Climate windows for Polynesian voyaging to New Zealand and Easter Island

Abstract

Significance South Pacific migration routes used in East Polynesian colonization (A.D. 800−1500) have been assumed to be commonly upwind, when based on an understanding of modern climate patterns. Instead, our novel paleowind field reconstructions at bidecadal resolution show that migration routes lay downwind from East Polynesia during known times of initial colonization of New Zealand and Easter Island. This finding is significant in showing that a windward seafaring capacity in Polynesian colonization voyaging was not essential, and that long-term temporal variation in sailing conditions due to the expansion of the tropics was important in shaping colonization histories. The paleoclimate reconstruction broadens colonization possibilities, and the method represents a new, globally applicable approach to understanding patterning in prehistoric maritime migration.

Low-resolution Australasian palaeoclimate records of the last 2000 years

“…The work compliments a recent review of all annually resolved records in the Southern Hemisphere cover-ing the Common Era (Neukom and Gergis, 2012), as well as other subregion synthesis efforts in Australasia (Freeman et al, 2011;Gouramanis et al, 2013;Lorrey et al, 2007Lorrey et al, , 2008Lorrey et al, , 2010. The outcomes of this study will be helpful to researchers by identifying the most reliable lowresolution records in the Australasian region for climate model-palaeoclimate data intercomparisons in the Southern Hemisphere .…”

“…The possibility of contamination by old carbon can be minimised through the use of short-lived plant macrofossils (Blois et al, 2011), when present, as well as dating of modern water samples to identify the presence of an old carbon reservoir (e.g. Gouramanis et al, 2010). Fluctuations in atmospheric 14 C through time may result from aperiodic changes in ocean-atmosphere-terrestrial radiocarbon partitioning, upper-atmosphere radiocarbon production, and oceanic upwelling dynamics (Rodgers et al, 2011) that lead to "wiggles" in the radiocarbon calibration curve.…”

“…Age model uncertainty can be minimised by overlapping age probability distribution functions through a sedimentary sequence, but this is not always possible due to the cost of radiocarbon dating and availability of suitable material. Current age modelling techniques are capable of quantifying interpolation uncertainty when deriving age-depth relationships (Goring et al, 2012;Blaauw and Christen, 2011;Bronk Ramsey, 2009;Hua et al, 2012). Probability functions at each dated horizon are calculated, and then accumulation behaviour between these horizons is iteratively resampled to create thousands of possible time series.…”

“…Prior values can be set, based on existing knowledge of particular archives and/or study sites (e.g. Hua et al, 2012;Goring et al, 2012), and varied by the program to determine the best fit (Blaauw and Christen, 2011). The sampling interval prior is an estimate of the realistic physical distance over which the accumulation rate can change.…”

“…Even if the published accumulation rate was inaccurate, the program considers how well the priors agree with the accumulation rate suggested by the data. This also allows for non-linear accumulation rates (Goring et al, 2012), which is an important consideration in the Australasian context. For example, a rapid increase in sedimentation rate is known to correspond to European settlement in Australia (Gell et al, 2009) and changes in land cultivation practices in the Malay Archipelago (Gharibreza et al, 2013;Rodysill et al, 2012).…”