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1

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

2

SNOW ON ANTARCTIC SEA ICE Robert A. Massom,1  

E-print Network

climate modeling and remote sensing would benefit by taking account of the differences be- tween the twoSNOW ON ANTARCTIC SEA ICE Robert A. Massom,1 Hajo Eicken,2 Christian Haas,3 Martin O. Jeffries,2

Warren, Stephen

3

Interdecadal changes in snow depth on Arctic sea ice  

NASA Astrophysics Data System (ADS)

plays a key role in the growth and decay of Arctic sea ice. In winter, it insulates sea ice from cold air temperatures, slowing sea ice growth. From spring to summer, the albedo of snow determines how much insolation is absorbed by the sea ice and underlying ocean, impacting ice melt processes. Knowledge of the contemporary snow depth distribution is essential for estimating sea ice thickness and volume, and for understanding and modeling sea ice thermodynamics in the changing Arctic. This study assesses spring snow depth distribution on Arctic sea ice using airborne radar observations from Operation IceBridge for 2009-2013. Data were validated using coordinated in situ measurements taken in March 2012 during the Bromine, Ozone, and Mercury Experiment (BROMEX) field campaign. We find a correlation of 0.59 and root-mean-square error of 5.8 cm between the airborne and in situ data. Using this relationship and IceBridge snow thickness products, we compared the recent results with data from the 1937, 1954-1991 Soviet drifting ice stations. The comparison shows thinning of the snowpack, from 35.1 ± 9.4 to 22.2 ± 1.9 cm in the western Arctic, and from 32.8 ± 9.4 to 14.5 ± 1.9 cm in the Beaufort and Chukchi seas. These changes suggest a snow depth decline of 37 ± 29% in the western Arctic and 56 ± 33% in the Beaufort and Chukchi seas. Thinning is negatively correlated with the delayed onset of sea ice freezeup during autumn.

Webster, Melinda A.; Rigor, Ignatius G.; Nghiem, Son V.; Kurtz, Nathan T.; Farrell, Sinead L.; Perovich, Donald K.; Sturm, Matthew

2014-08-01

4

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

5

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

6

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

7

Daily Snow and Sea Ice Temperature over Asia  

NSDL National Science Digital Library

This animation shows the global advance and retreat of daily snow cover along with daily sea ice surface temperature over Asia from September 2002 through May 2003. The snow cover was measured by the MODIS instrument on the Terra satellite, while the sea ice surface temperature was measured by the MODIS instrument on the Aqua satellite. Since these instruments cannot take measurements through clouds, in cloud-covered regions or areas with suspect data quality, the prior days value is retained until a valid data reading is obtained. This visualization designates an area as covered by snow when the instrument takes a valid measurement showing greater than ~50% snow coverage in that area. This area is assumed to be snow covered until the instrument takes a valid measurement showing less than 40% snow coverage in that same area. A color bar indicates the sea ice surface temperature values. The satellite instruments are unable to collect data through darkness. The region in polar darkness is shown as a grey cap over the pole that grows and shrinks seasonally. A date slider indicates the progression of time. SeaWiFS Land Reflectance shows the seasonal changes in landcover.

Starr, Cindy; Shirah, Greg; Newcombe, Marte; Hall, Dorothy

2004-09-25

8

Daily Snow and Sea Ice Temperature over Europe  

NSDL National Science Digital Library

This animation shows the global advance and retreat of daily snow cover along with daily sea ice surface temperature over Europe from September 2002 through May 2003. The snow cover was measured by the MODIS instrument on the Terra satellite, while the sea ice surface temperature was measured by the MODIS instrument on the Aqua satellite. Since these instruments cannot take measurements through clouds, in cloud-covered regions or areas with suspect data quality, the prior days value is retained until a valid data reading is obtained. This visualization designates an area as covered by snow when the instrument takes a valid measurement showing greater than ~50% snow coverage in that area. This area is assumed to be snow covered until the instrument takes a valid measurement showing less than 40% snow coverage in that same area. A color bar indicates the sea ice surface temperature values. The satellite instruments are unable to collect data through darkness. The region in polar darkness is shown as a grey cap over the pole that grows and shrinks seasonally. A date slider indicates the progression of time. SeaWiFS Land Reflectance shows the seasonal changes in landcover.

Starr, Cindy; Shirah, Greg; Newcombe, Marte; Hall, Dorothy

2004-09-25

9

Daily Snow and Sea Ice Temperature over North America  

NSDL National Science Digital Library

This animation shows the global advance and retreat of daily snow cover along with daily sea ice surface temperature over North America from September 2002 through May 2003. The snow cover was measured by the MODIS instrument on the Terra satellite, while the sea ice surface temperature was measured by the MODIS instrument on the Aqua satellite. Since these instruments cannot take measurements through clouds, in cloud-covered regions or areas with suspect data quality, the prior days value is retained until a valid data reading is obtained. This visualization designates an area as covered by snow when the instrument takes a valid measurement showing greater than ~50% snow coverage in that area. This area is assumed to be snow covered until the instrument takes a valid measurement showing less than 40% snow coverage in that same area. A color bar indicates the sea ice surface temperature values. The satellite instruments are unable to collect data through darkness. The region in polar darkness is shown as a grey cap over the pole that grows and shrinks seasonally. A date slider indicates the progression of time. SeaWiFS Land Reflectance shows the seasonal changes in landcover.

Starr, Cindy; Shirah, Greg; Newcombe, Marte; Hall, Dorothy

2004-09-25

10

Global Daily Snow and Sea Ice Surface Temperature  

NSDL National Science Digital Library

This animation shows the global advance and retreat of daily snow cover along with daily sea ice surface temperature over the Northern Hemisphere from September 2002 through May 2003. The snow cover was measured by the MODIS instrument on the Terra satellite, while the sea ice surface temperature was measured by the MODIS instrument on the Aqua satellite. Since these instruments cannot take measurements through clouds, in cloud-covered regions or areas with suspect data quality, the prior days value is retained until a valid data reading is obtained. This visualization designates an area as covered by snow when the instrument takes a valid measurement showing greater than ~50% snow coverage in that area. This area is assumed to be snow covered until the instrument takes a valid measurement showing less than 40% snow coverage in that same area. A color bar indicates the sea ice surface temperature values. The satellite instruments are unable to collect data through darkness. The region in polar darkness is shown as a grey cap over the pole that grows and shrinks seasonally. A date slider indicates the progression of time. SeaWiFS Land Reflectance shows the seasonal changes in landcover.

Starr, Cindy; Shirah, Greg; Newcombe, Marte; Hall, Dorothy

2004-09-25

11

Daily Snow and Sea Ice Temperature over the North Pole  

NSDL National Science Digital Library

This animation shows the global advance and retreat of daily snow cover along with daily sea ice surface temperature over the Northern Hemisphere from September 2002 through May 2003. The snow cover was measured by the MODIS instrument on the Terra satellite, while the sea ice surface temperature was measured by the MODIS instrument on the Aqua satellite. Since these instruments cannot take measurements through clouds, in cloud-covered regions or areas with suspect data quality, the prior days value is retained until a valid data reading is obtained. This visualization designates an area as covered by snow when the instrument takes a valid measurement showing greater than ~50% snow coverage in that area. This area is assumed to be snow covered until the instrument takes a valid measurement showing less than 40% snow coverage in that same area. A color bar indicates the sea ice surface temperature values. The satellite instruments are unable to collect data through darkness. The region in polar darkness is shown as a grey cap over the pole that grows and shrinks seasonally. A date slider indicates the progression of time. SeaWiFS Land Reflectance shows the seasonal changes in landcover.

Starr, Cindy; Shirah, Greg; Newcombe, Marte; Hall, Dorothy

2004-09-25

12

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

E-print Network

Thermal conductivity and heat transfer through the snow on the ice of the Beaufort Sea Matthew] Eighty-nine point measurements of the thermal conductivity (ks) of the snow on the sea ice estimates of the thermal conductivity of the snow (ks) based regression equations relating ks to snow

Sturm, Matthew

13

Assessment of radar-derived snow depth over Arctic sea ice  

NASA Astrophysics Data System (ADS)

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

14

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

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

15

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

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

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

18

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

19

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

NASA Astrophysics Data System (ADS)

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

King, M. D.

2013-12-01

20

Snow thickness retrieval over thick Arctic sea ice using SMOS satellite data  

NASA Astrophysics Data System (ADS)

The microwave interferometric radiometer of the European Space Agency's Soil Moisture and Ocean Salinity (SMOS) mission measures at a frequency of 1.4 GHz in the L-band. In contrast to other microwave satellites, low frequency measurements in L-band have a large penetration depth in sea ice and thus contain information on the ice thickness. Previous ice thickness retrievals have neglected a snow layer on top of the ice. Here, we implement a snow layer in our emission model and investigate how snow influences L-band brightness temperatures and whether it is possible to retrieve snow thickness over thick Arctic sea ice from SMOS data. We find that the brightness temperatures above snow-covered sea ice are higher than above bare sea ice and that horizontal polarisation is more affected by the snow layer than vertical polarisation. In accordance with our theoretical investigations, the root mean square deviation between simulated and observed horizontally polarised brightness temperatures decreases from 20.0 K to 4.4 K, when we include the snow layer in the simulations. Under cold Arctic conditions we find brightness temperatures to increase with increasing snow thickness. Because dry snow is almost transparent in L-band, this brightness temperature's dependence on snow thickness origins from the thermal insulation of snow and its dependence on the snow layer thickness. This temperature effect allows us to retrieve snow thickness over thick sea ice. For the best simulation scenario and snow thicknesses up to 35 cm, the average snow thickness retrieved from horizontally polarised SMOS brightness temperatures agrees within 0.7 cm with the average snow thickness measured during the IceBridge flight campaign in the Arctic in spring 2012. The corresponding root mean square deviation is 6.3 cm, and the correlation coefficient is r2 = 0.55.

Maaß, N.; Kaleschke, L.; Tian-Kunze, X.; Drusch, M.

2013-07-01

21

Snow thickness retrieval over thick Arctic sea ice using SMOS satellite data  

NASA Astrophysics Data System (ADS)

The microwave interferometric radiometer of the European Space Agency's Soil Moisture and Ocean Salinity (SMOS) mission measures at a frequency of 1.4 GHz in the L-band. In contrast to other microwave satellites, low frequency measurements in L-band have a large penetration depth in sea ice and thus contain information on the ice thickness. Previous ice thickness retrievals have neglected a snow layer on top of the ice. Here, we implement a snow layer in our emission model and investigate how snow influences L-band brightness temperatures and whether it is possible to retrieve snow thickness over thick Arctic sea ice from SMOS data. We find that the brightness temperatures above snow-covered sea ice are higher than above bare sea ice and that horizontal polarisation is more affected by the snow layer than vertical polarisation. In accordance with our theoretical investigations, the root mean square deviation between simulated and observed horizontally polarised brightness temperatures decreases from 20.9 K to 4.7 K, when we include the snow layer in the simulations. Although dry snow is almost transparent in L-band, we find brightness temperatures to increase with increasing snow thickness under cold Arctic conditions. The brightness temperatures' dependence on snow thickness can be explained by the thermal insulation of snow and its dependence on the snow layer thickness. This temperature effect allows us to retrieve snow thickness over thick sea ice. For the best simulation scenario and snow thicknesses up to 35 cm, the average snow thickness retrieved from horizontally polarised SMOS brightness temperatures agrees within 0.1 cm with the average snow thickness measured during the IceBridge flight campaign in the Arctic in spring 2012. The corresponding root mean square deviation is 5.5 cm, and the coefficient of determination is r2 = 0.58.

Maaß, N.; Kaleschke, L.; Tian-Kunze, X.; Drusch, M.

2013-12-01

22

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

Microsoft Academic Search

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

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

2007-01-01

23

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

24

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

NASA Technical Reports Server (NTRS)

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

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

2006-01-01

25

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

26

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

NASA Astrophysics Data System (ADS)

Elevated mercury concentrations have been reported in arctic coastal snow far from emission sources. The mercury is deposited during mercury depletion events (MDEs), a set of photochemical atmospheric reactions involving reactive halogens. The highest mercury concentrations are clustered near the coast, leading to speculation that sea ice or sea ice leads play a role in MDEs. The nature of this connection is not fully understood. We report mercury concentrations up to 820 ng/L in snow and frost flowers along sea ice leads near Barrow, Alaska. These concentrations are nine times higher than values from nearby coastal snow and are almost half of the mercury maximum contaminant level in United States drinking water. The high values were found only near leads that had convective plumes above open water suggesting that the same processes that produce a supersaturated environment for water vapor near sea ice leads may be instrumental in mercury deposition.

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

2005-02-01

27

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

28

MODIS Snow and Ice Production  

NASA Technical Reports Server (NTRS)

Daily, global snow cover maps, and sea ice cover and sea ice surface temperature (IST) maps are derived from NASA's Moderate Resolution Imaging Spectroradiometer (MODIS), are available at no cost through the National Snow and Ice Data Center (NSIDC). Included on this CD-ROM are samples of the MODIS snow and ice products. In addition, an animation, done by the Scientific Visualization studio at Goddard Space Flight Center, is also included.

Hall, Dorthoy K.; Hoser, Paul (Technical Monitor)

2002-01-01

29

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

Microsoft Academic Search

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

Matthew Sturm; Donald K. Perovich; Jon Holmgren

2002-01-01

30

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

SciTech Connect

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

Ledley, T.S.

1992-03-01

31

Sea Ice SAR Signature Dependence on Thaw and Refreeze Event in the Snow Cover  

NASA Astrophysics Data System (ADS)

As a result of the dependence of microwaves on the dielectric properties of the material they interfere with, the microwave signature of sea ice changes dramatically with the seasons as well as overnight when the snow layer is at the freezing point While pure ice and dry snow do not cause significant scattering and can be considered transparent throughout the winter season, the presence of liquid water, later on at spring, on air-ice or air-snow interfaces or within the snow cover turns the snow layer into an opaque medium and makes the air-snow interface the main contributor of the microwave backscattered to the SAR antenna. The availability of liquid water in the snow is the result of a shift in the thermodynamic balance of the snow layer and sea ice sheet. At spring, with the irradiance and air temperature increasing, the snow media quickly becomes isothermal. The snow layer is then a tri-phasic medium in which water changes state to balance radiations (short and long waves) and conductive heat fluxes variations. As a consequence, the surface layer of the snow cover is subject to a diurnal cycle of thaw during day time and refreeze at night which translates into a parallel diurnal cycle on snow wetness content. This cycle is of major relevance to microwave remote sensing applications and specifically to sea ice morphological features extraction. Using the output of a thermodynamic model of an isothermal snow cover forced by incoming L? and outgoing L? long-wave radiations, incident S? and reflected S? short-wave radiations and a turbulent atmospheric heat flux Qatm, an evaluation of the volume and surface components of a backscattered SAR is computed as a function of the SAR incident angle. We observe that when heat fluxes (irradiative and conductive) are positive, liquid water available in the top layer of the snow cover turns the air-snow interface into a specular reflector. Conversely, with wetness decreasing overnight, more energy can penetrate the snow medium, enhance the volume scattering contribution while turning the air-snow interface into an electromagnetically rough surface.

Hudier, E. J.; Tolszczuk-Leclerc, S.

2010-12-01

32

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

NASA Technical Reports Server (NTRS)

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

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

2009-01-01

33

Applications of ISES for snow, ice, and sea state  

NASA Technical Reports Server (NTRS)

There will be six facility instruments on the NASA NPOP-1 and NPOP-2 and additional instruments on the Japanese and European satellites. Also, there are the 24 selected NASA instruments that may be flown on one of the platforms. Many of these instruments can provide data that could be very useful for real-time data studies in the snow and ice area. Any one instrument is not addressed in particular, but emphasis is placed on what is potentially possible using the capabilities of some of these instruments.

Chang, Alfred T. C.; Delnore, Victor E.

1990-01-01

34

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

NASA Astrophysics Data System (ADS)

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

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

2007-12-01

35

Application of a Combined Rough Surface And Volume Scattering Theory to Sea Ice And Snow Backscatter  

Microsoft Academic Search

A radiative transfer theory which combines rough surface and volume scattering effects is applied to interpret backscatter measurements from snow and sea ice. The surface scattering effect is accounted for by the Kirchhoff model evaluated either with or without the deep phase modulation assumption. Hence, the major restriction on the surface model is that the horizontal roughness scale must be

Adrian K. Fung; Hyo Joon Eom

1982-01-01

36

Sea ice and snow thickness and physical properties of an ice floe in the western Weddell Sea and their changes during spring warming  

Microsoft Academic Search

Helicopter-borne and ground-based electromagnetic (EM) ice thickness and ruler-stick snow thickness measurements as well as ice-core analyses of ice temperature, salinity and texture were performed over a 5-week observation period between November 27, 2004, and January 2, 2005, on an ice floe in the western Weddell Sea at approximately 67°S, 55°W. The study was part of the Ice Station Polarstern

Christian Haas; Marcel Nicolaus; Sascha Willmes; Anthony Worby; David Flinspach

2008-01-01

37

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

38

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.

39

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

40

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

41

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

42

Arctic climate response to forcing from light-absorbing particles in snow and sea ice in CESM  

NASA Astrophysics Data System (ADS)

The presence of light-absorbing aerosol particles deposited on arctic snow and sea ice influences the surface albedo, causing greater shortwave absorption, warming, and loss of snow and sea ice, lowering the albedo further. The Community Earth System Model version 1 (CESM1) now includes the radiative effects of light-absorbing particles in snow on land and sea ice and in sea ice itself. We investigate the model response to the deposition of black carbon and dust to both snow and sea ice. For these purposes we employ a slab ocean version of CESM1, using the Community Atmosphere Model version 4 (CAM4), run to equilibrium for year 2000 levels of CO2 and fixed aerosol deposition. We construct experiments with and without aerosol deposition, with dust or black carbon deposition alone, and with varying quantities of black carbon and dust to approximate year 1850 and 2000 deposition fluxes. The year 2000 deposition fluxes of both dust and black carbon cause 1-2 °C of surface warming over large areas of the Arctic Ocean and sub-Arctic seas in autumn and winter and in patches of Northern land in every season. Atmospheric circulation changes are a key component of the surface-warming pattern. Arctic sea ice thins by on average about 30 cm. Simulations with year 1850 aerosol deposition are not substantially different from those with year 2000 deposition, given constant levels of CO2. The climatic impact of particulate impurities deposited over land exceeds that of particles deposited over sea ice. Even the surface warming over the sea ice and sea ice thinning depends more upon light-absorbing particles deposited over land. For CO2 doubled relative to year 2000 levels, the climate impact of particulate impurities in snow and sea ice is substantially lower than for the year 2000 equilibrium simulation.

Goldenson, N.; Doherty, S. J.; Bitz, C. M.; Holland, M. M.; Light, B.; Conley, A. J.

2012-02-01

43

Arctic climate response to forcing from light-absorbing particles in snow and sea ice in CESM  

NASA Astrophysics Data System (ADS)

The presence of light-absorbing aerosol particles deposited on arctic snow and sea ice influences the surface albedo, causing greater shortwave absorption, warming, and loss of snow and sea ice, lowering the albedo further. The Community Earth System Model version 1 (CESM1) now includes the radiative effects of light-absorbing particles in snow on land and sea ice and in sea ice itself. We investigate the model response to the deposition of black carbon and dust to both snow and sea ice. For these purposes we employ a slab ocean version of CESM1, using the Community Atmosphere Model version 4 (CAM4), run to equilibrium for year 2000 levels of CO2 and fixed aerosol deposition. We construct experiments with and without aerosol deposition, with dust or black carbon deposition alone, and with varying quantities of black carbon and dust to approximate year 1850 and 2000 deposition fluxes. The year 2000 deposition fluxes of both dust and black carbon cause 1-2 °C of surface warming over large areas of the Arctic Ocean and sub-Arctic seas in autumn and winter and in patches of Northern land in every season. Atmospheric circulation changes are a key component of the surface-warming pattern. Arctic sea ice thins by on average about 30 cm. Simulations with year 1850 aerosol deposition are not substantially different from those with year 2000 deposition, given constant levels of CO2. The climatic impact of particulate impurities deposited over land exceeds that of particles deposited over sea ice. Even the surface warming over the sea ice and sea ice thinning depends more upon light-absorbing particles deposited over land. For CO2 doubled relative to year 2000 levels, the climate impact of particulate impurities in snow and sea ice is substantially lower than for the year 2000 equilibrium simulation.

