Cycling of carbon and water in mountain ecosystems under changing climate and land use (CYCLAMEN)

<p>Land ecosystems presently sequester around 25% of the carbon dioxide (CO2) that is emitted into the atmosphere by human activity and thus, along with the oceans (absorbing a similar fraction), slow down the increase of atmospheric CO2. Whether land ecosystems will be able to continue to sequester atmospheric CO2 at similar rates in the future or whether carbon cycle-climate feedbacks will cause the land sink to saturate or even turn into a source, is a topic of controversial discussion. While taking up CO2 through the stomata, plants inevitably lose water through transpiration. Terrestrial evapotranspiration (ET) can have a feedback to (local) precipitation and therefore modulate near-surface climate. The terrestrial carbon and water cycles are highly connected and controlled by complex interactions between biological and abiotic drivers. Mountain ecosystems in the European Alps are a hot spot of climate and land-use changes. Over the last century, temperatures have increased in the region with a rate double that of the global average and are expected to rise rapidly. In addition, precipitation changes are highly complex with an increasing and a decreasing trend in the northern and southern Alps, respectively and different seasonal patterns. Socio-economic development in the Alps during the past centuries have caused large-scale changes in land-use and its intensity, which has contributed to the uncertainty about future land-atmosphere interactions. The objective of the CYCLAMEN project is to quantify and project the resilience and vulnerability of carbon and water cycling in North and South Tyrol. We aim at providing information for predicting likely future changes in climate and land-use over the region.</p><p>In the study we used a comprehensive and multidisciplinary approach to model biosphere-atmosphere interactions in the Alps. Data from eddy covariance stations spread across the region were chosen to test and calibrate the biosphere model SiB4. The meteorological data from the same stations was used to train a stochastic Weather Generator and simulate weather conditions under climate scenarios RCP8.5 and RCP2.6 until 2100. To account for future land- use/ land- cover (LULC) changes the SPA-LUCC model was used. Both the simulated weather conditions and the expected LULC were fed back to the SiB4 model to calculate ecosystem parameters, including carbon dioxide net ecosystem exchange and evapotranspiration. In parallel, an enhanced thermal remote sensing dataset was produced, specifically adapted for mountainous areas. This dataset will be the main driver for modelling ET with an energy balance model whose output will be cross compared with the one of the biosphere model SiB4.</p>

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Inter-comparison of two land-surface models applied at different scales and their feedbacks while coupled with a regional climate model

Hydrology and Earth System Sciences ◽

10.5194/hess-16-1017-2012 ◽

2012 ◽

Vol 16 (3) ◽

pp. 1017-1031 ◽

Cited By ~ 11

Author(s):

F. Zabel ◽

W. Mauser ◽

T. Marke ◽

A. Pfeiffer ◽

G. Zängl ◽

...

Keyword(s):

Land Use ◽

Land Surface ◽

Regional Climate ◽

Moderate Increase ◽

Net Radiation ◽

Land Surface Models ◽

Near Surface ◽

Temporal Behaviour ◽

Surface Models ◽

The Alps

Abstract. Downstream models are often used in order to study regional impacts of climate and climate change on the land surface. For this purpose, they are usually driven offline (i.e., 1-way) with results from regional climate models (RCMs). However, the offline approach does not allow for feedbacks between these models. Thereby, the land surface of the downstream model is usually completely different to the land surface which is used within the RCM. Thus, this study aims at investigating the inconsistencies that arise when driving a downstream model offline instead of interactively coupled with the RCM, due to different feedbacks from the use of different land surface models (LSM). Therefore, two physically based LSMs which developed from different disciplinary backgrounds are compared in our study: while the NOAH-LSM was developed for the use within RCMs, PROMET was originally developed to answer hydrological questions on the local to regional scale. Thereby, the models use different physical formulations on different spatial scales and different parameterizations of the same land surface processes that lead to inconsistencies when driving PROMET offline with RCM output. Processes that contribute to these inconsistencies are, as described in this study, net radiation due to land use related albedo and emissivity differences, the redistribution of this net radiation over sensible and latent heat, for example, due to different assumptions about land use impermeability or soil hydraulic reasons caused by different plant and soil parameterizations. As a result, simulated evapotranspiration, e.g., shows considerable differences of max. 280 mm yr−1. For a full interactive coupling (i.e., 2-way) between PROMET and the atmospheric part of the RCM, PROMET returns the land surface energy fluxes to the RCM and, thus, provides the lower boundary conditions for the RCM subsequently. Accordingly, the RCM responses to the replacement of the LSM with overall increased annual mean near surface air temperature (+1 K) and less annual precipitation (−56 mm) with different spatial and temporal behaviour. Finally, feedbacks can set up positive and negative effects on simulated evapotranspiration, resulting in a decrease of evapotranspiration South of the Alps a moderate increase North of the Alps. The inconsistencies are quantified and account for up to 30% from July to Semptember when focused to an area around Milan, Italy.

