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首页> 外文期刊>Paleoceanography >Southwest Pacific subtropics responded to last deglacial warming with changes in shallow water sources
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Southwest Pacific subtropics responded to last deglacial warming with changes in shallow water sources

机译：西南太平洋亚热带地区对上一次冰期变暖的响应是浅水源的变化

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This study examined sources of mixed layer and shallow subsurface waters in the subtropical Bay of Plenty, New Zealand, across the last deglaciation (~30–5 ka). δ~(18)O and δ~(13)C from planktonic foraminifera Globgerinoides bulloides and Globorotalia inflata in four sediment cores were used to reconstruct surface mixed layer thickness, δ~(18)O of seawater (δ~(18)OSW) and differentiate between high- and low-latitude water provenance. During the last glaciation, depleted planktonic δ~(18)OSW and enriched δ~(13)C (-0.4–0.1‰) indicate surface waters had Southern Ocean sources. A rapid δ~(13)C depletion of ~1‰in G. bulloides between 20 and 19 ka indicates an early, permanent shift in source to a more distal tropical component, likely with an equatorial Pacific contribution that persisted into the Holocene. At 18 ka, a smaller but similar shift in G. inflata δ~(13)C depletion of ~0.3‰suggests that deeper subsurface waters had a delayed reaction to changing conditions during the deglaciation. This contrasts with the isotopic records from nearby Hawke Bay, to the east of the North Island of New Zealand, which exhibited several changes in thermocline depth indicating switches between distal subtropical and proximal subantarctic influences during the early deglaciation ending only after the Antarctic Cold Reversal. Our results identify the midlatitude subtropics, such as the area around the North Island of New Zealand, as a key region to decipher high- versus low-latitude influences in Southern Hemisphere shallow water masses.
机译：这项研究研究了在上一次冰消期（〜30-5 ka）内，新西兰Plenty亚热带海湾混合层和浅层地下水的来源。用浮游有孔虫Globgerinoides Bulloides和Globorotalia inflata的四个沉积物中的δ〜（18）O和δ〜（13）C来重建海水的表面混合层厚度，δ〜（18）O（δ〜（18）OSW）并区分高纬度和低纬度的水源。在最后一次冰期期间，浮游生物的δ〜（18）OSW减少和δ〜（13）C的富集（-0.4–0.1‰）表明地表水具有南大洋来源。在20到19 ka之间的大圆弧菌中δ〜（13）C的快速耗竭〜1‰表示源头向永久性热带成分的早期，永久性转移，可能伴有赤道太平洋持续进入全新世。在18 ka时，膨胀的G. inflataδ〜（13）C损耗较小但相似，约为0.3‰，这表明深层地下水对冰消融过程中的变化条件具有延迟的反应。这与从附近的霍克湾到新西兰北岛东部的同位素记录形成了鲜明对比，该记录显示了跃层深度的几次变化，表明仅在南极寒流逆转之后，在早期冰消结束期间，亚热带和近南亚大陆的影响在远亚热带和近亚热带影响之间切换。我们的研究结果确定了中纬度的亚热带，例如新西兰北岛附近的地区，是解密南半球浅水区高纬度和低纬度影响的关键区域。

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