当前位置:首页 > 生物研究 > 生态学 > 正文

Nature:深海中蛋白石和二氧化碳的释放

南大洋被认为在推动大气二氧化碳浓度的冰期/间冰期变化中发挥一个重要作用,但造成冰川消失时二氧化碳释放的机制仍不清楚。

根据有关生源蛋白石输出的一份记录(该记录显示在过去55万年每次冰期终止时蛋白石的最大值),Nele Meckler等人提出,冰河期北大西洋中层水在冰消期的减少导致温暖的、低密度的表面水向下混合,最终触发南极海水翻转和二氧化碳向大气层的释放。

了解更多:

Deglacial pulses of deep-ocean silicate into the subtropical North Atlantic Ocean

Nature 28 March 2013 | doi: 10.1038/nature12006

Growing evidence suggests that the low atmospheric CO2 concentration of the ice ages resulted from enhanced storage of CO2 in the ocean interior, largely as a result of changes in the Southern Ocean. Early in the most recent deglaciation, a reduction in North Atlantic overturning circulation seems to have driven CO2 release from the Southern Ocean, but the mechanism connecting the North Atlantic and the Southern Ocean remains unclear. Biogenic opal export in the low-latitude ocean relies on silicate from the underlying thermocline, the concentration of which is affected by the circulation of the ocean interior. Here we report a record of biogenic opal export from a coastal upwelling system off the coast of northwest Africa that shows pronounced opal maxima during each glacial termination over the past 550,000 years. These opal peaks are consistent with a strong deglacial reduction in the formation of silicate-poor glacial North Atlantic intermediate water(GNAIW). The loss of GNAIW allowed mixing with underlying silicate-rich deep water to increase the silicate supply to the surface ocean. An increase in westerly-wind-driven upwelling in the Southern Ocean in response to the North Atlantic change has been proposed to drive the deglacial rise in atmospheric CO2. However, such a circulation change would have accelerated the formation of Antarctic intermediate water and sub-Antarctic mode water, which today have as little silicate as North Atlantic Deep Water and would have thus maintained low silicate concentrations in the Atlantic thermocline. The deglacial opal maxima reported here suggest an alternative mechanism for the deglacial CO2 release. Just as the reduction in GNAIW led to upward silicate transport, it should also have allowed the downward mixing of warm, low-density surface water to reach into the deep ocean. The resulting decrease in the density of the deep Atlantic relative to the Southern Ocean surface promoted Antarctic overturning, which released CO2 to the atmosphere.

阅读次数:  
更多 相关资讯:
    无相关信息

发表评论