• Fri. Dec 8th, 2023

Climate change may have turned half of Earth’s oceans green

Climate change may have turned half of Earth’s oceans green

In a recently published study Nature, researchers have claimed that climate change is the reason behind half of the world’s oceans turning green in the past 20 years. These findings are worrisome because scientists believed it would take a long time to collect data before observing ocean discoloration due to climate change.

A research team led by climate and ocean scientist BB Kell of the National Oceanography Center in Southampton, UK, analyzed data from the MODIS sensor on NASA’s Aqua satellite. Launched in 2002, the Aqua satellite is still in orbit around Earth, and its projected lifetime has exceeded 6 years.

The researchers looked at seven different wavelengths of light reflected from the oceans. The greening of the oceans is caused by the bloom of phytoplankton, microorganisms that contain the green pigment chlorophyll, similar to the green pigment found in tree leaves. By studying the wavelengths of light reflected off the surface of the ocean, scientists can estimate the amount of chlorophyll and measure the presence of phytoplankton or algae in the ocean.

Chlorophyll levels in seawater can vary over time, making it challenging for scientists to determine whether changes in water color are due to natural events or man-made climate change. Previously, it was believed that at least 40 years of observations It is necessary to make such measurements.

Using two decades of MODIS data, the researchers observed long-term changes in ocean color, with the most significant changes occurring in tropical and subtropical regions. Due to the lack of extreme seasons, these areas have relatively stable water color throughout the year, allowing researchers to infer long-term changes.

The intensity of seawater color depends on the measured wavelength of light, and the researchers’ findings indicate an overall increase in greenness.

After analyzing the wavelengths, the researchers compared the color changes to a model that predicts the responses of marine ecosystems to increasing greenhouse gases in the atmosphere. Their findings were consistent with the model, suggesting a link between the observed color changes and climate change.

However, uncertainties remain regarding the exact factors that influenced the color of the ocean. As stated in an article by Le Alexandra Witze, Kyle says: Nature, the color changes observed in some regions are not directly related to the increase in sea surface temperature. Another possibility is the distribution of nutrients in the ocean. Warmer ocean water becomes more stratified, making it harder for nutrients to reach the surface. This limited availability of nutrients can affect the survival of large phytoplankton. Changes in nutrient supply and subsequent ecosystem changes may be reflected in ocean water color.

However, the exact reason behind the change in color of sea water is not confirmed. Kell emphasized the importance of color as an indicator of ecosystem health, saying, “The reason we care about color is because color tells us what’s going on in the ecosystem.” However, it is clear that human-induced climate change is affecting ecosystems. Said“The ecosystem is being affected in ways we haven’t seen before.”

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