In the last 20-30 years, much progress has been made in the deployment of sustained, nationally and internationally coordinated ocean observing programs. These include the Argo array of profiling floats, ocean glider missions, the global drifter array, Ships of Opportunity (SOOP) eXpendable Bathythermograph (XBT) lines, deep water moorings, Global Ocean Ship-based Hydrographic Investigation Program (GOSHIP), and new pilot studies extending to boundary currents, the deep ocean, and the marginal ice zones. In general, many of the observing systems were originally designed to resolve ocean variability at timescales from sub-seasonal to longer; however, the data are now also essential for ocean forecasting and prediction projects. Improved satellite technologies and telecommunications has enabled much of the ocean observations data to be recovered in real-time. The advent of rapid and timely access to data has led to the increasing use of ocean data in operational oceanography systems for the purpose of providing increasing accurate and reliable global and regional ocean (eddy resolving) forecasts. In this chapter, we provide an overview of the global in situ ocean observing systems for measuring physical Essential Ocean Variables (EOVs), including all the major platforms, and the efforts of the international coordinating programs.
This paper examines the characteristics of planetary wave signatures that have been found in the Along Track Scanning Radiometer averaged sea surface temperature (ASST) record for 1991–1996. Longitude‐time plots for every latitude between 5° and 50°, north and south, reveal westward propagating wave‐like patterns at many locations, whose speed decreases with latitude like baroclinic Rossby waves. A two‐dimensional Radon transform method is used to measure the wave speed and its variation with location and time, which broadly matches the Rossby wave speeds predicted by the most recent theory and those measured by TOPEX altimetry, although there are some discrepancies. At low latitudes the thermally detected speeds are slower than expected, a possible consequence of sampling limitations. Wave signatures are clearest between 25° and 40°S, where the meridional temperature gradient is strongest. Here observed speeds are 20–30% greater than theoretical predictions. Planetary wave speed varies considerably with longitude. In general, it increases toward the west of ocean basins, and distinct differences between ocean basins are evident. The propagation characteristics of the waves appear to change abruptly at locations consistent with latitudinal variations in seafloor bathymetry, particularly midocean ridges. In addition, eastward propagating signatures are found in the Southern Ocean. The results demonstrate the value of the ASST data set as a tool for studying basin‐scale wave processes as a complement to the use of altimetry. By observing the thermal signature of Rossby waves the method has the potential to clarify their influence on air‐sea interaction processes and to contribute to climate modeling studies.
This paper presents a study of the characteristics of extra-tropical oceanic Rossby waves from datasets of Sea Surface Height (SSH), Sea Surface Temperature (SST) and ocean colour. The main focus is on the propagation speed of the waves and a comparison is made between the observational results and the speeds predicted by the classical theory and by the most recent extended theory of Rossby waves. There is also discussion, with an example, of the additional information that can be derived by a comparison of the wave signatures in the different datasets.
The OceanGliders program started in 2016 to support active coordination and enhancement of global glider activity. OceanGliders contributes to the international efforts of the Global Ocean Observation System (GOOS) for Climate, Ocean Health, and Operational Services. It brings together marine scientists and engineers operating gliders around the world: (1) to observe the long-term physical, biogeochemical, and biological ocean processes and phenomena that are relevant for societal applications; and, (2) to contribute to the GOOS through real-time and delayed mode data dissemination. The OceanGliders program is distributed across national and regional observing systems and significantly contributes to integrated, multi-scale and multi-platform sampling strategies. OceanGliders shares best practices, requirements, and scientific knowledge needed for glider operations, data collection and analysis. It also monitors global glider activity and supports the dissemination of glider data through regional and global databases, in real-time and delayed modes, facilitating data access to the wider community. OceanGliders currently supports national, regional and global initiatives to maintain and expand the capabilities and application of gliders to meet key global challenges such as improved measurement of ocean boundary currents, water transformation and storm forecast.
