Using kinetic energy measurements from altimetry to detect shifts in the positions of fronts in the Southern Ocean

Chambers, D. P.

doi:10.5194/os-14-105-2018

Cited by 19 publications

(15 citation statements)

References 33 publications

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“…While the higher values in OFAM3 may suggest an overestimated variability in these eddy-rich regions, we believe that the actual biases are smaller than indicated here. Previous studies suggest systematic negative biases of SST variability represented in gridded observation-based SST analysis products 13,23,24 . Specifically, these studies report a systematic underestimate of eddy kinetic energy in the Southern Ocean by as much as 60-70% when calculated from gridded altimetry data because of interpolation, which smooths variability, compared to along-track data.…”

Section: Resultsmentioning

confidence: 97%

Insights into projected changes in marine heatwaves from a high-resolution ocean circulation model

et al. 2020

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Global climate models project the intensification of marine heatwaves in coming decades due to global warming. However, the spatial resolution of these models is inadequate to resolve mesoscale processes that dominate variability in boundary current regions where societal and economic impacts of marine heatwaves are substantial. Here we compare the historical and projected changes in marine heatwaves in a 0.1°ocean model with 23 coarser-resolution climate models. Western boundary currents are the regions where the models disagree the most with observations and among themselves in simulating marine heatwaves of the past and the future. The lack of eddy-driven variability in the coarse-resolution models results in less intense marine heatwaves over the historical period and greater intensification in the coming decades. Although the projected changes agree well at the global scale, the greater spatial details around western boundary currents provided by the high-resolution model may be valuable for effective adaptation planning.

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Section: Resultsmentioning

confidence: 97%

Insights into projected changes in marine heatwaves from a high-resolution ocean circulation model

et al. 2020

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“…Accurately representing the horizontal circulation of the North Atlantic is a persistent challenge for ocean modellers. In particular, models commonly fail to simulate a Gulf Stream that separates from the North American coast at Cape Hatteras (35 • N, 75 • W) and a North Atlantic Current that flows north along the east side of the Grand Banks from 40 to 51 • N (Rossby, 1996;Chassignet and Marshall, 2008). In ACCESS-OM2 and ACCESS-OM2-025, the Gulf Stream flow is too weak and overshoots the separation latitude by about 4 • relative to observations (Fig.…”

Section: Atlantic Oceanmentioning

confidence: 99%

ACCESS-OM2 v1.0: a global ocean–sea ice model at three resolutions

Kiss

Hogg

Hannah³

et al. 2020

Geosci. Model Dev.

117

136

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Abstract. We introduce ACCESS-OM2, a new version of the ocean–sea ice model of the Australian Community Climate and Earth System Simulator. ACCESS-OM2 is driven by a prescribed atmosphere (JRA55-do) but has been designed to form the ocean–sea ice component of the fully coupled (atmosphere–land–ocean–sea ice) ACCESS-CM2 model. Importantly, the model is available at three different horizontal resolutions: a coarse resolution (nominally 1∘ horizontal grid spacing), an eddy-permitting resolution (nominally 0.25∘), and an eddy-rich resolution (0.1∘ with 75 vertical levels); the eddy-rich model is designed to be incorporated into the Bluelink operational ocean prediction and reanalysis system. The different resolutions have been developed simultaneously, both to allow for testing at lower resolutions and to permit comparison across resolutions. In this paper, the model is introduced and the individual components are documented. The model performance is evaluated across the three different resolutions, highlighting the relative advantages and disadvantages of running ocean–sea ice models at higher resolution. We find that higher resolution is an advantage in resolving flow through small straits, the structure of western boundary currents, and the abyssal overturning cell but that there is scope for improvements in sub-grid-scale parameterizations at the highest resolution.

