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23 results on '"Vorrath, Maria-Elena"'

1. A hydrothermal plume on the Southwest Indian Ridge revealed by a multi-proxy approach: Impact on iron and manganese distributions (GEOTRACES GS02)

Author

Baudet, Corentin, Bucciarelli, Eva, Sarthou, Géraldine, Boulart, Cédric, Pelleter, Ewan, Goddard-Dwyer, Millie, Whitby, Hannah, Zhang, Rui, Obernosterer, Ingrid, Gonzalez-Santana, David, Léon, Morgane, van Beek, Pieter, Sanial, Virginie, Jeandel, Catherine, Vivier, Frédéric, Vorrath, Maria-Elena, Liao, Wen-Hsuan, Germain, Yoan, and Planquette, Hélène

Published
2024
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3. Exploring site-specific carbon dioxide removal options with storage or sequestration in the marine environment - The 10 Mt CO2 yr-1 removal challenge for Germany

Author

Yao, Wanxuan, primary, Morganti, Teresa, additional, Wu, Jiajun, additional, Borchers, Malgorzata, additional, Anschütz, Anna-Adriana, additional, Bednarz, Lena-Katharina, additional, Bhaumik, Amrita, additional, Boettcher, Miranda, additional, Burkhard, Kremena, additional, Cabus, Tony, additional, Chua, Allison Sueyi, additional, Diercks, Isabel, additional, Mario, Esposito, additional, Fink, Michael, additional, Fouqueray, Mondane, additional, Gasanzade, Firdovsi, additional, Geilert, Sonja, additional, Hauck, Judith, additional, Havermann, Felix, additional, Hellige, Inga, additional, Hoog, Sven, additional, Jürchott, Malte, additional, Kalapurakkal, Habeeb Thanveer, additional, Kemper, Jost, additional, Kremin, Isabel, additional, Lange, Isabel, additional, Lencina-Avila, Jannine Marquez, additional, Liadova, Margarita, additional, Liu, Feifei, additional, Mathesius, Sabine, additional, Mehendale, Neha, additional, Nagwekar, Tanvi, additional, Philippi, Miriam, additional, Luz, Gustavo Leite Neves da, additional, Ramasamy, Murugan, additional, Stahl, Florian, additional, Tank, Lukas, additional, Vorrath, Maria-Elena, additional, Westmark, Lennart, additional, Wey, Hao-Wei, additional, Wollnik, Ronja, additional, Wölfelschneider, Mirco, additional, Bach, Wolfgang, additional, Bischof, Kai, additional, boersma, maarten, additional, Daewel, Ute, additional, Fernández-Méndez, Mar, additional, Geuer, Jana, additional, Keller, David Peter, additional, Kopf, Achim J., additional, Merk, Christine, additional, Moosdorf, Nils, additional, Oppelt, Natascha Maria, additional, Oschlies, Andreas, additional, Pongratz, Julia, additional, Proelss, Alexander, additional, Rehder, Gregor, additional, Rüpke, Lars Helmuth, additional, Szarka, Nora, additional, Thrän, Daniela, additional, Wallmann, Klaus, additional, and Mengis, Nadine, additional

Published
2024
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5. Marine carbon dioxide removal by alkalinization should no longer be overlooked

Author

Kowalczyk, Katarzyna A, Amann, Thorben, Strefler, Jessica, Vorrath, Maria-Elena, Hartmann, Jens, De Marco, Serena, Renforth, Phil, Foteinis, Spyros, Kriegler, Elmar, Kowalczyk, Katarzyna A, Amann, Thorben, Strefler, Jessica, Vorrath, Maria-Elena, Hartmann, Jens, De Marco, Serena, Renforth, Phil, Foteinis, Spyros, and Kriegler, Elmar

