The monitoring of hydrography covers the physical oceanographic parameters temperature, salinity, turbidity and water transparency. The topic also includes monitoring of waves, currents and sea ice extent and thickness.
Temperature and salinity are two supporting parameters in HELCOM monitoring.
Water transparency is related to increase in suspended algae and relevant for the assessment of eutrophication. Transparency and turbidity are used in monitoring (at least occassionally) but only Secchi depth is used as core indicator.
Turbidity describes an inherent optical quality, described often for example through attenuation of light. Secchi depth is a measure of apparent optical quality, but it is often used as a proxy of turbidity.
HELCOM core indicator linked to the sub-programme is: 'Water clarity'
Monitoring of waves, currents and sea level is required to assess permanent changes in hydrographic conditions as well as to describe natural variability of physical characteristics (wave exposure, upwelling, mixing conditions, and residence time) in relation to environmental assessments.
There is no HELCOM core indicator related to waves or currents.
Ice conditions in the Baltic Sea are monitored using earth observation data from satellites (SAR) to monitor sea ice extent. Monitoring is carried out from the beginning until the end of annual ice season, typically from November to May.
In situ measurements are used for measurement of sea ice thickness, which is carried out in coastal waters and open sea areas.
There is no HELCOM core indicator related to ice.
State and Conservation
Contact information: HELCOM Secretariat
Water column hydrological characteristics
Water column physical characteristics