Monthly Average Seaward Landfast Ice Edge Derived from Gradient Differences of RADARSAT Imagery for Northern Alaska, USA and Northwest Canada.

Metadata:


Identification_Information:
Citation:
Citation_Information:
Originator: University of Alaska Fairbanks
Publication_Date: 20051231
Title:
Monthly Average Seaward Landfast Ice Edge Derived from Gradient Differences of RADARSAT Imagery for Northern Alaska, USA and Northwest Canada.
Geospatial_Data_Presentation_Form: vector digital data
Other_Citation_Details:
See extended abstract on "Landfast sea ice extent and variability in the Alaskan Arctic derived from SAR imagery" presented at the International Geoscience and Remote Sensing Symposium, September 20-24, 2004, Anchorage, Alaska.
Online_Linkage: http://mms.gina.alaska.edu
Description:
Abstract:
This shapefile represents the Seaward Landfast Ice Edge (SLIE) along the coast of Northern Alaska (West of Barrow) and Northwest Canada (East to the Mackenzie Delta) for the study area which ranges from approximately 133 to 160 degrees West and 68 to 72.5 degrees North.  Landfast sea ice is a seasonal phenomena in the Alaskan Arctic and throughout its annual existence, between formation in late fall and break-up in late spring, it is shaped by a range of thermodynamic and dynamic forces (Barry et al. 1979; Shapiro and Metzner, 1989). The most apparent changes are those in landfast ice area and extent when floes of ice attach to and break off from its seaward edge. The position of the SLIE over the course of the year generally advances offshore to a stable position in mid-winter before retreating with the onset of spring. However, higher frequency changes in position also occur on timescales of days to weeks, which are generally small but occasionally affect the full width of the landfast ice. The location and stability of the SLIE at any point in time affects the activities of people and wildlife in the coastal arctic as it marks the boundary between stationary, continuous sea ice and drifting deforming pack ice. It is a vital consideration for people hunting or working on the ice in determining where food sources might be or where spilt oil might go. Since landfast ice occupies the shallowest water in the arctic, its presence or absence is also important for coastal process such as erosion and sediment entrainment.
Purpose:
These data were compiled by the University of Alaska Fairbanks to meet contract requirements for the US Mineral Management Service:  Mapping and Characterization of Recurring Spring Leads and Landfast ice in the Beaufort and Chukchi Seas (AK-03-06)
Supplemental_Information:
Following is an operational definition of Landfast ice stability that will be refined as extensive data sets are analyzed for the MMS study area.

(1) The general time period of stable landfast ice is bracketed by the first, sustained attachment in fall/winter and the break-up and decay of landfast ice in early summer. Preliminary work suggests that these dates have been shifting somewhat in the past 20 years. Here, the period of first, sustained attachment is defined as that time when a landfast ice cover of more than 1 km width is established that persists in-situ for more than 2 weeks over a given stretch of coastline. Break-up and decay are defined by the removal of substantial portions of the landfast ice to within less than 1 km from the beach, with concurrent substantial reductions in ice thickness through surface and bottom ablation. (2) During the general time period of stable landfast ice, it is the location of the seaward edge of the fast ice that determines stability in any given location. Hence, the simplest assessment of stability would include an indication of the amplitude of oscillations in seaward landfast ice edge during the course of the ice season as a measure of stability. In most cases, however, one can expect such oscillations to subside once the seaward sectors of the landfast ice are grounded by a combination of thick ice floes and pressure ridges. Thus, break-out events as major manifestations of fast-ice unstability could be characterized as breaking off of major sections of the landfast ice (ice fragments larger than 1 x 1 km in size) during this latter, "more stable" period of the landfast ice seasonal cycle.  (3) In order to distinguish between full break-out events and the attachment and detachment of "floating extentions" which are often observed in the Beaufort Sea during periods of stagnating ice motion, one would furthermore discriminate between break-out of landfast ice inshore and offshore of the deepest grounded ridges (if present and identifiable) or of the isobath typically associated with the deepest grounded pressure ridges (generally between 20 and 25 m; Reimnitz et al., 1978). For a floating extension to qualify as part of the landfast ice, it would have to be present for two weeks or more.
