Charctic Interactive Sea Ice Graph

How to use Charctic

Developed at NSIDC with support from NASA, the Charctic Interactive Sea Ice Graph enables users to more easily access and explore the National Oceanic and Atmospheric Administration program at NSIDC (NOAA@NSIDC) Sea Ice Index data set.

With this tool, you can:

• Visualize sea ice extent (area of ocean with at least 15 percent sea ice concentration) data for the Arctic and Antarctic.
• View and compare sea ice extent data for any year or any combination of years from 1979 to present (including near-real-time daily data).
• Alternate climatology displays between either average matched with standard deviation, or median matched with interquartile and interdecile ranges.
• Choose from a variety of palettes to distinguish between different years, and toggle on/off vertical gridlines.
• Start the graph at any month of the year.
• Zoom in on an area of interest and reset to the standard display.
• Get daily sea ice extent values by rolling your cursor over a line in the graph.
• See a corresponding daily sea ice concentration image by clicking on a line in the graph.
• Download your customized graph or any of the corresponding daily sea ice concentration images.

About Charctic data

NOAA@NSIDC data and images shown in Charctic use passive microwave data from the Defense Meteorological Satellite Program (DMSP) F17 and F18 Special Sensor Microwave Imager/Sounder (SSMIS). Data sets include the Sea Ice Index, Near-Real-time DMSP SSM/I-SSMIS Daily Polar Gridded Sea Ice Concentrations, and the NASA-produced Sea Ice Concentrations from Nimbus-7 SMMR and DMSP SSM/I Passive Microwave Data.

The underlying data used to produce these images and graphs may be obtained from NSIDC. NSIDC produces the daily extent values using a five-day trailing mean. Graphs may vary slightly from graphs displayed in Sea Ice Today because of differences in handling leap years. However, the underlying data values are the same that NSIDC displays for its daily extent image and graph.

Working with the images

Graph

What it shows: For both the Arctic and Antarctic, the graph compares sea ice extent (area of ocean with at least 15 percent sea ice concentration) between all years selected. 

Charctic shows sea ice growth and retreat throughout the calendar year.

The default display shows the current year, the record-low year, and climatology.

• Use the selection tool on the right to toggle years on/off. Click the show/hide all years button to turn all years on or off.
• Select from the Colors drop-down list box at the top to choose a different color palette.
• Hover the cursor over any date on any displayed extent line for a popup display of extent details. 
• Click on any date on any displayed extent line to pull up a sea ice concentration map for that date.

Year versus extent: Months of the year appear across the horizontal axis. The default display is the calendar year starting in January. Extent—measured in millions of square kilometers—appears along the vertical axis. 

• Select from the Start month drop-down list box at the top to choose a different starting month.
• Click and drag over a portion of the graph to zoom in. Click the Reset button to restore the default display.

Climatological data: The default display uses median with interquartile and interdecile ranges. The median extent line (charcoal gray) is the middle value for all the sea ice extents for the given hemisphere and the given date from 1981 to 2010. The darker gray band around the median line is the interquartile extent: the innermost 50 percent of all values for that date. The lighter gray band is the interdecile extent: the innermost 80 percent of all values for that date.

• Use the selection tool on the right to toggle between median-interquartile-interdecile and average-standard-deviation displays.
• Use the selection tool on the right to turn off climatology altogether if desired.

Note: NSIDC does not include a previous year’s extent line as the record low until that entire year has passed.

Maps

Sea ice concentration map: You can display the map for any date by clicking on the extent line. The map shows the concentration, expressed as a percentage, of sea ice cover. The color bar on the right side of the map shows the concentration, from 0 percent in dark blue to 100 percent in white. The data shown in this map are the basis for calculating sea ice extent. Concentrations below 15 percent are considered ice free.

Median extent line: In each map, the orange line shows the median ice edge for the current date over the years 1981 to 2010. Half of the years had smaller extents, and half had larger extents on this date from 1981 to 2010. The median line is based on ice extent, and the same line is used for both the extent and concentration maps.

Note: Occasional data-feed interruptions lead to missing data. Areas of missing data for any date appear in mustard yellow.