Results from the long-term deployment in the Byfjord during summer 2010. The upper panel shows a slight increase in oxygen concentrations, while the middle and lower panels show stable conditions for salinity and temperature, respectively. Click the figure for a larger version.

Between 19 June and 26 July a package of instruments was deployed at 20 metros depth in the Byfjord. Every night the instruments measured changes in temperature, salinity and oxygen concentrations. The results are shown in the Figure to the left.

Over the measurement period it was found that salinity and temperature remained constant. Temperature changed between 7.7 – 7.8°C while salinity hovered around 31.8. Such stable conditions are to be expected at 20 metros depth since it is below sill depth and the water exchange is limited to turbulent diffusive processes.

The oxygen concentration, on the other hand, seems to have risen slightly over the month. However, it remains below 1 micro molar throughout the measurement period and indicates severe hypoxia. The oxygen increase is not due to our pumping efforts since it commenced in mid-July, in the latter part of the long-term deployment.

The pumps in the Byfjord have finally started! Both pumps are pumping one cubic metre water per second each, resulting in large quantaties of water being circulated in the fjord. This will eventually allow new water to renew the basin water often – at least once per year. Without the pumps, renewal events only occured every fifth year, making the Byfjord anoxic below sill level (ca 14 metres).

Utsättning av pontonbrygga.

Utsättning av pumpdysan som fördelar vattnet nere i djupet.

Utsättning av pumphuset där vattnet sugs in.

Pontonbryggan och pumpar färdigmonterade!

Vattenprofil för Byfjorden den 12 juli 2010. Bilden visar temperatur (röd), salthalt (svart) och syrekoncentration (blå) från ytan till cirka 45 meters djup. Den streckade linjen visar juni månads mätning. Klicka på bilden för större version.

The monthly profile of the Byfjord was taken on July 12. Since June, the surface water has continued to warm and now reaches over 20°C down to about 9 metres depth. This corresponds to an increase of about 5°C since the profile taken on June 15. The coldest water is found just beneath the sill level an has a temperature of about 7°C. No change in temperature has occured in the deep-water.

A small reduction in salinity has taken place in the surface layer, probably due to increased river runoff.

Due to the warm water and an increased primary production, oxygen levels has dropped slightly in the surface layer. However, this happens every summer and there is still plenty of oxygen in the water. No additional oxygen has been added to the deep water. Thus the oxygen condition for the whole water column is normal.

Vattenprofil för Byfjorden den 15 juni 2010. Bilden visar temperatur (röd), salthalt (svart) och syrekoncentration (blå) från ytan till cirka 45 meters djup. Den streckade linjen visar maj månads mätning. Klicka på bilden för större version.

The monthly measurement in the Byfjord was conducted on Tuesday, 15 June. Since May, the temperatures have increased by approximately 7-9 degrees Celsius in the upper layer, while the water below sill depth (14 metres) retain the same cold temperatures of about 8 degrees Celsius. A clear two-layer regime also has been established, as shown by the salinity profile. The salinity above sill depth is homogeneous and  about 23, while below sill depth is homogeneous and about 31,5. Oxygen concentrations have decreased slightly in the water nearest to the surface due to less dissolved oxygen as the water warms. On the other hand, the oxygen near sill depth has increased as mixing has improved down to 14 metres. Below sill level no oxygen was recorded, which is normal for the fjord.

Anders Stigebrandt och Bengt Liljebladh

Över 90 procent av den fosfor som får Östersjöns giftiga alger att blomma upp om sommaren kommer från gamla synder. Med hjälp av stora syrepumpar prövar forskare i Göteborg en ny medicin för att bota det sjuka havet.

I Dagens Nyheter (31/5) finns ett reportage om BOX-projektet och hur det skulle kunna användas i ett större sammanhang för Östersjön. Artikeln går att ladda ner och läsa här.

Vattenprofil för Byfjorden den 17 maj 2010. Bilden visar temperatur (röd), salthalt (svart) och syrekoncentration (blå) från ytan till cirka 43 meters djup. Den streckade linjen visar april månads mätning. Klicka på bilden för större version.

Measurements were carried out in the Byfjord on Monday 17th May. Temperature show an increase since April, which is not surprising. The highest temperature was measured to approximately 11,4C at 3 metres depth. Salinity has also increased since April due to the lower runoff from the river Bäveån. Oxygen levels show a small decrease in the water column above sill depth (about 14 metres). Below the sill depth, oxygen quickly decrease to anoxic levels. The small amount of oxygen that was measured at 35 metres depth in April are no longer present.

The mooring has been on service since April, but is now redeployed. As we connected the mooring to our computer we noticed that a common eider had built her nest right underneath our antenna. While other eiders seemed to hesitate to our presence at the island, this edier stayed fearlessly put on her eggs througout the few minutes we needed to connect the mooring.

Ejdern låg orädd kvar och ruvade på sina ägg när vi kopplade in riggen i datorskåpet.

Vattenprofil för Byfjorden i april 2010. Bilden visar temperatur (röd), salthalt (svart) och syrekoncentration (blå) från ytan till cirka 45 meters djup. Den streckade linjen visar januari månads mätning. Klicka på bilden för större version.

After a long and cold winter the ice has finally melted away in the Byfjord. This permitted us to conduct the first CTD-cast in the fjord since January. According to the measurements, the temperature has risen above 8 degrees Celsius and the meltwater has lowered the salinity in the surface layer. In addition, the water above sill depth is well oxygenated indicating good mixing and a probable exchange of intermediary water over the past months. A smaller inflow has also occured to the deepwater with a local oxygen maximum at 35 metres depth. However, the oxygen concentrations are still low and the deepwater is still in a hypoxia phase.

Ice conditions in the Byfjord has been very severe this winter. Planned expeditions in February and March were cancelled. Photo by Lena Viktorsson.

The ice conditions in the Byfjord has been very severe over the past winter. From mid-January the ice reached several decimetres thickness.  This effectively prevented planned expeditions to take place in February and March. As soon as the ice conditions are improved we will conduct a new survey of the fjord. Our instruments have continuously gathered data of temperature, salinity, oxygen conditions and currents throughout the winter. The measurements are presented in real-time at our project site.

Since November 2009 a mooring has been placed in the Byfjord conducting measurements every twenty minutes. We have now conected the mooring with the internet, which gives us data automatically every three hours. Thanks to this we now invite you to help us keep an eye on the Byfjord and it’s marine environment through our website. Every three hours data is automatically uploaded to our servers and visually displayed in graphs on the page for temperature, salinity and oxygen measurements. This will allow you to study changes in the Byfjord over time by either studying the long-term evolution of the latest water profile (the last profile of the series uploaded to our servers) or a contour plot with all the measurements collects over the past two weeks. Later this year we will commence pumping of oxygen rich water from the surface to the deep water. This is done within the BOX project. When the pumping is initiated, studying changes in the Byfjord will become very important. Click here to visit the page. You can also read more about the Byfjord and the measurements we are doing by clicking on the tab named The Byfjord in the menu above.

Please keep in mind that we always appreciate comments regarding our measurements, projects and website. Don’t hesitate to contact us.