Includes bibliographical references. / Sea surface temperature (SST) fluctuations and changes around southern Africa have important consequences on regional weather, climate and the marine ecosystem. SST is a good indicator for upwelling strength in the Benguela Current system and therefore is linked to bio logical activity in that region. SS T is an important driver of the air-sea exchange of moisture and energy, especially in the Agulhas Current where high latent and sensible heat fluxes occur. It is important to quantify SST trends with accuracy for the long term monitoring and characterisation of weather, climate and marine ecosystem in southern Africa, especially in the context of climate change. Here various 1° x 1° SST datasets are used to calculate yearly time series, inter-annual fluctuations and trends in key oceanic regions of southern Africa. OI SST, Hadley SST, NOCS SST and ER SST (which has 2° x 2° resolution) are used in this study. I start calculating trends and inter- annual fluctuations for various domains and dataset in the recent satellite era since 1982 to compare the non-satellite products NOCS SST and ER SST with the satellite products Hadley SST and OI SST. The idea is to validate the no n-satellite products since 1982 and then use them to calculate trends around southern Africa before 1982. Trends and inter-annual fluctuation in the Angola Benguela Current system and the Agulhas Current retroflection system are therefore presented for all datasets for the 1982 - 2012 period. The datasets show different trends and different timing or amplitude of inter- annual variability. This prevents the estimation of changes in the region with confidence before the satellite era which was the initial objective of the study. The main reason is that ER SST is a 2° x 2° dataset and maybe not adequate for upwelling region and the Hadley SST 1° x 1° dataset include satellite data from 1980 which creates some non-homogeneity in time and probably an artificial cooling at the coast from the 1980’s when satellite data is introduced in the dataset to patch the observational gaps. It is therefore not advisable to use Hadley SST for trend studies including 1982 onwards. From 1982 to 2012 in the Benguela upwelling system, whereas OI SST and Hadley SST show mainly cooling trends of different magnitude, NOCS SST and ER SST show warming trends with NOCS showing significant (p < 0.05) warming trends which is suspicious. In the Northern Benguela and Retroflection all datasets show warming trends for the 1982 - 2012 period except from NOCS SST.

Includes bibliographical references. / The Seychelles-Chagos Thermocline Ridge (SCTR) is a region of upwelling present at 55°E- 90°E and 5°S-12°S in the southwest tropical Indian Ocean. It is a region of strong ocean-atmosphere interactions due to the high variability of the thermocline depth caused by the local Ekman pumping. Sea-viewing Wide Field-of-view Sensor (SeaWiFS) has shown high variability of surface chlorophyll-a (SChl-a) in the SCTR region. The Indian Ocean Dipole (IOD) and El Niño Southern Oscillation (ENSO) have also driven significant interannual variation of the depth of 20°C isotherm (D20) and SChl-a in the southern tropical Indian Ocean. A 50-years hindcast (RUN58-07) from a coupled bio-physical model was used to study the SChl-a concentration on an annual time scale and the interannual variability of D20 and SChla in the SCTR in response to IOD and ENSO events. Initial analysis revealed a high overestimation of SChl-a in the 50-year run. Therefore, a 44-years hindcast (RUN58-01) of the same coupled model was taken into consideration. Comparisons with observations show that the RUN58-07 reproduces the D20 and SSH better than the RUN58-01 but the RUN58-01 shows better agreement with SeaWiFS. Results reveal that the SCTR exhibits an annual cycle of SChl-a concentration, with a peak in austral winter (June-August) due to the strong southeasterlies, increasing wind stirring and induced upwelling. Vertical sections of the SCTR also indicate that an increase in surface concentration in austral winter is compensated by a decrease in subsurface phytoplankton blooms. Composite figures show that IOD events exhibit a greater influence on the subsurface and surface variability in the SCTR region. The IOD deepens and shoals the D20 in the SCTR and eastern Indian Ocean respectively whereas ENSO displays a weaker and less-extensive influence on the D20. The spatial distribution of SChl-a in the Indian Ocean is completely disrupted by IOD during which the SCTR becomes oligotrophic whereas the eastern Indian Ocean becomes highly productive. ENSO, however, does not display any significant biogeochemical signature in the SCTR. This study should improve our understanding of the interannual variability of the thermocline depth and chlorophyll-a in the SCTR region; and for the optimization of the management of fishery resources and marine ecosystems.

