 m where abundances were up to 42-fold higher compared with level ice. We propose that the summer ice melt impacted meiofauna and under-ice amphipod abundance and distribution through (a) flushing, and (b) enhanced salinity stress at thinner level sea ice (less than 3 m thickness). We further suggest that pressure ridges, which extend into deeper, high-salinity water, become accumulation regions for ice meiofauna and under-ice amphipods in summer. Pressure ridges thus might be crucial for faunal survival during periods of enhanced summer ice melt. Previous estimates of Arctic sea ice meiofauna and under-ice amphipods on regional and pan-Arctic scales likely underestimate abundances at least in summer because they typically do not include pressure ridges.

Gradinger, Rolf; Bluhm, Bodil; Iken, Katrin

2010-01-01

288

Constraining projections of summer Arctic sea ice  

NASA Astrophysics Data System (ADS)

We examine the recent (1979-2010) and future (2011-2100) characteristics of the summer Arctic sea ice cover as simulated by 29 Earth system and general circulation models from the Coupled Model Intercomparison Project, phase 5 (CMIP5). As was the case with CMIP3, a large intermodel spread persists in the simulated summer sea ice losses over the 21st century for a given forcing scenario. The 1979-2010 sea ice extent, thickness distribution and volume characteristics of each CMIP5 model are discussed as potential constraints on the September sea ice extent (SSIE) projections. Our results suggest first that the future changes in SSIE with respect to the 1979-2010 model SSIE are related in a complicated manner to the initial 1979-2010 sea ice model characteristics, due to the large diversity of the CMIP5 population: at a given time, some models are in an ice-free state while others are still on the track of ice loss. However, in phase plane plots (that do not consider the time as an independent variable), we show that the transition towards ice-free conditions is actually occurring in a very similar manner for all models. We also find that the year at which SSIE drops below a certain threshold is likely to be constrained by the present-day sea ice properties. In a second step, using several adequate 1979-2010 sea ice metrics, we effectively reduce the uncertainty as to when the Arctic could become nearly ice-free in summertime, the interval [2041, 2060] being our best estimate for a high climate forcing scenario.

Massonnet, F.; Fichefet, T.; Goosse, H.; Bitz, C. M.; Philippon-Berthier, G.; Holland, M. M.; Barriat, P.-Y.

2012-11-01

289

Can Arctic Sea Ice Summer Melt be Accelerated by Changes in Spring Cloud Properties?  

NASA Astrophysics Data System (ADS)

Ice-albedo feedback remains the major factor accelerating recently observed decline in the Arctic sea ice extent and thickness. The immediate effect of this feedback is offset by clouds, which decrease the amount of solar radiation reaching the surface in summer. However, once the surface albedo is decreased due to an increase in the open water fraction or enhanced snow melt, larger amounts of solar radiation are absorbed by the ocean mixed layer. This can cause earlier spring snow/ice melt, a delay in the fall freeze-up, and an overall decrease in the ice thickness. Studies with the Surface Heat Budget of the Arctic (SHEBA) data showed that the Arctic stratus clouds produce a net warming of 20 W m-2 in the surface layer during the spring season, which may accelerate the spring time melting of the ice pack. In the Arctic where the cloudiness is usually high, cloud radiative forcing depends mostly on the cloud microphysical properties, rather than on the cloud fraction. Liquid clouds have an order of magnitude larger optical thickness compared to ice clouds. Using the SHEBA data, we relate the seasonal changes in cloud short-wave and long-wave radiative forcing to the cloud ice/liquid water content. We will also present the results from a simple thermodynamic sea ice model to show the cloud effects on sea ice thickness and concentration.

Gorodetskaya, I.; Tremblay, B.; Liepert, B.; Cane, M.

2006-12-01

290

Studies in the Chupa Inlet, White Sea, Russia in March-April 2004 in the Frame of Ocean-Atmosphere-Sea Ice-Snowpack (OASIS) Interactions Program  

Microsoft Academic Search

The composition of aerosols, snow, ice and sea water was studied in the Chupa Inlet, the White Sea in the vicinity of the Polar Circle from March 26 to April 8, 2004. Concentrations of aerosols were very low and typical for background areas. One event of sharp aerosol concentration growth and high enrichment of aerosol by heavy metals have been

V. P. Shevchenko; L. L. Demina; A. S. Filippov; V. V. Gordeev; K. P. Koutsenogii; A. N. Novigatsky; V. V. Smirnov

2005-01-01

291

Preservation of glaciochemical time-series in snow and ice from the Penny Ice Cap, Baffin Island  

Microsoft Academic Search

A detailed investigation of major ion concentrations of snow and ice in the summit region of Penny Ice Cap (PIC) was performed to determine the effects of summer melt on the glaciochemical time-series. While ion migration due to meltwater percolation makes it difficult to confidently count annual layers in the glaciochemical profiles, time-series of these parameters do show good structure

Nancy S. Grumet; Cameron P. Wake; Greg A. Zielinski; David Fisher; Roy Koerner; John D. Jacobs

1998-01-01

292

Evaluating derived sea ice thickness estimates from two remote sensing data sets  

NASA Astrophysics Data System (ADS)

Satellites that monitor the polar regions collect a wealth of information about sea ice. While elevation data (ice freeboard + snow) are obtainable from certain satellites (e.g. ICESat), this estimate only measures approximately 10 percent of the total ice thickness. Significant uncertainties exist when extrapolating from ice freeboard to total ice thickness. Direct ice thickness measurements taken from on the ice are the most accurate but difficult to obtain, but submarines provide an effective method to monitor basin-wide draft. There is less uncertainty in extrapolating total thickness from the ice draft. Satellite imagery, while not providing direct measurement of ice thickness, can be used to infer ice type and hence an ice thickness range estimate based on interpretation of the imagery and ancillary data. This study compares Arctic ice thickness estimated from submarine data to ice thickness from an interpretive product that relies heavily on satellite data where the two data sets overlap spatially and temporally during the period 1996 through 1998. The first source (submarine data) is available from the National Snow and Ice Data Center, while the second source of raw NIC charts is available from the National Ice Center (NIC). Both data sources are converted to ice thickness prior to the evaluation. A raw data analysis is performed and ice thickness distribution maps are produced in ArcMap based on the ordinary kriging spatial interpolation technique. Results from the raw data analysis indicate a low correlation between the two data sets with the least agreement in the multiyear ice zone (>200 cm). The geostatistical results portray a similar ice thickness pattern in the Arctic, even though the submarine data contain more ice thickness variability than the NIC charts.

Ballagh, L. M.; Meier, W. N.; Barry, R. G.; Buttenfield, B. P.

2007-12-01

293

Summer sea ice in the recent Arctic: morphological properties in the Pacific sector from the CHINARE 2010 cruise  

NASA Astrophysics Data System (ADS)

The Chinese National Arctic Research Expedition (CHINARE) in the summer 2010, primarily from 21 July to 28 August, in the ice zone of Arctic Pacific Sector, between 150° W to 180° W to 88.5° N, conducted comprehensive scientific studies on atmosphere-ice-ocean interactions, using icebreaker R.V. Xuelong. Measurements made included underway visual observations of snow and ice conditions at half-hourly time scale and EM31-measured ice thickness at one 12-day and eight short-term (3-4 h each) ice stations. The visual observation data are compared with AMSR-E ice concentration, ice thickness measured by a hanging EM31 from the vessel, and video-recorded image-derived ice concentration and pond coverage. A grid of 8 profiles of ice thickness measurements (four repeats) was conducted at the 12-day ice station (∼86°50' N-87°20' N) in the central Arctic and an average 2 cm day-1 melt rate, primarily bottom melt, was found, after surface melting had almost ceased. The high bottom melt rate, as compared with previous results from other studies, is consistent with the high floe speed (mean 0.17 m s-1) that is also larger than that previously reported. We also found that the daily AMSR-E ice concentration data can be used to map the marginal ice zone (MIZ) and its change. There are clear differences between the MIZ and pack ice zone in terms of ice concentration, thickness, ice type, floe size, as well as pond coverage. Results indicate that, as compared with the 2005 data from the Healy/Oden Trans-Arctic Expedition for the Arctic Pacific Sector (9 August to 10 September), the 2010 was first-year ice dominant (vs. the multiyear ice dominant in 2005), 70% or less in ice concentration (vs. 90% in 2005), 94-114 cm in ice thickness (vs. 150 cm in 2005). No snow cover was observed on the ice south of 78° N and 8-10 cm mean snow depth due to new snowfall events, which melted away after 17 August (vs. no snow cover south of 84.3° N or ~10 cm snow depth further north in 2005). Those changes indicate the continuation of ice thinning, less concentration, and younger ice after the 2007 shift, when a record minimum sea ice extent was observed. Overall, the measurements provided a valuable dataset of sea ice morphological properties over the Arctic Pacific Sector in summer 2010, which confirms, by comparison with previous data, that a "new normal" of Arctic sea ice is now present and is a benchmark for measurements of possible future changes.

Xie, H.; Lei, R.; Ke, C.; Wang, H.; Li, Z.; Zhao, J.; Ackley, S. F.

2012-05-01

294

SIPEX--Exploring the Antarctic Sea Ice Zone  

ERIC Educational Resources Information Center

|Sea ice in the polar regions plays a key role in both regulating global climate and maintaining marine ecosystems. The international Sea Ice Physics and Ecosystem eXperiment (SIPEX) explored the sea ice zone around Antarctica in September and October 2007, investigating relationships between the physical sea ice environment and the structure of…

Zicus, Sandra; Dobson, Jane; Worby, Anthony

2008-01-01

295

Haline circulation induced by formation and melting of sea ice  

Microsoft Academic Search

A three-dimensional, coupled ice-ocean model is developed, and basic numerical experiments for examining effects of freshwater budget associated with formation and melting of sea ice on the thermohaline circulation are performed. Motion of sea ice affects the freshwater budget in two ways. First, if horizontally transports freshwater in the form of sea ice. Second, it alters the conditions of sea

Hiroyasu Hasumi; Nobuo Suginohara

1995-01-01

296

Sea Ice Volume Transport in the Southern Ocean  

Microsoft Academic Search

Recent Comparisons between NASA's long-term microwave records of sea ice extent in the Arctic Ocean and 13 IPCC AR4 climate models show sea ice extent declining faster than current models can predict. Although conditions for Antarctic sea ice are not as clear, regional climatic changes occurring in sea ice in the southern ocean have been documented. There is a need

E. R. Bernstein; C. A. Geiger; T. L. Deliberty

2009-01-01

297

Snow-ice-tephra-lava interactions during the 2010 Fimmvorduhals eruption  

NASA Astrophysics Data System (ADS)

On March 20th a small basaltic fissure opened at the northern edge of Fimmvorduhals, a popular hiking pass between Eyjafjallajökull, to the west, and Myrdalsjökull, to the east. Immediately prior to the eruption, the vent area was covered with typically 1-3 meters of snow and locally snow-covered, isolated remnants of glacial ice. Fieldwork conducted during June and July documented evidence for a variety of different types of interactions between volcanism (tephra and lava) and snow/ice, including direct contact (e.g. ash-covered snow, lava blocks on snow/ice, lava flows on ash-covered snow), indirect melting (e.g. arcuate snow/ice melting patterns at lava flow fronts, partly collapsed sheet lava flows), and the formation of small bomb-cored mounds via post-depositional snow melting. Many of these features are likely ephemeral, and may leave no trace in the geological record; however under certain circumstances they may leave subtle clues that could aide in identifying the presence of snow during eruptions. The field relationships documented are consistent with varied mechanisms of heat transfer during the eruption to the surrounding environment. The arcuate-shaped snow and ice-banks at the edges of flows appear to closely mimic the shape of the adjacent lava lobes. The geometric relationships are consistent with snow/ice melting several meters in front of the advancing flows by radiant heat from the front of the lava lobes. Also, in at least two areas we observed features that are consistent with snow melting beneath lava, possibly by slower heat conduction. One example is a small cave beneath the lava at the lava-snow contact. The other is a ~1 m thick sheet flow that has partly collapsed, forming a fracture that appears to have been controlled by incipient polygonal jointing; melting of underlying snow may have undermined part of the sheet flow based and facilitated its collapse. However, under at least two separate types of conditions lava seems to have little impact on snow/ice. Firstly, where lava flows onto the coarse apron of lapilli generated during the early part of the eruption, the lapilli layer (~13 cm thick) appears to have insulated the snow and prevented it from melting noticeably. Secondly, towards the distal ends of the flows, blocks of lava were heaved onto bounding snow/ice without producing noticeable melting. The bomb-cored mounds, which are the most evocative structures formed by tephra-snow interactions, are also probably the least likely to be preserved. The mounds appear to have formed by a complex sequence of events, and their stratigraphy, from bottom to top, is: snow, icy-snow, volcanic bomb, coarse black lapilli, and medium- to fine, greenish-gray ash. The mounds appear to record melting and deflation of the snow surface sometime after the deposition of the ash layer, which probably originated from the summit vent at Eyjafjallajökull.

