Ship and AUV observations near /within a warm ice-shelf cavity (Deliverable D2.3)

Ocean Cryosphere Exchanges in Antarctica: Impacts on Climate and the Earth system Ship and AUV observations near /within a warm ice-shelf cavity Deliverable D2.3 OCEAN:ICE is co-funded by the European Union, Horizon Europe Funding Programme for research and innovation under grant agreement Nr. 101060452 and by UK Research and Innovation https://ocean-ice.eu/ OCEAN:ICE – GA 101060452 Deliverable D2.3 2 About this document Deliverable: D2.3 Ship and AUV observations near /within a warm ice-shelf cavity Work Package: WP2 Cryosphere-ocean interaction, processes and feedbacks Delivery date: 17 October 2024 Type of document: Report Dissemination level: Public Lead beneficiary and author: PP10University of Gothenburg (UGOT): Anna Wåhlin; Stina Wahlgren, Xiaohan Yuan, Filip Stedt Contributors: Korea Polar Research Institute (KOPRI): Won Sang Lee, Sukyoung Yun, Clare Eayrs, Choon-Ki Lee, Seung-Tae Yoon and Ji Sung Na P13-United Kingdom Research and Innovation - British Antarctic Survey (UKRI-BAS): Alex Murphy Review: PP1: Danish Meteorological Institute (DMI), Chiara Bearzotti ([email protected]) Disclaimer: Funded by the European Union and UK Research and Innovation. Views and opinions expressed are however those of the authors only and do not necessarily reflect those of the European Union or UK Research and Innovation. Neither the European Union nor UK Research and Innovation can be held responsible for them. Cover sheet: AUV 'Ran' in front of Thwaites ice shelf, photo by Anna Wåhlin. OCEAN:ICE – GA 101060452 Deliverable D2.3 3 Table of contents 1. Publishable summary .................................................................................................................................... 4 2. Work performed and main achievements .................................................................................................... 4 2.1 Description of the work performed ......................................................................................................... 4 2.1.1 AUV missions .................................................................................................................................... 4 2.1.2 CTD data from the AUV .................................................................................................................... 5 2.1.3 Water sampler data .......................................................................................................................... 7 2.1.4. Acoustic and optical sensors on the AUV ........................................................................................ 8 2.1.5 Long range ADCP data ...................................................................................................................... 9 2.2 References ............................................................................................................................................. 11 2.3 Open Science ......................................................................................................................................... 11 3. Results ......................................................................................................................................................... 11 4. Impact .......................................................................................................................................................... 11 OCEAN:ICE – GA 101060452 Deliverable D2.3 4 1. Publishable summary This deliverable consists of several data sets obtained during the Korean Polar research vessel Araon cruise to the Amundsen Sea, Antarctica. This report consists of a summary of the data gathered - the data sets themselves will be published in an open data repository once the quality control is completed. 2. Work performed and main achievements 2.1 Description of the work performed A successful cruise to the Amundsen Sea was conducted on the Korean icebreaker RVIB Araon between 28 December 2024 and 15 Febuary 2024. In addition to the autonomous underwater vehicle (AUV) and ship data sets reported here, numerous data sets from drilling operations on land, helicopter-based sampling, and moored instrumentation was also obtained. Fig. 1: Map of the cruise region. Symbols indicate all the stations that were conducted during the cruise. From Lee et al (2024). 2.1.1 AUV missions A total of six dives were performed during the expedition. The last dive proved fatal, the AUV went missing. Figure 2 shows the location and mission tracks of each dive during the cruise. Ran has a suite of basic sensors (e.g., dual SBE19+ CTD systems, an EcoPuck, a HydroC carbon dioxide sensor, a DeepSUNA nitrate sensor, OCEAN:ICE – GA 101060452 Deliverable D2.3 5 Edgetech systems for side scan and sub bottom prifliers), and a number of sensors that are exchanged and/or not operated during each dive. Table 1 shows which sensors that were operated in each of the dives, and Figure 2 shows maps of the three dives. Table 1: Summary of all the AUV dives undertaken during the cruise. In total, 874 km was covered during the six dives, of which 637 km were under ice. After the end of the last mission the AUV never returned to its programmed meeting point and is assumed lost below Dotson ice shelf (the target for this last mission was to repeat a previous mission that was conducted successfully in 2022). Figure 2: Map showing the location of the five successful AUV missions. 