Goldenson, N.; Doherty, S. J.; Bitz, C. M.; Holland, M. M.; Light, B.; Conley, A. J.

2012-09-01

44

The effect of snow/sea ice type on the response of albedo and light penetration depth (e-folding depth) to increasing black carbon  

NASA Astrophysics Data System (ADS)

The optical properties of snow/sea ice vary with age and by the processes they were formed, giving characteristic types of snow and sea ice. The response of albedo and light penetration depth (e-folding depth) to increasing mass ratio of black carbon is shown to depend on the snow and sea ice type and the thickness of the snow or sea ice. The response of albedo and e-folding depth of three different types of snow (cold polar snow, wind-packed snow and melting snow) and three sea ice (multi-year ice, first-year ice and melting sea ice) to increasing mass ratio of black carbon is calculated using a coupled atmosphere-snow/sea ice radiative-transfer model (TUV-snow), over the optical wavelengths of 300-800 nm. The snow and sea ice types are effectively defined by a scattering cross-section, density and asymmetry parameter. The relative change in albedo and e-folding depth of each of the three snow and three sea ice types with increasing mass ratio of black carbon is considered relative to a base case of 1 ng g-1 of black carbon. The relative response of each snow and sea ice type is intercompared to examine how different types of snow and sea ice respond relative to each other. The relative change in albedo of a melting snowpack is a factor of four more responsive to additions of black carbon compared to cold polar snow over a black carbon increase from 1 to 50 ng g-1, while the relative change in albedo of a melting sea ice is a factor of two more responsive to additions of black carbon compared to multi-year ice for the same increase in mass ratio of black carbon. The response of e-folding depth is effectively not dependent on snow/sea ice type. The albedo of sea ice is more responsive to increasing mass ratios of black carbon than snow.

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

2014-09-01

45

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

Microsoft Academic Search

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

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

2007-01-01

46

Snow depth of the Weddell and Bellingshausen sea ice covers from IceBridge surveys in 2010 and 2011: An examination  

NASA Astrophysics Data System (ADS)

examine the snow radar data from the Weddell and Bellingshausen Seas acquired by eight IceBridge (OIB) flightlines in October of 2010 and 2011. In snow depth retrieval, the sidelobes from the stronger scattering snow-ice (s-i) interfaces could be misidentified as returns from the weaker air-snow (a-s) interfaces. In this paper, we first introduce a retrieval procedure that accounts for the structure of the radar system impulse response followed by a survey of the snow depths in the Weddell and Bellingshausen Seas. Limitations and potential biases in our approach are discussed. Differences between snow depth estimates from a repeat survey of one Weddell Sea track separated by 12 days, without accounting for variability due to ice motion, is -0.7 ± 13.6 cm. Average snow depth is thicker in coastal northwestern Weddell and thins toward Cape Norvegia, a decrease of >30 cm. In the Bellingshausen, the thickest snow is found nearshore in both Octobers and is thickest next to the Abbot Ice Shelf. Snow depth is linearly related to freeboard when freeboards are low but diverge as the freeboard increases especially in the thicker/rougher ice of the western Weddell. We find correlations of 0.71-0.84 between snow depth and surface roughness suggesting preferential accumulation over deformed ice. Retrievals also seem to be related to radar backscatter through surface roughness. Snow depths reported here, generally higher than those from in situ records, suggest dissimilarities in sample populations. Implications of these differences on Antarctic sea ice thickness are discussed.

Kwok, R.; Maksym, T.

2014-07-01

47

(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

48

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)

49

Scattering from a random layer with applications to snow, vegetation and sea ice  

NASA Technical Reports Server (NTRS)

Two approaches for computing scattering from a random layer with an irregular interface are shown using the radiative-transfer principle. One approach is applied to a random layer to develop a scattering model for snow and sea ice, while the other is used to generate a scattering model for vegetation. It is noted that to model the scattering characteristics of a special medium, it is necessary to relate the electromagnetic parameters to the measurable parameters of the scatterers in the medium. Such relations are given and used to calculate theoretical estimates to compare with measurements acquired by microwave scatterometers.

Fung, A. K.; Eom, H. J.

1983-01-01

50

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

51

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

52

Atmospheric Mercury in an Arctic OASIS (Ocean-Atmosphere-Sea Ice-Snow pack)  

NASA Astrophysics Data System (ADS)

It has become evident that chemical interactions between the atmosphere, snow, ice and ocean in Polar Regions have an impact on the composition of the overlying atmosphere and deposition to the surface. Mercury depletion events (MDEs) are important atmospheric processes associated with chemical interactions over the ocean surface yet much of their behaviour in this environment remains poorly understood. Within the context of International Polar Year (IPY) research activities, an intensive field campaign to make field measurements on mercury concentrations during the OASIS Barrow 2009 study was carried out this past March in Alaska. For the first time, an Out On The Ice (OOTI) sled was equipped to measure gaseous elemental mercury (GEM), reactive gas phase inorganic mercury (RGM) and mercury associated with particles (PHg) near open water (sea ice leads) on the Arctic Ocean. Results from these measurements showed lower re-emission of GEM following a deposition event from over the frozen ocean surface than re-emission recorded over the inland snow pack. It is believed that halogens can retain Hg+2 in snow which can make this mercury less susceptible to photoreduction and subsequent emission. Thus, the highly saline ocean environment appears able to retain mercury deposited by MDEs more effectively than less saline surfaces inland from where most mercury concentrations in snow and the re-emission of GEM have been reported. High concentrations of PHg and RGM were recorded over the frozen ice surface near the open leads ranging from 47 to 900 ± 240 pg/m-3 and 4 to 105 ± 24 pg/m-3, respectively, during the two-week OOTI intensive. This time period was dominated by MDEs where the average GEM concentration was 0.59 ± 0.40 ng/m-3 and with a range from 0.01 to 1.51 ng m-3. Analysis of the data shows that there is a linear relationship between GEM and PHg but not one between GEM and RGM over the ice. Further, PHg/RGM partitioning shows a relationship with water vapour content and temperature near the ice surface. These relationships and their importance to understanding the role of the atmosphere in MDEs will be discussed.

Steffen, A.; Bottenheim, J. W.; Staebler, R. M.; Netcheva, S.; Douglas, T. A.; Cole, A. S.; Scherz, C.; Lee, P.; Narayan, J.; Moores, J. E.; Ebinghaus, R.

2009-12-01

53

Snow and Ice Data Discovery and Access  

NSDL National Science Digital Library

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

Center, National S.

54

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

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

55

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

56

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

57

Snow and Ice.  

ERIC Educational Resources Information Center

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

Minneapolis Independent School District 275, Minn.

58

Comparison of coincident snow-freeboard and sea ice thickness profiles derived from helicopter-borne laser altimetry and electromagnetic induction sounding  

NASA Astrophysics Data System (ADS)

Sea ice thickness plays a critical role in global climate change, but it cannot be measured directly from space. Alternatively, sea ice freeboard is measured and converted to sea ice thickness with assumptions made for snow depth and snow/ice densities. This paper investigates the relationship between snow-freeboard (ice-freeboard plus snow) and total thickness (ice thickness plus snow) and addresses the uncertainties that arise from the unknown snow depth and snow/ice densities. A unique data set of coincident measurements of snow-freeboard and total thickness was collected in the Arctic and Antarctic. Snow-freeboard was determined by laser altimetry, and total thickness was determined by electromagnetic induction with a helicopter-borne instrument. Obtained total thickness/snow-freeboard ratios range from 2 to 12 in the Arctic and from 2 to 8 in the Antarctic. The principal finding is that the ratios vary greatly within each region, and a fixed ratio per profile should not be used, as this can induce incorrect ice thicknesses. The ratio uncertainties can induce a relative thickness error of 5.4% and 4.9% in the first-year and multiyear ice mode. Additionally, the coincident measurements allow the calculation of snow depth that can be used to densify existing in situ measurements. To assess accuracy, calculated snow depths were compared to in situ measurements and agree within ±5 cm. This increases if measurements and calculations differ spatially. The method of deriving snow-freeboard from laser altimetry is briefly described, and the variability of the total thickness/snow-freeboard ratio is shown for one profile in the Lincoln Sea and one in the Weddell Sea.

Goebell, Sibylle

2011-08-01

59

Optical remote sensing of snow on sea ice: Ground measurements, satellite data analysis, and radiative transfer modeling  

NASA Astrophysics Data System (ADS)

The successful launch of the Terra satellite on December 18, 1999 opened a new era of earth observation from space. This thesis is motivated by the need for validation and promotion of the use of snow and sea ice products derived from MODIS, one of the main sensors aboard the Terra and Aqua satellites. Three cruises were made in the Southern Ocean, in the Ross, Amundsen and Bellingshausen seas. Measurements of all-wave albedo, spectral albedo, BRDF, snow surface temperature, snow grain size, and snow stratification etc. were carried out on pack ice floes and landfast ice. In situ measurements were also carried out concurrently with MODIS. The effect of snow physical parameters on the radiative quantities such as all-wave albedo, spectral albedo and bidirectional reflectance are studied using statistical techniques and radiative transfer modeling, including single scattering and multiple scattering. The whole thesis consists of six major parts. The first part (chapter 1) is a review of the present research work on the optical remote sensing of snow. The second part (chapter 2) describes the instrumentation and data-collection of ground measurements of all-wave albedo, spectral albedo and bidirectional reflectance distribution function (BRDF) of snow and sea ice in the visible-near-infrared (VNIR) domain in Western Antarctica. The third part (chapter 3) contains a detailed multivariate correlation and regression analysis of the measured radiative quantities with snow physical parameters such as snow density, surface temperature, single and composite grain size and number density. The fourth part (chapter 4) describes the validation of MODIS satellite data acquired concurrently with the ground measurements. The radiances collected by the MODIS sensor are converted to ground snow surface reflectances by removing the atmospheric effect using a radiative transfer algorithm (6S). Ground measured reflectance is corrected for ice concentration at the subpixel level so that the in situ and space-borne measured reflectance data are comparable. The fifth part (chapter 5) investigates the single scattering properties (extinction optical depth, single albedo, and the phase function or asymmetry factor) of snow grains (single or composite), which were calculated using the geometrical optical method. A computer code, GOMsnow, is developed and is tested against benchmark results obtained from an exact Mie scattering code (MIE0) and a Monte Carlo code. The sixth part (chapter 6) describes radiative transfer modeling of spectral albedo using a multi-layer snow model with a multiple scattering algorithm (DISORT). The effect of snow stratification on the spectral albedo is explored. The vertical heterogeneity of the snow grain-size and snow mass density is investigated. It is found that optical remote sensing of snow physical parameters from satellite measurements should take the vertical variation of snow physical parameters into account. The albedo of near-infrared bands is more sensitive to the grain-size at the very top snow layer (<5cm), while the albedo of the visible bands is sensitive to the grain-size of a much thicker snow layer. Snow parameters (grain-size, for instance) retrieved with near-infrared channels only represent the very top snow layer (most probably 1--3 cm). Multi-band measurements from visible to near-infrared have the potential to retrieve the vertical profile of snow parameters up to a snow depth limited by the maximum penetration depth of blue light.

Zhou, Xiaobing

2002-01-01

60

Optical remote sensing of snow on sea ice: Ground measurements, satellite data analysis, and radiative transfer modeling  

Microsoft Academic Search

The successful launch of the Terra satellite on December 18, 1999 opened a new era of earth observation from space. This thesis is motivated by the need for validation and promotion of the use of snow and sea ice products derived from MODIS, one of the main sensors aboard the Terra and Aqua satellites. Three cruises were made in the

Xiaobing Zhou

2002-01-01

61

National Snow and Ice Data Center  

NSDL National Science Digital Library

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

Barry, Roger

2001-09-15

62

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

NASA Astrophysics Data System (ADS)

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

Brucker, Ludovic; Markus, Thorsten

2013-06-01

63

Correlations between Inter-Annual Variations in Arctic Sea Ice Extent, Greenland Surface Melt, and Boreal Snow Cover  

NASA Technical Reports Server (NTRS)

Intensification of global warming in recent decades has caused a rise of interest in year-to-year and decadal-scale climate variability in the Arctic. This is because the Arctic is believed to be one of the most sensitive and vulnerable regions to climatic changes. For over two decades satellite passive microwave observations have been utilized to continuously monitor the Arctic environment. Derived parameters include sea ice cover, snow cover and snow water equivalent over land, and Greenland melt extent and length of melt season. Most studies have primarily concentrated on trends and variations of individual variables. In this study we investigated how variations in sea ice cover, Greenland surface melt, and boreal snow cover are correlated. This was done on hemispheric as well as on regional scales. Latest results will be presented including data from the summer of 2004.

Markus, Thorstena; Stroeve, Julienne C.; Armstrong, Richard L.

2004-01-01

64

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

Microsoft Academic Search

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

Matthew Sturm; Donald K. Perovich; Jon Holmgren

2000-01-01

65

Bacteria in Snow and Glacier Ice  

Microsoft Academic Search

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

Vanya Miteva

66

Recent progress in snow and ice research  

SciTech Connect

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

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

1991-01-01

67

Studying Snow and Ice Changes  

NSDL National Science Digital Library

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

68

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

69

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

70

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

71

Snow melt on sea ice surfaces as determined from passive microwave satellite data  

NASA Technical Reports Server (NTRS)

SMMR data for the year 1979, 1980 and 1984 have been analyzed to determine the variability in the onset of melt for the Arctic seasonal sea ice zone. The results show melt commencing in either the Kara/Barents Seas or Chukchi Sea and progressing zonally towards the central Asian coast (Laptev Sea). Individual regions had interannual variations in melt onset in the 10-20 day range. To determine whether daily changes occur in the sea ice surface melt, the SMMR 18 and 37 GHz brightness temperature data are analyzed at day/night/twilight periods. Brightness temperatures illustrate diurnal variations in most regions during melt. In the East Siberian Sea, however, daily variations are observed in 1979, throughout the analysis period, well before any melt would usually have commenced. Understanding microwave responses to changing surface conditions during melt will perhaps give additional information about energy budgets during the winter to summer transition of sea ice.

Anderson, Mark R.

1987-01-01

72

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.

73

Combination of laser and radar altimeter height measurements to estimate snow depth during the 2004 Antarctic AMSR-E Sea Ice field campaign  

NASA Astrophysics Data System (ADS)

Among the most important parameters needed to evaluate the present and future state of Antarctic sea ice cover is the ice thickness. The retrieval of ice thickness using remote sensing techniques has been hampered by the absence of a capability to remotely measure snow thickness covering the sea ice. Data sets collected with Johns Hopkins Applied Physics Laboratory's Delay-Doppler Phase Monopulse (D2P) radar and NASA's Airborne Topographic Mapper (ATM) scanning lidar during NASA's Antarctic AMSR-E Sea Ice field campaign over the Bellingshausen Sea are used to demonstrate the potential of a remote-sensing technique for retrieval of snow cover thickness from an airborne platform. The technique takes advantage of the fact that the radar is most sensitive to the snow-ice interface while the lidar responds to the highly optically reflective snow surface. The difference between the radar- and laser-determined surfaces yields an estimate of snow thickness that appears to be reasonably consistent with expected values. The technique requires careful registration of the instrument footprints. Because there was no absolute range calibration of the lidar due to predeployment scheduling difficulties, the vertical offset between the instruments was resolved by determining the difference between measurements over leads. Elsewhere over sea ice the radar-defined surface is generally below the laser-defined surface consistent with the radar defining the snow-ice interface. Over a relatively small portion of the data, we observed opposite relationship between the sensor-defined surfaces for which we discuss a plausible physical explanation.

Leuschen, Carlton J.; Swift, Robert N.; Comiso, Josefino C.; Raney, R. Keith; Chapman, Rickey D.; Krabill, William B.; Sonntag, John G.

2008-04-01

74

Online Auxiliary Materials for Projected decline in snow depth on Arctic sea ice caused by progressively later  

E-print Network

for Marine-Earth Science and Technol- ogy (MIROC) 1 1 MPI-ESM-LR Max Planck Institute for Meteorology (MPI sea ice north of 70N rcp45 BCC-CSM1.1 CCSM4 CNRM-CM5 CanESM2 GFDL-CM3 HadGEM2-ES MIROC5 MPI-ESM-LR MRI (m) HistMonth:4 1981-2000 0 0.5 MPI-ESM-LR mean snow depth (m) HistMonth:4 1981-2000 0 0.5 MRI-CGCM3

Bitz, Cecilia

75

The Role of Snow and Ice in the Climate System  

SciTech Connect

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

Barry, Roger (NSIDC) [NSIDC

2007-12-19

76

Baltic Sea Ice Thickness Charts based on Thermodynamic Snow\\/Ice Model, C-band SAR Classification and Ice Motion Detection  

Microsoft Academic Search

We have studied the estimation of the Baltic Sea ice thickness based on a thermodynamic ice model and SAR data to produce ice thickness charts (ITCs) for navigation. Our new algorithm, also taking into account the ice motion between successive SAR images, has shown promising results.

Juha Karvonen; Bin Cheng; Markku Similä; Martti Hallikainen

2008-01-01

77

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

78

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

79

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

80

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

Microsoft Academic Search

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

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

2009-01-01

81

Primary Production in Antarctic Sea Ice  

NASA Technical Reports Server (NTRS)

A numerical model shows that in Antarctic sea ice, increased flooding in regions with thick snow cover enhances primary production in the infiltration (surface) layer. Productivity in the freeboard (sea level) layer is also determined by sea ice porosity, which varies with temperature. Spatial and temporal variation in snow thickness and the proportion of first-year ice thus determine regional differences in sea ice primary production. Model results show that of the 40 tera-grams of carbon produced annually in the Antarctic ice pack, 75 percent was associated with first-year ice and nearly 50 percent was produced in the Weddell Sea.

Arrigo, Kevin R.; Worthen, Denise L.; Lizotte, Michael P.; Dixon, Paul; Dieckmann, Gerhard

1997-01-01

82

Search for Ice and Snow  

NSDL National Science Digital Library

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

83

Meteorological factors controlling year-to-year variations in the spring onset of snow melt over the Arctic sea ice  

NASA Astrophysics Data System (ADS)

The spring onset of snow melt on the Arctic sea ice shows large inter-annual variability. Surface melt triggers positive feedback mechanisms between the albedo, snow properties and thickness, as well as sea ice thickness. Hence, it is important to quantify the factors contributing to inter-annual variability of the melt onset (MO) in various parts of the Arctic Ocean. Meteorological factors controlling surface heat budget and surface melting/freezing are the shortwave and longwave radiative fluxes and the turbulent fluxes of sensible and latent heat. These fluxes depend on the weather conditions, including the radiative impact of clouds, heat advection and wind speed. We make use of SSM/I-based MO time series (Markus, Miller and Stroeve) and the ECMWF ERA Interim reanalysis on the meteorological conditions and surface fluxes, both data sets spanning the period 1989-2008 and covering recent years with a rapid sea ice decline. The advantage is that SSM/I-based MO time series are independent of the ERA-Interim data. Our objective is to investigate if there exists a physically consistent and statistically significant relationship between MO timing and corresponding meteorological conditions. Results based on the regression analysis between the MO timing and seasonal anomalies of surface longwave radiative fluxes reveal strong relationships. Synoptic scale (3-14 days) anomalies in downward longwave radiation are essential in the Western Arctic. Regarding the longer history (20-60 days) the distinct contribution from the downward longwave radiative fluxes is captured within the whole study region. Positive anomalies in the downward longwave radiation dominate over the simultaneous negative anomalies in the downward shortwave radiation. The anomalies in downward radiative fluxes are consistent with the total column water vapor, sea level pressure and 10-m wind direction. Sensible and latent heat fluxes affect surface melt timing in the Beaufort Sea and in the Atlantic sector of the Arctic Basin. Stronger winds strengthen the relationship between the turbulent fluxes and the MO timing. The turbulent surface fluxes in spring are relatively weak, of the order of 1-10W/m2, compared to the downward shortwave and longwave radiative fluxes, which are of the order of 100-150W/m2. As soon as data uncertainties are comparable to the anomaly in turbulent fluxes, statistical relationships found between MO timing and preceding anomaly in turbulent fluxes do not necessarily prove their reasonal-causal relationship. This joint study of SSM/I-based MO record and the ERA-Interim meteorological fields region-wide with a focus on the seasonal transition demonstrates their consistency in time and space. Such result could be regarded as an important indicator that both data sets have the appropriate performance of the surface state in the Arctic Ocean. Nevertheless, an important additional effort is needed for to resolve better the cloud radiative and boundary layer turbulent processes over the sea ice.

