Paleoclimate reconstruction using biomarker and stable isotope analyses of lake sediments in the Bale Mountains, Ethiopia.

Während der Klimawandel und die globale Erwärmung das östliche Afrika schon heutzutage beeinflussen, ist das Wissen über die klimatischen Veränderungen der Vergangenheit begrenzt. Vor allem in den letzten 15.000 Jahren hat das östliche Afrika räumlich komplexe klimatische Veränderungen erlebt. Obwohl in Ostafrika mehrere paläoklimatische Studien durchgeführt wurden, welche die Temperaturänderungen und die hydrologische Vergangenheit von Seearchiven rekonstruierten, sind die treibenden Mechanismen und Telekonnektionen noch nicht vollständig verstanden. Ein tieferes Verständnis wird verhindert durch (i) das Fehlen von zeitlich weit zurückreichenden, qualitativ hochwertigen wissenschaftlichen Daten bezüglich Umweltveränderungen, insbesondere in der Region des Horns von Afrika, (ii) das Fehlen solcher Daten aus großen Höhen und (iii) unzureichend untersuchte Regionen wie der östliche Teil Äthiopiens und Somalia. Eines der am wenigsten untersuchten Hochgebirgsgebiete der Region sind die Bale Mountains, obwohl sie das größte Gebiet des Kontinents oberhalb von 4000 m ü. NN umfassen. Diese Dissertation zielt darauf ab, den derzeitigen Mangel an paläoklimatischen Rekonstruktionen in Hochgebirgen in der untersuchten Region am Horn von Afrika weiter zu verringern. Hochgelegene perennierende Seen, insbesondere Karseen, sind wertvolle Archive für paläoklimatische und ökologische Rekonstruktionen, da sie kontinuierliche Sedimente liefern, die durch menschliche Aktivitäten nicht gestört wurden. Der einzige ganzjährige See in den Bale Mountains, der Garba Guracha, liegt in der afro-alpinen Zone auf 3950 m ü. NN. Frühere paläolimnologische Untersuchungen ergaben, dass die kontinuierlichen Sedimente des Garba Guracha paläoklimatische und ökologische Informationen seit der letzten Vergletscherung beinhalten. Um das paläoklimatische Wissen über die Bale Mountains und damit über das östliche Afrika zu erweitern, wurden neue innovative Proxies, z. B. brGDGTs, δ18Ofucose, δ18Odiatom und δ2Hn-alkane, auf neu geborgene Sedimentkerne des Garba Guracha angewendet. Die Interpretation der Ergebnisse dieser Analysen ermöglichen ein tieferes Verständnis des Sedimentkerns, vor allem in Bezug auf die Sedimentologie, die Chronologie und die Quellen abgelagerten organischen Materials. Die hochauflösende Chronologie des Garba Guracha, die unter Verwendung verschiedener Datierungsmethoden und -komponenten (210Pb-Datierung, Radiokohlenstoffdatierung an der Gesamtsedimentfraktion, an Holzkohle und komponentenklassenspezifisch an n-Alkanen) erstellt wurde, ergibt ein basales Alter von ∼ 16 cal ka BP. Die geochemische Korrelation der Tephra-Schichten in den Garba-Guracha-Sedimenten mit datierten Tephra-Schichten aus anderen Seen der Region liefert eine externe Alterskontrolle, die die Robustheit der neuen Garba-Guracha-Chronologie und die Abwesenheit von systematischen Altersverschiebungen weiter untermauert. Ähnliche Altersangaben für n-Alkane und der Gesamtsedimentfraktion deuten darauf hin, dass die Biomarker in dem sehr kleinen afro-alpinen Einzugsgebiet kein Pre-aging vorweisen, was auf eine kurze Verweildauer oder/und eine hohe aquatische Produktivität schließen lässt. Die vorherrschende autochthone Produktion von organischem Material in dem im Vergleich zur Größe des Einzugsgebiets relativ großen See wurde durch relativ niedrige TOC/N Verhältnisse, relativ positive δ13C Werte und niedrige Werte der Zucker-Biomarker-Verhältnisse nachgewiesen. Der aquatische Ursprung von Fucose wird außerdem durch einen methodischen Vergleich von δ18Ofucose mit dem rein aquatischen δ18Odiatom Rekord unterstützt. Die gute Korrelation und ähnliche Amplitude von δ18Odiatom und δ18Ofucose (7,9 ‰ bzw. 7,1 ‰) unterstreichen nicht nur das Potenzial von δ18O-Zucker-Analysen in paläoklimatischen Studien, sondern lassen auch den Schluss zu, dass δ18Ofucose im Garba Guracha δ18OSeewasser widerspiegelt. Ohne den Einfluss des 'Amount effects' und des 'Source effects' völlig auszuschließen, interpretieren wir den δ18O-Datensatz des Garba Guracha daher als das Verhältnis von Niederschlag zu Verdunstung. Die hydrologische Vergangenheit des Garba Guracha wird von regionalen