Storer Benjamin A, Buzzicotti Michele, Khatri Hemant, Griffies Stephen M, Aluie Hussein
Department of Mechanical Engineering and Laboratory for Laser Energetics, University of Rochester, Rochester, NY, USA.
Department of Physics, University of Rome Tor Vergata and INFN, Rome, Italy.
Nat Commun. 2022 Sep 9;13(1):5314. doi: 10.1038/s41467-022-33031-3.
Advent of satellite altimetry brought into focus the pervasiveness of mesoscale eddies [Formula: see text] km in size, which are the ocean's analogue of weather systems and are often regarded as the spectral peak of kinetic energy (KE). Yet, understanding of the ocean's spatial scales has been derived mostly from Fourier analysis in small "representative" regions that cannot capture the vast dynamic range at planetary scales. Here, we use a coarse-graining method to analyze scales much larger than what had been possible before. Spectra spanning over three decades of length-scales reveal the Antarctic Circumpolar Current as the spectral peak of the global extra-tropical circulation, at ≈ 10 km, and a previously unobserved power-law scaling over scales larger than 10 km. A smaller spectral peak exists at ≈ 300 km associated with mesoscales, which, due to their wider spread in wavenumber space, account for more than 50% of resolved surface KE globally. Seasonal cycles of length-scales exhibit a characteristic lag-time of ≈ 40 days per octave of length-scales such that in both hemispheres, KE at 10 km peaks in spring while KE at 10 km peaks in late summer. These results provide a new window for understanding the multiscale oceanic circulation within Earth's climate system, including the largest planetary scales.
卫星测高的出现使人们关注到大小在[公式：见正文]千米的中尺度涡旋的普遍存在，这些涡旋是海洋中类似于天气系统的现象，常被视为动能（KE）的谱峰。然而，对海洋空间尺度的理解大多来自于在小的“代表性”区域进行的傅里叶分析，这些区域无法捕捉行星尺度上巨大的动态范围。在这里，我们使用一种粗粒化方法来分析比以前可能的尺度大得多的尺度。跨越三个数量级长度尺度的谱揭示了南极绕极流是全球温带环流的谱峰，在约10千米处，并且在大于10千米的尺度上存在以前未观测到的幂律标度。在约300千米处存在一个与中尺度相关的较小谱峰，由于它们在波数空间中分布更广，在全球解析表面动能中占比超过50%。长度尺度的季节循环表现出每个长度尺度倍频程约40天的特征滞后时间，使得在两个半球，10千米处的动能在春季达到峰值，而10千米处的动能在夏末达到峰值。这些结果为理解地球气候系统内的多尺度海洋环流，包括最大的行星尺度，提供了一个新窗口。
