Browsing by Author "Karas, Cyrus"

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    Enhanced deglacial carbon transport by Pacific southern-sourced intermediate and mode water
    (2025) Karas, Cyrus; Nurnberg, Dirk; Lambert, Fabrice; Shaffer, Gary; Lamy, Frank
    Southern-sourced Antarctic Intermediate Water (AAIW) and Subantarctic Mode Water (SAMW) are currently major sinks of atmospheric CO2. During the last deglaciation, atmospheric CO2 levels increased significantly during two specific time periods, Heinrich Stadial 1 (H1) ~18–14.6 ka BP (thousand years ago before present) and the Younger Dryas (YD) ~12.8–11.5 ka BP. Model simulation and proxy data studies suggest that AAIW/SAMW was crucial in explaining these changes during H1 and YD, but its variability and properties in the Southeast Pacific Ocean are still largely unknown. Here, we present records of benthic foraminiferal carbon isotopes, Mg/Ca-based water temperatures, paleosalinity reconstructions, and sortable silt mean grain size variations over the last 30 thousand years from Ocean Drilling Program (ODP) Site 1233, in the Southeast Pacific Ocean, which is bathed in AAIW/SAMW. Our proxy data suggest an increased northward circulation of high pCO2/ nutrient-enriched AAIW/SAMW during H1 and YD. Our data provides support for AAIW/SAMW as one of the important conduits for deglacial oceanic outgassing in the eastern equatorial Pacific upwelling.
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    Estimating coastal flood hazard of Tossa de Mar, Spain: a combined model - data interviews approach
    (SPRINGER, 2021) Hernandez Mora, Marina; Meseguer Ruiz, Oliver; Karas, Cyrus; Lambert, Fabrice
    Human settlements in coastal areas are highly vulnerable to extreme events, especially in the Mediterranean area, which houses a large number of tourists during the summer and autumn months. It is important to carry out hazard studies at local scale to improve our understanding of natural and anthropogenic processes involved in episodes of coastal flooding. We reconstruct and characterize an extreme weather event in Tossa de Mar (northeastern Spain) and the subsequent urban flooding that occurred in 2008. Our results show flood heights up to 1.27 m, with the maximum occurring between 24 and 64 h after the start of the event. This is broadly consistent with the reconstructions obtained through interviews and photographs. Based on model simulations, we produce a hazard map for the town based on hydrodynamic scenarios for different return periods. We show that the southern part of the town is more susceptible to flooding, whereas the northern part is relatively resilient to extreme events. We recommend the adaption of a currently existing dune by adding vegetation and slightly increasing its height. This low economic cost action would significantly reduce flooding and increase resilience in this area.