Abstract

To achieve the Paris climate target, deep emissions reductions have to be complemented with carbon dioxide removal (CDR). However, a portfolio of CDR options is necessary to reduce risks and potential negative side effects. Despite a large theoretical potential, ocean-based CDR such as ocean alkalinity enhancement (OAE) has been omitted in climate change mitigation scenarios so far. In this study, we provide a techno-economic assessment of large-scale OAE using hydrated lime (‘ocean liming’). We address key uncertainties that determine the overall cost of ocean liming (OL) such as the CO2 uptake efficiency per unit of material, distribution strategies avoiding carbonate precipitation which would compromise efficiency, and technology availability (e.g., solar calciners). We find that at economic costs of 130–295 $/tCO2 net-removed, ocean liming could be a competitive CDR option which could make a significant contribution towards the Paris climate target. As the techno-economic assessment identified no showstoppers, we argue for more research on ecosystem impacts, governance, monitoring, reporting, and verification, and technology development and assessment to determine whether ocean liming and other OAE should be considered as part of a broader CDR portfolio.

Published
2024
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6. Influence of shallow hydrothermal fluid release on the functioning of phytoplankton communities

Author

Tilliette, Chloé, Gazeau, Frédéric, Portlock, Gemma, Benavides, Mar, Bonnet, Sophie, Guigue, Catherine, Leblond, Nathalie, Lory, Caroline, Marie, Dominique, Montanes, Maryline, Pulido-villena, Elvira, Sarthou, Geraldine, Tedetti, Marc, Vorrath, Maria-elena, Whitby, Hannah, Guieu, Cécile, Tilliette, Chloé, Gazeau, Frédéric, Portlock, Gemma, Benavides, Mar, Bonnet, Sophie, Guigue, Catherine, Leblond, Nathalie, Lory, Caroline, Marie, Dominique, Montanes, Maryline, Pulido-villena, Elvira, Sarthou, Geraldine, Tedetti, Marc, Vorrath, Maria-elena, Whitby, Hannah, and Guieu, Cécile

Abstract

In the Western Tropical South Pacific (WTSP) Ocean, a hotspot of dinitrogen fixation has been identified. The survival of diazotrophs depends, among others, on the availability of dissolved iron (DFe) largely originating, as recently revealed, from shallow hydrothermal sources located along the Tonga-Kermadec arc that fertilize the Lau Basin with this element. On the opposite, these fluids, released directly close to the photic layer, can introduce numerous trace metals at concentrations that can be toxic to surface communities. Here, we performed an innovative 9-day experiment in 300 L reactors onboard the TONGA expedition, to examine the effects of hydrothermal fluids on natural plankton communities in the WTSP Ocean. Different volumes of fluids were mixed with non-hydrothermally influenced surface waters (mixing ratio from 0 to 14.5%) and the response of the communities was studied by monitoring numerous stocks and fluxes (phytoplankton biomass, community composition, net community production, N2 fixation, thiol production, organic carbon and metal concentrations in exported material). Despite an initial toxic effect of hydrothermal fluids on phytoplankton communities, these inputs led to higher net community production and N2 fixation rates, as well as elevated export of organic matter relative to control. This fertilizing effect was achieved through detoxification of the environment, rich in potentially toxic elements (e.g., Cu, Cd, Hg), likely by resistant Synechococcus ecotypes able to produce strong binding ligands, especially thiols (thioacetamide-like and glutathione-like compounds). The striking increase of thiols quickly after fluid addition likely detoxified the environment, rendering it more favorable for phytoplankton growth. Indeed, phytoplankton groups stressed by the addition of fluids were then able to recover important growth rates, probably favored by the supply of numerous fertilizing trace metals (notably Fe) from hydrothermal fluids and new n

Published
2023
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7. Upper-ocean temperature characteristics in the subantarctic southeastern Pacific based on biomarker reconstructions