Widespread flooding over parts of Malawi, Mozambique, and Madagascar occurred in January 2015. An impact assessment by the World Bank indicated huge damage to property, infrastructure, and agriculture over several regions in south-eastern Africa. The flooding was associated with tropical storm Chedza that developed in the Mozambique Channel on 11 January 2015. This study investigates the atmospheric circulation and potential mechanisms responsible for the heavy rainfall event that occurred between 11 and 17 January over Mozambique and Malawi using the Weather Research and Forecasting (WRF) model, the Global Forecast System (GFS) atmospheric reanalysis, satellite derived rainfall and wind data, and station rainfall data. Tropical Rainfall Measuring Mission (TRMM) rainfall estimates and rainfall station data indicated that southern Malawi and northern Mozambique experienced the majority of rainfall during the early stages of tropical storm Chedza while Madagascar experienced heavy falls when tropical storm Chedza tracked over the island on January 17. Furthermore, analysis of the station data revealed that the heavy rainfall over Mozambique occurred between 11 and 13 January with some stations recording about 80 % of their total January 2015 rainfall as resulting from this event. The WRF model run of the event indicated a low level easterly to southeasterly onshore flow over southern Mozambique that interacted with a northwesterly monsoonal flow to westerly flow along the northern flanks (periphery) of the storm in the northern Mozambique Channel, leading to surface moisture flux convergence in the regions of heavy rainfall. Furthermore, moisture from the southwest Indian Ocean was advected into the region during the heavy rainfall. It is suggested that multiple favourable factors which included strong moisture fluxes from the southwest Indian Ocean and equatorial South Indian Ocean, near surface convergence over the areas of heavy rainfall, and strong uplift acted together to create favourable conditions for the development of tropical storm Chedza and the associated heavy rainfall.

Includes bibliographical references. / Several species of marine organisms occurring off the southern African coast have been found to be identical to those occurring in the Madagascan coastal water although the reason for this is unknown. It has been proposed that eddies act as a vector of transport for planktonic larvae from the Madagascar island to the southern African east coast. In this study it is shown that eddies spawned off southern Madagascar entrain chlorophyll-a rich coastal waters into their periphery. This is indicative of the mechanism whereby organisms could become entrained in eddies. Approximately one eddy per year, usually cyclonic, interacts with the southern Madagascan coast, then from its origin crosses the southern Mozambique Channel and arrives at the African coast where it dissipates. By tracking eddies and combining their trajectories with drifter data and satellite remote sensing observations of ocean colour, it is shown that chlorophyll-a rich waters are entrained within the eddies, and these waters are mostly conserved during their passage across the channel. This study suggests that biota may be transported from Madagascar to Africa in eddies, providing further evidence that eddies are potentially a viable mechanism for the transport of organisms across the southern Mozambique Channel.

Analysis of tide gauge sea level observations of varying durations in the southwest Indian Ocean and the East coast of Africa (Lamu, Mombasa, Zanzibar, Durban, Port La Rue and Port Louis) show variability which are related to global, regional time scales, local weather and climatic changes, oceanographic and hydrological forcing that manifest in both short and long time scales. The investigations on the tide gauge sea level observations are conducted through the separation of the total sea level measurements into the contributing components (tides and residuals) using a Matlab in built software (t-tide). Short time scale sea level variability in the southwest Indian Ocean is due to the effects of tides which exhibit tidal range variations with latitude and shelf width, storm surges resulting from tropical cyclones passage especially in the mid-latitude region, atmospheric pressure fluctuations over the surface of the sea and local wind fields. Sea surface temperature variations during summer and winter result in differential heating of the ocean surface and contribute to the observed sea level variability at seasonal time scale especially in the region 25°S and southwards where the temperature differences are large. The equatorial region is characterized by a near constant sea surface temperature that sustains thermal expansion of the upper layer of the ocean water throughout the year. Monsoon periods show significant and variable wind speeds that impact on sea level variability in the southwest Indian Ocean and the East coast of Africa and are greatest during the summer monsoon (from June to August). On longer time scales (Interannual and decadal), sea level variations in this region is mostly influenced by the El Nino Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD). During the 1997/98 El Nino event, the sea levels are significantly higher than normal at the coast and the islands. During the 2000/2001 La Nina, the sea levels are significantly lower than normal at the coasts in the southwest Indian Ocean. Indian Ocean Dipole effects are significant in the southwest Indian Ocean during the period 2006 through to 2008 and are more enhanced in 2007. The annual highest sea levels in this region are influenced by the year to year changes in weather pattern and the perigean cycle of the tides on a 4.4 year period but their secular trends are not statistically significant.

