October 22, 2021 - Swirls of Color in the Adriatic Sea
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Swirls of teal, turquoise, and tan colored the waters of the Adriatic
Sea in mid-October 2021. The Moderate Resolution Imaging
Spectroradiometer (MODIS) on board NASA’s Terra satellite acquired a
true-color image of the scene on October 20.
The Adriatic Sea is the northernmost arm of the Mediterranean Sea,
separating the Italian Peninsula from the Balkans. Italy sits along the
western coast of the Adriatic and, in this image, Croatia can be seen
in the east. Many islands sit off the mainland of Croatia and the
waters are deep; the waters are shallower off of Italy and few islands
exist.
The jewel-toned colors are typical of blooms of phytoplankton which
often occur in the Adriatic Sea in the autumn, the season when
conditions are just right to encourage rapid growth of the microscopic
plant-like organisms. While it is possible that some of this color
could be associated with such a bloom, it is much more likely that most
of this color comes from sediment. Sediment frequently washes off of
the coast, is churned up from the shallow bottom in the western
Adriatic, or pours into the Sea from sediment-laden rivers. When
floating near the surface, sediment generally looks muddy-tan. As it
sinks underwater and disperses, the change in reflectivity makes
sediment appear green and then blue.
The Adriatic region has survived a stormy October, with severe storm
warnings issued in Croatia on October 6-7. Looking at satellite images
taken of the region through the month of October, it is evident that
the waters off the coast of Italy were clear on October 4. By October
5, storm clouds hovered over Italy, the Adriatic Sea, and Croatia and
remained present until October 13, when skies cleared. On that date,
the waters just off the Italian coast sported a halo of tans, greens,
and turquoise, which almost certainly was sediment washed off the coast
and rivers due to the storms. Since that date, the colors have
lightened and spread further into the Adriatic. The fanciful swirls
seen in the October 20 image are primarily created by dispersing
sediment riding the currents near the Italian shore.
Image Facts
Satellite: Terra
Date Acquired: 10/20/2021
Resolutions: 1km (254.5 KB), 500m (671.4 KB), 250m (1.5 MB)
Bands Used: 1,4,3
Image Credit: MODIS Land Rapid Response Team, NASA GSFC
https://modis.gsfc.nasa.gov/gallery/individual.php?db_date=2021-10-22
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