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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

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

Microsoft Academic Search

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

Ted Maksym; Thorsten Markus

2008-01-01

3

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

Microsoft Academic Search

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

Ted Maksym; Thorsten Markus

2008-01-01

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

Ultrawideband Radar Measurements of Thickness of Snow Over Sea Ice  

Microsoft Academic Search

An accurate knowledge of snow thickness and its variability over sea ice is crucial in determining the overall polar heat and freshwater budget, which influences the global climate. Recently, algorithms have been developed to extract snow thicknesses from satellite passive microwave data. However, validation of these data over the large footprint of the passive microwave sensor has been a challenge.

Pannirselvam Kanagaratnam; Thorsten Markus; Victoria Lytle; Brandon Heavey; Peter Jansen; Glenn Prescott; Siva Prasad Gogineni

2007-01-01

7

Airborne Surveys of Snow Depth over Arctic Sea Ice  

NASA Technical Reports Server (NTRS)

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 approx 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 approx 4 - 5 cm. The finite range resolution of the radar (approx 5 cm) and the relative amplitude of backscatter from the two interfaces limit the direct retrieval of snow depths much below approx 8 cm. Well-defined interfaces are observed over only relatively smooth surfaces within the radar footprint of approx 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. 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.

2011-01-01

8

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

9

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

10

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

11

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

12

Assessment of radar-derived snow depth over Arctic sea ice  

NASA Astrophysics Data System (ADS)

Knowledge of contemporaneous snow depth on Arctic sea ice is important both to constrain the regional climatology and to improve the accuracy of satellite altimeter estimates of sea ice thickness. We assess new data available from the NASA Operation IceBridge snow radar instrument and derive snow depth estimates across the western Arctic ice pack using a novel methodology based on wavelet techniques that define the primary reflecting surfaces within the snow pack. We assign uncertainty to the snow depth estimates based upon both the radar system parameters and sea ice topographic variability. The accuracy of the airborne snow depth estimates are examined via comparison with coincident measurements gathered in situ across a range of ice types in the Beaufort Sea. We discuss the effect of surface morphology on the derivation, and consequently the accuracy, of airborne snow depth estimates. We find that snow depths derived from the airborne snow radar using the wavelet-based technique are accurate to 1 cm over level ice. Over rougher surfaces including multiyear and ridged ice, the radar system is impacted by ice surface morphology. Across basin scales, we find the snow-radar-derived snow depth on first-year ice is at least ˜60% of the value reported in the snow climatology for the Beaufort Sea, Canada Basin, and parts of the central Arctic, since these regions were previously dominated by multiyear ice during the measurement period of the climatology. Snow on multiyear ice is more consistent with the climatology.

Newman, Thomas; Farrell, Sinead L.; Richter-Menge, Jacqueline; Connor, Laurence N.; Kurtz, Nathan T.; Elder, Bruce C.; McAdoo, David

2014-12-01

13

Sea Ice Thickness, Freeboard, and Snow Depth products from Operation IceBridge Airborne Data  

NASA Technical Reports Server (NTRS)

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 multisensor 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.

2013-01-01

14

Variability of snow and ice thermal, physical and optical properties pertinent to sea ice algae biomass during spring  

Microsoft Academic Search

Changes in the thermal, physical and optical properties of the snow–sea ice system and feedbacks between various temporal and spatial scales affect accumulation of microalgae at the sea ice bottom and are the focus of this research. During the spring transition period, May 4 to June 9, 2002, we closely monitored atmospheric conditions and properties of the snow–sea ice system,

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

2005-01-01

15

Contaminants in arctic snow collected over northwest Alaskan sea ice  

USGS Publications Warehouse

Snow cores were collected over sea ice from four northwest Alaskan Arctic estuaries that represented the annual snowfall from the 1995-1996 season. Dissolved trace metals, major cations and anions, total mercury, and organochlorine compounds were determined and compared to concentrations in previous arctic studies. Traces (<4 nanograms per liter, ng L-1) of cis- and trans-chlordane, dimethyl 2,3,5,6-tetrachloroterephthalate, dieldrin, endosulfan II, and PCBs were detected in some samples, with endosulfan I consistently present. High chlorpyrifos concentrations (70-80 ng L-1) also were estimated at three sites. The snow was highly enriched in sulfates (69- 394 mg L-1), with high proportions of nonsea salt sulfates at three of five sites (9 of 15 samples), thus indicating possible contamination through long-distance transport and deposition of sulfate-rich atmospheric aerosols. Mercury, cadmium, chromium, molybdenum, and uranium were typically higher in the marine snow (n = 15) in relation to snow from arctic terrestrial studies, whereas cations associated with terrigenous sources, such as aluminum, frequently were lower over the sea ice. One Kasegaluk Lagoon site (Chukchi Sea) had especially high concentrations of total mercury (mean = 214 ng L-1, standard deviation = 5 ng L-1), but no methyl mercury was detected above the method detection limit (0.036 ng L-1) at any of the sites. Elevated concentrations of sulfate, mercury, and certain heavy metals might indicate mechanisms of contaminant loss from the arctic atmosphere over marine water not previously reported over land areas. Scavenging by snow, fog, or riming processes and the high content of deposited halides might facilitate the loss of such contaminants from the atmosphere. Both the mercury and chlorpyrifos concentrations merit further investigation in view of their toxicity to aquatic organisms at low concentrations.

Garbarino, J.R.; Snyder-Conn, E.; Leiker, T.J.; Hoffman, G.L.

2002-01-01

16

Sea ice concentration, ice temperature, and snow depth using AMSR-E data  

Microsoft Academic Search

A summary of the theoretical basis and initial performance of the algorithms that are used to derive sea ice concentration, ice temperature, and snow depth on sea ice from newly acquired Earth Observing System-Aqua\\/Advanced Microwave Scanning Radiometer-EOS (AMSR-E) radiances is presented. The algorithms have been developed and tested using historical satellite passive microwave data and are expected to provide more

Josefino C. Comiso; Donald J. Cavalieri; Thorsten Markus

2003-01-01

17

Improving Surface Mass Balance Over Ice Sheets and Snow Depth on Sea Ice  

NASA Technical Reports Server (NTRS)

Surface mass balance (SMB) over ice sheets and snow on sea ice (SOSI) are important components of the cryosphere. Large knowledge gaps remain in scientists' abilities to monitor SMB and SOSI, including insufficient measurements and difficulties with satellite retrievals. On ice sheets, snow accumulation is the sole mass gain to SMB, and meltwater runoff can be the dominant single loss factor in extremely warm years such as 2012. SOSI affects the growth and melt cycle of the Earth's polar sea ice cover. The summer of 2012 saw the largest satellite-recorded melt area over the Greenland ice sheet and the smallest satellite-recorded Arctic sea ice extent, making this meeting both timely and relevant.

Koenig, Lora Suzanne; Box, Jason; Kurtz, Nathan

2013-01-01

18

The impact of snow depth, snow density and ice density on 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)

We assess different methods and input parameters, namely snow depth, snow density and ice density, used in freeboard-to-thickness conversion of Arctic sea ice. This conversion is an important part of sea ice thickness retrieval from spaceborne altimetry. A data base is created comprising sea ice freeboard derived from satellite radar altimetry between 1993 and 2012 and co-locate observations of total (sea ice + snow) and sea ice freeboard from the Operation Ice Bridge (OIB) and CryoSat Validation Experiment (CryoVEx) airborne campaigns, of sea ice draft from moored and submarine upward looking sonar (ULS), and of snow depth from OIB campaigns, Advanced Microwave Scanning Radiometer (AMSR-E) and the Warren climatology (Warren et al., 1999). We compare the different data sets in spatiotemporal scales where satellite radar altimetry yields meaningful results. An inter-comparison of the snow depth data sets emphasizes the limited usefulness of Warren climatology snow depth for freeboard-to-thickness conversion under current Arctic Ocean conditions reported in other studies. We test different freeboard-to-thickness and freeboard-to-draft conversion approaches. The mean observed ULS sea ice draft agrees with the mean sea ice draft derived from radar altimetry within the uncertainty bounds of the data sets involved. However, none of the approaches are able to reproduce the seasonal cycle in sea ice draft observed by moored ULS. A sensitivity analysis of the freeboard-to-thickness conversion suggests that sea ice density is as important as snow depth.

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

2015-01-01

19

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

20

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

21

Snow Dunes: A Controlling Factor of Melt Pond Distribution on Arctic Sea Ice  

NASA Technical Reports Server (NTRS)

The location of snow dunes over the course of the ice-growth season 2007/08 was mapped on level landfast first-year sea ice near Barrow, Alaska. Landfast ice formed in mid-December and exhibited essentially homogeneous snow depths of 4-6 cm in mid-January; by early February distinct snow dunes were observed. Despite additional snowfall and wind redistribution throughout the season, the location of the dunes was fixed by March, and these locations were highly correlated with the distribution of meltwater ponds at the beginning of June. Our observations, including ground-based light detection and ranging system (lidar) measurements, show that melt ponds initially form in the interstices between snow dunes, and that the outline of the melt ponds is controlled by snow depth contours. The resulting preferential surface ablation of ponded ice creates the surface topography that later determines the melt pond evolution.

Petrich, Chris; Eicken, Hajo; Polashenski, Christopher M.; Sturm, Matthew; Harbeck, Jeremy P.; Perovich, Donald K.; Finnegan, David C.

2012-01-01

22

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

23

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

24

A Comparison of Sea Ice Type, Sea Ice Temperature, and Snow Thickness Distributions in the Arctic Seasonal Ice Zones with the DMSP SSM/I  

NASA Technical Reports Server (NTRS)

Global climate studies have shown that sea ice is a critical component in the global climate system through its effect on the ocean and atmosphere, and on the earth's radiation balance. Polar energy studies have further shown that the distribution of thin ice and open water largely controls the distribution of surface heat exchange between the ocean and atmosphere within the winter Arctic ice pack. The thickness of the ice, the depth of snow on the ice, and the temperature profile of the snow/ice composite are all important parameters in calculating surface heat fluxes. In recent years, researchers have used various combinations of DMSP SSMI channels to independently estimate the thin ice type (which is related to ice thickness), the thin ice temperature, and the depth of snow on the ice. In each case validation efforts provided encouraging results, but taken individually each algorithm gives only one piece of the information necessary to compute the energy fluxes through the ice and snow. In this paper we present a comparison of the results from each of these algorithms to provide a more comprehensive picture of the seasonal ice zone using passive microwave observations.

St.Germain, Karen; Cavalieri, Donald J.; Markus, Thorsten

1997-01-01

25

Recent progress in snow and ice research  

Microsoft Academic Search

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

J. A. Richter-Menge; S. C. Colbeck; K. C. Jezek

1991-01-01

26

Simulated effects of a snow layer on retrieval of CryoSat-2 sea ice freeboard  

NASA Astrophysics Data System (ADS)

The impact of a snow layer on the location of the tracking point (RP) for ranging to the sea ice surface in CryoSat-2 synthetic aperture interferometric radar altimeter waveforms is simulated. With a range resolution of ~47 cm, the response of the air-snow (a-s) interface broadens the response of the snow-ice (s-i) interface and displaces the RP toward the altimeter. This effect is largest when the strengths of their returns are comparable and when snow thicknesses are >20 cm. On the other hand, the RP is displaced away from the altimeter when the reduced propagation speed in the snow layer is not accounted for. This analysis examines the dependence of these competing corrections on snow thickness and the relative scattering strengths of the interfaces and the sensitivity of two different tracking approaches (leading edge and centroid) to these snow parameters. Expected errors depend on a better understanding of the relative scattering strengths of the interfaces and snow layer.

Kwok, R.

2014-07-01

27

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

28

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

Microsoft Academic Search

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

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

2006-01-01

29

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

30

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

31

Snow and Ice: The Sequel  

NSDL National Science Digital Library

In this lesson, learners use WebImage, a Web-based customized version of ImageJ, to investigate changes in snow cover and sea ice in the Northern Hemisphere over a period of 24 years. The images are obtained from satellite measurements of visible and microwave radiation. The lesson follows from Snow and Ice: A Hemispherical View.

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

Recent Increases in Snow Accumulation and Decreases in Sea-Ice Concentration Recorded in a Coastal NW Greenland Ice Core  

NASA Astrophysics Data System (ADS)

A significant rise in summer temperatures over the past several decades has led to widespread retreat of the Greenland Ice Sheet (GIS) margin and surrounding sea ice. Recent observations from geodetic stations and GRACE show that ice mass loss progressed from South Greenland up to Northwest Greenland by 2005 (Khan et al., 2010). Observations from meteorological stations at the U.S. Thule Air Force Base, remote sensing platforms, and climate reanalyses indicate a 3.5C mean annual warming in the Thule region and a 44% decrease in summer (JJAS) sea-ice concentrations in Baffin Bay from 1980-2010. Mean annual precipitation near Thule increased by 12% over this interval, with the majority of the increase occurring in fall (SON). To improve projections of future ice loss and sea-level rise in a warming climate, we are currently developing multi-proxy records (lake sediment cores, ice cores, glacial geologic data, glaciological models) of Holocene climate variability and cryospheric response in NW Greenland, with a focus on past warm periods. As part of our efforts to develop a millennial-length ice core paleoclimate record from the Thule region, we collected and analyzed snow pit samples and short firn cores (up to 20 m) from the coastal region of the GIS (2Barrel site; 76.9317 N, 63.1467 W) and the summit of North Ice Cap (76.938 N, 67.671 W) in 2011 and 2012, respectively. The 2Barrel ice core was sampled using a continuous ice core melting system at Dartmouth, and subsequently analyzed for major anion and trace element concentrations and stable water isotope ratios. Here we show that the 2Barrel ice core spanning 1990-2010 records a 25% increase in mean annual snow accumulation, and is positively correlated (r = 0.52, p<0.01) with ERA-Interim precipitation. The 2Barrel annual sea-salt Na concentration is strongly correlated (r = 0.5-0.8, p<0.05) with summer and fall sea-ice concentrations in northern Baffin Bay near Thule (Figure 1). We hypothesize that the positive correlation represents a significant Na contribution from frost flowers growing on fall frazil ice. Ongoing analyses will evaluate the relationship between MSA concentrations and sea ice extent. Our results show that a deep ice core collected from this dynamic and climate-sensitive region of NW Greenland would produce a valuable record of late Holocene climate and sea ice extent.

Osterberg, E. C.; Thompson, J. T.; Wong, G. J.; Hawley, R. L.; Kelly, M. A.; Lutz, E.; Howley, J.; Ferris, D. G.

2013-12-01

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

Winter snow cover on the sea ice of the Arctic Ocean at the Surface Heat Budget of the Arctic Ocean (SHEBA)  

E-print Network

Winter snow cover on the sea ice of the Arctic Ocean at the Surface Heat Budget of the Arctic Ocean of the snow cover on the sea ice of the Arctic Ocean was observed during the Surface Heat Budget of the Arctic cover on the sea ice of the Arctic Ocean at the Surface Heat Budget of the Arctic Ocean (SHEBA

Sturm, Matthew

36

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

37

Soluble chromophores in marine snow, seawater, sea ice and frost flowers near Barrow, Alaska  

NASA Astrophysics Data System (ADS)

We measured light absorption in 42 marine snow, sea ice, seawater, brine, and frost flower samples collected during the OASIS field campaign between February 27 and April 15, 2009. Samples represented multiple sites between landfast ice and open pack ice in coastal areas approximately 5 km west of Barrow, Alaska. The chromophores that are most commonly measured in snow, H2O2, NO3-, and NO2-, on average account for less than 1% of sunlight absorption in our samples. Instead, light absorption is dominated by unidentified "residual" species, likely organic compounds. Light absorption coefficients for the frost flowers on first-year sea ice are, on average, 40 times larger than values for terrestrial snow samples at Barrow, suggesting very large rates of photochemical reactions in frost flowers. For our marine samples the calculated rates of sunlight absorption and OH production from known chromophores are (0.1-1.4) × 1014 (photons cm-3 s-1) and (5-70) × 10-12 (mol L-1 s-1), respectively. Our residual spectra are similar to spectra of marine chromophoric dissolved organic matter (CDOM), suggesting that CDOM is the dominant chromophore in our samples. Based on our light absorption measurements we estimate dissolved organic carbon (DOC) concentrations in Barrow seawater and frost flowers as approximately 130 and 360 ?M C, respectively. We expect that CDOM is a major source of OH in our marine samples, and it is likely to have other significant photochemistry as well.

Beine, Harry; Anastasio, Cort; Domine, Florent; Douglas, Thomas; Barret, Manuel; France, James; King, Martin; Hall, Sam; Ullmann, Kirk

2012-07-01

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

National Snow and Ice Data Center (NSIDC)  

NSDL National Science Digital Library

This site from NSIDC is a national information and referral center in support of polar and cryospheric research. It archives and distributes digital and analog snow and ice data and maintains information about snow cover, avalanches, glaciers, ice sheets, freshwater ice, sea ice, ground ice, permafrost, atmospheric ice, paleoglaciology, and ice cores. The site provides links to data products and services, sponsored activities, exploring the cryosphere and NSIDC history, photos, publications, and events.

The National Snow and Ice Data Center (NSIDC)

41

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

42

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

43

Snow and Ice Data Discovery and Access  

NSDL National Science Digital Library

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

National Snow and Ice Data Center

44

An AeroCom Assessment of Black Carbon in Arctic Snow and Sea Ice  

SciTech Connect

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.; Bellouin, N.; Berntsen, T.; Bian, Huisheng; Carslaw, K. S.; Chin, Mian; De Luca, N.; Diehl, Thomas; Ghan, Steven J.; Iversen, T.; Kirkevag, A.; Koch, Dorothy; Liu, Xiaohong; Mann, G. W.; Penner, Joyce E.; Pitari, G.; Schulz, M.; Seland, O.; Skeie, R. B.; Steenrod, Stephen D.; Stier, P.; Takemura, T.; Tsigaridis, Kostas; van Noije, T.; Yun, Yuxing; Zhang, Kai

2014-03-07

45

An AeroCom Assessment of Black Carbon in Arctic Snow and Sea Ice  

NASA Technical Reports Server (NTRS)

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 to 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 for an earlier phase of AeroCom models (phase I), and +4.1 (-13.0 to +21.4) ng/g for a more recent phase of AeroCom models (phase II), compared to the observational mean of 19.2 ng/g. 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 (60-90degN) 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/sq m and 0.18 (0.06-0.28) W/sq m 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/sq m 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.; Bernsten, T. K.; Bian, H.; Carslaw, K. S.; Chin, M.; DeLuca, N.; Diehl, T.; Ghan, S. J.; Iversen, T.; Kirkevag, A.; Koch, D.; Liu, X.; Mann, G. W.; Penner, J. E.; Pitari, G.; Schulz, M.; Seland, O; Skeie, R. B.; Steenrod, S. D.; Stier, P.; Tkemura, T.

2014-01-01

46

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.

Roger Barry

2001-09-15

47

The Role of Snow Thickness over Arctic Winter Sea Ice in the Survival and Dispersal of Brine-Derived Microbes  

NASA Astrophysics Data System (ADS)

The brines of polar winter sea ice are inhabited by significant densities of microbes (Bacteria and Archaea) that experience a range of extreme conditions depending on location in, and age of, the ice. Newly formed sea ice in winter expels microbes (and organic exudates) onto the surface of the ice, where they can be wicked into frost flowers or into freshly deposited snow, resulting in populations at the ice-air and air-snow interfaces characterized by even more extreme conditions. The influence of snow thickness over the ice on the fate of these microbes, and their potential for dispersal or mediation of exchanges with other components of the ice-snow system, is not well known. Examination of in situ temperature data from the Mass Balance Observatory (MBO) offshore of Barrow, Alaska, during the winter of 2011 allowed recognition of an hierarchy of fluctuation regimes in temperature and (by calculation) brine salinity, where the most stable conditions were encountered within the sea ice and the least stable highest in the snow cover, where temperature fluctuations were significantly more energetic as determined by an analysis of power spectral density. A prior analysis of snow thickness near the MBO had already revealed significant ablation events, potentially associated with bacterial mortality, that would have exposed the saline (microbe-rich) snow layer to wind-based dispersal. To better understand the survival of marine bacteria under these dynamic and extreme conditions, we conducted laboratory experiments with Arctic bacterial isolates, subjecting them to simulations of the freezing regimes documented at the MBS. The impact of the fluctuation regime was shown to be species-specific, with the organism of narrower temperature and salinity growth ranges suffering 30-50% mortality (which could be partially relieved by providing protection against salt-shock). This isolate, the psychrophilic marine bacterium Colwellia psychrerythraea strain 34H (temperature range of -12 to 18°C, salinity range of 20 to 50), was originally isolated from Arctic marine sediments. The other isolate, the psychrotolerant and extremely halophilic bacterium Psychrobacter sp. strain 7E (temperature range of -1 [possibly lower] to 25°C, salinity range of 32 to 125), not only survived the most extreme conditions but demonstrated a potentially effective dispersal strategy of cell fragmentation and miniaturization (resulting in higher cell numbers). This extremophile was isolated from upper winter sea-ice brine in the Beaufort Sea. Bacterial survival and dispersal from sea-ice brines in Arctic winter thus appears to depend on the nature of the organisms involved and on the thickness of snow cover, which determines how dynamic and extreme are the exposure conditions. The observed species-specific reactions to extreme and fluctuating conditions may help to explain the different structures of microbial communities inhabiting the range of environments defined by the ice-snow system and provide model organisms and research directions for future work to evaluate potential activity or exchanges with other components of the system.

Deming, J. W.; Ewert, M.; Bowman, J. S.

2013-12-01

48

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

49

A Comparison of Snow Depth on Sea Ice Retrievals Using Airborne Altimeters and an AMSR-E Simulator  

NASA Technical Reports Server (NTRS)

A comparison of snow depths on sea ice was made using airborne altimeters and an Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR-E) simulator. The data were collected during the March 2006 National Aeronautics and Space Administration (NASA) Arctic field campaign utilizing the NASA P-3B aircraft. The campaign consisted of an initial series of coordinated surface and aircraft measurements over Elson Lagoon, Alaska and adjacent seas followed by a series of large-scale (100 km ? 50 km) coordinated aircraft and AMSR-E snow depth measurements over portions of the Chukchi and Beaufort seas. This paper focuses on the latter part of the campaign. The P-3B aircraft carried the University of Colorado Polarimetric Scanning Radiometer (PSR-A), the NASA Wallops Airborne Topographic Mapper (ATM) lidar altimeter, and the University of Kansas Delay-Doppler (D2P) radar altimeter. The PSR-A was used as an AMSR-E simulator, whereas the ATM and D2P altimeters were used in combination to provide an independent estimate of snow depth. Results of a comparison between the altimeter-derived snow depths and the equivalent AMSR-E snow depths using PSR-A brightness temperatures calibrated relative to AMSR-E are presented. Data collected over a frozen coastal polynya were used to intercalibrate the ATM and D2P altimeters before estimating an altimeter snow depth. Results show that the mean difference between the PSR and altimeter snow depths is -2.4 cm (PSR minus altimeter) with a standard deviation of 7.7 cm. The RMS difference is 8.0 cm. The overall correlation between the two snow depth data sets is 0.59.

Cavalieri, D. J.; Marksu, T.; Ivanoff, A.; Miller, J. A.; Brucker, L.; Sturm, M.; Maslanik, J. A.; Heinrichs, J. F.; Gasiewski, A.; Leuschen, C.; Krabill, W.; Sonntag, J.

2011-01-01

50

4, 47374776, 2004 Sea salt in snow on  

E-print Network

ACPD 4, 4737­4776, 2004 Sea salt in snow on Arctic sea ice and in coastal regions F. Domine et al and Physics Discussions The origin of sea salt in snow on Arctic sea ice and in coastal regions F. Domine 1, 4737­4776, 2004 Sea salt in snow on Arctic sea ice and in coastal regions F. Domine et al. Title Page

Paris-Sud XI, Université de

51

Sea Ice  

NSDL National Science Digital Library

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

52

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

53

Whither Arctic Sea Ice?  

NSDL National Science Digital Library

In this activity students work with real datasets to investigate a real situation regarding disappearing Arctic sea ice. The case study has students working side-by-side with a scientist from the National Snow and Ice Data Center and an Inuit community in Manitoba.

Betsy Youngman

54

Snow and ice products from Suomi NPP VIIRS  

NASA Astrophysics Data System (ADS)

Visible Infrared Imager Radiometer Suite (VIIRS) instrument was launched in October 2011 on the satellite now known as the Suomi National Polar-orbiting Partnership. VIIRS was designed to improve upon the capabilities of the operational Advanced Very High Resolution Radiometer and provide observation continuity with NASA's Earth Observing System's Moderate Resolution Imaging Spectroradiometer (MODIS). VIIRS snow and ice products include sea ice surface temperature, sea ice concentration, sea ice characterization, a binary snow map, and fractional snow cover. Validation results with these "provisional" level maturity products show that ice surface temperature has a root-mean-square error of 0.6-1.0 K when compared to aircraft data and a similar MODIS product, the measurement accuracy and precision of ice concentration are approximately 5% and 15% when compared to passive microwave retrievals, and the accuracy of the binary snow cover (snow/no-snow) maps is generally above 90% when compared to station data. The ice surface temperature and snow cover products meet their accuracy requirements with respect to the Joint Polar Satellite System Level 1 Requirements Document. Sea Ice Characterization, which consists of two age categories, has not been observed to meet the 70% accuracy requirements of ice classification. Given their current performance, the ice surface temperature, snow cover, and sea ice concentration products should be useful for both research and operational applications, while improvements to the sea ice characterization product are needed before it can be used for these applications.

Key, Jeffrey R.; Mahoney, Robert; Liu, Yinghui; Romanov, Peter; Tschudi, Mark; Appel, Igor; Maslanik, James; Baldwin, Dan; Wang, Xuanji; Meade, Paul

2013-12-01

55

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

56

AMSR-E Algorithm Theoretical Basis Document: Sea Ice Products  

E-print Network

1 AMSR-E Algorithm Theoretical Basis Document: Sea Ice Products Thorsten Markus and Donald J 20771 1. Overview The AMSR-E sea ice standard level 3 products include sea ice concentration, sea ice temperature, and snow depth on sea ice. The AMSR-E standard sea ice concentration product is generated using

Waliser, Duane E.

57

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

58

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

59

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 source for operational sea-ice monitoring. However, the sea ice microwave emissivity is subject to pronounced seasonal variations and shows significant hemispheric contrasts that mainly arise from differences in the rate and strength of snow metamorphism and melt. We use the thermodynamic snow model SNTHERM and the microwave emission model MEMLS to identify the contribution of regional patterns in atmospheric energy fluxes to surface emissivity variations on Arctic and Antarctic sea ice between 2000 and 2009. The obtained emissivity data reveal a pronounced seasonal cycle with a 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 variations in surface microwave emissivity due to diurnal, regional and inter-annual variability of atmospheric forcing reach up to 3.4%, 4.3%, and 9.7% for 19 GHz, 37 GHz and 85 GHz channels, respectively. Small but significant emissivity trends can be observed in the Weddell Sea during November and December as well as in Fram Strait during February. The obtained emissivity data lend themselves for an assessment of sea-ice concentration and snow-depth algorithm accuracies.

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

2013-12-01

60

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

61

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

62

Rubber friction on ice and snow surfaces   

E-print Network

The friction of rubber on ice and snow surfaces is complex. Deeper scientific understanding is important for optimising performance of tyres in winter. Rubber, ice and snow systems exhibit frictional behaviour which ...

