How marine snow cools the planet

March 13, 2019

University of Sydney scientists have modelled how carbonate accumulation from 'marine snow' in oceans has absorbed carbon dioxide over millennia and been a key driver in keeping the planet cool for millions of years.

The study, published in Geology, also helps our understanding of the ocean's future capacity to store carbon dioxide, which is vital given warming-ocean acidity has increased 30 percent since 1800.

"Marine snow is the falling debris of dead organisms in the ocean, such as plankton and algae," said the study's lead author, Dr Adriana Dutkiewicz.

"The deep ocean floor is covered with the remains of these tiny sea creatures. They produce more than 25 percent of the oxygen we breathe and form the Earth's largest carbon sink. When organic particles fall from the surface ocean to the seafloor, a small but significant proportion of atmospheric carbon is stored away."

When compacted over millions of years, these marine snow deposits become carbonate structures, such as the White Cliffs of Dover and similar structures along England's south coast. These chalk cliffs and their related structures under the ocean act as millennia-old carbon capture devices.

"Deep-sea carbonates represent a huge volume, so even small changes in the sequestration of carbonate carbon into this enormous sink are quite important for understanding net changes in atmospheric carbon dioxide and climate," Dr Dutkiewicz said.

Her team found that the amount of carbon stored in carbonate layers on the seafloor has increased tremendously over time. About 80 million years ago, only one megatonne of carbon ended up in carbonate layers annually, growing to about 30 megatonnes about 35 million years ago and 200 megatonnes today.

While carbonates forming in shallow waters decreased, the rise in deeper deposits was far greater, creating a net increase in the total volume of carbonate sediments in the oceans in the past 80 million years.

The study used data from drilled core samples from the past 50 years to develop a dynamic model describing the formation of carbonate deposits back 120 million years to the Cretaceous period.

Marine snow forms a blanket on the seafloor up to many hundreds of metres thick. Understanding what it is composed of, what drives its composition and how it has changed through time is important. If the supply of marine snow increases, then more carbon is stored, reducing the atmosphere's CO2 content.

To understand how much carbon has been stored over time in sedimentary carbonates in the ocean basins, Dr Dutkiewicz and her colleagues from the EarthByte group in the School of Geosciences, University of Sydney, developed a computer model of carbonate accumulation in deep-sea sediments spanning the past 120 million years. The researchers used the model to look at the impact of carbonate accumulation on global climate through time.

The researchers believe that the growth of a significant carbon sink over millions of years may be responsible for the removal of carbon dioxide from the atmosphere that led to global cooling 50 million years ago, triggering the transition from a hothouse to an icehouse climate around 35 million years ago.

The recently released Australian Bureau of Meteorology (BOM) and CSIRO biennial State of the Climate report stresses the importance of oceans as carbon sinks, potentially holding future warming extremes at bay.

"We need to understand better how the ocean's capacity to store CO2 will be affected by future warming," said EarthByte team leader Professor Dietmar Muller. "Ocean acidity has increased by 30 percent since 1800, reducing the capacity of the ocean to store away carbon."

Dr Dutkiewicz urged funding agencies and the scientific community to devote more resources to synthesising the incredible amount of data collected over 50 years of ocean drilling expeditions at a total cost of about $US200 million.

"This enormous ocean drilling investment and data set should be used much more extensively for understanding Earth's deep carbon cycle," she said. "Once you have coherent databases, a wide array of questions could be addressed."
-end-
Download a video explainer of the research at this link.

Watch and embed a short video of global carbonate formation over 120 million years at this link.

Download photos of Dr Adriana Dutkiewicz and Professor Dietmar Muller at this link.

Media enquiries

Media adviser: Marcus Strom | marcus.strom@sydney.edu.au | +61 423 982 485

Professor Dietmar Muller | dietmar.muller@sydney.edu.au | +61 434 606 914

University of Sydney

Related Carbon Articles from Brightsurf:

The biggest trees capture the most carbon: Large trees dominate carbon storage in forests
A recent study examining carbon storage in Pacific Northwest forests demonstrated that although large-diameter trees (21 inches) only comprised 3% of total stems, they accounted for 42% of the total aboveground carbon storage.

Carbon storage from the lab
Researchers at the University of Freiburg established the world's largest collection of moss species for the peat industry and science

Carbon-carbon covalent bonds far more flexible than presumed
A Hokkaido University research group has successfully demonstrated that carbon-carbon (C-C) covalent bonds expand and contract flexibly in response to light and heat.

Metal wires of carbon complete toolbox for carbon-based computers
Carbon-based computers have the potential to be a lot faster and much more energy efficient than silicon-based computers, but 2D graphene and carbon nanotubes have proved challenging to turn into the elements needed to construct transistor circuits.

Cascades with carbon dioxide
Carbon dioxide (CO(2)) is not just an undesirable greenhouse gas, it is also an interesting source of raw materials that are valuable and can be recycled sustainably.

Two-dimensional carbon networks
Lithium-ion batteries usually contain graphitic carbons as anode materials. Scientists have investigated the carbonic nanoweb graphdiyne as a novel two-dimensional carbon network for its suitability in battery applications.

Can wood construction transform cities from carbon source to carbon vault?
A new study by researchers and architects at Yale and the Potsdam Institute for Climate Impact Research predicts that a transition to timber-based wood products in the construction of new housing, buildings, and infrastructure would not only offset enormous amounts of carbon emissions related to concrete and steel production -- it could turn the world's cities into a vast carbon sink.

Investigation of oceanic 'black carbon' uncovers mystery in global carbon cycle
An unexpected finding published today in Nature Communications challenges a long-held assumption about the origin of oceanic black coal, and introduces a tantalizing new mystery: If oceanic black carbon is significantly different from the black carbon found in rivers, where did it come from?

First fully rechargeable carbon dioxide battery with carbon neutrality
Researchers at the University of Illinois at Chicago are the first to show that lithium-carbon dioxide batteries can be designed to operate in a fully rechargeable manner, and they have successfully tested a lithium-carbon dioxide battery prototype running up to 500 consecutive cycles of charge/recharge processes.

How and when was carbon distributed in the Earth?
A magma ocean existing during the core formation is thought to have been highly depleted in carbon due to its high-siderophile (iron loving) behavior.

Read More: Carbon News and Carbon Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.