DOCSLIB.ORG

Multi-Decadal Increases in North Atlantic Coccolithophore Populations

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Multi-Decadal Increases in North Atlantic Coccolithophore Populations Ocean Carbon and Biogeochemistry Studying marine biogeochemical cycles and associated ecosystems in the face of environmental change Volume 9, Number 3 Fall 2016 News A chalkier ocean? Multi-decadal increases in North Atlantic coccolithophore populations Kristen Krumhardt1 and Sara Rivero-Calle2 1Environmental Studies Program and Institute of Arctic and Alpine Research, University of Colorado Boulder, Boulder, Colorado, USA 2Department of Marine and Environmental Biology, University of Southern California, Los Angeles, California, USA Coccolithophores and the carbon cycle Increasing atmospheric CO2 concentrations are resulting in both warmer sea surface temperatures due to the greenhouse effect and increas- ingly carbon-rich surface waters. The ocean has absorbed roughly one third of anthropogenic carbon emissions (1), causing a shift in car- bon chemistry equilibrium to more acidic conditions with lower calcium carbonate saturation states (ocean MODIS PIC May 2010 acidification). Organisms that pro- duce calcium carbonate structures are 0.0 0.1 0.2 0.4 0.6 0.8 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 thought to be particularly susceptible PIC concentration (mg m−3) to these changes (2-4). Coccolithophores are the most Figure 1. Moderate Resolution Imaging Spectroradiometer (MODIS) Aqua satellite-derived abundant type of calcifying uni- particulate inorganic carbon (PIC) concentration (mg m-3) averaged for the month of May 2010 cellular micro-algae in the ocean, highlights prominent coccolithophore blooms in the North Atlantic. producing microscopic calcium carbonate plates called coccoliths (5). Low-pH conditions inorganic carbon (PIC) through calcification. Detri- have been shown to disrupt the formation of coccoliths tal coccolithophore shells form aggregates with organic (calcification; e.g., (6)). Therefore, it is generally expected material, enhancing carbon export to the deep sea (7). that a higher-CO2 ocean will cause a reduction in cal- Coccolithophores also produce dimethyl sulfide (DMS), cification rates or a decrease in the abundance of these a climatically relevant trace gas that impacts cloud forma- calcifiers. Such changes could have far-reaching conse- tion, ultimately influencing Earth’s albedo (8, 9). At the quences for marine ecosystems, as well as global carbon ecosystem level, coccolithophores compete for nutrients cycling and carbon export to the deep sea. with other phytoplankton and provide energy for the rest Coccolithophores use sunlight to synthesize both of the marine food web. Coccolithophores have a broad organic carbon through photosynthesis and particulate range of irradiance, temperature, and salinity tolerances OCB NEWS • Fall 2016 1 Science Year show that coccolithophores have the ability to modulate 1970 1980 1990 2000 2010 organic carbon production and calcification in response 20 a) coccolithophore occurence (temperate/subpolar) to variable amounts of dissolved inorganic carbon (DIC) but that low pH only affects these processes below a 10 certain threshold (14 ). Another study indicated that % occurrence 15 ) −2 coccolithophores could adapt to warming and high CO 0 2 b) coccolithophore pigments (subtropical) g m μ levels over the course of a year, maintaining their relative 10 ( particulate organic carbon (POC) and PIC production hapto 5 per cell (15). One of the limitations of all laboratory Chla 400 experiments is that only a handful of species (and strains) c) Mauna Loa CO2 record 0 380 (ppm) are studied, which is only a tiny fraction of the diversity 2 360 present in the oceans. Given the challenges of extrapo- 340 2100 ) −1 air pCO lating laboratory results to real world oceans, studying 320 2080 2060 recent trends in natural populations may lead to import- mol kg d) DIC at BATS (subtropical) μ 2040 ant insights. 2020 DIC ( 0.6 2000 The North Atlantic is both a region with rapid 0.4 e) AMO accumulation of anthropogenic CO2 (1) and an import- 0.2 0.0 ant coccolithophore habitat (Fig. 1), making this region AMO −0.2 a good starting point to search for in situ evidence of −0.4 −0.6 anthropogenic carbon effects on diverse coccolithophore 1970 1980 1990 2000 2010 populations. Two recent studies did precisely that: Rive- Year ro-Calle et al. (2015)(16 ) in the subpolar North Atlantic, Figure 2. Time-series data from 1960 to 2015 on (a) CPR coccolithophore and Krumhardt et al. (2016)(17 ) in the North Atlantic annual occurrence in the temperate/subpolar North Atlantic, (b) 140m subtropical gyre. Using independent datasets, these two depth-integrated chlorophyll a from coccolithophores (haptophytes) at studies concluded that coccolithophores in the North At- BATS in