Climate change increases riverine carbon outgassing while export to the ocean remains uncertain

Abstract. Carbon fluxes in the Amazon Basin are considerably influenced by annual flooding during which terrigenous organic material is imported to the river. This regular interaction affects carbon pools within the riverine system, terrestrial carbon, and carbon exported to the ocean and released to the atmosphere. The processes of generation, conversion, and transport of organic carbon in this coupled terrigenous–riverine system strongly interact and are climate-sensitive, yet their response to climate change is still largely unknown. To quantify climate change effects on carbon pools and on carbon fluxes within the river and to the ocean and the atmosphere, we developed the riverine carbon model RivCM, which is directly coupled to the well-established dynamic vegetation and hydrology model LPJmL. We show here that RivCM successfully reproduces observed values in exported carbon and riverine carbon concentration. We evaluate future changes in riverine carbon by applying RivCM for climate forcing from five climate models and three CO2 emission scenarios (SRES). We find that climate change causes a doubling of riverine organic carbon in the Southern and Western basin while reducing it by 20 % in the eastern and northern parts. In contrast, the amount of riverine inorganic carbon shows a 2- to 3-fold increase in the entire basin, independent of the SRES scenario. The export of carbon to the atmosphere increases as well with an average of about 30 %. In contrast, changes in future export of organic carbon to the Atlantic Ocean depend on the SRES scenario and are projected to either decrease by about 8.9 % (SRES A1B) or increase by about 9.1 % (SRES A2). Such changes in the terrigenous–riverine system could have local and regional impacts on the carbon budget of the whole Amazon Basin and parts of the Atlantic Ocean. Changes in the riverine carbon could lead to a shift in the riverine nutrient supply and pH, while changes in the exported carbon to the ocean leads to changes in the supply of organic material that acts as food source in the Atlantic. On the larger scale the increased outgassing of CO2 could turn the Amazon Basin from a sink of carbon to a considerable source. Therefore we propose that the coupling of terrestrial and riverine carbon budget should be included in subsequent analysis of the future regional carbon budget.

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Climate change increases riverine carbon outgassing, while export to the ocean remains uncertain

Earth System Dynamics ◽

10.5194/esd-7-559-2016 ◽

2016 ◽

Vol 7 (3) ◽

pp. 559-582 ◽

Cited By ~ 5

Author(s):

F. Langerwisch ◽

A. Walz ◽

A. Rammig ◽

B. Tietjen ◽

K. Thonicke ◽

...

Keyword(s):

Climate Change ◽

Organic Carbon ◽

Atlantic Ocean ◽

Organic Material ◽

Large Scale ◽

Amazon Basin ◽

Carbon Budget ◽

Carbon Pools ◽

Carbon Budgets ◽

Sres Scenario

Abstract. Any regular interaction of land and river during flooding affects carbon pools within the terrestrial system, riverine carbon and carbon exported from the system. In the Amazon basin carbon fluxes are considerably influenced by annual flooding, during which terrigenous organic material is imported to the river. The Amazon basin therefore represents an excellent example of a tightly coupled terrestrial–riverine system. The processes of generation, conversion and transport of organic carbon in such a coupled terrigenous–riverine system strongly interact and are climate-sensitive, yet their functioning is rarely considered in Earth system models and their response to climate change is still largely unknown. To quantify regional and global carbon budgets and climate change effects on carbon pools and carbon fluxes, it is important to account for the coupling between the land, the river, the ocean and the atmosphere. We developed the RIVerine Carbon Model (RivCM), which is directly coupled to the well-established dynamic vegetation and hydrology model LPJmL, in order to account for this large-scale coupling. We evaluate RivCM with observational data and show that some of the values are reproduced quite well by the model, while we see large deviations for other variables. This is mainly caused by some simplifications we assumed. Our evaluation shows that it is possible to reproduce large-scale carbon transport across a river system but that this involves large uncertainties. Acknowledging these uncertainties, we estimate the potential changes in riverine carbon by applying RivCM for climate forcing from five climate models and three CO2 emission scenarios (Special Report on Emissions Scenarios, SRES). We find that climate change causes a doubling of riverine organic carbon in the southern and western basin while reducing it by 20 % in the eastern and northern parts. In contrast, the amount of riverine inorganic carbon shows a 2- to 3-fold increase in the entire basin, independent of the SRES scenario. The export of carbon to the atmosphere increases as well, with an average of about 30 %. In contrast, changes in future export of organic carbon to the Atlantic Ocean depend on the SRES scenario and are projected to either decrease by about 8.9 % (SRES A1B) or increase by about 9.1 % (SRES A2). Such changes in the terrigenous–riverine system could have local and regional impacts on the carbon budget of the whole Amazon basin and parts of the Atlantic Ocean. Changes in riverine carbon could lead to a shift in the riverine nutrient supply and pH, while changes in the exported carbon to the ocean lead to changes in the supply of organic material that acts as a food source in the Atlantic. On larger scales the increased outgassing of CO2 could turn the Amazon basin from a sink of carbon to a considerable source. Therefore, we propose that the coupling of terrestrial and riverine carbon budgets should be included in subsequent analysis of the future regional carbon budget.

