Atlantis Online
March 28, 2024, 05:08:25 am
Welcome, Guest. Please login or register.

Login with username, password and session length
News: Satellite images 'show Atlantis'
http://news.bbc.co.uk/1/hi/sci/tech/3766863.stm
 
  Home Help Arcade Gallery Links Staff List Calendar Login Register  

Winds favoured Polynesian migration

Pages: [1]   Go Down
  Print  
Author Topic: Winds favoured Polynesian migration  (Read 365 times)
0 Members and 13 Guests are viewing this topic.
Europa
Administrator
Superhero Member
*****
Posts: 4318



« on: October 20, 2014, 01:16:35 am »

Winds favoured Polynesian migration

Tuesday, 30 September 2014 Anna Salleh
ABC
Easter Island

A weakening of tradewinds was key to the Polynesian migration to Easter Island during the Medieval Period, say researchers (Source: Vladimir_Krupenkin/iStockphoto)
Related Stories

    Chicken DNA 'suggests Columbus was first', Science Online, 18 Mar 2014
    Coral yields precise Polynesian arrival date, Science Online, 08 Nov 2012
    Ancient DNA sheds light on Maori settlement, Science Online, 23 Oct 2012

Polynesians were able to sail downwind to Easter Island and New Zealand centuries ago, a new analysis of past climate has found.

There were narrow windows of time between 1140 and 1260 AD where the winds allowed this, say researchers in this week's Proceedings of the National Academy of Sciences.

"It's really incredible to think that for a 120-year period the Polynesians took advantage of these windows of opportunities and they crossed almost a third of the surface of the Earth," says co-author Associate Professor Ian Goodwin of Macquarie University.

Archaeological evidence suggests that from around 1000 years AD, Polynesians travelled in their ocean-sailing canoes east from Samoa to what is known as Central East Polynesia (CEP) -- which includes Society, Tuamotu, Marquesas, Gambier, Southern Cook and Austral Islands.

In a short period between 1140 and 1260 AD they then migrated on to New Zealand and Easter Island.

"It's always been quite a mystery as to why there was a concentration of colonisation in a period of a couple of hundred years and why it ceased after that," says Goodwin.

Especially since, according to today's prevailing winds, travelling to these later destinations would have been against the wind for most of the time, he adds.

While some researchers have proposed Polynesians must have had much more complex canoes than have been found to date, Goodwin and colleagues suggest this was not necessary.

They have found that during this short time there were actually a number of 'climate windows', lasting around 20 years each, where the winds were in favour of the long voyages to New Zealand and Easter Island.
Climate reconstruction

Between 800 and 1300, the Earth was in the grip of the Medieval Climate Anomaly (MCA) which saw warmer conditions in Europe, and the Vikings expanded into Greenland, Iceland and Labrador. Meanwhile, the Americas experienced a major drought, and the Mayan civilisation collapsed.

A key feature of the MCA was the expansion of tropical areas towards the poles, especially between the mid 1100s and the mid 1200s.

Goodwin and colleagues reconstructed, year by year, the weather patterns across the Southern Hemisphere during this period, by combining climate models with past climate clues from ice cores, corals, tree rings, stalagmites, and sediments.

"We used all these proxy records that hold an imprint of the past climate," he says. "For example, the more sea salt in ice cores, for example, the stronger the winds were at the time."

In some of these 'climate windows', the easterly tradewinds strengthened and moved southward, replacing the westerly winds.

This would have supported an easy downwind sail out of Central East Polynesia to New Zealand, says Goodwin.

"Downwind, they could have made these voyages from Central East Polynesia to New Zealand in 10 to 14 days, which is manageable when you consider they had women and kids, food and pigs," he says.
Wind reversal

In alternating climate windows, the researchers found there was a weakening of the tradewinds, that would have supported an easy downwind sail to Easter Island on the westerlies.

"After 1300 AD, we show that this expansion of the tropics disappears, the westerlies move northwards and then all these windows close," says Goodwin.

He says the dates of the "wind reversals" identified in the study help narrow down when migration occurred within the broad period identified by archaeological data, and support the idea there were multiple waves of migration.

The study also shows winds could have helped Amerindians to get to Easter Island as well as the Polynesians.

And it shows winds that support the migration of Polynesians from Tonga to sub-Antarctic islands such as Auckland Island, south of New Zealand.
Canoe find

In related research, also published this week in PNAS, Dilys Johns and colleagues from the University of Auckland report on the discovery of an East Polynesian ocean-sailing canoe, at Anaweka on the New Zealand coast.

Dated to approximately 1400 AD, the canoe was built in New Zealand and has a sea turtle carved on its hull that makes a connection with the wider Polynesian culture and art.

"If the Anaweka canoe was a double canoe, which seems likely, the documentary evidence suggests a canoe with a deck and shelter, a low bow and an upraised stern, and a sail set forward as in historic canoes of the Society and Southern Cook Islands, which have been identified as likely Polynesian homelands of Maori," the researchers write.
Report Spam   Logged

Share on Facebook Share on Twitter

Europa
Administrator
Superhero Member
*****
Posts: 4318



« Reply #1 on: October 20, 2014, 01:17:10 am »



A weakening of tradewinds was key to the Polynesian migration to Easter Island during the Medieval Period, say researchers (Source: Vladimir_Krupenkin/iStockphoto)
Report Spam   Logged
Europa
Administrator
Superhero Member
*****
Posts: 4318



« Reply #2 on: October 20, 2014, 01:17:24 am »

http://www.abc.net.au/science/articles/2014/09/30/4096801.htm?topic=ancient
Report Spam   Logged
Pages: [1]   Go Up
  Print  
 
Jump to:  

Powered by EzPortal
Bookmark this site! | Upgrade This Forum
SMF For Free - Create your own Forum
Powered by SMF | SMF © 2016, Simple Machines
Privacy Policy