und nordhemisphärischen klimatischen Veränderungen beeinflusst. Zu Beginn des Holozäns nahmen die Niederschläge zu, was zu einem überlaufenden See zwischen ∼ 10 und ∼ 7 cal ka BP führte (erkennbar an den negativsten δ18O-Werten im gesamten Kern). Diese Phase entspricht der African Humid Period, einer räumlich unterschiedlich ausgeprägten feuchten Phase im äquatorialen und nördlichen Afrika, die durch eine verstärkte Aktivität des Westafrikanischen Monsuns und, im Fall der östlich gelegenen Bale Mountains, des Ostafrikanischen Monsuns bedingt wurde. Während die hydrologischen Veränderungen der AHP in Ostafrika durch meridionale Klimaprozesse angetrieben zu werden scheinen, zeigt das hochgelegene Garba Guracha Archiv zusätzliche Ähnlichkeiten mit rekonstruierten Monsunveränderungen in Oman. Eine kontinuierliche Verschiebung hin zu positiveren δ18O-Werten beginnt um 7 cal ka BP und deutet auf einen allmählichen Übergang von feuchtem zu trockenem Klima hin. Die Temperaturen am Garba Guracha wurden mit Hilfe einer modifizierten MBT'5ME Kalibrierung durch Hinzunahme von 6-Methyl-brGDGT IIIa' rekonstruiert (MBT'5ME Bale-Mountain-Index - r2 = 0,93, p < 0,05). Eine Anpassung der Kalibration war nötig, da die 6-Methyl-brGDGTs in den modernen Seesedimenten der Bale Mountains in bislang unbekannten Mengen auftreten und die Temperatur-Kalibrierung beeinflussen. Die rekonstruierten Temperaturänderungen sind stark von überregionalen klimatischen Einflüssen, wie Insolationsveränderungen und der AHP beeinflusst. Zusätzliche lokale Einflüsse, wie noch nicht abgeschmolzene Eismassen im Einzugsgebiet oder die Veränderungen der Hydrologie sind nicht auszuschließen. Im hochgelegenen Garba Guracha herrschten kalte Temperaturen, bis es kurz nach Beginn des Holozäns zu einer deutlichen Erwärmung (3,0 °C in weniger als 600 Jahren) kam. Zwischen 9 und 6 cal ka BP herrschte ein thermisches Maximum, das mit feuchten Bedingungen zusammenfiel und gefolgt war von einem Temperaturrückgang der bis 1.4 cal ka BP andauerte. Die Ergebnisse dieser Dissertation zeigen regionale und globale Antriebsmechanismen für klimatische Veränderungen in den Bale Mountains auf und erweitern damit das paläoklimatische Wissen über das Horn von Afrika. Der innovative methodische Ansatz dieser Arbeit hebt das Potenzial von δ18O-Zuckeranalysen und n-Alkan-Datierungen hervor. Darüber hinaus unterstreichen die Ergebnisse die Notwendigkeit einer verstärkten Grundlagenforschung, wie z. B. lokaler brGDGT-Kalibrierungsstudien, um die bestehenden wissenschaftlichen Konzepte voranzutreiben und zu präzisieren.:1.1 Table of Content List of Abbreviations v List of Tables vi List of Figures vii List of papers ix Abstract x Zusammenfassung xii Acknowledgements xiv 1 Introduction 1 1.1 Motivation 2 1.2 Objectives of the thesis 5 1.3 Background – The Bale Mountains and biomarker 6 1.3.1 Study area and archive 6 1.3.2 A short introduction to selected biomarkers applied in environmental geochemistry 8 1.4 Methods used in the thesis 10 1.4.1 Monosaccharide sugar biomarkers 11 1.4.2 Total lipid extraction for n-alkane and brGDGTs analyses 11 1.4.3 Branched Glycerol Dialkyl Glycerol Tetraether analyses 12 1.4.4 Biogeochemical analyses 13 1.4.5 Radiocarbon dating 13 1.4.6 Age depth model 13 1.5 Structure of the thesis 15 1.6 References 16 2 Revisiting afro-alpine Lake Garba Guracha in the Bale Mountains of Ethiopia: rationale, chronology, geochemistry, and paleoenvironmental implications 27 Abstract 28 2.1 Introduction 29 2.1.1 Study site 29 2.2 Material and Methods 31 2.2.1 Chronology and dating 31 2.2.2 XRF scanning 34 2.2.3 Biogeochemical analyses 34 2.2.4 n-Alkane and sugar quantification 35 2.3 Results 35 2.3.1 The sedimentary sequence – Master core and lithofacies 35 2.3.2 Chronology 37 2.3.3 Geochemistry 39 2.4 Discussion 41 2.4.1 Chronology 41 2.4.2 Origin of organic matter 43 2.4.3 Environmental implications 45 2.4.4 Comparison with lake level and other records 49 2.5 Conclusions 50 2.6 Acknowledgements 50 2.7 References 51 3 The Holocene lake-evaporation history of the afro-alpine Lake Garba Guracha in the Bale Mountains, Ethiopia, based on δ18O records of sugar biomarker and diatoms 61 Abstract 62 3.1 Introduction 62 3.1.1 Regional setting 64 3.2 Material and methods 66 3.2.1 Material and sampling 66 3.2.2 Compound-specific δ18O analyses of sugar biomarkers 66 3.2.3 δ18O analyses of diatoms 67 3.3 Results 68 3.3.1 δ18Ofuc record of Garba Guracha 68 3.3.2 δ18Odiatom record of Garba Guracha 69 3.4 Discussion 69 3.4.1 The Garba Guracha δ18Osugar record - lake or leaf water? 