Author

Hagemann, Julia Rieke, Lembke-jene, Lester, Lamy, Frank, Vorrath, Maria-elena, Kaiser, Jérôme, Müller, Juliane, Arz, Helge W., Hefter, Jens, Jaeschke, Andrea, Ruggieri, Nicoletta, Tiedemann, Ralf, Hagemann, Julia Rieke, Lembke-jene, Lester, Lamy, Frank, Vorrath, Maria-elena, Kaiser, Jérôme, Müller, Juliane, Arz, Helge W., Hefter, Jens, Jaeschke, Andrea, Ruggieri, Nicoletta, and Tiedemann, Ralf

Abstract

Alkenones and Glycerol Dialkyl Glycerol Tetraether lipids (GDGT) as remnants of living organisms are widely used biomarkers for determining past oceans’ water temperatures. The organisms these proxy carriers stem from, are influenced by a number of environmental parameters, such as water depth, nutrient availability, light conditions or seasonality, which all may significantly bias the calibration to ambient water temperatures. Reliable temperature determinations remain thus challenging, especially in higher latitudes and for under-sampled regions. We analyzed 33 sediment surface samples from the Southern Chilean continental margin and the Drake Passage for alkenones and GDGTs and compared the results with gridded instrumental reference data from the World Ocean Atlas 2005 (WOA05), as well as previously published data from an extended study area covering the Central and Western South Pacific towards the New Zealand continental margin. We show that for alkenone-derived SSTs, the widely-used global core-top calibration of Müller et al. (1998) yields the smallest residuals, whereas the calibration of Sikes et al. (1997), adapted to higher latitudes and supposed to show summer SSTs, overestimates modern WOA05-based (summer and annual mean) SSTs. Our alkenone SSTs show a slight seasonal shift of ~1 °C at the Southern Chilean Margin and up to ~2 °C in the Drake Passage towards austral summer SSTs, whereas samples in the Central South Pacific reflect an annual mean signal. We show that for GDGT-based temperatures, a more complex pattern emerges. In areas north of the Subantarctic Front (SAF) the subsurface calibration of Kim et al. (2012a) best reflects temperatures from the WOA05, largely within the margin error of ±2.2 °C. Temperatures south of the SAF instead are significantly overestimated by up to 14 °C, irrespective of the applied calibration. Based on a qualitative assessment of the GDGT [2] / [3]-ratios, which likely indicate water depth of origin, our samples refl

Published
2023
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8. Deglacial and Holocene sea-ice and climate dynamics in the Bransfield Strait, northern Antarctic Peninsula

Author

Vorrath, Maria-Elena, primary, Müller, Juliane, additional, Cárdenas, Paola, additional, Opel, Thomas, additional, Mieruch, Sebastian, additional, Esper, Oliver, additional, Lembke-Jene, Lester, additional, Etourneau, Johan, additional, Vieth-Hillebrand, Andrea, additional, Lahajnar, Niko, additional, Lange, Carina B., additional, Leventer, Amy, additional, Evangelinos, Dimitris, additional, Escutia, Carlota, additional, and Mollenhauer, Gesine, additional

Published
2023
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9. Influence of shallow hydrothermal fluid release on the functioning of phytoplankton communities

Author

Tilliette, Chloé, primary, Gazeau, Frédéric, additional, Portlock, Gemma, additional, Benavides, Mar, additional, Bonnet, Sophie, additional, Guigue, Catherine, additional, Leblond, Nathalie, additional, Lory, Caroline, additional, Marie, Dominique, additional, Montanes, Maryline, additional, Pulido-Villena, Elvira, additional, Sarthou, Géraldine, additional, Tedetti, Marc, additional, Vorrath, Maria-Elena, additional, Whitby, Hannah, additional, and Guieu, Cécile, additional

Published
2023
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11. Deglacial and Holocene sea-ice and climate dynamicsin the Bransfield Strait, northern Antarctic Peninsula

Author

Vorrath, Maria-Elena, 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 13 800–13 000 years before present (13.8–13 ka), while seasonally ice-free conditions permitting (summer) phytoplankton productivity are reconstructed for the late Deglacial and the Early Holocene from 13 to 8.3 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

