Articles | Volume 16, issue 16
Research article 30 Aug 2019
Research article | 30 Aug 2019
Dissolved organic nutrients dominate melting surface ice of the Dark Zone (Greenland Ice Sheet)
Alexandra T. Holland et al.
No articles found.
Miranda J. Nicholes, Christopher Williamson, Martyn Tranter, Alexandra Holland, Marian Yallop, and Alexandre Anesio
Publication in BG not foreseenShort summary
This incubation experiment assessed the role of solar radiation and heterotrophic bacteria in the degradation of organic carbon in surface ice of the Greenland Ice Sheet. Although ultraviolet radiation was found to alter carbon composition, heterotrophic degradation caused the greatest changes to both carbon composition and quantity. Both processes are likely interlinked within the surface ice and are fundamental to controlling the composition of carbon exported to downstream environments.
Andrew J. Tedstone, Joseph M. Cook, Christopher J. Williamson, Stefan Hofer, Jenine McCutcheon, Tristram Irvine-Fynn, Thomas Gribbin, and Martyn Tranter
The Cryosphere, 14, 521–538,Short summary
Albedo describes how much light that hits a surface is reflected without being absorbed. Low-albedo ice surfaces melt more quickly. There are large differences in the albedo of bare-ice areas of the Greenland Ice Sheet. They are caused both by dark glacier algae and by the condition of the underlying ice. Changes occur over centimetres to metres, so satellites do not always detect real albedo changes. Estimates of melt made using satellite measurements therefore tend to be underestimates.
Joseph M. Cook, Andrew J. Tedstone, Christopher Williamson, Jenine McCutcheon, Andrew J. Hodson, Archana Dayal, McKenzie Skiles, Stefan Hofer, Robert Bryant, Owen McAree, Andrew McGonigle, Jonathan Ryan, Alexandre M. Anesio, Tristram D. L. Irvine-Fynn, Alun Hubbard, Edward Hanna, Mark Flanner, Sathish Mayanna, Liane G. Benning, Dirk van As, Marian Yallop, James B. McQuaid, Thomas Gribbin, and Martyn Tranter
The Cryosphere, 14, 309–330,Short summary
Melting of the Greenland Ice Sheet (GrIS) is a major source of uncertainty for sea level rise projections. Ice-darkening due to the growth of algae has been recognized as a potential accelerator of melting. This paper measures and models the algae-driven ice melting and maps the algae over the ice sheet for the first time. We estimate that as much as 13 % total runoff from the south-western GrIS can be attributed to these algae, showing that they must be included in future mass balance models.
Joseph M. Cook, Andrew J. Hodson, Alex S. Gardner, Mark Flanner, Andrew J. Tedstone, Christopher Williamson, Tristram D. L. Irvine-Fynn, Johan Nilsson, Robert Bryant, and Martyn Tranter
The Cryosphere, 11, 2611–2632,Short summary
Biological growth darkens snow and ice, causing it to melt faster. This is often referred to as
bioalbedo. Quantifying bioalbedo has not been achieved because of difficulties in isolating the biological contribution from the optical properties of ice and snow, and from inorganic impurities in field studies. In this paper, we provide a physical model that enables bioalbedo to be quantified from first principles and we use it to guide future field studies.
Andrew J. Tedstone, Jonathan L. Bamber, Joseph M. Cook, Christopher J. Williamson, Xavier Fettweis, Andrew J. Hodson, and Martyn Tranter
The Cryosphere, 11, 2491–2506,Short summary
The bare ice albedo of the south-west Greenland ice sheet varies dramatically between years. The reasons are unclear but likely involve darkening by inorganic particulates, cryoconite and ice algae. We use satellite imagery to examine dark ice dynamics and climate model outputs to find likely climatological controls. Outcropping particulates can explain the spatial extent of dark ice, but the darkening itself is likely due to ice algae growth controlled by meltwater and light availability.
Christopher James Williamson, Rupert Perkins, Matthew Voller, Marian Louise Yallop, and Juliet Brodie
Biogeosciences, 14, 4485–4498,Short summary
Red calcified seaweeds in UK rock pools have seasonal patterns in growth and photosynthesis driven by seawater temperature, light and the chemistry of rock pool water. This is important given future changes in environmental factors such as climate change and ocean acidification. Photosynthesis and calcification are strongly coupled and depend on light and temperature, whilst dissolution is regulated by rock pool water chemistry and is thus particularly vulnerable to environmental change.
James A. Bradley, Sandra Arndt, Marie Šabacká, Liane G. Benning, Gary L. Barker, Joshua J. Blacker, Marian L. Yallop, Katherine E. Wright, Christopher M. Bellas, Jonathan Telling, Martyn Tranter, and Alexandre M. Anesio
Biogeosciences, 13, 5677–5696,Short summary
Soil development following glacier retreat was characterized using a novel integrated field, laboratory and modelling approach in Svalbard. We found community shifts in bacteria, which were responsible for driving cycles in carbon and nutrients. Allochthonous inputs were also important in sustaining bacterial production. This study shows how an integrated model–data approach can improve understanding and obtain a more holistic picture of soil development in an increasingly ice-free future world.
