Hochet Antoine, Llovel William, Huck Thierry, Sévellec Florian
Univ Brest, CNRS, IFREMER, IRD, Laboratoire d'Océanographie Physique et Spatiale (LOPS, UMR 6523), IUEM, Brest, France.
INRIA, CNRS, ODYSSEY Team-Project, Brest, France.
Sci Rep. 2024 May 9;14(1):10644. doi: 10.1038/s41598-024-61447-y.
Along with the mean sea level rise due to climate change, the sea level exhibits natural variations at a large number of different time scales. One of the most important is the one linked with the seasonal cycle. In the Northern Hemisphere winter, the sea level is as much as 20 cm below its summer values in some locations. It is customary to associate these variations with the seasonal cycle of the sea surface net heat flux which drives an upper-ocean thermal expansion creating a positive steric sea level anomaly. Here, using a novel framework based on steric sea level variance budget applied to observations and to the Estimating the Circulation and Climate of the Ocean state estimate, we demonstrate that the steric sea level seasonal cycle amplitude results from a balance between the seasonal sea surface net heat flux and the oceanic advective processes. Moreover, for up to 50% of the ocean surface, surface heat fluxes act to damp the seasonal steric sea level cycle amplitude, which is instead forced by oceanic advection processes. We also show that eddies play an important role in damping the steric sea level seasonal cycle. Our study contributes to a better understanding of the steric sea level mechanisms which is crucial to ensure accurate and reliable climate projections.
随着气候变化导致平均海平面上升，海平面在大量不同时间尺度上呈现自然变化。其中最重要的一种变化与季节周期相关。在北半球冬季，某些地区的海平面比夏季值低多达20厘米。通常将这些变化与海面净热通量的季节周期联系起来，该周期驱动上层海洋热膨胀，产生正比容海平面异常。在此，我们使用一个基于比容海平面方差预算的新颖框架，将其应用于观测数据以及“估算海洋环流与气候”（Estimating the Circulation and Climate of the Ocean）状态估计，证明比容海平面季节周期振幅是由季节海面净热通量与海洋平流过程之间的平衡导致的。此外，在高达50%的海洋表面，表面热通量起到抑制比容海平面季节周期振幅的作用，而该振幅实际上是由海洋平流过程驱动的。我们还表明，涡旋在抑制比容海平面季节周期方面发挥着重要作用。我们的研究有助于更好地理解比容海平面机制，这对于确保准确可靠的气候预测至关重要。