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Deforestation in Amazonia impacts riverine carbon dynamics

Earth System Dynamics Discussions ◽

10.5194/esdd-6-2101-2015 ◽

2015 ◽

Vol 6 (2) ◽

pp. 2101-2136

Author(s):

F. Langerwisch ◽

A. Walz ◽

A. Rammig ◽

B. Tietjen ◽

K. Thonicke ◽

...

Keyword(s):

Climate Change ◽

Organic Carbon ◽

Atlantic Ocean ◽

Amazon Basin ◽

Inorganic Carbon ◽

Carbon Dynamics ◽

Model System ◽

Atmospheric Co2 ◽

Terrestrial Productivity ◽

The Impact

Abstract. Fluxes of organic and inorganic carbon within the Amazon basin are considerably controlled by annual flooding, which triggers the export of terrigenous organic material to the river and ultimately to the Atlantic Ocean. The amount of carbon imported to the river and the further conversion, transport and export of it, depend on terrestrial productivity and discharge, as well as temperature and atmospheric CO2. Both terrestrial productivity and discharge are influenced by climate and land use change. To assess the impact of these changes on the riverine carbon dynamics, the coupled model system of LPJmL and RivCM (Langerwisch et al., 2015) has been used. Vegetation dynamics (in LPJmL) as well as export and conversion of terrigenous carbon to and within the river (RivCM) are included. The model system has been applied for the years 1901 to 2099 under two deforestation scenarios and with climate forcing of three SRES emission scenarios, each for five climate models. The results suggest that, following deforestation, riverine particulate and dissolved organic carbon will strongly decrease by up to 90 % until the end of the current century. In parallel, discharge increases, leading to roughly unchanged net carbon transport during the first decades of the century, as long as a sufficient area is still forested. During the following decades the amount of transported carbon will decrease drastically. In contrast to the riverine organic carbon, the amount of riverine inorganic carbon is only determined by climate change forcing, namely increased temperature and atmospheric CO2 concentration. Mainly due to the higher atmospheric CO2 it leads to an increase in riverine inorganic carbon by up to 20 % (SRES A2). The changes in riverine carbon fluxes have direct effects on the export of carbon, either to the atmosphere via outgassing, or to the Atlantic Ocean via discharge. Basin-wide the outgassed carbon will increase slightly, but can be regionally reduced by up to 60 % due to deforestation. The discharge of organic carbon to the ocean will be reduced by about 40 % under the most severe deforestation and climate change scenario. The changes would have local and regional consequences on the carbon balance and habitat characteristics in the Amazon basin itself but also in the adjacent Atlantic Ocean.

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Deforestation in Amazonia impacts riverine carbon dynamics

Earth System Dynamics ◽

10.5194/esd-7-953-2016 ◽

2016 ◽

Vol 7 (4) ◽

pp. 953-968 ◽

Cited By ~ 2

Author(s):

Fanny Langerwisch ◽

Ariane Walz ◽

Anja Rammig ◽

Britta Tietjen ◽

Kirsten Thonicke ◽

...

