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How much carbon does the ocean absorb? – World Economic Forum

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  • The oceans play a critical role in capturing CO2 from the atmosphere.
  • Around 25% of all CO2 emissions are absorbed by the ocean, making it one of the world’s largest ‘carbon sinks’.
  • However, new evidence suggests this figure could be even higher.

The oceans cover over 70% of the Earth’s surface and play a crucial role in taking up CO2 from the atmosphere.

Estimates suggest that around a quarter of CO2 emissions that human activity generates each year is absorbed by the oceans.

However, in our recent Nature Communications paper, we show that the ocean carbon “sink” could be even larger.

We find that the very surface of the ocean tends to be markedly cooler than the water at a few metres depth, resulting in a substantially larger net uptake than previously thought.

Our findings have implications for our accounting of the CO2 we are emitting – namely, where does the large fraction of CO2 that is taken up each year by “natural” sinks actually go?

Each year, the Earth’s surface takes up billions of tonnes of CO2 from the atmosphere. These natural carbon sinks – oceans, plants and soils – help to buffer the continued emissions from human activity.

The ocean absorbs CO2 from the atmosphere because, as the atmospheric concentration increases, more is dissolved in the surface water. This water may then mix down, or sink as it is cooled, into the deep sea where the absorbed CO2 can stay locked up for hundreds of years as it slowly moves through the deep interior ocean and back to the atmosphere.

But the oceans have not always been a carbon sink.

Before the industrial era, the ocean was actually a net source of CO2. However, the increasing atmospheric CO2 concentrations, driven by human-caused emissions are forcing the ocean to now absorb this gas.

While the ability of the ocean to capture and store carbon has helped to slow the accumulation of atmospheric CO2 – and, hence, the pace of global warming – it has come at a cost. Increasing CO2 in the ocean alters the chemistry of seawater – an effect known as ocean acidification – which has negative impacts on marine life.

New observations

Each year, the global carbon budget is assessed to track how well, or not, humanity is achieving any reductions in greenhouse gas emissions.

This assessment involves calculating sources and sinks of CO2 across the world and determining the change in atmospheric CO2 concentrations.

Estimating the ocean sink is clearly needed to complete this assessment, but its importance has a knock-on impact for other parts of the overall budget.

The huge variations in land cover, vegetation, terrain and their year-to-year variations mean that it is currently very difficult to measure the total global land sink accurately. Solving this issue is complex and complicated. However, it can be estimated indirectly.

Scientists can calculate the total human-caused emissions and observe how much of this CO2 stays in the atmosphere. The remainder must have been absorbed by either the land or the ocean. So a good estimate of the ocean sink also enables calculation of how much is being taken up by the vegetation on land. Put simply, the CO2 that goes missing that doesn’t go into the ocean, must go into the land.

Nonetheless, quantifying the carbon absorbed by the vast oceans – whilst they are less variable when compared to the land – is still a complex problem. It requires measurements and observations from a range of sources including ships, buoys and even satellites.

Thankfully, satellite measurements are now becoming much easier to access as European and international agreements have made these widely available to scientists.

Such satellites have many uses, including ocean weather forecasting, so they are well maintained. The situation is a little different for measuring how much CO2 seawater contains, as these measurements are collected by researchers and then voluntarily collated into the Surface Ocean CO2 Atlas (SOCAT).

These – along with the other observations – form a critical part of our ability to determine the oceanic sink. Each year more than a million new measurements are added to SOCAT; a herculean effort involving scientists throughout the world.

Oceanographers and chemists working together

While previous estimates put the ocean sink at around 2bn tonnes of CO2 per year, we find that it could be 0.8-0.9bn tonnes larger. Over the whole 27-year study period of 1992-2018, this means the global oceans have taken up 67bn tonnes of CO2 rather than 43bn.

This advance in knowledge resulted from us working closely with specialists in sea temperature, physical oceanography and satellites. They explained that satellite sensors measure the temperature at the very surface of the ocean and that vertical changes in temperature occur near the surface.

This means that the temperature at the very surface of the water – its “skin” – is slightly cooler than the water below. This is because the ocean is heated by the sun and must get rid of this heat by evaporation and radiation from its skin. We realised that this meant that the CO2 in the water will also change near the surface, as the solubility of CO2 in the water is highly temperature dependent.

Though the temperature difference is usually quite small, it is systematically in one direction over most of the world’s oceans, resulting in a larger amount of CO2 entering the water.

These temperature characteristics are well studied in oceanography and they teach this theory on undergraduate degree programmes, but no one had clarified its full impact on carbon.

Ironically, this issue had been partly highlighted by marine carbon researchers and published in the journal Nature in 1992, but all of this information had since been ignored.

Our earlier work focused just on 2010 – and now on 1992-2018 – and brings all of this cross-disciplinary knowledge together. Our new study shows that the results are consistent with an independent method for calculating how much carbon has entered the ocean.

Implications of a larger ocean carbon sink

A larger ocean sink could imply that CO2 emissions are larger than currently thought or that the land sink is smaller than we currently think.

The sink seems to be increasing with time, especially in the last 20 years, and we believe this is because atmospheric CO2 has continued to rise rapidly, dissolving more every year into the surface waters.

You can see this in the charts below, which show the ocean-atmosphere exchange of CO2 over the study period for the whole world (top) and the northern and southern hemispheres (bottom). The coloured lines show different estimates, while the thick black line shows the average.

Following convention, the uptake of CO2 into the ocean is shown as negative, so descending lines indicate that the ocean is absorbing more CO2.

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Charts show atmosphere-ocean CO2 exchange for a) the globe, and b) for northern and southern hemispheres for 1992-2018.