Maksimovich, E.

2010-09-01

84

Snow and ice in a changing hydrological world.  

USGS Publications Warehouse

Snow cover on land (especially in the Northern Hemisphere) and sea ice (especially in the Southern Hemisphere) vary seasonally, and this seasonal change has an important affect on the world climate because snow and sea ice reflect solar radiation efficiently and affect other heat flow processes between atmosphere and land or ocean. Glaciers, including ice sheets, store most of the fresh water on Earth, but change dimensions relatively slowly. There is no clear evidence that the glacier ice volume currently is declining, but more needs to be known about mountain glacier and ice sheet mass balances. -from Author

Meier, M.F.

1983-01-01

85

Proposed Studentship Does black carbon and humic materials in snow and ice  

E-print Network

to investigate whether natural oxidation of black carbon and humic materials in snow and sea-ice can lessen in snow may be causing the earlier springs and loss of sea-ice in the Arctic. The Intergovernmental Panel experiments in a new sea-ice simulator at Royal Holloway: conducting experiments on the reflectivity and light

Royal Holloway, University of London

86

Variations of snow petrel breeding success in relation to sea-ice extent: detecting local response to large-scale processes?  

Microsoft Academic Search

Demographic parameters were estimated for snow petrels Pagodroma nivea nesting at the study colony of Reeve Hill near Casey station, Antarctica between 1984 and 2003. Average breeding success for the colony varied from 18.2% to 76.5%. Breeding effort, hatching and fledging success were subject to a high interannual variability. We examined the influence of regional sea-ice extent on the breeding

Frederique Olivier; Jan A. van Franeker; Jeroen C. S. Creuwels; Eric J. Woehler

2005-01-01

87

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

88

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

PubMed Central

Our knowledge about the microorganisms living in the high Arctic Ocean is still rudimentary compared to other oceans mostly because of logistical challenges imposed by its inhospitable climate and the presence of a multi-year ice cap. We have used 18S rRNA gene libraries to study the diversity of microbial eukaryotes in the upper part of the water column (0–170?m depth), the sea ice (0–1.5?m depth) and the overlying snow from samples collected in the vicinity of the North Pole (N88°35?, E015°59) at the very end of the long polar night. We detected very diverse eukaryotes belonging to Alveolata, Fungi, Amoebozoa, Viridiplantae, Metazoa, Rhizaria, Heterokonta, and Telonemia. Different alveolates (dinoflagellates and Marine Alveolate Groups I and II species) were the most abundant and diverse in gene libraries from water and sea ice, representing 80% of the total number of clones and operational taxonomic units. Only contaminants and/or species from continental ecosystems were detected in snow, suggesting wind- and animal- or human-mediated cosmopolitan dispersal of some taxa. By contrast, sea ice and seawater samples harbored a larger and more similar inter-sample protist diversity as compared with snow. The North Pole was found to harbor distinctive eukaryotic communities along the vertical gradient with an unparalleled diversity of core dinoflagellates, largely dominant in libraries from the water column, as compared to other oceanic locations. In contrast, phototrophic organisms typical of Arctic sea ice and plankton, such as diatoms and prasinophytes, were very rare in our samples. This was most likely due to a decrease of their populations after several months of polar night darkness and to the presence of rich populations of diverse grazers. Whereas strict phototrophs were scarce, we identified a variety of likely mixotrophic taxa, which supports the idea that mixotrophy may be important for the survival of diverse protists through the long polar night. PMID:21833337

Bachy, Charles; López-García, Purificación; Vereshchaka, Alexander; Moreira, David

2011-01-01

89

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

90

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

91

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

92

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.

93

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.

94

Sea ice terminology  

SciTech Connect

A group of definitions of terms related to sea ice is presented, as well as a graphic representation of late winter ice zonation of the Beaufort Sea Coast. Terms included in the definition list are belt, bergy bit, bight, brash ice, calving, close pack ice, compacting, compact pack ice, concentration, consolidated pack ice, crack, diffuse ice edge, fast ice, fast-ice boundary, fast-ice edge, first-year ice, flaw, flaw lead, floe, flooded ice, fractured, fractured zone, fracturing, glacier, grey ice, grey-white ice, growler, hummock, iceberg, iceberg tongue, ice blink, ice boundary, ice cake, ice edge, ice foot, ice free, ice island, ice shelf, large fracture, lead, medium fracture, multiyear ice, nilas, old ice, open pack ice, open water, pack ice, polar ice, polynya, puddle, rafted ice, rafting, ram, ridge, rotten ice, second-year ice, shearing, shore lead, shore polynya, small fracture, strip, tabular berg, thaw holes, very close pack ice, very open pack ice, water sky, young coastal ice, and young ice.

Not Available

1980-09-01

95

Development of an autonomous sea ice tethered buoy for the study of ocean-atmosphere-sea ice-snow pack interactions: the O-buoy  

NASA Astrophysics Data System (ADS)

A buoy based instrument platform (the "O-buoy") was designed, constructed, and field tested for year-round measurement of ozone, bromine monoxide, carbon dioxide, and meteorological variables over Arctic sea ice. The O-buoy operated in an autonomous manner with daily, bi-directional data transmissions using Iridium satellite communication. The O-buoy was equipped with three power sources: primary lithium-ion battery packs, rechargeable lead acid packs, and solar panels that recharge the lead acid packs, and can fully power the O-buoy during summer operation. This system was designed to operate under the harsh conditions present in the Arctic, with minimal direct human interaction, to aid in our understanding of the atmospheric chemistry that occurs in this remote region of the world. The current design requires approximately yearly maintenance limited by the lifetime of the primary power supply. The O-buoy system was field tested in Elson Lagoon, Barrow, Alaska from February to May 2009, and deployed in the Beaufort Sea in October 2009. Here, we describe the design and present preliminary data.

Knepp, T. N.; Bottenheim, J.; Carlsen, M.; Carlson, D.; Donohoue, D.; Friederich, G.; Matrai, P. A.; Netcheva, S.; Perovich, D. K.; Santini, R.; Shepson, P. B.; Simpson, W.; Valentic, T.; Williams, C.; Wyss, P. J.

2010-02-01

96

Synoptic controls on precipitation pathways and snow delivery to high-accumulation ice core sites in the Ross Sea region, Antarctica  

NASA Astrophysics Data System (ADS)

Dominant storm tracks to two ice core sites on the western margin of the Ross Sea, Antarctica (Skinner Saddle (SKS) and Evans Piedmont Glacier), are investigated to establish key synoptic controls on snow accumulation. This is critical in terms of understanding the seasonality, source regions, and transport pathways of precipitation delivered to these sites. In situ snow depth and meteorological observations are used to identify major accumulation events in 2007-2008, which differ considerably between sites in terms of their magnitude and seasonal distribution. While snowfall at Evans Piedmont Glacier occurs almost exclusively during summer and spring, Skinner Saddle receives precipitation year round with a lull during the months of April and May. Cluster analysis of daily back trajectories reveals that the highest-accumulation days at both sites result from fast-moving air masses, associated with synoptic-scale low-pressure systems. There is evidence that short-duration pulses of snowfall at SKS also originate from mesocyclone development over the Ross Ice Shelf and local moisture sources. Changes in the frequency and seasonal distribution of these mechanisms of precipitation delivery will have a marked impact on annual accumulation over time and will therefore need careful consideration during the interpretation of stable isotope and geochemical records from these ice cores.

Sinclair, K. E.; Bertler, N. A. N.; Trompetter, W. J.

2010-11-01

97

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

NASA Astrophysics Data System (ADS)

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

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

2012-07-01

98

Operational satellites and the global monitoring of snow and ice  

NASA Technical Reports Server (NTRS)

The altitudinal dependence of the global warming projected by global climate models is at least partially attributable to the albedo-temperature feedback involving snow and ice, which must be regarded as key variables in the monitoring for global change. Statistical analyses of data from IR and microwave sensors monitoring the areal coverage and extent of sea ice have led to mixed conclusions about recent trends of hemisphere sea ice coverage. Seasonal snow cover has been mapped for over 20 years by NOAA/NESDIS on the basis of imagery from a variety of satellite sensors. Multichannel passive microwave data show some promise for the routine monitoring of snow depth over unforested land areas.

Walsh, John E.

1991-01-01

99

Soot climate forcing via snow and ice albedos James Hansen*  

E-print Network

estimates for the effect of soot on snow and ice albedos (1.5% in the Arctic and 3% in Northern Hemisphere change sea level The Intergovernmental Panel on Climate Change (1) estimates the global climate forcing forcing, including BC from fossil fuels, biofuels, and outdoor biomass burning, and also including

100

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

101

Thickness distribution of Antarctic sea ice  

NASA Astrophysics Data System (ADS)

Ship-based observations are used to describe regional and seasonal changes in the thickness distribution and characteristics of sea ice and snow cover thickness around Antarctica. The data set comprises 23,373 observations collected over more than 2 decades of activity and has been compiled as part of the Scientific Committee on Antarctic Research (SCAR) Antarctic Sea Ice Processes and Climate (ASPeCt) program. The results show the seasonal progression of the ice thickness distribution for six regions around the continent together with statistics on the mean thickness, surface ridging, snow cover, and local variability for each region and season. A simple ridge model is used to calculate the total ice thickness from the observations of level ice and surface topography, to provide a best estimate of the total ice mass, including the ridged component. The long-term mean and standard deviation of total sea ice thickness (including ridges) is reported as 0.87 ± 0.91 m, which is 40% greater than the mean level ice thickness of 0.62 m. Analysis of the structure function along north/south and east/west transects revealed lag distances over which sea ice thickness decorrelates to be of the order of 100-300 km, which we use as a basis for presenting near-continuous maps of sea ice and snow cover thickness plotted on a 2.5° × 5.0° grid.

Worby, Anthony P.; Geiger, Cathleen A.; Paget, Matthew J.; van Woert, Michael L.; Ackley, Stephen F.; Deliberty, Tracy L.

2008-05-01

102

Sea Ice and Polar Climate in the NCAR CSM  

Microsoft Academic Search

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

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

1998-01-01

103

Sea ice and polar climate in the NCAR CSM  

Microsoft Academic Search

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

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

1998-01-01

104

Interferometric System for Measuring Thickness of Sea Ice  

NASA Technical Reports Server (NTRS)

The cryospheric advanced sensor (CAS) is a developmental airborne (and, potentially, spaceborne) radar-based instrumentation system for measuring and mapping the thickness of sea ice. A planned future version of the system would also provide data on the thickness of snow covering sea ice. Frequent measurements of the thickness of polar ocean sea ice and its snow cover on a synoptic scale are critical to understanding global climate change and ocean circulation.

Hussein, Ziad; Jordan, Rolando; McDonald, Kyle; Holt, Benjamin; Huang, John; Kugo, Yasuo; Ishimaru, Akira; Jaruwatanadilok, Semsak; Akins, Torry; Gogineni, Prasad

2006-01-01

105

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 ice9 The Dynamics of Snow and Ice Masses J.S. Wettlaufer Applied Physics Laboratory and Department of Physics, University of Washington, Seattle, WA 98105-5640, USA 9.1 Ice: Land, Sea and Air On Earth today

Wettlaufer, John S.

106

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

107

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

108

A model of the threedimensional evolution of Arctic melt ponds on firstyear and multiyear sea ice  

E-print Network

A model of the threedimensional evolution of Arctic melt ponds on firstyear and multiyear sea ice F ice. In the summer the upper layers of sea ice and snow melts producing meltwater that accumulates in Arctic melt ponds on the surface of sea ice. An accurate estimate of the fraction of the sea ice surface

Feltham, Daniel

109

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

110

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

111

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

Microsoft Academic Search

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

Gabriel J. Wolken; Martin Sharp; Libo Wang

2009-01-01

112

Impacts of Declining Arctic Sea Ice: An International Challenge  

Microsoft Academic Search

As reported by the National Snow and Ice Data Center in late August of 2008, Arctic sea ice extent had already fallen to its second lowest level since regular monitoring began by satellite. As of this writing, we were closing in on the record minimum set in September of 2007. Summers may be free of sea ice by the year

M. Serreze

2008-01-01

113

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

114

EOS Aqua AMSR-E Arctic Sea Ice Validation Program  

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

115

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

116

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

117

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

Microsoft Academic Search

The polar regions play a key role in the Earth's climate system, and sea ice has a major influence on ocean-atmosphere interaction and ocean circulation. Antarctic sea ice and its snow cover are integral components of the global climate system, yet their thickness and variability are poorly understood and subsequently their representation in global climate models is poor. Remote sensing

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

2009-01-01

118

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

119

Sea-ice thickness and mass at Ice Station Belgica, Bellingshausen Sea, Antarctica  

NASA Astrophysics Data System (ADS)

Ice Station Belgica was commenced in late winter 2007 in the Bellingshausen Sea as part of Sea Ice Mass Balance in Antarctica (SIMBA), an IPY 2007 cruise on the research vessel N.B. Palmer. A primary objective was to build on the work of previous Antarctic drift station experiments to geophysically characterize sea ice in terms of thickness, surface and ice bottom morphology, and ultimately area-unitized mass. A 24 day drift station was established at approximately 70°S and 93°W in mixed first-year and multi-year ice with three geophysical study sites selected on a 5 km 2 floe. A comprehensive time series assessment of elevation-surveyed transects ranging from 100 m to 300 m in length included snow surface elevation, snow depth, electromagnetic (EM) profiling, and direct drilling for ice draft and ice freeboard. Additional work included a snow surface morphology characterization of a 100 m×300 m area between the primary time series EM transects. Correlation of EM ice thicknesses with collocated drilled ice thickness yielded equations for the correction of EM underestimation of thick deformed ice, particularly at pressure ridges. Mean ice thickness from corrected EM was compared to isostatic ice thickness calculated from surface elevation, snow depth, ice freeboard and respective snow, slush, ice, and sea water densities. Results were consistent, with mean ice thicknesses for multi-year ice of 2.35 m, 2.34 m, and 2.41 m, with similar variance, for corrected EM, drilling, and buoyancy methods respectively. Additionally, a mean ice thickness of 2.31 m was calculated from ASPeCt observations of the ice field associated with the floe, using the method incorporating mean sail heights and fractional coverage of surface deformities or ridging. Temporal series assessment of ice freeboard indicated a slightly negative mean ice freeboard (<0.04 m), with clear evidence of new snow-ice formation from the freezing of slush. The three distinct snow and ice regions assessed on the Belgica floe had mean corrected EM ice thickness of 0.52±0.04 m (±1 std. deviation), 0.92±0.17 m, and 2.35±1.37 m, and mean snow depths of 0.08±0.03 m, 0.36±0.09 m, and 0.68±0.31 m respectively. Each ice type represented a sizable fraction of the floe's total area (˜20%, 40%, and 40% respectively from visual estimates) reflecting a complex dynamic and thermodynamic history of formation, as well as the difficulty in characterizing even a single floe by a single class or mean value for thickness and snow depth. Implications of these results are discussed with regards to the resolution of satellite-based altimetry and snow depth products and efforts to generate and validate satellite sea ice and snow thickness products.

Weissling, B. P.; Lewis, M. J.; Ackley, S. F.

2011-05-01

120

Microwave remote sensing of sea ice  

NASA Technical Reports Server (NTRS)

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

Comiso, J. C.

1988-01-01

121

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

2012-01-01

122

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

2013-01-01

123

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

2011-01-01

124

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

2014-01-01

125

Monitoring Snow on ice as Critical Habitat for Ringed Seals  

NASA Astrophysics Data System (ADS)

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

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

2007-12-01

126

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.

127

ICESat measurements of sea ice freeboard and estimates of sea ice thickness in the Weddell Sea  

NASA Astrophysics Data System (ADS)

Sea ice freeboard heights in the Weddell Sea of Antarctica are derived from the Ice, Cloud, and Land Elevation Satellite (ICESat) laser altimeter measurements, which have a unique range precision to flat surfaces of 2 cm within 70 m footprints spaced at 172 m along track. Although elevations of flat surfaces can be obtained to an accuracy of ˜10 cm (1?) per footprint, direct determination of freeboard heights is precluded by errors in knowledge of the geoid and temporal variability of the ocean surface. Therefore freeboards are determined relative to an ocean reference level detected over areas of open water and very thin ice within the sea ice pack using an along-track filtering method. The open water/thin ice selections show good agreement in the combined analysis of ICESat segments and Envisat Synthetic Aperture Radar (SAR) imagery. The average residual between the ICESat-measured ocean level and the EGM96 geoid is 1.4 m. Estimates of snow depth on the sea ice from AMSR-E passive microwave data along with nominal densities of snow, water, and sea ice are used to estimate sea ice thickness. Four periods of ICESat data in May-June (fall) and October-November (late winter) of 2004 and 2005 between longitudes 298°E and 360°E are analyzed. In the fall the mean freeboards are 0.28 m in 2004 and 0.29 m in 2005, and the mean thicknesses are 1.33 m in 2004 and 1.52 m in 2005. In late winter the freeboards grew to 0.37 m in 2004 and 0.35 in 2005, and the thicknesses grew to 2.23 m in 2004 and 2.31 m in 2005. The interannual differences in freeboard are small, and the larger interannual change in estimated thickness mainly represents differences in the snow depth estimates. Seasonal changes in the spatial patterns of freeboard and thickness over the 4 months correlate with the expected circulation of sea ice in the Weddell Sea, as indicated by sea ice velocity fields.

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

2008-02-01

128

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

129

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.

130

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

131

Arctic Sea Ice  

NASA Astrophysics Data System (ADS)

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

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

2004-12-01

132

The role of sea ice in structuring Antarctic ecosystems  

Microsoft Academic Search

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

Hajo Eicken

1992-01-01

133

Arctic Sea Ice  

NSDL National Science Digital Library

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

Meier, Beverly L.

2012-06-26

134

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

E-print Network

Snow Cover Effects on Glacier Ice Surface Temperature Margherita Maggioni*{ Michele Freppaz* Paolo.maggioni@unito.it Abstract Snowpack evolution and glacier ice surface temperatures were studied on the Indren glacier of an artificial increase in the snow density was evaluated. During the season rich in snow there was a prevalence

Williams, Mark W.

135

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

NASA Astrophysics Data System (ADS)

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

Shi, Wei; Wang, Menghua

2012-07-01

136

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

137

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

138

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

139

Transpolar observations of the morphological properties of Arctic sea ice  

Microsoft Academic Search

Numerous ground-based and satellite observations of polar sea ice offer substantial evidence of a reduction in the areal extent and thickness of the Arctic ice cover. During the 2005 Healy-Oden Trans-Arctic Expedition 2005 a trans-Arctic survey of the physical properties of the polar ice pack was conducted. The observational program consisted of four broad classes of snow and ice activities:

B. C. Elder; D. K. Perovich; T. C. Grenfell; J. Harbeck; B. Light; K. K. Everhart

2006-01-01

140

Atmospheric mercury over sea ice during the OASIS-2009 campaign  

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

141

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

NASA Technical Reports Server (NTRS)

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

Yung, Yuk L.

2004-01-01

142

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

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

143

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

144

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

145

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

146

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

147

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

148

Arctic Sea Ice Model Sensitivities  

NASA Astrophysics Data System (ADS)

Arctic sea ice is an important component of the global climate system and, due to feedback effects, the Arctic ice cover is changing rapidly. Predictive mathematical models are of paramount importance for accurate estimates of the future ice trajectory. However, the sea ice components of Global Climate Models (GCMs) vary significantly in their prediction of the future state of Arctic sea ice and have generally underestimated the rate of decline in minimum sea ice extent seen over the past thirty years. One of the contributing factors to this variability is the sensitivity of the sea ice state to internal model parameters. A new sea ice model that holds some promise for improving sea ice predictions incorporates an anisotropic elastic-decohesive rheology and dynamics solved using the material-point method (MPM), which combines Lagrangian particles for advection with a background grid for gradient computations. We evaluate the variability of this MPM sea ice code and compare it with the Los Alamos National Laboratory CICE code for a single year simulation of the Arctic basin using consistent ocean and atmospheric forcing. Sensitivities of ice volume, ice area, ice extent, root mean square (RMS) ice speed, central Arctic ice thickness,and central Arctic ice speed with respect to ten different dynamic and thermodynamic parameters are evaluated both individually and in combination using the Design Analysis Kit for Optimization and Terascale Applications (DAKOTA). We find similar responses for the two codes and some interesting seasonal variability in the strength of the parameters on the solution. Sandia National Laboratories is a multi-program laboratory operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U. S. Department of Energy’s National Nuclear Security Administration under Contract DE-AC04-94-AL85000.