69 3.4.2 The Garba Guracha δ18Odiatom record 70 3.4.3 Comparison of reconstructed δ18Olake water from δ18Ofuc versus δ18Odiatom 71 3.4.4 Paleoclimatic significance and proxy interpretation 72 3.4.5 Comparison with other records 75 3.5 Conclusions 77 3.6 Acknowledgements 78 3.7 References 78 4 A Holocene temperature (brGDGT) record from Garba Guracha, a high-altitude lake in Ethiopia 89 Abstract 90 4.1 Introduction 90 4.1.1 Regional setting 93 4.2 Material and Methods 94 4.2.1 Material and Sampling 94 4.2.2 Sample preparation and analysis 95 4.2.3 BrGDGTs – structure, statistical methods and proxy calculation 96 4.2.4 Quantitative data analyses 97 4.3 Result 97 4.3.1 BrGDGT patterns of surface sediments from lakes in the Bale Mountains 97 4.3.2 BrGDGT patterns of the Garba Guracha sediment core 100 4.4 Discussion 103 4.4.1 Possible MAT calibration functions inferred from the expanded eastern African surface sediment dataset 103 4.4.2 Paleotemperature reconstructions for the Garba Guracha sedimentary record - comparison of the different calibrations 104 4.4.3 Paleotemperature reconstructions for the Garba Guracha sedimentary record – regional comparison 106 4.5 Conclusions 111 4.6 Acknowledgements 111 4.7 References 112 5 Synthesis 121 5.1 Sedimentation and chronology - What is the time frame and age depth function of the Garba Guracha core? 122 5.2 Source identification What is the origin of the organic material in the Garba Guracha sediment core? 125 5.3 Hydrology δ18O as a proxy for Garba Guracha evaporation history 126 5.4 Hydrology δ2H – as a proxy for the Garba Guracha precipitation history 128 5.5 Temperature - brGDGTs - as a proxy for Garba Guracha MAT history 129 5.6 Garba Guracha environmental and climate reconstruction – Why and how has the climate changed? 131 5.6.1 Deglaciation 132 5.6.2 North hemisphere forcings in the Garba Guracha catchment during the Younger Dryas period 132 5.6.3 Changing climatic conditions beginning of the Holocene 133 5.6.4 The warm African Humid Period 133 5.6.5 The termination of the African Humid Period 134 5.6.6 The Late Holocene 135 5.7 Garba Guracha – Climatic implications and driving mechanisms 136 5.7.1 Comparison of high and low altitudes in eastern Africa 136 5.7.2 Atmospheric circulation 138 5.8 References 144 6 Conclusions and Outlook 157 A Supplements to Chapter 2 162 B Supplements to Chapter 3 168 C Supplements to Chapter 4 173 D Supplements to Chapter 5 182While climate change and global warming are affecting eastern Africa today, the understanding of past climatic changes is limited. Especially during the last 15.000 years, eastern Africa has experienced spatially complex climatic changes. Although several paleoclimatic studies have been conducted in eastern Africa, reconstructing temperature changes and the hydrological history of lake archives, the driving mechanisms and teleconnections are yet not fully understood. A deeper understanding is precluded by (i) the lack of long, high-quality records of environmental change, especially in the Horn of Africa region, (ii) the lack of high altitude records, and (iii) insufficiently studied regions like eastern Ethiopia and Somalia. One of the region's most understudied high-altitude areas are the Bale Mountains, even though they encompass the continent's largest area above 4000 m a. s. l. This dissertation aims to further reduce the current lack of paleoclimatic reconstructions in high altitudes in the understudied Horn of Africa region. High-altitude perennial lakes, especially cirque lakes, are valuable archives for paleoclimate and environmental reconstructions, yielding continuous sedimentation undisturbed by human activity. The only perennial lake in the Bale Mountains, the Garba Guracha, lies in the afro-alpine zone at 3950 m a. s. l. Previous paleolimnological research revealed that Garba Guracha comprises a continuous paleoclimatic and environmental sedimentary record since the last deglaciation. In order to enhance the paleoclimatic knowledge of the