The unprecedented coupled ocean-atmosphere summer heatwave in the New Zealand region 2017/18: drivers, mechanisms and impacts

Salinger, M. J.; Renwick, James; Behrens, Erik; Mullan, A. Brett; Diamond, Howard J.; Sirguey, Pascal; Smith, Robert G.; Trought, Michael C. T.; Alexander, Lisa V.; Cullen, Nicolas J.; Fitzharris, B. B.; Hepburn, Christopher D.; Parker, Amber; Sutton, Philip

doi:10.1088/1748-9326/ab012a

Cited by 122 publications

(120 citation statements)

References 54 publications

Supporting

Mentioning

115

Contrasting

Order By: Relevance

“…There are over 3,000 glaciers that exceed 0.01 km 2 , with the total ice volume estimated to be 37 km 3 water equivalent (w.e. ; Salinger et al, ). The mean elevation of glaciers in the Southern Alps is relatively low (1,904 ± 220 m a.s.l.)…”

Section: Methodsmentioning

confidence: 99%

The Influence of Weather Systems in Controlling Mass Balance in the Southern Alps of New Zealand

et al. 2019

Self Cite

View full text Add to dashboard Cite

The recent advance of some fast‐responding glaciers in New Zealand demonstrates that regional variability in atmospheric circulation can counteract the effects of global warming. Until recently, a key challenge in quantifying how weather systems influence glaciers has been the lack of observational data from high‐elevation sites in the Southern Alps. Using high‐quality meteorological and glaciological observations from Brewster Glacier over four summers and two winters, a physically based mass balance model is used to resolve daily ablation and solid precipitation. Composite analysis confirms ablation is largely controlled by changes in meridional airflow, with high ablation associated with north to northwest airflow, while low ablation is associated with south to southwest airflow. The largest snowfall events in the cool season also occur during northwesterly airflow, highlighting the importance of seasonality (i.e., whether an event occurs in the ablation or accumulation period) for mass balance. Application of a synoptic weather typing approach commonly used for the New Zealand region, known broadly as Kidson weather types, revealed that three established regimes (trough, zonal, and blocking) are less effective in resolving variability in ablation and snowfall than a simple procedure that groups weather types using geostrophic flow direction. The frequency of four weather types can explain approximately 40% of the variance in mass balance over a 42‐year period. This highlights that future regional variability or trends in large‐scale circulation and their seasonality, superimposed on background warming, will be important in shaping glacier mass balance in the coming decades.

show abstract

Section: Methodsmentioning

confidence: 99%

The Influence of Weather Systems in Controlling Mass Balance in the Southern Alps of New Zealand

et al. 2019

Self Cite

View full text Add to dashboard Cite

show abstract

“…This configuration uses 75 vertical z-levels, with layer thickness varying between 1 m at the surface and 200 m, and with a maximum depth of 6200 m. Most (55) of the vertical layers are in the upper 2000 m. In addition, a partial cell approach has been used to improve nearbottom flows (Barnier et al, 2006). More specific model details and description of model performance of this configuration can be found in Storkey et al (2018); Kuhlbrodt et al (2018), and Salinger et al (2019).…”

Section: Model Descriptionmentioning

confidence: 99%

“…Atmospheric forcing fields from JRA-55-DO (Tsujino et al, 2018) have been used to complete a 60year model hindcast from 1958 to 2018. This hindcast has already been used to characterize the summer 2017/18 MHW in the Tasman Sea (Salinger et al, 2019). The modeled SSTs have been saved as daily averages, while all other oceanic fields are available as monthly means.…”

Section: Model Descriptionmentioning

confidence: 99%

“…This link encourages the exploitation of ocean models to predict heatwaves based on oceanic states, such as heat content and currents. The predictive skill of ocean heat content and currents is higher than that of atmospheric variability, such as blocking high-pressure systems (which contribute to MHWs and caused the recent summer 2017/18 MHW (Salinger et al, 2019)). This is because ocean heat content variability is more persistent in time than weather patterns.…”

Section: Introductionmentioning

confidence: 97%

See 1 more Smart Citation

Meridional Oceanic Heat Transport Influences Marine Heatwaves in the Tasman Sea on Interannual to Decadal Timescales

