InfoWas – Developing an Information System for Water Quality in the North and Baltic Seas – Forecasting Oxygen Deficiency Zones

Seasonally occurring oxygen deficiency zones (ODZs) are a regular feature in the coastal zones of the Baltic and North Seas, and their frequency has increased over the last years. The development of ODZs is favoured in areas of high primary production supported by excess nutrient loads from land, sluggish ventilation and strong salinity and/or temperature gradients. For forecasting the risk of oxygen deficiency, we redefine the oxygen deficiency index (ODI) originally developed for the North Sea by Große et al. (2016) to account for the fundamental differences between Baltic and North Seas (e.g., haline vs. thermal stratification) and to obtain a common ODI, applicable to both seas and in an operational context. The InfoWas system is based on the results from the operational physical-biogeochemical model (HBM-ERGOM) at the BSH. The model system is further coupled with the Parallel Data Assimilation Framework (PDAF) developed at the Alfred Wegener Institute (AWI). Since ODZs in coastal zones can become hazardous to organisms and can cause ecological and economic consequences for the environment, the fisheries and the tourism-industries, combining the operational InfoWas system with the revised ODI offers intuitive, short-term forecasts of the risk of oxygen deficiency on a high spatio-temporal resolution for the entire coastal zone of the North and Baltic Seas. These easily interpretable forecasts will help to quickly inform environmental agencies of potentially upcoming harmful events and to act in advance in order to diminish environmental and economic consequences.