Today's Headlines - 02 August 2023
Climate change is altering the colour of the oceans
GS Paper - 3 (Environment)
The colour of the Earth’s oceans has significantly altered over the past two decades, most likely due to human-induced climate change, according to a new study. Over 56 per cent of the oceans, more than the total land area on the planet, has experienced the shift in colour, it added. The study, ‘Global climate-change trends detected in indicators of ocean ecology’, was published in the journal Nature.
What makes the oceans colourful in the first place?
In most regions across the world, the oceans appear blue or navy blue for a reason. This happens due to “the absorption and scattering of light”.
When the sunlight falls on deep and clear water, colours with longer wavelengths, such as red, yellow and green, are absorbed by the water molecules but blue and violet, which have a much shorter wavelength, are reflected back.
When sunlight hits the ocean, some of the light is reflected back directly but most of it penetrates the ocean surface and interacts with the water molecules that it encounters.
The red, orange, yellow, and green wavelengths of light are absorbed so that the remaining light we see is composed of the shorter wavelength blues and violets.
But when the water isn’t deep or clean, an ocean can appear to be of a different colour.
For instance, along Argentina’s coastline, where major rivers merge into the Atlantic Ocean, the ocean exudes a brown tint because of dead leaves and sediments spewing from the rivers.
In other parts of the world, the oceans appear green, which happens due to the existence of phytoplankton on the upper surface of the water.
Phytoplanktons are microscopic marine algae that contain the green-coloured pigment chlorophyll.
The pigment helps them absorb sunlight, which they use to capture carbon dioxide from the atmosphere and convert it into sugars. Moreover, chlorophyll absorbs the red and blue portions of the light spectrum — or photosynthesis — and reflects green light.
What methods were used to carry out the study?
To conduct the study, Cael and his team first analysed data from Moderate Resolution Imaging Spectroradiometer (MODIS), aboard NASA’s Aqua satellite, which has been monitoring ocean colour since 2002 — the measurements are taken in terms of the amount of light coming off the surface of the oceans, at all seven of the different wavelengths of light, from violet to red.
The examination of 20 years worth of data indicated that in more than 50 per cent of the world’s oceans, the colour has changed.
Then, to check if the phenomenon has occurred due to climate change, researchers used a climate model – a computer representation of the Earth.
This model simulated the planet’s oceans under two scenarios: one with the addition of greenhouse gases, and the other without it.
The greenhouse-gas model predicted that a significant trend should show up within 20 years and that this trend should cause changes to ocean colour in about 50 percent of the world’s surface oceans — almost exactly what Cael found in his analysis of real-world satellite data.
#upsc #news #headline #climate #colour #oceans #pigment #phytoplankton #chlorophyll #sediments #spewing #rivers #spectrum #methods #MODIS #NASA #Aqua #satellite #world #earth #wavelength #gases #greenhouse #data #planet
Climate change is altering the colour of the oceans
GS Paper - 3 (Environment)
The colour of the Earth’s oceans has significantly altered over the past two decades, most likely due to human-induced climate change, according to a new study. Over 56 per cent of the oceans, more than the total land area on the planet, has experienced the shift in colour, it added. The study, ‘Global climate-change trends detected in indicators of ocean ecology’, was published in the journal Nature.
What makes the oceans colourful in the first place?
In most regions across the world, the oceans appear blue or navy blue for a reason. This happens due to “the absorption and scattering of light”.
When the sunlight falls on deep and clear water, colours with longer wavelengths, such as red, yellow and green, are absorbed by the water molecules but blue and violet, which have a much shorter wavelength, are reflected back.
When sunlight hits the ocean, some of the light is reflected back directly but most of it penetrates the ocean surface and interacts with the water molecules that it encounters.
The red, orange, yellow, and green wavelengths of light are absorbed so that the remaining light we see is composed of the shorter wavelength blues and violets.
But when the water isn’t deep or clean, an ocean can appear to be of a different colour.