Keyword(s):

Land Use ◽

Organic Carbon ◽

Land Use Change ◽

Atlantic Ocean ◽

Amazon Basin ◽

Inorganic Carbon ◽

Carbon Dynamics ◽

Model System ◽

Atmospheric Co2 ◽

Terrestrial Productivity

Abstract. Fluxes of organic and inorganic carbon within the Amazon basin are considerably controlled by annual flooding, which triggers the export of terrigenous organic material to the river and ultimately to the Atlantic Ocean. The amount of carbon imported to the river and the further conversion, transport and export of it depend on temperature, atmospheric CO2, terrestrial productivity and carbon storage, as well as discharge. Both terrestrial productivity and discharge are influenced by climate and land use change. The coupled LPJmL and RivCM model system (Langerwisch et al., 2016) has been applied to assess the combined impacts of climate and land use change on the Amazon riverine carbon dynamics. Vegetation dynamics (in LPJmL) as well as export and conversion of terrigenous carbon to and within the river (RivCM) are included. The model system has been applied for the years 1901 to 2099 under two deforestation scenarios and with climate forcing of three SRES emission scenarios, each for five climate models. We find that high deforestation (business-as-usual scenario) will strongly decrease (locally by up to 90 %) riverine particulate and dissolved organic carbon amount until the end of the current century. At the same time, increase in discharge leaves net carbon transport during the first decades of the century roughly unchanged only if a sufficient area is still forested. After 2050 the amount of transported carbon will decrease drastically. In contrast to that, increased temperature and atmospheric CO2 concentration determine the amount of riverine inorganic carbon stored in the Amazon basin. Higher atmospheric CO2 concentrations increase riverine inorganic carbon amount by up to 20 % (SRES A2). The changes in riverine carbon fluxes have direct effects on carbon export, either to the atmosphere via outgassing or to the Atlantic Ocean via discharge. The outgassed carbon will increase slightly in the Amazon basin, but can be regionally reduced by up to 60 % due to deforestation. The discharge of organic carbon to the ocean will be reduced by about 40 % under the most severe deforestation and climate change scenario. These changes would have local and regional consequences on the carbon balance and habitat characteristics in the Amazon basin itself as well as in the adjacent Atlantic Ocean.

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Potential effects of climate change on inundation patterns in the Amazon Basin

Hydrology and Earth System Sciences ◽

10.5194/hess-17-2247-2013 ◽

2013 ◽

Vol 17 (6) ◽

pp. 2247-2262 ◽

Cited By ~ 36

Author(s):

F. Langerwisch ◽

S. Rost ◽

D. Gerten ◽

B. Poulter ◽

A. Rammig ◽

...

Keyword(s):

Climate Change ◽

Amazon Basin ◽

Climate Models ◽

Climate Projections ◽

Flooding Regime ◽

Key Factor ◽

Inundation Duration ◽

Flooded Area ◽

Global Vegetation ◽

Ipcc Ar4

Abstract. Floodplain forests, namely the Várzea and Igapó, cover an area of more than 97 000 km2. A key factor for their function and diversity is annual flooding. Increasing air temperature and higher precipitation variability caused by climate change are expected to shift the flooding regime during this century, and thereby impact floodplain ecosystems, their biodiversity and riverine ecosystem services. To assess the effects of climate change on the flooding regime, we use the Dynamic Global Vegetation and Hydrology Model LPJmL, enhanced by a scheme that realistically simulates monthly flooded area. Simulation results of discharge and inundation under contemporary conditions compare well against site-level measurements and observations. The changes of calculated inundation duration and area under climate change projections from 24 IPCC AR4 climate models differ regionally towards the end of the 21st century. In all, 70% of the 24 climate projections agree on an increase of flooded area in about one third of the basin. Inundation duration increases dramatically by on average three months in western and around one month in eastern Amazonia. The time of high- and low-water peak shifts by up to three months. Additionally, we find a decrease in the number of extremely dry years and in the probability of the occurrence of three consecutive extremely dry years. The total number of extremely wet years does not change drastically but the probability of three consecutive extremely wet years decreases by up to 30% in the east and increases by up to 25% in the west. These changes implicate significant shifts in regional vegetation and climate, and will dramatically alter carbon and water cycles.