Climate change and variability are major societal challenges, and the ocean is an integral part of this complex and variable system. Key to the understanding of the ocean's role in the Earth's climate system is the study of ocean and sea-ice physical processes, including its interactions with the atmosphere, cryosphere, land and biosphere. These processes include those linked to ocean circulation; the storage and redistribution of heat, carbon, salt and other water properties; and air-sea exchanges of heat, momentum, freshwater, carbon and other gasses. Measurements of ocean physics variables are fundamental to reliable earth prediction systems for a range of applications and users. In addition, knowledge of the physical environment is fundamental to growing understanding of the ocean's biogeochemistry and biological/ecosystem variability and function. Through the progress from OceanObs'99 to OceanObs'09, the ocean observing system has evolved from a platform centric perspective to an integrated observing system. The challenge now is for the observing system to evolve to respond to an increasingly diverse end user group. The Ocean Observations Physics and Climate panel (OOPC), formed in 1995, has undertaken many activities that led to observing system-related agreements. Here, OOPC will explore the opportunities and challenges for the development of a fit-for-purpose, sustained and prioritized ocean observing system, focusing on physical variables that maximize support for fundamental research, climate monitoring, forecasting on different timescales, and society. OOPC recommendations are guided by the Framework for Ocean Observing (Lindstrom et al. 2012) which emphasizes identifying user requirements by considering time and space scales of the Essential Ocean Variables. This approach provides a framework for reviewing the adequacy of the observing system, looking for synergies in delivering an integrated observing system for a range of applications and focusing innovation in areas where existing technologies do not meet these requirements.
In order to gain a better understanding of the interactions of processes and properties of the earth system and how these are changing with time, it is essential that there is a sustained stream of high quality data on the marine environment. This must extend from its surface to the underlying seabed and use a matrix of interlinked platform types, each with specific advantages. Included in this matrix is the global array of fixed point or Eulerian observatories which have several unique capabilities. These include the ability to collect samples (water, biota and particles), to support sensors which have a high demand for space or power, to make observations in locations beyond the reach of satellites, gliders and floats and to observe and sample the seafloor. Considerable progress has been made in the operability of these observatories over the past decade and some, such as the Global Tropical Moored Buoy Array, make physical and meteorological observations that are well integrated. There has been considerable progress in sensor development, platform design, and in the principles and protocols required for data management. There is however a significant requirement now to interlink observations on biogeochemistry within the global Eulerian array and between Eulerian observatories and the other observing systems in the matrix. Large scale computational models closely coupled to the various observational approaches are required for much of this work and this challenge is being addressed by a number of groups. For this to be achieved there must be a change in mind-set of many of the funding organisations so that the financial resources are sustained. This is essential in order to prevent breakage of data streams and loss of the skill base of staff at the end of every funding round. There are examples of this change in approach in the USA (OOI (Observatories Initiative)) and in Canada (NEPTUNE (North East Pacific Time-series Undersea Networked Experiments)) but elsewhere in the world, short term funding is usually the normal mechanism which is expected to address long term environmental questions of major societal relevance.
The largest earthquake of 2010 by magnitude (MW8.8), and the subject of this article, struck south-central Chile in the early hours of 27 February 2010. The earthquake was a “mega-thrust” event, involving the rupture of a section of the Nazca-South American plate boundary, where the Nazca plate dips at a shallow angle beneath the Pacific margin of South America.
Understanding this event and its effects, including tsunami is of particular significance to urban centres that share close proximity to “subduction zones”. These include Seattle, Vancouver, Tokyo and Wellington, together with smaller New Zealand towns of the eastern North Island and upper South Island. The tectonic setting of south-central Chile has similarities to the East Coast of the North Island, and the modern built environment of Chile shares attributes with New Zealand. However, New Zealand has not experienced a large subduction earthquake in the North Island region in at least 200 years, so an understanding of the Chile event and its impact is important for bench-marking of local practices and building resilience.
This report summarises the observations of the NZSEE/EQC teams, supplemented by media updates on the Chilean reconstruction experience one year after the earthquake.
