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The El Niño-Southern Oscillation (ENSO), known for exceptional heavy rainfalls, droughts and inundations in the Pacific and Indian Ocean realm, is one of the largest oceanic and atmospheric phenomena on Earth influencing global climate patterns. Over the last decades, a strong warming in the high latitudes of both hemispheres has been observed to coincide with the rise of a third ENSO type — “El Niño/La Niña Modoki”, also called Central Pacific ENSO. During El Niño Modoki (La Niña Modoki) events, sea-surface temperature (SST) is higher (lower) in the central equatorial Pacific, flanked by colder (warmer) SSTs in the western or eastern Pacific, associated with a twin Walker Circulation. The study aims to understand the underlying spatio-temporal dynamics and processes of Central Pacific ENSO and a possible link to anthropogenic impacts from a paleo-perspective to improve the predictability of Central Pacific ENSO variations in the future. Therefore, high-resolution (c. 1–2 kyr resolution) proxy records of SST variability are generated from marine sediment cores from the western, central, and eastern equatorial Pacific from the Middle-Pleistocene to present. The SST reconstructions are based on Mg/Ca ratios of planktic foraminifers and biomarker (alkenone) analyses. Based on preliminary and published data, a lower east–west SST gradient and colder SSTs in the central Pacific occurred during warmer periods. La Niña Modoki conditions apparently become more frequent with increasing CO2 conditions pointing at the likelihood that La Niña Modoki conditions will become more prevalent in the near future. Accordingly, an increase in precipitation on both sides of the Pacific realm could be expected.

Tsunami deposits are required to assess the long-term hazard of tsunamis, in particular in regions with a short and fragmented historical record. In the North Sea region, evidence of tsunamis is scarce. However, the Shetland Islands are an exception, as they provide abundant deposits of the Storegga tsunami c. 8150 cal. a BP, and more fragmented evidence of younger events ~5500 and ~1500 cal. a BP. Sediments of the youngest tsunami – the so-called Dury Voe event – are considered uncertain and have only been found at two sites so far, as thin landward fining and landward thinning sand sheets which are vertically confined by peat. Here, we present sedimentary evidence for a tsunami from the small coastal lake of Loch Flugarth, northern Mainland. Three gravity cores of up to 91 cm length were taken behind the barrier separating the lake from a shallow marine embayment. The cores show organic-rich background deposition with many sub-cm-scale sand layers, reflecting recurring storm overwash and a sediment source limited to the active beach and uppermost subtidal. A basal 13 cm-thick sand layer, dated to 426–787 cal. a CE based on 14C-AMS, 137Cs and Bayesian age-depth modelling, was found in all three cores. High-resolution grain-size analysis identified four normally graded sublayers with inversely graded traction carpets in the lower part of two sublayers. An organic-rich “mud” drape and “mud” cap, respectively, cover the upper two sublayers, which also contain small rip-up clasts. Grain-size distributions shows a difference between the basal sand layer and the thin storm layers, which are coarser and better sorted. Principal component analysis of XRF core scanning data also distinguishes both sand units, mostly driven by Zr, Fe and Ti in the basal sand. This, in combination with increased magnetic susceptibility, may be related to higher heavy mineral content reflecting an additional marine sediment source for the tsunami deposit. Based on reinterpretation of chronological data from the two published sites and the chronostratigraphy of the present study, the Dury Voe tsunami seems to be younger than previously estimated, i.e. closer to 1400–1300 cal. a BP. The source of the tsunami remains unclear. As there is no evidence for this event outside the Shetlands, the size of the tsunami is expected to be smaller than the Storegga tsunami, which affected most of the North Sea basin.

Severe storms, their extreme waves and surges pose the greatest natural hazard to the coasts of northwestern Europe, commonly resulting in infrastructural damages and high financial losses. Proxy records of past storminess are important for assessing future risks that may arise from storm surges and assessing whether storm activity has increased in recent decades. High-resolution records of North Atlantic storminess are generally limited to instrumental weather data or historical documentation of the past 50 to 200 years. Since the most destructive and severe storms passing over Europe originate in the North Atlantic, the Shetland Islands serve as a window to cyclogenesis in this region. In our research, we extracted lacustrine sediments of the coastal freshwater lake Loch of Flugarth on Mainland, Shetland Islands, that is separated from the ocean by a low sand and gravel barrier. A series of distinct sand layers intercalated in the otherwise fine-grained, organic-rich lake deposits and examined using particle-size analysis, microfossils, TOC and XRF, may represent storm overwash or aeolian transport mechanisms, both either pointing towards individual storm events or shorter phases of high storm activity. Based on radiocarbon data of some selected layers, the investigated sediment sequence covers ca. 1500 years and a Bayesian age-depth model is being established. In combination with a hydrodynamic wave model based on Delft3D-Flow, we simulate a critical threshold value at which waves may reach the lake to determine the sensitivity of the sedimentary archive. With the inclusion of historical documentation and observations, our multi-methodological approach aims at reaching a better understanding of the recurrence pattern of extreme storm events on the Shetland Islands over the last 1500 years. This implies further insights into the parameters driving extra-tropical storms in the wider region as well as the role and variability of the North Atlantic Oscillation across the targeted time frame.