Skouvaklis, Gerasimos

2011-06-28

63

Frost flowers growing in the Arctic ocean-atmosphere-sea ice-snow interface: 1. Chemical composition  

NASA Astrophysics Data System (ADS)

Frost flowers, intricate featherlike crystals that grow on refreezing sea ice leads, have been implicated in lower atmospheric chemical reactions. Few studies have presented chemical composition information for frost flowers over time and many of the chemical species commonly associated with Polar tropospheric reactions have never been reported for frost flowers. We undertook this study on the sea ice north of Barrow, Alaska to quantify the major ion, stable oxygen and hydrogen isotope, alkalinity, light absorbance by soluble species, organochlorine, and aldehyde composition of seawater, brine, and frost flowers. For many of these chemical species we present the first measurements from brine or frost flowers. Results show that major ion and alkalinity concentrations, stable isotope values, and major chromophore (NO3- and H2O2) concentrations are controlled by fractionation from seawater and brine. The presence of these chemical species in present and future sea ice scenarios is somewhat predictable. However, aldehydes, organochlorine compounds, light absorbing species, and mercury (part 2 of this research and Sherman et al. (2012)) are deposited to frost flowers through less predictable processes that probably involve the atmosphere as a source. The present and future concentrations of these constituents in frost flowers may not be easily incorporated into future sea ice or lower atmospheric chemistry scenarios. Thinning of Arctic sea ice will likely present more open sea ice leads where young ice, brine, and frost flowers form. How these changing ice conditions will affect the interactions between ice, brine, frost flowers and the lower atmosphere is unknown.

Douglas, Thomas A.; Domine, Florent; Barret, Manuel; Anastasio, Cort; Beine, Harry J.; Bottenheim, Jan; Grannas, Amanda; Houdier, Stephan; Netcheva, Stoyka; Rowland, Glenn; Staebler, Ralf; Steffen, Alexandra

2012-07-01

64

Snow Ice Crystals  

NSDL National Science Digital Library

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

Furukawa, Y.

65

AIRPORT SNOW AND ICE CONTROL Session Highlights  

E-print Network

AIRPORT SNOW AND ICE CONTROL Session Highlights In September and October of 2003, AirTAP once again sponsored working sessions--one in Rochester and another in Park Rapids--on airport snow and ice control his thoughts on the responsibility of the airport operator regarding snow and ice control. Air

Minnesota, University of

66

Fluffy Snow to Glacier Ice  

NSDL National Science Digital Library

In this activity, students build on their growing knowledge of ice and glacier growth. The students examine images of core samples and make observations about the decreasing size of gas bubbles with increasing depth in the core. The students model permeability. From this experiment, they will develop an understanding of the movement of air through snow and ice and why this information is critical to researchers studying the past climate of our Earth.

Sharon Shutey

67

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

68

NASA Sea Ice and Snow Validation Program for the DMSP SSM/I: NASA DC-8 flight report  

NASA Technical Reports Server (NTRS)

In June 1987 a new microwave sensor called the Special Sensor Microwave Imager (SSM/I) was launched as part of the Defense Meteorological Satellite Program (DMSP). In recognition of the importance of this sensor to the polar research community, NASA developed a program to acquire the data, to convert the data into sea ice parameters, and finally to validate and archive both the SSM/I radiances and the derived sea ice parameters. Central to NASA's sea ice validation program was a series of SSM/I aircraft underflights with the NASA DC-8 airborne Laboratory. The mission (the Arctic '88 Sea Ice Mission) was completed in March 1988. This report summarizes the mission and includes a summary of aircraft instrumentation, coordination with participating Navy aircraft, flight objectives, flight plans, data collected, SSM/I orbits for each day during the mission, and lists several piggyback experiments supported during this mission.

Cavalieri, D. J.

1988-01-01

69

National Snow and Ice Data Center  

NSDL National Science Digital Library

Established by the National Oceans and Atmospheric Administration (NOAA) in 1982 as an information and referral center for glaciological research, the National Snow and Ice Data Center (NSIDC) maintains data information on "snow cover and avalanches, glaciers and ice sheets, floating ice, ground ice and permafrost, atmospheric ice, paleoglaciology and ice cores." In addition to its role as an information resource, NSIDC "archives analogue and digital snow and ice data, creates and distributes data products, and maintains a large library collection in support of snow and ice research." From Global Annual Freezing and Thawing Indices to the Former Soviet Union Monthly Precipitation Archive, users may explore myriad snow and ice data. For information on current research and available data, or answers to frequently asked questions, see the NSIDC's Notes and Updates sections.

National Snow and Ice Data Center (U.S)

1997-01-01

70

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

71

National Snow and Ice Data Center: All About Snow  

NSDL National Science Digital Library

The National Snow and Ice Data Center (NSIDC) provides innumerable educational materials about snow at this website. Students can find answers to many of their snow questions in the Q & A link. The site features remarkable pictures of blizzards and snow. Users can find an enlightening account about how early settlers dealt with snow in the Midwest and Northeast United States. The Avalanche Awareness link addresses common concerns about the causes, dangers, anatomy, and locations of avalanches. The website also offers numerous links to educational, data collections, and snow science sites.

72

Albedo evolution of seasonal Arctic sea ice  

NASA Astrophysics Data System (ADS)

There is an ongoing shift in the Arctic sea ice cover from multiyear ice to seasonal ice. Here we examine the impact of this shift on sea ice albedo. Our analysis of observations from four years of field experiments indicates that seasonal ice undergoes an albedo evolution with seven phases; cold snow, melting snow, pond formation, pond drainage, pond evolution, open water, and freezeup. Once surface ice melt begins, seasonal ice albedos are consistently less than albedos for multiyear ice resulting in more solar heat absorbed in the ice and transmitted to the ocean. The shift from a multiyear to seasonal ice cover has significant implications for the heat and mass budget of the ice and for primary productivity in the upper ocean. There will be enhanced melting of the ice cover and an increase in the amount of sunlight available in the upper ocean.

Perovich, Donald K.; Polashenski, Christopher

2012-04-01

73

Sea Ice, an Antarctic Habitat  

NSDL National Science Digital Library

A 'click-and-learn' sub site hosted by the Alfred Wegener Institute Foundation for Polar and Marine Research (AWI), this is a succinct, educational tour of sea-ice and its associated ecological communities. Short synopses introduce the dynamics of sea-ice formation, the microstructure of sea-ice (including crystal structure, brine channels, and ice algae), the effects of ice melt on resident organisms, the logistics of sea-ice research, and _land fast-ice_ and platelet ice habitats. Introductions also exist for the following organisms: krill; whales (i.e., Orcas, southern bottlenosesd dolphins, minke whales); sea birds (i.e., skuas and snow petrals), penguins (i.e., emperor, adelie, and chinstraps), and seals (i.e., weddell, crabeater, leopard, and ross.) Enlargeable thumbnail images accompany the habitat and inhabitant descriptions. Further investigations (at an accelerated level) are prompted with the inclusion of bibliographic references and scientific research presentations (in PDF format) on fast-ice and platelet ice, as well as links to the main site for the AWI.

74

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.

Alan Gould

75

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

76

2013 Arctic Sea Ice Minimum - Duration: 0:27.  

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 ...

77

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

78

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

79

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

80

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

81

Some Results from a Time-Dependent Thermodynamic Model of Sea Ice  

Microsoft Academic Search

A one-dimensional thermodynamic model of sea ice is presented that includes the effects of snow cover, ice salinity, and internal heating due to penetration of solar radiation. Surfaceenergy balances determine rates of ablation and accretion; diffusion equations govern heat transport within the ice and snow. The incoming radiative and turbulent fluxes, oceanic heat flux, ice salinity, snow accumulation, and surface

Gary A. Maykut; Norbert Untersteiner

1971-01-01

82

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.

2012-08-03

83

An optical model for the microwave properties of sea ice  

NASA Technical Reports Server (NTRS)

The complex refractive index of sea ice is modeled and used to predict the microwave signatures of various sea ice types. Results are shown to correspond well with the observed values of the complex index inferred from dielectic constant and dielectric loss measurements performed in the field, and with observed microwave signatures of sea ice. The success of this modeling procedure vis a vis modeling of the dielectric properties of sea ice constituents used earlier by several others is explained. Multiple layer radiative transfer calculations are used to predict the microwave properties of first-year sea ice with and without snow, and multiyear sea ice.

Gloersen, P.; Larabee, J. K.

1981-01-01

84

Sea ice in the China Sea  

SciTech Connect

In every winter, sea ice occurring in Bohai Sea and the North Yellow Sea is the first-year ice which is going through generating, developing and thawing processes. Therefore, it is necessary to spatially and temporally describe ice period, freezing range, thickness variations and general motion of sea ice. The purpose of this paper is to provide initial general situation and features of sea ice for forecasting and researching sea ice.

Deng Shuqi [National Research Center for Marine Environmental Forecasts, Beijing (China)

1993-12-31

85

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

86

Sea ice pCO2 dynamics and air-ice CO2 fluxes during the Sea Ice Mass Balance in the Antarctic (SIMBA) experiment - Bellingshausen Sea, Antarctica  

NASA Astrophysics Data System (ADS)

Temporal evolution of pCO2 profiles in sea ice in the Bellingshausen Sea, Antarctica, in October 2007 shows physical and thermodynamic processes controls the CO2 system in the ice. During the survey, cyclical warming and cooling 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 show 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 reduced the amplitude of these changes: snow cover influences the sea ice carbonate system by modulating the temperature and therefore the salinity of the sea ice cover. Results indicate that pCO2 was undersaturated with respect to the atmosphere both in the in situ bulk ice (from 10 to 193 ?atm) and brine (from 65 to 293 ?atm), causing the sea ice to act as a sink for atmospheric CO2 (up to 2.9 mmol m-2 d-1), despite supersaturation of the underlying seawater (up to 462 ?atm).

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

2014-12-01

87

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

88

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

89

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

90

Antarctica: Sea Ice  

NSDL National Science Digital Library

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

91

Modelling of Superimposed Ice Formation and SubSurface Melting in the Baltic Sea  

Microsoft Academic Search

Superimposed ice formation and sub-surface melting were modelled using a one-dimensional thermodynamic sea ice model with the Baltic Air-Sea-Ice Study (BASIS) field data. During a thermal equilibrium stage in winter 1997\\/98, ice showed little mass change at the ice-water interface. The observations indicated snow-to-ice transformation at the snow-ice interface. Numerical modelling suggested that the re-freezing of the surface melt water

Bin Cheng; Jouko Launianen; Timo Vihma

92

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

93

14 CFR 139.313 - Snow and ice control.  

Code of Federal Regulations, 2013 CFR

...2013-01-01 2013-01-01 false Snow and ice control. 139.313 Section 139.313...AIRPORTS Operations § 139.313 Snow and ice control. (a) As determined by the...prepare, maintain, and carry out a snow and ice control plan in a manner authorized by...

2013-01-01

94

14 CFR 139.313 - Snow and ice control.  

Code of Federal Regulations, 2014 CFR

...2014-01-01 2014-01-01 false Snow and ice control. 139.313 Section 139.313...AIRPORTS Operations § 139.313 Snow and ice control. (a) As determined by the...prepare, maintain, and carry out a snow and ice control plan in a manner authorized by...

2014-01-01

95

14 CFR 139.313 - Snow and ice control.  

Code of Federal Regulations, 2012 CFR

...2012-01-01 2012-01-01 false Snow and ice control. 139.313 Section 139.313...AIRPORTS Operations § 139.313 Snow and ice control. (a) As determined by the...prepare, maintain, and carry out a snow and ice control plan in a manner authorized by...

2012-01-01

96

14 CFR 139.313 - Snow and ice control.  

Code of Federal Regulations, 2011 CFR

...2011-01-01 2011-01-01 false Snow and ice control. 139.313 Section 139.313...AIRPORTS Operations § 139.313 Snow and ice control. (a) As determined by the...prepare, maintain, and carry out a snow and ice control plan in a manner authorized by...

2011-01-01

97

Snow and Ice: A Hemispherical View  

NSDL National Science Digital Library

In this lesson, learners compare snow and ice cover in the Northern Hemisphere over a period of two years. The images are obtained from measurements of visible and microwave radiation taken by satellites and sent back to Earth and are analyzed with a customized version of ImageJ running as an applet within a browser.

98

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

99

Record Sea Ice Minimum  

NASA Technical Reports Server (NTRS)

Arctic sea ice reached a record low in September 2007, below the previous record set in 2005 and substantially below the long-term average. This image shows the Arctic as observed by the Advanced Microwave Scanning Radiometer for EOS (AMSR-E) aboard NASA's Aqua satellite on September 16, 2007. In this image, blue indicates open water, white indicates high sea ice concentration, and turquoise indicates loosely packed sea ice. The black circle at the North Pole results from an absence of data as the satellite does not make observations that far north. Three contour lines appear on this image. The red line is the 2007 minimum, as of September 15, about the same time the record low was reached, and it almost exactly fits the sea ice observed by AMSR-E. The green line indicates the 2005 minimum, the previous record low. The yellow line indicates the median minimum from 1979 to 2000.

2007-01-01

100

Albedo of the ice covered Weddell and Bellingshausen Seas  

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

101

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.

102

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

103

The role of snow-surface coupling, radiation, and turbulent mixing in modeling a stable boundary layer over Arctic sea ice  

NASA Astrophysics Data System (ADS)

To enhance the understanding of the impact of small-scale processes in the polar climate, this study focuses on the relative role of snow-surface coupling, radiation and turbulent mixing in an Arctic stable boundary layer. We extend the GABLS1 (GEWEX Atmospheric Boundary-Layer Study 1) model intercomparison for turbulent mixing with the other relevant physical processes in the stable boundary layer over sea ice. We use the Single Column Model (SCM) version of the Weather Research and Forecasting (WRF) mesoscale meteorological model and run different combinations of boundary layer and radiation schemes, using a state-of-the art land surface scheme. With this intercomparison of schemes, we confirm a wide variety in the state of the atmosphere and the surface variables for the selected parameterization schemes. To understand this variety, a sensitivity analysis for one particular combination of parameterization schemes is performed, using a novel analysis method of process diagrams. The variation between the sensitivity runs indicates a relative orientation of model sensitivities to variations in each of the governing processes and these can explain the variety of model results obtained in the intercomparison of different parameterization schemes. Moreover, we apply the same method for several geostrophic wind speeds to represent a large range of synoptic conditions. Results indicate a shift in process significance for different wind regimes. For low wind regimes, the model sensitivity is larger for surface coupling and radiation, while for high wind speeds, the largest sensitivity is found for the turbulent mixing process. An interesting non-linear feature was found for turbulent mixing for frequently occurring wind speeds and low wind speed cases, where the 2 m temperature increases for decreased amounts of mixing.

Sterk, H. A. M.; Steeneveld, G. J.; Holtslag, A. A. M.

2013-02-01

104

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. PMID:14699053

Hansen, James; Nazarenko, Larissa

2004-01-01

105

2 Internal melting in Antarctic sea ice: Development of ``gap layers'' 3 S. F. Ackley,1  

E-print Network

of the snow cover, followed by melt pond formation on 50 top of the ice is the dominant surface characteristic of Arctic 51summer sea ice [Perovich et al., 2002]. Melt ponds are not 52often observed on Antarctic sea ice accelerate melting by 63increasing the absorption of solar radiation within the sea 64ice. Algal blooms

Texas at San Antonio, University of

106

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.

Beverly L. Meier

2012-06-26

107

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.

108

Sea-ice Environmental Research Facility  

NASA Astrophysics Data System (ADS)

The Sea-ice Environmental Research Facility (SERF) is the first experimental sea-ice facility in Canada. Located in Winnipeg on the campus of the University of Manitoba, the main feature of SERF is an outdoor seawater pool (60 feet long, 30 feet wide and 8 feet deep) with a movable roof, numerous in situ sensors and instruments, and an on site trailer laboratory. Sea ice can be created at the pool under various controlled conditions (e.g., seawater chemistry, snow cover, heating) with the additions of chemical, isotopic and/or microbiological tracers. During the 2011-2012 inaugural year of operation, several types of sea ice including pancake ice and frost flowers were successfully created at the SERF pool. Real-time monitoring was carried out on surface and optical properties and on the evolution of temperature, salinity, dissolved oxygen, pH, alkalinity, pCO2, and mercury in and across the sea ice environment. The results demonstrate that SERF could provide a unique research platform for hypothesis-driven, mesocosm-scale studies to examine geophysical properties and biogeochemical processes in the sea ice environment.

Rysaard, S.; Wang, F.; Papakyriakou, T. N.; Barber, D. G.

2012-12-01

109

Superimposed ice formation and surface energy fluxes on sea ice during the spring melt freeze period in the Baltic Sea  

NASA Astrophysics Data System (ADS)

The development of land-fast sea ice and overlying snow was monitored during a 4 week period, until the snow cover had completely disappeared, at a site in the Gulf of Bothnia, Baltic Sea (63.57° N, 19.85° E). The meteorological and radiative boundary conditions were continuously recorded. During the observation period, a 15 cm thick snow layer on the ice was transformed into a 7 cm thick granular ice layer (superimposed ice) on the ice surface, contributing significantly (about 11%) to the total ice thickness. Approximately 1 cm w.e. of the snow was sublimated. Neither snow-ice formation nor basal ice growth was significant during the same period. The salinity and isotopic (?18O) composition of the ice indicated that prior to the experiment a 7 cm layer of superimposed ice had already formed. Hence, superimposed ice layers contributed 22% of the total ice thickness by the time all snow had disappeared. The advancing spring, decrease in surface albedo, diurnal cycle in the incoming solar radiation, and synoptic-scale changes in the cloud cover and the air ice turbulent heat fluxes caused variations in the heat budget of the snowpack. Superimposed ice formation due to refreezing of meltwater occurred during most nights of the study period, and the most important refreezing periods were under such synoptic conditions that the air and snow surface temperatures also remained below zero during daytime. In contrast to typical summer conditions in polar oceans, low snow surface temperatures acted as the primary heat sink for the refreezing of meltwater.

Granskog, Mats A.; Vihma, Timo; Pirazzini, Roberta; Cheng, Bin

110

Anomalous snow accumulation over the southeast region of the Greenland ice sheet during 2002-2003 snow season  

NASA Technical Reports Server (NTRS)

Our objective is to determine seasonal snow accumulation in the percolation zone of the Greenland ice sheet on the daily-weekly basis over the large scale. Our approach utilizes data from the Greenland Climate Network (GC-Net) and from the SeaWinds Scatterometer on the QuikSCAT satellite (QSCAT) to measure snow accumulation (SA) in the percolation zone of the Greenland ice sheet. GC-Net measurements provide crucial in-situ data to facilitate the interpretation of QSCAT backscatter signature for the development of an algorithm to map SA.

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

2005-01-01

111

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

NASA Astrophysics Data System (ADS)

The amount of solar radiation transmitted through Arctic sea ice is determined by the thickness and physical properties of snow and sea ice. Light transmittance is highly variable in space and time since thickness and physical properties of snow and sea ice are highly heterogeneous on variable time and length scales. We present field measurements of under-ice irradiance along transects under undeformed land-fast sea ice at Barrow, Alaska (March, May, and June 2010). The measurements were performed with a spectral radiometer mounted on a floating under-ice sled. The objective was to quantify the spatial variability of light transmittance through snow and sea ice, and to compare this variability along its seasonal evolution. Along with optical measurements, snow depth, sea ice thickness, and freeboard were recorded, and ice cores were analyzed for chlorophyll a and particulate matter. Our results show that snow cover variability prior to onset of snow melt causes as much relative spatial variability of light transmittance as the contrast of ponded and white ice during summer. Both before and after melt onset, measured transmittances fell in a range from one third to three times the mean value. In addition, we found a twentyfold increase of light transmittance as a result of partial snowmelt, showing the seasonal evolution of transmittance through sea ice far exceeds the spatial variability. However, prior melt onset, light transmittance was time invariant and differences in under-ice irradiance were directly related to the spatial variability of the snow cover.

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

2013-06-01

112

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

NASA Astrophysics Data System (ADS)

Sea 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

113

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

114

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.

WGBH Educational Foundation Teachers' Domain

115

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.

2007-01-01

116

Albedo of the ice-covered Weddell and Bellingshausen Sea  

NASA Astrophysics Data System (ADS)

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

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

2011-11-01

117

Beyond Point Measurements: Sea Ice Floes Characterized in 3-D  

NASA Astrophysics Data System (ADS)

A new methodology for coincident floe-scale measurements of the surface elevation, snow depth, and ice draft (the thickness below the water line) of Antarctic sea ice has been demonstrated during two recent research voyages: the Australian-led Sea Ice Physics and Ecosystem Experiment II (SIPEX II) to East Antarctica in September-November 2012 and the United Kingdom-led Ice Mass Balance in the Bellingshausen Sea (ICEBell) voyage to the Weddell and Bellingshausen Seas in November 2010 (Figure 1a).

Williams, Guy D.; Maksym, Ted; Kunz, Clayton; Kimball, Peter; Singh, Hanumant; Wilkinson, Jeremy; Lachlan-Cope, Tom; Trujillo, Ernesto; Steer, Adam; Massom, Rob; Meiners, Klaus; Heil, Petra; Lieser, Jan; Leonard, Katherine

2013-02-01

118

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

119

Recent variations of sea ice and air temperature in high latitudes  

Microsoft Academic Search

Feedbacks resulting from the retreat of sea ice and snow contribute to the polar amplification of the greenhouse warming projected by global climate models. A gridded sea-ice database, for which the record length is now approaching four decades for the Arctic and two decades for the Antarctic, is summarized here. The sea-ice fluctuations derived from the data set are characterized

William L. Chapman; John E. Walsh

1993-01-01

120

A continuum model of melt pond evolution on Arctic sea ice Daniela Flocco1  

E-print Network

A continuum model of melt pond evolution on Arctic sea ice Daniela Flocco1 and Daniel L. Feltham1 the Northern Hemisphere summer, absorbed solar radiation melts snow and the upper surface of Arctic sea ice to generate meltwater that accumulates in ponds. The melt ponds reduce the albedo of the sea ice cover during

Feltham, Daniel

121

Amundsen Sea sea-ice variability, atmospheric circulation, and spatial variations in snow isotopic composition from new West Antarctic firn cores  

E-print Network

Recent work has documented dramatic changes in the West Antarctic Ice Sheet (WAIS) over the past 30 years (e.g., mass loss, glacier acceleration, surface warming) due largely to the influence of the marine environment. ...

Criscitiello, Alison Sara

2014-01-01

122

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

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

123

Atmospheric mercury over sea ice during the OASIS-2009 campaign  

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

124

Remote sensing as a research tool. [sea ice surveillance from aircraft and spacecraft  

NASA Technical Reports Server (NTRS)

The application of aircraft and spacecraft remote sensing techniques to sea ice surveillance is evaluated. The effects of ice in the air-sea-ice system are examined. The measurement principles and characteristics of remote sensing methods for aircraft and spacecraft surveillance of sea ice are described. Consideration is given to ambient visible light, IR, passive microwave, active microwave, and laser altimeter and sonar systems. The applications of these systems to sea ice surveillance are discussed and examples are provided. Particular attention is placed on the use of microwave data and the relation between ice thickness and sea ice interactions. It is noted that spacecraft and aircraft sensing techniques can successfully measure snow cover; ice thickness; ice type; ice concentration; ice velocity field; ocean temperature; surface wind vector field; and air, snow, and ice surface temperatures.

Carsey, F. D.; Zwally, H. J.

1986-01-01

125

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

126

Numerical modeling of sea ice in the climate system  

E-print Network

of ice and snow changes the way of life for humans, plants, and animals and amplifies the climate, University of Washington Worldwide emissions of CO2 from human energy-related activities are currently about modeling exercises that I led at the summer school. I will begin part one with a brief history of sea ice

Bitz, Cecilia

127

Numerical modeling of sea ice in the climate system  

E-print Network

of ice and snow changes the way of life for humans, plants, and animals and amplifies the climate, University of Washington Worldwide emissions of CO2 from human energy-related activities are currently about begin in part one with a brief history of sea ice modeling in climate models. Next, I lay out

Bitz, Cecilia

128

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

129

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

130

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

131

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

NASA Astrophysics Data System (ADS)

We evaluated the impact of subgrid-scale ice thickness distribution on the heat flux on and through sea ice in a numerical model. An ice-ocean coupled model with a subgrid-scale ice thickness distribution scheme, COCO4.5, is forced by an atmospheric climatology to simulate the present state of the sea ice and ocean. The modeled climatology reproduces the ice cover reasonably well with a realistic ice thickness distribution. The heat flux on and through the sea ice is established using the grid-averaged sea-ice and snow-on-ice thickness from the results of the simulation. When the grid-averaged thickness is calculated as a weighted arithmetic mean, the conductive heat flux through the ice and snow is underestimated compared with that actually driving the model. This underestimation becomes smaller in magnitude when either a weighted harmonic mean or a weighted arithmetic mean with a modification based on the ratio of these two types of means is used. Rearrangement of the ice categories shows that the flux bias decreases with an increase in the number of categories. We also perform a sensitivity experiment in which the model is forced by the biased heat flux identified using the arithmetic mean of the ice thickness. A significant decrease in ice volume is found, notably in the Arctic Ocean. These results suggest that sea-ice models without an ice thickness distribution scheme underestimate the conductive heat flux through ice, and thereby the resultant sea-ice thickness, because the ice thickness from these models typically corresponds to the weighted arithmetic mean thickness.

Komuro, Yoshiki; Suzuki, Tatsuo

2013-11-01

132

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

133

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

134

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

135

Selection of Effective and Efficient Snow Removal and Ice Control Technologies for Cold Region Bridges  

Microsoft Academic Search

In cold regions, snow and ice pose serious hazards to motorists. In order to minimize their detrimental effects caused by snow and ice on roadways, snow removal and ice control measures are necessary. So far, there is no single solution for snow and ice control on roadways. The aim of this work is to provide a procedure of selection of

Jing Zhang; Debendra K. Das; Rorik Peterson

136

Modeling the winter-spring transition of first-year ice in the western Weddell Sea  

NASA Astrophysics Data System (ADS)

A new halodynamic scheme is coupled with the Los Alamos sea ice model to simulate western Weddell Sea ice during the winter-spring transition. One-dimensional temperature and salinity profiles are consistent with the warming and melt stages exhibited in first-year ice cores from the 2004 Ice Station POLarstern (ISPOL) expedition. Results are highly sensitive to snowfall. Simulations which use reanalysis precipitation data do not retain a snow cover beyond mid-December, and the warming transition occurs too rapidly. Model performance is greatly improved by prescribing a snowfall rate based on reported snow thicknesses. During ice growth prior to ISPOL, simulations indicate a period of thick snow and upper ice salinity enrichment. Gravity drainage model parameters impact the simulation immediately, while effects from the flushing parameter (snow porosity at the ice top) appear as the freeboard becomes negative. Simulations using a snow porosity of 0.3, consistent with that of wet snow, agree with salinity observations. The model does not include lateral sources of sea-water flooding, but vertical transport processes account for the high upper-ice salinities observed in ice cores at the start of the expedition. As the ice warms, a fresh upper-ice layer forms, and the high salinity layer migrates downward. This pattern is consistent with the early spring development stages of high-porosity layers observed in Antarctic sea ice that are associated with rich biological production. Future extensions of the model may be valuable in Antarctic ice-biogeochemical applications.

Jeffery, N.; Hunke, E. C.

2014-09-01

137

Surface albedo measurements over sea ice in the Baltic Sea during the spring snowmelt period  

NASA Astrophysics Data System (ADS)

The snow/ice albedo was studied during a 4 week field experiment over first-year sea ice in the Gulf of Bothnia, Baltic Sea, in spring 2004. Observations were made on radiative fluxes, cloud cover, wind, air temperature and humidity, as well as snow/ice temperature, thickness, density and grain size. The albedo variation during the observation period was large: the daily mean albedo ranged from 0.79 over a new snow cover to 0.30 over bare, melting ice. The evolution of the albedo was related to the surface properties, but existing parameterizations based on Arctic data did not explain the observations well. The snow thickness was found to be the most critical factor affecting the albedo. A new parameterization was derived for the albedo dependence on snow thickness, to be applied over the Baltic Sea in spring, when periods of melting and freezing alternate but the ice is still relatively thick (about 0.6 m). The diurnal cycle of solar radiation was large, and the snow/ice metamorphism due to the melting during daylight and refreezing during the night caused a diurnal albedo cycle with a maximum in the early morning and a minimum in the afternoon, with an albedo difference up to 0.14 between the two.

