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1

MODIS Snow and Sea Ice Products  

NASA Technical Reports Server (NTRS)

In this chapter, we describe the suite of Earth Observing System (EOS) Moderate-Resolution Imaging Spectroradiometer (MODIS) Terra and Aqua snow and sea ice products. Global, daily products, developed at Goddard Space Flight Center, are archived and distributed through the National Snow and Ice Data Center at various resolutions and on different grids useful for different communities Snow products include binary snow cover, snow albedo, and in the near future, fraction of snow in a 5OO-m pixel. Sea ice products include ice extent determined with two different algorithms, and sea ice surface temperature. The algorithms used to develop these products are described. Both the snow and sea ice products, available since February 24,2000, are useful for modelers. Validation of the products is also discussed.

Hall, Dorothy K.; Riggs, George A.; Salomonson, Vincent V.

2004-01-01

2

Albedo of summer snow on sea ice, Ross Sea, Antarctica  

Microsoft Academic Search

Surface all-wave albedo and physical parameters (grain radius, mass density, surface temperature, and stratification) of an austral summer snow cover on sea ice were measured in the Ross Sea during January-February 1999. It was observed that (1) from north to south the snow surface temperature decreases, albedo increases, snow mass density decreases, snow composite grain radius decreases, and number density

Xiaobing Zhou; Shusun Li; Kim Morris; Martin O. Jeffries

2007-01-01

3

Spring Snow Depth on Arctic Sea Ice using the IceBridge Snow Depth Product (Invited)  

NASA Astrophysics Data System (ADS)

Snow has dual roles in the growth and decay of Arctic sea ice. In winter, it insulates sea ice from colder air temperatures, slowing its growth. From spring into summer, the albedo of snow determines how much insolation is transmitted through the sea ice and into the underlying ocean, ultimately impacting the progression of the summer ice melt. Knowing the snow thickness and distribution are essential for understanding and modeling sea ice thermodynamics and the surface heat budget. Therefore, an accurate assessment of the snow cover is necessary for identifying its impacts in the changing Arctic. This study assesses springtime snow conditions on Arctic sea ice using airborne snow thickness measurements from Operation IceBridge (2009-2012). The 2012 data were validated with coordinated in situ measurements taken in March 2012 during the BRomine, Ozone, and Mercury EXperiment field campaign. We find a statistically significant correlation coefficient of 0.59 and RMS error of 5.8 cm. The comparison between the IceBridge snow thickness product and the 1937, 1954-1991 Soviet drifting ice station data suggests that the snow cover has thinned by 33% in the western Arctic and 44% in the Beaufort and Chukchi Seas. A rudimentary estimation shows that a thinner snow cover in the Beaufort and Chukchi Seas translates to a mid-December surface heat flux as high as 81 W/m2 compared to 32 W/m2. The relationship between the 2009-2012 thinner snow depth distribution and later sea ice freeze-up is statistically significant, with a correlation coefficient of 0.59. These results may help us better understand the surface energy budget in the changing Arctic, and may improve our ability to predict the future state of the sea ice cover.

Webster, M.; Rigor, I. G.; Nghiem, S. V.; Kurtz, N. T.; Farrell, S. L.

2013-12-01

4

Interactions between snow and melt ponds in sea ice models  

NASA Astrophysics Data System (ADS)

Snow cover on sea ice at the end of the winter persists into the early part of the sea ice melt season, and the spatial distribution of snow affects the surface topography, the distribution of initial melt pond formation and its subsequent evolution. After the initial formation of melt ponds, the low albedo of the ponds compared to snow or bare ice causes the ponds to preferentially absorb solar radiation and therefore further affects surface ice melt. A physically based melt pond model was coupled to the thermodynamic-dynamic Louvain-la-Neuve Sea-Ice Model (LIM, version 3), which recently includes a representation of snow properties and processes. In the new snow scheme, snow is represented in multiple layers with varying thermo-physical properties, and simple parameterizations for blowing snow and fresh water refreezing into the snow were implemented. Several simulations were performed using the combined snow and melt pond configuration to study the impacts of the processes described above on the Arctic sea ice melt pond fractions. Preliminary results lead to two expected but uncorroborated model behaviors. In the simulations, blowing snow tends to decrease the average snow depth on sea ice due to losses into leads, thus allowing wider but shallower ponds on multiyear ice, while no significant effect is noticeable on first-year ice. Similarly, the refreezing of water in the snow curtails the amount of meltwater available to feed melt ponds on thick ice categories, where some snow may persist through the melt season, but has a limited or no impact on thin ice where snow melts away rapidly.

Lecomte, Olivier; Fichefet, Thierry; Flocco, Daniela; Schroeder, David; Vancoppenolle, Martin

2014-05-01

5

Snow, Wind, Sun, and Time - How snow-driven processes control the Arctic sea ice  

NASA Astrophysics Data System (ADS)

Snowfall on Arctic sea ice is important for a number of reasons. The snowpack insulates sea ice from the cold winter atmosphere, redistribution of snow alters the surface roughness of the ice, light scattering in the snow increases ice albedo and reduces light transmission, and the weight of early season snow can result in ice surface flooding. An integrated set of field observations were collected to better understand how snowfall and, particularly, snow redistribution processes impact Arctic ice mass balance. Coincident measurements of snow depth and ice thickness on un-deformed first year ice indicate that snow dunes 'lock' in place early in the winter growth season, resulting in thinner ice beneath the dunes due to lower rates of energy loss. Coincident ground-based LiDAR measurements of surface topography and snow depth show that snow dune formation is largely responsible for the topographic relief of otherwise flat first year ice. Past work has shown that pond formation during the early melt season is strongly guided by the snow-controlled relative surface heights at a given site. Here multiple study sites are examined in an effort to better understand how differing patterns of snow redistribution can impact the overall extent of melt ponds, and therefore ice albedo. The results enhance basic knowledge of how snow processes control sea ice mass balance, and evoke several questions which must be answered in order to understand how changing precipitation regimes may affect sea ice in the Arctic.

Polashenski, C.; Druckenmiller, M. L.; Perovich, D. K.

2012-12-01

6

Airborne surveys of snow depth over Arctic sea ice  

NASA Astrophysics Data System (ADS)

During the spring of 2009, an ultrawideband microwave radar was deployed as part of Operation IceBridge to provide the first cross-basin surveys of snow thickness over Arctic sea ice. In this paper, we analyze data from three ˜2000 km transects to examine detection issues, the limitations of the current instrument, and the regional variability of the retrieved snow depth. Snow depth is the vertical distance between the air-snow and snow-ice interfaces detected in the radar echograms. Under ideal conditions, the per echogram uncertainty in snow depth retrieval is ˜4-5 cm. The finite range resolution of the radar (˜5 cm) and the relative amplitude of backscatter from the two interfaces limit the direct retrieval of snow depths much below ˜8 cm. Well-defined interfaces are observed over only relatively smooth surfaces within the radar footprint of ˜6.5 m. Sampling is thus restricted to undeformed, level ice. In early April, mean snow depths are 28.5 ± 16.6 cm and 41.0 ± 22.2 cm over first-year and multiyear sea ice (MYI), respectively. Regionally, snow thickness is thinner and quite uniform over the large expanse of seasonal ice in the Beaufort Sea, and gets progressively thicker toward the MYI cover north of Ellesmere Island, Greenland, and the Fram Strait. Snow depth over MYI is comparable to that reported in the climatology by Warren et al. (1999). Ongoing improvements to the radar system and the utility of these snow depth measurements are discussed.

Kwok, R.; Panzer, B.; Leuschen, C.; Pang, S.; Markus, T.; Holt, B.; Gogineni, S.

2011-11-01

7

The Effects of Snow Depth Forcing on Southern Ocean Sea Ice Simulations  

NASA Technical Reports Server (NTRS)

The spatial and temporal distribution of snow on sea ice is an important factor for sea ice and climate models. First, it acts as an efficient insulator between the ocean and the atmosphere, and second, snow is a source of fresh water for altering the already weak Southern Ocean stratification. For the Antarctic, where the ice thickness is relatively thin, snow can impact the ice thickness in two ways: a) As mentioned above snow on sea ice reduces the ocean-atmosphere heat flux and thus reduces freezing at the base of the ice flows; b) a heavy snow load can suppress the ice below sea level which causes flooding and, with subsequent freezing, a thickening of the sea ice (snow-to-ice conversion). In this paper, we compare different snow fall paramterizations (incl. the incorporation of satellite-derived snow depth) and study the effect on the sea ice using a sea ice model.

Powel, Dylan C.; Markus, Thorsten; Stoessel, Achim

2003-01-01

8

Large-Scale Surveys of Snow Depth on Arctic Sea Ice from Operation IceBridge  

NASA Technical Reports Server (NTRS)

We show the first results of a large ]scale survey of snow depth on Arctic sea ice from NASA fs 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.

2011-01-01

9

Airborne radar surveys of snow depth over Antarctic sea ice during Operation IceBridge  

NASA Astrophysics Data System (ADS)

Over the last decade, multiple satellite-based laser and radar altimeters, optimized for polar observations, have been launched with one of the major objectives being the determination of global sea ice thickness and distribution [5, 6]. Estimation of sea-ice thickness from these altimeters relies on freeboard measurements and the presence of snow cover on sea ice affects this estimate. Current means of estimating the snow depth rely on daily precipitation products and/or data from passive microwave sensors [2, 7]. Even a small uncertainty in the snow depth leads to a large uncertainty in the sea-ice thickness estimate. To improve the accuracy of the sea-ice thickness estimates and provide validation for measurements from satellite-based sensors, the Center for Remote Sensing of Ice Sheets deploys the Snow Radar as a part of NASA Operation IceBridge. The Snow Radar is an ultra-wideband, frequency-modulated, continuous-wave radar capable of resolving snow depth on sea ice from 5 cm to more than 2 meters from long-range, airborne platforms [4]. This paper will discuss the algorithm used to directly extract snow depth estimates exclusively using the Snow Radar data set by tracking both the air-snow and snow-ice interfaces. Prior work in this regard used data from a laser altimeter for tracking the air-snow interface or worked under the assumption that the return from the snow-ice interface was greater than that from the air-snow interface due to a larger dielectric contrast, which is not true for thick or higher loss snow cover [1, 3]. This paper will also present snow depth estimates from Snow Radar data during the NASA Operation IceBridge 2010-2011 Antarctic campaigns. In 2010, three sea ice flights were flown, two in the Weddell Sea and one in the Amundsen and Bellingshausen Seas. All three flight lines were repeated in 2011, allowing an annual comparison of snow depth. In 2011, a repeat pass of an earlier flight in the Weddell Sea was flown, allowing for a comparison of snow depths with two weeks elapsed between passes. [1] Farrell, S.L., et al., "A First Assessment of IceBridge Snow and Ice Thickness Data Over Arctic Sea Ice," IEEE Tran. Geoscience and Remote Sensing, Vol. 50, No. 6, pp. 2098-2111, June 2012. [2] Kwok, R., and G. F. Cunningham, "ICESat over Arctic sea ice: Estimation of snow depth and ice thickness," J. Geophys. Res., 113, C08010, 2008. [3] Kwok, R., et al., "Airborne surveys of snow depth over Arctic sea ice," J. Geophys. Res., 116, C11018, 2011. [4] Panzer, B., et al., "An ultra-wideband, microwave radar for measuring snow thickness on sea ice and mapping near-surface internal layers in polar firn," Submitted to J. Glaciology, July 23, 2012. [5] Wingham, D.J., et al., "CryoSat: A Mission to Determine the Fluctuations in Earth's Land and Marine Ice Fields," Advances in Space Research, Vol. 37, No. 4, pp. 841-871, 2006. [6] Zwally, H. J., et al., "ICESat's laser measurements of polar ice, atmosphere, ocean, and land," J. Geodynamics, Vol. 34, No. 3-4, pp. 405-445, Oct-Nov 2002. [7] Zwally, H. J., et al., "ICESat measurements of sea ice freeboard and estimates of sea ice thickness in the Weddell Sea," J. Geophys. Res., 113, C02S15, 2008.

Panzer, B.; Gomez-Garcia, D.; Leuschen, C.; Paden, J. D.; Gogineni, P. S.

2012-12-01

10

Sensitivity of simulated Arctic sea ice to realistic ice thickness distributions and snow parameterizations  

NASA Astrophysics Data System (ADS)

Sea ice and snow on sea ice to a large extent determine the surface heat budget in the Arctic Ocean. In spite of the advances in modeling sea-ice thermodynamics, a good number of models still rely on simple parameterizations of the thermodynamics of ice and snow. Based on simulations with an Arctic sea-ice model coupled to an ocean general circulation model, we analyzed the impact of changing two sea-ice parameterizations: (1) the prescribed ice thickness distribution (ITD) for surface heat budget calculations, and (2) the description of the snow layer. For the former, we prescribed a realistic ITD derived from airborne electromagnetic induction sounding measurements. For the latter, two different types of parameterizations were tested: (1) snow thickness independent of the sea-ice thickness below, and (2) a distribution proportional to the prescribed ITD. Our results show that changing the ITD from seven uniform categories to fifteen nonuniform categories derived from field measurements, and distributing the snow layer according to the ITD, leads to an increase in average Arctic-wide ice thickness by 0.56 m and an increase by 1 m in the Canadian Arctic Archipelago and Canadian Basin. This increase is found to be a direct consequence of 524 km3 extra thermodynamic growth during the months of ice formation (January, February, and March). Our results emphasize that these parameterizations are a key factor in sea-ice modeling to improve the representation of the sea-ice energy balance.

Castro-Morales, K.; Kauker, F.; Losch, M.; Hendricks, S.; Riemann-Campe, K.; Gerdes, R.

2014-01-01

11

Sea ice and snow evolution in Rijpfjorden, Svalbard, and the importance of superimposed ice formation  

NASA Astrophysics Data System (ADS)

Many Svalbard fjords are usually covered or partly covered by seasonal landfast ice during winter and spring months, which provides a stable research platform for studying sea ice properties. In winter 2010/2011 Rijpfjorden (80°N, 22°E), a fjord at the north coast of the Nordaustlandet (Svalbard), was covered by landfast sea ice from early November 2010 to 11 July 2011. To monitor spring sea ice evolution in this fjord, an Ice Mass Balance (IMB) buoy was deployed between April and June 2011. Ice cores were collected at the time when the IMB was installed and recovered. From April to June, there was no significant change at the ice bottom in terms of bottom freezing or melting. However, the ice core samples suggested a growth of superimposed ice of about 6 cm at ice/snow interface, which account for 86% of the total variation of ice thickness between April and June. A one-dimensional thermodynamic sea ice model was applied to simulate snow and ice thicknesses, and the snow/ice transition during the freezing and melting season in Rijpfjorden using external forcing from a nearby shore-based weather station and the operational analysis and short-term forecasts of the European Centre for Medium-Range Weather Forecasts (ECMWF). Atmospheric conditions under which transformation from snow to ice occur are described. The findings improve our understanding of Arctic sea ice evolution, and they also help for better interpretation of satellite ice thickness products.

Wang, C.; Gerland, S.; Spreen, G.; Cheng, B.; Eltoft, T.

2013-12-01

12

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

NASA Astrophysics Data System (ADS)

Black carbon in sea ice will decrease sea ice surface albedo through increased absorption of incident solar radiation, exacerbating sea ice melting. Previous literature has reported different albedo responses to additions of black carbon in sea ice and has not considered how a snow cover may mitigate the effect of black carbon in sea ice. Sea ice is predominately snow covered. Visible light absorption and light scattering coefficients are calculated for a typical first year and multi-year sea ice and "dry" and "wet" snow types that suggest black carbon is the dominating absorbing impurity. The albedo response of first year and multi-year sea ice to increasing black carbon, from 1-1024 ng g-1, in a top 5 cm layer of a 155 cm thick sea ice was calculated using the radiative transfer model: TUV-snow. Sea ice albedo is surprisingly unresponsive to black carbon additions up to 100 ng g-1 with a decrease in albedo to 98.7% of the original albedo value due to an addition of 8 ng g-1 of black carbon in first year sea ice compared to an albedo decrease to 99.6% for the same black carbon mass ratio increase in multi-year sea ice. The first year sea ice proved more responsive to black carbon additions than the multi-year ice. Comparison with previous modelling of black carbon in sea ice suggests a more scattering sea ice environment will be less responsive to black carbon additions. 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 were added onto the sea ice surface and the snow surface albedo calculated with the same increase in black carbon in the underlying sea ice. Just a 0.5 cm layer of snow greatly diminishes the effect of black carbon on surface albedo, and a 2-5 cm layer (less than half the e-folding depth of snow) is enough to "mask" any change in surface albedo owing to additional black carbon in sea ice, but not thick enough to ignore the underlying sea ice.

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

2013-03-01

13

Modeling the Effects of Wind Redistribution on the Snow Mass Budget of Polar Sea Ice  

Microsoft Academic Search

A two-dimensional numerical model of blowing snow specifically designed for sea ice environments is pre- sented. This new model is used to quantify the snow mass lost because of blowing snow into leads, blowing snow sublimation, and the effects of snow redistribution in the presence of surface irregularities (e.g., pressure ridges and snowdrifts) and on the conductive heat flux through

Stephen J. Déry; L.-B. Tremblay

2004-01-01

14

Sea ice thickness, freeboard, and snow depth products from Operation IceBridge airborne data  

NASA Astrophysics Data System (ADS)

The study of sea ice using airborne remote sensing platforms provides unique capabilities to measure a wide variety of sea ice properties. These measurements are useful for a variety of topics including model evaluation and improvement, assessment of satellite retrievals, and incorporation into climate data records for analysis of interannual variability and long-term trends in sea ice properties. In this paper we describe methods for the retrieval of sea ice thickness, freeboard, and snow depth using data from a multi-sensor suite of instruments on NASA's Operation IceBridge airborne campaign. We assess the consistency of the results through comparison with independent data sets that demonstrate that the IceBridge products are capable of providing a reliable record of snow depth and sea ice thickness. We explore the impact of inter-campaign instrument changes and associated algorithm adaptations as well as the applicability of the adapted algorithms to the ongoing IceBridge mission. The uncertainties associated with the retrieval methods are determined and placed in the context of their impact on the retrieved sea ice thickness. Lastly, we present results for the 2009 and 2010 IceBridge campaigns, which are currently available in product form via the National Snow and Ice Data Center.

Kurtz, N. T.; Farrell, S. L.; Studinger, M.; Galin, N.; Harbeck, J. P.; Lindsay, R.; Onana, V. D.; Panzer, B.; Sonntag, J. G.

2013-07-01

15

Impact of declining Arctic sea ice on 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, H.; Walsh, J. E.; Kim, Y.; Nakai, T.; Ohata, T.

2012-12-01

16

Considering the optical properties of snow (and sea ice) as a function of snowpack (and sea ice) chemistry and considering photochemistry of snow (and sea ice) as a function of optical properties of the snow and sea ice -what can we learn? (Invited)  

NASA Astrophysics Data System (ADS)

The deposition of aerosol to snowpack can change the optical properties of snowpack and provide a radiative forcing for modern climate change. Changing the optical properties of snow and sea ice will change the photochemistry occurring in snow and seaice and the atmosphere directly above them. So how will the chemistry of snow and sea ice effect modern climate change and how will modern climate change effect the photochemistry in snow and sea ice. The talk will explore the interplay between climate change, photolytic reactions in snow and sea-ice and the optical properties of snow and sea-ice. It will focus on the dependence of snow and ice optical properties on the chemistry of material deposited to the snow/sea ice and then focus on the photochemistry in the snowpack from optical properties of the snow and sea ice. Specifically: 1) The effect of deposited aerosol on the reflectivity, light penetration and photolytic reactions in snowpack responsible for fluxes of chemicals from snow to the atmosphere and production of radical species within the snow and sea ice. The transmission of photosynthetic radiation will also be considered as a function of the light absorbing material in the snow and sea ice. Simulations will be presented demonstrating that different sea ices and snowpacks respond to deposited aerosol (including black carbon, HULIS and mineral dust) differently - depending on their physical properties. How much more sensitive is a melting snowpack to deposited aerosol than a cold polar snowpack? 2) The potential effects of climate change on the optical properties of snow and sea-ice and thus the potential effects of climate change on the photolytic production of radicals and gases within the snowpack as well as the transmission of PAR through the snow and seaice will be shown. The talk will present results from simulation, using sea ice grown in tanks at RHUL (the first results) and modelling of snow and seaice optical and chemical properties.

King, M. D.

2013-12-01

17

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

18

Review of Electromagnetic Methods to Investigate Arctic and Antarctic Sea Ice and Snow  

Microsoft Academic Search

During the last 5 years we have applied a variety of near-surface electric (ie, resistivity) and electromagnetic methods to investigate sea ice and snow on sea ice in the Antarctic and Arctic. Here we present field cases and lessons learned on the applicability for resolving distinct target parameters. The geophysical challenges of sea ice include its composition of (a) homogeneous,

A. Pfaffling; C. Haas; M. MeilAeNder-Larsen; J. Bishop; D. Flinspach; D. Otto; J. E. Reid; A. P. Worby

2007-01-01

19

What forces the Redistribution of Snow over Smooth Landfast Sea Ice?  

NASA Astrophysics Data System (ADS)

An understanding of the temporal evolution of snow over sea ice at different spatial scales is critical for the improvement of snow distribution parameterization in sea ice models and for the study of physical-biological coupling. Snow depth on sea ice is primarily controlled by the interaction between surface condition (i.e. type and roughness of sea ice) and the meteorological conditions of the area. Statistical analyses of the evolution of snow distribution over smooth first-year sea ice suggest that several changes in snow distribution correspond to changes in depositional and drifting events. Changes in the probability density functions (PDFs) indicate that deeper and larger snow drifts formed after snowfall or drifting events. At the microscale, snow events caused the infilling of the valleys between snowdrifts, creating larger areas of uniform snow depth. The ability to reproduce the snow distribution over sea ice was tested using SnowModel. Results from two independent model runs suggest that the model was not able to adequately reproduce the range in the observed snow distribution. The lack of agreement may in part be due to the spatial domain of the model compared to the location of the sampling sites, as well as the use of meteorological data from land stations. Results comparing meteorological variables from land- and ice stations suggest that air temperature on land can be used as a proxy measure for that on ice, while simple associations for other meteorological variables do not exist. This is a significant limitation to the study of the evolution of snow distribution since on ice measurements are not routinely collected in the Arctic.

Iacozza, J.; Barber, D. G.

2009-04-01

20

Arctic Ocean sea ice snow depth evaluation and bias sensitivity in CCSM  

NASA Astrophysics Data System (ADS)

Sea ice cover in the Arctic Ocean is a continued focus of attention. This study investigates the impact of the snow overlying the sea ice in the Arctic Ocean. The impact of snow depth biases in the Community Climate System Model (CCSM) is shown to impact not only the sea ice, but also the overall Arctic climate. Following the identification of seasonal biases produced in CCSM simulations, the thermodynamic transfer through the snow-ice column is perturbed to determine model sensitivity to these biases. This study concludes that perturbations on the order of the observed biases result in modification of the annual mean conductive flux through the snow-ice column of 0.5 W m2 relative to an unmodified simulation. The results suggest that the ice has a complex response to snow characteristics, with ice of different thicknesses producing distinct reactions. Our results indicate the importance of an accurate simulation of snow on the Arctic sea ice. Consequently, future work investigating the impact of current precipitation biases and missing snow processes, such as blowing snow, densification, and seasonal changes, is warranted.

Blazey, B. A.; Holland, M. M.; Hunke, E. C.

2013-12-01

21

Snow Depth and Ice Thickness Measurements From the Beaufort and Chukchi Seas Collected During the AMSR-Ice03 Campaign  

NASA Technical Reports Server (NTRS)

In March 2003, a field validation campaign was conducted on the sea ice near Barrow, AK. The goal of this campaign was to produce an extensive dataset of sea ice thickness and snow properties (depth and stratigraphy) against which remote sensing products collected by aircraft and satellite could be compared. Chief among these were products from the Polarimetric Scanning Radiometer (PSR) flown aboard a NASA P-3B aircraft and the Aqua Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR-E). The data were collected in four field areas: three on the coastal sea ice near Barrow, AK, and the fourth out on the open ice pack 175 km northeast of Barrow. The snow depth ranged from 9.4-20.8 cm in coastal areas (n = 9881 for three areas) with the thinnest snow on ice that had formed late in the winter. Out in the main pack ice, the snow was 20.6 cm deep (n = 1906). The ice in all four areas ranged from 138-219 cm thick (n = 1952), with the lower value again where the ice had formed late in the winter. Snow layer and grain characteristics observed in 118 snow pits indicated that 44% of observed snow layers were depth hoar; 46% were wind slab. Snow and ice measurements were keyed to photomosaics produced from low-altitude vertical aerial photographs. Using these, and a distinctive three-way relationship between ice roughness, snow surface characteristics, and snow depth, strip maps of snow depth, each about 2 km wide, were produced bracketing the traverse lines. These maps contain an unprecedented level of snow depth detail against which to compare remote sensing products. The maps are used in other papers in this special issue to examine the retrieval of snow properties from the PSR and AMSR-E sensors.

Sturm, M.; Holmgren, J.; Maslanik, J. A.; Perovich, D. K.; Richter-Menge, J.; Stroeve, J. C.; Markus, T.; Heinrichs, J. F.; Tape, K.

2006-01-01

22

Review of Electromagnetic Methods to Investigate Arctic and Antarctic Sea Ice and Snow  

NASA Astrophysics Data System (ADS)

During the last 5 years we have applied a variety of near-surface electric (ie, resistivity) and electromagnetic methods to investigate sea ice and snow on sea ice in the Antarctic and Arctic. Here we present field cases and lessons learned on the applicability for resolving distinct target parameters. The geophysical challenges of sea ice include its composition of (a) homogeneous, vertically anisotropic, one-dimensional (level) ice 0.5 to 4 m thick, and (b) highly heterogeneous, partly water impregnated three-dimensional pressure ridge features 2 to 10 m thick. Snow on sea ice is generally dry (until melt onset) and spans a thickness range of some centimetres up to a few meters. We applied several different types of equipment covering the frequency range from DC to radar for different tasks and targets. Ground Penetrating Radar (GPR) proved to be fast and portable for snow thickness profiling with the limitation of a minimum snow thickness around 10 cm. Electromagnetic induction (EMI) is a classic sea ice thickness profiling method used hand held on the ice, ship-borne suspended from outrigger-like constructions as well as airborne as helicopter towed sensors. Mostly regional ice plus snow thickness is derived from EMI measurements. Attempts have been made to retrieve internal ice properties such as porosity or age (conductivity) from EM soundings. DC-resistivity sounding clearly shows the vertical conductivity anisotropy of level sea ice, due to its crystalline structure and aging processes. Electrical Resistivity Tomography was conducted on Baltic and Arctic sea ice to determine the porosity of pressure ridge keels. Our results show the potentials and limitations of the different methods for climate related and engineering sea ice studies. geophysics.com/projects

Pfaffling, A.; Haas, C.; Meil{\\Ae}Nder-Larsen, M.; Bishop, J.; Flinspach, D.; Otto, D.; Reid, J. E.; Worby, A. P.

2007-12-01

23

Snow Depth and Ice Thickness Measurements From the Beaufort and Chukchi Seas Collected During the AMSR-Ice03 Campaign  

Microsoft Academic Search

In March 2003, a field validation campaign was conducted on the sea ice near Barrow, AK. The goal of this campaign was to produce an extensive dataset of sea ice thickness and snow properties (depth and stratigraphy) against which remote sensing products collected by aircraft and satellite could be compared. Chief among these were products from the Polarimetric Scanning Radiometer

Matthew Sturm; James A. Maslanik; Donald K. Perovich; Julienne C. Stroeve; J. Richter-Menge; T. Markus; J. Holmgren; J. F. Heinrichs; K. Tape

2006-01-01

24

Validation of Airborne FMCW Radar Measurements of Snow Thickness Over Sea Ice in Antarctica  

NASA Technical Reports Server (NTRS)

Antarctic sea ice and its snow cover are integral components of the global climate system, yet many aspects of their vertical dimensions are poorly understood, making their representation in global climate models poor. Remote sensing is the key to monitoring the dynamic nature of sea ice and its snow cover. Reliable and accurate snow thickness data are currently a highly sought after data product. Remotely sensed snow thickness measurements can provide an indication of precipitation levels, predicted to increase with effects of climate change in the polar regions. Airborne techniques provide a means for regional-scale estimation of snow depth and distribution. Accurate regional-scale snow thickness data will also facilitate an increase in the accuracy of sea ice thickness retrieval from satellite altimeter freeboard estimates. The airborne data sets are easier to validate with in situ measurements and are better suited to validating satellite algorithms when compared with in situ techniques. This is primarily due to two factors: better chance of getting coincident in situ and airborne data sets and the tractability of comparison between an in situ data set and the airborne data set averaged over the footprint of the antennas. A 28-GHz frequency modulated continuous wave (FMCW) radar loaned by the Center for Remote Sensing of Ice Sheets to the Australian Antarctic Division is used to measure snow thickness over sea ice in East Antarctica. Provided with the radar design parameters, the expected performance parameters of the radar are summarized. The necessary conditions for unambiguous identification of the airsnow and snowice layers for the radar are presented. Roughnesses of the snow and ice surfaces are found to be dominant determinants in the effectiveness of layer identification for this radar. Finally, this paper presents the first in situ validated snow thickness estimates over sea ice in Antarctica derived from an FMCW radar on a helicopterborne platform.

Galin, Natalia; Worby, Anthony; Markus, Thorsten; Leuschen, Carl; Gogineni, Prasad

2012-01-01

25

Peculiarities of hydrocarbon distribution in the snow-ice cover of different regions of the white sea  

NASA Astrophysics Data System (ADS)

This paper presents data on the content of hydrocarbons (HCs) in the snow-ice cover of the coastal regions of the Dvina and Kandalaksha gulfs, White Sea, in 2008-2012 in comparison with the content of organic carbon, lipids, and the suspension. The accumulation of HCs in the snow-ice cover depends on the degree of pollution of the atmosphere, formation conditions of ice, and intensity of biogeochemical processes at the ice-water boundary. Thus, the highest concentrations in the water basin of Arkhangelsk are identified in snow and in the upper part of the ice. The peculiarities of formation of the snow-ice cover in Rugozero Bay of the Kandalaksha Gulf leads to the concentration of HCs in different snow and ice layers. The decreased HC content in the snow-ice cover of the White Sea, in comparison with previous studies, is caused by recession of industrial production in recent years.

Nemirovskaya, I. A.

2014-03-01

26

A Coordinated Ice-based and Airborne Snow and Ice Thickness Measurement Campaign on Arctic Sea Ice  

NASA Astrophysics Data System (ADS)

A rare opportunity presented itself in March 2011 when the Naval Research Laboratory (NRL) and NASA IceBridge teamed with scientists from the U.S. Army Corps of Engineers Cold Regions Research and Engineering Laboratory (CRREL) to coordinate a multi-scale approach to mapping snow depth and sea ice thickness distribution in the Arctic. Ground-truth information for calibration/validation of airborne and CryoSat-2 satellite data were collected near a manned camp deployed in support of the US Navy's Ice Expedition 2011 (ICEX 2011). The ice camp was established at a location approximately 230 km north of Prudhoe Bay, Alaska, at the edge of the perennial ice zone. The suite of measurements was strategically organized around a 9-km-long survey line that covered a wide range of ice types, including refrozen leads, deformed and undeformed first year ice, and multiyear ice. A highly concentrated set of in situ measurements of snow depth and ice thickness were taken along the survey line. Once the survey line was in place, NASA IceBridge flew a dedicated mission along the survey line, collecting data with an instrument suite that included the Airborne Topographic Mapper (ATM), a high precision, airborne scanning laser altimeter; the Digital Mapping System (DMS), nadir-viewing digital camera; and the University of Kansas ultra-wideband Frequency Modulated Continuous Wave (FMCW) snow radar. NRL also flew a dedicated mission over the survey line with complementary airborne radar, laser and photogrammetric sensors (see Brozena et al., this session). These measurements were further leveraged by a series of CryoSat-2 under flights made in the region by the instrumented NRL and NASA planes, as well as US Navy submarine underpasses of the 9-km-long survey line to collect ice draft measurements. This comprehensive suite of data provides the full spectrum of sampling resolutions from satellite, to airborne, to ground-based, to submarine and will allow for a careful determination of snow depth on sea ice and characterization of the regional sea ice thickness distribution. This poster will present preliminary data from the measurement campaign. This includes the in situ measurements of snow depth and ice thickness along the survey line. The NASA IceBridge airborne survey consisted of eleven parallel flight lines along the main in situ transect and two perpendicular passes at the northern and southern ends of the survey line, coincident with two corner reflectors. We will present initial IceBridge data, including ATM sea ice elevation and DMS photography which we use to estimate surface roughness and delineate sea ice provinces nearby the in situ survey. Preliminary data from the NRL over flights of the survey line will be presented in the poster by Brozena et al. (this session). The in situ and airborne data collected during the March 2011 campaign will be fully-documented and archived on the NASA IceBridge websites at NSIDC, allowing for their free access by the broad research community.

Richter-Menge, J.; Farrell, S.; Elder, B. C.; Gardner, J. M.; Brozena, J. M.

2011-12-01

27

Estimation of Sea Ice Thickness Distributions through the Combination of Snow Depth and Satellite Laser Altimetry Data  

NASA Technical Reports Server (NTRS)

Combinations of sea ice freeboard and snow depth measurements from satellite data have the potential to provide a means to derive global sea ice thickness values. However, large differences in spatial coverage and resolution between the measurements lead to uncertainties when combining the data. High resolution airborne laser altimeter retrievals of snow-ice freeboard and passive microwave retrievals of snow depth taken in March 2006 provide insight into the spatial variability of these quantities as well as optimal methods for combining high resolution satellite altimeter measurements with low resolution snow depth data. The aircraft measurements show a relationship between freeboard and snow depth for thin ice allowing the development of a method for estimating sea ice thickness from satellite laser altimetry data at their full spatial resolution. This method is used to estimate snow and ice thicknesses for the Arctic basin through the combination of freeboard data from ICESat, snow depth data over first-year ice from AMSR-E, and snow depth over multiyear ice from climatological data. Due to the non-linear dependence of heat flux on ice thickness, the impact on heat flux calculations when maintaining the full resolution of the ICESat data for ice thickness estimates is explored for typical winter conditions. Calculations of the basin-wide mean heat flux and ice growth rate using snow and ice thickness values at the 70 m spatial resolution of ICESat are found to be approximately one-third higher than those calculated from 25 km mean ice thickness values.

Kurtz, Nathan T.; Markus, Thorsten; Cavalieri, Donald J.; Sparling, Lynn C.; Krabill, William B.; Gasiewski, Albin J.; Sonntag, John G.

2009-01-01

28

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

29

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

30

Modelling changes in the dielectric and scattering properties of young snow-covered sea ice at GHz frequencies  

NASA Technical Reports Server (NTRS)

Observations of the physical properties of the snow cover and underlying young fast ice in Resolute Passage, Canada, were made during the winter of 1982. Detailed measurements of snow density and ice and snow temperatures, salinities, and brine volumes were made over a period of 46 d, beginning when the ice was 0.4 m thick and about 9 d old. The recorded values are used in a theoretical mixture model to predict the dielectric properties of the snow cover over the microwave frequency range. The results of this analysis are then used to investigate the effects of the snow properties on the radar backscatter signatures of young sea ice. The results show that backscatter is a function of the incidence angle and can change significantly over short periods of time during the early evolutionary phase of ice and snow-cover development. This has important consequences for the identification of young ice forms from SAR or SLAR images.

Drinkwater, Mark R.; Crocker, G. B.

1988-01-01

31

Snow Radar Derived Surface Elevations and Snow Depths Multi-Year Time Series over Greenland Sea-Ice During IceBridge Campaigns  

NASA Astrophysics Data System (ADS)

This paper presents estimates of snow depth over sea ice from the 2009 through 2011 NASA Operation IceBridge [1] spring campaigns over Greenland and the Arctic Ocean, derived from Kansas University's wideband Snow Radar [2] over annually repeated sea-ice transects. We compare the estimates of the top surface interface heights between NASA's Atmospheric Topographic Mapper (ATM) [3] and the Snow Radar. We follow this by comparison of multi-year snow depth records over repeated sea-ice transects to derive snow depth changes over the area. For the purpose of this paper our analysis will concentrate on flights over North/South basin transects off Greenland, which are the closest overlapping tracks over this time period. The Snow Radar backscatter returns allow for surface and interface layer types to be differentiated between snow, ice, land and water using a tracking and classification algorithm developed and discussed in the paper. The classification is possible due to different scattering properties of surfaces and volumes at the radar's operating frequencies (2-6.5 GHz), as well as the geometries in which they are viewed by the radar. These properties allow the returns to be classified by a set of features that can be used to identify the type of the surface or interfaces preset in each vertical profile. We applied a Support Vector Machine (SVM) learning algorithm [4] to the Snow Radar data to classify each detected interface into one of four types. The SVM algorithm was trained on radar echograms whose interfaces were visually classified and verified against coincident aircraft data obtained by CAMBOT [5] and DMS [6] imaging sensors as well as the scanning ATM lidar. Once the interface locations were detected for each vertical profile we derived a range to each interface that was used to estimate the heights above the WGS84 ellipsoid for direct comparisons with ATM. Snow Radar measurements were calibrated against ATM data over areas free of snow cover and over GPS land surveyed areas of Thule and Sondrestrom air bases. The radar measurements were compared against the ATM and the GPS measurements that were located in the estimated radar footprints, which resulted in an overall error of ~ 0.3 m between the radar and ATM. The agreement between ATM and GPS survey is within +/- 0.1 m. References: [1] http://www.nasa.gov/mission_pages/icebridge/ [2] Panzer, B. et. al, "An ultra-wideband, microwave radar for measuring snow thickness on sea ice and mapping near-surface internal layers in polar firn," Submitted to J. of Glaciology Instr. and Tech., July 23, 2012. [3] Krabill, William B. 2009 and 2011, updated current year. IceBridge ATM L1B Qfit Elevation and Return Strength. Boulder, Colorado USA: National Snow and Ice Data Center. Digital media. [4] Chih-Chung Chang and Chih-Jen Lin. "Libsvm: a library for support vector machines", ACM Transactions on Intelligent Systems and Technology, 2:2:27:1-27:27, 2011. [5] Krabill, William B. 2009 and 2011, updated current year. IceBridge CAMBOT L1B Geolocated Images, [2009-04-25, 2011-04-15]. Boulder, Colorado USA: National Snow and Ice Data Center. Digital media. [6] Dominguez, Roseanne. 2011, updated current year. IceBridge DMS L1B Geolocated and Orthorectified Images. Boulder, Colorado USA: National Snow and Ice Data Center. Digital media

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

2012-12-01

32

Examining Dual Frequency X- and Ku-band Backscatter of Snow on Lake Ice and First-Year Sea Ice in the Sub-Arctic Hudson Bay Lowlands  

NASA Astrophysics Data System (ADS)

Fully polarimetric dual frequency ground-based scatterometer observations were collected at X- and Ku-band (9.6 and 17.2 GHz, respectively) near Churchill, Manitoba, Canada in the winter of 2010-11 as part of the Canadian Snow and Ice Experiment (CASIX). Backscatter measurements were collected for five landcover types: lake ice, sea ice, dry tundra, open forest and wetland tundra (sedge fen); the combination of which comprises a unique dataset of dual-frequency backscatter signatures. Correlative data collected, including snow and ice properties, are utilized to characterize active microwave interactions and contribute to the development of snow/ice retrieval algorithms. This study presents backscatter signatures for lake and sea ice obtained during winter 2010-11. The seasonal backscatter evolution is compared to changes in snow and ice properties, including depth, density, snow water equivalent (SWE), ice thickness, ice type, and bubble concentration within the ice. Results over lake ice suggest that increases in backscatter at both X- and Ku-band frequencies correspond to increases in SWE, but are confounded by changes in the sub-nivian ice composition. Surface ice types (snow ice, rafted ice), high bubble concentrations at the ice/water interface and pressure/deformation cracks in the ice serve to confound backscatter at several monitoring sites. Over sea ice, preliminary results indicate that increased salinity levels near the ice/snow interface is the predominate factor influencing backscatter signatures. Physical phenomena encountered at sea ice sites are further explored to assess potential influences on scattering signatures. Preliminary findings presented here document the first ground-based dual frequency X- and Ku-band backscatter signatures collected over first year sea ice, and contribute to the scientific objectives of the proposed Cold Regions Hydrology High-resolution Observatory (CoReH2O), a candidate Earth Explorer mission of the European Space Agency.