Bale Mountains and hence of eastern Africa, new innovative proxies, e.g. brGDGTs, δ18Ofucose, δ18Odiatom, and δ2Hn alkane were applied to newly retrieved sediment cores of Garba Guracha. The application of these analyses and the interpretation of the results imply a deeper understanding of the retrieved sediment cores, concerning mainly sedimentology, chronology and organic matter source identification. The high resolution chronology of Garba Guracha, established using different dating methods and compounds (210Pb dating, radiocarbon dating of bulk sedimentary OM, compound class specific n alkanes, and charcoal), yields a basal age of ∼ 16 cal ka BP. The geochemical correlation of tephra layers in the Garba Guracha sediments to dated tephra layers of the region provides an external age control, further supporting the robustness of the new Garba Guracha chronology and the non existence of systematic age offsets. Similar ages obtained for n alkanes and bulk sediments suggest no pre aging of the biomarker in the very small afro-alpine catchment indicating short residence times or/and high aquatic productivity. Predominant autochthonous production of organic matter in the relative large lake compared to the catchment size has been proven by relatively low TOC/N ratios and relatively positive δ13C values. The aquatic origin of the sugar biomarker fucose is further supported by a methodological comparison of δ18Ofucose to a pure aquatic δ18Odiatom record. The good correlation and similar ranges of δ18Odiatom and δ18Ofucose (7.9 ‰ and 7.1 ‰, respectively) not only highlight the potential of δ18Osugar analyses in paleoclimatic studies but also lead to the conclusion that the Garba Guracha δ18Ofucose record reflects δ18Olake water. Therefore, without completely excluding the influence of the ‘amount effect’ and the ‘source-effect’, we interpret the record to reflect primarily the precipitation to evaporation ratio (P/E). The hydrological history of Garba Guracha is influenced by regional and northern hemisphere climatic changes. Precipitation increased at the onset of the Holocene, resulting in an overflowing lake between ∼ 10 and ∼ 7 cal ka BP (noted by the most negative δ18O values in the record). This humid phase corresponds to the African Humid Period (AHP), a spatially complex humid phase across equatorial and northern Africa, driven by enhanced West African Monsoon (WAM) and, in the case of the easterly-situated Bale Mountains, East African Monsoon (EAM) activity. While hydrological changes during the AHP in eastern Africa seem to be driven by meridional climatic processes, the high-altitude Garba Guracha archive shows additional similarities to reconstructed monsoonal changes in Oman. A continuous transition towards more positive δ18O values begins at 7 cal ka BP and indicates a gradual shift from humid to drier climate. The reconstructed temperature history is strongly linked to supraregional climatic changes associated with insolation forcing and the AHP, as well as with local anomalies associated with catchment deglaciation and hydrology. Cold temperatures prevailed in the high-altitude Garba Guracha until significant warming (3.0 °C in less than 600 years) occurred shortly after the Holocene onset. A thermal maximum prevailed between 9 and 6 cal ka BP, coinciding with humid conditions, followed by a temperature decrease until 1.4 cal ka BP. The temperatures at the Garba Guracha were reconstructed using a modified MBT'5ME calibration by adding 6 methyl brGDGT IIIa' (resulting in the MBT'5ME Bale Mountain index, r2 = 0.93, p < 0.05) due to an uncommon variation in 6 methyl brGDGTs in the modern lake surface sediment samples. The results of this dissertation reveal regional and global driving mechanisms of climatic changes in the Bale Mountains, further expanding paleoclimatic knowledge about the Horn of Africa. The innovative methodological approach of this thesis highlights the potential of δ18Osugar analyses and n alkane dating. Moreover, the results underline the need for intensified basic research like local brGDGT calibration studies to advance and specify existing scientific concepts.:1.1 Table of Content List of Abbreviations v List of Tables vi List of Figures vii List of papers ix Abstract x Zusammenfassung xii Acknowledgements