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Projected changes of alpine grassland carbon dynamics in response to climate change and elevated CO2concentrations under Representative Concentration Pathways (RCP) scenarios

10.1101/595926 ◽

2019 ◽

Author(s):

Pengfei Han ◽

Xiaohui Lin ◽

Wen Zhang ◽

Guocheng Wang

Keyword(s):

Climate Change ◽

Tibetan Plateau ◽

Carbon Cycle ◽

Carbon Budget ◽

Carbon Fluxes ◽

Carbon Dynamics ◽

Alpine Grassland ◽

The Tibetan Plateau ◽

Rcp Scenarios ◽

Representative Concentration Pathways

AbstractThe Tibetan Plateau is an important component of the global carbon cycle due to the large permafrost carbon pool and its vulnerability to climate warming. The Tibetan Plateau has experienced a noticeable warming over the past few decades and is projected to continue warming in the future. However, the direction and magnitude of carbon fluxes responses to climate change and elevated CO2concentration under Representative Concentration Pathways (RCP) scenarios in the Tibetan Plateau grassland are poorly known. Here, we used a calibrated and validated biogeochemistry model, CENTURY, to quantify the contributions of climate change and elevated CO2on the future carbon budget in the alpine grassland under three RCP scenarios. Though the Tibetan Plateau grassland was projected a net carbon sink of 16 ~ 25 Tg C yr-1in the 21st century, the capacity of carbon sequestration was predicted to decrease gradually because climate-driven increases in heterotrophic respiration (Rh) (with linear slopes 0.49 ~ 1.62 g C m-2yr-1) was greater than the net primary production (NPP) (0.35 ~ 1.52 g C m-2yr-1). However, the elevated CO2contributed more to plant growth (1.9% ~ 7.3%) than decomposition (1.7% ~ 6.1%), which could offset the warming-induced carbon loss. The interannual and decadal-scale dynamics of the carbon fluxes in the alpine grassland were primarily controlled by temperature, while the role of precipitation became increasingly important in modulating carbon cycle. The strengthened correlation between precipitation and carbon budget suggested that further research should consider the performance of precipitation in evaluating carbon dynamics in a warmer climate scenario.

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The Response of the Northwest Atlantic Ocean to Climate Change

Journal of Climate ◽

10.1175/jcli-d-19-0117.1 ◽

2020 ◽

Vol 33 (2) ◽

pp. 405-428 ◽

Cited By ~ 4

Author(s):

Michael A. Alexander ◽

Sang-ik Shin ◽

James D. Scott ◽

Enrique Curchitser ◽

Charles Stock

Keyword(s):

Climate Change ◽

High Resolution ◽

Atlantic Ocean ◽

Gulf Stream ◽

Large Scale ◽

Climate Models ◽

Gulf Of Maine ◽

Global Climate Models ◽

The Other ◽

Surface Salinity

AbstractROMS, a high-resolution regional ocean model, was used to study how climate change may affect the northwestern Atlantic Ocean. A control (CTRL) simulation was conducted for the recent past (1976–2005), and simulations with additional forcing at the surface and lateral boundaries, obtained from three different global climate models (GCMs) using the RCP8.5 scenario, were conducted to represent the future (2070–99). The climate change response was obtained from the difference between the CTRL and each of the three future simulations. All three ROMS simulations indicated large increases in sea surface temperatures (SSTs) over most of the domain except off the eastern U.S. seaboard resulting from weakening of the Gulf Stream. There are also substantial intermodel differences in the response, including a southward shift of the Gulf Stream in one simulation and a slight northward shift in the other two, with corresponding changes in eddy activity. The depth of maximum warming varied among the three simulations, resulting in differences in the bottom temperature response in coastal regions, including the Gulf of Maine and the West Florida Shelf. The surface salinity decreased in the northern part of the domain and increased in the south in all three experiments, although the freshening extended much farther south in one ROMS simulation relative to the other two, and also relative to the GCM that provided the large-scale forcing. Thus, while high resolution allows for a better representation of currents and bathymetry, the response to climate change can vary considerably depending on the large-scale forcing.

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Traces of sunlight in carbon biochemistry of shallow subarctic lakes

10.5194/egusphere-egu2020-15070 ◽

2020 ◽

Author(s):

Marttiina Rantala ◽

Henriikka Kivilä ◽

Carsten Meyer-Jacob ◽

Maxime Wauthy ◽

Milla Rautio ◽

...

