Variability in Solomon Sea circulation derived from altimeter sea level data
TL;DR: In this paper, the authors explore sea level and western boundary currents in this poorly understood portion of the ocean and find that the highest sea level variability is concentrated in the eastern Solomon Sea, particularly at the mouth of the Solomon Strait.
Abstract: The Solomon Sea is a key region in the Pacific Ocean where equatorial and subtropical circulations are connected. The region exhibits the highest levels in sea level variability in the entire south tropical Pacific Ocean. Altimeter data was utilized to explore sea level and western boundary currents in this poorly understood portion of the ocean. Since the geography of the region is extremely intricate, with numerous islands and complex bathymetry, specifically reprocessed along-track data in addition to standard gridded data were utilized in this study. Sea level anomalies (SLA) in the Solomon Sea principally evolve at seasonal and interannual time scales. The annual cycle is phased by Rossby waves arriving in the Solomon Strait, whereas the interannual signature corresponds to the basin-scale ENSO mode. The highest SLA variability are concentrated in the eastern Solomon Sea, particularly at the mouth of the Solomon Strait, where they are associated with a high eddy kinetic energy signal that was particularly active during the phase transition during the 1997-1998 ENSO event. Track data appear especially helpful for documenting the fine structure of surface coastal currents. The annual variability of the boundary currents that emerged from altimetry compared quite well with the variability seen at the thermocline level, as based on numerical simulations. At interannual time scales, western boundary current transport anomalies counterbalance changes in western equatorial Pacific warm water volume, confirming the phasing of South Pacific western boundary currents to ENSO. Altimetry appears to be a valuable source of information for variability in low latitude western boundary currents and their associated transport in the South Pacific.
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TL;DR: The Adaptive Leading Edge Subwaveform retracker (ALES) as discussed by the authors selects part of each returned echo and models it with a classic Brown functional form, by means of least square estimation whose convergence is found through the Nelder-Mead nonlinear optimisation technique.
185 citations
Cites background from "Variability in Solomon Sea circulat..."
...…et al., 2011; Herbert185 et al., 2011), the West Florida Shelf (Liu et al., 2012), Drake Passage (Ferrari et al., 2013)186 and the Solomon Sea (Melet et al., 2010).187 To create a time series, data points along the satellite tracks have to be collinear:188 it is necessary to have…...
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TL;DR: The issue of sustained measurements of sea level in the coastal zone is examined, first by summarizing the long-term observations from tide gauges, then by showing how those are now complemented by improved satellite altimetry products in the Coastal ocean.
Abstract: We examine the issue of sustained measurements of sea level in the coastal zone, first by summarizing the long-term observations from tide gauges, then showing how those are now complemented by improved satellite altimetry products in the coastal ocean. We present some of the progresses in coastal altimetry, both from dedicated reprocessing of the radar waveforms and from the development of improved corrections for the atmospheric effects. This trend towards better altimetric data at the coast comes also from technological innovations such as Ka-band altimetry and SAR altimetry, and we discuss the advantages deriving from the AltiKa Ka-band altimeter and the SIRAL altimeter on CryoSat-2 that can be operated in SAR mode. A case study along the UK coast demonstrates the good agreement between coastal altimetry and tide gauge observations, with root mean square differences as low as 4 cm at many stations, allowing the characterization of the annual cycle of sea level along the UK coasts. Finally, we examine the evolution of the sea level trend from the open to the coastal ocean along the western coast of Africa, comparing standard and coastally improved products. Different products give different sea level trend profiles, so the recommendation is that additional efforts are needed to study sea level trends in the coastal zone from past and present satellite altimeters. Further improvements are expected from more refined processing and screening of data, but in particular from the constant improvements in the geophysical corrections.
126 citations
Cites methods from "Variability in Solomon Sea circulat..."
...Along-track data from the three datasets were post-processed with various filters to remove the remaining erroneous data, using a strategy similar to that used in Melet et al. (2010)....
