Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY 10964;
School of Earth and Ocean Sciences, University of Victoria, Victoria, BC V8W 2Y2, Canada.
Proc Natl Acad Sci U S A. 2021 Aug 17;118(33). doi: 10.1073/pnas.2026839118.
During the last interglacial (LIG) period, global mean sea level (GMSL) was higher than at present, likely driven by greater high-latitude insolation. Past sea-level estimates require elevation measurements and age determination of marine sediments that formed at or near sea level, and those elevations must be corrected for glacial isostatic adjustment (GIA). However, this GIA correction is subject to uncertainties in the GIA model inputs, namely, Earth's rheology and past ice history, which reduces precision and accuracy in estimates of past GMSL. To better constrain the GIA process, we compare our data and existing LIG sea-level data across the Bahamian archipelago with a suite of 576 GIA model predictions. We calculated weights for each GIA model based on how well the model fits spatial trends in the regional sea-level data and then used the weighted GIA corrections to revise estimates of GMSL during the LIG. During the LIG, we find a 95% probability that global sea level peaked at least 1.2 m higher than today, and it is very unlikely (5% probability) to have exceeded 5.3 m. Estimates increase by up to 30% (decrease by up to 20%) for portions of melt that originate from the Greenland ice sheet (West Antarctic ice sheet). Altogether, this work suggests that LIG GMSL may be lower than previously assumed.
在上一个间冰期（LIG）期间，全球平均海平面（GMSL）高于现在，可能是由更高的高纬度太阳辐射驱动的。过去的海平面估计需要对在海平面或接近海平面形成的海洋沉积物进行海拔测量和年龄确定，并且必须对冰川均衡调整（GIA）进行校正。然而，这种 GIA 校正受到 GIA 模型输入的不确定性的影响，即地球的流变学和过去的冰期历史，这降低了过去 GMSL 估计的精度和准确性。为了更好地约束 GIA 过程，我们将我们的数据和现有的 LIG 海平面数据与一套 576 个 GIA 模型预测进行了比较。我们根据模型对区域海平面数据空间趋势的拟合程度为每个 GIA 模型计算了权重，然后使用加权 GIA 校正来修正 LIG 期间的 GMSL 估计值。在 LIG 期间，我们发现全球海平面至少有 95%的可能性比今天高出 1.2 米以上，而超过 5.3 米的可能性非常小（5%）。对于源自格陵兰冰盖（西南极冰盖）的融水部分，估计值增加了多达 30%（减少了多达 20%）。总的来说，这项工作表明 LIG GMSL 可能低于先前的假设。