12. Barium excess as remineralization proxy in the Southern Ocean - Indian sector (SWINGS-GS02)

Author

Le Roy, Emilie, primary, Jacquet, Stéphanie, additional, Dufour, Aurélie, additional, Baudet, Corentin, additional, Cardinal, Damien, additional, González-Santana, David, additional, Hamelin, Bruno, additional, Vorrath, Maria-Elena, additional, Jeandel, Catherine, additional, Planquette, Helene, additional, Liao, Wen-Hsuan, additional, and Piejus, Marine, additional

Published
2023
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14. Supplementary material to "Deglacial and Holocene sea ice and climate dynamics at the Western Antarctic Peninsula"

Author

Vorrath, Maria-Elena, primary, Müller, Juliane, additional, Cárdenas, Paola, additional, Mieruch, Sebastian, additional, Esper, Oliver, additional, Opel, Thomas, additional, Lembke-Jene, Lester, additional, Etourneau, Johan, additional, Vieth-Hillebrand, Andrea, additional, Lahajnar, Niko, additional, Lange, Carina B., additional, Leventer, Amy, additional, Evangelinos, Dimitris, additional, Escutia, Carlota, additional, and Mollenhauer, Gesine, additional

Published
2022
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15. Deglacial and Holocene sea ice and climate dynamics at the Western Antarctic Peninsula

Author

Vorrath, Maria-Elena, primary, Müller, Juliane, additional, Cárdenas, Paola, additional, Mieruch, Sebastian, additional, Esper, Oliver, additional, Opel, Thomas, additional, Lembke-Jene, Lester, additional, Etourneau, Johan, additional, Vieth-Hillebrand, Andrea, additional, Lahajnar, Niko, additional, Lange, Carina B., additional, Leventer, Amy, additional, Evangelinos, Dimitris, additional, Escutia, Carlota, additional, and Mollenhauer, Gesine, additional

Published
2022
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16. Antarctic sea ice over the past 130 000 years – Part 1: a review of what proxy records tell us

Author

Crosta, Xavier, primary, Kohfeld, Karen E., additional, Bostock, Helen C., additional, Chadwick, Matthew, additional, Du Vivier, Alice, additional, Esper, Oliver, additional, Etourneau, Johan, additional, Jones, Jacob, additional, Leventer, Amy, additional, Müller, Juliane, additional, Rhodes, Rachael H., additional, Allen, Claire S., additional, Ghadi, Pooja, additional, Lamping, Nele, additional, Lange, Carina B., additional, Lawler, Kelly-Anne, additional, Lund, David, additional, Marzocchi, Alice, additional, Meissner, Katrin J., additional, Menviel, Laurie, additional, Nair, Abhilash, additional, Patterson, Molly, additional, Pike, Jennifer, additional, Prebble, Joseph G., additional, Riesselman, Christina, additional, Sadatzki, Henrik, additional, Sime, Louise C., additional, Shukla, Sunil K., additional, Thöle, Lena, additional, Vorrath, Maria-Elena, additional, Xiao, Wenshen, additional, and Yang, Jiao, additional

Published
2022
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17. Antarctic sea ice over the past 130,000 years, Part 1: A review of what proxy records tell us

Author

Crosta, Xavier, primary, Kohfeld, Karen E., additional, Bostock, Helen C., additional, Chadwick, Matthew, additional, Du Vivier, Alice, additional, Esper, Oliver, additional, Etourneau, Johan, additional, Jones, Jacob, additional, Leventer, Amy, additional, Müller, Juliane, additional, Rhodes, Rachel H., additional, Allen, Claire S., additional, Ghadi, Pooja, additional, Lamping, Nele, additional, Lange, Carina, additional, Lawler, Kelly-Anne, additional, Lund, David, additional, Marzocchi, Alice, additional, Meissner, Katrin J., additional, Menviel, Laurie, additional, Nair, Abhilash, additional, Patterson, Molly, additional, Pike, Jennifer, additional, Prebble, Joseph G., additional, Riesselman, Christina, additional, Sadatzki, Henrik, additional, Sime, Louise C., additional, Shukla, Sunil K., additional, Thöle, Lena, additional, Vorrath, Maria-Elena, additional, Xiao, Wenshen, additional, and Yang, Jiao, additional

