Improved clouds over Southern Ocean amplify Antarctic precipitation response to ozone depletion in an earth system model

Abstract. Marine ecosystems are increasingly stressed by human-induced changes. Marine ecosystem drivers that contribute to stressing ecosystems – including warming, acidification, deoxygenation and perturbations to biological productivity – can co-occur in space and time, but detecting their trends is complicated by the presence of noise associated with natural variability in the climate system. Here we use large initial-condition ensemble simulations with an Earth system model under a historical/RCP8.5 (representative concentration pathway 8.5) scenario over 1950–2100 to consider emergence characteristics for the four individual and combined drivers. Using a 1-standard-deviation (67% confidence) threshold of signal to noise to define emergence with a 30-year trend window, we show that ocean acidification emerges much earlier than other drivers, namely during the 20th century over most of the global ocean. For biological productivity, the anthropogenic signal does not emerge from the noise over most of the global ocean before the end of the 21st century. The early emergence pattern for sea surface temperature in low latitudes is reversed from that of subsurface oxygen inventories, where emergence occurs earlier in the Southern Ocean. For the combined multiple-driver field, 41% of the global ocean exhibits emergence for the 2005–2014 period, and 63% for the 2075–2084 period. The combined multiple-driver field reveals emergence patterns by the end of this century that are relatively high over much of the Southern Ocean, North Pacific, and Atlantic, but relatively low over the tropics and the South Pacific. For the case of two drivers, the tropics including habitats of coral reefs emerges earliest, with this driven by the joint effects of acidification and warming. It is precisely in the regions with pronounced emergence characteristics where marine ecosystems may be expected to be pushed outside of their comfort zone determined by the degree of natural background variability to which they are adapted. The results underscore the importance of sustained multi-decadal observing systems for monitoring multiple ecosystems drivers.

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Emergent constraints on the Southern Ocean anthropogenic carbon and heat uptake

10.5194/egusphere-egu21-5336 ◽

2021 ◽

Author(s):

Thomas Frölicher ◽

Jens Terhaar ◽

Fortunat Joos

Keyword(s):

Southern Ocean ◽

Ocean Circulation ◽

Earth System Model ◽

System Model ◽

Carbon Uptake ◽

Earth System ◽

Excess Heat ◽

The Past ◽

Heat Uptake ◽

Anthropogenic Carbon

<p>The Southern Ocean south of 30&#176;S, occupying about a third of global surface ocean area, accounts for approximately 40% of the past anthropogenic carbon uptake and about 75% of excess heat uptake by the ocean. However, Earth system models have large difficulties in reproducing the Southern Ocean circulation, and therefore its historical and future anthropogenic carbon and excess heat uptake. In the first part of the talk, we show that there exists a tight relation across two Earth system model ensembles (CMIP5 and CMIP6) between present-day sea surface salinity in the subtropical-polar frontal zone, the formation region of mode and intermediate waters, and the past and future anthropogenic carbon uptake in the Southern Ocean. By using observations and Earth system model results, we constrain the projected cumulative Southern Ocean anthropogenic carbon uptake over 1850-2100 by the CMIP6 model ensemble to 158 &#177; 6 Pg C under the low-emissions scenario SSP1-2.6 and to 279 &#177; 14 Pg C under the high emissions scenario SSP5-8.5. Our results suggest that the Southern Ocean anthropogenic carbon sink is 14-18% larger and 46-54% less uncertain than estimated by the unconstrained CMIP6 Earth system model results. The identified constraint demonstrated the importance of the freshwater cycle for the Southern Ocean circulation and carbon cycle. In the second part of the talk, potential emergent constraints for the Southern Ocean excess heat uptake will be discussed.</p>

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Multidecadal preconditioning of the Maud Rise polynya region

Ocean Science ◽

10.5194/os-16-1443-2020 ◽

2020 ◽

Vol 16 (6) ◽

pp. 1443-1457

Author(s):

René M. van Westen ◽

Henk A. Dijkstra

Keyword(s):

High Resolution ◽

Southern Ocean ◽

Large Scale ◽

Heat Content ◽

Earth System Model ◽

System Model ◽

Earth System ◽

Model Resolution ◽

Community Earth System Model ◽

Maud Rise

Abstract. In this paper, we consider Maud Rise polynya formation in a long (250-year) high-resolution (ocean 0.1∘, atmosphere 0.5∘ horizontal model resolution) of the Community Earth System Model. We find a dominant multidecadal timescale in the occurrence of these Maud Rise polynyas. Analysis of the results leads us to the interpretation that a preferred timescale can be induced by the variability of the Weddell Gyre, previously identified as the Southern Ocean Mode. The large-scale pattern of heat content variability associated with the Southern Ocean Mode modifies the stratification in the Maud Rise region and leads to a preferred timescale in convection through preconditioning of the subsurface density and consequently to polynya formation.

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Southern Ocean convection shutdown controls potential for long-term climate warming by greenhouse gases

10.21203/rs.3.rs-361384/v1 ◽

2021 ◽

Author(s):

Ada Gjermundsen ◽

Aleksi Nummelin ◽

D. Olivié ◽

Mats Bentsen ◽

Øyvind Seland ◽

...