Gunn, G. E.; Duguay, C. R.; Howell, S.; Kelly, R. E.; Silis, A.

2011-12-01

33

Effect of snow covering and ocean mixed layer on the irreversibility of sea-ice retreat  

NASA Astrophysics Data System (ADS)

The seasonal change of sea-ice extent constitutes one of the largest variations in surface albedo on seasonal time-scales. Because of this large seasonal change and the high difference in surface albedo between sea-ice and open oceans, the dynamical processes related to the presence of sea-ice are crucial drivers in the climate system. Single-column models and more comprehensive climate models have been proved to be very useful to understand these physical processes and their relations and role in the formation of sea-ice. All these models show that different scenarios can be produced in a warming climate depending on the considered region in the (huge) parameter space: smooth or abrupt transitions to seasonally or annual ice-free conditions. Still it is unclear which is the dominant physical process that is responsible for the occurrence of abrupt ice retreat and gives rise to irreversibility. We start from the toy model developed by Eisenman (2012) JGR 117, D01111, which represents the essential physics of thermodynamic sea ice in a single column, and we add to this model the effects of snow covering and seasonal variation of the ocean mixed layer. We investigate how the abrupt threshold during ice retreat depends on these additional effects. In particular, we find that the presence of snow reduces the bistability region and we discuss different regimes which depend on the mixed layer time-scale. Temperature profiles in the mixed layer are obtained by performing coupled ice-ocean simulations of the Arctic Ocean with the MIT general circulation model at 36 km horizontal resolution.

Tomasini, Matteo; Brunetti, Maura; Marshall, Shawn

2014-05-01

34

Examining the ability of snow and sea ice to maintain halogen activation  

NASA Astrophysics Data System (ADS)

During Arctic springtime, photochemistry converts sea salts to reactive halogens (e.g. bromine atoms and bromine monoxide) that then drastically change the oxidation chemistry of the overlying atmosphere. These halogen activation events are widespread and ubiquitous across the Arctic Basin, particularly on the sea ice and nearby, affecting ozone, mercury, and organic oxidation processes. Heterogeneous chemistry that recycles reservoirs of halogens (e.g. HBr or sea salt Br-) to reactive halogens appears necessary to create a "bromine explosion" and maintain halogen activation. In this study, we examine the end-of-season transition between the period of halogen activation in springtime to the period during which activation ceases in summer. This transition is very abrupt in nearly all records of Arctic BrO, including campaigns at Barrow, Alaska, and on the sea ice as observed by O-Buoys. In this work, we examine the environmental conditions that change at the day that halogen chemistry is no longer supported. It appears that atmospherically accessible ice surface area, afforded by "dry" snow, is critical to maintain halogen activation, and surface melting, even without much loss of snowpack, terminates this chemistry. A variety of snow properties, including microwave signatures (sensitive to snow wetness), near infrared albedo changes, and temperature are investigated to get more insight into both the underlying chemical mechanism and how one might be able to use remote sensing to determine areas where halogen activation can/cannot occur.

Simpson, W. R.; Walsh, S. J.; Peterson, P. K.; Gleason, E.; Shepson, P.; Pratt, K. A.; Halfacre, J. W.; Oltmans, S. J.; Domine, F.; Nghiem, S. V.; Perovich, D. K.; Sturm, M.

2012-12-01

35

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

36

Observations of Snow Water Equivalent Change on Landfast First-Year Sea Ice in Winter Using Synthetic Aperture Radar Data  

Microsoft Academic Search

In this paper, we examine the utility of synthetic aperture radar (SAR) backscatter data to detect a change in snow water equivalent (SWE) over landfast first-year sea ice during winter at relatively cold temperatures. We begin by reviewing the theoretical framework for linking microwave scattering from SAR to the thermodynamic and electrical properties of first-year sea ice. Previous research has

John J. Yackel; David G. Barber

2007-01-01

37

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

38

Freeboard, Snow Depth and Sea-Ice Roughness in East Antarctica from In Situ and Multiple Satellite Data  

NASA Technical Reports Server (NTRS)

In October 2003 a campaign on board the Australian icebreaker Aurora Australis had the objective to validate standard Aqua Advanced Microwave Scanning Radiometer (AMSR-E) sea-ice products. Additionally, the satellite laser altimeter on the Ice, Cloud and land Elevation Satellite (ICESat) was in operation. To capture the large-scale information on the sea-ice conditions necessary for satellite validation, the measurement strategy was to obtain large-scale sea-ice statistics using extensive sea-ice measurements in a Lagrangian approach. A drifting buoy array, spanning initially 50 km 100 km, was surveyed during the campaign. In situ measurements consisted of 12 transects, 50 500 m, with detailed snow and ice measurements as well as random snow depth sampling of floes within the buoy array using helicopters. In order to increase the amount of coincident in situ and satellite data an approach has been developed to extrapolate measurements in time and in space. Assuming no change in snow depth and freeboard occurred during the period of the campaign on the floes surveyed, we use buoy ice-drift information as well as daily estimates of thin-ice fraction and rough-ice vs smooth-ice fractions from AMSR-E and QuikSCAT, respectively, to estimate kilometer-scale snow depth and freeboard for other days. The results show that ICESat freeboard estimates have a mean difference of 1.8 cm when compared with the in situ data and a correlation coefficient of 0.6. Furthermore, incorporating ICESat roughness information into the AMSR-E snow depth algorithm significantly improves snow depth retrievals. Snow depth retrievals using a combination of AMSR-E and ICESat data agree with in situ data with a mean difference of 2.3 cm and a correlation coefficient of 0.84 with a negligible bias.

Markus, Thorsten; Masson, Robert; Worby, Anthony; Lytle, Victoria; Kurtz, Nathan; Maksym, Ted

2011-01-01

39

(abstract) A Polarimetric Model for Effects of Brine Infiltrated Snow Cover and Frost Flowers on Sea Ice Backscatter  

NASA Technical Reports Server (NTRS)

A polarimetric scattering model is developed to study effects of snow cover and frost flowers with brine infiltration on thin sea ice. Leads containing thin sea ice in the Artic icepack are important to heat exchange with the atmosphere and salt flux into the upper ocean. Surface characteristics of thin sea ice in leads are dominated by the formation of frost flowers with high salinity. In many cases, the thin sea ice layer is covered by snow, which wicks up brine from sea ice due to capillary force. Snow and frost flowers have a significant impact on polarimetric signatures of thin ice, which needs to be studied for accessing the retrieval of geophysical parameters such as ice thickness. Frost flowers or snow layer is modeled with a heterogeneous mixture consisting of randomly oriented ellipsoids and brine infiltration in an air background. Ice crystals are characterized with three different axial lengths to depict the nonspherical shape. Under the covering multispecies medium, the columinar sea-ice layer is an inhomogeneous anisotropic medium composed of ellipsoidal brine inclusions preferentially oriented in the vertical direction in an ice background. The underlying medium is homogeneous sea water. This configuration is described with layered inhomogeneous media containing multiple species of scatterers. The species are allowed to have different size, shape, and permittivity. The strong permittivity fluctuation theory is extended to account for the multispecies in the derivation of effective permittivities with distributions of scatterer orientations characterized by Eulerian rotation angles. Polarimetric backscattering coefficients are obtained consistently with the same physical description used in the effective permittivity calculation. The mulitspecies model allows the inclusion of high-permittivity species to study effects of brine infiltrated snow cover and frost flowers on thin ice. The results suggest that the frost cover with a rough interface significantly increases the backscatter from thin saline ice and the polarimetric signature becomes closer to the isotropic characteristics. The snow cover also modifies polarimetric signatures of thin sea ice depending on the snow mixture and the interface condition.

Nghiem, S. V.; Kwok, R.; Yueh, S. H.

1995-01-01

40

The impact of early summer snow properties on land-fast sea-ice X-band backscatter  

NASA Astrophysics Data System (ADS)

Snow cover on sea ice and its impact on radar backscatter, particularly after the onset of freeze-thaw processes requires increased understanding. We present a data set that comprises in-situ measured snow properties from the land-fast sea ice of the Atka Bay, Antarctica, in combination with high-resolution TerraSAR-X backscatter data. Both data sets are discussed for the transition period from austral winter to summer (November 2012 - January 2013). The changes in the seasonal snow cover are reflected in the evolution of TerraSAR-X backscatter. We are able to explain between 62 % and 80 % of the spatio-temporal variations of the TerraSAR-X backscatter signal with up to three snow-pack parameters by using a simple linear model. Especially after the onset of melt processes, the majority of the TerraSAR-X backscatter variations are influenced by snow depth, snow/ice-interface temperature and snow-pack grain size and thereby imply the potential to also retrieve snow physical properties from X-Band backscatter.

Paul, Stephan; Willmes, Sascha; Hoppmann, Mario; Hunkeler, Priska; Heinemann, Günther

2014-05-01

41

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

42

Influence of snow cover and algae on the spectral dependence of transmitted irradiance through Arctic landfast first-year sea ice  

Microsoft Academic Search

Extensive spatial and temporal observations of sea ice algae remain limited due in part to current destructive and time intensive sampling techniques. In this paper we examine the influence of snow cover and ice algal biomass on the spectral dependence of photosynthetically available radiation transmitted through the snow-ice matrix using a data set collected in Resolute Passage, Canada, from 3

C. J. Mundy; J. K. Ehn; D. G. Barber; C. Michel

2007-01-01

43

NASA sea ice and snow validation plan for the Defense Meteorological Satellite Program special sensor microwave/imager  

NASA Technical Reports Server (NTRS)

This document addresses the task of developing and executing a plan for validating the algorithm used for initial processing of sea ice data from the Special Sensor Microwave/Imager (SSMI). The document outlines a plan for monitoring the performance of the SSMI, for validating the derived sea ice parameters, and for providing quality data products before distribution to the research community. Because of recent advances in the application of passive microwave remote sensing to snow cover on land, the validation of snow algorithms is also addressed.

Cavalieri, Donald J. (editor); Swift, Calvin T. (editor)

1987-01-01

44

Snow and Ice.  

ERIC Educational Resources Information Center

This experimental edition provides a number of activities useful for investigating snow and ice with elementary school children. Commencing with games with ice cubes, the activities lead through studies of snowflakes, snowdrifts, effects of wind and obstacles on the shape and formation of drifts, to a study of animals living under snow. The…

Minneapolis Independent School District 275, Minn.

45

EMAC-95 Snow and Ice airborne campaign  

Microsoft Academic Search

The European Multisensor Airborne Campaign-94\\/95 (EMAC-94\\/95) is organised by ESA and it covers six thematic areas. One of them is snow and ice, including both sea ice and land ice. A total of 17 research teams and 34 institutes are involved in the EMAC-95 Snow and Ice activities and data analysis. The main test sites are located in Finland (sea

Martti Hallikainen; Evert Attema; M. Wooding

1995-01-01

46

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

47

National Snow and Ice Data Center  

NSDL National Science Digital Library

NSIDC offers data and information about the cryosphere; that portion of the Earth where water is in solid form, typically snow or ice. Topics include snow, glaciers, permafrost, sea ice, news and features, and others. The State of the Cryosphere section provides an overview of the status of snow and ice as indicators of climate change. An image and photo gallery provides historic photographs and satellite imagery of cryospheric conditions in both the Arctic and Antarctica.

Barry, Roger

2001-09-15

48

Arctic-scale assessment of satellite passive microwave-derived snow depth on sea ice using Operation IceBridge airborne data  

NASA Astrophysics Data System (ADS)

Snow depth on sea ice (SD) is a key geophysical variable, knowledge of which is critical for calculating the energy and mass balance budgets. Moreover, accurate knowledge of the SD distribution is important to retrieve sea-ice thicknesses from altimetry data. So far, only space-based microwave radiometers (e.g., Advanced Microwave Scanning Radiometer for Earth Observing System; AMSR-E) provide operational SD on seasonal sea-ice retrievals. A thorough assessment of these retrievals is needed on a large scale and on a variety of sea-ice types. Our study presents such an assessment on Arctic sea ice using NASA's airborne Operation IceBridge (OIB) SDs, retrieved from radar measurements. Between 2009 and 2011, ˜610 12.5 km satellite grid cells were covered by seasonal sea ice where both satellite SD retrievals and OIB data were available. Using all the available data, the difference between the AMSR-E product and the averaged OIB snow-radar-derived SD is 0.00±0.07 m. Satellite-derived SD was accurate in the Beaufort Sea and the Canadian Archipelago but underestimated (˜0.07 m) in the Nares Strait. The RMSE between the two products ranges between 0.03 and 0.15 m. The RMSE is less than 0.06 m over a shallow snow cover (<0.20 m), in areas where satellite-retrieved ice concentrations are higher than 90%, surface smooth, and ice thicker than ˜0.5 m. Locally the AMSR-E algorithm can significantly underestimate SD. Several regions where the retrievals were less accurate (error >0.10 m) have been identified and related to the presence of either low ice concentration or significant fraction of multiyear ice within the grid cell that has not been flagged.

Brucker, Ludovic; Markus, Thorsten

2013-06-01

49

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

50

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

51

Bacteria in Snow and Glacier Ice  

Microsoft Academic Search

By definition, the cryosphere is the portion of the Earth where water is in solid form as snow or ice. It includes vast areas\\u000a of sea ice, freshwater ice, glaciers, ice sheets, snow cover and permafrost. Because of the extremely harsh climatic conditions,\\u000a these frozen environments had been considered for a long time to be devoid of life or serving

Vanya Miteva

52

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

53

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

54

Sea ice - Multiyear cycles and white ice  

NASA Technical Reports Server (NTRS)

The multiyear thickness cycles represent one of the interesting features of the sea ice studies performed by Semtner (1976) and Washington et al. (1976) with simple thermodynamic models of sea ice. In the present article, a description is given of results which show that the insulating effect of snow on the surface of the sea ice is important in producing these multiyear cycles given the physics included in the model. However, when the formation of white ice is included, the cycles almost disappear. White ice is the ice which forms at the snow-ice interface when the snow layer becomes thick enough to depress the ice below the water level. Water infiltrates the snow by coming through the ice at leads and generally freezes there, forming white ice.

Ledley, T. S.

1985-01-01

55

Remote sensing of snow and ice  

NASA Technical Reports Server (NTRS)

This paper reviews remote sensing of snow and ice, techniques for improved monitoring, and incorporation of the new data into forecasting and management systems. The snowcover interpretation of visible and infrared data from satellites, automated digital methods, radiative transfer modeling to calculate the solar reflectance of snow, and models using snowcover input data and elevation zones for calculating snowmelt are discussed. The use of visible and near infrared techniques for inferring snow properties, microwave monitoring of snowpack characteristics, use of Landsat images for collecting glacier data, monitoring of river ice with visible imagery from NOAA satellites, use of sequential imagery for tracking ice flow movement, and microwave studies of sea ice are described. Applications of snow and ice research to commercial use are examined, and it is concluded that a major problem to be solved is characterization of snow and ice in nature, since assigning of the correct properties to a real system to be modeled has been difficult.

Rango, A.

1979-01-01

56

2 – 8 GHz FMCW radar for estimating snow depth on antarctic sea ice  

Microsoft Academic Search

This paper presents the development and initial results from a prototype airborne Frequency Modulated Continuous Wave (FMCW) snow thickness radar operating at 2-8 GHz. The FMCW radar was constructed at the Center for Remote Sensing of Ice Sheets (CReSIS), Kansas University (USA), and is the product of a collaborative effort between Kansas University, the University of Tasmania (Australia) and the

N. Galin; A. Worby; R. Massom; G. Brooker; C. Leuschen; S. P. Gogineni; P. Jansen

2008-01-01

57

Large-Scale Patterns of Snow Melt on Arctic Sea Ice Mapped from Meteorological Satellite Imagery,  

National Technical Information Service (NTIS)

The seasonal progression of snow melt on Arctic pack ice is mapped from satellite shortwave imagery (0.4-1.1 micrometers) for four spring/summer seasons (1977, 1979, 1984 and 1985). This provides the first detailed information on the temporal change of th...

G. Scharfen R. G. Barry D. A. Robinson G. Kukla M. C. Serreze

1987-01-01

58

Analysis of Interannual Variations of Snow Melt on Arctic Sea Ice Mapped from Meteorological Satellite Imagery,  

National Technical Information Service (NTIS)

The seasonal progression of snow melt on the Arctic ice pack was mapped from shortwave satellite imagery for 1977, 1979, 1984 and 1985. The four years showed substantial differences in the timing of the melt interval. The progression of melt in May and Ju...

D. A. Robinson G. Scharfen R. G. Barry G. Kukla

1987-01-01

59

Snow accumulation rate retrieval across the Greenland ice facies using SeaWinds on QuikSCAT  

NASA Astrophysics Data System (ADS)

Recent accelerated mass loss from the Greenland ice sheet moderated by increased Arctic precipitation highlights the importance of a comprehensive understanding of the mechanisms controlling mass balance. Knowledge of the spatiotemporal variability of snow accumulation is critical to accurately quantify mass balance, yet the details are poorly understood on the scale of an ice sheet. Data acquired from the SeaWinds scatterometer on the QuikSCAT satellite together with spatially calibrated snow accumulation data from the Polar MM5 mesoscale climate model are used to develop a snow accumulation rate retrieval algorithm that exploits the sensitivity of Ku-band microwave radar to the unique stratigraphy within each of the Greenland ice facies. A layer of accumulating snow overlying a layer of ice exhibits an inverse relationship with radar backscatter that is approximately linear (dB) and a function of both snow accumulation rates and the microwave scattering characteristics of the underlying ice layer. Snow accumulation rates are retrieved using two types of QuikSCAT data: 1) data obtained from a single orbital pass at 25km resolution and 2) data spatial and temporally averaged using multiple orbital passes at ~2km and ~4km resolutions generated by the Scatterometer Image Reconstruction (SIR) algorithm. Regions displaying distinct scattering characteristics within each of the Greenland ice facies are threshold delineated using indices derived from parameterized layered melt and refreeze models. Freeze-up and melt onset dates are identified on a pixel-by-pixel basis using a Markov model, which follows the change in backscatter over time and classifies transitions between melting, refreezing and frozen states. Time series of twice-daily backscatter measurements over the time period 1999 - 2009 are linearly regressed from freeze-up to melt onset, negative slopes are correlated with Polar MM5 snow accumulation data and empirical relationships are established within each of the regions. Snow accumulation maps are presented at annual, winter season, and monthly time scales and comparisons are made between QuikSCAT data sets.

Miller, J.; Forster, R. R.; Long, D. G.; Schröder, R.; McDonald, K. C.; Box, J. E.

2011-12-01

60

Extinction of Ultraviolet-A Visible and Near - Wavelength Light in Snow and Antarctic Sea Ice.  

NASA Astrophysics Data System (ADS)

The optical properties of sea ice are important in the understanding of sea ice thermodynamics, growth and decay processes, polar climates, and remote sensing. The optical properties of ice have been fairly well described, but most studies have focused on wavelengths longer than 400 nm, and on Arctic sea ice. With increased interest in the effects of changing ultraviolet light levels from Antarctic ozone depletion, there has been recent work done on the extinction of ultraviolet light in Antarctic sea ice, including the study reported here. A spectrometer was modified, and taken on two trips to Antarctica to measure the extinction of light in sea ice. Extinction in summer and in winter sea ice were measured in the wavelength range 320 to 900 nm with the resolution range of 1 to 6 nm. This wavelength range covers the ultraviolet A band (320-400 nm), photosynthetically active region (PAR, 400-700 nm), and a small part of the near infrared (NIR, 700-1000 nm). The extinction coefficient in the middle of melting sea ice had a minimum of 0.6 m^{-1 } in the range of 450-500 nm, rising to 1 m ^{-1} at 350 nm, and 1.8 at 700 nm. Winter sea ice had spectrally flat extinction between 320-600 nm with values ranging from 1.7-5 m ^{-1} for different ice floes. This is in contrast to an expected minimum around 450 nm from absorption by ice and water. Extinction increased to 10 -15 m^{-1} at 900 nm in the winter sea ice. Both warm and cold ice had increased extinction at all wavelengths near the bottom of the floes. Algae were identified in several ice floes by the chlorophyll absorption peaks at 330, 430 and 680 nm. The presence of algae in the ice was associated with an increase in the extinction by a factor of up to 5 for wavelengths shorter than 600 nm, with a much smaller effect on longer wavelengths. Absorption by algae was evident at nearly all depths in some of the ice, but was mostly concentrated in the bottom 15% to 35%.

Quakenbush, Timothy Kyle

61

National Snow and Ice Data Center World Data Center-A for Glaciology. Annual Report 2000.  

National Technical Information Service (NTIS)

The National Snow and Ice Data Center (NSIDC) is an information and referral center supporting polar and cryospheric research. We distribute data and maintain information about snow cover, avalanches, glaciers, ice sheets, freshwater ice, sea ice, ground ...

2001-01-01

62

National Snow and Ice Data Center  

NSDL National Science Digital Library

The National Snow and Ice Data Center researches the cryosphere, and this website provides plenty of information on their work on the world of ice and snow. The Education Center homepage of their website will cause visitor's teeth to chatter just from looking at all the photos. There are several links to comprehensive discussions about Sea Ice, Snow, Frozen Ground, and Glaciers. One of those, called "All About Snow", has a link to an amazing "Gallery" of pictures of snow, such as the shocking photo of a 1966 blizzard in North Dakota that almost covered the utility poles, which is found in the "blizzards" section. Visitors should not miss the breath-taking photos of Sastrugi (wind-sculpted snow) in the "snow phenomena and formations" section of the gallery. Back on the homepage, visitors interested in a more condensed look at ice, should check out the "Quick Facts" link under "Basic Information" on the homepage, to find Quick Facts sections on "Arctic Sea Ice", "Ice Sheets", "Ice Shelves", and "Icebergs".

63

Application of a Three-Component Scattering Model for Snow-covered First-Year Arctic Sea Ice  

NASA Astrophysics Data System (ADS)

In this study, we examine the utility of a three-component scattering model to quantify the sensitivity of radar incidence angle to snow thickness over landfast first-year sea ice (FYI) during the early spring melt transition. This model utilizes the Freeman-Durden decomposition technique to segregate total power (SPAN) of each pixel into three simple scattering mechanisms (Surface, Volume and Double-Bounce) which is well adopted for naturally occurring terrain (Freeman and Durden, 1992; 1998) using airborne Polarimetric synthetic aperture radar (AIRSAR) data. Our model is based on (i) surface scattering from top of the snow-covered FYI (Smooth, Rough and Deformed); (ii) volume scattering contributed from snow-ice and ice-water interface layers which consists of grain size, brine volume, wetness and orientation of snow grain to radar; (iii) double-bounce scattering contributed from ice ridges. This study used C-band fully Polarimetric synthetic aperture radar (POLSAR) data acquired on May 15 and 18, 2009 at Hudson Bay, Churchill during cold (? -8°C) surface air temperature at two specific incidence angles (28.9° & 39°). The model is used to discriminate snow-covered FYI types namely smooth ice (SI), rough ice (RI) and deformed ice (DI). This model is then used to quantify various snow-thicknesses on FYI. We observed that surface scattering (Ps) contributed the dominant scattering mechanism (Ps: SI-76.85% at 28.9° and 69.48% at 39°; RI-65.97% at 28.9° and 57.13% at 39°; and DI- 60.3% at 28.9° and 46.31% at 39°) which decreases with increasing incidence angle and surface roughness; volume scattering (Pv) contributed as a second dominant scattering mechanism (Pv: SI-20.01% at 28.9° and 28.29% at 39°; RI-32.18% at 28.9° and 40.68% at 39°; and DI-38.42% at 28.9° and 52.03% at 39°) which increases with surface roughness and incidence angle; and double-bounce scattering(Pd) contributed very negligible amount to the total scattering (Pd: SI-3.14% at 28.9° and 2.23% at 39°; RI-1.85% at 28.9° and 2.19% at 39°; and DI-1.27% at 28.9° and 1.66% at 39°) which increases with incidence angle except for smooth ice. Similarly, surface scattering increases with snow thickness and decreases with incidence angle; volume scattering increases with incidence angle and decreases with increasing snow thickness and double-bounce scattering contributed very little amount to the total SPAN. It was also evaluated that the snow thickness has significant effect on our scattering model particularly in thin snow cover (8.83±4.17 cm) when compared with a thick (25±1.41 cm) cover.

Hossain, M.; Yackel, J. J.

2011-12-01

64

2013 Arctic Sea Ice Minimum  

NASA Video Gallery

After an unusually cold summer in the northernmost latitudes, Arctic sea ice appears to have reached its annual minimum summer extent for 2013 on Sept. 13, the NASA-supported National Snow and Ice ...

65

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

66

The Role of Snow and Ice in the Climate System  

SciTech Connect

Global snow and ice cover (the 'cryosphere') plays a major role in global climate and hydrology through a range of complex interactions and feedbacks, the best known of which is the ice - albedo feedback. Snow and ice cover undergo marked seasonal and long term changes in extent and thickness. The perennial elements - the major ice sheets and permafrost - play a role in present-day regional and local climate and hydrology, but the large seasonal variations in snow cover and sea ice are of importance on continental to hemispheric scales. The characteristics of these variations, especially in the Northern Hemisphere, and evidence for recent trends in snow and ice extent are discussed.

Barry, Roger (NSIDC) [NSIDC

2007-12-19

67

Protective Coverings for Ice and Snow - Aqueous Foam Studies.  

National Technical Information Service (NTIS)

Summer deterioration of their surfaces 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. Sawduct has been used by the Navy for protecting compacted-snow areas,...

N. S. Stehle

1964-01-01

68

Observations of the PCB distribution within and in-between ice, snow, ice-rafted debris, ice-interstitial water, and seawater in the Barents Sea marginal ice zone and the North Pole area.  

PubMed

To evaluate the two hypotheses of locally elevated exposure of persistent organic pollutants (POPs) in ice-associated microenvironments and ice as a key carrier for long-range transport of POPs to the Arctic marginal ice zone (MIZ), dissolved and particulate polychlorinated biphenyls (PCBs) were analyzed in ice, snow, ice-interstitial water (IIW), seawater in the melt layer underlying the ice, and in ice-rafted sediment (IRS) from the Barents Sea MIZ to the high Arctic in the summer of 2001. Ultra-clean sampling equipment and protocols were specially developed for this expedition, including construction of a permanent clean room facility and a stainless steel seawater intake system on the I/B ODEN as well as two mobile 370 l ice-melting systems. Similar concentrations were found in several ice-associated compartments. For instance, the concentration of one of the most abundant congeners, PCB 52, was typically on the order of 0.1-0.3 pg l(-1) in the dissolved (melted) phase of the ice, snow, IIW, and underlying seawater while its particulate organic-carbon (POC) normalized concentrations were around 1-3 ng gPOC(-1) in the ice, snow, IIW, and IRS. The solid-water distribution of PCBs in ice was well correlated with and predictable from K(ow) (ice log K(oc)-log K(ow) regressions: p<0.05, r2=0.78-0.98, n=9), indicating near-equilibrium partitioning of PCBs within each local ice system. These results do generally not evidence the existence of physical microenvironments with locally elevated POP exposures. However, there were some indications that the ice-associated system had harbored local environments with higher exposure levels earlier/before the melting/vegetative season, as a few samples had PCB concentrations elevated by factors of 5-10 relative to the typical values, and the elevated levels were predominantly found at the station where melting had putatively progressed the least. The very low PCB concentrations and absence of any significant concentration gradients, both in-between different matrices and over the Eurasian Arctic basin scale, suggest that ice is not an important long-range transport purveyor of POPs to the Arctic MIZ ecosystem. PMID:15866279

Gustafsson, O; Andersson, P; Axelman, J; Bucheli, T D; Kömp, P; McLachlan, M S; Sobek, A; Thörngren, J-O

2005-04-15

69

The Arctic snow and air temperature budget over sea ice during winter  

Microsoft Academic Search

Arctic cooling through the fall-winter transition is calculated from a coupled atmosphere-sea ice thermal model and compared to temperature soundings and surface measurements made north of Svalbard during the Coordinated Eastern Arctic Experiment (CEAREX). A typical winter, clear-sky vertical temperature structure of the polar air mass is composed of a surface-based temperature inversion or an inversion above a very shallow

James E. Overland; Peter S. Guest

1991-01-01

70

Snow cover and short-term synoptic events drive biogeochemical dynamics in winter Weddell Sea pack ice (AWECS cruise - June to August 2013)  

NASA Astrophysics Data System (ADS)

This paper presents the preliminary results of an integrated multidisciplinary study of pack ice biogeochemistry in the Weddell Sea during the winter 2013 (June-August). The sea ice biogeochemistry group was one of the components of the AWECS (Antarctic Winter Ecosystem and Climate Study) cruise (Polarstern ANTXXIX-6). A total of 12 stations were carried out by the sea ice biogeochemistry group, which collected a suite of variables in the fields of physics, inorganic chemistry, gas content and composition, microbiology, biogeochemistry, trace metals and the carbonate system in order to give the best possible description of the sea ice cover and its interactions at interfaces. Samples were collected in the atmosphere above (gas fluxes), in the snow cover, in the bulk ice (ice cores), in the brines (sackholes) and in the sea water below (0m, 1m, 30 m). Here we present the results of basic physico-chemical (T° , bulk ice salinity, brine volumes, brine salinity, Rayleigh numbers) and biological (Chla) measurements in order to give an overview of the general status of the Weddell Sea winter pack ice encountered, and discuss how it controls climate relevant biogeochemical processes. Our results from the first set of 9 stations, mainly sampled along the Greenwich meridian and the easternmost part of the Weddell Sea definitively refute the view of a biogeochemically 'frozen' sea ice during the Winter. This has already been demonstrated for the Spring and Summer, but we now see that sea ice sustains considerable biological stocks and activities throughout the Winter, despite the reduced amount of available PAR radiation. Accretion of the snow cover appears to play an essential role in driving biogeochemical activity, through warming from insulation, thus favouring brine transport, be it through potential convection, surface brine migration (brine tubes) or flooding. This results in a 'widening' of the internal autumn layer (quite frequent in this rafting-dominated sea ice cover) and increase of the chla burden with age. Results from the second set of 3 stations in the western branch of the Weddell Sea gyre confirm that it comprises a mixture of older fast/second year ice floes with younger first-year ice floes. The older ice had the highest Chlaconcentrations of the entire cruise (>200 ?gl-1), in an internal community enclosed within desalinized impermeable upper and lower layers. The first-year ice differs from that in the eastern Weddell Sea as it is dominated by columnar ice and (weak) algal communities are only found on the bottom or near the surface (no internal maximum).

Tison, Jean-Louis; Delille, Bruno; Dieckmann, Gherard; de Jong, Jeroen; Janssens, Julie; Rintala, Janne; Luhtanen, Annemari; Gussone, Niklaus; Uhlig, Christiane; Nomura, Daïki; Schoemann, Véronique; Zhou, Jiayun; Carnat, Gauthier; Fripiat, François

2014-05-01

71

Sea Ice  

NASA Technical Reports Server (NTRS)

Sea ice covers vast areas of the polar oceans, with ice extent in the Northern Hemisphere ranging from approximately 7 x 10(exp 6) sq km in September to approximately 15 x 10(exp 6) sq km in March and ice extent in the Southern Hemisphere ranging from approximately 3 x 10(exp 6) sq km in February to approximately 18 x 10(exp 6) sq km in September. These ice covers have major impacts on the atmosphere, oceans, and ecosystems of the polar regions, and so as changes occur in them there are potential widespread consequences. Satellite data reveal considerable interannual variability in both polar sea ice covers, and many studies suggest possible connections between the ice and various oscillations within the climate system, such as the Arctic Oscillation, North Atlantic Oscillation, and Antarctic Oscillation, or Southern Annular Mode. Nonetheless, statistically significant long-term trends are also apparent, including overall trends of decreased ice coverage in the Arctic and increased ice coverage in the Antarctic from late 1978 through the end of 2003, with the Antarctic ice increases following marked decreases in the Antarctic ice during the 1970s. For a detailed picture of the seasonally varying ice cover at the start of the 21st century, this chapter includes ice concentration maps for each month of 2001 for both the Arctic and the Antarctic, as well as an overview of what the satellite record has revealed about the two polar ice covers from the 1970s through 2003.

Parkinson, Claire L.; Cavalieri, Donald J.

2005-01-01

72

Sea Ice  

NASA Technical Reports Server (NTRS)

During 2013, Arctic sea ice extent remained well below normal, but the September 2013 minimum extent was substantially higher than the record-breaking minimum in 2012. Nonetheless, the minimum was still much lower than normal and the long-term trend Arctic September extent is -13.7 per decade relative to the 1981-2010 average. The less extreme conditions this year compared to 2012 were due to cooler temperatures and wind patterns that favored retention of ice through the summer. Sea ice thickness and volume remained near record-low levels, though indications are of slightly thicker ice compared to the record low of 2012.

Perovich, D.; Gerland, S.; Hendricks, S.; Meier, Walter N.; Nicolaus, M.; Richter-Menge, J.; Tschudi, M.

2013-01-01

73

The microwave emissivity variability of snow covered first-year sea ice from late winter to early summer: a model study  

NASA Astrophysics Data System (ADS)

Satellite observations of microwave brightness temperatures between 19 GHz and 85 GHz are the main data sources for operational sea-ice monitoring and retrieval of ice concentrations. However, microwave brightness temperatures depend on the emissivity of snow and ice, which is subject to pronounced seasonal variations and shows significant hemispheric contrasts. These mainly arise from differences in the rate and strength of snow metamorphism and melt. We here use the thermodynamic snow model SNTHERM forced by European Re-Analysis (ERA) interim data and the Microwave Emission Model of Layered Snowpacks (MEMLS), to calculate the sea-ice surface emissivity and to identify the contribution of regional patterns in atmospheric conditions to its variability in the Arctic and Antarctic. The computed emissivities reveal a pronounced seasonal cycle with large regional variability. The emissivity variability increases from winter to early summer and is more pronounced in the Antarctic. In the pre-melt period (January-May, July-November) the standard deviations in surface microwave emissivity due to diurnal, regional and inter-annual variability of atmospheric forcing reach up to ?? = 0.034, 0.043, and 0.097 for 19 GHz, 37 GHz and 85 GHz channels, respectively. Between 2000 and 2009, small but significant positive emissivity trends were observed in the Weddell Sea during November and December as well as in Fram Strait during February, potentially related to earlier melt onset in these regions. The obtained results contribute to a better understanding of the uncertainty and variability of sea-ice concentration and snow-depth retrievals in regions of high sea-ice concentrations.

Willmes, S.; Nicolaus, M.; Haas, C.

2014-05-01

74

Physics of Ice and Snow as Affects Thermal Pressure.  

National Technical Information Service (NTIS)

The physics of ice affects the development and magnitude of thermal ice pressures on lakes and restricted areas of the sea. The crystal structure of ice, the structure of ice covers and snow are related to physical and mechanical properties. Properties ac...

L. Bergdahl

1977-01-01

75

The role of sea ice dynamics in global climate change  

NASA Technical Reports Server (NTRS)

The topics covered include the following: general characteristics of sea ice drift; sea ice rheology; ice thickness distribution; sea ice thermodynamic models; equilibrium thermodynamic models; effect of internal brine pockets and snow cover; model simulations of Arctic Sea ice; and sensitivity of sea ice models to climate change.

Hibler, William D., III

1992-01-01

76

Polarimetric backscattering from sea ice  

NASA Technical Reports Server (NTRS)

Polarimetric backscattering from sea ice is presented. Theoretical models for backscattering are first presented for various ice types. Then, theoretical results are compared with experimental data for new thin ice, first-year ice, and multi-year ice. Sea ice is modeled as a layer medium containing random scatterers and rough interfaces. For multi-year sea ice with snow cover, the sea ice layer is modeled as an ice background with embedded spheroidal air bubbles and the snow layer as air with ice grains. The hummocky topography on multi-year ice is characterized by a Gaussian distribution which has an averaging effect on backscattering coefficients. First-year sea ice is described by an ice medium hosting ellipsoidal brine inclusions. These inclusions are oriented preferentially in the vertical direction due to the columnar structure of first-year sea ice. Azimuthally, the orientation of the brine pockets are random corresponding to the random c-axes in sea ice, unless the axes are oriented by sea currents. For thin ice in newly opened leads, it has been observed that there exists a thin brine layer with very high salinity on the top surface of the new ice. This brine layer is depicted as a medium with high permittivity which can significantly affect electromagnetic scattering signatures from the lower thin ice layer, with a higher fractional volume of brine inclusions due to higher salinity as compared to thick first-year sea ice. The rough medium interfaces are described as Gaussian rough surfaces characterized by root-mean-square heights and surface correlation lengths. The contribution from rough surface, calculated under the Kirchhoff approximation or small perturbation method, is assumed to be independent from volume scattering. The total loss including absorption and scattering losses in the scattering media is represented by the imaginary part of effective permittivity obtained from the strong fluctuation theory. The polarimetric scattering coefficients for different ice types are then derived under the distorted Born approximation.

Nghiem, S. V.; Kwok, R.; Yueh, S. H.

1993-01-01

77

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'

78

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

79

Overview of EMAC-95 snow and ice airborne campaign in Finland  

Microsoft Academic Search

The 1995 European Multisensor Airborne Campaign (EMAC-95) on snow and ice was funded by European Space Agency (ESA) and national authorities. The main test sites were in Finland (sea ice, snow in boreal areas) and Norway (land ice, snow in mountainous areas). The airborne instruments included two microwave radiometer systems (Helsinki University of Technology HUTRAD and UK Meteorological Office system)

M. Hallikainen; P. Ahola; K. Rautiainen; J. Pihlflyckt; T. Tirri; M. Makynen; J. Lahtinen; H. Servomaa; P. Makkonen; J. Grandell; M. Kemppinen; M. Nikulainen; H. Taskinen; S. Tauriainen; M. Roschier

1996-01-01

80

Mercuric reductase genes (merA) and mercury resistance plasmids in High Arctic snow, freshwater and sea-ice brine.  

