Antarctic Bottom Water and North Atlantic Deep Water in CMIP6 models

Ocean science, Journal Year: 2021, Volume and Issue: 17(1), P. 59 - 90

Published: Jan. 13, 2021

Abstract. Deep and bottom water formation are crucial components of the global ocean circulation, yet they were poorly represented in previous generation climate models. We here quantify biases Antarctic Bottom Water (AABW) North Atlantic (NADW) formation, properties, transport, extent 35 models that participated latest Climate Model Intercomparison Project (CMIP6). Several CMIP6 correctly forming AABW via shelf processes, but 28 Southern Ocean all form deep open-ocean convection too deeply, often, and/or over large an area. Models convect least most accurate NADW. The four CESM2 with their overflow parameterisation among In Atlantic, colder AABW, stronger abyssal overturning at 30∘ S, further north layer extends. saltier NADW, Meridional Overturning Circulation (AMOC), south NADW Indian Pacific oceans contrast, fresher ones which extend furthest regardless strength overturning, likely because also weakest fronts Circumpolar Current. There clear improvements since CMIP5: several represent or parameterise fewer exhibit convection, more right location Labrador Sea, density reduced, is realistic. However, required, e.g. by generalising use parameterisations coupling to interactive ice sheet models, before hence heat carbon storage, accurately.

Language: Английский

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Assessment of GCMs simulation performance for precipitation and temperature from CMIP5 to CMIP6 over the Tibetan Plateau

International Journal of Climatology, Journal Year: 2021, Volume and Issue: 41(7), P. 3994 - 4018

Published: Feb. 12, 2021

Abstract General circulation models (GCMs) are indispensable for climate change adaptive study over the Tibetan Plateau (TP), which is potential trigger and amplifier in global fluctuations. With release of Coupled Model Intercomparison Project Phase 6 (CMIP6), 24 GCMs from CMIP5 CMIP6 were comparatively evaluated precipitation air temperature simulations based on China Meteorological Forcing Dataset (CMFD). Rank score results showed that generally performed better than surface TP. According to multimodel ensembles (MMEs) optimal each variable, overestimation was both present CMIP6, but MMEs relatively lower mid‐west northern edge Furthermore, offered a performance summer autumn. For temperature, able reduce large cold bias appeared northwest areas about 1°C had smaller spring winter. Moreover, investigation into simulation effects at different elevation zones demonstrated improved ability mainly concentrated 2,000–3,000 m 5,000 m, where more 200%. Additionally, less 2°C zone, with minimum −0.22°C distributed region altitudes 3,000 4,000 while biases 4,000–5,000 those MMEs. Findings obtained this could provide scientific reference related research perform Multimodel effectively by 40 mm annual scale. Improved shows significant dependency, especially precipitation.

Language: Английский

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A regime shift in seasonal total Antarctic sea ice extent in the twentieth century

Nature Climate Change, Journal Year: 2022, Volume and Issue: 12(1), P. 54 - 62

Published: Jan. 1, 2022

Language: Английский

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Understanding Models' Global Sea Surface Temperature Bias in Mean State: From CMIP5 to CMIP6

Geophysical Research Letters, Journal Year: 2023, Volume and Issue: 50(4)

Published: Feb. 22, 2023

Abstract This paper evaluates sea surface temperature (SST) biases of coupled models participating in Coupled Model Intercomparison Project Phase 5 (CMIP5) and CMIP6. Overall, CMIP6 perform better than CMIP5 ones reproducing SST climatology, with lower multi‐model ensemble mean (MME) globally averaged absolute bias (1.17 vs. 1.31 K). MME global annual shifts from cooling (−0.09 ± 0.52 K) to warming (0.23 0.60 Regionally, over the Northwest Pacific North Atlantic are reduced by 20% 18%, while Northeast Pacific, Southeast Southern Ocean increased 25%, 16% 107% respectively. These changes mainly attributed combined effects aggravated positive (or alleviated negative) clear‐sky downward longwave radiation, negative cloud radiative effect, partially enhanced shortwave radiation.

Language: Английский

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Impact of horizontal resolution on global ocean–sea ice model simulations based on the experimental protocols of the Ocean Model Intercomparison Project phase 2 (OMIP-2)

Geoscientific model development, Journal Year: 2020, Volume and Issue: 13(9), P. 4595 - 4637

Published: Sept. 29, 2020

Abstract. This paper presents global comparisons of fundamental climate variables from a suite four pairs matched low- and high-resolution ocean sea ice simulations that are obtained following the OMIP-2 protocol (Griffies et al., 2016) integrated for one cycle (1958–2018) JRA55-do atmospheric state runoff dataset (Tsujino 2018). Our goal is to assess robustness climate-relevant improvements in (mean variability) associated with moving coarse (∼ 1∘) eddy-resolving 0.1∘) horizontal resolutions. The models diverse their numerics parameterizations, but each low-resolution pair so as isolate, extent possible, effects resolution. A variety observational datasets used fidelity simulated temperature salinity, surface height, kinetic energy, heat volume transports, distribution. provides crucial benchmark future studies comparing improving different schemes any this study or similar ones. biases familiar, gross features – position, strength, variability western boundary currents, equatorial Antarctic Circumpolar Current significantly improved models. However, despite fact “resolve” most these features, salinity inconsistent among model families, some regions show increased bias over counterparts. Greatly enhanced resolution does not deliver unambiguous improvement all