Haklar, J.; Edwards, B. R.; Gudmundsson, M. T.

2010-12-01

298

Frazil deposition under growing sea ice  

NASA Astrophysics Data System (ADS)

Platelet ice may be an important component of Antarctic landfast sea ice. Typically, it is found at depth in first-year landfast sea ice cover, near ice shelves. To explain why platelet ice is not commonly observed at shallower depths, we consider a new mechanism. Our hypothesis is that platelet ice eventually appears due to the sudden deposition of frazil ice against the fast ice-ocean interface, providing randomly oriented nucleation sites for crystal growth. Brine rejected in plumes from landfast ice generates stirring sufficient to prevent frazil ice from attaching to the interface, forcing some of it to remain in suspension until ice growth rate and brine rejection slow to the point that frazil can stick. We calculate a brine plume velocity and match this to frazil rise velocity. We consider both laminar and turbulent environments. We find that brine plume velocities are generally powerful enough to prevent a significant range of frazil sizes from sticking in the case of laminar flow and that, in the turbulent case, there may be a critical ice thickness at which most remaining circulating frazil suddenly settles.

McGuinness, M. J.; Williams, M. J. M.; Langhorne, P. J.; Purdie, C.; Crook, J.

2009-07-01

299

Sea Ice Emissivities and Effective Temperatures at MHS Frequencies: An Analysis of Airborne Microwave Data Measured During Two Arctic Campaigns  

Microsoft Academic Search

Satellite-based sounding of the temperature and hu- midity of the lower troposphere is only carried out over open sea surfaces because of large uncertainties in the surface emissivity and effective emitting temperature of other surfaces. The study of sea ice and snow surface emissivities at Microwave Humidity Sounder (MHS) frequencies has been the focus of two airborne campaigns carried out

R. Chawn Harlow

2011-01-01

300

A continuum anisotropic model of sea-ice dynamics  

Microsoft Academic Search

We develop the essential ingredients of a new, continuum and anisotropic model of sea-ice dynamics designed for eventual use in climate simulation. These ingredients are a constitutive law for sea-ice stress, relating stress to the material properties of sea ice and to internal variables describing the sea-ice state, and equations describ- ing the evolution of these variables. The sea-ice cover

V. Wilchinsky; Daniel L. Feltham

2004-01-01

301

Ice, Cloud, and land Elevation (ICESat) satellite Data Management and Delivery at the National Snow and Ice Data Center  

Microsoft Academic Search

The Geoscience Laser Altimeter System (GLAS) instrument aboard the Ice, Cloud, and land Elevation (ICESat) satellite launched on 12 January 2003. The primary objective of the ICESat mission is to provide global measurements of polar ice sheet elevation to discern changes in ice volume (mass balance) over time. Secondary objectives of the mission are to measure sea ice roughness and

D. Fowler; D. Korn

2006-01-01

302

Transpolar observations of the morphological properties of Arctic sea ice  

Microsoft Academic Search

During the 5 August to 30 September 2005 Healy Oden Trans-Arctic Expedition a trans-Arctic survey of the physical properties of the polar ice pack was conducted. The observational program consisted of four broad classes of snow and ice characterization activities: observations made while the ship was in transit, ice station measurements, helicopter survey flights, and the deployment of autonomous ice

Donald K. Perovich; Thomas C. Grenfell; Bonnie Light; Bruce C. Elder; Jeremy Harbeck; Christopher Polashenski; Walter B. Tucker III; Casey Stelmach

2009-01-01

303

Handbook for Sea Ice Analysis and Forecasting.  

National Technical Information Service (NTIS)

Background information and techniques used to analyze and forecast sea ice conditions are presented. Emphasis has ben placed on operationally-oriented analysis and forecast rules and aids and the use of climatological charts containing parameters related ...

W. J. Stringer D. G. Barnett R. H. Godin

1984-01-01

304

Sea Ice Climatic Atlas. Volume 1. Antarctic.  

National Technical Information Service (NTIS)

Through 1972, reliable sea ice information in the Antarctic was based on relatively few shore stations and ships reports augmented by limited aerial reconnaissance data. These data were further restricted to relatively small areas observed primarily durin...

1985-01-01

305

Fungal spores as potential ice nuclei in fog\\/cloud water and snow  

Microsoft Academic Search

INTRODUCTION: In discussions about climate change and precipitation frequency biological ice nucleation has become an issue. While bacterial ice nucleation (IN) is already well characterized and even utilized in industrial processes such as the production of artificial snow or to improve freezing processes in food industry, less is known about the IN potential of fungal spores which are also ubiquitous

Heidi Bauer; Fabio L. T. Goncalves; Elisabeth Schueller; Hans Puxbaum

2010-01-01

306

Airborne Measurement of Sea-Ice Thickness  

Microsoft Academic Search

The Naval Research Laboratory (NRL) is planning a major program of measurement and modeling of sea-ice thickness in the Arctic. The program will include in-situ, airborne and satellite measurements as well as development of coupled models of ocean, atmosphere and sea-ice. The authors' primary responsibility in this program will be the airborne measurement segment of the program utilizing the freeboard

Joan Gardner; John Brozena

2010-01-01

307

The Thickness Distribution of Sea Ice.  

National Technical Information Service (NTIS)

The polar oceans contain sea ice of many thicknesses ranging from open water to thick pressure ridges. Since many of the physical properties of the ice depend upon its thickness, it is natural to expect its large-scale geophysical properties to depend on ...

A. S. Thorndike D. A. Rothrock G. A. Maykut R. Colony

1975-01-01

308

Pancake ice formation in the Weddell Sea  

NASA Astrophysics Data System (ADS)

The ice formation resulting from two low temperature events at the Weddell Sea ice edge during April 2000 is presented. Pancake and frazil ice were sampled at seven stations at varying distances from the ice edge. The ice cover was further characterized from above, using helicopter aerial photography, and from below, using a remotely operated vehicle. Previously undescribed two-layer pancake types were observed and classified. A novel pancake growth mechanism is introduced to account for these, involving the washing of frazil ice over the pancake top surface and its subsequent freezing. The process was directly observed in ice tank experiments. Layer thicknesses seen in the field were compared to the ice growth that would occur both under calm conditions and from free-surface frazil ice growth. Classical, bottom accretion, pancake growth was found to proceed at a rate similar to that of thin congelation ice. Top-layer growth was more rapid, at approximately double the congelation rate. Overall ice volume production was similar to congelation ice for the thin pancakes considered (˜20 cm), though subsequent thickening was expected to be faster as the rapid top-layer process continued and the equivalent congelation growth slowed. It is suggested that parameterization of this new process is important for models that aim to simulate the rapid advance and thickening of wave-influenced ice covers.

Doble, Martin J.; Coon, Max D.; Wadhams, Peter

2003-07-01

309

Low-frequency variability in the arctic atmosphere, sea ice, and upper-ocean climate system  

SciTech Connect

The low-frequency natural variability of the arctic climate system is modeled using a single-column, energy balance model of the atmosphere, sea ice, and upper-ocean system. Variability in the system is induced by forcing with realistic, random perturbations in the atmospheric energy transport and cloudiness. The model predicts that the volume of perennial sea ice varies predominantly on decadal timescales, while other arctic climate variables vary mostly on intraannual and interannual timescales. The variance of the simulated sea ice volume is most sensitive to perturbations of the atmospheric forcing in late spring, at the onset of melt. The variance of the simulated sea ice volume is most sensitive to perturbations of the atmospheric forcing in the late spring, at the onset of melt. The variance of sea ice volume increases with the mean sea ice thickness and with the number of layers resolved in the sea ice model. This suggests that much of the simulated variance develops when the surface temperature decouples from the sea ice interior during the late spring, when melting snow abruptly exposes the sea ice surface and decreases the surface albedo. The minimum model requirements to simulate the natural variability in the arctic climate are identified. The implications of the low-frequency, natural variability in sea ice volume for detecting a climate change are discussed. Finally, calculations suggest that the variability in the thermodynamic forcing of the polar cap could lead to a freshening in North Atlantic that is comparable to the freshening associated with the Great Salinity Anomaly. 28 refs., 14 figs., 5 tabs.

Bitz, C.M.; Battisti, D.S. [Univ. of Washington, Seattle, WA (United States); Moritz, R.E. [Univ. of Washington, Seattle, WA (United States); Beesley, J.A. [Univ. of Washington, Seattle, WA (United States)

1996-02-01

310

The central role of diminishing sea ice in recent Arctic temperature amplification.  

PubMed

The rise in Arctic near-surface air temperatures has been almost twice as large as the global average in recent decades-a feature known as 'Arctic amplification'. Increased concentrations of atmospheric greenhouse gases have driven Arctic and global average warming; however, the underlying causes of Arctic amplification remain uncertain. The roles of reductions in snow and sea ice cover and changes in atmospheric and oceanic circulation, cloud cover and water vapour are still matters of debate. A better understanding of the processes responsible for the recent amplified warming is essential for assessing the likelihood, and impacts, of future rapid Arctic warming and sea ice loss. Here we show that the Arctic warming is strongest at the surface during most of the year and is primarily consistent with reductions in sea ice cover. Changes in cloud cover, in contrast, have not contributed strongly to recent warming. Increases in atmospheric water vapour content, partly in response to reduced sea ice cover, may have enhanced warming in the lower part of the atmosphere during summer and early autumn. We conclude that diminishing sea ice has had a leading role in recent Arctic temperature amplification. The findings reinforce suggestions that strong positive ice-temperature feedbacks have emerged in the Arctic, increasing the chances of further rapid warming and sea ice loss, and will probably affect polar ecosystems, ice-sheet mass balance and human activities in the Arctic. PMID:20428168

Screen, James A; Simmonds, Ian

2010-04-29

311

Influence of ice and snow covers on the UV exposure of terrestrial microbial communities: dosimetric studies.  

