Atlantic oscillating currents strengthened faster at high northern latitudes
A single peer-reviewed study used drifting buoys to examine Atlantic currents that oscillate near a frequency associated with Earth’s rotation. The two-decade comparison found strengthening across the basin, with increases at high northern latitudes and a decline at lower northern latitudes. Short-lived wind fluctuations featured prominently in model experiments examining that regional pattern. The findings describe contrasting changes in surface motion rather than a uniform basin-wide response.
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Northern and southern trends diverged
A single peer-reviewed study found that Atlantic currents oscillating near a frequency associated with Earth’s rotation increased in speed by an average 3.8 per cent per decade during 2003–2022, with uncertainty of 1.7 per cent. High northern latitudes showed a 7.6 per cent increase, while low northern latitudes registered a 3.6 per cent decline. Speeds rose in the southern regions examined. The basin average thus includes northern regions moving in opposite directions.[1]
Surface drifters separate the oscillations
Researchers isolated these motions from velocity measurements collected by buoys drifting at the ocean surface. The global archive contained 19,396 trajectories from 1987–2022, with the trend calculation using the more densely sampled recent two decades. These oscillations help transfer wind energy into ocean mixing. The team compared measurements with two wind datasets and a simplified model of the upper water layer’s response. Uneven geographical coverage by the drifters contributed to uncertainty in the estimated trends.[1]
Short wind fluctuations feature in the model
The wind datasets linked much of the strengthening to fluctuations on timescales between about an hour and two days. Varying the depth of the upper mixed water layer in model experiments changed the Atlantic-wide trend little, although local differences remained. The model simplifies processes including vertical velocity differences and three-dimensional circulation. Current speed was the quantity directly measured in this analysis; changes in deep-ocean carbon uptake were not measured separately.[1]
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