Abstract
Todays physical oceanography and primary and secondary production was investigated for the entire Arctic Ocean with the physical-biologically coupled SINMOD model. To obtain indications on the effect of climate change in the 21th century the magnitude of change, and where and when these may take place SINMOD was forced with down-scaled climate trajectories of the International Panel of Climate Change with the A1B climate scenario which appears to predict an average global atmospheric temperature increase of 3.5 to 4 °C at the end of this century. It is projected that some surface water features of the physical oceanography in the Arctic Ocean and adjacent regions will change considerably. The largest changes will occur along the continuous domains of Pacific and in particular regarding Atlantic Water advection and the inflow shelves. Withdrawal of ice will increase primary production, but stratification will persist or, for the most, get stronger as a function of ice-melt and thermal warming along the inflow shelves. Thus the nutrient dependent new and harvestable production will not increase proportionally with increasing photosynthetic active radiation. The greatest increases in primary production are found along the Eurasian perimeter of the Arctic Ocean (up to 40 g C m-2 y-1) and in particular in the northern Barents and Kara Seas (40-80 g C m-2 y-1) where less ice-cover implies less Arctic Water and thus less stratification. Along the shelf break engirdling the Arctic Ocean upwelling and vertical mixing supplies nutrients to the euphotic zone when ice-cover withdraws northwards. The production of Arctic copepods along the Eurasian perimeter of the Arctic Ocean will increase significantly by the end of this century (2-4 g C m-2 y-1). Primary and secondary production will decrease along the southern sections of the continuous advection domains of Pacific and Atlantic Water due to increasing thermal stratification. In the central Arctic Ocean primary production will not increase much due to stratification-induced nutrient limitation.
Highlights
Primary production in the Arctic Ocean (AO) is predominately controlled by extreme variations in light, which further is strongly modulated by ice and snow cover as well as the density of ice algae and phytoplankton (e.g., Leu et al, 2015)
There has been an unprecedented decline in sea-ice cover and the loss rate accelerated by a factor of ∼5 in 1996 (e.g., Wadhams, 2012; Kwok et al, 2013; Barber et al, 2015), but increases in random fluctuations, as an early warning signal, were observed already in 1990 (Carstensen and Weydmann, 2012)
Section A starts in the Barents Sea (40◦E) across the North Pole into the Beaufort Sea (140◦W) and section B across the Fram Strait along at 79◦N (Figure 2)
Summary
Primary production in the Arctic Ocean (AO) is predominately controlled by extreme variations in light, which further is strongly modulated by ice and snow cover as well as the density of ice algae and phytoplankton (e.g., Leu et al, 2015). After the melt of most of the multiyear ice the Arctic will, for the most, have a seasonal ice cover (some ice close to Greenland and Canada may not totally melt). When this new state will occur is unknown, but it may only be 1–2 decades away, accompanied by a gigantic light experiment, the new Arctic lightscape (Varpe et al, 2015). It is timely to study the physical constrains of primary production of the entire AO that lie ahead of us
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