The Forgotten Azores Current: A Long-Term Perspective

Abstract

The Atlantic Meridional Overturning Circulation (AMOC) and its surface limb, the Gulf Stream, are in their weakest state since the last millennium. The consequences of this weakening in the Northeast Atlantic are not yet known. We show that the slowdown of the Gulf Stream in the 1960s, 1970s, and after 2000 may have caused a delayed weakening of the Azores Current. Concurrently, the Azores Front associated with the Azores Current migrated northward since the 1970s due to gradual changes in the Atlantic Multidecadal Oscillation and ocean heat content. We argue that the AMOC slowdown is also detectable in the low-energy region of the Northeast Atlantic and that the dynamics of Azores Current tightly connects to that of the dynamics of the Gulf Stream and AMOC on decadal and longer time scales.

Revisiting the multidecadal variability of North Atlantic Ocean circulation and climate

“…Temperature and density changes in the subtropical gyre dominate the entire NA amid the different climate trajectories of the subpolar gyre (roughly separated from the subtropical gyre by the line of zero WSC, as shown in Figure 2). Based on previous findings (Seidov et al, 2017;Seidov et al, 2019b;Frazão et al, 2022), we argue that the Gulf Stream and its continuation dominates the climate of the subtropical gyre, the eastern part of the subpolar gyre, and the Nordic Seas .…”

“…The Atlantic Water intrusion into the Norwegian Sea also depends on the strength of those currents, and therefore, the changes in the Nordic Seas follow those in Boxes 1 and 2. There are lags in signal traveling across the Atlantic, but as discussed earlier, those lags are short (i.e., ~2 to 3 years) when compared to our decadal time scales (Frazão et al, 2022).…”

“…It has recently been shown that the thermohaline and dynamic signal in the Azores Current correlates with the signal in the Gulf Stream with a lag of approximately two years (Frazão et al, 2022). This period is much shorter than the decadal averaging, which could explain the decadal similarity between Boxes 1 (Figure 5C) and 2 (Figure 5E).…”

Regional Variations of the Azores High Across Glacial‐Interglacial Timescales

“… Location and general context of the Azores. (a) Scheme of the North Atlantic Subtropical Gyre (black arrows) and the atmospheric pressure systems: Azores High (orange “H”) and Icelandic Low (blue “L”; Cresswell‐Clay et al., 2022; Frazão et al., 2022; Martin‐Garcia, 2019). The red rectangle indicates the location of panel (b); (b) Distribution of the Azores islands and their tectonic context after Hildenbrand et al.…”

“…Directly under the influence of the Azores Current and the Azores High Pressure (Figure 1a; Cresswell-Clay et al, 2022;Frazão et al, 2022;Martin-Garcia, 2019), the Azores Archipelago encompasses nine volcanic islands spreading ∼600 km over the triple junction of the North America, Nubia, and Eurasia lithospheric plates (Figure 1b), allowing observations and comparisons at local to regional scales. Most of these islands have been volcanically active over the past 1 million years (Myr), with periods of relative quiescence (e.g., Costa et al, 2014Costa et al, , 2015Hildenbrand, Madureira, et al, 2008;Hildenbrand et al, 2012Hildenbrand et al, , 2014Marques et al, 2018;Sibrant et al, 2015).…”