PubMed

Bacillus subtilis spore biological dosimeters and electronic dosimeters were used to investigate the exposure of terrestrial microbial communities in micro-habitats covered by snow and ice in Antarctica. The melting of snow covers of between 5- and 15-cm thickness, depending on age and heterogeneity, could increase B. subtilis spore inactivation by up to an order of magnitude, a relative increase twice that caused by a 50% ozone depletion. Within the snow-pack at depths of less than approximately 3 cm snow algae could receive two to three times the DNA-weighted irradiance they would receive on bare ground. At the edge of the snow-pack, warming of low albedo soils resulted in the formation of overhangs that provided transient UV protection to thawed and growing microbial communities on the soils underneath. In shallow aquatic habitats, thin layers of heterogeneous ice of a few millimetres thickness were found to reduce DNA-weighted irradiances by up to 55% compared to full-sky values with equivalent DNA-weighted diffuse attenuation coefficients (K(DNA)) of >200 m(-1). A 2-mm snow-encrusted ice cover on a pond was equivalent to 10 cm of ice on a perennially ice covered lake. Ice covers also had the effect of stabilizing the UV exposure, which was often subject to rapid variations of up to 33% of the mean value caused by wind-rippling of the water surface. These data show that changing ice and snow covers cause relative changes in microbial UV exposure at least as great as those caused by changing ozone column abundance. PMID:12208033

Cockell, Charles S; Rettberg, Petra; Horneck, Gerda; Wynn-Williams, David D; Scherer, Kerstin; Gugg-Helminger, Anton

2002-08-01

312

Small antennas for communication over sea ice  

NASA Astrophysics Data System (ADS)

The invention described herein relates to an antenna system which makes use of the waveguide properties of sea ice. The antenna system broadly includes at least one antenna wire extending along and preferably in contact with a sea ice surface for transmitting and receiving substantially vertically polarized radio waves. In a first embodiment, the antenna system has a single antenna wire connected to a tuner at one end and grounded to seawater at a second end. The antenna system also has a second length of wire attached to the tuner. The second wire passes through a hole in the sea ice and is also grounded to the seawater beneath the sea ice. In an alternative embodiment, only the second wire is grounded to the seawater beneath the sea ice. The single antenna wire in this embodiment is ungrounded. In yet another embodiment, the antenna system comprises a dipole antenna wire laying on the surface of the sea ice and being connected to a radio for transmitting and receiving radio signals.

Mileski, Paul

1993-10-01

313

Testing of a coupled ice-ocean model in a sea ice forecasting system  

Microsoft Academic Search

The Naval Research Laboratory has developed a coupled ice-ocean model which covers most of the sea ice-covered regions of the Northern Hemisphere. This model was designed to replace the three existing Navy sea ice forecast systems: the Polar Ice Prediction System (PIPS) and the two regional systems, the Polar Ice Prediction System-Barents Sea (RPIPS-B)-and the Polar Ice Prediction System-Greenland Sea

R. H. Preller; P. G. Posey

1994-01-01

314

Summer Sea ice in the Pacific Arctic sector from the CHINARE-2010 cruise  

NASA Astrophysics Data System (ADS)

The Fourth Chinese National Arctic Research Expedition (CHINARE) from July 1 to Sep. 23, 2010, the last Chinese campaign in Arctic Ocean contributing to the fourth International Polar Year (IPY), conducted comprehensive scientific studies on ocean-ice-atmosphere interaction and the marine ecosystem’s response to climatic change in Arctic. This paper presents an overview on sea ice (ice concentration, floe size, melt pond coverage, sea ice and snow thickness) of the Pacific Arctic sector, in particular between 150°W to 180°W to 86°N, based on: (1) underway visual observations of sea ice at half-hourly and automatic cameras recording (both side looking from the icebreaker R.V. Xuelong) every 10 to 15 seconds; (2) a downward-looking video mounted on the left side of the vessel at a height of 7 m above waterline recording overturning of ice floes; (3) on-site measurements of snow and ice thickness using drilling and electromagnetic instrument EM31 (9.8 kHz) at eight short-term (~3 hours each) and one 12-day ice stations; (4) six flights of aerial photogrammetry from helicopter, and (5) Satellite data (AMSE-E ice concentration and ENVISAT ASAR) and NIC ice charts) that extended the observations/measurements along beyond the ship track and airborne flights. In the northward leg, the largest ice concentration zone was in the area starting from ~75°N (July 29), with ice concentration of 60-90% (mean ~80%), ice thickness of 1.5-2m, melt ponds of 10-50% of ice, ridged ice of 10-30% of ice, and floe size of 100’s meters to kms. The 12-day ice station (from Aug 7-19), started at 86.92°N/178.88°W and moved a total of 175.7km, was on an ice floe over 100 km2 in size and ~2 m in mean thickness. There were two heavy and several slight snowfall events in the period (July 29 to Aug 19). Snow thickness varies from 5cm to 15 cm, and melted about 5cm during the 12-day ice camp. In the southward leg, the largest sea ice concentration zone was in the area between 87°N to 80°N (from August 21 to August 24). In this area, the ice concentration varied from 70-100%, melt pond varied from 20-50% of ice, ridged ice varied from 10-30% of ice, and floe size was dominated by 10’s km to several km’s in one or two dimensions. The overall ice thickness decreased southward from 1.8-2m to 0.6-1m. The ice type of the area is multiyear ice dominated, with small portion of first year ice. In the area from ~85°N to 83.5°N, we see dirty ice (brownish, rich hills and valleys, mostly multiyear ice), varying from 10-20% of ice. Similar dirty ice was only seen from 72°N-75°N in the northward leg (July 24-29), then not seen until the northern region. The ice situation in this cruise will be compared with that from the CHINARE-2008 cruise, in a similar area and season, so change of the two years for this sector of Arctic Ocean during the middle-later summer can be deduced.

Ackley, S. F.; Xie, H.; Lei, R.; Huang, W.; Chinare 2010 Arctic Sea Ice Group

2010-12-01

315

Development of a sampling and flow injection analysis technique for iron determination in the sea ice environment  

Microsoft Academic Search

A trace metal clean method for sampling and analysis of iron is set up and applied to sea ice and its associated snow, brine, and underlying seawater sampled during the Antarctic expedition “ARISE in the East” (Antarctic Remote Ice Sensing Experiment, AA03-V1, September–October 2003, 64–65°S\\/112–119°E, RV Aurora Australis). For clean sampling, a non-contaminating electropolished stainless steel ice corer is designed

Delphine Lannuzel; Jeroen de Jong; Véronique Schoemann; Anne Trevena; Jean-Louis Tison; Lei Chou

2006-01-01

316

Spatial and temporal variability of Arctic summer sea-ice albedo and its dependence on meltwater hydraulics  

Microsoft Academic Search

Next to ice extent and thickness, the area-averaged albedo of the summer sea-ice cover is a key parameter in determining the large-scale heat exchange over the Arctic Ocean. Various remote sensing applications have yielded a substantial data base for the former two parameters, not least due to the efforts of the National Snow and Ice Data Center (NSIDC) over the

H. Eicken; D. K. Perovich; T. C. Grenfell; J. A. Richter-Menge; K. Frey

2001-01-01

317

An Impact of Subgrid-Scale Ice–Ocean Dynamics on Sea-Ice Cover  

Microsoft Academic Search

A coupled sea-ice-ocean numerical model is used to study the impact of an ill-resolved subgrid-scale sea- ice-ocean dynamical process on the areal coverage of the sea-ice field. The process of interest is the transmission of stress from the ocean into the sea-ice cover and its subsequent interaction with the sea-ice internal stress field. An idealized experiment is performed to highlight

David M. Holland

2001-01-01

318

Simultaneous retrieval of aerosol and surface properties over bright targets including snow and ice using multi- and hyperspectral data  

NASA Astrophysics Data System (ADS)

Retrieval of surface properties of highly reflecting targets such as snow and ice is a challenging problem due to the influence of aerosols which varies considerably in space and time. Also, accounting for the bidirectional properties of a bright surface such as snow is very important for reliable retrievals. The main purpose of the work described in this paper is to explore the opportunities and possibilities offered by multi- and hyperspectral data such as those available provided by MODIS, GLI, the Advanced Land Imager (ALI), and Hyperion to retrieve reliable aerosol and surface properties. Over snow and ice surfaces these include aerosol optical depth and single scattering albedo, the mean size of snow grains and ice "particles" (inclusions), and the spectral and broadband snow/ice albedo. In particular the following question will be addressed: To what extent can multi- and hyperspectral data help improve our knowledge of snow and ice parameters that are important for understanding global climate change?

Stamnes, Knut; Li, Wei; Spurr, Robert; Eide, Hans A.; Stamnes, Jakob J.

2004-11-01

319

Transition from the DMSP SSM/I to SSMIS sensors for NSIDC near-real-time snow and ice climate records  

NASA Astrophysics Data System (ADS)

The National Snow and Ice Data Center (NSIDC) Distributed Active Archive Center (DAAC) distributes numerous satellite derived snow and ice data products that rely on the Defense Meteorological Satellite Program (DMSP) passive microwave SSM/I (Special Sensor Microwave/Imager) and SSMIS (Special Sensor Microwave Imager/Sounder) sensors. The SSM/I sensor started collecting data in 1987, providing a continuous record of snow and sea ice for over two decades. As capabilities developed to produce near-real-time products, interest in such products increased. As a result there are now expectations from both the scientific community and the general public to have continuous access to reasonably reliable near-real-time climate parameters (e.g., sea ice concentration). When sensors or satellites fail or are decommissioned, a transition must be made to continue the data time-series in a consistent manner. The recent failure of the F-13 SSM/I sensor created, for the first time, a need for NSIDC to transition its near-real-time snow and ice products to rely on a new sensor and platform (F-17 SSMIS). The process that surrounds such a transition is usually long and detail intensive, accomplished over several months. However, with demand high for immediate climate information, NSIDC was on a tight schedule to develop and implement a near-real-time inter-sensor calibration that would enable a seamless transition of its near-real-time snow and ice products, while maintaining a high-standard for data consistency and quality for scientific investigation of the cryosphere. This poster provides an overview of the process required and obstacles encountered, to continue the satellite data record for a highly popular and consistent line of products made available by NSIDC.

Gibbons, P.; Meier, W.; Scott, D.

2010-12-01

320

Sea-ice dynamics strongly promote Snowball Earth initiation and destabilize tropical sea-ice margins  

NASA Astrophysics Data System (ADS)

The Snowball Earth bifurcation, or runaway ice-albedo feedback, is defined for particular boundary conditions by a critical CO2 and a critical sea-ice cover (SI), both of which are essential for evaluating hypotheses related to Neoproterozoic glaciations. Previous work has shown that the Snowball Earth bifurcation, denoted as (CO2, SI)*, differs greatly among climate models. Here, we study the effect of bare sea-ice albedo, sea-ice dynamics and ocean heat transport on (CO2, SI)* in the atmosphere-ocean general circulation model ECHAM5/MPI-OM with Marinoan (~ 635 Ma) continents and solar insolation (94% of modern). In its standard setup, ECHAM5/MPI-OM initiates a~Snowball Earth much more easily than other climate models at (CO2, SI)* ? (500 ppm, 55%). Replacing the model's standard bare sea-ice albedo of 0.75 by a much lower value of 0.45, we find (CO2, SI)* ? (204 ppm, 70%). This is consistent with previous work and results from net evaporation and local melting near the sea-ice margin. When we additionally disable sea-ice dynamics, we find that the Snowball Earth bifurcation can be pushed even closer to the equator and occurs at a hundred times lower CO2: (CO2, SI)* ? (2 ppm, 85%). Therefore, the simulation of sea-ice dynamics in ECHAM5/MPI-OM is a dominant determinant of its high critical CO2 for Snowball initiation relative to other models. Ocean heat transport has no effect on the critical sea-ice cover and only slightly decreases the critical CO2. For disabled sea-ice dynamics, the state with 85% sea-ice cover is stabilized by the Jormungand mechanism and shares characteristics with the Jormungand climate states. However, there is no indication of the Jormungand bifurcation and hysteresis in ECHAM5/MPI-OM. The state with 85% sea-ice cover therefore is a soft Snowball state rather than a true Jormungand state. Overall, our results demonstrate that differences in sea-ice dynamics schemes can be at least as important as differences in sea-ice albedo for causing the spread in climate models' estimates of the Snowball Earth bifurcation. A detailed understanding of Snowball Earth initiation therefore requires future research on sea-ice dynamics to determine which model's simulation is most realistic.