For instance, along Argentina’s coastline, where major rivers merge into the Atlantic Ocean, the ocean exudes a brown tint because of dead leaves and sediments spewing from the rivers.
In other parts of the world, the oceans appear green, which happens due to the existence of phytoplankton on the upper surface of the water.
Phytoplanktons are microscopic marine algae that contain the green-coloured pigment chlorophyll.
The pigment helps them absorb sunlight, which they use to capture carbon dioxide from the atmosphere and convert it into sugars. Moreover, chlorophyll absorbs the red and blue portions of the light spectrum — or photosynthesis — and reflects green light.
What methods were used to carry out the study?
To conduct the study, Cael and his team first analysed data from Moderate Resolution Imaging Spectroradiometer (MODIS), aboard NASA’s Aqua satellite, which has been monitoring ocean colour since 2002 — the measurements are taken in terms of the amount of light coming off the surface of the oceans, at all seven of the different wavelengths of light, from violet to red.
The examination of 20 years worth of data indicated that in more than 50 per cent of the world’s oceans, the colour has changed.
Then, to check if the phenomenon has occurred due to climate change, researchers used a climate model – a computer representation of the Earth.
This model simulated the planet’s oceans under two scenarios: one with the addition of greenhouse gases, and the other without it.
The greenhouse-gas model predicted that a significant trend should show up within 20 years and that this trend should cause changes to ocean colour in about 50 percent of the world’s surface oceans — almost exactly what Cael found in his analysis of real-world satellite data.
#upsc #news #headline #climate #colour #oceans #pigment #phytoplankton #chlorophyll #sediments #spewing #rivers #spectrum #methods #MODIS #NASA #Aqua #satellite #world #earth #wavelength #gases #greenhouse #data #planet
Today's Headlines - 22 August 2023
Extreme heat mean for the Mediterranean Sea
GS Paper - 3 (Environment)
Frequent heat waves cause huge damage to underwater ecosystems and researchers expect more of them in the future.
What are the solutions to heat stress?
Extreme heat has plagued the Mediterranean for weeks. Wildfires raged across at least nine countries in the region from Algeria to Greece.
But the soaring temperatures are not only a danger for people and ecosystems on land; they’re also harming marine life.
Without a doubt global climate change is the main reason for the heat waves in the sea. It’s causing the ocean to warm.
Why are high sea temperatures a problem?
In a warming world, marine creatures are in danger of suffocating. Gases like oxygen and carbon dioxide dissolve better at colder temperatures, so that means the warmer the water; the less oxygen is available to breathe.
Conversely, higher temperatures also cause an increase in metabolism, which in turn means animals have to breathe even more than usual). That combination also heightens the risk of death by starvation for marine life.
The rise in temperature accelerates metabolism, and the organisms need more food to maintain this metabolic rate.
Algal blooms are more common in hotter waters too. Such blooms can further deplete oxygen levels and produce toxins harmful for fish, marine mammals and birds, for instance.
What species and ecosystems are worst hit by marine heat waves?
High water temperatures are most harmful for animals living at the bottom of oceans, lakes or rivers.
These benthic species include corals, mussels, sponges, starfish and plants like sea grasses, and are often attached to rock or solid ground. They can’t migrate when it gets too hot.
Scientists observed mass deaths of benthic species along thousands of kilometers of Mediterranean coastline between 2015 and 2019.
Many benthic species are crucial to the marine ecosystem. They filter the water and keep seas, rivers and lakes clean by eating dead organisms.
Some species are an important food source for other creatures or are harvested by humans. Benthics like soft corals, seaweed and seagrasses provide some of the main ocean habitats.
Heat is particularly harmful for Posidonia oceanica or Neptune grass. And the large, slow-growing seagrass is found only in the Mediterranean. Previous heat waves have decimated the species, which is bad news for the climate.
What does extreme heat in the Mediterranean mean for people?