PubMed

Bacterial reduction in Hg(2+) to Hg(0) , mediated by the mercuric reductase (MerA), is important in the biogeochemical cycling of Hg in temperate environments. Little is known about the occurrence and diversity of merA in the Arctic. Seven merA determinants were identified among bacterial isolates from High Arctic snow, freshwater and sea-ice brine. Three determinants in Bacteriodetes, Firmicutes and Actinobacteria showed < 92% (amino acid) sequence similarity to known merA, while one merA homologue in Alphaproteobacteria and 3 homologues from Betaproteobacteria and Gammaproteobacteria were > 99% similar to known merA's. Phylogenetic analysis showed the Bacteroidetes merA to be part of an early lineage in the mer phylogeny, whereas the Betaproteobacteria and Gammaproteobacteria merA appeared to have evolved recently. Several isolates, in which merA was not detected, were able to reduce Hg(2+) , suggesting presence of unidentified merA genes. About 25% of the isolates contained plasmids, two of which encoded mer operons. One plasmid was a broad host-range IncP-? plasmid. No known incompatibility group could be assigned to the others. The presence of conjugative plasmids, and an incongruent distribution of merA within the taxonomic groups, suggests horizontal transfer of merA as a likely mechanism for High Arctic microbial communities to adapt to changing mercury concentration. PMID:23909591

Møller, Annette K; Barkay, Tamar; Hansen, Martin A; Norman, Anders; Hansen, Lars H; Sørensen, Søren J; Boyd, Eric S; Kroer, Niels

2014-01-01

81

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

82

Biogeochemistry in Sea Ice: CICE model developments  

SciTech Connect

Polar primary production unfolds in a dynamic sea ice environment, and the interactions of sea ice with ocean support and mediate this production. In spring, for example, fresh melt water contributes to the shoaling of the mixed layer enhancing ice edge blooms. In contrast, sea ice formation in the fall reduces light penetration to the upper ocean slowing primary production in marine waters. Polar biogeochemical modeling studies typically consider these types of ice-ocean interactions. However, sea ice itself is a biogeochemically active medium, contributing a significant and, possibly, essential source of primary production to polar regions in early spring and fall. Here we present numerical simulations using the Los Alamos Sea Ice Model (CICE) with prognostic salinity and sea ice biogeochemistry. This study investigates the relationship between sea ice multiphase physics and sea ice productivity. Of particular emphasis are the processes of gravity drainage, melt water flushing, and snow loading. During sea ice formation, desalination by gravity drainage facilitates nutrient exchange between ocean and ice maintaining ice algal blooms in early spring. Melt water flushing releases ice algae and nutrients to underlying waters limiting ice production. Finally, snow loading, particularly in the Southern Ocean, forces sea ice below the ocean surface driving an upward flow of nutrient rich water into the ice to the benefit of interior and freeboard communities. Incorporating ice microphysics in CICE has given us an important tool for assessing the importance of these processes for polar algal production at global scales.

Jeffery, Nicole [Los Alamos National Laboratory; Hunke, Elizabeth [Los Alamos National Laboratory; Elliott, Scott [Los Alamos National Laboratory; Turner, Adrian [Los Alamos National Laboratory

2012-06-18

83

Surface processes on perennial Antarctic sea ice  

NASA Astrophysics Data System (ADS)

Antarctic perennial sea ice surface processes differ markedly from those that dominate in the Arctic. These processes - surface flooding, formation of snow ice and superimposed ice, and the development of porous gap layers which harbour rich biological communities - entirely control the growth of perennial ice, yet understanding has been hampered by limited observations, particularly of temporal evolution of the ice. We investigate the controls on surface sea ice properties and mass balance with two recent data sets: (1) summer sea ice core data obtained in the Bellingshausen Sea in 2007 and the Amundsen Sea in 2009, and (2) Ice Mass Balance buoys (IMBs) deployed in the Amundsen and Weddell Seas in February 2009 that provide data over almost an entire annual cycle - the longest continuous record of snow and sea ice mass balance in the Antarctic to date. These data are compared with results of a complex one-dimensional thermodynamic and fluid transport model to constrain estimates of snow accumulation, melt, and snow-to-ice conversion. The role of fluid transport in controlling gap layer formation and ice mass balance is discussed. Ice core data show a high degree of regional variability in surface ice types. In extreme cases superimposed ice may comprise a meter or more of the ice thickness, much more than has previously reported. Gap layer communities were widespread throughout the region, but manifested in several distinct forms suggesting multiple mechanisms of formation. Their presence appears to be controlled in part by the interplay between flooding, snow melt, and superimposed ice formation. This highlights the need for improved understanding of snow and summer melt processes in the Antarctic for understanding the impact of climate variability on both sea ice mass balance and biological communities.

Maksym, T. L.; Stammerjohn, S. E.; Pasquer, B.; Jackson, K.; Wilkinson, J.

2009-12-01

84

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

85

Boundary layer dynamics during the Ocean-Atmosphere-Sea-Ice-Snow (OASIS) 2009 experiment at Barrow, AK  

NASA Astrophysics Data System (ADS)

atmospheric turbulence measurements were conducted from seven sonic anemometers on two different towers in Barrow, AK, during the spring of 2009 as part of the Ocean-Atmosphere-Sea-Ice-Snow (OASIS) campaign. This was the largest number of side-by-side atmospheric turbulence measurements in the Arctic at one time. These analyses allowed for (1) a comparison of the instrumental measurement approaches and (2) a comparison of the variability of the lower atmospheric surface layer at these measurement heights and tower sites. Friction velocity estimates were affected for a sonic anemometer that was operated on the tower in the near vicinity of a building module. Boundary layer height (BLH) was estimated from sonic anemometer measurements based both on a turbulence variable estimator and a temperature gradient method. Results from both methods were compared to radiosonde-estimated BLH and generally underestimated the BLH for shallower depths. Conditions with low BLH (< 100 m) often lasted for several days. The seven ozone depletion events (ODE) that were observed during the OASIS campaign had a tendency of coinciding with BLH of less than 50 m and stable atmospheric conditions; however, there was not a clear relationship between the occurrence of ODE and wind speed or wind direction as ODE occurred under a wide range of conditions of BLH, wind speed, local wind direction, and atmospheric stability. Comparisons of these surface layer dynamics to sites in Antarctica and Greenland reveal that boundary layer dynamics are not the primary driving force that fosters the unique ozone chemistry at this coastal Arctic site.

Boylan, Patrick; Helmig, Detlev; Staebler, Ralf; Turnipseed, Andrew; Fairall, Chris; Neff, William

2014-03-01

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] [Satellite Research Lab., Camp Springs, MD (United States); and others

1996-05-01

88

Seasonality of halogen deposition in polar snow and ice  

NASA Astrophysics Data System (ADS)

The atmospheric chemistry of iodine and bromine in polar regions is of interest due to the key role of halogens in many atmospheric processes, particularly tropospheric ozone destruction. Bromine is emitted from the open ocean but is enriched above first-year sea ice during springtime bromine explosion events, whereas iodine is emitted from biological communities hosted by sea ice. It has been previously demonstrated that bromine and iodine are present in Antarctic ice over glacial-interglacial cycles. Here we investigate seasonal variability of bromine and iodine in polar snow and ice, to evaluate their emission, transport and deposition in Antarctica and the Arctic and better understand potential links to sea ice. We find that bromine enrichment (relative to sea salt content) and iodine concentrations in polar ice do vary seasonally in Arctic snow and Antarctic ice and we relate such variability to satellite-based observations of tropospheric halogen concentrations. Peaks of bromine enrichment in Arctic snow and Antarctic ice occur in spring and summer, when sunlight is present. Iodine concentrations are largest in winter Antarctic ice strata, contrary to contemporary observations of summer maxima in iodine emissions.

Spolaor, A.; Vallelonga, P.; Gabrieli, J.; Martma, T.; Björkman, M. P.; Isaksson, E.; Cozzi, G.; Turetta, C.; Kjær, H. A.; Curran, M. A. J.; Moy, A. D.; Schönhardt, A.; Blechschmidt, A.-M.; Burrows, J. P.; Plane, J. M. C.; Barbante, C.

2014-03-01

89

Effects of snow removal and algal photoacclimation on growth and export of ice algae  

Microsoft Academic Search

Net growth of ice algae in response to changes in overlying snow cover was studied after manipulating snow thickness on land-fast,\\u000a Arctic sea ice. Parallel laboratory experiments measured the effect of changing irradiance on growth rate of the ice diatom,\\u000a Nitzschia frigida. After complete removal of thick snow (?9 cm), in situ ice algae biomass declined (over 7–12 days), while removal of

Andrew R. Juhl; Christopher Krembs

2010-01-01

90

[Spectral features analysis of sea ice in the Arctic Ocean].  

PubMed

Sea ice in the Arctic Ocean plays an important role in the global climate change, and its quick change and impact are the scientists' focus all over the world. The spectra of different kinds of sea ice were measured with portable ASD FieldSpec 3 spectrometer during the long-term ice station of the 4th Chinese national Arctic Expedition in 2010, and the spectral features were analyzed systematically. The results indicated that the reflectance of sea ice covered by snow is the highest one, naked sea ice the second, and melted sea ice the lowest. Peak and valley characteristics of spectrum curves of sea ice covered by thick snow, thin snow, wet snow and snow crystal are very significant, and the reflectance basically decreases with the wavelength increasing. The rules of reflectance change with wavelength of natural sea ice, white ice and blue ice are basically same, the reflectance of them is medium, and that of grey ice is far lower than natural sea ice, white ice and blue ice. It is very significant for scientific research to analyze the spectral features of sea ice in the Arctic Ocean and to implement the quantitative remote sensing of sea ice, and to further analyze its response to the global warming. PMID:22715789

Ke, Chang-qing; Xie, Hong-jie; Lei, Rui-bo; Li, Qun; Sun, Bo

2012-04-01

91

Frost flowers growing in the Arctic ocean-atmosphere-sea ice-snow interface: 2. Mercury exchange between the atmosphere, snow, and frost flowers  

NASA Astrophysics Data System (ADS)

Frost flowers are ice crystals that grow on refreezing sea ice leads in Polar Regions by wicking brine from the sea ice surface and accumulating vapor phase condensate. These crystals contain high concentrations of mercury (Hg) and are believed to be a source of reactive halogens, but their role in Hg cycling and impact on the fate of Hg deposited during atmospheric mercury depletion events (AMDEs) are not well understood. We collected frost flowers growing on refreezing sea ice near Barrow, Alaska (U.S.A.) during an AMDE in March 2009 and measured Hg concentrations and Hg stable isotope ratios in these samples to determine the origin of Hg associated with the crystals. We observed decreasing ?199Hg values in the crystals as they grew from new wet frost flowers (mean ?199Hg = 0.77 ± 0.13‰, 1 s.d.) to older dry frost flowers (mean ?199Hg = 0.10 ± 0.05‰, 1 s.d.). Over the same time period, mean Hg concentrations in these samples increased from 131 ± 6 ng/L (1 s.d.) to 180 ± 28 ng/L (1 s.d.). Coupled with a previous study of Hg isotopic fractionation during AMDEs, these results suggest that Hg initially deposited to the local snowpack was subsequently reemitted during photochemical reduction reactions and ultimately accumulated on the frost flowers. As a result of this process, frost flowers may lead to enhanced local retention of Hg deposited during AMDEs and may increase Hg loading to the Arctic Ocean.

Sherman, Laura S.; Blum, Joel D.; Douglas, Thomas A.; Steffen, Alexandra

2012-07-01

92

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

93

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

Microsoft Academic Search

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

T. Fichefet; M. A. Morales Maqueda

1997-01-01

94

Oxygen isotope composition of water and snow-ice cover of isolated lakes at various stages of separation from the White Sea  

NASA Astrophysics Data System (ADS)

This study aimed to analyze the oxygen isotope composition of water, ice, and snow in water bodies isolated from the White Sea and to identify the structural peculiarities of these pools during the winter period. The studies were performed during early spring in Kandalaksha Bay of the White Sea, in Velikaya Salma Strait and in Rugoserskaya Inlet. The studied water bodies differ in their degree of isolation from the sea. In particular, Ermolinskaya Inlet has normal water exchange with the sea; the Lake on Zelenyi Cape represents the first stage of isolation; i. e., it has permanent water exchange with the sea by the tide. Kislo-Sladkoe Lake receives sea water from time to time. Trekhtsvetnoe Lake is totally isolated from the sea and is a typical meromictic lake. Finally, Nizhnee Ershovskoe Lake exhibits some features of a saline water body. The oxygen isotope profile of the water column in Trekhtsvetnoe Lake allows defining three layers; this lake may be called typically meromictic. The oxygen isotope profile of the water column in Kislo-Sladkoe Lake is even from the surface to the bottom. The variability of ?18O is minor in Lake on Zelenyi Cape. A surface layer (0-1 m) exists in Nizhnee Ershovskoe Lake, and the oxygen isotope variability is well pronounced. Deeper, where the freshwater dominates, the values of ?18Îvary insignificantly disregarding the water depth and temperature. This fresh water lake is not affected by the seawater and is not stratified according to the isotope profile. It is found that applying the values of ?18Î and profiles of temperature and salinity may appear as an effective method in defining the water sources feeding the water bodies isolated from the sea environment.

Lisitzin, A. P.; Vasil'chuk, Yu. K.; Shevchenko, V. P.; Budantseva, N. A.; Krasnova, E. D.; Pantyulin, A. N.; Filippov, A. S.; Chizhova, Ju. N.

2013-04-01

95

Blue-ice and snow runways <  

NSF Publications Database

Concepts for such runways include "blue-ice" runways on glacier ice and runways on compacted snow. 2.2.1.2 Development of a blue-ice runway at the Pegasus site (Pegasus II) The concept for the Pegasus II runway is to develop a runway directly on exposed blue ice. 2.2.2.1 Development of a blue-ice runway at Mount Howe The closest potential blue-ice runway site to the South Pole is at Mount Howe, where the exposed blue-ice surface is suitable as a runway with relatively little smoothing.

96

An enhancement of the NASA Team sea ice algorithm  

Microsoft Academic Search

An enhancement of the NASA Team sea ice concentration algorithm overcomes the problem of a low ice concentration bias associated with surface snow effects that are particularly apparent in Southern Ocean sea ice retrievals. The algorithm has the same functional form as the NASA Team algorithm, but uses a wider range of frequencies (19-85 GHz). It accommodates ice temperature variability

Thorsten Markus; Donald J. Cavalieri

2000-01-01

97

Arctic sea ice minimum extent  

NASA Astrophysics Data System (ADS)

The extent of Arctic sea ice dropped to 3.41 million square kilometers on 16 September, 760,000 square kilometers below the minimum ice extent in 2007, which had been the low mark since the satellite record began in 1979, the National Snow and Ice Data Center (NSIDC) announced. Overall ice extent is 50% below where it was in the 1970s, NSIDC research scientist Walt Meier said during a 19 September briefing. He added that there is also a decrease in ice thickness. Meier said that sea ice varies from year to year with lots of ups and downs. “We wouldn't expect it to keep going down, straight off the map so to speak,” he said. “Typically after a record low, we've seen it rebound.” Meier added that the general long-term trend is for the Arctic to continue to become generally ice free. He said it is difficult to know how long it will take for that condition to be reached; because of strong variations, Arctic sea ice extent could plateau for some time.

Showstack, Randy

2012-10-01

98

Critical behavior of transport in sea ice  

Microsoft Academic Search

Geophysical materials such as sea ice, rocks, soils, snow, and glacial ice are composite media with complex, random microstructures. The effective fluid, gas, thermal, and electromagnetic transport properties of these materials play an important role in the large-scale dynamics and behavior of many geophysical systems. A striking feature of such media is that subtle changes in microstructural characteristics can induce

K. M. Golden

2003-01-01

99

Volcanic deposits in Antarctic snow and ice  

NASA Astrophysics Data System (ADS)

Major volcanic eruptions are able to spread large amounts of sulfuric acid all over the world. Acid layers of volcanic origin were detected for the first time a few years ago by Hammer in Greenland ice. The present paper deals with volcanic deposits in the Antarctic. The different methods that can be used to find volcanic acid deposits in snow and ice cores are compared: electrical conductivity, sulfate, and acidity measurements. Numerous snow and ice samples collected at several Antarctic locations were analyzed. The results reveal that the two major volcanic events recorded by H2SO4, fallout in Antarctic ice over the last century are the eruptions of Krakatoa (1883) and Agung (1963), both located at equatorial latitudes in the southern hemisphere. The volcanic signals are found to be particularly well defined at central Antarctic locations apparently in relation to the low snow accumulation rates in these areas. It is demonstrated that volcanic sulfuric acid in snow is not even partially neutralized by ammonia. The possible influence of Antarctic volcanic activity on snow chemistry is also discussed, using the three recent eruptions of the Deception Island volcano as examples. Only one of them seems to have had a significant effect on the chemistry of snow at a location 200 km from this volcano. It is concluded that Antarctic volcanic ice records are less complicated than Greenland records because of the limited number of volcanos in the southern hemisphere and the apparently higher signal to background ratio for acidity in Antarctica than in Greenland.

Delmas, Robert J.; Legrand, Michel; Aristarain, Alberto J.; Zanolini, FrançOise

1985-12-01

100

Annual cycle of landfast sea ice in Prydz Bay, east Antarctica  

Microsoft Academic Search

Under the Chinese National Antarctic Research Expedition program in 2006, the annual thermal mass balance of landfast ice in the vicinity of Zhongshan Station, Prydz Bay, east Antarctica, was investigated. Sea ice formed from mid-February onward, and maximum ice thickness occurred in late November. Snow cover remained thin, and blowing snow caused frequent redistribution of the snow. The vertical ice

Ruibo Lei; Zhijun Li; Bin Cheng; Zhanhai Zhang; Petra Heil

2010-01-01

101

Snow is a Form of Ice  

NSDL National Science Digital Library

This is a lesson about condensation, snow and snowflakes. Learners will investigate how water and ice exist in the atmosphere as they study water vapor condensing, find that clouds are made of tiny droplets of water, and notice that snow forms in clouds. Activities include demonstrations by the teacher, small group miming, speaking, drawing, and/or writing. In addition to commonly found classroom materials, dry ice, an aquarium or terrarium container, magnifying glass are needed. This is lesson 6 of 12 in the unit, Exploring Ice in the Solar System.

102

Is sea salt in ice cores a proxy of past sea ice extent?  

NASA Astrophysics Data System (ADS)

A number of marine, coastal and ice core proxies have been used to try to assess the past extent of sea ice. Sea salt has been proposed as a proxy for past ice extent, at least in the Southern Ocean. The idea is that the sea ice surface itself holds a source of sea salt, that is stronger than the source from the open ocean it replaces. That a sea ice source exists is apparent from observations of the ratio of sulphate to sodium in coastal aerosol and snow samples. While the idea behind using sea salt as a proxy is attractive, and leads to sensible inferences, many doubts remain. Firstly the exact nature of the source remains uncertain, and secondly it is not clear if ice extent, as opposed to changes in atmospheric transport and lifetime, would dominate variability in the ice core record of sea salt. Here we use a model of atmospheric transport and chemistry (p-TOMCAT) to assess the consequences of a sea ice source, focussing particularly on a source that has been proposed to arise from the sublimation of salty blowing snow. We will briefly report some new observations from a winter cruise, that will allow us to comment on the likelihood that blowing snow does pose a significant source. We will then present results from the model (implemented using existing parameters). The model has been run with seasonally and interannually varying sea ice extent and meteorology for the Antarctic, tracking, at different ice core sites, the concentration that arises from the open ocean and sea ice sources. We have already shown that the model, after tuning, is able to reproduce the magnitude and seasonal cycle of sea salt at a range of sites globally. By varying each component separately we explore which factors (sea ice presence, wind speed at source, transporting winds) and which source regions control the delivery of sea salt to sites in Antarctica. Such work suggests that sea salt cannot be used as a sea ice proxy on interannual timescales, but may be suitable on longer timescales. By employing much larger sea ice extents, such as at the last glacial maximum (LGM), we find a strong increase in concentration at ice core sites when ice extent increases. The increase in modelled sea salt concentration tails off sharply as ice approaches the LGM extent, so that the sensitivity of the proxy is greater at lower ice extents, for example in interglacials. We will discuss the implications of this work for the proposed use of sea salt as a sea ice proxy.

Levine, James; Wolff, Eric; Frey, Markus; Jenkins, Hazel; Jones, Anna; Yang, Xin

2014-05-01

103

Sea Ice Ecosystems  

NASA Astrophysics Data System (ADS)

Polar sea ice is one of the largest ecosystems on Earth. The liquid brine fraction of the ice matrix is home to a diverse array of organisms, ranging from tiny archaea to larger fish and invertebrates. These organisms can tolerate high brine salinity and low temperature but do best when conditions are milder. Thriving ice algal communities, generally dominated by diatoms, live at the ice/water interface and in recently flooded surface and interior layers, especially during spring, when temperatures begin to rise. Although protists dominate the sea ice biomass, heterotrophic bacteria are also abundant. The sea ice ecosystem provides food for a host of animals, with crustaceans being the most conspicuous. Uneaten organic matter from the ice sinks through the water column and feeds benthic ecosystems. As sea ice extent declines, ice algae likely contribute a shrinking fraction of the total amount of organic matter produced in polar waters.

Arrigo, Kevin R.

2014-01-01

104

Sea ice ecosystems.  

PubMed

Polar sea ice is one of the largest ecosystems on Earth. The liquid brine fraction of the ice matrix is home to a diverse array of organisms, ranging from tiny archaea to larger fish and invertebrates. These organisms can tolerate high brine salinity and low temperature but do best when conditions are milder. Thriving ice algal communities, generally dominated by diatoms, live at the ice/water interface and in recently flooded surface and interior layers, especially during spring, when temperatures begin to rise. Although protists dominate the sea ice biomass, heterotrophic bacteria are also abundant. The sea ice ecosystem provides food for a host of animals, with crustaceans being the most conspicuous. Uneaten organic matter from the ice sinks through the water column and feeds benthic ecosystems. As sea ice extent declines, ice algae likely contribute a shrinking fraction of the total amount of organic matter produced in polar waters. PMID:24015900

Arrigo, Kevin R

2014-01-01

105

Geophysics of sea ice in the Baltic Sea: A review  

NASA Astrophysics Data System (ADS)

With improved observation methods, increased winter navigation, and increased awareness of the climate and environmental changes, research on the Baltic Sea ice conditions has become increasingly active. Sea ice has been recognized as a sensitive indicator for changes in climate. Although the inter-annual variability in the ice conditions is large, a change towards milder ice winters has been detected from the time series of the maximum annual extent of sea ice and the length of the ice season. On the basis of the ice extent, the shift towards a warmer climate took place in the latter half of the 19th century. On the other hand, data on the ice thickness, which are mostly limited to the land-fast ice zone, basically do not show clear trends during the 20th century, except that during the last 20 years the thickness of land-fast ice has decreased. Due to difficulties in measuring the pack-ice thickness, the total mass of sea ice in the Baltic Sea is, however, still poorly known. The ice extent and length of the ice season depend on the indices of the Arctic Oscillation and North Atlantic Oscillation. Sea ice dynamics, thermodynamics, structure, and properties strongly interact with each other, as well as with the atmosphere and the sea. The surface conditions over the ice-covered Baltic Sea show high spatial variability, which cannot be described by two surface types (such as ice and open water) only. The variability is strongly reflected to the radiative and turbulent surface fluxes. The Baltic Sea has served as a testbed for several developments in the theory of sea ice dynamics. Experiences with advanced models have increased our understanding on sea ice dynamics, which depends on the ice thickness distribution, and in turn redistributes the ice thickness. During the latest decade, advance has been made in studies on sea ice structure, surface albedo, penetration of solar radiation, sub-surface melting, and formation of superimposed ice and snow ice. A high vertical resolution has been found as a prerequisite to successfully model thermodynamic processes during the spring melt period. A few observations have demonstrated how the river discharge and ice melt affect the stratification of the oceanic boundary layer below the ice and the oceanic heat flux to the ice bottom. In general, process studies on ice-ocean interaction have been rare. In the future, increasingly multidisciplinary studies are needed with close links between sea ice physics, geochemistry and biology.

Vihma, Timo; Haapala, Jari

2009-03-01

106

Impact of snow cover on CO2 dynamics in Antarctic pack ice  

NASA Astrophysics Data System (ADS)

Temporal evolution of pCO2 profiles in sea ice in the Bellingshausen Sea, Antarctica, in October 2007 shows that the CO2 system in the ice was primarily controlled by physical and thermodynamic processes. During the survey, a succession of warming and cold events strongly influenced the physical, chemical and thermodynamic properties of the ice cover. Two sampling sites with contrasting characteristics of ice and snow thickness were sampled: one had little snow accumulation (from 8 to 25 cm) and larger temperature and salinity variations than the second site, where the snow cover was up to 38 cm thick and therefore better insulated the underlying sea ice. We confirm that each cooling/warming event was associated with an increase/decrease in the brine salinity, total alkalinity (TA), total dissolved inorganic carbon (TCO2), and in situ brine and bulk ice CO2 partial pressures (pCO2). Thicker snow covers muted these changes, suggesting that snow influences changes in the sea ice carbonate system through its impact on the temperature and salinity of the sea ice cover. During this survey, pCO2 was undersaturated with respect to the atmosphere both in situ, in the bulk ice (from 10 to 193 ?atm), and in the brine (from 65 to 293 ?atm), and the ice acted as a sink for atmospheric CO2 (up to 2.9 mmol m-2 d-1), despite the underlying supersaturated seawater (up to 462 ?atm).

Geilfus, N.-X.; Tison, J.-L.; Ackley, S. F.; Rysgaard, S.; Miller, L. A.; Delille, B.

2014-06-01

107

Validation of a snow water equivalence algorithm over landfast first-year sea ice using RADARSAT-1  

Microsoft Academic Search

Our understanding of snow distribution (i.e., spatial statistical properties) and magnitude (i.e., snow water equivalent (SWE)) in the polar regions is severely restricted due to the heterogeneity, both in space and time, of this solid precipitate. In this paper we present the theoretical framework for linking microwave scattering from a synthetic aperture radar (SAR) to the thermodynamic and electrical properties

J. J. Yackel; D. G. Barber

2002-01-01

108

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

109

First Moderate Resolution Imaging Spectroradiometer (MODIS) Snow and Ice Workshop  

NASA Technical Reports Server (NTRS)

This document is a compilation of summaries of talks presented at a 2-day workshop on Moderate Resolution maging Spectroradiometer (MODIS) snow and ice products. The objectives of the workshop were to: inform the snow and ce community of potential MODIS products, seek advice from the participants regarding the utility of the products, and letermine the needs for future post-launch MODIS snow and ice products. Four working groups were formed to discuss at-launch snow products, at-launch ice products, post-launch snow and ice products and utility of MODIS snow and ice products, respectively. Each working group presented recommendations at the conclusion of the workshop.

Hall, Dorothy K. (Editor)

1995-01-01

110

Remote sensing of snow and ice: A review of the research in the United States 1975 - 1978  

NASA Technical Reports Server (NTRS)

Research work in the United States from 1975-1978 in the field of remote sensing of snow and ice is reviewed. Topics covered include snowcover mapping, snowmelt runoff forecasting, demonstration projects, snow water equivalent and free water content determination, glaciers, river and lake ice, and sea ice. A bibliography of 200 references is included.

Rango, A.

1979-01-01

111

14 CFR 139.313 - Snow and ice control.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 2010-01-01 false Snow and ice control. 139.313 Section...OF AIRPORTS Operations § 139.313 Snow and ice control. (a) As determined...certificate holder whose airport is located where snow and icing conditions occur must...

2010-01-01

112

14 CFR 139.313 - Snow and ice control.  

Code of Federal Regulations, 2010 CFR

...2009-01-01 2009-01-01 false Snow and ice control. 139.313 Section...OF AIRPORTS Operations § 139.313 Snow and ice control. (a) As determined...certificate holder whose airport is located where snow and icing conditions occur must...

2009-01-01

113

An assessment of IceBridge airborne data quality over Arctic sea ice via comparison with in situ measurements gathered in the Beaufort Sea  

NASA Astrophysics Data System (ADS)

The Arctic sea ice pack has experienced rapid changes over the last decade with well documented losses in ice extent. More recently, observations suggest a decline in sea ice thickness leading to a basin-wide loss of ice volume. Fundamental to our capabilities to monitor and forecast these changes are observations from airborne and satellite-based laser and radar altimeters. The accurate mapping of sea ice thickness, using these instruments, requires the largest identified contributors to thickness errors to be better constrained: namely the uncertainties in sea ice freeboard and snow depth. To quantify these errors a 9 km long survey line was established in March 2011 near the US Navy ICEX2011 ice camp in the Beaufort Sea. The survey line was strategically located to cover a wide range of Arctic ice types: refrozen leads, deformed and undeformed first year ice, and multiyear ice. Survey measurements included estimates of ice thickness using the EM31 (an electromagnetic ground-conductivity meter), direct measurements of sea ice freeboard, snow thickness using a snow magnaprobe and snow pits to characterize the snow layer. The primary goal of the ICEX experiment was to provide an assessment of the remaining errors associated with aircraft-derived snow depth and sea ice thickness as a function of ice type. An Operation IceBridge (OIB) aircraft overflight of the survey line was conducted on the 23rd March 2011 from an altitude of ~465 m. The OIB instrument suite on the aircraft included: the Ku-band radar altimeter (13-17 GHz), the snow radar (2-8 GHz), the Airborne Topographical Mapper (ATM) laser altimeter and the Digital Mapping System (DMS) digital camera, which together provide estimates of sea ice freeboard, thickness, surface roughness and snow depth. We present a new methodology for analyzing the snow radar data for the extraction and estimation of snow depth utilizing a novel wavelet-based layer-picking technique. The snow depths derived from the snow radar are compared with an independent estimate of snow depth provided via the combination of Ku-band radar and ATM data. The direct comparison between the radar-derived snow depths and those measured in situ, allows the accuracy of the airborne data to be assessed with respect to the ice types present at the survey site. Combining knowledge of snow depth with sea ice freeboard, derived from the ATM data, we estimate sea ice thickness. We categorize sea ice thickness uncertainty as a function of ice type via one-on-one comparison with the field measurements. Finally, our data were corrected for ice drift and interpreted within the context of the ice surface morphology based on the DMS imagery.

Newman, T.; Farrell, S. L.; Richter-Menge, J.; Connor, L. N.; Kurtz, N. T.; Elder, B. C.

2012-12-01

114

Record Arctic Sea Ice Loss in 2007  

NASA Technical Reports Server (NTRS)

This image of the Arctic was produced from sea ice observations collected by the Advanced Microwave Scanning Radiometer (AMSR-E) Instrument on NASA's Aqua satellite on September 16, overlaid on the NASA Blue Marble. The image captures ice conditions at the end of the melt season. Sea ice (white, image center) stretches across the Arctic Ocean from Greenland to Russia, but large areas of open water were apparent as well. In addition to record melt, the summer of 2007 brought an ice-free opening though the Northwest Passage that lasted several weeks. The Northeast Passage did not open during the summer of 2007, however, as a substantial tongue of ice remained in place north of the Russian coast. According to the National Snow and Ice Data Center (NSIDC), on September 16, 2007, sea ice extent dropped to 4.13 million square kilometers (1.59 million square miles)--38 percent below average and 24 percent below the 2005 record.

2007-01-01

115

EOS Aqua AMSR-E Arctic Sea Ice Validation Program  

NASA Technical Reports Server (NTRS)

A coordinated Arctic sea ice validation field campaign using the NASA Wallops P-3B aircraft was successfully completed in March 2003. This campaign was part of the program for validating the Earth Observing System (EOS) Aqua Advanced Microwave Scanning Radiometer (AMSR-E) sea ice products. The AMSR-E, designed and built by the Japanese National Space Development Agency for NASA, was launched May 4,2002 on the EOS Aqua spacecraft. The AMSR-E sea ice products include sea ice concentration, sea ice temperature, and snow depth on sea ice. The primary instrument on the P-3B aircraft was the NOAA ETL Polarimetric Scanning Radiometer (PSR) covering the same frequencies and polarizations as the AMSR-E. This paper describes the objectives of each of the seven flights, the Arctic regions overflown, and the coordination among satellite, aircraft, and surface-based measurements. Two of the seven aircraft flights were coordinated with scientists making surface measurements of snow and ice properties including sea ice temperature and snow depth on sea ice at a study area near Barrow, AK and at a Navy ice camp located in the Beaufort Sea. The remaining flights covered portions of the Bering Sea ice edge, the Chukchi Sea, and Norton Sound. Comparisons among the satellite and aircraft PSR data sets are presented.

Cavalieri, D. J.; Markus, T.; Gasiewski, A.; Klein, M.; Maslanik, J.; Sturm, M.; Stroeve, J.; Heinrichs, J.

2004-01-01

116

Roughness of Weddell Sea Ice and Estimates of the Air-Ice Drag Coefficient  

Microsoft Academic Search

The roughness of a sheet of sea ice encodes its deformational history and determines its aerodynamic coupling with the overlying air and underlying water. Here we report snow surface, ice surface, and ice underside roughness computed from 47 surface elevation profiles collected during a transect of the Weddell Sea. The roughness for each surface, parameterized as the standard deviation of

Edgar L. Andreas; Manfred A. Lange; Stephen F. Ackley; Peter Wadhams

1993-01-01

117

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

118

Enhanced Sea Ice Concentration and Ice Temperature Algorithms for AMSR  

NASA Technical Reports Server (NTRS)

Accurate quantification of sea ice concentration and ice temperature from satellite passive microwave data is important because they provide the only long term, spatially detailed and consistent data set needed to study the climatology of the polar regions. Sea ice concentration data are used to derive large-scale daily ice extents that are utilized in trend analysis of the global sea ice cover. They are also used to quantify the amount of open water and thin ice in polynya and divergence regions which together with ice temperatures are in turn needed to estimate vertical heat and salinity fluxes in these regions. Sea ice concentrations have been derived from the NASA Team and Bootstrap algorithms while a separate technique for deriving ice temperature has been reported. An integrated technique that will utilizes most of the channels of AMSR (Advanced Microwave Scanning Radiometer) has been developed. The technique uses data from the 6 GHz and 37 GHz channels at vertical polarization obtain an initial estimate of sea ice concentration and ice temperature. The derived ice temperature is then utilized to estimate the emissivities for the corresponding observations at all the other channels. A procedure for calculating the ice concentration similar to the Bootstrap technique is then used but with variables being emissivities instead of brightness temperatures to minimizes errors associated with spatial changes in ice temperatures within the ice pack. Comparative studies of ice concentration results with those from other algorithms, including the original Bootstrap algorithm and those from high resolution satellite visible and infrared data will be presented. Also, results from a simulation study that demonstrates the effectiveness of the technique in correcting for spatial variations in ice temperatures will be shown. The ice temperature results are likewise compared with satellite infrared and buoy data with the latter adjusted to account for the effects of the snow cover.

Comiso, Josefino C.; Manning, Will; Gersten, Robert

1998-01-01

119

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

120

Forthcoming Northern Hemisphere Snow and Ice Earth System Data Records  

NASA Astrophysics Data System (ADS)

For approximately the past five years, a multi-institutional team has been assembling satellite-derived Northern Hemisphere (NH) snow cover Earth System Data Records (ESDR). With the culmination of our NASA-supported Making Earth Science Data Records for Use in Research Environments (MEaSUREs) project come mid 2014, it is timely to bring the user community that encompasses the research community, decision-makers, and stakeholders up to date on our progress and with products soon to be available. Datasets include snow extent and melt state over NH continents, snowmelt state over Greenland, snowmelt onset and age of sea ice. Fused snow extent and melt state products over land and ice are also being generated. Visible and microwave satellite data are employed in these efforts. Datasets of both individual and integrated ESDRs will be available for downloading from the National Snow and Ice Data Center. Products are being generated at 25 km (1999-2010) or 100 km (1967-2010) resolution using the Equal-Area Scalable Earth Grid 2.0 and are available in netCDF format. Extensive metadata will accompany the datasets. Project data and information are also available at http://snowcover.org. Here, we will present examples of the development and utility of these individual and fused datasets.

Robinson, D. A.; Estilow, T. W.; Anderson, M. R.; Hall, D. K.; Henderson, G. R.; Mote, T. L.; Tschudi, M. A.

2013-12-01

121

Soot climate forcing via snow and ice albedos  

NASA Astrophysics Data System (ADS)

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. aerosols | air pollution | climate change | sea level

Hansen, James; Nazarenko, Larissa

2004-01-01

122

Estimation of snow water equivalent over first-year sea ice using AMSR-E and surface observations  

Microsoft Academic Search

A SWE retrieval algorithm developed in-situ using passive microwave surface based radiometer data is applied to the Advanced Microwave Scanning Radiometer for Earth Observation System (AMSR-E). Snow water equivalent is predicted from two pixels located in Canadian Arctic Shelf Exchange Study (CASES) overwintering study area in Franklin Bay, N.W.T., Canada. Results show that the satellite SWE predictions are statistically valid

A. Langlois; R. Scharien; T. Geldsetzer; J. Iacozza; D. G. Barber; J. Yackel

2008-01-01

123

Microwave remote sensing of sea ice  

NASA Technical Reports Server (NTRS)

The long term objectives are: (1) to understand the physics of the multispectral microwave radiative characteristics of sea ice as it goes through different phases; (2) to improve characterization of sea ice cover using satellite microwave sensors; and (3) to study ice/ocean physical and biological processes associated with polynya formations and variability of the marginal sea ice region. Two field experiments were conducted to pursue these objectives. One involved measurements of radiative and physical characteristics of sea ice from a ship during a 3-month long cruise through the Weddell Sea ice pack during the Austral winter of 1986. The other involved similar measurements from two aircrafts and a submarine over the Central Arctic and Greenland Sea region. Preliminary results have already led to an enhanced understanding of the microwave signatures of pancake ice, nilas, first year ice, multiyear ice and effects of snow cover. Coastal and deep ocean polynyas and their role in bottom water formation and ocean circulation were studied using a time series of ice images from SMMR. An unsupervised cluster analysis of Arctic sea ice using SMMR and THIR emissivity and brightness temperature data was implemented. The analysis indicates the existence of several unique and persistent clusters in the Central Arctic region during winter and that the sum of the area of these clusters excluding those of first year ice is about 20 percent less than minimum ice cover area inferred from a previous summer data. This result is consistent with saline surface for some multiyear ice floes as observed during MIZEZ and suggests that a significant fraction of multiyear ice floes in the Arctic have first year ice signatures.

Comiso, J. C.

1988-01-01

124

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

125

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 ...

