What Makes Complex Systems Complex?

This paper explores some of the factors that make complex systems complex. We first examine the history of complex systems. It was Aristotle’s insight that how elements are joined together helps determine the properties of the resulting whole. We find (a) that scientific reductionism does not provide a sufficient explanation; (b) that to understand complex systems, one must identify and trace energy flows; and (c) that disproportionate causality, including global tipping points, are all around us. Disproportionate causality results from the wide availability of energy stores. We discuss three categories of emergent phenomena—static, dynamic, and adaptive—and recommend retiring the term emergent, except perhaps as a synonym for creative. Finally, we find that virtually all communication is stigmergic

Understanding variability across the Crossroad transect from 3 years (2013 to 2015) of hydrographic data

The southwest continental shelf of Africa is characterized by a strong western boundary current with three interdependent components, namely the Agulhas Current, Agulhas Retroflection and Agulhas Return Current. This system plays a key role in setting oceanic conditions south of Africa. The Crossroad transect intersects both the Agulhas Current and Agulhas Return Current; a monitoring line established in 2013 to sample both the currents and determine inter-ocean fluxes, as well as the influence of the Agulhas Current on the Agulhas Bank shelf. The objective of the study was to examine both mesoscale and submesoscale features that influence the dynamic and variant nature of the Agulhas system. In this study we make use of Ship board Acoustic Doppler Current Profiler (SADCP), Conductivity Temperature and Depth (CTD), Thermosalinograph (TSG) and satellite Sea Surface Height data as main observations for analysis. The study also examines both the spatial and temporal characteristics of water properties across the Crossroad transect. The fundamental findings of the study include the abundance of both the mesoscale and submesoscale features observed in the Agulhas system, which are often overlooked. In addition, a noticeable variability in current measurements was observed, where velocity ranging from 2 to 2.5 m/s represented the Agulhas Current and 1.4 to 1.7 m/s, Agulhas Return Current. The position of the Agulhas Current and Agulhas Return Current displayed variation from 2013 to 2015, with the Agulhas Return Current exhibiting a meandering pattern in 2014 along the transect. Furthermore, an intrusion of cool (8 to 13 °C), lower salinity (34.8 to 35 psu) South Indian Central Water masses were also observed along the Agulhas Bank. The ability to combine altimetry and in situ data also contributed to the analysis of the results. Therefore, given the inherent advantage of satellite and in situ measurements, an overview of the variability across the Crossroad transect was determined

Oceanography, Climate and Vegetation development of tropical Africa during the last glacial: Palynology and geochemistry of marine sediments of ODP Site 1078 (off Angola)

In the last decades climate change research became more and more important due to the increasing impact of human activities on the Earth s climate system. The consideration of perspectives and results from paleoclimate observations has proven useful for climate change research, the verification of model outputs and thus future projections. The late Quaternary is characterised by large and abrupt climatic shifts on millennial and centennial time scales, the so-called Dansgaard-Oeschger (D-O) cycles and Heinrich Stadials (HS). Both, the D-O cycle and HS are thought to originate in the North Atlantic and are transmitted through the atmosphere and ocean circulation which results in a near-global footprint. It has been suggested that the abrupt climatic shifts associated with HS are the effect of a reduction in the strength of the Atlantic Meridional Overturning Circulation (AMOC). According to the hypothesis of the bipolar seesaw, a reduction in the AMOC leads to a build-up of heat in the South Atlantic. Although the tropics have the potential to alter the global atmosphere-ocean dynamics through changes in the heat and freshwater balance, little is known of their role in relation to abrupt climate perturbations. This thesis contains a compilation of high-resolution pollen records from South America and Africa covering the last glacial that documents the impact, timing and amplitude of abrupt climate change on the tropical vegetation. This thesis also focuses on the reconstruction of the vegetation, climate and oceanography of southern hemisphere Africa during the last glacial using marine sediments of Ocean Program Drilling Site 1078 (off Angola)

Oceanography, Climate and Vegetation development of tropical Africa during the last glacial: Palynology and geochemistry of marine sediments of ODP Site 1078 (off Angola)

