Iceberg Spanning 39 Nautical Miles Skims Past Clarence Island

A photograph of Iceberg D-30A near Clarence Island was taken on September 6, 2023, utilizing the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite.

Subsequent to circumventing the Antarctic Peninsula, the iceberg identified as D-30A made slight contact with the diminutive Clarence Island, completed a rotation, and proceeded to drift toward the north.

The U.S. National Ice Center disclosed in June 2021 that a new tabular iceberg, named D-30, emerged following the collision of Iceberg D-28 with the Borchgrevink Ice Shelf in the Queen Maud Land area of East Antarctica. Shortly after its formation, the iceberg divided once more, giving rise to D-30A.

Having meandered for over two years, this iceberg, which measures 39 nautical miles in length and 11 nautical miles in width (equivalent to 72 kilometers in length and 20 kilometers in width)—nearly the size of Rhode Island—brushed past Clarence Island in September 2023.

Satellite Depictions of D-30A

NASA’s Aqua satellite, utilizing its MODIS sensor, captured the image of D-30A in proximity to Clarence Island on September 6, 2023. Additional MODIS imagery revealed the iceberg approaching the island in late August, making contact with its southeastern coast and subsequently performing a rotation around the island during the initial fortnight of September. By the end of September, the iceberg had moved away and drifted northward.

According to Christopher Shuman, a glaciologist at the University of Maryland, Baltimore County, stationed at NASA’s Goddard Space Flight Center, the iceberg was able to move past Clarence Island likely due to the steep underwater drop-off on the island’s eastern side, which permitted the iceberg to pass through without becoming grounded.

Ecological Ramifications

The arrival of a substantial iceberg in the proximity of a small island like Clarence can instigate a range of impacts, both beneficial and detrimental, on local flora and fauna. Iron-rich meltwater from icebergs can, for example, enrich oceanic waters, thus stimulating the growth of beneficial phytoplankton. Conversely, a large iceberg situated offshore could hinder the foraging activities of penguins. Clarence Island is a habitat for more than 100,000 breeding pairs of chinstrap penguins. Heather Lynch, an ecologist at Stony Brook University, noted that in this specific instance, the timing was fortunate as the breeding chinstraps had not yet returned to their colony. A disruption during the breeding season could have had severe implications.

Roseanne Smith, a researcher with the British Antarctic Survey, elucidated that iceberg scouring may have been the more significant impact in this particular case. Such scouring can have a devastating effect on local benthic flora and fauna, but due to the steep decline of the seabed on the island’s eastern side, the impact was likely localized. Scouring can also have benefits, contributing to increased benthic biodiversity under certain conditions.

Antecedent Trajectory and Subsequent Courses

Before its encounter with Clarence Island, D-30A had been adrift along the Antarctic Coast, influenced by the Antarctic Coastal Current, for several months during 2021. It was later pushed northwest by the ocean currents of the Weddell Gyre into the open waters of the East Weddell Sea. In November 2022, the iceberg made a significant northerly turn, traversing an area commonly referred to as “Iceberg Alley,” en route to Clarence Island.

The future course of D-30A will be dictated by meteorological conditions and ocean currents. Icebergs in this region are often propelled east by the robust Antarctic Circumpolar Current flowing through the Drake Passage, situated between South America’s Cape Horn and the South Shetland Islands of Antarctica. Subsequently, they often drift northwards across the Southern Ocean into the South Atlantic, where they tend to dissolve rapidly in the warmer waters.

The image was captured by NASA’s Earth Observatory, credited to Wanmei Liang, and made use of MODIS data sourced from NASA EOSDIS LANCE and GIBS/Worldview.

Frequently Asked Questions (FAQs) about Iceberg D-30A

More about Iceberg D-30A

• NASA’s Earth Observatory
• Moderate Resolution Imaging Spectroradiometer (MODIS)
• U.S. National Ice Center
• British Antarctic Survey
• University of Maryland, Baltimore County, Glaciology Department
• Stony Brook University, Ecology Department
• Antarctic Coastal Current Studies
• Weddell Gyre Research
• Drake Passage and Antarctic Circumpolar Current
• Iceberg Scouring and Benthic Ecosystems