In this study, we investigate the role that the solubility and biological pumps have on CO₂ variability across the Agulhas Current system ( Agulhas Current and the Agulhas Return Current). The Agulhas Current system transports heat and salt from the Indian Ocean into the South Atlantic Ocean via the Agulhas leakage, which influences the Atlantic Meridional Overturning Circulation (AMOC). This study presents for the first time a characterization of the role the Agulhas Current system (Agulhas and Agulhas Return Currents) has on the uptake of anthropogenic CO₂. Fugacity of carbon dioxide (fCO₂ ) values were obtained from a ship-based underway pCO₂ (partial pressure of carbon dioxide) system and the air-sea CO₂ fluxes were computed using 6-hourly wind speeds from the NOAA Blended Sea Winds. An experiment was conducted during the Crossroads scientific monitoring line in May 2013, where surface dissolved inorganic carbon, total alkalinity and CO₂ flux were compared between the Agulhas and Agulhas Return Currents and the region directly south over the Agulhas Plateau. Our findings highlighted that the solubility and biological pumps played minimal to no role in the drawdown of carbon across the sub-Tropical zone and the Agulhas Current system (Agulhas and Agulhas Return Currents), due to opposing effect between chlorophyll and temperature on pCO₂ that explained why although there was carbon drawdown by primary production in the Agulhas and Agulhas Return Current regions, this does not play a role in enhancing the air-sea exchange of CO₂. The solubility pump was responsible for CO₂ in the sub-Antarctic zone. The biological and solubility pumps were responsible for CO₂ sink in the Agulhas Plateau eddy. The highest CO₂ flux in the study was observed in the Agulhas Plateau eddy at a flux value of -8.12 mmolC.m-².day-¹ due to the cooler mean sea surface temperature of ~16.5 °C. This is the first time that such as study has been undertaken and aims to provide a better understanding of the role of Western Boundary Currents such as the Agulhas Current has in the uptake of CO₂.

Eddies within oceans act as vehicles, transporting smaller bodies of water, with certain oceanographic characteristics, from one place to another within a larger body of water. The South West Indian Ridge [SWIR] is a topographically complex bathymetric feature which amplifies the production of mesoscale eddies in and around the Antarctic Circumpolar Current [ACC]. Within the Southern Ocean [SO], a section of this ridge - the Andrew Bain Fracture Zone [ABFZ] - has been found to be the starting line of an eastward extending eddy corridor. Earlier research shows an area of diminishing mesoscale variability within this corridor which extends down from 45°S to approximately 60S. A recent study focused on a southward extending anticyclonic eddy corridor and proved its existence. The anticyclonic [warm core] eddies which are propagating south, not previously investigated through in situ means, were observed during the 2014 Marion Island Relief Cruise [MIRC2014] aboard the SA Agulhas II. Two anticyclonic mesoscale eddies [one juvenile and one mature] were bisected with transects of conductivity, temperature and depth stations and expendable bathythermograph deployments. This paper used the in situ data captured during the MIRC2014 to study the internal structure of the two eddies. The objectives of this study were also to examine both the recent and the historical trajectory characteristics of the southward advecting anticyclonic eddies, to confirm the origin of the two sampled eddies, and to assess the structural differences between the two anticyclonic eddies. This paper plots the behaviour of the anticyclonic mesoscale eddies found within the area of the southward eddy corridor, firstly using website available data collected over a two year period [May 2012 - May 2014] and then utilizing a previously compiled data set to plot the historical dynamics [October 1992 - April 2012]. The trajectories of the southward anticyclones during that time period were found to be predominantly southward, typically following the south west slope of the SWIR. The two MIRC2014 eddies were confirmed to originate from the ABFZ section of the SWIR. Each eddy had a similar grouping of water masses; Antarctic Bottom Water, Circumpolar Deep Water, Antarctic Intermediate Water, Winter Water and Sub-Antarctic Surface Water: water masses characteristic of the Antarctic Polar Frontal Zone [APFZ]. The in situ measurement and analysis of these eddies allowed the first comparison between a juvenile and a mature anticyclonic eddy in the recently discovered southward extending eddy corridor. Thermal section comparisons of these two sampled anticyclonic eddies showed that, over time, these anticyclonic eddies appear to shrink in surface diameter, deepen and lose heat to host waters. This loss of heat occurs due to the degradation of water mass boundary integrity over time and is theorised to accelerate as time passes. This study shows that the southward extending eddy corridor is a means of shifting heat and salt further south within the SO, large sections of which are sink areas for atmospheric CO₂. This poleward heat transport influences the capability of the SO to absorb atmospheric CO₂, since higher temperatures negatively affect the ocean's CO₂ uptake capability. The results of this study are proposed to be a catalyst for future in situ sampling across eddies in this area, in order that heat and salt transport, through this southward anticyclonic eddy corridor, can be monitored for fluctuations. As this carbon sink is vitally important with regards to climate change, the quantification of the heat and salt sources of the SO, which alter the SO's ability to absorb CO₂, is imperative.

