The following conclusions can be drawn from this work:

  1. Prior to the INHG, the data are suggestive of strong frontal systems operative over Site 1083, with little interglacial-glacial contrast in the productivity signal.
  2. Following the INHG, a wind-driven upwelling regime developed over Site 1083, which was more intense during glacial periods as reflected in the abundance changes in Chaetoceros resting spores. However such an upwelling regime is not reflected within the record of productivity, implying that productivity was not controlled by upwelling intensity. Productivity was instead controlled by the supply of nutrients to the photic zone from the AAIW, as suggested by the 15N record and the abundance of endemic Southern Ocean species within the diatom assemblage.
  3. The nutrient budget of the photic zone may have been a reflection of a change in upwelling intensity where more nutrients were advected to the surface per unit time; or a change in the fertility of the AAIW, in which more nutrients were advected to the surface per unit volume of water. Although the actual mode of nutrient supply is undetermined from this study, it is likely to have been from a combination of these models.

Following the INHG, productivity levels surged to a peak at each interglacial-glacial transition. Such elevated levels of CO2 drawdown could have provided an important feedback mechanism for the rapid decline into planetary glaciation.

It is not known whether the difference in the system holds for the time period prior to the that of this investigation. Therefore, additional investigation is required to further examine the possible relationship between oceanic productivity and climate before the intensification of the Northern Hemisphere glaciation at ~2.54 Ma.