the subtropical North Atlantic (µg m-2) with a 2-year Gaussian filter lantic appear to be increasing in abundance and, contrary (dark green) and a linear regression (dashed line), (c) global atmospheric to the prevailing paradigm, responding positively to the CO2 concentration from Mauna Loa (ppm), (d) dissolved inorganic carbon extra carbon in the upper mixed layer. (DIC) at BATS (µmol kg-1) with a 2-year Gaussian filter (darker turquoise), and (e) the Atlantic Multidecadal Oscillation (AMO) index. Evidence from long-term in situ monitoring (two independent case studies) (10, 11). Moreover, their relatively low nutrient require- Rivero-Calle et al. (2015) used data from the Continu- ments and slow growth rates offer a competitive advantage ous Plankton Recorder (CPR), a filtering device installed under projected global warming and ocean stratification on ships of opportunity, to assess changes in coccolitho- (5). This plasticity and opportunistic behavior can be phore populations from 1965 to 2010 in the subpolar critical for persistence in a changing oceanic environment. North Atlantic. This highly productive, temperate region Given the wide range of biogeochemical and ecological is dominated by large phytoplankton and characterized by processes impacted by coccolithophores, it is important to strong seasonal changes in the mixed layer depth, nutri- assess how anthropogenic changes may affect coccolitho- ent upwelling, and gas exchange that lead to intense, well phore growth and calcification. established spring phytoplankton blooms. Many laboratory studies have investigated the impact Because coccolithophore cells are smaller than the mesh of future environmental conditions on coccolithophores size used by the CPR, they cannot be accurately quanti- by decreasing pH, increasing dissolved inorganic carbon, fied in the CPR data set. Some coccolithophore cells do, and increasing temperature to mimic end-of-century however, get caught in the mesh and their occurrence projections. However, these have often yielded conflict- (i.e. probability of presence) can be calculated and serve ing results: Some show a decrease, while others show no as a proxy for coccolithophore abundance. Using re- change or even increased calcification (e.g., (6, 12, 13)). corded presence or absence of coccolithophores over this For example, laboratory simulations of contemporary multidecadal time-series, the authors showed that coc- oceanic changes (increasing CO2 and decreasing pH) colithophore occurrence in the subpolar North Atlantic OCB NEWS • Fall 2016 2 Science increased from being present in only 1% of samples to > downwelling, resulting in an oligotrophic environment. 20% over the past five decades (Fig. 2). Despite relatively low productivity, subtropical gyres cover To assess the importance of a wide range of diverse vast expanses of the global ocean and are thus important environmental drivers on changes in coccolithophore oc- on a global scale. currence, Rivero-Calle and co-authors used random forest In the North Atlantic subtropical gyre, researchers at statistical models. Specifically, they examined more than BATS have performed phytoplankton pigment analyses 20 possible biological and physical predictors, including since the late 1980s, as well as a suite of other oceano- CO2 concentrations, nutrients, sea surface temperature graphic measurements (nutrients, temperature, salinity, and the Atlantic Multidecadal Oscillation (AMO), as well etc.). This rich dataset provided insight into phyto- as possible predators and competitors. Global and local plankton dynamics occurring at BATS over the past two CO2 concentrations were shown to be the best predictors decades. Coccolithophores contain a suite of pigments of coccolithophore occurrence. The AMO, which has distinctive to haptophytes. Though there are many species been in a positive phase since the mid-1990s (Fig. 2) and is of non-calcifying haptophytes in the ocean (18), the main associated with anomalously warmer temperatures over the contributors to the haptophyte community in oligotro- North Atlantic, was also a good predictor of coccolitho- phic gyres are coccolithophores (19). Using a constant phore occurrence, but not as strong of a predictor as CO2. haptophyte pigment to chlorophyll a ratio Krumhardt et The authors hypothesize that the synergistic effects of al. (2016) quantified relative abundance of the coccolitho- increasing anthropogenic CO2, the recent positive phase of phore chlorophyll a (Chlahapto) over the BATS time-series. the AMO, and increasing global temperatures contributed A simple linear regression revealed that coccolithophore to the observed increase in coccolithophore occurrence in pigments have increased in the upper euphotic zone by the CPR samples from 1965 to 2010. 37% from 1990 to 2012 (Figure 2). On the other hand, Complementing the Rivero-Calle et al.
