Nasa images of change9/12/2023 “It’s worth looking at the whole spectrum, rather than just trying to estimate one number from bits of the spectrum.” “So I thought, doesn’t it make sense to look for a trend in all these other colors, rather than in chlorophyll alone?” Cael says. They predicted that such changes should be apparent within 20, rather than 30 years of monitoring. Therefore, any signal of climate-change-driven changes should be easier to detect over the smaller, normal variations of other ocean colors. In 2019, Dutkiewicz and her colleagues published a separate paper, showing through a new model that the natural variation in other ocean colors is much smaller compared to that of chlorophyll. It would therefore take several decades to pick out a meaningful, climate-change-driven signal amid the normal noise. The reason, the team argued, was that the large, natural variations in chlorophyll from year to year would overwhelm any anthropogenic influence on chlorophyll concentrations. To do so, scientists have tracked changes in chlorophyll, based on the ratio of how much blue versus green light is reflected from the ocean surface, which can be monitored from spaceīut around a decade ago, Henson, who is a co-author of the current study, published a paper with others, which showed that, if scientists were tracking chlorophyll alone, it would take at least 30 years of continuous monitoring to detect any trend that was driven specifically by climate change. Scientists are therefore keen to monitor phytoplankton across the surface oceans and to see how these essential communities might respond to climate change. Phytoplankton are also a powerful muscle in the ocean’s ability to capture and store carbon dioxide. Phytoplankton are the foundation of the marine food web that sustains progressively more complex organisms, on up to krill, fish, and seabirds and marine mammals. The pigment helps plankton harvest sunlight, which they use to capture carbon dioxide from the atmosphere and convert it into sugars. Generally, waters that are deep blue reflect very little life, whereas greener waters indicate the presence of ecosystems, and mainly phytoplankton - plant-like microbes that are abundant in upper ocean and that contain the green pigment chlorophyll. The ocean’s color is a visual product of whatever lies within its upper layers. The study’s co-authors also include Stephanie Henson of the National Oceanography Center, Kelsey Bisson at Oregon State University, and Emmanuel Boss of the University of Maine. “It’s another way that humans are affecting the biosphere.” Cael PhD ’19 of the National Oceanography Center in Southampton, U.K. “This gives additional evidence of how human activities are affecting life on Earth over a huge spatial extent,” adds lead author B. And these changes are consistent with man-induced changes to our climate.” “To actually see it happening for real is not surprising, but frightening. “I’ve been running simulations that have been telling me for years that these changes in ocean color are going to happen,” says study co-author Stephanie Dutkiewicz, senior research scientist in MIT’s Department of Earth, Atmospheric and Planetary Sciences and the Center for Global Change Science. But they are pretty sure of one thing: Human-induced climate change is likely the driver. The shift in ocean color indicates that ecosystems within the surface ocean must also be changing, as the color of the ocean is a literal reflection of the organisms and materials in its waters.Īt this point, the researchers cannot say how exactly marine ecosystems are changing to reflect the shifting color. In particular, the researchers found that tropical ocean regions near the equator have become steadily greener over time. These color shifts, though subtle to the human eye, have occurred over 56 percent of the world’s oceans - an expanse that is larger than the total land area on Earth. In a study appearing today in Nature, the team writes that they have detected changes in ocean color over the past two decades that cannot be explained by natural, year-to-year variability alone. The ocean’s color has changed significantly over the last 20 years, and the global trend is likely a consequence of human-induced climate change, report scientists at MIT, the National Oceanography Center in the U.K., and elsewhere.
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