The amount of carbon that flows from land to the sea is twice as much as previously thought.

Schematic diagram showing new estimates of carbon transport in rivers, groundwater, and coastal ecosystems from land to sea.Credit: Eun Young Kwon

Every year, 600-900 million tonnes of carbon flow through rivers into the ocean, either in particles or in melted form. Researchers have long known that this does not represent the total amount of carbon transported from land to sea. However, the remaining contributors are primarily from coastal ecosystems such as carbon-rich mangrove forests, and are notorious for being difficult to measure due to the release of groundwater into the ocean.

New research published in the journal World biogeochemical cycle It will also be led by Dr. Eun Young Kwon, Project Leader of the IBS Center for Climate Physics South Korea, to provide new estimates of this elusive element of the global carbon cycle. This study takes advantage of the presence of two stable carbon isotopes. 12With C 13C, the latter is slightly heavier because there is another neutron in the nucleus. Concentration ratio between these two carbon isotopes ( 13C) Provides a means of tracking carbon through various elements of the carbon cycle, including the atmosphere, oceans, river systems, and biosphere.Know the typical 13For terrestrial biosphere C values ​​and coastal vegetation, it is now possible to track how this amount is diluted in the ocean. “Carbon isotope values ​​act like invisible dyes that tell us something about where they came from and how much they were initially released,” said the lead author of the study. Dr. Kwon says.

Using ocean observations 13C and current estimates, Dr. Kwon and her international team were able to calculate how much carbon would be needed from land to explain ocean data. The calculation is a bit more complicated because carbon can deposit in the deep sea as deposits and outgassing into the atmosphere.In addition, fossil fuel combustion also changes 13Carbon C in the atmosphere and ultimately in the ocean.

After considering these effects, the author was surprised. They found that carbon transfer from land to sea was much higher, ranging from 900 million to 100 million tonnes per year (see figure). Most of the approximately 300-1.3 billion tonnes of non-river carbon input annually occurs primarily along the coastline of the Indian Ocean and Pacific Ocean. “This is in line with the idea that groundwater emissions and coastal ecosystems, the so-called blue carbon, play a fundamental role in the global carbon cycle,” says Dr. Kwon.

One of the remaining open questions is which marine process is responsible for transporting dissolved carbon from coastal areas to the open ocean, some of which is released into the atmosphere. “This question will be solved in the future with a series of new earth system model simulations just performed on the supercomputer Aleph,” said Axel Timmermann, co-author of the study and director of the IBS Center for Climate Physics.

Fish supplies about 1.65 billion tonnes of carbon annually to feces and other substances.

For more information:
EY Kwon et al, stable carbon isotopes suggest large-scale terrestrial carbon input into the world ocean, World biogeochemical cycle (2021). DOI: 10.1029 / 2020GB006684

Provided by Institute for Basic Science

Quote: The amount of carbon flowing from land to the sea is twice as much as previously thought (March 18, 2021), on March 18, 2021 Obtained from carbon-ocean-previously-thought.html.

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The amount of carbon that flows from land to the sea is twice as much as previously thought.

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