The East Australian Current, upwellings and downwellings off eastern-most Australia in summer

Cresswell, GR; Peterson, JL; Pender, Lindsay

doi:10.1071/mf16051

Cited by 11 publications

(5 citation statements)

References 17 publications

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“…The opposite was the case for non-reference-mission ATG series given their location well on the shelf and closer to TGs (owing to their different ground-track spacing). The FORT gauge provides an interesting example given its location adjacent to a complex western boundary current system and narrow shelf widths (~25 km, Cresswell et al 2017). VLMs for this gauge computed using only on-and off-shelf CPs revealed residual difference of ~0.5 mm/year.…”

Section: Discussionmentioning

confidence: 99%

Vertical deformation and residual altimeter systematic errors around continental Australia inferred from a Kalman-based approach

Rezvani

Watson²,

King³

2022

J Geod

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We further developed a space–time Kalman approach to investigate time-fixed and time-variable signals in vertical land motion (VLM) and residual altimeter systematic errors around the Australian coast, through combining multi-mission absolute sea-level (ASL), relative sea-level from tide gauges (TGs) and Global Positioning System (GPS) height time series. Our results confirmed coastal subsidence in broad agreement with GPS velocities and unexplained by glacial isostatic adjustment alone. VLM determined at individual TGs differs from spatially interpolated GPS velocities by up to ~ 1.5 mm/year, yielding a ~ 40% reduction in RMSE of geographic ASL variability at TGs around Australia. Our mission-specific altimeter error estimates are small but significant (typically within ~ ± 0.5–1.0 mm/year), with negligible effect on the average ASL rate. Our circum-Australia ASL rate is higher than previous results, suggesting an acceleration in the ~ 27-year time series. Analysis of the time-variability of altimeter errors confirmed stability for most missions except for Jason-2 with an anomaly reaching ~ 2.8 mm/year in the first ~ 3.5 years of operation, supported by analysis from the Bass Strait altimeter validation facility. Data predominantly from the reference missions and located well off narrow shelf regions was shown to bias results by as much as ~ 0.5 mm/year and highlights that residual oceanographic signals remain a fundamental limitation. Incorporating non-reference-mission measurements well on the shelf helped to mitigate this effect. Comparing stacked nonlinear VLM estimates and altimeter systematic errors with the El Niño-Southern Oscillation shows weak correlation and suggests our approach improves the ability to explore nonlinear localized signals and is suitable for other regional- and global-scale studies.

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Section: Discussionmentioning

confidence: 99%

Vertical deformation and residual altimeter systematic errors around continental Australia inferred from a Kalman-based approach

Rezvani

Watson²,

King³

2022

J Geod

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“…China Wall, Henderson’s Reef) and areas with unconsolidated rocky substrates 31 . Further, most of the rocky reef south of Moreton Island where the continental shelf is very narrow (only ~ 25 km wide) 53 , would have emersed, limiting habitat availability and restricting the distributions of rocky reef marine organisms along much of the NSW coast.…”

Section: Discussionmentioning

confidence: 99%

Climate change threatens unique evolutionary diversity in Australian kelp refugia

Nimbs

Wernberg

Davis

et al. 2023

Sci Rep

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Climate change has driven contemporary decline and loss of kelp forests globally with an accompanying loss of their ecological and economic values. Kelp populations at equatorward-range edges are particularly vulnerable to climate change as these locations are undergoing warming at or beyond thermal tolerance thresholds. Concerningly, these range-edge populations may contain unique adaptive or evolutionary genetic diversity that is vulnerable to warming. We explore haplotype diversity by generating a Templeton–Crandall–Sing (TCS) network analysis of 119 Cytochrome C Oxidase (COI) sequences among four major population groupings for extant and putatively extinct populations only known from herbarium specimens of the dominant Laminarian kelp Ecklonia radiata in the south-western Pacific, a region warming at 2–4 times the global average. Six haplotypes occurred across the region with one being widespread across most populations. Three unique haplotypes were found in a deep-water range-edge population off Moreton Island, Queensland, which likely represents both a contemporary and historic refuge during periods of climatic change. Hindcasting E. radiata cover estimates using extant data, we reveal that this region likely supported the highest kelp cover in eastern Australia during the last glacial maximum. The equatorward range edge, deep-water kelp populations off Moreton Island represent a genetically diverse evolutionary refuge that is currently threatened by warming and requires prompt ex-situ conservation measures.

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“…To mitigate the influence of dynamic changes in regions such as the EAC, and potential effects of gradients across the continental shelf, we have selected altimetry CPs to be within 20-120 km of the Australian coast. Given the average width of the shelf along the east coast is ~25 km (Cresswell et al, 2017), we note that ~15.2%, 6.7% and 6.2% of our ATG observations were formed using CPs located off the shelf, pertaining to the Jason-series, Envisat-series and Sentinel-3A constellations, respectively. Unsurprisingly, our analysis shows increased ATG noise as the CP distances from the coast or TGs increased, with the highest magnitudes often associated with the off-shelf CPs where oceanic signals are likely to be substantially different from at the TG locations .…”

Section: Discussionmentioning

confidence: 99%

Vertical Deformation and Residual Altimeter Systematic Errors around Continental Australia Inferred from a Kalman-Based Approach

Rezvani¹,

Watson²,

King³

2021

Preprint

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We further developed a space-time Kalman approach to estimate time-variable signals in residual altimeter systematic errors and vertical land motion (VLM) around the Australian coast since the 1990s, through combining multi-mission absolute sea-level (ASL), relative sea-level (RSL) from tide gauges (TGs) and GPS heights records. Our results confirmed continent-wide subsidence and TG-specific VLMs yielding a ~40% reduction in RMSE of geographical ASL variability, compared with rates determined using spatially interpolated GPS velocities that fail to capture localized trends by up to ~1.5 mm/yr. Stacked time series of non-linear deformation at TGs and nearby GPS showed some correlation, suggesting the technique was partially successful in reflecting the surface loading. Site-by-site inspection revealed spurious non-linearity likely caused by residual oceanographic signals present between the TG and altimeter measurement locations. Our average mission-specific error estimates are small but significant, typically within ~±0.5-1.0 mm/yr, with negligible effect implied on the overall rate of ASL. Analysis of the time variability of altimeter errors confirmed stability for most missions except for Jason-2 with an anomaly reaching ~2.8 mm/yr in the first ~3.5 years of operation which is supported by analysis from the Bass Strait altimeter validation facility. Weak correlation with the dominant climate mode suggests potential deficiencies in the resolution of the time-variable gravity field used for orbit determination as a possible cause, yet other drivers cannot be discounted. Our approach advances the ability to estimate TG-specific VLMs and regional altimeter systematic errors, and highlights that residual oceanographic signals remain a fundamental limitation to such techniques.

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The East Australian Current, upwellings and downwellings off eastern-most Australia in summer

Cited by 11 publications

References 17 publications

Vertical deformation and residual altimeter systematic errors around continental Australia inferred from a Kalman-based approach

Vertical deformation and residual altimeter systematic errors around continental Australia inferred from a Kalman-based approach

Climate change threatens unique evolutionary diversity in Australian kelp refugia

Vertical Deformation and Residual Altimeter Systematic Errors around Continental Australia Inferred from a Kalman-Based Approach

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