Peterson, K. J.; Bochev, P.; Paskaleva, B.

2010-12-01

149

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

150

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

NASA Astrophysics Data System (ADS)

A new meltpond parameterization has been developed for the CICE sea ice model, taking advantage of the level ice tracer available in the model. The ponds evolve according to physically based process descriptions, assuming a depth-area ratio for changes in pond volume. A novel aspect of the new scheme is that the ponds are carried as tracers on the level ice area of each thickness category, thus limiting their spatial extent based on the simulated sea ice topography. This limiting is meant to approximate the horizontal drainage of melt water into depressions in ice floes. Simulated melt pond processes include collection of liquid melt water and rain into ponds, drainage through permeable sea ice or over the edges of floes, infiltration of snow by pond water, and refreezing of ponds. Furthermore, snow that falls on top of ponds whose top surface has refrozen blocks radiation from penetrating into the ponds and sea ice below. Along with a control simulation, we present a range of sensitivity tests to parameters related to each subprocess described by the parameterization. With the exception of one parameter that alters the albedo of snow-covered pond ice, results are not highly sensitive to these parameters unless an entire process is removed. The snow simulation itself is critical, because the volume of snow deposition and rate of snow melt largely determine the timing and extent of the simulated melt ponds. Nevertheless, compensating effects moderate the model's sensitivity to precipitation changes. For instance, infiltration of the snow by melt water postpones the appearance of ponds and the subsequent acceleration of melting through albedo feedback, while snow on top of refrozen pond ice also reduces the ponds' effect on the radiation budget. By construction, the model simulation of level and ridged ice is also important for this parameterization. We find that as sea ice thins, either through time or when comparing sensitivity tests, the area of level ice increases. This leads to an enhanced thinning feedback in the model, because a greater ice area may be exposed to ponding and further thinning due to lowered albedo.

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

2013-11-01

151

Arctic sea ice freeboard heights from satellite altimetry  

NASA Astrophysics Data System (ADS)

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

Renganathan, Vidyavathy

152

CryoLand - GMES Service Snow and Land Ice - Interoperability, Service Integration and User Access  

Microsoft Academic Search

\\u000a The CryoLand project implements and validates a standardized and sustainable service on snow and land ice monitoring as a\\u000a Downstream Service of GMES. It will provide geospatial product coverages of seasonal snow (snow extent, snow mass, melt state),\\u000a glaciers (area, snow \\/ ice extent, ice velocities, glacier dammed lakes), and lake \\/ river ice (extent, temporal variations,\\u000a snow burden) derived

Gerhard Triebnig; Andrei Diamandi; Richard Hall; Eirik Malnes; Lars Marklund; Sari Metsämäki; Thomas Nagler; Jouni Pulliainen; Helmut Rott; Christian Schiller; Rune Solberg; Andreas Wiesmann

153

Temporal dynamics of ikaite in experimental sea ice  

NASA Astrophysics Data System (ADS)

Ikaite (CaCO3 · 6H2O) is a metastable phase of calcium carbonate that normally forms in a cold environment and/or under high pressure. 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 outdoor pool of the Sea-ice Environmental Research Facility (SERF) in Manitoba, Canada. During the experiment, ikaite precipitated in sea ice when temperatures were below -4 °C, creating three distinct zones of ikaite concentrations: (1) a millimeter-to-centimeter-thin surface layer containing frost flowers and brine skim with bulk ikaite concentrations of >2000 ?mol kg-1, (2) an internal layer with ikaite concentrations of 200-400 ?mol kg-1, and (3) a bottom layer with ikaite concentrations of <100 ?mol kg-1. Snowfall events caused the sea ice to warm and ikaite crystals to dissolve. Manual removal of the snow cover allowed the sea ice to cool and brine salinities to increase, resulting in rapid ikaite precipitation. The observed ikaite concentrations were on the same order of magnitude as modeled by FREZCHEM, which further supports the notion that ikaite concentration in sea ice increases with decreasing temperature. Thus, varying snow conditions may play a key role in ikaite precipitation and dissolution in sea ice. This could have a major implication for CO2 exchange with the atmosphere and ocean that has not been accounted for previously.

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

2014-08-01

154

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

E-print Network

Processes driving sea ice variability in the Bering Sea in an eddying ocean/sea ice model: Mean 17 September 2014 Available online 28 September 2014 Keywords: Sea ice Ice growth/melt Sea ice motion Heat flux Climate dynamics Bering Sea a b s t r a c t The seasonal cycle of sea ice variability

Eisenman, Ian

155

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

156

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

157

Sea Ice Thickness Variability in Fram Strait  

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

158

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

159

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

160

AVHRR\\/3 Experimental Global Snow and Ice Detection Algorithm  

Microsoft Academic Search

The six channel Advanced Very High Resolution Radiometer\\/3 (AVHRR\\/3) was first flown on NOAA-15 in May 1998. Channel 3A (1.6 microns) is time shared with the older Channel 3B (3.7 microns). Channel 3A was specifically designed for snow and ice detection. An experimental global snow and ice detection algorithm using the experimental Clouds from AVHRR (CLAVR) processing system was developed

C. A. Dean; V. R. Anne; B. H. Ramsay

2001-01-01

161

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

162

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

NASA Astrophysics Data System (ADS)

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

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

2009-12-01

163

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

164

The Sea Ice Board Game  

NSDL National Science Digital Library

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

Bertram, Kathryn B.

2008-10-01

165

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

166

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

NASA Astrophysics Data System (ADS)

Sea ice volume has decreased in the last decades, evoked by changes in sea ice area and thickness. Estimates of sea ice area and thickness rely on a number of geophysical parameters which introduce large uncertainties. To quantify these uncertainties we use freeboard retrievals from ICESat and investigate different assumptions about snow depth, sea ice density and area. We find that uncertainties in ice area are of minor importance for the estimates of sea ice volume during the cold season in the Arctic basin. The choice of mean ice density used when converting sea ice freeboard into thickness mainly influences the resulting mean sea ice thickness, while snow depth on top of the ice is the main driver for the year-to-year variability, particularly in late winter. The absolute uncertainty in the mean sea ice thickness is 0.28 m in February/March and 0.21 m in October/November. The uncertainty in snow depth contributes up to 70% of the total uncertainty and the ice density 30-35%, with higher values in October/November. We find large uncertainties in the total sea ice volume and trend. The mean total sea ice volume is 10 120 ± 1280 km3 in October/November and 13 250 ± 1860 km3 in February/March for the time period 2005-2007. Based on these uncertainties we obtain trends in sea ice volume of -1450 ± 530 km3 a-1 in October/November and -880 ± 260 km3 a-1 in February/March over the ICESat period (2003-2008). Our results indicate that, taking into account the uncertainties, the decline in sea ice volume in the Arctic between the ICESat (2003-2008) and CryoSat-2 (2010-2012) periods may have been less dramatic than reported in previous studies. However, more work and validation is required to quantify these changes and analyse possible unresolved biases in the freeboard retrievals.

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

2014-04-01

167

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

168

Numerical simulations on artificial reduction of snow and ice ablation  

NASA Astrophysics Data System (ADS)

This snow modeling study investigates two methods to artificially reduce ablation in Alpine glacier ski resorts. Using the snow cover model SNTHERM, a first set of sensitivity studies focuses on the potential effects of artificial compaction of snow during winter. In comparison to a reference run representing the natural conditions, a stepwise increase of the model's new snow density toward 500 kg m-3 yields no more than 218 kg m-2 water equivalent being saved at the end of the ablation period. Further studies consider effects of covering the snow surface with different materials in spring. The physical properties and the energetic processes at the model's surface node are parameterized accordingly. The results show that 2489 kg m-2 water equivalent are saved compared to the reference run. Thus 15% of the winter snow cover as well as the whole amount of the underlying glacier ice are preserved. This indicates that surface covering reduces snow and ice ablation more effectively than snow compaction, which is confirmed by field measurements.

Olefs, M.; Obleitner, F.

2007-06-01

169

Satellite observations of sea ice  

NASA Technical Reports Server (NTRS)

An overview is presented of Antarctic and Arctic sea ice studies using data from the Nimbus-5 ESMR and the Nimbus-7 SMMR passive microwave radiometers. Four years (1973-1976) of ESMR data for the Antarctic Ocean define the characteristics of the seasonal cycle including regional contrasts and interannual variations. Major advances include the discovery of the Weddell polynya and the presence of substantial areas of open water in the Antarctic winter pack ice. Regional differences in sea ice extent on time-scales of about a month are shown to be associated with variations in surface-wind fields. In the Arctic, the computation of sea ice concentration is complicated by the presence of multiyear ice, but the amount of multiyear ice becomes an important measurable quantity with dual-polarized, multifrequency passive microwave sensors. Analysis of SMMR data demonstrates its advantage for studying the spatial and temporal variability of the Arctic ice cover. Large observed interannual variations in the distribution of the multiyear pack ice and the presence of significant divergent areas in the central Arctic during winter contrast markedly with the classical view of the Arctic pack ice.

Cavalieri, D. J.; Zwally, H. J.

1985-01-01

170

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

171

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

172

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

173

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.

174

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

175

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

NSDL National Science Digital Library

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

Bhat, Venugopal; Plans, Nasa -.

176

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

177

Polar Sea Ice Processes  

NSDL National Science Digital Library

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

Smith, Elizabeth; Alfultus, Michael

2000-06-01

178

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

179

The sensitivity of a one-dimensional thermodynamic sea ice model to changes in cloudiness  

NASA Technical Reports Server (NTRS)

A thermodynamic sea ice-lead model is used to assess the importance of cloud cover changes to modeled ice thickness. For regions of either permanent multiyear ice or seasonal sea ice, the cloud amount variations have relatively little impact. However, for regions where the presence of summer ice is variable from year to year, the predicted ice thickness is strongly dependent on cloud cover. In general, with a snow covered surface, decreased cloud leads to surface cooling while increased cloud gives rise to a surface warming. For a melting bare ice surface, the reverse occurs. The ice model response time is too long for interannual variations in cloud amount to explain interannual variations in ice thickness and extent. Nevertheless, the implication of the results is that numerical modeling of sea ice distribution requires accurate cloud data or cloud prediction and that trends in cloud cover may lead to significant perturbations in sea ice extent and thickness.

Shine, K. P.; Crane, R. G.

1984-01-01

180

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

181

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

NASA Astrophysics Data System (ADS)

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

Komuro, Yoshiki; Suzuki, Tatsuo

2013-04-01

182

Consistent and contrasting decadal Arctic sea ice thickness predictions from a highly optimized sea ice  

E-print Network

Consistent and contrasting decadal Arctic sea ice thickness predictions from a highly optimized sea of Arctic Ocean sea ice thickness made by a modern dynamic-thermodynamic sea ice model and forced comprehensive data sets of observations made between 1979 and 2001 of sea ice thickness, draft, extent

Feltham, Daniel

183

QuikSCAT Antarctic Sea Ice (WMS)  

NSDL National Science Digital Library

The sea ice around Antarctica grows dramatically from late February, when large parts of the coast are ice-free, to October, when the amount of sea ice effectively doubles the size of the continent. The SeaWinds Scatterometer instrument on the QuikSCAT satellite captures this dramatic ebb and flow and shows the sea ice as dynamic and always moving, even in areas that are ice-bound. This animation shows the sea ice around Antarctica from SeaWinds during 2004. SeaWinds can see individual icebergs if they are large enough, and a large iceberg can be seen for most of the year south of South America as it moves from the Antarctic Peninsula to the South Sandwich Islands. Also visible are the very convoluted and dynamic border between the sea ice and the open sea and holes in the sea ice created by the movement around fixed land features such as islands.

Kekesi, Alex; Mitchell, Horace

2005-03-28

184

EOS Aqua AMSR-E Arctic Sea Ice Validation Program: Intercomparison Between Modeled and Measured Sea Ice Brightness Temperatures  

NASA Technical Reports Server (NTRS)

During March 2003, an extensive field campaign was conducted near Barrow, Alaska to validate AQUA Advanced Microwave Scanning Radiometer (AMSR) sea ice products. Field, airborne and satellite data were collected over three different types of sea ice: 1) first year ice with little deformation, 2) first year ice with various amounts of deformation and 3) mixed first year ice and multi-year ice with various degrees of deformation. The validation plan relies primarily on comparisons between satellite, aircraft flights and ground-based measurements. Although these efforts are important, key aspects such as the effects of atmospheric conditions, snow properties, surface roughness, melt processes, etc on the sea ice algorithms are not sufficiently well understood or documented. To improve our understanding of these effects, we combined the detailed, in-situ data collection from the 2003 field campaign with radiance modeling using a radiative transfer model to simulate the top of the atmosphere AMSR brightness temperatures. This study reports on the results of the simulations for a variety of snow and ice types and compares the results with the National Oceanographic and Atmospheric Administration Environmental Technology Laboratory Polarimetric Scanning Radiometer (NOAA) (ETL) (PSR) microwave radiometer that was flown on the NASA P-3.

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

2004-01-01

185

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

NASA Astrophysics Data System (ADS)

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

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

2005-12-01

186

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.

187

Comparison of the sea-ice thickness distribution in the Lincoln Sea and adjacent Arctic Ocean in 2004 and 2005  

Microsoft Academic Search

Results of helicopter-borne electromagnetic measurements of total (ice plus snow) sea-ice thickness performed in May 2004 and 2005 in the Lincoln Sea and adjacent Arctic Ocean up to 86° N are presented. Thickness distributions south of 84° N are dominated by multi-year ice with modal thicknesses of 3.9 m in 2004 and 4.2 m in 2005 (mean thicknesses 4.67 and

C. Haas; S. Hendricks; M. Doble

2006-01-01

188

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

189

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

190

Organic iodine in Antarctic sea ice: A comparison between winter in the Weddell Sea and summer in the Amundsen Sea  

NASA Astrophysics Data System (ADS)

studies have recognized sea ice as a source of reactive iodine to the Antarctic boundary layer. Volatile iodinated compounds (iodocarbons) are released from sea ice, and they have been suggested to contribute to the formation of iodine oxide (IO), which takes part in tropospheric ozone destruction in the polar spring. We measured iodocarbons (CH3I, CH2ClI, CH2BrI, and CH2I2) in sea ice, snow, brine, and air during two expeditions to Antarctica, OSO 10/11 to the Amundsen Sea during austral summer and ANT XXIX/6 to the Weddell Sea in austral winter. These are the first reported measurements of iodocarbons from the Antarctic winter. Iodocarbons were enriched in sea ice in relation to seawater in both summer and winter. During summer, the positive relationship to chlorophyll a biomass indicated a biological origin. We suggest that CH3I is formed biotically in sea ice during both summer and winter. For CH2ClI, CH2BrI, and CH2I2, an additional abiotic source at the snow/ice interface in winter is suggested. Elevated air concentrations of CH3I and CH2ClI during winter indicate that they are enriched in lower troposphere and may take part in the formation of IO at polar sunrise.

Granfors, Anna; Ahnoff, Martin; Mills, Matthew M.; Abrahamsson, Katarina

2014-12-01

191

March 2003 EOS Aqua AMSR-E Arctic Sea Ice Field Campaign  

NASA Technical Reports Server (NTRS)

An overview of the March 2003 coordinated sea ice field campaign in the Alaskan Arctic is presented with reference to the papers in this special section. This campaign is part of the program to validate the Aqua Advanced Microwave Scanning Radiometer for Earth Observing System (AMSR-E) sea ice products. Standard AMSR-E sea ice products include sea ice concentration, sea ice temperature, and snow depth on sea ice. The validation program consists of three elements, namely: 1) satellite data comparisons; 2) coordinated satellite/aircraft surface measurements; and 3) modeling and sensitivity analyses. Landsat-7 and RADARSAT observations were used in comparative studies with the retrieved AMSR-E sea ice concentrations. The aircraft sensors provided high-resolution microwave imagery of the surface, atmospheric profiles of temperature and humidity, and digital records of sea ice conditions. When combined with in situ measurements, aircraft data were used to validate the AMSR-E sea ice temperature and snow-depth products. The modeling studies helped interpret the field-data comparisons, provided insight on the limitations of the AMSR-E sea ice algorithms, and suggested potential improvements to the AMSR-E retrieval algorithms.

Cavalieri, Donald J.; Markus, Thorsten; Maslanik, James A.; Sturm, Matthew; Lobl, Elena

2006-01-01

192

GATOR-GCMM: A global- through urban-scale air pollution and weather forecast model, 1. Model design and treatment of subgrid soil, vegetation, roads, rooftops, water, sea ice, and snow  

NASA Astrophysics Data System (ADS)

A model that treats nesting of gas, size- and composition-resolved aerosol, radiative, and meteorological parameters from the global through urban scales (<5-km grid spacing) was developed. The model treats multiple one-way-nested layers and multiple air quality and meteorological domains in each layer between the global and the urban scales. This latter feature allows forecast of air pollution and weather at several urban or regional sites during the same simulation. Regardless of the number of domains used during a single continuous simulation, the central memory required never exceeds 1.5 times and 2.1 times that of the largest domain for gas and gas/aerosol simulations, respectively. A submodule was developed for all domains to treat ground temperatures, latent heat fluxes, and sensible heat fluxes over subgrid soil types (with and without vegetation), water, sea ice, and urban areas. Urban areas are divided into road surfaces, rooftops, vegetation, and bare soil. Snow is treated over all surface types. The global-through-urban model is applied in a companion paper to study elevated ozone, ozone in national parks, and weather during a field campaign in northern and central California.

Jacobson, Mark Z.

2001-03-01

193

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

194

The surface energy balance of Antarctic snow and blue ice  

Microsoft Academic Search

Little is known about the surface energy balance of Antarctic blue-ice areas although there have been some studies of the surface energy balance of snow surfaces. Therefore, a detailed meteorological experiment was carried out in the vicinity of a blue-ice area in the Heimefrontfjella, Dronning Maud Land, Antarctica, during the austral summer of 1992\\/93. Since not all the surface fluxes

Richard Bintanja; Michiel R. van den Broeke

1995-01-01

195

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

196

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

197

Soot climate forcing via snow and ice albedos  

Microsoft Academic Search

Plausible estimates for the effect of soot on snow and ice albedos (1.5% in the Arctic and 3% in Northern Hemisphere land areas) yield a climate forcing of +0.3 W\\/m2 in the Northern Hemisphere. The \\

James Hansen; Larissa Nazarenko

2004-01-01

198

Snow and Ice Field Handbook for Snowplow Operators  

E-print Network

Minnesota Snow and Ice Control Field Handbook for Snowplow Operators Second Revision Manual Number to the plow operators who keep our roads safe all winter long. It is based on the Manual of Practice Graphic Design: Cadie Wright Adhikary, CTS Acknowledgments #12;Contents Basic Concepts

Minnesota, University of

199

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

NSDL National Science Digital Library

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

University, The O.

200

An inter-sensor comparison of the microwave signatures of Arctic sea ice  

NASA Technical Reports Server (NTRS)

Active and passive microwave and physical properties of Arctic sea ice in the marginal ice zone were measured during the summer. Results of an intercomparison of data acquired by an aircraft synthetic aperture radar, a passive microwave imager and a helicopter-mounted scatterometer indicate that early-to-mid summer sea ice microwave signatures are dominated by snowpack characteristics. Measurements show that the greatest contrast between thin first-year and multiyear sea ice occurs when operating actively between 5 and 10 GHz. Significant information about the state of melt of snow and ice is contained in the active and passive microwave signatures.

Onstott, R. G.

1986-01-01

201

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.