This document is a summary of research conducted to develop and apply climate analysis tools toward a better understanding of the past and future of hydroclimate variability in the state of Utah. Two pilot studies developed data management and climate analysis tools subsequently applied to our region of interest. The first investigated the role of natural atmospheric forcing in the inter-annual variability of precipitation of the Sahel region in Africa, and found a previously undocumented link with the East Atlantic mode, which explains 29% of variance in regional precipitation. An analysis of output from an operational seasonal climate forecast model revealed a failure in the model to reproduce this linkage, thus highlighting a shortcoming in model performance. The second pilot study studied long-term trends in the strength of the Great Plains low-level jet, an driver of storm development in the region’s wet spring season. Our analysis showed that since 1979 the low-level jet has strengthened as shifted the timing of peak activity, resulting in shifts both in time and location for peak precipitation, possibly the result of anthropogenic forcing. Our third study used a unique tree-ring dataset to create a reconstruction of April 1 snow water equivalent, an important measure of water supply in the Intermountain West, for the state of Utah to 1850. Analysis of the reconstruction shows the majority of snowpack variability occurs monotonically over the whole state at decadal to multidecadal frequencies. The final study evaluated decadal prediction performance of climate models participating in the Coupled Model Intercomparison Project 5. We found that the analyzed models exhibit modest skill in prediction of the Pacific Decadal Oscillation and better skill in prediction of global temperature trends post 1960.

In the last few decades, we have been witness to unprecedented changes in precipitation and temperature. Such alterations to our climate system have important implications for terrestrial ecosystems that billions of people depend on for their livelihood. The situation is especially tenuous for those living directly off the landscape via resources from natural ecosystems or subsistence agriculture as in much of tropical Africa. Studies of past climates provide potential analogues and help validate models essential for elucidating mechanisms that link changes in climate mean and variability and how they may affect ecosystem distribution and productivity. However, despite the importance of the paleo-record for insight into the future, tropical proxy records are rare, low resolution, and too short to capture important intervals that may act as analogs, such as the Last Interglacial (MIS 5e; ~130-115ka).Long, high-resolution drill cores from Lake Malawi, southeast Africa, provide a record of tropical climate and vegetation that extends back ~1.2mya, comprising many continuous glacial-interglacial cycles. My primary research involves conducting pollen analyses on these cores. First, I analyzed a high-resolution interval of the shortest Malawi core in order to better understand abrupt vegetation transitions during the Last Deglaciation. Further analysis was conducted on the longest Malawi core, beginning with an interval covering all of the Penultimate Glacial through the Last Interglacial. The resultant pollen data has shown that abrupt, large-scale landscape transitions from forest to desert follow local insolation and lake levels at the site, with a strong dependence of forest/woodland vegetation types on mean rainfall as well as rainfall seasonality. The interpretation of paleodata requires a good understanding of modern processes, thus another project has focused on using model simulations of the Last Interglacial and modern satellite NDVI time series to highlight dynamical and statistical relationships between vegetation and climate change. This work suggests that despite suggested links between monsoon intensity and SSTs in the southern African tropics, insolation controls on atmospheric circulation are the primary drivers of vegetation reorganization. In addition, this work highlights the importance of rainfall seasonality and dry season length in addition to precipitation controls on vegetation.