Voigt, A.; Abbot, D. S.

2012-12-01

321

Sea-ice dynamics strongly promote Snowball Earth initiation and destabilize tropical sea-ice margins  

NASA Astrophysics Data System (ADS)

The Snowball Earth bifurcation, or runaway ice-albedo feedback, is defined for particular boundary conditions by a critical CO2 and a critical sea-ice cover (SI), both of which are essential for evaluating hypotheses related to Neoproterozoic glaciations. Previous work has shown that the Snowball Earth bifurcation, denoted as (CO2, SI)*, differs greatly among climate models. Here, we revisit the initiation of a Snowball Earth in the atmosphere-ocean general circulation model ECHAM5/MPI-OM for Marinoan (~630 Ma) continents and solar insolation decreased to 94%. In its standard setup, ECHAM5/MPI-OM initiates a Snowball Earth much more easily than other climate models at (CO2, SI)* ? (500 ppm, 55%). Previous work has shown that the Snowball Earth bifurcation can be pushed equatorward if a low bare sea ice albedo is assumed because bare sea ice is exposed by net evaporation in the descent region of the Hadley circulation. Consistent with this, when we replace the model's standard bare sea-ice albedo of 0.75 by a much lower value of 0.45, we find (CO2, SI)* ? (204 ppm, 70%). When we additionally disable sea-ice dynamics, we find that the Snowball Earth bifurcation can be pushed even closer to the equator and occurs at a much lower CO2: (CO2, SI)* ? (2 ppm, 85%). Therefore, both lowering the bare sea-ice albedo and disabling sea-ice dynamics increase the critical sea-ice cover in ECHAM5/MPI-OM, but sea-ice dynamics have a much larger influence on the critical CO2. For disabled sea-ice dynamics, the state with 85% sea-ice cover is stabilized by the Jormungand mechanism and shares characteristics with the Jormungand climate states. However, there is no Jormungand bifurcation between this Jormungand-like state and states with mid-latitude sea-ice margins. Our results indicate that differences in sea-ice dynamics schemes can be as important as sea ice albedo for causing the spread in climate model's estimates of the location of the Snowball Earth bifurcation.

Voigt, A.; Abbot, D. S.

2012-07-01

322

Sea ice mechanics in Arctic Ocean dynamics (Invited)  

NASA Astrophysics Data System (ADS)

Realistic models of sea ice processes and properties are needed to assess sea ice thickness, extent and concentration and, when run within GCMs, provide prediction of climate change. However, there are currently fundamental problems with sea ice dynamical models. Specifically, ad hoc tuning of model parameters such as ice strength and air to ocean drag ratios are employed in order to reproduce data sets of sea ice extent, concentration and buoy motion. Parameter tuning is required because current sea ice models, up till recently, have not resolved physical processes below grid sizes of 100km. Such tuning can, at best, provide a good fit to reality over limited periods of time. As ice floes are of typical dimension of 0.1-10km, the continuity assumption breaks down below 100km so that discontinuities in, e.g., ice velocity, thickness and motion, cannot be modelled. I present some recent experimental results in sea ice mechanics from mid-scale experiments, conducted in the Hamburg model ship ice tank, simulating sea ice floe motion and interaction. I examine the scaling relations of the slip of sea ice floes, the micro-mechanics of sea ice friction and how a simple two-parameter model, describing the mechanical state and slip rate of the floes, can capture key elements of sea ice rheology. I then discuss the methodology of how sub-continuum scale material rheology of sea ice and configuration of sea ice floes and leads has been incorporated into models.

Sammonds, P.

2009-12-01

323

Improving the spatial distribution of modeled Arctic sea ice thickness  

Microsoft Academic Search

The spatial distribution of ice thickness\\/draft in the Arctic Ocean is examined using a sea ice model. A comparison of model predictions with submarine observations of sea ice draft made during cruises between 1987 and 1997 reveals that the model has the same deficiencies found in previous studies, namely ice that is too thick in the Beaufort Sea and too

Paul A. Miller; Seymour W. Laxon; Daniel L. Feltham

2005-01-01

324

Active Microwave Measurements of Artificial Sea Ice.  

National Technical Information Service (NTIS)

A 5 m x 15 m outdoor tank of 1.2 m depth was filled with sea water, and polarimetric radar backscatter data were collected at 1.8, 5, and 10 GHz for incidence angles 0 to 60 deg. Observations commenced with open water and continued until 30 cm of sea ice ...

R. G. Onstott S. H. Gaboury J. Bredow P. Gogineni

1988-01-01

325

Transmission of sunlight through melting Arctic sea ice (Invited)  

Microsoft Academic Search

The transmission of solar radiation through sea ice affects internal warming and melting of the ice cover, contributes heat to the ocean, and determines light availability for primary productivity within and beneath the ice cover. In situ measurements of the spectral extinction of shortwave radiation in sea ice were made for both bare and ponded multiyear ice and bare first-year

B. Light; D. K. Perovich; T. C. Grenfell; K. Runciman

2009-01-01

326

Summer Sea Ice Albedo in the Arctic in CMIP5 models  

NASA Astrophysics Data System (ADS)

Spatial and temporal variations of summer sea ice albedo over the Arctic are analyzed using an ensemble of historical CMIP5 model simulations. The results are compared to the CLARA-SAL product that is based on long-term satellite observations. The summer sea ice albedo varies substantially among CMIP5 models and many models show large biases compared to the CLARA-SAL product. Single summer months show an extreme spread of ice albedo among models; July-values vary between 0.3 and 0.7 for individual models. The CMIP5 ensemble mean, however, agrees relatively well in the Central Arctic but shows too high ice albedo near the ice edges and coasts. In most models, the ice albedo is spatially too uniformly distributed. The summer to summer variations seem to be underestimated in many global models and almost no model is able to fully reproduce the temporal evolution of ice albedo throughout the summer. While the satellite observations indicate the lowest ice albedos during August, the models show minimum values in July and substantially higher values in August. Instead, the June values are often lower in the models than in the satellite observations. This is probably due to too high surface temperatures in June, leading to an early start of the melt season and too cold temperatures in August causing an earlier refreezing in the models. The summer sea ice albedo in the CMIP5 models is strongly governed by surface temperature and snow conditions, particularly during the period of melt onset in early summer and refreezing in late summer. The summer surface net solar radiation of the ice covered Arctic areas is highly related to the ice albedo in the CMIP5 models. However, the impact of the ice albedo on the sea ice conditions in the CMIP5 models is not clearly visible. This indicates the importance of other Arctic and large scale processes for the sea ice conditions.

Koenigk, T.; Devasthale, A.; Karlsson, K.-G.

2013-09-01

327

Arctic sea ice freeboard from CryoSat-2: Validation using data from the first IceBridge underflight  

NASA Astrophysics Data System (ADS)

Exact determination of thickness changes in Arctic sea ice is a primary goal of ESA's CryoSat-2 mission. Since its launch on April 8, 2010, CryoSat has collected data to map sea ice thickness and thereby monitor climate-driven ice thickness change. On April 20, 2010 just 12 days after CryoSat's launch - during NASA's IceBridge Spring 2010 campaign, the NASA DC-8 conducted a spatially and temporally coincident survey along some 670 km of a CryoSat ground-track in the northernmost Arctic Ocean. The DC-8 survey was flown out and back along the CryoSat ground-track. The DC-8 collected two laser altimetry datasets: (1) Laser Vegetation Imaging Sensor (LVIS) data, and (2) scanning laser Airborne Topographic Mapper (ATM) data. IceBridge also collected a number of other important data types including digital photography of sea ice, snow thickness radar, Ku-band radar altimetry and gravimetry, which are coincident and nearly simultaneous with SAR-mode Synthetic aperture Interferometric Radar ALtimeter (SIRAL) data collected by CryoSat. LVIS data were collected on the outbound high-altitude (25,000 feet) flight leg while ATM data were collected on the return, low-altitude (1500 feet) flight leg. CryoSat's SIRAL altimeter data are used to retrieve freeboard, i.e., the height of the ice surface above that of the local sea surface (observed in leads). Freeboard can be used to estimate sea ice thickness by assuming the ice is in isostatic equilibrium. In this investigation we compare freeboard retrievals from CryoSat with freeboard estimates derived using IceBridge data. Corrections for snow thickness are applied using IceBridge radar data. Freeboards retrieved using (a) LVIS data and (b) ATM data, are compared with CryoSat freeboard estimates. These two comparisons taken together provide an important assessment of CryoSat's capabilities to precisely map freeboard and thickness change of Arctic sea ice.

Connor, L. N.; Laxon, S. W.; McAdoo, D. C.; Ridout, A.; Cullen, R.; Farrell, S.; Francis, R.

2011-12-01

328

A model for the consolidation of rafted sea ice  

Microsoft Academic Search

Rafting is one of the important deformation mechanisms of sea ice. This process is widespread in the north Caspian Sea, where multiple rafting produces thick sea ice features, which are a hazard to offshore operations. Here we present a one-dimensional, thermal consolidation model for rafted sea ice. We consider the consolidation between the layers of both a two-layer and a

E. Bailey; D. L. Feltham; P. R. Sammonds

2010-01-01

329

Age and thickness distribution of polynya sea ice in the Laptev Sea determined by satellite SAR imagery and airborne EM  

NASA Astrophysics Data System (ADS)

The importance and annual amount of sea ice volume produced during polyna opening events in the Siberian Laptev Sea is still controversially discussed. So far, published information about sea ice volume production are purely based on indirect thickness measurements of thin ice using remote sensing techniques or on computer simulations of sea ice growth based on reanalysis climate data. We recorded a sea ice thickness transect of approximately 160 km length using helicopter electromagnetics (HEM) in the region of the so called West New Siberian (WNS) Polynya located directly north of the Lena delta in April 2008. In addition, a time series of synthetic aperture radar (SAR) images covering the complete polynya region was analyzed and ice area fragments were tracked from their origin to the moment when we recorded their thickness. Both data sets together, HEM and SAR, provide the opportunity to classify overflown ice areas in terms of age, area and thickness and therefore in terms of volume. From December 2007 to April 2008 approximately 50.000 km2 of sea-ice area was produced in the WNS polynya, which is more than the size of Switzerland. The youngest surveyed sea-ice was 6 days old and had a mean total and a mean level-ice thickness of 0.2 m. The oldest surveyed ice floe had an age of 104 days and a mean total thickness of 2.4 +/- 0.3 m and a mean level ice thickness of 1.8 +/- 0.3 m. The error is based on the HEM instrument accuracy and a lag of snow thickness data. Assuming that ice thickness along the HEM transect was representative for entire overflown ice areas, our calculations result that the produced sea ice area contained a volume of approximately 86 km3. This is about 1.8 % of the Arctic wide ice production between October 2007 and March 2008, as it was published by Kwok et al. 2009 on the basis of ICE-Sat ice thickness data. The combined HEM and SAR study enabled us furthermore to analyze thickness vs. age relations of first year ice floes. Mean thickness showed to be a bad indicator for ice age determination and vice versa, due to the dynamic component of sea-ice growth. The most surprising result was a 16 days old ice floe which was piled up to deformed sea ice with a mean thickness of 2.4 m. Mean level-ice thickness is a far better indicator for ice age, although we found mean thickness variations for level ice of the same age of about 0.5 m. Reference: Kwok, R., Cunningham, G.F., Wensnahan, M., Rigor, I., Zwally, H.J., Yi,D., Thinning and volume loss of the Arctic Ocean sea ice cover: 2003-2008, Journal of Geophysical Research, 114, 2009

Rabenstein, L.; Krumpen, T.; Hendricks, S.; Hoelemann, J.

