A new paper has been published in the Proceedings of the National Academy by Christophe Barbraud and Henri Weimerskirch entitled ” Antarctic birds breed later in response to climate change”
“In the northern hemisphere, there is compelling evidence for climate-related advances of spring events, but no such long-term biological time series exist for the southern hemisphere. We have studied a unique data set of dates of first arrival and laying of first eggs over a 55-year period for the entire community of Antarctic seabirds in East Antarctica. The records over this long period show a general unexpected tendency toward later arrival and laying, an inverse trend to those observed in the northern hemisphere. Overall, species now arrive at their colonies 9.1 days later, on average, and lay eggs an average of 2.1 days later than in the early 1950s. Furthermore, these delays are linked to a decrease in sea ice extent that has occurred in eastern Antarctica, which underlies the contrasted effects of global climate change on species in Antarctica.”
This paper is a very effective example of why a focus on regional climate variability and change is needed (and why the use of global average metrics such as a global averaged surface temperature are so misleading).
The paper comments not only on bird breeding behavior, but also on recent trends in sea ice areal extent and sea ice season. They found that there has been a
“large (12-20%) reduction in sea ice extent since the 1950s..”,
“…the duration of the sea ice season tended to increase by >40 days in eastern Antarctica since the late 1970s…”.
The concluded that
“Although these contrasting trends seem counterintuitive, recent research suggests that sea ice extent is connected to large-scale features of the global climate system (such as the Southern Oscillation Index or the Southern Annular Mode), whereas the length of the sea ice season is connected to more regional features such as temperature…”.
A message from this paper is that we need a regional focus on climate variabiltiy and change. The concurrent observed decrease in sea ice extent and the increase in the length of the sea ice season should also be compared with the multi-decadal global climate projections of Antarctic sea ice change to assess their skill at predicting thes trends.