The Shetland Islands, an archipelago in the Northern Isles of Scotland, are featured in this Copernicus Sentinel-2 image.
Lying roughly 100 km (62 mi) north of the Scottish mainland, the Shetland Islands separate the Atlantic Ocean on the west from the North Sea to the east. The archipelago comprises around 100 islands and islets, with fewer than 20 of them inhabited. The islands cover an area of around 1,468 sq km (569 sq mi) and have a rugged coastline approximately 2,700 sq km (1,040 sq mi) long.
The largest island, known as the Mainland, has an area of around 900 sq km (350 sq mi), making it the third-largest Scottish island. The next largest are Yell, Unst, and Fetlar, which lie in the north, as well as Bressay and Whalsay, which lie to the east. Lerwick, located on Mainland, is the capital and largest settlement of the archipelago.
The most striking feature in this week’s image, captured on 1 July 2021, is the vivid, turquoise-colored bloom visible to the east of the islands. This type of bloom is slightly different from the harmful cyanobacteria often visible around the Baltic Sea.
In the absence of any known samples being analyzed, it is assumed that it is a coccolithophore bloom – a type of microscopic marine algae living in the upper layer of the sea. Like all phytoplankton, coccolithophores contain chlorophyll and have the tendency to multiply rapidly near the surface.
In large numbers, coccolithophores periodically shed their tiny scales called ‘coccoliths’ into the surrounding waters. These calcium-rich coccoliths turn the normally dark water into a bright, milky-turquoise color. Although invisible to the eye, in large quantities, they are easy to spot in satellite imagery. These types of algae play a huge role in the ocean uptake of atmospheric carbon dioxide, as their shells sink to deeper ocean depths after they die, storing carbon in the process.
This year’s edition of the United Nations climate change conference – COP26 – is taking place in Scotland from October 31 to November 12. The summit aims to inspire faster and more ambitious action from the international community to achieve the goal of limiting global temperature rise to 1.5°C (2.7°F). As in previous years, ESA has a strong presence at COP26, showcasing how satellite data strengthens our understanding of climate from space.
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