2012-04-01

330

Ice core evidence for a 20th century decline of sea ice in the Bellingshausen Sea, Antarctica  

Microsoft Academic Search

This study uses ice core methanesulphonic acid (MSA) records from the Antarctic Peninsula, where temperatures have been warming faster than anywhere else in the Southern Hemisphere, to reconstruct the 20th century history of sea ice change in the adjacent Bellingshausen Sea. Using satellite-derived sea ice and meteorological data, we show that ice core MSA records from this region are a

Nerilie J. Abram; Elizabeth R. Thomas; Joseph R. McConnell; Robert Mulvaney; Thomas J. Bracegirdle; Louise C. Sime; Alberto J. Aristarain

2010-01-01

331

Anisotropic Continuum Model of Granulated Sea Ice  

NASA Astrophysics Data System (ADS)

A continuum model describing sea ice as a layer of granulated thick ice intersected by long and narrow regions of thinner ice, leads, is developed. Sea ice is considered to be a two-dimensional granular material, whose deformation occurs through motion of floes generated in ice fracturing under applied stress. We consider dynamics of mesoscale leads generated under tensile stress, whose dimensions is larger than those of floes, so that deformation of the surrounding ice is described through the granular plastic rheology, but still sufficiently smaller than the basin scale, so that they can be modelled using continuum approach. The model consists of the stress expression depending on orientational distribution of lead characteristics, thick ice thickness and rheology. It also includes evolution equations for the orientational distribution of leads, their thickness and width expressed through second-rank tensors. The results of the calculations show that the model produces reasonable behaviour in simple flows. The consideration of the thick ice as granular material elliminates the problem of infinite lead opening under pure shear produced by an earlier model considering thick ice deformation only through ridging.

Wilchinsky, A. V.; Feltham, D. L.

2004-12-01

332

Tracer studies of pathways and rates of meltwater transport through Arctic summer sea ice  

NASA Astrophysics Data System (ADS)

At the Surface Heat Budget of the Arctic Ocean (SHEBA) program's field site in the northern Chukchi Sea, snow and ice meltwater flow was found to have a strong impact on the heat and mass balance of sea ice during the summer of 1998. Pathways and rates of meltwater transport were derived from tracer studies (H218O, 7Be, and release of fluorescent dyes), complemented by in situ sea-ice permeability measurements. It was shown that the balance between meltwater supply at the surface (averaging between 3.5 and 10.5 mm d-1) and ice permeability (between <10-11 and >10-9 m2) determines the retention and pooling of meltwater, which in turn controls ice albedo. We found that the seasonal evolution of first-year and multiyear ice permeability and surface morphology determine four distinct stages of melt. At the start of the ablation season (stage 1), ponding is widespread and lateral melt flow dominates. Several tens of cubic meters of meltwater per day were found to drain hundreds to thousands of square meters of ice through flaws and permeable zones. Significant formation of underwater ice, composed between <30 and >50% of meteoric water, formed at these drainage sites. Complete removal of snow cover, increase in ice permeability, and reductions in hydraulic gradients driving fluid flow mark stage 2, concurrent with a reduction in pond coverage and albedo. During stage 3, maximum permeabilities were measured, with surface meltwater penetrating to 1 m depth in the ice and convective overturning and desalination found to dominate the lower layers of first-year and thin multiyear ice. Enhanced fluid flow into flaws and permeable zones was observed to promote ice floe breakup and disintegration, concurrent with increases in pond salinities and 7Be. Advective heat flows of several tens of watts per square meter were derived, promoting widening of ponds and increases in pond coverage. Stage 4 corresponds to freeze-up. Roughly 40% of the total surface melt was retained by the ice cover within the ice matrix as well as in surface and under-ice ponds (with a total net retention of 15%). Based on this work, areas of improvement for fully prognostic simulations of ice albedo are identified, calling for parameterizations of sea-ice permeability and the integration of ice topography and refined ablation schemes into atmosphere-ice-ocean models.

Eicken, H.; Krouse, H. R.; Kadko, D.; Perovich, D. K.

2002-10-01

333

A review of sea ice proxy information from polar ice cores  

NASA Astrophysics Data System (ADS)

Sea ice plays an important role in Earth's climate system. The lack of direct indications of past sea ice coverage, however, means that there is limited knowledge of the sensitivity and rate at which sea ice dynamics are involved in amplifying climate changes. As such, there is a need to develop new proxy records for reconstructing past sea ice conditions. Here we review the advances that have been made in using chemical tracers preserved in ice cores to determine past changes in sea ice cover around Antarctica. Ice core records of sea salt concentration show promise for revealing patterns of sea ice extent particularly over glacial–interglacial time scales. In the coldest climates, however, the sea salt signal appears to lose sensitivity and further work is required to determine how this proxy can be developed into a quantitative sea ice indicator. Methane sulphonic acid (MSA) in near-coastal ice cores has been used to reconstruct quantified changes and interannual variability in sea ice extent over shorter time scales spanning the last ˜160 years, and has potential to be extended to produce records of Antarctic sea ice changes throughout the Holocene. However the MSA ice core proxy also requires careful site assessment and interpretation alongside other palaeoclimate indicators to ensure reconstructions are not biased by non-sea ice factors, and we summarise some recommended strategies for the further development of sea ice histories from ice core MSA. For both proxies the limited information about the production and transfer of chemical markers from the sea ice zone to the Antarctic ice sheets remains an issue that requires further multidisciplinary study. Despite some exploratory and statistical work, the application of either proxy as an indicator of sea ice change in the Arctic also remains largely unknown. As information about these new ice core proxies builds, so too does the potential to develop a more comprehensive understanding of past changes in sea ice and its role in both long and short-term climate changes.

Abram, Nerilie J.; Wolff, Eric W.; Curran, Mark A. J.

2013-11-01

334

Snow Facies Over Ice Sheets Derived From Envisat Active and Passive Observations  

Microsoft Academic Search

This paper aims to separate different snow regions over the terrestrial ice sheets based on their measured microwave signatures. It takes advantage of coregistered data from passive and active sensors on the Environmental Satellite (Envisat) to directly derive a snow facies indicator in a point-by-point basis. This paper represents the first attempt of this kind in exploiting nadir-viewing and dual-frequency

Ngan Tran; Frédérique Rémy; Hui Feng; Pierre Féménias

2008-01-01

335

Snow-ice-tephra-lava interactions during the 2010 Fimmvorduhals eruption  

Microsoft Academic Search

On March 20th a small basaltic fissure opened at the northern edge of Fimmvorduhals, a popular hiking pass between Eyjafjallajökull, to the west, and Myrdalsjökull, to the east. Immediately prior to the eruption, the vent area was covered with typically 1-3 meters of snow and locally snow-covered, isolated remnants of glacial ice. Fieldwork conducted during June and July documented evidence

J. Haklar; B. R. Edwards; M. T. Gudmundsson

2010-01-01

336

Controls on Arctic sea ice from first-year and multi-year ice survival rates  

Microsoft Academic Search

The recent decrease in Arctic sea ice cover has transpired with a significant loss of multi-year (MY) ice. The transition to an Arctic that is populated by thinner first-year (FY) sea ice has important implications for future trends in area and volume. We develop a reduced model for Arctic sea ice with which we investigate how the survivability of FY

K. Armour; C. M. Bitz; E. C. Hunke; L. Thompson

2009-01-01

337

A methodology to eliminate snow- and ice-contaminated solutions from GPS coordinate time series  

NASA Astrophysics Data System (ADS)

derived from continuously operating GPS sites are used throughout the world for geophysical research. These positions are estimated assuming that the GPS signals have not been obstructed by either snow or ice on the GPS antenna. Unfortunately, in many regions of the world, this assumption is not correct. Snow and ice attenuate and scatter the GPS signal in a way that leads to significant positioning errors. These positioning outliers are typically removed by assuming geophysical models of displacement. In this study an algorithm is developed that uses signal strength data to determine when the GPS signal has been impacted by snow or ice. This information is then used to remove outliers in GPS coordinate time series. The signal strength-based algorithm was tested on 6 years of data from the EarthScope Plate Boundary Observatory network. The algorithm improves the precision of ~10% of these coordinate time series, with most of the improvement found for sites operating in Alaska.

Larson, Kristine M.

2013-08-01

338

National Snow and Ice Data Center (NSIDC): Antarctic Glaciers Accelerating in Response to 2002 Ice Sheet Collapse  

NSDL National Science Digital Library

This National Snow and Ice Data Center's (NSIDC) press release at this website addresses the new findings of Antarctic glacial melting. Students and educators can learn how satellite images assist scientists in studying Earth's changes. Visitors can find a map of the study area, images of the ice sheet, and a tutorial explaining why glacial melting has accelerated. The website offers an abstract of the scientific journal article thoroughly explaining the phenomenon. Individuals can find links to additional information about this new discovery.

339

Arctic Circle Traverse 2010 (ACT10): South East Greenland snow accumulation variability from firn coring and ice sounding radar  

Microsoft Academic Search

The Greenland Ice Sheet plays an important role in Earth's climate system evolution. The snow accumulation rate is the largest single mass budget term. With only 14% of the ice sheet area, Southeast Greenland contains the highest accumulation rates, accounting for one third of the total snow accumulation and annual variability. The high accumulation rates have made the region less

R. R. Forster; C. Miege; J. E. Box; J. McConnell; V. B. Spikes; E. W. Burgess

2010-01-01

340

76 FR 7238 - Pipeline Safety: Dangers of Abnormal Snow and Ice Build-Up on Gas Distribution Systems  

Federal Register 2010, 2011, 2012, 2013

...appear to have been related to either the stress of snow and ice or the malfunction of...appear to have been related to either the stress of snow and ice or malfunction of pressure...greatest risk. Damage may result from the stresses imposed by the additional loading of...

2011-02-09

341

Arctic sea ice decline and ice export in the CMIP5 historical simulations  

NASA Astrophysics Data System (ADS)

Arctic sea ice properties and Fram Strait ice export from six CMIP5 Global Climate and Earth System Models are evaluated and investigated for the period 1957–2005. Over the last decades most ensemble members simulate a decreasing September sea ice area and a slow, general thinning of the sea ice cover. While the different ensemble members both under- and overestimate the decline in observed September sea ice area, none of the members reproduce the observed thinning.

Langehaug, H. R.; Geyer, F.; Smedsrud, L. H.; Gao, Y.

