Deep ocean circulation in the subpolar North Atlantic observed by acoustically-tracked floats

Zou, Sijia; Bower, Amy S.; Lozier, M. Susan; Furey, Heather H.

doi:10.1016/j.pocean.2023.102975

Cited by 4 publications

(3 citation statements)

References 95 publications

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“…We emphasize that, although the ensemble trend correlation between Nordic Seas and OSNAP-East overturning is significant, a variance explained of approximately 25% (r max ~0.5; Fig. 9c) implies that other water masses than Nordic Seas overflow waters are also of major importance for subpolar overturning changes 6,44 . Trends in FSC overflow transport (Fig.…”

Section: Implications For Overturning Circulation In the Subpolar Nor...mentioning

confidence: 88%

Future strengthening of the Nordic Seas overturning circulation

et al. 2023

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The overturning circulation in the Nordic Seas involves the transformation of warm Atlantic waters into cold, dense overflows. These overflow waters return to the North Atlantic and form the headwaters to the deep limb of the Atlantic meridional overturning circulation (AMOC). The Nordic Seas are thus a key component of the AMOC. However, little is known about the response of the overturning circulation in the Nordic Seas to future climate change. Here we show using global climate models that, in contrast to the North Atlantic, the simulated density-space overturning circulation in the Nordic Seas increases throughout most of the 21st century as a result of enhanced horizontal circulation and a strengthened zonal density gradient. The increased Nordic Seas overturning is furthermore manifested in the overturning circulation in the eastern subpolar North Atlantic. A strengthened Nordic Seas overturning circulation could therefore be a stabilizing factor in the future AMOC.

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Section: Implications For Overturning Circulation In the Subpolar Nor...mentioning

confidence: 88%

Future strengthening of the Nordic Seas overturning circulation

et al. 2023

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“…By contrast, floats that escaped the Iceland basin did so by multiple pathways: across the Reykjanes Ridge via gaps north of the Charlie Gibbs Fracture Zone, westward through the Charlie Gibbs Fracture Zone and southward to the West European Basin [25,48–50]. Finally, as detailed in Zou et al [49], there is no evidence for a robust ISOW pathway into the Irminger Sea from the Charlie Gibbs Fracture Zone, a result recently confirmed from a calculation of the mean velocity field at the depth of the overflow waters using OSNAP float data [51]. This analysis showed no evidence for a deep boundary current that wraps around the Reykjanes Ridge connecting the Iceland and Irminger basins, a pathway that has traditionally been considered the main route for ISOW to leave the Iceland basin.…”

Section: Osnap Resultsmentioning

confidence: 92%

Overturning in the subpolar North Atlantic: a review

Lozier

2023

Phil. Trans. R. Soc. A.

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The Overturning in the Subpolar North Atlantic Program (OSNAP) was initiated in the spring of 2010 through a collaborative effort involving the USA, the UK, Germany, the Netherlands and Canada. A key feature of OSNAP is a trans-basin observing system deployed in the summer of 2014 for the continuous measure of volume, heat and freshwater fluxes in the subpolar North Atlantic. This review focuses on advancements made possible by the collective OSNAP observations. Chief among those advancements is the quantification of the dominant role of the eastern subpolar North Atlantic in the production of dense waters that reside in the lower limb of the overturning: the Irminger and Iceland basins contributed approximately three times as much dense water compared with the Labrador Sea over the observational period. Other advancements include elucidation of the relationship between convective activity in the basin interior and boundary current anomalies; the spread of overflow waters in the subpolar region; the seasonality of the meridional volume, heat and freshwater fluxes; and the challenges involved in designing a simpler, less costly observing system. Collectively, OSNAP measurements are laying a framework on which to assess the overturning circulation's vulnerability to continued warming and freshening as climate change continues apace. This article is part of a discussion meeting issue ‘Atlantic overturning: new observations and challenges’.

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“…The floats drifting southward from the ERR array to the BFZ, along the flank of the RR, did so at maximum speeds of over 15 cm/s (Ramsey et al., 2020), and with mean speeds about 10 cm/s (Zou et al., 2023). Floats took an average of 66 days ± 36 days to reach the BFZ.…”

Section: Resultsmentioning

confidence: 99%

Variability of Iceland Scotland Overflow Water Across the Reykjanes Ridge: 2‐Years of Moored Observations in the Bight Fracture Zone

Furey,

Bower,

Ramsey

et al. 2024

JGR Oceans

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This study presents the first continuous observations of Iceland Scotland Overflow Water (ISOW) passing through the Bight Fracture Zone (BFZ), the northernmost deep bathymetric channel across the Reykjanes Ridge between the Iceland and Irminger Basins in the subpolar North Atlantic. Data from two 2‐year moorings, measuring temperature, salinity, and current velocity from 2015 to 2017, along with a set of deep ISOW‐embedded RAFOS floats, are used to investigate ISOW transport and water property variability through the BFZ, as well as advective pathways between the Iceland and Irminger Basins. The mooring‐derived record‐mean ISOW transport through the BFZ was −0.59 ± 0.27 × 1e6 m3/s (westward) and varied seasonally with weaker transport in winter and stronger transport in summer. Flow direction of ISOW through the BFZ was consistently westward except in winter, when week‐long flow reversals were frequently observed. The previously reported subpolar North Atlantic freshening event of the 2010s is evident in the BFZ mooring records beginning about January 2017. About one‐quarter of floats deployed in ISOW at 1800‐m depth upstream in the Iceland Basin show a direct advective pathway into the BFZ that appears to be primarily determined by bathymetry. Another quarter of the floats crossed over the ridge to the Irminger Sea through other gaps prior to reaching the Charlie‐Gibbs Fracture Zone.

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Deep ocean circulation in the subpolar North Atlantic observed by acoustically-tracked floats

Cited by 4 publications

References 95 publications

Future strengthening of the Nordic Seas overturning circulation

Future strengthening of the Nordic Seas overturning circulation

Overturning in the subpolar North Atlantic: a review

Variability of Iceland Scotland Overflow Water Across the Reykjanes Ridge: 2‐Years of Moored Observations in the Bight Fracture Zone

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