Fetterer, Florence

202

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

USGS Publications Warehouse

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

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

2000-01-01

203

Satellite and In Situ Observations of Arctic Sea Ice Floe Breakup and Melt  

NASA Astrophysics Data System (ADS)

During the summer melt season the Arctic sea ice cover undergoes a major transformation. In spring the ice cover consists of large, angular floes covered by snow. By late-summer it is an ensemble of smaller rounded ice floes embedded in a lace of open water, with a surface that is a mix of bare ice and melt ponds. We integrated in situ observations of sea ice mass balance with high resolution, visible satellite imagery from April to October 2013 to follow the evolution of the seasonal marginal ice zone in the Beaufort Sea. The autonomous sea ice mass balance buoy recorded a time series of ice temperature, ice growth, snow depth, ice thickness, and surface and bottom melting. The satellite images were collected by tracking the movement of the buoy as it drifted with the ice cover. Each image covered an area of about 250 km2 with a spatial resolution of just over one meter. From the images we computed ice concentration, pond fraction, floe perimeter, pond fraction, floe and pond size distribution, and the timing of melt and freezeup. Ridges and cracks formed in winter were followed into summer to investigate their effect on the floe size distribution. Measurements from the ice mass balance buoys are scaled up using the imagery to generate area estimates of the evolution of the sea ice mass loss during summer melt. There was an increase in pond coverage starting in mid-June and an increase in floe perimeter as melt proceeded into July and August.

Richter-Menge, J.; Perovich, D. K.

2013-12-01

204

Community-based sea ice thickness observatories in the Arctic  

NASA Astrophysics Data System (ADS)

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

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

2007-12-01

205

Sea Ice Rheology Daniel L. Feltham  

E-print Network

Sea Ice Rheology Daniel L. Feltham Centre for Polar Observation and Modelling, Department of Earth-4189/08/0115-0091$20.00 Key Words Arctic, Antarctic, climate model Abstract The polar oceans of Earth are covered by sea ice. On timescales much greater than a day, the motion and deformation of the sea ice cover (i.e., its dynamics

Feltham, Daniel

206

3, 9991020, 2007 Summer sea ice  

E-print Network

CPD 3, 999­1020, 2007 Summer sea ice during the early Holocene H. Goosse et al. Title Page Abstract on the early Holocene climate constrains the summer sea ice projections for the 21st century H. Goosse, E #12;CPD 3, 999­1020, 2007 Summer sea ice during the early Holocene H. Goosse et al. Title Page

Boyer, Edmond

207

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

208

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

NASA Astrophysics Data System (ADS)

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

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

2009-12-01

209

Antenna for Imaging Sea Ice  

NASA Technical Reports Server (NTRS)

Antenna for imaging of polar regions has terrestrial applications. Antenna consists of four horizontally-polarized 19.0 by 0.6-m planar waveguide arrays and appropriate feed networks mounted on single aluminum supporting structure. Antenna suitable for high quality imaging of sea ice in polar regions above 60 degrees latitude.

Barath, F. T.; Jordan, R. L.

1984-01-01

210

The Sea Ice Board Game  

ERIC Educational Resources Information Center

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

Bertram, Kathryn Berry

2008-01-01

211

CryoSat-2 validation on land and sea ice in the western Ross Sea Region, Antarctica, based on near-surface remote sensing methods  

NASA Astrophysics Data System (ADS)

The SAR Interferometric Radar Altimeter system (SIRAL) onboard ESA's CryoSat is designed to yield improved accuracy on ice surface elevation over conventional radar altimeters. The aim of this study is to validate CryoSat-2 measurements on land and sea ice in the Pacific Sector of Antarctica by the application of independent near-surface remote sensing methods. Information on snow and ice characteristics, e.g. density and surface roughness, is collected simultaneously in order to better understand the interaction of the radar signal with sea and land ice. The investigation area is located in the vicinity of New Zealand's Scott Base (77°51'S, 166°45'E, 14 m a.s.l.). Sea ice formation processes found here, close to the Ross Ice Shelf and McMurdo Ice Shelf, may be quite typical for Antarctica as a whole as about half of the Antarctic coastline is bordered by ice shelves. The outflow of very cold water from underneath the ice shelf favours the formation of frazil and platelet ice - important ingredients which need a better understanding in order to reliably measure and predict changes in Antarctic sea ice coverage. For land ice, this area is also quite favourable with respect to the investigation of snow/ice-microwave interaction, because a large variety of common snow or ice surface classes can be found within a reasonable short distance from Scott Base. The field work was conducted over two field seasons (2008 and 2009). The remote sensing instruments used include a helicopter borne electromagnetic inductivity device ("HEM bird") for sea ice thickness, a ground penetrating radar system to map internal snow layers as well as snow depth on sea ice, and a laser profiler and high resolution optical camera. The laser profiler and camera was operated either from the ground or mounted on an unmanned aerial vehicle (UAV). For the planning of the field work and to obtain auxiliary information we used satellite data from Envisat and ALOS in various imaging modes and geometries. Information on snow properties was obtained from snow pit measurements and ice core drilling. Main results are a sea ice thickness map for the McMurdo Sound, 3D information on snow in the percolation and dry snow zone, and information on surface roughness. We present first results from our measurements on land and sea ice properties and compare these results to satellite signatures from spaceborne sensors.

Rack, Wolfgang; Haas, Christian; Krützmann, Nikolai; Clavano, Wendy; Pinchin, James; Gough, Alex; Langhorne, Pat

2010-05-01

212

Snow, Water and Ice: Understanding and Solving Water Backup and Ice Accumulation  

Microsoft Academic Search

As the winter of 2000-01 in the northern United States showed, there is a great deal of misunderstanding among architects and contractors with regard to ice damming and its resultant water backup, eave ice accumulations, snow accumulations, and the potential for personal injury and building damage. This paper proposes to take a practical approach to reviewing these issues across a

Thomas W. Hutchinson; Matt Millen

213

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...

214

Changes in Sea Ice: Antarctic vs. Arctic  

NASA Astrophysics Data System (ADS)

Since the dramatic retreat of Arctic sea ice in summer 2007, the summer extent of the Arctic sea ice cover has been at the lowest levels on record, with a new record minimum seen in 2012. The steep decline occurred after years of shrinking and thinning of the ice cover not only in summer but also in other seasons. Meanwhile, satellite passive microwave images show that there has been a modest net increase in the Antarctic sea ice extent since 1979. This upward trend is caused by a significant increase in ice concentration in most of the Indian sector and parts of the Atlantic and Pacific sectors including areas in the Weddell and Ross seas, as shown by satellite ice concentration data. However, satellite data also show that ice concentration has decreased considerably in some areas in the Atlantic and Pacific sectors, particularly around the Antarctic Peninsula. This highlights the complex variability and trend patterns of the Antarctic sea ice cover. In an effort to shed light on the behavior of the Antarctic sea ice cover, a comparative model study is conducted to examine its variability and trends relative to the behavior of the Arctic sea ice cover over 1979-2012, using the Global Ice-Ocean Modeling and Assimilation System (GIOMAS). We compare changes in sea ice extent, volume, motion, deformation, internal interaction, ridging, growth, and melt in both polar regions. We also explore the differences in sea ice response to changes in atmospheric and oceanic forcing in the polar regions.

Zhang, J.

2013-12-01

215

Detection of ice crust formation on snow with satellite data  

NASA Astrophysics Data System (ADS)

Short term thawing of the snow surface and subsequent refreeze can lead to the formation of ice crusts. These events are related to specific meteorological conditions such us rain-on-snow events and/or temporary increase of air temperature above zero degree Celsius. The structure change in the snow pack has adverse effect especially on wild life and also the local community related to reindeer herding. Active microwave satellite data can be used to monitor changes of snow related to thawing. So far they have been mostly employed for spring thaw detection. Coarse spatial resolution sensors such as scatterometer feature short revisit intervals. Seawinds QuikScat (Ku-band, 25km, 1999-2009) acquired data several times per day at high latitudes. This allows precise detection of the timing of thaw events. Also the change of structure in the snow itself impacts the backscatter. Values increase significantly. A method has been developed to monitor these events at high latitudes (>60°N) on circumpolar scale. Validation is carried out based on air temperature records and snow course data over Northern Eurasia. Events during midwinter of the last nine years (November - February 2000/1 - 2008/9) have been frequent in northern Europe, European Russia and Alaska. They have occurred up to once a year in central Siberia, the Russian Far East and most of northern Canada. Monitoring is important as such events are discussed in relation to climate change especially over Northern Eurasia.

Bartsch, Annett; Bulygina, Olga N.; Kumpula, Timo; Forbes, Bruce; Stammler, Florian

2010-05-01

216

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

217

Coincident 3D mapping of sea ice surface elevation and ice draft in the Beaufort Sea  

Microsoft Academic Search

Co-incident measurements of sea ice freeboard, thickness and draft were made during the Applied Physics Laboratory Ice Station (APLIS), in April 2007. The campaign was the first time that full three-dimensional mapping of sea ice freeboard and sea ice draft have been achieved simultaneously. Freeboard was measured across a swath width of 300 m at 1 m spatial resolution, using

M. J. Doble; R. Forsberg; C. Haas; S. Hanson; S. Hendriks; T. Martin; H. Skourup; P. Wadhams

2007-01-01

218

Arctic sea ice volume changes and its consequences  

Microsoft Academic Search

Satellite measurements of Arctic sea ice freeboard and observations of other sea ice properties related to sea ice thickness indicate a sizable loss of sea ice volume in the Arctic Ocean in recent years. What are the causes for these losses and how is the sea ice volume decline related to long-term changes in the Arctic? What consequences for sea

Rüdiger Gerdes; Cornelia Köberle; Frank Kauker

2010-01-01

219

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

Microsoft Academic Search

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

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

1998-01-01

220

Inter-annual and Seasonal Variability of Sea Ice Thickness North of Alert, Ellesmere Island and in the Lincoln Sea  

NASA Astrophysics Data System (ADS)

Satellite observations demonstrate a decreasing summer Arctic sea ice extent over the past ~37 years, as well as a smaller perennial sea ice zone, with a significantly accelerated decline in the last decade. Recent ice extent observations are significantly lower than predicted by any model employed by the Intergovernmental Panel on Climate Change (IPCC). The disagreement of the modeled and observed results, along with the large variability of model results, can be in part attributed to a lack of consistent and long term sea ice mass balance observations for the High Arctic. This study presents aerial sea-ice thickness data north of Alert, Nunavut, during April-May of 2004-2009 (excluding 2006), acquired with airplane and helicopter (HEM) electromagnetic induction systems. These observations are a unique 5 year time series of sea-ice thickness and the most extensive observations of multi-year sea ice thickness in this region of the Arctic Ocean. These data help to better understand the interannual variability of ice thickness and ice mass balance in the perennial ice zone. Results demonstrate thinning of sea ice from 2004 to 2008. Ground based snow and ice thickness surveys of ice floes in the Lincoln Sea were conducted in May 2009. Furthermore we deployed GPS buoys on these floes in order to revisit them and repeat the ground based surveys, in August 2009, during the CCG Larsen’s passage through Nares Strait. In addition, HEM sea-ice thickness profiles will be conducted along the cruise track and will be presented with the survey observations and HEM thickness data from May 2009 in order to describe the seasonal variability of sea ice exported from the Lincoln Sea into Nares Strait. All observations will be complemented with NCEP meteorological data to help characterize the observed results of the study. Operation of the HEM bird (August 2009), from the CCGS Henry Larsen Icebreaker, in Nares Strait over validation sites.

Lange, B. A.; Haas, C.; Hendricks, S.; Beckers, J.

2009-12-01

221

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

Microsoft Academic Search

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

D. M. SMITH

1996-01-01

222

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.

223

ICESat measurements of sea ice freeboard and estimates of sea ice thickness in the Weddell Sea  

Microsoft Academic Search

Sea ice freeboard heights in the Weddell Sea of Antarctica are derived from the Ice, Cloud, and Land Elevation Satellite (ICESat) laser altimeter measurements, which have a unique range precision to flat surfaces of 2 cm within 70 m footprints spaced at 172 m along track. Although elevations of flat surfaces can be obtained to an accuracy of ?10 cm

H. Jay Zwally; Donghui Yi; Ron Kwok; Yunhe Zhao

2008-01-01

224

Operational sea ice charts: An integrated data product suitable for observing long-term changes in Arctic sea ice?  

NASA Astrophysics Data System (ADS)

Passive microwave data has been the primary source for observing large-scale trends and variability in Arctic sea ice. This provides a consistent record of ice conditions since 1978. However, there are known deficiencies in the passive microwave data, including low spatial resolution that limits the precision of the ice edge location and an underestimation of summer ice area due to surface melt water. Operational ice analyses aim to provide the most accurate estimate of ice conditions using the best available information, including high spatial resolution satellite data. The manual analyses used to produce the charts provide consistent integration of the various sources as well as quality control of the final products. The National Snow and Ice Data Center, in collaboration with the U.S. National Ice Center (NIC), has updated the NIC ice chart climatology through 2004 and released hemispheric field in a format that is easy to access and analyze. This climatology provides a 30-year record of ice conditions and also yields information on different ice types (e.g., fast ice) that cannot be easily obtained from passive microwave data. However, the quality and quantity of data that is used to produce the ice charts has varied over time, leading to inconsistencies in the timeseries. For example, since 1995 the NIC charts have relied significantly on high resolution synthetic aperture radar imagery from Radarsat-1. This has resulted in higher area and extent estimates in the ice charts compared to earlier years that need to be accounted for if long-term trends are to be estimated from the ice chart climatology. On the other hand, ice charts from the Radarsat-1 era can provide a useful comparison for possible changes in the passive microwave data due to more extreme melt over the past ten years. Here we examine the new NIC ice chart climatology to investigate the consistency of the timeseries through statistical analysis and comparison with the passive microwave record.

Meier, W. N.; Fetterer, F.; Fowler, C.; Clemente-Colon, P.; Street, T.

2006-12-01

225

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

226

Sea ice detection with space-based LIDAR  

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

227

Variability and trends in sea ice extent and ice production in the Ross Sea  

Microsoft Academic Search

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.

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

2011-01-01

228

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....

229

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

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

230

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

231

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

232

Intercomparison of passive microwave sea ice concentration retrievals over the high-concentration Arctic sea ice  

Microsoft Academic Search

Measurements of sea ice concentration from the Special Sensor Microwave Imager (SSM\\/I) using seven different algorithms are compared to ship observations, sea ice divergence estimates from the Radarsat Geophysical Processor System, and ice and water surface type classification of 59 wide-swath synthetic aperture radar (SAR) scenes. The analysis is confined to the high-concentration Arctic sea ice, where the ice cover

Søren Andersen; Rasmus Tonboe; Lars Kaleschke; Georg Heygster; Leif Toudal Pedersen

2007-01-01

233

4, 107128, 2007 Sea-ice-drift  

E-print Network

OSD 4, 107­128, 2007 Sea-ice-drift dynamics and pack fracture A. Chmel et al. Title Page Abstract aspects of the sea-ice-drift dynamics and pack fracture A. Chmel 1 , V. N. Smirnov 2 , and L. V. Panov 2 1 to: A. Chmel (chmel@mail.ioffe.ru) 107 #12;OSD 4, 107­128, 2007 Sea-ice-drift dynamics and pack

Paris-Sud XI, Université de

234

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

235

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

236

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

NASA Astrophysics Data System (ADS)

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

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

2007-12-01

237

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

238

Operational Products Archived at the National Snow and Ice Data Center  

NASA Astrophysics Data System (ADS)

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

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

2009-12-01

239

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

240

Polar Sea Ice Mapping Using SeaWinds Data Hyrum S. Anderson and David G. Long  

E-print Network

Polar Sea Ice Mapping Using SeaWinds Data Hyrum S. Anderson and David G. Long Brigham Young for mapping polar sea ice extent. In this study, a new al- gorithm for polar sea ice mapping is developed of Bayes detection to produce sea ice extent maps. Statistical models for sea ice and ocean are represented

Long, David G.

241

Terrestrial Sea Ice Morphology: Considerations for Europa  

NASA Astrophysics Data System (ADS)

The Galileo mission has returned the first high-resolution (21 m/pixel) images of the surface of Europa. These images reveal structures with morphologies reminiscent of those seen on terrestrial sea ice. Although it is premature to make one-to-one analogies between sea ice and Europa's surface, a review of the types of surface features commonly formed on Earth and of various sea-ice processes can provide insight into the complex geology of Europa. For example, deformation of terrestrial sea ice results from winds, tides, and currents and from thermally induced stresses; the resulting features include fractures ranging in width from millimeters to kilometers, pressure ridges, shear ridges, and rafted ice. Potential agents of deformation on Europa are more likely to be limited to tidal flexing and possibly convection, but could produce similar features and perhaps account for the ridges and fractures seen in many areas. Subtle differences in albedo and color in terrestrial sea ice result from differences in ice thickness and grain size, attributed to factors such as the rate of ice-crystal growth, water turbulence, age of the ice, and deformation. Similar factors could account for differences observed in the bright icy plains of Europa. Moreover, salts in both the solid form and as brine vary in concentration and composition as a function of space and time on Earth, leading to differences in density and the strength of ice sheets. Salts are also suspected in the europan ice and could lead to similar differences, enhancing the creation of topographic relief from density contrasts and the formation of fractures from brittle failure of the ice. Differences in the environments between Europa and terrestrial sea ice in terms of parameters such as temperature, gravity, time, and ice compositions suggest caution in drawing direct analogies. Future work by the planetary and sea-ice communities must include understanding the terrestrial processes sufficiently for extrapolation to Europa.

Greeley, Ronald; Sullivan, Robert; Coon, Max D.; Geissler, Paul E.; Tufts, B. Randall; Head, James W.; Pappalardo, Robert T.; Moore, Jeffrey M.

1998-09-01

242

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

243

Springtime atmospheric transport controls Arctic summer sea-ice extent  

NASA Astrophysics Data System (ADS)

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

Kapsch, Marie; Graversen, Rune; Tjernström, Michael

2013-04-01

244

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

245

Quantifying Uncertainties in the Seasonal Cycle of Arctic Sea Ice  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

246

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

247

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

248

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

NASA Astrophysics Data System (ADS)

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

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

2003-04-01

249

Monitoring of sea ice in Far East Russia  

Microsoft Academic Search

In Far East Russia, the Sea of Okhotsk is covered by sea ice in winter every year. The Amur River plays an important role of generating sea ice. Sea ice goes south by the monsoon. In this paper, we present a four-dimensional histogram method and a threshold method for detecting the sea ice pixels of NOAA AVHRR images. We used

Koichi KAWANO; Jun-ichi KUDOH

2004-01-01

250

Impacts of Declining Arctic Sea Ice: An International Challenge  

NASA Astrophysics Data System (ADS)

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

Serreze, M.

2008-12-01

251

Measurements of thermal infrared spectral reflectance of frost, snow, and ice  

NASA Technical Reports Server (NTRS)

Because much of Earth's surface is covered by frost, snow, and ice, the spectral emissivities of these materials are a significant input to radiation balance calculations in global atmospheric circulation and climate change models. Until now, however, spectral emissivities of frost and snow have been calculated from the optical constants of ice. We have measured directional hemispherical reflectance spectra of frost, snow, and ice from which emissivities can be predicted using Kirchhoff's law (e = 1-R). These measured spectra show that contrary to conclusions about the emissivity of snow drawn from previously calculated spectra, snow emissivity departs significantly from blackbody behavior in the 8-14 micrometer region of the spectrum; snow emissivity decreases with both increasing particle size and increasing density due to packing or grain welding; while snow emissivity increases due to the presence of meltwater.

Salisbury, John W.; D'Aria, Dana M.; Wald, Andrew

1994-01-01

252

Trends in the draft and extent of seasonal pack ice, Canadian Beaufort Sea  

NASA Astrophysics Data System (ADS)

Continuous observations by sub-sea sonar form a 12-year draft record for seasonal pack ice in the Beaufort Sea. There has been a small trend (0.07 m/decade) to thinner ice, but this has low statistical significance; net change is comparable to the uncertainty of measurement. Although ice concentration at the monitoring site has increased by 0.14 since 1991, there is little evidence for trend in ice-covered area over the continental shelf in the longer (36-year) ice-chart record. However, local air temperature has increased by 1.6 +/- 0.6°C during the last three decades. Clearly longer time series are needed to detect and understand change. Changing snow cover, ice circulation and ice deformation may obscure the direct effects of warming climate on seasonal pack ice.