Published
2022
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18. Supplementary material to "Antarctic sea ice over the past 130,000 years, Part 1: A review of what proxy records tell us"

Author

Crosta, Xavier, primary, Kohfeld, Karen E., additional, Bostock, Helen C., additional, Chadwick, Matthew, additional, Du Vivier, Alice, additional, Esper, Oliver, additional, Etourneau, Johan, additional, Jones, Jacob, additional, Leventer, Amy, additional, Müller, Juliane, additional, Rhodes, Rachel H., additional, Allen, Claire S., additional, Ghadi, Pooja, additional, Lamping, Nele, additional, Lange, Carina, additional, Lawler, Kelly-Anne, additional, Lund, David, additional, Marzocchi, Alice, additional, Meissner, Katrin J., additional, Menviel, Laurie, additional, Nair, Abhilash, additional, Patterson, Molly, additional, Pike, Jennifer, additional, Prebble, Joseph G., additional, Riesselman, Christina, additional, Sadatzki, Henrik, additional, Sime, Louise C., additional, Shukla, Sunil K., additional, Thöle, Lena, additional, Vorrath, Maria-Elena, additional, Xiao, Wenshen, additional, and Yang, Jiao, additional

Published
2022
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20. Dissolved iron pattern impacted by shallow hydrothermal sources along a transect through the Tonga-Kermadec arc

Author

Tilliette, Chloé, Taillandier, Vincent, Bouruet-Aubertot, Pascale, Grima, Nicolas, Maes, Christophe, Montanes, Maryline, Sarthou, Géraldine, Vorrath, Maria-Elena, Arnone, Verónica, Bressac, Matthieu, González-Santana, David, Gazeau, Frédéric, Guieu, Cécile, Laboratoire d'océanographie de Villefranche (LOV), Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut de la Mer de Villefranche (IMEV), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Processus et interactions de fine échelle océanique (PROTEO), Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Laboratoire d'Océanographie Physique et Spatiale (LOPS), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Instituto de Oceanografía y Cambio Global (IOCAG), and Université de Las Palmas de Gran Canaria [Espagne] (ULPGC)

Subjects
Changement climatique, [SDE]Environmental Sciences, Climate change
Published
2022

21. DFe patterns impacted by shallow hydrothermal sources along a transect through the Tonga-Kermadec arc

Author

Tilliette, Chloé, primary, Taillandier, Vincent, additional, Bouruet-Aubertot, Pascale, additional, Grima, Nicolas, additional, Maes, Christophe, additional, Montanes, Maryline, additional, Sarthou, Geraldine, additional, Vorrath, Maria-Elena, additional, Arnone, Veronica, additional, Bressac, Matthieu, additional, González-Santana, David, additional, GAZEAU, Frédéric, additional, and Guieu, Cécile, additional

Published
2022
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22. Upper ocean temperature characteristics in the subantarctic Southeast Pacific based on biomarker reconstructions.

