Have you ever observed different shades of blue on sea surface under shimmering skies?
Well, that is just the surface matter.
Deep down, water can experience different lights when climate change causes ice to melt, affecting seas and oceans.
A new study reveals that as the planet experiences global warming, it causes disappearance of ice in the polar region, which in turn exposes oceans to much greater penetration of light, altering the colors of light in deep waters.
These transformative changes have far-reaching consequences for photosynthetic organisms such as ice algae and phytoplankton.
Published in Nature Communications, the research co-headed by marine biologists Monika Soja-Wo?niak and Jef Huisman from the Institute for Biodiversity and Ecosystem Dynamics (IBED) at the University of Amsterdam, looks at ways the loss of sea ice alters the underwater light environment, Science Daily reported.
The study spotlights that climate change in the polar regions does more than just melt ice.
It affects fundamental shifts in key processes such as light transmission and energy flow in marine ecosystems.
The Science Daily report says “sea ice and seawater differ fundamentally in how they transmit light. Sea ice strongly scatters light and reflects much of it, while allowing only a small amount to penetrate.
Yet, this limited amount of light still contains almost the full range of visible wavelengths. In contrast, seawater absorbs red and green light, while blue light penetrates deep into the water column. “This is what gives the ocean its blue color.”
The publication notes that ice and liquid water differ in the role of molecular vibrations. Earlier work by Maayke Stomp and Prof. Huisman demonstrated that these molecular absorption features create ‘spectral niches’ — distinct sets of wavelengths available for photosynthetic organisms.
Further, the repot notes that phytoplankton and cyanobacteria have evolved a diversity of pigments tuned to the different spectral niches, shaping their global distribution across oceans, coastal waters, and lakes.
This is in stark contrasts with what happens in water, where ice molecules are locked into a rigid crystal lattice. This fixed structure suppresses their ability for molecular vibrations and thereby alters their absorption features.
The report explains that as a result, ice lacks the absorption bands of liquid water, and hence a broader spectrum of light is preserved under sea ice. This fundamental difference plays a key role in the spectral shift that occurs as sea ice melts.
The disappearance of light gives way to open water due to which the underwater light environment shifts from a broad spectrum of colors to a narrower, blue-dominated spectrum. This spectral change is crucial for photosynthesis, according to the daily.
“The photosynthetic pigments of algae living under sea ice are adapted to make optimal use of the wide range of colors present in the little amount of light passing through ice and snow,” says lead author Monika Soja-Woniak.
The author adds, “when the ice melts, these organisms suddenly find themselves in a blue-dominated environment, which provides a lesser fit for their pigments.”
