Study Finds Changes in Sunlight Depth in World’s Oceans
- The Earth & I Editorial Team
- 4 days ago
- 2 min read
Some Areas Darkened by 21%; Others Lightened by 10% in 20 Years
World Oceans Day—celebrated each year on June 8—was designated in 2008 by the UN to “raise global awareness of the benefits humankind derives from the oceans and our individual and collective duty to use its resources sustainably.” A recent study by researchers at the University of Plymouth, UK, has found that a portion of the world’s oceans have darkened from 2003 to 2022. This is concerning because marine life depends on light for hunting, migration, and reproduction. Changes in depth of the photic zone (or sunlit/euphotic zone)—which has depths of 0 meters to 200 meters (656 ft)—were used to determine the darkening and lightening of the oceans. Plankton depend on this zone for photosynthesis. Key findings from the study include:
The total ocean surface area is roughly 360 million square kilometers (138 million square miles).
However, in the past two decades, over 21% (75,341,181 square kilometers or 29 million square miles) of ocean waters experienced darkening. Another 10% (37,269,515 square kilometers or 14 million square miles) experienced lightening.
During the day, about 19% of the world’s oceans had their photic zones reduced by more than 10 meters (32.8 ft). Of this amount, about 47% was a reduction of 50 to 100 meters (164 ft to 328 ft) while 13% was a reduction of more than 100 meters.
During nighttime, just under 14% of the world’s oceans had their photic zones reduced by more than 10 meters. Of this amount, about 4% was a reduction of 50 to 100 meters and less than 0.1% was a reduction of over 100 meters.
There were no changes in the photic zone depths for about 70.9% and 69.7% of the total ocean surface area during either day or night, respectively.
Photic zone depths increased (meaning more lightening) for about 9.3% and 9.8% of the total ocean surface area during the day and nighttime, respectively.
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