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Institut de recherche pour le développement1, Princeton University2, Commonwealth Scientific and Industrial Research Organisation3, University of Tasmania4, University of Hawaii5, University of Auckland6, Centre national de la recherche scientifique7, National Institute of Water and Atmospheric Research8, Scripps Health9, Australian Institute of Marine Science10, Bureau of Meteorology11, Pacific Marine Environmental Laboratory12
TL;DR: A review of recent advancements and current knowledge gaps and important emerging research directions can be found in this article, with a refined description of the SPCZ behavior, boundary currents, pathways, and water mass transformation, including the previously undocumented Solomon Sea.
Abstract: The Southwest Pacific Ocean Circulation and Climate Experiment (SPICE) is an international research program under the auspices of CLIVAR. The key objectives are to understand the Southwest Pacific Ocean circulation and the South Pacific Convergence Zone (SPCZ) dynamics, as well as their influence on regional and basin-scale climate patterns. South Pacific thermocline waters are transported in the westward flowing South Equatorial Current (SEC) toward Australia and Papua-New Guinea. On its way, the SEC encounters the numerous islands and straits of the Southwest Pacific and forms boundary currents and jets that eventually redistribute water to the equator and high latitudes. The transit in the Coral, Solomon, and Tasman Seas is of great importance to the climate system because changes in either the temperature or the amount of water arriving at the equator have the capability to modulate the El Nino-Southern Oscillation, while the southward transports influence the climate and biodiversity in the Tasman Sea. After 7 years of substantial in situ oceanic observational and modeling efforts, our understanding of the region has much improved. We have a refined description of the SPCZ behavior, boundary currents, pathways, and water mass transformation, including the previously undocumented Solomon Sea. The transports are large and vary substantially in a counter-intuitive way, with asymmetries and gating effects that depend on time scales. This paper provides a review of recent advancements and discusses our current knowledge gaps and important emerging research directions.
126 citations
TL;DR: X-TRACK as mentioned in this paper is a post-processing software for satellite altimetry data in coastal ocean areas, which is tailored for extending the use of satellite data to coastal ocean applications and provides freely available along-track sea level anomaly time series that cover today all the coastal oceans.
102 citations
TL;DR: In 2016, the Indonesian-Australian Basin and areas including the Timor Sea and Kimberley shelf experienced the longest and most intense marine heatwave from remotely sensed SST dating back to 1982 as discussed by the authors.
Abstract: During austral summer 2015–2016, prolonged extreme ocean warming events, known as marine heatwaves (MHWs), occurred in the waters around tropical Australia. MHWs arose first in the southeast tropical Indian Ocean in November 2015, emerging progressively east until March 2016, when all waters from the North West Shelf to the Coral Sea were affected. The MHW maximum intensity tended to occur in March, coinciding with the timing of the maximum sea surface temperature (SST). Large areas were in a MHW state for 3–4 months continuously with maximum intensities over 2°C. In 2016, the Indonesian‐Australian Basin and areas including the Timor Sea and Kimberley shelf experienced the longest and most intense MHW from remotely sensed SST dating back to 1982. In situ temperature data from temperature loggers at coastal sites revealed a consistent picture, with MHWs appearing from west to east and peaking in March 2016. Temperature data from moorings, an Argo float, and Slocum gliders showed the extent of warming with depth. The events occurred during a strong El Nino and weakened monsoon activity, enhanced by the extended suppressed phase of the Madden‐Julian Oscillation. Reduced cloud cover in January and February 2016 led to positive air‐sea heat flux anomalies into the ocean, predominantly due to the shortwave radiation contribution with a smaller additional contribution from the latent heat flux anomalies. A data‐assimilating ocean model showed regional changes in the upper ocean circulation and a change in summer surface mixed layer depths and barrier layer thicknesses consistent with past El Nino events.
96 citations
Cites background from "Variability in Solomon Sea circulat..."
...In the western Solomon Sea, 2016 currents were intensified and consistent with the characteristic of higher eddy kinetic energy following an El Ni~ no event (Melet et al., 2010), and the Coral Sea had a more complex, eddy-rich field (Figure 11b)....