2019

Self Cite

View full text Add to dashboard Cite

Marine heatwaves (MHWs) pose an increasing threat to the ocean's wellbeing as global warming progresses. Forecasting MHWs is challenging due to the various factors that affect their occurrence, including large variability in the atmospheric state. In this study we demonstrate a causal link between ocean heat content and the area and intensity of MHWs in the Tasman Sea on interannual to decadal time scales. Ocean heat content variations are more persistent than 'weather-related' atmospheric drivers (e.g., blocking high pressure systems) for MHWs and thus provide better predictive skill on timescales longer than weeks. Using data from a forced global ocean sea-ice model, we show that ocean heat content fluctuations in the Tasman Sea are predominantly controlled by oceanic meridional heat transport from the subtropics, which in turn is mainly characterized by the interplay of the East Australian Current and the Tasman Front. Variability in these currents is impacted by wind stress curl anomalies north of this region, following Sverdrup's and Godfrey's 'Island Rule' theories. Data from models and observations show that periods with positive upper (2000 m) ocean heat content anomalies or rapid increases in ocean heat content are characterized by more frequent, larger, longer and more intense MHWs on interannual to decadal timescales. Thus, the oceanic heat content in the Tasman Sea acts as a preconditioner and has a prolonged predictive skill compared to the atmospheric state (e.g., surface heat fluxes), making ocean heat content a useful indicator and measure of the likelihood of MHWs.

show abstract

“…The occurrence of sustained temperature extremes leads to marine heatwave (MHW) conditions in the ocean (Hobday et al, ). MHW conditions are caused by local processes that directly affect ocean temperature, such as extreme air‐sea heat fluxes and changes in the ocean circulation (Behrens et al, ; Holbrook et al, ; Salinger et al, ), which may ultimately be caused by large‐scale climate forcing via teleconnection processes (Holbrook et al, ).…”

Section: Introductionmentioning

confidence: 99%

Sensitivity of Marine Heatwave Metrics to Ocean Model Resolution

Pilo

Holbrook

Kiss

et al. 2019

Geophysical Research Letters

View full text Add to dashboard Cite

Sustained extreme temperature events in the ocean, referred to as marine heatwaves (MHWs), generate substantial ecological, social, and economic impacts. Ocean models provide insights to the drivers, persistence, and dissipation of MHWs. However, the sensitivity of MHW metrics to ocean model resolution is unknown. Here, we analyze global MHW metrics in three configurations of a global ocean-sea ice model at coarse (1 • ), eddy-permitting (0.25 • ), and eddy-rich (0.1 • ) resolutions. We show that all configurations qualitatively represent broad-scale global patterns of MHWs. These simulated MHWs are, however, weaker, longer-lasting, and less frequent than in observations. The 0.1 • configuration, despite local biases, performs best both globally and regionally. Based on these results, model projections of future MHW metrics using coarse-resolution models are expected to be biased toward weaker and less frequent MHWs, when compared with results using an eddy-rich model. Plain Language SummaryMarine heatwaves (MHWs) are persistent extreme temperatures in the ocean. They have a negative impact on marine life, fisheries, and tourism, and are becoming more frequent and more intense. One way to understand how MHWs form, intensify, and decay is by analyzing results from computer simulations of the ocean. However, these simulations are a simplification of reality, and depending on how they are designed they represent different aspects of the ocean circulation. It is still unknown how much the resolution of an ocean simulation matters when representing MHWs. In this work, we compare the performance of three ocean simulations-with low, medium, and high resolutions-when representing MHWs. We find that, regardless of their resolution, all simulations have weaker, longer, and less-frequent MHWs, when compared with the real world. Despite these differences, we find that simulations with medium and high-resolutions realistically represent global spatial patterns of MHWs. However, the ocean simulation with high resolution is preferable when studying regional patterns of MHWs. These results show how simulated MHWs differ from the real world, helping us to improve ocean simulations to be more realistic. In addition, we now better understand how computer simulations of future oceans, under climate change conditions, represent these extreme events. Key Points:• Marine heatwaves are weaker, longer-lasting, and less frequent in models than in observations • The higher the model resolution, the less biased the marine heatwave metrics • Eddy-permitting models can be used for global marine heatwave analyses, but eddy-rich models are optimal for regional analyses

show abstract

The unprecedented coupled ocean-atmosphere summer heatwave in the New Zealand region 2017/18: drivers, mechanisms and impacts

Cited by 122 publications

References 54 publications

The Influence of Weather Systems in Controlling Mass Balance in the Southern Alps of New Zealand

The Influence of Weather Systems in Controlling Mass Balance in the Southern Alps of New Zealand

Meridional Oceanic Heat Transport Influences Marine Heatwaves in the Tasman Sea on Interannual to Decadal Timescales

Sensitivity of Marine Heatwave Metrics to Ocean Model Resolution

Contact Info

Product

Resources

About