2013-11-01

342

Improved identification of clouds and ice/snow covered surfaces in SCIAMACHY observations  

NASA Astrophysics Data System (ADS)

In the ultra-violet, visible and near infra-red wavelength range the presence of clouds can strongly affect the satellite-based passive remote sensing observation of constituents in the troposphere, because clouds effectively shield the lower part of the atmosphere. Therefore, cloud detection algorithms are of crucial importance in satellite remote sensing. However, the detection of clouds over snow/ice surfaces is particularly difficult in the visible wavelengths as both clouds an snow/ice are both white and highly reflective. The SCIAMACHY Polarisation Measurement Devices (PMD) Identification of Clouds and Ice/snow method (SPICI) uses the SCIAMACHY measurements in the wavelength range between 450 nm and 1.6 ?m to make a distinction between clouds and ice/snow covered surfaces, specifically developed to identify cloud-free SCIAMACHY observations. For this purpose the on-board SCIAMACHY PMDs are used because they provide higher spatial resolution compared to the main spectrometer measurements. In this paper we expand on the original SPICI algorithm (Krijger et al., 2005a) to also adequately detect clouds over snow-covered forests which is inherently difficult because of the similar spectral characteristics. Furthermore the SCIAMACHY measurements suffer from degradation with time. This must be corrected for adequate performance of SPICI over the full SCIAMACHY time range. Such a correction is described here. Finally the performance of the new SPICI algorithm is compared with various other datasets, such as from FRESCO, MICROS and AATSR, focusing on the algorithm improvements.

Krijger, J. M.; Tol, P.; Istomina, L. G.; Schlundt, C.; Schrijver, H.; Aben, I.

2011-10-01

343

Turbulence beneath sea ice and leads: A coupled sea ice/large-eddy simulation study  

NASA Astrophysics Data System (ADS)

The importance of leads, sea ice motion, and frazil ice on the wintertime ocean boundary layer was examined by using a large-eddy simulation turbulence model coupled to a thermodynamic slab ice model. Coupling was achieved through exchange coefficients that accounted for the differing diffusion rates of heat and salinity. Frazil ice concentrations were modeled by using an ice crystal parameterization with constant crystal size and shape. Stationary ice without leads produced cellular structures similar to atmospheric convection without winds. Ice motion caused this pattern to break down into a series of streaks aligned with the flow. Eddy fluxes were strongly affected by ice motion with relatively larger entrainment fluxes at the mixed layer base under moving ice, whereas stationary ice produced larger fluxes near the top of the boundary layer. Opening of leads caused significant changes in the turbulent structure of the boundary layer. Leads in stationary ice produced concentrated plumes of higher-salinity water beneath the lead. Ice motion caused the lead convection to follow preexisting convective rolls, enhancing the roll circulation salinity and vertical velocity under the lead. Comparison of model time series data with observations from the Arctic Leads Experiment showed general agreement for both pack ice and lead conditions. Simulated heat flux carried by frazil ice had a prominent role in the upper boundary layer, suggesting that frazil ice is important in the heat budget of ice-covered oceans.

Skyllingstad, Eric D.; Denbo, Donald W.

2001-02-01

344

Sea ice melting in the marginal ice zone.  

USGS Publications Warehouse

The heat and salt flux boundary conditions together with the freezing curve relationship are a necessary component of any ice- sea water thermodynamic model. A neutral two-layer oceanic planetary boundary layer model that incorporates these boundary conditions is used. The results are discussed. -from Author

Josberger, E. G.

1983-01-01

345

Rapid formation of a sea ice barrier east of Svalbard  

Microsoft Academic Search

Daily SeaWinds scatterometer images acquired by the QuikSCAT satellite show an elongated sea ice feature that formed very rapidly (~1-2 days) in November 2001 east of Svalbard over the Barents Sea. This sea ice structure, called ``the Svalbard sea ice barrier,'' spanning approximately 10° in longitude and 2° in latitude, restricts the sea route and poses a significant navigation hazard.

S. V. Nghiem; M. L. Van Woert; G. Neumann

2005-01-01

346

Rapid formation of a sea ice barrier east of Svalbard  

Microsoft Academic Search

Daily SeaWinds scatterometer images acquired by the QuikSCAT satellite show an elongated sea ice feature that formed very rapidly (?1–2 days) in November 2001 east of Svalbard over the Barents Sea. This sea ice structure, called “the Svalbard sea ice barrier,” spanning approximately 10° in longitude and 2° in latitude, restricts the sea route and poses a significant navigation hazard.

S. V. Nghiem; M. L. Van Woert; G. Neumann

2005-01-01

347

Assimilation of sea ice motion in a finite-element sea ice model  

NASA Astrophysics Data System (ADS)

A finite-element sea ice model (FESIM) is applied in a data assimilation study with the singular evolutive interpolated Kalman (SEIK) filter. The model has been configured for a regional Arctic domain and is forced with a combination of daily NCEP reanalysis data for 2-m air temperature and 10-m winds with monthly mean humidities from the ECMWF reanalysis and climatological fields for precipitation and cloudiness. We assimilate 3-day mean ice drift fields derived from passive microwave satellite data. Based on multivariate covariances (which describe the statistical relationship between anomalies in different model fields), the sea ice drift data assimilation produces not only direct modifications of the ice drift but also updates for sea ice concentration and thickness, which in turn yield sustainable corrections of ice drift. We use observed buoy trajectories as an independent data set to validate the analyzed sea ice drift field. A good agreement between modeled and observed tracks is achieved already in the reference simulation. Application of the SEIK filter with satellite-derived drift fields further improves the agreement. Spatial and temporal variability of ice thickness increases due to the assimilation procedure; a comparison to thickness data from a submarine-based upward looking sonar indicates that the thickness distribution becomes more realistic. Validation with regard to satellite data shows that the velocity data assimilation has only a small effect on ice concentration, but a general improvement of the ice concentration within the pack is still evident.

Rollenhagen, K.; Timmermann, R.; Janji?, T.; SchröTer, J.; Danilov, S.

2009-05-01

348

What About Sea Ice? People, animals, and climate change in the polar regions: An online resource for the International Polar Year and beyond  

NASA Astrophysics Data System (ADS)

Decreasing Arctic sea ice has been one of the most noticeable changes on Earth over the past quarter-century. The years 2002 through 2005 have had much lower summer sea ice extents than the long-term (1979-2000). Reduced sea ice extent has a direct impact on Arctic wildlife and people, as well as ramifications for regional and global climate. Students, educators, and the general public want and need to have a better understanding of sea ice. Most of us are unfamiliar with sea ice: what it is, where it occurs, and how it affects global climate. The upcoming International Polar Year will provide an opportunity for the public to learn about sea ice. Here, we provide an overview of sea ice, the changes that the sea ice is undergoing, and information about the relation between sea ice and climate. The information presented here is condensed from the National Snow and Ice Data Center's new 'All About Sea Ice' Web site (http://www.nsidc.org/seaice/), a comprehensive resource of information for sea ice.

Renfrow, S.; Meier, W. N.; Wolfe, J.; Scott, D.; Leon, A.; Weaver, R.

2005-12-01

349

Impact of subgrid-scale ice thickness distribution on heat flux on and through sea ice  

NASA Astrophysics Data System (ADS)

We evaluated the impact of subgrid-scale ice thickness distribution on the heat flux on and through sea ice in a numerical model. An ice-ocean coupled model with a subgrid-scale ice thickness distribution scheme, COCO4.5, is forced by an atmospheric climatology to simulate the present state of the sea ice and ocean. The modeled climatology reproduces the ice cover reasonably well with a realistic ice thickness distribution.

Komuro, Yoshiki; Suzuki, Tatsuo

2013-11-01

350

Climate implications of changing Arctic sea ice  

NASA Astrophysics Data System (ADS)

Straddling the mid-Atlantic ridge, Iceland may be best known to the world for its fiery volcanic history, violent earthquakes, and massive jökulhlaups—episodic outbursts of sub-glacial lakes melted by underlying magma. But this poem, written by Matthias Jochumsson in 1888 and titled simply “The Sea Ice” [Jochumsson, 1915] illustrates why the most insidious disruption to the Icelandic people is the havoc wrought by the quiet approach of sea ice. No other natural disaster has brought such cruelty famine, and death. From Jochumsson: “Where is the ocean, where is the bright, free, silvery ocean?… When you [sea ice] appear, the nation and its history are extinguished; then is death, and deep, dark night…”

Miller, Gifford H.; Geirsdottir, Áslaug; Koerner, Roy M.

351

Sea ice thickness from CryoSat2  

NASA Astrophysics Data System (ADS)

Arctic sea ice has undergone major changes in recent years but there remains much uncertainty about its ultimate fate, in particular the timing of an ice-free Arctic in summer. Although satellite measurements of ice extent are well-established, wide-area measurements of sea ice thickness are key to understanding the fate of Arctic sea ice cover in the future. Satellite altimeters can provide direct measurements of sea ice freeboard from which sea ice thickness can be calculated. We present the first data on sea ice thickness from Cryosat-2, validated by in situ and aircraft data. We describe the primary uncertainties for sea ice thickness retrieval, and outline strategies for addressing these in the future.

Laxon, S. W.; Ridout, A.; Giles, K. A.; Willatt, R. C.; Wingham, D.; Hendricks, S.; Haas, C.; Beckers, J.

2011-12-01

352

Morphology and Ecology of Diatoms in Sea Ice from the Weddell Sea.  

National Technical Information Service (NTIS)

Diatom species composition and relative abundances were determined for ice cores obtained from Weddell Sea pack ice during the October-November 1981 Weddell Polynya Expedition (WEPOLEX). Ice thickness and salinity indicate that the ice was less than one y...

D. B. Clarke S. F. Ackley M. Kumai

1984-01-01

353

Sea ice rheology and the sub-grid scale  

NASA Astrophysics Data System (ADS)

The sea ice component of global climate models (GCMs) must contain representations of sea ice stress appropriate to their spatial grid resolution. We explore the relationship between the sea ice stress and sub-grid scale floe and lead interaction using a clearly defined methodology. The calculation of GCM sea ice stress depends upon the assumed mechanical behaviour of sea ice, the geometry of floes and leads, and the manner in which a collection of floes and leads deform in response to large-scale atmospheric and oceanic forcing. We discuss the sensitivity of GCM sea ice stress to the sub-grid scale sea ice state, calculations using Radarsat SAR data coincident with the SHEBA site, and implications for sea ice modelling.

Taylor, P. D.; Feltham, D. L.; Sammonds, P.; Hatton, D.

2007-12-01

354

Anomalies of sea-ice transports in the Arctic  

Microsoft Academic Search

In the Arctic, sea-ice motion and ice export are prominent processes and good indicators of Arctic climate system variability. Sea-ice drift is simulated using a dynamic-thermodynamic sea-ice model, validated with retrievals from SSM\\/I satellite observations. Both datasets agree well in reproducing the main Arctic drift patterns. In order to study inner Arctic transports and ice volume anomalies, the Arctic Ocean

Torge Martin; Thomas Martin

2006-01-01

355

Mapping of ice layer extent and snow accumulation in the percolation zone of the Greenland ice sheet  

Microsoft Academic Search

The Greenland ice sheet underwent record extensive melt in 2002 and prolonged melt in 2003. The severe melting created a significant and extensive ice layer over the Greenland ice sheet. An innovative approach is developed to detect the ice layer formation using data acquired by the SeaWinds scatterometer on the QuikSCAT satellite. QuikSCAT backscatter together with in situ data from

S. V. Nghiem; K. Steffen; G. Neumann; R. Huff

2005-01-01

356

Energy and ozone fluxes over sea ice  

NASA Astrophysics Data System (ADS)

We present surface layer measurements made over Hudson Bay sea ice during February/March 2008 from the COBRA (Impact of combined iodine and bromine release on the Arctic atmosphere) experiment which formed part of the International OASIS (Ocean-Atmosphere-Sea Ice-Snowpack) IPY programme. All components of the local surface energy balance were measured and it was defined by net radiative cooling throughout most of the day, mainly balanced by the conductive heat flux from the warmer sea water to the cooler sea ice at the surface, and a small net radiative warming for a few hours after midday. Unique ground-level ozone fluxes were measured by eddy covariance and deposition velocities ranged from +0.5 mm s -1 (deposition) to -1.5 mm s -1 (emission). Ozone profile measurements suggested ozone flux divergence within the surface layer. The observed bi-directional fluxes and flux divergence with height reveal the complexity of surface ozone fluxes in the Arctic spring time surface layer, and show that ozone exchange with the sea ice surface is best probed using the eddy covariance method alongside frequent or continuous profile measurements. In this study, the local in-situ ozone-halogen photochemistry was identified as weakly controlling the measured ozone flux, whereas horizontal advection and vertical mixing were considered more important in influencing fluxes. Under these conditions, several measurement sites would be desirable in order to quantify the contribution of advection to the local surface exchange.

