Ocean Science最新文献

{"title":"Joint observation–model mixed-layer heat and salt budgets in the eastern tropical Atlantic","authors":"R. D. Ngakala, G. Alory, C. Da-Allada, Olivia Estelle Kom, Julien, Jouanno, W. Rath, E. Baloïtcha","doi":"10.5194/os-19-535-2023","DOIUrl":"https://doi.org/10.5194/os-19-535-2023","url":null,"abstract":"Abstract. In this study, we use a joint observation–model approach\u0000to investigate the mixed-layer heat and salt annual mean as well as seasonal\u0000budgets in the eastern tropical Atlantic. The regional PREFCLIM (PREFACE Climatology)\u0000observational climatology provides the budget terms with a relatively low\u0000spatial and temporal resolution compared to the online NEMO (Nucleus for European Modeling\u0000of the Ocean; Madec, G., 2014) model, and this\u0000is later resampled as in PREFCLIM climatology. In addition, advection\u0000terms are recomputed offline from the model as PREFCLIM gridded advection\u0000computation. In the Senegal, Angola, and Benguela regions, the seasonal cycle of\u0000mixed-layer temperature is mainly governed by surface heat fluxes; however,\u0000it is essentially driven by vertical heat diffusion in the equatorial region.\u0000The seasonal cycle of mixed-layer salinity is largely controlled by\u0000freshwater flux in the Senegal and Benguela regions; however, it follows the\u0000variability of zonal and meridional salt advection in the equatorial and Angola\u0000regions, respectively. Our results show that the time-averaged spatial\u0000distribution of NEMO offline heat and salt advection terms compares much better\u0000to PREFCLIM horizontal advection terms than the online heat and salt advection\u0000terms. However, the seasonal cycle of horizontal advection in selected\u0000regions shows that NEMO offline terms do not always compare well with\u0000PREFCLIM, sometimes less than online terms. Despite this difference, these\u0000results suggest the important role of small-scale variability in mixed-layer\u0000heat and salt budgets.\u0000","PeriodicalId":19535,"journal":{"name":"Ocean Science","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2023-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90465785","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Global water level variability observed after the Hunga Tonga-Hunga Ha'apai volcanic tsunami of 2022","authors":"A. Devlin, D. Jay, S. Talke, Jiayi Pan","doi":"10.5194/os-19-517-2023","DOIUrl":"https://doi.org/10.5194/os-19-517-2023","url":null,"abstract":"Abstract. The eruption of the Hunga Tonga-Hunga Ha'apai volcano on 15 January 2022 provided a rare opportunity to understand global tsunami\u0000impacts of explosive volcanism and to evaluate future hazards, including\u0000dangers from “volcanic meteotsunamis” (VMTs) induced by the atmospheric\u0000shock waves that followed the eruption. The propagation of the volcanic and\u0000marine tsunamis was analyzed using globally distributed 1 min measurements\u0000of air pressure and water level (WL) (from both tide gauges and deep-water\u0000buoys). The marine tsunami propagated primarily throughout the Pacific,\u0000reaching nearly 2 m at some locations, though most Pacific locations\u0000recorded maximums lower than 1 m. However, the VMT resulting from the\u0000atmospheric shock wave arrived before the marine tsunami and propagated\u0000globally, producing water level perturbations in the Indian Ocean, the\u0000Mediterranean, and the Caribbean. The resulting water level response of many\u0000Pacific Rim gauges was amplified, likely related to wave interaction with\u0000bathymetry. The meteotsunami repeatedly boosted tsunami wave energy as it\u0000circled the planet several times. In some locations, the VMT was amplified\u0000by as much as 35-fold relative to the inverse barometer due to near-Proudman\u0000resonance and topographic effects. Thus, a meteotsunami from a larger\u0000eruption (such as the Krakatoa eruption of 1883) could yield atmospheric\u0000pressure changes of 10 to 30 mb, yielding a 3–10 m near-field tsunami that\u0000would occur in advance of (usually) larger marine tsunami waves, posing\u0000additional hazards to local populations. Present tsunami warning systems do\u0000not consider this threat.