Climate is the principal driving force of hydrological extremes like floods and attributing generating mechanisms is an essential prerequisite for understanding past, present, and future flood variability. Successively enhanced radiative forcing under global warming enhances atmospheric water-holding capacity and is expected to increase the likelihood of strong floods. In addition, natural climate variability affects the frequency and magnitude of these events on annual to millennial time-scales. Particularly in the mid-latitudes of the Northern Hemisphere, correlations between meteorological variables and hydrological indices suggest significant effects of changing climate boundary conditions on floods. To date, however, understanding of flood responses to changing climate boundary conditions is limited due to the scarcity of hydrological data in space and time. Exploring paleoclimate archives like annually laminated (varved) lake sediments allows to fill this gap in knowledge offering precise dated time-series of flood variability for millennia. During river floods, detrital catchment material is eroded and transported in suspension by fluid turbulence into downstream lakes. In the water body the transport capacity of the inflowing turbidity current successively diminishes leading to the deposition of detrital layers on the lake floor. Intercalated into annual laminations these detrital layers can be dated down to seasonal resolution. Microfacies analyses and X-ray fluorescence scanning (µ-XRF) at 200 µm resolution were conducted on the varved Mid- to Late Holocene interval of two sediment profiles from pre-alpine Lake Ammersee (southern Germany) located in a proximal (AS10prox) and distal (AS10dist) position towards the main tributary River Ammer. To shed light on sediment distribution within the lake, particular emphasis was (1) the detection of intercalated detrital layers and their micro-sedimentological features, and (2) intra-basin correlation of these deposits. Detrital layers were dated down to the season by microscopic varve counting and determination of the microstratigraphic position within a varve. The resulting chronology is verified by accelerator mass spectrometry (AMS) 14C dating of 14 terrestrial plant macrofossils. Since ~5500 varve years before present (vyr BP), in total 1573 detrital layers were detected in either one or both of the investigated sediment profiles. Based on their microfacies, geochemistry, and proximal-distal deposition pattern, detrital layers were interpreted as River Ammer flood deposits. Calibration of the flood layer record using instrumental daily River Ammer runoff data from AD 1926 to 1999 proves the flood layer succession to represent a significant time-series of major River Ammer floods in spring and summer, the flood season in the Ammersee region. Flood layer frequency trends are in agreement with decadal variations of the East Atlantic-Western Russia (EA-WR) atmospheric pattern back to 200 yr BP (end of the used atmospheric data) and solar activity back to 5500 vyr BP. Enhanced flood frequency corresponds to the negative EA-WR phase and reduced solar activity. These common links point to a central role of varying large-scale atmospheric circulation over Europe for flood frequency in the Ammersee region and suggest that these atmospheric variations, in turn, are likely modified by solar variability during the past 5500 years. Furthermore, the flood layer record indicates three shifts in mean layer thickness and frequency of different manifestation in both sediment profiles at ~5500, ~2800, and ~500 vyr BP. Combining information from both sediment profiles enabled to interpret these shifts in terms of stepwise increases in mean flood intensity. Likely triggers of these shifts are gradual reduction of Northern Hemisphere orbital summer forcing and long-term solar activity minima. Hypothesized atmospheric response to this forcing is hemispheric cooling that enhances equator-to-pole temperature gradients and potential energy in the troposphere. This energy is transferred into stronger westerly cyclones, more extreme precipitation, and intensified floods at Lake Ammersee. Interpretation of flood layer frequency and thickness data in combination with reanalysis models and time-series analysis allowed to reconstruct the flood history and to decipher flood triggering climate mechanisms in the Ammersee region throughout the past 5500 years. Flood frequency and intensity are not stationary, but influenced by multi-causal climate forcing of large-scale atmospheric modes on time-scales from years to millennia. These results challenge future projections that propose an increase in floods when Earth warms based only on the assumption of an enhanced hydrological