Load more

Recommended publications
  • The Role of Reforestation in Carbon Sequestration
    New Forests (2019) 50:115–137 https://doi.org/10.1007/s11056-018-9655-3 The role of reforestation in carbon sequestration L. E. Nave1,2 · B. F. Walters3 · K. L. Hofmeister4 · C. H. Perry3 · U. Mishra5 · G. M. Domke3 · C. W. Swanston6 Received: 12 October 2017 / Accepted: 24 June 2018 / Published online: 9 July 2018 © Springer Nature B.V. 2018 Abstract In the United States (U.S.), the maintenance of forest cover is a legal mandate for federally managed forest lands. More broadly, reforestation following harvesting, recent or historic disturbances can enhance numerous carbon (C)-based ecosystem services and functions. These include production of woody biomass for forest products, and mitigation of atmos- pheric ­CO2 pollution and climate change by sequestering C into ecosystem pools where it can be stored for long timescales. Nonetheless, a range of assessments and analyses indicate that reforestation in the U.S. lags behind its potential, with the continuation of ecosystem services and functions at risk if reforestation is not increased. In this context, there is need for multiple independent analyses that quantify the role of reforestation in C sequestration, from ecosystems up to regional and national levels. Here, we describe the methods and report the fndings of a large-scale data synthesis aimed at four objectives: (1) estimate C storage in major ecosystem pools in forest and other land cover types; (2) quan- tify sources of variation in ecosystem C pools; (3) compare the impacts of reforestation and aforestation on C pools; (4) assess whether these results hold or diverge across ecore- gions.
    [Show full text]
  • Carbon Dynamics of Subtropical Wetland Communities in South Florida DISSERTATION Presented in Partial Fulfillment of the Require
    Carbon Dynamics of Subtropical Wetland Communities in South Florida DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University By Jorge Andres Villa Betancur Graduate Program in Environmental Science The Ohio State University 2014 Dissertation Committee: William J. Mitsch, Co-advisor Gil Bohrer, Co-advisor James Bauer Jay Martin Copyrighted by Jorge Andres Villa Betancur 2014 Abstract Emission and uptake of greenhouse gases and the production and transport of dissolved organic matter in different wetland plant communities are key wetland functions determining two important ecosystem services, climate regulation and nutrient cycling. The objective of this dissertation was to study the variation of methane emissions, carbon sequestration and exports of dissolved organic carbon in wetland plant communities of a subtropical climate in south Florida. The plant communities selected for the study of methane emissions and carbon sequestration were located in a natural wetland landscape and corresponded to a gradient of inundation duration. Going from the wettest to the driest conditions, the communities were designated as: deep slough, bald cypress, wet prairie, pond cypress and hydric pine flatwood. In the first methane emissions study, non-steady-state rigid chambers were deployed at each community sequentially at three different times of the day during a 24- month period. Methane fluxes from the different communities did not show a discernible daily pattern, in contrast to a marked increase in seasonal emissions during inundation. All communities acted at times as temporary sinks for methane, but overall were net -2 -1 sources. Median and mean + standard error fluxes in g CH4-C.m .d were higher in the deep slough (11 and 56.2 + 22.1), followed by the wet prairie (9.01 and 53.3 + 26.6), bald cypress (3.31 and 5.54 + 2.51) and pond cypress (1.49, 4.55 + 3.35) communities.
