Acceleration of ocean warming, salinification, deoxygenation and acidification in the surface subtropical North Atlantic Ocean

Abstract Ocean chemical and physical conditions are changing. Here we show decadal variability and recent acceleration of surface warming, salinification, deoxygenation, carbon dioxide (CO2) and acidification in the subtropical North Atlantic Ocean (Bermuda Atlantic Time-series Study site; 1980s to present). Surface temperatures and salinity exhibited interdecadal variability, increased by ~0.85 °C (with recent warming of 1.2 °C) and 0.12, respectively, while dissolved oxygen levels decreased by ~8% (~2% per decade). Concurrently, seawater DIC, fCO2 (fugacity of CO2) and anthropogenic CO2 increased by ~8%, 22%, and 72% respectively. The winter versus summer fCO2 difference increased by 4 to 8 µatm decade−1 due to seasonally divergent thermal and alkalinity changes. Ocean pH declined by 0.07 (~17% increase in acidity) and other acidification indicators by ~10%. Over the past nearly forty years, the highest increase in ocean CO2 and ocean acidification occurred during decades of weakest atmospheric CO2 growth and vice versa.

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Reconstructing Western Boundary Current Stability in the North Atlantic Ocean for the Past 700 Kyr From Globorotalia truncatulinoides Coiling Ratios

Paleoceanography and Paleoclimatology ◽

10.1029/2020pa003958 ◽

2020 ◽

Vol 35 (12) ◽

Author(s):

Katharina Billups ◽

Maoli Vizcaíno ◽

Josephine Chiarello ◽

Emily A. Kaiser

Keyword(s):

Atlantic Ocean ◽

North Atlantic ◽

North Atlantic Ocean ◽

Western Boundary Current ◽

Western Boundary ◽

Boundary Current ◽

The Past ◽

The North ◽

Globorotalia Truncatulinoides ◽

The North Atlantic

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Rapid freshening of the deep North Atlantic Ocean over the past four decades

Nature ◽

10.1038/416832a ◽

2002 ◽

Vol 416 (6883) ◽

pp. 832-837 ◽

Cited By ~ 358

Author(s):

Bob Dickson ◽

Igor Yashayaev ◽

Jens Meincke ◽

Bill Turrell ◽

Stephen Dye ◽

...

Keyword(s):

Atlantic Ocean ◽

North Atlantic ◽

North Atlantic Ocean ◽

The Past

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Predictability and Decadal Variability of the North Atlantic Ocean State Evaluated from a Realistic Ocean Model

Journal of Climate ◽

10.1175/jcli-d-16-0323.1 ◽

2017 ◽

Vol 30 (2) ◽

pp. 477-498 ◽

Cited By ~ 6

Author(s):

Florian Sévellec ◽

Alexey V. Fedorov

Keyword(s):

Atlantic Ocean ◽

Surface Temperature ◽

Sea Surface Temperature ◽

North Atlantic ◽

Decadal Variability ◽

North Atlantic Ocean ◽

Meridional Overturning Circulation ◽

Sea Surface ◽

The North ◽

The North Atlantic

This study investigates the excitation of decadal variability and predictability of the ocean climate state in the North Atlantic. Specifically, initial linear optimal perturbations (LOPs) in temperature and salinity that vary with depth, longitude, and latitude are computed, and the maximum impact on the ocean of these perturbations is evaluated in a realistic ocean general circulation model. The computations of the LOPs involve a maximization procedure based on Lagrange multipliers in a nonautonomous context. To assess the impact of these perturbations four different measures of the North Atlantic Ocean state are used: meridional volume and heat transports (MVT and MHT) and spatially averaged sea surface temperature (SST) and ocean heat content (OHC). It is shown that these metrics are dramatically different with regard to predictability. Whereas OHC and SST can be efficiently modified only by basin-scale anomalies, MVT and MHT are also strongly affected by smaller-scale perturbations. This suggests that instantaneous or even annual-mean values of MVT and MHT are less predictable than SST and OHC. Only when averaged over several decades do the former two metrics have predictability comparable to the latter two, which highlights the need for long-term observations of the Atlantic meridional overturning circulation in order to accumulate climatically relevant data. This study also suggests that initial errors in ocean temperature of a few millikelvins, encompassing both the upper and deep ocean, can lead to ~0.1-K errors in the predictions of North Atlantic sea surface temperature on interannual time scales. This transient error growth peaks for SST and OHC after about 6 and 10 years, respectively, implying a potential predictability barrier.

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Analyzing the Influence of the North Atlantic Ocean Variability on the Atlantic Meridional Mode on Decadal Time Scales

Atmosphere ◽

10.3390/atmos11010003 ◽

2019 ◽

Vol 11 (1) ◽

pp. 3

Author(s):

Sandro F. Veiga ◽

Emanuel Giarolla ◽

Paulo Nobre ◽

Carlos A. Nobre

Keyword(s):

Atlantic Ocean ◽

North Atlantic ◽

Decadal Variability ◽

North Atlantic Ocean ◽

Heat Content ◽

Ocean Heat Content ◽

Causality Analysis ◽

Ocean Variability ◽

The North ◽

The North Atlantic

Important features of the Atlantic meridional mode (AMM) are not fully understood. We still do not know what determines its dominant decadal variability or the complex physical processes that sustain it. Using reanalysis datasets, we investigated the influence of the North Atlantic Ocean variability on the dominant decadal periodicity that characterizes the AMM. Statistical analyses demonstrated that the correlation between the sea surface temperature decadal variability in the Atlantic Ocean and the AMM time series characterizes the Atlantic multidecadal oscillation (AMO). This corroborates previous studies that demonstrated that the AMO precedes the AMM. A causal inference with a newly developed rigorous and quantitative causality analysis indicates that the AMO causes the AMM. To further understand the influence of the subsurface ocean on the AMM, the relationship between the ocean heat content (0–300 m) decadal variability and AMM was analyzed. The results show that although there is a significant zero-lag correlation between the ocean heat content in some regions of the North Atlantic (south of Greenland and in the eastern part of the North Atlantic) and the AMM, their cause-effect relationship on decadal time scales is unlikely. By correlating the AMO with the ocean heat content (0–300 m) decadal variability, the former precedes the latter; however, the causality analysis shows that the ocean heat content variability drives the AMO, corroborating several studies that point out the dominant role of the ocean heat transport convergence on AMO.

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