as marine biota

Carbon is essential to all life. However, the burning of fossil fuels and the consequent build-up of carbon dioxide in the atmosphere has led to severe concerns regarding climate change. Here, International Innovation takes a look at the movement of this essential element through the Earth’s system

OCEANThe ocean is the largest carbon reservoir in the fast domain, holding around:

ATMOSPHERE

The carbon cycle can be separated into two different, but interacting domains:

The fast domain – is considered the most important when considering anthropogenic climate change. It is made up of large exchange fluxes and relatively rapid carbon store turnovers. Turnover times of the reservoirs within the fast domain range from a few years to millennia.

The slow domain – consists of huge carbon stores in rocks and sediments, which exchange

carbon with the fast domain through volcanic eruptions, chemical weathering and erosion. Turnover times of the reservoirs in this domain span 10,000 years or longer.

The natural exchange between the two domains is relatively small (<0.3 PgC yr-1). However, fossil fuel extraction from geological reservoirs, and subsequent combustion has caused an unparalleled transfer of fossil carbon from the slow to the fast domain, causing a significant human-induced perturbation in the natural carbon cycle.

38,000 PgCas dissolved inorganic carbon (DIC)

700 PgCas dissolved organic carbon (DOC)

0.9 PgC y r -1

is transferred from rivers to oceansA total of

Carbon is stored in the atmosphere as CO2

78.4 PgC y r -1Ocean-atmosphere gas exchange:

Atmosphere-ocean gas exchange:

80 PgC y r -1

Net flux to the ocean:

1.6 PgC y r -1

~ 3 PgC

Total current store of CO2 in the atmosphere: 828 PgC

THE CARBON CYCLE: THE FACTS

32 INTERNATIONAL INNOVATION

Source: Intergovernmental Panel on Climate Change (IPCC) 2013 report, Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, ed T F Stocker, D Qin, G K Plattner, M Tignor, S K Allen, J Boschung, A Nauels, Y Xia, V Bex and P M Midgley, Cambridge University Press, Cambridge, UK, and New York, NY, USA

L I THOSPHERE The lithosphere contains

ANTHROPOGEN IC EM ISS I ONS O F C A R B O N

Fossil fuels: 7 . 8 ± 0 . 6 PgC y r -1

T ERRESTR IAL B IOSPHERE Carbon in the terrestrial biosphere has multiple stores:

wetland soils: 300-700 PgC

living biomass: ~ 450-650 PgCdead organic matter/soils: 1500-2400 PgC

permafrost soils: 1700 PgCNet flux to the biosphere: 4 . 3 PgC y r -1

Net land use change: 1 . 1 ± 0 . 8 PgC y r -1

6 6- 1 00 , 000 , 000 PgC

gas : 383- 1 1 35 PgC

o i l : 1 73-264 PgC

coa l : 446-54 1 PgC

Fossil fuels store carbon as:

0 . 1 PgC y r -1Lithosphere to atmosphere flux:

as marine sediments and sedimentary rock

Net Flux of carbon to the atmosphere:

PgC yr-1 = Pentagrams of carbon per year1 PgC = 1015 g carbon = 1 billion metric tonnes carbon

Respiration processes releaseback into the atmosphere

1 1 8 . 7 PgC y r -1

Plant photosynthesis removes CO2 from the atmosphere at a rate of 1 2 3 ± 8 PgC y r -1

THE CARBON CYCLE: THE FACTS

WWW.RESEARCHMEDIA.EU 33