126

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

127

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

NASA Technical Reports Server (NTRS)

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) multispectral radiometer. Results indicate bidirectional reflectance is higher for snow-covered sea ice than melt-season sea ice at all wavelengths between 0.47 and 2.3 pm, with the difference increasing with wavelength. Bidirectional reflectance of snow-covered tundra is higher than for snow-free tundra for measurements less than 1.64 pm, with the difference decreasing with wavelength. Bidirectional reflectance patterns of all measured surfaces show maximum reflectance in the forward scattering direction of the principal plane, with identifiable specular reflection for the melt-season sea ice and snow-free tundra cases. The snow-free tundra had the most significant backscatter, and the melt-season sea ice the least. For sea ice, bidirectional reflectance changes due to snowmelt were more significant than differences among the different types of melt-season sea ice. Also the spectral-hemispherical (plane) albedo of each measured arctic surface was computed. Comparing measured nadir reflectance to albedo for sea ice and snow-covered tundra shows albedo underestimated 5-40%, with the largest bias at wavelengths beyond 1 pm. For snow-free tundra, nadir reflectance underestimates plane albedo by about 30-50%.

Arnold, G. Thomas; Tsay, Si-Chee; King, Michael D.; Li, Jason Y.; Soulen, Peter F.

1999-01-01

128

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

129

Nagaoka Ni Okeru Kisho Kansoku Shiryo (Meteorological Data at the Nagaoka Institute of Snow and Ice Studies).  

National Technical Information Service (NTIS)

Meteorological data have been collected since March 1971 as an important basis for the snow and ice studies at the Nagaoka Institute of Snow and Ice Studies. It is located at 37 deg 25 min N, 138 deg 53 min E, and 7 cm above sea level in the south of the ...

M. Shimizu T. Kimura M. Nakao

1993-01-01

130

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

131

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.

132

Sea Ice 1987 - 2012  

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.

133

Arctic Sea Ice  

NSDL National Science Digital Library

In this activity, learners explore how the area of Arctic sea ice has changed over recent years. First, learners graph the area of Arctic sea ice over time from 1979 to 2007. Then, learners use this information to extrapolate what the area will be in 2018 and graph their predictions. In part two of the activity, learners make a flip book to simulate the sea changes they just graphed. This resource includes background information related to the Northwest Passage and questions for learners to answer after completing this activity.

Meier, Beverly L.

2012-06-26

134

Iodine emissions from the sea ice of the Weddell Sea  

NASA Astrophysics Data System (ADS)

Iodine compounds were measured above, below and within the sea ice of the Weddell Sea during a cruise in 2009, to elucidate the mechanism of local enhancement and volatilisation of iodine. I2 mixing ratios of up to 12.4 pptv were measured 10 m above the sea ice, and up to 31 pptv was observed above surface snow on the nearby Brunt Ice Shelf - large amounts. Atmospheric IO of up to 7 pptv was measured from the ship, and the average sum of HOI and ICl was 1.9 pptv. These measurements confirm the Weddell Sea as an iodine hotspot. Average atmospheric concentrations of CH3I, C2H5I, CH2ICl, 2-C3H7I, CH2IBr and 1-C3H7I were each 0.2 pptv or less. On the Brunt Ice Shelf, enhanced concentrations of CH3I and C2H5I (up to 0.5 and 1 pptv, respectively) were observed in firn air, with a diurnal profile that suggests the snow may be a source. In the sea ice brine, iodocarbons concentrations were over 10 times those of the sea water below. The sum of iodide + iodate was depleted in sea ice samples, suggesting some missing iodine chemistry. Flux calculations suggest I2 dominates the iodine atom flux to the atmosphere, but models cannot reconcile the observations and suggest either a missing iodine source or other deficiencies in our understanding of iodine chemistry. The observation of new particle formation, consistent with the model predictions, strongly suggests an iodine source. This combined study of iodine compounds is the first of its kind in this unique region of sea ice rich in biology and rich in iodine chemistry.

Atkinson, H. M.; Huang, R.-J.; Chance, R.; Roscoe, H. K.; Hughes, C.; Davison, B.; Schönhardt, A.; Mahajan, A. S.; Saiz-Lopez, A.; Hoffmann, T.; Liss, P. S.

2012-05-01

135

Iodine emissions from the sea ice of the Weddell Sea  

NASA Astrophysics Data System (ADS)

Iodine compounds were measured above, below and within the sea ice of the Weddell Sea during a cruise in 2009, to make progress in elucidating the mechanism of local enhancement and volatilisation of iodine. I2 mixing ratios of up to 12.4 pptv were measured 10 m above the sea ice, and up to 31 pptv was observed above surface snow on the nearby Brunt Ice Shelf - large amounts. Atmospheric IO of up to 7 pptv was measured from the ship, and the average sum of HOI and ICl was 1.9 pptv. These measurements confirm the Weddell Sea as an iodine hotspot. Average atmospheric concentrations of CH3I, C2H5I, CH2ICl, 2-C3H7I, CH2IBr and 1-C3H7I were each 0.2 pptv or less. On the Brunt Ice Shelf, enhanced concentrations of CH3I and C2H5I (up to 0.5 and 1 pptv respectively) were observed in firn air, with a diurnal profile that suggests the snow may be a source. In the sea ice brine, iodocarbons concentrations were over 10 times those of the sea water below. The sum of iodide + iodate was depleted in sea ice samples, suggesting some missing iodine chemistry. Flux calculations suggest I2 dominates the iodine atom flux to the atmosphere, but models cannot reconcile the observations and suggest either a missing iodine source or other deficiencies in our understanding of iodine chemistry. The observation of new particle formation, consistent with the model predictions, strongly suggests an iodine source. This combined study of iodine compounds is the first of its kind in this unique region of sea ice rich in biology and rich in iodine chemistry.

Atkinson, H. M.; Huang, R.-J.; Chance, R.; Roscoe, H. K.; Hughes, C.; Davison, B.; Schönhardt, A.; Mahajan, A. S.; Saiz-Lopez, A.; Hoffmann, T.; Liss, P. S.

2012-11-01

136

Seafloor Control on Sea Ice  

NASA Technical Reports Server (NTRS)

The seafloor has a profound role in Arctic sea ice formation and seasonal evolution. Ocean bathymetry controls the distribution and mixing of warm and cold waters, which may originate from different sources, thereby dictating the pattern of sea ice on the ocean surface. Sea ice dynamics, forced by surface winds, are also guided by seafloor features in preferential directions. Here, satellite mapping of sea ice together with buoy measurements are used to reveal the bathymetric control on sea ice growth and dynamics. Bathymetric effects on sea ice formation are clearly observed in the conformation between sea ice patterns and bathymetric characteristics in the peripheral seas. Beyond local features, bathymetric control appears over extensive ice-prone regions across the Arctic Ocean. The large-scale conformation between bathymetry and patterns of different synoptic sea ice classes, including seasonal and perennial sea ice, is identified. An implication of the bathymetric influence is that the maximum extent of the total sea ice cover is relatively stable, as observed by scatterometer data in the decade of the 2000s, while the minimum ice extent has decreased drastically. Because of the geologic control, the sea ice cover can expand only as far as it reaches the seashore, the continental shelf break, or other pronounced bathymetric features in the peripheral seas. Since the seafloor does not change significantly for decades or centuries, sea ice patterns can be recurrent around certain bathymetric features, which, once identified, may help improve short-term forecast and seasonal outlook of the sea ice cover. Moreover, the seafloor can indirectly influence cloud cover by its control on sea ice distribution, which differentially modulates the latent heat flux through ice covered and open water areas.

Nghiem, S. V.; Clemente-Colon, P.; Rigor, I. G.; Hall, D. K.; Neumann, G.

2011-01-01

137

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.

138

Sea salt as an ice core proxy for past sea ice extent: A process-based model study  

NASA Astrophysics Data System (ADS)

ice is a reflection of, and a feedback on, the Earth's climate. We explore here, using a global atmospheric chemistry-transport model, the use of sea salt in Antarctic ice cores to obtain continuous long-term, regionally integrated records of past sea ice extent, synchronous with ice core records of climate. The model includes the production, transport, and deposition of sea salt aerosol from the open ocean and "blowing snow" on sea ice. Under current climate conditions, we find that meteorology, not sea ice extent, is the dominant control on the atmospheric concentration of sea salt reaching coastal and continental Antarctic sites on interannual timescales. However, through a series of idealized sensitivity experiments, we demonstrate that sea salt has potential as a proxy for larger changes in sea ice extent (e.g., glacial-interglacial). Treating much of the sea ice under glacial conditions as a source of salty blowing snow, we demonstrate that the increase in sea ice extent alone (without changing the meteorology) could drive, for instance, a 68% increase in atmospheric sea salt concentration at the site of the Dome C ice core, which exhibits an approximate twofold glacial increase in sea salt flux. We also show how the sensitivity of this potential proxy decreases toward glacial sea ice extent—the basis of an explanation previously proposed for the lag observed between changes in sea salt flux and ?D (an ice core proxy for air temperature) at glacial terminations. The data thereby permit simultaneous changes in sea ice extent and climate.

Levine, J. G.; Yang, X.; Jones, A. E.; Wolff, E. W.

2014-05-01

139

Snow and Ice Removal in an Urban Environment  

Microsoft Academic Search

Although important answers regarding the efficient removal of snow and ice reside in the domain of good planning and the behavioral sciences, the primary thesis of this paper is that cities can significantly improve their snow and ice removal operations by improving the routing of salt spreader trucks. A dynamic routing heuristic totally different from the static routing in general

Thomas M. Cook; Bradley S. Alprin

1976-01-01

140

Arctic Sea ice model sensitivities.  

SciTech Connect

Arctic sea ice is an important component of the global climate system and, due to feedback effects, the Arctic ice cover is changing rapidly. Predictive mathematical models are of paramount importance for accurate estimates of the future ice trajectory. However, the sea ice components of Global Climate Models (GCMs) vary significantly in their prediction of the future state of Arctic sea ice and have generally underestimated the rate of decline in minimum sea ice extent seen over the past thirty years. One of the contributing factors to this variability is the sensitivity of the sea ice state to internal model parameters. A new sea ice model that holds some promise for improving sea ice predictions incorporates an anisotropic elastic-decohesive rheology and dynamics solved using the material-point method (MPM), which combines Lagrangian particles for advection with a background grid for gradient computations. We evaluate the variability of this MPM sea ice code and compare it with the Los Alamos National Laboratory CICE code for a single year simulation of the Arctic basin using consistent ocean and atmospheric forcing. Sensitivities of ice volume, ice area, ice extent, root mean square (RMS) ice speed, central Arctic ice thickness,and central Arctic ice speed with respect to ten different dynamic and thermodynamic parameters are evaluated both individually and in combination using the Design Analysis Kit for Optimization and Terascale Applications (DAKOTA). We find similar responses for the two codes and some interesting seasonal variability in the strength of the parameters on the solution.

Peterson, Kara J.; Bochev, Pavel Blagoveston; Paskaleva, Biliana Stefanova

2010-12-01

141

Interannual Variability of Snow and Ice and Impact on the Carbon Cycle  

NASA Technical Reports Server (NTRS)

The goal of this research is to assess the impact of the interannual variability in snow/ice using global satellite data sets acquired in the last two decades. This variability will be used as input to simulate the CO2 interannual variability at high latitudes using a biospheric model. The progress in the past few years is summarized as follows: 1) Albedo decrease related to spring snow retreat; 2) Observed effects of interannual summertime sea ice variations on the polar reflectance; 3) The Northern Annular Mode response to Arctic sea ice loss and the sensitivity of troposphere-stratosphere interaction; 4) The effect of Arctic warming and sea ice loss on the growing season in northern terrestrial ecosystem.

Yung, Yuk L.

2004-01-01

142

Sea ice radiative forcing, sea ice area, and climate sensitivity  

NASA Astrophysics Data System (ADS)

Changes in sea ice cover affect climate sensitivity by modifying albedo and surface heat flux exchange, which in turn affect the absorbed solar radiation at the surface as well as cloud cover, atmospheric water content and poleward atmospheric heat transport. Here, we use a configuration of the Community Earth System Model 1.0.4 with a slab ocean model and a thermodynamic-dynamic sea ice model to investigate the overall net effect of feedbacks associated with the sea ice loss. We analyze the strength of the overall sea ice feedback in terms of two factors: the sensitivity of sea ice area to changes in temperature, and the sensitivity of sea ice radiative forcing to changes in sea ice area. In this model configuration, sea ice area decreases by ~3 × 1012 m2 per K of global warming, while the effective global radiative forcing per square meter of sea ice loss is ~0.1 × 10-12 W m-2. The product of these two terms (~0.3 W m-2 K-1) approximately equals the difference in climate feedback parameter found in simulations with sea ice response (1.05 W m-2 K-1) and simulations without sea ice response (1.31 W m-2 K-1 or 1.35 W m-2 K-1, depending on the method used to disable changes in sea ice cover). Thus, we find that in our model simulations, sea ice response accounts for about 20% to 22% of the climate sensitivity to an imposed change in radiative forcing. In our model, the additional radiative forcing resulting from a loss of all sea ice in the 'pre-industrial' state is comparable to but somewhat less than the radiative forcing from a doubling of atmospheric CO2 content.

Caldeira, Ken; Cvijanovic, Ivana

2014-05-01

143

Comparisons of Arctic In-Situ Snow and Ice Data with Airborne Passive Microwave Measurements  

NASA Technical Reports Server (NTRS)

As part of the AMSR-E sea ice validation campaign in March 2003, aircraft flights over the Arctic sea ice were coordinated with ground measurements of snow and sea ice properties. The surface-based measurements were in the vicinity of Barrow, AK, and at a Navy ice camp located in the Beaufort Sea. The NASA P-3 aircraft was equipped with the NOAA ETL PSR microwave radiometer that has the same frequencies as the AMSR-E sensor. The goal was to validate the standard AMSR-E products ice temperature and snow depth on sea ice. Ground measurements are the only way to validate these parameters. The higher spatial resolution of the PSR instrument (between 30 and 500 m, depending on altitude) enables a better comparison between ground measurements and microwave data because of the expected smaller spatial variability. Maps of PSR data can then be used for further down-scaling to AMSR-E pixel areas. Initial results show a good qualitative agreement between the in-situ snow depths and the PSR data. Detailed studies are underway and latest results will be presented.

Markus, T.; Cavalien, D. J.; Gasiewski, A.; Sturm, M.; Klein, M.; Maslanik, J.; Stroeve, J.; Heinrichs, J.; Holmgren, J.; Irisov, V.

2004-01-01

144

[Study on the basic characteristics of Bohai Sea ice reflectance spectra].  

PubMed

For monitoring sea ice in Bohai Sea, the present paper performed a field observation experiment on sea ice reflectance spectrum in Bohai Sea by control experiment. In the experiment, three groups of sea ice samples from the Bayuquan in Liaodong Gulf were collected, which were clean even ice of different thickness, sea ice covered by melt snow layer and sea ice with sands. According to the series of observation data during the two years, the reflectance spectrum curve of clean even ice has double peaks (a big one and a small one) when the ice thickness is less than 30 cm. The principal reflection peak is in good relation to the thickness of the sea ice. The principal reflection spectral peak of ice covered by melt snow layer is obviously higher than that of the spectrum of clean even ice without the snow layer with the same ice thickness. The principal reflection spectral peak of the sea ice with sands increases sharply, and the spectrum curve arises slightly in the wavelength rang between 675 and 725 mm and then declines. Covering snow and sands are the key factors to result in the fact that the same ice thicknesses present different spectrum characteristics and the same spectrum characteristics present different thicknesses. PMID:18479022

Li, Ning; Xie, Feng; Gu, Wei; Cui, Wei-Jia; Huang, Shu-Qing; Liu, Zhen

2008-02-01

145

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

146

Quality, Community, and the Sea Ice Record  

NASA Astrophysics Data System (ADS)

Over time, as the yearly minimum Arctic sea ice extent has continued to decline, the designated community for the passive microwave sea ice products held at the National Snow and Ice Data Center has expanded. Once comprised solely of cryospheric researchers, the community is now comprised of users from all walks of life. These new users typically have expertise outside that within the cryospheric community and they come to NSIDC with different expectations for format, quality, documentation, and services. At the same time, the passive microwave sea ice record has become critical to an understanding of the global climate system - sea ice is one of the Global Climate Observing System (GCOS) Essential Climate Variables (ECVs) and development of a passive microwave sea ice extent earth science data record is a high priority. Yet achieving consensus on an algorithm has historically been very difficult with multiple algorithms currently in use. Similarly, mechanisms to accurately quantify the quality of the data have historically also been problematic. These issues are particularly relevant to climate projections by general circulation climate models. Research has shown that climate models are underestimating the rate of sea ice decline compared to observations, a notable problem given the importance of sea ice in the climate system. Use of observational data to compare and constrain model simulations will be essential to improve model performance. However, data characteristics and data quality measures are essential to properly use observations with models. In this presentation, we provide an overview of the issues , describe recent work in these areas, and discuss the path forward.

Duerr, R. E.; Meier, W.; Stroeve, J. C.

2009-12-01

147

Synergy mechanism and measurement of ice and snow tourism resources value  

Microsoft Academic Search

With the development of the economy, ice and snow tourism has became a hot issue of tourism industry, and the development of the ice and snow tourism has been paid more and more attention. How to accurately understand the synergy mechanism of ice and snow tourism resources value is the precondition of scientifically developing ice and snow tourism resources and

Wu Wei-wei; Lu Yan-li; Zhang Chun-yan

2010-01-01

148

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.] [National Center for Atmospheric Research, Boulder, CO (United States). Climate and Global Dynamics Div.; Maslanik, J.A. [Univ. of Colorado, Boulder, CO (United States)] [Univ. of Colorado, Boulder, CO (United States)

1998-06-01

149

Polarimetric Signatures of Sea Ice. Part 1; Theoretical Model  

NASA Technical Reports Server (NTRS)

Physical, structural, and electromagnetic properties and interrelating processes in sea ice are used to develop a composite model for polarimetric backscattering signatures of sea ice. Physical properties of sea ice constituents such as ice, brine, air, and salt are presented in terms of their effects on electromagnetic wave interactions. Sea ice structure and geometry of scatterers are related to wave propagation, attenuation, and scattering. Temperature and salinity, which are determining factors for the thermodynamic phase distribution in sea ice, are consistently used to derive both effective permittivities and polarimetric scattering coefficients. Polarimetric signatures of sea ice depend on crystal sizes and brine volumes, which are affected by ice growth rates. Desalination by brine expulsion, drainage, or other mechanisms modifies wave penetration and scattering. Sea ice signatures are further complicated by surface conditions such as rough interfaces, hummocks, snow cover, brine skim, or slush layer. Based on the same set of geophysical parameters characterizing sea ice, a composite model is developed to calculate effective permittivities and backscattering covariance matrices at microwave frequencies for interpretation of sea ice polarimetric signatures.

Nghiem, S. V.; Kwok, R.; Yueh, S. H.; Drinkwater, M. R.

1995-01-01

150

Polarimetric signatures of sea ice. 1: Theoretical model  

NASA Technical Reports Server (NTRS)

Physical, structral, and electromagnetic properties and interrelating processes in sea ice are used to develop a composite model for polarimetric backscattering signatures of sea ice. Physical properties of sea ice constituents such as ice, brine, air, and salt are presented in terms of their effects on electromagnetic wave interactions. Sea ice structure and geometry of scatterers are related to wave propagation, attenuation, and scattering. Temperature and salinity, which are determining factors for the thermodynamic phase distribution in sea ice, are consistently used to derive both effective permittivities and polarimetric scattering coefficients. Polarmetric signatures of sea ice depend on crystal sizes and brine volumes, which are affected by ice growth rates. Desalination by brine expulsion, drainage, or other mechanisms modifies wave penetration and scattering. Sea ice signatures are further complicated by surface conditions such as rough interfaces, hummocks, snow cover, brine skim, or slush layer. Based on the same set of geophysical parameters characterizing sea ice, a composite model is developed to calculate effective permittivities and backscattering covariance matrices at microwave frequencies to interpretation of sea ice polarimetric signatures.

Nghiem, S. V.; Kwok, R.; Yueh, S. H.; Drinkwater, M. R.

1995-01-01

151

Modeling of Antarctic sea ice in a general circulation model  

SciTech Connect

A dynamic-thermodynamic sea ice model is developed and coupled with the Melbourne University general circulation model to simulate the seasonal cycle of the Antarctic sea ice distributions The model is efficient, rapid to compute, and useful for a range of climate studies. The thermodynamic part of the sea ice model is similar to that developed by Parkinson and Washington, the dynamics contain a simplified ice rheology that resists compression. The thermodynamics is based on energy conservation at the top surface of the ice/snow, the ice/water interface, and the open water area to determine the ice formation, accretion, and ablation. A lead parameterization is introduced with an effective partitioning scheme for freezing between and under the ice floes. The dynamic calculation determines the motion of ice, which is forced with the atmospheric wind, taking account of ice resistance and rafting. The simulated sea ice distribution compares reasonably well with observations. The seasonal cycle of ice extent is well simulated in phase as well as in magnitude. Simulated sea ice thickness and concentration are also in good agreement with observations over most regions and serve to indicate the importance of advection and ocean drift in the determination of the sea ice distribution. 64 refs., 15 figs., 2 tabs.

Wu, Xingren; Budd, W.F. [Antarctic Cooperative Research Centre, Tasmania (Australia)] [Antarctic Cooperative Research Centre, Tasmania (Australia); Simmonds, I. [School of Earth Sciences, Victoria (Australia)] [School of Earth Sciences, Victoria (Australia)

1997-04-01

152

Evolution of microwave sea ice signatures during early summer and midsummer in the marginal ice zone  

NASA Technical Reports Server (NTRS)

Emissivities at frequencies from 5 to 94 GHz and backscatter at frequencies from 1 to 17 GHz were measured from sea ice in Fram Strait during the marginal Ice Zone Experiment in June and July of 1983 and 1984. The ice observed was primarily multiyear; the remainder, first-year ice, was often deformed. Results from this active and passive microwave study include the description of the evolution of the sea ice during early summer and midsummer; the absorption properties of summer snow; the interrelationship between ice thickness and the state and thickness of snow; and the modulation of the microwave signature, especially at the highest frequencies, by the freezing of the upper few centimeters of the ice.

Onstott, R. G.; Grenfell, T. C.; Matzler, C.; Luther, C. A.; Svendsen, E. A.

1987-01-01

153

MODIS Data at the National Snow and Ice Data Center: Improvements for Collection 6  

NASA Astrophysics Data System (ADS)

For more than a decade, the National Snow and Ice Data Center (NSIDC) has archived and distributed snow cover and sea ice products derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) instruments, onboard NASA's Earth Observing System (EOS) Aqua and Terra satellites. As the MODIS science team studies and refines the algorithms that generate these products, the Earth Observing System Data and Information System (EOSDIS) periodically reprocesses an entire collection of MODIS data and produces a new suite of products incorporating the latest enhancements. Collection 6 represents the next revision to NSIDC's MODIS archive, mainly affecting the snow-cover products. Based on scores of journal papers and workshop proceedings, Collection 6 specifically addresses the needs of the MODIS science community by targeting the scenarios that have historically confounded snow detection and introduced errors into the snow-cover and fractional snow-cover maps. Although MODIS snow-cover maps are typically 90 percent accurate or better under good observing conditions, Collection 6 uses revised algorithms to discriminate between snow and clouds, resolve uncertainties along the edges of snow-covered region, and detect summer snow cover in mountains. Furthermore, Collection 6 applies modified and additional snow detection screens and new Quality Assessment protocols that enhance the overall accuracy of the snow maps compared with Collection 5. Finally, Collection 6 introduces new MODIS snow products, including a daily climate modeling-grid, cloud gap-filled (CGF) snow-cover map. The CGF algorithm generates cloud-free maps by using the most recent clear observation of the surface when the current day is cloudy, and tracks cloud persistence to account for uncertainties created by the age of a snow observation. By considering prior days, the CGF dramatically increases the number of observable grid cells and can potentially improve the accuracy of other snow-cover products that require cloud-reduced or cloud-free observations. References Riggs, G. and D. K. Hall. 2012. Improved Snow Mapping Accuracy with Revised MODIS Snow Algorithm. Presented at the 69th Eastern Snow Conference, Claryville, NY.

Johnston, T.; Fowler, D. K.; McAllister, M.; Hall, D. K.; Riggs, G. A.

2012-12-01

154

EOS Aqua AMSR-E Arctic Sea Ice Validation Program: Arctic2003 Aircraft Campaign Flight Report  

NASA Technical Reports Server (NTRS)

In March 2003 a coordinated Arctic sea ice validation field campaign using the NASA Wallops P-3B aircraft was successfully completed. This campaign was part of the program for validating the Earth Observing System (EOS) Aqua Advanced Microwave Scanning Radiometer (AMSR-E) sea ice products. The AMSR-E, designed and built by the Japanese National Space Development Agency for NASA, was launched May 4, 2002 on the EOS Aqua spacecraft. The AMSR-E sea ice products to be validated include sea ice concentration, sea ice temperature, and snow depth on sea ice. This flight report describes the suite of instruments flown on the P-3, the objectives of each of the seven flights, the Arctic regions overflown, and the coordination among satellite, aircraft, and surface-based measurements. Two of the seven aircraft flights were coordinated with scientists making surface measurements of snow and ice properties including sea ice temperature and snow depth on sea ice at a study area near Barrow, AK and at a Navy ice camp located in the Beaufort Sea. Two additional flights were dedicated to making heat and moisture flux measurements over the St. Lawrence Island polynya to support ongoing air-sea-ice processes studies of Arctic coastal polynyas. The remaining flights covered portions of the Bering Sea ice edge, the Chukchi Sea, and Norton Sound.

Cavalieri, D. J.; Markus,T.

2003-01-01

155

Sea Ice Variability in the Bering Sea  

NASA Astrophysics Data System (ADS)

The Bering Sea consists of a shallow continental shelf in the northeast and a deep basin in the southwest. Sea ice in the Bering Sea concentrating in the shelf region exhibits large seasonal and interannual variations, which significantly impact the local marine ecosystem. Understanding of the physical mechanisms governing this sea-ice variability, however, remains incomplete. To better understand regional sea-ice variability we use a fine resolution (1/10-degree) global ocean and sea-ice model and available observations. The simulation consists of the Los Alamos National Laboratory Parallel Ocean Program (POP) and CICE models, and was run with Coordinated Ocean-ice Reference Experiment (CORE2) interannually varying atmospheric forcing for 1970-1989. Here we analyze 1980-1989; the first 10 years are treated as the spin-up period. We examine the partitioning of the ice volume tendencies into thermodynamic and dynamic components, as well as corresponding surface atmospheric and oceanic variables, in order to understand the relationship between sea ice variability and varying atmospheric and oceanic conditions. Focusing on the seasonal cycle first, we find that sea ice is mainly formed in the northern Bering Sea with the maximum ice growth rate occurring along the coast. Winds cause sea ice to drift southwestward from the north to the western ice edge. Along the ice edge, ice is melted by warm waters carried by the Bering Slope Current, especially in the west in winter; while in fall and spring, basal melting of sea ice spreads into the interior of ice pack. The ice growth rate is larger in winter than in fall and spring. Ice transport from the north to the southwest becomes weaker in fall and spring than in winter. The Bering Sea is ice free in summer. Surface melting is insignificant in all seasons. The interannual variability of sea ice in the Bering Sea can be largely explained by thermodynamics on the large scale. The dynamic ice transport, however, is often important locally, especially around the ice margins with ocean and land. Local dynamic and thermodynamic ice volume changes usually have opposite signs with similar magnitudes, implying a negative feedback between them. Through the surface heat flux budget, we find that sensible heat flux dominates the surface heat exchange with the atmosphere, which controls the ice growth in the north. Ocean-ice heat flux largely determines the basal melting along the ice edge in the south. Through the force balance analysis, we find that the ice motion is in steady state on the monthly timescale. Ice velocity correlates well with the wind stress, which is nearly balanced by the opposite ocean stress. Internal ice stress is not substantial except near the land boundaries in the north.

Li, L.; Miller, A. J.; McClean, J.; Eisenman, I.; Hendershott, M.

2013-12-01

156

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. Along with a control simulation, we present a range of sensitivity tests to parameters related to each subprocess described by the parameterization. With the exception of one parameter that alters the albedo of snow-covered pond ice, results are not highly sensitive to these parameters unless an entire process is removed. The snow simulation itself is critical, because the volume of snow deposition and rate of snow melt largely determine the timing and extent of the simulated melt ponds. Nevertheless, compensating effects moderate the model's sensitivity to precipitation changes. For instance, infiltration of the snow by melt water postpones the appearance of ponds and the subsequent acceleration of melting through albedo feedback, while snow on top of refrozen pond ice also reduces the ponds' effect on the radiation budget. By construction, the model simulation of level and ridged ice is also important for this parameterization. We find that as sea ice thins, either through time or when comparing sensitivity tests, the area of level ice increases. This leads to an enhanced thinning feedback in the model, because a greater ice area may be exposed to ponding and further thinning due to lowered albedo.

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

2013-11-01

157

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 European Union's (EU) project DAMOCLES (Developing Arctic Modeling and Observing Capabilities for Long-term Environmental Studies). In order to better understand the seasonal variation of the microwave emission of sea ice observed from space, the monthly variations of the microwave emissivity of first-year and multi-year sea ice have been derived for the frequencies of the microwave imagers like AMSR-E (Advanced Microwave Scanning Radiometer on EOS) and sounding frequencies of AMSU (Advanced Microwave Sounding Unit), and have been used to develop an optimal estimation method to retrieve sea ice and atmospheric parameters simultaneously. In addition, a sea ice microwave emissivity model has been used together with a thermodynamic model to establish relations between the emissivities from 6 GHz to 50 GHz. At the latter frequency, the emissivity is needed for assimilation into atmospheric circulation models, but is more difficult to observe directly. The size of the snow grains on top of the sea ice influences both its albedo and the microwave emission. A method to determine the effective size of the snow grains from observations in the visible range (MODIS) is developed and demonstrated in an application on the Ross ice shelf. 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.; von Hoyningen-Huene, W.; Girard-Ardhuin, F.; 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.

2012-12-01

158

Melt ponds on Arctic sea ice determined from MODIS satellite data using an artificial neural network  

Microsoft Academic Search

Melt ponds on sea ice strongly reduce the surface albedo and accelerate the decay of Arctic sea ice. Due to different spectral properties of snow, ice, and water, the fractional coverage of these distinct surface types can be derived from multispectral sensors like MODIS using a spectral unmixing algorithm. The unmixing was implemented using a multilayer perceptron (MLP) to reduce

A. Rösel; L. Kaleschke; G. Birnbaum

2011-01-01

159

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

160

Snow and Ice Applications of AVHRR in Polar Regions: Report of a Workshop  

NASA Technical Reports Server (NTRS)

The third symposium on Remote Sensing of Snow and Ice, organized by the International Glaciological Society, took place in Boulder, Colorado, 17-22 May 1992. As part of this meeting a total of 21 papers was presented on snow and ice applications of Advanced Very High Resolution Radiometer (AVHRR) satellite data in polar regions. Also during this meeting a NASA sponsored Workshop was held to review the status of polar surface measurements from AVHRR. In the following we have summarized the ideas and recommendations from the workshop, and the conclusions of relevant papers given during the regular symposium sessions. The seven topics discussed include cloud masking, ice surface temperature, narrow-band albedo, ice concentration, lead statistics, sea-ice motion and ice-sheet studies with specifics on applications, algorithms and accuracy, following recommendations for future improvements. In general, we can affirm the strong potential of AVHRR for studying sea ice and snow covered surfaces, and we highly recommend this satellite data set for long-term monitoring of polar process studies. However, progress is needed to reduce the uncertainty of the retrieved parameters for all of the above mentioned topics to make this data set useful for direct climate applications such as heat balance studies and others. Further, the acquisition and processing of polar AVHRR data must become better coordinated between receiving stations, data centers and funding agencies to guarantee a long-term commitment to the collection and distribution of high quality data.

Steffen, K.; Bindschadler, R.; Casassa, G.; Comiso, J.; Eppler, D.; Fetterer, F.; Hawkins, J.; Key, J.; Rothrock, D.; Thomas, R.; Weaver, R.; Welch, R.

1993-01-01

161

Arctic sea ice freeboard heights from satellite altimetry  

NASA Astrophysics Data System (ADS)

The Arctic sea ice cover is most sensitive to climate change and variability, mainly due to the ice-albedo feedback effect. With an increase in the average temperature across the Arctic during the past few decades, sea ice has been melting rapidly. The decline in the sea ice extent was estimated as 10% per decade since satellite observations began in 1979. Sea ice thickness is an important parameter that moderates the heat exchange between the ocean and the atmosphere, extent of sea ice deformation and sea ice circulation in the Arctic Ocean. In addition, sea ice thermodynamics and dynamics depend on the thickness of the sea ice cover. In order to estimate the trend in the sea ice volume, both the extent and thickness must be known. Hence, it is important to measure the sea ice freeboard (a representative fraction of the thickness) distribution in the Arctic Ocean. In this thesis, the total ice freeboards (height of the snow/ice surface above the sea level) were derived from satellite laser altimetry. NASA's Ice Cloud and Land Elevation Satellite (ICESat) carries a Geoscience Laser Altimetry System (GLAS) onboard, and provides dense coverage of snow (or sea ice) surface heights in the Arctic Ocean up to 86° N. The total freeboard height at each ICESat footprint location was computed by removing the instantaneous sea surface height from the ice/snow surface height. In this study, the instantaneous sea surface heights were modeled using a combination of geodetic and oceanographic models. In order to improve the accuracy of the freeboard estimation, an accuracy assessment of the ocean tide models (one of the component models in the sea surface height estimation) in the Arctic Ocean was performed. The Arctic Ocean Tide Inverse Model (AOTIM-5) was found to have the best accuracy in the Arctic Ocean and was, therefore, used in the sea ice freeboard estimation. It was also shown that the present generation of ocean tide models have ignored the ice-tide interaction processes in the model parameterization, as they are not constrained by observations from sea ice covered regions. A sensitivity analysis of the freeboard estimation procedure indicates an uncertainty of ˜0.24 m over a length scale of 100 km. The estimated total ice freeboards were compared with freeboard measurements from other methods (e.g. 'lowest level'), and a good agreement was found between the two methods at regional scales. The sea ice thickness, in the multi-year ice region north of Greenland and Ellesmere Island, was also derived from the total ice freeboard heights by assuming a hydrostatic equilibrium condition. The estimated thicknesses were compared with the thickness measurements from a Helicopter-borne Electromagnetic Induction technique. The difference between the means of the two thickness distributions was ˜0.53 m, which is well below the accuracy of the thickness estimates of ˜0.98 m. The sea ice freeboard estimation procedure, demonstrated in this study, can also be applied to upcoming laser and radar altimetry missions, such as Cryosat-2 and ICESat-2, to continuously monitor the regional, seasonal and inter-annual changes in the Arctic sea ice freeboard (and thickness) distribution.

Renganathan, Vidyavathy

162

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

163

A large-scale numerical model of sea ice  

NASA Technical Reports Server (NTRS)

The described large-scale sea ice model, which is capable of coupling with atmospheric and oceanic models of comparable resolution, simulates the yearly cycle of ice in both the Northern and Southern Hemispheres. Model results for the yearly cycle of sea ice thickness and extent in both the Arctic and the Antarctic are presented. Horizontally the model resolution is approximately 200 km, while vertically four layers - ice, snow, ocean, and atmosphere - are considered. Thermodynamic processes based on energy balances at the various interfaces and dynamic processes based on wind stress, water stress, Coriolis force, internal ice resistance, and the stress from the tilt of the sea surface are incorporated. It is assumed that the ice within a given grid square is of uniform thickness, although each square has a variable percentage of its area ice free.

Parkinson, C. L.; Washington, W. M.

1979-01-01

164

Observations of Recent Arctic Sea Ice Volume Loss and Its Impact on Ocean-Atmosphere Energy Exchange and Ice Production  

NASA Technical Reports Server (NTRS)

Using recently developed techniques we estimate snow and sea ice thickness distributions for the Arctic basin through the combination of freeboard data from the Ice, Cloud, and land Elevation Satellite (ICESat) and a snow depth model. These data are used with meteorological data and a thermodynamic sea ice model to calculate ocean-atmosphere heat exchange and ice volume production during the 2003-2008 fall and winter seasons. The calculated heat fluxes and ice growth rates are in agreement with previous observations over multiyear ice. In this study, we calculate heat fluxes and ice growth rates for the full distribution of ice thicknesses covering the Arctic basin and determine the impact of ice thickness change on the calculated values. Thinning of the sea ice is observed which greatly increases the 2005-2007 fall period ocean-atmosphere heat fluxes compared to those observed in 2003. Although there was also a decline in sea ice thickness for the winter periods, the winter time heat flux was found to be less impacted by the observed changes in ice thickness. A large increase in the net Arctic ocean-atmosphere heat output is also observed in the fall periods due to changes in the areal coverage of sea ice. The anomalously low sea ice coverage in 2007 led to a net ocean-atmosphere heat output approximately 3 times greater than was observed in previous years and suggests that sea ice losses are now playing a role in increasing surface air temperatures in the Arctic.

Kurtz, N. T.; Markus, T.; Farrell, S. L.; Worthen, D. L.; Boisvert, L. N.

2011-01-01

165

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

166

Sea Ice on the Southern Ocean  

NASA Technical Reports Server (NTRS)

Year-round satellite records of sea ice distribution now extend over more than two decades, providing a valuable tool to investigate related characteristics and circulations in the Southern Ocean. We have studied a variety of features indicative of oceanic and atmospheric interactions with Antarctic sea ice. In the Amundsen & Bellingshausen Seas, sea ice extent was found to have decreased by approximately 20% from 1973 through the early 1990's. This change coincided with and probably contributed to recently warmer surface conditions on the west side of the Antarctic Peninsula, where air temperatures have increased by approximately 0.5 C/decade since the mid-1940's. The sea ice decline included multiyear cycles of several years in length superimposed on high interannual variability. The retreat was strongest in summer, and would have lowered the regional mean ice thickness, with attendant impacts upon vertical heat flux and the formation of snow ice and brine. The cause of the regional warming and loss of sea ice is believed to be linked to large-scale circulation changes in the atmosphere and ocean. At the eastern end of the Weddell Gyre, the Cosmonaut Polyna revealed greater activity since 1986, a recurrence pattern during recent winters and two possible modes of formation. Persistence in polynya location was noted off Cape Ann, where the coastal current can interact more strongly with the Antarctic Circumpolar Current. As a result of vorticity conservation, locally enhanced upwelling brings warmer deep water into the mixed layer, causing divergence and melting. In the Ross Sea, ice extent fluctuates over periods of several years, with summer minima and winter maxima roughly in phase. This leads to large interannual cycles of sea ice range, which correlate positively with meridinal winds, regional air temperatures and subsequent shelf water salinities. Deep shelf waters display considerable interannual variability, but have freshened by approximately 0.03/decade since the late 1950's. That could have slowed the thermohaline circulation beneath the Ross Ice Shelf and the properties or volume of local bottom water production.

Jacobs, Stanley S.

1998-01-01

167

Arctic sea ice decay simulated for a CO 2 -induced temperature rise  

Microsoft Academic Search

A large scale numerical time-dependent model of sea ice that takes into account the heat fluxes in and out of the ice, the seasonal occurrence of snow, and ice motions has been used in an experiment to determine the response of the Arctic Ocean ice pack to a warming of the atmosphere. The degree of warming specified is that expected

Claire L. Parkinson; William W. Kellogg

1979-01-01

168

Sea-ice velocity fields estimation on Ross Sea with NOAA-AVHRR  

SciTech Connect

A complete methodology is proposed for automatic tracking of sea-ice in daylight AVHRR data. Two aspects are specially outlined: the use of partially cloudy monocular images and the estimation of ice pack trajectories along an image sequence. First, a classification technique is applied for the detection of snow-ice regions. Then, an optimal matching filter is used for the sea-ice motion estimation. The derived vector field is homogeneous and shows the ice pack motion along three days image data.

