June 14, 2023 - Colorful Van Diemen Gulf, Northern Territory, Australia

Van Dieman
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Gorgeous jewel-toned colors created a spectacular glow in the Van
Diemen Gulf in June 2023. The Moderate Resolution Imaging
Spectroradiometer (MODIS) on board NASA’s Terra satellite acquired a
true-color image of the colorful Van Diemen Gulf on June 13. Similar
colors tint the water north of the Tiwi Islands, especially the two
main islands of Bathurst (west) and Melville (east). These islands sit
so close together that they often look like a single, larger, island
from above.

Sometimes nicknamed “the bathtub”, in honor of it’s warm and shallow
waters, the Van Diemen Gulf spans the waters of Australia’s Northern
Territory between Melville Island, the Cobourg Peninsula, and the
mainland coast. The large semi-enclosed embayment has a surface area of
about 16,000 square kilometers (6,178 square miles) and is less than 20
meters (66 feet) deep. It also has a large tidal range measuring around
3 meters (9.8 feet) overall in the rainy season and even greater in the
southeast end, near where the Alligator Rivers pour into the Gulf. The
large change in height between low and high tides create strong tidal
currents, which scour sediment off the Gulf’s floor and keep it
suspended in the waters, especially during or shortly after the rainy
season. This is the same time that sediment load in the numerous rivers
that reach the Van Diemen Gulf is at their peak.

The rainy season in western Top End typically begins in November and
ends by mid-May. Given that waters are still high and rivers full in
mid-June, the colors captured in Van Diemen Gulf in this image are
almost certainly primarily from sediment. Sediment appears mud-colored
near the surface but reflectivity changes as it sinks, so deeper
sediment appears green and sometimes blue. Similar colors can be
created by blooms of microscopic plant-like organisms called
phytoplankton, but studies have shown that sediment concentrations can
be high enough in the Gulf to suppress the growth of phytoplankton. The
colors off of the Tiwi Islands are also likely primarily sediment, but
conditions in the open water off the islands can also be favorable for
phytoplankton growth.

Image Facts
Satellite: Terra
Date Acquired: 6/13/2023
Resolutions: 1km (20.5 KB), 500m (71.3 KB), 250m (229.8 KB)
Bands Used: 1,4,3
Image Credit: MODIS Land Rapid Response Team, NASA GSFC



https://modis.gsfc.nasa.gov/gallery/individual.php?db_date=2023-06-14

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