Ventilation variability of Labrador Sea Water and its impact on oxygen and anthropogenic carbon: a review

Rhein, Monika; Steinfeldt, Reiner; Kieke, Dagmar; Stendardo, I.; Yashayaev, Igor

doi:10.1098/rsta.2016.0321

Cited by 71 publications

(90 citation statements)

References 55 publications

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“…Warming is suggested as the reason for the upper ocean deoxygenation, while changes in large‐scale ocean circulation influence oxygen changes in the deep ocean. At smaller spatiotemporal scales, regional climate modes exert stronger influence in the oxygen variability, for example, within the thermocline (Deutsch et al, ; Rhein et al, ). In fact, in different ocean regions, both increasing and decreasing oxygen have been observed at shorter timescales (Fröb et al, ; Johnson & Gruber, ; McDonagh et al, ; Stendardo & Gruber, ; Stramma et al, , ).…”

Section: Introductionmentioning

confidence: 99%

Mechanisms and Early Detections of Multidecadal Oxygen Changes in the Interior Subpolar North Atlantic

Tjiputra

Goris

Lauvset

et al. 2018

Geophysical Research Letters

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The oxygen response in the subpolar North Atlantic (SPNA) to future climate change is poorly understood. We investigate the multidecadal variability in interior oxygen and its association with the subpolar gyre index (a gyre strength proxy) for models and data. During positive phases, persistent strong Labrador Sea (LS) lateral and vertical mixing entrains oxygen-rich water into the interior southern SPNA and vice versa during negative phases. This is indicated by the observed anomalously fresh, cold, and low apparent oxygen utilization, resembling LS water mass during positive phases. We use this relationship to benchmark Earth system models. Under a high CO 2 future, the best performing models project a steady decline in SPNA oxygen, driven partly by lower solubility and increases in apparent oxygen utilization. The deoxygenation depends on the sensitivity of the LS mixing to warming. The time of emergence of interior oxygen is projected to be decades earlier than that of temperature and salinity. Plain Language Summary An important indicator for marine ecosystem health andbiodiversity is oceanic oxygen, which is projected to decline considerably with the ongoing climate change. Understanding when, where, and how fast the oxygen may change is of importance for society and the broader scientific community. In this study, we show that the interior oxygen in the North Atlantic subpolar gyre is sensitive to the gyre strength and winter mixing in the Labrador Sea. We demonstrate that in a future warmer climate where the ocean becomes more stratified, the interior water mass will experience rapid deoxygenation due to both lower oxygen solubility and increased biological consumption. The latter is caused by a reduced ventilation and a more sluggish circulation. The deoxygenation signals due to climate change are projected to be evident in the early 21st century. The study provides a compelling argument to establish and maintain a long-term monitoring system for the interior oxygen, especially in the study region.

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Section: Introductionmentioning

confidence: 99%

Mechanisms and Early Detections of Multidecadal Oxygen Changes in the Interior Subpolar North Atlantic

Tjiputra

Goris

Lauvset

et al. 2018

Geophysical Research Letters

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“…Twelve papers were presented at the meeting, and the final versions of 10 of these are included in this volume [9][10][11][12][13][14][15][16][17][18]. Ralph Keeling (paper not included in this volume) reviewed what we know about recent oxygen trends based on results from oceanic and atmospheric O 2 measurements.…”

Section: Overviewmentioning

confidence: 99%

“…Rhein [9] reviewed the ventilation variability of Labrador Sea water (LSW) and its impact on oxygen and anthropogenic carbon. The ocean is a main player in the climate system.…”

Section: Overviewmentioning

confidence: 99%

Ocean ventilation and deoxygenation in a warming world: introduction and overview

Shepherd

Brewer

Oschlies

et al. 2017

Phil. Trans. R. Soc. A.