    [Show full text]
  • CO2-Fixing One-Carbon Metabolism in a Cellulose-Degrading Bacterium
    CO2-fixing one-carbon metabolism in a cellulose- degrading bacterium Clostridium thermocellum Wei Xionga, Paul P. Linb, Lauren Magnussona, Lisa Warnerc, James C. Liaob,d, Pin-Ching Manessa,1, and Katherine J. Choua,1 aBiosciences Center, National Renewable Energy Laboratory, Golden, CO 80401; bDepartment of Chemical and Biomolecular Engineering, University of California, Los Angeles, CA 90095; cNational Bioenergy Center, National Renewable Energy Laboratory, Golden, CO 80401; and dAcademia Sinica, Taipei City, Taiwan 115 Edited by Lonnie O. Ingram, University of Florida, Gainesville, FL, and approved September 23, 2016 (received for review April 6, 2016) Clostridium thermocellum can ferment cellulosic biomass to for- proposed pathway involving CO2 utilization in C. thermocellum is mate and other end products, including CO2. This organism lacks the malate shunt and its variant pathway (7, 14), in which CO2 is formate dehydrogenase (Fdh), which catalyzes the reduction of first incorporated by phosphoenolpyruvate carboxykinase (PEPCK) 13 CO2 to formate. However, feeding the bacterium C-bicarbonate to form oxaloacetate and then is released either by malic enzyme or and cellobiose followed by NMR analysis showed the production via oxaloacetate decarboxylase complex, yielding pyruvate. How- of 13C-formate in C. thermocellum culture, indicating the presence ever, other pathways capable of carbon fixation may also exist but of an uncharacterized pathway capable of converting CO2 to for- remain uncharacterized. mate. Combining genomic and experimental data, we demon- In recent years, isotopic tracer experiments followed by mass strated that the conversion of CO2 to formate serves as a CO2 spectrometry (MS) (15, 16) or NMR measurements (17) have entry point into the reductive one-carbon (C1) metabolism, and emerged as powerful tools for metabolic analysis.
    [Show full text]
  • Phytoplankton As Key Mediators of the Biological Carbon Pump: Their Responses to a Changing Climate
    sustainability Review Phytoplankton as Key Mediators of the Biological Carbon Pump: Their Responses to a Changing Climate Samarpita Basu * ID and Katherine R. M. Mackey Earth System Science, University of California Irvine, Irvine, CA 92697, USA; [email protected] * Correspondence: [email protected] Received: 7 January 2018; Accepted: 12 March 2018; Published: 19 March 2018 Abstract: The world’s oceans are a major sink for atmospheric carbon dioxide (CO2). The biological carbon pump plays a vital role in the net transfer of CO2 from the atmosphere to the oceans and then to the sediments, subsequently maintaining atmospheric CO2 at significantly lower levels than would be the case if it did not exist. The efficiency of the biological pump is a function of phytoplankton physiology and community structure, which are in turn governed by the physical and chemical conditions of the ocean. However, only a few studies have focused on the importance of phytoplankton community structure to the biological pump. Because global change is expected to influence carbon and nutrient availability, temperature and light (via stratification), an improved understanding of how phytoplankton community size structure will respond in the future is required to gain insight into the biological pump and the ability of the ocean to act as a long-term sink for atmospheric CO2. This review article aims to explore the potential impacts of predicted changes in global temperature and the carbonate system on phytoplankton cell size, species and elemental composition, so as to shed light on the ability of the biological pump to sequester carbon in the future ocean.
    [Show full text]
  • From Nano-Gels to Marine Snow: a Synthesis of Gel Formation Processes and Modeling Efforts Involved with Particle Flux in the Ocean
    gels Review From Nano-Gels to Marine Snow: A Synthesis of Gel Formation Processes and Modeling Efforts Involved with Particle Flux in the Ocean Antonietta Quigg 1,* , Peter H. Santschi 2 , Adrian Burd 3, Wei-Chun Chin 4 , Manoj Kamalanathan 1, Chen Xu 2 and Kai Ziervogel 5 1 Department of Marine Biology, Texas A&M University at Galveston, Galveston, TX 77553, USA; [email protected] 2 Department of Marine and Coastal Environmental Science, Texas A&M University at Galveston, Galveston, TX 77553, USA; [email protected] (P.H.S.); [email protected] (C.X.) 3 Department of Marine Science, University of Georgia, Athens, GA 30602, USA; [email protected] 4 Department of Bioengineering, University of California, Merced, CA 95343, USA; [email protected] 5 Institute for the Study of Earth, Oceans and Space, University of New Hampshire, Durham, NH 03824, USA; [email protected] * Correspondence: [email protected] Abstract: Marine gels (nano-, micro-, macro-) and marine snow play important roles in regulating global and basin-scale ocean biogeochemical cycling. Exopolymeric substances (EPS) including transparent exopolymer particles (TEP) that form from nano-gel precursors are abundant materials in the ocean, accounting for an estimated 700 Gt of carbon in seawater. This supports local microbial communities that play a critical role in the cycling of carbon and other macro- and micro-elements in Citation: Quigg, A.; Santschi, P.H.; the ocean. Recent studies have furthered our understanding of the formation and properties of these Burd, A.; Chin, W.-C.; Kamalanathan, materials, but the relationship between the microbial polymers released into the ocean and marine M.; Xu, C.; Ziervogel, K.
