365NEWSX
365NEWSX
Subscribe

Welcome

Heat and carbon coupling reveals ocean warming due to circulation changes - Nature.com

Heat and carbon coupling reveals ocean warming due to circulation changes - Nature.com

Heat and carbon coupling reveals ocean warming due to circulation changes - Nature.com
Aug 12, 2020 7 mins, 52 secs

Anthropogenic global surface warming is proportional to cumulative carbon emissions1,2,3; this relationship is partly determined by the uptake and storage of heat and carbon by the ocean4.

The rates and patterns of ocean heat and carbon storage are influenced by ocean transport, such as mixing and large-scale circulation5,6,7,8,9,10.

However, existing climate models do not accurately capture the observed patterns of ocean warming, with a large spread in their projections of ocean circulation and ocean heat uptake8,11.

Additionally, assessing the influence of ocean circulation changes (specifically, the redistribution of heat by resolved advection) on patterns of observed and simulated ocean warming remains a challenge.

Here we establish a linear relationship between the heat and carbon uptake of the ocean in response to anthropogenic emissions.

This relationship is determined mainly by intrinsic parameters of the Earth system—namely, the ocean carbon buffer capacity, the radiative forcing of carbon dioxide and the carbon inventory of the ocean.

We use this relationship to reveal the effect of changes in ocean circulation from carbon dioxide forcing on patterns of ocean warming in both observations and global Earth system models from the Fifth Coupled Model Intercomparison Project (CMIP5).

We show that historical patterns of ocean warming are shaped by ocean heat redistribution, which CMIP5 models simulate poorly.

However, we find that projected patterns of heat storage are primarily dictated by the pre-industrial ocean circulation (and small changes in unresolved ocean processes)—that is, by the patterns of added heat owing to ocean uptake of excess atmospheric heat rather than ocean warming by circulation changes.

Climate models show more skill in simulating ocean heat storage by the pre-industrial circulation compared to heat redistribution, indicating that warming patterns of the ocean may become more predictable as the climate warms.

The observed ocean heat uptake10 is available at https://laurezanna.github.io/publication/zanna-et-al-2017b/.

The CMIP5 and observational estimates of total, added and redistributed heat are available at https://laurezanna.github.io/publication/bronselaer-zanna-2020/.

Warming caused by cumulative carbon emissions towards the trillionth tonne.

Google Scholar .

The proportionality of global warming to cumulative carbon emissions.

Google Scholar .

Irreversible climate change due to carbon dioxide emissions.

Google Scholar .

Sensitivity of climate to cumulative carbon emissions due to compensation of ocean heat and carbon uptake.

Google Scholar .

The passive and active nature of ocean heat uptake in idealized climate change experiments.

Google Scholar .

Global ocean storage of anthropogenic carbon.

Google Scholar .

Connecting changing ocean circulation with changing climate.

Google Scholar .

The Flux-Anomaly-Forced Model Intercomparison Project (FAFMIP) contribution to CMIP6: investigation of sea-level and ocean climate change in response to CO2 forcing.

Google Scholar J

Recent increase in oceanic carbon uptake driven by weaker upper-ocean overturning?

Google Scholar .

Global reconstruction of historical ocean heat storage and transport.

Google Scholar .

Dominance of the Southern Ocean in anthropogenic carbon and heat uptake in CMIP5 models.

Google Scholar .

(eds) Climate Change 2013: The Physical Science Basis: Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (Cambridge Univ. Press, 2013).

Is a decline of AMOC causing the warming hole above the North Atlantic in observed and modeled warming patterns.

Google Scholar .

Climate-driven changes to ocean circulation and their inferred impacts on marine dispersal patterns.

Google Scholar J

Google Scholar .

Changes in dissolved oxygen in the Southern Ocean with climate change.

Google Scholar M

Observed fingerprint of a weakening Atlantic Ocean overturning circulationJ

Google Scholar .

Setting cumulative emissions targets to reduce the risk of dangerous climate change.

Google Scholar .

A conceptual model of ocean heat uptake under climate change.

Google Scholar .

Impact of mesoscale eddy transfer on heat uptake in an eddy-parameterizing ocean model.

Google Scholar .

Reconstruction of the history of anthropogenic CO2 concentrations in the ocean.

Google Scholar .

Carbon dioxide exchange between atmosphere and ocean and the questions of an increase of atmospheric CO2 during the past decades.

Google Scholar .

Improved estimates of ocean heat content from 1960 to 2015.

Google Scholar .

Google Scholar H

Southern Ocean warming delayed by circumpolar upwelling and equatorward transport.

Google Scholar J

Identifying a human signal in the North Atlantic warming hole.

Google Scholar .

Drivers of uncertainty in simulated ocean circulation and heat uptake.

Google Scholar .

Agreement of CMIP5 simulated and observed ocean anthropogenic CO2 uptake.

Google Scholar .

Google Scholar .

Google Scholar .

Google Scholar .

Uncertainties in CMIP5 climate projections due to carbon cycle feedbacks.

Google Scholar .

Decadal variations and trends of the global ocean carbon sink.

Google Scholar .

Decadal trends in the ocean carbon sinkP

Google Scholar .

On the climatic impact of ocean circulationP

Google Scholar .

Marine heatwaves under global warming.

Google Scholar .

The sensitivity of future ocean oxygen to changes in ocean circulation.

Google Scholar .

Mechanisms of ocean heat uptake in a coupled climate model and the implications for tracer-based predictions of ocean heat uptake.

Google Scholar O

Google Scholar .

