Interplay between seasonal arctic sea-ice processes and halocline stability - towards understanding arctic gas and matter fluxes

• Applicant: Dr. Dorothea Bauch
• Subject Area: Oceanography
• Term: from 2019 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 429838323

• Final Report Year: 2025

Final Report Abstract

The Arctic Ocean halocline was investigated applying stable water (18O and D) isotopes methods in ice and water column over a full annual cycle within the frame of the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) program. We successfully collected and analysed a consecutive and largely uninterrupted isotope dataset from the water column (18O) and from ice cores (18O and D) through all 5 legs of the expedition in the Transpolar Drift (TPD) between the eastern central Arctic via the North Pole and south of Fram Strait. To assess the stability of the Arctic Ocean halocline, 18O data in the water column was combined with salinity to quantify river water contributions (f r) and the signal due to sea-ice formation or melting (fSIM). The unique winter data from 2019/2020 show variable sea-ice (fSIM) and river water (fr) signals at constant salinities in the upper ~80m of the water column. Such variations were not observed within the TPD during summer expeditions before and document local freezing events. The Arctic halocline is known to be mostly advected from the shelf regions and with our data we were able to quantify the advected versus the local modification throughout the winter and thereby detected clear regional differences: The advected signal is with ~2.0+-0.7m and ~3.7+-0.7m significantly different in the lower and higher salinity regions of the TPD, respectively. Our findings confirm that shelf waters from different Siberian shelf regions i.e. the Kara and the Laptev seas do not mix within the TPD (Paffrath et al., 2021; Laukert, Bauch et al., under revision) and indicate sea-ice formation rates to differ in these regions, travel paths of shelf waters to differ, or both. With a time series of ice cores taken from different ice types we were able to show marine signatures in 18O to be reliable recorded in newly formed ice in first-year ice (FYI) or below second-year ice (SYI) with an about constant fractionation throughout the drift. Summer surface melting caused intrusion of low 18O snow melt into fully permeable FYI from the top as well as from the bottom of the ice when meltwater collects below the ice. In contrast to FIY, SYI that experiences a second melt season remained mostly impermeable and no new intrusion of snow melt into surface or bottom layers was observed. With the significant losses of sea ice over the last few decades, another goal was to investigate sea-ice processes in direct connection with biogeochemical components in the light of the “new arctic”. By combining stable oxygen isotope analysis with geochemical provenance tracers investigated by MOSAIC collaborators we were able to draw important general conclusions on the transport of river-derived matter and matter dispersal along the TPD. These findings have significant importance for downstream marine ecosystems, biogeochemical cycles, food security, and human health — as “matter” refers to an extensive array of critical dissolved and particulate substances originating from Siberian rivers, including nutrients, metals, gases, carbon, microplastics, and other pollutants. Thus, the TPD’s impact extends far beyond its role in distributing fresh water and shaping large-scale oceanic and climate dynamics. This project constitutes a foundation for stable water isotope data of the “new arctic” and important results on the Arctic Ocean halocline formation and matter fluxes and dispersal in the TPD were achieved. The unique winter dataset collected as a time series in the TPD will continue to be of outstanding importance as a regional winter dataset. It was surprising, that the water column data was so strongly dominated by the regional signal.

Publications

• Sea-ice salinity, temperature, density, nutrient, oxygen and hydrogen isotope composition from the coring sites during MOSAiC leg 5 in August-September 2020.
  Salganik, E., Whitmore, L.M., Bauch, D., Chamberlain, E., Dietrich, U., Droste, E.S., Fong, A.A., Heitmann, L., Nicolaus, M., Kolabutin, N., Li, Y., Ludwichowski, K.-U., Marent, A., Mellat, M., Meyer, H., Nomura, D., Schmidt, K., Shimanchuk, E., Thielke, L., Torres-Valdés, S., Webb, A.L., Weiner, M. & Granskog, M.A.
  
• Insights into the origins, molecular characteristics and distribution of iron-binding ligands in the Arctic Ocean. Marine Chemistry, 231, 103936.
  Williford, Tatiana; Amon, Rainer M.W.; Benner, Ronald; Kaiser, Karl; Bauch, Dorothea; Stedmon, Colin; Yan, Ge; Walker, Sally A.; van der Loeff, Michiel Rutgers & Klunder, Maarten B.
  