xiv 1 Introduction 1 1.1 Motivation 2 1.2 Objectives of the thesis 5 1.3 Background – The Bale Mountains and biomarker 6 1.3.1 Study area and archive 6 1.3.2 A short introduction to selected biomarkers applied in environmental geochemistry 8 1.4 Methods used in the thesis 10 1.4.1 Monosaccharide sugar biomarkers 11 1.4.2 Total lipid extraction for n-alkane and brGDGTs analyses 11 1.4.3 Branched Glycerol Dialkyl Glycerol Tetraether analyses 12 1.4.4 Biogeochemical analyses 13 1.4.5 Radiocarbon dating 13 1.4.6 Age depth model 13 1.5 Structure of the thesis 15 1.6 References 16 2 Revisiting afro-alpine Lake Garba Guracha in the Bale Mountains of Ethiopia: rationale, chronology, geochemistry, and paleoenvironmental implications 27 Abstract 28 2.1 Introduction 29 2.1.1 Study site 29 2.2 Material and Methods 31 2.2.1 Chronology and dating 31 2.2.2 XRF scanning 34 2.2.3 Biogeochemical analyses 34 2.2.4 n-Alkane and sugar quantification 35 2.3 Results 35 2.3.1 The sedimentary sequence – Master core and lithofacies 35 2.3.2 Chronology 37 2.3.3 Geochemistry 39 2.4 Discussion 41 2.4.1 Chronology 41 2.4.2 Origin of organic matter 43 2.4.3 Environmental implications 45 2.4.4 Comparison with lake level and other records 49 2.5 Conclusions 50 2.6 Acknowledgements 50 2.7 References 51 3 The Holocene lake-evaporation history of the afro-alpine Lake Garba Guracha in the Bale Mountains, Ethiopia, based on δ18O records of sugar biomarker and diatoms 61 Abstract 62 3.1 Introduction 62 3.1.1 Regional setting 64 3.2 Material and methods 66 3.2.1 Material and sampling 66 3.2.2 Compound-specific δ18O analyses of sugar biomarkers 66 3.2.3 δ18O analyses of diatoms 67 3.3 Results 68 3.3.1 δ18Ofuc record of Garba Guracha 68 3.3.2 δ18Odiatom record of Garba Guracha 69 3.4 Discussion 69 3.4.1 The Garba Guracha δ18Osugar record - lake or leaf water? 69 3.4.2 The Garba Guracha δ18Odiatom record 70 3.4.3 Comparison of reconstructed δ18Olake water from δ18Ofuc versus δ18Odiatom 71 3.4.4 Paleoclimatic significance and proxy interpretation 72 3.4.5 Comparison with other records 75 3.5 Conclusions 77 3.6 Acknowledgements 78 3.7 References 78 4 A Holocene temperature (brGDGT) record from Garba Guracha, a high-altitude lake in Ethiopia 89 Abstract 90 4.1 Introduction 90 4.1.1 Regional setting 93 4.2 Material and Methods 94 4.2.1 Material and Sampling 94 4.2.2 Sample preparation and analysis 95 4.2.3 BrGDGTs – structure, statistical methods and proxy calculation 96 4.2.4 Quantitative data analyses 97 4.3 Result 97 4.3.1 BrGDGT patterns of surface sediments from lakes in the Bale Mountains 97 4.3.2 BrGDGT patterns of the Garba Guracha sediment core 100 4.4 Discussion 103 4.4.1 Possible MAT calibration functions inferred from the expanded eastern African surface sediment dataset 103 4.4.2 Paleotemperature reconstructions for the Garba Guracha sedimentary record - comparison of the different calibrations 104 4.4.3 Paleotemperature reconstructions for the Garba Guracha sedimentary record – regional comparison 106 4.5 Conclusions 111 4.6 Acknowledgements 111 4.7 References 112 5 Synthesis 121 5.1 Sedimentation and chronology - What is the time frame and age depth function of the Garba Guracha core? 122 5.2 Source identification What is the origin of the organic material in the Garba Guracha sediment core? 125 5.3 Hydrology δ18O as a proxy for Garba Guracha evaporation history 126 5.4 Hydrology δ2H – as a proxy for the Garba Guracha precipitation history 128 5.5 Temperature - brGDGTs - as a proxy for Garba Guracha MAT history 129 5.6 Garba Guracha environmental and climate reconstruction – Why and how has the climate changed? 131 5.6.1 Deglaciation 132 5.6.2 North hemisphere forcings in the Garba Guracha catchment during the Younger Dryas period 132 5.6.3 Changing climatic conditions beginning of the Holocene 133 5.6.4 The warm African Humid Period 133 5.6.5 The termination of the African Humid Period 134 5.6.6 The Late Holocene 135 5.7 Garba Guracha – Climatic implications and driving mechanisms 136 5.7.1 Comparison of high and low altitudes in eastern Africa 136 5.7.2 Atmospheric circulation 138 5.8 References 144 6 Conclusions and Outlook 157 A Supplements to Chapter 2 162 B Supplements to Chapter 3 168 C Supplements to Chapter 4 173 D Supplements to Chapter 5 18

