Positive Atlantic Multidecadal Oscillation has driven poleward redistribution of the West Antarctic Peninsula biota through a food-chain mechanism.

The West Antarctic Peninsula (WAP) has recorded a significant poleward range shift in marine biota, including Adélie penguins, Antarctic krill and phytoplankton. The ecological changes have been widely attributed to Pacific/Southern Hemisphere variabilities. However, the teleconnection from the North Atlantic Ocean, which also could induce changes in the WAP physical environments, has been overlooked. Here we combine state-of-the-art observational/modelling databases to quantify the poleward redistribution since the 1980s of three key members of the WAP biota and explored their response to several climatic oscillations. The abundance of Adélie penguins, Antarctic krill and phytoplankton in the WAP all show a decrease in the north and an increase in the south, leading to a poleward shift of their distribution centers by ~0.8-2.3°. A more positive Atlantic Multidecadal Oscillation (AMO) has contributed to the poleward redistribution of phytoplankton/krill/penguin with a time lag of 0/1/5 yr, indicating a food-chain related mechanism. +AMO in spring resulted in reduced sea ice, earlier ice retreat and enhanced winds in the northern WAP, which constrained phytoplankton blooms and krill reproduction, thereby decreasing the krill recruitment 1 yr later and consequently the penguin recruitment 5 yr later. In the southern WAP, where the sea ice cover was nearly permanent in the 1980s, reduced sea ice and earlier ice retreat promoted phytoplankton growth and krill/penguin reproduction. Our results emphasize the global nature of climate-ecological coupling; the influence of the Northern Hemisphere climate system on Antarctic/Southern Ocean biota is a non-negligible factor for the ecosystem management.