Time_Period_of_Content:
Time_Period_Information:
Range_of_Dates/Times:
Beginning_Date: 1996
Ending_Date: 2004
Currentness_Reference:
ground condition
Status:
Progress: Complete
Maintenance_and_Update_Frequency: None planned
Spatial_Domain:
Bounding_Coordinates:
West_Bounding_Coordinate: -160.813048
East_Bounding_Coordinate: -133.824195
North_Bounding_Coordinate: 72.620297
South_Bounding_Coordinate: 68.714097
Keywords:
Theme:
Theme_Keyword_Thesaurus: Aquatic Sciences and Fisheries Thesaurus
Theme_Keyword: raster
Theme_Keyword: landfast
Theme_Keyword: sea ice
Theme_Keyword: grounded ice
Place:
Place_Keyword_Thesaurus: Dictionary of Alaska Place Names
Place_Keyword: Arctic Ocean
Place_Keyword: Chukchi Sea
Place_Keyword: Beaufort Sea
Place_Keyword: North Slope
Place_Keyword: Alaska
Place_Keyword: Canada
Access_Constraints: None.
Use_Constraints:
Any hardcopies or published datasets utilizing these data sets shall clearly indicate their source.  If the user has modified the data in any way they are obligated to describe the types of modifications that they have performed.  User specifically agrees not to misrepresent these datasets, nor to imply that any changes that they made were approved by the University of Alaska.
Point_of_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: Dr. Hajo Eicken
Contact_Organization: Geophysical Institute
Contact_Position: Unversity of Alaska Fairbanks
Contact_Address:
Address_Type: mailing and physical address
Address:
903 Koyukuk Dr., P.O. Box 757320
City: Fairbanks
State_or_Province: Alaska
Postal_Code: 99775-7320
Country: USA
Contact_Voice_Telephone: 907-474-7280
Contact_Facsimile_Telephone: 907-474-7290
Contact_Electronic_Mail_Address: hajo.eicken@gi.alaska.edu
Data_Set_Credit:
The funding for this effort was provided by the US Mineral Management Service for Mapping and Characterization of Recurring Spring Leads and Landfast ice in the Beaufort and Chukchi Seas (AK-03-06, MMS-71707)
Native_Data_Set_Environment:
Microsoft Windows 2000 Version 5.1 (Build 2600) Service Pack 1; ESRI ArcCatalog 8.3.0.800
Cross_Reference:
Citation_Information:
Originator: Barry, R, R.E. Moritz and J.C. Rogers,
Publication_Date: 1979
Title:
The Fast Ice Regimes of the Beaufort and Chukchi Sea Coasts, Alaska.
Edition: 1
Geospatial_Data_Presentation_Form: document
Series_Information:
Series_Name: Cold Regions Science and Technology
Issue_Identification: 1, pp129-152
Cross_Reference:
Citation_Information:
Originator: Shapiro, L.H and R.C. Metzner
Publication_Date: 1989
Title:
Nearshore Ice Conditions from Radar Data, Point Barrow Area, Alaska.
Geospatial_Data_Presentation_Form: document
Series_Information:
Series_Name: Geophysical Institute Report
Issue_Identification: UAG-R (132)
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Data_Quality_Information:
Logical_Consistency_Report:
Map projection and datum were confirmed and checked to conform with base data sets and imagery.  

It should be noted that water on the surface of the ice will affect the backscatter, without necessarily affecting the stability of the ice or causing it to move. This situation is common in the Spring.  Thus, if the ice immediately beyond a flooded area exhibits consistency, then the SLIE line is drawn beyond the flooded area. This is consistent with our definition of SLIE (Seaward Landfast Ice Edge.)  As the ice at the mouth of a river becomes unstable during the Spring, a "hole" may develop in the landfast ice which we will not detect with this approach. This will be discussed further in reports associated with this study.
Completeness_Report:
Complete.
Positional_Accuracy:
Horizontal_Positional_Accuracy:
Horizontal_Positional_Accuracy_Report:
+/-  3 pixels based on co-location techniques of source imagery.
Quantitative_Horizontal_Positional_Accuracy_Assessment:
Horizontal_Positional_Accuracy_Value: 300
Horizontal_Positional_Accuracy_Explanation:
Visual inspection.
Lineage:
Process_Step:
Process_Description:
A combination of automated and manual techiques have been employed to derive the Seaward Landfast Ice Edge (SLIE) shown in this data set.  The MMS study area was divided into 10 subregions in order to obtain subscenes from 500 x 500 km RADARSAT scenes that were free from mosaicking edges prior to calculating the gradient fields.  Custom IDL routines were developed to derive the net difference between gradient fields of 3 consecutive colocated Radarsat subscenes.  The average period between scenes was 8 days.  An automated procedure was developed to consider 3 consecutive mosaics at a time representing an average period of 17 days. From these a magnitude image of the horizontal and vertical components of gradient difference is created.  The landfast ice is characterized by dark regions of low gradient difference adjacent to the land and typically bounded by bright, linear regions of high gradient difference.  The SLIE is identified by bright regions of high gradient difference. After thresholding the image at a gray value corresponding to a net backscatter gradient difference of 8 dB / km, the SLIE is more easily detected in some areas and can be manually delineated. A technique for automatically delineating the SLIE from the gradient difference images proves elusive at this time, since the SLIE can sometimes be less distinct in some areas and bright regions sometimes occur along the coast particularly in springtime when surface flooding from rivers occurs.  For this reason, the SLIE is manually delineated over gradient image mosaics compiled from the 10 subscenes.  Monthly averages were processed and exported to GeoTIFF format using IDL routines.  The final steps included converting GeoTiffs to ArcGIS format, defining the map projection and associating XML based metadata templates in preparation for posting to the project web site.