2.1.2 CTD data from the AUV Ran is equipped with dual systems for conductivity and temperature (SBE19+) and oxygen (SBE43), pumped OCEAN:ICE – GA 101060452 Deliverable D2.3 6 with two SBE5T pumps, one for each system. Figure 3 shows a photo of the two systems mounted inside the AUV. Fig. 3: The two CTD systems mounted inside the AUV. Photo: Anna Wåhlin Problems with the starboard CTD system The conductivity in the starboard CTD appears to have been drifting in between missions (Figure 4). Fig. 4: Drift of the starboard CTD system. Panels show Absolute salinity (SA) versus conservative temperature (CT) for the three missions below Thwaites ice shelf. Red markers show data from ANA14B_02 (a, d), ANA14B_03 (b, e) and ANA14B_04b (c, f), based on the starboard CTD package (top panels) and the port CTD package (bottom panels). Black semitransparent markers show data from missions 2, 3 and 4 in all panels. The difference between missions of the deep water in top panels is due to the starboard sensor drift. OCEAN:ICE – GA 101060452 Deliverable D2.3 7 On the first of the missions, the starboard CTD system was not operating. In the following four missions it was operational, and when the drift was discovered it was decided to use the port CTD for all missions (mission 1 - 5). Offset from ship CTD The conductivity offset between the starboard AUV package and the ship CTD was 0.001 S/m. This will be updated after post cruise calibration of ship CTD. Dissolved oxygen In the first mission, the starboard oxygen sensor was broken, and the port one did not record any data. In the second mission the starboard sensor was replaced to SBE43-2637, but the offset was found to be very high (recorded -1.02 ml/l in deep water below Thwaites, compared to the ship CTD). The port sensor was found to be broken. In the third mission the port SBE43 was replaced to SBE43-3700, and the offset on this sensor was found to be zero compared to the ship CTD. This sensor was used for missions 3, 4 and 5. Table 2: Summary of the CTD sensors used and offset for each mission. Mission CTD system SBE43 offset C (S/m) offset T (oC) offset DO (ml/l) ANA14B_01 Port - 0.001 0 - ANA14B_02 Port SBE43-2637 0.001 0 -1.02 ANA14B_03 Port SBE43-3700 0.001 0 0 ANA14B_04b Port SBE43-3700 0.001 0 0 ANA14B_05 Port SBE43-3700 0.001 0 0 ANA14B_06 Port SBE43-3700 0.001 0 0 2.1.3 Water sampler data The water sampler was mounted when we did not have the Pinnacle ADCP mounted (i.e. missions ANA14B_04, ANA14B_05 and ANA14B_06). Due to some changes in the software, all the samples in ANA14B_04 failed. Thus, only one mission (ANA14B_05) had correct water samples. The location for the samples are shown in Figure 5, and the average properties of each water sample is shown in Table 3. OCEAN:ICE – GA 101060452 Deliverable D2.3 8 Fig. 5: Maps showing the AUV tracks and location of water samples in mission ANA14B_05. Gray area indicates the ice shelf, black markers show the locations during which the water sampler was pumping water into each sample, and the color indicates (a) Dissolved oxygen (b) meltwater fraction (c) Conservative temperature according to color bars. Table 3: Position, depth, conservative temperature, absolute salinity, and dissolved oxygen for the 14 water samples taken during mission ANA14B_05. The first sample is a blank. 2.1.4. Acoustic and optical sensors on the AUV Downward-looking multibeam Ran is equipped with a EM2040 downward-looking multibeam. The system was operated on ANA14B_01, ANA14B_02, and ANA14B_03. Preliminary versions of the data sets were left on the cruise NAS drive. Post processing steps remaining is to QC the data more carefully and to apply the post processed navigation data with the processing. Upward-looking multibeam Ran is equipped with a EM2040CX upward-looking multibeam. The system was operated on ANA14B_04b, ANA14B_05, and ANA14B_06. Preliminary versions of the data sets were left on the cruise NAS drive. Post OCEAN:ICE – GA 101060452 Deliverable D2.3 9 processing steps remaining is to QC the data more carefully and to apply the post processed navigation data with the processing. EcoPuck data Ran is equipped with an FLBBDC6k EcoPuck with serial number 5028. The system was operated on all missions and is part of the basic suite of sensors. Preliminary versions of the data sets were left on the cruise NAS drive. Post processing steps remaining is to apply the post processed navigation data with the processing. 2.1.5 Long range ADCP data An upward-looking Pinnacle long range ADCP (45 kHz) was mounted on the AUV for three missions: one in Fererro bay (ANA14B_01) and two under the eastern part of Thwaites ice shelf (ANA14B_02, ANA14B_03). The ADCP was run in narrow band mode, with a range of 1300 m, cell size of 32 m and pinging every 2.4 s (ANA14B_01) and 4 s (ANA14B_02, ANA14B_03) respectively. During the first mission under Thwaites (ANA14B_02), the ADCP stopped recording data after 14.5 hours. The problem was likely related to the internal memory card. We reformatted the memory card before the third mission and had no problems during the third mission.