Warming seas are already affecting fishing activities in the area. Fishermen are catching fewer familiar species and instead are finding more invasive fish which they have difficulty selling.
Rabbitfish and lionfish are edible, but other invasive fish aren’t. Some are even poisonous, like the puffer fish.
Habitat loss could also lead to an overall decline in fish populations, while disappearing seagrass means coasts will be more exposed to future storms.
This could also have a knock-on effect for tourism because divers will be less likely to visit an impoverished underwater landscape.
#upsc #news #headline #extreme #mediterranean #sea #enviroment #heat #ecosystem #future #undrwater #wildfires #algeria #greece #global #climate #temperature #ocean #metabolism #algalblooms #birds #marine #oxygen #levels #lakes #rivers #soildground #benthic #mediterranean #coastline #foodsource #organisms #soft #corals #seaweed #rabbitfish #stroms #populations #lionfish #activities #neptunegrass #posidoniaoceanica #toxins #breathe
Extreme heat mean for the Mediterranean Sea
GS Paper - 3 (Environment)
Frequent heat waves cause huge damage to underwater ecosystems and researchers expect more of them in the future.
What are the solutions to heat stress?
Extreme heat has plagued the Mediterranean for weeks. Wildfires raged across at least nine countries in the region from Algeria to Greece.
But the soaring temperatures are not only a danger for people and ecosystems on land; they’re also harming marine life.
Without a doubt global climate change is the main reason for the heat waves in the sea. It’s causing the ocean to warm.
Why are high sea temperatures a problem?
In a warming world, marine creatures are in danger of suffocating. Gases like oxygen and carbon dioxide dissolve better at colder temperatures, so that means the warmer the water; the less oxygen is available to breathe.
Conversely, higher temperatures also cause an increase in metabolism, which in turn means animals have to breathe even more than usual). That combination also heightens the risk of death by starvation for marine life.
The rise in temperature accelerates metabolism, and the organisms need more food to maintain this metabolic rate.
Algal blooms are more common in hotter waters too. Such blooms can further deplete oxygen levels and produce toxins harmful for fish, marine mammals and birds, for instance.
What species and ecosystems are worst hit by marine heat waves?
High water temperatures are most harmful for animals living at the bottom of oceans, lakes or rivers.
These benthic species include corals, mussels, sponges, starfish and plants like sea grasses, and are often attached to rock or solid ground. They can’t migrate when it gets too hot.
Scientists observed mass deaths of benthic species along thousands of kilometers of Mediterranean coastline between 2015 and 2019.
Many benthic species are crucial to the marine ecosystem. They filter the water and keep seas, rivers and lakes clean by eating dead organisms.
Some species are an important food source for other creatures or are harvested by humans. Benthics like soft corals, seaweed and seagrasses provide some of the main ocean habitats.
Heat is particularly harmful for Posidonia oceanica or Neptune grass. And the large, slow-growing seagrass is found only in the Mediterranean. Previous heat waves have decimated the species, which is bad news for the climate.
What does extreme heat in the Mediterranean mean for people?
Warming seas are already affecting fishing activities in the area. Fishermen are catching fewer familiar species and instead are finding more invasive fish which they have difficulty selling.
Rabbitfish and lionfish are edible, but other invasive fish aren’t. Some are even poisonous, like the puffer fish.
Habitat loss could also lead to an overall decline in fish populations, while disappearing seagrass means coasts will be more exposed to future storms.
This could also have a knock-on effect for tourism because divers will be less likely to visit an impoverished underwater landscape.
#upsc #news #headline #extreme #mediterranean #sea #enviroment #heat #ecosystem #future #undrwater #wildfires #algeria #greece #global #climate #temperature #ocean #metabolism #algalblooms #birds #marine #oxygen #levels #lakes #rivers #soildground #benthic #mediterranean #coastline #foodsource #organisms #soft #corals #seaweed #rabbitfish #stroms #populations #lionfish #activities #neptunegrass #posidoniaoceanica #toxins #breathe