In the last decades climate change research became more and more important due to the increasing impact of human activities on the Earth s climate system. The consideration of perspectives and results from paleoclimate observations has proven useful for climate change research, the verification of model outputs and thus future projections. The late Quaternary is characterised by large and abrupt climatic shifts on millennial and centennial time scales, the so-called Dansgaard-Oeschger (D-O) cycles and Heinrich Stadials (HS). Both, the D-O cycle and HS are thought to originate in the North Atlantic and are transmitted through the atmosphere and ocean circulation which results in a near-global footprint. It has been suggested that the abrupt climatic shifts associated with HS are the effect of a reduction in the strength of the Atlantic Meridional Overturning Circulation (AMOC). According to the hypothesis of the bipolar seesaw, a reduction in the AMOC leads to a build-up of heat in the South Atlantic. Although the tropics have the potential to alter the global atmosphere-ocean dynamics through changes in the heat and freshwater balance, little is known of their role in relation to abrupt climate perturbations. This thesis contains a compilation of high-resolution pollen records from South America and Africa covering the last glacial that documents the impact, timing and amplitude of abrupt climate change on the tropical vegetation. This thesis also focuses on the reconstruction of the vegetation, climate and oceanography of southern hemisphere Africa during the last glacial using marine sediments of Ocean Program Drilling Site 1078 (off Angola)

The variation of climate sensitive tidal ocean-dynamo signals on sub-decadal and seasonal time scales

Motional induction describes the induction of electric currents through charged particles moving perpendicular to an ambient magnetic field. A well-known device that uses motional induction to induce electric currents is the bicycle dynamo. The induction of electric currents in the ocean due to the motion of saltwater within the ambient geomagnetic field is, by contrast, lesser-known; this phenomenon is called the ocean-dynamo effect which indicates the similarity of both phenomena. The electromagnetic field signals emitted by ocean-dynamo induced electric currents are primarily sensitive to three factors: 1. the number of moving charged particles, 2. the magnetic field strength of the ambient field, and 3. the velocity with which the particles move perpendicular to said magnetic field. The amount of electrically charged particles in the seawater, a saline solution, is measured with the electrical seawater conductivity σ. σ is determined by the saline solution's chemical equilibrium, which in return is predominantly defined by the physical properties of seawater temperature and salinity. Thus, changes in the spatial distribution of seawater temperature and salinity cause changes in the spatial distribution of electrical seawater conductivity, which in return affect the ocean-dynamo signals. In theory, ocean-dynamo signals are therefore suitable for ocean observation applications. Out of all ocean-induced electromagnetic signals, signals induced by ocean tides play a unique role. The signatures of the periodic tidal flow are the only ocean-dynamo signals that have been successfully observed in magnetometer observations, space-borne and land-based. In addition to the proven measurability, the signals are also modelled with sufficient accuracy so that, on a global scale, observed tidal ocean-dynamo signatures agree well with model predictions. These two preconditions allow for an investigation of the relationship between ocean dynamics and tidal ocean-dynamo signals, a much-needed advancement towards practical ocean observation applications. In the past, sensitivity studies of tidal ocean-dynamo signals have focused mainly on changes on long time scales. By contrast, the present cumulative thesis examines the influence of ocean dynamics on tidal ocean-dynamo signals on short and intermediate time scales. In particular, it investigates the mechanisms and effects of ocean dynamics and recent seawater temperature and salinity changes on tidal ocean-dynamo signals. Furthermore, it investigates the detectability and measurability of short-term variations of said signals in magnetometer observations. Out of the presented three research studies, the first is a model-based characterization of tidal ocean-dynamo amplitude variations attributed to the El Niño/Southern Oscillation (ENSO). The study shows that tidal ocean-dynamo signal changes precede the onset of warm and cold ENSO phases and attributes these findings to the underlying oceanic processes. Furthermore, the study provides an assessment of the measurability of ENSO-induced tidal ocean-dynamo amplitude variations. The second study covers a time series analysis of modeled tidal ocean-dynamo amplitudes on a global scale. Here, the amplitudes were modeled based on existing oceanic seawater temperature and salinity observations. Based on the analysis of the underlying in-situ data, the study assesses recent developments in signal amplitudes to resolve a conflict between existing model-based sensitivity studies. Furthermore, the study identifies the heightened sensitivity of coastal tidal ocean-dynamo signals and provides a physical explanation for this fact. The third study focuses on local ocean phenomena and analyses time series of coastal island magnetometer observations. It presents evidence for seasonal amplitude variations and trends in amplitudes and phases of tidal ocean-dynamo signals. The advancements in the field contribute to the transition from retrospective or model-based analysis to an actual inference of the oceanic temperature and salinity dynamics from magnetometer observations

Anomaly Detection in Time Series: Theoretical and Practical Improvements for Disease Outbreak Detection