Pirazzini, Roberta; Vihma, Timo; Granskog, Mats A.; Cheng, Bin

138

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

139

Radiative Energy Disposition in the Coupled Atmosphere-Snow-Ice-Ocean System  

NASA Astrophysics Data System (ADS)

The radiative interaction between the atmosphere and the surface is a factor of paramount importance in the Arctic where the net radiation is the largest component of the surface energy budget. The effect of clouds on the surface energy budget has important implications for the extension of the polar ice cover, which is highly sensitive to the surface irradiance. Also, the cloud cover is very important for the primary production, since it regulates the amount of light available for photosynthesis. Solar radiation affects snow metamorphism, which reduces the surface albedo, leading to further metamorphism (grain growth), increased snow temperature and reduction in snow and ice thicknesses (surface albedo feedback mechanism). Changes in the thickness of snow and sea ice will change the optical properties of the snow and ice system and hence cause a change in the amount of UV radiation and Photosynthetically Available Radiation (PAR) reaching the aquatic environment. Furthermore, a potential increase in ice temperature will change its transparency due to melting and enlargement of brine pockets. Accurate modelling of irradiances in snow and ice requires sophisticated methods. It is very important to take into account the tight radiative coupling between the atmosphere and the snow-sea ice-ocean system, and also the change in refractive index that occurs at the interface between the atmosphere/snow and sea ice/ocean. Such coupling effects may cause the downward irradiance to increase by 75% just beneath the air-ice interface, and the enhancement is much larger under clear sky than under cloudy conditions. A combination of field measurements, state-of-the-art radiative transfer modelling, and satellite data is required to enhance our understanding of the disposition of solar energy in this coupled system. The purpose of this presentation is to outline studies including field measurements and modeling required to quantify cloud-radiation-surface interactions and feedbacks, so as to enhance our understanding of the solar energy disposition in this coupled system, and how it affects climate evolution, and primary production in the polar regions, and the Arctic in particular.

Stamnes, K.; Hamre, B.; Gerland, S.; Eide, H.; Frette, O.; Stamnes, J. J.

2005-05-01

140

Spatial Variability of Light Transmittance through Arctic Sea Ice in Summer  

NASA Astrophysics Data System (ADS)

The amount of solar light transmitting through snow and sea ice is of critical importance for various physical and biological processes in the sea ice and the uppermost ocean. The vertical partitioning of short-wave radiation between atmosphere, snow, sea ice, and ocean affects freezing and melting at the sea-ice bottom as well as the timing and amount of biological processes, particularly primary production. Due to their different absorption spectra, snow, sea ice, sea water, biota, sediments, and impurities affect the spectral composition of the light in its way from the atmosphere into the ocean. Measuring spectral short-wave irradiance synchronously under and above sea ice enables distinguishing the different components that influence under-ice irradiance and the quantification of their importance. The number of studies of spectral irradiance measurements under sea ice has increased during the last years. However, observations that allow insights into the spatial variability of under-ice irradiance are still sparse, and little is known about how light conditions change on different scales from meters to kilometers. We have measured spectral irradiance (350 to 920 nm) synchronously under and above Arctic sea ice in summer 2011. Our optical measurements were co-located with observations of various physical sea-ice and snow properties and additional biological sampling. In order to assess the spatial variability on different scales, we have operated the radiometer on a remotely operated vehicle (ROV) below the ice surface. Launching the ROV from different ice floes in the central Arctic allowed us to study various snow and ice conditions, also including melt ponds and open leads. Analyzing the horizontal transects reveals the spatial variability of light conditions as a function of snow cover, sediment load, and biomass.

Nicolaus, M.; Katlein, C.; Hoppmann, M.; Hendricks, S.

2011-12-01

141

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

142

Winter Ice and Snow as Models of Igneous Rock Formation.  

ERIC Educational Resources Information Center

Examines some features of ice and snow that offer teachers and researchers help in understanding many aspects of igneous processes and configurations. Careful observation of such processes as melting, decay, evolution, and snow accumulation provide important clues to understanding processes by which many kinds of rocks form. (Author/JN)

Romey, William D.

1983-01-01

143

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

144

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

145

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

146

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

147

A Low Frequency Radar for Direct Measurement of Sea Ice Thickness: Implications of Ice Surface Roughness  

NASA Astrophysics Data System (ADS)

Sea ice thickness is thought to be a primary indicator of global greenhouse warming, yet it has proven to be one of the most difficult variables to measure particularly on meaningful synoptic and climatic scales, including from satellites. An instrument concept study and associated field experiment system development are underway to measure the sea ice thickness directly with VHF radar. This system precludes the use of very wide bandwidth as in radar sounder, but instead uses new instrument technology as a combined spatial- and frequency-domain interferometer. Thickness is derived from phase obtained from a combination of slightly different narrow-band frequencies and incidence angles. The use of VHF is required to overcome the lossy nature of sea ice and penetrate to many meters of thickness to detect the sea-ice ocean interface. The approach relies heavily on the larger contrast in dielectric constant between the sea-ice/ocean than the sea-ice/snow as well as the sea ice bottom roughness, that results in a stronger backscatter return from the sea-ice ocean interface than sea-ice snow interface. The detailed formulations of the theoretical basis of this concept are presented in accompanying paper. Key information on surface roughness characteristics at relatively fine-scales, particularly of ice undersides for which comparatively little is known, and sea ice medium composition (for example, brine inclusions and air bubbles) are needed to develop the scientific basis of these technologies, as well as to develop the measurement strategy of a spaceborne sensor. In this presentation, we present an overview of the radar concept, fine-scale bottom roughness measurements from different upward looking sonar data sets, and an approach for a meaningful spatial and temporal measurement strategy for a future spaceborne instrument.

Holt, B.; Hussein, Z.; McDonald, K.; Pak, K.; Perovich, D.; Sturm, M.

2004-12-01

148

Frazil deposition under growing sea ice  

Microsoft Academic Search

Platelet ice may be an important component of Antarctic landfast sea ice. Typically, it is found at depth in first-year landfast sea ice cover, near ice shelves. To explain why platelet ice is not commonly observed at shallower depths, we consider a new mechanism. Our hypothesis is that platelet ice eventually appears due to the sudden deposition of frazil ice

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

2009-01-01

149

C-Band Backscatter Measurements of Winter Sea-Ice in the Weddell Sea, Antarctica  

NASA Technical Reports Server (NTRS)

During the 1992 Winter Weddell Gyre Study, a C-band scatterometer was used from the German ice-breaker R/V Polarstern to obtain detailed shipborne measurement scans of Antarctic sea-ice. The frequency-modulated continuous-wave (FM-CW) radar operated at 4-3 GHz and acquired like- (VV) and cross polarization (HV) data at a variety of incidence angles (10-75 deg). Calibrated backscatter data were recorded for several ice types as the icebreaker crossed the Weddell Sea and detailed measurements were made of corresponding snow and sea-ice characteristics at each measurement site, together with meteorological information, radiation budget and oceanographic data. The primary scattering contributions under cold winter conditions arise from the air/snow and snow/ice interfaces. Observations indicate so e similarities with Arctic sea-ice scattering signatures, although the main difference is generally lower mean backscattering coefficients in the Weddell Sea. This is due to the younger mean ice age and thickness, and correspondingly higher mean salinities. In particular, smooth white ice found in 1992 in divergent areas within the Weddell Gyre ice pack was generally extremely smooth and undeformed. Comparisons of field scatterometer data with calibrated 20-26 deg incidence ERS-1 radar image data show close correspondence, and indicate that rough Antarctic first-year and older second-year ice forms do not produce as distinctively different scattering signatures as observed in the Arctic. Thick deformed first-year and second-year ice on the other hand are clearly discriminated from younger undeformed ice. thereby allowing successful separation of thick and thin ice. Time-series data also indicate that C-band is sensitive to changes in snow and ice conditions resulting from atmospheric and oceanographic forcing and the local heat flux environment. Variations of several dB in 45 deg incidence backscatter occur in response to a combination of thermally-regulated parameters including sea-ice brine volume, snow and ice complex dielectric properties, and snow physical properties.

Drinkwater, M. R.; Hosseinmostafa, R.; Gogineni, P.

1995-01-01

150

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

151

Sea ice and icing risk for offshore wind turbines  

Microsoft Academic Search

There are two important issues related to wind turbines performances in offshore sites that locate in cold cli- mates: sea ice (flows, driving ice, land-fast ice) and the presence of atmospheric icing (due to water in the air as in-cloud operation, rainfall and sea sprays) which may potentially lead to ice formation on turbines' struc- tures. Icing of rotor blades

L. Battisti; R. Fedrizzi; A. Brighenti; T. Laakso

152

Observations: Changes in Snow, Ice and Frozen Ground  

E-print Network

. Fitzharris (New Zealand), O. Frauenfeld (USA, Austria), H. Fricker (USA), G. H. Gudmundsson (UK, Iceland), C Kingdom and New York, NY, USA. #12;338 Observations: Changes in Snow, Ice and Frozen Ground Chapter 4 in Glaciers and Ice Caps................ 356 4.5.1 Background

Jellinek, Mark

153

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

1999-01-01

154

Investigation of radar backscattering from second-year sea ice  

NASA Technical Reports Server (NTRS)

The scattering properties of second-year ice were studied in an experiment at Mould Bay in April 1983. Radar backscattering measurements were made at frequencies of 5.2, 9.6, 13.6, and 16.6 GHz for vertical polarization, horizontal polarization and cross polarizations, with incidence angles ranging from 15 to 70 deg. The results indicate that the second-year ice scattering characteristics were different from first-year ice and also different from multiyear ice. The fading properties of radar signals were studied and compared with experimental data. The influence of snow cover on sea ice can be evaluated by accounting for the increase in the number of independent samples from snow volume with respect to that for bare ice surface. A technique for calculating the snow depth was established by this principle and a reasonable agreement has been observed. It appears that this is a usable way to measure depth in snow or other snow-like media using radar.

Lei, Guang-Tsai; Moore, Richard K.; Gogineni, S. P.

1988-01-01

155

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

156

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

NASA Astrophysics Data System (ADS)

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

Song, Mirong; Liu, Jiping

2013-04-01

157

Antarctic Ice: Sea Level Change  

NSDL National Science Digital Library

This video segment, adapted from a NOVA broadcast, explains what might happen to global sea level if atmospheric warming caused the collapse and melting of the West Antarctica Ice Sheet. The segment is three minutes nineteen seconds in length.

158

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.

WGBH Educational Foundation

2008-01-17

159

Managing IceBridge Airborne Mission Data at the National Snow and Ice Data Center  

NASA Astrophysics Data System (ADS)

Operation IceBridge (OIB) is a NASA airborne geophysical survey mission conducting laser altimetry, ice-penetrating radar profiling, gravimetry and other geophysical measurements to monitor and characterize the Earth's cryosphere. The IceBridge mission will operate from 2009 until after the launch of ICESat-II (currently planned for 2015), and provides continuity of measurements between that mission and its predecessor. Data collection sites include the Greenland and Antarctic Ice Sheets and the sea ice pack regions of both poles. These regions include some of the most rapidly changing areas of the cryosphere. IceBridge is also collecting data in East Antarctica via the University of Texas ICECAP program and in Alaska via the University of Alaska, Fairbanks glacier mapping program. The NSIDC Distributed Active Archive Center at the University of Colorado at Boulder provides data archive and distribution support for the IceBridge mission. Our IceBridge work is based on two guiding principles: ensuring preservation of the data, and maximizing usage of the data. This broadens our work beyond the typical scope of a data archive. In addition to the necessary data management, discovery, distribution, and outreach functions, we are also developing tools that will enable broader use of the data, and integrating diverse data types to enable new science research. Researchers require expeditious access to data collected from the IceBridge missions; our archive approach balances that need with our long-term preservation goal. We have adopted a "fast-track" approach to publish data quickly after collection and make it available via FTP download. Subsequently, data sets are archived in the NASA EOSDIS ECS system, which enables data discovery and distribution with the appropriate backup, documentation, and metadata to assure its availability for future research purposes. NSIDC is designing an IceBridge data portal to allow interactive data search, exploration, and subsetting via a map-based interface. This portal will provide flight line rendering and multi-instrument data previewing capabilities to facilitate use of the wide array of data types, resolutions, and configurations in this dynamic airborne mission. Together with the IceBridge Science Team and Ice Bridge Science Working Groups, NSIDC is generating value-added products from the Ice Bridge data streams and other ancillary data. These products will provide simple, useful combinations of Ice Bridge products and regional maps of important geophysical parameters from other sources. Planned value-added products include: (1) gridded products in which new profiles from Ice Bridge (e.g. elevation or ice thickness) are combined with existing DEMs or bed maps to produce revised grids and (2) flight-profile multi-instrument products in which data from several instruments are combined into ice sheet profiles (surface elevation, ice thickness, internal reflection data, bed reflection intensity, and gravimetry), sea ice profiles (freeboard, snow cover, and thickness), and surface data profiles (elevation, slope, roughness, near-surface layering, and imagery).

Brodzik, M.; Kaminski, M. L.; Deems, J. S.; Scambos, T. A.

2010-12-01

160

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

USGS Publications Warehouse

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

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

2012-01-01

161

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.

162

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

163

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

NSDL National Science Digital Library

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

Venugopal Bhat

164

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

NSDL National Science Digital Library

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

1900-01-01

165

Polar Sea Ice Processes  

NSDL National Science Digital Library

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

Elizabeth Smith

166

Antarctic Sea ice--a habitat for extremophiles.  

PubMed

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

Thomas, D N; Dieckmann, G S

2002-01-25

167

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

168

Effects of sea ice dynamics on the Antarctic sea ice distribution in a coupled ocean atmosphere model  

Microsoft Academic Search

Impact of sea ice dynamics on the Southern Ocean sea ice distribution is investigated using a coupled ocean-sea ice-atmosphere general circulation model (OAGCM) and a separate offline sea ice model driven by monthly mean climatological boundary conditions. Sea ice dynamics considerably affects sea ice distribution of the OAGCM as well as of the offline model. When sea ice dynamics (advection)

T. Ogura; A. Abe-Ouchi; H. Hasumi

2004-01-01

169

Bacteria Assists in Formation of Ice and Snow  

NSDL National Science Digital Library

NPR Talk of the Nation Science Friday Audio Story: New work in the journal Science suggests that bacteria may have played an important role in guiding the formation of the snow and rain forming ice crystals found in high-level clouds. The researchers looked at snow samples from around the globe — including Montana, France and Antarctica — and found that cells and cell fragments were a significant part of the aerosol particles that lead to the formation of ice and raindrops. Brent C. Christner, a member from the research team, talks with guest host Joe Palca about the connection between microbiology and meteorology.

170

Evidence of Ice Free Seas  

NSDL National Science Digital Library

In this activity, students make a model sea floor sediment core using two types of buttons to represent fossil diatoms. They then compare the numbers of diatom fossils in the sediment at different depths to determine whether the seas were free of ice while the diatoms were alive.

LuAnn Dahlman

171

30 CFR 57.11016 - Snow and ice on walkways and travelways.  

Code of Federal Regulations, 2011 CFR

...2011-07-01 2011-07-01 false Snow and ice on walkways and travelways. 57.11016...and Underground § 57.11016 Snow and ice on walkways and travelways. Regularly...sanded, salted, or cleared of snow and ice as soon as...

2011-07-01

172

30 CFR 57.11016 - Snow and ice on walkways and travelways.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 2013-07-01 false Snow and ice on walkways and travelways. 57.11016...and Underground § 57.11016 Snow and ice on walkways and travelways. Regularly...sanded, salted, or cleared of snow and ice as soon as...

2013-07-01

173

30 CFR 57.11016 - Snow and ice on walkways and travelways.  

Code of Federal Regulations, 2014 CFR

...2014-07-01 2014-07-01 false Snow and ice on walkways and travelways. 57.11016...and Underground § 57.11016 Snow and ice on walkways and travelways. Regularly...sanded, salted, or cleared of snow and ice as soon as...

2014-07-01

174

30 CFR 56.11016 - Snow and ice on walkways and travelways.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 2013-07-01 false Snow and ice on walkways and travelways. 56.11016...MINES Travelways § 56.11016 Snow and ice on walkways and travelways. Regularly...sanded, salted, or cleared of snow and ice as soon as...

2013-07-01

175

30 CFR 56.11016 - Snow and ice on walkways and travelways.  

Code of Federal Regulations, 2012 CFR

...2012-07-01 2012-07-01 false Snow and ice on walkways and travelways. 56.11016...MINES Travelways § 56.11016 Snow and ice on walkways and travelways. Regularly...sanded, salted, or cleared of snow and ice as soon as...

2012-07-01

176

30 CFR 56.11016 - Snow and ice on walkways and travelways.  

Code of Federal Regulations, 2011 CFR

...2011-07-01 2011-07-01 false Snow and ice on walkways and travelways. 56.11016...MINES Travelways § 56.11016 Snow and ice on walkways and travelways. Regularly...sanded, salted, or cleared of snow and ice as soon as...

2011-07-01

177

30 CFR 57.11016 - Snow and ice on walkways and travelways.  

Code of Federal Regulations, 2012 CFR

...2012-07-01 2012-07-01 false Snow and ice on walkways and travelways. 57.11016...and Underground § 57.11016 Snow and ice on walkways and travelways. Regularly...sanded, salted, or cleared of snow and ice as soon as...

2012-07-01

178

30 CFR 56.11016 - Snow and ice on walkways and travelways.  

Code of Federal Regulations, 2014 CFR

...2014-07-01 2014-07-01 false Snow and ice on walkways and travelways. 56.11016...MINES Travelways § 56.11016 Snow and ice on walkways and travelways. Regularly...sanded, salted, or cleared of snow and ice as soon as...

2014-07-01

179

Geophysical Aspects of Sea-ice Nomenclatures  

NSDL National Science Digital Library

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

180

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

181

Black Carbon and Dust in Snow and Ice on Snow Dome, Mt. Olympus  

NASA Astrophysics Data System (ADS)

Deposition of black carbon (BC) and dust on highly reflective snow and glacier ice causes darkening of the surface, resulting in greater absorption of solar energy, heating of the snow/ice, and accelerated snow and glacier melt. The deposition of BC and dust may be affecting the timing and availability of water resources in the Pacific Northwest where the majority of runoff comes from snow and glacier melt, but minimal related research has taken place in this region. A recent modeling study suggested that BC deposition is causing a decrease in spring snow water equivalent and a shift to earlier peak runoff in the spring in the Western United States. Additionally, limited observations made in the early 1980s in Washington State determined that light absorbing impurities (e.g., BC and dust) were reducing the snow albedo. Since 2009, we have collected snow and ice samples from glaciers and the seasonal snowpack from spatially distributed sites in Washington State to determine impurity content, and to assess how impurity concentrations vary in relation to emission source proximity. Here we present results from the summer 2012 fieldwork on Snow Dome, Mt. Olympus in Washington State. Mt. Olympus is located upwind from major regional sources of BC and dust, but may receive BC from ocean shipping and trans-Pacific transport of BC and dust from large Asian sources. We used a field spectrometer to measure spectral albedo on Snow Dome, and analyzed surface snow samples and shallow ice cores to characterize the spatial and temporal variability of impurity deposition. Total impurity load was determined gravimetrically. Dust concentrations are inferred from ICPMS analyses and BC concentrations are determined using a Single Particle Soot Photometer (SP2), with select samples also analyzed for BC using a Sunset EC-OC to facilitate method inter-comparison. We assess the role that absorbing impurities may play in accelerating melt at Snow Dome, and briefly compare our results to other sites in Washington State that are downwind of large regional emission sources.

Kaspari, S.; Delaney, I.; Skiles, M.; Dixon, D. A.

2012-12-01

182

Variability of Arctic Sea Ice as Viewed from Space  

NASA Technical Reports Server (NTRS)

Over the past 20 years, satellite passive-microwave radiometry has provided a marvelous means for obtaining information about the variability of the Arctic sea ice cover and particularly about sea ice concentrations (% areal coverages) and from them ice extents and the lengths of the sea ice season. This ability derives from the sharp contrast between the microwave emissions of sea ice versus liquid water and allows routine monitoring of the vast Arctic sea ice cover, which typically varies in extent from a minimum of about 8,000,000 sq km in September to a maximum of about 15,000,000 sq km in March, the latter value being over 1.5 times the area of either the United States or Canada. The vast Arctic ice cover has many impacts, including hindering heat, mass, and y momentum exchanges between the oceans and the atmosphere, reducing the amount of solar radiation absorbed at the Earth's surface, affecting freshwater transports and ocean circulation, and serving as a vital surface for many species of polar animals. These direct impacts also lead to indirect impacts, including effects on local and perhaps global atmospheric temperatures, effects that are being examined in general circulation modeling studies, where preliminary results indicate that changes on the order of a few percent sea ice concentration can lead to temperature changes of 1 K or greater even in local areas outside of the sea ice region. Satellite passive-microwave data for November 1978 through December 1996 reveal marked regional and interannual variabilities in both the ice extents and the lengths of the sea ice season, as well as some statistically significant trends. For the north polar ice cover as a whole, maximum ice extents varied over a range of 14,700,000 - 15,900,000 km(2), while individual regions showed much greater percentage variations, e.g., with the Greenland Sea experiencing a range of 740,000 - 1,1110,000 km(2) in its yearly maximum ice coverage. Although variations from year to year and region to region are large, overall the Arctic ice extents did show a statistically significant, 2.8%/ decade negative trend over the 18.2-year period. Ice season lengths, which vary from only a few weeks near the ice margins to the full year in the large region of perennial ice coverage, also experienced interannual variability, and mapping their trends allows detailed geographic information on exactly where the ice season lengthened and where it shortened. Over the 18 years, ice season lengthening occurred predominantly in the western hemisphere and was strongest in the western Labrador Sea, while ice season shortening occurred predominantly in the eastern hemisphere and was strongest in the eastern Barents Sea. Much information about other important Arctic sea ice variables has also been obtained from satellite data, including information about melt ponding, temperature, snow cover, and ice velocities. For instance, maps of ice velocities have now been made from satellite scatterometry data, including information about melt ponding, temperature, snow cover, and ice velocities.

Parkinson, Claire L.

1998-01-01

183

Summer Arctic sea ice albedo in CMIP5 models  

NASA Astrophysics Data System (ADS)

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

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

2014-02-01

184

Observed and Modeled Trends in Southern Ocean Sea Ice  

NASA Technical Reports Server (NTRS)

Conceptual models and global climate model (GCM) simulations have both indicated the likelihood of an enhanced sensitivity to climate change in the polar regions, derived from the positive feedbacks brought about by the polar abundance of snow and ice surfaces. Some models further indicate that the changes in the polar regions can have a significant impact globally. For instance, 37% of the temperature sensitivity to a doubling of atmospheric CO2 in simulations with the GCM of the Goddard Institute for Space Studies (GISS) is attributable exclusively to inclusion of sea ice variations in the model calculations. Both sea ice thickness and sea ice extent decrease markedly in the doubled CO, case, thereby allowing the ice feedbacks to occur. Stand-alone sea ice models have shown Southern Ocean hemispherically averaged winter ice-edge retreats of 1.4 deg latitude for each 1 K increase in atmospheric temperatures. Observations, however, show a much more varied Southern Ocean ice cover, both spatially and temporally, than many of the modeled expectations. In fact, the satellite passive-microwave record of Southern Ocean sea ice since late 1978 has revealed overall increases rather than decreases in ice extents, with ice extent trends on the order of 11,000 sq km/year. When broken down spatially, the positive trends are strongest in the Ross Sea, while the trends are negative in the Bellingshausen/Amundsen Seas. Greater spatial detail can be obtained by examining trends in the length of the sea ice season, and those trends show a coherent picture of shortening sea ice seasons throughout almost the entire Bellingshausen and Amundsen Seas to the west of the Antarctic Peninsula and in the far western Weddell Sea immediately to the east of the Peninsula, with lengthening sea ice seasons around much of the rest of the continent. This pattern corresponds well with the spatial pattern of temperature trends, as the Peninsula region is the one region in the Antarctic with a strong record of temperature increases. Still, although the patterns of the temperature and ice changes match fairly well, there is a substantial ways to go before these patterns are understood (and can be modeled) in the full context of global change.

Parkinson, Claire L.

2003-01-01

185

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

186

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

187

Fracture of multiyear sea ice  

NASA Astrophysics Data System (ADS)

The fracture and flow of multiyear sea ice was investigated under triaxial compression and uniaxial tension in the temperature range -40° to -3.5°C, for strain rates from 10-7 to 10-2s-1 and for confining pressures up to 30 MPa using 40 mm diameter specimens. Specimens both in the horizontal plane of the multiyear floe and perpendicular to this plane were tested. The results of short-rod fracture toughness tests on multiyear and first-year sea ice at temperatures -20°C are also reported. The multiyear sea ice came from an unridged portion of a single floe about 7 m thick, which was found to be massive and not blocky with large voids. The ice had low salinity and high porosity. The inelastic deformation of multiyear sea ice was found to be strongly dependent upon strain rate, temperature, and confining pressure. In compression, four main types of deformation were observed. (1) Under uniaxial compression, completely brittle fracture at high strain rates (of 10-3 to 10-2 s-1) was characterized by multiple axial splitting. (2) Application of even a small confining pressure inhibited splitting, and fracture took place by the formation of a narrow shear fault inclined at 45±3°. (3) At higher confining pressures, plastic deformation accompanied substantial cracking activity. (4) However, at still higher confining pressures, cracking was completely inhibited and deformation was entirely plastic. At -20°C, shear fracture occurred according to a maximum shear stress criterion and hence was pressure independent, with crack nucleation dominating the fracture behavior. At -40°C, however, the shear fracture stress was found to be strongly pressure dependent up to 14 MPa and could be described in terms of a Coulombic failure envelope. The unusual 45° orientation of ice shear fractures, together with the unusual pressure dependencies of ice peak strengths, may be explained by the fact that low-stress slip and cleavage occurs in the basal planes of ice crystals.

Sammonds, P. R.; Murrell, S. A. F.; Rist, M. A.

1998-09-01

188

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

189

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

Microsoft Academic Search

The National Snow and Ice Data Center (NSIDC) at the University of Colorado, Boulder - one of eight NASA Distributed Active Archive Centers (DAACs) - archives and distributes several products from sensors on the suite of NASA Earth Observing System (EOS) satellites. These include the sun-synchronous polar-orbiting Aqua (launched 4 May 2002) and Terra (launched 18 December 1999) platforms and

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

2004-01-01

190

Dual Frequency Radar Observations of Snow and Ice Properties: Esa's COREH2O Candidate Satellite Mission  

NASA Astrophysics Data System (ADS)

The satellite mission COld REgions Hydrology High-resolution Observatory (CoReH2O) is a candidate Earth Explorer mission within the Living Planet Programme of the European Space Agency. Detailed scientific and technical feasibility studies (Phase-A) for defining the satellite mission are going on. The mission will perform spatially detailed measurements of snow and ice in order to advance the modeling and prediction of water balance and streamflow in cold regions, and to improve the parameterization of snow and ice processes for climate models and numerical weather prediction. The primary snow and ice parameters to be delivered by the satellite are the area extent and mass (the water equivalent, SWE) of snow cover on land surfaces and the mass of winter snow accumulating on glaciers. In addition, the mission will make observations of various sea ice and lake ice parameters. The grid size of the final snow and ice products will vary between 200 m and 500 m, depending on the parameter and application. The sensor will be a dual-frequency dual-polarized SAR, operating at Ku-band (17.2 GHz) and X-band (9.6 GHz), VV and VH polarizations, with a swath width of about 100 km. Two mission phases with different repeat cycles and coverage are proposed. During the first two years a three-day repeat cycle is planned providing frequent repeat coverage over limited areas, in order to match the time scale of meteorological forcing by typical mid- and high-latitude weather systems. This orbit addresses in particular the parameterization of snow and ice processes in hydrological models and mesoscale atmospheric circulation models. The second mission phase shall deliver near complete observations of the global snow and ice areas at a repeat cycle of 12 to 15 days. Primary motivations for this phase are the validation of continental-scale hydrological models and climate models, and the development of downscaling techniques for coarse resolution satellite snow measurements. A processing line for mapping snow extent and retrieving SWE has been developed and tested with simulated and experimental data. The performance of the retrieval algorithm has been tested with simulated and experimental data for wide range of conditions for snow packs and background targets. The retrieval algorithm has also been tested with data from field campaigns in Finland, Canada and Alaska, employing backscatter measurements made by ground-based scatterometers and airborne sensors. Retrievals of SWE with the experimental data are within the benchmarks for quality of SWE products specified by the scientific community. Retrievals with simulated data show on average good results, but problems for compliance are emerging under certain target conditions such as snow cover in forested areas. Measures to improve the performance in these cases are being investigated, for example by relaxing the product size from 200 m to 500 m.

