![• Broecker has proposed an alternative explanation for the increase in CO2 since
the mid-Holocene (Broecker et al . 1999, 2001): that of a long-term response of
the oceanic carbonate system to a ca. 500 Gt increase in terrestrial biomass
during the Early Holocene. Mechanism involves four stages:
(i) an ‘instantaneous’ increase in deep water [𝐶𝑂3
2−
] as a response to the
biomass increase;
(ii) a deepening of the calcite lysocline resulting in an imbalance between
carbonate input and output
(iii) calcite preservation to restore balance (Broecker et al. 1993; Chapman et al.
1996));
(iv) leading to a decrease in [𝐶𝑂3
2−
] and long-term (of the order of 5kyr) increase
in atmospheric CO2.](https://image.slidesharecdn.com/creservoirccycle-180422012705/85/C-reservoir-amp-c-cycle-12-320.jpg)
C reservoir & c cycle
- 1. CARBON RESERVOIRS AND CARBON CYCLE S U B M I T T E D T O - P R O F . P . C H O U D H U R Y S U B M I T T E D B Y - R A J D E E P D A S D E P T . O F E C O L O G Y A N D R O L L - 0 1 1 7 1 7 N O - 2 2 0 1 0 3 9 5 E N V I R O N M E N T A L S C I E N C E 2 N D S E M E S T E R , D E P T . O F E C O L O G Y A N D E N V I R O N M E N T A L S C I E N C E
- 2. WHAT IS THE CARBON CYCLE? The Carbon cycle is the circulation and transformation of carbon back and forth between living things and the environment. Carbon is an element, something that cannot be broken down into a simpler substance and is often referred to as the “building block of life” because living things are based on carbon and carbon compounds. The amount of Carbon on the Earth and Earth’s atmosphere is fixed, but that fixed amount of carbon is dynamic, always changing into different carbon compounds and moving between living and non-living things.
- 3. Carbon in Atmosphere Plants use carbon to make food Animal eats plants and take in carbon Plants and animals die Bodies not decomposed after many years, becomes part of the oil and coal deposits Decomposers break down dead things, releasing carbon to atmosphere and soil Fossil fuels are burned; carbon is returned to atmosphere Carbon slowly released from
- 4. 7 Processes that transfer carbon i. Photosynthesis ii. Respiration iii. Consumption iv. Decomposition v. Combustion vi. Weathering vii. Dissolve/Vaporize
- 5. i. Photosynthesis: Plants Consume and release 𝑪𝑶 𝟐 Plants, some bacteria, and some protistans use the energy from the sunlight to produce glucose from carbon dioxide. If a plant is to survive, grow and reproduce, it must make a net in carbon, that is, carbon gained through photosynthesis must be than carbon lost through respiration. ii. & iii. Respiration/ Consumption: Animals consume and release carbon If we think of photosynthesis as the process of making fuel, then respiration can be thought of as the process of burning that fuel, using it for maintenance and growth.
- 6. iv. Decomposition: Plants and animals die When plants and animals die, most of their bodies are decomposed and carbon atoms are returned to the atmosphere. Some are not decomposed fully and end up in geosphere deposits underground (soil, oil, coal, etc.,) or at the bottom of ocean. v. Natural Combustion: Forest and grass fires are a natural, required part of the carbon cycle that releases carbon into the atmosphere and geosphere. Fire returns carbon to the soil and “cleans out” unhealthy plants, allowing new plants to grow.
- 7. vi. Dissolve/ Vaporize: Carbon Slowly Returns to Atmosphere Carbon in rocks and underground deposits is released very slowly into the atmosphere. This process takes many years and is usually caused by weathering. vii. Weathering: Oceans store large amounts of carbon. Largest exchange of carbon in carbon cycle is the dissolving and vaporization of carbon dioxide between the atmosphere and ocean surface.
- 8. CARBON RESERVOIRS • The carbon dioxide that makes up a small constituent of the atmosphere is part of a vast planetary cycle, in which carbon circulates among three active reservoirs and undergoes several changes of chemical form viz., the atmosphere, the oceans, and the terrestrial. • The pre-industrial oceanic carbon reservoir has been estimated at 38240Gt as compared with 600Gt in the atmosphere and1930Gt in the terrestrial biosphere (850Gt as biomass and 1080Gt as soil) (Brovkin et al. 2002).
- 9. • Of the three reservoirs the oceanic one contains by far the largest amount of carbon. The atmosphere is the smallest in terms of carbon storage, but it plays a significant role in the cycle as a conduit between the other two reservoirs. • In 1958 the average annual concentration in the atmosphere was 315 microliter of air, which works out to a concentration of about 0.03 percent and a total of 671 gigatons of carbon in the atmosphere. 1n 1988 the concentration was 351 microliters per liter, or 748 gigatons of carbon. • Based on data from the Geochemical Ocean Sections Study, about 37,000 gigatons of dissolved inorganic carbon is found in the ocean. In 1979 Kenneth Moper and Egon Degens estimated that the oceans contain an additional 1,000 gigatons of disoved organic carbon and 30 gigatons of particulate organic carbon.
