1. Fjords

2. Distribution
Fjords formed by glaciers, consequently occur at high latitudes
Northern hemisphere: Canada, USA (one fjord), Norway, Island, Greenland, Scotland, Sweden (one fjord)
Southern hemisphere: Chile, New Zealand

3. Topography
Outer sill, sill depth and area at opening essential for exchange with outer waters
Polls, very shallow sill
Fjords are deep; depth more important characteristics than supply of freshwater
Sognefjorden 1300 m

4. Sketch fjord

5. Transport (advection)
Estuarine circulation
Exchange intermeditate layer
Deep water renewals
Tidal exchange

6. Estuarine circulation
Supply of freshwater gives surplus of water which runs out of the estuary/fjord
Mixes with salt water, so that volume of outgoing water increases, including outwards transport of salt water
Results in an ingoing, compensation current of salt water

8. Example estuarine circulation; experiment with hydroelectric power plant

9. Biological implication: brackish water plankton

12. Oceanic fauna

15. In this situation estuarine circulation important, but text books often give a misleading picture of its importance in fjords
Fjords are deep, and only a thin, upper layer impacted by freshwater (though the most productive vertical strata)
The ”engine” in ES generally to weak compared to other current systems

16. Exchange in the intermediate layer may be very important
Exchange between fjord and outer coastal waters, beneath the brackish layer, but above sill depth
Importance of exchange in the intermediate layer increases by depth and area at fjord opening

20. Deep water/oxygen

21. Fish and krill in hypoxic waters Bunnefjorden

22. Oxygen reduced at depth, but still normally sufficient oxygen also in the deep basin water (basin water = beneath sill depth)
Gradual dilution of deep water over time due to mixing with upper layers, make the deep water less dense
Replacement of the deep water when water at (above) sill depth outside the fjord higher density than basin water within the fjord
Deep water renewals often during winter, due to temperature, salinity (at sill depth) and wind conditions
Frequencies of renewals varies among fjords

23. Nordfjord, many years between renewals, still no oxygen deficiency at 400 m depth

24. Fjords of limited vaule for fisheries
Aquaculture
Sprat
Overwintering herring

25. Fauna
The fauna in fjords simlar to coastal and oceanic fauna, no praticular fjord fauna
The depth of fjords very important; large depth facilitates presence of deep-sea (mesopelagic) species otherwise only found in the open ocean
Fjords with different optical properties have different fauna

26. Benthosema glaciale

27. Periphylla periphylla

28. Fjords as model systems
Fjords can be used as model systems for oceans
Easy access to organisms which otherwise only can be studied at large depths offshore
Inexpensive, simple logistics
Examples: mortality overwintering Calanus exposed to different types of predators, the ecology of krill, mesopelagic fish, deep sea jellyfish