Multi-proxy analyses of a peat bog on Isla de los Estados, easternmost Tierra del Fuego: a unique record of the variable Southern Hemisphere Westerlies since the last deglaciation

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• 作者：Svante Bjö ; rck ; ^{svante.bjorck@geol.lu.se} ; Mats Rundgren ; Karl Ljung ; Ingmar Unkel¹ ; Å ; sa Wallin
• 关键词：Paleoclimate ; Tierra del Fuego ; South Atlantic ; Southern Hemisphere Westerlies ; Aeolian proxies ; Pollen analysis ; Last deglaciation ; Holocene
• 刊名：Quaternary Science Reviews
• 出版年：2012
• 期刊代码：78_02773791
• 类别：ear
• 出版时间：24 May, 2012
• 卷：42
• 期：Complete
• 页码：1-14
• 文件大小：2052 K

摘要

We have analyzed an almost 14,000聽year old peat sequence on the island of Isla de los Estados (55掳聽S, 64掳聽W), east of Tierra del Fuego, in the core of the Southern Hemisphere Westerlies. A multitude of methods have been used: high resolution ¹⁴C dating; detailed lithologic descriptions including humification degree; loss on ignition; magnetic susceptibility; bulk density; pollen and spore analysis and determination of Aeolian sand influx. By combining proxies for wind and precipitation we have been able to reconstruct how the westerlies have varied over time in the Atlantic sector of the Southern Ocean. It shows that this westerly wind belt was most intense at the onset of the record, 13,600-13,200聽cal聽BP, coinciding with the mid to late part of the Antarctic Cold Reversal, followed by a gradual decline. At 12,200聽cal聽BP the westerlies seem to have shifted to a position south of Tierra del Fuego and this phase, the calmest and driest period on the island throughout the sequence, ended at 10,000聽cal聽BP when the westerlies moved equatorward again. Since then the westerlies have been present but with a variable impact on the 55掳聽S latitude of the Atlantic. Mostly conditions have been fairly similar to today, but occasionally with a wider or narrower and/or weaker or stronger wind belt. At 7200聽cal聽BP wind intensity began to increase and between 4500 and 3500聽cal聽BP these southern latitudes experienced a distinct wind and precipitation maximum, both in terms of perseverance and intensity. Our results show a both wide and strong wind belt, with possible niveo-aeolian activity in Tierra del Fuego in winter, and possibly creating milder summers around the Antarctic Peninsula. In the later part of the Holocene, expansion-contraction phases of the wind belt, especially in winter, seem to have been a common phenomenon.