{"id":82685,"date":"2023-07-14T15:36:00","date_gmt":"2023-07-14T19:36:00","guid":{"rendered":"https:\/\/www.carilec.org\/?p=82685"},"modified":"2023-07-14T15:38:45","modified_gmt":"2023-07-14T19:38:45","slug":"oceans-are-turning-greener-due-to-climate-change","status":"publish","type":"post","link":"https:\/\/carilec.org\/oceans-are-turning-greener-due-to-climate-change\/","title":{"rendered":"Oceans are turning greener due to climate change"},"content":{"rendered":"

Researchers are investigating exactly why this is happening and what it might signify.<\/h3>\n

Alexandra Witze<\/a><\/p>\n

More than half of the world\u2019s oceans have become greener in the past 20 years, probably because of global warming. The discovery, reported today in\u00a0Nature<\/i>1<\/a><\/sup>, is surprising because scientists thought they would need many more years of data before they could spot signs of climate change in the colour of the oceans.<\/p>\n

\u201cWe are affecting the ecosystem in a way that we haven\u2019t seen before,\u201d says lead author B. B. Cael, an ocean and climate scientist at the National Oceanography Centre in Southampton, UK.<\/p>\n

The ocean can change colour for many reasons, such as when nutrients well up from its depths and feed enormous blooms of phytoplankton, which contain the green pigment chlorophyll. By studying the wavelengths of sunlight reflected off the ocean\u2019s surface, scientists can estimate how much chlorophyll there is and thus how many living organisms such as phytoplankton and algae are present. In theory, biological productivity should change as ocean waters become warmer with climate change.<\/p>\n

But the amount of chlorophyll in surface waters can vary markedly from year to year, making it hard to differentiate any changes induced by climate change from the big natural swings. Scientists thought it might take up to 40 years of observations to spot any trends2<\/a><\/sup>.<\/p>\n

Another complicating factor is that numerous satellites have measured ocean colour over time, and each did so in a slightly different way, so the data cannot be combined. Cael\u2019s team decided to analyse data from MODIS, a sensor aboard NASA\u2019s Aqua satellite, which was launched in 2002 and is still orbiting Earth, far surpassing its anticipated six-year lifetime. The researchers looked for trends in seven different wavelengths of light from the ocean, rather than sticking with the single wavelength used to track chlorophyll. \u201cI\u2019ve thought for a long time that we could do better by looking at the full colour spectrum,\u201d Cael says.<\/p>\n

With two decades of MODIS data, the scientists were able to see long-term changes in ocean colour. They observed notable shifts in 56% of the world\u2019s ocean surface, mostly in the waters between the latitudes of 40\u00ba S and 40\u00ba N. These tropical and subtropical waters generally don\u2019t vary much in colour throughout the year, because the regions don\u2019t experience extreme seasons \u2014 and so small long-term changes are more apparent there, Cael says.<\/p>\n

The intensity of the colour change depends on the wavelength of light measured. In general, the waters are becoming greener over time.<\/p>\n

To see if the shifts could be linked to climate change, the researchers compared the observations to the results of a model3<\/a><\/sup>\u00a0that simulated how marine ecosystems might respond to increasing levels of greenhouse gases in the atmosphere. The observed changes matched those in the model.<\/p>\n

Shades of green<\/h2>\n

Now, the question is what is turning the oceans greener. It\u2019s probably not a direct effect of increasing sea surface temperatures, Cael says, because the areas where colour change was observed do not match up with those where temperatures have generally risen. One possibility is that the shift might have something to do with how nutrients are distributed in the ocean. As surface waters warm, the upper layers of the ocean become more stratified, making it harder for nutrients to rise to the surface. When there are fewer nutrients, smaller phytoplankton are better at surviving than larger ones, and so changes in nutrient levels could lead to changes in the ecosystem that are reflected in changes in the water’s overall colour.<\/p>\n

But this is just one idea; the researchers can\u2019t yet say exactly why the changes are happening. \u201cThe reason we care about the colour is because the colour tells us something about what\u2019s happening in the ecosystem,\u201d Cael says.<\/p>\n

The discovery ramps up expectations for the next big mission to monitor ocean colour \u2014 NASA\u2019s Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) satellite. Set to launch in January 2024, PACE will measure ocean colour in many more wavelengths than any previous satellite, a capability known as being \u2018hyperspectral\u2019.<\/p>\n

\u201cAll of this definitely confirms the need for global hyperspectral missions such as PACE,\u201d says Ivona Cetini\u0107, an oceanographer at NASA\u2019s Goddard Space Flight Center in Greenbelt, Maryland, who works on PACE. The spacecraft \u201cshould allow us to understand the ecological implications of the observed trends in ocean ecosystem structure in years to come\u201d.<\/p>\n

SOURCE: \"\"<\/strong><\/p>\n","protected":false},"excerpt":{"rendered":"

Researchers are investigating exactly why this is happening and what it might signify. 12 July 2023 Alexandra Witze More than […]<\/p>\n","protected":false},"author":165,"featured_media":82687,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[16],"tags":[],"class_list":["post-82685","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-news"],"acf":[],"aioseo_notices":[],"featured_image":"https:\/\/carilec.org\/wp-content\/uploads\/2023\/07\/Phytoplankton.png","month_date":"Jul","day_date":"14","_links":{"self":[{"href":"https:\/\/carilec.org\/api\/wp\/v2\/posts\/82685","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/carilec.org\/api\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/carilec.org\/api\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/carilec.org\/api\/wp\/v2\/users\/165"}],"replies":[{"embeddable":true,"href":"https:\/\/carilec.org\/api\/wp\/v2\/comments?post=82685"}],"version-history":[{"count":0,"href":"https:\/\/carilec.org\/api\/wp\/v2\/posts\/82685\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/carilec.org\/api\/wp\/v2\/media\/82687"}],"wp:attachment":[{"href":"https:\/\/carilec.org\/api\/wp\/v2\/media?parent=82685"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/carilec.org\/api\/wp\/v2\/categories?post=82685"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/carilec.org\/api\/wp\/v2\/tags?post=82685"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}