Why Climate Change Lends New Color to the Ocean?

 

The once-dark blue ocean is gradually taking on a greener hue. The colour of the ocean's surface indicates the ecology just below it, so pay attention to it even if it doesn't seem as important as, say, record warm sea surface temperatures. Microscopic photosynthesizing creatures called phytoplankton form dense communities on the water's surface, essential to the aquatic food web and carbon cycle. This colour change in the water verifies a pattern predicted by climate change and indicates alterations to the ecosystems found in the world's oceans.

Scientists at the UK's National Oceanography Centre, led by B. B. Cael, found that the colour of 56% of the ocean's surface has changed significantly during the previous two decades. NASA's Aqua satellite's MODIS (Moderate Resolution Imaging Spectroradiometer) sensor collected ocean colour data, which they analyzed to determine that the change is largely due to the ocean becoming greener.

Darker hues of green on the chart above represent more substantial changes (higher signal-to-noise ratio) in ocean surface colour between 2002 and 2022. As a corollary, Cael stated, "These are places we can detect a change in the ocean ecosystem in the last 20 years." The study focused on tropical and subtropical regions, excluding higher latitudes, which are in the dark for part of the year, and coastline waters, where the data are typically quite noisy.

The black dots on the map show twelve percent of the ocean's surface, where chlorophyll levels also varied during the study period. The chlorophyll concentration has long been used by remote sensing scientists as a proxy for phytoplankton biomass and productivity. To be fair, those calculations only factor in a small subset of the colours we can see. The green numbers represent a more complete picture of the ecosystem because they are based on the full spectrum of hues. Read More!