Sea surface temperature control on the distribution of far-traveled Southern Ocean ice-rafted detritus during the Pliocene
Sea surface temperature control on the distribution of far-traveled Southern Ocean ice-rafted detritus during the Pliocene
复制标题
DOI：
10.1002/2014pa002625
复制
发表时间：
2014-06-01
期刊：
影响因子：
--
通讯作者：
Gonzales, J. J.
中科院分区：
文献类型：
--
作者：
Cook, C. P.;Hill, D. J.;Gonzales, J. J.
沉积在南大洋的冰筏碎屑（IRD）的通量和物源可以揭示过去南极冰盖在不同气候条件下的不稳定性信息。在这里，我们提出了一个上新世IRD物源记录的基础上的40 Ar/39 Ar年龄的冰筏角状颗粒从大洋钻探计划网站1165，位于印度洋附近的Praviz湾南大洋部分，沿着与模拟的敏感性测试结果的冰山轨迹和它们的空间融化模式下的海面温度（SST）的范围。我们的物源结果表明，IRD，因此冰山在Preniz湾地区主要来自（一）当地Preniz湾地区和（二）偏远的威尔克斯土地边缘位于低洼的极光冰下盆地的口。一系列的IRD脉冲，达到10倍的背景IRD通量水平，以前确定在站点1165之间的3.3和3.0 Ma。我们的新结果表明，IRD的平均比例来自远威尔克斯陆缘后3.3马翻倍。我们的冰山融化模型表明，在上新世中期，在冷却SST的情况下，冰山融化的速度较慢，这使得威尔克斯地的冰山在融化前走得更远。因此，下降的SST可以解释在站点1165观察到的IRD来源记录的大部分。在上新世早期IRD层，采样在亚轨道分辨率约4.6马，我们发现的证据，来自威尔克斯土地在非常温暖的间冰期冰山显着增加。这暗示了南极洲东部冰盖在极光冰下盆地的大规模不稳定，因为远距离移动的冰山必须克服温暖SST中的融化。我们的研究结果强调了在解释IRD通量和远距离位置的起源记录时考虑SST的重要性。
The flux and provenance of ice-rafted detritus (IRD) deposited in the Southern Ocean can reveal information about the past instability of Antarctica's ice sheets during different climatic conditions. Here we present a Pliocene IRD provenance record based on the 40Ar/39Ar ages of ice-rafted hornblende grains from Ocean Drilling Program Site 1165, located near Prydz Bay in the Indian Ocean sector of the Southern Ocean, along with the results of modeled sensitivity tests of iceberg trajectories and their spatial melting patterns under a range of sea surface temperatures (SSTs). Our provenance results reveal that IRD and hence icebergs in the Prydz Bay area were mainly sourced from (i) the local Prydz Bay region and (ii) the remote Wilkes Land margin located at the mouth of the low-lying Aurora Subglacial Basin. A series of IRD pulses, reaching up to 10 times background IRD flux levels, were previously identified at Site 1165 between 3.3 and 3.0 Ma. Our new results reveal that the average proportion of IRD sourced from distal Wilkes Land margin doubles after 3.3 Ma. Our iceberg trajectory-melting models show that slower iceberg melting under cooling SSTs over this middle Pliocene interval allowed Wilkes Land icebergs to travel farther before melting. Hence, declining SSTs can account for a large part of the observed IRD provenance record at Site 1165. In early Pliocene IRD layers, sampled at suborbital resolution around 4.6 Ma, we find evidence for significant increases in icebergs derived from Wilkes Land during very warm interglacials. This is suggestive of large-scale destabilization of the East Antarctic Ice Sheet in the Aurora Subglacial Basin, as far-traveled icebergs would have to overcome enhanced melting in warmer SSTs. Our results highlight the importance of considering SSTs when interpreting IRD flux and provenance records in distal locations.