Process_Date: 2004
Process_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: Andy Mahoney
Contact_Organization: University of Alaska Fairbanks, Geophysical Institute
Contact_Position: PhD Candidate
Contact_Address:
Address_Type: mailing and physical address
Address:
903 Koyukuk Dr., P.O. Box 757320
City: Fairbanks
State_or_Province: AK
Postal_Code: 99775-7320
Country: USA
Contact_Voice_Telephone: 907-474-5648
Contact_Facsimile_Telephone: 907-474-7290
Contact_Electronic_Mail_Address: Mahoney@gi.alaska.edu
Hours_of_Service: business hours
Contact Instructions:
Email preferred.
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Spatial_Data_Organization_Information:
Direct_Spatial_Reference_Method: Vector
Point_and_Vector_Object_Information:
SDTS_Terms_Description:
SDTS_Point_and_Vector_Object_Type: G-polygon
Point_and_Vector_Object_Count: 1179
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Spatial_Reference_Information:
Horizontal_Coordinate_System_Definition:
Planar:
Map_Projection:
Map_Projection_Name: Albers Conical Equal Area
Albers_Conical_Equal_Area:
Standard_Parallel: 55.000000
Standard_Parallel: 65.000000
Longitude_of_Central_Meridian: -154.000000
Latitude_of_Projection_Origin: 50.000000
False_Easting: 0.000000
False_Northing: 0.000000
Planar_Coordinate_Information:
Planar_Coordinate_Encoding_Method: coordinate pair
Coordinate_Representation:
Abscissa_Resolution: 0.002048
Ordinate_Resolution: 0.002048
Planar_Distance_Units: meters
Geodetic_Model:
Horizontal_Datum_Name: North American Datum of 1983
Ellipsoid_Name: Geodetic Reference System 80
Semi-major_Axis: 6378137.000000
Denominator_of_Flattening_Ratio: 298.257222
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Entity_and_Attribute_Information:
Detailed_Description:
Entity_Type:
Entity_Type_Label: polygon
Entity_Type_Definition:
polygon
Entity_Type_Definition_Source:
ESRI
Attribute:
Attribute_Label: FID
Attribute_Definition:
Internal feature number.
Attribute_Definition_Source:
ESRI
Attribute_Domain_Values:
Enumerated_Domain:
Enumerated_Domain_Value: FID
Enumerated_Domain_Value_Definition:
Internal feature number.
Enumerated_Domain_Value_Definition_Source:
ESRI
Attribute:
Attribute_Label: Shape
Attribute_Definition:
Feature geometry.
Attribute_Definition_Source:
ESRI
Attribute_Domain_Values:
Enumerated_Domain:
Enumerated_Domain_Value: Shape
Enumerated_Domain_Value_Definition:
Feature geometry.
Enumerated_Domain_Value_Definition_Source:
ESRI
Unrepresentable_Domain:
Coordinates defining the features.