    [Show full text]
  • B.-Gioli -Co2-Fluxes-In-Florance.Pdf
    Environmental Pollution 164 (2012) 125e131 Contents lists available at SciVerse ScienceDirect Environmental Pollution journal homepage: www.elsevier.com/locate/envpol Methane and carbon dioxide fluxes and source partitioning in urban areas: The case study of Florence, Italy B. Gioli a,*, P. Toscano a, E. Lugato a, A. Matese a, F. Miglietta a,b, A. Zaldei a, F.P. Vaccari a a Institute of Biometeorology (IBIMET e CNR), Via G.Caproni 8, 50145 Firenze, Italy b FoxLab, Edmund Mach Foundation, Via E. Mach 1, San Michele all’Adige, Trento, Italy article info abstract Article history: Long-term fluxes of CO2, and combined short-term fluxes of CH4 and CO2 were measured with the eddy Received 15 September 2011 covariance technique in the city centre of Florence. CO2 long-term weekly fluxes exhibit a high Received in revised form seasonality, ranging from 39 to 172% of the mean annual value in summer and winter respectively, while 12 January 2012 CH fluxes are relevant and don’t exhibit temporal variability. Contribution of road traffic and domestic Accepted 14 January 2012 4 heating has been estimated through multi-regression models combined with inventorial traffic and CH4 consumption data, revealing that heating accounts for more than 80% of observed CO2 fluxes. Those two Keywords: components are instead responsible for only 14% of observed CH4 fluxes, while the major residual part is Eddy covariance fl Methane fluxes likely dominated by gas network leakages. CH4 uxes expressed as CO2 equivalent represent about 8% of Gas network leakages CO2 emissions, ranging from 16% in summer to 4% in winter, and cannot therefore be neglected when assessing greenhouse impact of cities.
    [Show full text]
  • Uts Marine Biology Fact Sheet
    UTS MARINE BIOLOGY FACT SHEET Topic: Phytoplankton and Cloud Formation 1.The CLAW Hypothesis Background: In 1987 four people (Charlson, Lovelock, Andrea, & Warren) introduced a theory that a natural gas called Dimethylsulfide (DMS), produced by microscopic plants in the ocean (phytoplankton), was a major contributor to the formation of clouds in the atmosphere. This theory was named the CLAW Hypothesis (from the first letter of each of their surnames). Fast facts: . Phytoplankton produce DMSP (dimethylsulphoniopropionate), an organic sulphur compound, which is converted to DMS in the ocean. The majority of this DMS is consumed by bacteria but around 10% escapes into the atmosphere. When DMS is released into the air, a chemical reaction takes place (called an oxidation reaction) and sulphate aerosols are formed – a gas which acts as cloud condensation nuclei (CCN). This means it combines with water droplets in the atmosphere to form clouds. As a result, more clouds increase the reflectivity of the sun’s rays (earth albedo) which decreases the amount of light reaching the earth’s surface, and contributes to cooling the overall climate. A decrease in light causes a decrease in phytoplankton productivity of DMS. (Phytoplankton are primary producers which rely on light to function). This sequence of events is called a Negative Feedback Loop, because phytoplankton increase DMS production but DMS forms clouds which lowers the amount of light reaching the earth, resulting in less phytoplankton and less DMS. DMS emissions are a key step in the global sulphur cycle, which circulates sulphur throughout the earth, oceans, and atmosphere. It is an essential component in the growth of all living things.
