FINNISH ENVIRONMENT INSTITUTE (SYKE) (FI)
The overall goal of the ESA funded project Baltic+ SeaLaBio (Sea-Land Biogeochemical linkages) running from Dec 2018 to May 2020 is to develop methods for assessing carbon dynamics and eutrophication in the Baltic Sea through integrated use of EO, models, and ground-based data
The poor state of the Baltic Sea again became apparent during summer 2018 in form of massive and long-lasting cyanobacteria blooms. Warm and sunny weather, combined with good availability of nutrients led to the worst algae situation in a decade. Climate change is expected to cause further warming in this region making these events more and more common in the future.
The decades of dumping untreated waste water into the Baltic Sea and the use of fertilizers in agriculture have resulted in strong internal loading. While the water treatment situation has improved and fertilizers are being used more responsibly, the flux of carbon and nutrients from land to sea is still great and in many areas largely unknown. The Sentinel satellites of the Copernicus programme offer an excellent opportunity for characterizing and monitoring the fluxes and processes occurring in coastal zones. This in turn will lead to improved process understanding.
With this in mind, the Baltic+ SeaLaBio research project aims to find an answer to the question:
• Can we quantify the carbon flux from land to sea with Sentinel-3 (S3) OLCI and Sentinel-2 (S2) MSI data in the Baltic Sea region? And if not, what are the main obstacles and potential solutions to be addressed in the future?
In addition to frequent cyanobacteria blooms, the high absorption by colored dissolved organic matter (CDOM) causes problems to the utilization of EO for monitoring the state of the Baltic Sea. The available processors for S3 and S2 often provide overestimated values for Chlorophyll a and underestimate CDOM. The main source of these problems is the failure of the atmospheric correction to provide reasonable marine reflectances. Thus, the project focuses especially on improving the atmospheric correction and in-water inversion algorithms for S3 and S2 images. The developed methods will be validated with in situ data collected from different parts of the Baltic Sea. We will also improve the spatial resolution of a biogeochemical (BGC) model (Ecological ReGional Ocean Model, ERGOM) and compare its output against the EO results.
S3 OLCI has a better band combination for water quality estimation than S2 but its spatial resolution limits its use in river estuaries and archipelagos common in the coastal areas of the Baltic Sea. Hence, the synergistic use of these two data sources can lead to improved coverage in coastal regions without compromising the thematic quality of the data.
The project will actively disseminate its progress and results in various Baltic Sea and EO events.