Attribute:
Attribute_Label: AREA
Attribute_Definition:
Polygon Area in Meters
Attribute_Definition_Source:
AREA
Attribute_Domain_Values:
Enumerated_Domain:
Enumerated_Domain_Value: AREA
Enumerated_Domain_Value_Definition:
Polygon Area in Meters
Enumerated_Domain_Value_Definition_Source:
AREA
Attribute:
Attribute_Label: PERIMETER
Attribute_Definition:
PERIMETER of Polygon in Meters
Attribute_Definition_Source:
ESRI
Attribute_Domain_Values:
Enumerated_Domain:
Enumerated_Domain_Value: PERIMETER
Enumerated_Domain_Value_Definition:
PERIMETER of Polygon in Meters
Enumerated_Domain_Value_Definition_Source:
ESRI
Attribute:
Attribute_Label: SLIEyyyymm
Attribute_Definition:
Seaward Landfast Ice Edge Year / Month
Attribute_Definition_Source:
UAF / ESRI
Attribute_Domain_Values:
Enumerated_Domain:
Enumerated_Domain_Value: SLIEyyyymm
Enumerated_Domain_Value_Definition:
Seaward Landfast Ice Edge Year / Month
Enumerated_Domain_Value_Definition_Source:
UAF / ESRI (this field is a remant of the internal fields associated with the ESRI coverage format which has been truncated in the conversion to shapefile format)
Attribute:
Attribute_Label: SLIEyyyymm
Attribute_Definition:
Seaward Landfast Ice Edge Year / Month
Attribute_Definition_Source:
UAF / ESRI
Attribute_Domain_Values:
Enumerated_Domain:
Enumerated_Domain_Value: SLIEyyyymm
Enumerated_Domain_Value_Definition:
Seaward Landfast Ice Edge Year / Month
Enumerated_Domain_Value_Definition_Source:
UAF & ESRI (this field is a remant of the internal fields associated with the ESRI coverage format which has been truncated in the conversion to shapefile format)
Attribute:
Attribute_Label: GRID_CODE
Attribute_Definition:
Cell Value Derived from ESRI Grid format
Attribute_Definition_Source:
ESRI
Attribute_Domain_Values:
Enumerated_Domain:
Enumerated_Domain_Value: GRID_CODE (where 255 = SLIE)
Enumerated_Domain_Value_Definition:
Cell Value Derived from ESRI Grid format
Enumerated_Domain_Value_Definition_Source:
ESRI
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Distribution_Information:
Distributor:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: UAF Geographic Information Network of Alaska (GINA)
Contact_Person: Dr. Virgil (Buck) Sharpton
Contact_Position: President's Professor of Remote Sensing
Contact_Address:
Address_Type: mailing and physical address
Address:
903 Koyukuk Drive
City: Fairbanks
State_or_Province: Alaska
Postal_Code: 99775-7320
Country: USA
Contact_Voice_Telephone: 907.474.6663
Contact_Electronic_Mail_Address: buck.sharpton@gina.alaska.edu
Hours_of_Service: 8:00 a.m. - 5:00 p.m. AST
Resource_Description: Downloadable Data
Distribution_Liability:
The University of Alaska makes no express or implied warranties (including warranties of merchantability and fitness) with respect to the character, function, or capabilities of the electronic services or products or their appropriateness for any users purposes. In no event will the University of Alaska be liable for any incidental, indirect, special, consequential or other damages suffered by the user or any other person or entity whether from the use of the electronic services or products, any failure thereof or otherwise, and in no event will the State of Alaska's liability to the requestor or anyone else exceed the fee paid for the electronic service or product.
Standard_Order_Process:
Digital_Form:
Digital_Transfer_Information:
Format_Name: ESRI Grid
Format_Version_Date: 2004
Format_Specification:
ESRI Grid
Transfer_Size: 2.384
Digital_Transfer_Option:
Online_Option:
Computer_Contact_Information:
Network_Address:
Network_Resource_Name: http://mms.gina.alaska.edu
Access_Instructions:
web browser and/or FTP
Fees: None
Ordering_Instructions:
These data will be made available at the request of the US Mineral Management Service via online tools provided by the Geographic Information Network of Alaska (GINA) at the University of Alaska Fairbanks.
Available_Time_Period:
Time_Period_Information:
Range_of_Dates/Times:
Beginning_Date: 1993
Ending_Date: 2003
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Metadata_Reference_Information:
Metadata_Date: 20050429
Metadata_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: Nuna Technologies
Contact_Person: Allison Graves Gaylord
Contact_Position: Owner / GIS Specialist
Contact_Address:
Address_Type: mailing address
Address:
P.O. Box 1483
City: Homer
State_or_Province: AK
Postal_Code: 99723-1483
Country: USA
Contact_Voice_Telephone: 907.399.1120
Contact_Facsimile_Telephone: 907.235.3476
Contact_Electronic_Mail_Address: nunatech@usa.net
Metadata_Standard_Name: FGDC Content Standards for Digital Geospatial Metadata
Metadata_Standard_Version: FGDC-STD-001-1998
Metadata_Time_Convention: local time
Metadata_Access_Constraints: None.
Metadata_Use_Constraints:
If the user has modified the data in any way they are obligated to describe the types of modifications they have performed in the supporting metadata file. User specifically agrees not to imply that changes they made were approved by the University of Alaska.
Metadata_Security_Information:
Metadata_Security_Classification_System: None.
Metadata_Security_Classification: Unclassified
Metadata_Security_Handling_Description:
None.
Metadata_Extensions:
Online_Linkage: http://www.esri.com/metadata/esriprof80.html
Profile_Name: ESRI Metadata Profile
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