    [Show full text]
  • Soil Carbon Sequestration and Greenhouse Gas Mitigation: a Role
    Soil Carbon Sequestration and Greenhouse Gas Mitigation: A Role for American Agriculture Dr. Charles W. Rice and Debbie Reed, MSc. Professor of Agronomy Kansas State University Department of Agronomy Manhattan, KS Agriculture and Climate Change Specialist DRD Associates Arlington, VA March 2007 1 TABLE OF CONTENTS Executive Summary (pg. 5) Global Climate Change (7) Greenhouse Gases and American Agriculture (8) The Role of Agriculture in Combating Rising Greenhouse Gas Emissions and Climate Change (8) Agricultural Practices that Combat Climate Change (10) Decreasing emissions (10) Enhancing sinks (10) Displacing emissions (11) How American Agriculture Can Reduce U.S. GHG Emissions and Combat Climate Change (multi-page spread: 12-14) Building Carbon Sinks: Soil Carbon Sequestration (12) Cropland (12) Agronomy (12) Nutrient Management (12) Tillage/Residue Management (13) Land cover/land use change (13) Grazingland management and pasture improvement (13) Grazing intensity (13) Increased productivity (including fertilization) (13) Nutrient management (13) Fire management (13) Restoration of degraded lands (13) Decreasing GHG Emissions: Manure Management (14) Displacing GHG Emissions: Biofuels (14) Table 1: Estimates of potential carbon sequestration of agricultural practices (14) Economic Benefits of Conservation Tillage and No-Till Systems (15) Table 2: Change in yield, net dollar returns, emissions, and soil carbon when converting from conventional tillage to no tillage corn production in Northeast Kansas (15) Co-Benefits of Soil Carbon Sequestration: “Charismatic Carbon” (16) Table 3: Plant nutrients supplied by soil organic matter (SOM) (16) 2 New Technologies to Further Enhance Soil Carbon Storage (16) Biochar (16) Modification of the Plant-Soil System (17) Meeting the Climate Challenge: The Role of Carbon Markets (17) Mandatory v.
    [Show full text]
  • Ocean Storage
    277 6 Ocean storage Coordinating Lead Authors Ken Caldeira (United States), Makoto Akai (Japan) Lead Authors Peter Brewer (United States), Baixin Chen (China), Peter Haugan (Norway), Toru Iwama (Japan), Paul Johnston (United Kingdom), Haroon Kheshgi (United States), Qingquan Li (China), Takashi Ohsumi (Japan), Hans Pörtner (Germany), Chris Sabine (United States), Yoshihisa Shirayama (Japan), Jolyon Thomson (United Kingdom) Contributing Authors Jim Barry (United States), Lara Hansen (United States) Review Editors Brad De Young (Canada), Fortunat Joos (Switzerland) 278 IPCC Special Report on Carbon dioxide Capture and Storage Contents EXECUTIVE SUMMARY 279 6.7 Environmental impacts, risks, and risk management 298 6.1 Introduction and background 279 6.7.1 Introduction to biological impacts and risk 298 6.1.1 Intentional storage of CO2 in the ocean 279 6.7.2 Physiological effects of CO2 301 6.1.2 Relevant background in physical and chemical 6.7.3 From physiological mechanisms to ecosystems 305 oceanography 281 6.7.4 Biological consequences for water column release scenarios 306 6.2 Approaches to release CO2 into the ocean 282 6.7.5 Biological consequences associated with CO2 6.2.1 Approaches to releasing CO2 that has been captured, lakes 307 compressed, and transported into the ocean 282 6.7.6 Contaminants in CO2 streams 307 6.2.2 CO2 storage by dissolution of carbonate minerals 290 6.7.7 Risk management 307 6.2.3 Other ocean storage approaches 291 6.7.8 Social aspects; public and stakeholder perception 307 6.3 Capacity and fractions retained
    [Show full text]
  • M1 Project: Climate - Biosphere Interactions Using ODE Models
    M1 Project: Climate - Biosphere interactions using ODE models Jan Rombouts Erasmus Mundus Master in Complex Systems Science Ecole´ Polytechnique, Paris Supervisors: Michael Ghil, Regis Ferri`ere Ecole´ Normal Sup´erieure,Paris June 30, 2014 Abstract There are many examples of the complex interactions of climate and vegetation through various feedback mechanisms. Climatic models have begun to take into ac- count vegetation as an important player in the evolution of the climate. Climate models range from complicated, large scale GCMs to simple conceptual models. It is this last type of modeling that I looked at in my project. Conceptual models usually use differential equations and techniques from dynamical systems theory to investi- gate basic mechanisms in the climate system. They have in particular been applied to investigate glacial-interglacial cycles. These models have not often included vege- tation as one of their variables, and this is what I've looked at in the project. First I investigate a simple, two equation model, and show that even in such a simple model, interesting oscillatory behaviour can be observed. Then I go on to study models with three equations, based on an existing model for temperature and ice sheet evolution. I extend this model in two ways: by adding a vegetation variable, and by adding a carbon dioxide variable. Again, oscillations are observed, but the existence depends on parameters that are linked to the vegetation. Finally I put it all together in a model with four equations. These models show that vegetation is an important factor, and can account for some specific features of glacial-interglacial cycles.
