Dynamics and Temporal Variability of the North Atlantic Current in the Iceland Basin (2014–2022)

IF 3.3 2区 地球科学 Q1 OCEANOGRAPHY
Tiago S. Dotto, N. Penny Holliday, Neil Fraser, Ben Moat, Yvonne Firing, Kristin Burmeister, Darren Rayner, Stuart Cunningham, Emma Worthington, William E. Johns
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Abstract

The North Atlantic Current (NAC) is a major source of heat toward the subpolar gyre and northern seas. However, its variability and drivers are not well understood. Here, we evaluated 8 years of continuous daily measurements as part of the international program Overturning in the Subpolar North Atlantic Program to investigate the NAC in the Iceland Basin. We found that the NAC volume and freshwater anomaly transport and heat content (HC) were highly variable with significant variability at timescales of 16–120 days to annual. Intraseasonal to short interannual variability was associated with mesoscale and intermittent mesoscale features abundant in the region. Composites analysis revealed that strong NAC periods were associated with less eddy kinetic energy in the Iceland Basin, which was consistent with the presence of frontal-like structures instead of eddy-like structures. On longer timescales, the westward migration of the eastern boundary of the subpolar North Atlantic (SPNA) gyre favors a stronger NAC volume transport and HC in the region. Stronger zonal wind stress triggers a fast response that piles water up between the SPNA and subtropical gyres, which increases the sea surface height gradient and drives the acceleration of the NAC. The strengthening of the NAC increases the heat and salt transport northward. During our study period, both heat and salt increased across the moorings. These observations are important for understanding the heat and freshwater variability in the SPNA, which ultimately impacts the Atlantic meridional overturning circulation.

Abstract Image

2014-2022年冰岛盆地北大西洋洋流动态与时间变率
北大西洋暖流(NAC)是向亚极环流和北部海域输送热量的主要来源。然而,其可变性和驱动因素尚未得到很好的理解。在这里,我们评估了8年连续的每日测量,作为国际项目的一部分,在亚极地北大西洋项目中翻转,以调查冰岛盆地的NAC。研究发现,在16 ~ 120 d至年的时间尺度上,NAC体积、淡水异常输运和热含量(HC)变化显著。季节内至短年际变化与该地区丰富的中尺度和间歇中尺度特征有关。复合分析表明,冰岛盆地强NAC期涡动能较小,这与冰岛盆地存在锋状构造而非涡状构造相一致。在较长时间尺度上,北大西洋次极环流东边界的西移有利于该地区更强的NAC体积输送和HC。较强的纬向风应力触发了快速响应,使水在副热带环流和南亚热带环流之间堆积,增加了海面高度梯度,推动了南亚热带环流的加速。NAC的增强增加了热盐向北输送。在我们的研究期间,整个系泊处的热量和盐分都增加了。这些观测结果对于理解SPNA的热量和淡水变化非常重要,而这些变化最终会影响大西洋经向翻转环流。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Journal of Geophysical Research-Oceans
Journal of Geophysical Research-Oceans Earth and Planetary Sciences-Oceanography
CiteScore
7.00
自引率
13.90%
发文量
429
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