Predicting which marine systems are close to abrupt transitions into oxygen-deficient conditions (“anoxia”) is notoriously hard but important—as rising temperatures and coastal eutrophication drive many marine systems toward such tipping points. Rapid oxic-to-anoxic transitions occurred regularly within the eastern Mediterranean Sea on (multi)centennial time scales, and hence, its sedimentary archive allows exploring statistical methods that can indicate approaching tipping points. The here presented high-resolution reconstructions of past oxygen dynamics in the Mediterranean Sea reveal that early-warning signals in these deoxygenation time series occurred long before fast transitions to anoxia. These statistical indicators (i.e., rise in autocorrelation and variance) are hallmarks of so-called critical slowing down, signaling a steady loss of resilience of the oxygenated state as the system approaches a tipping point. Hence, even without precise knowledge of the mechanisms involved, early-warning signals for widespread anoxia in marine systems are recognizable using an appropriate statistical approach.

中文翻译：

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海洋缺氧事件的预警信号

预测哪些海洋系统接近于突然转变为缺氧条件（“缺氧”）是出了名的困难但很重要——因为气温上升和沿海富营养化将许多海洋系统推向这样的临界点。在（多）百年时间尺度上，东地中海定期发生快速的好氧到缺氧转变，因此，其沉积档案允许探索可以指示接近临界点的统计方法。这里展示的地中海过去氧气动力学的高分辨率重建表明，这些脱氧时间序列中的预警信号发生在快速过渡到缺氧之前很久。这些统计指标（即自相关和方差的上升）是所谓的临界放缓的标志，当系统接近临界点时，发出氧合状态的弹性逐渐丧失的信号。因此，即使不准确了解所涉及的机制，也可以使用适当的统计方法识别海洋系统中广泛缺氧的早期预警信号。