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Changes of ocean ventilation rates and deoxygenation are two of the less obvious but important indirect impacts expected as a result of climate change on the oceans. They are expected to occur because of (i) the effects of increased stratification on ocean circulation and hence its ventilation, due to reduced upwelling, deep-water formation and turbulent mixing, (ii) reduced oxygenation through decreased oxygen solubility at higher surface temperature, and (iii) the effects of warming on biological production, respiration and remineralization. The potential socio-economic consequences of reduced oxygen levels on fisheries and ecosystems may be far-reaching and significant. At a Royal Society Discussion Meeting convened to discuss these matters, 12 oral presentations and 23 posters were presented, covering a wide range of the physical, chemical and biological aspects of the issue. Overall, it appears that there are still considerable discrepancies between the observations and model simulations of the relevant processes. Our current understanding of both the causes and consequences of reduced oxygen in the ocean, and our ability to represent them in models are therefore inadequate, and the reasons for this remain unclear. It is too early to say whether or not the socio-economic consequences are likely to be serious. However, the consequences are ecologically, biogeochemically and climatically potentially very significant, and further research on these indirect impacts of climate change via reduced ventilation and oxygenation of the oceans should be accorded a high priority. This article is part of the themed issue ‘Ocean ventilation and deoxygenation in a warming world’.

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“…The water mass transformation processes that create North Atlantic Deep Water (NADW) have two drivers: (i) buoyancy fluxes at the air/sea interface, creating dense mode water in the subpolar gyre (densest one is Labrador Sea Water; LSW); and (ii) entrainment processes at the Greenland-Scotland Ridges, where dense water masses that enter from the Nordic Seas are transformed into Denmark Strait Overflow Water (densest part of the NADW) and the Iceland Scotland Overflow Water. The hydrographic variability of subpolar Mode Water masses is well documented and also correlated with air/sea buoyancy fluxes (Yashayaev and Loder, 2017). Variability of the hydrography of the overflow waters is more complex because of the entrainment of ambient waters adding twice the volume to the overflow (Jochumsen et al, 2015).…”

Section: Case Study: Atlantic Oceanmentioning

confidence: 99%

Adequacy of the Ocean Observation System for Quantifying Regional Heat and Freshwater Storage and Change

et al. 2019

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Considerable advances in the global ocean observing system over the last two decades offers an opportunity to provide more quantitative information on changes in heat and freshwater storage. Variations in these storage terms can arise through internal variability and also the response of the ocean to anthropogenic climate change. Disentangling these competing influences on the regional patterns of change and elucidating their governing processes remains an outstanding scientific challenge. This challenge is compounded by instrumental and sampling uncertainties. The combined use of ocean observations and model simulations is the most viable method to assess the forced signal from noise and ascertain the primary drivers of variability and change. Moreover, this approach offers the potential for improved seasonal-to-decadal predictions and the possibility to develop powerful multi-variate constraints on climate model future projections. Regional heat storage changes dominate the steric contribution to sea level rise over most of the ocean and are vital to understanding both global and regional heat budgets. Variations in regional freshwater storage are particularly relevant to our understanding of changes in the hydrological cycle and can potentially be used to verify local ocean mass addition from terrestrial and cryospheric systems associated with contemporary sea level rise. This White Paper will examine the ability of the current ocean observing system to quantify changes in regional heat and freshwater storage. In particular we will seek to answer the question: What time and space scales are currently Frontiers in Marine Science | www.frontiersin.org 1 August 2019 | Volume 6 | Article 416Palmer et al.Regional Heat and Freshwater Observations resolved in different regions of the global oceans? In light of some of the key scientific questions, we will discuss the requirements for measurement accuracy, sampling, and coverage as well as the synergies that can be leveraged by more comprehensively analyzing the multi-variable arrays provided by the integrated observing system.

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Ventilation variability of Labrador Sea Water and its impact on oxygen and anthropogenic carbon: a review

Cited by 71 publications

References 55 publications

Mechanisms and Early Detections of Multidecadal Oxygen Changes in the Interior Subpolar North Atlantic

Mechanisms and Early Detections of Multidecadal Oxygen Changes in the Interior Subpolar North Atlantic

Ocean ventilation and deoxygenation in a warming world: introduction and overview

Adequacy of the Ocean Observation System for Quantifying Regional Heat and Freshwater Storage and Change

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