Image: Carbon Brief

Our findings may also mean that the exchanges of carbon between the ocean and land – including those from large rivers like the Amazon, and that we currently consider to be relatively similar from year to year – are in fact more variable.

The answer will be difficult to determine, but is likely to need a cross-disciplinary approach involving modelling, satellite and ship-based scientists. Accounting for these new results will also likely involve some revision to the way in which we quantify global carbon budgets.

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Asteroid samples escaping from jammed NASA spacecraft – Phys.org

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In this image taken from video released by NASA, the Osiris-Rex spacecraft touches the surface of asteroid Bennu on Tuesday, Oct. 20, 2020. (NASA via AP)

A NASA spacecraft is stuffed with so much asteroid rubble from this week’s grab that it’s jammed open and precious particles are drifting away in space, scientists said Friday.

Scientists announced the news three days after the named Osiris-Rex briefly touched asteroid Bennu, NASA’s first attempt at such a mission.

The mission’s lead scientist, Dante Lauretta of the University of Arizona, said Tuesday’s operation 200 million miles away collected far more material than expected for return to Earth—in the hundreds of grams. The sample container on the end of the robot arm penetrated so deeply into the asteroid and with such force, however, that rocks got sucked in and became wedged around the rim of the lid.

Scientists estimate the sampler pressed as much as 19 inches (48 centimeters) into the rough, crumbly, black terrain.

“We’re almost a victim of our own success here,” Lauretta said at a hastily arranged news conference.

Lauretta said there is nothing can do to clear the obstructions and prevent more bits of Bennu from escaping, other than to get the samples into their as soon as possible.

So, the flight team was scrambling to put the sample container into the capsule as early as Tuesday—much sooner than originally planned—for the long trip home.

“Time is of the essence,” said Thomas Zurbuchen, chief of NASA’s science missions.

This is NASA’s first asteroid sample-return mission. Bennu was chosen because its carbon-rich material is believed to hold the preserved building blocks of our solar system. Getting pieces from this cosmic time capsule could help scientists better understand how the planets formed billions of years ago and how life originated on Earth.

Scientists were stunned—and then dismayed—on Thursday when they saw the pictures coming from Osiris-Rex following its wildly successful touch-and-go at Bennu two days earlier.

A cloud of asteroid particles could be seen swirling around the spacecraft as it backed away from Bennu. The situation appeared to stabilize, according to Lauretta, once the robot arm was locked into place. But it was impossible to know exactly how much had already been lost.

The requirement for the $800 million-plus mission was to bring back a minimum 2 ounces (60 grams).

Regardless of what’s on board, Osiris-Rex will still leave the vicinity of the asteroid in March—that’s the earliest possible departure given the relative locations of Earth and Bennu. The samples won’t make it back until 2023, seven years after the spacecraft rocketed away from Cape Canaveral.

Osiris-Rex will keep drifting away from Bennu and will not orbit it again, as it waits for its scheduled departure.

Because of the sudden turn of events, scientists won’t know how much the sample capsule holds until it’s back on Earth. They initially planned to spin the spacecraft to measure the contents, but that maneuver was canceled since it could spill even more debris.

“I think we’re going to have to wait until we get home to know precisely how much we have,” Lauretta told reporters. “As you can imagine, that’s hard. … But the good news is we see a lot of material.”

Japan, meanwhile, is awaiting its second batch of samples taken from a different asteroid, due back in December.


Explore further

NASA spacecraft sent asteroid rubble flying in sample grab


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Two flights into Abbotsford have had recent COVID-19 exposures – Maple Ridge News

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Two flights to Abbotsford have each had a recent COVID-19 exposure, according to the B.C. Centre for Disease Control (CDC).

The agency indicates on its website that the flights involved were WestJet flight 637 from Calgary to Abbotsford on Wednesday, Oct. 14 (rows nine to 15) and Swoop flight 107 from Hamilton to Abbotsford on Monday, Oct. 19 (rows 20 to 26).

The CDC advises that anyone who was on these flights should self-monitor for symptoms for 14 days.

RELATED: Vancouver airport to pilot pre-flight COVID-19 tests for select WestJet passengers

Passengers on domestic flights are not required to self-isolate, but those who have travelled outside of Canada are required to self-isolate for 14 days upon their arrival.

Passengers seated on a plane with a case of COVID-19 that was later identified are no longer directly notified of their potential exposure. Instead, anyone who has travelled is asked to monitor the CDC website.

Passengers seated in the affected rows are considered to be at higher risk of exposure due to their proximity to the case.

RELATED: WestJet to offer full refunds for flights cancelled due to COVID-19 pandemic



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Two flights into Abbotsford have had recent COVID-19 exposures – Surrey Now-Leader

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Two flights to Abbotsford have each had a recent COVID-19 exposure, according to the B.C. Centre for Disease Control (CDC).

The agency indicates on its website that the flights involved were WestJet flight 637 from Calgary to Abbotsford on Wednesday, Oct. 14 (rows nine to 15) and Swoop flight 107 from Hamilton to Abbotsford on Monday, Oct. 19 (rows 20 to 26).

The CDC advises that anyone who was on these flights should self-monitor for symptoms for 14 days.

RELATED: Vancouver airport to pilot pre-flight COVID-19 tests for select WestJet passengers

Passengers on domestic flights are not required to self-isolate, but those who have travelled outside of Canada are required to self-isolate for 14 days upon their arrival.

Passengers seated on a plane with a case of COVID-19 that was later identified are no longer directly notified of their potential exposure. Instead, anyone who has travelled is asked to monitor the CDC website.

Passengers seated in the affected rows are considered to be at higher risk of exposure due to their proximity to the case.

RELATED: WestJet to offer full refunds for flights cancelled due to COVID-19 pandemic



vhopes@abbynews.com

Like us on Facebook and follow us on Twitter

Coronavirus

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