Duguay, C.; Rott, H.; Cline, D. W.; Essery, R.; Etchevers, P.; Hajnsek, I.; Kern, M.; Macelloni, G.; Malnes, E.; Pulliainen, J. T.; Yueh, S. H.

2012-12-01

191

Radiometric measurements of snow and ice surfaces in Antartica  

NASA Astrophysics Data System (ADS)

First results of a ground radiometric campaign carried out in Antarctica during the last Italian scientific expedition in winter 1994/95 are here presented. The measurements were collected by means of a 4-channel radiometer, fitting with the MSS and first 4 TM spectral intervals. More than 100 measurements were taken in different sites, concerning three main categories: snow cover, continental ice, and marine ice. The investigation consisted in the collection of radiance information accompanied by observations of physical properties of the surfaces according to the standards by the International Glaciological Society. The reflectance values of different snow/ice covers indicate some interesting remarks to the use of these results as a method for the calibration of satellite imagery to a better understanding of this particular environment.

Zilioli, Eugenio; Cagnati, Anselmo

1995-11-01

192

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

193

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

194

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

195

Sea Ice Index  

NSDL National Science Digital Library

This site presents average ice conditions estimated using satellite passive microwave data for the most recent month available, as well as snapshots of trends and anomalies that compare these recent conditions with the mean for the month.

Florence Fetterer

196

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

197

Sea Ice Yearly Minimum in the Arctic  

NSDL National Science Digital Library

This series of visualizations show the annual Arctic sea ice minimum from 1979 to 2010. The decrease in Arctic sea ice over time is shown in an animation and a graph plotted simultaneously, but can be parsed so that the change in sea ice area can be shown without the graph.

GSFC/Science Visualization Studio

198

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

199

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...

200

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

201

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

202

Finite-Element Sea Ice Model (FESIM), version 2  

NASA Astrophysics Data System (ADS)

The Finite-Element Sea-Ice Model, used as a component of the Finite-Element Sea ice Ocean Model, is presented. Version 2 includes the elastic-viscous-plastic (EVP) and viscous-plastic (VP) solvers and employs a flux corrected transport algorithm to advect the ice and snow mean thicknesses and concentration. The EVP part also includes a modified approach proposed recently by Bouillon et al., which is characterized by an improved stability compared to the standard EVP approach. The model is formulated on unstructured triangular meshes. It assumes a collocated placement of ice velocities, mean thicknesses and concentration at mesh vertices, and relies on a piecewise-linear (P1) continuous elements. Simple tests for the modified EVP and VP solvers are presented to show that they may produce very close results provided the number of iterations is sufficiently high.

Danilov, S.; Wang, Q.; Timmermann, R.; Iakovlev, N.; Sidorenko, D.; Kimmritz, M.; Jung, T.; Schröter, J.

2015-02-01

203

Arctic sea ice as a granular plastic  

Microsoft Academic Search

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

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

1998-01-01

204

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.

205

Northern Alaskan land surface response to reduced Arctic sea ice extent  

NASA Astrophysics Data System (ADS)

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

Higgins, Matthew E.; Cassano, John J.

2012-05-01

206

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

207

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

Microsoft Academic Search

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

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

2008-01-01

208

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

209

Sea Ice Concentrations from Nimbus-7 SMMR and DMSP SSM/I Passive Microwave Data  

NSDL National Science Digital Library

The National Snow and Ice Data Center (NSIDC) (described in the October 2, 1998 Scout Report) provides the Sea Ice Concentrations from Nimbus-7 SMMR and DMSP SSM/I Passive Microwave Data set. The dataset ranges from October 1978 to December 1996 and includes "daily and monthly averaged sea ice concentrations in binary and .gif format derived from Nimbus-7 SMMR and DMSP SSM/I F8, F11, and F13 daily brightness temperatures at a grid cell size of 25 X 25 km." Summaries of these sea ice concentrations datasets are also available.

210

Brine-ecosystem interactions in sea ice  

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

211

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

212

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

213

Fracture of multiyear sea ice  

Microsoft Academic Search

The fracture and flow of multiyear sea ice was investigated under triaxial compression and uniaxial tension in the temperature range -40 ø to -3.5øC, for strain rates from 10 -7 to 10 -2 s -1, and for confining pressures up to 30 MPa using 40 mm diameter specimens. Specimens both in the horizontal plane of the multiyear floe and perpendicular

P. R. Sammonds; S. A. F. Murrell; M. A. Rist

1998-01-01

214

Fracture of multiyear sea ice  

Microsoft Academic Search

The fracture and flow of multiyear sea ice was investigated under triaxial compression and uniaxial tension in the temperature range -40° to -3.5°C, for strain rates from 10-7 to 10-2s-1, and for confining pressures up to 30 MPa using 40 mm diameter specimens. Specimens both in the horizontal plane of the multiyear floe and perpendicular to this plane were tested.

P. R. Sammonds; S. A. F. Murrell; M. A. Rist

1998-01-01

215

Ice Sheets and Sea Level  

NSDL National Science Digital Library

In this exercise, learners use basic arithmetic to determine the amount that sea level would rise around the globe with the melting of the Greenland and Antarctic ice sheets. Basic data for this calculation is provided. This resource is from PUMAS - Practical Uses of Math and Science - a collection of brief examples created by scientists and engineers showing how math and science topics taught in K-12 classes have real world applications.

2012-08-03

216

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

NASA Astrophysics Data System (ADS)

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

Nicolaus, M.; Katlein, C.

2012-09-01

217

Sea Ice detection with space-based LIDAR  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

218

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

NASA Astrophysics Data System (ADS)

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

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

2007-12-01

219

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.

LuAnn Dahlman

220

The Thickness Distribution of Sea Ice  

Microsoft Academic Search

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 largescale geophysical properties to depend on the relative abundance of the various ice types. The ice pack is treated as a mixture whose constituents

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

1975-01-01

221

Spatial variation of biogeochemical properties of landfast sea ice in the Gulf of Bothnia, Baltic Sea  

NASA Astrophysics Data System (ADS)

Horizontal variation of landfast sea-ice properties was studied in the Gulf of Bothnia, Baltic Sea, during March 2004. In order to estimate their variability among and within different spatial levels, 72 ice cores were sampled on five spatial scales (with spacings of 10 cm, 2.5 m, 25 m, 250 m and 2.5 km) using a hierarchical sampling design. Entire cores were melted, and bulk-ice salinity, concentrations of chlorophyll a (Chl a), phaeophytin (Phaeo), dissolved nitrate plus nitrite (DIN) as well as dissolved organic carbon (DOC) and nitrogen (DON) were determined. All sampling sites were covered by a 5.5-23 cm thick layer of snow. Ice thicknesses of cores varied from 26 to 58 cm, with bulk-ice salinities ranging between 0.2 and 0.7 as is typical for Baltic Sea ice. Observed values for Chl a (range: 0.8-6.0 ?g Chl a L-1 ; median: 2.9 ?g Chl a L-1) and DOC (range: 37-397 ?M; median: 95 ?M) were comparable to values reported by previous sea-ice studies from the Baltic Sea. Analysis of variance among different spatial levels revealed significant differences on the 2.5 km scale for ice thickness, DOC and Phaeo (with the latter two being positively correlated with ice thickness). For salinity and Chl a, the 250 m scale was found to be the largest scale where significant differences could be detected, while snow depth only varied significantly on the 25 m scale. Variability on the 2.5 m scale contributed significantly to the total variation for ice thickness, salinity, Chl a and DIN. In the case of DON, none of the investigated levels exhibited variation that was significantly different from the considerable amount of variation found between replicate cores. Results from a principal component analysis suggest that ice thickness is one of the main elements structuring the investigated ice habitat on a large scale, while snow depth, nutrients and salinity seem to be of secondary importance.

Steffens, M.; Granskog, M. A.; Kaartokallio, H.; Kuosa, H.; Luodekari, K.; Papadimitriou, S.; Thomas, D. N.

222

Halocarbons associated with Arctic sea ice  

NASA Astrophysics Data System (ADS)

Short-lived halocarbons were measured in Arctic sea-ice brine, seawater and air above the Greenland and Norwegian seas (~81°N, 2-5°E) in mid-summer, from a melting ice floe at the edge of the ice pack. In the ice floe, concentrations of C2H5I, 2-C3H7I and CH2Br2 showed significant enhancement in the sea ice brine, of average factors of 1.7, 1.4 and 2.5 times respectively, compared to the water underneath and after normalising to brine volume. Concentrations of mono-iodocarbons in air are the highest ever reported, and our calculations suggest increased fluxes of halocarbons to the atmosphere may result from their sea-ice enhancement. Some halocarbons were also measured in ice of the sub-Arctic in Hudson Bay (~55°N, 77°W) in early spring, ice that was thicker, colder and less porous than the Arctic ice in summer, and in which the halocarbons were concentrated to values over 10 times larger than in the Arctic ice when normalised to brine volume. Concentrations in the Arctic ice were similar to those in Antarctic sea ice that was similarly warm and porous. As climate warms and Arctic sea ice becomes more like that of the Antarctic, our results lead us to expect the production of iodocarbons and so of reactive iodine gases to increase.

Atkinson, Helen M.; Hughes, Claire; Shaw, Marvin J.; Roscoe, Howard K.; Carpenter, Lucy J.; Liss, Peter S.

2014-10-01

223

USGS and NOAA Monitor Arctic Sea Ice  

USGS Multimedia Gallery

USGS scientist Jonathan Childs and NOAA oceanographer Pablo Clemente-Colón, also Chief Scientist of the National Ice Center, looking out on the Arctic sea ice. This was during a scientific expedition to map the Arctic seafloor....

224

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

225

ASPECTS OF ARCTIC SEA ICE OBSERVABLE BY SEQUENTIAL PASSIVE MICROWAVE OBSERVATIONS FROM THE NIMBUS-5 SATELLITE.  

USGS Publications Warehouse

Observations made from 1972 to 1976 with the Electrically Scanning Microwave Radiometer on board the Nimbus-5 satellite provide sequential synoptic information of the Arctic sea ice cover. This four-year data set was used to construct a fairly continuous series of three-day average 19-GHz passive microwave images which has become a valuable source of polar information, yielding many anticipated and unanticipated discoveries of the sea ice canopy observed in its entirety through the clouds and during the polar night. Short-term, seasonal, and annual variations of key sea ice parameters, such as ice edge position, ice types, mixtures of ice types, ice concentrations, and snow melt on the ice, are presented for various parts of the Arctic.

Campbell, William J.; Gloersen, Per; Zwally, H. Jay

1984-01-01

226

Historical Antarctic mean sea ice area, sea ice trends, and winds in CMIP5 simulations  

E-print Network

In contrast to Arctic sea ice, average Antarctic sea ice area is not retreating but has slowly increased since satellite measurements began in 1979. While most climate models from the Coupled Model Intercomparison Project ...

Mahlstein, Irina

227

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

228

Ice and Climate News, No. 9, June 2007 Snow and Ice on Kilimanjaro  

E-print Network

- sities of Massachusetts and Ohio State (USA), Innsbruck (Austria), and Otago (New Zealand), as well than a decade, English Geographers dismissed and even ridiculed Rebmann's report of tropical snow. And although superimposed ice formation reduces mass loss on horizontal surfaces, evidence indicates

Massachusetts at Amherst, University of

229

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

230

Top/bottom multisensor remote sensing of Arctic sea ice  

NASA Astrophysics Data System (ADS)

The Arctic sea ice cover has been studied using near simultaneous observations by passive and active (synthetic aperture radar, SAR) microwave sensors, upward looking and sidescan sonars, a lidar profilometer, and an infrared sensor. Data from two aircraft and a submarine over an approximately 100 km track of central Arctic sea ice were registered and analyzed to evaluate the characteristics of the ice cover and the utility of each sensor in ice studies. The results of comparative and correlation analyses are as follows. The probability density functions of ice draft from sonar and elevation from lidar were found to be almost identical when isostasy is taken into account. This result suggests that the basic ice thickness distribution can be derived from the surface topography measurements alone. Reasonable correlation was found between SAR backscatter and ice draft (or elevation) especially when scales were adjusted such that 15-20 SAR pixels were averaged. However, surface roughness derived directly from standard deviations in the lidar elevation data was found to be poorly correlated to the SAR backscatter. These results indicate that the SAR values are affected more by scattering from the ice than from the snow-covered surface. The active and passive microwave sensors are shown to generally complement each other as the two sensors are especially sensitive to different physical properties of the sea ice. Undeformed first-year ice showed low backscatter values but high brightness temperatures while some multiyear ice showed high backscatter values and low brightness temperature. However, surfaces identified as multiyear ice by the passive system have a large spread in the unaveraged SAR backscatter, indicating limitations when using a one-channel SAR for ice type identification at the highest resolution. Also, ridged ice identified by sonar and SAR data covers a large range of passive microwave emissivity, suggesting considerable variability in the age and salinity of this type of ice. Significant variations (about 0.11) in the minimum emissivity of consolidated multiyear ice are observed in different regions of the Arctic using the high-resolution (30 m) passive microwave data. This suggests that regional variations in texture and scattering characteristics of multiyear ice in the Arctic are present, likely influenced by different histories of formation of the ice in different regions.

Comiso, J. C.; Wadhams, P.; Krabill, W. B.; Swift, R. N.; Crawford, J. P.; Tucker, W. B., III

1991-02-01

231

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

232

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

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

233

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

234

Sea Ice and Products and Services of the National Ice Center  

NSDL National Science Digital Library

This two-hour module examines sea ice, icebergs, and the products and services of the National Ice Center and the North American Ice Service. Topics include climatology and current trends in sea ice extent and thickness; the development, classification, and drift of sea ice and icebergs; fractures, leads and polynyas; and the satellite detection of sea ice using visible, infrared, and microwave sensors.

COMET

2011-04-19

235

Comparing springtime ice-algal chlorophyll a and physical properties of multi-year and first-year sea ice from the lincoln sea.  

PubMed

With near-complete replacement of Arctic multi-year ice (MYI) by first-year ice (FYI) predicted to occur within this century, it remains uncertain how the loss of MYI will impact the abundance and distribution of sea ice associated algae. In this study we compare the chlorophyll a (chl a) concentrations and physical properties of MYI and FYI from the Lincoln Sea during 3 spring seasons (2010-2012). Cores were analysed for texture, salinity, and chl a. We identified annual growth layers for 7 of 11 MYI cores and found no significant differences in chl a concentration between the bottom first-year-ice portions of MYI, upper old-ice portions of MYI, and FYI cores. Overall, the maximum chl a concentrations were observed at the bottom of young FYI. However, there were no significant differences in chl a concentrations between MYI and FYI. This suggests little or no change in algal biomass with a shift from MYI to FYI and that the spatial extent and regional variability of refrozen leads and younger FYI will likely be key factors governing future changes in Arctic sea ice algal biomass. Bottom-integrated chl a concentrations showed negative logistic relationships with snow depth and bulk (snow plus ice) integrated extinction coefficients; indicating a strong influence of snow cover in controlling bottom ice algal biomass. The maximum bottom MYI chl a concentration was observed in a hummock, representing the thickest ice with lowest snow depth of this study. Hence, in this and other studies MYI chl a biomass may be under-estimated due to an under-representation of thick MYI (e.g., hummocks), which typically have a relatively thin snowpack allowing for increased light transmission. Therefore, we suggest the on-going loss of MYI in the Arctic Ocean may have a larger impact on ice-associated production than generally assumed. PMID:25901605

Lange, Benjamin A; Michel, Christine; Beckers, Justin F; Casey, J Alec; Flores, Hauke; Hatam, Ido; Meisterhans, Guillaume; Niemi, Andrea; Haas, Christian

2015-01-01

236

Modelling of superimposed ice formation during the spring snowmelt period in the Baltic Sea  

NASA Astrophysics Data System (ADS)

Development of landfast sea ice and its snow cover was monitored in the Gulf of Bothnia, Baltic Sea, for a period of 4 weeks during the early melt season of 2004. During this period, approximately 90% of the snow layer was transformed into superimposed ice, while the rest sublimated. A one-dimensional thermodynamic snow/ice model was used to simulate this process. The modelled snowmelt and superimposed ice growth were consistent with the observations, but the net accumulation of superimposed ice was slightly overestimated. The errors in calculation of temporal variations of the refreezing were probably due to the uncertainties in the external forcing and simplification of snow processes in the model. The modelled snow thickness was sensitive to the atmospheric forcing, and the influence was amplified when the albedo was parameterized as a function of surface temperature. In the sensitivity tests without this feedback, the direct effect of the inaccuracy in the albedo parameterization was minor. Errors in the parameterized longwave radiation were critical for the modelled snow surface temperature during night-time, but did not have a large effect on the mass balance during this spring melt period.

Cheng, Bin; Vihma, Timo; Pirazzini, Roberta; Granskog, Mats A.

237

EASTERN SNOW CONFERENCE Fairlee, Vermont, USA. 2008.  

E-print Network

of snow and ice surfaces. This effort is one step toward the long-term goal of rendering absolute scale ice mass balance. Images of snow and ice scenes pose difficulties in image analysis due to low knowledge of the long term distribution and changes of the sea ice mass balance. To accomplish this

Geiger, Cathleen

238

The History of Snow and Ice on the Summits of Hawai`i  

E-print Network

The History of Snow and Ice on the Summits of Hawai`i Norbert*on of past climate · No instrumental records · Historical Accounts (Texts, Paintings?) ­ snow cover years that Mr. Young has been on the island, he has never seen Mouna Kaah free from snow" ­ 1825

Schörghofer, Norbert

239

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

NASA Astrophysics Data System (ADS)

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 a sea ice proxy. It is also shown that this negative MSA-sea ice relationship cannot be explained by the influence that the extensive summer ice pack in the Weddell Sea has on MSA production area and transport distance. A historical record of sea ice from the northern Weddell Sea shows that the negative relationship between MSA and winter sea ice exists over interannual (˜7-year period) and multidecadal (˜20-year period) timescales. National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis data suggest that this negative relationship is most likely due to variations in the strength of cold offshore wind anomalies traveling across the Weddell Sea, which act to synergistically increase sea ice extent (SIE) while decreasing MSA delivery to the ice core sites. Hence our findings show that in some locations atmospheric transport strength, rather than sea ice conditions, is the dominant factor that determines the MSA signal preserved in near-coastal ice cores. A cautious approach is thus required in using ice core MSA for reconstructing past sea ice conditions, including the need for networks of ice core records and multiproxy studies to assess the significance of past MSA changes at different locations around Antarctica.

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

2007-08-01

240

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

241

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

242

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

NASA Astrophysics Data System (ADS)

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

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

2009-04-01

243

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

244

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

Microsoft Academic Search

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

WEI WENSHOU; GAO CUNHAI

1992-01-01

245

A Decade of Arctic Sea Ice Thickness Change from Airborne and Satellite Altimetry (Invited)  

NASA Astrophysics Data System (ADS)

Altimeters on both airborne and satellite platforms provide direct measurements of sea ice freeboard from which sea ice thickness may be calculated. Satellite altimetry observations of Arctic sea ice from ICESat and CryoSat-2 indicate a significant decline in ice thickness, and volume, over the last decade. During this time the ice pack has experienced a rapid change in its composition, transitioning from predominantly thick, multi-year ice to thinner, increasingly seasonal ice. We will discuss the regional trends in ice thickness derived from ICESat and IceBridge altimetry between 2003 and 2013, contrasting observations of the multi-year ice pack with seasonal ice zones. ICESat ceased operation in 2009, and the final, reprocessed data set became available recently. We extend our analysis to April 2013 using data from the IceBridge airborne mission, which commenced operations in 2009. We describe our current efforts to more accurately convert from freeboard to ice thickness, with a modified methodology that corrects for range errors, instrument biases, and includes an enhanced treatment of snow depth, with respect to ice type. With the planned launch by NASA of ICESat-2 in 2016 we can expect continuity of the sea ice thickness time series through the end of this decade. Data from the ICESat-2 mission, together with ongoing observations from CryoSat-2, will allow us to understand both the decadal trends and inter-annual variability in the Arctic sea ice thickness record. We briefly present the status of planned ICESat-2 sea ice data products, and demonstrate the utility of micro-pulse, photon-counting laser altimetry over sea ice.

Farrell, S. L.; Richter-Menge, J.; Kurtz, N. T.; McAdoo, D. C.; Newman, T.; Zwally, H.; Ruth, J.

2013-12-01

246

Coupling GELATO 4 sea-ice model to NEMO 3: a new ocean/sea-ice model for global climate studies at CNRM  

NASA Astrophysics Data System (ADS)

A new configuration of the ocean-sea ice model in use at the Centre National de Recherches Météorologiques (CNRM, Météo-France, France) is presented. The sea-ice component of the global coupled model is an updated version of GELATO (Salas-Melia, 2002). GELATO is a dynamic-thermodynamic model, and includes elastic-visco-plastic rheology, redistribution of ice floes of different thicknesses, and also takes into account leads, snow cover and snow ice formation. The new version of GELATO sea-ice model includes also a tracer of ice age. GELATO 4 is coupled to the NEMO3.3 global ocean model (Madec et al., 2008), a hydrostatic, primitive equation, finite difference ocean model in the 1°-configuration ORCA1. In this new configuration, the straits in the Arctic Ocean are opened, leading to more realistic features in the sea-ice state compared to previous systems. Model performance is evaluated by performing a hindcast of the Arctic and Antarctic sea-ice covers, forced by the ERA40-based atmospheric forcing DFS4 (DRAKKAR Forcing Set 4, Brodeau et al., 2009) during the 1958-2004 period. To test the impact of a more refined description of melting sea-ice surface albedo, a new sea-ice albedo scheme was also implemented in GELATO. The scheme is based on Pedersen et al.(2009) parametrization, and includes melt ponds evolution. Performance with this latter refinement is also evaluated. The NEMO3.3-GELATO4 model is meant to be used at CNRM for Coupled Model Intercomparison Project phase 5 (CMIP5) experiments, and also for investigations dealing with seasonal-to-decadal predictability in the Arctic.

Chevallier, Matthieu; Salas-Melia, David

2010-05-01

247

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

248

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

249

6, 1105111066, 2006 Sea ice, frost flowers  

E-print Network

ACPD 6, 11051­11066, 2006 Sea ice, frost flowers and halogen activation W. R. Simpson et al. Title than potential frost flower contact W. R. Simpson 1 , D. Carlson 1 , G. Hoenninger 1,2, , T. A. Douglas. Simpson (ffwrs@uaf.edu) 11051 #12;ACPD 6, 11051­11066, 2006 Sea ice, frost flowers and halogen activation

Paris-Sud XI, Université de

250

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

251

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

252

Observations of the snowcover on sea ice in the Gulf of Bothnia  

Microsoft Academic Search

During March 1988, detailed measurements of the physical properties and depth distributions of the snow cover on the sea ice in the Gulf of Bothnia were made as part of BEPERS-88 (Bothnian Experiment in Preparation for ERS-1). The observations included profiles of the density, crystal structure. salinity, temperature, and brine volume (at 1-2 cm depth intervals), and 1084 snow depth measurements.

G. Crocker

1992-01-01

253

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

254

Mycosporine-like amino acids in Antarctic sea ice algae, and their response to UVB radiation.  

PubMed

Mycosporine like amino acids (MAAs) were detected in low concentration in sea ice algae growing in situ at Cape Evans, Antarctica. Four areas of sea ice were covered with plastics of different UV absorption exposing the bottom- ice algal community to a range of UV doses for a period of 15 days. Algae were exposed to visible radiation only; visible + UV radiation; and visible + enhanced UV radiation. MAA content per cell at the start of the experiment was low in snow-covered plots but higher in samples from ice with no snow cover. During the study period, the MAA content per cell reduced in all treatments, but the rate of this decline was less under both ambient UV and visible radiation than under snow covered plots. While low doses of UVB radiation may have stimulated some MAA production (or at least slowed its loss), relatively high doses of UVB radiation resulted in almost complete loss of MAAs from ice algal cells. Despite this reduction in MAA content per cell, the diatoms in all samples grew well, and there was no discernible effect on viability. This suggests that MAAs may play a minor role as photoprotectants in sea ice algae. The unique structure of the bottom ice algal community may provide a self-shading effect such that algal cells closest to the surface of the ice contain more MAAs than those below them and confer a degree of protection on the community as a whole. PMID:12132687

Ryan, Ken G; McMinn, Andrew; Mitchell, Kevin A; Trenerry, Louise

2002-01-01

255

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

2014-08-01

256

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

NASA Astrophysics Data System (ADS)

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 the Moderate Resolution Image Spectroradiometer (MODIS) using a spectral unmixing algorithm. The unmixing was implemented using a multilayer perceptron to reduce computational costs. Arctic-wide melt pond fractions and sea ice concentrations are derived from the level 3 MODIS surface reflectance product. The validation of the MODIS melt pond data set was conducted with aerial photos from the MELTEX campaign 2008 in the Beaufort Sea, data sets from the National Snow and Ice Data Center (NSIDC) for 2000 and 2001 from four sites spread over the entire Arctic, and with ship observations from the trans-Arctic HOTRAX cruise in 2005. The root-mean-square errors range from 3.8 % for the comparison with HOTRAX data, over 10.7 % for the comparison with NSIDC data, to 10.3 % and 11.4 % for the comparison with MELTEX data, with coefficient of determination ranging from R2=0.28 to R2=0.45. The mean annual cycle of the melt pond fraction per grid cell for the entire Arctic shows a strong increase in June, reaching a maximum of 15 % by the end of June. The zonal mean of melt pond fractions indicates a dependence of the temporal development of melt ponds on the geographical latitude, and has its maximum in mid-July at latitudes between 80° and 88° N. Furthermore, the MODIS results are used to estimate the influence of melt ponds on retrievals of sea ice concentrations from passive microwave data. Results from a case study comparing sea ice concentrations from ARTIST Sea Ice-, NASA Team 2-, and Bootstrap-algorithms with MODIS sea ice concentrations indicate an underestimation of around 40 % for sea ice concentrations retrieved with microwave algorithms.

Rösel, A.; Kaleschke, L.; Birnbaum, G.

2012-04-01

257

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

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

258

Satellite Remote Sensing: Passive-Microwave Measurements of Sea Ice  

NASA Technical Reports Server (NTRS)

Satellite passive-microwave measurements of sea ice have provided global or near-global sea ice data for most of the period since the launch of the Nimbus 5 satellite in December 1972, and have done so with horizontal resolutions on the order of 25-50 km and a frequency of every few days. These data have been used to calculate sea ice concentrations (percent areal coverages), sea ice extents, the length of the sea ice season, sea ice temperatures, and sea ice velocities, and to determine the timing of the seasonal onset of melt as well as aspects of the ice-type composition of the sea ice cover. In each case, the calculations are based on the microwave emission characteristics of sea ice and the important contrasts between the microwave emissions of sea ice and those of the surrounding liquid-water medium.

Parkinson, Claire L.; Zukor, Dorothy J. (Technical Monitor)

2001-01-01

259

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

NASA Astrophysics Data System (ADS)

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

Gradinger, Rolf; Bluhm, Bodil; Iken, Katrin

2010-01-01

260

Black carbon in Arctic snow and its effect on surface albedo  

E-print Network

#12;8 Tundra of northern Yakutia, April 2008 #12;9 Tundra of northern Yakutia, April 2008 A surface and in boreal forest) Arctic snow - Tundra in spring - Sea ice in spring (covered with snow) - Greenland Ice

261

The seasonality of Antarctic sea ice trends  

NASA Astrophysics Data System (ADS)

Antarctic sea ice is experiencing a weak overall increase in area that is the residual of opposing regional trends. This study considers their seasonal pattern. In addition to traditional ice concentration and total ice area, temporal derivatives of these quantities are investigated ("intensification" and "expansion," respectively). This is crucial to the attribution of trends, since changes in forcing directly affect ice areal change (rather than ice area). Diverse regional trends all contribute significantly to the overall increase. Trends in the Weddell and Amundsen-Bellingshausen regions compensate in magnitude and seasonality. The largest concentration trends, in autumn, are actually caused by intensification trends during spring. Autumn intensification trends directly oppose autumn concentration trends in most places, seemingly as a result of ice and ocean feedbacks. Springtime trends are reconcilable with wind trends, but further study of changes during the spring melting season is required to unravel the Antarctic sea ice increase.

