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2 results on '"Vorrath, Maria-Helena"'

1. Deglacial and Holocene sea-ice and climate dynamics in the Bransfield Strait, northern Antarctic Peninsula

Author

Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research (Germany), European Commission, Ministerio de Economía, Industria y Competitividad (España), Vorrath, Maria-Helena, Müller, Juliane, Cárdenas, Paola, Opel, Thomas, Mieruch, Sebastian, Esper, Oliver, Lembke-Jene, Lester, Etourneau, Johan, Vieth-Hillebrand, Andrea, Lahajnar, Niko, Lange, Carina B., Leventer, Amy, Evangelinos, Dimitris, Escutia, Carlota, Mollenhauer, Gesine, Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research (Germany), European Commission, Ministerio de Economía, Industria y Competitividad (España), Vorrath, Maria-Helena, Müller, Juliane, Cárdenas, Paola, Opel, Thomas, Mieruch, Sebastian, Esper, Oliver, Lembke-Jene, Lester, Etourneau, Johan, Vieth-Hillebrand, Andrea, Lahajnar, Niko, Lange, Carina B., Leventer, Amy, Evangelinos, Dimitris, Escutia, Carlota, and Mollenhauer, Gesine

Abstract

The reconstruction of past sea-ice distribution in the Southern Ocean is crucial for an improved understanding of ice-ocean-Atmosphere feedbacks and the evaluation of Earth system and Antarctic ice sheet models. The Antarctic Peninsula (AP) has been experiencing a warming since the start of regular monitoring of the atmospheric temperature in the 1950s. The associated decrease in sea-ice cover contrasts the trend of growing sea-ice extent in East Antarctica. To reveal the long-Term sea-ice history at the northern Antarctic Peninsula (NAP) under changing climate conditions, we examined a marine sediment core from the eastern basin of the Bransfield Strait covering the last Deglacial and the Holocene. For sea-ice reconstructions, we focused on the specific sea-ice biomarker lipid IPSO25, a highly branched isoprenoid (HBI), and sea-ice diatoms, whereas a phytoplankton-derived HBI triene (C25:3) and warmer open-ocean diatom assemblages reflect predominantly ice-free conditions. We further reconstruct ocean temperatures using glycerol dialkyl glycerol tetraethers (GDGTs) and diatom assemblages and compare our sea-ice and temperature records with published marine sediment and ice core data. A maximum ice cover is observed during the Antarctic Cold Reversal 13ĝ€¯800-13ĝ€¯000 years before present (13.8-13ĝ€¯ka), while seasonally ice-free conditions permitting (summer) phytoplankton productivity are reconstructed for the late Deglacial and the Early Holocene from 13 to 8.3ĝ€¯ka. An overall decreasing sea-ice trend throughout the Middle Holocene coincides with summer ocean warming and increasing phytoplankton productivity. The Late Holocene is characterized by highly variable winter sea-ice concentrations and a sustained decline in the duration and/or concentration of spring sea ice. Overall diverging trends in GDGT-based TEX86L and RI-OH' subsurface ocean temperatures (SOTs) are found to be linked to opposing spring and summer insolation trends, respectively.

Published
2023

2. ICEPRO: an international collaboration effort for improving paleoclimate research in the Southern Ocean

Author

Etourneau, Johan, Escutia, Carlota, Leventer, Amy, Flores, José-Abel, Rigual-Hernández, Andrés S., Evangelinos, Dimitris, Kim, Jung-Hyun, Dunbar, Robert, Hennig, Andrew, Armand, Leanne K., Armbrecht, Linda, Ericksen, Ruth, Cortese, Giuseppe, Tiwari, Manish, Mohan, Rahul, Müller, Julianne, Vorrath, Maria-Helena, Robinson, Rebecca, Santis, Laura De, Bilj, Peter, Sangiorgi, Francesca, van den Flierdt, Tina, Jiménez-Espejo, Francisco J., Gutiérrez Pastor, Julia, and Deflandre, Bruno

Abstract

9th SCAR Open Science Conference and XXXVI SCAR Meetings. Hobart, Tasmania, Australia. 31 July - 11 August 2020, The Southern Ocean (SO) is an active regulator of global climate through its influence on the modulation of the global ocean circulation, the phytoplankton productivity as well as nutrient cycles, the transfer of energy and gas between the ocean and the atmosphere, and sea level. Despite its importance, seasonal and sparse distribution of instrumental data across the SO prevent a robust assessment of the physical and biological response and feedback on future climate change. Paleoclimate data are therefore essential to document the natural variability of environmental conditions and identify their drivers from decadal-to-millennial timescales. However, in paleoclimate studies, several questions remain unaddressed due to the lack of robust proxy calibration. While some tools are better constrained than others, the mechanisms controlling them are not fully understood. A critical step to improve their use is to conduct a systematic multi-annual collection of samples and data throughout the SO. ICEPRO has been initiated to strengthen existing collaborations and creating new connections among several partners regularly crossing through different transects the SO and who have the opportunity to sample the water column and marine sediments spanning at least the last 2,000 years. Such collaborative work could therefore cover most of the important regions of the SO, thus allowing a better monitoring of modern environmental and hydrological conditions, and ultimately improve calibration of tools commonly used for paleoreconstructions. Here we aim to present ICEPRO, its first steps and results we obtained from the last Antarctic cruises as well as our future ambitions.

Published
2020

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