\u0000","PeriodicalId":19535,"journal":{"name":"Ocean Science","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2023-04-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82032049","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"An analogues-based forecasting system for Mediterranean marine-litter concentration","authors":"G. Jordà, J. Soto‐Navarro","doi":"10.5194/os-19-485-2023","DOIUrl":"https://doi.org/10.5194/os-19-485-2023","url":null,"abstract":"Abstract. In this work, we explore the performance of a statistical forecasting system\u0000for marine-litter concentration in the Mediterranean Sea. In particular, we\u0000assess the potential skills of a system based on the analogues method. The\u0000system uses a historical database of marine-litter concentration simulated\u0000by a high-resolution realistic model and is trained to identify\u0000meteorological situations in the past that are similar to the forecasted\u0000ones. Then, the corresponding marine-litter concentrations of the past\u0000analogue days are used to construct the marine-litter concentration\u0000forecast. Due to the scarcity of observations, the forecasting system has\u0000been validated against a synthetic reality (i.e., the outputs from a marine-litter-modeling system). Different approaches have been tested to refine\u0000the system, and the results show that using integral definitions for the\u0000similarity function, based on the history of the meteorological situation,\u0000improves the system performance. We also find that the system accuracy\u0000depends on the domain of application being better for larger regions. Also,\u0000the method performs well in capturing the spatial patterns but performs worse\u0000in capturing the temporal variability, especially the extreme values. Despite\u0000the inherent limitations of using a synthetic reality to validate the\u0000system, the results are promising, and the approach has potential to become a\u0000suitable cost-effective forecasting method for marine-litter concentration.\u0000","PeriodicalId":19535,"journal":{"name":"Ocean Science","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2023-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85579146","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Improving statistical projections of ocean dynamic sea-level change using pattern recognition techniques","authors":"Víctor Malagón-Santos, A. Slangen, T. Hermans, Sönke Dangendorf, M. Marcos, N. Maher","doi":"10.5194/os-19-499-2023","DOIUrl":"https://doi.org/10.5194/os-19-499-2023","url":null,"abstract":"Abstract. Regional emulation tools based on statistical relationships, such as pattern scaling, provide a computationally inexpensive way of projecting ocean\u0000dynamic sea-level change for a broad range of climate change scenarios. Such approaches usually require a careful selection of one or more predictor\u0000variables of climate change so that the statistical model is properly optimized. Even when appropriate predictors have been selected, spatiotemporal\u0000oscillations driven by internal climate variability can be a large source of statistical model error. Using pattern recognition techniques that\u0000exploit spatial covariance information can effectively reduce internal variability in simulations of ocean dynamic sea level, significantly reducing\u0000random errors in regional emulation tools. Here, we test two pattern recognition methods based on empirical orthogonal functions (EOFs), namely\u0000signal-to-noise maximizing EOF pattern filtering and low-frequency component analysis, for their ability to reduce errors in pattern scaling of\u0000ocean dynamic sea-level change. We use the Max Planck Institute Grand Ensemble (MPI-GE) as a test bed for both methods, as it is a type of\u0000initial-condition large ensemble designed for an optimal characterization of the externally forced response. We show that the two methods tested\u0000here more efficiently reduce errors than conventional approaches such as a simple ensemble average. For instance, filtering only two realizations by\u0000characterizing their common response to external forcing reduces the random error by almost 60 %, a reduction that is only achieved by averaging\u0000at least 12 realizations. We further investigate the applicability of both methods to single-realization modeling experiments, including four CMIP5\u0000simulations for comparison with previous regional emulation analyses. Pattern filtering leads to a varying degree of error reduction depending on\u0000the model and scenario, ranging from more than 20 % to about 70 % reduction in global-mean root mean squared error compared with unfiltered\u0000simulations. Our results highlight the relevance of pattern recognition methods as a tool to reduce errors in regional emulation tools of ocean\u0000dynamic sea-level change, especially when one or only a few realizations are available. Removing internal variability prior to tuning regional\u0000emulation tools can optimize the performance of the statistical model, leading to substantial differences in emulated dynamic sea level compared to\u0000unfiltered simulations.