Holland, Paul R.

2014-06-01

262

Object-based Image Classification of Arctic Sea Ice and Melt Ponds through Aerial Photos  

NASA Astrophysics Data System (ADS)

The last six years have marked the lowest Arctic summer sea ice extents in the modern era, with a new record summer minimum (3.4 million km2) set on 13 September 2012. It has been predicted that the Arctic could be free of summer ice within the next 25-30. The loss of Arctic summer ice could have serious consequences, such as higher water temperature due to the positive feedback of albedo, more powerful and frequent storms, rising sea levels, diminished habitats for polar animals, and more pollution due to fossil fuel exploitation and/ or increased traffic through the Northwest/ Northeast Passage. In these processes, melt ponds play an important role in Earth's radiation balance since they strongly absorb solar radiation rather than reflecting it as snow and ice do. Therefore, it is necessary to develop the ability of predicting the sea ice/ melt pond extents and space-time evolution, which is pivotal to prepare for the variation and uncertainty of the future environment, political, economic, and military needs. A lot of efforts have been put into Arctic sea ice modeling to simulate sea ice processes. However, these sea ice models were initiated and developed based on limited field surveys, aircraft or satellite image data. Therefore, it is necessary to collect high resolution sea ice aerial photo in a systematic way to tune up, validate, and improve models. Currently there are many sea ice aerial photos available, such as Chinese Arctic Exploration (CHINARE 2008, 2010, 2012), SHEBA 1998 and HOTRAX 2005. However, manually delineating of sea ice and melt pond from these images is time-consuming and labor-intensive. In this study, we use the object-based remote sensing classification scheme to extract sea ice and melt ponds efficiently from 1,727 aerial photos taken during the CHINARE 2010. The algorithm includes three major steps as follows. (1) Image segmentation groups the neighboring pixels into objects according to the similarity of spectral and texture information; (2) random forest ensemble classifier can distinguish the following objects: water, submerged ice, shadow, and ice/snow; and (3) polygon neighbor analysis can further separate melt ponds from submerged ice according to the spatial neighboring relationship. Our results illustrate the spatial distribution and morphological characters of melt ponds in different latitudes of the Arctic Pacific sector. This method can be applied to massive photos and images taken in past years and future years, in deriving the detailed sea ice and melt pond distribution and changes through years.

Miao, X.; Xie, H.; Li, Z.; Lei, R.

2013-12-01

263

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

NASA Astrophysics Data System (ADS)

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

Flocco, Daniela; Feltham, Daniel; Schroeder, David

2013-04-01

264

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.

Los Alamos National National Laboratory

265

L-band radiometry for sea ice applications  

NASA Astrophysics Data System (ADS)

Although sea ice remote sensing has reached the level of operational exploitation with well established retrieval methods, several important tasks are still unsolved. In particular during freezing and melting periods with mixed ice and water surfaces, estimates of ice concentration with passive and active microwave sensors remain challenging. Newly formed thin ice is also hard to distinguish from open water with radiometers for frequencies above 8 GHz. The SMOS configuration (planned launch 2009) with a radiometer at 1.4 GHz is a promising technique to complement observations at higher microwave frequencies. ESA has initiated a project to investigate the possibilities for an additional Level-2 sea ice data product based on SMOS. In detail, the project objectives are (1) to model the L band emission of sea ice, and to assess the potential (2) to retrieve sea ice parameters, especially concentration and thickness, and (3) to use cold water regions for an external calibration of SMOS. Modelling of L band emission: Several models have are investigated. All of them work on the same basic principles and have a vertically-layered, plane-parallel geometry. They are comprised of three basic components: (1) effective permittivities are calculated for each layer based on ice bulk and micro-structural properties; (2) these are integrated across the total depth to derive emitted brightness temperature; (3) scattering terms can also be added because of the granular structure of ice and snow. MEMLS (Microwave Emission Model of Layered Snowpacks (Wiesmann and Matzler 1999)) is one such model that contains all three elements in a single Matlab program. In the absence of knowledge about the internal structure of the sea ice, three-layer (air, ice and water) dielectric slab models which take as input a single effective permittivity for the ice layer are appropriate. By ignoring scattering effects one can derive a simple analytic expression for a dielectric slab as shown by Apinis and Peake (1976). This expression was used by Menashi et al. (1993) to derive the thickness of sea ice from UHF (0.6 GHz) radiometer. Second, retrieval algorithms for sea ice parameters with emphasis on ice-water discrimination from L-band observations considering the specific SMOS observations modes and geometries are investigated. A modified Menashi model with the permittivity depending on brine volume and temperature suggests a thickness sensitivity of up to 150 cm for low salinity (multi year or brackish) sea ice at low temperatures. At temperatures approaching the melting point the thickness sensitivity reduces to a few centimetres. For first year ice the modelled thickness sensitivity is roughly half a meter. Runs of the model MEMLS with input data generated from a 1-d thermodynamic sea ice model lead to similar conclusio. The results of the forward model may strongly vary with the input microphysical details. E.g. if the permittivity is modelled to depend in addition on the sea ice thickness as supported by several former field campaigns for thin ice, the model predictions change strongly. Prior to the launch of SMOS, an important source of observational data is the SMOS Sea-Ice campaign held near Kokkola, Finland, March 2007 conducted as an add-on of the POL-ICE campaign. Co-incident L-band observations taken with the EMIRAD instrument of the Technical University of Denmark, ice thickness values determined from the EM bird of AWI and in situ observations during the campaign are combined. Although the campaign data are to be use with care, for selected parts of the flights the sea ice thickness can be retrieved correctly. However, as the instrumental conditions and calibration were not optimal, more in situ data, preferably from the Arctic, will be needed before drawing clear conclusions about a future the sea ice thickness product based on SMOS data. Use of additional information from other microwave sensors like AMSR-E might be needed to constrain the conditions, e.g. on sea ice concentration and temperature. External calibration: to combine SMOS ice info

Heygster, G.; Hedricks, S.; Mills, P.; Kaleschke, L.; Stammer, D.; Tonboe, R.

2009-04-01

266

Tertiary ice sheet dynamics: The snow gun hypothesis  

SciTech Connect

The authors abserve strong negative correlation between Tertiary low- to mid-latitude planktonic foraminiferal {delta}{sup 18}O and the difference between these data and coeval benthic foraminiferal {delta}{sup 18}O. Late Quaternary data do not show this correlation. Coupling statistical model/{delta}{sup 18}O comparisons and evidence for Antarctic ice and ocean temperature variation, they infer that Tertiary ice volume, recorded by tropical planktonic {delta}{sup 18}O became lost in the noise. This renders low correlation between Teritiary planktonic and benthic {delta}{sup 18}O time series compared to late Quaternary data. They contend that Tertiary ice sheet growth was commonly driven by warming of deep water from low- to mid-latitude, cooled. Because tectonic forcing and orbital forcing at low-latitude primarily controlled production and temperature variations of this Warm Saline Deep Water, these influences largely dictated Tertiary ice volume fluctuations. Through the Tertiary, they infer ice volume fluctuations to be an important component of sea level history on timescales between 10{sup 3} and 10{sup 7} years.

Prentice, M.L. (Univ. of Maine, Orono (USA)); Matthews, R.K. (Brown Univ., Providence, RI (USA))

1991-04-10

267

SIPEX--Exploring the Antarctic Sea Ice Zone  

ERIC Educational Resources Information Center

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

Zicus, Sandra; Dobson, Jane; Worby, Anthony

2008-01-01

268

Influences of sea ice on eastern Bering Sea phytoplankton  

NASA Astrophysics Data System (ADS)

The influence of sea ice on the species composition and cell density of phytoplankton was investigated in the eastern Bering Sea in spring 2008. Diatoms, particularly pennate diatoms, dominated the phytoplankton community. The dominant species were Grammonema islandica (Grunow in Van Heurck) Hasle, Fragilariopsis cylindrus (Grunow) Krieger, F. oceanica (Cleve) Hasle, Navicula vanhoeffenii Gran, Thalassiosira antarctica Comber, T. gravida Cleve, T. nordenskiöeldii Cleve, and T. rotula Meunier. Phytoplankton cell densities varied from 0.08×104 to 428.8×104 cells/L, with an average of 30.3×104 cells/L. Using cluster analysis, phytoplankton were grouped into three assemblages defined by ice-forming conditions: open water, ice edge, and sea ice assemblages. In spring, when the sea ice melts, the phytoplankton dispersed from the sea ice to the ice edge and even into open waters. Thus, these phytoplankton in the sea ice may serve as a "seed bank" for phytoplankton population succession in the subarctic ecosystem. Moreover, historical studies combined with these results suggest that the sizes of diatom species have become smaller, shifting from microplankton to nannoplankton-dominated communities.

Zhou, Qianqian; Wang, Peng; Chen, Changping; Liang, Junrong; Li, Bingqian; Gao, Yahui

2015-03-01

269

Evolution of summer Arctic sea ice albedo in CCSM4 simulations: Episodic summer snowfall and frozen summers  

NASA Astrophysics Data System (ADS)

albedo of Arctic sea ice is calculated from summertime output of twentieth century Community Climate System Model v.4 (CCSM4) simulations. This is compared with an empirical record based on the generalized observations of the summer albedo progression along with melt onset dates determined from remote sensing. Only the contributions to albedo from ice, snow, and ponds are analyzed; fractional ice area is not considered in this assessment. Key factors dictating summer albedo evolution are the timing and extent of ponding and accumulation of snow. The CCSM4 summer sea ice albedo decline was found, on average, to be less pronounced than either the empirical record or the CLARA-SAL satellite record. The modeled ice albedo does not go as low as the empirical record, nor does the low summer albedo last as long. In the model, certain summers were found to retain snow on sea ice, thus inhibiting ice surface melt and the formation or retention of melt ponds. These "frozen" summers were generally not the summers with the largest spring snow accumulation, but were instead summers that received at least trace snowfall in June or July. When these frozen summers are omitted from the comparison, the model and empirical records are in much better agreement. This suggests that the representation of summer Arctic snowfall events and/or their influence on the sea ice conditions are not well represented in CCSM4 integrations, providing a target for future model development work.

Light, Bonnie; Dickinson, Suzanne; Perovich, Donald K.; Holland, Marika M.

2015-01-01

270

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

271

Exploring the utility of quantitative network design in evaluating Arctic sea-ice thickness sampling strategies  

NASA Astrophysics Data System (ADS)

We present a quantitative network design (QND) study of the Arctic sea ice-ocean system using a software tool that can evaluate hypothetical observational networks in a variational data assimilation system. For a demonstration, we evaluate two idealised flight transects derived from NASA's Operation IceBridge airborne ice surveys in terms of their potential to improve ten-day to five-month sea-ice forecasts. As target regions for the forecasts we select the Chukchi Sea, an area particularly relevant for maritime traffic and offshore resource exploration, as well as two areas related to the Barnett Ice Severity Index (BSI), a standard measure of shipping conditions along the Alaskan coast that is routinely issued by ice services. Our analysis quantifies the benefits of sampling upstream of the target area and of reducing the sampling uncertainty. We demonstrate how observations of sea-ice and snow thickness can constrain ice and snow variables in a target region and quantify the complementarity of combining two flight transects. We further quantify the benefit of improved atmospheric forecasts and a well-calibrated model.

Kaminski, T.; Kauker, F.; Eicken, H.; Karcher, M.

2015-03-01

272

Sea Ice Extension for the Earth as a System Learning Activity  

NSDL National Science Digital Library

Maps displaying global environmental data (specifically Solar Energy and Average Temperature) through the course of a year are compared in order to understand how the Earth works as a system focusing on Polar Regions. Students then explore data from schools located in Alaska and Antarctica to understand processes that drive the temperature patterns; students then visit the National Snow and Ice Data Center Web site to learn more about the Cryosphere (focusing on Albedo and Sea Ice); finally students visit NOAA's web site looking at data of Sea Ice data anomalies. (Link to the relevant pages in these web sites are listed below.)

Gary Randolph

273

The anisotropic scattering coefficient of sea ice  

NASA Astrophysics Data System (ADS)

Radiative transfer in sea ice is subject to anisotropic, multiple scattering. The impact of anisotropy on the light field under sea ice was found to be substantial and has been quantified. In this study, a large data set of irradiance and radiance measurements under sea ice has been acquired with a Remotely Operated Vehicle (ROV) in the central Arctic. Measurements are interpreted in the context of numerical radiative transfer calculations, laboratory experiments, and microstructure analysis. The ratio of synchronous measurements of transmitted irradiance to radiance shows a clear deviation from an isotropic under-ice light field. We find that the angular radiance distribution under sea ice is more downward directed than expected for an isotropic light field. This effect can be attributed to the anisotropic scattering coefficient within sea ice. Assuming an isotropic radiance distribution under sea ice leads to significant errors in light-field modeling and the interpretation of radiation measurements. Quantification of the light field geometry is crucial for correct conversion of radiance data acquired by Autonomous Underwater Vehicles (AUVs) and ROVs.

Katlein, Christian; Nicolaus, Marcel; Petrich, Chris

2014-02-01

274

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

275

9 The Dynamics of Snow and Ice Masses J.S. Wettlaufer  

E-print Network

principally because of their role in global warming and ice-age events. It is in this sense that ice persists. The swift ice streams of West Antarctica are believed to modulate sea-level by influencing

Wettlaufer, John S.

276

Impacts of a mushy-layer thermodynamic approach in global sea-ice simulations using the CICE sea-ice model  

NASA Astrophysics Data System (ADS)

We perform global simulations of the Los Alamos sea-ice model, CICE, with a new thermodynamics component that has a fully prognostic, variable bulk salinity vertical profile based on mushy layer physics. The processes of gravity drainage, melt-water flushing and snow-ice formation are parameterized to allow the bulk salinity to evolve with time. We analyze the seasonal and spatial variation of sea-ice bulk salinity, area, volume and thickness and compare these quantities to simulations using the previous thermodynamic component. Adjusting one of the gravity drainage parameters, we find good agreement between simulation results and fieldwork ice-core observations of sea-ice bulk salinity. As expected, bulk salinity is highest during periods of ice growth and lowest after periods of ice melt. In the northern hemisphere the new thermodynamics component produces thicker ice than the previous thermodynamics component. Of the nine major differences between the two models, differences in how salinities are calculated and how melt-pond flushing is parameterized are the principal causes of this thickness difference. Thickness differences are smaller in the southern hemisphere than in the northern hemisphere since a greater fraction of ice melts, and differences cannot accumulate year-on-year. Model differences in how ice thickness changes and snow-ice formation are calculated are the most important causes of the different thickness between the two thermodynamic components in the southern hemisphere. The melt-pond area and volume are found to be highly sensitive to a parameter choice controlling drainage through macroscopic holes in the ice, in both hemispheres.

Turner, Adrian K.; Hunke, Elizabeth C.

2015-02-01

277

A sensitivity study of the sea ice simulation in the global coupled climate model, HadGEM3  

NASA Astrophysics Data System (ADS)

We present the results of a wide-ranging sea ice sensitivity study, performed with a fully-coupled global atmosphere-ice-ocean climate model. We investigate sensitivity to a selection of sea ice parameters, varied within the range of observational uncertainty, and additionally study the effect on the sea ice of increased resolution in the atmosphere and ocean-ice models, as well as dynamics and physics changes in the atmosphere. In the Arctic, we find that the sea ice thickness is most sensitive to the albedo of the overlying snow layer (because of its influence on surface melt) and the thermal conductivities of ice and snow (because of their role in regulating heat flux from the ocean to the atmosphere through the ice). We find the winter Arctic ice extent to be sensitive to the resolution of the ocean-ice model, through increased sea surface temperatures in the Labrador Sea at higher resolution. The Arctic ice extent is reduced under increased atmospheric resolution, because of increased poleward heat transport. In the Antarctic, the sensitivity to sea ice parameters is weaker, and atmosphere and ocean forcing dominate; in particular, increased resolution of the atmosphere and ocean-ice models leads to the enhancement of a warm bias in the Southern Ocean, which has a large impact on sea ice thickness and extent. Inclusion of a selection of these parameters in combination, together with changes to the atmosphere and ocean models, leads to significant improvements in representation of Arctic sea ice extent, thickness and volume in a new global coupled model configuration.

Rae, J. G. L.; Hewitt, H. T.; Keen, A. B.; Ridley, J. K.; Edwards, J. M.; Harris, C. M.

2014-02-01

278

A sensitivity study of the sea ice simulation in the global coupled climate model, HadGEM3  

NASA Astrophysics Data System (ADS)

We will present some results from the first sea ice sensitivity study to be performed with a fully-coupled global atmosphere-ice-ocean climate model. Results will be presented for sensitivity to a selection of sea ice parameters, varied within the range of observational uncertainty, and additionally for the sensitivity of the sea ice to increased resolution in the atmosphere and ocean-ice models, as well as dynamics and physics changes in the atmosphere. In the Arctic, the sea ice thickness is most sensitive to the albedo of the overlying snow layer (because of its influence on surface melt) and the thermal conductivities of ice and snow (because of their role in regulating heat flux from the ocean to the atmosphere through the ice). The winter Arctic ice extent is found to be sensitive to an increase in resolution of the ocean-ice model, because of increased sea surface temperatures in the Labrador Sea at higher resolution. In addition, the Arctic ice extent is reduced under increased atmospheric resolution, because better representation of mid-latitude storms leads to increased poleward heat transport. In the Antarctic, the sensitivity to sea ice parameters is weaker, and atmosphere and ocean forcing dominate; in particular, increased resolution of the atmosphere and ocean-ice models leads to the enhancement of a warm bias in the Southern Ocean, which has a large impact on sea ice thickness and extent. Inclusion of a selection of these parameters in combination, together with changes to the atmosphere and ocean models, leads to significant improvements in depiction of sea ice extent, thickness and volume.

Rae, Jamie; Hewitt, Helene; Keen, Ann; Ridley, Jeff; Edwards, John; Harris, Chris; West, Alex

2014-05-01

279

Surface Impedance Tomography for Antarctic Sea Ice  

E-print Network

Surface Impedance Tomography for Antarctic Sea Ice C. Sampsona , K. M. Goldena , A. Gullya , A. P-0090 USA bAustralian Antarctic Division and ACE CRC, University of Tasmania, Private Bag 80, Hobart, 7001

Golden, Kenneth M.

280

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

281

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

2014-09-01

282

Assimilating SMOS sea ice thickness into a coupled ice-ocean model using a local SEIK filter  

NASA Astrophysics Data System (ADS)

The impact of assimilating sea ice thickness data derived from ESA's Soil Moisture and Ocean Salinity (SMOS) satellite together with Special Sensor Microwave Imager/Sounder (SSMIS) sea ice concentration data of the National Snow and Ice Data Center (NSIDC) in a coupled sea ice-ocean model is examined. A period of 3 months from 1 November 2011 to 31 January 2012 is selected to assess the forecast skill of the assimilation system. The 24 h forecasts and longer forecasts are based on the Massachusetts Institute of Technology general circulation model (MITgcm), and the assimilation is performed by a localized Singular Evolutive Interpolated Kalman (LSEIK) filter. For comparison, the assimilation is repeated only with the SSMIS sea ice concentrations. By running two different assimilation experiments, and comparing with the unassimilated model, independent satellite-derived data, and in situ observation, it is shown that the SMOS ice thickness assimilation leads to improved thickness forecasts. With SMOS thickness data, the sea ice concentration forecasts also agree better with observations, although this improvement is smaller.

Yang, Qinghua; Losa, Svetlana N.; Losch, Martin; Tian-Kunze, Xiangshan; Nerger, Lars; Liu, Jiping; Kaleschke, Lars; Zhang, Zhanhai

2014-10-01

283

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. PMID:24204642

Assmy, Philipp; Ehn, Jens K.; Fernández-Méndez, 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

284

Floating ice-algal aggregates below melting arctic sea ice.  

PubMed

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. PMID:24204642

Assmy, Philipp; Ehn, Jens K; Fernández-Méndez, 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

285

How reversible is sea ice loss?  

NASA Astrophysics Data System (ADS)

It is well accepted that increasing atmospheric CO2 results in global warming, leading to a decline in polar sea ice area. Here, the specific question of whether there is a tipping point in the sea ice cover is investigated. The global climate model HadCM3 is used to map the trajectory of sea ice area under idealised scenarios. The atmospheric CO2 is first ramped up to four times pre-industrial levels (4 × CO2), then ramped down to pre-industrial levels. We also examine the impact of stabilising climate at 4 × CO2 prior to ramping CO2 down to pre-industrial levels. Against global mean temperature, Arctic sea ice area is reversible, while the Antarctic sea ice shows some asymmetric behaviour - its rate of change slower, with falling temperatures, than its rate of change with rising temperatures. However, we show that the asymmetric behaviour is driven by hemispherical differences in temperature change between transient and stabilisation periods. We find no irreversible behaviour in the sea ice cover.

Ridley, J. K.; Lowe, J. A.; Hewitt, H. T.

2012-02-01

286

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

287

Processes driving sea ice variability in the Bering Sea in an eddying ocean/sea ice model: Mean seasonal cycle  

NASA Astrophysics Data System (ADS)

The seasonal cycle of sea ice variability in the Bering Sea, together with the thermodynamic and dynamic processes that control it, are examined in a fine resolution (1/10°) global coupled ocean/sea-ice model configured in the Community Earth System Model (CESM) framework. The ocean/sea-ice model consists of the Los Alamos National Laboratory Parallel Ocean Program (POP) and the Los Alamos Sea Ice Model (CICE). The model was forced with time-varying reanalysis atmospheric forcing for the time period 1970-1989. This study focuses on the time period 1980-1989. The simulated seasonal-mean fields of sea ice concentration strongly resemble satellite-derived observations, as quantified by root-mean-square errors and pattern correlation coefficients. The sea ice energy budget reveals that the seasonal thermodynamic ice volume changes are dominated by the surface energy flux between the atmosphere and the ice in the northern region and by heat flux from the ocean to the ice along the southern ice edge, especially on the western side. The sea ice force balance analysis shows that sea ice motion is largely associated with wind stress. The force due to divergence of the internal ice stress tensor is large near the land boundaries in the north, and it is small in the central and southern ice-covered region. During winter, which dominates the annual mean, it is found that the simulated sea ice was mainly formed in the northern Bering Sea, with the maximum ice growth rate occurring along the coast due to cold air from northerly winds and ice motion away from the coast. South of St Lawrence Island, winds drive the model sea ice southwestward from the north to the southwestern part of the ice-covered region. Along the ice edge in the western Bering Sea, model sea ice is melted by warm ocean water, which is carried by the simulated Bering Slope Current flowing to the northwest, resulting in the S-shaped asymmetric ice edge. In spring and fall, similar thermodynamic and dynamic patterns occur in the model, but with typically smaller magnitudes and with season-specific geographical and directional differences.

Li, Linghan; McClean, Julie L.; Miller, Arthur J.; Eisenman, Ian; Hendershott, Myrl C.; Papadopoulos, Caroline A.

2014-12-01

288

The role of snow/ice cover in the formation of a local Himalayan circulation  

NASA Astrophysics Data System (ADS)

Observations and model simulations were conducted in a typical Himalayan valley to investigate the role of snow/ice cover in the formation of the local diurnal wind. An unusual local circulation was observed in the Himalayas with a strong down-valley flow dominant from noon to midnight, greatly differing from those in other mountainous regions. Two experiments with snow/ice cover included/excluded were performed using the Regional Atmospheric Modeling System (RAMS) to reconstruct the Himalayan circulation, and to reveal the role of snow/ice in this circulation. The results show that the wind system in the Himalayas is composed of both glacier winds driven by the snow/ice cover and classical mountain-valley winds. In particular, the glacier winds establish the distinctive feature of the Himalayan local circulation, i.e., the strong down-valley flow in the afternoon.

Ma, Shupo; Zhou, Libo; Zou, Han; Zhang, Meigen; Li, Peng

2013-04-01

289

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

290

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

Microsoft Academic Search

Bacillus subtilis spore biological dosimeters and electronic dosimeters were used to investigate the exposure of terrestrial microbial communities in micro-habitats covered by snow and ice in Antarctica. The melting of snow covers of between 5- and 15-cm thickness, depending on age and heterogeneity, could increase B. subtilis spore inactivation by up to an order of magnitude, a relative increase twice

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

2002-01-01

291

ALBEDO MODELS FOR SNOW AND ICE ON A FRESHWATER LAKE. (R824801)  

EPA Science Inventory

Abstract Snow and ice albedo measurements were taken over a freshwater lake in Minnesota for three months during the winter of 1996¯1997 for use in a winter lake water quality model. The mean albedo of new snow was measured as 0.83±0.028, while the...

292

It is the North Pole: Sea ice observations at the North Pole Environmental Observatory  

NASA Astrophysics Data System (ADS)

In recent years the periphery of the Arctic sea ice cover has undergone significant changes, with a reduction in summer ice extent, a thinning of the ice, and a shift from multiyear to first year ice. Here we examine sea ice conditions in the Central Arctic near the North Pole using autonomous measurements of sea ice mass balance and motion made at the North Pole Environmental Observatory since 2000. The measurements include snow depth, ice thickness, surface melt, bottom melt, and ice motion. While results from 2000 to 2012 exhibit no definitive trends, there are a number of interesting findings. There is large interannual variability, with surface melting ranging from 0.02 m to 0.50 m and bottom melting from 0.10 m to 0.57 m. The years with the largest amount of surface melting were also years of record minimum ice extent; 2005, 2007, and 2012. The largest amounts of bottom melting have occurred in the past few years. For all years the end of melt season ice thickness was at least 1.2 m. Ice floes follow a predictable trajectory from the North Pole exiting out the Fram Strait. There is a tendency towards an increase in the ice floe speed averaged from April to October, ranged from a minimum of 3.06 km per day in 2001 to a maximum of 8.26 km per day in 2010.

Perovich, D. K.; Richter-Menge, J.; Elder, B. C.; Polashenski, C.; Arbetter, T.; Brennick, O.

2013-12-01

293

Coastal landfast sea ice decay and breakup in northern Alaska: Key processes and seasonal prediction  

NASA Astrophysics Data System (ADS)

Seasonal breakup of landfast sea ice consists of movement and irreversible ice detachment in response to winds or oceanic forces in the late stages of ice decay. The breakup process of landfast sea ice in the Chukchi Sea at Barrow, Alaska, was analyzed for the years 2000 through 2010 on the basis of local observations of snow and ice conditions, weather records, image sequences obtained from cameras, coastal X band marine radar, and satellite imagery. We investigated the relation of breakup to winds, tides, and nearshore current measurements from a moored acoustic Doppler current profiler. Two breakup modes are distinguished at Barrow on the basis of the degree of ice decay. Mechanical breakup due to wind and oceanic forces follows ablation and weakening of the ice. Thermal breakup is the result of ice disintegration under melt ponds, requiring little force to induce dispersion. Grounded pressure ridges are pivotal in determining the breakup mode. The timing of thermal breakup of the nearshore ice cover was found to correlate with the measured downwelling solar radiation in June and July. This linkage allows for the development of an operational forecast of landfast ice breakup. Results from forecasts during 2 years demonstrate that thermal breakup can be predicted to within a couple of days 2 weeks in advance. The cumulative shortwave energy absorbed by the ice cover provides for a measure of the state of ice decay and potential for disintegration. Discriminating between the two modes of breakup bears the potential to greatly increase forecasting skill.

Petrich, Chris; Eicken, Hajo; Zhang, Jing; Krieger, Jeremy; Fukamachi, Yasushi; Ohshima, Kay I.

2012-02-01

294

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.