Melling, Humfrey; Riedel, David A.; Gedalof, Ze'ev

2005-12-01

253

Sea Ice Biogeochemistry: A Guide for Modellers  

PubMed Central

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

Tedesco, Letizia; Vichi, Marcello

2014-01-01

254

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

255

Photodegradation of organophosphorus pesticides in water, ice and snow  

NASA Astrophysics Data System (ADS)

Organophosphorus pesticides (OPs) represent more polar compounds with better water solubility and higher degradation rates than organochlorine pesticides, which makes them attractive for a wide application in the agriculture. A fact, that they have been detected in the polar regions, suggests that even though they can be degraded, they still belong to the group of compounds capable of long-range transport. In the cold regions, snow and ice affect the processes of OPs deposition, accumulation and transformation and they can significantly alter their life-times, degradation and elimination rates. However, our knowledge on photodegradation processes of OPs in the matrices of ice and snow is still very limited. This study is focused on the photochemical behaviour of fenitrothion and methyl-parathion as two currently used organophosphorus pesticides. Methyl-parathion is one of the most extensively applied pesticides and both, methyl-parathion and fenitrothion are susceptible to a direct photolysis. Photodegradation is considered to be an important transformation process for both, but the mechanism of degradation in the cold environments has not been studied yet. Filling this gap is crucial for an enhancement of our understanding to the fate of the organic compounds in pristine arctic environments.

Kurkova, R.; Weber, J.; Klanova, J.; Klan, P.; Halsall, C.

2009-04-01

256

Controls on Arctic Sea Ice from First-Year and Multiyear Ice Survivability KYLE C. ARMOUR  

E-print Network

estimates of the FY and MY ice area by direct observation and by model estimates of sea ice age (JohannessenControls on Arctic Sea Ice from First-Year and Multiyear Ice Survivability KYLE C. ARMOUR 1 December 2010) ABSTRACT Recent observations of Arctic sea ice show that the decrease in summer ice

Reif, Rafael

257

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

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

258

Frost flower formation on sea ice and lake ice  

NASA Astrophysics Data System (ADS)

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

Style, Robert W.; Worster, M. Grae

2009-06-01

259

Atmospheric and oceanic drag on sea ice  

NASA Astrophysics Data System (ADS)

Pressure ridges, keels, floe edges and melt pond edges all introduce discrete obstructions to the flow of the air or ocean over the ice, and are a source of form drag. For typical ice covers the form drag contribution to the total drag is of comparable or greater magnitude to the surface or skin drag. In current climate models form drag is only accounted for by tuning of the air-ice and air-ocean drag coefficients, i.e. by altering the roughness length in a surface drag parameterization. The existing approach of skin drag parameter tuning, while numerically convenient, is poorly constrained by observations and fails to describe correctly the physics associated with the air-ice and ocean-ice drag. Here we combine recent theoretical developments to deduce the total neutral form drag coefficients from the key parameters of the ice cover such as ice concentration, size and area of the ridges and keels, freeboard and floe draft and size of melt ponds. We validate the assumptions of this parameterisation against remote sensing observations from airborne missions (IceBridge) and high resolution satellites. We incorporate the drag coefficients into the sea ice component of a climate model (the CICE model). This stage necessitates that the sea ice characteristics obtained locally from observations are mapped to the averaged sea ice quantities provided by the sea ice model at the larger grid cell length scale. We present results over the Arctic of a stand-alone version of the model and show the influence of the new drag parameterisation on the motion and mass of the ice cover. The new parameterisation allows the drag coefficients to be coupled to the sea ice state and therefore to evolve spatially and temporally. We test the predictions of the model against measured drag coefficients in several regions of the Arctic and find good agreement between model and observations.

Tsamados, M.; Feltham, D. L.

2012-12-01

260

Diatom-induced silicon isotopic fractionation in Antarctic sea ice  

NASA Astrophysics Data System (ADS)

We measured silicon-isotopic composition of dissolved silicon and biogenic silica collected by sequential melting from spring 2003 Antarctic pack ice (Australian sector). Sea ice is a key ecosystem in the Southern Ocean and its melting in spring has been often thought to have a seeding effect for the surface waters, triggering blooms in the mixed layer. This work is the first investigation of the silicon isotopes' proxy in sea ice and allows to estimate the activity of sea-ice diatoms in the different brine structures and the influence of sea- ice diatoms on the spring ice edge blooms. The relative use of the dissolved silicon pool by sea-ice diatoms is usually assessed by calculating nutrient:salinity ratios in the brines. However such an approach is biased by difficulties in evaluating the initial nutrient concentrations in the different brines structures, and by the impossibility to account for late sporadic nutrient replenishments. The silicon-isotopic composition of biogenic silica is a convenient alternative since it integrates an average Si utilization on all generations of diatoms. Measurements were performed on a MC-ICP-MS, in dry plasma mode using external Mg doping. Results are expressed as delta29Si relative to the NBS28 standard. From three sea ice cores with contrasted physico-chemical characteristics, we report significant isotopic fractionations linked to the diatoms activity, with distinct silicon biogeochemical dynamics between different brine structure. The diatoms in snow ice and in brine pockets of frazil or congelation ice have the most positive silicon-isotopic composition (+0.53 to +0.86 p.mil), indicating that they grow in a closed system and use a significant part of the small dissolved silicon pool. In the brine channels and skeletal layer, diatoms display a relatively less positive Si-isotopic composition (+0.41 to +0.70 p.mil), although it is still heavier compared to equilibrium fractionation (+0.38 p.mil). This suggests that they have grown in a semi-closed system in which the dissolved silicon pool (i.e. brines) is partially replenished. Finally, we show that the average silicon-isotopic composition of the sea-ice diatoms (+0.63 p.mil) is very distinct from the one of biogenic silica in the seasonal ice zone mixed layer (+0.08 p.mil) indicating that sea- ice diatoms either contribute to an insignificant part of the whole diatoms biomass in the upper water layer (without affecting the silicon-isotopic budget), and/or that they are directly exported below the mixed layer. In this latter case, we will study the possibility to use the distinct signature of the sea ice diatoms as a tracer of paleo-sea ice extension in oceanic sediments.

Francois, F.; Damien, C.; Jean-Louis, T.; Anthony, W.; Luc, A.

2006-12-01

261

Investigation of radar discrimination of sea ice  

NASA Technical Reports Server (NTRS)

The ability of radar to discriminate sea ice types and their thickness was studied. Radar backscatter measurements at 400 MHz (multi-polarization) and 13.3 GHz (VV polarization) obtained from NASA Earth Resources Aircraft Program Mission 126 were analyzed in detail. The scatterometer data were separated into seven categories of sea ice according to age and thickness as interpreted from stereo aerial photographs. The variations of radar backscatter cross-section with sea ice thickness at various angles are presented at the two frequencies. There is a reversal of angular character of radar return from sea ice less than 18 cm thick at the two frequencies. Multi-year ice (sea ice greater than 180 cm thick) gives strongest return at 13.3 GHz. First-year ice (30 cm to 90 cm thick) gives strongest return at 400 MHz. Open water can be differentiated at both the frequencies. Four-polarization 16.5 GHz radar imagery was also obtained. Open water and three categories of sea ice can be identified on the images. The results of the imagery analysis are consistent with the radar scatterometer results.

Parashar, S. K.; Biggs, A. W.; Fung, A. K.; Moore, R. K.

1974-01-01

262

Sea ice concentration temporal variability over the Weddell Sea and its relationship with tropical sea surface temperature  

USGS Publications Warehouse

Principal Components Analysis (PCA) in S-Mode (correlation between temporal series) was performed on sea ice monthly anomalies, in order to investigate which are the main temporal patterns, where are the homogenous areas located and how are they related to the sea surface temperature (SST). This analysis provides 9 patterns (4 in the Amundsen and Bellingshausen Seas and 5 in the Weddell Sea) that represent the most important temporal features that dominated sea ice concentration anomalies (SICA) variability in the Weddell, Amundsen and Bellingshausen Seas over the 1979-2000 period. Monthly Polar Gridded Sea Ice Concentrations data set derived from satellite information generated by NASA Team algorithm and acquired from the National Snow and Ice Data Center (NSIDC) were used. Monthly means SST are provided by the National Center for Environmental Prediction reanalysis. The first temporal pattern series obtained by PCA has its homogeneous area located at the external region of the Weddell and Bellingshausen Seas and Drake Passage, mostly north of 60°S. The second region is centered in 30°W and located at the southeast of the Weddell. The third area is localized east of 30°W and north of 60°S. South of the first area, the fourth PC series has its homogenous region, between 30° and 60°W. The last area is centered at 0° W and south of 60°S. Correlation charts between the five Principal Components series and SST were performed. Positive correlations over the Tropical Pacific Ocean were found for the five PCs when SST series preceded SICA PC series. The sign of the correlation could relate the occurrence of an El Niño/Southern Oscillation (ENSO) warm (cold) event with posterior positive (negative) anomalies of sea ice concentration over the Weddell Sea.

Barreira, S.; Compagnucci, R.

2007-01-01

263

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

264

Recent variations of sea ice and air temperature in high latitudes  

SciTech Connect

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 by (1) temporal scales of several seasons to several years and (2) spatial scales of 30[degrees]-180[degrees] of longitude. The ice data are examined in conjunction with air temperature data for evidence of recent climate change in the polar regions. The arctic sea-ice variations over the past several decades are compatible with the corresponding air temperatures, which show a distinct warming that is strongest over northern land areas during the winter and spring. The temperature trends over the sub arctic seas are smaller and even negative in the southern Greenland region. Statistically significant decreases of the summer extent of arctic ice are apparent in the sea-ice data, and new summer minima have been achieved three times in the past 15 years. There is no significant trend of ice extent in the Arctic during winter or in the Antarctic during any season. The seasonal and geographical changes of sea-ice coverage are consistent with the more recent greenhouse experiments performed with coupled atmosphere-ocean models.

Chapman, W.L.; Walsh, J.E. (Univ. of Illinois, Urbana (United States))

1993-01-01

265

Constraining projections of summer Arctic sea ice  

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

266

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

NASA Technical Reports Server (NTRS)

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

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

2006-01-01

267

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

268

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

NASA Astrophysics Data System (ADS)

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

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

2009-04-01

269

Climate, Ocean, and Sea Ice Modeling Project  

NSDL National Science Digital Library

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

Laboratory, Los A.

270

Quaternary Sea Ice Reconstruction: Proxy Data and Modeling  

NASA Astrophysics Data System (ADS)

The satellite-based observation of distinct contrasts between Arctic and Antarctic sea ice development provides a strong motivation to improve our knowledge of physical and biological processes governing sea ice occurrence and the role of sea ice as a polar climate amplifier. For further insight into such processes, sea ice records must be extended beyond instrumental observations.

Gersonde, R.; De Vernal, A.; Wolff, E. W.

2014-11-01

271

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

272

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

2014-12-01

273

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

274

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

275

Optimization of a Sea Ice Model Using Basinwide Observations of Arctic Sea Ice Thickness, Extent, and Velocity  

E-print Network

Optimization of a Sea Ice Model Using Basinwide Observations of Arctic Sea Ice Thickness, Extent 2004, in final form 27 June 2005) ABSTRACT A stand-alone sea ice model is tuned and validated using satellite-derived, basinwide observations of sea ice thickness, extent, and velocity from the years 1993

Feltham, Daniel

276

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

PubMed

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

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

2011-03-01

277

Short Term Variability of Sea Ice Thickness in the Beaufort Sea  

Microsoft Academic Search

To investigate the relationship between variability of sea ice thickness and ice dynamics, helicopter borne electromagnetic sea ice thickness sounding was performed at the APLIS ice camp in the Beaufort sea in April 2007. The field campaign includes sea ice thickness observations close to the camp with repeated flight tracks of different length scales and a transect ranging from 75°N

S. Hendricks; J. Hutchings

2007-01-01

278

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

279

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

NASA Astrophysics Data System (ADS)

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

280

Impact of underwater-ice evolution on Arctic summer sea ice  

E-print Network

Impact of underwater-ice evolution on Arctic summer sea ice Dirk Notz,1,4 Miles G. McPhee,2 M. Grae to make predictions of bottom ablation rates of sea ice given the far-field properties of the ocean from-lasting sea ice and thus smaller ice-free areas, which might be an important mechanism affecting the surface

Worster, M. Grae

281

Sea ice feedback and Cenozoic evolution of Antarctic climate and ice Robert DeConto,1  

E-print Network

Sea ice feedback and Cenozoic evolution of Antarctic climate and ice sheets Robert DeConto,1 David; published 24 August 2007. [1] The extent and thickness of Antarctic sea ice have important climatic effects explores the role of sea ice and related feedbacks in the Cenozoic evolution of Antarctic climate and ice

Massachusetts at Amherst, University of

282

Ice in the environment: connections to atmospheric chemistry  

Microsoft Academic Search

Ice in the environment, whether in the form of ice particles in clouds or sea ice and snow at the Earth's surface, has a profound influence on atmospheric composition and climate. The interaction of trace atmospheric gases with snow and sea ice surfaces largely controls atmospheric composition in polar regions. The heterogeneous chemistry of ice particles in clouds also plays

V Faye McNeill; Meredith G Hastings

2008-01-01

283

Recent advances in sea-ice microbiology.  

PubMed

Over the past 50 years there has been much effort invested in the investigation of the ecology of sea ice. Sea ice is an ephemeral feature of the Arctic and Southern Oceans and smaller water bodies such as the Baltic and Caspian Seas. The semisolid ice matrix provides a range of habitats in which a diverse range of microbial organisms thrive. In the past 5 years there has been considerable steps forward in sea-ice research, in particular regarding the analysis of sea-ice microstructure and the investigation of the diversity and adaptation of microbial communities. These studies include: (i) controlled simulated and in situ studies on a micrometer scale to unravel the dynamic of the microhabitat with consequences for the organisms; (ii) the introduction of molecular approaches to uncover the diversity of uncultured still unknown microorganisms; and (iii) studies into the molecular adaptation of selected model organisms to the extreme environment. This minireview presents some of the most recent findings from sea-ice studies within the framework of these aims. PMID:15819843

Mock, Thomas; Thomas, David N

2005-05-01

284

EDITORIAL: Ice in the environment: connections to atmospheric chemistry Ice in the environment: connections to atmospheric chemistry  

Microsoft Academic Search

Ice in the environment, whether in the form of ice particles in clouds or sea ice and snow at the Earth's surface, has a profound influence on atmospheric composition and climate. The interaction of trace atmospheric gases with snow and sea ice surfaces largely controls atmospheric composition in polar regions. The heterogeneous chemistry of ice particles in clouds also plays

V. Faye McNeill; Meredith G. Hastings

2008-01-01

285

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

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

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

288

Transpolar observations of the morphological properties of Arctic sea ice  

Microsoft Academic Search

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

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

2009-01-01

289

Understanding changes in the Arctic basin sea ice mass budget as simulated by CCSM4: Implications from melt season characteristics and the surface albedo feedback  

Microsoft Academic Search

Observations reveal alarming drops in Arctic sea ice extent, and climate models project that further changes will occur that could have global repercussions. An important aspect of this change is the surface albedo feedback, driven by the contrast between the albedos of snow\\/ice and the open ocean. In response to warming, this feedback enhances ice melt and amplifies surface warming

D. A. Pollak; M. M. Holland; D. A. Bailey

2010-01-01

290

The convective desalination of sea ice  

E-print Network

containing both liquid brine and solid (pure water) ice. Frad is the flux of penetrating solar radiation. Thus the thermal properties of sea ice are composed of those of the solid and liquid phases that make up sea ice. Fixed-salinity models used in older... the transport of light elements from the inner core that can contribute to driving the geodynamo that generates the Earth’s magnetic field (Fearn et al., 1981). Therefore, the study of convection within mushy layers has a broad range of ap- plications and has...

Rees Jones, David

2014-07-01

291

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

Microsoft Academic Search

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

David M. Holland

2001-01-01

292

CryoSat-2 validation on land and sea ice in the western Ross Sea Region, Antarctica, based on near-surface remote sensing methods  

Microsoft Academic Search

The SAR Interferometric Radar Altimeter system (SIRAL) onboard ESA's CryoSat is designed to yield improved accuracy on ice surface elevation over conventional radar altimeters. The aim of this study is to validate CryoSat-2 measurements on land and sea ice in the Pacific Sector of Antarctica by the application of independent near-surface remote sensing methods. Information on snow and ice characteristics,

Wolfgang Rack; Christian Haas; Nikolai Krützmann; Wendy Clavano; James Pinchin; Alex Gough; Pat Langhorne

2010-01-01

293

Arctic sea ice freeboard heights from satellite altimetry  

Microsoft Academic Search

The Arctic sea ice cover is most sensitive to climate change and variability, mainly due to the ice-albedo feedback effect. With an increase in the average temperature across the Arctic during the past few decades, sea ice has been melting rapidly. The decline in the sea ice extent was estimated as 10% per decade since satellite observations began in 1979.

Vidyavathy Renganathan

2010-01-01

294

Processes driving sea ice variability in the Bering Sea in an eddying ocean/sea ice model: anomalies from the mean  

E-print Network

Processes driving sea ice variability in the Bering Sea in an eddying ocean/sea ice model 2014 # Springer-Verlag Berlin Heidelberg 2014 Abstract A fine-resolution (1/10°) ocean/sea ice model to determine the basin-scale and local balances controlling the variability of sea ice anomalies from the mean

Eisenman, Ian

295

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

296

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

297

Influence of snow and ice crystal formation and accumulation on mercury deposition to the Arctic.  

PubMed

Mercury is deposited to the Polar Regions during springtime atmospheric mercury depletion events (AMDEs) but the relationship between snow and ice crystal formation and mercury deposition is not well understood. The objective of this investigation was to determine if mercury concentrations were related to the type and formation of snow and ice crystals. On the basis of almost three hundred analyses of samples collected in the Alaskan Arctic, we suggestthat kinetic crystals growing from the vapor phase, including surface hoar, frost flowers, and diamond dust, yield mercury concentrations that are typically 2-10 times higher than that reported for snow deposited during AMDEs (approximately 80 ng/L). Our results show that the crystal type and formation affect the mercury concentration in any given snow sample far more than the AMDE activity prior to snow collection. We present a conceptual model of how snow grain processes including deposition, condensation, reemission, sublimation, and turbulent diffusive uptake influence mercury concentrations in snow and ice. These processes are time dependent and operate collectively to affect the retention and fate of mercury in the cryosphere. The model highlights the importance of the formation and postdeposition crystallographic history of snow or ice crystals in determining the fate and concentration of mercury in the cryosphere. PMID:18441801

Douglas, Thomas A; Sturm, Matthew; Simpson, William R; Blum, Joel D; Alvarez-Aviles, Laura; Keeler, Gerald J; Perovich, Donald K; Biswas, Abir; Johnson, Kelsey

2008-03-01

298

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...

299

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.

300

Study on Urban Traffic Safety Remedy Countermeasures on the Ice-Snow Road  

Microsoft Academic Search

In recent years, not only in the north cities, the ice-snow pavement of urban roads has become the major cause of the traffic accidents in the winter, but also in the south cities, the contingency rescue on the ice-snow roads has been found very weak.This paper takes Harbin as an example to analyze the present existed problems in handling the

Hong-Liang Qu; Jiang-Wei Chu; De-Cai Li

2010-01-01

301

The Secret of the Svalbard Sea Ice Barrier  

NASA Technical Reports Server (NTRS)

An elongated sea ice feature called the Svalbard sea ice barrier rapidly formed over an area in the Barents Sea to the east of Svalbard posing navigation hazards. The secret of its formation lies in the bottom bathymetry that governs the distribution of cold Arctic waters masses, which impacts sea ice growth on the water surface.