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...In the western Solomon Sea, 2016 currents were intensified and consistent with the characteristic of higher eddy kinetic energy following an El Ni~no event (Melet et al., 2010), and the Coral Sea had a more complex, eddy-rich field (Figure 11b)....
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TL;DR: A review of the state-of-the-art in the field of finite element solutions (FES) atlases can be found in this paper, where the authors introduce the FES2004 tidal atlas and validate the model against in situ and satellite data.
Abstract: During the 1990s, a large number of new tidal atlases were developed, primarily to provide accurate tidal corrections for satellite altimetry applications. During this decade, the French tidal group (FTG), led by C. Le Provost, produced a series of finite element solutions (FES) tidal atlases, among which FES2004 is the latest release, computed from the tidal hydrodynamic equations and data assimilation. The aim of this paper is to review the state of the art of tidal modelling and the progress achieved during this past decade. The first sections summarise the general FTG approach to modelling the global tides. In the following sections, we introduce the FES2004 tidal atlas and validate the model against in situ and satellite data. We demonstrate the higher accuracy of the FES2004 release compared to earlier FES tidal atlases, and we recommend its use in tidal applications. The final section focuses on the new dissipation term added to the equations, which aims to account for the conversion of barotropic energy into internal tidal energy. There is a huge improvement in the hydrodynamic tidal solution and energy budget obtained when this term is taken into account.
1,553 citations
"Variability in Solomon Sea circulat..." refers methods in this paper
...Tidal corrections were derived from the higher-accuracy FES2004 model (Lyard et al. 2006)....
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...Tidal corrections were derived from the higher-accuracy FES2004 model ( Lyard et al. 2006 )....
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TL;DR: In this article, a new conceptual model for ENSO has been constructed based upon the positive feedback of tropical ocean atmosphere interaction proposed by Bjerknes as the growth mechanism and the recharge discharge of the equatorial heat content as the phase transition mechanism suggested by Cane and Zebiak and by Wyrtki.
Abstract: A new conceptual model for ENSO has been constructed based upon the positive feedback of tropical ocean‐ atmosphere interaction proposed by Bjerknes as the growth mechanism and the recharge‐discharge of the equatorial heat content as the phase-transition mechanism suggested by Cane and Zebiak and by Wyrtki. This model combines SST dynamics and ocean adjustment dynamics into a coupled basinwide recharge oscillator that relies on the nonequilibrium between the zonal mean equatorial thermocline depth and wind stress. Over a wide range of the relative coupling coefficient, this recharge oscillator can be either self-excited or stochastically sustained. Its period is robust in the range of 3‐5 years. This recharge oscillator model clearly depicts the slow physics of ENSO and also embodies the delayed oscillator (Schopf and Suarez; Battisti and Hirst) without requiring an explicit wave delay. It can also be viewed as a mixed SST‐ocean dynamics oscillator due to the fact that it arises from the merging of two uncoupled modes, a decaying SST mode and a basinwide ocean adjustment mode, through the tropical ocean‐atmosphere coupling. The basic characteristics of this recharge oscillator, including the relationship between the equatorial western Pacific thermocline depth and the eastern Pacific SST anomalies, are in agreement with those of ENSO variability in the observations and simulations with the Zebiak‐Cane model.
1,322 citations
"Variability in Solomon Sea circulat..." refers background in this paper
...It is the incompletely balanced meridional interior transport by western boundary currents which leads to low frequency changes in the WWV consistent with the oscillator as hypothesized by Jin (1997)....
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Book•
01 Jan 1994
TL;DR: In this article, what drives the ocean currents? temperature, salinity, density and the oceanic pressure field the Coriolis force, geostropy, Rossby waves and the westwood intensification Ekman layer transports, Ekman pumping and the Sverdrup balance water mass formation, subduction and oceanic heat budget Antarctic oceanography Arctic oceanography.