Robert Raiswell, Jon R. Hawkings, Liane G. Benning, Alex R. Baker, Ros Death, Samuel Albani, Natalie Mahowald, Michael D. Krom, Simon W. Poulton, Jemma Wadham, and Martyn Tranter
Biogeosciences, 13, 3887–3900,Short summary
Iron is an essential nutrient for plankton growth. One important source of iron is wind-blown dust. The polar oceans are remote from dust sources but melting icebergs supply sediment that contains iron which is potentially available to plankton. We show that iceberg sediments contain more potentially bioavailable iron than wind-blown dust. Iceberg sources will become increasingly important with climate change and increased plankton growth can remove more carbon dioxide from the atmosphere.
Emily C. O'Donnell, Jemma L. Wadham, Grzegorz P. Lis, Martyn Tranter, Amy E. Pickard, Marek Stibal, Paul Dewsbury, and Sean Fitzsimons
Biogeosciences, 13, 3833–3846,Short summary
We use a novel ion chromatographic analysis that provides the first identification and quantification of major low-molecular-weight dissolved organic carbon (LMW-DOC) compounds in basal ice. LMW-DOC concentrations were dependent on the bioavailability of the overridden organic carbon, which in turn was influenced by the type of overridden material. The overridden material may thus act as a direct (abiotic leaching) and indirect (microbial cycling) source of DOC to the subglacial environment.
Fotis Sgouridis, Andrew Stott, and Sami Ullah
Biogeosciences, 13, 1821–1835,Short summary
Soil denitrification is considered the most un-constrained process in the global N cycle due to uncertain in situ N2 flux measurements, particularly in natural and semi-natural terrestrial ecosystems. The 15N gas-flux method was adapted by lowering the 15N tracer application rate to 0.04–0.5 kg 15N ha−1. The minimum detectable flux rates were 4 μg N m−2 h−1 and 0.2 ng N m−2 h−1 for the N2 and N2O fluxes respectively. The acetylene inhibition technique underestimated denitrification rates by a factor of 4.
E. C. Lawson, J. L. Wadham, M. Tranter, M. Stibal, G. P. Lis, C. E. H. Butler, J. Laybourn-Parry, P. Nienow, D. Chandler, and P. Dewsbury
Biogeosciences, 11, 4015–4028,
Related subject area
Earth System Science/Response to Global Change: Climate ChangeOcean carbon uptake under aggressive emission mitigationEffects of Earth system feedbacks on the potential mitigation of large-scale tropical forest restorationWetter environment and increased grazing reduced the area burned in northern Eurasia from 2002 to 2016Physiological responses of Skeletonema costatum to the interactions of seawater acidification and the combination of photoperiod and temperatureTechnical note: Interpreting pH changesTiming of drought in the growing season and strong legacy effects determine the annual productivity of temperate grasses in a changing climateContrasting responses of woody and herbaceous vegetation to altered rainfall characteristics in the SahelSensitivity of 21st-century projected ocean new production changes to idealized biogeochemical model structureControls of ocean carbon cycle feedbacks from different ocean basins and meridional overturning in CMIP6Reduced growth with increased quotas of particulate organic and inorganic carbon in the coccolithophore Emiliania huxleyi under future ocean climate change conditionsOcean-related global change alters lipid biomarker production in common marine phytoplanktonMulti-decadal changes in structural complexity following mass coral mortality on a Caribbean reefStable isotopes track the ecological and biogeochemical legacy of mass mangrove forest dieback in the Gulf of Carpentaria, AustraliaGlobal climate response to idealized deforestation in CMIP6 modelsDoes drought advance the onset of autumn leaf senescence in temperate deciduous forest trees?Carbon–concentration and carbon–climate feedbacks in CMIP6 models and their comparison to CMIP5 modelsEcosystem physio-phenology revealed using circular statisticsUnderstanding the uncertainty in global forest carbon turnoverCharacterizing deepwater oxygen variability and seafloor community responses using a novel autonomous landerPhysical and biogeochemical impacts of RCP8.5 scenario in the Peru upwelling systemIs there warming in the pipeline? A multi-model analysis of the Zero Emissions Commitment from CO2Foraminiferal holobiont thermal tolerance under future warming – roommate problems or successful collaboration?Impacts of enhanced weathering on biomass production for negative emission technologies and soil hydrologyPotential predictability of marine ecosystem driversIs deoxygenation detectable before warming in the thermocline?Spatio-temporal variations and uncertainty in land surface modelling for high latitudes: univariate response analysisMicrostructure and composition of marine aggregates as co-determinants for vertical particulate organic carbon transfer in the global oceanQuantifying impacts of the 2018 drought on European ecosystems in comparison to 2003Reviews and syntheses: How do abiotic and biotic processes respond to climatic variations in the Nam Co catchment (Tibetan Plateau)?Simulation of factors affecting Emiliania huxleyi blooms in Arctic and sub-Arctic seas by CMIP5 climate models: model validation and selectionParticulate trace metal dynamics in response to increased CO2 and iron availability in a coastal mesocosm experimentZooplankton diel vertical migration and downward C flux into the oxygen minimum zone in the highly productive upwelling region off northern ChileA meta-analysis of microcosm experiments shows that dimethyl sulfide (DMS) production in polar waters is insensitive to ocean acidificationForest aboveground biomass stock and resilience in a tropical landscape of ThailandEnhanced Weathering and related element fluxes – a cropland mesocosm approachTrees do not always act their age: size-deterministic tree ring standardization for long-term trend estimation in shade-tolerant treesRapid