Flores, M.M.; Maitre, H. [ENST, Paris (France)] [ENST, Paris (France); Parmiggiani, F. [IMGA-CNR, Modena (Italy)] [IMGA-CNR, Modena (Italy)

1995-09-01

169

About uncertainties in sea ice thickness retrieval from satellite radar altimetry: results from the ESA-CCI Sea Ice ECV Project Round Robin Exercise  

NASA Astrophysics Data System (ADS)

One goal of the European Space Agency Climate Change Initiative sea ice Essential Climate Variable project is to provide a quality controlled 20 year long data set of Arctic Ocean winter-time sea ice thickness distribution. An important step to achieve this goal is to assess the accuracy of sea ice thickness retrieval based on satellite radar altimetry. For this purpose a data base is created comprising sea ice freeboard derived from satellite radar altimetry between 1993 and 2012 and collocated observations of snow and sea ice freeboard from Operation Ice Bridge (OIB) and CryoSat Validation Experiment (CryoVEx) air-borne campaigns, of sea ice draft from moored and submarine Upward Looking Sonar (ULS), and of snow depth from OIB campaigns, Advanced Microwave Scanning Radiometer aboard EOS (AMSR-E) and the Warren Climatology (Warren et al., 1999). An inter-comparison of the snow depth data sets stresses the limited usefulness of Warren climatology snow depth for freeboard-to-thickness conversion under current Arctic Ocean conditions reported in other studies. This is confirmed by a comparison of snow freeboard measured during OIB and CryoVEx and snow freeboard computed from radar altimetry. For first-year ice the agreement between OIB and AMSR-E snow depth within 0.02 m suggests AMSR-E snow depth as an appropriate alternative. Different freeboard-to-thickness and freeboard-to-draft conversion approaches are realized. The mean observed ULS sea ice draft agrees with the mean sea ice draft computed from radar altimetry within the uncertainty bounds of the data sets involved. However, none of the realized approaches is able to reproduce the seasonal cycle in sea ice draft observed by moored ULS satisfactorily. A sensitivity analysis of the freeboard-to-thickness conversion suggests: in order to obtain sea ice thickness as accurate as 0.5 m from radar altimetry, besides a freeboard estimate with centimetre accuracy, an ice-type dependent sea ice density is as mandatory as a snow depth with centimetre accuracy.

Kern, S.; Khvorostovsky, K.; Skourup, H.; Rinne, E.; Parsakhoo, Z. S.; Djepa, V.; Wadhams, P.; Sandven, S.

2014-03-01

170

Albedo over rough snow and ice surfaces  

NASA Astrophysics Data System (ADS)

Surface albedo determines the shortwave radiation balance, arguably the largest energy balance component of snow and ice surfaces. Consequently, incorporation of the spatio-temporal variability of albedo is essential when assessing the surface energy balance of snow and ice surfaces. This can be done by using ground-based measurements or albedo data derived from remote sensing, or by modelling albedo based on radiative transfer models or empirically based parameterizations. One decisive factor when incorporating albedo data is the representativeness of surface albedo, certainly over rough surfaces where albedo measurements at a specific location (i.e., apparent albedo) can differ strongly from the material albedo or the true albedo (i.e., effective albedo) depending on the position of the sun/sensor and the surface roughness. This stresses the need for a comprehensive understanding of the effect of surface roughness on albedo and its impact when using albedo data for validation of remote sensing imagery, interpretation of automated weather station (AWS) radiation data or incorporation in energy balance models. To assess the effect of surface roughness on albedo an intra-surface radiative transfer (ISRT) model was combined with albedo measurements on a penitente field on Glaciar Tapado in the semi-arid Andes of Northern Chile. The ISRT model shows albedo reductions between 0.06 and 0.35 relative to flat surfaces with a uniform material albedo. The magnitude of these reductions primarily depends on the penitente geometry, but the shape and spatial variability of the material albedo also play a major role. Secondly, the ISRT model was used to reveal the effect of using apparent albedo to infer the effective albedo over a rough surface. This effect is especially strong for narrow penitentes, resulting in sampling biases up to ±0.05. The sampling biases are more pronounced when the sensor is low above the surface, but remain relatively constant throughout the day. Consequently, the only beneficial approach to minimize the sampling bias of surface albedo over rough surfaces is to use a large number of samples at various places. Thirdly, the temporal evolution of broadband albedo over a penitente-covered surface was analyzed to place the experiments and their uncertainty into a larger temporal context. Time series of albedo measurements at an automated weather station over two seasons reveal albedo decreases early in the ablation season. These decreases stabilize from February onwards with variations being caused by fresh snow-fall events. The 2009/2010 and 2011/2012 seasons differ notably, where the latter shows lower albedo caused by larger penitentes. Finally, a comparison of the ground-based albedo observations with Landsat and MODIS-derived albedo showed that both satellite derived albedo products capture the albedo evolution with root mean square errors of 0.08 and 0.15, respectively, but also illustrate their shortcomings related to temporal resolution and spatial heterogeneity over mountain glaciers.

Lhermitte, Stef; Abermann, Jakob; Kinnard, Christophe

2014-05-01

171

The Canadian CoReH2O Snow and Ice Experiment 2009-2010  

NASA Astrophysics Data System (ADS)

The Canadian CoReH2O Snow and Ice (Can-CSI) Experiment 2009 is designed to investigate the electromagnetic response of snow and ice throughout the 2009-2010 winter season in the Hudson Bay lowlands in order to support science development activities of the Cold Regions Hydrology High Resolution (CoReH2O) mission. CoReH2O is a candidate mission in the Earth Explorer programme at ESA that is in the feasibility stage of the competition. CoReH2O's objectives are to provide detailed spaceborne observations of key snow, ice and water cycle variables for improved characterization of the cryosphere. The Can-CSI Experiment 2009 aims to support the CoReH2O mission science justification by undertaking active and passive microwave observations of seasonal changes in terrestrial snow, lake ice and lake snow, and sea ice in the Hudson Bay lowland regions. The selected study domain contains a wide range of land surface types from shrub tundra, to wetland fen, to open canopy to open lakes and to Hudson Bay to undertake snow and ice measurements. The specific science objectives of the project are to quantify and characterize the active microwave response of seasonal snow and ice at 9.5 and 17.2 GHz frequencies and to explore the active-passive microwave relationships between these two measurement approaches. To achieve this, the experiment is building a comprehensive data set of ground based active microwave measurements at 9.5 and 17.2 GHz frequencies and with multi polarization capability and passive microwave remote sensing observations at 6, 19, 37 and 89 GHz frequencies. Supporting measurements of cold season hydrologic processes are also being made and include conventional snow and lake ice surveys, measurements of snow and ice electrical properties, meteorological observations, and supporting satellite active and passive microwave observations from existing satellite based systems. Together with other similar experiments planned in Europe, this cold season active and passive microwave observation experiment will contribute to the CoReH2O science preparation

Kelly, Richard; Duguay, Claude; King, Joshua; Derksen, Chris; Toose, Peter; Silis, Arvids; Longlois, Alexandre; Rutter, Nick; Royer, Alain

2010-05-01

172

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

173

Helicopter borne radar derived snow thickness estimates over fast ice in East Antarctica  

NASA Astrophysics Data System (ADS)

The polar regions play a key role in the Earth's climate system, and sea ice has a major influence on ocean-atmosphere interaction and ocean circulation. Antarctic sea ice and its snow cover are integral components of the global climate system, yet their thickness and variability are poorly understood and subsequently their representation in global climate models is poor. Remote sensing is the key to monitoring the dynamic nature and changes of sea ice and its snow cover. Snow depth on sea ice is operationally derived from the EOS Aqua Advanced Microwave Scanning Radiometer (AMSR-E) measurements but thorough validation is still an issue. To address this, research is currently directed to airborne snow depth investigation techniques capable of covering large areas to validate satellite data. In October - November, 2008 a helicopter equipped with a laser altimeter, a 2 - 8 GHz FMCW radar and a digital camera was flown over the fast ice near to the Australian base, Davis, 68.35' S, 77.58' E. An area 80 x 200 m was over flown repeatedly by the helicopter at varying altitudes and velocities for cross validation and precision assessment purposes. Thorough in-situ measurements were gathered over the area for ground truth purposes. From this data it is seen that the range of snow thickness is up to 300mm, placing stringent requirements on the accuracy of the radar that theoretically has a vertical resolution of 25mm. The process of extracting snow thickness estimates from the helicopter borne radar measurements has so far been hampered by the noise in the radar not only by the instability of the helicopter, but also by the aggravation of the noise with increasing altitude. Fortunately, it was found that the noise is of a predicable nature and it has been possible to clean up the radar signal. Subsequently, implementing this denoising algorithm across the full gathered dataset, in this paper the first helicopter borne radar derived snow thickness estimates over fast ice in Antarctica are presented and compared with the in-situ data. Five mile long transects over which ship based observation data was gathered will also be analysed for snow thickness distribution.

Galin, N.; Markus, T.; Worby, A. P.; Leuschen, C.; Gogineni, P. S.

2009-12-01

174

Palaeoclimate: The sea ice thickens  

NASA Astrophysics Data System (ADS)

Little is known about the presence of high-latitude sea ice before 2.6 million years ago. A reanalysis of marine sediments from the Arctic Ocean indicates an intermittent presence of perennial sea ice as early as 44 million years ago.

Stickley, Catherine E.

2014-03-01

175

Seafloor Control on Sea Ice.  

National Technical Information Service (NTIS)

The seafloor has a profound role in Arctic sea ice formation and seasonal evolution. Ocean bathymetry controls the distribution and mixing of warm and cold waters, which may originate from different sources, thereby dictating the pattern of sea ice on the...

D. K. Hall G. Neumann I. G. Rigor P. Clemente-Colon S. V. Nghiem

2011-01-01

176

A New Suite of Northern Hemisphere Snow and Ice Earth System Data Records  

NASA Astrophysics Data System (ADS)

A multi-institutional team has been assembling satellite-derived Northern Hemisphere (NH) snow cover Earth System Data Records (ESDR), through support from the NASA Making Earth Science Data Records for Use in Research Environments (MEaSUREs) program. Datasets of both individual and integrated ESDRs are being generated and are soon to be available to download from the National Snow and Ice Data Center. Project data and information are also available at http://snowcover.org. Products are being generated at 25 km (1999-present) or 100 km (1967-present) resolution using the Equal-Area Scalable Earth Grid 2.0 and are available in netCDF format. Extensive metadata will accompany the datasets. Products include snow extent and melt state over NH continents, snow melt state over Greenland, snow melt onset and age of sea ice. Fused snow extent and melt state products over land and ice are also being generated. Visible and microwave satellite data are employed in these efforts. Here, we will present examples of the development and utility of these individual and fused datasets.

Robinson, D. A.; Estilow, T. W.; Anderson, M. R.; Hall, D. K.; Henderson, G. R.; Mote, T. L.; Tschudi, M. A.

2012-12-01

177

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

178

Ocean circulation and sea ice distribution in a finite element global sea ice-ocean model  

NASA Astrophysics Data System (ADS)

A newly developed global Finite Element Sea Ice-Ocean Model (FESOM) is presented. The ocean component is based on the Finite Element model of the North Atlantic (FENA) but has been substantially updated and extended. In addition to a faster realization of the numerical code, state-of-the-art parameterizations of subgrid-scale processes have been implemented. A Redi/GM scheme is employed to parameterize the effects of mesoscale eddies on lateral tracer distribution. Vertical mixing and convection are parameterized as a function of the Richardson number and the Monin-Obukhov length. A finite element dynamic-thermodynamic sea ice-model has been developed and coupled to the ocean component. Sea ice thermodynamics have been derived from the standard AWI sea ice model featuring a prognostic snow layer but neglecting internal heat storage. The dynamic part offers the viscous-plastic and elastic-viscous-plastic rheologies. All model components are discretized on a triangular/tetrahedral grid with a continuous, conforming representation of model variables. The coupled model is run in a global configuration and forced with NCEP daily atmospheric reanalysis data for 1948-2007. Results are analysed with a slight focus on the Southern Hemisphere. Many aspects of sea ice distribution and hydrography are found to be in good agreement with observations. As in most coarse-scale models, Gulf Stream transport is underestimated, but transports of the Kuroshio and the Antarctic Circumpolar Current appear realistic. The seasonal cycles of Arctic and Antarctic sea ice extents and Antarctic sea ice thickness are well captured; long- and short-term variability of ice coverage is found to be reproduced realistically in both hemispheres. The coupled model is now ready to be used in a wide range of applications.

Timmermann, Ralph; Danilov, Sergey; Schröter, Jens; Böning, Carmen; Sidorenko, Dmitry; Rollenhagen, Katja

179

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 atmospheric and oceanic circulation. Iodine (I) and bromine (Br) have been measured in a shallow firn core drilled at the summit of the Holtedahlfonna glacier (Northwest Spitsbergen, Svalbard). Changing I concentrations can be linked to the March-May 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 March-May sea ice coincides with enlargement of the open-ocean surface which enhances marine primary production and consequent I emission. The observed Br enrichment could be explained by greater Br emissions during the Br explosions that have been observed to occur mainly 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. B.; Isaksson, E.; Varin, C.; Vallelonga, P.; Plane, J. M. C.; Barbante, C.

2013-10-01

180

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

181

Surface Roughness Impact on the Sea Ice Thickness Measurements Based on LIDAR/Radar Altimetry  

NASA Astrophysics Data System (ADS)

The Radar and/or LIDAR measurements of sea ice freeboard provide an indirect approach to infer sea ice thickness via isostasy. The underlying assumption is that the LIDAR signal returns at the air/snow interface and radar signal at the snow/ice interface. Thus the surface roughness at the air, snow and ice interface has a significant impact on the LIDAR/Radar returns, which can lead to very significant errors in the ice thickness retrievals. Recent Cryosat-2 validation results suggest that its altimetry-based technique is very effective in mapping hemispheric sea ice thickness. However, in some cases significant bias exists in the Cryosat-2 data product. To understand the performance of those data depends on our skills in quantifying the impacts of the secondary parameters, such as surface roughness of snow and ice surfaces and the penetration depth of the snow/ice by the radar. To this end, we analyze airborne radar and lidar altimeter data collected during a Cryosat-2 under-flight by the NRL and the NASA IceBridge missions, as well as the in-situ data from the coordinated CRREL/NRL field campaign. In this presentation we will show some surface roughness data from airborne LIDAR for leveled and deformed first year ice, and ice pressure ridges. Their impacts on radar returns and sea ice thickness retrieval will be presented.

Li, L.; Truesdale, D.; Posey, P.; Allard, R.; Gardner, J. M.; Brozena, J. M.; Richter-Menge, J.

2013-12-01

182

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

183

Physical characteristics of summer sea ice across the Arctic Ocean  

USGS Publications Warehouse

Sea ice characteristics were investigated during July and August on the 1994 transect across the Arctic Ocean. Properties examined from ice cores included salinity, temperature, and ice structure. Salinities measured near zero at the surface, increasing to 3-4??? at the ice-water interface. Ice crystal texture was dominated by columnar ice, comprising 90% of the ice sampled. Surface albedos of various ice types, measured with radiometers, showed integrated shortwave albedos of 0.1 to 0.3 for melt ponds, 0.5 for bare, discolored ice, and 0.6 to 0.8 for a deteriorated surface or snow-covered ice. Aerial photography was utilized to document the distribution of open melt ponds, which decreased from 12% coverage of the ice surface in late July at 76??N to almost none in mid-August at 88??N. Most melt ponds were shallow, and depth bore no relationship to size. Sediment was pervasive from the southern Chukchi Sea to the north pole, occurring in bands or patches. It was absent in the Eurasian Arctic, where it had been observed on earlier expeditions. Calculations of reverse trajectories of the sediment-bearing floes suggest that the southernmost sediment was entrained during ice formation in the Beaufort Sea while more northerly samples probably originated in the East Siberian Sea, some as far west as the New Siberian Islands.

Tucker, III, W. B.; Gow, A. J.; Meese, D. A.; Bosworth, H. W.; Reimnitz, E.

1999-01-01

184

The influence of the atmosphere-snow-ice-ocean interactions on the levels of hexachlorocyclohexanes in the Arctic cryosphere  

NASA Astrophysics Data System (ADS)

The ?- and ?-hexachlorocyclohexanes (HCHs) are being scavenged from the atmosphere by falling snow, with the average total scavenging ratios (WT) of 3.8 × 104 and 9.6 × 103, respectively. After deposition, HCH snow concentrations can decrease by 40% because of snowpack ventilation and increase by 50% because of upward migration of brine from the ice. HCH vertical distribution in sufficiently cold winter sea ice, which maintains brine volume fractions <5%, reflects the ice growth history. Initially, the entrapment of brine (and HCHs) in ice depends on the rates of ice growth and desalination. However, after approximately the first week of ice formation, ice growth rate becomes dominant. Deviations of HCH concentrations from the values predicted by the ice bulk salinity (rate of brine entrapment) can be explained by spatial variability of HCHs in surface water. HCH burden in the majority of the ice column remains locked throughout most of the season until the early spring when snow meltwater percolates into the ice, delivering HCHs to the upper ocean via desalination by flushing. Percolation can lead to an increase in ?- and ?-HCH in the sea ice by up to 2%-18% and 4%-32%, respectively.

Pu?Ko, M.; Stern, G. A.; MacDonald, R. W.; Rosenberg, B.; Barber, D. G.

2011-02-01

185

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

186

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

187

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

NASA Astrophysics Data System (ADS)

Sea ice volume has decreased 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 about 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 ± 1280 km3 in October/November and 13 250 ± 1860 km3 in February/March for the time period 2005-2007. Based on these uncertainties we obtain trends in sea ice volume of -1450 ± 530 km3 a-1 in October/November and -880 ± 260 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. However, more work and validation is required to quantify these changes and analyse possible unresolved biases in the freeboard retrievals.

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

2014-04-01

188

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

189

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

190

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

191

Arctic Sea Ice Satellite Observations  

NSDL National Science Digital Library

In this interactive activity produced for Teachers' Domain, learn how Arctic sea ice has changed over the past 25 years in terms of maximum winter extent, concentration, and the timing of breakup each spring.

Foundation, Wgbh E.

2008-01-17

192

Surface-based passive microwave studies of multiyear sea ice  

NASA Technical Reports Server (NTRS)

Results are presented on surface-based multifrequency passive microwave observations of multiyear (MY) sea ice in the eastern Arctic Basin, the Beaufort Sea, the Canadian archipelago, and the northern Greenland Sea. The analyses of these data show that the magnitude of the spectral gradient of emissivity is directly related to the existence and the thickness of a decomposed surface ice layer with very high porosity. Spectra for melt ponds with a frozen surface layer closely resembled those of lake ice and showed a positive spectral gradient. The variance among emissivity spectra for MY ice was caused primarily by the distributions of melt ponds and by the presence of significant amounts of scattering inhomogeneities in the snow and the upper 20-30-cm layer of the ice.

Grenfell, T. C.

1992-01-01

193

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

NSDL National Science Digital Library

Students 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 migration and survival.

2007-01-01

194

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.

195

Measuring the thermodynamic state of sea ice using synthetic aperture radar (SAR) time series data  

Microsoft Academic Search

The study of atmosphere-sea ice-ocean processes using synthetic aperture radar (SAR) endeavors to improve estimates of energy flows and climate state variables from seasonally dynamic Arctic sea ice. This paper works toward this goal by characterizing the seasonal coevolution of the thermodynamic, electrical, brine volume, mechanical and microwave scattering characteristics of a snow covered landfast first-year (FY) sea ice volume

J. J. Yackel; D. G. Barber

1998-01-01

196

Snow and Ice Crust Changes over Northern Eurasia since 1966  

NASA Astrophysics Data System (ADS)

When temperature of snow cover reaches zero Celsius first time since its establishment, snowmelt starts. In many parts of the world this process can be lengthy. The initial amount of heat that “arrives” to the snowpack might be insufficient for complete snowmelt, during the colder nights re-freeze of the melted snow may occur (thus creating the ice crust layers), and a new cold front (or the departure of the warm front that initiated melt) can decrease temperatures below the freezing point again and stop the snowmelt completely. It well can be that first such snowmelt occurs in winter (thaw day) and for several months thereafter snowpack stays on the ground. However, even the first such melt initiates a process of snow metamorphosis on its surface changing snow albedo and generating snow crust as well as on its bottom generating ice crust. Once emerged, the crusts will not disappear until the complete snowmelt. Furthermore, these crusts have numerous pathways of impact on the wild birds and animals in the Arctic environment as well as on domesticated reindeers. In extreme cases, the crusts may kill some wild species and prevent reindeers’ migration and feeding. Ongoing warming in high latitudes created situations when in the western half of Eurasian continent days with thaw became more frequent. Keeping in mind potential detrimental impacts of winter thaws and associated with them snow/ice crust development, it is worthwhile to study directly what are the major features of snow and ice crust over Eurasia and what is their dynamics. For the purpose of this study, we employed the national snow survey data set archived at the Russian Institute for Hydrometeorological Information. The dataset has routine snow surveys run throughout the cold season each decade (during the intense snowmelt, each 5 days) at all meteorological stations of the former USSR, thereafter, in Russia since 1966. Prior to 1966 snow surveys are also available but the methodology of observations has substantially changed at that year. Therefore, this analysis includes only data of 585 Russian stations from 1966 to 2008 that have all years of data with a minimal number of missing observations. Surveys run separately along all types of environment typical for the site for 1 to 2 km, describing the current snow cover properties including characteristics of snow and ice crust. Joint analysis of these characteristics of crust together with a suite of synoptic information at the stations allows us to empirically assess the process of snow and ice crust formation and development throughout the cold season and outline major factors responsible for their dynamics. Finally, regional averaging and time series analysis of both, these factors and the crust characteristics themselves, answer the question about the regional climatic changes of snow and ice crusts over Northern Eurasia, including those crust characteristics that are of practical importance for reindeer husbandry. These results for the Russian Federation will be presented at the Meeting.

Bulygina, O.; Groisman, P. Y.; Razuvaev, V.; Radionov, V.

2009-12-01

197

Arctic sea ice decline: Projected changes in timing and extent of sea ice in the Bering and Chukchi Seas  

USGS Publications Warehouse

The Arctic region is warming faster than most regions of the world due in part to increasing greenhouse gases and positive feedbacks associated with the loss of snow and ice cover. One consequence has been a rapid decline in Arctic sea ice over the past 3 decades?a decline that is projected to continue by state-of-the-art models. Many stakeholders are therefore interested in how global warming may change the timing and extent of sea ice Arctic-wide, and for specific regions. To inform the public and decision makers of anticipated environmental changes, scientists are striving to better understand how sea ice influences ecosystem structure, local weather, and global climate. Here, projected changes in the Bering and Chukchi Seas are examined because sea ice influences the presence of, or accessibility to, a variety of local resources of commercial and cultural value. In this study, 21st century sea ice conditions in the Bering and Chukchi Seas are based on projections by 18 general circulation models (GCMs) prepared for the fourth reporting period by the Intergovernmental Panel on Climate Change (IPCC) in 2007. Sea ice projections are analyzed for each of two IPCC greenhouse gas forcing scenarios: the A1B `business as usual? scenario and the A2 scenario that is somewhat more aggressive in its CO2 emissions during the second half of the century. A large spread of uncertainty among projections by all 18 models was constrained by creating model subsets that excluded GCMs that poorly simulated the 1979-2008 satellite record of ice extent and seasonality. At the end of the 21st century (2090-2099), median sea ice projections among all combinations of model ensemble and forcing scenario were qualitatively similar. June is projected to experience the least amount of sea ice loss among all months. For the Chukchi Sea, projections show extensive ice melt during July and ice-free conditions during August, September, and October by the end of the century, with high agreement among models. High agreement also accompanies projections that the Chukchi Sea will be completely ice covered during February, March, and April at the end of the century. Large uncertainties, however, are associated with the timing and amount of partial ice cover during the intervening periods of melt and freeze. For the Bering Sea, median March ice extent is projected to be about 25 percent less than the 1979-1988 average by mid-century and 60 percent less by the end of the century. The ice-free season in the Bering Sea is projected to increase from its contemporary average of 5.5 months to a median of about 8.5 months by the end of the century. A 3-month longer ice- free season in the Bering Sea is attained by a 1-month advance in melt and a 2-month delay in freeze, meaning the ice edge typically will pass through the Bering Strait in May and January at the end of the century rather than June and November as presently observed.

Douglas, D. C.

2010-01-01

198

Winter spring dynamics in sea-ice carbon cycling in the coastal Arctic Ocean  

NASA Astrophysics Data System (ADS)

An understanding of microbial interactions in first-year sea ice on Arctic shelves is essential for identifying potential responses of the Arctic Ocean carbon cycle to changing sea-ice conditions. This study assessed dissolved and particulate organic carbon (DOC, POC), exopolymeric substances (EPS), chlorophyll a, bacteria and protists, in a seasonal (24 February to 20 June 2004) investigation of first-year sea ice and associated surface waters on the Mackenzie Shelf. The dynamics of and relationships between different sea-ice carbon pools were investigated for the periods prior to, during and following the sea-ice-algal bloom, under high and low snow cover. A predominantly heterotrophic sea-ice community was observed prior to the ice-algal bloom under high snow cover only. However, the heterotrophic community persisted throughout the study with bacteria accounting for, on average, 44% of the non-diatom particulate carbon biomass overall the study period. There was an extensive accumulation of sea-ice organic carbon following the onset of the ice-algal bloom, with diatoms driving seasonal and spatial trends in particulate sea-ice biomass. DOC and EPS were also significant sea-ice carbon contributors such that sea-ice DOC concentrations were higher than, or equivalent to, sea-ice-algal carbon concentrations prior to and following the algal bloom, respectively. Sea-ice-algal carbon, DOC and EPS-carbon concentrations were significantly interrelated under high and low snow cover during the algal bloom ( r values ? 0.74, p < 0.01). These relationships suggest that algae are primarily responsible for the large pools of DOC and EPS-carbon and that similar stressors and/or processes could be involved in regulating their release. This study demonstrates that DOC can play a major role in organic carbon cycling on Arctic shelves.

Riedel, Andrea; Michel, Christine; Gosselin, Michel; LeBlanc, Bernard

2008-12-01

199

Jet Formation at the Sea Ice Edge  

NASA Astrophysics Data System (ADS)

The sea ice edge presents a region of many feedback processes between the atmosphere, ocean and sea ice, which are inadequately represented in current climate models. Here we focus on on-ice atmospheric and oceanic flows at the sea ice edge. Mesoscale jet formation due to the Coriolis effect is well understood over sharp changes in surface roughness such as coastlines. This sharp change in surface roughness is experienced by the atmosphere flowing over, and ocean flowing under, a compacted sea ice edge. We have studied a dynamic sea ice edge responding to atmospheric and oceanic jet formation. The shape and strength of atmospheric and oceanic jets during on-ice flows is calculated from existing studies of the sea ice edge and prescribed to idealised models of the sea ice edge. An idealised analytical model of sea ice drift is developed and compared to a sea ice climate model (the CICE model) run on an idealised domain. The response of the CICE model to jet formation is tested at various resolutions. We find that the formation of atmospheric jets during on-ice winds at the sea ice edge increases the wind speed parallel to the sea ice edge and results in the formation of a sea ice edge jet. The modelled sea ice edge jet is in agreement with an observed jet although more observations are needed for validation. The increase in ice drift speed is dependent upon the angle between the ice edge and wind and can result in a 40% increase in ice transport along the sea ice edge. The possibility of oceanic jet formation during on-ice currents and the resultant effect upon the sea ice edge is less conclusive. Observations and climate model data of the polar oceans has been analysed to show areas of likely atmospheric jet formation, with the Fram Strait being of particular interest.

Heorton, Harry; Feltham, Daniel

2014-05-01

200

Processes and imagery of first-year fast sea ice during the melt season  

NASA Technical Reports Server (NTRS)

In June and July 1982, a field program was conducted in the Canadian Arctic on Prince Patrick Island to study sea ice during the melt season with in situ measurements and microwave instrumentation operated near the surface and from aircraft. The objective of the program was to measure physical characteristics together with microwave backscatter and emission coefficients of sea ice during this major period of transition. The present paper is concerned with a study of both surface measurements and imagery of first-year fast ice during the melt season. The melting process observed in first-year fast ice was found to begin with the gradual reduction of the snow cover. For a two- to three-day period in this melt stage, a layer of superimposed ice nodules formed at the snow/ice interface as meltwater froze around ice and snow grains.

Holt, B.; Digby, S. A.

1985-01-01

201

Water, Ice, and Snow - Issue 5, August 2008  

NSDL National Science Digital Library

In this issue of the free online magazine, Beyond Penguins and Polar Bears, explore what the polar regions can teach us about the water cycle and the states and changes of matter. Find lesson plans about the many forms of water, ice, and snow found in the polar regions and how to use science notebooks to integrate literacy and science.

University, The O.

202

Soot climate forcing via snow and ice albedos  

Microsoft Academic Search

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 \\

James Hansen; Larissa Nazarenko

2004-01-01

203

An Analysis of Airport Snow Removal and Ice Control.  

National Technical Information Service (NTIS)

The report is divided into two major sections. The first describes an approach using modelling techniques by which airport snow removal and ice control systems may be evaluated on a cost-effectiveness basis, taking into account factors such as the followi...

D. J. Tighe L. A. Garland J. C. Caird

1970-01-01

204

Snow crystal imaging using scanning electron microscopy: III. Glacier ice, snow and biota  

USGS Publications Warehouse

Low-temperature scanning electron microscopy (SEM) was used to observe metamorphosed snow, glacial firn, and glacial ice obtained from South Cascade Glacier in Washington State, USA. Biotic samples consisting of algae (Chlamydomonas nivalis) and ice worms (a species of oligochaetes) were also collected and imaged. In the field, the snow and biological samples were mounted on copper plates, cooled in liquid nitrogen, and stored in dry shipping containers which maintain a temperature of -196??C. The firn and glacier ice samples were obtained by extracting horizontal ice cores, 8 mm in diameter, at different levels from larger standard glaciological (vertical) ice cores 7.5 cm in diameter. These samples were cooled in liquid nitrogen and placed in cryotubes, were stored in the same dry shipping container, and sent to the SEM facility. In the laboratory, the samples were sputter coated with platinum and imaged by a low-temperature SEM. To image the firn and glacier ice samples, the cores were fractured in liquid nitrogen, attached to a specimen holder, and then imaged. While light microscope images of snow and ice are difficult to interpret because of internal reflection and refraction, the SEM images provide a clear and unique view of the surface of the samples because they are generated from electrons emitted or reflected only from the surface of the sample. In addition, the SEM has a great depth of field with a wide range of magnifying capabilities. The resulting images clearly show the individual grains of the seasonal snowpack and the bonding between the snow grains. Images of firn show individual ice crystals, the bonding between the crystals, and connected air spaces. Images of glacier ice show a crystal structure on a scale of 1-2 mm which is considerably smaller than the expected crystal size. Microscopic air bubbles, less than 15 ??m in diameter, clearly marked the boundaries between these crystal-like features. The life forms associated with the glacier were easily imaged and studied. The low-temperature SEM sample collecting and handling methods proved to be operable in the field; the SEM analysis is applicable to glaciological studies and reveals details unattainable by conventional light microscopic methods.Low temperature scanning electron microscopy (SEM) was used to observe metamorphosed snow, glacial firn, and glacial ice obtained from South Cascade Glacier in Washington State, USA. Biotic samples consisting of algae and ice worms were also collected and imaged. The SEM images provide a clear and unique view of the surface of the samples because they are generated from electrons emitted or reflected only from the surface of the sample. The SEM has a great depth of field with a wide range of magnifying capabilities.

Rango, A.; Wergin, W. P.; Erbe, E. F.; Josberger, E. G.

2000-01-01

205

ICESat Observations of Arctic Sea Ice: A First Look  

NASA Technical Reports Server (NTRS)

Analysis of near-coincident ICESat and RADARSAT imagery shows that the retrieved elevations from the laser altimeter are sensitive to new openings (containing thin ice or open water) in the sea ice cover as well as to surface relief of old and first-year ice. The precision of the elevation estimates, measured over relatively flat sea ice, is approx. 2 cm. Using the thickness of thin-ice in recent openings to estimate sea level references, we obtain the sea-ice freeboard along the altimeter tracks. This step is necessitated by the large uncertainties in the sea surface topography compared to that required for accurate determination of freeboard. Unknown snow depth introduces the largest uncertainty in the conversion of freeboard to ice thickness. Surface roughness is also derived, for the first time, from the variability of successive elevation estimates along the altimeter track. Overall, these ICESat measurements provide an unprecedented view of the Arctic Ocean ice cover at length scales at and above the spatial dimension of the altimeter footprint of approx. 70 m.

Kwok, Ron; Zwally, H. Jay; Yi, Donghui

2004-01-01

206

ICESat Observations of Arctic Sea Ice: A First Look  

NASA Technical Reports Server (NTRS)

Analysis of near-coincident ICESat and RADARSAT imagery shows that the retrieved elevations from the laser altimeter are sensitive to new openings (containing thin ice or open water) in the sea ice cover as well as to surface relief of old and first-year ice. The precision of the elevation estimates, measured over relatively flat sea ice, is approx. 2 cm Using the thickness of thin-ice in recent openings to estimate sea level references, we obtain the sea-ice free-board along the altimeter tracks. This step is necessitated by the large uncertainties in the time-varying sea surface topography compared to that required for accurate determination of free-board. Unknown snow depth introduces the largest uncertainty in the conversion of free-board to ice thickness. Surface roughness is also derived, for the first time, from the variability of successive elevation estimates along the altimeter track Overall, these ICESat measurements provide an unprecedented view of the Arctic Ocean ice cover at length scales at and above the spatial dimension of the altimeter footprint.

Kwok, Ron; Zwally, H. Jay; Yi, Dong-Hui

2004-01-01

207

Export of Algal Biomass from the Melting Arctic Sea Ice  

NASA Astrophysics Data System (ADS)

In the Arctic, under-ice primary production is limited to summer months and is restricted not only by ice thickness and snow cover but also by the stratification of the water column, which constrains nutrient supply for algal growth. Research Vessel Polarstern visited the ice-covered eastern-central basins between 82° to 89°N and 30° to 130°E in summer 2012, when Arctic sea ice declined to a record minimum. During this cruise, we observed a widespread deposition of ice algal biomass of on average 9 grams of carbon per square meter to the deep-sea floor of the central Arctic basins. Data from this cruise will contribute to assessing the effect of current climate change on Arctic productivity, biodiversity, and ecological function.

Boetius, Antje; Albrecht, Sebastian; Bakker, Karel; Bienhold, Christina; Felden, Janine; Fernández-Méndez, Mar; Hendricks, Stefan; Katlein, Christian; Lalande, Catherine; Krumpen, Thomas; Nicolaus, Marcel; Peeken, Ilka; Rabe, Benjamin; Rogacheva, Antonina; Rybakova, Elena; Somavilla, Raquel; Wenzhöfer, Frank; aff1

2013-03-01

208

Microstructural Considerations of Transporting Sea Ice Samples from Polar Regions  

NASA Astrophysics Data System (ADS)

High latitude regions are at the forefront of climate change research as these regions have and will experience the greatest impact due to changing environmental conditions (e.g. Antarctic and recent Arctic stratospheric ozone holes, large temperature increases on the Antarctic Peninsula, changes in the extent and age of Arctic sea ice). One of the major challenges of polar scientific research is the preservation of frozen sea ice samples during their transport back to the laboratory and subsequent storage. Small fluctuations in temperature have been shown to have a significant effect on the microstructure of snow and ice samples. This is especially true for sea ice specimens where transport and storage temperatures are often only slightly below the eutectic point for its different constituents (i.e. salts). Furthermore, sea ice can have a 30 deg C in situ vertical temperature gradient that is lost during transport and storage. Sea ice plays a critical role in mediating the exchange of heat, gases, and chemical species across the ocean-atmosphere interface. The kinetics of these exchanges is highly dependent upon the brine channel microstructure, which is strongly coupled to temperature. To determine the degree of microstructural variation between samples shipped at different temperatures, ten samples of a single sea ice core collected in March 2012 were transported from Barrow, Alaska to Hanover, NH using two common techniques: with blue ice packs enclosed in a Styrofoam box (~ -25 deg C) and in a dry liquid nitrogen cryoshipper (~ -182 deg C). In addition, snow lying on the sea ice and blowing snow samples were collected and shipped via both techniques. All samples were then stored for analysis in a cold room maintained at ~ -33 deg C. The microstructure of both sets of samples was analyzed using x-ray micro-computed tomography (?-CT), with samples on a Peltier cold stage to maintain a scanning temperature of -20 deg C. We compare sea ice porosity and brine channel morphology between the samples shipped at -25 deg C and those from the same core depth shipped at -182 deg C. This work informed the transport and analysis of our samples collected in Antarctica in October - November 2012.

Lieb-Lappen, R.; Obbard, R. W.

2012-12-01

209

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

210

Improved Upper Ocean/Sea Ice Modeling in the GISS GCM for Investigating Climate Change  

NASA Technical Reports Server (NTRS)

This project built on our previous results in which we highlighted the importance of sea ice in overall climate sensitivity by determining that for both warming and cooling climates, when sea ice was not allowed to change, climate sensitivity was reduced by 35-40%. We also modified the Goddard Institute for Space Studies (GISS) 8 deg x lO deg atmospheric General Circulation Model (GCM) to include an upper-ocean/sea-ice model involving the Semtner three-layer ice/snow thermodynamic model, the Price et al. (1986) ocean mixed layer model and a general upper ocean vertical advection/diffusion scheme for maintaining and fluxing properties across the pycnocline. This effort, in addition to improving the sea ice representation in the AGCM, revealed a number of sensitive components of the sea ice/ocean system. For example, the ability to flux heat through the ice/snow properly is critical in order to resolve the surface temperature properly, since small errors in this lead to unrestrained climate drift. The present project, summarized in this report, had as its objectives: (1) introducing a series of sea ice and ocean improvements aimed at overcoming remaining weaknesses in the GCM sea ice/ocean representation, and (2) performing a series of sensitivity experiments designed to evaluate the climate sensitivity of the revised model to both Antarctic and Arctic sea ice, determine the sensitivity of the climate response to initial ice distribution, and investigate the transient response to doubling CO2.

