Ventilation of bottom water in the North Sea–Baltic Sea transition zone

Abstract. The bottom water of the North Sea-Baltic Sea transition zone suffers from seasonal hypoxia, usually during late summer and autumn. These hypoxic events are critical for the benthic ecosystems and the concentration of dissolved oxygen is an important measure of the water quality. However, to model the subsurface dissolved oxygen is a major challenge, especially in estuaries and coastal regions. In this study a simple oxygen consumption model is coupled to a 3-D hydrodynamical model in order to analyse oxygen variations in the transition zone. The benthic and pelagic consumption of oxygen is modelled as a function of water temperature and oxygen concentration. A quantitative assessment of the model demonstrates that the model is able to resolve both seasonal and interannual variations in dissolved oxygen. Results from several experimental simulations highlight the importance of physical processes in the regulation of dissolved oxygen. Advective oxygen transport and wind induced mixing are two key processes that control the extent of hypoxia in the transition zone.

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Optical measurements in the North Sea-Baltic Sea transition zone. I. On the origin of the deep water in the Kattegat

Continental Shelf Research ◽

10.1016/0278-4343(95)00075-5 ◽

1996 ◽

Vol 16 (10) ◽

pp. 1329-1342 ◽

Cited By ~ 58

Author(s):

N.K. Højerslev ◽

N. Holt ◽

T. Aarup

Keyword(s):

Baltic Sea ◽

Transition Zone ◽

North Sea ◽

Deep Water ◽

Optical Measurements ◽

The North ◽

The North Sea

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The impacts of physical processes on oxygen variations in the North Sea-Baltic Sea transition zone

Ocean Science ◽

10.5194/os-8-37-2012 ◽

2012 ◽

Vol 8 (1) ◽

pp. 37-48 ◽

Cited By ~ 11

Author(s):

L. Jonasson ◽

J. L. S. Hansen ◽

Z. Wan ◽

J. She

Keyword(s):

Dissolved Oxygen ◽

Baltic Sea ◽

Transition Zone ◽

North Sea ◽

Late Summer ◽

Physical Processes ◽

The North ◽

The North Sea ◽

Seasonal Hypoxia ◽

Benthic Ecosystems

Abstract. The bottom water of the North Sea–Baltic Sea transition zone suffers from seasonal hypoxia, usually during late summer and autumn. These hypoxic events are critical for the benthic ecosystems and the concentration of dissolved oxygen is an important measure of the water quality. However, to model the subsurface dissolved oxygen is a major challenge, especially in estuaries and coastal regions. In this study a simple oxygen consumption model is coupled to a 3-D hydrodynamical model in order to analyse oxygen variations in the transition zone. The benthic and pelagic consumption of oxygen is modelled as a function of water temperature and oxygen concentration. A quantitative assessment of the model demonstrates that the model is able to resolve both seasonal and interannual variations in dissolved oxygen. Results from several experimental simulations highlight the importance of physical processes in the regulation of dissolved oxygen. Advective oxygen transport and wind induced mixing are two key processes that control the extent of hypoxia in the transition zone.

Download Full-text