Nghiem, Son V.; Van Woert, Michael L.; Neumann, Gregory

2004-01-01

302

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

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

303

Annual primary production in Antarctic sea ice during 2005-2006 from a sea ice state estimate  

NASA Astrophysics Data System (ADS)

the data-bounded Sea Ice Ecosystem State (SIESTA) model, we estimate total Antarctic sea ice algal primary production to be 23.7 Tg C a-1 for the period July 2005-June 2006, of which 80% occurred in the bottom 0.2 m of ice. Simulated sea ice primary production would constitute 12% of total annual primary production in the Antarctic sea ice zone, and ˜1% of annual Southern Ocean primary production. Model sea ice algal growth was net nutrient limited, rather than light limited, for the vast majority of the sunlit season. The seasonal distribution of integrated ice algal biomass matches available observations. The vertical algal distribution was weighted toward the ice bottom compared to observations, indicating that interior ice algal communities may be under-predicted in the model, and that nutrient delivery via gravity-induced convection is not sufficient to sustain summertime algal biomass. Bottom ice algae were most productive in ice of 0.36 m thickness, whereas interior algal communities were most productive in ice of 1.10 m thickness. Sensitivity analyses that tested different atmospheric forcing inputs, sea ice parameterizations, and nutrient availability caused mean and regional shifts in sea ice state and ice algal production even when sea extent and motion was specified. The spatial heterogeneity of both ice state and algal production highlight the sensitivity of the sea ice ecosystem to physical perturbation, and demonstrate the importance of quality input data and appropriate parameterizations to models of sea ice and associated biology.

Saenz, Benjamin T.; Arrigo, Kevin R.

2014-06-01

304

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

305

Summer Sea Ice Albedo in the Arctic in CMIP5 models  

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

306

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

307

Ice in Caspian Sea and Aral Sea, Kazakhstan  

NASA Technical Reports Server (NTRS)

In this MODIS image from December 3, 2001, winter sea ice can be seen forming in the shallow waters of the northern Caspian (left) and Aral (upper right) Seas. Despite the inflow of the Volga River (upper left), the northern portion of the Caspian Sea averages only 17 ft in depth, and responds to the region's continental climate, which is cold in winter and hot and dry in the summer. The southern part of the Sea is deeper and remains ice-free throughout the winter. The dirty appearance of the ice may be due to sediment in the water, but may also be due to wind-driven dust. The wind in the region can blow at hurricane-force strength and can cause the ice to pile up in hummocks that are anchored to the sea bottom. The eastern portion of the Aral Sea is also beginning to freeze. At least two characteristics of the Aral Sea 'compete' in determining whether its waters will freeze. The Sea is shallow, which increases the likelihood of freezing, but it is also very salty, which means that lower temperatures are required to freeze it than would be required for fresh water. With average December temperatures of 18o F, it's clearly cold enough to allow ice to form. As the waters that feed the Aral Sea continue to be diverted for agriculture, the Sea becomes shallower and the regional climate becomes even more continental. This is because large bodies of water absorb and retain heat, moderating seasonal changes in temperature. Credit: Jacques Descloitres, MODIS Land Rapid Response Team, NASA/GSFC

2002-01-01

308

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

309

Fram Strait sea ice outflow  

NASA Technical Reports Server (NTRS)

We summarize 24 years of ice export estimates and examine, over a 9-year record, the associated variability in the time-varying upward-looking sonar (ULS) thickness distributions of the Fram Strait. A more thorough assessment of the PMW (passive microwave) ice motion with 5 years of synthetic aperture radar (SAR)observations shows the uncertainties to be consistent with that found by Kwok and Rothrock [1999], giving greater confidence to the record of ice flux calculations.

Kwok, R.; Cunningham, G. F.; Pang, S. S.

2004-01-01

310

Laser Altimetry Sampling Strategies over Sea Ice  

NASA Technical Reports Server (NTRS)

With the conclusion of the science phase of the Ice, Cloud and land Elevation Satellite (ICESat) mission in late 2009, and the planned launch of ICESat-2 in late 2015, NASA has recently established the IceBridge program to provide continuity between missions. A major goal of IceBridge is to obtain a sea-ice thickness time series via airborne surveys over the Arctic and Southern Oceans. Typically two laser altimeters, the Airborne Topographic Mapper (ATM) and the Land, Vegetation and Ice Sensor (LVIS), are utilized during IceBridge flights. Using laser altimetry simulations of conventional analogue systems such as ICESat, LVIS and ATM, with the multi-beam system proposed for ICESat-2, we investigate differences in measurements gathered at varying spatial resolutions and the impact on sea-ice freeboard. We assess the ability of each system to reproduce the elevation distributions of two seaice models and discuss potential biases in lead detection and sea-surface elevation, arising from variable footprint size and spacing. The conventional systems accurately reproduce mean freeboard over 25km length scales, while ICESat-2 offers considerable improvements over its predecessor ICESat. In particular, its dense along-track sampling of the surface will allow flexibility in the algorithmic approaches taken to optimize the signal-to-noise ratio for accurate and precise freeboard retrieval.

Farrell, Sinead L.; Markus, Thorsten; Kwok, Ron; Connor, Laurence

2011-01-01

311

How to Calculate Sea Ice Changes  

NSDL National Science Digital Library

This set of three videos illustrates how math is used in satellite data analysis. The videos feature NASA senior climate scientist Claire Parkinson. Parkinson explains how the Arctic and Antarctic sea ice covers are measured from satellite data and how math is used to determine trends in the data. In the first video, she leads viewers from satellite data collection through obtaining a time series of monthly average sea ice extents for November 1978 â December 2012, for the Arctic and Antarctic. In the second video, she begins with the time series from the first video, removes the seasonal cycle by calculating yearly averages, and proceeds to calculate the slopes of the lines to get trends in the data, revealing decreasing sea ice coverage in the Arctic and increasing sea ice coverage in the Antarctic. In the third video, she uses a more advanced technique to remove the seasonal cycle and shows that the trends are close to the same, whichever method is used. She emphasizes the power of math and that the techniques shown for satellite sea ice data can also be applied to a wide range of data sets.

312

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

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

313

Impacts of Recent Perennial Sea Ice Reduction on BrO Observations at Barrow, Alaska  

NASA Astrophysics Data System (ADS)

Polar sunrise in the Arctic has been associated with production of reactive halogens from sea salt(e.g. Br, BrO). While effects of these halogen species are well known(e.g. ozone depletion, mercury deposition), their production is not fully understood, but thought to be linked to heterogeneous chemistry taking place on saline ice surfaces(e.g saline snow, first year sea ice). Given the recent decline of perennial sea ice in the Arctic, it is imperative to understand the role of younger, more saline, first year ice in halogen activation processes. We used multiple axis differential optical absorption spectroscopy(MAX-DOAS) at Barrow, Alaska to observe BrO during the spring/early summer of 2008,2009,2012, and 2013. While average BrO boundary layer vertical column densities(BL-VCD) agreed within error during 2008 and 2009, the average observed BL-VCD doubled from 1e13 mol/cm^2 in 2008 and 2009, to 2e13 mol/cm^2 in 2012. We explore potential explanations for this observed increase using satellite maps of synoptic sea ice classes, MODIS imagery of local sea ice features, and back trajectory modelling. Potential impacts of the 2012 record minimum sea ice extent on observed halogen activation during the spring of 2013 are also discussed.

Peterson, P.; Simpson, W. R.; Donohoue, D.; Nghiem, S. V.; Friess, U.; Platt, U.

2013-12-01

314

As the Ice Keeps Thinning Update on Arctic People-Sea Ice  

E-print Network

As the Ice Keeps Thinning Update on Arctic People-Sea Ice Connections, 2007­2009 Igor Krupnik `people' projects supporting indigenous climate and sea ice observations: · Understanding environmental · Sea Ice Knowledge and Use (SIKU) # 166 · Exchange for Local Observations and Knowledge (ELOKA) # 187

Kuligowski, Bob

315

Ocean-to-Ice Heat Flux and Diminished Arctic Sea Ice Cover (Invited)  

Microsoft Academic Search

Ocean-to-Ice Heat Flux and the Decline of the Arctic Sea Ice Cover Heat transport from the ocean to the base of the sea ice plays a significant role in the enthalpy balance of the Arctic Ocean sea ice cover. In this presentation, we touch on two aspects of heat storage and transport in the upper Arctic Ocean: (1) the role

W. J. Shaw; T. P. Stanton

2010-01-01

316

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

317

Global Sea Ice Charting at the National Ice Center  

NASA Astrophysics Data System (ADS)

The National Ice Center (NIC) is a U.S. government tri-agency operational center comprised of components from the United States Navy, the National Oceanic and Atmospheric Administration (NOAA), and the U. S. Coast Guard (USCG). The mission of the NIC is to provide the highest quality strategic and tactical ice services tailored to meet operational requirements of U.S. national interests. This includes broad responsibilities to monitor all frozen ocean regions of the world in support of coastal and marine sea ice operations and research. Sea ice conditions are routinely monitored and mapped using satellite imagery along with ancillary model and in-situ data. Active microwave images from Synthetic Aperture Radar (SAR) sensors are the data of choice for NIC analysts because of their high spatial resolution (~100 m). SAR is in fact the primary data source for ice analysis when available. The high spatial resolution of available SAR data and the reliability shown by the RADARSAT- 1 mission in particular have made the use of these data critical for vessels operating in or near the ice. Limited data from the ESA Envisat Advanced SAR (ASAR) are also used in the analyses when available. Preparations for the use of the Phased Array type L-band SAR (PALSAR) aboard the soon to be launched Japanese ALOS satellite are also underway. Scatterometer backscatter imagery from QuikSCAT is also routinely used for basin-scale and circumpolar ice edge mapping. Automated algorithms for ice type and melt ponds detection as well as the synergy between these observations and the QuikSCAT wind vectors off the marginal ice zone (MIZ) are been explored. ESA Envisat Advanced SAR (ASAR) Global Monitoring Mode (GMM) mosaics of the Arctic and Antarctic regions are becoming an important tool for sea ice edge delineation too. Although SAR observations are the choice for NIC analysts to produce high spatial resolution products gear toward tactical support, passive microwave data such as those from the Special Sensor Microwave/Imager (SSM/I) provide better temporal and synoptic view of the Polar Regions albeit at a significantly reduced spatial resolution compared to that of active sensors. Automated SSM/I algorithms provide for near-real time production of sea ice parameters including concentration and multiyear fraction. The retrieval of sea ice drift vectors from passive microwave with SSM/I is operational and it is being also implemented using the Advanced Microwave Scanning Radiometer (AMSR-E), a research instrument available aboard the Aqua satellite. As in the case of QuikSCAT, NIC is also exploring the use of sea ice parameters retrieved from WindSat and the synergy of these observations with the WindSat wind vectors off the MIZ through a newly formed sea ice algorithm working group.

Clemente-Colon, P.

2006-12-01

318

The nutrient cycle through snow and ice, a review  

Microsoft Academic Search

This paper reviews the merging of the nutrient cycle with the water cycle in the seasonal alpine snow cover, emphasizing physical processes at the snowpack and snow grain scale. Nutrients are incorporated into snowflakes growing in the atmosphere, they are part of the dry deposition from the atmosphere to the snowpack and they reach the snow as plant litter. The

Michael Kuhn

2001-01-01

319

Propaganda, News, or Education: Reporting Changing Arctic Sea Ice Conditions  

NASA Astrophysics Data System (ADS)

The National Snow and Ice Data Center provides information on Arctic sea ice conditions via the Arctic Sea Ice News & Analysis (ASINA) website. As a result of this effort to explain climatic data to the general public, we have attracted a huge amount of attention from our readers. Sometimes, people write to thank us for the information and the explanation. But people also write to accuse us of bias, slant, or outright lies in our posts. The topic of climate change is a minefield full of political animosity, and even the most carefully written verbiage can appear incomplete or biased to some audiences. Our strategy has been to report the data and stick to the areas in which our scientists are experts. The ASINA team carefully edits our posts to make sure that all statements are based on the science and not on opinion. Often this means using some technical language that may be difficult for a layperson to understand. However, we provide concise definitions for technical terms where appropriate. The hope is that by communicating the data clearly, without an agenda, we can let the science speak for itself. Is this an effective strategy to communicate clearly about the changing climate? Or does it downplay the seriousness of climate change? By writing at a more advanced level and avoiding oversimplification, we require our readers to work harder. But we may also maintain the attention of skeptics, convincing them to read further and become more knowledgeable about the topic.

Leitzell, K.; Meier, W.

2010-12-01

320

INVESTIGATION OF SEASONAL SEA-ICE THICKNESS VARIABILITY IN THE ROSS SEA Beth A. Schellenberg  

E-print Network

and others). The fact that sea ice covers about 7% of the earth's surface at any one time and varies seaINVESTIGATION OF SEASONAL SEA-ICE THICKNESS VARIABILITY IN THE ROSS SEA Beth A. Schellenberg P1.23 1. INTRODUCTION A number of studies suggest a connections between sea-ice variability

Geiger, Cathleen

321

A review of sea ice density  

Microsoft Academic Search

The density of sea ice is an important property in many applications. However, due to its multi-phase composition of solid ice, solid salts, liquids and gas, the definition and measurement of density is not straightforward. The reported values vary over a wide range from 0.72 Mg m?3 to 0.94 Mg m?3, with an average of approximately 0.91 Mg m?3. The

G. W. Timco; R. M. W. Frederking

1996-01-01

322

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

323

Fram Strait sea ice outflow  

NASA Technical Reports Server (NTRS)

We summarize 24 years (1978??2) of ice export estimates and examine, over a 9-year record, the associated variability in the time-varying upward-looking sonar (ULS) thickness distributions of the Fram Strait.

Kwok, R.; Cunningham, G. F.; Pang, S. S.

2004-01-01

324

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

PubMed

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

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

2002-08-01

325

An unstructuredgrid, finitevolume sea ice model: Development, validation, and application  

E-print Network

finitevolume solver. Implementing UGCICE into the Arctic Ocean finitevolume community ocean model provides found in CICE and then for sea ice simulation in the Arctic Ocean under climatologic forcing conditions of the sea ice concentration, ice coverage, and ice drifting in the Arctic Ocean and adjacent coastal regions

Chen, Changsheng

326

Near-Real Time Microwave Sea Ice Products for Operational Sea Ice Analysis  

NASA Astrophysics Data System (ADS)

The U.S. National Ice Center (NIC) provides operational ice analyses for all ice-covered regions. These analyses are created from available high and low resolution imagery (including AVHRR, OLS, and Radarsat), reconnaissance data, ice forecasts, and climatology. Recently, the NIC has transitioned from weekly analyses to bi-weekly analyses for the Arctic and Antarctic. Daily operational SSM/I ice concentration products supplement these bi-weekly analyses. The product in the Arctic is from the NIC Hybrid Algorithm, a combination of the NASA Team algorithm, the NASA Team Thin Ice algorithm, and the Cal/Val algorithm. The Antarctic product employs the enhanced NASA Team (NT2) algorithm. In addition to these two operational algorithms, a variety of experimental products are posted daily on the NIC Science Web Page (http://www.natice.noaa.gov/science/). These include several other SSM/I concentration products (e.g., original NASA Team, Bootstrap, Cal/Val), a QuikScat ice coverage product, and sea ice concentration forecasts (from 1 to 5 days). Additional products are also planned, including an ice motion product and an SSM/I 85-GHz channel ice extent product. The goal of these experimental products is to provide improved operational ice analyses more efficiently. Here we present examples of the NIC products as well as the latest results from ongoing evaluation studies. These products are consistent with and complementary to the NSIDC sea ice products, but the focus is on the NIC mission of operational support.

Meier, W. N.; Van Woert, M.; Chase, M.

2001-12-01

327

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

328

Continuum sea ice rheology determined from subcontinuum mechanics  

E-print Network

Continuum sea ice rheology determined from subcontinuum mechanics P. D. Taylor,1 D. L. Feltham,1; published 25 November 2006. [1] A method is presented to calculate the continuum-scale sea ice stress-scale stress depends upon: the imposed strain rate; the subcontinuum scale, material rheology of sea ice

Feltham, Daniel

329

POLAR SEA ICE MAPPING FOR SEAWINDS Hyrum S. Anderson  

E-print Network

POLAR SEA ICE MAPPING FOR SEAWINDS by Hyrum S. Anderson A thesis submitted to the faculty, College of Engineering and Technology #12;viii #12;ABSTRACT POLAR SEA ICE MAPPING FOR SEAWINDS Hyrum S sea ice. Advances in microwave remote sensing technology have allowed a large-scale and detailed study

Long, David G.

330

POLAR SEA-ICE CLASSIFICATION USING ENHANCED RESOLUTION NSCAT DATA  

E-print Network

POLAR SEA-ICE CLASSIFICATION USING ENHANCED RESOLUTION NSCAT DATA Q. P. Remund and D. G. Long is shown to have high correlation with the NSIDC SSM/I derived multiyear ice maps. INTRODUCTION Polar sea is scientifically useful information. Several methods have been employed in the past to classify polar sea ice. Some

Long, David G.

331

Arctic Sea Ice Decline: Observations, Projections, Mechanisms, and Implications  

E-print Network

175 Arctic Sea Ice Decline: Observations, Projections, Mechanisms, and Implications Geophysical Is the Trajectory of Arctic Sea Ice? Harry L. Stern and Ronald W. Lindsay Polar Science Center, Applied Physics space of the Arctic sea ice thickness distribution, in which each dimension or component is the time

Lindsay, Ron

332

ARKTOS: An intelligent system for SAR sea ice image classification  

E-print Network

the reasoning process of sea ice experts. ARKTOS automatically segments a SAR image of sea ice, generates descriptors for the segments of the image, and then uses expert system rules to classify these sea ice features. ARKTOS also utilizes multisource data...

Soh, L. K.; Tsatsoulis, Costas; Gineris, D.; Bertoia, C.

2004-01-01

333

Bayesian Sea Ice Detection With the Advanced Scatterometer ASCAT  

Microsoft Academic Search

This paper details the construction of a Bayesian sea ice detection algorithm for the C-band Advanced Scatterometer ASCAT onboard MetOp based on probabilistic distances to ocean wind and sea ice geophysical model functions. The performance of the algorithm is validated against coincident active and passive microwave sea ice extents on a global scale across the seasons. The comparison between the

Maria Belmonte Rivas; Jeroen Verspeek; Anton Verhoef; Ad Stoffelen

2012-01-01

334

Reconciling Glacial Snow Lines With Tropical Sea Surface Temperatures  

NASA Astrophysics Data System (ADS)

Reconstructions of tropical snow lines during the last glacial maximum (LGM) 21,000 years ago are incompatible with the sea surface temperature (SST) reconstructions of the CLIMAP project, when assuming present day atmospheric lapse rates (e.g. Pe- teet and Rind 1985). Since proxy data for the vertical structure of the atmosphere during glacial times do not exist, numerical experiments with an atmospheric gen- eral circulation model for glacial and interglacial climates have been performed. Our model experiments reveal that slightly cooler tropical SSTs relative to the ones by CLIMAP (1981) are sufficient to simulate proper glacial freezing temperature levels. The depression of tropical snow lines in our LGM experiment can be attributed to two effects: Less moisture content provides an increased environmental lapse rate in the free atmosphere. This effect is strongest in the tropical middle troposphere where we observe an additional two degrees cooling. Secondly, the surface temperature near tropical glaciers is further cooled by a longer duration of snow cover. Our model result provides a consistent view of the last glacial maximum climate with much colder tem- peratures than today in the tropical mountains in concordance with moderate lowering of tropical SSTs.

Lorenz, S. J.; Lohmann, G.

335

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

336

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

Microsoft Academic Search

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

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

2005-01-01

337

Early inventory of black carbon particulate size in accumulated snow and ice  

NASA Astrophysics Data System (ADS)

Although size distributions of black carbon (BC) aerosol in the ambient atmosphere have become increasingly available in recent years, in snow and ice it is nearly unexplored. Here, we follow up on first measurements of the size distribution of refractory black carbon (BC) particulate in snow that showed that BC in snow can lie in a larger size range than is typically observed in the ambient atmosphere. This observation has implications for BC light absorption in the cryosphere, as well as for the processes that govern BC removal from the atmosphere by snow and BC aging on the surface. Snow samples from the American and Canadian Mid-West and Greenland, and ice core samples from the Cascades, were stored as sampled without additional thaw/free cycles until they were analyzed in the laboratory with a single particle soot photometer/Collison nebulizer setup. Although many samples were too clean (~<1 ng-BC/g-H2O) to allow measurement of high-quality BC size distributions, we were able to assess BC size in some snow samples and in presumed forest-fire emission layers captured in ice cores. Our results provide first constraints on the range and variability of the BC mass size distribution in the cryosphere, and on possible implications for the BC mass absorption cross section and role of BC in reduction of snow albedo.