Muller, Jennifer B. A.; Dorsey, James R.; Flynn, Michael; Gallagher, Martin W.; Percival, Carl J.; Shallcross, Dudley E.; Archibald, Alexander; Roscoe, Howard K.; Obbard, Rachel W.; Atkinson, Helen M.; Lee, James D.; Moller, Sarah J.; Carpenter, Lucy J.

2012-02-01

357

Intercomparisons of Antarctic sea ice types from visual ship, RADARSAT-1 SAR, Envisat ASAR, QuikSCAT, and AMSR-E satellite observations in the Bellingshausen Sea  

NASA Astrophysics Data System (ADS)

Antarctic Sea Ice Processes and Climate (ASPeCt) visual ship-based observations were conducted in the Bellingshausen Sea during the Sea Ice Mass Balance in the Antarctic (SIMBA) cruise in austral spring 2007. A total of 59 ASPeCt observations are compared to coincident satellite active and passive microwave data. Envisat and RADARSAT-1 C-Band HH-polarization radar backscatter values (called NRCS henceforth) are derived on km-scales for six individual ice types and ice type mixtures. C-Band HH-polarized and Ku-Band VV-polarized NRCS are extracted on several 10 km-scale areas from coincident Envisat, RADARSAT-1, and QuikSCAT radar images for areas primarily covered with multiyear, deformed first-year, and undeformed young ice, as well as ice of the marginal ice zone (MIZ). The C-Band NRCS permits distinction between first-year, MIZ, and undeformed young ice. However, NRCS of the multiyear ice zone overlaps with that of the other ice zones and types. Ku-Band NRCS obtained for the same ice types permits discrimination of the first-year ice zone only. Obtained NRCS agree with those of previous studies and suggest a high degree of deformation and considerable potential for flooding for the first-year ice case. In comparison to large scale NRCS, AMSR-E snow depth values form two clearly separated clusters, one for 0.24-0.35 m depth (first-year ice zone) and one for 0.36-0.54 m depth (multiyear ice zone). However, a comparison to ASPeCt observations suggests a remarkable underestimation of the snow depth by AMSR-E in the multiyear-first-year-ice transition zone and for first-year cake ice. Nevertheless, a fusion of the coarse AMSR-E snow depth ranges for interior pack ice regions with radar imagery at large scale, appears promising for mapping the major zones (MIZ and Pack Ice) and ice types (first-year and multiyear) of Antarctic sea ice on a circumpolar basis.

Ozsoy-Cicek, Burcu; Kern, Stefan; Ackley, Stephen F.; Xie, Hongjie; Tekeli, Ahmet E.

2011-05-01

358

From the Sun to the Ice - Then Where? A Bi-polar, Integrated View of the Role of Polar Snow and Floating Ice Covers in the Earth's Heat Budget During IPY 2007/08  

NASA Astrophysics Data System (ADS)

The polar regions play a key role in the disposition of energy and in particular solar radiation in the earth's climate system. With the largest seasonal variations in surface albedo occurring over the polar oceans and with substantial changes in the extent and nature of the snow and ice covers in recent decades, the polar regions are a critical link between top-of-the atmosphere radiative fluxes and solar energy absorbed by the earth system. While recent studies have greatly improved our knowledge of the heat budget of the polar oceans, we are still far from understanding a number of fundamental questions related to the role of snow and ice in the global radiation budget and their importance for albedo feedback processes. For example, currently albedo parameterizations in large-scale sea ice and climate models are only partially successful in taking into account the physical processes driving seasonal and interannual albedo changes. In fact, the majority of models employ different albedo parameterizations for northern and southern hemisphere snow and sea ice. This is dictated by the strong contrasts in snow and ice melt processes in Arctic and Antarctic, which in of themselves are not all that well understood. Our own research in the Western Arctic and in the southern Ross Sea indicates that snow may play a crucial, currently underestimated role in governing these processes and hence the nature and magnitude of ice-albedo feedback processes. Here, we propose that an integrated, bi-polar examination of the interaction between snow and floating ice covers (sea and lake ice), coupled with a global-scale analysis of the role of polar ice masses in affecting the earth's radiation budget would provide an interesting and scientifically significant cryospheric thread within the framework of the IPY 2007/08. This work would also address other important aspects such as large-scale cloud radiative forcing over ice surfaces and spatio-temporal partitioning of the radiation reaching the surface. At the same time, such a program would provide direct linkages to the aims of the International Heliospheric Year. The observational effort would comprise a pan-polar approach to ground-based measurements along with satellite remote sensing, augmented by numerical simulations. Based on studies of the energy and mass balance of Arctic and Antarctic snow and ice covers, we will show how such a cryospheric component could be integrated into the overall aims of the IPY. IPY will provide an extraordinary opportunity to capture the imagination of the general public and school children. Our proposed effort will take advantage of this opportunity to convey information about the solar radiation and about the role the polar regions play in global climate. There will be an extensive educational outreach component that will include media contacts, web sites, classroom programs, and public lectures. Examples of such approaches, e.g., the Alaska Lake Ice and Snow Observatory Network (ALISON, www.gi.alaska.edu/alison) or Barrow Coastal Ice Observations (www.arcticice.org) will be discussed.

Eicken, H.; Grenfell, T.; Jeffries, M.; Perovich, D.; Sturm, M.

2003-12-01

359

Thermal evolution of permeability and microstructure in sea ice  

Microsoft Academic Search

The fluid permeability k of sea ice constrains a broad range of processes, such as the growth and decay of seasonal ice, the evolution of summer ice albedo, and biomass build-up. Such processes are critical to how sea ice and associated ecosystems respond to climate change. However, studies of k and its dependence on brine porosity $\\\\phi$ and microstructure are

K. M. Golden; H. Eicken; A. L. Heaton; J. Miner; D. J. Pringle; J. Zhu

2007-01-01

360

Formation of an aggregate scale in Arctic sea ice  

Microsoft Academic Search

The ice pack covering northern seas is a mixture of thick ridged and rafted ice, undeformed ice, and open water. Conventional Eulerian Arctic sea ice models use a plastic yield surface to characterize the constitutive behavior of the pack. An alternative is to adopt a discontinuous Lagrangian approach and explicitly model the formation of leads and pressure ridges. We use

Mark A. Hopkins; Susan Frankenstein; Alan S. Thorndike

2004-01-01

361

Eastern-Western Arctic Sea Ice Analyses 1989.  

National Technical Information Service (NTIS)

This document contains a compilation of the weekly sea ice analyses produced by the Navy/NOAA Joint Ice Center. The Eastern-Western Sea Ice Analysis is produced every year by June or July. The maps show the boundaries and edges of ice formation in Arctic ...

1989-01-01

362

A Destabilizing Thermohaline Circulation-Atmosphere-Sea Ice Feedback  

Microsoft Academic Search

Some of the interactions and feedbacks between the atmosphere, thermohaline circulation, and sea ice are illustrated using a simple process model. A simplified version of the annual-mean coupled ocean-atmosphere box model of Nakamura, Stone, and Marotzke is modified to include a parameterization of sea ice. The model includes the thermodynamic effects of sea ice and allows for variable coverage. It

Steven R. Jayne; Jochem Marotzke

1999-01-01

363

A destabilizing thermohaline circulation-atmosphere-sea ice feedback  

Microsoft Academic Search

Some of the interactions and feedbacks between the atmosphere, thermohaline circulation, and sea ice are illustrated using a simple process model. A simplified version of the annual-mean coupled ocean-atmosphere box model of Nakamura, Stone, and Marotzke is modified to include a parameterization of sea ice. The model includes the thermodynamic effects of sea ice and allows for variable coverage. It

S. R. Jayne; J. Marotzke

1999-01-01

364

Ice and ocean processes in the Bellingshausen Sea, Antarctica  

Microsoft Academic Search

In the vicinity of the Antarctic Peninsula observations show diminishing sea ice and a rapid warming of atmosphere and ocean. These changes have led to the collapse of ice shelves and retreat, acceleration, and thinning of inland ice. However, ocean observations in the center of the nearby Bellingshausen Sea are spatially and temporally coarse. In this study, ocean and sea

Paul R. Holland; Adrian Jenkins; David M. Holland

2010-01-01

365

A Multiband Remote Sensing Study of Melting Shorefast Sea Ice  

Microsoft Academic Search

Near-shore waters along Alaska's Beaufort sea coast are covered by shorefast sea ice 9 to 10 months each year, and by April the fast ice extends 10 to 50 km seaward along the coast. Recent scientific interest in sea ice dynamics (Maykut et al., 1972) and the prospects for offshore petroleum development in the region (Clark, 1976) highlight the need

Richard E. Moritz; Luis A. Bartolucci

1977-01-01

366

Increasing Antarctic Sea Ice under Warming Atmospheric and Oceanic Conditions  

Microsoft Academic Search

Estimates of sea ice extent based on satellite observations show an increasing Antarctic sea ice cover from 1979 to 2004 even though in situ observations show a prevailing warming trend in both the atmosphere and the ocean. This riddle is explored here using a global multicategory thickness and enthalpy distribution sea ice model coupled to an ocean model. Forced by

Jinlun Zhang

2007-01-01

367

Ice-free glacial northern Asia due to dust deposition on snow  

Microsoft Academic Search

During the Last Glacial Maximum (LGM, 21 kyr BP), no large ice sheets were present in northern Asia, while northern Europe\\u000a and North America (except Alaska) were heavily glaciated. We use a general circulation model with high regional resolution\\u000a and a new parameterization of snow albedo to show that the ice-free conditions in northern Asia during the LGM are favoured\\u000a by

Gerhard Krinner; Olivier Boucher; Yves Balkanski

2006-01-01

368

Microwave study of the formation of brine layers on homogeneous saline ice sheets  

Microsoft Academic Search

When sea water freezes into sea ice, brine and pure ice are produced. Due to the effects of the expulsion of brine from the sea ice interior and the wicking action of snow and frost flowers deposited on the air-ice interface, brine may accumulate on the upper ice sheet surface. Brine is a concentrated solution of sea salts and water,

R. G. Onstott; M. P. Madden

1994-01-01

369

Sea-ice melting processes inferred from ice–upper ocean relationships in the Ross Sea, Antarctica  

Microsoft Academic Search

Sea-ice melting processes are inferred from various summer sea-ice and upper ocean data obtained in the Ross Sea in January 1999. Using spatially (30 km) averaged continuous data, an ice concentration–water temperature plot (CT-plot) shows that the temperature at a depth of ?7 m increases as ice concentration decreases in the ice interior region. The CT-plot is explained by a

Sohey Nihashi; Kay I. Ohshima; Martin O. Jeffries; Toshiyuki Kawamura

2005-01-01

370

Implications of Arctic Sea Ice Reduction on Arctic Tropospheric Chemical Change (Invited)  

NASA Astrophysics Data System (ADS)