• Insights Into Water Mass Origins in the Central Arctic Ocean From In‐Situ Dissolved Organic Matter Fluorescence. Journal of Geophysical Research: Oceans, 126(7).
  Stedmon, Colin A.; Amon, Rainer M. W.; Bauch, Dorothea; Bracher, Astrid; Gonçalves‐Araujo, Rafael; Hoppmann, Mario; Krishfield, Richard; Laney, Samuel; Rabe, Benjamin; Reader, Heather & Granskog, Mats A.
  
• Separating individual contributions of major Siberian rivers in the Transpolar Drift of the Arctic Ocean. Scientific Reports, 11(1).
  Paffrath, Ronja; Laukert, Georgi; Bauch, Dorothea; Rutgers, van der Loeff Michiel & Pahnke, Katharina
  
• Deciphering the Properties of Different Arctic Ice Types During the Growth Phase of MOSAiC: Implications for Future Studies on Gas Pathways. Frontiers in Earth Science, 10.
  Angelopoulos, Michael; Damm, Ellen; Simões, Pereira Patric; Abrahamsson, Katarina; Bauch, Dorothea; Bowman, Jeff; Castellani, Giulia; Creamean, Jessie; Divine, Dmitry V.; Dumitrascu, Adela; Fons, Steven W.; Granskog, Mats A.; Kolabutin, Nikolai; Krumpen, Thomas; Marsay, Chris; Nicolaus, Marcel; Oggier, Marc; Rinke, Annette; Sachs, Torsten ... & Haas, Christian
  
• Impacts of glacier and sea ice melt on methane pathways on the Northeast Greenland shelf. Continental Shelf Research, 243, 104752.
  Verdugo, Josefa; Damm, Ellen; Schaffer, Janin; Bauch, Dorothea; Meyer, Hanno & Kaiser, Jan
  
• Neodymium isotopes trace marine provenance of Arctic sea ice. Geochemical Perspectives Letters, 22, 10-15.
  Laukert, G.; Peeken, I.; Bauch, D.; Krumpen, T.; Hathorne, E.C.; Werner, K.; Gutjahr, M. & Frank, M.
  
• Overview of the MOSAiC expedition: Physical oceanography. Elem Sci Anth, 10(1).
  Rabe, Benjamin; Heuzé, Céline; Regnery, Julia; Aksenov, Yevgeny; Allerholt, Jacob; Athanase, Marylou; Bai, Youcheng; Basque, Chris; Bauch, Dorothea; Baumann, Till M.; Chen, Dake; Cole, Sylvia T.; Craw, Lisa; Davies, Andrew; Damm, Ellen; Dethloff, Klaus; Divine, Dmitry V.; Doglioni, Francesca; Ebert, Falk ... & Zhu, Jialiang
  
• Oxygen and hydrogen isotopic ratios from sea ice bottom, false bottom ice, under-ice meltwater layer and surface melt pond samples collected during MOSAiC leg 4 (PS122.4).
  Lange, B.A., Granskog, M.A., Meyer, H., Bauch, D., Smith, M.M., von Albedyll, L., Raphael, I., Matero, I. & Salganik, E.
  
• Physical properties of sea ice cores for biogeochemistry studies measured on legs 1 to 3 of the MOSAiC expedition. PANGAEA.
  Angelopoulos, M., Damm, E., Simões Pereira, P., Abrahamsson, K., Bauch, D., Bowman, J.S., Castellani, G., Creamean, J., Divine, D.V., Dumitrascu, A., Eggers, L., Fong, A.A., Fons, S.W., Gradinger, R., Granskog, M.A., Grosse, J., Haapala, J., Haas, C., Hoppe, C.J.M., Høyland, K.V., Immerz, A., Kolabutin, N., Krumpen, T., Lei, R., Marsay, C.M., Maus, S., Nicolaus, M., Nubom, A., Oggier, M., Olsen, L.M., Rember, R., Ren, J., Rinke, A., Sachs, T., Sheikin, I., Shimanchuk, E., Torres-Valdés, S., Spahic, S., Stefels, J., Stephens, M., Torstensson, A., Ulfsbo, A., Verdugo, J., Wang, L., Wischnewski, L. & Zhan, L.
  
