By the middle of the century the Arctic Ocean may be open water during summer, even with moderate CO₂ emissions.

KUNNGJØRING PRØVEFORELESNING Institutt for geovitenskap Det matematisk-naturvitenskapelige fakultet Universitetet i Bergen Ph.d.-kandidat Wanyee Wong holder prøveforelesning over følgende oppgitte emne for ph.d.-graden: Constraining the chronology of ocean sediments – an overview of available approaches and their advantages and limitations Tid og sted: Fredag 19. september 2025, kl. 13.15 Auditorium 4, Realfagbygget Komité: Professor Ulysses Silas Ninnemann, Institutt for geovitenskap (leder for komiteen) Professor Anna Nele Meckler, Institutt for geovitenskap Førsteamanuensis Bjarte Hannisdal, Institutt for geovitenskap Adgang for interesserte tilhørere. VELKOMMEN!

Speaker: Zhetao Tan from the Laboratoire de Météorologie Dynamique, École Normale Supérieure (LMD/ENS). Abstract Global climate change has triggered widespread shifts in the ocean’s physical and biogeochemical state. The essential ocean variables (EOVs), such as temperature, salinity, oxygen, and pH, known as climatic impact-drivers (CIDs), provide critical risk information for climate impacts across ocean sectors. Yet, a global three-dimensional view of long-term compound changes and their underlying physical processes remains limited, largely due to limitations in data availability (e.g., data quality, data coverage, and data processing techniques). This presentation will first introduce recent advances in observational data processing techniques developed by the speaker and his collaborators over the past five years, including improved quality control, systematic bias correction, and spatial mapping. Using these state-of-the-art in-situ and gridded products based on the advanced data processing techniques, the presentation will show the examination of long-term compound CIDs in the global scale (put temperature, salinity, dissolved oxygen, and pH together in the same framework), identify the climate hotspots of the above concurrent change, and assess when and how these compound signals emerge. Results reveal a large-scale and deep-reaching compound ocean state change triggered by global warming, most prominently in the Atlantic Ocean. Finally, as a region study to understand the physical processes of the above compound climate change, the presentation will report recent findings that the South Atlantic upper-ocean water masses are responding to compound climate change over the past 45 years through distinct but connected processes: Air-sea surface-driven exchanges dominate the long-term warming and salinization changes in the Surface Water (SW), vertical displacement shapes the changes in the volume-expanded South Atlantic Central Water (SACW), and advective anthropogenic heat redistribution governs the warming and thinning changes in the core Antarctic Intermediated Water (AAIW). Speaker information Dr. Zhetao Tan is a post-doc fellow at the Laboratoire de Météorologie Dynamique, École Normale Supérieure (LMD/ENS), working on the OCEAN:ICE project funded by Horizon Europe. His research interests include physical oceanography, operational oceanography, and ocean climate change impact, with a particular focus on ocean observations and data quality improvements, water mass and ocean circulation, ocean compound climate change. Particularly, he mainly focused on the study of ‘climate impact-drivers’ (e.g., temperature, salinity, dissolved oxygen etc.) which connect physical ocean changes to broader climate impacts. He hold his Ph.D from the Institute of Atmospheric Physics, Chinese Academy of Sciences (IAP/CAS) in 2024. He is also a member of the International Quality Controlled Ocean Database (IQuOD), and the SOOP-XBT data management team (XBT-DMT).

Hi everyone, We will have our next Stormtracks group meeting on Wednesday (24.09), from 13:00 to 14:00 at U105. Next week, Dave Schneider from CIRES, CU Boulder will present his work titled “Observed and modelled trends in Southern Hemisphere winds and ocean warming (with ice cores! and snow!)” The meeting will be hybrid and here is the zoom link for those who want to join remotely: https://uib.zoom.us/j/62886269543?pwd=ajWbi97zr0hbniaoQdZkUtD2EUSSri.1 Meeting ID: 628 8626 9543; Password: qSKTfKU3 If anyone would like to meet him, he will be around on Wednesday and Thursday next week. The meeting schedule for this semester is in the following google doc. Please do fill in a slot when you would like to speak. We have a few open slots. Ongoing works are most encouraged! https://docs.google.com/document/d/1yjicxkFp_8Y17LVftgksb1SnqSUSUXogg0pOFZfbK0g/edit?usp=sharing Have a nice weekend and see you all there next week! :) Cheers, ~Hari and Yangfan