Increased dissolved terrestrial input to the coastal ocean during the last deglaciation
Increased dissolved terrestrial input to the coastal ocean during the last deglaciation
复制标题
末次冰消期期间，沿海海洋的溶解陆地输入增加
DOI：
10.1029/2008gc002219
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发表时间：
2009
期刊：
影响因子：
3.7
通讯作者：
B. Haley
中科院分区：
文献类型：
--
作者：
G. Klinkhammer;A. Mix;B. Haley
在这里，我们提出了一个新的paleoproxy，有孔虫方解石的Mn/Ca比，适用于沉积物积累在极东热带北太平洋（ETNP）在过去的30,000年的第一次downcore结果。Mn/Ca的结果进行了比较，氧同位素和海洋表面温度从Mg/Ca计算。我们使用流通时间分辨分析确定金属比率，以最大限度地减少次生矿化的影响。用于本研究的有孔虫种类在不同深度钙化。这些变种物种的核心顶部比例的变化成比例的溶解锰在水柱中的浓度在钙化的深度。由于陆地输入和氧化还原反应控制了当今海洋中溶解锰的水平，因此应该可以使用有孔虫的Mn/Ca比值作为过去这些过程的替代。混合层物种的Mn/Ca（G. ruber）的研究表明，在末次盛冰期期间，ETNP表面沃茨的溶解陆地输入低于今天，但随着最初的海平面上升而开始增加，并在15 ka B. P.达到最大值，然后在中全新世（7-5 ka）海平面上升结束时下降到今天的水平。深层钙化物种（N。dutertrei）与G.在同一时间段内，与18°C温跃层的变浅一致。底栖物种Mn/Ca（U. peregrina）在15 ka时没有显示出最大值，这表明Mn在冰消期间有效地在水柱中矿化。假设从末次冰期到全新世中期是一个生产力增加的时期，正如Mn升高可能暗示的那样，氧最小区（OMZ）在冰消期至少与今天一样发达。OMZ的扩展可能有助于我们观察到的Mn/Ca趋势。
Here we present the first downcore results for a new paleoproxy, the Mn/Ca ratio of foraminiferal calcite, applied to sediment accumulated in the extreme Eastern Tropical North Pacific (ETNP) over the last 30,000 years. The Mn/Ca results are compared to oxygen isotopes and sea surface temperature calculated from Mg/Ca. We determined metal ratios using flow‐through time‐resolved analysis to minimize the effects of secondary mineralization. The foraminiferal species used for this study calcify at different depths. Core top ratios of these variant species change in proportion to the concentration of dissolved manganese in the water column at the depth of calcification. Since terrestrial input and oxidation reduction reactions control the levels of dissolved Mn in the oceans today, it therefore should be possible to use the Mn/Ca ratios of foraminifera as a proxy for these processes in the past. Mn/Ca of a mixed‐layer species (G. ruber) suggest that dissolved terrestrial input to the surface waters of the ETNP during the last glacial maximum was lower than today but began to increase with initial sea level rise and reached a maximum at 15 ka B.P. before coming down to present‐day levels at the end of sea level rise in the mid‐Holocene (7–5 ka). Ratios of a deeper calcifying species (N. dutertrei) mimic those of G. ruber over this same time period, consistent with shoaling of the 18°C thermocline. Mn/Ca of a benthic species (U. peregrina) does not show a maximum at 15 ka, suggesting that Mn was efficiently remineralized in the water column during deglaciation. Assuming that the period from the last glacial until the mid‐Holocene was a time of increased productivity, as elevated Mn might imply, the oxygen minimum zone (OMZ) was at least as well developed during deglaciation as it is today. Expansion of the OMZ may have contributed to the Mn/Ca trends we observe through time.