1997-01-01

211

Improved Upper Ocean/Sea Ice Modeling in the GISS GCM for Investigating Climate Change  

NASA Technical Reports Server (NTRS)

This project built on our previous results in which we highlighted the importance of sea ice in overall climate sensitivity by determining that for both warming and cooling climates, when sea ice was not allowed to change, climate sensitivity was reduced by 35-40%. We also modified the GISS 8 deg x lO deg atmospheric GCM to include an upper-ocean/sea-ice model involving the Semtner three-layer ice/snow thermodynamic model, the Price et al. (1986) ocean mixed layer model and a general upper ocean vertical advection/diffusion scheme for maintaining and fluxing properties across the pycnocline. This effort, in addition to improving the sea ice representation in the AGCM, revealed a number of sensitive components of the sea ice/ocean system. For example, the ability to flux heat through the ice/snow properly is critical in order to resolve the surface temperature properly, since small errors in this lead to unrestrained climate drift. The present project, summarized in this report, had as its objectives: (1) introducing a series of sea ice and ocean improvements aimed at overcoming remaining weaknesses in the GCM sea ice/ocean representation, and (2) performing a series of sensitivity experiments designed to evaluate the climate sensitivity of the revised model to both Antarctic and Arctic sea ice, determine the sensitivity of the climate response to initial ice distribution, and investigate the transient response to doubling CO2.

1998-01-01

212

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 the Beaufort Sea ice near Barrow, Alaska, in March 2009 as part of the Ocean-Atmosphere-Sea Ice-Snowpack (OASIS) and OASIS-Canada International Polar Year programmes. These results represent the first atmospheric mercury speciation measurements collected on the sea ice. Concentrations of PHg averaged 393.5 pg m-3 (range 47.1-900.1 pg m-3) and RGM concentrations averaged 30.1 pg m-3 (range 3.5-105.4 pg m-3) during the two-week-long study. The mean concentration of GEM during the study was 0.59 ng m-3 (range 0.01-1.51 ng m-3) and was depleted compared to annual Arctic ambient boundary layer concentrations. It is shown that when ozone (O3) and bromine oxide (BrO) chemistry were active there is a positive linear relationship between GEM and O3, a negative one between PHg and O3, a positive correlation between RGM and BrO, and none between RGM and O3. 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, with significantly higher emission over the tundra. Elevated chloride levels in snow over sea ice are proposed to be the cause of lower GEM emissions over the sea ice because chloride has been shown to suppress photoreduction processes of RGM to GEM in snow. Since the snowpack on sea ice retains more mercury than inland snow, current models of the Arctic mercury cycle may greatly underestimate atmospheric deposition fluxes because they are based predominantly on land-based measurements. Land-based measurements of atmospheric mercury deposition may also underestimate the impacts of sea ice changes on the mercury cycle in the Arctic. The predicted changes in sea ice conditions and a more saline future snowpack in the Arctic could enhance retention of atmospherically deposited mercury and increase 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.

2013-07-01

213

Passive microwave data for snow and ice research - Planned products from the DMSP SSM/I system  

NASA Technical Reports Server (NTRS)

Recommendations which have been made for processing and distributing passive microwave data for snow and ice research obtained with the Defense Meteorological Satellite Program (DMSP) Special Sensor Microwave Imager (SSM/I) are discussed. The general objectives for SSM/I data are reviewed, and the sensor and data flow are described. The SSM/I sea ice products are discussed, and algorithm/product validation is addressed. Proposed services and implementation after SSM/I launch are summarized.

Weawer, Ronald; Barry, Roger G.; Morris, Charles

1987-01-01

214

Snow and Ice in the Earth System Viewed by Space Scatterometer Observatory  

Microsoft Academic Search

Snow and ice have an important role in the Earth climate system due to their interactions with land, ocean, and atmosphere in complex feedback processes. This paper presents recent results from satellite scatterometer which serves as a space observatory to study the role of snow and ice from aggregation to hemispheric and global scales. Hemispheric snow cover is mapped on

S. V. Nghiem; G. Neumann

2002-01-01

215

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 oc...

216

Ice core records as sea ice proxies: An evaluation from the Weddell Sea region of Antarctica  

Microsoft Academic Search

Ice core records of methanesulfonic acid (MSA) from three sites around the Weddell Sea are investigated for their potential as sea ice proxies. It is found that the amount of MSA reaching the ice core sites decreases following years of increased winter sea ice in the Weddell Sea; opposite to the expected relationship if MSA is to be used as

Nerilie J. Abram; Robert Mulvaney; Eric W. Wolff; Manfred Mudelsee

2007-01-01

217

Ice core records as sea ice proxies: An evaluation from the Weddell Sea region of Antarctica  

Microsoft Academic Search

(1) Ice core records of methanesulfonic acid (MSA) from three sites around the Weddell Sea are investigated for their potential as sea ice proxies. It is found that the amount of MSA reaching the ice core sites decreases following years of increased winter sea ice in the Weddell Sea; opposite to the expected relationship if MSA is to be used

Nerilie J. Abram; Robert Mulvaney; Eric W. Wolff; Manfred Mudelsee

2007-01-01

218

Sensitivity of Antarctic sea ice to form drag parameterization  

NASA Astrophysics Data System (ADS)

A new drag parametrization accounting explicitly for form drag has been recently formulated and applied to the Arctic sea ice (Lupkes et al, 2012 and Tsamados et al, 2014). We summarize here the fundamental elements of this formulation and we then adapt it to the Antarctic sea ice. Considering the general expression of the momentum balance of sea ice, we analyze the total (neutral) drag coefficients by studying separately air-ice and ocean-ice momentum fluxes, and by introducing the parameterization for both the atmospheric neutral drag coeffcient (ANDC) and the oceanic neutral drag coeffcient (ONDC). The two coefficients are calculated as a sum of their skin frictional contribution and form drag contribution, which comes from ridges and floe edges for the ANDC and keels and floe edges for the ONDC. Due to the contrasting geography of the two polar regions, there are important differences, both dynamic and thermodynamic, between Arctic and Antarctic sea ice. In the Antarctic, sea ice is younger, less ridged (hence thinner and smoother). Due to the intense snowfalls, the snow cover is generally thicker than in the Arctic, with values that vary significantly both seasonally and regionally and can affect the roughness of the surface and can lead to flooding of the ice. At the outer boundary of the Southern Ocean, the ice is unconstrained by land, divergent and subject to meridional advection, which leads to a much faster ice drift than in the Arctic. We show here how the new parameterization accounting for form drag influences the Antarctic sea ice characteristics.

Barbic, Gaia; Tsamados, Michel; Petty, Alek; Schroeder, David; Holland, Paul; Feltham, Daniel

2014-05-01

219

CO2 deposition over the multi-year ice of the western Weddell Sea  

Microsoft Academic Search

Field measurements by eddy correlation (EC) indicate an average uptake of 0.6 g CO2 m?2 d?1 by the ice-covered western Weddell Sea in December 2004. At the same time, snow that covers ice floes of the western Weddell Sea becomes undersaturated with CO2 relative to the atmosphere during early summer. Gradients of CO2 from the ice to the atmosphere do

H. J. Zemmelink; B. Delille; J. L. Tison; E. J. Hintsa; L. Houghton; J. W. H. Dacey

2006-01-01

220

Differential Sea Ice Drift.  

National Technical Information Service (NTIS)

The development of an accurate predictive model for the motion and deformation of arctic pack ice is believed by most engineers and scientists concerned with arctic research and development to be of prime importance both for practical operational purposes...

W. D. Hibler W. F. Weeks A. Kovacs S. F. Ackley

1975-01-01

221

Minimal Antarctic sea ice during the Pliocene  

Microsoft Academic Search

Antarctic sea-ice concentration at Ocean Drilling Program Sites 1165 (64.380°S, 67.219°E) and 1166 (67.696°S, 74.787°E) was lower than today through much of the Pliocene. The low sea-ice concentration is evident from the proportion of the diatom Eucampia antarctica with intercalary valves (Eucampia index). This sea-ice proxy was calibrated by using modern diatom data obtained from core-top samples and winter sea-ice

J. M. Whitehead; S. Wotherspoon; S. M. Bohaty

2005-01-01

222

Validation of EOS Aqua AMSR Sea Ice Products for East Antarctica  

NASA Technical Reports Server (NTRS)

This paper presents results from AMSR-E validation activities during a collaborative international cruise onboard the RV Aurora Australis to the East Antarctic sea ice zone (64-65 deg.S, 110-120 deg.E) in the early Austral spring of 2003. The validation strategy entailed an IS-day survey of the statistical characteristics of sea ice and snowcover over a Lagrangian grid 100 x 50 km in size (demarcated by 9 drifting ice beacons) i.e. at a scale representative of Ah4SR pixels. Ice conditions ranged h m consolidated first-year ice to a large polynya offshore from Casey Base. Data sets collected include: snow depth and snow-ice interface temperatures on 24 (?) randomly-selected floes in grid cells within a 10 x 50 km area (using helicopters); detailed snow and ice measurements at 13 dedicated ice stations, one of which lasted for 4 days; time-series measurements of snow temperature and thickness at selected sites; 8 aerial photography and thermal-IR radiometer flights; other satellite products (SAR, AVHRR, MODIS, MISR, ASTER and Envisat MERIS); ice drift data; and ancillary meteorological (ship-based, meteorological buoys, twice-daily radiosondes). These data are applied to a validation of standard AMSR-E ice concentration, snowcover thickness and ice-temperature products. In addition, a validation is carried out of ice-surface skin temperature products h m the NOAA AVHRR and EOS MODIS datasets.

Massom, Rob; Lytle, Vicky; Allison, Ian; Worby, Tony; Markus, Thorsten; Scambos, Ted; Haran, Terry; Enomoto, Hiro; Tateyama, Kazu; Pfaffling, Andi

2004-01-01

223

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

224

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

225

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.

226

The U.S. Navy's Emerging Sea Ice Prediction Capabilities  

NASA Astrophysics Data System (ADS)

The U.S. Navy's regional and global coupled sea ice modeling activities are described. The Arctic Cap Nowcast Forecast System (ACNFS) is a 3.5 km coupled sea ice-ocean model that produces 7 day forecasts of the Arctic sea ice state in all ice covered areas in the northern hemisphere (poleward of 40°N). The ocean component is the HYbrid Coordinate Ocean Model (HYCOM) and is coupled to the Los Alamos National Laboratory Community Ice CodE (CICE) via the Earth System Modeling Framework (ESMF). The ocean and sea ice models are run in an assimilative cycle with the Navy's Coupled Ocean Data Assimilation (NCODA) system. The ACNFS was transitioned to operations at the Naval Oceanographic Office in 2013 to serve its customer, the National Ice Center. The Global Ocean forecast System (GOFS3.1) is essentially an extension of ACNFS to the globe at 1/12° (equatorial) resolution, still 3.5 km in the Arctic, and it will provide sea ice predictions for the Arctic and Antarctic. Testing and validation is underway and an operational transition is planned for 2015, when GOFS3.1 will replace the ACNFS. A relocatable regional capability is being developed by coupling CICE to the Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS). This new system will have an advanced snow-ice albedo representation and produce coupled forecasts out to 7-10 days with resolutions for the atmosphere and sea ice models at 1-3 km. Examples of these emerging capabilities will be presented.

Allard, Richard; Campbell, Tim; Hebert, David; Metzger, E. Joseph; Posey, Pamela; Wallcraft, Alan; Smedstad, Ole Martin; Gaberšek, Saša; Jin, Yi; Wang, Shouping

2014-05-01

227

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

228

Surveying Arctic Sea Ice  

USGS Multimedia Gallery

Two U.S. Coast Guard members are being transported by crane from U.S. Coast Guard Cutter Healy onto a piece of multi-year ice. This was during a scientific expedition to map the Arctic seafloor. The expedition was a joint effort using two ships, Healy and the Canadian Coast Guard Ship Louis S. St. L...

2008-12-29

229

Polar Ice Prediction System-A Sea Ice Forecasting System.  

National Technical Information Service (NTIS)

The Polar Ice Prediction System PIPS, based on the Hibler dynamic/thermodynamic sea ice model, was developed as an upgrade to the existing sea ice products available at the Navy's Fleet Numerical Oceanography Center (FNOC). It was also designed to provide...

P. G. Posey R. H. Preller

1989-01-01

230

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

231

Ecological consequences of sea-ice decline.  

PubMed

After a decade with nine of the lowest arctic sea-ice minima on record, including the historically low minimum in 2012, we synthesize recent developments in the study of ecological responses to sea-ice decline. Sea-ice loss emerges as an important driver of marine and terrestrial ecological dynamics, influencing productivity, species interactions, population mixing, gene flow, and pathogen and disease transmission. Major challenges in the near future include assigning clearer attribution to sea ice as a primary driver of such dynamics, especially in terrestrial systems, and addressing pressures arising from human use of arctic coastal and near-shore areas as sea ice diminishes. PMID:23908231

Post, Eric; Bhatt, Uma S; Bitz, Cecilia M; Brodie, Jedediah F; Fulton, Tara L; Hebblewhite, Mark; Kerby, Jeffrey; Kutz, Susan J; Stirling, Ian; Walker, Donald A

2013-08-01

232

The Effect of Atmosphere-Snow-Ice-Ocean Coupling on Hexachlorocyclohexane Pathways within the Arctic Marine Environment  

NASA Astrophysics Data System (ADS)

The importance of the cryosphere, and of sea ice in particular, for contaminant transport and redistribution in the Arctic was pointed out in the literature. However, studies on contaminants in sea ice are scarce, and entirely neglect the sea ice geophysical and thermodynamic characteristics as well as interactions between various cryospheric compartments. This thesis addresses those gaps. Ice formation was shown to have a significant concentrating impact on the levels of HCHs in the water just beneath the ice. Both geophysical and thermodynamic conditions in sea ice were shown to be crucial in understanding pathways of accumulation or rejection of HCHs. Although HCH burden in the majority of the ice column remains locked throughout most of the season until the early spring, upward migration of brine from the ice to the snow in the winter has an effect on levels of HCHs in the snow by up to 50 %. In the spring, when snow melt water percolates into the ice delivering HCHs to the upper ocean via desalination by flushing, levels of HCHs in the ice can increase by up to 2 %-18 % and 4 %-32 % for ?- and ?-HCH, respectively. Brine contained within sea ice currently exhibits the highest HCH concentrations in any abiotic Arctic environment, exceeding under-ice water concentrations by a factor of 3 in the spring. This circumstance suggests that the brine ecosystem has been, and continues to be, the most exposed to HCHs. ?-HCH levels were shown to decrease rapidly in the last two decades in the Polar Mixed Layer (PML) and the Pacific Mode Layer (PL) of the Beaufort Sea due to degradation. If the rate of degradation does not change in the near future, the majority of ?-HCH could be eliminated from the Beaufort Sea by 2020, with concentrations in 2040 dropping to < 0.006 ng/L and < 0.004 ng/L in the PML and the PL, respectively. Elimination of ?-HCH from sea water takes significantly longer than from the atmosphere, with a lag of approximately two decades.

Pucko, Monika Agnieszka

233

Additions to the public archive of submarine-based measurements of sea-ice draft  

Microsoft Academic Search

For over 45 years the US Navy has acquired data on Arctic sea-ice draft using upward looking sonar. For some time draft data declassified by the US Navy have been available at National Snow and Ice Data Center (NSIDC) spanning the years 1986 to 1998 with a small amount of supplemental data from 1976. These records come from data originally

D. A. Rothrock; M. R. Wensnahan; D. L. Bentley; F. Fetterer

2006-01-01

234

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

235

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

236

Antarctic sea ice mapping using the AVHRR  

SciTech Connect

A sea ice mapping scheme based on Advanced Very High Resolution Radiometer (AVHRR) data from the National Oceanic and Atmospheric Administration (NOAA) polar orbiting satellites has been developed and applied to daylight images taken between November 1989 to January 1990 and November 1990 to January 1991 over the Weddell and the Ross Seas. After masking the continent and ice shelves, sea ice is discriminated from clouds and open sea using thresholds applied to the multidimensional space formed by AVHRR Channel 2, 3, and 4 radiances. Sea ice concentrations in cloud-free regions are then computed using the tie-point method. Results based on the analysis of more than 70 images show that the proposed scheme is capable of properly discriminating between sea ice, open sea, and clouds, under most conditions, thus allowing high resolution sea ice maps to be produced during the austral summer season.

Zibordi, G. (Inst. for the Study of Geophysical and Environmental Methodologies, Modena (Italy)); Van Woert, M.L. (San Diego State Univ., CA (United States). SeaSpace, Inc.)

1993-08-01

237

CBSIT 2009: Airborne Validation of Envisat Radar Altimetry and In Situ Ice Camp Measurements Over Arctic Sea Ice  

NASA Technical Reports Server (NTRS)

The past few years have seen the emergence of satellite altimetry as valuable tool for taking quantitative sea ice monitoring beyond the traditional surface extent measurements and into estimates of sea ice thickness and volume, parameters that arc fundamental to improved understanding of polar dynamics and climate modeling. Several studies have now demonstrated the use of both microwave (ERS, Envisat/RA-2) and laser (ICESat/GLAS) satellite altimeters for determining sea ice thickness. The complexity of polar environments, however, continues to make sea ice thickness determination a complicated remote sensing task and validation studies remain essential for successful monitoring of sea ice hy satellites. One such validation effort, the Arctic Aircraft Altimeter (AAA) campaign of2006. included underflights of Envisat and ICESat north of the Canadian Archipelago using NASA's P-3 aircraft. This campaign compared Envisat and ICESat sea ice elevation measurements with high-resolution airborne elevation measurements, revealing the impact of refrozen leads on radar altimetry and ice drift on laser altimetry. Continuing this research and validation effort, the Canada Basin Sea Ice Thickness (CBSIT) experiment was completed in April 2009. CBSIT was conducted by NOAA. and NASA as part of NASA's Operation Ice Bridge, a gap-filling mission intended to supplement sea and land ice monitoring until the launch of NASA's ICESat-2 mission. CBIST was flown on the NASA P-3, which was equipped with a scanning laser altimeter, a Ku-band snow radar, and un updated nadir looking photo-imaging system. The CB5IT campaign consisted of two flights: an under flight of Envisat along a 1000 km track similar to that flown in 2006, and a flight through the Nares Strait up to the Lincoln Sea that included an overflight of the Danish GreenArc Ice Camp off the coast of northern Greenland. We present an examination of data collected during this campaign, comparing airborne laser altimeter measurements with (1) Envisat RA-2 returns retracked optimally for sea ice and (2) in situ measurements of sea ice thickness and snow depth gathered from ice camp surveys. Particular attention is given to lead identification and classification using the continuous photo-imaging system along the Envisat underflight as well as the performance of the snow radar over the ice camp survey lines.

Connor, Laurence; Farrell, Sinead; McAdoo, David; Krabill, William; Laxon, Seymour; Richter-Menge, Jacqueline; Markus, Thorsten

2010-01-01

238

Extraction of winter total sea-ice concentration in the Greenland and Barents Seas from SSM\\/I data  

Microsoft Academic Search

Significantly different sea-ice concentrations estimated by the well known Bootstrap and NASA\\/Team SSM\\/I algorithms are found to occur when the brightness temperature of horizontally polarized radiation is depressed, possibly as a result of ice layers in the snow cover. Furthermore, discontinuous ice concentrations, which do not reflect real concentration variations, sometimes occur when the Bootstrap algorithm switches between polarization and

D. M. SMITH

1996-01-01

239

Photochemistry of phenanthrene, pyrene, and fluoranthene in ice and snow  

NASA Astrophysics Data System (ADS)

Although polycyclic aromatic hydrocarbons (PAHs) are common pollutants in snow, there is little quantitative data about their rates of photodegradation in this environment. To begin to address this gap, we have measured the degradation kinetics of phenanthrene, pyrene, and fluoranthene on ice, as these are the most abundant PAHs in arctic snow. Frozen aqueous solutions of individual PAHs, with and without added hydrogen peroxide (HOOH) as a source of hydroxyl radical ( rad OH), were illuminated with simulated sunlight. For all three PAHs, direct photodecay is the main mechanism of degradation, while rad OH-initiated indirect photodegradation is a minor sink. Rate constants (±1 SE) for direct photodegradation extrapolated to midday, surface snow conditions at Summit, Greenland on the summer solstice are 3.8 (±0.8) × 10 -5, 28 (±3) × 10 -5, and 1.4 (±0.7) × 10 -5 s -1 for phenanthrene, pyrene, and fluoranthene, respectively. Apparent quantum efficiencies for photodegradation with simulated sunlight were 3.8 (±0.8) × 10 -3, 4.3 (±0.5) × 10 -4, and 2 (±1) × 10 -5, respectively. Calculated PAH lifetimes in surface snow under Summit conditions are 1-19 h during mid-summer, but increase to >100 days in the dark winter. While the short photodegradation lifetimes in the summer suggest that there should be no appreciable PAH levels in this season, past measurements at Summit sometimes show significant levels of these PAHs in summer surface snow. This discrepancy is likely due to differences in PAH location between lab samples (where the PAHs are probably in quasi-liquid layers) and real snow (where PAHs are likely primarily associated with particulate matter).

Ram, Keren; Anastasio, Cort

240

Arctic sea ice freeboard from IceBridge acquisitions in 2009: Estimates and comparisons with ICESat  

NASA Astrophysics Data System (ADS)

During the spring of 2009, the Airborne Topographic Mapper (ATM) system on the IceBridge mission acquired cross-basin surveys of surface elevations of Arctic sea ice. In this paper, the total freeboard derived from four ˜2000 km transects are examined and compared with those from the 2009 ICESat campaign. Total freeboard, the sum of the snow and ice freeboards, is the elevation of the air-snow interface above the local sea surface. Prior to freeboard retrieval, signal dependent range biases are corrected. With data from a near co-incident outbound and return track on 21 April, we show that our estimates of the freeboard are repeatable to within ˜4 cm but dependent locally on the density and quality of sea surface references. Overall difference between the ATM and ICESat freeboards for the four transects is 0.7 (8.5) cm (quantity in bracket is standard deviation), with a correlation of 0.78 between the data sets of one hundred seventy-eight 50 km averages. This establishes a level of confidence in the use of ATM freeboards to provide regional samplings that are consistent with ICESat. In early April, mean freeboards are 41 cm and 55 cm over first year and multiyear sea ice (MYI), respectively. Regionally, the lowest mean ice freeboard (28 cm) is seen on 5 April where the flight track sampled the large expanse of seasonal ice in the western Arctic. The highest mean freeboard (71 cm) is seen in the multiyear ice just west of Ellesmere Island from 21 April. The relatively large unmodeled variability of the residual sea surface resolved by ATM elevations is discussed.

Kwok, R.; Cunningham, G. F.; Manizade, S. S.; Krabill, W. B.

2012-02-01

241

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.

242

The Third Generation of the Interactive Multisensor Snow and Ice Mapping System (IMS V3)  

NASA Astrophysics Data System (ADS)

Since its inception in 1998, the NOAA Interactive Multisensor Snow and Ice Mapping System (IMS) has sought to provide the most timely, accurate and reliable snow and ice cover gridded data to a broad user community. The output of this product has improved incrementally in resolution, timeliness, and accuracy, with the most notable upgrade of IMS Version 2 (V2) in February 2004. New output requirements, the need for metadata, satellite advancements, and the desire for a broader suite of snow and ice variables mandates another significant overhaul in the IMS system requirements. The intent of the IMS Version 3 (V3) is to improve the output accuracy, timeliness, resolution, metadata, cost, and add flexibility for future enhancements. The IMS production is scheduled for an operational transition to the National Ice Center (NIC) in March 2008. The NIC currently uses a vector-based GIS production system for sea ice charting, which is in contrast to the current raster-based production of the IMS. Integration of the IMS into a vector-based system should allow many of the previously mentioned improvements in the output, while integrating NIC systems. While production will be vector-based, output products will include a more diverse yet integrated collection of raster products. Raster products remain the preferred input source for weather and climate models which are the primary users of the IMS. While this alteration from raster-to-vector based analysis will likely provide significant improvements, care must be taken in the transition from one production methodology to another to preserve its benefit to numerical weather prediction and climate monitoring.

Helfrich, S.; Clemente-Colón, P.; Young, S.

2007-12-01

243

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

244

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

245

A model of the three-dimensional evolution of Arctic melt ponds on first-year and multiyear sea ice  

NASA Astrophysics Data System (ADS)

During winter the ocean surface in polar regions freezes over to form sea ice. In the summer the upper layers of sea ice and snow melts producing meltwater that accumulates in Arctic melt ponds on the surface of sea ice. An accurate estimate of the fraction of the sea ice surface covered in melt ponds is essential for a realistic estimate of the albedo for global climate models. We present a melt-pond-sea-ice model that simulates the three-dimensional evolution of melt ponds on an Arctic sea ice surface. The advancements of this model compared to previous models are the inclusion of snow topography; meltwater transport rates are calculated from hydraulic gradients and ice permeability; and the incorporation of a detailed one-dimensional, thermodynamic radiative balance. Results of model runs simulating first-year and multiyear sea ice are presented. Model results show good agreement with observations, with duration of pond coverage, pond area, and ice ablation comparing well for both the first-year ice and multiyear ice cases. We investigate the sensitivity of the melt pond cover to changes in ice topography, snow topography, and vertical ice permeability. Snow was found to have an important impact mainly at the start of the melt season, whereas initial ice topography strongly controlled pond size and pond fraction throughout the melt season. A reduction in ice permeability allowed surface flooding of relatively flat, first-year ice but had little impact on the pond coverage of rougher, multiyear ice. We discuss our results, including model shortcomings and areas of experimental uncertainty.

Scott, F.; Feltham, D. L.

2010-12-01

246

A dynamic-thermodynamic sea ice model on an Arakawa C-grid for coupled ocean and sea ice state estimation  

NASA Astrophysics Data System (ADS)

As part of an ongoing effort to obtain a best possible, time-evolving analysis of most available ocean and sea ice data, a dynamic and thermodynamic sea-ice model has been coupled to the Massachusetts Institute of Technology general circulation model (MITgcm). Ice mechanics follow a viscous-plastic rheology and the ice momentum equations are solved numerically using either line-successive-over-relaxation (LSOR) or elastic-viscous-plastic (EVP) dynamic models. Ice thermodynamics are represented using either a zero-heat-capacity formulation or a two-layer formulation that conserves enthalpy. The model includes prognostic variables for snow and for sea-ice salinity. The above sea ice model components were borrowed from current-generation climate models but they were reformulated on an Arakawa C grid in order to match the MITgcm oceanic grid and they were modified in many ways to permit efficient and accurate automatic differentiation. This paper describes the MITgcm sea ice model; it presents example Arctic and Antarctic results from a realistic, eddy-permitting, global ocean and sea-ice configuration; it compares B-grid and C-grid dynamic solvers and the effects of other numerical details of the parameterized dynamics and thermodynamics in a regional Arctic configuration; and it presents example results from coupled ocean and sea-ice adjoint-model integrations.

Losch, M.; Menemenlis, D.; Heimbach, P.; Campin, J.-M.; Hill, C.

2009-04-01

247

U. S. National/Naval Ice Center Digital Sea Ice Data and Climatology  

NASA Astrophysics Data System (ADS)

Weekly sea ice charts produced by the National Ice Center (NIC) from 1972 through 1994 have recently been released to the public in support of environmental research. These charts were originally intended as navigation aids for vessels operating in Northern Hemisphere sea ice-infested waters. However, it was recognized early on that these data represent a unique resource for Arctic researchers, adding significantly to sea ice data sets compiled by Walsh (1978) and others. Ice concentration records commonly derived from satellite passive microwave data are similar to the NIC data set in terms of resolution, extent and period of record, but these microwave data may suffer from systematic biases related to the imaging process and algorithms used to infer ice concentration from raw data. Although the NIC digital sea ice data set has its own limitations, its starting point precedes that of the passive microwave record and avoids some of its inherent biases. This paper describes the spatial and thematic characteristics of the NIC historical data set, as well as the digital and analog data and analysis methods used to create the data set. This study also briefly investigates long-term change in Arctic ice cover. The NIC data set reveals that sea ice concentration patterns in the Atlantic and Pacific sectors of the Arctic vary in response to changes in the North Atlantic Oscillation. This result is consistent with the findings of other researchers, who used other data sets. These data have been permanently archived and are now available from the National Snow and Ice Data Center (NSIDC) in Boulder Colorado.

Dedrick, K. R.; Partington, K.; Van Woert, M. L.

2001-12-01

248

The CReSIS Radar Suite for Measurements of the Ice Sheets and Sea Ice during Operation Ice Bridge  

NASA Astrophysics Data System (ADS)

The University of Kansas, Center for Remote Sensing of Ice Sheets (CReSIS) has developed a suite of radar instrumentation operating at frequencies ranging from 180 MHz to 18 GHz to monitor the major Greenland and Antarctic ice sheets at varying resolution from the surface to the bed as well as the surface topography and snow cover characteristics of sea ice. The radar suite includes a VHF multi-channel coherent radar depth sounder/imager (MCoRDS/I) to measure ice sheet thickness, internal layering, and image ice-bed interface with fine resolution; a UHF accumulation radar to measure shallow (up to 500 m) ice sheet thickness, internal layering, and accumulation rates at decimeter resolutions; an ultra-wideband “snow” radar to measure thickness of snow over sea ice and accumulation rates at centimeter scale resolution; and a wideband Ku-band altimeter to measure surface topography and accumulation layer for comparison with CryoSat-2. To support recent NASA Operation Ice Bridge activities, CReSIS radars were adapted for installation and operation on the NASA DC-8 for deployments primarily to Antarctica for measurements over glacial ice in West Antarctica and sea ice, and on the NASA P-3 for deployments to Greenland and Arctic sea ice. The major integration activities included the development of antenna subsystems specifically tailored for the DC-8 and P-3 aircraft. This included a low-profile radar depth sounder/imager antenna assembly for the DC-8 with a minimal impact on the aircraft range, one of the largest VHF antenna arrays for the P-3, and a set of internal antennas structures and radomes for the P-3 bomb bay. The design and development of the antenna assemblies were focused on meeting a combination of instrument and mission requirements. We will present a description of each radar system including the antenna assemblies, instrument block diagrams, modes of operation, installation specifics for each OIB deployment, example results, and availability of data to external investigators.

Leuschen, C.; Gogineni, P. S.; Allen, C.; Paden, J. D.; Hale, R.; Rodriguez-Morales, F.; Harish, A.; Seguin, S.; Arnold, E.; Blake, W.; Byers, K.; Crowe, R.; Lewis, C.; Panzer, B.; Patel, A.; Shi, L.

2010-12-01

249

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

250

Ground Wave Propagation over Arctic Sea Ice.  

National Technical Information Service (NTIS)

Radio ground wave propagation in the Arctic Ocean occurs over mixed paths. The mixed paths include layered or homogeneous sea ice and sea water. Amplitude and phase variations occurring as 'dropoff' or 'recovery' effects at the ice-sea water boundaries pr...

A. W. Biggs

1970-01-01

251

Distinguishing Clouds from Ice over the East Siberian Sea, Russia  

NASA Technical Reports Server (NTRS)

As a consequence of its capability to retrieve cloud-top elevations, stereoscopic observations from the Multi-angle Imaging SpectroRadiometer (MISR) can discriminate clouds from snow and ice. The central portion of Russia's East Siberian Sea, including one of the New Siberian Islands, Novaya Sibir, are portrayed in these views from data acquired on May 28, 2002.

The left-hand image is a natural color view from MISR's nadir camera. On the right is a height field retrieved using automated computer processing of data from multiple MISR cameras. Although both clouds and ice appear white in the natural color view, the stereoscopic retrievals are able to identify elevated clouds based on the geometric parallax which results when they are observed from different angles. Owing to their elevation above sea level, clouds are mapped as green and yellow areas, whereas land, sea ice, and very low clouds appear blue and purple. Purple, in particular, denotes elevations very close to sea level. The island of Novaya Sibir is located in the lower left of the images. It can be identified in the natural color view as the dark area surrounded by an expanse of fast ice. In the stereo map the island appears as a blue region indicating its elevation of less than 100 meters above sea level. Areas where the automated stereo processing failed due to lack of sufficient spatial contrast are shown in dark gray. The northern edge of the Siberian mainland can be found at the very bottom of the panels, and is located a little over 250 kilometers south of Novaya Sibir. Pack ice containing numerous fragmented ice floes surrounds the fast ice, and narrow areas of open ocean are visible.

The East Siberian Sea is part of the Arctic Ocean and is ice-covered most of the year. The New Siberian Islands are almost always covered by snow and ice, and tundra vegetation is very scant. Despite continuous sunlight from the end of April until the middle of August, the ice between the island and the mainland typically remains until August or September.

The Multi-angle Imaging SpectroRadiometer views almost the entire Earth every 9 days. These images were acquired during Terra orbit 12986 and cover an area of about 380 kilometers x 1117 kilometers. They utilize data from blocks 24 to 32 within World Reference System-2 path 117.

MISR was built and is managed by NASA's Jet Propulsion Laboratory, Pasadena, CA, for NASA's Office of Earth Science, Washington, DC. The Terra satellite is managed by NASA's Goddard Space Flight Center, Greenbelt, MD. JPL is a division of the California Institute of Technology.

2002-01-01

252

The role of satellites in snow and ice measurements  

NASA Technical Reports Server (NTRS)

Earth-orbiting polar satellites are desirable platforms for the remote sensing of snow and ice. Geostationary satellites at a very high altitude (35,900 km) are also desirable platforms for many remote sensors, for communications relay, for flood warning systems, and for telemetry of data from unattended instrumentation in remote, inaccessible places such as the Arctic, Antarctic, or mountain tops. Optimum use of satellite platforms is achieved only after careful consideration of the temporal, spatial, and spectral requirements of the environmental mission. The National Environmental Satellite Service will maintain both types of environmental satellites as part of its mission.

Wiesnet, D. R.

1974-01-01

253

Visible and near-ultraviolet absorption spectrum of ice from transmission of solar radiation into snow  

Microsoft Academic Search

Snow is a scattering-dominated medium whose scattering is independent of wavelength at 350-600 nm. The attenuation of solar radiation in snow can be used to infer the spectral absorption coefficient of pure ice, by reference to a known value at 600 nm. The method is applied to clean Antarctic snow; the absorption minimum is at 390 nm, and the inferred

Stephen G. Warren; Richard E. Brandt; Thomas C. Grenfell

2006-01-01

254

Decoupling of ice production and ice extent in seasonally ice covered marginal seas  

NASA Astrophysics Data System (ADS)

While the seasonally ice covered marginal seas are ice free in the summer, there may be substantial production and transport of ice during the winter. The predominant ice types in these seas are frazil/grease ice, pancake ice and thin sheet ice. Relative production of the different ice types has a dramatic effect on the amount of brine production and the local energy exchange rate between the ocean and the atmosphere. We have developed a model which utilizes daily observations of SMMR and SSM/I microwave radiometers to track the volume and areal ice concentrations of each ice type; allowing us to evaluate the contribution of each ice type to the ice mass, salt, and fresh water redistribution. From this framework, we have calculated the spatial distribution of the annual net salt and fresh water flux to the Bering Sea over a 15 year period. The results indicate there may be a de-coupling between sea ice coverage and sea ice production for the Bering Sea, with the ice production being much less variable than the sea ice coverage. These results are interesting because, to first order, ice production is not responsive to variability in atmospheric forcing from year to year. In this paper, we will discuss the relative importance of different causal mechanisms, and examine linkages and feedbacks between the sea ice, ocean and atmosphere.

Pruis, M.; Toudal, L.; Coon, M. D.

2004-12-01

255

Antarctic sea ice thickness data archival and recovery at the Australian Antarctic Data Centre  

NASA Astrophysics Data System (ADS)

A new effort is underway to establish a portal for Antarctic sea ice thickness data at the Australian Antarctic Data Centre (http://aadc-maps.aad.gov.au/aadc/sitd/). The intention is to provide a central online access point for a wide range of sea ice data sets, including sea ice and snow thickness data collected using a range of techniques, and sea ice core data. The recommendation to establish this facility came from the SCAR/CliC- sponsored International Workshop on Antarctic Sea Ice Thickness, held in Hobart in July 2006. It was recognised, in particular, that satellite altimetry retrievals of sea ice and snow cover thickness rely on large-scale assumptions of the sea ice and snow cover properties such as density, freeboard height, and snow stratigraphy. The synthesis of historical data is therefore particularly important for algorithm development. This will be closely coordinated with similar efforts in the Arctic. A small working group was formed to identify suitable data sets for inclusion in the archive. A series of standard proformas have been designed for converting old data, and to help standardize the collection of new data sets. These proformas are being trialled on two Antarctic sea ice research cruises in September - October 2007. The web-based portal allows data custodians to remotely upload and manage their data, and for all users to search the holdings and extract data relevant to their needs. This presentation will report on the establishment of the data portal, recent progress in identifying appropriate data sets and making them available online. maps.aad.gov.au/aadc/sitd/

Worby, A. P.; Treverrow, A.; Raymond, B.; Jordan, M.

2007-12-01

256

Recent Change of Arctic Sea Ice Cover  

Microsoft Academic Search

A high resolution coupled ice-ocean model of the Pan-Arctic region forced with realistic atmospheric data is used to investigate causes and long-term variability trends of the Arctic Ocean and its sea ice. Model results suggest that the recent decrease of sea ice cover might be in part due to the delayed effect of thermodynamic interactions at the ice-ocean interface, in

W. Maslowski; J. L. Clement; C. E. Williams; W. Walczowski

2004-01-01

257

Drifting snow measurements on the Greenland Ice Sheet and their application for model evaluation  

NASA Astrophysics Data System (ADS)

This paper presents autonomous drifting snow observations performed on the Greenland Ice Sheet in the fall of 2012. High-frequency Snow Particle Counter (SPC) observations at ~1 m above the surface provided drifting snow number fluxes and size distributions; these were combined with meteorological observations at six levels. We identify two types of drifting snow events: katabatic events are relatively cold and dry, with prevalent winds from the southeast, whereas synoptic events are short-lived, warm and wet. Precipitating snow during synoptic events disturbs the drifting snow measurements. Output of the regional atmospheric climate model RACMO2, which includes the drifting snow routine PIEKTUK-B, agrees well with the observed near-surface climate at the site, as well as with the frequency and timing of drifting snow events. Direct comparisons with the SPC observations at 1 m reveal that the model overestimates the typical size of drifting snow particles, as well as the horizontal snow transport at this level.

Lenaerts, J. T. M.; Smeets, C. J. P. P.; Nishimura, K.; Eijkelboom, M.; Boot, W.; van den Broeke, M. R.; van de Berg, W. J.

2014-01-01

258

Variability and Trends in Sea Ice Extent and Ice Production in the Ross Sea  

NASA Technical Reports Server (NTRS)

Salt release during sea ice formation in the Ross Sea coastal regions is regarded as a primary forcing for the regional generation of Antarctic Bottom Water. Passive microwave data from November 1978 through 2008 are used to examine the detailed seasonal and interannual characteristics of the sea ice cover of the Ross Sea and the adjacent Bellingshausen and Amundsen seas. For this period the sea ice extent in the Ross Sea shows the greatest increase of all the Antarctic seas. Variability in the ice cover in these regions is linked to changes in the Southern Annular Mode and secondarily to the Antarctic Circumpolar Wave. Over the Ross Sea shelf, analysis of sea ice drift data from 1992 to 2008 yields a positive rate of increase in the net ice export of about 30,000 sq km/yr. For a characteristic ice thickness of 0.6 m, this yields a volume transport of about 20 cu km/yr, which is almost identical, within error bars, to our estimate of the trend in ice production. The increase in brine rejection in the Ross Shelf Polynya associated with the estimated increase with the ice production, however, is not consistent with the reported Ross Sea salinity decrease. The locally generated sea ice enhancement of Ross Sea salinity may be offset by an increase of relatively low salinity of the water advected into the region from the Amundsen Sea, a consequence of increased precipitation and regional glacial ice melt.