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Historical Land Uses and Their Changes in the European Alps

Environmental Science ◽

10.1093/obo/9780199363445-0114 ◽

2019 ◽

Author(s):

Ulrike Tappeiner ◽

Erich Tasser

Keyword(s):

Land Use ◽

20Th Century ◽

Land Reclamation ◽

Alpine Region ◽

Ecosystem Functions ◽

Mountain Range ◽

European Alps ◽

Ligurian Sea ◽

Arable Farming ◽

The Alps

The Alps are the highest and largest mountain range in Europe. They extend from the Ligurian Sea to the Pannonian Basin in an arc 744 miles (1,200 km) long and between 93 and 155 miles (150–250 km) wide. The settlement history of this large European landscape is closely linked to the settlement of Europe as a whole, whereby the inner Alpine region was not permanently settled until around 4500 bce because of topographical and climatic disadvantages. Dense forest cover initially made it difficult to use large grazing areas, but transhumance gradually developed in the Alpine region when the animals spent their summers high up in the mountains and their winters in the valleys. At about the same time, the Alpine self-sufficiency economy of arable farming and livestock breeding was added, which made permanent settlement possible. However, the most intensive settlement and land reclamation advance took place in the Middle Ages. In the 19th century, industrialization reached the Alpine region a little delayed, and globalization in the middle of the 20th century. This also led to a fundamental change in society. The previous agricultural society was replaced by the service society of the 20th century. Developments since the late 1950s have taken place against the background of developments in the European Union (EU) as a whole, above all the Common Agricultural Policy and the European Spatial Development Perspective (ESDP), but these developments were and still are influenced by additional agreements specific to the Alps, such as the Alpine Convention, the Alpine Protection Commission (CIPRA), and the Alpine Working Community (Arge Alp). All these factors mean that historical and current development of land use in the Alpine region has been and is always linked to developments in Europe. Many studies on land use in the Alpine region should therefore be seen in this context. Moreover, past land use often has long-lasting legacy effects on ecosystems and their development. Therefore, in this article we deal not only with historical land use but also with current and future developments and their impacts on ecosystem functions and services.

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Recent trends and drivers of regional sources and sinks of carbon dioxide

Biogeosciences ◽

10.5194/bg-12-653-2015 ◽

2015 ◽

Vol 12 (3) ◽

pp. 653-679 ◽

Cited By ~ 323

Author(s):

S. Sitch ◽

P. Friedlingstein ◽

N. Gruber ◽

S. D. Jones ◽

G. Murray-Tortarolo ◽

...

Keyword(s):

Carbon Dioxide ◽

Land Use ◽

Land Cover ◽

General Circulation ◽

Significant Trend ◽

Atmospheric Co2 ◽

Plant Production ◽

Land Cover Changes ◽

Growing Season Length ◽

Ocean Models

Abstract. The land and ocean absorb on average just over half of the anthropogenic emissions of carbon dioxide (CO2) every year. These CO2 "sinks" are modulated by climate change and variability. Here we use a suite of nine dynamic global vegetation models (DGVMs) and four ocean biogeochemical general circulation models (OBGCMs) to estimate trends driven by global and regional climate and atmospheric CO2 in land and oceanic CO2 exchanges with the atmosphere over the period 1990–2009, to attribute these trends to underlying processes in the models, and to quantify the uncertainty and level of inter-model agreement. The models were forced with reconstructed climate fields and observed global atmospheric CO2; land use and land cover changes are not included for the DGVMs. Over the period 1990–2009, the DGVMs simulate a mean global land carbon sink of −2.4 ± 0.7 Pg C yr−1 with a small significant trend of −0.06 ± 0.03 Pg C yr−2 (increasing sink). Over the more limited period 1990–2004, the ocean models simulate a mean ocean sink of −2.2 ± 0.2 Pg C yr−1 with a trend in the net C uptake that is indistinguishable from zero (−0.01 ± 0.02 Pg C yr−2). The two ocean models that extended the simulations until 2009 suggest a slightly stronger, but still small, trend of −0.02 ± 0.01 Pg C yr−2. Trends from land and ocean models compare favourably to the land greenness trends from remote sensing, atmospheric inversion results, and the residual land sink required to close the global carbon budget. Trends in the land sink are driven by increasing net primary production (NPP), whose statistically significant trend of 0.22 ± 0.08 Pg C yr−2 exceeds a significant trend in heterotrophic respiration of 0.16 ± 0.05 Pg C yr−2 – primarily as a consequence of widespread CO2 fertilisation of plant production. Most of the land-based trend in simulated net carbon uptake originates from natural ecosystems in the tropics (−0.04 ± 0.01 Pg C yr−2), with almost no trend over the northern land region, where recent warming and reduced rainfall offsets the positive impact of elevated atmospheric CO2 and changes in growing season length on carbon storage. The small uptake trend in the ocean models emerges because climate variability and change, and in particular increasing sea surface temperatures, tend to counter\\-act the trend in ocean uptake driven by the increase in atmospheric CO2. Large uncertainty remains in the magnitude and sign of modelled carbon trends in several regions, as well as regarding the influence of land use and land cover changes on regional trends.

