Holocene sea-level change across the indo-pacific : a new theory with implications for low-lying islands and coastal communities, ancient seafaring and maritime migration
Creators: name: Harrington, Juliette
Publisher: name: The Australian National University
Year: 2014
Subjects: subject: Sea Level Indo-Pacific Region
subject: Sea Level HoloceneIndo-Pacific Region
subject: Sunspots
subject: Paleogeography HoloceneIndo-Pacific Region
subject: Human beings Migrations History
subject: Maritime anthropology Indo-Pacific Region

description: Utilising reconstructed sunspot data, a statistically significant correlation between sunspot forcing and both palaeo and modern sea-level change was found. Evidence suggests that Indo-Pacific highstands occur over decadal to centennial timescales. The cause of these sea-level highstands (or maximum sea-level height prior to sea-level fall) is still under debate. Previous observational studies suggested that the underlying mechanisms of ENSO are responsive to solar forcing variations over decades to centuries. Here it is shown that sunspot forcing and low-frequency ENSO results in highstands across the Indo-Pacific. Operating at interannual timescales, El Nino relates to sea-level fall in the west Pacific and positive IOD relates to sea-level fall in the east Indian Ocean, while La Nina and negative IOD have the opposite effect. A statistically significant correlation between modern sunspot and both El Nino/posIOD and La Nina/negIOD has been identified. The latter may suggest a low-frequency correlation between sunspot increase and sea-level rise in addition to the correlation between sunspot decrease and sea-level fall. Thus, parameters used in current models may need to be adjusted to include the effects of solar forcing on sea-level change for past and future quantification. Decadal to centennial sea-level change has been shown to occur at a meter-scale level. Predicted global warming and an increase in sunspot forcing may have critical future implications for low-lying coastal and island communities across the Indo-Pacific, including high-density locations such as Sydney, Darwin, and Broome. This new empirical theory that suggests a pattern of sea-level change may act as a guide to understanding prehistoric movements across the Pacific and elsewhere. Decreased solar forcing and sea-level fall over decades to centuries is associated with widespread aridity, diminished reef fishing and island abandonment in the mid to west equatorial Pacific. During this time weakened southeast Tradewinds may have facilitated seafaring networks, and both eastward and higher latitude maritime migrations. The timing of these statistically correlated environmental occurrences is co-incident with Pacific migrations including the Lapita migration, and both pulses of the Polynesian expansion. These results suggest that long-term environmental change was an important contributing factor on the timing and motivation for prehistoric Pacific maritime migration. Further these findings suggest that the hotly debated AD1300 event was not an isolated incident but rather one of a number of sustained environmental conditions that occurred over the Holocene in response to decreased solar forcing.