cycle. / Globale Klimamodelle prognostizieren eine Zunahme von Starkhochwassern infolge der Klimaerwärmung. Weiterhin werden natürliche Klimafaktoren die Intensität und Häufigkeit solcher Ereignisse auf Zeitskalen von Jahren bis Jahrtausenden beeinflussen. Für ein umfassendes Verständnis hochwassergenerierender Klimamechanismen müssen daher lange Zeiträume und regionale Muster in Betracht gezogen werden. Aufgrund der Limitierung der meisten instrumentellen Abflusszeitreihen auf die letzten 100 Jahre, bieten diese nur einen sehr begrenzten Einblick in das Spektrum möglicher Klima-Hochwasser Zusammenhänge. Die Nutzung natürlicher Hochwasserarchive, wie warvierter Seesedimente, erlaubt die Untersuchung von Hochwasseraktivität auf Zeitskalen von Jahrtausenden. Durch Hochwasser in einen See eingetragenes detritisches Material bildet, eingeschaltet in den jährlichen Sedimentationszyklus, eine charakteristische Abfolge von Hochwasserlagen auf dem Seeboden. Das Zählen jährlicher Laminierungen und die Position innerhalb eines jährlichen Sedimentationszyklus ermöglichen die Datierung von Hochwasserlagen mit saisonaler Genauigkeit. Der Ammersee bildet ein ideales Archiv zur Rekonstruktion von Hochwassern. Detritisches Material wird durch nur einen Hauptzufluss, die Ammer, in das rinnenförmige Becken transportiert. Die warvierten Sedimente erlauben eine zuverlässige Detektion und Datierung selbst mikroskopischer Hochwasserlagen. An zwei warvierten Sedimentprofilen des Ammersees sind hochauflösende Mikrofazies und Röntgenfluoreszenz (µ-XRF) Analysen durchgeführt worden. Zum besseren Verständnis der Sedimentverteilung im See lag der Fokus der Untersuchungen auf der Detektion detritischer Lagen anhand ihrer sedimentologischen und geochemischen Eigenschaften und der Korrelation dieser Lagen zwischen beiden Sedimentprofilen. Die Datierung der detritschen Lagen erfolgte durch Warvenzählung und wurde durch AMS Radiokarbondatierungen bestätigt. In den Sedimenten der letzten 5500 Jahre wurden 1573 detritische Lagen gefunden. Aufgrund ihrer Eigenschaften lassen sich diese Lagen als Ammerhochwasserlagen interpretieren: (1) Die Mikrofazies deutet auf eine Ablagerung nach Starkabflussereignissen hin. (2) Die geochemische Zusammensetzung beweist die terrestrische Herkunft des Materials. (3) Das proximal-distale Ablagerungsmuster deutet auf die Ammer als Eintragsquelle des Materials hin. Eine Kalibrierung mit instrumentellen Hochwasserdaten der Ammer im Zeitraum von AD 1926 bis 1999 bestätigt die Sukzession der detritischen Lagen als eine Zeitreihe starker Ammerhochwasser im Frühling und Sommer, der Hochwassersaison am Ammersee. Die Häufigkeit der Hochwasserlagen in den letzten 5500 Jahren weist eine deutliche dekadische Variabilität auf. Trends in der Häufigkeit von Hochwasserlagen korrelieren negativ mit dem Index der East Atlantic-Western Russia Oszillation (EA-WR) während der letzten 250 Jahre (Zeitraum der durch die genutzten atmosphärischen Daten abgedeckt ist) und der solaren Aktivität während des kompletten Zeitraums. Diese Übereinstimmungen deuten möglicherweise auf einen solaren Einfluss auf die atmosphärische Zirkulation über Europa und damit auf die Häufigkeit von Hochwassern am Ammersee hin. Weiterhin weist die Zeitreihe der Hochwasserlagen drei Veränderungen der durchschnittlichen Lagenhäufigkeit und -mächtigkeit vor etwa 5500, 2800 und 500 Jahren auf. Die Kombination der Daten beider Sedimentprofile ermöglicht es, diese Veränderungen als schrittweise Anstiege der Hochwasserintensität zu interpretieren. Vermutliche Auslöser sind graduelle Reduktion der solaren Insolation in der Nordhemisphäre und langfristige Minima der solaren Aktivität. Die wahrscheinliche atmosphärische Reaktion auf dieses Klimaforcing ist ein verstärkter Temperaturgradient zwischen den niederen und hohen Breiten, der zu einer Erhöhung der potenziellen Energie in der Atmosphäre und verstärkter Baroklinität führt. Diese Energie wird transferiert in eine Verstärkung der zyklonalen Westwindzirkulation, extremere Niederschläge und eine Intensivierung der Hochwasser am Ammersee. Die Interpretation der Häufigkeit und Mächtigkeit von Hochwasserlagen in den Sedimenten des Ammersees ermöglicht eine Rekonstruktion der Hochwassergeschichte und die Identifizierung hochwasserauslösender Klimafaktoren in der Ammerseeregion während der letzten 5500 Jahre. Hochwasserhäufigkeit und -intensität sind nicht stationär, sondern durch komplexe Veränderungen im Klimasystem auf Zeitskalen von Jahren bis Jahrtausenden geprägt. In diesem Zusammenhang erscheinen die Resultate globaler Klimamodelle, die einen Anstieg des Hochwasserrisikos allein auf Basis eines thermodynamisch intensivierten hydrologischen Kreislaufs infolge der Klimaerwärmung prognostizieren, als stark simplifiziert.