Schwarz, J. P.; Gao, R.; Perring, A. E.; Markovic, M. Z.; Doherty, S. J.; Polashenski, C.; Kaspari, S.; Dibb, J. E.; Scheuer, E. M.; Fahey, D. W.

2013-12-01

338

Sensitivity of CryoSat-2 Arctic sea-ice volume trends on radar-waveform interpretation  

NASA Astrophysics Data System (ADS)

Several studies have shown that there is considerable evidence that the Arctic sea-ice is thinning during the last decades. When combined with the observed rapid reduction of ice-covered area this leads to a decline in sea-ice volume. The only remote sensing technique capable of quantifying this ice volume decrease at global scale is satellite altimetry. In this context the CryoSat-2 satellite was launched in 2010 and is equipped with the Ku-band SAR radar altimeter SIRAL, which we use to derive sea-ice freeboard defined as the height of the ice surface above the local sea level. In the context of quantifying Arctic ice-volume decrease at global scale, the CryoSat-2 satellite was launched in 2010 and is equipped with the Ku-band SAR radar altimeter SIRAL, which we use to derive sea-ice freeboard defined as the height of the ice surface above the sea level. Accurate CryoSat-2 range measurements over open water and the ice surface in the order of centimeters are necessary to achieve the required accuracy of the freeboard to thickness conversion. Besides uncertainties of the actual sea-surface height and limited knowledge of ice and snow properties, the penetration of the radar signal into the snow cover and therefore the interpretation of radar echoes is crucial. This has consequences in the selection of retracker algorithms which are used to track the main scattering horizon and assign a range estimate to each CryoSat measurement. In this paper we apply a retracker algorithm with thresholds of 40%, 50% and 80% of the first maximum of radar echo power, spanning the range of values used in current literature. For the 40% threshold we assume that the main scattering horizon lies at a certain depth between the surface and snow-ice interface as verified through coincident CryoSat-2 and airborne laser altimetry measurements. This contrasts with the 50% and 80% thresholds where we assume the ice-snow interface as the main scattering horizon similar to other published studies. Using the selected retrackers we evaluate the uncertainties of trends in sea-ice freeboard and higher level products that arise from the choice of the retracker threshold only, independently from the uncertainties related to snow and ice properties. Our study shows that the choice of retracker thresholds does have a non-negligible impact on magnitude estimates of sea-ice freeboard, thickness and volume, but that the main trends in these parameters are less affected. Specifically we find declines of Arctic sea-ice volume of 9.7% (40% threshold), 10.9% (50% threshold) and 6.9% (80% threshold) between March 2011 and March 2013. In contrast to that we find increases in Arctic sea-ice volume of 27.88% (40% threshold), 25.71% (50% threshold) and 32.65% (80% threshold) between November 2011 and November 2013. Furthermore we obtain a significant increase of freeboard from March 2013 to November 2013 in the area for multi-seasonal sea-ice north of Greenland and the Canadian Archipelago. Since this is unlikely it gives rise to the assumption that applying different retracker thresholds depending on seasonal properties of the snow load is necessary in the future.

Ricker, R.; Hendricks, S.; Helm, V.; Skourup, H.; Davidson, M.

2014-04-01

339

Sea-ice roughness and drag coefficients in a dynamic thermodynamic sea-ice model for the Arctic  

Microsoft Academic Search

A quantitative relationship between observed sea-ice roughness and simulated large-scale deformation work is established in order to provide new means for model validation and a better representation of the sea-ice component in climate modelling. Sea-ice roughness is introduced as an additional prognostic variable in a dynamic thermodynamic sea-ice model with a viscous-plastic rheology. It is defined as the accumulated work

Nadja Steiner; Markus Harder; Peter Lemke

1999-01-01

340

Micrometeorological survey of air-sea ice CO2 fluxes in arctic coastal waters  

NASA Astrophysics Data System (ADS)

We carried out a 6 month study that aimed to robustly track CO2 exchange between land-fast sea-ice and the atmosphere during the winter and spring season. A meteorological mast equipped for eddy-covariance measurements was installed on land-fast sea-ice near Barrow (Alaska), 1 km off the coast, from the end of January 2009 to the beginning of June 2009, before ice break-up. These data were supported by continuous measurements of solar radiation, snow depth, ice thickness and temperature profile in the ice. Biogeochemical data necessary for the understanding of the CO2 dynamics in sea-ice were obtained through discrete ice coring. Two regimes were detected for the CO2 exchanges linked with the status of the sea-ice: a winter regime and a spring summer regime. From 27 of March onwards brine volume at the sea ice-snow interface was above the threshold of permeability for liquid according to Golden et al (1998). During this period, we observed some conspicuous CO2 fluxes events tightly linked to wind speed. The flux was directed from the sea-ice to the atmosphere and reached up to 0.6 umol m-2 s-1 (51.8 mmol m-2 d-1). This flux to the atmosphere is expected as sea-ice at the air interface is permeable during a large part of the period and brines are oversaturated compared to the atmosphere. CO2 may accumulate in the snow layer which thus acts as a buffer that is flushed under occurrence of high wind speeds and associated pressure pumping. During the spring-summer period i.e. from 27 of April onwards, we observed a marked increase in sea ice temperature. Temperature profiles suggest that convective events occurred within the ice cover between April 27 and May 05. Within these convective events, two regimes were observed. First, for a period of 5 days, pCO2 was still above the threshold of saturation and CO2 fluxes were still mainly positive but lower than in the winter period, ranging from 0.1 to 0.2 umol m-2 s-1. This flux was only moderately controlled by windspeed perhaps due to the reduced snow cover. Further temperature increase led to a second flux regime where pCO2 of the brines were undersatured and sea ice shifted from a source to a sink of CO2 for the atmosphere, ranging from 0 to 0.1 umol m-2 s-1. These latter fluxes showed a diurnal pattern with no exchange during the night and downward fluxes during the day. The physical and bio-chemical processes occurring within sea-ice that control these fluxes will be discussed in more depth in the presentation.

Heinesch, Bernard; Tison, Jean-Louis; Carnat, Gauthier; Heicken, Hajo; Geilfus, Nicolas-Xavier; Goosens, Thomas; Papakyriakou, Tim; Yernaux, Michel; Delille, Bruno

2010-05-01

341

A Comparison of Sea Ice Surface Elevation, Freeboard and Thickness Estimates from Cryosat-2 and Operational IceBridge in High Latitude Areas of Arctic  

NASA Astrophysics Data System (ADS)

The European Space Agency Cryosat-2 mission has been providing high-spatial resolution cryosphere observations with space-borne synthetic aperture interferometric radar altimeter (SIRAL) since 2010. Sea ice elevation, freeboard and thickness estimation by Cryosat-2 SAR products are compared with the observations by airborne topographic mapper (ATM) and snow radar of the NASA Operational IceBridge (OIB) in Arctic. During the May 2011 around 70~88 degree North, the two dataset are well co-located (within 1 degree latitude/longitude) and contemporary (within one day) with each other, observing mainly multi-year ice during that winter. Results showed that: (1) Surface elevation (with respect to WGS 84 ellipsoid) measured by Cryosat-2 tend to observe a lower (around 0.5 to 1 meters) surface elevation as the SIRAL is a snow penetrating Ku-band radar, and the OIB airborne topographic mapper is an LiDAR; (2) Snow depth estimation by UCL-04 model associated with Cryosat-2 product tend to be higher (around 0.1~0.5 meters) than that measured by snow radar used during the OIB flights; (3) The mean sea surface high estimation from these two products tend to be slightly differ; (4) Ice thickness estimated with Cryosat-2 products tend to be higher than that of the OIB, due to higher snow density modeled by UCL-04.

Xia, W.; Xie, H.

2013-12-01

342

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...

2008-12-29

343

Ocean Atmosphere Sea Ice Soil User's Guide  

E-print Network

such as the natural variability, El Ni~no Southern Oscillation (ENSO) or the greenhouse gas global warming effectOASIS3 Ocean Atmosphere Sea Ice Soil User's Guide oasis3 prism 2­2, June 2004 Sophie Valcke 1 tool for coupling independent general circulation models of the atmosphere and the ocean (A/O­ GCMs

344

Ocean Atmosphere Sea Ice Soil User's Guide  

E-print Network

such as the natural variability, El Ni~no Southern Oscillation (ENSO) or the greenhouse gas global warming effectOASIS3 Ocean Atmosphere Sea Ice Soil User's Guide oasis3 prism 2­3, August 2004 Sophie Valcke 1 tool for coupling independent general circulation models of the atmosphere and the ocean (A/O­ GCMs

345

Ocean Atmosphere Sea Ice Soil User's Guide  

E-print Network

Oscillation (ENSO) or the greenhouse gases global warming effect. The models can possibly run on variousOASIS 2.0 Ocean Atmosphere Sea Ice Soil User's Guide and Reference Manual November 1995 Laurent an efficient and easy­to­use tool for coupling independent general circulation models of the atmosphere

346

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...

347

A Multiphase Study of the Chemical Composition of Air, Aerosol Particles, Snow, and Ice Forms Collected Near Barrow, Alaska Provides Information on Bromine Activation  

NASA Astrophysics Data System (ADS)

Unique chemistry that releases halogens from sea salts into the atmosphere depletes ozone and deposits mercury in the springtime in the Arctic. It is believed that Br(-) is present in the snow pack and other ice reservoirs over the ice-covered ocean during winter, and is liberated by poorly understood chemistry in the springtime. We undertook a study of halogens in different ice reservoirs like snow, aerosol particles, and in the gas phase in the vicinity of Barrow, Alaska in the springtime of 2007. For the first time, we observed a time series of most of the relevant bromine reservoirs simultaneously. The size and time-resolved aerosol data help us to complete a picture of what ice reservoirs are involved in releasing Br(-) into the gas phase. The smallest particles sampled with a 3-stage DRUM impactor contain a larger fraction of sulfate than the larger particles, and probably are the result of Arctic Haze sulfate pollution overlaid on a background of mostly larger sea-salt particles. The smallest particles are mostly enhanced in Br(-) (as compared to sea salt reference) while larger-sized particles could show near sea-salt Br(-) enrichment factors or slight Br- depletions. Enhancement in Br(-) can come from termination of halogen activation chemistry, which produces HBr. These HBr molecules would then be scavenged efficiently by the smaller particles due to their high surface area, which is consistent with our data. Depletion of Br(-) indicates halogen activation to the gas phase. During halogen activation events, surface snow shows higher depletions than the aerosol particles. Because the surface snow received its salts from the sea-salt aerosol that is mostly enhanced in Br(-) or is comparable to sea salt, and we observe depletions in snow, this indicates that snowpack is releasing halogens to the atmosphere. Knowing what ice surfaces contribute more to active Br(-) species can help us to predict ozone depletion and mercury deposition events. This mechanistic understanding is needed to make meaningful predictions of how Arctic pollution and Arctic atmospheric chemistry will respond to the drastic changes in sea ice.

Alvarez-Aviles, L.; Simpson, W. R.; Carlson, D. A.; Sturm, M.; Douglas, T. A.; Laskin, A.

2007-12-01

348

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

NASA Astrophysics Data System (ADS)

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

Nghiem, S. V.

2009-12-01

349

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

350

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

351

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

352

ConcepTest: Effect of Ice Sheet on Sea Level  

NSDL National Science Digital Library

During the last ice age there was a large ice sheet over much of Canada and the northern U.S. What was the effect on global sea levels? a. Sea level was higher b. Sea level was lower c. Sea level was the same as ...

353

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

354

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

355

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

356

Time-dependence of sea-ice concentration and multiyear ice fraction in the Arctic Basin  

Microsoft Academic Search

The time variation of the sea-ice concentration and multiyear ice fraction within the pack ice in the Arctic Basin is examined, using microwave images of sea ice recently acquired by the Nimbus-5 spacecraft and the NASA CV-990 airborne laboratory. The images used for these studies were constructed from data acquired from the Electrically Scanned Microwave Radiometer (ESMR) which records radiation

P. Gloersen; H. J. Zwally; A. T. C. Chang; D. K. Hall; W. J. Campbell; R. O. Ramseier

1978-01-01

357

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

358

Intercomparison of passive microwave sea ice concentration retrievals over the high-concentration Arctic sea ice  

NASA Astrophysics Data System (ADS)

Measurements of sea ice concentration from the Special Sensor Microwave Imager (SSM/I) using seven different algorithms are compared to ship observations, sea ice divergence estimates from the Radarsat Geophysical Processor System, and ice and water surface type classification of 59 wide-swath synthetic aperture radar (SAR) scenes. The analysis is confined to the high-concentration Arctic sea ice, where the ice cover is near 100%. During winter the results indicate that the variability of the SSM/I concentration estimates is larger than the true variability of ice concentration. Results from a trusted subset of the SAR scenes across the central Arctic allow the separation of the ice concentration uncertainty due to emissivity variations and sensor noise from other error sources during the winter of 2003-2004. Depending on the algorithm, error standard deviations from 2.5 to 5.0% are found with sensor noise between 1.3 and 1.8%. This is in accord with variability estimated from analysis of SSM/I time series. Algorithms, which primarily use 85 GHz information, consistently give the best agreement with both SAR ice concentrations and ship observations. Although the 85 GHz information is more sensitive to atmospheric influences, it was found that the atmospheric contribution is secondary to the influence of the surface emissivity variability. Analysis of the entire SSM/I time series shows that there are significant differences in trend between sea ice extent and area, using different algorithms. This indicates that long-term trends in surface and atmospheric properties, unrelated to sea ice concentration, influence the computed trends.

Andersen, SøRen; Tonboe, Rasmus; Kaleschke, Lars; Heygster, Georg; Pedersen, Leif Toudal

2007-08-01

359

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

360

Sensitivity of ocean circulation and sea-ice conditions to loss of West Antarctic ice shelves and ice sheet  

Microsoft Academic Search

We use a global coupled ocean-sea ice model to test the hypothesis that the disintegration of the West Antarctic ice sheet (WAIS), or just its ice shelves, may modify ocean circulation and sea-ice conditions in the Southern Ocean. We compare the results of three model runs: (1) a control run with a standard (modern) configuration of landmask in West Antarctica,

Marion Bougamont; Elizabeth C. Hunke; Slawek Tulaczyk

2007-01-01

361

Atmospheric and land surface response to reduced Arctic sea ice extent  

NASA Astrophysics Data System (ADS)

With the Arctic climate system changing at unprecedented rates and sea ice extent at near-record lows, an improved understanding of the relationship between sea ice and climate system components is warranted. In a series of model downscaling experiments using present day and projected end of 21 st century sea ice extent, the direct impact of sea ice on the Arctic atmosphere and land surface is examined. Using the Community Atmospheric Model (CAM), future projections of reduced sea ice are found to result in a decrease in sea level pressure (SLP) across northern North American and the central Arctic and an increase in SLP across much of Siberia in winter. The self-organizing map (SOM) technique is used to understand these mean changes from a synoptic climatology perspective. The decreases seen in SLP are found to be the result of an increased frequency of strong Arctic cyclones and an increased intensity of Aleutian lows, while the strengthened Siberian high is due to an increased frequency of a several synoptic scale patterns with strong high-pressure ridges. With a reduction in sea ice, precipitation increases significantly throughout the Arctic due almost entirely to higher levels of atmospheric moisture rather than increased cyclone frequency. In addition, very large increases in winter near-surface atmospheric temperature are simulated, and approximately half of the temperature change can be attributed to advection and half to diabatic heating. The Weather and Research Forecasting Model (WRF) is then forced with lateral boundary conditions from the CAM experiments to examine the land surface response to future sea ice projections across the North Slope of Alaska. Despite warmer near-surface atmospheric temperatures, it is found that spring melt is delayed throughout much of the North Slope due to increased snow pack, and the growing season length is shortened. Increased snow pack in the future sea ice scenario results in warmer soil temperatures for most seasons. However, in the summer soil temperatures are reduced due to increased albedo. These changes imply that sea ice extent acts as a negative feedback on Arctic vegetation growth and have implications for the terrestrial carbon budget.

Higgins, Matthew E.

362

Comparative study of technical measures to reduce snow and ice ablation in Alpine glacier ski resorts  

Microsoft Academic Search

We present technical methods aiming at a reduction of snow and ice ablation within an Austrian glacier ski resort. From April 2004 to September 2005 we carried out field studies at Schaufelferner (2870 m a.s.l.) and Gai?karferner (3100 m a.s.l.), two glaciers situated in the Stubai Alps. We injected water into the winter snow and studied the effects of compaction and artificial

M. Olefs; A. Fischer

2008-01-01

363

Degree–day factors for snow and ice for Dokriani Glacier, Garhwal Himalayas  

Microsoft Academic Search

In the present study, degree–day factors for snow and ice were determined over Dokriani Glacier located in the Garhwal Himalayas. The field experiments were made at an altitude of about 4000m. Effect of a thin fine dust layer on both degree–day factors was also examined. Average values of degree–day factor for clean and dusted snow were computed to be 5.7

P. Singh; N Kumar; M Arora

2000-01-01

364

Uptake of acetone, ethanol and benzene to snow and ice: effects of surface area and temperature  

Microsoft Academic Search

The interactions of gas-phase acetone, ethanol and benzene with smooth ice films and artificial snow have been studied. In one technique, the snow is packed into a cylindrical column and inserted into a low-pressure flow reactor coupled to a chemical-ionization mass spectrometer for gas-phase analysis. At 214 and 228 K, it is found for acetone and ethanol that the adsorbed

J P D Abbatt; T Bartels-Rausch; M Ullerstam; T J Ye

2008-01-01

365

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

366

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

NASA Astrophysics Data System (ADS)

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

367

Arctic sea ice thickness and volume declining  

NASA Astrophysics Data System (ADS)

The record low extent of Arctic sea ice area in September 2012 made headlines. Studies using models have suggested that sea volume has also been declining. A new study by Laxon et al. confirms this with observational data. The authors used satellite radar observations from the European Space Agency CryoSat-2 mission to estimate Arctic sea ice thickness and volume for the falls and winters of 2010-2011 and 2011-2012. By comparing these new data with earlier estimates from NASA's ICESat satellite, they found that the average ice volume declined by 4291 cubic kilometers in fall and 1479 cubic kilometers in winter between the period from 2003 to 2008 and the 2010-2012 period. The average volume of ice loss over both the fall and winter periods was found to be about 500 cubic kilometers per year, equivalent to a 0.075 meter per year decrease in thickness. (Geophysical Research Letters, doi:10.1002/grl.50193, 2013)

Balcerak, Ernie

2013-04-01

368

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, the forecast comprises several ice properties that are distributed as prognostic variables, 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 Sea during the severe winter 2011 and employs 15 to 25 min averages of ship speed.

Löptien, U.; Axell, L.

2014-12-01

369

Fracture prevalence during an unusual period of snow and ice in the Netherlands  

PubMed Central

Background The objective of the current study was to assess the effect of an unusual 10-day snow and ice period on the prevalence of fractures in an emergency department (ED) in the Netherlands. Furthermore, patients with fractures during the snow and ice period were compared to those in the control period with respect to gender, age, location of accident, length of stay, disposition, and anatomical site of the injury. Methods Fracture prevalence during a 10-day study period with snow and ice (January 14, 2013 until January 23, 2013) was compared to a similar 10-day control period without snow or ice (January 16, 2012 until January 25, 2012). The records of all patients with a fracture were manually selected. Besides this, basic demographics, type of fracture, and location of the accident (inside or outside) were compared. Results A total of 1,785 patients visited the ED during the study period and 1,974 during the control period. A fracture was found in 224 patients during the study period and in 109 patients during the control period (P <0.01). More fractures sustained outside account for this difference. No differences were found in gender, mean age, and length of ED stay. However, during the snow and ice period the percentage of fractures in the middle-aged (31–60 yrs) was significantly higher than in the control period (P <0.01). Conclusions The number of fractures sustained more than doubled during a period with snow and ice as compared to the control period. In contrast to other studies outside the Netherlands, not the elderly, but the middle-aged were most affected by the slippery conditions. PMID:24872860

2014-01-01

370