- 11. • The most recent assessment of the Intergovernmental Panel on Climate Change (IPCC) (Houghton et al. 2001) has estimated CO2 levels in year 2100 are between ca.500 and 1000ppm compared with annual average levels which have recently reached 370ppm .The estimates of the associated temperature change are between 1.5 and 5.5◦C and those of sea-level change between 0.1 and 0.9m. The uncertainties in the estimates reflect, in part, incomplete understanding of the carbon cycle. • Indermuhle et al. (1999) proposed that the 20ppm increase in CO2 since the mid Holocene (ca.8000 years ago) was caused by a ca.200Gt decrease in the terrestrial biomass over this period. This is very large and equivalent to ca.30 years of fossil
- 12. • Broecker has proposed an alternative explanation for the increase in CO2 since the mid-Holocene (Broecker et al . 1999, 2001): that of a long-term response of the oceanic carbonate system to a ca. 500 Gt increase in terrestrial biomass during the Early Holocene. Mechanism involves four stages: (i) an ‘instantaneous’ increase in deep water [𝐶𝑂3 2− ] as a response to the biomass increase; (ii) a deepening of the calcite lysocline resulting in an imbalance between carbonate input and output (iii) calcite preservation to restore balance (Broecker et al. 1993; Chapman et al. 1996)); (iv) leading to a decrease in [𝐶𝑂3 2− ] and long-term (of the order of 5kyr) increase in atmospheric CO2.
- 13. • There are at least 3 arguments in favour of the fact that the observed increase in atmospheric 𝐶𝑂2 is due to emissions related to human activity: i. The rise in atmospheric 𝐶𝑂2 concentration closely follows the increase in emissions related to fossil fuel burning. ii. The inter-hemispheric gradient in atmospheric 𝐶𝑂2 concentration is growing in parallel with 𝐶𝑂2 emissions. That is, there is more land mass in the Northern hemisphere, and therefore more human activity, and thus; higher emission, which is reflected in the 𝐶𝑂2 growth in the Northern hemisphere
- 14. iii. Fossil Fuels and biospheric carbon are low in Carbon 13. The ratio of carbon 13 to carbon 12 in the atmosphere has been decreasing.
- 15. • Terrestrial Carbon Processes:
- 16. • Gross primary production (GPP): is the sum of gross C fixation by autotrophic C-fixing tissues per unit ground or water area and time. • Net primary production (NPP): is GPP - AR. It includes not only the growth of primary producers (biomass and tissue turnover above and belowground in terrestrial ecosystems) but also the C transfer to herbivores and root symbionts (for example, mycorrhizal fungi), the excretion of organic C from algae, etc. Global terrestrial NPP has been estimated to be 60 Gt C/yr., that is, about the half of GPP is incorporated in new plant tissue. The other half is returned the atmosphere as 𝐶𝑂2 by autotrophic respiration, that is, respiration by plant tissues.
- 17. • Net Biome Production (NBP): is the carbon accumulated by the terrestrial biosphere when carbon losses from non- respiratory processes are taken into account including fires, harvests/ removals, erosion and export of dissolved organic carbon by rivers to the oceans. NBP is small fraction of the initial uptake of 𝐶𝑂2 from the atmosphere and can be or negative at equilibrium it would be zero. • NBP is a critical parameter to consider for long term carbon storage. NBP is estimated to have averaged 0.2+/-0.7 Gt during 1980s and 1.4+/-0.7 Gt C/yr., during 1990.
- 18. Indicator of Human Influence during the Industrial Era
- 19. • Key Points: i. Global atmospheric concentrations of carbon dioxide, methane, nitrous oxide have all risen significantly over the last few hundred years. ii. Historical measurements show that the current global atmospheric concentrations of carbon dioxide, methane, and nitrous oxide are unprecedented compared with the past 800,000 years iii. Carbon dioxide concentrations have increased substantially since the beginning of the industrial era, rising from an annual average of 280 ppm in the late 1700s to 401 ppm as measured at Mauna Loa in 2015—a 43 percent increase. Almost all of this increase due to Human activities. iv. The concentration of methane in the atmosphere has more than doubled since preindustrial times, reaching approximately 1,800 ppb in recent years. This increase is predominantly due to agriculture and fossil fuel use. v. Over the past 800,000 years, concentrations of nitrous oxide in the atmosphere rarely exceeded 280 ppb. Levels have risen since the 1920s, however, reaching a new high of 328 ppb in 2015. This increase is primarily due to agriculture.
- 20. REFERENCE • Barker, S., Higgins, J.A., Elderfield, H.,The Future of the cycle: Review, The Royal Society, 10,1098/rsta.2003.1238 • Schlesinger, W., Andrews, J., Soil Respiration and Global Carbon Cycle, DOI:10.1023/A:1006247623877 • Chapin F.S., Reconciling Carbon-Cycle Concept, Terminology, and Methods, Ecosystems (2006) 9:1041-1050 • Ingram, J.S.I., Managing carbon sequestration in soils: concepts and terminology, Agriculture, Ecosystems and Environment 87 (2001) 111-117 • https://teeic.indianaffairs.gov/carbon/carboncycle • http://globecarboncycle.unh.edu/CarbonPoolsFluxes.shtml • https://www.epa.gov/climate-indicators/
- 21. THANK YOU