The preservation of calcium carbonate deposits on the seafloor is one of the factors that regulates Earth's carbon cycle over longer timescales. Fluctuations in the carbonate compensation depth (CCD), the depth below which calcium carbonate is completely dissolved, can therefore significantly alter the ocean's capacity to sequester or release atmospheric carbon. High-latitude deep oceans are particularly important to the carbon cycle given their large capacity to store carbon dioxide. Here we present carbonate content results from an abyssal Subantarctic record (Site U1514) that spans the early Miocene and the onset of the Miocene Climatic Optimum. We show that carbonate preservation was highly variable from 19.9 to 17 Ma, with multiple episodes of total carbonate dissolution. Carbonate preservation then improved gradually after 17 Ma following the onset of the Miocene Climatic Optimum. Episodes of carbonate dissolution occurred preferentially at long eccentricity minima while periods of long eccentricity maxima improved carbonate preservation. These patterns of carbonate accumulation are in opposite phase to lower latitude Atlantic and Pacific records, which suggests that different mechanisms of carbonate accumulation/preservation were in place in high and low-latitude oceans. Comparison of Site U1514 with Antarctic records indicates an influence of ice sheet oscillations on carbonate preservation at the Subantarctic seafloor. We propose that carbonate dissolution occurred via the northward expansion of southern-derived undersaturated waters during periods of Antarctic ice sheet expansion. These findings indicate that the Subantarctic Southern Ocean was highly sensitive to Antarctic ice sheet fluctuations during the early Miocene, consistent with observations from Antarctica that show intensified polar amplification under a warmer climate.

海底碳酸钙沉积物的保存是在较长时间内调节地球碳循环的因素之一。因此，碳酸盐补偿深度（CCD）的波动（碳酸钙完全溶解在该深度以下）会极大地改变海洋封存或释放大气中碳的能力。由于高纬度深海储存二氧化碳的能力强，因此对于碳循环特别重要。在这里，我们展示了深部亚极纪实记录（站点U1514）的碳酸盐含量结果，该记录跨越了中新世早期和中新世气候最佳时期的开始。我们显示，碳酸盐保存在19.9至17 Ma范围内高度可变，总碳酸盐溶解量有多次发作。中新世气候最佳时期开始后的17 Ma后，碳酸盐的保存逐渐改善。碳酸盐溶解的事件优先发生在长的最小离心率上，而长的最大离心率则改善了碳酸盐的保存。这些碳酸盐积累的模式与低纬度大西洋和太平洋记录相反，这表明在高纬度和低纬度海洋中存在不同的碳酸盐积累/保存机制。U1514站点与南极记录的比较表明，冰盖振荡对亚南极海底碳酸盐保存的影响。我们认为，在南极冰盖扩张时期，碳酸盐溶解是通过南极欠饱和水向北扩张而发生的。