Action #5: Mapping the deep-water oxygen conditions

Objectives: Sub-surface oxygen conditions in the Gulf of Finland are very sensitive to atmospheric forcing. The area occupied by hypoxic water varies between 0 – 7000 km2 and considerable changes can occur within a few days, i.e. in much shorter time scales than conventional monitoring can capture. The main aim of the topic is to estimate oxygen distribution in the gulf with at least weekly temporal resolution. Latter allows the calculation of statistics of the near-bottom oxygen conditions.

Action Lead and other Partners (with contact persons): TALTECH (Liblik), SYKE (Seppälä), FMI (Laakso), IOW (Bittig)

JS3 Platforms included: Utö Observatory (FMI, SYKE), Keri Observatory (TALTECH); Gliders (FMI, TALTECH), profiling buoys (FMI, SYKE, TALTECH), Argo floats (FMI), monitoring by R/V (All).

Other data sources and external partners for implementation: HELCOM ICES database and operational model data from CMEMS, including the input from GoF PSS topic ii).

Overall timetable of action: Collection of data February 2020 – September 2021, a compilation of weekly near-bottom oxygen maps and statistics April 2021 – April 2022.

Description of action: The oxygen depletion issue in the near-bottom layers of the Baltic Sea is a cross-border issue and its monitoring needs a coordinated international collaboration. The Action includes data collection, developing the mapping method and producing the near-bottom oxygen maps in the GoF. The core in-situ dataset will be based on measurements at observatories (Keri and Utö), monitoring by R/Vs and Argo float measurements. The two possible directions for the oxygen maps production can be foreseen: 1) Available CMEMS biogeochemical operative modelling product dedicated to the Baltic Sea will be validated with in-situ measurements (GoF PSS topic ii) and if possible, systematic empirical corrections for the modelled fields will be estimated. If the corrections are reliable over time and/or various states of the sea, they will be used to estimate near-bottom oxygen conditions in the GoF by CMEMS products; 2) Spatial maps compiled by conventional monitoring will be combined with the high temporal resolution measurements conducted at observatories. The linkage between the two could be utilized to create oxygen maps in a weekly temporal resolution. The topic calls for coordinated international collaboration in planning long term deployments and short-term missions and sharing of results. The action needs to include a joint identification of vulnerable areas and especially communicating which are the most important areas lacking consistent observations. Planning the new observation sites, sharing experiences in the deployments and communicating best practices for QC are important components of the topic. The flow of data into joint databases (e.g. CMEMS) needs to be guaranteed for all platforms. The implementation of the topic is a step forward in the coordinated international monitoring of the subsurface oxygen distributions in the area of PSS.

Timetable for Action:

  • Collection of the data (February 2020 – September 2021).
  • Compiling the datasets (April 2021 – October 2021).
  • Developing the method for the compilation of oxygen maps (May 2021 – September 2021).
  • Compiling the oxygen maps, adjusting the method (November 2021 – March 2022).
  • Compiling the report on the oxygen dynamics (April-May 2022).

Best practices used or developed: The best method(s) for the estimation of near-bottom oxygen distribution in the GoF will be documented.

Data flows: Action will not arrange operative data flows, but collects the data from partners in autumn 2021.

Data QC routines: Action will not deal with QC routines, but relies on GoF PSS #1.

Data management issues: Minor issues can occur when partners must agree on data formats.

Expected results: The main result is the time series of the near-bottom oxygen distributions (maps) in relevant timescales for the GoF.

Users of results: Researchers dealing with the Eastern Baltic Sea, authorities responsible for the assessments of the environmental status of marine areas.

Dissemination of results: Results will be shared by JERICO e-infrastructure, At least one scientific paper is planned to publish on the topic during the project period. Results will be introduced to the relevant working group in HELCOM.

Links: The Action links to WP2 T2.4 highlighting the coupling of observations and modelling communities, further detailing how these connections may be improved.