Enhanced Atlantic sea-level rise relative to the Pacific under high carbon emission rates

Journal name:
Nature Geoscience
Volume:
9,
Pages:
210–214
Year published:
DOI:
doi:10.1038/ngeo2641
Received
Accepted
Published online

Thermal expansion of the ocean in response to warming is an important component of historical sea-level rise1. Observational studies show that the Atlantic and Southern oceans are warming faster than the Pacific Ocean2, 3, 4, 5. Here we present simulations using a numerical atmospheric-ocean general circulation model with an interactive carbon cycle to evaluate the impact of carbon emission rates, ranging from 2 to 25GtCyr−1, on basin-scale ocean heat uptake and sea level. For simulations with emission rates greater than 5GtCyr−1, sea-level rise is larger in the Atlantic than Pacific Ocean on centennial timescales. This basin-scale asymmetry is related to the shorter flushing timescales and weakening of the overturning circulation in the Atlantic. These factors lead to warmer Atlantic interior waters and greater thermal expansion. In contrast, low emission rates of 2 and 3GtCyr−1 will cause relatively larger sea-level rise in the Pacific on millennial timescales. For a given level of cumulative emissions, sea-level rise is largest at low emission rates. We conclude that Atlantic coastal areas may be particularly vulnerable to near-future sea-level rise from present-day high greenhouse gas emission rates.

At a glance

Figures

  1. Ensemble mean Atlantic Meridional Overturning Circulation (AMOC) averaged over model years 181-200.
    Figure 1: Ensemble mean Atlantic Meridional Overturning Circulation (AMOC) averaged over model years 181–200.

    Units are Sv, where 1Sv ≡ 106m3s−1. The average of the three ensemble members is shown for each of the idealized emission scenarios. a, Pre-industrial control run. b, 2GtCyr−1. c, 5GtCyr−1. d, 25GtCyr−1.

  2. Atlantic minus Pacific differences in basin-average volume mean ocean temperature and dissolved inorganic carbon (DIC) concentration.
    Figure 2: Atlantic minus Pacific differences in basin-average volume mean ocean temperature and dissolved inorganic carbon (DIC) concentration.

    Temperature units are °C; DIC units are molkg−1. Solid lines represent ensemble means for each emission scenario; shading represents the range among ensemble members. Dots designate when the simulations reach 200GtC of cumulative carbon emissions. a, Temperature change, surface to 700m. b, Temperature change, surface to 2,000m. c, Temperature change, 2,000–5,500m. d, Temperature change, surface to 5,500m. eh, Same as ad except for DIC.

  3. Basin area-average differences in SLR as a function of emission rate.
    Figure 3: Basin area-average differences in SLR as a function of emission rate.

    Units are m. Solid lines represent ensemble means for each emission scenario; shading represents the range among ensemble members. Dots indicate either 200GtC of cumulative carbon emissions (ad) or 200yr (eh). ac, Global, Pacific and Atlantic SLR versus time. d, Atlantic minus Pacific SLR versus time. eg, Same as ac, except SLR versus cumulative emissions. h, Ratio of Atlantic to Pacific SLR (smoothed by a 100GtC boxcar filter) versus cumulative emissions. Grey dashes represent mean Atlantic to Pacific SLR ratio (0.83) from the control simulation.

  4. Spatial patterns of SLR under varying emission rates.
    Figure 4: Spatial patterns of SLR under varying emission rates.

    Units are m (ac) and standard deviation (σ, di). The average of the three ensemble members is shown for each emission scenario. ac, SLR differences for years 61–100 relative to the control simulation for the 2, 5 and 25GtCyr−1 scenarios. df, Emergent SLR difference patterns (see Methods) for the 2, 5 and 25GtCyr−1 scenarios. gi, Normalized difference patterns in SLR (same method as df) after 2,000GtC of cumulative emissions in the 2, 5 and 25GtCyr−1 scenarios.

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Affiliations

  1. NOAA/Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey 08540, USA

    • J. P. Krasting,
    • J. P. Dunne,
    • R. J. Stouffer &
    • R. W. Hallberg

Contributions

J.P.K. designed the study and conducted the experiments. J.P.K. and J.P.D. performed the analysis of the results. All authors contributed to the interpretation of the results and assisted in writing the manuscript.

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The authors declare no competing financial interests.

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