\u0000","PeriodicalId":19535,"journal":{"name":"Ocean Science","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2023-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84277999","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Multiple mechanisms for chlorophyll a concentration variations in coastal upwelling regions: a case study east of Hainan Island in the South China Sea","authors":"Junyi Li, Min Li, Chao Wang, Q. Zheng, Ying Xu, Tianyu Zhang, L. Xie","doi":"10.5194/os-19-469-2023","DOIUrl":"https://doi.org/10.5194/os-19-469-2023","url":null,"abstract":"Abstract. Using satellite observations from 2003 to 2020 and cruise\u0000observations from 2019 and 2021, this study reveals an unexpected minor role\u0000of upwelling in seasonal and interannual variations in chlorophyll a (Chl a)\u0000concentrations in the coastal upwelling region east of Hainan Island (UEH)\u0000in the northwestern South China Sea (NWSCS). The results show strong\u0000seasonal and interannual variability in the Chl a concentration in the core\u0000upwelling area of the UEH. Different from the strongest upwelling in summer,\u0000the Chl a concentration in the UEH area reaches a maximum of 1.18 mg m−3\u0000in autumn and winter, with a minimum value of 0.74 mg m−3 in summer.\u0000The Chl a concentration in summer increases to as high as 1.0 mg m−3 with\u0000weak upwelling, whereas the maximum Chl a concentration in October increases\u0000to 2.5 mg m−3. The analysis of environmental factors shows that,\u0000compared to the limited effects of upwelling, the along-shelf coastal\u0000current from the northern shelf and the increased precipitation are\u0000crucially important to the Chl a concentration variation in the study area.\u0000These results provide new insights for predicting marine productivity in\u0000upwelling areas, i.e., multiple mechanisms, especially horizontal advection,\u0000should be considered in addition to the upwelling process.\u0000","PeriodicalId":19535,"journal":{"name":"Ocean Science","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2023-04-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81678959","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Current observed global mean sea level rise and acceleration estimated from satellite altimetry and the associated measurement uncertainty","authors":"A. Guerou, B. Meyssignac, P. Prandi, M. Ablain, A. Ribes, F. Bignalet-Cazalet","doi":"10.5194/os-19-431-2023","DOIUrl":"https://doi.org/10.5194/os-19-431-2023","url":null,"abstract":"Abstract. We present the latest release of the global mean sea level (GMSL) record produced by the French space agency Centre National d’Etudes Spatiales (CNES) and distributed on the AVISO+ website. This dataset is based on reprocessed along-track data, so-called L2P 21, of the reference missions TOPEX/Poseidon (TP) and Jason-1, Jason-2 and Jason-3. The L2P 21 CNES/AVISO+ GMSL record covers the period January 1993 to December 2021 and is now delivered with an estimate of its measurement uncertainties following the method presented in Ablain et al. (2019). Based on the latest calibration (Cal) and validation (Val) knowledge, we updated the uncertainty budget of the reference altimetry mission measurements and demonstrate that the CNES/AVISO+ GMSL record now achieves stability of performances of ± 0.3 mm yr−1 at the 90 % confidence level (C.L.) for its trend and ±0.05 mm yr−2 (90 % C.L.) for its acceleration over the 29 years of the altimetry record. Thanks to an analysis of the relative contribution of each measurement uncertainty budget contributor, i.e. the altimeter, the radiometer, the orbit determination and the geophysical corrections, we identified the current limiting factors to the GMSL monitoring stability and accuracy. We find that the radiometer wet troposphere correction (WTC) and the high-frequency errors with timescales shorter than 1 year are the major contributors to the GMSL measurement uncertainty over periods of 10 years (30 %–70 %), for both the trend and acceleration estimations. For longer periods of 20 years, the TP data quality is still a limitation, but more interestingly, the International Terrestrial Reference Frame (ITRF) realization uncertainties becomes dominant over all the other sources of uncertainty. Such a finding challenges the altimetry observing system as it is designed today and highlights clear topics of research to be explored in the future to help the altimetry community to improve the GMSL measurement accuracy and stability.