• Physical properties of sea ice cores from L sites measured on leg 1 of the MOSAiC expedition. PANGAEA
  Angelopoulos, M., Damm, E., Simões Pereira, P., Abrahamsson, K., Bauch, D., Bowman, J.S., Dumitrascu, A., Marsay, C.M., Rinke, A., Sachs, T., Stefels, J., Stephens, M., Verdugo, J., Wang, L. & Zhan, L.
  
• Physical properties of sea ice cores from site BGC1 measured on legs 1 to 3 of the MOSAiC expedition. PANGAEA
  Angelopoulos, M., Damm, E., Simões Pereira, P., Abrahamsson, K., Bauch, D., Bowman, J.S., Dumitrascu, A., Marsay, C.M., Rinke, A., Sachs, T., Stefels, J., Stephens, M., Verdugo, J., Wang, L. & Zhan, L.
  
• Physical properties of sea ice cores from site BGC2 measured on legs 1 to 3 of the MOSAiC expedition. PANGAEA
  Angelopoulos, M., Damm, E., Simões Pereira, P., Abrahamsson, K., Bauch, D., Bowman, J.S., Dumitrascu, A., Marsay, C.M., Rinke, A., Sachs, T., Stefels, J., Stephens, M., Verdugo, J., Wang, L. & Zhan, L.
  
• Physical properties of sea ice cores from site BGC3 measured on legs 1 to 3 of the MOSAiC expedition. PANGAEA
  Angelopoulos, M., Damm, E., Simões Pereira, P., Abrahamsson, K., Bauch, D., Bowman, J.S., Dumitrascu, A., Marsay, C.M., Rinke, A., Sachs, T., Stefels, J., Stephens, M., Verdugo, J., Wang, L. & Zhan, L.
  
• Physical properties of sea ice cores from site MCS-SYI measured on legs 1 to 3 of the MOSAiC expedition. PANGAEA
  Angelopoulos, M., Abrahamsson, K., Bauch, D., Bowman, J.S., Castellani, G., Creamean, J., Damm, E., Divine, D.V., Dumitrascu, A., Eggers, L., Fong, A.A., Fons, S.W., Gradinger, R., Granskog, M.A., Grosse, J., Haapala, J., Haas, C., Hoppe, C.J.M., Høyland, K.V., Immerz, A., Kolabutin, N., Krumpen, T., Lei, R., Marsay, C.M., Maus, S., Nicolaus, M., Nubom, A., Oggier, M., Olsen, L.M., Rember, R., Ren, J., Rinke, A., Sachs, T., Sheikin, I., Shimanchuk, E., Simões Pereira, P., Spahic, S., Stefels, J., Stephens, M., Torres-Valdés, S., Torstensson, A., Ulfsbo, A., Verdugo, J., Wang, L., Wischnewski, L. & Zhan, L.
  
• Physical properties of sea ice cores from site MCS_FYI measured on legs 1 to 3 of the MOSAiC expedition. PANGAEA
  Angelopoulos, M., Abrahamsson, K., Bauch, D., Bowman, J.S., Castellani, G., Creamean, J., Damm, E., Divine, D.V., Dumitrascu, A., Eggers, L., Fong, A.A., Fons, S.W., Gradinger, R., Granskog, M.A., Grosse, J., Haapala, J., Haas, C., Hoppe, C.J.M., Høyland, K.V., Immerz, A., Kolabutin, N., Krumpen, T., Lei, R., Marsay, C.M., Maus, S., Nicolaus, M., Nubom, A., Oggier, M., Olsen, L.M., Rember, R., Ren, J., Rinke, A., Sachs, T., Sheikin, I., Shimanchuk, E., Simões Pereira, P., Spahic, S., Stefels, J., Stephens, M., Torres-Valdés, S., Torstensson, A., Ulfsbo, A., Verdugo, J., Wang, L., Wischnewski, L. & Zhan, L.
  