Complex Problem Solving through Human-AI Collaboration: Literature Review on Research Contexts

Solving complex problems has been proclaimed as one major challenge for hybrid teams of humans and artificial intelligence (AI) systems. Human-AI collaboration brings immense opportunities in these complex tasks, in which humans struggle, but full automation is also impossible. Understanding and designing human-AI collaboration for complex problem solving is a wicked and multifaceted research problem itself. We contribute to this emergent field by reviewing to what extent existing research on instantiated human-AI collaboration already addresses this challenge. After clarifying the two key concepts (complex problem solving and human-AI collaboration), we perform a systematic literature review. We extract research contexts and assess them considering different complexity features. We thereby provide an overview of existing and guidance for designing new, suitable research contexts for studying complex problem solving through human-AI collaboration and present an outlook for further work on this research challenge

Learning by Doing: Educators’ Perspective on an Illustrative Tool for AI-Generated Scaffolding for Students in Conceptualizing Design Science Research Studies

Design science research (DSR) is taught in university courses and used by students for their final theses. For successfully learning DSR, it is important to learn to apply it to real-world problems. However, students not only need to learn the new DSR paradigm (meta-level) but also need to develop an understanding of the problem domain (content-level). In this paper, we focus on content-level support (CLS), proposing an illustrative tool to aid students when learning to develop a conceptual design with DSR (e.g., for a prototype). Following the DSR paradigm, we deductively identify students’ issues and use the scaffolding approach to develop design requirements (DRs) and design principles (DPs). To offer AI-generated scaffolding, we use the generative language model (GLM) “GPT-3.” We evaluate our illustrative design through 13 expert interviews. Our results show that providing students with CLS is perceived to be helpful, but the interaction with the student needs to be designed carefully to circumvent unintended usage patterns. We contribute DPs and an illustrative instantiation thereof toward a DSR tool support ecosystem. More broadly, we contribute to the understanding of how humans can be supported by AI to solve problems, an important challenge in human-AI collaboration research

