The Southern Ocean is widely recognized as a potential cause of the lower atmospheric concentration of CO₂ during ice ages, but the mechanism is debated. Focusing on the Southern Ocean surface, we review biogeochemical paleoproxy data and carbon cycle concepts that together favor the view that both the Antarctic and Subantarctic Zones (AZ and SAZ) of the Southern Ocean played roles in lowering ice age CO₂ levels. In the SAZ, the data indicate dust-driven iron fertilization of phytoplankton growth during peak ice age conditions. In the ice age AZ, the area-normalized exchange of water between the surface and subsurface appears to have been reduced, a state that we summarize as “isolation” of the AZ surface. Under most scenarios, this change would have stemmed the leak of biologically stored CO₂ that occurs in the AZ today. SAZ iron fertilization during the last ice age fits with our understanding of ocean processes as gleaned from modern field studies and experiments; indeed, this hypothesis was proposed prior to evidentiary support. In contrast, AZ surface isolation is neither intuitive nor spontaneously generated in climate model simulations of the last ice age.

In a more prospective component of this review, the suggested causes for AZ surface isolation are considered in light of the subarctic North Pacific (SNP), where the paleoproxies of productivity and nutrient consumption indicate similar upper ocean biogeochemical changes over glacial cycles, although with different timings at deglaciation. Among the proposed initiators of glacial AZ surface isolation, a single mechanism is sought that can explain the changes in both the AZ and the SNP. The analysis favors a weakening and/or equatorward shift in the upwelling associated with the westerly winds, occurring in both hemispheres. This view is controversial, especially for the SNP, where there is evidence of enhanced upper water column ventilation during the last ice age. We offer an interpretation that may explain key aspects of the AZ and SNP observations. In both regions, with a weakening in westerly wind-driven upwelling, nutrients may have been “mined out” of the upper water column, possibly accompanied by a poleward “slumping” of isopycnals. In the AZ, this would have encouraged declines in both the nutrient content and the formation rate of new deep water, each of which would have contributed to the lowering of atmospheric CO₂. Through several effects, the reduction in AZ upwelling may have invigorated the upwelling of deep water into the low latitude pycnocline, roughly maintaining the pycnocline’s supply of water and nutrients so as to (1) support the high productivity of the glacial SAZ and (2) balance the removal of water from the pycnocline by the formation of Glacial North Atlantic Intermediate Water. The proposed return route from the deep ocean to the surface resembles that of Broecker’s (1991) “global ocean conveyor,” but applying to the ice age as opposed to the modern ocean.

众所周知，南大洋是导致冰河时期大气中CO ₂浓度降低的潜在原因，但其机理尚有争议。着眼于南大洋表面，我们回顾了生物地球化学古过氧化氢数据和碳循环概念，这些观点共同支持了南大洋的南极和次南极带（AZ和SAZ）都在降低冰期CO _2中起作用的观点。水平。在SAZ中，数据表明在冰河高峰期条件下，浮游植物生长的粉尘驱动的铁肥。在冰期AZ，地表与次表层之间水的面积归一化交换似乎已减少，这种状态我们概括为AZ表面的“隔离”。在大多数情况下，这种变化将阻止如今在AZ中发生的生物存储CO ₂泄漏。上一个冰期的SAZ铁肥符合我们对现代实地研究和实验收集到的海洋过程的理解。实际上，这个假设是在证据支持之前提出的。相反，在上一个冰河时期的气候模型模拟中，既不直观也不自然地生成AZ表面隔离。

在本综述的更具有前瞻性的部分中，根据北极亚太平洋北太平洋（SNP）考虑了建议的AZ表面隔离的成因，在该地区，生产力和营养物消耗的古近表明，冰川周期的上层海洋生物地球化学变化相似，尽管不同脱冰的时间。在提议的冰川AZ表面隔离的引发剂中，寻求一种可以解释AZ和SNP两者变化的单一机制。分析倾向于在两个半球发生的与西风有关的上升流中减弱和/或向赤道移动。这种观点是有争议的，特别是对于SNP，那里有证据表明在上一个冰河时代，上部水柱的通风得到了加强。我们提供的解释可能会解释AZ和SNP观测的关键方面。在这两个地区，由于西风驱动的上升流减弱，养分可能已经从上部水柱中“挖出”，可能伴随着等位面极速“下沉”。在亚利桑那州，这会鼓励营养成分和新深水形成速率的下降，而每一种下降都会导致大气中一氧化碳的降低₂。通过多种影响，AZ上升流的减少可能使深水上升到低纬度比奥克星上升，从而大致维持了比克星的水和养分供应，从而（1）支持冰川SAZ的高生产力和（2）通过形成冰北大西洋中级水来平衡从多菌灵中除去水。提议的从深海到地面的返回路线类似于Broecker（1991）的“全球海洋输送机”，但适用于冰河时代，而不是现代海洋。