National Geographic Society Map of Antarctica

SeaWinds is a weather radar system launched by NASA in June 1999. In addition to its primary role of measuring oceanic winds, this spaceborne scatterometer significantly contributes to non-ocean studies in vegetation and polar ice.

The polar regions play a central role in regulating global climate, and it is important to accurately record and monitor the extent and surface conditions of the earth's major ice masses. Spaceborne radar remote sensors are uniquely well-suited for mapping the polar regions since the radar can image the surface through clouds, both day and night. Active radar instruments are useful for studying snow and ice. Similarly, radars are also useful for vegetation studies because different vegetation types and densities have different radar responses.

A radar scatterometer measures the radar echo or radar backscattering cross-section (termed "sigma-0" by scientists) of the Earth's surface. Measurements of sigma-0 over the ocean are used to infer the near-surface wind speed and velocity. Measurements of sigma-0 in the polar regions and over land can be used to study ice and vegetation. For example, areas which reflect more microwaves back to the radar are typically rougher and appear brighter in the images than smoother areas which reflect less. The electrical properties of the surface also affect the image brightness and the presence of water on the surface has a very significant effect with wet surfaces generally appearing darker.

With its frequent coverage, the SeaWinds instrument is a powerful and unique tool for monitoring the health of the large ice sheets. The continuing time-series of data is a valuable contribution to assessments of the effects and impact of global change in the polar regions. For more information on these studies visit the Microwave Remote Sensing (MERS) Laboratory (BYU) website at http://www.ee.byu.edu/ee/mers/mers-home.html.

Antarctica Fig 1

Figure 1 illustrates an image formed from SeaWinds sigma-0 measurements over a portion of the ocean near Antarctica and helps demonstrate the wealth of information contained in the scatterometer data. This image was constructed from a single day of scatterometer data (May 24, 2000). The brighter central area in the image is Antarctica. It is bright due to high radar return echoes from glacial snow and ice covering the continent. The darker outer area in the center of the image is the sea-ice pack surrounding Antarctica. The variations in sea ice show the circulation patterns in the sea ice and are due to the snow cover, thickness, and history of the ice since formation. This information is essential to understand the effects of the ice pack on the ocean and climate systems.

Ronne Ice Shelf Figure 1a

The long white, rectangular object at the top of the image (marked by arrows) designated A-43A, A-43B, A44 are three massive icebergs calved from the Ronne Ice Shelf in the Weddell Sea in early May 2000 (see Figure 1a). Iceberg A-43 calved off the the Ronne Ice Shelf on May 4th and on May 6th, the iceberg broke in half, creating A-43A and A-43B. Iceberg A-44 calved about the same time that A-43 broke in half. For a detailed image of these icebergs visit the National Ice Center website at http://www.natice.noaa.gov/pub-info/Icebergs/A43A44break.gif.

Ronne Ice Shelf Figure 1b

The white, rectangular object at the bottom of the image, a "super" iceberg designated B-15 and a smaller companion iceberg (B-16) are located approximately 78 20S / 170 38W and 78 05S / 177 13W, respectively (see Figure 1b for close-up -- image is inverted). Iceberg B-15, is roughly 158 Nautical Miles (NM) long by 20 NM wide and covers approximately 10915 square km (about as long as the state of Maryland). Iceberg B-16 is 20 NM long by 08 NM wide. For a more detailed image of these icebergs visit the National Ice Center website at http://www.natice.noaa.gov/icebergs.htm.

For more detailed information on these and other giant icebergs visit the National Ice Center Website at http://www.natice.noaa.gov/icebergs.htm. For more information on polar oceanography research, visit the JPL Polar Oceanography website at http://polar.jpl.nasa.gov/.