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Future snowfall in the Alps: projections based on the EURO-CORDEX regional climate models

The Cryosphere ◽

10.5194/tc-12-1-2018 ◽

2018 ◽

Vol 12 (1) ◽

pp. 1-24 ◽

Cited By ~ 31

Author(s):

Prisco Frei ◽

Sven Kotlarski ◽

Mark A. Liniger ◽

Christoph Schär

Keyword(s):

Climate Models ◽

Climate Model ◽

Regional Climate ◽

Regional Climate Models ◽

European Alps ◽

Emission Scenarios ◽

Heavy Snowfall ◽

Rcp Scenarios ◽

Near Surface ◽

The Alps

Abstract. Twenty-first century snowfall changes over the European Alps are assessed based on high-resolution regional climate model (RCM) data made available through the EURO-CORDEX initiative. Fourteen different combinations of global and regional climate models with a target resolution of 12 km and two different emission scenarios are considered. As raw snowfall amounts are not provided by all RCMs, a newly developed method to separate snowfall from total precipitation based on near-surface temperature conditions and accounting for subgrid-scale topographic variability is employed. The evaluation of the simulated snowfall amounts against an observation-based reference indicates the ability of RCMs to capture the main characteristics of the snowfall seasonal cycle and its elevation dependency but also reveals considerable positive biases especially at high elevations. These biases can partly be removed by the application of a dedicated RCM bias adjustment that separately considers temperature and precipitation biases.Snowfall projections reveal a robust signal of decreasing snowfall amounts over most parts of the Alps for both emission scenarios. Domain and multi-model mean decreases in mean September–May snowfall by the end of the century amount to −25 and −45 % for representative concentration pathway (RCP) scenarios RCP4.5 and RCP8.5, respectively. Snowfall in low-lying areas in the Alpine forelands could be reduced by more than −80 %. These decreases are driven by the projected warming and are strongly connected to an important decrease in snowfall frequency and snowfall fraction and are also apparent for heavy snowfall events. In contrast, high-elevation regions could experience slight snowfall increases in midwinter for both emission scenarios despite the general decrease in the snowfall fraction. These increases in mean and heavy snowfall can be explained by a general increase in winter precipitation and by the fact that, with increasing temperatures, climatologically cold areas are shifted into a temperature interval which favours higher snowfall intensities. In general, percentage changes in snowfall indices are robust with respect to the RCM postprocessing strategy employed: similar results are obtained for raw, separated, and separated–bias-adjusted snowfall amounts. Absolute changes, however, can differ among these three methods.

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Global and regional effects of land-use change on climate in 21st century simulations with interactive carbon cycle

Earth System Dynamics Discussions ◽

10.5194/esdd-5-443-2014 ◽

2014 ◽

Vol 5 (1) ◽

pp. 443-472 ◽

Cited By ~ 11

Author(s):

L. R. Boysen ◽

V. Brovkin ◽

V. K. Arora ◽

P. Cadule ◽

N. de Noblet-Ducoudré ◽

...

