The instruments in the Byfjord have been recovered for an annual maintenance. This means that the hourly updated graphs for salinity, temperature, oxygen and current measurements will be offline for a few days. We hope to redeploy the instruments in late May or early June.

Although the instruments are designed to withstand a harsh marine environment for an extended period of time, we need to recover them for maintenance at least once per year. Free swimming larvae quickly colonise the surface of our instruments, potentially preventing proper measurements to be made. During the service window we will continue with our monthly samples of oxygen and nutrients in the Byfjord, as well as making a weekly CTD cast in the fjord for temperature, salinity and oxygen.

Profile of the Byfjord water column on 2 December 2010. The inflow has renewed most of the resident basin water. Click for a bigger version.

Over the past week a large inflow event has taken place in the Byfjord. All water down to 35 metres depth has been renewed. As a consequence the dissolved oxygen concentrations have risen sharply in the deep water. Meanwhile, due to mixing with the surface water, lower oxygen concentrations are found above sill depth, but remain at good levels. Hydrogen sulphide is only found at 40 metres or deeper.

This inflow is a direct effect of the pumping efforts by the BOX-project. The density is reduced and alleviates new water from the adjacent fjord to flow in an renew the resident basin water. It is very likely that this inflow would not have taken place if pumping were not applied in the fjord.

Variability in salinity, temperature and oxygen concentrations over the past year in the Byfjord. The data were collected between October 2009 and September 2010. Grey areas show minimum and maximum observed values at each depth, and the black line shows yearly mean. Due to severe ice conditions, there are no observations from January thourh March. Click on the image for a larger version.

We have visited the Byfjord every month over the past year and made measurements of the water column. It is time to summerise the variability of the past year.

Not surprisingly, the largest variations have taken place above sill depth, closest to the surface. The salinity lies over 20 in the surface layer, but large fresh water pulses has made the surface water even fresher. Over the past year, the salinity has varied by 10 units, between a salinity of 20 and 30. However, below sill depth, the variations are very small. An inflow event took place in March, contributing to the largest salinity change in the deep-water of approximately 0.6 salinity units.

Air temperatures are reflected in the water temperature of the surface layer. During the three months of ice cover, the water temperature dropped, while the opposite respons occured between June and July when a heat wave increased the temperatures by 6 degrees Celsius. In the deepwater, the temperature has stayed at around 7 degrees Celsius throughout the year, with only smaller variations of about 0.03 degrees Celsius.

Wind acts on the surface layer, constantly mixing it. Therefore, the oxygen supply is very good above sill depth. Below sill depth, oxygen can only be added due to the slow process of diffusion or through inflow events. The inflow event in March did renew the bottom water, slightly rising the oxygen concentrations. However, the amount of oxygen only lasted for a month before anoxia was re-established. Some of the resident water was lifted upwards due to the inflow event. This impacts the available oxygen just above sill depth, as low oxygen or hydrogen sulphide enters a rich oxygen environment. Large variations has therefore been observed in the water just above sill depth over the past year.

We will continue to monitor the Byfjord and report our monthly measurements on this webpage the coming year.

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!

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.

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.