Comiso, Josefino; Kwok, Ronald; Martin, Seelye; Gordon, Arnold L.

2011-01-01

259

Measurement of suspended particulate matter under near-inertial drifiting sea ice  

NASA Astrophysics Data System (ADS)

This study has attempted to investigate the dynamic behavior of suspended particulate matters (SPM) under the sea ice. Main objectives are (1) to report the role of rapidly-melting summer sea ice as a new source of SPM, and (2) to estimate the vertical and temporal variation in size and settling flux of SPM under sea ice using novel holographic and acoustic techniques. Mooring observation of hydrography, hydrodynamics and suspended particles distribution under a drifting sea ice revealed the mixing and entrainment pattern in the upper mixed layer of the marginal ice zone. The ice floe where the mooring system was installed drifted as near-inertial motion with approximately 12-h cycle. Due to the high melt rates of the sea ice during the summertime, a large amount of particulate matters embedded in the sea ice were released into the underlying water column. Using the mooring package, an on-ice experiment was performed to estimate the vertical and temporal variation in SPM. SPM concentration under the sea ice fluctuated in the range of 60-100 mg/l during the rapidly-melting summertime. Results suggest that combined effects of the increase in insolation, ice algal production, and the decrease in ice and snow cover and multi-year sea ice extent could create favorable conditions for enhancing the concentration and flux of SPM during the rapidly-melting summer season. With the thinning and retreat trend of Arctic sea ice, it is expected that under-ice water column will in future receive a much higher rate of discharge of particulate matters from melting sea ice.

Ha, Ho Kyung; Kim, Yong Hoon; Lee, Hyunjung; Hwang, Byongjun

2014-05-01

260

Sea ice, climate and Fram Strait  

NASA Technical Reports Server (NTRS)

When sea ice is formed the albedo of the ocean surface increases from its open water value of about 0.1 to a value as high as 0.8. This albedo change effects the radiation balance and thus has the potential to alter climate. Sea ice also partially seals off the ocean from the atmosphere, reducing the exchange of gases such as carbon dioxide. This is another possible mechanism by which climate might be affected. The Marginal Ice Zone Experiment (MIZEX 83 to 84) is an international, multidisciplinary study of processes controlling the edge of the ice pack in that area including the interactions between sea, air and ice.

Hunkins, K.

1984-01-01

261

Quantile regression analysis of Arctic sea ice extent  

NASA Astrophysics Data System (ADS)

Surface and satellite-based observations show a decrease in the Arctic sea ice extent during the past 46 years with a minimum in 2007. 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 seasonal ice free Arctic as soon as 2012. 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 which characterizes the rate of change of the conditional mean. However, in climate data and climate change studies a broader description of the data is desirable, namely concerning changes in the spread or shape of the distribution over time. Quantile regression extends the classical linear regression framework of estimation of conditional mean models to the estimation of conditional quantile models. Here, quantile regression is applied to analyse the time series of Arctic sea ice extent from January 1979 to December 2007, available at the National Snow and Ice Data Center.

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

2009-04-01

262

National Snow and Ice Data Center, World Data Center for Glaciology, Boulder Annual Report, 2001. 25 Years of Snow and Ice Data and Research.  

National Technical Information Service (NTIS)

The National Snow and Ice Data Center (NSIDC) and World Data Center for Glaciology (WDC), Boulder, is part of the University of Colorado Cooperative Institute for Research in Environmental Sciences (CIRES), and is affiliated with the NOAA National Geophys...

2001-01-01

263

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

264

EAM-Weddell Sea Ice Camp  

NSF Publications Database

... Sea Ice Camp) To: Polar Ocean Sciences Program Manager, DPP Ocean Projects Manager, DPP Field ... 17, 1991. National Science Foundation. 1991. Ocean Projects Manager, DPP, Memorandum: Environmental ...

265

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

266

Characterization of ice binding proteins from sea ice algae.  

PubMed

Several polar microalgae are able to live and thrive in the extreme environment found within sea ice, where growing ice crystals may cause mechanical damage to the cells and reduce the organisms' living space. Among the strategies adopted by these organisms to cope with the harsh conditions in their environment, ice binding proteins (IBPs) seem to play a key role and possibly contribute to their success in sea ice. IBPs have the ability to control ice crystal growth. In nature they are widespread among sea ice microalgae, and their mechanism of function is of interest for manifold potential applications. Here we describe methods for a classical determination of the IBP activity (thermal hysteresis, recrystallization inhibition) and further methods for protein characterization (ice pitting assay, determination of the nucleating temperature). PMID:24852640

Bayer-Giraldi, Maddalena; Jin, EonSeon; Wilson, Peter W

2014-01-01

267

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

268

Singlet molecular oxygen on natural snow and ice  

NASA Astrophysics Data System (ADS)

Singlet molecular oxygen (1O2*) is a reactive intermediate formed when a chromophore absorbs light and subsequently transfers energy to dissolved oxygen. As an oxidant, 1O2* reacts rapidly with a number of electron-rich environmental pollutants. In our work, we show enhanced kinetics for 1O2* in frozen solutions, where its rate of formation (Rf) and steady state concentration ([1O2*]) can be many orders of magnitude higher than found in the same unfrozen solution. Our goal here is to identify the contribution of 1O2* to the decay of pollutants on snow and ice. We conducted experiments in laboratory solutions made to simulate the concentrations and characteristics of natural snow, as well as in natural snow collected in the Sierra Nevada mountains of California and at Summit, Greenland. Natural snow contains a mixture of inorganic salts and organic species that can function as sources and/or sinks for oxidants, as well as contribute colligative control on the volume of quasi-liquid layers that occur at the surface and grain boundaries of ice. In our experiments, solutions typically contained up to five components: (1) Furfuryl alcohol (FFA), a commonly used probe for 1O2*, (2) Rose Bengal (RB), a 1O2* sensitizer, (3) HOOH, a photochemical precursor for hydroxyl radical (?OH), (4) glycerol to simulate unknown, naturally occurring sinks for ?OH, and (5) sodium sulfate to control the total concentration of solutes. We illuminated samples in a temperature-controlled solar simulator and subsequently measured the loss of FFA using high performance liquid chromatography. To differentiate reactions of 1O2* from other sinks (e.g. ?OH), selective sink species were added to determine the fraction of FFA loss due to direct photolysis, reaction with 1O2*, and reaction with ?OH. We verified reactions of 1O2* with FFA by two methods. First, we utilized the kinetic solvent isotope effect, where an enhancement of FFA loss in a mixture of D2O/water is indicative 1O2* since [1O2*] is higher in D2O than it is in pure water. Secondly, we conducted tests looking at pyranone formed from the reaction of FFA + 1O2*. A combination of these methods will allow us to determine 1O2* kinetics in natural snow, where its sources and sinks are unknown. This research will help determine the importance of 1O2* to the decay of pollutants in cold regions.

Bower, J. P.; Anastasio, C.

2010-12-01

269

Earth Exploration Toolbook Chapter: Whither Arctic Sea Ice?  

NSDL National Science Digital Library

DATA: Sea Ice Images TOOLS: ImageJ, Spreadsheet application SUMMARY: Animate 30 years of sea ice images and measure the ice extent each year to produce a graph. Compare the ice extents to air temperatures.

Youngman, Betsy; Mccaffrey, Mark; Prakash, Anupma; Rogan, Brian

270

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

271

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

272

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

273

The importance of large scale sea ice drift and ice type distribution on ice extent in the Weddell Sea  

NASA Astrophysics Data System (ADS)

In austral winter large parts of Antarctic Seas are covered by sea ice. This modifies the exchange of heat, mass and momentum between ocean and atmosphere. The knowledge of ice extent and its variability is necessary for an adequate simulation of those fluxes and thus for climate modelling. The goal of this study is the observation of interannual and seasonal ice extent variations and their underlying causes. Variability is analysed by using monthly means of microwave and scatterometer satellite data. Results are correlated with ice drift variations calculated from a Finite Element Sea ice-Ocean Model (FESOM) and with satellite derived sea ice drift products to determine the dependency of ice extent on sea ice drift. An additional cause for changing ice extent could be the variability of ice type distribution, i.e. the contribution of first and second year ice to the total ice covered area. These ice types are determined on monthly time scales from scatterometer satellite data. Ice class distribution and sea ice drift variability are compared with the characteristics and variability of the Southern Annular Mode (SAM) to evaluate the relative importance of different sea ice parameters for shaping Weddell Sea ice extent and its variability.

Schwegmann, S.; Haas, C.; Timmermann, R.; Gerdes, R.; Lemke, P.

2009-12-01

274

Optical Thickness and Effective Radius Retrievals of Liquid Water Clouds over Ice and Snow Surface  

NASA Technical Reports Server (NTRS)

Cloud optical thickness and effective radius retrievals from solar reflectance measurements traditionally depend on a combination of spectral channels that are absorbing and non-absorbing for liquid water droplets. Reflectances in non-absorbing channels (e.g., 0.67, 0.86 micrometer bands) are largely dependent on cloud optical thickness, while longer wavelength absorbing channels (1.6, 2.1, and 3.7 micrometer window bands) provide cloud particle size information. Retrievals are complicated by the presence of an underlying ice/snow surface. At the shorter wavelengths, sea ice is both bright and highly variable, significantly increasing cloud retrieval uncertainty. However, reflectances at the longer wavelengths are relatively small and may be comparable to that of dark open water. Sea ice spectral albedos derived from Cloud Absorption Radiometer (CAR) measurements during April 1992 and June 1995 Arctic field deployments are used to illustrate these statements. A modification to the traditional retrieval technique is devised. The new algorithm uses a combination of absorbing spectral channels for which the snow/ice albedo is relatively small. Using this approach, preliminary retrievals have been made with the MODIS Airborne Simulator (MAS) imager flown aboard the NASA ER-2 during FIRE-ACE. Data from coordinated ER-2 and University of Washington CV-580 aircraft observations of liquid water stratus clouds on June 3 and June 6, 1998 have been examined. Size retrievals are compared with in situ cloud profile measurements of effective radius made with the CV-580 PMS FSSP probe, and optical thickness retrievals are compared with extinction profiles derived from the Gerber Scientific "g-meter" probe. MAS retrievals are shown to be in good agreement with the in situ measurements.

Platnick, S.; King, M. D.; Tsay, S.-C.; Arnold, G. T.; Gerber, H.; Hobbs, P. V.; Rangno, A.

1999-01-01

275

ICESat Observations of Seasonal and Interannual Variations of Sea-Ice Freeboard and Estimated Thickness in the Weddell Sea, Antarctica (2003-2009)  

NASA Technical Reports Server (NTRS)

Sea-ice freeboard heights for 17 ICESat campaign periods from 2003 to 2009 are derived from ICESat data. Freeboard is combined with snow depth from Advanced Microwave Scanning Radiometer for Earth Observing System (AMSR-E) data and nominal densities of snow, water and sea ice, to estimate sea-ice thickness. Sea-ice freeboard and thickness distributions show clear seasonal variations that reflect the yearly cycle of growth and decay of the Weddell Sea (Antarctica) pack ice. During October-November, sea ice grows to its seasonal maximum both in area and thickness; the mean freeboards are 0.33-0.41 m and the mean thicknesses are 2.10-2.59 m. During February-March, thinner sea ice melts away and the sea-ice pack is mainly distributed in the west Weddell Sea; the mean freeboards are 0.35-0.46 m and the mean thicknesses are 1.48-1.94 m. During May-June, the mean freeboards and thicknesses are 0.26-0.29 m and 1.32-1.37 m, respectively. The 6 year trends in sea-ice extent and volume are (0.023+/-0.051) x 10(exp 6)sq km/a (0.45%/a) and (0.007+/-1.0.092) x 10(exp 3)cu km/a (0.08%/a); however, the large standard deviations indicate that these positive trends are not statistically significant.

Yi, Donghui; Robbins, John W.

2010-01-01

276

On the stability of low-latitude sea-ice edges in a comprehensive coupled climate model  

NASA Astrophysics Data System (ADS)

The Snowball Earth hypothesis assumes that a strong ice-albedo feedback inhibits stable low-latitude sea-ice edges. In contrast, we recently proposed the "Jormungand" mechanism that allows stable low-latitude ice edges in atmosphere-only climate models without continents and ocean heat transport (Abbot et al., 2011). These low-latitude sea-ice edges are possible by virtue of net evaporation in the subtropics and a low albedo for snow-free sea ice, because these two factors combine such as to strongly weaken the ice-albedo feedback in the subtropics. Here, we show that the Jormungand mechanism in principle also works in coupled climate simulations with ECHAM5/MPI-OM when we use a low bare sea-ice albedo and disable sea-ice dynamics. These simulations apply Marinoan boundary conditions (635 Million years before present) and, due to the Jormungand mechanism, produce stable low-latitude sea-ice edges at 5-10o. Nevertheless, when we take into account sea-ice dynamics, the sea-ice edge becomes unstable once it passes 20o. This destabilizing effect of sea-ice dynamics results from strong equatorward wind-induced sea-ice advection in the Hadley cell region. Moreover, we find that sea-ice dynamics promote Snowball initiation. Without sea-ice dynamics, Snowball initiation requires a CO2 reduction to 4 ppmv, while a reduction to 204 ppmv is sufficient when sea-ice dynamics are included. Because climate models differ in their representation of sea-ice dynamics, our results might help to explain the reported climate model dependence of both the radiative forcing needed for Snowball initiation and the sea-ice latitude at which the collapse to a Snowball occurs.

Voigt, A.; Abbot, D. S.

2012-04-01

277

Unlocking a Sea Ice Secret  

SciTech Connect

Dr. Rachel Obbard and her research group from Dartmouth College traveled to the Antarctic to collect samples of sea ice. Next stop: the GeoSoilEnviroCARS x-ray beamline at the Advanced Photon Source at Argonne National Laboratory in Illinois. This U.S. Department of Energy Office of Science synchrotron x-ray research facility gave the Obbard team the frontier scientific tools they needed to study the path bromide takes as it travels from the ocean to the atmosphere.

Dr. Rachel Obbard

2013-04-22

278

Quantifying Uncertainties in the Seasonal Cycle of Arctic Sea Ice  

NASA Astrophysics Data System (ADS)

Many climate models project that the Arctic Ocean will be free of summertime sea ice within a century when forced with representative future greenhouse gas emission scenarios. To determine whether uncertainties in sea ice physics can also lead to an ice-free Arctic, we ran present-day ensemble simulations with the Community Climate System Model (CCSM4) that varied 7 parameters in the Community Ice Code (CICE4) over expert-provided ranges. The September minimum in sea ice extent computed by the ensemble ranges from 0.5 to 7.7 million km2, the lower end of which is significantly less than current observed values and lower than the models in the Coupled Model Intercomparison Project Phase 5 (CMIP5). CCSM4 can therefore simulate a summertime Arctic that is effectively free of sea ice either by increasing greenhouse gas forcing or by keeping the forcing constant and varying CICE4 parameters within recommended ranges. We identified three key CICE4 parameters related to radiative and thermal properties of snow that drive this extreme ensemble variability. Given observational data, machine learning algorithms were also used to quantify and constrain probability distribution functions for these parameters, which can be sampled to provide probabilistic assessments of sea ice characteristics simulated by CICE4. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 and was funded by the Uncertainty Quantification Strategic Initiative Laboratory Directed Research and Development Project at LLNL under project tracking code 10-SI-013 (UCRL LLNL-ABS-641752).

Lucas, D. D.; Covey, C. C.; Klein, R.; Tannahill, J.; Ivanova, D. P.

2013-12-01

279

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

280

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

281

Impacts of Declining Arctic Sea Ice: An International Challenge  

NASA Astrophysics Data System (ADS)

As reported by the National Snow and Ice Data Center in late August of 2008, Arctic sea ice extent had already fallen to its second lowest level since regular monitoring began by satellite. As of this writing, we were closing in on the record minimum set in September of 2007. Summers may be free of sea ice by the year 2030. Recognition is growing that ice loss will have environmental impacts that may extend well beyond the Arctic. The Arctic Ocean will in turn become more accessible, not just to tourism and commercial shipping, but to exploitation of oil wealth at the bottom of the ocean. In recognition of growing accessibility and oil operations, the United States Coast Guard set up temporary bases this summer at Barrow and Prudhoe Bay, AK, from which they conducted operations to test their readiness and capabilities, such as for search and rescue. The Canadians have been busy showing a strong Arctic presence. In August, a German crew traversed the Northwest Passage from east to west in one of their icebreakers, the Polarstern. What are the major national and international research efforts focusing on the multifaceted problem of declining sea ice? What are the areas of intersection, and what is the state of collaboration? How could national and international collaboration be improved? This talk will review some of these issues.

Serreze, M.

2008-12-01

282

Forward electromagnetic scattering models for sea ice  

Microsoft Academic Search

Recent advances in forward modeling of the electromagnetic scattering properties of sea ice are presented. In particular, the principal results include the following: (1) approximate calculations of electromagnetic scattering from multilayer random media with rough interfaces, based on the distorted Born approximation and radiative transfer (RT) theory; (2) comprehensive theory of the effective complex permittivity of sea ice based on

K. M. Golden; M. Cheney; Kung-Hau Ding; A. K. Fung; Thomas C. Grenfell; D. Isaacson; Jin Au Kong; S. V. Nghiem; J. Sylvester; P. Winebrenner

1998-01-01

283

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

284

Eastern - Western Arctic Sea Ice Analysis 1985.  

National Technical Information Service (NTIS)

This publication is the twelfth in a continuing yearly series of Arctic sea ice atlases prepared in the Joint Ice Center at the Naval Polar Oceanography Center, Suitland. The atlas contains weekly charts depicting Northern Hemisphere and Great Lakes ice c...

1985-01-01

285

Benefits of Remote Sensing of Sea Ice.  

National Technical Information Service (NTIS)

Remote sensing of sea ice is important to exploration, transportation, environmental monitoring, and resource development in ice-infested waters. The vast expanse and dynamic nature of ice in the Canadian Arctic, the East Coast Offshore and the Gulf of St...

A. K. McQuillan

1973-01-01

286

Simulation of a sea ice ecosystem using a hybrid model for slush layer desalination  

NASA Astrophysics Data System (ADS)

Porous, slushy layers are a common feature of Antarctic sea ice and are often colonized by high concentrations of algae. Despite its potential importance to the physics and biogeochemistry of the sea ice ecosystem, current knowledge of the evolution of sea ice slush layers is limited. Here we present a model of sea ice that is capable of reproducing the vertical biophysical evolution of sea ice that contains slush layers. The model uses a novel hybrid desalination scheme to calculate salt fluxes and brine motion during freezing using one of two different methods depending on the brine fraction of the ice. Model runs using atmospheric and snow depth forcing from the Ice Station Weddell experiment show that model is able to simulate the magnitude and timing of sea ice temperature, salinity, and associated algal growth of observed slush layers, as well as the surrounding sea ice. The model was designed with regional-scale simulations in mind and we show that the model performs well at lower vertical resolutions, as long as the slush layer is resolved. Incorporation of our model of slush ice desalination into regional and global simulations has potential to improve model estimates of salt, heat, and biochemical fluxes in polar marine environments.

Saenz, Benjamin T.; Arrigo, Kevin R.

2012-05-01

287

A toy model of sea ice growth  

NASA Technical Reports Server (NTRS)

My purpose here is to present a simplified treatment of the growth of sea ice. By ignoring many details, it is possible to obtain several results that help to clarify the ways in which the sea ice cover will respond to climate change. Three models are discussed. The first deals with the growth of sea ice during the cold season. The second describes the cycle of growth and melting for perennial ice. The third model extends the second to account for the possibility that the ice melts away entirely in the summer. In each case, the objective is to understand what physical processes are most important, what ice properties determine the ice behavior, and to which climate variables the system is most sensitive.

Thorndike, Alan S.

1992-01-01

288

Arctic Sea Ice Deformation in Satellite Remote Sensing Data and in a Coupled Sea Ice-Ocean Model  

Microsoft Academic Search

Sea ice movement is driven by surface wind and ocean currents. The spatial inhomogeneity of these forces causes internal sea ice stress gradients, which eventually cause ice to ridge or break up. This sea ice deformation is an important process for (1) the sea ice mass balance, (2) brine rejection into the ocean, (3) regulation of ocean-to-air heat and gas

G. Spreen; R. Kwok; D. Menemenlis; A. T. Nguyen

2010-01-01

289

A Gibbs thermodynamic potential of sea ice  

Microsoft Academic Search

A thermodynamic potential function for air-free sea ice, specific Gibbs free energy (free enthalpy) G(s,t,p), has been computed in terms of sea ice salinity s, temperature t and pressure p. Its numerical application is restricted to brine salinities up to 40 g\\/kg and to applied pressures not exceeding 10 MPa. Using the assumption of brine–ice equilibrium the Gibbs potential is

Rainer Feistel; Eberhard Hagen

1998-01-01

290

The role of sea ice in the temperature-precipitation feedback of glacial cycles  

NASA Astrophysics Data System (ADS)

The response of the hydrological cycle to climate variability and change is a critical open question, where model reliability is still unsatisfactory, yet upon which past climate history can shed some light. Sea ice is a key player in the climate system and in the hydrological cycle, due to its strong albedo effect and its insulating effect on local evaporation and air-sea heat flux. Using an atmospheric general circulation model with specified sea surface temperature and sea-ice distribution, the role of sea ice in the hydrological cycle is investigated under last glacial maximum (LGM) and present day conditions, and by studying its contribution to the "temperature-precipitation feedback". By conducting a set of sensitivity experiments in which the albedo and thickness of the sea ice are varied, the various effects of sea ice in the hydrological cycle are isolated. It is demonstrated that for a cold LGM like state, a warmer climate (as a result of reduced sea-ice cover) leads to an increase in snow precipitation over the ice sheets. The insulating effect of the sea ice on the hydrological cycle is found to be larger than the albedo effect. These two effects interact in a nonlinear way and their total effect is not equal to summing their separate contribution.

Gildor, Hezi; Ashkenazy, Yosef; Tziperman, Eli; Lev, Ilit

2013-11-01

291

Sea Ice Biogeochemistry: A Guide for Modellers  

PubMed Central

Sea ice is a fundamental component of the climate system and plays a key role in polar trophic food webs. Nonetheless sea ice biogeochemical dynamics at large temporal and spatial scales are still rarely described. Numerical models may potentially contribute integrating among sparse observations, but available models of sea ice biogeochemistry are still scarce, whether their relevance for properly describing the current and future state of the polar oceans has been recently addressed. A general methodology to develop a sea ice biogeochemical model is presented, deriving it from an existing validated model application by extension of generic pelagic biogeochemistry model parameterizations. The described methodology is flexible and considers different levels of ecosystem complexity and vertical representation, while adopting a strategy of coupling that ensures mass conservation. We show how to apply this methodology step by step by building an intermediate complexity model from a published realistic application and applying it to analyze theoretically a typical season of first-year sea ice in the Arctic, the one currently needing the most urgent understanding. The aim is to (1) introduce sea ice biogeochemistry and address its relevance to ocean modelers of polar regions, supporting them in adding a new sea ice component to their modelling framework for a more adequate representation of the sea ice-covered ocean ecosystem as a whole, and (2) extend our knowledge on the relevant controlling factors of sea ice algal production, showing that beyond the light and nutrient availability, the duration of the sea ice season may play a key-role shaping the algal production during the on going and upcoming projected changes.

Tedesco, Letizia; Vichi, Marcello

2014-01-01

292

Sea ice biogeochemistry: a guide for modellers.  

PubMed

Sea ice is a fundamental component of the climate system and plays a key role in polar trophic food webs. Nonetheless sea ice biogeochemical dynamics at large temporal and spatial scales are still rarely described. Numerical models may potentially contribute integrating among sparse observations, but available models of sea ice biogeochemistry are still scarce, whether their relevance for properly describing the current and future state of the polar oceans has been recently addressed. A general methodology to develop a sea ice biogeochemical model is presented, deriving it from an existing validated model application by extension of generic pelagic biogeochemistry model parameterizations. The described methodology is flexible and considers different levels of ecosystem complexity and vertical representation, while adopting a strategy of coupling that ensures mass conservation. We show how to apply this methodology step by step by building an intermediate complexity model from a published realistic application and applying it to analyze theoretically a typical season of first-year sea ice in the Arctic, the one currently needing the most urgent understanding. The aim is to (1) introduce sea ice biogeochemistry and address its relevance to ocean modelers of polar regions, supporting them in adding a new sea ice component to their modelling framework for a more adequate representation of the sea ice-covered ocean ecosystem as a whole, and (2) extend our knowledge on the relevant controlling factors of sea ice algal production, showing that beyond the light and nutrient availability, the duration of the sea ice season may play a key-role shaping the algal production during the on going and upcoming projected changes. PMID:24586604

Tedesco, Letizia; Vichi, Marcello

2014-01-01

293

Probabilistic Forecasting of Arctic Sea Ice Extent  

NASA Astrophysics Data System (ADS)

Sea ice in the Arctic is changing rapidly. Most noticeable has been the series of record, or near-record, annual minimums in sea ice extent in the past six years. The changing regime of sea ice has prompted much interest in seasonal prediction of sea ice extent, particularly as opportunities for Arctic shipping and resource exploration or extraction increase. This study presents a daily sea ice extent probabilistic forecast method with a 50-day lead time. A base projection is made from historical data and near-real-time sea ice concentration is assimilated on the issue date of the forecast. When considering the September mean ice extent for the period 1995-2012, the performance of the 50-day lead time forecast is very good: correlation=0.94, Bias = 0.14 ×106 km^2 and RMSE = 0.36 ×106 km^2. Forecasts for the daily minimum contains equal skill levels. The system is highly competitive with any of the SEARCH Sea Ice Outlook estimates. The primary finding of this study is that large amounts of forecast skill can be gained from knowledge of the initial conditions of concentration (perhaps more than previously thought). Given the simplicity of the forecast model, improved skill should be available from system refinement and with suitable proxies for large scale atmosphere and ocean circulation.

Slater, A. G.

2013-12-01

294

Frost flower formation on sea ice and lake ice  

NASA Astrophysics Data System (ADS)

Frost flowers are clusters of ice crystals found on freshly formed sea ice and occasionally on frozen lakes. They belong to a class of vapour-related phenomena that includes freezing fog, hoar frost and dew. It has hitherto been supposed that they form by condensation from a supersaturated atmosphere or from water wicked up through porous sea ice. Here we show that they can form on solid, pure ice sublimating into an unsaturated atmosphere. We derive a general regime diagram showing the atmospheric conditions under which the different vapour-related phenomena occur and confirm our predictions of frost-flower formation with a series of laboratory experiments. Our results can be used in climate models to predict occurrence of frost flowers, which significantly enhance albedo and provide the substrate for chemical production of ozone-depleting bromine monoxide, and in paleo-climate reconstructions by relating observations of sea-salt aerosols in ice cores to atmospheric conditions.

Style, Robert W.; Worster, M. Grae

2009-06-01

295

Radar backscattering from snow facies of the Greenland ice sheet: Results from the AIRSAR 1991 campaign  

NASA Technical Reports Server (NTRS)

In June 1991, the NASA/JPL airborne SAR (AIRSAR) acquired C- (lambda = 5.6cm), L- (lambda = 24cm), and P- (lambda = 68m) band polarimetric SAR data over the Greenland ice sheet. These data are processed using version 3.55 of the AIRSAR processor which provides radiometrically and polarimetrically calibrated images. The internal calibration of the AIRSAR data is cross-checked using the radar response from corner reflectors deployed prior to flight in one of the scenes. In addition, a quantitative assessment of the noise power level at various frequencies and polarizations is made in all the scenes. Synoptic SAR data corresponding to a swath width of about 12 by 50 km in length (compared to the standard 12 x 12 km size of high-resolution scenes) are also processed and calibrated to study transitions in radar backscatter as a function of snow facies at selected frequencies and polarizations. The snow facies on the Greenland ice sheet are traditionally categorized based on differences in melting regime during the summer months. The interior of Greenland corresponds to the dry snow zone where terrain elevation is the highest and no snow melt occurs. The lowest elevation boundary of the dry snow zone is known traditionally as the dry snow line. Beneath it is the percolation zone where melting occurs in the summer and water percolates through the snow freezing at depth to form massive ice lenses and ice pipes. At the downslope margin of this zone is the wet snow line. Below it, the wet snow zone corresponds to the lowest elevations where snow remains at the end of the summer. Ablation produces enough meltwater to create areas of snow saturated with water, together with ponds and lakes. The lowest altitude zone of ablation sees enough summer melt to remove all traces of seasonal snow accumulation, such that the surface comprises bare glacier ice.

Rignot, Eric; Jezek, K.; Vanzyl, J. J.; Drinkwater, Mark R.; Lou, Y. L.

1993-01-01

296

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

297

Spatial Variability of Barrow-Area Shore-Fast Sea Ice and Its Relationships to Passive Microwave Emissivity  

NASA Technical Reports Server (NTRS)

Aircraft-acquired passive microwave data, laser radar height observations, RADARSAT synthetic aperture radar imagery, and in situ measurements obtained during the AMSR-Ice03 experiment are used to investigate relationships between microwave emission and ice characteristics over several space scales. The data fusion allows delineation of the shore-fast ice and pack ice in the Barrow area, AK, into several ice classes. Results show good agreement between observed and Polarimetric Scanning Radiometer (PSR)-derived snow depths over relatively smooth ice, with larger differences over ridged and rubbled ice. The PSR results are consistent with the effects on snow depth of the spatial distribution and nature of ice roughness, ridging, and other factors such as ice age. Apparent relationships exist between ice roughness and the degree of depolarization of emission at 10,19, and 37 GHz. This depolarization .would yield overestimates of total ice concentration using polarization-based algorithms, with indications of this seen when the NT-2 algorithm is applied to the PSR data. Other characteristics of the microwave data, such as effects of grounding of sea ice and large contrast between sea ice and adjacent land, are also apparent in the PSR data. Overall, the results further demonstrate the importance of macroscale ice roughness conditions such as ridging and rubbling on snow depth and microwave emissivity.

Maslanik, J. A.; Rivas, M. Belmonte; Holmgren, J.; Gasiewski, A. J.; Heinrichs, J. F.; Stroeve, J. C.; Klein, M.; Markus, T.; Perovich, D. K.; Sonntag, J. G.; Tape, K.

2006-01-01

298

Monitoring Fram Strait sea ice outflow and thin ice thickness  

NASA Technical Reports Server (NTRS)

We propose to: 1) use sequential SAR maps to monitor the profile of sea ice motion through Fram Strait over the period 2003 throught 2005; and 2) explore the potential of using L-band polarimetric data to determine the thickness of thin ice over the same region.

Kwok, R.

2001-01-01

299

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 inter-model spread persists in the simulated summer sea ice losses over the 21st century for a given forcing scenario. The initial 1979-2010 sea ice properties (including the 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 SSIE anomalies (compared 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). In a new diagram (that does not consider the time as an independent variable) we show that the transition towards ice-free conditions is actually occuring in a very similar manner for all models. For these reasons, some quantities that do not explicitly depend on time, such as the year at which SSIE drops below a certain threshold, are likely to be constrained. 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 (between 2041 and 2060 for a high climate forcing scenario).

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

2012-07-01

300

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.

Fichefet, Thierry; Massonnet, François; Goosse, Hugues; Bitz, Cecilia; Philippon-Berthier, Gwenaëlle; Holland, Marika; Barriat, Pierre-Yves

2013-04-01

301

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

302

Influence of sea ice cover on high latitude precipitation: Inferences from precipitation isotope measurements and a 2D model  

Microsoft Academic Search

The most widely cited climate feedback in the Arctic region is ice cover. Warming climate reduces the sea ice extent, which causes a lower surface albedo, resulting in more absorbed insolation and further warming - a positive feedback. Conversely, warming is also likely to result in increased Arctic evaporation and precipitation, leading to increased snow cover and a higher Arctic

E. S. Posmentier; A. Faiia; X. Feng; F. A. Michel

2009-01-01

303

Decadal Variability of Sea Ice Motion in the Weddell Sea for the Period of 1979 to 2006  

NASA Astrophysics Data System (ADS)

The knowledge and understanding of sea ice drift variability is essential for an assessment of, e.g., varying ice production rates, deformation processes, ice export and also stratification changes in the ocean. The goal of this study is the determination of the decadal variability of sea ice motion in the Weddell Sea and its relation to atmospheric forcing. Yearly and monthly mean drift vector fields for every 10-year period are computed from observations from 1979-2006 and from simulations with the Finite Element Sea ice-Ocean Model (FESOM) for 1948-2008. Ice motion patterns are analysed with respect to the long-term mean in order to identify decadal changes in the typical drift patterns. Observed motion vector fields for Antarctic sea ice are provided by the National Snow and Ice Data Center (NSIDC). The vector fields are created from a combination of satellite data from the 37 GHz and 85 GHz channels of the Scanning Multichannel Microwave Radiometer (SMMR, 1978-1987) and the Special Sensor Microwave/Imager (SSM/I, 1987-2006) as well as from the Advanced Very High Resolution Radiometer (AVHRR, 1981-2000). The gridded data sets have a spatial resolution of 25 km and are available for a temporal resolution of one day. Data from the NCEP/NCAR reanalysis have been used to force the model simulations and are also used to identify the driving forces for ice drift variability.

Schwegmann, S.; Haas, C.; Timmermann, R.; Gerdes, R.; Lemke, P.

2009-04-01

304

Evidence for radionuclide transport by sea ice  

USGS Publications Warehouse

Ice and ice-borne sediments were collected across the Arctic Basin during the Arctic Ocean Section, 1994 (AOS-94), a recent US/Canada trans- Arctic expedition. Sediments were analysed for 137Cs, clay mineralogy and carbon. Concentrations of 137Cs ranged from 5 to 73 Bq kg-1 in the ice- borne sediments. Concentrations of ice samples without sediment were all less than 1 Bq m-3. The sediment sample with the highest 137Cs concentration (73 Bq kg-1)was collected in the Beaufort Sea. This concentration was significantly higher than in bottom sediments collected in the same area, indicating an ice transport mechanism from an area with correspondingly higher concentrations. Recent results from the application of ice transport models and sediment analyses indicate that it is very likely that sediments are transported by ice, from the Siberian shelf areas to the Beaufort Sea.

Meese, D. A.; Reimnitz, E.; Tucker, III, W. B.; Gow, A. J.; Bischof, J.; Darby, D.

1997-01-01

305

Ice Types in the Beaufort Sea, Alaska  

NASA Technical Reports Server (NTRS)

Determining the amount and type of sea ice in the polar oceans is crucial to improving our knowledge and understanding of polar weather and long term climate fluctuations. These views from two satellite remote sensing instruments; the synthetic aperture radar (SAR) on board the RADARSAT satellite and the Multi-angle Imaging SpectroRadiometer (MISR), illustrate different methods that may be used to assess sea ice type. Sea ice in the Beaufort Sea off the north coast of Alaska was classified and mapped in these concurrent images acquired March 19, 2001 and mapped to the same geographic area.

To identify sea ice types, the National Oceanic and Atmospheric Administration (NOAA) National Ice Center constructs ice charts using several data sources including RADARSAT SAR images such as the one shown at left. SAR classifies sea ice types primarily by how the surface and subsurface roughness influence radar backscatter. In the SAR image, white lines delineate different sea ice zones as identified by the National Ice Center. Regions of mostly multi-year ice (A) are separated from regions with large amounts of first year and younger ice (B-D), and the dashed white line at bottom marks the coastline. In general, sea ice types that exhibit increased radar backscatter appear bright in SAR and are identified as rougher, older ice types. Younger, smoother ice types appear dark to SAR. Near the top of the SAR image, however, red arrows point to bright areas in which large, crystalline 'frost flowers' have formed on young, thin ice, causing this young ice type to exhibit an increased radar backscatter. Frost flowers are strongly backscattering at radar wavelengths (cm) due to both surface roughness and the high salinity of frost flowers, which causes them to be highly reflective to radar energy.

Surface roughness is also registered by MISR, although the roughness observed is at a different spatial scale. Older, rougher ice areas are predominantly backward scattering to the MISR cameras, whereas younger, smoother ice types are predominantly forward scattering. The MISR map at right was generated using a statistical classification routine (called ISODATA) and analyzed using ice charts from the National Ice Center. Five classes of sea ice were found based upon the classification of MISR angular data. These are described, based on interpretation of the SAR image, by the image key. Very smooth ice areas that are predominantly forward scattering are colored red. Frost flowers are largely smooth to the MISR visible band sensor and are mapped as forward scattering. Areas mapped as blue are predominantly backward scattering, and the other three classes have statistically distinct angular signatures and fall within the middle of the forward/backward scattering continuum. Some areas that may be first year or younger ice between the multi year ice floes are not discernible to SAR, illustrating how MISR potentially can make a unique contribution to sea ice mapping.

The Multi-angle Imaging SpectroRadiometer observes the daylit Earth continuously and every 9 days views the entire globe between 82 degrees north and 82 degrees south latitude. This data product was generated from a portion of the imagery acquired during Terra orbit 6663. The MISR image has been cropped to include an area that is 200 kilometers wide, and utilizes data from blocks 30 to 33 within World Reference System-2 path 71.

MISR was built and is managed by NASA's Jet Propulsion Laboratory,Pasadena, CA, for NASA's Office of Earth Science, Washington, DC. The Terra satellite is managed by NASA's Goddard Space Flight Center, Greenbelt, MD. JPL is a division of the California Institute of Technology.

2003-01-01

306

Changing snow characteristics over the Greenland Ice Sheet and the impact on surface mass balance in the 21st century.  

NASA Astrophysics Data System (ADS)

We assess the changing characteristics of the snow and firn layer covering the Greenland ice sheet and the feedback it has on the surface mass balance (SMB). For this, we use output of a high-resolution (11 km) regional atmospheric climate model, forced at the lateral boundaries by the global climate model HadGEM2-ES for the RCP4.5 scenario. For this modest warming scenario the surface mass balance (SMB) will turn negative around 2070 and the additional contribution to sea level rise will be as large as 7±1 cm for the period 2011-2100 from surface processes only. Furthermore the SMB will become more sensitive to summer temperature than to (winter) accumulation, and as a result shows a stronger inter-annual variability. Towards the end of the 21st century, averaged over the Greenland ice sheet, summer (JJA) 2 m temperature increases by 3.5 K, compared to the 1990-2010 period. As a result the firn layer becomes warmer, denser and grain size of the snow increases lowering the albedo. Temperature increase of the snow at 5 m depth is strongest in the present day lower accumulation zone, up to 20 K. In this region latent heat release from the refreezing of melt water is largest. By the end of this century 60% of the 'snow' cover at 5 m depth consists of ice, compared to 30% at present. These changes imply a significant change in the refreezing potential of the Greenland ice sheet. Currently 46±4% of the produced liquid water (melt water + rain) is refrozen in the snow pack. The loss of poor space reduces this refreezing capacity to less than 30% towards the end of this century.

van Angelen, J.; Lenaerts, J.; van den Broeke, M. R.; Fettweis, X.; van Meijgaard, E.