The waters off the coast of Tasmania have become gradually warmer and saltier
over the past 60 years according to a coast station time series, with sea surface temperatures
rising at a rate more than double the global average. I demonstrate that
this is related to a strengthening and more southerly reach of the East Australian
Current (EAC) extension. The station also shows a strong decadal timescale signal
in temperature and salinity. In this thesis, I use a combination of the Maria Island
time series and Tasman Box XBT sections, 50 year atmosphere and ocean state
estimates, and idealised forcing experiments with a global ocean model to build a
picture of how the EAC system is changing, and what is driving it. I find that
changes at Maria Island are closely related to changes in the wind stress curl in the
South Pacific, with Maria Island lagging the winds by 3 years. This propagation
speed is too fast for 1st Mode baroclinic Rossby wave adjustment which would take
10-15 years, so a faster mechanism is needed.
The observed variability at Maria Island is part of a bigger picture of decadal variability
in the Southwest Pacific region. The EAC takes one of two paths at the point
of separation at 32°S; it either continues down the coast as the EAC Extension, or
separates and flows across the Tasman Sea to New Zealand as the Tasman Front.
On decadal timescales either the Tasman Front or the EAC Extension is favoured,
which form part of two gyre scale states. When the Tasman Front is favoured, a
single gyre structure is seen, which mainly sits to the north of New Zealand; whereas
when the EAC extension is favoured, a double gyre structure exists, with a second
gyre centre east of New Zealand. Analysis of ocean reanalyses suggests that an enhanced
wind stress curl maximum in the South Pacific appears to favour the EAC
extension over the Tasman Front.
From model forcing experiments, where the wind stress curl maximum is enhanced
in a 20°S longitude region for a period of a year, I am able to demonstrate a rapid
mechanism by which the EAC can respond to changes in the South Pacific winds.
Ocean ridges and islands provide a mechanism for conversion between fast barotropic
and slow baroclinic Rossby waves. Due to the position of New Zealand, barotropic
Rossby waves can travel across to New Zealand, travel around New Zealand as a
coastal Kelvin wave, and then take 3 years to cross to interact with the EAC as a
baroclinic Rossby wave. This shows that islands and bathymetry, as well as basin
size, can dictate the rate at which oceans respond to changes in wind forcing. In
addition intrinsic ocean variability exists, so that decadal variability in the ocean
can be set up by a single pulse of wind forcing, due to the multiple ways in which
the ocean responds to wind forcing. The model was also able to recreate the anticorrelation
between the EAC Extension and the Tasman Front. This thesis illustrates a very close relationship between the variability in the EAC
western boundary current system and basin scale wind stress variability. In addition
I identify a rapid mechanism by which the ocean can adjust in the presence of
islands and ridges to explain the observed 3 year time lag. This suggests that both
barotropic and baroclinic physics are needed to explain the timescales of observed
low frequency variability in the ocean.
Sustained observations allow for the tracking of change in oceanography and ecosystems, however, these are rare, particularly for the Southern Hemisphere. To address this in part, the Australian Integrated Marine Observing System (IMOS) implemented a network of nine National Reference Stations (NRS). The network builds on one long-term location, where monthly water sampling has been sustained since the 1940s and two others that commenced in the 1950s. In-situ continuously moored sensors and an enhanced monthly water sampling regime now collect more than 50 data streams. Building on sampling for temperature, salinity and nutrients, the network now observes dissolved oxygen, carbon, turbidity, currents, chlorophyll a and both phytoplankton and zooplankton. Additional parameters for studies of ocean acidification and bio-optics are collected at a sub-set of sites and all data is made freely and publically available. Our preliminary results demonstrate increased utility to observe extreme events, such as marine heat waves and coastal flooding; rare events, such as plankton blooms; and have, for the first time, allowed for consistent continental scale sampling and analysis of coastal zooplankton and phytoplankton communities. Independent water sampling allows for cross validation of the deployed sensors for quality control of data that now continuously tracks daily, seasonal and annual variation. The NRS will provide multi-decadal time series, against which more spatially replicated short-term studies can be referenced, models and remote sensing products validated, and improvements made to our understanding of how large-scale, long-term change and variability in the global ocean are affecting Australia's coastal seas and ecosystems. The NRS network provides an example of how a continental scaled observing systems can be developed to collect observations that integrate across physics, chemistry and biology.
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