Abiotic components

Meteorological conditions

Thu, 03 Dec 2009 08:36:01 +0000

Atmospheric forcing exerts influence on marine ecosystems through winds and air-sea interactions. Variations in large-scale atmospheric circulation cause changes in upper ocean circulation, ice extent, and hydrographic properties of the water column. Changes in marine environments in turn cause biological responses such as timing of spring phytoplankton bloom, zooplankton production, patterns of fish eggs and larvae drift, encounter rate of larvae and their prey, survival and recruitment (Ottersen et al., 2004; Rey, 1993; Skjoldal and Rey, 1989; Sundby, 1991; 1995; 2000).

Oceanographic conditions - General circulation

Thu, 03 Dec 2009 08:39:01 +0000

The Norwegian Atlantic Current carries warm and salty Atlantic water northwards along the Norwegian continental shelf break outside the Norwegian Coastal Current (Figure 2.1.1). When entering the Barents Sea it splits into two main branches. The first branch flows northeast along the Hopen Trench. The second branch flows eastward parallel to the coastal current towards Novaya Zemlya archipelago; this branch is called the Murman Current. Eventually, the modified Atlantic Water enters the Arctic Ocean between Novaya Zemlya and Franz Josef Land. The relative strength of these two branches depends on local wind conditions in the Barents Sea. Smaller Atlantic water currents also enter the Barents Sea from north-west region; they generally branch into subsurface flows, and do not extend very far south, but may have substantial impact on climate conditions in the northwestern Barents Sea.

Oceanographic conditions - Currents and transports

Thu, 03 Dec 2009 08:41:24 +0000

Observed current in the Fugløya-Bear Island region is predominantly barotropic, and reveals large fluctuations in both current speed and lateral structure (Ingvaldsen et al., 2002; 2004). In general, the current is wide and slow during summer and fast, with possibly several cores, during winter. The volume transport resembles the velocity field and varies with season due to close coupling with regional atmospheric pressure. Numerical models forced with wind predict that southwesterly winds, which is predominant during winter, accelerates flow of Atlantic Water into the Barents Sea; whereas, weaker and more fluctuating northeasterly winds, common during summer, slows transport. The same conclusion is reached using current measurements in the exit area of northeast Barents Sea. Since 1997, monitoring transport of Atlantic Water into the Barents Sea indicates highly variable net transport that averages 2 Sv (Sv = 106 m3s-1). The average transport of Atlantic Water into the Barents Sea during 1997-2007 is 2.2 Sv during winter and 1.8 Sv during summer. During years in which the Barents Sea changes from cold to warm marine climate, the seasonal cycle can be inverted. Moreover, an annual event of northerly wind causes a pronounced spring minimum inflow to the western Barents Sea; at times even an outward flow.

Oceanographic conditions - Water masses and stratification

Thu, 03 Dec 2009 08:43:18 +0000

Atlantic Water is commonly defined as having salinity >35.0 and temperatures >3oC. Between Norway and Bear Island, the temperature of Atlantic Water varies seasonally and inter-annually from 3.5-7.5 oC. As a rule, both temperature and salinity decrease in northwards and eastwards in the Barents Sea (Figure 2.3.6). For this reason, water with salinity as low as 34.95 is often classified as water of Atlantic origin. In the southwestern Barents Sea, Atlantic water is normally predominant. Interannual temperature variation in the Barents Sea is illustrated in Figure 2.3.7, which presents annual temperature observations during the last 100 years for the Kola region (Bochkov, 1982; 2005) in the southern Barents Sea.