An international study coordinated by Enea reveals that the poor ocean areas of nutrients and biodiversity have almost doubled in just over twenty years. Marine desertification, linked to climate change, risks compromising the health of the oceans and altering the balance of the global climate
The alarm from the oceans: desertified areas on the rise
The surface of the oceans poor in nutrients and biodiversity has grown from 2.4% to 4.5% of the global total in just over twenty years. This phenomenon, defined oceanic desertificationrepresents a growing threat to marine ecosystems and the planet’s climate. To reveal it is a study published in the magazine Geophysical Research Lettersconducted by the laboratory AENEAS Climate models and services. They collaborated theIsmar-CNR And the Chinese Soed laboratory.
The role of phytoplankton and the decline of chlorophyll
The study focused on Fotoplankton, the basis of the Marina food chain It is an important climate regulator thanks to its ability to absorb atmospheric CO₂ through photosynthesis. The researchers observed a worrying drop in chlorophyll, indicator of the health of phytoplankton and the productivity of the oceans.
The causes of global warming for Enea
Second Clear timeEnea researcher of the laboratory models and climatic services, desertification is particularly evident in the northern Pacific. Each year 70 thousand km² of nutrients disappear.
This drop could be a symptom of a physiological adaptation to the new environmental conditions «Due to global warming, which causes hot water, lighter, remains on the surface, preventing mixing with colder water rich in nutrients that is in depth. Less mixing therefore means less “food” that reaches the surface to support the growth of phytoplankton and, consequently, of the entire food chain “.
From the study it also emerges that The quantity of chlorophyll is decreaseda key indicator of the health and productivity of phytoplankton. In practice, a greater presence of chlorophyll indicates a greater abundance of phytoplankton.
“However, according to the study, this drop may not indicate a reduction of the phytoplanttonic population, but an adaptation of these organisms to the new growth conditions imposed by climate change, such as the increase in the temperature and the reduction of the availability of nutrients”underlines the researcher.
Global scale analysis: the subtropical vortices
The study was based on the analysis of satellite data collected between 1998 and 2022, relating to the five main ones Subropical Gyres: in the northern and southern Atlantic, in the northern and southern Pacific and in the Indian Ocean. These vortices, influenced by winds, terrestrial rotation and morphology of continents, are dynamic systems fundamental for the distribution of nutrients in the oceans.
“In recent decades there has been an expansion of these vortices, associated with the reduction of chlorophyll, raising doubts and concerns for the implications on ocean productivity and on the global climatic balance”, continues Chiara Volta.
Concluding that «Despite the decrease in chlorophyll observed in the poorest area of nutrients of the subtropical vortices, the phytoplanttonic biomass has remained substantially stable over time. Taking into account that, by their nature, the satellite data are limited to providing a description of what happens on the ocean surface, the next steps to be taken will be to study the changes of the phytoplanttonic community along the water column and quantify their impact on ocean productivity on a regional and global scale “.