Keyword(s):

Southern Ocean ◽

Atmospheric Carbon Dioxide ◽

Marine Boundary Layer ◽

Carbon Dioxide Concentration ◽

Coupled Model ◽

Earth System Model ◽

System Model ◽

Earth System ◽

Near Surface ◽

Surface Warming

Abstract The effective climate sensitivity (EffCS) estimates the equilibrium near-surface temperature increase due to an doubling of the atmospheric carbon dioxide concentration, and is a widely used metric to characterise potential global warming. Cloud feedback, with considerable contribution from marine boundary layer clouds over the Southern Ocean (SO), has been identified as the main source to the spread and the increase in EffCS in the Earth System Models participating in phase 6 of the Coupled Model Intercomparison Project (CMIP6). We trace the difference in EffCS between the Community Earth System Model (CESM2, EffCS of 5.3K) and the Norwegian Earth System model (NorESM2; EffCS of 2.5K), to SO circulation response. NorESM2 stores more heat at depth than CESM2, which delays the SO surface warming, SO cloud response, and ultimately the global surface warming by centuries in comparison to CESM2. The link between SO and EffCS is seen across 41 CMIP6 models; those with a low EffCS exhibit substantial deep SO warming. The observed slow surface but fast subsurface SO warming supports the notion of SO control over EffCS.

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OCEANFILMS sea-spray organic aerosol emissions – Part 1: implementation and impacts on clouds

10.5194/acp-2018-70 ◽

2018 ◽

Cited By ~ 5

Author(s):

Susannah M. Burrows ◽

Richard Easter ◽

Xiaohong Liu ◽

Po-Lun Ma ◽

Hailong Wang ◽

...

Keyword(s):

Southern Ocean ◽

Radiative Forcing ◽

Cloud Condensation Nuclei ◽

Organic Aerosol ◽

Earth System Model ◽

Sea Salt ◽

System Model ◽

Sea Spray ◽

Earth System ◽

Aerosol Emissions

Abstract. The OCEANFILMS parameterization for sea-spray organic aerosol emissions has been implemented into a global Earth system model, the Energy Exascale Earth System Model (E3SM). OCEANFILMS is a physically-based model that links sea spray chemistry with ocean biogeochemistry using a Langmuir partitioning approach. Here we describe the implementation within E3SM and investigate the impacts of the parameterization on the model's aerosols, clouds and climate. Four sensitivity cases are tested, in which organic emissions either strictly add to or strictly replace sea salt emissions (in mass and number), and are either fully internally or fully externally mixed with sea salt. The simulation with internally-mixed, added organics agrees best with observed seasonal cycles of organic matter in marine aerosol. In this configuration, marine organic aerosols contribute an additional source of cloud condensation nuclei, adding up to 30 cm−3 to Southern Ocean boundary-layer CCN concentrations (supersaturation = 0.1 %). The addition of this new aerosol source strengthens shortwave radiative cooling by clouds by −0.36 W/m2 in the global annual mean, and contributes more than −3.5 W/m2 to summertime zonal mean cloud forcing in the Southern Ocean, with maximum zonal mean impacts of about −4 W/m2 around 50° S–60° S. This is consistent with a previous top-down, satellite-based empirical estimate of the radiative forcing by marine organic aerosol over the Southern Ocean.

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Emergence of multiple ocean ecosystem drivers in a large ensemble suite with an earth system model

Biogeosciences Discussions ◽

10.5194/bgd-11-18189-2014 ◽

2014 ◽

Vol 11 (12) ◽

pp. 18189-18227 ◽

Cited By ~ 6

Author(s):

K. B. Rodgers ◽

J. Lin ◽

T. L. Frölicher

Keyword(s):

Southern Ocean ◽

Marine Ecosystems ◽

Earth System Model ◽

Mitigation Strategies ◽

System Model ◽

Global Ocean ◽

Earth System ◽

Biological Productivity ◽

Ocean Ecosystem ◽

Ecosystem Drivers

Abstract. Marine ecosystems are increasingly impacted by human-induced changes. Ocean ecosystem drivers – including warming, acidification, deoxygenation and perturbations to biological productivity – can co-occur in space and time, but detecting their trends is complicated by the presence of noise associated with natural variability in the climate system. Here we use Large Initial-Condition Ensemble Simulations with a comprehensive Earth System Model under a historical/RCP8.5 pathway over 1950–2100 to consider emergence characteristics for the four individual and combined drivers. Using a one-standard deviation (67% confidence) threshold of signal-to-noise to define emergence with a 30 yr trend window, we show that ocean acidification emerges much earlier than other drivers, namely during the 20th century over most of the global ocean. For biological productivity, the anthropogenic signal does not emerge from the noise over most of the global ocean before the end of the 21st century. The early emergence pattern for sea surface temperature in low latitudes is reversed from that of subsurface oxygen inventories, where emergence occurs earlier in the Southern Ocean. For the combined multiple-driver field, 41% of the global ocean exhibits emergence for the 2005–2014 period, and 63% for the 2075–2084 period. The combined multiple-driver field reveals emergence patterns by the end of this century that are relatively high over much of the Southern Ocean, North Pacific, and Atlantic, but relatively low over the tropics and the South Pacific. In regions with pronounced emergence characteristics, marine ecosystems can be expected to be pushed outside of their comfort zone determined by the degree of natural background variability to which they are adapted. The results here thus have implications not only for optimization of the ocean observing system, but also for risk assessment and mitigation strategies.

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