Why in Broadcast?

• According to a study, the colour of the Earth’s oceans has significantly altered over the past two decades, most likely due to human-induced climate change.

Impacts of the Change in Colour of Ocean

• According to the study, change in colour of the oceans doesn’t impact marine life directly.
• It indicates that marine ecosystems are in a state of flux and they could completely go out of balance in the future.
• Changes in the ecosystem could impact the productivity, amount of carbon oceans store and the food supply for fisheries.

Reason For the Colour of Oceans

• In most regions, the oceans appear blue or navy blue due to “the absorption and scattering of light.
• When the sunlight falls on deep and clear water, colours with longer wavelengths are absorbed by the water molecules but blue and violet, which have a much shorter wavelength, are reflected back.
• But when the water isn’t deep or clean, an ocean can appear to be of a different colour.
• When oceans appear green, it happens due to the existence of phytoplankton on the upper surface of the water.

Methods used to carry out the study

• Data from Moderate Resolution Imaging Spectroradiometer (MODIS), aboard NASA’s Aqua satellite.
• It has been monitoring ocean colour since 2002.
• Measurements in terms of the amount of light coming off the surface of the oceans, at all wavelengths of light, from violet to red.
• The examination of 20 years data indicated that in more than 50% of the world’s oceans, the colour has changed.

Climate model

• It is a computer representation of the Earth.
• This model simulated the planet’s oceans under two scenarios

• One with the addition of greenhouse gases,
• Other without GHGs.

• A significant trend should show up within 20 years and this trend should cause changes to ocean colour in about 50% of the world’s surface oceans, almost exactly similar to real-world satellite data.

Reasons Behind the Colour Change

• A shift in colour is happening in those regions where the oceans are getting more stratified.
• The stratification has increased, due to climate change, making it harder for water layers to mix with each other.

Consequences of Climate Change

• Oceans are able to absorb less carbon dioxide from the atmosphere.
• The oxygen absorbed isn’t able to mix properly with cooler ocean waters below, threatening the survival of marine life.
• Nutrients aren’t able to travel up to the surface of the oceans from below.
• This directly impacts phytoplankton, which thrives, on the upper surface of the oceans.