Keyword(s):

Land Use ◽

Land Cover ◽

Land Cover Change ◽

21St Century ◽

Statistical Significance ◽

Regional Scale ◽

Atmospheric Co2 ◽

Carbon Gain ◽

Near Surface ◽

Effects Of Land Use

Abstract. Biogeophysical (BGP) and biogeochemical (BGC) effects of land-use and land cover change (LULCC) are separated at the global and regional scales in new interactive CO2 simulations for the 21st century. Results from four Earth System models (ESMs) are analyzed for the future RCP8.5 scenario from simulations with and without land-use and land cover change (LULCC) contributing to the Land-Use and Climate, IDentification of robust impacts (LUCID) project. Over the period, 2006–2100, LULCC causes the atmospheric CO2 concentration to increase by 12, 22, and 66 ppm in CanESM2, MIROC-ESM, and MPI-ESM-LR, respectively. Statistically significant changes in global near-surface temperature are found in three models with a BGC-induced global mean annual warming between 0.07 and 0.23 K. BGP-induced responses are simulated by three models in areas of intense LULCC of varying sign and magnitude (between −0.47 and 0.10 K). Global land carbon losses due to LULCC are simulated by all models: 218, 57, 35 and 34 Gt C by MPI-ESM-LR, MIROC-ESM, IPSL-CM5A-LR and CanESM2, respectively. On the contrary, the CO2-fertilization effect caused by elevated atmospheric CO2 concentrations due to LULCC leads to a land carbon gain of 39 Gt C in MPI-ESM-LR and is almost negligible in the other models. A substantial part of the spread in models' responses to LULCC is attributed to the differences in implementation of LULCC (e.g. whether pastures or crops are simulated explicitly) and the simulation of specific processes. Simple idealized experiments with clear protocols for implementing LULCC in ESMs are needed to increase the understanding of model responses and the statistical significance of results, especially, when analyzing the regional-scale impacts of LULCC.

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Trends and drivers of regional sources and sinks of carbon dioxide over the past two decades

Biogeosciences Discussions ◽

10.5194/bgd-10-20113-2013 ◽

2013 ◽

Vol 10 (12) ◽

pp. 20113-20177 ◽

Cited By ~ 42

Author(s):

S. Sitch ◽

P. Friedlingstein ◽

N. Gruber ◽

S. D. Jones ◽

G. Murray-Tortarolo ◽

...

Keyword(s):

Carbon Dioxide ◽

Land Use ◽

Land Cover ◽

General Circulation ◽

Net Primary Production ◽

Significant Trend ◽

Atmospheric Co2 ◽

Plant Production ◽

Land Cover Changes ◽

Ocean Models

Abstract. The land and ocean absorb on average over half of the anthropogenic emissions of carbon dioxide (CO2) every year. These CO2 "sinks" are modulated by climate change and variability. Here we use a suite of nine Dynamic Global Vegetation Models (DGVMs) and four Ocean Biogeochemical General Circulation Models (OBGCMs) to quantify the global and regional climate and atmospheric CO2 – driven trends in land and oceanic CO2 exchanges with the atmosphere over the period 1990–2009, attribute these trends to underlying processes, and quantify the uncertainty and level of model agreement. The models were forced with reconstructed climate fields and observed global atmospheric CO2; Land Use and Land Cover Changes are not included for the DGVMs. Over the period 1990–2009, the DGVMs simulate a mean global land carbon sink of −2.4 ± 0.7 Pg C yr−1 with a small significant trend of −0.06 ± 0.03 Pg C yr−2 (increasing sink). Over the more limited period 1990–2004, the ocean models simulate a mean ocean sink of –2.2 ± 0.2 Pg C yr–1 with a trend in the net C uptake that is indistinguishable from zero (−0.01 ± 0.02 Pg C yr−2). The two ocean models that extended the simulations until 2009 suggest a slightly stronger, but still small trend of −0.02 ± 0.01 Pg C yr−2. Trends from land and ocean models compare favourably to the land greenness trends from remote sensing, atmospheric inversion results, and the residual land sink required to close the global carbon budget. Trends in the land sink are driven by increasing net primary production (NPP) whose statistically significant trend of 0.22 ± 0.08 Pg C yr−2 exceeds a significant trend in heterotrophic respiration of 0.16 ± 0.05 Pg C yr−2 – primarily as a consequence of wide-spread CO2 fertilisation of plant production. Most of the land-based trend in simulated net carbon uptake originates from natural ecosystems in the tropics (−0.04 ± 0.01 Pg C yr−2), with almost no trend over the northern land region, where recent warming and reduced rainfall offsets the positive impact of elevated atmospheric CO2 on carbon storage. The small uptake trend in the ocean models emerges because climate variability and change, and in particular increasing sea surface temperatures, tend to counteract the trend in ocean uptake driven by the increase in atmospheric CO2. Large uncertainty remains in the magnitude and sign of modelled carbon trends in several regions, and on the influence of land use and land cover changes on regional trends.