The automatic collection and increasing availability of health data provides a new opportunity for techniques to monitor this information. By monitoring pre-diagnostic data sources, such as over-the-counter cough medicine sales or emergency room chief complaints of cough, there exists the potential to detect disease outbreaks earlier than traditional laboratory disease confirmation results. This research is particularly important for a modern, highly-connected society, where the onset of disease outbreak can be swift and deadly, whether caused by a naturally occurring global pandemic such as swine flu or a targeted act of bioterrorism. In this dissertation, we first describe the problem and current state of research in disease outbreak detection, then provide four main additions to the field. First, we formalize a framework for analyzing health series data and detecting anomalies: using forecasting methods to predict the next day's value, subtracting the forecast to create residuals, and finally using detection algorithms on the residuals. The formalized framework indicates the link between the forecast accuracy of the forecast method and the performance of the detector, and can be used to quantify and analyze the performance of a variety of heuristic methods. Second, we describe improvements for the forecasting of health data series. The application of weather as a predictor, cross-series covariates, and ensemble forecasting each provide improvements to forecasting health data. Third, we describe improvements for detection. This includes the use of multivariate statistics for anomaly detection and additional day-of-week preprocessing to aid detection. Most significantly, we also provide a new method, based on the CuScore, for optimizing detection when the impact of the disease outbreak is known. This method can provide an optimal detector for rapid detection, or for probability of detection within a certain timeframe. Finally, we describe a method for improved comparison of detection methods. We provide tools to evaluate how well a simulated data set captures the characteristics of the authentic series and time-lag heatmaps, a new way of visualizing daily detection rates or displaying the comparison between two methods in a more informative way

Late Quaternary paleoceanographic history of the Pacific sector of the Southern Ocean based on diatom evidence

The last transition from a full glacial to a full interglacial state is of special importance to investigate processes that control the Earthâ s climate evolution especially regarding the interhemispheric climate variability. The Southern Ocean as southern limb of the Atlantic Meridional Overturning Circulation plays a crucial role in propagating signalsbetween the Pacific, Atlantic and Indian Ocean. Sea surface temperature (SST) and sea-ice extent are important surface water parameters related to the oceanic frontal and current systems as well as to water mass formation via brine release and bioproductivity changes. This thesis provides for the first time summer SSTs and winter sea-ice estimates in the Pacific sector of the Southern Ocean on a wide spatial range and for time slices within the last 30,000 years whose paleoceanographic history is crucial for the understanding of global climate change. The investigated environmental parameters point to the sensitivity of this Southern Ocean sector, concerning the drainage of the WAIS and the impact of atmospheric changes that has the high potential of triggering climate change

Marine Data Fusion for Analyzing Spatio-Temporal Ocean Region Connectivity

This thesis develops methods to automate and objectify the connectivity analysis between ocean regions. Existing methods for connectivity analysis often rely on manual integration of expert knowledge, which renders the processing of large amounts of data tedious. This thesis presents a new framework for Data Fusion that provides several approaches for automation and objectification of the entire analysis process. It identifies different complexities of connectivity analysis and shows how the Data Fusion framework can be applied and adapted to them. The framework is used in this thesis to analyze geo-referenced trajectories of fish larvae in the western Mediterranean Sea, to trace the spreading pathways of newly formed water in the subpolar North Atlantic based on their hydrographic properties, and to gauge their temporal change. These examples introduce a new, and highly relevant field of application for the established Data Science methods that were used and innovatively combined in the framework. New directions for further development of these methods are opened up which go beyond optimization of existing methods. The Marine Science, more precisely Physical Oceanography, benefits from the new possibilities to analyze large amounts of data quickly and objectively for its exact research questions. This thesis is a foray into the new field of Marine Data Science. It practically and theoretically explores the possibilities of combining Data Science and the Marine Sciences advantageously for both sides. The example of automating and objectifying connectivity analysis between marine regions in this thesis shows the added value of combining Data Science and Marine Science. This thesis also presents initial insights and ideas on how researchers from both disciplines can position themselves to thrive as Marine Data Scientists and simultaneously advance our understanding of the ocean

How magnetics and granulometry of continental margin sediments reflect terrestrial and marine environments of South America and West Africa

Continental margins are supplied by terrigenous clastic, as well as by biogenic marine sediments and, thus, act as natural archives for various environmental conditions. This thesis delineates sediment-distribution patterns off SE South America (20-55 deg. S) and NW Africa (14-17 deg. N) mainly based on rock-magnetic properties supplemented by clastic grain-size distributions, major-element concentrations, planktic and benthic foraminiferal assemblages, as well as stable-isotope signatures obtained from surface and down-core sediment samples. These investigations, spanning the last 19 kyr, reveal insights about prevalent climatic conditions on land (i.e., intensities of South American Monsoon System & Southern Westerly Wind Belt, or North-African Harmattan & trade winds) with impacts on major terrestrial sediment sources and transport paths. However, they also enable to draw conclusions about marine environmental conditions linked to ocean-current systems (i.e., Brazil & Malvinas Currents)

Communicating climate risk: a toolkit

The Communicating Climate Risk toolkit draws together best practice on the effective communication of climate information from across STEM, social sciences, and arts and humanities. It provides users with insights, recommendations, and tools for all forms of climate-related communication and decision-making, and identifies open problems