\u0000","PeriodicalId":19535,"journal":{"name":"Ocean Science","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2023-04-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84843022","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Intraseasonal variability of the South Vietnam upwelling, South China Sea: influence of atmospheric forcing and ocean intrinsic variability","authors":"M. Herrmann, Thai To Duy, C. Estournel","doi":"10.5194/os-19-453-2023","DOIUrl":"https://doi.org/10.5194/os-19-453-2023","url":null,"abstract":"Abstract. The South Vietnam upwelling (SVU) develops off the Vietnamese coast (South\u0000China Sea, SCS) during the southwest summer monsoon over four main areas: the\u0000northern coastal upwelling (NCU), the southern coastal upwelling (SCU), the\u0000offshore upwelling (OFU) and the shelf off the Mekong River mouth (MKU). An\u0000ensemble of 10 simulations with perturbed initial conditions were run with\u0000the fine-resolution SYMPHONIE model (1 km inshore) to investigate the daily\u0000to intraseasonal variability of the SVU and the influence of the ocean\u0000intrinsic variability (OIV) during the strong SVU of summer 2018. The intraseasonal variability is similar for the SCU, MKU and OFU, driven to the\u0000first order by the wind variability. The MKU and SCU are induced by stable ocean\u0000dynamics (the northeastward then eastward boundary current) and have very\u0000little chaotic variability. The OIV has a stronger influence on OFU. In\u0000July, OFU mainly develops along the northern flank of the eastward jet. The\u0000influence of the OIV is strongest and related to the chaotic variability of the\u0000meridional position of the jet. In August, this position is stable and OFU\u0000develops mainly in the area of positive wind curl and cyclonic eddies north\u0000of the jet. The influence of the OIV, weaker than in July, is related to the\u0000organization of this mesoscale circulation. The NCU shows a behavior different\u0000from that observed in the other areas. In the heart of summer, a large-scale\u0000circulation formed by the eastward jet and eddy dipole is well established\u0000with an alongshore current preventing the NCU development. In early and late\u0000summer, this circulation is weaker, allowing a mesoscale circulation of\u0000strongly chaotic nature to develop in the NCU area. During those periods,\u0000the OIV influence on the NCU is very strong and related to the organization of\u0000this mesoscale circulation: the NCU is favored (annihilated) by\u0000offshore-oriented (alongshore) structures.\u0000","PeriodicalId":19535,"journal":{"name":"Ocean Science","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2023-04-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76822481","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A simple diagnostic based on sea surface height with an application to central Pacific ENSO","authors":"Jufen Lai, R. Greatbatch, M. Claus","doi":"10.5194/os-19-421-2023","DOIUrl":"https://doi.org/10.5194/os-19-421-2023","url":null,"abstract":"Abstract. We use output from a freely running NEMO model simulation for the equatorial Pacific to investigate the utility of linearly removing the local influence of vertical displacements of the thermocline from variations in sea surface height. We show that the resulting time series of residual sea surface height, denoted ηnlti, measures variations in near-surface heat content that are independent of the local vertical displacement of the thermocline and can arise from horizontal advection, surface heat flux, and diapycnal mixing processes. We find that the variance of ηnlti and its correlation with sea surface temperature are focused on the Niño4 region. Furthermore, ηnlti averaged over the Niño4 region is highly correlated with indices of central Pacific El Niño–Southern Oscillation (CP ENSO), and its variance in 21-year running windows shows a strong upward trend over the past 50 years, corresponding to the emergence of CP ENSO following the 1976/77 climate shift. We show that ηnlti can be estimated from observations, using satellite altimeter data and a linear multi-mode model. The time series of ηnlti, especially when estimated using the linear model, show pronounced westward propagation in the western equatorial Pacific, arguing for an important role for zonal advective feedback in the dynamics of CP ENSO, in particular for cold events. We also present evidence that the role of the thermocline displacement in influencing sea surface height increased strongly after 2000 in the eastern part of the Niño4 region, at a time when CP ENSO was particularly active. Finally, the diagnostic is easy to compute and can be easily applied to mooring data or coupled climate models.\u0000","PeriodicalId":19535,"journal":{"name":"Ocean Science","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2023-04-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80836088","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The sensitivity of primary productivity in Disko Bay, a coastal Arctic ecosystem, to changes in freshwater discharge and sea ice cover","authors":"E. Møller, A. Christensen, J. Larsen, K. Mankoff, M. Ribergaard, Mikael K. Sejr, P. Wallhead, M. Maar","doi":"10.5194/os-19-403-2023","DOIUrl":"https://doi.org/10.5194/os-19-403-2023","url":null,"abstract":"Abstract. The Greenland ice sheet is melting, and the rate of ice\u0000loss has increased 6-fold since the 1980s. At the same time, the Arctic sea\u0000ice extent is decreasing. Meltwater runoff and sea ice reduction