HUMAN-AI COLLABORATION IN CONCEPTUALIZING DESIGN SCIENCE RESEARCH STUDIES: PERCEIVED HELPFULNESS OF GENERATIVE LANGUAGE MODEL\u27S SUGGESTIONS

Solving complex problems was named a new challenge for research on human-AI collaboration. In our study we focus on a particular means to solving complex problems: design science research (DSR). We investigate whether AI, more specifically, generative language models (GLM), can support an individual in conceptualizing DSR studies by making helpful suggestions. To do so we use extracts of a published DSR study and have GPT-3, a GLM provide suggestions for aspects of this study. These suggestions are then evaluated in a survey (n=33) regarding their helpfulness. Results show that GLM suggestions are perceived to be helpful, with some variation depending on expertise. Reported interest in using such a tool in the future was high. Describing how GLM can offer helpful suggestions we contribute toward a DSR tool support ecosystem and, more generally, towards knowledge on how humans and (generative) AI systems can team up to solve complex problems

A User-centric Taxonomy for Conversational Generative Language Models

Conversational generative language models (GLMs) like ChatGPT are being rapidly adopted. Previous research on non-conversational GLMs showed that formulating prompts is critical for receiving good outputs. However, it is unclear how conversational GLMs are used when solving complex problems that require multi-step interactions. This paper addresses this research gap based on findings from a large participant event we conducted, where ChatGPT was iteratively and in a multi-step manner used while solving a complex problem. We derived a taxonomy of prompting behavior employed for solving complex problems as well as archetypes. While the taxonomy provides common knowledge on GLMs usage based on analyzed input-prompts, the different archetypes facilitate the classification of operators according to their usage. With both we provide exploratory knowledge and a foundation for design science research endeavors, which can be referred to, enabling further research and development of prompt engineering, prompting tactics, and prompting strategies on common ground