environmental responses to climate-induced hydrographic changes in the Baltic Sea entranceTrend analysis of the airborne fraction and sink rate of anthropogenically released CO2Ideas and perspectives: Synergies from co-deployment of negative emission technologiesAssessment of time of emergence of anthropogenic deoxygenation and warming: insights from a CESM simulation from 850 to 2100 CEDispersal distances and migration rates at the arctic treeline in Siberia – a genetic and simulation-based studySimulating growth-based harvest adaptive to future climate changeMonitoring changes in forestry and seasonal snow using surface albedo during 1982–2016 as an indicatorOcean acidification reduces hardness and stiffness of the Portuguese oyster shell with impaired microstructure: a hierarchical analysisLegacies of past land use have a stronger effect on forest carbon exchange than future climate change in a temperate forest landscapeReviews and syntheses: Changing ecosystem influences on soil thermal regimes in northern high-latitude permafrost regionsVariable metabolic responses of Skagerrak invertebrates to low O2 and high CO2 scenariosOcean acidification increases the sensitivity of and variability in physiological responses of an intertidal limpet to thermal stressComparing soil carbon loss through respiration and leaching under extreme precipitation events in arid and semiarid grasslandsIncreasing coastal slump activity impacts the release of sediment and organic carbon into the Arctic Ocean
Sean M. Ridge and Galen A. McKinley
Biogeosciences, 18, 2711–2725,Short summary
Approximately 40 % of the CO2 emissions from fossil fuel combustion and cement production have been absorbed by the ocean. The goal of the UNFCCC Paris Agreement is to reduce humanity's emissions so as to limit global warming to no more than 2 °C, and ideally less than 1.5 °C. If we achieve this level of mitigation, the ocean's uptake of carbon will be strongly reduced. Excess carbon trapped in the near-surface ocean will begin to mix back to the surface and will limit additional uptake.
Alexander Koch, Chris Brierley, and Simon L. Lewis
Biogeosciences, 18, 2627–2647,Short summary
Estimates of large-scale tree planting and forest restoration as a carbon sequestration tool typically miss a crucial aspect: the Earth system response to the increased land carbon sink from new vegetation. We assess the impact of tropical forest restoration using an Earth system model under a scenario that limits warming to 2 °C. Almost two-thirds of the carbon impact of forest restoration is offset by negative carbon cycle feedbacks, suggesting a more modest benefit than in previous studies.
Wei Min Hao, Matthew C. Reeves, L. Scott Baggett, Yves Balkanski, Philippe Ciais, Bryce L. Nordgren, Alexander Petkov, Rachel E. Corley, Florent Mouillot, Shawn P. Urbanski, and Chao Yue
Biogeosciences, 18, 2559–2572,Short summary
We examined the trends in the spatial and temporal distribution of the area burned in northern Eurasia from 2002 to 2016. The annual area burned in this region declined by 53 % during the 15-year period under analysis. Grassland fires in Kazakhstan dominated the fire activity, comprising 47 % of the area burned but accounting for 84 % of the decline. A wetter climate and the increase in grazing livestock in Kazakhstan are the major factors contributing to the decline in the area burned.
Hangxiao Li, Tianpeng Xu, Jing Ma, Futian Li, and Juntian Xu
Biogeosciences, 18, 1439–1449,Short summary
Few studies have investigated effects of ocean acidification and seasonal changes in temperature and day length on marine diatoms. We cultured a marine diatom under two CO2 levels and three combinations of temperature and day length, simulating different seasons, to investigate combined effects of these factors. Acidification had contrasting effects under different combinations, indicating that the future ocean may show different effects on diatoms in different clusters of factors.
Andrea J. Fassbender, James C. Orr, and Andrew G. Dickson
Biogeosciences, 18, 1407–1415,Short summary
A decline in upper-ocean pH with time is typically ascribed to ocean acidification. A more quantitative interpretation is often confused by failing to recognize the implications of pH being a logarithmic transform of hydrogen ion concentration rather than an absolute measure. This can lead to an unwitting misinterpretation of pH data. We provide three real-world examples illustrating this and recommend the reporting of both hydrogen ion concentration and pH in studies of ocean chemical change.
Claudia Hahn, Andreas Lüscher, Sara Ernst-Hasler, Matthias Suter, and Ansgar Kahmen
Biogeosciences, 18, 585–604,Short summary
While existing studies focus on the immediate effects of drought events on grassland productivity, long-term effects are mostly neglected. But, to conclude universal outcomes, studies must consider comprehensive ecosystem mechanisms. In our study, we found that the resistance of growth rates to drought in grasses varies across seasons, and positive legacy effects of drought indicate a high resilience. The high resilience compensates for immediate drought effects on grasses to a large extent.
Wim Verbruggen, Guy Schurgers, Stéphanie Horion, Jonas Ardö, Paulo N. Bernardino, Bernard Cappelaere, Jérôme Demarty, Rasmus Fensholt, Laurent Kergoat, Thomas Sibret, Torbern Tagesson, and Hans Verbeeck
Biogeosciences, 18, 77–93,Short summary
A large part of Earth's land surface is covered by dryland ecosystems, which are subject to climate extremes that are projected to increase under future climate scenarios. By using a mathematical vegetation model, we studied the impact of single years of extreme rainfall on the vegetation in the Sahel. We found a contrasting response of grasses and trees to these extremes, strongly dependent on the way precipitation is spread over the rainy season, as well as a long-term impact on CO2 uptake.