both\u0000influence light and nutrient availability in the coastal ocean, with\u0000implications for the timing, distribution, and magnitude of phytoplankton\u0000production. However, the integrated effect of both glacial and sea ice melt\u0000is highly variable in time and space, making it challenging to quantify. In\u0000this study, we evaluate the relative importance of these processes for the\u0000primary productivity of Disko Bay, west Greenland, one of the most important\u0000areas for biodiversity and fisheries around Greenland. We use a\u0000high-resolution 3D coupled hydrodynamic–biogeochemical model for 2004–2018 validated against in situ observations and remote sensing products. The model-estimated net primary production (NPP) varied between 90–147 gC m−2 yr−1 during 2004–2018, a period with variable freshwater discharges\u0000and sea ice cover. NPP correlated negatively with sea ice cover and\u0000positively with freshwater discharge. Freshwater discharge had a strong\u0000local effect within ∼ 25 km of the source-sustaining productive hot\u0000spots during summer. When considering the annual NPP at bay scale, sea ice\u0000cover was the most important controlling factor. In scenarios with no sea\u0000ice in spring, the model predicted a ∼ 30 % increase in annual\u0000production compared to a situation with high sea ice cover. Our study\u0000indicates that decreasing ice cover and more freshwater discharge can work\u0000synergistically and will likely increase primary productivity of the coastal\u0000ocean around Greenland.\u0000","PeriodicalId":19535,"journal":{"name":"Ocean Science","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2023-04-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77742928","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Water mass transformation variability in the Weddell Sea in ocean reanalyses","authors":"Shanice Bailey, S. Jones, R. Abernathey, A. Gordon, X. Yuan","doi":"10.5194/os-19-381-2023","DOIUrl":"https://doi.org/10.5194/os-19-381-2023","url":null,"abstract":"Abstract. This study investigates the variability of water mass transformation (WMT) within the Weddell Gyre (WG).\u0000The WG serves as a pivotal site for the Meridional Overturning Circulation (MOC) and ocean ventilation because it is the primary origin of the largest volume of water mass in the global ocean: Antarctic Bottom Water (AABW).\u0000Recent mooring data suggest substantial seasonal and interannual variability of AABW properties exiting the WG, and studies have linked the variability to the large-scale climate forcings affecting wind stress in the WG region.\u0000However, the specific thermodynamic mechanisms that link variability in surface forcings to variability in water mass transformations and AABW export remain unclear.\u0000This study explores how current state-of-the-art data-assimilating ocean reanalyses can help fill the gaps in our understanding of the thermodynamic drivers of AABW variability in the WG via WMT volume budgets derived from Walin's classic WMT framework. The three ocean reanalyses used are the following: Estimating the Circulation and Climate of the Ocean state estimate (ECCOv4), Southern Ocean State Estimate (SOSE) and Simple Ocean Data Assimilation (SODA).\u0000From the model outputs, we diagnose a closed form of the water mass budget for AABW that explicitly accounts for transport across the WG boundary, surface forcing, interior mixing and numerical mixing.\u0000We examine the annual mean climatology of the WMT budget terms, the seasonal climatology and finally the interannual variability. Our finding suggests that the relatively coarse resolution of these models did not realistically capture AABW formation, export and variability.\u0000In ECCO and SOSE, we see strong interannual variability in AABW volume budget.\u0000In SOSE, we find an accelerating loss of AABW during 2005–2010, driven largely by interior mixing and changes in surface salt fluxes.\u0000ECCO shows a similar trend during a 4-year time period starting in late 2007 but also reveals such trends to be part of interannual variability over a much longer time period.\u0000Overall, ECCO provides the most useful time series for understanding the processes and mechanisms that drive WMT and export variability in the WG.\u0000SODA, in contrast, displays unphysically large variability in AABW volume, which we attribute to its data assimilation scheme.\u0000We also examine correlations between the WMT budgets and large-scale climate indices, including El Niño–Southern Oscillation (ENSO) and Southern Annular Mode (SAM), and find no strong relationships.\u0000","PeriodicalId":19535,"journal":{"name":"Ocean Science","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2023-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86881468","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}