Keyword(s):

Climate Change ◽

Organic Carbon ◽

Time Scales ◽

Carbon Pools ◽

Uv Spectrum ◽

Subarctic Lakes ◽

Climate Fluctuations ◽

Underwater Light ◽

Long Time ◽

Experimental Treatments

<p>Sunlight fuels the drawdown and evasion of carbon in shallow northern lakes. Amplified polar warming is altering the sunlit transport and transformation of aquatic carbon at an alarming rate entailing potential for climate feedbacks. We combined experimental and retrospective approaches to explore the synoptic interlinks between underwater light, aquatic carbon biochemistry, landscape carbon cycling and climate change in two shallow subarctic lakes with divergent light and carbon regime (a clear lake low in organic carbon and a dark organic rich lake). In situ enclosures (treatments under full sunlight, sunlight without the ultraviolet [UV] spectrum, no light) were first deployed on the lakes to decipher the effect of photochemical alteration on the spectral, elemental and isotopic properties of lake water organic carbon pools under short term (four weeks) exposure. We then focused on elemental, isotopic and spectral fingerprints archived in the sediments of the lakes to trace coeval variability in aquatic primary production, terrestrial carbon transport, and underwater light under centennial climate fluctuations. We observed distinct differences in carbon biochemistry between the experimental treatments illustrating the importance of sunlight, and particularly the UV spectrum, in shaping the carbon pools of the lakes already over short time scales. Over the past centennia, sediment biogeochemical composition carried signatures of change in carbon origins (algal vs terrestrial) and shifting underwater light regime. The results shed light on how climate change and sunlight shape carbon flows in shallow northern lakes over short and long time scales.</p>

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Modeling the change in soil organic carbon of grassland in response to climate change: Effects of measured versus modelled carbon pools for initializing the Rothamsted Carbon model

Agriculture Ecosystems & Environment ◽

10.1016/j.agee.2010.12.018 ◽

2011 ◽

Vol 140 (3-4) ◽

pp. 372-381 ◽

Cited By ~ 48

Author(s):

Xianli Xu ◽

Wen Liu ◽

Gerard Kiely

Keyword(s):

Climate Change ◽

Organic Carbon ◽

Soil Organic Carbon ◽

Carbon Pools ◽

Climate Change Effects ◽

Rothamsted Carbon Model

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Potential effects of climate change on inundation patterns in the Amazon Basin

Hydrology and Earth System Sciences Discussions ◽

10.5194/hessd-9-261-2012 ◽

2012 ◽

Vol 9 (1) ◽

pp. 261-300 ◽

Cited By ~ 5

Author(s):

F. Langerwisch ◽

S. Rost ◽

D. Gerten ◽

B. Poulter ◽

A. Rammig ◽

...

Keyword(s):

Climate Change ◽

Amazon Basin ◽

Climate Models ◽

Flooding Regime ◽

Inundation Area ◽

Key Factor ◽

Inundation Duration ◽

Flooded Area ◽

Global Vegetation ◽

Ipcc Ar4

Abstract. A key factor for the functioning and diversity of Amazonian rain forests is annual flooding. However, increasing air temperature and higher precipitation variability, caused by climate change, are expected to shift the flooding regime, and thereby negatively impact floodplain ecosystems, their biodiversity and riverine ecosystem services during this century. To assess the effects of climate changes on the flooding regime, we use the Dynamic Global Vegetation and Hydrology Model LPJmL, enhanced by a scheme that realistically simulates floodable area and inundation. Regarding hydrograph and inundation area, simulation results under contemporary conditions compare well against observations. The changes of calculated river discharge and inundation, under climate change projections from 24 IPCC AR4 climate models, differ regionally towards the end of the 21st century. Flooded area increases in about one third of the basin, with a probability larger than 70%. Inundation duration increases dramatically by on average three months in Western and around one month in Eastern Amazonia. The time of high- and low-water-peak shifts by up to three months. We find a slight decrease in the number of extremely dry years as well as a decrease of the probability of the occurrence of three consecutive extremely dry years. The total number of extremely wet years does not change drastically but the probability of three consecutive extremely wet years decreases by up to 30% in the East and increases by up to 25% in the West. These changes implicate significant shifts in regional vegetation and climate, and will dramatically alter carbon and water cycles.

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