Genevieve Jay Brett, Daniel B. Whitt, Matthew C. Long, Frank Bryan, Kate Feloy, and Kelvin J. Richards
Revised manuscript accepted for BGShort summary
We quantify one form of uncertainty in modeled 21st-century changes in phytoplankton growth. The supply of nutrients from deep to surface waters decreases in the warmer future ocean, but the effect on phytoplankton growth also depends on changes in available light, how much light and nutrient the plankton need, and how fast they can grow. These phytoplankton properties can be summarized as a biological timescale: when it is short, future growth decreases twice as much as when it is long.
Anna Katavouta and Richard G. Williams
Revised manuscript accepted for BGShort summary
Diagnostics of the latest generation earth system models reveal the ocean will continue to absorb a large fraction of the anthropogenic carbon released to the atmosphere in the next century, with the Atlantic Ocean storing a large amount of this carbon relative to its size. The ability of the ocean to absorb carbon will reduce in the future as the ocean warms and acidifies. This reduction is larger in the Atlantic Ocean due to a weakening of the meridional overturning with changes in climate.
Yong Zhang, Sinéad Collins, and Kunshan Gao
Biogeosciences, 17, 6357–6375,Short summary
Our results show that ocean acidification, warming, increased light exposure and reduced nutrient availability significantly reduce the growth rate but increase particulate organic and inorganic carbon in cells in the coccolithophore Emiliania huxleyi, indicating biogeochemical consequences of future ocean changes on the calcifying microalga. Concurrent changes in nutrient concentrations and pCO2 levels predominantly affected E. huxleyi growth, photosynthetic carbon fixation and calcification.
Rong Bi, Stefanie M. H. Ismar-Rebitz, Ulrich Sommer, Hailong Zhang, and Meixun Zhao
Biogeosciences, 17, 6287–6307,Short summary
Lipids provide crucial insight into the trajectory of ecological functioning in changing environments. We experimentally explore responses of lipid biomarker production in phytoplankton to projected changes in temperature, nutrients and pCO2. Differential responses of lipid biomarkers indicate rearrangements of cellular carbon pools under future ocean scenarios. Such variations in lipid biomarker production would have important impacts on marine ecological functions and biogeochemical cycles.
George Roff, Jennifer Joseph, and Peter J. Mumby
Biogeosciences, 17, 5909–5918,Short summary
In recent decades, extensive mortality of reef-building corals throughout the Caribbean region has led to the erosion of reef frameworks and declines in biodiversity. Using field observations, models, and high-precision U–Th dating, we quantified changes in the structural complexity of coral reef frameworks over the past 2 decades. Structural complexity was stable at reef scales, yet bioerosion led to declines in small-scale microhabitat complexity with cascading effects on cryptic fauna.
Yota Harada, Rod M. Connolly, Brian Fry, Damien T. Maher, James Z. Sippo, Luke C. Jeffrey, Adam J. Bourke, and Shing Yip Lee
Biogeosciences, 17, 5599–5613,Short summary
In 2015–2016, an extensive area of mangroves along ~ 1000 km of coastline in the Gulf of Carpentaria, Australia, experienced dieback as a result of a climatic extreme event that included drought conditions and low sea levels. Multiannual field campaigns conducted from 2016 to 2018 show substantial recovery of the mangrove vegetation. However, stable isotopes suggest long-lasting changes in carbon, nitrogen and sulfur cycling following the dieback.
Lena R. Boysen, Victor Brovkin, Julia Pongratz, David M. Lawrence, Peter Lawrence, Nicolas Vuichard, Philippe Peylin, Spencer Liddicoat, Tomohiro Hajima, Yanwu Zhang, Matthias Rocher, Christine Delire, Roland Séférian, Vivek K. Arora, Lars Nieradzik, Peter Anthoni, Wim Thiery, Marysa M. Laguë, Deborah Lawrence, and Min-Hui Lo
Biogeosciences, 17, 5615–5638,Short summary
We find a biogeophysically induced global cooling with strong carbon losses in a 20 million square kilometre idealized deforestation experiment performed by nine CMIP6 Earth system models. It takes many decades for the temperature signal to emerge, with non-local effects playing an important role. Despite a consistent experimental setup, models diverge substantially in their climate responses. This study offers unprecedented insights for understanding land use change effects in CMIP6 models.
Bertold Mariën, Inge Dox, Hans J. De Boeck, Patrick Willems, Sebastien Leys, Dimitri Papadimitriou, and Matteo Campioli
Revised manuscript accepted for BGShort summary
The drivers of the onset of autumn leaf senescence for several deciduous tree species are still unclear. Therefore, we addressed (i) if drought impacts the timing of autumn leaf senescence and (ii) if the relationship between drought and autumn leaf senescence depends on the tree species. Our study suggests that the timing of autumn leaf senescence is conservative across years and species, and even independent of drought stress.
Vivek K. Arora, Anna Katavouta, Richard G. Williams, Chris D. Jones, Victor Brovkin, Pierre Friedlingstein, Jörg Schwinger, Laurent Bopp, Olivier Boucher, Patricia Cadule, Matthew A. Chamberlain, James R. Christian, Christine Delire, Rosie A. Fisher, Tomohiro Hajima, Tatiana Ilyina, Emilie Joetzjer, Michio Kawamiya, Charles D. Koven, John P. Krasting, Rachel M. Law, David M. Lawrence, Andrew Lenton, Keith Lindsay, Julia Pongratz, Thomas Raddatz, Roland Séférian, Kaoru Tachiiri, Jerry F. Tjiputra, Andy Wiltshire, Tongwen Wu, and Tilo Ziehn
Biogeosciences, 17, 4173–4222,Short summary
Since the preindustrial period, land and ocean have taken up about half of the carbon emitted into the atmosphere by humans. Comparison of different earth system models with the carbon cycle allows us to assess how carbon uptake by land and ocean differs among models. This yields an estimate of uncertainty in our understanding of how land and ocean respond to increasing atmospheric CO2. This paper summarizes results from two such model intercomparison projects that use an idealized scenario.