2012-12-01

307

Verification of simulated sea-ice concentrations from sea-ice/ocean models using satellite data  

NASA Astrophysics Data System (ADS)

Sea-ice concentrations in the Laptev Sea simulated by the coupled North Atlantic - Arctic Ocean - Sea-Ice Model (NAOSIM) and Finite Element Sea-Ice Ocean Model (FESOM) are verified using sea-ice concentrations from AMSR-E satellite data and a polynya classification method for winter 2007/08. Simulated sea-ice fields from different model runs are compared with emphasis on the impact of an integrated fast-ice mask. Sea-ice models are not able to simulate polynyas realistically when used in their operational versions. Without fast ice, our investigations indicate that the simulation of large leads and smoothed sea-ice concentration fields compensates the absence of the polynyas. After implementation of a fast-ice mask the polynya location is realistically simulated, but the total open water area is largely overestimated. The study shows that further model improvements are necessary in order to achieve the important step from the simulation of large-scale features in the Arctic towards a more detailed simulation of smaller-scaled features (here polynyas) in an Arctic shelf sea.

Adams, Susanne; Willmes, Sascha; Heinemann, Günther; Rozman, Polona; Timmermann, Ralph; Schröder, David

2010-05-01

308

Arctic Sea Ice Thickness from Satellite Observations, Aircraft Field Campaign Measurements, and Numerical Model Simulations  

NASA Astrophysics Data System (ADS)

Sea ice is an important indicator and effective modulator of regional and global climate change because it significantly affects the complex exchanges of momentum, heat, and mass between the sea and atmosphere. At present, there are datasets for Arctic sea ice thickness from satellite observations, aircraft field campaign measurements, numerical model simulations, and some in-situ measurements. Among satellite derived data sets, one satellite ice thickness product has been generated using NASA's Ice, Cloud and Land Elevation Satellite (ICESat) Geoscience Laser Altimeter System (GLAS) observations (Kwok et al., 2009), another has been produced from long-term optical (visible, near-IR, and thermal IR) imager data from NOAA Polar Orbiting Satellites (Wang et al., 2010). The approaches are completely different: the ICESat product estimates ice thickness from surface elevation; the optical imager approach estimates ice thickness by solving the surface energy budget equation. NASA's IceBridge program fills the gap between the loss of ICESat in 2010 and the launch of ICESat-2 in 2016. IceBridge employs an aircraft for altimeter and other measurements of the ice sheets and sea ice. The IceBridge Snow Radar, Digital Mapping System (DMS), Continuous Airborne Mapping By Optical Translator (CAMBOT), and Airborne Topographic Mapper (ATM) instruments can be used to estimate ice thickness with a methodology similar to that used for ICESat. Ice thickness has also been modeled with the numerical model called Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS) (Zhang and Rothrock, 2003). Arctic sea ice thickness estimates from these different data sources will be examined and inter-compared to evaluate their consistency and validity with in-situ measurements. Arctic sea ice thickness variations over time and space will be also investigated.

Wang, X.; Kwok, R.; Zhang, J.; Liu, Y.; Key, J.

2013-12-01

309

Climate, Ocean, and Sea Ice Modeling Project  

NSDL National Science Digital Library

This site provides an overview of the Climate, Ocean and Sea Ice Modeling Project (COSIM) and its mission to develop sea ice and ocean models which can be applied to coupled climate models. Research areas include polar processes, thermohaline circulation, ocean biogeochemistry, and eddy resolving ocean simulations. Available models include the Parallel Ocean Program (POP), the Los Alamos Sea Ice Model, and eventually the hybrid vertical coordinate version of POP. In addition, COSIM researchers have provided substantial input and development to the Miami Isopycnal Coordinate Ocean Model and its hybrid vertical coordinate equivalent Hybrid Coordinate Ocean Model. Links to these model pages contain model downloads, documentation and data.

Laboratory, Los A.

310

Extracellular macromolecules in sea-ice: Effects on sea-ice structure and their implications  

NASA Astrophysics Data System (ADS)

Brine inclusions within sea-ice offer a favorable environment for certain marine microorganisms which live and thrive within the ice. These assemblages are a crucial element in the polar ecosystem. Partly entrained by ice platelets into the ice sheet, microorganisms closely interact with the liquid and solid phases of this porous environment (brine and ice), likely influencing their properties. Extracellular polysaccharide substances (EPS) and antifreeze proteins (AFP) have been identified as major elements with the potential to affect ice structure and processes, due to their capability to interact with ice crystals (selected planes in the case of AFPs) and with water molecules and salt ions present in the brine. EPS present in sea water can be selectively retained in the ice during ice formation, with implications for ice structure. Likewise, EPS and AFP released by sea-ice organisms would have a local effect, altering the microenvironment for the benefit of the organism. Macroscopic and microscopic observations showed effects on ice microstructure and a possible increase in brine fraction within the ice caused by AFPs and EPS, implicating changes in ice porosity and permeability. In the following we describe some of the interactions between sea-ice macromolecules, EPS and AFP, and the sea-ice system. We show their influence in ice structure, and discuss probable implications and consequences for microbial survival, distribution of dissolved material between sea-ice and the water column, and possible effects on the seasonal evolution of the ice. All of these could be relevant to the understanding of biogeochemical processes and the limits of habitability, as well as suggest possible applications of these substances.

Ewert, M.; Bayer-Giraldi, M.

2012-04-01

311

Snow1 Interacts with Ice1 and Regulates CBF Expressions and Freezing Tolerance in Arabidopsis.  

National Technical Information Service (NTIS)

The present invention relates to a protein (Snow1), mutants thereof, and nucleic acids encoding said protein, that interacts with Ice1 and which activates CBF3 promoter activity thus regulating freezing tolerance in plants.

A. Kapoor J. K. Zhu M. Agarwal

2004-01-01

312

National Snow and Ice Data Center. World Data Center for Glaciology, Boulder Annual Report, 2004.  

National Technical Information Service (NTIS)

The National Snow and Ice Data Center (NSIDC) and World Data Center for Glaciology (WDC), Boulder, is part of the University of Colorado Cooperative Institute for Research in Environmental Sciences (CIRES), and is affiliated with the National Oceanic and ...

2005-01-01

313

National Snow and Ice Data Center. World Data Center for Glaciology, Boulder Annual Report, 2005.  

National Technical Information Service (NTIS)

Scientists around the world are studying the cryosphere, deciphering frozen clues that reveal how the Earths cold regions impacted past climate, and how changes in these regions may affect present and future climate. The National Snow and Ice Data Center ...

2006-01-01

314

Neogene History of Antarctic Sea-ice and Development of the Sea-ice Diatom Community  

Microsoft Academic Search

Sea-ice plays an important role in the modern Antarctic climate system and in this region's linkage to lower latitude regions. Today, the seasonal sea-ice cover decouples oceanic heat transfer to the atmosphere, which amplifies winter's low temperatures and shifts sources of moisture far to the north. The sea-ice zone is an important site for biological productivity and bottom water formation,

D. M. Harwood; S. M. Bohaty; J. M. Whitehead

2002-01-01

315

Mercury distribution and transport across the ocean-sea-ice-atmosphere interface in the Arctic Ocean.  

PubMed

The Arctic sea-ice environment has been undergoing dramatic changes in the past decades; to which extent this will affect the deposition, fate, and effects of chemical contaminants remains virtually unknown. Here, we report the first study on the distribution and transport of mercury (Hg) across the ocean-sea-ice-atmosphere interface in the Southern Beaufort Sea of the Arctic Ocean. Despite being sampled at different sites under various atmospheric and snow cover conditions, Hg concentrations in first-year ice cores were generally low and varied within a remarkably narrow range (0.5-4 ng L(-1)), with the highest concentration always in the surface granular ice layer which is characterized by enriched particle and brine pocket concentration. Atmospheric Hg depletion events appeared not to be an important factor in determining Hg concentrations in sea ice except for frost flowers and in the melt season when snowpack Hg leaches into the sea ice. The multiyear ice core showed a unique cyclic feature in the Hg profile with multiple peaks potentially corresponding to each ice growing/melting season. The highest Hg concentrations (up to 70 ng L(-1)) were found in sea-ice brine and decrease as the melt season progresses. As brine is the primary habitat for microbial communities responsible for sustaining the food web in the Arctic Ocean, the high and seasonally changing Hg concentrations in brine and its potential transformation may have a major impact on Hg uptake in Arctic marine ecosystems under a changing climate. PMID:21288021

Chaulk, Amanda; Stern, Gary A; Armstrong, Debbie; Barber, David G; Wang, Feiyue

2011-03-01

316

Characteristics of forming mutiyear sea ice in modern climatic conditions  

NASA Astrophysics Data System (ADS)

The goal of the work was to study the thermodynamic evolution of sea ice in modern climate conditions. The model describes repetitive changing the processes of winter ice growth, snow summer melting and dissolution of ice upper layer and its autumn re-crystallization. Ice block uses classical (frontal) variant of Stefan problem and takes into consideration the processes of melt water pool forming and freezing which are often absent in the analogous models. The essential values of ice cover surface which is not identified with air temperature are calculated from heat balance. As atmospheric forcing the repetitive data of atmospheric NCEP/NCAR reanalysis for 2006-2007 years are used. According to calculations for the North Hole point the forming of modern multi-year ice cover is slower than in the former years. For 10 years its maximal thickness slightly exceeded 4 m and did not reach thermodynamically equilibrium value. The important parameter affecting ice thickness evolution is the rate of melt water drainage during period of melt pool forming. The difference of ice thicknesses for 10 years at average drainage rate between 0 and 1 cm/day was close to 2 m that is equivalent to constant heat flow from the ocean equal to 3 W/m2. The result most close to characteristic melt water pool average depths (0.2 m) correspond to drainage rate of 1 cm/day. With the beginning of cooling the compensation of heat flux to the atmosphere occurs in consequence of melt water layer crystallization. Therefore, sea ice thickness does not increase as long as the liquid thickness reaches some critical value determined by its initial salinity and depth. Taking into consideration the significant area occupying by the melt ponds as well as their depths it is obvious that the over ice water layer is a qualitative element of ice cover those forming and re-crystallization considerably determines evolution of sea ice depth. The work was supported by Russian Foundation for Basic Research (projects ## 07-05-00393 and 08-05-00129).

Bogorodsky, P. V.; Pnyushkov, A. V.

2009-04-01

317

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

Microsoft Academic Search

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

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

2010-01-01

318

A model of energy budgets over water, snow, and ice surfaces  

NASA Astrophysics Data System (ADS)

The recently formulated maximum entropy production (MEP) model over land surfaces has been generalized to water-snow-ice surfaces. Analytical solutions of energy budget in terms of the partition of surface radiative fluxes into (turbulent and/or conductive) heat fluxes at the earth-atmosphere interface are derived as functions of surface temperature (e.g., sea surface temperature). The MEP model does not require data of wind speed, air temperature-humidity, and surface roughness. Test of the MEP model using observations from several field experiments is encouraging. Potential applications of the proposed model for understanding long-term trends in surface heat fluxes and for closing global surface energy budget at the Earth's atmosphere are suggested.

Wang, Jingfeng; Bras, Rafael L.; Nieves, Veronica; Deng, Yi

2014-05-01

319

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

Microsoft Academic Search

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

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

2009-01-01

320

Comparing Arctic Sea Ice Kinematics from Satellite Remote Sensing Data to Coupled Sea Ice-Ocean Model Results  

Microsoft Academic Search

The Arctic sea ice in many respects is an important component of the Earth's climate system, e.g., sea ice governs the ocean to atmosphere heat flux, freezing and melting influences the upper ocean salinity and density, and sea ice dynamics act as a latent energy transport. During recent years substantial changes of the Arctic sea ice cover have been observed.

G. Spreen; D. Menemenlis; R. Kwok; A. T. Nguyen

2009-01-01

321

Influence of the Gulf Stream on the Barents Sea ice retreat and Eurasian coldness  

NASA Astrophysics Data System (ADS)

Abnormal winter sea-ice retreat over the Barents Sea has been considered as a leading clue to the recent midlatitude severe winters. Barents Sea is considered as a hot spot for the rapid Arctic climate change due to the intense air-sea interaction induced by the sea-ice decrease; however, the underlying mechanisms remain uncertain, in particular causal relation of sea-ice retreat and atmospheric forcing and response. To understand this causality, we selected typical cases, defined as averaged warm and averaged cold years of December using the NCEP Climate Forecast System Reanalysis (CFSR). The composite analysis, revealed that anticyclonic anomaly is obvious over the northwestern Eurasia. The western Barents Sea and Sbarvard locates at the strong pressure gradient zone, prevailing southerly winds. Over the Barents Sea, the difference in daily mean air temperature between warm and cold winters is more than 10°, suggesting that warm advection prevails during warm years. Therefore, during warm years, decrease in sea-ice cover is induced by southerly warm advection. The positive anomalies of precipitation from the southeast of Greenland to Barents Sea and negative anomalies of them from Nordic Sea to western Eurasia means the poleward shift of cyclone tracks, suggesting that the moisture transport is also changed poleward. Because the cyclones tend to shift poleward in less sea ice year over the Barents Sea, it is natural that the snow depth over the sea ice near the Fram Strait shows a positive anomaly during warm winters. Here we show that the poleward shift of sea surface temperature over the Gulf Stream, where is situated upstream from the Barents Sea, modifies the horizontal distribution of tropospheric condensational heating resulted from change in convection over the warm current, likely acting as a bridge to the Barents Sea by forcing planetary waves. This remote atmospheric response modifies cyclone tracks poleward, resulting in anomalous warm advection over the Barents Sea sector.

Sato, Kazutoshi; Inoue, Jun; Watanabe, Masahiro

2014-05-01

322

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.

323

Effects of Arctic Sea Ice Decline on Weather and Climate: A Review  

NASA Astrophysics Data System (ADS)

The areal extent, concentration and thickness of sea ice in the Arctic Ocean and adjacent seas have strongly decreased during the recent decades, but cold, snow-rich winters have been common over mid-latitude land areas since 2005. A review is presented on studies addressing the local and remote effects of the sea ice decline on weather and climate. It is evident that the reduction in sea ice cover has increased the heat flux from the ocean to atmosphere in autumn and early winter. This has locally increased air temperature, moisture, and cloud cover and reduced the static stability in the lower troposphere. Several studies based on observations, atmospheric reanalyses, and model experiments suggest that the sea ice decline, together with increased snow cover in Eurasia, favours circulation patterns resembling the negative phase of the North Atlantic Oscillation and Arctic Oscillation. The suggested large-scale pressure patterns include a high over Eurasia, which favours cold winters in Europe and northeastern Eurasia. A high over the western and a low over the eastern North America have also been suggested, favouring advection of Arctic air masses to North America. Mid-latitude winter weather is, however, affected by several other factors, which generate a large inter-annual variability and often mask the effects of sea ice decline. In addition, the small sample of years with a large sea ice loss makes it difficult to distinguish the effects directly attributable to sea ice conditions. Several studies suggest that, with advancing global warming, cold winters in mid-latitude continents will no longer be common during the second half of the twenty-first century. Recent studies have also suggested causal links between the sea ice decline and summer precipitation in Europe, the Mediterranean, and East Asia.

Vihma, Timo

2014-03-01

324

Heilongjiang Ice-Snow Tourism Industry Competitiveness Evaluation Index System Design  

Microsoft Academic Search

\\u000a Practice in Heilongjiang province is the earliest provinces of ice-snow tourism industry, In Heilongjiang province of ice-snow\\u000a tourism industry as the most distinctive industries, in its economic development plays a leading and radiation. Based on comprehensive\\u000a a large number of documents, professional consulting and reference related evaluation index system, constructing the contains\\u000a five basic factors criterion layer and nineteen concrete

Liang Zhang; XiaoMei Zhang

325

Research on the Development Evaluation of Snow-ice Tourism Resources  

Microsoft Academic Search

The purpose of this paper is to discuss the framework and measurement of development evaluation of the snow-ice tourism resources. The definition and category of snow-ice tourism resources are identified. A destination-oriented CSSRR(Core, Supportive, Subsidiary and Reserved Resources) category is introduced to help understand the tourism resources. Then a hierarchy assessment framework is developed to establish levels of attraction. Assessment

Zhang Chun-yan; Hu Yun-quan

2007-01-01

326

Forecasting Bering Sea ice edge behavior  

SciTech Connect

A coupled ice/ocean dynamics model is developed to provide Arctic offshore operators with 5- to 7-day forecasts of ice motions, ice conditions, and ice edge motions. An adaptive grid is introduced to follow the ice edge, and the grid may move independently of the ice motion. The grid can be Lagrangian or Eulerian at different locations away from the ice edge. Ice stress is described using an elastic-plastic model with strength determined by the ice conditions. The ocean dynamics model describes time-dependent, three-dimensional behavior, including wind-driven currents and barotropic and baroclinic flows. The thermal energy budget of the ice cover is coupled to the ocean, with mass and salt interchange accompanying freezing or melting. Near the marginal ice zone (MIZ), surface winds (determined by reducing and turning the geostrophic winds) are enhanced to reflect observed behavior. The model was tested by simulating ice edge motions observed during the 1983 Marginal Ice Zone Experiment-West and during drilling of the 1983 north Aleutian shelf Continental Offshore Stratigraphic Test well. Simulations of ice edge movement in the Bering Sea compare with observed data to within about 5 km/d. The model correctly describes mixed-layer evolution in the marginal ice zone as fresh meltwater is mixed downward by turbulence. Along-edge baroclinic flows due to density gradients across the ice edge are simulated by the model, in agreement with observations. Increased ice drift speeds generate higher melt rates due to increased turbulence levels, with the result that ice edge advance is moderated in spite of higher ice drift speeds.

Pritchard, R.S. (Naval Postgraduate School, Monterey, CA (United States)); Mueller, A.C. (Flow Industries, Inc., Kent, WA (United States)); Yang, Y.S. (Arco Oil and Gas Co., Dallas, TX (United States)); Hanzlick, D.J.

1990-01-15

327

Interaction of oil with arctic sea ice  

SciTech Connect

The purpose of the paper is to summarize relavant knowledge about the interactions between arctic sea ice and oil. The completion of further experimental oil spill studies, along with recent laboratory studies of the interaction of oil and sea ice and studies of environmental conditions, makes an updating of those works desirable. An attempt is made to identify the major factors in the interaction between oil and arctic sea ice and to present them in a way that defines the scope of the problem. Generally, the paper is restricted to factors that can be expected to play a major role in the sequence of events following a large under-ice blowout in the Beaufort Sea during winter.

Thomas, D.R.

1983-02-01

328

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

329

Floating Ice-Algal Aggregates below Melting Arctic Sea Ice  

PubMed Central

During two consecutive cruises to the Eastern Central Arctic in late summer 2012, we observed floating algal aggregates in the melt-water layer below and between melting ice floes of first-year pack ice. The macroscopic (1-15 cm in diameter) aggregates had a mucous consistency and were dominated by typical ice-associated pennate diatoms embedded within the mucous matrix. Aggregates maintained buoyancy and accumulated just above a strong pycnocline that separated meltwater and seawater layers. We were able, for the first time, to obtain quantitative abundance and biomass estimates of these aggregates. Although their biomass and production on a square metre basis was small compared to ice-algal blooms, the floating ice-algal aggregates supported high levels of biological activity on the scale of the individual aggregate. In addition they constituted a food source for the ice-associated fauna as revealed by pigments indicative of zooplankton grazing, high abundance of naked ciliates, and ice amphipods associated with them. During the Arctic melt season, these floating aggregates likely play an important ecological role in an otherwise impoverished near-surface sea ice environment. Our findings provide important observations and measurements of a unique aggregate-based habitat during the 2012 record sea ice minimum year.

Assmy, Philipp; Ehn, Jens K.; Fernandez-Mendez, Mar; Hop, Haakon; Katlein, Christian; Sundfjord, Arild; Bluhm, Katrin; Daase, Malin; Engel, Anja; Fransson, Agneta; Granskog, Mats A.; Hudson, Stephen R.; Kristiansen, Svein; Nicolaus, Marcel; Peeken, Ilka; Renner, Angelika H. H.; Spreen, Gunnar; Tatarek, Agnieszka; Wiktor, Jozef

2013-01-01

330

Satellite microwave observations of the interannual variability of snowmelt on sea ice in the Southern Ocean  

NASA Astrophysics Data System (ADS)

Snowmelt processes on Antarctic sea ice are examined. We present a simple snowmelt indicator based on diurnal brightness temperature variations from microwave satellite data. The method is validated through extensive field data from the western Weddell Sea and lends itself to the investigation of interannual and spatial variations of the typical snowmelt on Antarctic sea ice. We use in situ measurements of physical snow properties to show that despite the absence of strong melting, the summer period is distinct from all other seasons with enhanced diurnal variations of snow wetness. A microwave emission model reveals that repeated thawing and refreezing causes the typical microwave emissivity signatures that are found on perennial Antarctic sea ice during summer. The proposed melt indicator accounts for the characteristic phenomenological stages of snowmelt in the Southern Ocean and detects the onset of diurnal snow wetting. An algorithm is presented to map large-scale snowmelt onset, based on satellite data from the period between 1988 and 2006. The results indicate strong meridional gradients of snowmelt onset with the Weddell, Amundsen and Ross Seas showing earliest (beginning of October) and most frequent snowmelt. Moreover, a distinct interannual variability of melt onset dates and large areas of first-year ice where no diurnal freeze-thawing occurs at the surface are determined.

Willmes, S.; Haas, C.; Nicolaus, M.; Bareiss, J.

2009-04-01

331

Satellite microwave observations of the interannual variability of snowmelt on sea ice in the Southern Ocean  

NASA Astrophysics Data System (ADS)

Snowmelt processes on Antarctic sea ice are examined. We present a simple snowmelt indicator based on diurnal brightness temperature variations from microwave satellite data. The method is validated through extensive field data from the western Weddell Sea and lends itself to the investigation of interannual and spatial variations of the typical snowmelt on Antarctic sea ice. We use in-situ measurements of physical snow properties to show that despite the absence of strong melting, the summer period is distinct from all other seasons with enhanced diurnal variations of snow wetness. A microwave emission model reveals that repeated thawing and refreezing cause the typical microwave emissivity signatures that are found on perennial Antarctic sea ice during summer. The proposed melt indicator accounts for the characteristic phenomenological stages of snowmelt in the Southern Ocean and detects the onset of diurnal snow wetting. An algorithm is presented to map large-scale snowmelt onset based on satellite data from the period between 1988 and 2006. The results indicate strong meridional gradients of snowmelt onset with the Weddell, Amundsen, and Ross Seas showing earliest (beginning of October) and most frequent snowmelt. Moreover, a distinct interannual variability of melt onset dates and large areas of first-year ice where no diurnal freeze thawing occurs at the surface are determined.

Willmes, Sascha; Haas, Christian; Nicolaus, Marcel; Bareiss, JöRg

2009-03-01

332

Attribution of Recent Arctic Sea Ice Melting to Human Influence  

NASA Astrophysics Data System (ADS)

During recent three decades Arctic sea ice extent (SIE) has been decreasing with its rate accelerating. There have been, however, limited studies which have identified human influence on the Arctic sea ice using a formal detection approach. This study conducts an updated detection analysis of recent Arctic SIE during 1979-2012 by comparing observed changes with those from CMIP5 (Coupled Model Intercomparison Project Phase 5) multi-model simulations. We use the NSIDC (National Snow and Ice Data Center) sea ice index as observations. The simulated Arctic SIEs are calculated from available ensembles of CMIP5 multi-models which have been performed under natural plus anthropogenic forcing (ALL: historical combined with RCP4.5, 112 runs from 40 models), natural forcing only (NAT: historicalNat, 48 runs from 10 models) and greenhouse gas forcing only (GHG: historicalGHG, 35 runs from 9 models). Anthropogenic forcing (ANT) responses are estimated from differences between ALL and NAT. We apply an optimal fingerprinting method where observations are regressed onto model-simulated signals (multi-model means of ALL, NAT, and GHG). Here the internal variability noise is estimated from historical simulations after removing multi-model averages. The observations display decreasing trends across all months with stronger amplitude in summer than other seasons, which is reasonably reproduced by CMIP5 simulations. Results from one-signal analyses show that the ALL, ANT, and GHG signals are all detected when considering four months (Mar, Jun, Sep, and Dec) together and also from September to January when looking at individual months. Results from two-signal analyses show that ANT is separable from NAT and also that GHG is separable from other non-GHG forcings. Scaling factors of the detected ANT and GHG signals include unity, indicating that observed Arctic sea ice melting during the satellite period is largely attributable to human-induced increases in GHGs.

Heo, Joonghyeok; Min, Seung-Ki

2014-05-01

333

EOS Aqua AMSR-E Arctic Sea-Ice Validation Program: Arctic2006 Aircraft Campaign Flight Report  

NASA Technical Reports Server (NTRS)

In March 2006, a coordinated Arctic sea-ice validation field campaign using the NASA Wallops P-3B aircraft was successfully completed. This campaign was the second Alaskan Arctic field campaign for validating the Earth Observing System (EOS) Aqua Advanced Microwave Scanning Radiometer (AMSR-E) sea-ice products. The first campaign was completed in March 2003. The AMSR-E, designed and built by the Japanese Space Agency for NASA, was launched May 4, 2002 on the EOS Aqua spacecraft. The AMSR-E sea-ice products to be validated include sea-ice concentration, sea-ice temperature, and snow depth on sea ice. The focus of this campaign was on the validation of snow depth on sea ice and sea-ice temperature. This flight report describes the suite of instruments flown on the P-3, the objectives of each of the six flights, the Arctic regions overflown, and the coordination among satellite, aircraft, and surface-based measurements.

Cavalieri, D. J.; Markus, T.

2006-01-01

334

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

335

Arctic sea ice decline: Faster than forecast  

Microsoft Academic Search

From 1953 to 2006, Arctic sea ice extent at the end of the melt season in September has declined sharply. All models participating in the Intergovernmental Panel on Climate Change Fourth Assessment Report (IPCC AR4) show declining Arctic ice cover over this period. However, depending on the time window for analysis, none or very few individual model simulations show trends

Julienne Stroeve; Marika M. Holland; Walt Meier; Ted Scambos; Mark Serreze

2007-01-01

336

Linking Sea Ice Physical Properties with Under-Ice and In-Ice Ecosystems  

NASA Astrophysics Data System (ADS)

Impacts of climate change have been most pronounced in Polar Regions. Most alarming is the accelerating decline in Arctic sea ice cover. The changing ice cover is likely to have implications for sea ice-associated ecosystems because they rely largely on carbon produced by ice-associated algae. In order to fully understand these ecosystems and to be able to accurately represent them in models there is a need to understand both the physical and biological components of the system. The study presented here is part of AWI's research group Iceflux which takes an interdisciplinary approach to quantify the trophic carbon flux within sea ice associated ecosystems in the Arctic and Antarctic. Here we will present preliminary results from the ARK XXVII/3 Polarstern Cruise (Aug-Oct, 2012) to the Central Arctic Ocean. Biological samples will be acquired from the under-ice surface waters using the Surface and Under-Ice Trawl (SUIT) and from within the sea ice by extracting ice cores. To characterize the biophysical properties of the sea ice and under-ice environments several sensors were mounted on the SUIT including: spectral radiometer, ADCP, CTD, fluorometer, altimeter (distance to ice bottom) and video camera. Observations include ice thickness, biological diversity, biomass, light transmission, under-ice water properties and chlorophyll a content (in- and under-ice). Preliminary results will provide a description of the local- to meso-scale spatial variability of biological abundance in and under the ice and the relationship with different sea ice characteristics. The SUIT system will be deployed, for the first time, under MYI; including extensively surveyed ice station floes. The effectiveness and efficiency of the SUIT system under MYI will be presented and compared to results from previous deployments.

Lange, B. A.; Flores, H.; David, C. L.; Nicolaus, M.

2012-12-01

337

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

338

Differentiation of Land-Based Snow and Ice by the Moderate Resolution Imaging Spectroradiometer (MODIS)  

NASA Astrophysics Data System (ADS)

The extent of snow and ice over land is a key factor in the global radiation budget and the hydrologic cycle, and is essential information for regional- and global-scale climate modeling. Remote sensing of land cover via satellite provides an opportunity for automated measurement of snow and ice over expanded spatial areas and is amenable to study using moderate-resolution sensors such as the Moderate Resolution Imaging Spectroradiometer (MODIS). MODIS consists of 36 discrete spectral bands from the visible through the thermal infrared parts of the electromagnetic spectrum and three spatial resolutions of 250m (bands 1-2), 500m (bands 3-7), and 1km (bands 8-36), and daily or near-daily temporal coverage. The first MODIS sensor is aboard NASA's Earth Observing System (EOS) Terra spacecraft, which was launched in December 1999. The EOS Aqua satellite was launched in May 2002, and carries the second MODIS sensor. Five years of MODIS data are now available and are useful for the creation of time series data sets. The spectral bands from MODIS of greatest potential in discrimination between snow and bare (non-snow covered) ice on land surfaces are shown to be useful for development of automated algorithms to distinguish land-based snow and bare ice based on their optical properties. An advantage of automated algorithms is the consistency of results within the time series and therefore the reduction of subjectivity in identifying climatologically-significant trends. Preliminary results of automated algorithms to distinguish snow and bare ice show that it is very difficult to separate snow and ice, for example on Greenland, using classification techniques. Clouds also present a challenge in discrimination of snow and bare ice over land. However, progress has been made and results showing a time series of data for an area in southwestern Greenland will be presented.

Casey, K. A.; Hall, D. K.

2005-05-01

339

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)] [Univ. of Washington, Seattle, WA (United States); Moritz, R.E. [Univ. of Washington, Seattle, WA (United States)] [Univ. of Washington, Seattle, WA (United States); Beesley, J.A. [Univ. of Washington, Seattle, WA (United States)] [Univ. of Washington, Seattle, WA (United States)

1996-02-01

340

Real-Time Observations of Optical Properties of Arctic Sea Ice with an Autonomous System  

NASA Astrophysics Data System (ADS)

The recent drastic changes in the Arctic sea ice cover have altered the interaction of solar radiation and sea ice. To improve our understanding of this interaction, a Spectral Radiation Buoy (SRB) for measuring sea ice optical properties was developed, based on a system used during the last International Polar Year at the drift of "Tara" across the Arctic Ocean. A first version of the SRB was deployed on drifting ice in the high Arctic in April 2012. It includes three Satlantic spectral radiometers (two in air, one under ice), covering the wavelength range from 347 nm to 804 nm with 3.3 nm spectral resolution, a bio-shutter to protect the under-ice radiometer, a data logger to handle and store collected data, and an Iridium satellite modem to transfer data in real-time. The under-ice radiometer is mounted on an adjustable under-ice arm, and the other instruments are mounted on a triangular frame frozen into the ice. The SRB measures simultaneously, autonomously and continuously the spectral fluxes of incident and reflected solar radiation, as well as under-ice irradiance, water temperature and water pressure every hour. So far, between mid April and early August 2012, the system has drifted about 600 km, from the starting position near the North Pole towards the Fram Strait. The data collected during this deployment, so far, already demonstrate that this system is suitable for autonomous and long-term observations over and under sea ice in harsh conditions. Along with the SRB, commercially available Ice Mass Balance buoys (IMB) were deployed on the same ice floe. In the vicinity of the site, manned baseline measurements of snow and sea ice physical properties have been carried out during the SRB deployment. The combined datasets allow description of the evolution of the ice floe during seasonal melt. With snow melt, the spectral surface albedo decreased and the transmittance through the snow and ice increased after mid-April, especially when melt ponds started to develop in July.

Wang, C.; Gerland, S.; Nicolaus, M.; Granskog, M. A.; Hudson, S. R.; Perovich, D. K.; Karlsen, T. I.; Fossan, K.

2012-12-01

341

Statistical Analyses of High-Resolution Aircraft and Satellite Observations of Sea Ice: Applications for Improving Model Simulations  

NASA Astrophysics Data System (ADS)

Satellite-derived estimates of ice thickness and observations of ice extent over the last decade point to a downward trend in the basin-scale ice volume of the Arctic Ocean. This loss has broad-ranging impacts on the regional climate and ecosystems, as well as implications for regional infrastructure, marine navigation, national security, and resource exploration. New observational datasets at small spatial and temporal scales are now required to improve our understanding of physical processes occurring within the ice pack and advance parameterizations in the next generation of numerical sea-ice models. High-resolution airborne and satellite observations of the sea ice are now available at meter-scale resolution or better that provide new details on the properties and morphology of the ice pack across basin scales. For example the NASA IceBridge airborne campaign routinely surveys the sea ice of the Arctic and Southern Oceans with an advanced sensor suite including laser and radar altimeters and digital cameras that together provide high-resolution measurements of sea ice freeboard, thickness, snow depth and lead distribution. Here we present statistical analyses of the ice pack primarily derived from the following IceBridge instruments: the Digital Mapping System (DMS), a nadir-looking, high-resolution digital camera; the Airborne Topographic Mapper, a scanning lidar; and the University of Kansas snow radar, a novel instrument designed to estimate snow depth on sea ice. Together these instruments provide data from which a wide range of sea ice properties may be derived. We provide statistics on lead distribution and spacing, lead width and area, floe size and distance between floes, as well as ridge height, frequency and distribution. The goals of this study are to (i) identify unique statistics that can be used to describe the characteristics of specific ice regions, for example first-year/multi-year ice, diffuse ice edge/consolidated ice pack, and convergent/divergent ice zones, (ii) provide datasets that support enhanced parameterizations in numerical models as well as model initialization and validation, (iii) parameters of interest to Arctic stakeholders for marine navigation and ice engineering studies, and (iv) statistics that support algorithm development for the next-generation of airborne and satellite altimeters, including NASA's ICESat-2 mission. We describe the potential contribution our results can make towards the improvement of coupled ice-ocean numerical models, and discuss how data synthesis and integration with high-resolution models may improve our understanding of sea ice variability and our capabilities in predicting the future state of the ice pack.

Farrell, S. L.; Kurtz, N. T.; Richter-Menge, J.; Harbeck, J. P.; Onana, V.

2012-12-01

342

Sea ice tracking by nested correlations  

NASA Technical Reports Server (NTRS)

Spatial differences in sea ice displacement affect ice stress, ice production, and the mass balance of the ice cover. Concepts about the spatial structure of this field have been undernourished because of a paucity of data with high spatial detail and because of the tedium of extracting such measurements from images manually. A method is described that measures displacements from synthetic aperture radar digital imagery with fine spatial resolution, and does so fully automatically. Many small areas of ice common to two images are identified by correlating the two images. The strategy is to acquire a crude displacement field first from highly averaged images, and to refine this field with images of successively higher resolution. The median discrepancy between automatically and manually measured displacements is three pixels (0.075 km). The algorithm operates successfully on compact ice with large floes and modest rotation rates; it is believed it will prove applicable to most of the arctic ice cover throughout the year.

Fily, Michael; Rothrock, D. A.

1987-01-01

343

First-year sea-ice contact predicts bromine monoxide (BrO) levels better than potential frost flower contact  

NASA Astrophysics Data System (ADS)

Reactive halogens are responsible for boundary-layer ozone depletion and mercury deposition in Polar Regions during springtime. To investigate the source of reactive halogens in the air arriving at Barrow, Alaska, we measured BrO, a marker of reactive halogen chemistry, and correlated its abundance with airmass histories derived from meteorological back trajectories and remotely sensed sea ice properties. The BrO is found to be positively correlated to first-year sea-ice contact (R2=0.55), and weakly negatively correlated to potential frost flower (PFF) contact (R2=0.04). These data indicate that snow contaminated with sea salts on first-year sea ice is a more probable bromine source than are frost flowers. Recent climate-driven changes in Arctic sea ice are likely to alter frost flower and first year sea ice prevalence, suggesting a significant change in reactive halogen abundance, which will alter the chemistry of the overlying Arctic atmosphere.

Simpson, W. R.; Carlson, D.; Hoenninger, G.; Douglas, T. A.; Sturm, M.; Perovich, D.; Platt, U.

2006-11-01

344

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

345

The importance of diurnal processes for the seasonal cycle of sea-ice microwave brightness temperatures during early summer in the Weddell Sea, Antarctica  

NASA Astrophysics Data System (ADS)

Over the perennial sea ice in the western and central Weddell Sea, Antarctica, the onset of summer is accompanied by a significant decrease of sea-ice brightness temperatures (Tb) as observed by passive-microwave radiometers such as the Special Sensor Microwave/Imager (SSM/I). The summer-specific Tb drop is the dominant feature in the seasonal cycle of Tb data and represents a conspicuous difference to most Arctic sea-ice regions, where the onset of summer is mostly marked by a rise in Tb. Data from a 5 week drift station through the western Weddell Sea in the 2004/05 austral summer, Ice Station POLarstern (ISPOL), helped with identifying the characteristic processes for Antarctic sea ice. In situ glaciological and meteorological data, in combination with SSM/I swath satellite data, indicate that the cycle of repeated diurnal thawing and refreezing of snow ('freeze-thaw cycles') is the dominant process in the summer season, with the absence of complete snow wetting. The resulting metamorphous snow with increased grain size, as well as the formation of ice layers, leads to decreasing emissivity, enhanced volume scattering and increased backscatter. This causes the summer Tb drop.

Willmes, Sascha; Bareiss, Jörg; Haas, Christian; Nicolaus, Marcel

346

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

347

Dynamics of the sea ice edge in Davis Strait  

Microsoft Academic Search

Sea ice concentration derived from satellite data were used to quantify sea ice characteristics in the Baffin Bay Davis Strait Labrador Sea area. The ice edge in Davis Strait extends from Disko Bay in West Greenland 2500 km south to Newfoundland. The mean intercept at the West Greenland coast between 1979 and 2002 was located at 66.9°N, assuming the ice

M. P. Heide-Jørgensen; H. Stern; K. L. Laidre

2007-01-01

348

Massive phytoplankton blooms under Arctic sea ice.  

PubMed

Phytoplankton blooms over Arctic Ocean continental shelves are thought to be restricted to waters free of sea ice. Here, we document a massive phytoplankton bloom beneath fully consolidated pack ice far from the ice edge in the Chukchi Sea, where light transmission has increased in recent decades because of thinning ice cover and proliferation of melt ponds. The bloom was characterized by high diatom biomass and rates of growth and primary production. Evidence suggests that under-ice phytoplankton blooms may be more widespread over nutrient-rich Arctic continental shelves and that satellite-based estimates of annual primary production in these waters may be underestimated by up to 10-fold. PMID:22678359

Arrigo, Kevin R; Perovich, Donald K; Pickart, Robert S; Brown, Zachary W; van Dijken, Gert L; Lowry, Kate E; Mills, Matthew M; Palmer, Molly A; Balch, William M; Bahr, Frank; Bates, Nicholas R; Benitez-Nelson, Claudia; Bowler, Bruce; Brownlee, Emily; Ehn, Jens K; Frey, Karen E; Garley, Rebecca; Laney, Samuel R; Lubelczyk, Laura; Mathis, Jeremy; Matsuoka, Atsushi; Mitchell, B Greg; Moore, G W K; Ortega-Retuerta, Eva; Pal, Sharmila; Polashenski, Chris M; Reynolds, Rick A; Schieber, Brian; Sosik, Heidi M; Stephens, Michael; Swift, James H

2012-06-15

349