295

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

PubMed

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

Screen, James A; Simmonds, Ian

2010-04-29

296

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

297

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

298

Sea Ice Yearly Minimum 1979-2007  

NSDL National Science Digital Library

At the end of each summer, sea ice cover in the Arctic Ocean reaches its minimum extent and what is left is what is called the perennial ice cover (mainly thick multi-year ice floes). The area of perennial ice has been steadily decreasing since the satellite record began in 1979, at a rate of about 10 percent per decade. This visualization shows the annual minimum extent of sea ice in the Arctic Ocean from 1979 to 2007. A graph is overlaid that shows the area in millions of square kilometers for each year's minimum day. The previous record minimum (2005) and the new 2007 record minimum, far below the previous record and 38 percent lower than the climatological average, are highlighted. The visualization may be streamed from the website or downloaded in several formats.

299

Assessment of EOS Aqua AMSR-E Arctic Sea Ice Concentrations using Landsat-7 and Airborne Microwave Imagery  

NASA Technical Reports Server (NTRS)

An assessment of Advanced Microwave Scanning Radiometer Earth Observing System (AMSR-E) sea ice concentrations under winter conditions using ice concentrations derived from Landsat-7 Enhanced Thematic Mapper Plus (ETM+) imagery obtained during the March 2003 Arctic sea ice validation field campaign is presented. The National Oceanic and Atmospheric Administration Environmental Technology Laboratory's Airborne Polarimetric Scanning Radiometer Measurements, which were made from the National Aeronautics and Space Administration P 3B aircraft during the campaign, were used primarily as a diagnostic tool to understand the comparative results and to suggest improvements to the AMSR-E ice concentration algorithm. Based on the AMSR-E/ETM+ comparisons, a good overall agreement with little bias (approx. 1%) for areas of first year and young sea ice was found. Areas of new ice production result in a negative bias of about 5% in the AMSR-E ice concentration retrievals, with a root mean square error of 8%. Some areas of deep snow also resulted in an underestimate of the ice concentration (approx. 10%). For all ice types combined and for the full range of ice concentrations, the bias ranged from 0% to 3%, and the rms errors ranged from 1% to 7%, depending on the region. The new-ice and deep-snow biases are expected to be reduced through an adjustment of the new-ice and ice-type C algorithm tie points.

Cavalieri, Donald J.; Markus, Thorsten; Hall, Dorothy K.; Gasiewski, Albin J.; Klein, Marian; Ivanoff, Alvaro

2006-01-01

300

Interactions of wind-transported snow with a rift in the Ross Ice Shelf, Katherine C. Leonard,1  

E-print Network

] suggested that sudden ice shelf collapse similar to the 2002 disintegration of Larsen B may have beenInteractions of wind-transported snow with a rift in the Ross Ice Shelf, Antarctica Katherine C Ice Shelf captures all wind-transported snow traveling in saltation and a substantial fraction

Boyce, C. Kevin

301

The effect of sea ice on the solar energy budget in the astmosphere-sea ice-ocean system: A model study  

NASA Technical Reports Server (NTRS)

A coupled one-dimensional multilayer and multistream radiative transfer model has been developed and applied to the study of radiative interactions in the atmosphere, sea ice, and ocean system. The consistent solution of the radiative transfer equation in this coupled system automatically takes into account the refraction and reflection at the air-ice interface and allows flexibility in choice of stream numbers. The solar radiation spectrum (0.25 micron-4.0 micron) is divided into 24 spectral bands to account adequately for gaseous absorption in the atmosphere. The effects of ice property changes, including salinity and density variations, as well as of melt ponds and snow cover variations over the ice on the solar energy distribution in the entire system have been studied quantitatively. The results show that for bare ice it is the scattering, determined by air bubbles and brine pockets, in just a few centimeters of the top layer of ice that plays the most important role in the solar energy absorption and partitioning in the entire system. Ice thickness is important to the energy distribution only when the ice is thin, while the absorption in the atmosphere is not sensitive to ice thickness exceeds about 70 cm. The presence of clouds moderates all the sensitivities of the absorptive amounts in each layer to the variations in the ice properties and ice thickness. Comparisons with observational spectral albedo values for two simple ice types are also presented.

Jin, Z.; Stamnes, Knut; Weeks, W. F.; Tsay, Si-Chee

1994-01-01

302

Evaluate the application of ERTS-A data for detecting and mapping sea ice  

NASA Technical Reports Server (NTRS)

The author has identified the following significant results. Sea ice is detectable in all of the ERTS-1 MSS bands and can be distinguished from clouds through a number of interpretive keys. Considerable information on ice type can be derived from the ERTS-1 data. Ice types that appear to be identifiable include: ice floes of various categories, pack ice of various concentrations, ice belts, brash ice, rotten ice, fast ice, leads, fractures, cracks, puddles, thaw holes, and flooded ice. Although larger icebergs can be seen, it is difficult to distinguish them from ice floes. Ice features as small as the small floe of 20 to 100 m across can be detected, and the sizes of features somewhat smaller than 100 m can be measured from enlarged ERTS-1 prints. The multispectral analysis of the ERTS-1 MSS-7 bands provides much information on ice type and ice surface features that cannot be derived from a single spectral band. For example, thaw holes can often be distinguished from puddles because of their different appearances in the two bands. These surface features can be indicative of ice age. Furthermore, snow lines on glaciers can be reliably mapped through the joint use of the MSS-4 and 7 data.

Barnes, J. C. (principal investigator)

1973-01-01

303

Phytoplankton blooms beneath the sea ice in the Chukchi sea  

NASA Astrophysics Data System (ADS)

In the Arctic Ocean, phytoplankton blooms on continental shelves are often limited by light availability, and are therefore thought to be restricted to waters free of sea ice. During July 2011 in the Chukchi Sea, a large phytoplankton bloom was observed beneath fully consolidated pack ice and extended from the ice edge to >100 km into the pack. The bloom was composed primarily of diatoms, with biomass reaching 1291 mg chlorophyll a m-2 and rates of carbon fixation as high as 3.7 g C m-2 d-1. Although the sea ice where the bloom was observed was near 100% concentration and 0.8-1.2 m thick, 30-40% of its surface was covered by melt ponds that transmitted 4-fold more light than adjacent areas of bare ice, providing sufficient light for phytoplankton to bloom. Phytoplankton growth rates associated with the under-ice bloom averaged 0.9 d-1 and were as high as 1.6 d-1. We argue that a thinning sea ice cover with more numerous melt ponds over the past decade has enhanced light penetration through the sea ice into the upper water column, favoring the development of these blooms. These observations, coupled with additional biogeochemical evidence, suggest that phytoplankton blooms are currently widespread on nutrient-rich Arctic continental shelves and that satellite-based estimates of annual primary production in waters where under-ice blooms develop are ~10-fold too low. These massive phytoplankton blooms represent a marked shift in our understanding of Arctic marine ecosystems.

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.; Bates, Nicholas R.; Benitez-Nelson, Claudia R.; Brownlee, Emily; Frey, Karen E.; Laney, Samuel R.; Mathis, Jeremy; Matsuoka, Atsushi; Greg Mitchell, B.; Moore, G. W. K.; Reynolds, Rick A.; Sosik, Heidi M.; Swift, James H.

2014-07-01

304

A new algorithm to measure sea ice concentration from passive microwave remote sensing  

NASA Astrophysics Data System (ADS)

Studies of spatial and temporal properties of sea ice distribution in polar regions help to monitor global environmental changes and reveal their natural and anthropogenic factors, as well as make forecasts of weather, marine transportation and fishing conditions, assess perspectives of mineral mining on the continental shelf, etc. Contact methods of observation are often insufficient to meet the goals, very complicated technically and organizationally and not always safe for people involved. Remote sensing techniques are believed to be the best alternative. Its include monitoring of polar regions by means of passive microwave sensing with the aim to determine spatial distribution, types, thickness and snow cover of ice. However, the algorithms employed today to retrieve sea ice characteristics from passive microwave sensing data for different reasons give significant errors, especially in summer period and also near ice edges and in cases of open ice. One of the error sources is the current practice of using empirical dependencies and adjustment coefficients for the retrieval of ice characteristics and neglecting the physics of the process. We discuss an electrodynamic model of the sea surface - sea ice - snow cover - atmosphere system developed with account taken of physical and structural properties of the ambient. Model calculations of ice brightness temperature in different concentrations and snow covers are in good agreement with SSM/I measurement data. On the base of this model we develop a new algorithm for the retrieval of sea ice concentration from passive microwave sensing data - Variation Arctic Sea Ice Algorithm (VASIA). In contrast to the well-known techniques (NASA TEAM, Bootstrap, ASI, NORSEX et al), it takes into account the real physical parameters of ice, snow and open water rather than empirical and adjustment coefficients. Satellite data were provided by the POLE-RT-Fields SSM/I and SSMIS data collection for polar regions retrieved from the GLOBAL-RT database. The results of the proposed algorithm for Arctic ice cover concentration are compared to NASA-TEAM2 technique. The proposed algorithm of sea ice concentration retrieval from microwave radiometry data gives good results within the assumed approximations. Lower ice concentration produced by VASIA for September is related to the problem of melt ponds (pools of open water on sea ice). Melt ponds are an important element of the Arctic climate system. Covering up to 50% of the surface of drifting ice in summer, they are characterized by low albedo values and absorb several times more incident shortwave radiation than the rest of the snow and ice cover. Emission from melt ponds corresponds to that of open water resulting in significant underestimating of ice concentration in summer. The work was sponsored by RFBR projects N 13-05-00272 and N 13-05- 41443 as well as the Russian Federation Governmental grant (Agreement N 11.G34.31.0078) for investigations guided by outstanding scientists.

Repina, Irina; Sharkov, Evgeniy; Komarova, Nataliya; Raev, Mikhail; Tikhonov, Vasilii; Boyarskiy, Dmitriy

305

Dynamic ikaite production and dissolution in sea ice - control by temperature, salinity and pCO2 conditions  

NASA Astrophysics Data System (ADS)

Ikaite is a hydrous calcium carbonate mineral (CaCO3 · 6H2O). It is only found in a metastable state, and decomposes rapidly once removed from near-freezing water. Recently, ikaite crystals have been found in sea ice and it has been suggested that their precipitation may play an important role in air-sea CO2 exchange in ice-covered seas. Little is known, however, of the spatial and temporal dynamics of ikaite in sea ice. Here we present evidence for highly dynamic ikaite precipitation and dissolution in sea ice grown at an out-door pool of the Sea-ice Environmental Research Facility (SERF). During the experiment, ikaite precipitated in sea ice with temperatures below -3 °C, creating three distinct zones of ikaite concentrations: (1) a mm to cm thin surface layer containing frost flowers and brine skim with bulk concentrations of > 2000 ?mol kg-1, (2) an internal layer with concentrations of 200-400 ?mol kg-1 and (3) a~bottom layer with concentrations of < 100 ?mol kg-1. Snowfall events caused the sea ice to warm, dissolving ikaite crystals under acidic conditions. Manual removal of the snow cover allowed the sea ice to cool and brine salinities to increase, resulting in rapid ikaite precipitation. The modeled (FREZCHEM) ikaite concentrations were in the same order of magnitude as observations and suggest that ikaite concentration in sea ice increase with decreasing temperatures. Thus, varying snow conditions may play a key role in ikaite precipitation and dissolution in sea ice. This will have implications for CO2 exchange with the atmosphere and ocean.

Rysgaard, S.; Wang, F.; Galley, R. J.; Grimm, R.; Lemes, M.; Geilfus, N.-X.; Chaulk, A.; Hare, A. A.; Crabeck, O.; Else, B. G. T.; Campbell, K.; Papakyriakou, T.; Sørensen, L. L.; Sievers, J.; Notz, D.

2013-12-01

306

The GISP2 ice core and snow-atmosphere chemical exchange  

NASA Astrophysics Data System (ADS)

Polar snow and ice are among the most valuable, or perhaps are the most valuable, tools for reconstructing past climatic conditions. Glacial-ice records large changes over time scales ranging from intraannual to glacial-interglacial transitions. Changes in the ice are thought to largely reflect changes in atmospheric chemistry and dynamics resulting from variations in biogeochemical cycling due to climatic, and other, perturbations [Oeschger and Langway, 1989].However, two broad classes of processes, air-to-snow transfer and post-depositional modification, combine to filter and potentially distort atmospheric signals before they can be preserved in the glacial record [Neftel, 1991]. Recognizing the critical need to understand air-snow transfer and postdepositional modifications to unravel the climate information recorded in ice cores, the International Commission on Snow and Ice (ICSI) established a working group on Snow-Atmosphere Chemical Exchange. With support from the National Science Foundation, Division of Polar Programs, the ICSI working group organized a workshop to develop a science plan for a 3- to 5-year research effort focused on exchange processes. The workshop will follow the current Greenland Ice Sheet Project Two (GISP2) drilling effort at Summit, Greenland.

Bales, Roger; Dibb, Jack; Neftel, Albrecht

307

Potential Applications of Satellite Based Low Frequency Microwave Measurements of Snow and Ice  

NASA Technical Reports Server (NTRS)

In this presentation we will examine some potential applications of low frequency microwave radar and radiometer data to remote sensing of snow and ice conditions over land. We focus on the following low frequency bands; L-band (1.28 GHz), S-band (2.69 GHz), and C-band (5.0 GHz). To predict the effect of snow cover on microwave emission, we need to characterize the dielectric properties of the snow in terms of important physical parameters such as snow density, temperature, and wetness. For the case of dry snow, we use an empirical mixing formula which gives the effective complex permittivity of snow as a function of density, temperature, and frequency. For wet snow, we use another mixing formula which gives the effective complex permittivity as a function of snow wetness. With dry snow, the loss at low microwave frequencies is very small so the corresponding penetration depths are very large (eg., 100 m). Clearly seasonal snow covers are far too thin to have a direct scattering or emission effect on these low frequency bands. There are, however, indirect effects introduced because of altered reflection at the snow/soil boundary, and an extra reflecting interface at the snow/air boundary. For C-band, layers of snow with different densities can have an impact if the number of layers grows sufficiently large. (eg., many meters of snow pack with cm-scale density layering.) Wet snow poses a more difficult problem. Liquid water is much more effective than ice at scattering and absorbing L-band radiation, so even a small amount of wetness will greatly reduce penetration. For example, with a snow wetness of 1 percent (volume fraction), and a density of 300 kg/cu. m, the penetration depths for L-band, S-band, and C-band are about 1.6 m, 0.3 m, and 0.15 m respectively. Very wet snow has more than 10 percent liquid water, and the corresponding L-band penetration is less than 0.2 m. Because the penetration distance is a strong function of frequency, it may be possible to identify a particular class of snow where the wetness is a few percent, and the depth is around one meter by looking at the frequency gradient.

West, Richard D.

2000-01-01

308

Snow algae in an ice core drilled on Grigoriev Ice cap in the Kyrgyz Tien Shen Mountains  

NASA Astrophysics Data System (ADS)

Snow algae are photosynthetic microorganisms and are living on the surfase of glaciers. They grow on melting surface from spring to summer and their biomass and community structure are changed with physical and chemical conditions on glaciers. Ice cores drilled from glaciers also contain snow algae that grew in the past. Studying biomass and community structure of snow algae in ice cores could reveal the temporal variation in snow algae in the past, and also environmental conditions relating propagation of snow algae. In this study, we anlalyzed snow algae preserved in an ice core of Grigoriev Ice cap located in eastern Kyrgyzstan of the central Asia, and to describe their temporal variations for the last 200 years. The ice core drilling was carried out on September in 2007 on the Grigoriev Ice cap in the Kyrgyz Tien Shen Mountains. A 87 m long ice core from the surface to the bedrock was recovered at the top of the ice cap. The core was horizontally cut every 5 cm (total 1212 samples). The samples were melted and preserved as a 3% formalin solution. After the sample water was filtered through a hydrophilized PTFE membrane filter, observed by microscope. Snow algae in the sample water were counting. The algal biomass was represented by the cell number per unit water volume. Here, we showed the results between the surface to the 64 m in depth. We also analyzed the snow algal communities on the surface of the ice cap collected from five different sites from the top down to the terminus. Microscopy revealed that the ice core contained three taxa of filamentous cyanobacteria, an unicellular cyanobacterium, and two green algae. They were also found on the ice or snow surface of the i Ice cap. The quantitative analyses of the algae in the part of upper 64 m deep of the ice core samples revealed that the algal biomass varied significantly and showed many peaks. Furthermore, the biomass profile differed among the taxa. The filamentous cyanobacterium varied from 0.0 to 4.6 x 103?m3 mL-1 (mean: 56?m3 mL-1 ), the unicellular cyanobacterium varied from 0.0 to 3.0 x 104?m3 mL-1 (mean: 1.2 x 103?m3 mL-1 ), and Green algae varied from 0.0 to 2.3 x 104?m3 mL-1 (mean: 2.2 x 103?m3 mL-1 ). Based on the dating by pollen grains, the 64 m core covers 237 years. The results suggest that the snow algae did not grow every year on the top of the ice cap, and their biomass and community structure varied greatly from year to year. The total biomass after the 1960s was significantly higher than those before the 1950s. This suggested suggests that the surface conditions changed more favorable to the growth of algae in the 1960s. Annal variation of the algal biomass was found to be significantly correlated with air temperature at the nearest observing station from Grigoriev the iIce cap and hydrogen stable isotope (?D) in the ice core. The results suggest that the algal growth is more preferable in warmer year.

Honda, M.; Takeuchi, N.; Sera, S.; Fujita, K.; Okamoto, S.; Naoki, K.; Aizen, V. B.

2012-12-01

309

A Supplementary Clear-Sky Snow and Ice Recognition Technique for CERES Level 2 Products  

NASA Technical Reports Server (NTRS)

Identification of clear-sky snow and ice is an important step in the production of cryosphere radiation budget products, which are used in the derivation of long-term data series for climate research. In this paper, a new method of clear-sky snow/ice identification for Moderate Resolution Imaging Spectroradiometer (MODIS) is presented. The algorithm's goal is to enhance the identification of snow and ice within the Clouds and the Earth's Radiant Energy System (CERES) data after application of the standard CERES scene identification scheme. The input of the algorithm uses spectral radiances from five MODIS bands and surface skin temperature available in the CERES Single Scanner Footprint (SSF) product. The algorithm produces a cryosphere rating from an aggregated test: a higher rating corresponds to a more certain identification of the clear-sky snow/ice-covered scene. Empirical analysis of regions of interest representing distinctive targets such as snow, ice, ice and water clouds, open waters, and snow-free land selected from a number of MODIS images shows that the cryosphere rating of snow/ice targets falls into 95% confidence intervals lying above the same confidence intervals of all other targets. This enables recognition of clear-sky cryosphere by using a single threshold applied to the rating, which makes this technique different from traditional branching techniques based on multiple thresholds. Limited tests show that the established threshold clearly separates the cryosphere rating values computed for the cryosphere from those computed for noncryosphere scenes, whereas individual tests applied consequently cannot reliably identify the cryosphere for complex scenes.

Radkevich, Alexander; Khlopenkov, Konstantin; Rutan, David; Kato, Seiji

2013-01-01

310

Temporary liquid water in upper snow/ice sub-surfaces on Mars?  

NASA Astrophysics Data System (ADS)

It is investigated whether conditions for melting can be temporarily created in the upper sub-surface parts of snow/ice-packs on Mars at subzero surface temperatures by means of the solid-state greenhouse effect, as occurs in snow- and ice-covered regions on Earth. The conditions for this possible temporary melting are quantitatively described for bolometric albedo values A = 0.8 and A = 0.2, and with model parameters typical for the thermo-physical conditions at snow/ice sites on the surface of present Mars. It is demonstrated by numerical modelling that there are several sets of parameters which will lead to development of layers of liquid water just below the top surface of snow- and ice-packs on Mars. This at least partial liquefaction occurs repetitively (e.g. diurnally, seasonally), and can in some cases lead to liquid water persisting through the night-time in the summer season. This liquid water can form in sufficient amounts to be relevant for macroscopic physical (rheology, erosion), for chemical, and eventually also for biological processes. The creation of temporary pockets of sub-surface water by this effect requires pre-existing snow or ice cover, and thus is more likely to take place at high latitudes, since the present deposits of snow/ice can mainly be found there. Possible rheologic and related erosion consequences of the appearance of liquid sub-surface water in martian snow/ice-packs are discussed in view of current observations of recent rheologic processes.

Möhlmann, Diedrich T. F.

2010-05-01

311

Snow and Ice Climatology of the Western United States and Alaska from MODIS  

NASA Astrophysics Data System (ADS)

The climate and hydroclimate of the Western US and Alaska are tightly coupled to their snow and ice cover. The Western US depends on mountain snowmelt for the majority of its water supply to agriculture, industrial and urban use, hydroelectric generation, and recreation, all driven by increasing population and demand. Alaskan snow and glacier cover modulate regional climate and, as with the Western US, dominate water supply and hydroelectric generation in much of the state. Projections of climate change in the Western US and Alaska suggest that the most pronounced impacts will include reductions of mountain snow and ice cover, earlier runoff, and a greater fraction of rain instead of snow. We establish a snow and ice climatology of the Western US and Alaska using physically based MODIS Snow Covered Area and Grain size model (MODSCAG) for fractional snow cover, the MODIS Dust Radiative Forcing in Snow model (MODDRFS) for radiative forcing by light absorbing impurities in snow, and the MODIS Permanent Ice model (MODICE) for annual minimum exposed snow. MODSCAG and MODDRFS use EOS MOD09GA historical reflectance data (2000-2012) to provide daily and 8-day composites and near real time products since the beginning of 2013, themselves ultimately composited to 8-day products. The compositing method considers sensor-viewing geometry, solar illumination, clouds, cloud shadows, aerosols and noisy detectors in order to select the best pixel for an 8-day period. The MODICE annual minimum exposed snow and ice product uses the daily time series of fractional snow and ice from MODSCAG to generate annual maps. With this project we have established an ongoing, national-scale, consistent and replicable approach to assessing current and projected climate impacts and climate-related risk in the context of other stressors. We analyze the products in the Northwest, Southwest, and Alaska/Arctic regions of the National Climate Assessment for the last decade, the nation's hottest on record. In the Northwest we use the observations to investigate earlier snowmelt, in the Southwest drought, and in Alaska to measure the change in glacier area. We compare the MODIS retrievals to a time series of AVIRIS retrievals at higher spatial resolution spanning 289km2 and 61km2 in the California's Sierra Nevada and Colorado's Senator Beck Basin. We continue to nest specific investigations of regions and topics that have high priority due to existing or anticipated climate stresses, generally in the context of a variety of other concerns.

Rittger, K. E.; Painter, T. H.; Mattmann, C. A.; Seidel, F. C.; Burgess, A.; Brodzik, M.

2013-12-01

312

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 horizontal snow transport at this level, which can be related to an overestimation of saltation and the typical size of drifting snow particles.

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.

2014-04-01

313

Modeling angular-dependent spectral emissivity of snow and ice in the thermal infrared atmospheric window.  

PubMed

A model of angular-dependent emissivity spectra of snow and ice in the 8-14 ?m atmospheric window is constructed. Past field research revealed that snow emissivity varies depending on snow grain size and the exitance angle. Thermography images acquired in this study further revealed that not only welded snow particles such as sun crust, but also disaggregated particles such as granular snow and dendrite crystals exhibit high reflectivity on their crystal facets, even when the bulk snow surface exhibits blackbody-like behavior as a whole. The observed thermal emissive behaviors of snow particles suggest that emissivity of the bulk snow surface can be expressed by a weighted sum of two emissivity components: those of the specular and blackbody surfaces. Based on this assumption, a semi-empirical emissivity model was constructed; it is expressed by a linear combination of specular and blackbody surfaces' emissivities with a weighting parameter characterizing the specularity of the bulk surface. Emissivity spectra calculated using the model succeeded in reproducing the past in situ measured directional spectra of various snow types by employing a specific weighting parameter for each snow type. PMID:24216578

Hori, Masahiro; Aoki, Teruo; Tanikawa, Tomonori; Hachikubo, Akihiro; Sugiura, Konosuke; Kuchiki, Katsuyuki; Niwano, Masashi

2013-10-20

314

Studies of Antarctic Sea Ice Concentrations from Satellite Data and Their Applications  

NASA Technical Reports Server (NTRS)

Large changes in the sea ice cover have been observed recently. Because of the relevance of such changes to climate change studies it is important that key ice concentration data sets used for evaluating such changes are interpreted properly. High and medium resolution visible and infrared satellite data are used in conjunction with passive microwave data to study the true characteristics of the Antarctic sea ice cover, assess errors in currently available ice concentration products, and evaluate the applications and limitations of the latter in polar process studies. Cloud-free high resolution data provide valuable information about the natural distribution, stage of formation, and composition of the ice cover that enables interpretation of the large spatial and temporal variability of the microwave emissivity of Antarctic sea ice. Comparative analyses of co-registered visible, infrared and microwave data were used to evaluate ice concentrations derived from standard ice algorithms (i.e., Bootstrap and Team) and investigate the 10 to 35% difference in derived values from large areas within the ice pack, especially in the Weddell Sea, Amundsen Sea, and Ross Sea regions. Landsat and OLS data show a predominance of thick consolidated ice in these areas and show good agreement with the Bootstrap Algorithm. While direct measurements were not possible, the lower values from the Team Algorithm results are likely due to layering within the ice and snow and/or surface flooding, which are known to affect the polarization ratio. In predominantly new ice regions, the derived ice concentration from passive microwave data is usually lower than the true percentage because the emissivity of new ice changes with age and thickness and is lower than that of thick ice. However, the product provides a more realistic characterization of the sea ice cover, and are more useful in polar process studies since it allows for the identification of areas of significant divergence and polynya activities. Also, heat and salinity fluxes are proportionately increased in these areas compared to those from the thicker ice areas. A slight positive trend in ice extent and area from 1978 through 2000 is observed consistent with slight continental cooling during the period. However, the confidence in this result is only moderate because the overlap period for key instruments is just one month and the sensitivity to changes in sensor characteristics, calibration and threshold for the ice edge is quite high.

Comiso, Josefino C.; Steffen, Konrad; Zukor, Dorothy J. (Technical Monitor)

2001-01-01

315

Multi-year Arctic Sea Ice - Duration: 0:43.  

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...

316

Comparative Views of Arctic Sea Ice Growth  

NASA Technical Reports Server (NTRS)

NASA researchers have new insights into the mysteries of Arctic sea ice, thanks to the unique abilities of Canada's Radarsat satellite. The Arctic is the smallest of the world's four oceans, but it may play a large role in helping scientists monitor Earth's climate shifts.

Using Radarsat's special sensors to take images at night and to peer through clouds, NASA researchers can now see the complete ice cover of the Arctic. This allows tracking of any shifts and changes, in unprecedented detail, over the course of an entire winter. The radar-generated, high-resolution images are up to 100 times better than those taken by previous satellites.

The two images above are separated by nine days (earlier image on the left). Both images represent an area (approximately 96 by 128 kilometers; 60 by 80 miles)located in the Baufort Sea, north of the Alaskan coast. The brighter features are older thicker ice and the darker areas show young, recently formed ice. Within the nine-day span, large and extensive cracks in the ice cover have formed due to ice movement. These cracks expose the open ocean to the cold, frigid atmosphere where sea ice grows rapidly and thickens.

Using this new information, scientists at NASA's Jet Propulsion Laboratory (JPL), Pasadena, Calif., can generate comprehensive maps of Arctic sea ice thickness for the first time. 'Before we knew only the extent of the ice cover,' said Dr. Ronald Kwok, JPL principal investigator of a project called Sea Ice Thickness Derived From High Resolution Radar Imagery. 'We also knew that the sea ice extent had decreased over the last 20 years, but we knew very little about ice thickness.'

'Since sea ice is very thin, about 3 meters (10 feet) or less,'Kwok explained, 'it is very sensitive to climate change.'

Until now, observations of polar sea ice thickness have been available for specific areas, but not for the entire polar region.

The new radar mapping technique has also given scientists a close look at how the sea ice cover grows and contorts over time. 'Using this new data set, we have the first estimates of how much ice has been produced and where it formed during the winter. We have never been able to do this before,' said Kwok. 'Through our radar maps of the Arctic Ocean, we can actually see ice breaking apart and thin ice growth in the new openings.'

RADARSAT gives researchers a piece of the overall puzzle every three days by creating a complete image of the Arctic. NASA scientists then put those puzzle pieces together to create a time-lapsed view of this remote and inhospitable region. So far, they have processed one season's worth of images.

