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Project Description

Marine ecosystem consequences of climate induced changes in water masses off West-Spitsbergen (MariClim)

Project manager: Geir Wing Gabrielsen, Norwegian Polar Institute (NPI), N-9296 Tromsø, Norway. Project management group: Haakon Hop (NPI) and Harald Svendsen (University of Bergen).

1 Goal, main hypothesis and objectives


The overall goal of this project is to determine the influence of climate variability and change on the energy transfer in the marine pelagic ecosystem in different water masses on the west coast of Spitsbergen. The project will compare the pelagic food webs in fronts involving Arctic (ArW) and Atlantic water masses (AW) in this high-Arctic region.

The extent of the ice cover in the Nordic Seas in spring has decreased since 1860 due to the net thermal effect of the northbound currents (Vinje 2001). A continuation of this trend is predicted by general circulation models (GCMs, IPCC 2000). If these predictions are correct, a permanent warming of the Arctic's climate and a further decrease of the sea ice extent in the Barents Sea and the Arctic Ocean will occur. Variations in the inflow of AW and outflow of ArW masses are shown to be strongly related to changes in the atmospheric pressure systems over the Arctic Ocean (Proshutinsky et al. 1999) and the North Atlantic Oscillation (Dickson et al. 2000) on inter-annual and decadal scales. These pressure systems are strongly linked to the atmospheric heat balance, and climate changes may thus alter the strength of the large-scale oceanic circulation in the region. This would change the relative amount of source water (ArW and AW), which is mixed and transformed into water masses on the shelf off West-Spitsbergen and also in the adjacent fjords.

The new Arctic Marine Laboratory in Ny-Ålesund, Kongsfjorden, gives this project a The Kongsfjorden-Krossfjorden shelf and unique opportunity to perform controlled fjord system (Fig. 1) is particularly suitable experiments on the energy transfer in Arctic for studies of effects of climate change on marine food chains. ecosystems because it lies adjacent to both Arctic and Atlantic water masses. In addition, there is a significant amount of observations available from this area (reviews, Hop et al. 2002; Svendsen et al. 2002). The inclusion of these observations and existing time-series for this area is imperative for the detection of changes. In particular we have long time series of zooplankton composition for this area. The relative composition of zooplankton depends on water masses and sea ice concentration. Changes in the zooplankton composition will result in altered energy transfer within the pelagic food web with potential consequences for growth and survival of seabirds.


Fig 1. Main currents on West-Spitsbergen with Kongsfjorden-Krossfjorden indicated.


Our main hypothesis is:

Climate change will affect the distribution of warm AW and cold ArW masses of shelf and fjord regimes in West-Spitsbergen. This will alter the zooplankton composition and subsequently change the energy transfer within the pelagic food web with consequences for upper trophic levels.

Ecological consequences of climate change on the marine pelagic ecosystem, during cold and warm scenarios, are illustrated in Fig. 2. A cold climate scenario would result from less influx of AW to the shelf and fjord areas in West-Spitsbergen, whereas a warm climate scenario would occur because of an increased influx of AW. The energy flow in the marine pelagic food web would be dominated by either Arctic or Atlantic zooplankton species. Seabirds such as the Little auk (Alle alle), that rely on large Arctic Calanus species with high lipid content may decline if their food base diminishes during the warm scenario. The Black-legged kittiwake (Rissa tridactyla) may also be negatively affected, but because this species also preys on the Polar cod (Boreogadus saida) as well as other large zooplankton such as Themisto libellula, it may be less affected. Thus, it is important to understand the predator-prey relationships between Polar cod, Calanus and Themisto within the intermediate part of the pelagic food web to be able to explain food web effects on Kittiwakes. The ecological consequences of climate variability will be studied within the time frame of the project, and the effects of climate changes will be addressed based on the collected data as well as time-series that exist for the physical environment and marine pelagic ecosystem of Kongsfjorden and adjacent waters.

Fig2

Fig. 2. Cold and warm climate scenarios with potential effects on the structure and energy flow in the marine pelagic food web off West-Spitsbergen. + indicates a positive effect with expected increase in population size. ’ indicates a negative effect with expected decrease in population size.

The project tasks are centred on working hypotheses with associated objectives:

Working hypotheses and objectives

H1: Climate change will alter the volume transport and characteristics of AW, the recirculating deep ArW and Arctic surface water. Subsequently the exchange of water masses in the gradient shelf slope -West-Spitsbergen fjords will be affected, and by that also the fast ice condition in Kongsfjorden.

Objective 1.1: Investigate a-geostrophic processes in the shelf slope current West-Spitsbergen Current (WSC) and in the coastal current boarding the fjord mouths that govern the exchange between AW, ArW and the adjacent West-Spitsbergen fjords.

Objective 1.2: Verify the effect of climatic variability on fjord-shelf circulation, exchange patterns, and fast ice evolution.

H2: Variability in water circulation patterns is the main mechanism regulating the distribution and size structure of zooplankton and pelagic fish.

Objective 2.1: Determine how variations in water mass characteristics affect the spatial and temporal distribution of zooplankton.

Objective 2.2: Determine the changes in abundance of zooplankton and Polar cod across the main fronts of the Kongsfjorden Kongsfjord shelf.

H3: Changes in size and energy content of key zooplankton prey will influence the energy transfer in the pelagic food web with consequences for growth and survival of Little auk and Black-legged kittiwake chicks.

Objective 3.1: Determine predator-prey relationships in selected components of the pelagic system.

Objective 3.2: Determine experimentally if changes in energy content of zooplankton prey influence the energy transfer to juvenile Polar cod.

Objective 3.3: Determine how the availability of suitable prey affects the foraging behaviour, energy transfer and chick survival in Little auk and Kittiwake.

For the full project description, please view this pdf-file.