Figure 4: Distribution of extinction group study sites and modern productivity.

Location of core sites on maps showing the mathematical estimates of modern net primary production, and modern unevenness of annual primary production (figure adapted from ref. 53). Sites shown indicate where the Mid Pleistocene benthic foraminiferal extinction group has been studied; the DSDP/ODP site numbers are given for higher-resolution studies⁷ that correspond to the sites used to construct Fig. 3. (a) Global average net primary productivity⁵³. (b) The geographic distribution of the seasonal variation of net primary production (seasonality) for the years 1998–2007. The colours refer to the % of the year over which 50% productivity takes place, such that purple indicates no seasonality (colours modified from ref. 53). We propose that glacial MPT seasonality may have been higher than modern seasonality. Note that seasonality is generally lowest in regions where primary productivity is low.