'We can see large cracks in the ice cover, where most ice grows,' said Kwok. 'These cracks are much longer than previously thought, some as long as 2,000 kilometers (1,200 miles),' Kwok continued. 'If the ice is thinning due to warming, we'll expect to see more of these long cracks over the Arctic Ocean.'

Scientists believe this is one of the most significant breakthroughs in the last two decades of ice research. 'We are now in a position to better understand the sea ice cover and the role of the Arctic Ocean in global climate change,' said Kwok.

Radar can see through clouds and any kind of weather system, day or night, and as the Arctic regions are usually cloud-covered and subject to long, dark winters, radar is proving to be extremely useful. However, compiling these data into extremely detailed pictures of the Arctic is a challenging task.

'This is truly a major innovation in terms of the quantities of data being processed and the novelty of the methods being used,' said Verne Kaupp, director of the Alaska SAR Facility at the University of Alaska, Fairbanks.

The mission is a joint project between JPL, the Alaska SAR Facility, and the Canadian Space Agency. Launched by NASA in 1995, the Radarsat satellite is operated by the Canadian Space Agency. JPL manages the Sea Ice Thickness Derived From High Resolution Radar Imagery pro

2000-01-01

317

The convective desalination of sea ice  

E-print Network

cycle brings substantial changes to both the Arctic Ocean and the seas surrounding Antarctica. In the Arctic Ocean, for instance, at its September minimum, the areal extent of the sea ice is some 5 million square kilometres, while at its March maximum... resulted in the International Bathymetric Chart of the Arctic Ocean (IBCAO) and the forthcoming Inter- national Bathymetric Chart of the Southern Ocean (IBSCO) (see, respectively, Jakobsson et al., 2012; Arndt & Schenke, 2012). Indeed, recent advances...

Rees Jones, David

2014-07-01

318

Formation of an aggregate scale in Arctic sea ice  

Microsoft Academic Search

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

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

2004-01-01

319

Drifting Arctic sea ice archives changes in ocean surface conditions  

Microsoft Academic Search

?18O profiles in drifting Arctic sea ice are coupled with back trajectories of ice drift and an ice growth model to reconstruct the surface hydrography of the Arctic Ocean interior. The results compare well with ?18O values obtained by traditional oceanographic methods and known water mass distributions. Analysis of the stable isotopic composition of sea ice floes sampled at strategic

Stephanie Pfirman; William Haxby; Hajo Eicken; Martin Jeffries; Dorothea Bauch

2004-01-01

320

Understanding the Sea Ice Zone: Scientists and Communities Partnering to Archive, Analyze and Disseminate Local Ice Observations  

NASA Astrophysics Data System (ADS)

Knowledge of sea ice is critical to the hunting, whaling, and cultural activities of many Indigenous communities in Northern and Western Alaska. Experienced hunters have monitored seasonal changes of the sea ice over many years, giving them a unique expertise in assessing the current state of the sea ice as well as any anomalies in seasonal sea ice conditions. The Seasonal Ice Zone Observing Network (SIZONet), in collaboration with the Exchange for Local Observations and Knowledge of the Arctic (ELOKA), has developed an online application for collecting, storing, and analyzing sea ice observations contributed by local experts from coastal Alaskan communities. Here we present the current iteration of the application, outline future plans and discuss how the development process and resulting system have improved our collective understanding of sea ice processes and changes. The SIZONet application design is based on the needs of the research scientists responsible for entering observation data into the database, the needs of local sea ice experts contributing their observations and knowledge, and the information needs of Alaska coastal communities. Entry forms provide a variety of input methods, including menus, check boxes, and free text input. Input options strive to balance flexibility in capturing concepts and details with the need for analytical consistency. Currently, research staff at the University of Alaska Fairbanks use the application to enter observations received via written or electronic communications from local sea ice experts. Observation data include current weather conditions, snow and ice quantity and quality, and wildlife sighted or taken. Future plans call for direct use of the SIZONet interface by local sea ice experts as well as students, both as contributors to the data collection and as users seeking meaning in the data. This functionality is currently available to a limited number of community members as we extend the application to support specific roles for particular users (or groups of users); this role-based access will be necessary to support a diverse user population while maintaining the integrity of the data and protecting personal information, or the location of sensitive sites, captured in the data records. Additionally, future improvements to the interface will include the ability to upload photos and videos to capture visual records of the environment. The SIZONet application was developed to provide a robust interface for working with observational data. The contributed nature of the data, however, presents a unique set of collaborative benefits and challenges as we work towards the final implementation of the application. The successful partnership supporting the observation network is a direct function of the long-term relationships established between university-based researchers and community members.

Collins, J. A.; Oldenburg, J.; Liu, M.; Pulsifer, P. L.; Kaufman, M.; Eicken, H.; Parsons, M. A.

2012-12-01

321

Snow Cover Effects on Glacier Ice Surface Temperature Margherita Maggioni*{  

E-print Network

and faceted crystals prevailed, due to the higher temperature gradient. From these two winter seasons gradient, which is in turn related to basal temperature. The temperature at the basal snow 23 and 25uC. The bottom temperature of the snow cover (BTS) is a diagnostic feature for the presence

Williams, Mark W.

322

Quaternary Sea-ice history in the Arctic Ocean based on a new Ostracode sea-ice proxy  

USGS Publications Warehouse

Paleo-sea-ice history in the Arctic Ocean was reconstructed using the sea-ice dwelling ostracode Acetabulastoma arcticum from late Quaternary sediments from the Mendeleyev, Lomonosov, and Gakkel Ridges, the Morris Jesup Rise and the Yermak Plateau. Results suggest intermittently high levels of perennial sea ice in the central Arctic Ocean during Marine Isotope Stage (MIS) 3 (25-45 ka), minimal sea ice during the last deglacial (16-11 ka) and early Holocene thermal maximum (11-5 ka) and increasing sea ice during the mid-to-late Holocene (5-0 ka). Sediment core records from the Iceland and Rockall Plateaus show that perennial sea ice existed in these regions only during glacial intervals MIS 2, 4, and 6. These results show that sea ice exhibits complex temporal and spatial variability during different climatic regimes and that the development of modern perennial sea ice may be a relatively recent phenomenon. ?? 2010.

Cronin, T. M.; Gemery, L.; Briggs, W.M.; Jakobsson, M.; Polyak, L.; Brouwers, E.M.

2010-01-01

323

LEFM size requirements for the fracture testing of sea ice  

Microsoft Academic Search

The stress-separation curve obtained for the in-situ response of first-year sea ice is used to obtain specimen size requirements for sea ice fracture tests. Issues of notch sensitivity and minimum size requirements for the applicability of linear elastic fracture mechanics are addressed. The role of time dependent deformations in studying sea ice fracture is examined.

S. V. Mulmule; J. P. Dempsey

2000-01-01

324

Distinguishing ice from snow for melt modeling using daily observations from MODIS  

NASA Astrophysics Data System (ADS)

In high mountainous regions of the Earth during melt periods, both seasonal snow and glacier ice melt may contribute to surface water and ground water feeding streams. In these regions there are often few in-situ observations that can help distinguish between the two components of melt, particularly across large mountain ranges. Understanding the contribution of melt water from the seasonal snow and glacier ice sources informs us about the current state of the water cycle and how a changing climate may alter the water cycle. In this study, we analyze daily time series of MODIS data products to distinguish ice from snow as the seasonal snowpack recedes, revealing melt over glacier ice surfaces. Broadband albedo increases as ice is exposed because of larger grain sizes and dust/debris on the glacier surface. To investigate the grain sizes we use estimates from the MODIS Snow Covered Area and Grain Size Model (MODSCAG) and MODIS Dust Radiative Forcing in Snow (MODDRFS) derived from MODIS surface reflectance (MOD09GA). MODSCAG uses the shape of the spectrum selected by a spectral mixture analysis model while MODDRFS uses the Normalized Difference Grain Size Index (NDGSI). Comparison of the grain sizes with grain sizes derived from the Airborne Visible/Infrared Imaging Spectrometer have demonstrated higher accuracy for the NDGSI approach. In addition to analysis of grain sizes, we use 2 standard albedo products from the MODIS, the Terra Daily Snow Cover algorithm (MOD10A1) that uses a narrow-to-broadband conversion scheme to create an integrated broadband albedo and Surface Reflectance BRDF/Albedo (MOD43) product that provides albedo in three broad bands. We focus on the Hunza River basin, in the Upper Indus located in Northern Pakistan. We use the annual minimum ice and snow from the MODICE Persistent Ice and Snow (MODICE) algorithm to identify glaciated regions for analysis. The methods (MODSCAG, MODDRFS, MOD10A1, MOD43) all show sensitivity to exposed glacier surfaces. Further work will use a time series of melt modeling in this region to determine the contributions from seasonal snow versus glacier ice melt.

Rittger, Karl; Bryant, Anne C.; Brodzik, Mary J.; Painter, Thomas H.; Armstrong, Richard

2014-05-01

325

Ocean and Sea Ice SAF Technical Note  

E-print Network

Ocean and Sea Ice SAF Technical Note SAF/OSI/CDOP/KNMI/TEC/RP/176 ASCAT coastal winds validation 2010 Minor Added sections 2 and 8 Version 1.2 January 2011 Minor Comments of DRI included Version 1.3 February 2011 Minor Comments (2) of DRI included Version 1.4 July 2011 Minor Extended comparison in section

Stoffelen, Ad

326

Moving from Ship to 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 Arctic sea ice. This was during a scientific expedition to map the Arctic seafloor. The expedition was a joint effort using two ships, the Healy and the Canadian Coast Guard Ship...

327

Checking Stability of Arctic Sea Ice  

USGS Multimedia Gallery

Two U.S. Coast Guard members are checking the stability of a piece of multi-year Arctic sea ice. They were lowered by crane from U.S. Coast Guard Cutter Healy. This was during a scientific expedition to map the Arctic seafloor. The expedition was a joint effort using two ships, Healy and the Canadia...

328

Chlorophyll a in Antarctic sea ice from historical ice core data  

NASA Astrophysics Data System (ADS)

Sea ice core chlorophyll a data are used to describe the seasonal, regional and vertical distribution of algal biomass in Southern Ocean pack ice. The Antarctic Sea Ice Processes and Climate - Biology (ASPeCt - Bio) circumpolar dataset consists of 1300 ice cores collected during 32 cruises over a period of 25 years. The analyses show that integrated sea ice chlorophyll a peaks in early spring and late austral summer, which is consistent with theories on light and nutrient limitation. The results indicate that on a circum-Antarctic scale, surface, internal and bottom sea ice layers contribute equally to integrated biomass, but vertical distribution shows distinct differences among six regions around the continent. The vertical distribution of sea ice algal biomass depends on sea ice thickness, with surface communities most commonly associated with thin ice (<0.4 m), and ice of moderate thickness (0.4-1.0 m) having the highest probability of forming bottom communities.

Meiners, K. M.; Vancoppenolle, M.; Thanassekos, S.; Dieckmann, G. S.; Thomas, D. N.; Tison, J.-L.; Arrigo, K. R.; Garrison, D. L.; McMinn, A.; Lannuzel, D.; van der Merwe, P.; Swadling, K. M.; Smith, W. O., Jr.; Melnikov, I.; Raymond, B.

2012-11-01

329

The refreezing of melt ponds on Arctic sea ice  

NASA Astrophysics Data System (ADS)

The presence of melt ponds on the surface of Arctic sea ice significantly reduces its albedo, inducing a positive feedback leading to sea ice thinning. While the role of melt ponds in enhancing the summer melt of sea ice is well known, their impact on suppressing winter freezing of sea ice has, hitherto, received less attention. Melt ponds freeze by forming an ice lid at the upper surface, which insulates them from the atmosphere and traps pond water between the underlying sea ice and the ice lid. The pond water is a store of latent heat, which is released during refreezing. Until a pond freezes completely, there can be minimal ice growth at the base of the underlying sea ice. In this work, we present a model of the refreezing of a melt pond that includes the heat and salt balances in the ice lid, trapped pond, and underlying sea ice. The model uses a two-stream radiation model to account for radiative scattering at phase boundaries. Simulations and related sensitivity studies suggest that trapped pond water may survive for over a month. We focus on the role that pond salinity has on delaying the refreezing process and retarding basal sea ice growth. We estimate that for a typical sea ice pond coverage in autumn, excluding the impact of trapped ponds in models overestimates ice growth by up to 265 million km3, an overestimate of 26%.

Flocco, Daniela; Feltham, Daniel L.; Bailey, Eleanor; Schroeder, David

2015-02-01

330

An ice core record of net snow accumulation and seasonal snow chemistry at Mt. Waddington, southwest British Columbia, Canada  

NASA Astrophysics Data System (ADS)

We recovered a 141 m ice core from Combatant Col (51.39°N, 125.22°W, 3000 m asl) on the flank of Mt. Waddington, southern Coast Mountains, British Columbia, Canada. Aerosols and other impurities in the ice show unambiguous seasonal variations, allowing for annual dating of the core. Clustered melt layers, originating from summer surface heating, also aid in the dating of the core. Seasonality in water stable isotopes is preserved throughout the record, showing little evidence of diffusion at depth, and serves as an independent verification of the timescale. The annual signal of deuterium excess is especially well preserved. The record of lead deposition in the core agrees with those of ice cores from Mt. Logan and from Greenland, with a sharp drop-off in concentration in the 1970s and early 1980s, further validating the timescales. Despite significant summertime melt at this mid-latitude site, these data collectively reveal a continuous and annually resolved 36-year record of snow accumulation. We derived an accumulation time series from the Mt. Waddington ice core, after correcting for ice flow. Years of anomalously high or low snow accumulation in the core correspond with extremes in precipitation data and geopotential height anomalies from reanalysis data that make physical sense. Specifically, anomalously high accumulation years at Mt. Waddington correlate with years where "Pineapple Express" atmospheric river events bring large amounts of moisture from the tropical Pacific to western North America. The Mt. Waddington accumulation record thus reflects regional-scale climate. These results demonstrate the potential of ice core records from temperate glaciers to provide meaningful paleoclimate information. A longer core to bedrock (250-300 m) at the Mt. Waddington site could yield ice with an age of several hundred to 1000 years.

Neff, P. D.; Steig, E. J.; Clark, D. H.; McConnell, J. R.; Pettit, E. C.; Menounos, B.

2011-12-01

331

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

NSDL National Science Digital Library

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

332

Variations in the age of Arctic sea-ice and summer sea-ice extent  

Microsoft Academic Search

Three of the past six summers have exhibited record low sea-ice extent on the Arctic Ocean. These minima may have been dynamically induced by changes in the surface winds. Based on results of a simple model that keeps track of the age of ice as it moves about on the Arctic Ocean, we show that the areal coverage of thick

Ignatius G. Rigor; John M. Wallace

2004-01-01

333

On producing sea ice deformation dataset from SAR-derived sea ice motion  

NASA Astrophysics Data System (ADS)

We propose a method to compute nearly noise-free sea ice deformation fields from SAR-derived motion and present the results of its application to RGPS sea ice trajectories. The method is based on two steps. The first step consists of using a triangulation of the positions taken from the sea ice trajectories to define a mesh on which a first estimate of sea ice deformation is computed. The second step consists of applying a specific smoother to the deformation field to reduce the artificial noise that arises along discontinuities in the sea ice motion field. From the comparison between unfiltered and filtered fields, we estimate that the artificial noise causes an overestimation of about 60% of opening and closing. The artificial noise also has a strong impact on the statistical distribution of the deformation and on the scaling exponents estimated with multi-fractal analysis. These findings may have serious implications for previous studies as the constant overestimation of the opening and closing could lead to a large overestimation of freezing in leads, salt rejection and sea ice ridging.

Bouillon, S.; Rampal, P.

2014-10-01

334

An Improved Cryosat-2 Sea Ice Freeboard Retrieval Algorithm Through the Use of Waveform Fitting  

NASA Technical Reports Server (NTRS)

We develop an empirical model capable of simulating the mean echo power cross product of CryoSat-2 SAR and SAR In mode waveforms over sea ice covered regions. The model simulations are used to show the importance of variations in the radar backscatter coefficient with incidence angle and surface roughness for the retrieval of surfaceelevation of both sea ice floes and leads. The numerical model is used to fit CryoSat-2 waveforms to enable retrieval of surface elevation through the use of look-up tables and a bounded trust region Newton least squares fitting approach. The use of a model to fit returns from sea ice regions offers advantages over currently used threshold retrackingmethods which are here shown to be sensitive to the combined effect of bandwidth limited range resolution and surface roughness variations. Laxon et al. (2013) have compared ice thickness results from CryoSat-2 and IceBridge, and found good agreement, however consistent assumptions about the snow depth and density of sea ice werenot used in the comparisons. To address this issue, we directly compare ice freeboard and thickness retrievals from the waveform fitting and threshold tracker methods of CryoSat-2 to Operation IceBridge data using a consistent set of parameterizations. For three IceBridge campaign periods from March 20112013, mean differences (CryoSat-2 IceBridge) of 0.144m and 1.351m are respectively found between the freeboard and thickness retrievals using a 50 sea ice floe threshold retracker, while mean differences of 0.019m and 0.182m are found when using the waveform fitting method. This suggests the waveform fitting technique is capable of better reconciling the seaice thickness data record from laser and radar altimetry data sets through the usage of consistent physical assumptions.

Kurtz, Nathan T.; Galin, N.; Studinger, M.

2014-01-01

335

Observed Anomalous Atmospheric Circulation in Summers of Unusual Arctic Sea Ice Reduction  

NASA Astrophysics Data System (ADS)

This study presents the atmospheric patterns (circulation, precipitation and temperature) associated with changes in Arctic sea ice extent (SIE) in summertime. Significant features and dynamical linkages of the parameter fields are presented. Sea ice extent and concentration are from the National Snow & Ice Data Center (NSIDC), while sea level pressure, winds, temperature, radiation, precipitation and snowfall - used to characterize storms, cloud cover, warming/cooling effects, large-scale wave trains and jet streams - come from the European Re-Analysis Interim (ERA-Interim) re-analysis. The storm track characteristic is analyzed using the Kevin Hodges TRACK algorithm, based on zonal and meridional winds at 850 hPa. Significant patterns result from compositing anomalous high (+1 STD, 23 months) and low (-1 STD, 17 months) standardized SIE reduction months in summer (May-August, MJJA) over 1979-2013. For high SIE reduction months, a relative anticyclonic circulation over the Arctic Ocean emerges. Resulting is a tendency for storms to shun the Arctic Ocean, following a more zonal path, and hence contributing to a weakening of the climatological Arctic Ocean Cyclone Maximum. For the Arctic Ocean, a reduced cloud cover results in less precipitation, where the particular decrease in snowfall over sea ice in August lowers the albedo and hence increases the ice reduction. The warming over the continents increases the land-sea temperature contrast, resulting in increased cyclogenesis especially along the Siberian coast. In mid-latitudes, the shift in storm tracks results in an increase in storms and rainfall over northwestern Europe and southern Scandinavia. The presentation adds to the ongoing discussion on Arctic sea ice and mid-latitude extreme weather, and also contributes to the understanding of feedback mechanisms in the region. With the current declining trend in sea ice expected to continue in the coming decades, the understanding of anomalous circulation patterns associated to sea-ice loss is important for assessing changes in the Arctic climate system and their impacts.

Knudsen, Erlend; Orsolini, Yvan; Furevik, Tore; Hodges, Kevin

2014-05-01

336

Arctic Sea Ice: Trends, Stability and Variability  

NASA Astrophysics Data System (ADS)

A stochastic Arctic sea-ice model is derived and analyzed in detail to interpret the recent decay and associated variability of Arctic sea-ice under changes in greenhouse gas forcing widely referred to as global warming. The approach begins from a deterministic model of the heat flux balance through the air/sea/ice system, which uses observed monthly-averaged heat fluxes to drive a time evolution of sea-ice thickness. This model reproduces the observed seasonal cycle of the ice cover and it is to this that stochastic noise---representing high frequency variability---is introduced. The model takes the form of a single periodic non-autonomous stochastic ordinary differential equation. Following an introductory chapter, the two that follow focus principally on the properties of the deterministic model in order to identify the main properties governing the stability of the ice cover. In chapter 2 the underlying time-dependent solutions to the deterministic model are analyzed for their stability. It is found that the response time-scale of the system to perturbations is dominated by the destabilizing sea-ice albedo feedback, which is operative in the summer, and the stabilizing long wave radiative cooling of the ice surface, which is operative in the winter. This basic competition is found throughout the thesis to define the governing dynamics of the system. In particular, as greenhouse gas forcing increases, the sea-ice albedo feedback becomes more effective at destabilizing the system. Thus, any projections of the future state of Arctic sea-ice will depend sensitively on the treatment of the ice-albedo feedback. This in turn implies that the treatment a fractional ice cover as the ice areal extent changes rapidly, must be handled with the utmost care. In chapter 3, the idea of a two-season model, with just winter and summer, is revisited. By breaking the seasonal cycle up in this manner one can simplify the interpretation of the basic dynamics. Whereas in the fully time-dependent seasonal model one finds stable seasonal ice cover (vanishing in the summer but reappearing in the winter), in previous two-season models such a state could not be found. In this chapter the sufficient conditions are found for a stable seasonal ice cover, which reside in including a time variation in the shortwave radiance during summer. This provides a qualitative interpretation of the continuous and reversible shift from perennial to seasonally-varying states in the more complex deterministic model. In order to put the stochastic model into a realistic observational framework, in chapter 4, the analysis of daily satellite retrievals of ice albedo and ice extent is described. Both the basic statistics are examined and a new method, called multi-fractal temporally weighted detrended fluctuation analysis, is applied. Because the basic data are taken on daily time scales, the full fidelity of the retrieved data is accessed and we find time scales from days and weeks to seasonal and decadal. Importantly, the data show a white-noise structure on annual to biannual time scales and this provides the basis for using a Wiener process for the noise in the stochastic Arctic sea-ice model. In chapter 5 a generalized perturbation analysis of a non-autonomous stochastic differential equation is developed and then applied to interpreting the variability of Arctic sea-ice as greenhouse gas forcing increases. The resulting analytic expressions of the statistical moments provide insight into the transient and memory-delay effects associated with the basic competition in the system: the ice-albedo feedback and long wave radiative stabilization along with the asymmetry in the nonlinearity of the deterministic contributions to the model and the magnitude and structure of the stochastic noise. A systematic study of the impact of the noise structure, from additive to multiplicative, is undertaken in chapters 6 and 7. Finally, in chapter 8 the matter of including a fractional ice cover into a deterministic model is addressed. It is found that a simple but crucial mistake

Moon, Woosok

337

Variability of Arctic Sea Ice as Determined from Satellite Observations  

NASA Technical Reports Server (NTRS)

The compiled, quality-controlled satellite multichannel passive-microwave record of polar sea ice now spans over 18 years, from November 1978 through December 1996, and is revealing considerable information about the Arctic sea ice cover and its variability. The information includes data on ice concentrations (percent areal coverages of ice), ice extents, ice melt, ice velocities, the seasonal cycle of the ice, the interannual variability of the ice, the frequency of ice coverage, and the length of the sea ice season. The data reveal marked regional and interannual variabilities, as well as some statistically significant trends. For the north polar ice cover as a whole, maximum ice extents varied over a range of 14,700,000 - 15,900,000 sq km, while individual regions experienced much greater percent variations, for instance, with the Greenland Sea having a range of 740,000 - 1,110,000 sq km in its yearly maximum ice coverage. In spite of the large variations from year to year and region to region, overall the Arctic ice extents showed a statistically significant, 2.80% / decade negative trend over the 18.2-year period. Ice season lengths, which vary from only a few weeks near the ice margins to the full year in the large region of perennial ice coverage, also experienced interannual variability, along with spatially coherent overall trends. Linear least squares trends show the sea ice season to have lengthened in much of the Bering Sea, Baffin Bay, the Davis Strait, and the Labrador Sea, but to have shortened over a much larger area, including the Sea of Okhotsk, the Greenland Sea, the Barents Sea, and the southeastern Arctic.

Parkinson, Claire L.

1999-01-01

338

The Alaska Lake Ice and Snow Observatory Network (ALISON): Hands-on Experiential K- 12 Learning in the North  

Microsoft Academic Search

The Alaska Lake Ice and Snow Observatory Network (ALISON) was initiated by Martin Jeffries (UAF polar scientist), Delena Norris-Tull (UAF education professor) and Ron Reihl (middle school science teacher, Fairbanks North Star Borough School District). The snow and ice measurement protocols were developed in 1999-2000 at the Poker Flat Research Range (PFRR) by Geophysical Institute, University of Alaska scientists and

K. Morris; M. Jeffries

2008-01-01

339

Microwave emission from snow and glacier ice. [brightness temperature for snow fields  

NASA Technical Reports Server (NTRS)

The microwave brightness temperature for snow fields was studied assuming that the snow cover consists of closely packed scattering spheres which do not interact coherently. The Mie scattering theory was used to compute the volume scattering albedo. It is shown that in the wavelength range from 0.8 to 2.8 cm, most of the micro-radiation emanates from a layer 10 meters or less in thickness. It is concluded that it is possible to determine snow accumulation rates as well as near-surface temperature.

Chang, T. C.; Gloersen, P.; Schmugge, T.; Wilheit, T. T.; Zwally, H. J.

1975-01-01

340

How to Be Safe in Ice and Snow  

MedlinePLUS

... in the snow. Keeping your hands warm and dry is important because fingers are very sensitive to the cold. Drink Up! Sounds like advice for hot weather, not cold weather, right? Well, the truth is ...

341

Satellites - New global observing techniques for ice and snow  

NASA Technical Reports Server (NTRS)

The possibility that the variation in areal extent of the snow cover may be related by empirical means to the average monthly run-off in a given watershed was demonstrated by comparing run-off records from the Indus River Basin in south-east Asia with a series of snow-cover maps obtained from Nimbus-3 and 4 imagery. Similar studies using the higher spatial resolution available with ERTS-1 imagery were carried out for the Wind River Mountains watersheds in Wyoming, where it was found that the empirical relationship varied with mean elevation of the watershed. In addition, digital image enhancement techniques are shown to be useful for identifying glacier features thought to be related to extent of snow cover, moraine characteristics, debris coverage, and the like. Finally, longer wavelength observations using sensors on board the Nimbus-5 satellite are shown to be useful for indicating crystal size distributions and onset of melting on glacier snow cover.

Gloersen, P.; Salomonson, V. V.

1975-01-01

342

Remote sensing of sea ice thickness by a combined spatial and frequency domain interferometer: formulations, instrument design, and development  

NASA Astrophysics Data System (ADS)

The thickness of Arctic sea ice plays a critical role in Earth's climate and ocean circulation. An accurate measurement of this parameter on synoptic scales at regular intervals would enable characterization of this important component for the understanding of ocean circulation and the global heat balance. Presented in this paper is a low frequency VHF interferometer technique and associated radar instrument design to measure sea ice thickness based on the use of backscatter correlation functions. The sea ice medium is represented as a multi-layered medium consisting of snow, sea-ice and sea water, with the interfaces between layers characterized as rough surfaces. This technique utilizes the correlation of two radar waves of different frequencies and incident and observation angles, scattered from the sea ice medium. The correlation functions relate information about the sea ice thickness. Inversion techniques such as the genetic algorithm, gradient descent, and least square methods, are used to derive sea ice thickness from the phase information related by the correlation functions. The radar instrument is designed to be implemented on a spacecraft and the initial test-bed will be on a Twin Otter aircraft. Radar system and instrument design and development parameters as well as some measurement requirements are reviewed. The ability to obtain reliable phase information for successful ice thickness retrieval for various thickness and surface interface geometries is examined.

