SMHI produces twice weekly sea surface temperature maps of the entire Baltic, including the Gulf of Riga, Kattegat and Skagerrak (Eastern North Sea). These are based on a combination of satellite, ship of opportunity and fixed platform data. During the ice season, daily maps are published, showing water temperature, ice parameters and the location of ice breaking services (Figure 1).
Satellite SST originates as the EUMETSAT OSI-SAF (Ocean and Sea Ice Satellite Application Facility) NAR (North Atlantic Region) product. This is a 2 km resolution stereopolar map of the North Atlantic and European Seas showing the latest sea surface temperature data derived from AVHRR (Advanced Very High Resolution Radiometer) carried on the low earth orbit MetOp and NOAA-19 satellites. The NAR product is disseminated via EUMETCast in Grib2 format, although SMHI chooses to retrieves a netCDF version from IFREMER via ftp. Data are then converted to png and hdf5 formats for easy viewing, and to allow comparison with in-situ data sources.

Figure 1: Example of Baltic sea surface temperature map	Figure 2: Daily sea ice map
Latest SST chart	Latest ice chart
SST and Sea ice archive

Additional information for production of ice maps comes from Radarsat SAR images. These have the benefit of being cloud independent, have very high spatial resolution and give detail of the ice structure. Data are received by KSAT in Tromsö (Norway) on behalf of ESA. The resulting images for the Baltic are downloaded by SMHI from FMI (Finnish Meteorological Institute) through the MyOcean cooperation.

As of January 2010, it is not possible to accurately determine chlorophyll a concentrations in the Baltic. This is because land runoff (approximately 660 km³ per year) introduces large amounts of humic material to the Baltic. This matter gives a similar optical signal to chlorophyll a, making quantitative estimates of chlorophyll concentration difficult to determine.
During summer the Baltic is subject to massive blooms of cyanobacteria – dominated by the Nodularia Spumigena, Aphanizomenon flos-aquae and Anabaena spp. Nodularia in particular floats to the surface towards the end of its life, building large slicks. These slicks have nuisance value, and can be hazardous to pets. They are also visible in the visible AVHRR channels, and at a higher resolution in the MODIS products on the TERRA and AQUA satellites.

Figure 3. Decaying cyanobacteria bloom on the surface of the BalticImage courtesy of the Swedish Coastguard
SMHI has operated a warning service for these harmful algal blooms since 2002, based on daily interpretations of AVHRR images. These are supported where possible by MODIS products. Observed algal slicks are plotted using SeaTrackWeb, the oil spill tracking system coupled to the HIROMB Operational Model. Where a slick is likely to drift in land, local authorities are warned.

Figure 4. High resolution satellite image of a cyanobacteria bloom in the Baltic. Image processed by SMHI

In the Baltic, SMHI uses a range of voluntary observing vessels to support operational production. Temperature observations are made daily at fixed positions by commercial vessels. At present, 6 observation points are active, with three of those in the southern Baltic Proper. These observations are supported by thrice-weekly manual observations at seven coastal stations, and higher frequency observations at buoy locations. In total, 35 stations are reported.
These observations are further improved by ferrybox/underway observations in the Baltic. Figure 5 shows active ferrybox routes in the Baltic. In addition, these are supported by data from research vessels. The Baltic is fortunate in having well coordinated environmental monitoring, under the auspices of the HELCOM COMBINE Programme. This means that, for example, the Swedish research vessel Argos is at sea measuring surface parameters (temperature, salinity and chlorophyll fluorescence) every two minutes, and making vertical CTD casts at fixed stations for 14 weeks per year during environmental monitoring cruises, and for a further 16 weeks during fishery investigations. Surface parameters are reported with a maximum 10 minute delay to SMHI’s headquarter, while CTD profiles are reported daily. Data are made available immediately to BOOS (Baltic Operational Oceanographic System) members via the BOOS ftp system, and data are assimilated twice daily into SMHI’s operational models.

Figure 5. Current (solid lines) and proposed (dashed) ferrybox lines in the Baltic. from Karlson et al, 2009

SMHI currently operates two “full profile” mooring buoys, at Läsö E. in the Kattegat, and Huvudskär in the Baltic Proper. These buoys (Figure 6) are Oceanor Seawatch buoys, measuring currents (ADCP), temperature and conductivity (salinity) at 17 depths plus chlorophyll fluorescence at the surface as well as directional waves and meteorological parameters. Data are sent hourly via Orbcomm to SMHI, where they are made available via BOOS ftp, OpenDAP and to SEPRISE.

Figure 6. Research Vessel Argos making calibration measurements at the Läsö E. Seawatch buoy
In addition to these sites, directional Waverider buoys are operated west of Väderöarna in the Skagerrak, in the Southern Baltic near the intersection of the Polish, Swedish, Russian and Lithuanian Exclusive Economic Zones, and at Finngrundet, in the southern Bothnian Sea. These data are made available in the same way as the “full profile” mooring data.

Figure 7. About to deploy a directional Waverider in the Baltic winter

The Baltic is home to some of the world’s longest sea level records: Stockholm sea level data form the world’s longest continuous sea level record, stretching back to 1774, while Swinoujscie extends back to 1811. The Swedish sea level network currently consists of 23 gauges: 6 lie in the Gulf of Bothnia, 9 in the Baltic Proper, 3 in the Sound and 5 in the Kattegat/Skagerrak. All gauges are float gauges in stilling wells, recording sea level on paper charts. Nineteen gauges are also equipped with digitizers and report data electronically every hour. These hourly data consist of an hourly mean as well as six 10 minute mean, maximum and minimum values. Data are made available in real time to the public through SMHI:s web page, through SEPRISE, the BOOS ftp service, and to the global community (including the PSMSL and IOC GLOSS) via GTS and OpenDAP.

SMHI is the Swedish national oceanographic data host, as well as Sweden’s major producer of oceanographic data. As well as the real-time data described above, the data centre receives delayed mode data collected by other marine institutes and local authorities in Sweden. These data are quality controlled by the centre. Problems with data quality are resolved in dialogue with data providers. While the centre has particularly long experience of handling nutrient and hydrographic data, it has recently developed web map services for making higher trophic level data available, spanning biological parameters from bacterioplankton to sea eagles and seal numbers.

Data collected as part of Sweden’s commitment to HELCOM are reported annually to the ICES databank. ICES are datahosts for HELCOM delayed mode data. Data from selected coastal monitoring sites required for EIONET and State of the Environment reporting are submitted annually to the EEA.
The data centre also acts as the Oceanographic Data Centre for BALTEX. BALTEX is an international project contributing to the World Meteorological Organization’s GEWEX (Global Energy and Water cycles Experiment). SMHI even hosts the BALTEX Hydrological and Radar data centres. BALTEX data are freely available to registered BALTEX scientists.