Daniel E. Pabon-Moreno, Talie Musavi, Mirco Migliavacca, Markus Reichstein, Christine Römermann, and Miguel D. Mahecha
Biogeosciences, 17, 3991–4006,Short summary
Ecosystem CO2 uptake changes in time depending on climate conditions. In this study, we analyze how different climate variables affect the timing when CO2 uptake is at a maximum (DOYGPPmax). We found that the joint effects of radiation, temperature, and vapor pressure deficit are the most relevant controlling factors of DOYGPPmax and that if they increase, DOYGPPmax will happen earlier. These results help us to better understand how CO2 uptake could be affected by climate change.
Thomas A. M. Pugh, Tim Rademacher, Sarah L. Shafer, Jörg Steinkamp, Jonathan Barichivich, Brian Beckage, Vanessa Haverd, Anna Harper, Jens Heinke, Kazuya Nishina, Anja Rammig, Hisashi Sato, Almut Arneth, Stijn Hantson, Thomas Hickler, Markus Kautz, Benjamin Quesada, Benjamin Smith, and Kirsten Thonicke
Biogeosciences, 17, 3961–3989,Short summary
The length of time that carbon remains in forest biomass is one of the largest uncertainties in the global carbon cycle. Estimates from six contemporary models found this time to range from 12.2 to 23.5 years for the global mean for 1985–2014. Future projections do not give consistent results, but 13 model-based hypotheses are identified, along with recommendations for pragmatic steps to test them using existing and novel observations, which would help to reduce large current uncertainty.
Natalya D. Gallo, Kevin Hardy, Nicholas C. Wegner, Ashley Nicoll, Haleigh Yang, and Lisa A. Levin
Biogeosciences, 17, 3943–3960,Short summary
Environmental exposure histories can affect organismal sensitivity to climate change and ocean deoxygenation. The natural variability of environmental conditions for nearshore deep-sea habitats is poorly known due to technological challenges. We develop and test a novel, autonomous, hand-deployable lander outfitted with environmental sensors and a camera system and use it to characterize high-frequency oxygen, temperature, and pH variability at 100–400 m as well as seafloor community responses.
Vincent Echevin, Manon Gévaudan, Dante Espinoza-Morriberón, Jorge Tam, Olivier Aumont, Dimitri Gutierrez, and François Colas
Biogeosciences, 17, 3317–3341,Short summary
The coasts of Peru encompass the richest fisheries in the entire ocean. It is therefore very important for this country to understand how the nearshore marine ecosystem may evolve under climate change. Fine-scale numerical models are very useful because they can represent precisely the evolution of key parameters such as temperature, water oxygenation, and plankton biomass. Here we study the evolution of the Peruvian marine ecosystem in the 21st century under the worst-case climate scenario.
Andrew H. MacDougall, Thomas L. Frölicher, Chris D. Jones, Joeri Rogelj, H. Damon Matthews, Kirsten Zickfeld, Vivek K. Arora, Noah J. Barrett, Victor Brovkin, Friedrich A. Burger, Micheal Eby, Alexey V. Eliseev, Tomohiro Hajima, Philip B. Holden, Aurich Jeltsch-Thömmes, Charles Koven, Nadine Mengis, Laurie Menviel, Martine Michou, Igor I. Mokhov, Akira Oka, Jörg Schwinger, Roland Séférian, Gary Shaffer, Andrei Sokolov, Kaoru Tachiiri, Jerry Tjiputra, Andrew Wiltshire, and Tilo Ziehn
Biogeosciences, 17, 2987–3016,Short summary
The Zero Emissions Commitment (ZEC) is the change in global temperature expected to occur following the complete cessation of CO2 emissions. Here we use 18 climate models to assess the value of ZEC. For our experiment we find that ZEC 50 years after emissions cease is between −0.36 to +0.29 °C. The most likely value of ZEC is assessed to be close to zero. However, substantial continued warming for decades or centuries following cessation of CO2 emission cannot be ruled out.
Doron Pinko, Sigal Abramovich, and Danna Titelboim
Biogeosciences, 17, 2341–2348,Short summary
Future warming threatens many marine organisms; among these are large benthic foraminifera. These symbiont-bearing protists are major carbonate producers and ecosystem engineers. To assess the relative contribution of host and symbiont algae to the holobiont thermal tolerance, we evaluated the calcification rate and photosynthetic activity under future warming scenarios.
Wagner de Oliveira Garcia, Thorben Amann, Jens Hartmann, Kristine Karstens, Alexander Popp, Lena R. Boysen, Pete Smith, and Daniel Goll
Biogeosciences, 17, 2107–2133,Short summary
Biomass-based terrestrial negative emission technologies (tNETS) have high potential to sequester CO2. Many CO2 uptake estimates do not include the effect of nutrient deficiencies in soils on biomass production. We show that nutrients can be partly resupplied by enhanced weathering (EW) rock powder application, increasing the effectiveness of tNETs. Depending on the deployed amounts of rock powder, EW could also improve soil hydrology, adding a new dimension to the coupling of tNETs with EW.
