Role of Mixed Layer Depth in the Location and Development of the Northeast Pacific Warm Blobs

Shi, Jian; Tang, Cong; Liu, Qinyu; Zhang, Yu; Yang, Hao; Li, Chun

doi:10.1029/2022gl098849

Cited by 13 publications

(10 citation statements)

References 29 publications

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“…Moreover, the MLD slightly changed during the warm blobs compared to the climatology (Figure 3). Consistently, previous studies found that parts of warm water masses existed below the mixed layer in summer due to the shoaling of the mixed layer (Chen et al, 2021b;Shi et al, 2022).…”

Section: Evolution Of the Northeast Pacific Warm Blobs In 2021 And 2022supporting

confidence: 89%

Characteristics and mechanisms of long-lasting 2021–2022 summer Northeast Pacific warm blobs

Chen

Shen

et al. 2023

Front. Mar. Sci.

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Warm blobs are persistently warmer-than-normal seawaters over the Northeast Pacific (NEP), which cause substantial impacts on marine ecosystems and climate. Recently, the warm blobs occurred consecutively in spring and summer of 2021 and 2022. The warm blob in 2021 was mostly located east of 155°W, while it shifted to west of 155°W in 2022. Based on a mixed-layer heat budget analysis, we find that atmospheric processes positively and dominantly contributed in May 2021 and July 2022. Specifically, less latent heat loss from the ocean caused by reducing background westerlies and evaporation intensified the 2021 warm blob, while more shortwave radiation heating due to decreased low clouds intensified the one in 2022. However, the positive contribution of the atmospheric processes cannot maintain a season due to their strong internal variability. The seasonal persistence of the warm blobs, instead, is owing to the offset between the atmospheric and oceanic processes. We highlight the importance of atmospheric processes in the evolution of the NEP warm blobs in spring and summer, which lacks sufficient investigation but can provide more potential predictability for the NEP warm blobs.

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Section: Evolution Of the Northeast Pacific Warm Blobs In 2021 And 2022supporting

confidence: 89%

Characteristics and mechanisms of long-lasting 2021–2022 summer Northeast Pacific warm blobs

Chen

Shen

et al. 2023

Front. Mar. Sci.

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“…The percentage change of Indian Ocean MLD is ∼5% in most regions in ssp126 and 10% in ssp585. Giving that a small percentage of OML shoaling is also efficient in amplifying the heating processes in the OML, thereby facilitating the surface layer warming and the occurrence of marine heatwaves (Amaya et al, 2021;Elzahaby et al, 2022;Shi et al, 2022). These changes would cause heat stress on marine ecosystems and potentially impact the monsoon climate (Saranya et al, 2022).…”

Section: Summary and Discussionmentioning

confidence: 99%

“…MLD changes significantly impact regional climate. For example, the Northeast Pacific OML has been observed to significantly shoal since 1980, which can exacerbate SST changes (Alexander and Penland, 1996;Alexander et al, 2000Alexander et al, , 2018 and, thus, increase the frequency of marine heatwaves (Amaya et al, 2021;Elzahaby et al, 2022;Shi et al, 2022). OML shoaling may also weaken sea surface cooling processes caused by tropical cyclones (Wu et al, 2005;Anilkumar et al, 2006;Lin and Wu, 2008;Mei et al, 2015;Lin et al, 2017).…”

mentioning

confidence: 99%

Indian Ocean mixed layer depth changes under global warming

Gao

Long²,

Shi³

et al. 2023

Front. Clim.

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The surface ocean mixed layer (OML) is critical for climate and biological systems. Changes in ocean mixed layer depth (MLD) of the Indian Ocean under global warming are examined utilizing outputs from 24 climate models in the Coupled Model Intercomparison Project phase 6 (CMIP6) models and the Community Earth System Model 1.0 with Community Atmosphere Model version 5 (CESM1–CAM5). The results show that the MLD generally decreases in low- and high-emissions Shared Socioeconomic Pathway (SSP) scenarios (ssp126 and ssp585). In ssp126 and ssp585, the multi-model ensemble-mean OML, respectively shoals about 5 and 10% over both the northern tropics and southern subtropics, with high model consistency. This robust OML shoaling appears in the 1980s and is closely associated with increased surface buoyancy forcing and weakened winds. In contrast, the OML in the south equatorial Indian Ocean slightly deepens and displays large intermodel differences in the sign and magnitude of the changes. The effects of direct CO2 increase and wind changes on OML changes are further quantified by CESM1–CAM5 partially coupled experiments. The results show that the increased surface net heat flux from direct CO2 increase dominates OML shoaling in the northern tropics. In the southern subtropics, the increased surface heat flux, reduced wind speed, and wind-driven divergence all facilitate the OML shoaling. In the south equatorial Indian Ocean, wind changes generally deepen the OML, consistent with the CMIP6 results. Moreover, the OML shoaling-related upper ocean stratification changes are contributed by both temperature and salinity changes in the northern tropics but dominated by temperature changes south of 10°S. These results highlight the regional differences in MLD changes and their forcing, which is important for understanding regional climate changes and corresponding changes in extreme events and biological systems under global warming.

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“…Marine heatwaves (MHWs) are prolonged periods of abnormally high sea surface temperatures (SSTs) that occur in specific regions, analogous to heatwaves on land but with significant impacts on the marine environment. Noteworthy MHW episodes have been observed in various regions in recent decades, such as the Mediterranean Sea in 2003 (Olita et al 2007, Garrabou et al 2009, the Tasman Sea during 2015-2016 (Oliver et al 2017), and the Northeast Pacific in 2014 and 2019 (Bond et al 2015, Di Lorenzo and Mantua 2016, Amaya et al 2020, Chen et al 2021a, 2021b, Shi et al 2022. MHWs have significant impacts on marine ecosystems and associated economic activities (Mills et al 2013, Pershing et al 2018.…”

Section: Introductionmentioning

confidence: 99%

Distinct anthropogenic greenhouse gas and aerosol induced marine heatwaves

Ren,

Liu,

Allen

et al. 2024

Environ. Res.: Climate

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In the era of escalating climate change, understanding human impacts on marine heatwaves (MHWs) becomes essential. This study harnesses climate model historical and single forcing simulations to delve into the individual roles of anthropogenic greenhouse gases and aerosols in shaping the characteristics of global MHWs over the past several decades. The results suggest that greenhouse gas variations lead to longer-lasting, more frequent, and intense MHWs. In contrast, anthropogenic aerosols markedly curbs the intensity and growth of MHWs. Further analysis of the sea surface temperature (SST) probability distribution reveals that anthropogenic greenhouse gases and aerosols have opposing effects on the tails of the SST probability distribution, causing the tails to expand and contract, respectively. Climate extremes such as MHWs are accordingly promoted and reduced. Our study underscores the significant impacts of anthropogenic greenhouse gases and aerosols on MHWs, which go far beyond the customary concept that these anthropogenic forcings modulate climate extremes by shifting global SST probabilities via modifying the mean-state SST.

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Role of Mixed Layer Depth in the Location and Development of the Northeast Pacific Warm Blobs

Cited by 13 publications

References 29 publications

Characteristics and mechanisms of long-lasting 2021–2022 summer Northeast Pacific warm blobs

Characteristics and mechanisms of long-lasting 2021–2022 summer Northeast Pacific warm blobs

Indian Ocean mixed layer depth changes under global warming

Distinct anthropogenic greenhouse gas and aerosol induced marine heatwaves

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