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Global and regional effects of land-use change on climate in 21st century simulations with interactive carbon cycle

Earth System Dynamics ◽

10.5194/esd-5-309-2014 ◽

2014 ◽

Vol 5 (2) ◽

pp. 309-319 ◽

Cited By ~ 40

Author(s):

L. R. Boysen ◽

V. Brovkin ◽

V. K. Arora ◽

P. Cadule ◽

N. de Noblet-Ducoudré ◽

...

Keyword(s):

Land Use ◽

Land Cover ◽

Land Cover Change ◽

21St Century ◽

Statistical Significance ◽

Regional Scale ◽

Carbon Pool ◽

Atmospheric Co2 ◽

Near Surface ◽

Effects Of Land Use

Abstract. Biogeophysical (BGP) and biogeochemical (BGC) effects of land-use and land cover change (LULCC) are separated at the global and regional scales in new interactive CO2 simulations for the 21st century. Results from four earth system models (ESMs) are analyzed for the future RCP8.5 scenario from simulations with and without land-use and land cover change (LULCC), contributing to the Land-Use and Climate, IDentification of robust impacts (LUCID) project. Over the period 2006–2100, LULCC causes the atmospheric CO2 concentration to increase by 12, 22, and 66 ppm in CanESM2, MIROC-ESM, and MPI-ESM-LR, respectively. Statistically significant changes in global near-surface temperature are found in three models with a BGC-induced global mean annual warming between 0.07 and 0.23 K. BGP-induced responses are simulated by three models in areas of intense LULCC of varying sign and magnitude (between −0.47 and 0.10 K). Modifications of the land carbon pool by LULCC are disentangled in accordance with processes that can lead to increases and decreases in this carbon pool. Global land carbon losses due to LULCC are simulated by all models: 218, 57, 35 and 34 Gt C by MPI-ESM-LR, MIROC-ESM, IPSL-CM5A-LR and CanESM2, respectively. On the contrary, the CO2-fertilization effect caused by elevated atmospheric CO2 concentrations due to LULCC leads to a land carbon gain of 39 Gt C in MPI-ESM-LR and is almost negligible in the other models. A substantial part of the spread in models' responses to LULCC is attributed to the differences in implementation of LULCC (e.g., whether pastures or crops are simulated explicitly) and the simulation of specific processes. Simple idealized experiments with clear protocols for implementing LULCC in ESMs are needed to increase the understanding of model responses and the statistical significance of results, especially when analyzing the regional-scale impacts of LULCC.

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Snowfall in the Alps: Evaluation and projections based on the EURO-CORDEX regional climate models

10.5194/tc-2017-7 ◽

2017 ◽

Cited By ~ 2

Author(s):

Prisco Frei ◽

Sven Kotlarski ◽

Mark A. Liniger ◽

Christoph Schär

Keyword(s):

Climate Models ◽

Climate Model ◽

Regional Climate ◽

Regional Climate Models ◽

High Elevation ◽

European Alps ◽

Emission Scenarios ◽

Heavy Snowfall ◽

Near Surface ◽

The Alps

Abstract. Twenty-first century snowfall changes over the European Alps are assessed based on high-resolution regional climate model (RCM) data made available through the EURO-CORDEX initiative. Fourteen different combinations of global and regional climate models with a target resolution of 12 km, and two different emission scenarios are considered. A newly developed method to separate snowfall from total precipitation based on near-surface temperature conditions and accounting for subgrid topographic variability is employed. The evaluation of the simulated snowfall amounts against an observation-based reference indicates the ability of RCMs to capture the main characteristics of the snowfall seasonal cycle and its elevation dependency, but also reveals considerable positive biases especially at high elevations. These biases can partly be removed by the application of a dedicated RCM bias correction that separately considers temperature and precipitation biases. Snowfall projections reveal a robust signal of decreasing snowfall amounts over most parts of the Alps for both emission scenarios. Domain and multimodel-mean decreases of mean September-May snowfall by the end of the century amount to −25 % and −45 % for RCP4.5 and RCP8.5, respectively. Snowfall in low-lying areas in the Alpine forelands could be reduced by more than −80 %. These decreases are driven by the projected warming and are strongly connected to an important decrease of snowfall frequency and snowfall fraction and are also apparent for heavy snowfall events. In contrast, high-elevation regions could experience slight snowfall increases in mid-winter for both emission scenarios despite the general decrease of the snowfall fraction. These increases in mean and heavy snowfall can be explained by a general increase of winter precipitation and by the fact that, with increasing temperatures, climatologically cold areas are shifted into a temperature interval which favours higher snowfall intensities.

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