Language: Английский

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The Seasonal and Regional Transition to an Ice‐Free Arctic

Geophysical Research Letters, Journal Year: 2020, Volume and Issue: 48(1)

Published: Dec. 7, 2020

Abstract The Arctic sea ice cover is currently retreating and will continue its retreat in a warming world. However, the loss of neither regionally nor seasonally uniform. Here, we present first regional seasonal assessment future CMIP6 models under low (SSP126) high (SSP585) emission scenarios, thus spanning range change. We find that loss—at predominantly limited to summer season—will SSP585 take place all regions months. lost shelf seas regardless scenario, whereas ice‐free conditions winter before end this century only occur Barents Sea. transition found spread through Atlantic Pacific regions, with change starting Sea Chukchi Sea, respectively.

Language: Английский

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Arctic Warming Revealed by Multiple CMIP6 Models: Evaluation of Historical Simulations and Quantification of Future Projection Uncertainties

Journal of Climate, Journal Year: 2021, Volume and Issue: 34(12), P. 4871 - 4892

Published: March 19, 2021

Abstract The Arctic has experienced a warming rate higher than the global mean in past decades, but previous studies show that there are large uncertainties associated with future temperature projections. In this study, near-surface temperatures analyzed from 22 models participating phase 6 of Coupled Model Intercomparison Project (CMIP6). Compared ERA5 reanalysis, most CMIP6 underestimate observed during 1979–2014. largest cold biases found over Greenland Sea Barents Sea, and Kara Sea. Under SSP1-2.6, SSP2-4.5, SSP5-8.5 scenarios, multimodel ensemble exhibits significant is more twice global/Northern Hemisphere mean. spread contributor to overall uncertainty projections, which accounts for 55.4% total at start projections 2015 remains 32.9% end 2095. Internal variability 39.3% decreases 6.5% twenty-first century, while scenario rapidly increases 5.3% 60.7% period It model consistent bias oceanic regions models, connected excessive sea ice area caused by weak Atlantic poleward heat transport. These results suggest intermodel exist models’ simulation projection different responses ocean land greenhouse gas forcing. Future research needs pay attention characteristics mechanisms Ocean reduce spread.

Language: Английский

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Projections of Arctic sea ice conditions and shipping routes in the twenty-first century using CMIP6 forcing scenarios

Environmental Research Letters, Journal Year: 2020, Volume and Issue: 15(10), P. 104079 - 104079

Published: Aug. 26, 2020

Abstract The accelerated decline in Arctic sea ice recent decades suggests the possibility of future trans-Arctic shipping routes linking Atlantic and Pacific oceans, with significant implications for global economy. We present a projection conditions activities during 21st century based on 16 CMIP6 models calibrated to remove spatial biases. multimodel ensemble mean shows that is likely be ice-free September by 2076 2055 under SSP2-4.5 SSP5-8.5 scenarios, respectively, whereas extent >2 × 10 6 km 2 throughout SSP1-2.6 scenario. thins over time, leading reduction area an thickness >120 cm (i.e. threshold which inaccessible Type A vessels) 34–100% late (2086–2100) three scenarios. Given declines ice, most commonly traversed route along North West Passage tends migrate from southern northern century. optimum Northern Sea Route shifts northward Transpolar becoming available. Quantitatively, maritime accessibility vessels via increases ∼6.7, 4.2 2.1% 2021–2035 14.7, 29.2 67.5% 2086–2100 SSP1-2.6, respectively. season extends 5 ∼7.5 (9) months (SSP2-4.5) scenario becomes navigable all year round These findings may aid developing strategic planning governments providing advice industry.

Language: Английский

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A Spatial Evaluation of Arctic Sea Ice and Regional Limitations in CMIP6 Historical Simulations

Journal of Climate, Journal Year: 2021, Volume and Issue: 34(15), P. 6399 - 6420

Published: May 11, 2021

Abstract The Arctic sea ice response to a warming climate is assessed in subset of models participating phase 6 the Coupled Model Intercomparison Project (CMIP6), using several metrics comparison with satellite observations and results from Pan-Arctic Ice Ocean Modeling Assimilation System Regional Model. Our study examines historical representation extent, volume, thickness spatial analysis metrics, such as integrated edge error, Brier score, probability score. We find that CMIP6 multimodel mean captures annual cycle 1979–2014 trends remarkably well. However, individual experience wide range uncertainty distribution when compared against measurements reanalysis data. expose common regional model biases, which temporal analyses alone do not capture. identify large errors subregions, implying possible specific limitations or lack some key physical processes. postulate many them could be related oceanic forcing, especially marginal shelf seas, where seasonal changes are adequately simulated. therefore conclude an model’s ability represent observed/reanalysis still remains challenge. propose useful tools diagnose limitations, narrow down processes affecting them, guide future improvements critical projections change.

Language: Английский

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Changes in sea ice and future accessibility along the Arctic Northeast Passage

Global and Planetary Change, Journal Year: 2020, Volume and Issue: 195, P. 103319 - 103319

Published: Sept. 11, 2020

Language: Английский

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