Variability of the directly observed, middepth subpolar North Atlantic circulation

Palter, Jaime B.; Caron, Charles-André; Law, Kara Lavender; Willis, J. K.; Trossman, David S.; Yashayaev, Igor; Gilbert, Denis

doi:10.1002/2015gl067235

Cited by 19 publications

(24 citation statements)

References 28 publications

(56 reference statements)

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“…During the strong convection, older water masses enriched in DIC nat were replaced by water masses high in C ant due to their most recent contact to the atmosphere and relatively low in DIC nat as DIC nat from remineralization has not yet accumulated. In contrast to that, the peak in 2005 in the C ant inventory could be related to the advection of C ant -enriched water masses formed in the Labrador Sea or in the region south of Cape Farewell into the Irminger Sea (Straneo et al, 2003;Palter et al, 2016), but this strong signal may also reflect the true error or reveal measurement bias.…”

Section: Resultsmentioning

confidence: 61%

Inorganic carbon and water masses in the Irminger Sea since 1991

et al. 2018

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Abstract. The subpolar region in the North Atlantic is a major sink for anthropogenic carbon. While the storage rates show large interannual variability related to atmospheric forcing, less is known about variability in the natural dissolved inorganic carbon (DIC) and the combined impact of variations in the two components on the total DIC inventories. Here, data from 15 cruises in the Irminger Sea covering the 24-year period between 1991 and 2015 were used to determine changes in total DIC and its natural and anthropogenic components. Based on the results of an extended optimum multiparameter analysis (eOMP), the inventory changes are discussed in relation to the distribution and evolution of the main water masses. The inventory of DIC increased by 1.43 ± 0.17 mol m −2 yr −1 over the period, mainly driven by the increase in anthropogenic carbon (1.84 ± 0.16 mol m −2 yr −1 ) but partially offset by a loss of natural DIC (−0.57 ± 0.22 mol m −2 yr −1 ). Changes in the carbon storage rate can be driven by concentration changes in the water column, for example due to the ageing of water masses, or by changes in the distribution of water masses with different concentrations either by local formation or advection. A decomposition of the trends into their main drivers showed that variations in natural DIC inventories are mainly driven by changes in the layer thickness of the main water masses, while anthropogenic carbon is most affected by concentration changes. The storage rates of anthropogenic carbon are sensitive to data selection, while changes in DIC inventory show a robust signal on short timescales associated with the strength of convection.

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Section: Resultsmentioning

confidence: 61%

Inorganic carbon and water masses in the Irminger Sea since 1991

et al. 2018

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“…However, in order for these water masses to potentially precondition the water column in the Irminger Sea for convection in winter 2014–2015, a fast eastward advection would be required. This is implausible given the observed mid-depth large-scale circulation30. The February to April mixed layer density evolution also reveals no eastward propagation of dense waters, particularly in 2013–2014.…”

Section: Resultsmentioning

confidence: 86%

Irminger Sea deep convection injects oxygen and anthropogenic carbon to the ocean interior

et al. 2016

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Deep convection in the subpolar North Atlantic ventilates the ocean for atmospheric gases through the formation of deep water masses. Variability in the intensity of deep convection is believed to have caused large variations in North Atlantic anthropogenic carbon storage over the past decades, but observations of the properties during active convection are missing. Here we document the origin, extent and chemical properties of the deepest winter mixed layers directly observed in the Irminger Sea. As a result of the deep convection in winter 2014–2015, driven by large oceanic heat loss, mid-depth oxygen concentrations were replenished and anthropogenic carbon storage rates almost tripled compared with Irminger Sea hydrographic section data in 1997 and 2003. Our observations provide unequivocal evidence that ocean ventilation and anthropogenic carbon uptake take place in the Irminger Sea and that their efficiency can be directly linked to atmospheric forcing.

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“…The first decade of direct measurements from the RAPID array shows a significant decrease in AMOC strength at 26°N since 2004 AD (Smeed et al 2014). A decline is also reported in float-derived estimates of the subsurface circulation (Palter et al 2016) and altimetryinferred estimates of the upper subpolar gyre strength (Häk-kinen and Rhines 2004;Hakkinen and Rhines 2009). Other observational records, such as the deep densities in the Labrador Sea or the wider subpolar gyre, can offer invaluable indirect information on changes in ocean dynamics, as suggested by model outputs (Robson et al 2014a;Hermanson et al 2014).…”

Section: Introductionmentioning

confidence: 72%