Abstract: Introduction - what drives the ocean currents? temperature, salinity, density and the oceanic pressure field the Coriolis force, geostropy, Rossby waves and the westwood intensification Ekman layer transports, Ekman pumping and the Sverdrup balance water mass formation, subduction and the oceanic heat budget Antarctic oceanography Arctic oceanography -the path of North Atlantic Deep Water the Pacific Ocean hydrology of the Pacific Ocean adjacent seas of the Pacific Ocean the Indian Ocean hydrology of the Indian Ocean adjacent seas of the Indian Ocean and the Australasian Mediterranean Sea the Atlantic Ocean hydrology of the Atlantic Ocean aspects of advanced regional oceanography the oceans and the world's mean climate El Nino and the Southern oscillation (ENSO) the ocean and climate change.
1,261 citations
"Variability in Solomon Sea circulat..." refers background in this paper
...It is intensified during the boreal summer, then weakened or even reversed direction to southeastward during the boreal winter, in relation to seasonal variations of along shore monsoonal wind forcing ( Tomczak and Godfrey 1993 ; Q u and Lindstrom 2002, Ueki et al. 2003)....
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TL;DR: In this article, a series of sensitivity tests were performed with a z-coordinate, global eddy-permitting (1/4°) ocean/sea-ice model (the ORCA-R025 model configuration developed for the DRAKKAR project) to evaluate the impact of recent state-of-the-art numerical schemes on model solutions.
Abstract: Series of sensitivity tests were performed with a z-coordinate, global eddy-permitting (1/4°) ocean/sea-ice model (the ORCA-R025 model configuration developed for the DRAKKAR project) to carefully evaluate the impact of recent state-of-the-art numerical schemes on model solutions. The combination of an energy–enstrophy conserving (EEN) scheme for momentum advection with a partial step (PS) representation of the bottom topography yields significant improvements in the mean circulation. Well known biases in the representation of western boundary currents, such as in the Atlantic the detachment of the Gulf Stream, the path of the North Atlantic Current, the location of the Confluence, and the strength of the Zapiola Eddy in the south Atlantic, are partly corrected. Similar improvements are found in the Pacific, Indian, and Southern Oceans, and characteristics of the mean flow are generally much closer to observations. Comparisons with other state-of-the-art models show that the ORCA-R025 configuration generally performs better at similar resolution. In addition, the model solution is often comparable to solutions obtained at 1/6 or 1/10° resolution in some aspects concerning mean flow patterns and distribution of eddy kinetic energy. Although the reasons for these improvements are not analyzed in detail in this paper, evidence is shown that the combination of EEN with PS reduces numerical noise near the bottom, which is likely to affect current–topography interactions in a systematic way. We conclude that significant corrections of the mean biases presently seen in general circulation model solutions at eddy-permitting resolution can still be expected from the development of numerical methods, which represent an alternative to increasing resolution.
661 citations
"Variability in Solomon Sea circulat..." refers methods in this paper
...To improve the bathymetry representation with z-coordinates, a partial step parameterization is used to allow bottom cells depth to be adaptative and to differ from the vertical prescribed levels (Barnier et al., 2006)....
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TL;DR: In this paper, a global simulation of the ocean response to atmospheric wind and pressure forcing has been run during the Topex/Poseidon (T/P) period (1992-2002), using a new hydrodynamic finite element (FE) model, MOG2D-G.
Abstract: [1] A global simulation of the ocean response to atmospheric wind and pressure forcing has been run during the Topex/Poseidon (T/P) period (1992–2002), using a new hydrodynamic finite element (FE) model, MOG2D-G. Model outputs are compared to in situ observations with tide gauge data (TG) and bottom pressure gauge data (BPR), and also with T/P altimetric cross over points (noted CO). Intercomparisons were performed over the 1993–1999 period. The model correction reduces the sea level variance by more than 50% at TG locations, and by more than 15% at T/P CO, when compared to the classical inverse barometer correction (IB). The model impact differs between high and low latitudes: in the very energetic high latitudes areas, MOG2D-G is efficient in reducing the variance, while at low latitudes, the results are similar to the IB static response. In shallow water, the model shows an oceanic response very different from the IB response. In conclusion, MOG2D-G models the high frequency (HF) atmospheric forced variability of the global ocean with unprecedented accuracy.
621 citations