[A-CG52] Science in the Arctic Region

[ACG52-P05] Preliminary ArcWatch-2 expedition XCTD deployment program results

Ke-Hsien Fu¹, Bo-Shian Wang¹, Wen-Chuan Wu², *Ying-Chih Fang², Dai-Jyun Yu², Céline Heuzé³, Benjamin Rabe⁴, Mario Hoppmann⁴, Sandra Tippenhauer⁴, Jacob Allerholt⁴, Simran Suresh⁴, Hau Man Wong³, Jialiang Zhu⁵, Oliver Huhn⁶ (1.National Academy of Marine Research, Kaohsiung, Taiwan, 2.Department of Oceanography, College of Marine Sciences, National Sun Yat-sen University, Kaohsiung, Taiwan, 3.Department of Earth Sciences, University of Gothenburg, Gothenburg, Sweden, 4.Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung, Bremerhaven, Germany, 5.College of Oceanic and Atmospheric Sciences, Ocean University of China, Qingdao, China, 6.Institute of Environmental Physics, University of Bremen, Bremen, Germany)

Keywords:ArcWatch-2 expedition, XCTD, Hydrographic transects, Central Arctic Ocean

The ArcWatch-2 (PS144) expedition took place in the central Arctic Ocean during August – October 2024. ArcWatch is an ongoing project involving a set of three expeditions that also represent a continuation of long-term observations in the central Arctic. PS144 was the second ArcWatch expedition and reassessed the hydrography of the Eurasian and Makarov Basins after prior expeditions in 2007, 2011 and 2015. For the Taiwanese academic community, this was the first time a local scientist was on board the icebreaker R/V Polarstern. The scientific task of the Taiwanese team in the ArcWatch-2 expedition was to deploy expendable CTD (XCTD) probes to provide a quality-assured hydrographic data set for the five targeted hydrographic transects with a horizontal resolution of ~15 – 20 km. Overall, the operation resulted in 91 water column profiles to a depth of ~2000 m, out of a total 107 XCTD deployments. One transect was north of Svalbard, while the remaining four were in the central Arctic Ocean. The two longest transects spanning ~700 – 800 km traverse the Lomonosov and Gakkel Ridges covering the Makarov, Amundsen, and Nansen Basins. This poster presents preliminary results using data from the four transects in the central Arctic Ocean. Interleaving and lateral spreading of Atlantic Water between depths ~150 – 500 m are their most distinctive features. The upper surface mixed layer and cold halocline layer exhibit strong horizontal thermohaline gradients. Ongoing work includes a detailed comparison to the measurements derived from the last ArcWatch expedition. We expect to see some sub-decadal variation in the central Arctic Ocean. We welcome the exchange of ideas with colleagues in polar research and the promotion of international collaboration with us.