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“…Frontal regions are also sites of pronounced exchange between the deep and surface ocean: both the upwelling (rising) of deeper waters and subduction (descending) of surface waters to the abyssal ocean is enhanced in frontal zones 16,17 . Additionally, fronts can catalyse the generation of meso-scale "eddies" 18,19 and sub-meso scale "filaments" which are able to bring nutrients from the deep ocean to the surface where they can be consumed by biological components of the system 20,21 . These details are shown schematically in Fig.…”

Section: The Physical Oceanography Of Southern Ocean Frontsmentioning

confidence: 99%

“…The primary assumption of these analyses is that if a contour SSH shifts, then its associated fronts will shift with it. However, more recent work employing "local" definitions (see section 2) has shown that this is not necessarily true, with numerous studies failing to detect any long-term trend in the position of the ACC fronts 19,25,41,42,94,95 , although there is some evidence of localized frontal movements and changes in frontal intensity 40,41 . Additionally, some recent studies provide only limited evidence of a systematic response of fronts to changing atmospheric forcing 25,35,42 .…”

Section: Observed and Projected Changes In Southern Ocean Frontsmentioning

confidence: 99%

Defining Southern Ocean fronts and their influence on biological and physical processes in a changing climate

et al. 2020

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The Southern Ocean is a critical component of the global climate system and an important ecoregion that contains a diverse range of interdependent flora and fauna. The Southern Ocean also hosts numerous fronts: sharp boundaries between waters with different characteristics. As they strongly influence exchanges between the ocean, atmosphere and cryosphere, fronts are of fundamental importance to the climate system. However, rapid advances in physical oceanography over the past 20 years have challenged previous definitions of fronts and their response to anthropogenic climate change. Here, we review the implications of this recent research for the study of climate, ecology and biology in the Southern Ocean. We include a frontal definition "user guide" to clarify the current debate and facilitate future research. The Southern Ocean, generally defined as the global ocean south of about 35 • S that encircles the Antarctic continent, is unique oceanographic environment due to the lack of continental barriers blocking its flow and the strong winds that blow over its surface 1. At large scales, the Southern Ocean is characterised by both the intense eastward flowing Antarctic Circumpolar Current (ACC), one of the most powerful current systems on Earth, and strongly tilted isopycnals (lines of constant density) that shallow to the south. Observations of the Southern Ocean dating back to the Discovery expedition in the 1920s revealed that the transition from warmer subtropical waters to colder Antarctic waters does not occur smoothly, but is concentrated into a series of sharp transition zones, aligned generally east-west, that have come to be called fronts 2. Further observations revealed that salinity, oxygen, nutrients and various other tracers showed similar behaviour, and that between the fronts, water properties are relatively homogeneous. As such, fronts delimit the boundaries between different water-masses with distinct environmental characteristics 3. These fronts also tend to coincide with the location of narrow yet very intense currents known as "jets" 4 that dominate the ACC's flow 5. The Southern Ocean is divided by fronts into a number of distinct biophysical zones, and hence a number of distinct habitats, which in turn support distinct biota 6, 7. Numerous studies have shown that seabirds and marine mammals tend to congregate and forage in and around fronts 7. As the Earth continues to warm due to anthropogenic climate change, it is vital that we understand how these fronts and jets will respond to changes in the global climate system, and what influence that might have on associated ecosystems 8-10. Due to its remoteness and harsh climate, undertaking field studies in the Southern Ocean is both difficult and expensive. As a result, the Southern Ocean is amongst the most data-sparse of all major ocean basins, which has hindered progress on key questions regarding its dynamics and ecological communities 10. In recent decades however, a deluge of new data from satellites and Argo profiling floats, along with e...

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Using kinetic energy measurements from altimetry to detect shifts in the positions of fronts in the Southern Ocean

Cited by 19 publications

References 33 publications

Insights into projected changes in marine heatwaves from a high-resolution ocean circulation model

Insights into projected changes in marine heatwaves from a high-resolution ocean circulation model

ACCESS-OM2 v1.0: a global ocean–sea ice model at three resolutions

Defining Southern Ocean fronts and their influence on biological and physical processes in a changing climate

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