initial nutrient level. As nutrients are drawn down, a subsurface chlorophyll maximum
develops (Fig. 11.19).
Fig. 11.19 Time-series of (a) nitrate (mmol m−3) and (b) chlorophyll (mg m−3) during
an ice-edge upwelling phytoplankton bloom in the Canadian Beaufort Sea. Data from
47 hydrocasts were interpolated and plotted.
(^) (After Mundy et al. 2009.)
Primary production in the Arctic Ocean has been measured with the standard ^14 C
technique, but the spatial and temporal extents of such measurements are limited.
During the polar winter, phytoplankton production is obviously light-limited.
Seasonal production begins as soon as the snow melts (Sherr et al. 2003), with ice
algae blooming first, followed by phytoplankton. During the spring and summer
seasons, nutrient supply is the more important controlling factor, and by mid-summer
the shelf water and basin water often become depleted in nitrate and phosphate.
Annual rates of primary production are only about half of those measured in the
Antarctic and vary with hydrographic conditions in the marginal seas and the central
basins (Table 11.2).
Table 11.2 Primary production in the Arctic Ocean
(subregion values from Sakshaug 2004).
(^) g C m−2 yr−1Tg C yr−1
Central Arctic
Canadian Basin
Eurasian Basin >11 >50
Inflow seas