Part II: Carbon system formulation and baseline simulation characteristics.

Google Scholar .

Google Scholar .

Google Scholar .

A new look at ocean ventilation time scales and their uncertainties.

Google Scholar .

Spatial and seasonal variability of the air–sea equilibration timescale of carbon dioxideA

Google Scholar .

Google Scholar .

Google Scholar .

Google Scholar .

Nonlinearity of ocean carbon cycle feedbacks in CMIP5 Earth system models.

Google Scholar .

Climate change impacts on net primary production (NPP) and export production (EP) regulated by increasing stratification and phytoplankton community structure in the CMIP5 models.

Google Scholar .

Google Scholar .

Multi-century changes in ocean and land contributions to climate- carbon feedbacks.

Google Scholar .

Google Scholar .

(eds) Climate Change 2007: The Physical Science Basis.

Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (Cambridge Univ. Press, 2007).

Google Scholar .

Google Scholar .

Google Scholar .

Investigating the causes of the response of the thermohaline circulation to past and future climate changesW

Google Scholar W

Exceptional twentieth-century slowdown in Atlantic Ocean overturning circulation.

Google Scholar .

Abrupt cooling over the North Atlantic in modern climate models.

Google Scholar .

Google Scholar .

ORNL/CDIAC-162, ND-P093 (Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, US Department of Energy, 2015).

Google Scholar .

MATLAB Program Developed for CO2 System Calculations https://cdiac.ess-dive.lbl.gov/ftp/co2sys/CO2SYS_calc_MATLAB_v1.1/ (Carbon Dioxide Information Analysis Center, US Department of Energy, 2011).

We acknowledge the MITgcm team for making their code publicly available, the World Climate Research Programme’s Working Group on Coupled Modelling, which is responsible for CMIP5, and the climate modelling groups for producing and making available the output of their models.

a, b, Using the free-circulation model, the fixed-layer depth of the pre- industrial control mean (a) and the change in mixed-layer depth (relative to the control) (b), for years 61–80 of the 1%CO2 free circulation.

The grey shading shows the error in the estimate that is due to the assumption of linearity and to various other processes and feedback mechanisms ignored, such as land carbon uptake

Thin lines show individual models (ESM2M is shown in green for reference) and dashed lines show the models that simulate ocean heat loss in the mid-twentieth century that are excluded from the mean and range

The blue solid line shows the observations (using ref. 10 for heat) and its blue shading shows the 66% confidence interval from observations

a, b, The year 61–80 zonal-mean ocean redistributed heat, here expressed as the zonal-mean temperature change, and calculated using the diagnosed fields from the ESM2M fixed-circulation experiment (a), and using the expression Had(y, z, t) = α(t)Cant(y, z, t) (b)

The parameters (y, z, t) indicate the zonal-mean quantities instead of vertical integrals, and α(t) is calculated globally as before, except here divided by volume, density and specific heat capacity so that values are given in terms of temperature instead of heat capacity

Ocean redistributed heat Had(y, z, t) = α(t)Cant(y, z, t) in terms of temperature instead of than heat

Changes are shown as the linear trends over the indicated periods multiplied by the length of the period

c, d, Changes in the CMIP5 historical RCP8.5 ensemble

The hatching indicates where the changes are not significant at the 66% uncertainty level

The hatching indicates where the changes are not significant at the 66% uncertainty level; the uncertainty is from the mean of the ensemble due to inter-model spread

a, ESM2M zonal-mean contribution of DIC (green), DIC+ALK (blue) and DIC+ALK+T (red) towards the change in ocean surface \({p}_{{{\rm{CO}}}_{2}}\)

b, ESM2M zonal-mean mixed layer change, relative to the pre-industrial control, in ∆DIC (green), fixed-circulation added temperature ∆Tad (red), and ∆CFC 12 (purple)

a, b, Zonal-mean contribution of DIC (green), DIC + ALK (blue) and DIC + ALK + T (total; red), towards the change in ocean surface \({p}_{{{\rm{CO}}}_{2}}\) at year 70 of the 1%CO2 simulation with IPSL-CM5A-LR, relative to the pre-industrial control (a), and at year 2011 best-estimate from observations, relative to year 1765, using GLODAPv265,66,67 for mean-state fields and ∆DIC (Cant) from ref

c, d, Zonal-mean contribution of ∆DIC (green) and \(\partial {p}_{{{\rm{CO}}}_{2}}/\partial {\rm{DIC}}\) (blue) towards ocean surface \({p}_{{{\rm{CO}}}_{2}}\) changes at year 70 of the 1%CO2 simulation with IPSL-CM5A-LR (c), and year 2011 from observations (using GLODAPv2 for mean states fields37 and ∆DIC from ref. 24; d)

c, d, The perturbed (c) and overturning (d) barotropic streamfunctions in the MITgcm climate change simulation after 70 yr of warming (taken as the mean of years 61–80)

a–d, Upper 2,000 m column-integrated anomalies in the MITgcm climate change experiments, for free-circulation carbon (a), free-circulation heat (b), fixed-circulation carbon (c), and fixed-circulation heat (d)

e, f, The re-distributions of carbon (e) and heat (f) are taken as the difference between the free-circulation and fixed-circulation anomalies

Heat and carbon coupling reveals ocean warming due to circulation changes

Summarized by 365NEWSX ROBOTS

RECENT NEWS

SUBSCRIBE

Get monthly updates and free resources.

CONNECT WITH US

© Copyright 2024 365NEWSX - All RIGHTS RESERVED