Thomas L. Frölicher, Luca Ramseyer, Christoph C. Raible, Keith B. Rodgers, and John Dunne
Biogeosciences, 17, 2061–2083,Short summary
Climate variations can have profound impacts on marine ecosystems. Here we show that on global scales marine ecosystem drivers such as temperature, pH, O2 and NPP are potentially predictable 3 (at the surface) and more than 10 years (subsurface) in advance. However, there are distinct regional differences in the potential predictability of these drivers. Our study suggests that physical–biogeochemical forecast systems have considerable potential for use in marine resource management.
Angélique Hameau, Thomas L. Frölicher, Juliette Mignot, and Fortunat Joos
Biogeosciences, 17, 1877–1895,Short summary
Ocean deoxygenation and warming are observed and projected to intensify under continued greenhouse gas emissions. Whereas temperature is considered the main climate change indicator, we show that in certain regions, thermocline doxygenation may be detectable before warming.
Didier G. Leibovici, Shaun Quegan, Edward Comyn-Platt, Garry Hayman, Maria Val Martin, Mathieu Guimberteau, Arsène Druel, Dan Zhu, and Philippe Ciais
Biogeosciences, 17, 1821–1844,Short summary
Analysing the impact of environmental changes due to climate change, e.g. geographical spread of climate-sensitive infections (CSIs) and agriculture crop modelling, may require land surface modelling (LSM) to predict future land surface conditions. There are multiple LSMs to choose from. The paper proposes a multivariate spatio-temporal data science method to understand the inherent uncertainties in four LSMs and the variations between them in Nordic areas for the net primary production.
Joeran Maerz, Katharina D. Six, Irene Stemmler, Soeren Ahmerkamp, and Tatiana Ilyina
Biogeosciences, 17, 1765–1803,Short summary
Marine micro-algae bind carbon dioxide, CO2. During their decay, snowflake-like aggregates form that sink, remineralize and transport organically bound CO2 to depth; this is referred to as the biological carbon pump. In our model study, we elucidate how variable aggregate composition impacts the global pattern of vertical carbon fluxes. Our mechanistic model approach advances the representation of the global biological carbon pump and promotes a more realistic projection under climate change.
Allan Buras, Anja Rammig, and Christian S. Zang
Biogeosciences, 17, 1655–1672,Short summary
This study compares the climatic conditions and ecosystem response of the extreme European drought of 2018 with the previous extreme drought of 2003. Using gridded climate data and satellite-based remote sensing information, our analyses qualify 2018 as the new European record drought with wide-ranging negative impacts on European ecosystems. Given the observation of forest-legacy effects in 2019 we call for Europe-wide forest monitoring to assess forest vulnerability to climate change.
Sten Anslan, Mina Azizi Rad, Johannes Buckel, Paula Echeverria Galindo, Jinlei Kai, Wengang Kang, Laura Keys, Philipp Maurischat, Felix Nieberding, Eike Reinosch, Handuo Tang, Tuong Vi Tran, Yuyang Wang, and Antje Schwalb
Biogeosciences, 17, 1261–1279,Short summary
Due to the high elevation, the Tibetan Plateau (TP) is affected more strongly than the global average by climate warming. As a result of increasing air temperature, several environmental processes have accelerated, such as melting glaciers, thawing permafrost and grassland degradation. We review several modern and paleoenvironmental changes forced by climate warming in the lake system of Nam Co to shape our understanding of global warming effects on current and future geobiodiversity.
Natalia Gnatiuk, Iuliia Radchenko, Richard Davy, Evgeny Morozov, and Leonid Bobylev
Biogeosciences, 17, 1199–1212,Short summary
We analysed the ability of 34 climate models to reproduce main factors affecting the coccolithophore Emiliania huxleyi blooms in six Arctic and sub-Arctic seas. Furthermore, we proposed a procedure of ranking and selecting these models based on the model’s skill in reproducing 10 important oceanographic, meteorological, and biochemical variables in comparison with observation data and demonstrated that the proposed methodology shows a better result than commonly used all-model averaging.
M. Rosario Lorenzo, María Segovia, Jay T. Cullen, and María T. Maldonado
Biogeosciences, 17, 757–770,Short summary
Pritha Tutasi and Ruben Escribano
Biogeosciences, 17, 455–473,Short summary
Vertical migration of zooplankton has rarely been studied under the effect of a variable community structure, which depending on the behavior and size of its groups can strongly alter the magnitude of C being actively taken to depth by migrants. Here, we address this issue in a highly productive upwelling system, where a high amount of zooplankton can daily move below the mixed layer despite presence of an extremely low–oxygen water and so contribute to a significant export of C to depth.
Frances E. Hopkins, Philip D. Nightingale, John A. Stephens, C. Mark Moore, Sophie Richier, Gemma L. Cripps, and Stephen D. Archer
Biogeosciences, 17, 163–186,Short summary
We investigated the effects of ocean acidification (OA) on the production of climate active gas dimethylsulfide (DMS) in polar waters. We found that polar DMS production was unaffected by OA – in contrast to temperate waters, where large increases in DMS occurred. The regional differences in DMS response may reflect natural variability in community adaptation to ambient carbonate chemistry and should be taken into account in predicting the influence of future DMS emissions on Earth's climate.