• Stable water isotopes and conductivities of a lead case study during leg 5 of the MOSAiC expedition.
  Meyer, H., Mellat, M., Nomura, D., Damm, E., Bauch, D., Weiner, M. & Marent, A.
  
• Meltwater layer dynamics in a central Arctic lead: Effects of lead width, re-freezing, and mixing during late summer. Elem Sci Anth, 11(1).
  Nomura, Daiki; Kawaguchi, Yusuke; Webb, Alison L.; Li, Yuhong; Dall’osto, Manuel; Schmidt, Katrin; Droste, Elise S.; Chamberlain, Emelia J.; Kolabutin, Nikolai; Shimanchuk, Egor; Hoppmann, Mario; Gallagher, Michael R.; Meyer, Hanno; Mellat, Moein; Bauch, Dorothea; Gabarró, Carolina; Smith, Madison M.; Inoue, Jun; Damm, Ellen & Delille, Bruno
  
• Stable water isotopes of sea ice at Main Coring Site (MCS) during MOSAiC expedition.
  Mellat, M., Meyer, H., Werner, M., Brunello, C.F., Granskog, M.A., Damm, E., Bauch, D., Weiner, M. & Marent, A.
  
• Stable water isotopes of seawater at Ocean City during MOSAiC expedition.
  Mellat, M., Meyer, H., Bauch, D., Damm, E., Werner, M., Brunello, C.F., Weiner, M. & Marent, A.
  
• Isotopic signatures of snow, sea ice, and surface seawater in the central Arctic Ocean during the MOSAiC expedition. Elem Sci Anth, 12(1).
  Mellat, Moein; Brunello, Camilla F.; Werner, Martin; Bauch, Dorothea; Damm, Ellen; Angelopoulos, Michael; Nomura, Daiki; Welker, Jeffrey M.; Schneebeli, Martin; Granskog, Mats A.; Hoerhold, Maria; Macfarlane, Amy R.; Arndt, Stefanie & Meyer, Hanno
  
• Stable water isotopes of sea ice at biogeochemistry sites (BGC) and Main Coring Sites (MCS) during MOSAiC expedition, leg 1.
  Bauch, D., Meyer, H., Damm, E., D’Angelo, A., Mellat, M., Granskog, M.A., Weiner, M. & Marent, A.
  
• Stable water isotopes of sea ice at biogeochemistry sites (BGC) and Main Coring Sites (MCS) during MOSAiC expedition, leg 2.
  Bauch, D., Meyer, H., Damm, E., D’Angelo, A., Mellat, M., Granskog, M.A., Weiner, M. & Marent, A.
  
• Stable water isotopes of sea ice at biogeochemistry sites (BGC) and Main Coring Sites (MCS) during MOSAiC expedition, leg 3.
  Bauch, D., Meyer, H., Damm, E., D’Angelo, A., Mellat, M., Granskog, M.A., Weiner, M. & Marent, A.
  
• Stable water isotopes of sea ice at biogeochemistry sites (BGC) and Main Coring Sites (MCS) during MOSAiC expedition, leg 4.
  Bauch, D., Meyer, H., Damm, E., D’Angelo, A., Mellat, M., Granskog, M.A., Weiner, M. & Marent, A.
  
• Stable water isotopes of seawater samples from the MOSAiC expedition 2019/2020.
  Bauch, D., Andersen, N., Damm, E., D’Angelo, A. & Nomura, D.
  
• The Eurasian Arctic Ocean along the MOSAiC drift in 2019-2020: An interdisciplinary perspective on physical properties and processes. California Digital Library (CDL).
  Schulz, Kirstin; Koenig, Zoe; Muilwijk, Morven; Bauch, Dorothea; Hoppe, Clara J. M.; Droste, Elise; Hoppmann, Mario; Chamberlain, Emelia J.; Laukert, Georgi; Stanton, Tim; Quintanilla, Zurita Alejandra; Fer, Ilker; Heuzé, Céline; Karam, Salar; Mieruch-Schnuelle, Sebastian; Baumann, Till; Vredenborg, Myriel; Tippenhauer, Sandra & Granskog, Mats A.