Hussein, Ziad A.; Holt, Benjamin; McDonald, Kyle C.; Jordan, Rolando; Huang, John; Kuga, Yasuo; Ishimaru, Akira; Jaruwatanadilok, Sermsak; Gogineni, Prasad; Akins, Torry; Heavey, Brandon; Perovich, Don; Sturm, Matthew

2005-10-01

343

Sea ice dynamics as a control for halogen deposition in polar regions  

NASA Astrophysics Data System (ADS)

Bromine and iodine chemistry is extremely active at the sea ice margins of both polar regions, with enhanced concentrations of BrO and IO in the air column compared to the open ocean surface or snow-covered land. So-called "Bromine explosions" occur principally over first-year sea ice close to the sea ice edge, and are the major source of reactive bromine in the polar atmosphere. This results in an increase of bromide (Br-) deposited to the snowpack, compared with the Br-Na sea water mass ratio. The main source of iodine is phytoplankton, which colonize the underside of sea ice, producing iodocarbons and probably I2. Though it has been discovered that atmospheric iodine around Antarctica is produced from algae growing on the underside of the relatively thin/seasonal sea ice, satellite measurements do not show exceptional iodine activity above Arctic sea ice. However, in opposition to Antarctica, boundary layer observations show relatively small atmospheric IO concentrations downwind of ice-free open ocean, including leads and polynias. Analysis of bromine and iodine has been carried out in the Talos Dome ice core (Antarctica) which covers the last 215 ky, and in a shallow/firn core drilled at the summit of the Holtedahlfonna glacier (Northern Spitsbergen, Svalbard), covering the last 10 years. Talos Dome Br- is positively correlated with temperature and negatively correlated with sodium (Na). Based on the Br-/Na seawater ratio, bromide is depleted in the ice during glacial periods and enriched during interglacial periods. Total iodine, consisting of iodide (I-) and iodate (IO3-), peaks during glacials with lower values during interglacial periods. Although iodate is believed to be the most stable iodine species in atmospheric aerosols, it was present only in the ice core only during glacial maxima. Glacial-interglacial changes in the multi-year sea ice extent will almost certainly alter the distance between the sea ice edge and Antarctic plateau, which will influence the total bromide flux (arising both from sea salt and Br- from bromine explosions) and its ratio with sodium. A simple 1-D transport model of this scenario is able to reproduce the measured fluxes of bromine and sodium. The seasonal sea ice extent will also alter the surface area available to algal colonization, and hence iodine emission. In support of the Antarctic results, analysis of iodine and bromine in the Svalbard shallow/firn core appears to confirm the linkage between sea ice and these halogens. In particular, changes in I concentration are associated with the extent of sea ice at spring time, while Br, evaluated as enrichment relative to the Br/Na sea water mass ratio, is influenced by changes in the seasonal sea ice area. The Arctic and Antarctic ice core results suggest that sea ice dynamics are arguably the primary driver of halogen fluxes in polar regions and that both halogens could be used to understand the past variability of sea ice.

Spolaor, Andrea; Plane, John M. C.; Vallelonga, Paul; Gabrieli, Jacopo; Cozzi, Giulio; Turetta, Clara; Kohler, Jack; Isaksson, Elisabeth; Barbante, Carlo

2013-04-01

344

Sea ice classification using dual polarization SAR data  

NASA Astrophysics Data System (ADS)

Sea ice is an indicator of climate change and also a threat to the navigation security of ships. Polarimetric SAR images are useful in the sea ice detection and classification. In this paper, backscattering coefficients and texture features derived from dual polarization SAR images are used for sea ice classification. Firstly, the HH image is recalculated based on the angular dependences of sea ice types. Then the effective gray level co-occurrence matrix (GLCM) texture features are selected for the support vector machine (SVM) classification. In the end, because sea ice concentration can provide a better separation of pancake ice from old ice, it is used to improve the SVM result. This method provides a good classification result, compared with the sea ice chart from CIS.

Huiying, Liu; Huadong, Guo; Lu, Zhang

2014-03-01

345

Ensemble of sea ice initial conditions for interannual climate predictions  

NASA Astrophysics Data System (ADS)

Polar climate studies are severely hampered by the sparseness of the sea ice observations. We aim at filling this critical gap by producing two 5-member sea ice historical simulations strongly constrained by ocean and atmosphere observational data and covering the 1958-2006 and 1979-2012 periods. This is the first multi-member sea ice reconstruction covering more than 50 years. The obtained sea ice conditions are in reasonable agreement with the few available observations. These best estimates of sea ice conditions serve subsequently as initial sea ice conditions for a set of 28 3-year-long retrospective climate predictions. We compare it to a set in which the sea ice initial conditions are taken from a single-member sea ice historical simulation constrained by atmosphere observations only. We find an improved skill in predicting the Arctic sea ice area and Arctic near surface temperature but a slightly degraded skill in predicting the Antarctic sea ice area. We also obtain a larger spread between the members for the sea ice variables, thus more representative of the forecast error.

Guemas, Virginie; Doblas-Reyes, Francisco J.; Mogensen, Kristian; Keeley, Sarah; Tang, Yongming

2014-11-01

346

Transformation of the snow crystal to a particle of ice  

NASA Astrophysics Data System (ADS)

To study the physical properties of snow under different meteorological conditions a mathematical model and numerical computer program were created and applied for some numerical modelling estimates. The non-linear mathematical model consists of partial differential equations and can be subdivided into a thermal part with phase changes in porous media, diffusion, structural transformation and mechanical parts. The model was applied to simulate the evolution of structural, thermal and mechanical parameters in a snow profile subject to meteorological parameters (air temperature and moisture, wind velocity, precipitation, density). The snow structure is very sensitive to the temporal variations of all external parameters: temperature, humidity, precipitation and wind-pumping. Snow deposited in cold weather conditions is transformed through densification, metamorphism and recrystallisation. Snow crystals have unstable shapes. The tendency for mass and heat to be redistributed through sublimation is to minimise the surface free energy. The result of these processes is to change the shape of a snow crystal to that of a sphere. The transformation of the initial singular stellar crystal to a number of small grains with the same mass as the original crystal is described mathematically. It gives the rates of the transformations. Based on this mathematical approach we can predict changes of the crystal shapes, number of crystals and other physical properties inside a snowpack subject to different meteorological conditions.

Guseva-Lozinski, Elena

347

Arctic Sea Ice Freeboard from Icebridge Acquisitions in 2009: Estimates and Comparisons with ICEsat  

NASA Technical Reports Server (NTRS)

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, Glenn F.; Manizade, S. S.; Krabill, W. B.

2012-01-01

348

The Met Office Hadley Centre sea ice and sea surface temperature data set, version 2: 1. Sea ice concentrations  

NASA Astrophysics Data System (ADS)

We present a new version of the sea ice concentration component of the Met Office Hadley Centre sea ice and sea surface temperature data set, HadISST.2.1.0.0. Passive microwave data are combined with historical sources, such as sea ice charts, to create global analyses on a 1° grid from 1850 to 2007. Climatology was used when no information about the sea ice was available. Our main aim was to create a homogenous data set by calculating and applying bias adjustments using periods of overlaps between the different data sources used. National Ice Center charts from 1995 to 2007 have been used as a reference to achieve this. In particular, large bias adjustments have been applied to the passive microwave data in both the Antarctic and Arctic summers. Overall, HadISST.2.1.0.0 contains more ice than HadISST1.1, with higher concentrations, shorter marginal ice zones, and larger extents and areas in some regions and periods. A new method for estimating the concentrations within the ice pack using the distance from the ice edge has been developed and evaluated. This was used when only the extents were known or the original concentration fields were heterogeneous. A number of discontinuities in the HadISST1.1 record are no longer found in HadISST.2.1.0.0.

Titchner, Holly A.; Rayner, Nick A.

2014-03-01

349

Arctic sea ice animation (Tom Agnew, Environment Canada) Lecture 12 HAS222d Intro to energy and environment 2009  

E-print Network

by the stratification of the air #12;water evaporates from the Great Lakes when cold north winds blow over them. It soonArctic sea ice animation (Tom Agnew, Environment Canada) #12;Lecture 12 HAS222d Intro to energy condenses back into water, as cloud droplets which then rain or snow out...The lake water has become cloud

350

Space Radar Image of Weddell Sea Ice  

NASA Technical Reports Server (NTRS)

This is the first calibrated, multi-frequency, multi-polarization spaceborne radar image of the seasonal sea-ice cover in the Weddell Sea, Antarctica. The multi-channel data provide scientists with details about the ice pack they cannot see any other way and indicates that the large expanse of sea-ice is, in fact, comprised of many smaller rounded ice floes, shown in blue-gray. These data are particularly useful in helping scientists estimate the thickness of the ice cover which is often extremely difficult to measure with other remote sensing systems. The extent, and especially thickness, of the polar ocean's sea-ice cover together have important implications for global climate by regulating the loss of heat from the ocean to the cold polar atmosphere. The image was acquired on October 3, 1994, by the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) onboard the space shuttle Endeavour. This image is produced by overlaying three channels of radar data in the following colors: red (C-band, HH-polarization), green (L-band HV-polarization), and blue (L-band, HH-polarization). The image is oriented almost east-west with a center location of 58.2 degrees South and 21.6 degrees East. Image dimensions are 45 kilometers by 18 kilometers (28 miles by 11 miles). Most of the ice cover is composed of rounded, undeformed blue-gray floes, about 0.7 meters (2 feet) thick, which are surrounded by a jumble of red-tinged deformed ice pieces which are up to 2 meters (7 feet) thick. The winter cycle of ice growth and deformation often causes this ice cover to split apart, exposing open water or 'leads'. Ice growth within these openings is rapid due to the cold, brisk Antarctic atmosphere. Different stages of new-ice growth can be seen within the linear leads, resulting from continuous opening and closing. The blue lines within the leads are open water areas in new fractures which are roughened by wind. The bright red lines are an intermediate stage of new-ice growth perhaps 5 to 10 centimeters (2 to 4 inches) thick. The more extensive dark zones are covered by a slightly thicker layer of smooth, level ice up to 70 centimeters (28 inches) thick. Spaceborne Imaging Radar-C and X-band Synthetic Aperture Radar (SIR-C/X-SAR) is part of NASA's Mission to Planet Earth. The radars illuminate Earth with microwaves allowing detailed observations at any time, regardless of weather or sunlight conditions. SIR-C/X-SAR uses three microwave wavelengths: L-band (24 cm), C-band (6 cm) and X-band (3 cm). The multi-frequency data will be used by the international scientific community to better understand the global environment and how it is changing. The SIR-C/X-SAR data, complemented by aircraft and ground studies, will give scientists clearer insights into those environmental changes which are caused by nature and those changes which are induced by human activity. SIR-C was developed by NASA's Jet Propulsion Laboratory. X-SAR was developed by the Dornier and Alenia Spazio companies for the German space agency, Deutsche Agentur fuer Raumfahrtangelegenheiten (DARA), and the Italian space agency, Agenzia Spaziale Italiana (ASI), with the Deutsche Forschungsanstalt fuer Luft und Raumfahrt e.v.(DLR), the major partner in science, operations, and data processing of X-SAR.

1994-01-01

351

Sea-ice behavior and biological productivity in the Amundsen Sea: New insight from West Antarctic Ice Sheet records  

NASA Astrophysics Data System (ADS)

Our understanding of past sea-ice dynamics is limited due to the short duration of instrumental and satellite observational records. Proxies for sea ice can potentially extend these observations in both space and time, but require further development and regional validation. Here we evaluate the use of methanesulfonic acid (MSA) as a sea-ice proxy in the Amundsen Sea and Pine Island Bay by comparing MSA concentrations in nearby firn cores with satellite-derived reconstructions of sea-ice concentration. MSA in ice cores has been proposed as a potential proxy due to its link with the breakup of sea ice. After sea-ice breakup, phytoplankton blooms release dimethylsulfoniopropionate (DMSP) which degrades to dimethyl sulfide (DMS) by several biologically-mediated processes. DMS is subsequently oxidized in the atmosphere to MSA which is deposited by precipitation onto the ice sheet. We present new records of MSA concentrations from the rapidly changing Thwaites Glacier on the West Antarctic Ice Sheet (WAIS). Due to high annual accumulation rates in this region, these firn-cores provide a monthly- to seasonally-resolved record of MSA over the past ~20 years. Comparing our glaciochemical records with satellite-derived reconstructions of daily sea-ice concentration in the Amundsen Sea and Pine Island Bay over the same time interval, we find large annual increases in MSA concentration contemporaneous with both summer sea-ice break-up and winter polynya events. In summer, a more rapid sea-ice decline results in higher MSA concentrations in the adjacent ice sheet. The consistent non-summer peaks may be indicative of biological productivity in coastal polynyas during the austral winter (during times of low but non-zero insolation), or release of DMS stored in sea ice (during times of either non-zero or zero insolation). Sea ice plays a significant role in the mass and energy exchange in the ocean-atmosphere-ice-sheet system, and may also be important in modulating coastal ice-sheet dynamics. Moreover, changes in sea-ice extent have been hypothesized to play a role in past rapid climate change. Our results show that variability in marine biogenic activity, which is tightly coupled to the timing and nature of seasonal sea-ice breakup and shorter-duration polynya events, is robustly reflected in MSA concentrations in precipitation on the Thwaites Glacier. MSA, therefore, is likely a reliable sea-ice proxy in this dynamic region. Future efforts will be directed towards providing a longer-term record of sea-ice behavior utilizing a suite of recently collected ice cores from across the Pine Island and Thwaites Glaciers.

Criscitiello, A. S.; Das, S. B.; Evans, M.; Frey, K. E.; Joughin, I. R.; Medley, B.; Conway, H.

2011-12-01

352

Using MODIS to Map Changes in Earth's Annual Minimum Exposed Snow and Ice  

NASA Astrophysics Data System (ADS)

Current data archives do not include a complete global map of exposed snow and ice, at any scale. The Global Land Ice Measurements from Space (GLIMS) project has acquired a wealth of glacier perimeters in many locations, but the GLIMS collection is limited to descriptions of glaciers for snapshots in time. We present results from the MODIS Persistent Ice (MODICE) algorithm that characterize changes in global annual minimum exposed snow and ice from 2001 to 2011. We include validation of the MODICE algorithm using glacier outlines derived for submission to GLIMS, from semi-automated methods with SPOT, ASTER and Landsat Thematic Mapper imagery in selected locations, including the Cordillera Blanca in Peru, regions of Alaska and the Himalayas and Karakoram mountains of high Asia. Comparisons demonstrate strong agreement between MODICE results and the higher resolution outlines. MODICE provides an enhanced, comprehensive and systematic approach to monitoring changes in glacier areas at regional scales and annual resolution.

Brodzik, M.; Painter, T.; Racoviteanu, A.; Armstrong, R. L.

2012-12-01

353

Ultraviolet radiation and its extinction in antarctic sea ice  

SciTech Connect

This paper reports on the attentuation of radiation in sea ice with special attention to UV radiation. Changes in stratospheric ozone result in changes in the UV radiation, much more biologically active when compared with the visible spectrum, and can have a large effect on life. In this area of the Antarctic sea, a significant fraction of phytoplankton lives under and in the sea ice. This paper discusses the extinction of radiation in sea ice. 7 refs., 3 figs.

Wendler, G.; Quakenbush, T. (Univ. of Alaska, Fairbanks, AK (United States))

1993-01-01

354

Development of sea ice monitoring with aerial remote sensing technology  

NASA Astrophysics Data System (ADS)

In the north China Sea district, sea ice disaster is very serious every winter, which brings a lot of adverse effects to shipping transportation, offshore oil exploitation, and coastal engineering. In recent years, along with the changing of global climate, the sea ice situation becomes too critical. The monitoring of sea ice is playing a very important role in keeping human life and properties in safety, and undertaking of marine scientific research. The methods to monitor sea ice mainly include: first, shore observation; second, icebreaker monitoring; third, satellite remote sensing; and then aerial remote sensing monitoring. The marine station staffs use relevant equipments to monitor the sea ice in the shore observation. The icebreaker monitoring means: the workers complete the test of the properties of sea ice, such as density, salinity and mechanical properties. MODIS data and NOAA data are processed to get sea ice charts in the satellite remote sensing means. Besides, artificial visual monitoring method and some airborne remote sensors are adopted in the aerial remote sensing to monitor sea ice. Aerial remote sensing is an important means in sea ice monitoring because of its strong maneuverability, wide watching scale, and high resolution. In this paper, several methods in the sea ice monitoring using aerial remote sensing technology are discussed.

Jiang, Xuhui; Han, Lei; Dong, Liang; Cui, Lulu; Bie, Jun; Fan, Xuewei

2014-11-01

355

Linking the northern hemisphere sea-ice reduction trend and the quasi-decadal arctic sea-ice oscillation  

Microsoft Academic Search

The nature of the reduction trend and quasi-decadal oscillation in Northern Hemisphere sea-ice extent is investigated. The trend and oscillation that seem to be two separate phenomena have been found in data. This study examines a hypothesis that the Arctic sea-ice reduction trend in the last three decades amplified the quasi-decadal Arctic sea-ice oscillation (ASIO) due to a positive ice\\/ocean-albedo

J. Wang; M. Ikeda; S. Zhang; R. Gerdes

2005-01-01

356

Sea ice microorganisms: environmental constraints and extracellular responses.  

PubMed

Inherent to sea ice, like other high latitude environments, is the strong seasonality driven by changes in insolation throughout the year. Sea-ice organisms are exposed to shifting, sometimes limiting, conditions of temperature and salinity. An array of adaptations to survive these and other challenges has been acquired by those organisms that inhabit the ice. One key adaptive response is the production of extracellular polymeric substances (EPS), which play multiple roles in the entrapment, retention and survival of microorganisms in sea ice. In this concept paper we consider two main areas of sea-ice microbiology: the physico-chemical properties that define sea ice as a microbial habitat, imparting particular advantages and limits; and extracellular responses elicited in microbial inhabitants as they exploit or survive these conditions. Emphasis is placed on protective strategies used in the face of fluctuating and extreme environmental conditions in sea ice. Gaps in knowledge and testable hypotheses are identified for future research. PMID:24832800

Ewert, Marcela; Deming, Jody W

2013-01-01

357

Sea Ice Microorganisms: Environmental Constraints and Extracellular Responses  

PubMed Central

Inherent to sea ice, like other high latitude environments, is the strong seasonality driven by changes in insolation throughout the year. Sea-ice organisms are exposed to shifting, sometimes limiting, conditions of temperature and salinity. An array of adaptations to survive these and other challenges has been acquired by those organisms that inhabit the ice. One key adaptive response is the production of extracellular polymeric substances (EPS), which play multiple roles in the entrapment, retention and survival of microorganisms in sea ice. In this concept paper we consider two main areas of sea-ice microbiology: the physico-chemical properties that define sea ice as a microbial habitat, imparting particular advantages and limits; and extracellular responses elicited in microbial inhabitants as they exploit or survive these conditions. Emphasis is placed on protective strategies used in the face of fluctuating and extreme environmental conditions in sea ice. Gaps in knowledge and testable hypotheses are identified for future research. PMID:24832800

Ewert, Marcela; Deming, Jody W.

2013-01-01

358

Use of Enhanced-resolution QuikScat\\/SeaWinds Data for Operational Ice Services and Climate Research: Sea Ice Edge, Type, Concentration and Drift  

Microsoft Academic Search

Enhanced resolution QuikScat\\/SeaWinds (QSer) data recently entered the daily ice chart operation of the national ice services. Algorithms have been developed to extract four important sea ice parameters from this data over the whole Arctic: sea ice edge, type, concentration and drift. This paper will summarize the different algorithms with a more detailed presentation of the sea ice concentration algorithm.

Jörg Haarpaintner; Marcos Porcires

2006-01-01

359

/ http://www.sciencemag.org/content/early/recent / 7 June 2012 / Page 1/ 10.1126/science.1215065 The seasonal sea ice and snow cover in the Arctic Ocean strongly reflect  

E-print Network

solar radiation. Consequently, current estimates of pan-Arctic primary productivity assume the historically dominant multiyear ice pack (2 to 4 m), and especially by a high surface melt pond fraction (25 to 50%). Optical measurements showed that the ice beneath these melt ponds transmitted fourfold more

Benitez-Nelson, Claudia

360

Ice formation and growth shape bacterial community structure in Baltic Sea drift ice.  

PubMed

Drift ice, open water and under-ice water bacterial communities covering several developmental stages from open water to thick ice were studied in the northern Baltic Sea. The bacterial communities were assessed with 16S rRNA gene terminal-restriction fragment length polymorphism and cloning, together with bacterial abundance and production measurements. In the early stages, open water and pancake ice were dominated by Alphaproteobacteria and Actinobacteria, which are common bacterial groups in Baltic Sea wintertime surface waters. The pancake ice bacterial communities were similar to the open-water communities, suggesting that the parent water determines the sea-ice bacterial community in the early stages of sea-ice formation. In consolidated young and thick ice, the bacterial communities were significantly different from water bacterial communities as well as from each other, indicating community development in Baltic Sea drift ice along with ice-type changes. The thick ice was dominated by typical sea-ice genera from classes Flavobacteria and Gammaproteobacteria, similar to those in polar sea-ice bacterial communities. Since the thick ice bacterial community was remarkably different from that of the parent seawater, results indicate that thick ice bacterial communities were recruited from the rarer members of the seawater bacterial community. PMID:25764550

Eronen-Rasimus, Eeva; Lyra, Christina; Rintala, Janne-Markus; Jürgens, Klaus; Ikonen, Vilma; Kaartokallio, Hermanni

2015-02-01

361

Open water detection from Baltic sea ice SAR imagery  

Microsoft Academic Search

The algorithm for separating Baltic Sea Ice and open water from our operational SAR data are presented. The algorithm is based on segment wise autocorrelation with some simple additional rules to improve the classification. The algorithm results are compared to the open water and sea ice separation available in daily digitized ice charts and the algorithm performance is also compared

Juha Karvonen; M. Simila; M. Makynen

2004-01-01

362

Ross Sea Ice Motion, Area Flux, and Deformation  

Microsoft Academic Search

The sea ice motion, area export, and deformation of the Ross Sea ice cover are examined with satellite passive microwave and RADARSAT observations. The record of high-resolution synthetic aperture radar (SAR) data, from 1998 and 2000, allows the estimation of the variability of ice deformation at the small scale (10 km) and to assess the quality of the longer record

R. Kwok

2005-01-01

363

Ice and AIS: ship speed data and sea ice forecasts in the Baltic Sea  

NASA Astrophysics Data System (ADS)

The Baltic Sea is a seasonally ice covered marginal sea located in a densely populated area in northern Europe. Severe sea ice conditions have the potential to hinder the intense ship traffic considerably. Thus, sea ice fore- and nowcasts are regularly provided by the national weather services. Typically, several ice properties are allocated, but their actual usefulness is difficult to measure and the ship captains must determine their relative importance and relevance for optimal ship speed and safety ad hoc. The present study provides a more objective approach by comparing the ship speeds, obtained by the Automatic Identification System (AIS), with the respective forecasted ice conditions. We find that, despite an unavoidable random component, this information is useful to constrain and rate fore- and nowcasts. More precisely, 62-67% of ship speed variations can be explained by the forecasted ice properties when fitting a mixed effect model. This statistical fit is based on a test region in the Bothnian Bay during the severe winter 2011 and employes 15 to 25 min averages of ship speed.

Löptien, U.; Axell, L.

2014-07-01

364

An investigation into the effects of ice and snow accumulation on drumskin radome antennas and methods of their removal  

Microsoft Academic Search

The first phase of this investigation was the development of an electrical model of a drumskin radome antenna coated with a layer of ice or snow. The characteristic effects of different ice\\/snow distributions were derived from this. The second phase was the construction of model anti\\/de-icing systems which were then tested in a climatic laboratory. This led to the development

P. M. Young; R. L. Stuckey

1987-01-01

365

Combined Satellite - and ULS-Derived Sea-Ice Flux in the Weddell Sea  

NASA Technical Reports Server (NTRS)

Several years of daily microwave satellite ice-drift are combined with moored Upward Looking Sonar (ULS) ice-drafts into an ice volume flux record at points along a flux gate across the Weddell Sea, Antarctica.

Drinkwater, M.; Liu, X.; Harms, S.

2000-01-01

366

The evolution of spring sea ice albedo in the Canadian arctic archipelago  

SciTech Connect

In this investigation, we examined the spatial and temporal characteristics of the visible and infrared albedo of sea ice In a seasonal zone using Advanced Very High Resolution Radiometer (AVHRR) visible and near-infrared data. Sea ice surface albedo data were inverted from satellite top-of-atmosphere radiances by correcting for sensor calibration drift and estimating atmospheric and view angle effects. Pairwise comparison methods and principal component analysis was used to identify the major and minor scale variance structures in the multitemporal satellite albedo dataset. Results indicate that during the onset of melt conditions, there is large scale variability in the regional patterns of surface albedo in a marginal ice zone. Analysis of satellite and surface data indicate that these surface albedo patterns conform closely to sea ice snow distribution. Also, time and conditions of consolidation appear to determine the macro-morphological characteristics of the ice surface, which in turn control the time series and spatial variability of sea ice surface albedo.

De Abreu, R.A. [Canada Centre for Remote Sensing, Ottawa, Ontario (Canada); LeDrew, E.F. [Univ. of Waterloo, Ontario (Canada)

1997-08-01

367

The application of ERTS imagery to monitoring Arctic sea ice. [mapping ice in Bering Sea, Beaufort Sea, Canadian Archipelago, and Greenland Sea  

NASA Technical Reports Server (NTRS)

The author has identified the following significant results. Because of the effect of sea ice on the heat balance of the Arctic and because of the expanding economic interest in arctic oil and minerals, extensive monitoring and further study of sea ice is required. The application of ERTS data for mapping ice is evaluated for several arctic areas, including the Bering Sea, the eastern Beaufort Sea, parts of the Canadian Archipelago, and the Greenland Sea. Interpretive techniques are discussed, and the scales and types of ice features that can be detected are described. For the Bering Sea, a sample of ERTS-1 imagery is compared with visual ice reports and aerial photography from the NASA CV-990 aircraft. The results of the investigation demonstrate that ERTS-1 imagery has substantial practical application for monitoring arctic sea ice. Ice features as small as 80-100 m in width can be detected, and the combined use of the visible and near-IR imagery is a powerful tool for identifying ice types. Sequential ERTS-1 observations at high latitudes enable ice deformations and movements to be mapped. Ice conditions in the Bering Sea during early March depicted in ERTS-1 images are in close agreement with aerial ice observations and photographs.

Barnes, J. C. (principal investigator); Bowley, C. J.

1974-01-01

368

Fracture of Antarctic FY Sea Ice  

Microsoft Academic Search

The break-up of sea ice in McMurdo Sound has been investigated during two field trips in the fall of 2000 and 2001 via in-situ\\u000a cyclic loading and fracture experiments. Details regarding the test site, setup and methods used in the in-situ experiments\\u000a have been reported [1],[2]. A viscoelastic cohesive crack model [3],[4],[5] is being used to model the cracking behaviour

J. P. Dempsey; S. Wang; D. M. Cole

369

Increasing atmospheric antimony contamination in the northern hemisphere: snow and ice evidence from Devon Island,  

E-print Network

Increasing atmospheric antimony contamination in the northern hemisphere: snow and ice evidence recently developed clean laboratory techniques, antimony (Sb) and scandium (Sc) deposition were measured, Canadian High Arctic. Antimony concentrations ranged from 0.07 to 108 pg gÀ1 with a median of 0.98 pg gÀ1

Short, Daniel

370

Cloud Detection over Snow and Ice Using MISR Data , Eugene E. Clothiaux  

E-print Network

Cloud Detection over Snow and Ice Using MISR Data Tao Shi , Bin Yu , Eugene E. Clothiaux , and Amy J. Braverman Abstract Clouds play a major role in Earth's climate and cloud detection prediction and global climate model studies. To advance the observational capabilities of detecting clouds

Yu, Bin

371

MISR Cloud Detection over Ice and Snow Based on Linear Correlation Matching  

E-print Network

MISR Cloud Detection over Ice and Snow Based on Linear Correlation Matching Tao Shi , Bin Yu , and Amy Braverman Abstract Cloud detection is a crucial step in any climate modelling or prediction data to retrieve or estimate the cloud height and hence cloud detection. However, cloud detection even

Sekhon, Jasjeet S.

372

The National Snow and Ice Data Center's Image and Photo Gallery  

NSDL National Science Digital Library

This website features an extensive collection of freely usable images from the National Snow and Ice Data Center related to a variety of topics, such as arctic climatology, glaciers, blizzards, and icebergs. Also included are links to Moderate Resolution Imaging Spectroradiometer (MODIS), RADARSAT Antarctic Mapping Mission (RAMP), and Surface Heat Budget of the Arctic Ocean (SHEBA) images.