The Holocene lake-evaporation history of the afro-alpine Lake Garba Guracha in the Bale Mountains, Ethiopia, based on δ18O records of sugar biomarker and diatoms

In eastern Africa, there are few long, high-quality records of environmental change at high altitudes, inhibiting a broader understanding of regional climate change. We investigated a Holocene lacustrine sediment archive from Lake Garba Guracha, Bale Mountains, Ethiopia, (3,950 m a.s.l.), and reconstructed high-altitude lake evaporation history using δ18O records derived from the analysis of compound-specific sugar biomarkers and diatoms. The δ18Odiatom and δ18Ofuc records are clearly correlated and reveal similar ranges (7.9‰ and 7.1‰, respectively). The lowest δ18O values occurred between 10 and 7 cal ka BP and were followed by a continuous shift towards more positive δ18O values. Due to the aquatic origin of the sugar biomarker and the similar trends of δ18Odiatom, we suggest that our lacustrine δ18Ofuc record reflects δ18Olake water. Therefore, without completely excluding the influence of the ‘amount-effect’ and the ‘source-effect‘, we interpret our record to reflect primarily the precipitation-to-evaporation ratio (P/E). We conclude that precipitation increased at the beginning of the Holocene, leading to an overflowing lake between ~10 and ~8 cal ka BP, indicated by low δ18Olake water values interpreted as reduced evaporative enrichment. This is followed by a continuous trend towards drier conditions, indicating at least a seasonally closed lake system

Summer paleohydrology during the Late Glacial and Early Holocene based on δ2H and δ18O from Bichlersee, Bavaria.

Isotope-based records provide valuable information on past climate changes. However, it is not always trivial to disentangle past changes in the isotopic composition of precipitation from possible changes in evaporative enrichment, and seasonality may need to be considered. Here, we analyzed δ2H on n-alkanes and δ18O on hemicellulose sugars in sediments from Bichlersee, Bavaria, covering the Late Glacial and Early Holocene. Our δ2Hn-C31 record documents past changes in the isotopic composition of summer precipitation and roughly shows the isotope pattern known from Greenland. Both records show lower values during the Younger Dryas, but at Bichlersee the signal is less pronounced, corroborating earlier suggestions that the Younger Dryas was mainly a winter phenomenon and less extreme during summer. δ18Ofucose records the isotopic composition of the lake water during summer and is sensitive to evaporative enrichment. Coupling δ2Hn-C31 and δ18Ofucose allows calculating lake water deuterium-excess and thus disentangling changes in the isotopic composition of precipitation and evaporative enrichment. Our deuterium-excess record reveals that the warm Bølling-Allerød and Early Holocene were characterized by more evaporative enrichment compared to the colder Younger Dryas. Site-specific hydrological conditions, seasonality, and coupling δ2H and δ18O are thus important when interpreting isotope records

Central Mongolian lake sediments reveal new insights on climate change and equestrian empires in the Eastern Steppes

The repeated expansion of East Asian steppe cultures was a key driver of Eurasian history, forging new social, economic, and biological links across the continent. Climate has been suggested as important driver of these poorly understood cultural expansions, but paleoclimate records from the Mongolian Plateau often suffer from poor age control or ambiguous proxy interpretation. Here, we use a combination of geochemical analyses and comprehensive radiocarbon dating to establish the first robust and detailed record of paleohydrological conditions for Lake Telmen, Mongolia, covering the past ~ 4000 years. Our record shows that humid conditions coincided with solar minima, and hydrological modeling confirms the high sensitivity of the lake to paleoclimate changes. Careful comparisons with archaeological and historical records suggest that in the vast semi-arid grasslands of eastern Eurasia, solar minima led to reduced temperatures, less evaporation, and high biomass production, expanding the power base for pastoral economies and horse cavalry. Our findings suggest a crucial link between temperature dynamics in the Eastern Steppe and key social developments, such as the emergence of pastoral empires, and fuel concerns that global warming enhances water scarcity in the semi-arid regions of interior Eurasia