We examine the drastic reduction of Arctic sea ice in this decade and discuss the potential implications on bromine, ozone, and mercury change in the Arctic troposphere. We are witnessing extraordinary change in the Arctic sea ice cover. In the context of a half century change, perennial sea ice, the class of thicker and older ice important to the stability of Arctic sea ice, has been declining precipitously in this decade. Perennial ice extent declines at rate of 0.5 million km2 per decade in the 1970s-1990s while there is no discernable trend in the 1950s-1960s. Abruptly, the rate of decrease has tripled to 1.5 million km2 per decade in the 2000s. A record was set in the reduction of Arctic perennial ice extent in winter 2008. By 1 March 2008, perennial ice extent was reduced by one million km2 compared to that at the same time in 2007, which continued the precipitous declining trend observed in this decade. While the record low of total ice extent in summer 2007 is a historical mark of sea ice loss, the distribution and extent of different sea ice classes in spring (March-May) are critical information to understand the implications of sea ice reduction on photochemical processes, such as bromine explosions, ozone depletion episodes (ODEs), gaseous elementary mercury depletion episodes (MDEs), which occur at the time of polar sunrise. In this regard, the drastic reduction of perennial ice means that the Arctic becomes dominated by seasonal ice consisting of thinner ice, more leads, polynyas, frost flowers, and salty snow (due to seawater spray from open water), representing the overall saltier condition of the Arctic sea ice cover conducive to ice-mediated chemical processes leading to Arctic tropospheric ODEs and MDEs. To date (2009), the extent of perennial sea ice remains low and the extent of the thinner and saltier seasonal ice continues to dominate the Arctic sea ice cover. The shift of the state of Arctic sea ice cover to the dominance domain of seasonal ice can impact photochemical processes, leading to potentially significant implications on Arctic chemical change. Such implications, within the context of Arctic climatic change, are to be investigated in order to assess consequential changes in the Arctic habitat that may affect the health of people and wildlife. Regarding Arctic climatic change, seemingly opposing scenarios of Arctic chemical change have been hypothesized. In the first scenario, if sea ice cover continues to reduce in a warming trend in the 21st century, frost flower growth and bromine explosions might be suppressed and thus there would be less ozone and mercury depletion. Alternatively, in a different scenario, if the extent of seasonal ice during spring time in the Arctic continues to expand together with more cold spells due to temperature extremes exacerbated by climatic change, the abundance of seasonal ice, leads, and frost flowers may lead to more prevalent episodic events of bromine explosion and more intensive tropospheric ozone and mercury depletion in cold episodes. However, fundamental science questions remain to be addressed, and we have formed an international science team to plan for a future interdisciplinary research on those issues.

Nghiem, S. V.

2009-12-01

371

Microwave brightness temperatures of laboratory-grown undeformed first-year ice with an evolving snow cover  

NASA Astrophysics Data System (ADS)

A laboratory experiment was performed to study a case in which a snow cover introduced on an established saline ice sheet resulted in physical processes that significantly affected the microwave brightness temperature over a period of a few weeks. Saline ice was grown to a thickness of 240 mm in an outdoor pool at ambient air temperatures. Precipitation, was allowed by use of a movable roof. Brightness temperatures were measured at 10 and 85 GHz before and for several weeks after one snowfall. During the same period, the vertical temperature profile and crystallography of the snow column, as well as ice structure and salinity at the original ice surface, were monitored. The 10-GHz brightness temperature dropped by as much as 100 K from bare ice values during the first few days after the snow fell, because of a saline slush layer which formed at the bottom of the snow. The saline water in the slush layer apparently was forced up through the unbroken ice by the added snow load. The slush layer eventually froze into an added highly emissive frazil ice layer which raised the 10-GHz brightness temperature to above its bare ice values. The frazil ice layer was similar to superimposed frazil ice observed on freezing leads in high-latitude ice packs. The 85-GHz brightness temperature did not change from bare ice values soon after the snowfall but dropped by about 40 K over the following 20 days. We use a simple dielectric model to qualitatively test the dependence of 10-GHz brightness temperature on relevant physical conditions at the bottom of the snow. At 85 GHz the snow layer was optically thick, and the brightness temperature drop was probably the result of increased volume scatter from the growing snow grains.

Lohanick, A. W.

1993-03-01

372

Microwave brightness temperatures of laboratory-grown undeformed first-year ice with an evolving snow cover  

SciTech Connect

A laboratory experiment was performed to study a case in which a snow cover introduced on an established saline ice sheet resulted in physical processes that significantly affected the microwave brightness temperature over a period of a few weeks. Saline ice was grown to a thickness of 240 mm in an outdoor pool at ambient air temperatures. Precipitation was allowed by use of a movable roof. Brightness temperatures were measured at 10 and 85 GHz before and for several weeks after one snowfall. During the same period, the vertical temperature profile and crystallography of the snow column, as well as ice structure and salinity at the original ice surface, were monitored. The 10-GHz brightness temperature dropped by as much as 100 K from bare ice values during the first few days after the snow fell, because of a saline slush layer which formed at the bottom of the snow. The saline water in the slush layer apparently was forced up through the unbroken ice by the added snow load. The slush layer eventually froze into an added highly emissive frazil ice layer which raised the 10-GHz brightness temperature to above its bare ice values. The frazil ice layer was similar to superimposed frazil ice observed on freezing leads in high-latitude ice packs. The 85-GHz brightness temperature did not change from bare ice values soon after the snowfall but dropped by about 40 K over the following 20 days. We use a simple dielectric model to qualitatively test the dependence of 10-GHz brightness temperature on relevant physical conditions at the bottom of the snow. At 85 GHz the snow layer was optically thick, and the brightness temperature drop was probably the result of increased volume scatter from the growing snow grains. 24 refs., 7 figs.

Lohanick, A.W. (Naval Research Lab., Hanover, NH (United States))

1993-03-15

373

Tracking the Record Sea Ice Minimum in the Arctic Using National Ice Center Charts  

Microsoft Academic Search

The National\\/Naval Ice Center (NIC), in Suitland, MD, produces routine analyses of sea ice coverage in the Arctic. We create a Northern Hemispheric analyses based on bi-weekly charts for over 30 individual areas. Weekly charts of several key areas such as the High Arctic, Beaufort Sea, Chukchi Sea, North Sea, and Kara Sea are also produced. To create these charts,

J. Woods; P. Clemente-Colón; J. Brinkley; S. Helfrich; W. Huang; B. Melchior; T. Arbetter

2007-01-01

374

A Measurement of Sea Ice Albedo over the Southwestern Okhotsk Sea  

Microsoft Academic Search

In order to estimate sea ice albedo around the marginal sea ice zone of the southwestern Okhotsk Sea, we conducted the measurement of albedo aboard the ice breaker Soya in early February of 1996 and 1997. Using upward and downward looking pyranometers mounted at the bow of the ship, we obtained albedo data. We also measured ice concentration and thickness

Takenobu Toyota; Jinro Ukita; Kay I. Ohshima; Masaaki Wakatsuchi; Ken-Ichiro Muramoto

1999-01-01

375

On the aggregate-scale partitioning of solar radiation in Arctic sea ice during the Surface Heat Budget of the Arctic Ocean (SHEBA) field experiment  

Microsoft Academic Search

The partitioning of the incident solar irradiance among reflection to the atmosphere, absorption in the snow and ice, and transmission to the ocean is a critical component of the summer melt cycle of Arctic sea ice. Observations from a year-long field experiment (Surface Heat Budget of the Arctic Ocean (SHEBA)) showed that of the solar radiation incident between 1 April

Donald K. Perovich

2005-01-01

376

On the aggregate-scale partitioning of solar radiation in Arctic sea ice during the Surface Heat Budget of the Arctic Ocean (SHEBA) field experiment  

Microsoft Academic Search

(1) The partitioning of the incident solar irradiance among reflection to the atmosphere, absorption in the snow and ice, and transmission to the ocean is a critical component of the summer melt cycle of Arctic sea ice. Observations from a year-long field experiment (Surface Heat Budget of the Arctic Ocean (SHEBA)) showed that of the solar radiation incident between 1

Donald K. Perovich

2005-01-01

377

Analysis of Snow and Ice Surface Roughness Utilizing Higher-order Vario Functions and Geostatistical Classification  

Microsoft Academic Search

Study of the surface roughness of snow fields, glaciers, and ice sheets requires mea- surement and analysis of the surface's three-dimensional features, anisotropies, and complex microtopography. Observing that the notions of relief and surface roughness differ only with respect to scale, we consider surface roughness a spatial variable de- fined as the derivative of (micro)topography. In a project aimed at

Ute C. Herzfeld

2002-01-01

378

30 CFR 56.11016 - Snow and ice on walkways and travelways.  

Code of Federal Regulations, 2010 CFR

30 Ç Mineral Resources Ç 1 Ç 2009-07-01 Ç 2009-07-01 Ç false Ç Snow and ice on walkways and travelways. Ç 56.11016 Ç Section 56.11016 Ç Mineral Resources Ç MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR Ç METAL AND NONMETAL MINE SAFETY AND HEALTH Ç SAFETY AND HEALTH...

2009-07-01

379

Snow and ice-core stable isotopes time series and precipitation in Altai Mountains (Siberia)  

Microsoft Academic Search

The Altai's glaciers provide information on internal and external hydrological cycles over the Eurasia, storing long-term records of fresh water transport from Atlantic and Pacific Oceans and the Central Asia closed drainage basin. The 22 m firn-ice cores and 3 m snow pits from the Belukha firn Plateau (4109 - 4115 m) were used to recover climatic records through physical

E. M. Aizen; V. B. Aizen; K. Fujita; S. A. Nikitin; K. Kreutz

2003-01-01

380

Trans-polar observations of the morphological properties of Arctic sea ice  

NASA Astrophysics Data System (ADS)

Numerous ground-based and satellite observations of polar sea ice offer substantial evidence of a reduction in the areal extent and thickness of the Arctic ice cover. During the 2005 Healy-Oden Trans-Arctic Expedition 2005 a trans-Arctic survey of the physical properties of the polar ice pack was conducted. The observational program consisted of four broad classes of snow and ice activities: observations made while the ship was in transit; measurements made at 30 ice stations; 11 helicopter photographic survey flights; and the deployment of autonomous ice mass balance buoys. In transit observations revolved about the ice watch, which reported ice conditions, including ice thicknesses, classes and concentrations of the primary, secondary, and tertiary categories using the ASPECT protocol at two-hour intervals. Pond fractions were large early in the cruise reaching peak values of 0.5 and averaging at 0.25. These large values were concurrent with the southernmost latitudes of the ice pack. Ice concentrations ranged from 0.8 to 1.0 above 79 N, save for an area between 88 30 N and 89 30 N, where a large area of polynyas was observed. Surveys of snow depth and ice thickness were conducted at 23 ice stations along the cruise track, where ice cores and soot were also sampled. Thickness observations suggest a general latitudinal trend of increasing ice thickness moving northward. Thickness surveys showed considerable variability from floe to floe and within a single floe. Average floe thicknesses varied from 1.0 to 2.6 m, and the standard deviation of thickness on an individual floe was as large as one meter. The upper 10 to 12 cm of the ice typically consisted of a loose decomposed surface granular layer overlying a drained layer. The decomposed layer thickness gradually solidified from summer maximum values of 8-10 cm in mid-August to about 1 cm after freezup. The average optical-equivalent soot content was 4 ng soot/g for new snow, 8 for the surface granular layer of MY ice and 17 for the interior of MY ice.

Elder, B. C.; Perovich, D. K.; Grenfell, T. C.; Harbeck, J.; Light, B.; Everhart, K. K.

2006-12-01