    [Show full text]
  • Biomineralization and Global Biogeochemical Cycles Philippe Van Cappellen Faculty of Geosciences, Utrecht University P.O
    1122 Biomineralization and Global Biogeochemical Cycles Philippe Van Cappellen Faculty of Geosciences, Utrecht University P.O. Box 80021 3508 TA Utrecht, The Netherlands INTRODUCTION Biological activity is a dominant force shaping the chemical structure and evolution of the earth surface environment. The presence of an oxygenated atmosphere- hydrosphere surrounding an otherwise highly reducing solid earth is the most striking consequence of the rise of life on earth. Biological evolution and the functioning of ecosystems, in turn, are to a large degree conditioned by geophysical and geological processes. Understanding the interactions between organisms and their abiotic environment, and the resulting coupled evolution of the biosphere and geosphere is a central theme of research in biogeology. Biogeochemists contribute to this understanding by studying the transformations and transport of chemical substrates and products of biological activity in the environment. Biogeochemical cycles provide a general framework in which geochemists organize their knowledge and interpret their data. The cycle of a given element or substance maps out the rates of transformation in, and transport fluxes between, adjoining environmental reservoirs. The temporal and spatial scales of interest dictate the selection of reservoirs and processes included in the cycle. Typically, the need for a detailed representation of biological process rates and ecosystem structure decreases as the spatial and temporal time scales considered increase. Much progress has been made in the development of global-scale models of biogeochemical cycles. Although these models are based on fairly simple representations of the biosphere and hydrosphere, they account for the large-scale changes in the composition, redox state and biological productivity of the earth surface environment that have occurred over geological time.
    [Show full text]
  • The Case Against Climate Regulation Via Oceanic Phytoplankton Sulphur Emissions P
    REVIEW doi:10.1038/nature10580 The case against climate regulation via oceanic phytoplankton sulphur emissions P. K. Quinn1 & T. S. Bates1 More than twenty years ago, a biological regulation of climate was proposed whereby emissions of dimethyl sulphide from oceanic phytoplankton resulted in the formation of aerosol particles that acted as cloud condensation nuclei in the marine boundary layer. In this hypothesis—referred to as CLAW—the increase in cloud condensation nuclei led to an increase in cloud albedo with the resulting changes in temperature and radiation initiating a climate feedback altering dimethyl sulphide emissions from phytoplankton. Over the past two decades, observations in the marine boundary layer, laboratory studies and modelling efforts have been conducted seeking evidence for the CLAW hypothesis. The results indicate that a dimethyl sulphide biological control over cloud condensation nuclei probably does not exist and that sources of these nuclei to the marine boundary layer and the response of clouds to changes in aerosol are much more complex than was recognized twenty years ago. These results indicate that it is time to retire the CLAW hypothesis. loud condensation nuclei (CCN) can affect the amount of solar The CLAW hypothesis further postulated that an increase in DMS radiation reaching Earth’s surface by altering cloud droplet emissions from the ocean would result in an increase in CCN, cloud number concentration and size and, as a result, cloud reflectivity droplet concentrations, and cloud albedo, and a decrease in the amount C 1 or albedo . CCN are atmospheric particles that are sufficiently soluble of solar radiation reaching Earth’s surface.
    [Show full text]