Nidhi Jha, Nitin Kumar Tripathi, Wirong Chanthorn, Warren Brockelman, Anuttara Nathalang, Raphaël Pélissier, Siriruk Pimmasarn, Pierre Ploton, Nophea Sasaki, Salvatore G. P. Virdis, and Maxime Réjou-Méchain
Biogeosciences, 17, 121–134,Short summary
Carbon stocks and dynamics are both uncertain in tropical forests, especially in Asia. We here quantify the carbon stock and recovery rate of a Thai landscape using airborne lidar and four decades of Landsat data. We show that the landscape has a high carbon stock despite its disturbance history and that secondary forests are accumulating carbon at high rate. Our study shows the potential synergy of remote sensing and field data to characterize the carbon dynamics of tropical forests.
Thorben Amann, Jens Hartmann, Eric Struyf, Wagner de Oliveira Garcia, Elke K. Fischer, Ivan Janssens, Patrick Meire, and Jonas Schoelynck
Biogeosciences, 17, 103–119,Short summary
Weathering is a major control on atmospheric CO2 at geologic timescales. Enhancement of this process can be used to actively remove CO2 from the atmosphere. Field results are still scarce and with this experiment we try to add some near-natural insights into dissolution processes. Results show CO2 sequestration potentials but also highlight the strong variability of outcomes that can be expected in natural environments. Such experiments are of the utmost importance to identify key processes.
Rachel Dietrich and Madhur Anand
Biogeosciences, 16, 4815–4827,Short summary
In shade-tolerant tree species, growth is not strictly related to tree age. In this study we show that novel tree ring standardization models that incorporate tree size in the year of ring formation produce more accurate chronologies than those produced by contemporary, age-based standardization models. These findings are important for accurate and reliable long-term trend reconstruction in tree ring studies in all species but are especially so for shade-tolerant species.
Laurie M. Charrieau, Karl Ljung, Frederik Schenk, Ute Daewel, Emma Kritzberg, and Helena L. Filipsson
Biogeosciences, 16, 3835–3852,Short summary
We reconstructed environmental changes in the Öresund during the last 200 years, using foraminifera (microfossils), sediment, and climate data. Five zones were identified, reflecting oxygen, salinity, food content, and pollution levels for each period. The largest changes occurred ~ 1950, towards stronger currents. The foraminifera responded quickly (< 10 years) to the changes. Moreover, they did not rebound when the system returned to the previous pattern, but displayed a new equilibrium state.
Mikkel Bennedsen, Eric Hillebrand, and Siem Jan Koopman
Biogeosciences, 16, 3651–3663,Short summary
Is the fraction of anthropogenically released CO2 that remains in the atmosphere increasing? Is the rate at which the ocean and land sinks take up CO2 from the atmosphere decreasing? We analyse these questions by means of a statistical dynamic multivariate model from which we estimate the unobserved trend processes together with the parameters that govern them. We find no statistical evidence of an increasing airborne fraction, but we do find statistical evidence of a decreasing sink rate.
Thorben Amann and Jens Hartmann
Biogeosciences, 16, 2949–2960,Short summary
With the recent publication of the IPCC special report on the 1.5 °C target and increased attention on carbon dioxide removal (CDR) technologies, we think it is time to advance from the current way of looking at specific strategies to a more holistic CDR perspective, since multiple "side effects" may lead to additional CO2 uptake into different carbon pools. This paper explores potential co-benefits between terrestrial CDR strategies to facilitate a maximum CO2 sequestration effect.
Angélique Hameau, Juliette Mignot, and Fortunat Joos
Biogeosciences, 16, 1755–1780,Short summary
The observed decrease of oxygen and warming in the ocean may adversely affect marine ecosystems and their services. We analyse results from an Earth system model for the last millennium and the 21st century. We find changes in temperature and oxygen due to fossil fuel burning and other human activities to exceed natural variations in many ocean regions already today. Natural variability is biased low in earlier studies neglecting forcing from past volcanic eruptions and solar change.
Stefan Kruse, Alexander Gerdes, Nadja J. Kath, Laura S. Epp, Kathleen R. Stoof-Leichsenring, Luidmila A. Pestryakova, and Ulrike Herzschuh
Biogeosciences, 16, 1211–1224,Short summary
How fast might the arctic treeline in northern central Siberia migrate northwards under current global warming? To answer this, we newly parameterized dispersal processes in the individual-based and spatially explicit model LAVESI-WIND based on parentage analysis. Simulation results show that northernmost open forest stands are migrating at an unexpectedly slow rate into tundra. We conclude that the treeline currently lags behind the strong warming and will remain slow in the upcoming decades.
Rasoul Yousefpour, Julia E. M. S. Nabel, and Julia Pongratz
Biogeosciences, 16, 241–254,Short summary
Global forest resources are accounted for to establish their potential to sink carbon in woody biomass. Climate prediction models realize the effects of future global forest utilization rates, defined by population demand and its evolution over time. However, forest management approaches consider the supply side to realize a sustainable forest carbon stock and adapt the harvest rates to novel climate conditions. This study simulates such an adaptive sustained yield approach.