Author

Hagemann, Julia Rieke, Lembke-Jene, Lester, Lamy, Frank, Vorrath, Maria-Elena, Kaiser, Jérôme, Müller, Juliane, Arz, Helge W., Hefter, Jens, Jaeschke, Andrea, Ruggieri, Nicoletta, and Tiedemann, Ralf

Subjects
OCEAN temperature, BIOMARKERS, WATER depth, CALIBRATION, CLIMATOLOGY
Abstract

Alkenones and Glycerol Dialkyl Glycerol Tetraether lipids (GDGT) as remnants of living organisms are widely used biomarkers for determining past oceans' water temperatures. The organisms these proxy carriers stem from, are influenced by a number of environmental parameters, such as water depth, nutrient availability, light conditions or seasonality, which all may significantly bias the calibration to ambient water temperatures. Reliable temperature determinations remain thus challenging, especially in higher latitudes and for under-sampled regions. We analyzed 33 sediment surface samples from the Southern Chilean continental margin and the Drake Passage for alkenones and GDGTs and compared the results with gridded instrumental reference data from the World Ocean Atlas 2005 (WOA05), as well as previously published data from an extended study area covering the Central and Western South Pacific towards the New Zealand continental margin. We show that for alkenone-derived SSTs, the widely-used global core-top calibration of Müller et al. (1998) yields the smallest residuals, whereas the calibration of Sikes et al. (1997), adapted to higher latitudes and supposed to show summer SSTs, overestimates modern WOA05-based (summer and annual mean) SSTs. Our alkenone SSTs show a slight seasonal shift of ~1 °C at the Southern Chilean Margin and up to ~2 °C in the Drake Passage towards austral summer SSTs, whereas samples in the Central South Pacific reflect an annual mean signal. We show that for GDGT-based temperatures, a more complex pattern emerges. In areas north of the Subantarctic Front (SAF) the subsurface calibration of Kim et al. (2012a) best reflects temperatures from the WOA05, largely within the margin error of ±2.2 °C. Temperatures south of the SAF instead are significantly overestimated by up to 14 °C, irrespective of the applied calibration. Based on a qualitative assessment of the GDGT [2] / [3]-ratios, which likely indicate water depth of origin, our samples reflect a subsurface (0 to 200 m water depth) rather than a surface (0–50 m water depth) signal. The overestimation of surface and subsurface temperatures south of the SAF highlights the need for a re-assessment of existing calibrations in the polar Southern Ocean, and leads to limitations in reliably both obtaining absolute values and assessing relative changes. Therefore, we suggest a modified Southern Ocean calibration for surface and subsurface GDGT-based temperatures, which shows a lower temperature sensitivity of the TEXL86 and yields principally lower absolute temperatures, which align more closely with WOA05-derived values. [ABSTRACT FROM AUTHOR]

Published
2022
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23. Deglacial and Holocene sea ice and climate dynamics at the Western Antarctic Peninsula.

Author

Vorrath, Maria-Elena, Müller, Juliane, Cárdenas, Paola, Mieruch, Sebastian, Esper, Oliver, Opel, Thomas, Lembke-Jene, Lester, Etourneau, Johan, Vieth-Hillebrand, Andrea, Lahajnar, Niko, Lange, Carina B., Leventer, Amy, Evangelinos, Dimitris, Escutia, Carlota, and Mollenhauer, Gesine

Subjects
SEA ice, CLIMATE change, OCEAN temperature, PHYTOPLANKTON
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 Western Antarctic Peninsula (WAP) is experiencing rapid warming and the associated decrease in sea ice cover contrasts the trend of growing sea ice extent in eastern Antarctica. To reveal the long-term sea ice history at the WAP 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 open ocean diatom assemblages reflect predominantly ice-free conditions. We further reconstruct ocean temperatures using glycerol dialkyl glycerol tetraether (GDGTs) and diatom assemblages, and compare our sea ice and temperature records with published marine sediment and ice core data. Our results document a retreat of the WAP ice shelf at 13.9 ka BP (before present). Maximum sea ice cover is observed during the Antarctic Cold Reversal, while a still extended but variable sea ice coverage characterized the core site during the early Holocene. An overall decreasing sea ice trend throughout the Middle Holocene is accompanied by a successive ocean warming and increasing phytoplankton productivity. The Late Holocene is characterized by unstable (winter) sea ice conditions and a further sea ice decline until 0.5 ka BP. [ABSTRACT FROM AUTHOR]

Published
2022
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