Terhikki Manninen, Tuula Aalto, Tiina Markkanen, Mikko Peltoniemi, Kristin Böttcher, Sari Metsämäki, Kati Anttila, Pentti Pirinen, Antti Leppänen, and Ali Nadir Arslan
Biogeosciences, 16, 223–240,Short summary
The surface albedo time series CLARA-A2 SAL was used to study trends in the timing of the melting season of snow and preceding albedo value in Finland during 1982–2016 to assess climate change. The results were in line with operational snow depth data, JSBACH land ecosystem model, SYKE fractional snow cover and greening-up data. In the north a clear trend to earlier snowmelt onset, increasing melting season length, and decrease in pre-melt albedo (related to increased stem volume) was observed.
Yuan Meng, Zhenbin Guo, Susan C. Fitzer, Abhishek Upadhyay, Vera B. S. Chan, Chaoyi Li, Maggie Cusack, Haimin Yao, Kelvin W. K. Yeung, and Vengatesen Thiyagarajan
Biogeosciences, 15, 6833–6846,Short summary
The paper revealed a potential structural deterioration induced by ocean acidification on the shells of an ecologically and economically important oyster, which is critical to forecasting the survival and production of edible oysters in the future ocean. Importantly, this is a multidisciplinary collaboration including aquaculture, crystallography, medical and materials science, which could be applied to other biomineral systems to hierarchically analyse the impact of ocean acidification.
Dominik Thom, Werner Rammer, Rita Garstenauer, and Rupert Seidl
Biogeosciences, 15, 5699–5713,Short summary
Over the past decades temperate forests were a carbon (C) sink to the atmosphere. Yet the drivers of C uptake and how these affect the future carbon cycle remain uncertain. Our simulation and study revealed that the future C sink of central European forest landscapes is strongly driven by historic land use, while climate change reduces forest C uptake. Compared to land-use change, past natural disturbances (wind and bark beetles) have only marginal effects on the future carbon cycle.
Michael M. Loranty, Benjamin W. Abbott, Daan Blok, Thomas A. Douglas, Howard E. Epstein, Bruce C. Forbes, Benjamin M. Jones, Alexander L. Kholodov, Heather Kropp, Avni Malhotra, Steven D. Mamet, Isla H. Myers-Smith, Susan M. Natali, Jonathan A. O'Donnell, Gareth K. Phoenix, Adrian V. Rocha, Oliver Sonnentag, Ken D. Tape, and Donald A. Walker
Biogeosciences, 15, 5287–5313,Short summary
Vegetation and soils strongly influence ground temperature in permafrost ecosystems across the Arctic and sub-Arctic. These effects will cause differences rates of permafrost thaw related to the distribution of tundra and boreal forests. As the distribution of forests and tundra change, the effects of climate change on permafrost will also change. We review the ecosystem processes that will influence permafrost thaw and outline how they will feed back to climate warming.
Aisling Fontanini, Alexandra Steckbauer, Sam Dupont, and Carlos M. Duarte
Biogeosciences, 15, 3717–3729,Short summary
Invertebrate species of the Gullmar Fjord (Sweden) were exposed to four different treatments (high/low oxygen and low/high CO2) and respiration measured. Respiration responses of species of contrasting habitats and life-history strategies to single and multiple stressors was evaluated. Results show that the responses of the respiration were highly species specific as we observed both synergetic as well as antagonistic responses, and neither phylum nor habitat explained trends in respiration.
Jie Wang, Bayden D. Russell, Meng-Wen Ding, and Yun-Wei Dong
Biogeosciences, 15, 2803–2817,Short summary
To understand ecological impacts of CO2-induced ocean acidification and temperature rise, a key question is if organisms become more vulnerable under multiple stressors. Here we tested heart rate and gene expression levels of a limpet under varying pCO2 and temperature. Results showed that while many individuals are more vulnerable to heat stress under high CO2 and increased temperature, some animals have the ability to alter their physiology to help them survive under future conditions.
Ting Liu, Liang Wang, Xiaojuan Feng, Jinbo Zhang, Tian Ma, Xin Wang, and Zongguang Liu
Biogeosciences, 15, 1627–1641,Short summary
Compared to the respiration process, few studies have examined soil carbon leaching possibly enhanced by extreme precipitation events (EPEs). We show that soil carbon leaching was much higher than CO2 loss through respiration under EPEs in grassland soils through incubation experiments. The soil carbon leaching process should be incorporated into soil carbon models when estimating carbon balance in grassland ecosystems, especially considering the projected increase in EPEs with climate change.
Justine L. Ramage, Anna M. Irrgang, Anne Morgenstern, and Hugues Lantuit
Biogeosciences, 15, 1483–1495,Short summary
We describe the evolution of thaw slumps between 1952 and 2011 along the Yukon Coast, Canada, and calculate the contribution of the slumps to the carbon budget in this area. The number of slumps has increased by 73 % over the period. These slumps displaced more than 16 billion m3 of material and mobilized 146 t of carbon. This represents 0.6 % of the annual carbon flux released from shoreline retreat, which shows that the contribution of slumps to the nearshore carbon budget is non-negligible.
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This paper provides a preliminary data set for dissolved nutrient abundance in the Dark Zone of the Greenland Ice Sheet. This 15-year marked darkening has since been attributed to glacier algae blooms, yet has not been accounted for in current melt rate models. We conclude that the dissolved organic phase dominates surface ice environments and that factors other than macronutrient limitation control the extent and magnitude of the glacier algae blooms.
This paper provides a preliminary data set for dissolved nutrient abundance in the Dark Zone of...