Author: Neville

Measuring sea level rise

Influences on sea levels

Many meteorological and oceanographic processes, with different time and spatial scales, affect sea levels around Australia. Influences on sea levels can be dynamic and vary from place to place. Many of these processes are considered cyclical – they oscillate back and forth. Although these processes do not have a permanent imprint on the long-term mean (or average) sea level, they can make it difficult to determine underlying trends in sea level.

The timeframes for major influences on sea levels are summarised in the table below (adapted from New Zealand National Institute of Water and Atmospheric Research, Goring & Bell 2001).

Driver

Sea-level response

Indicative timescales

Gravitational attraction of astronomical bodies

Tides

Hours, with some influences extending over multiple years

Wind

Set-up

Days

Changing atmospheric pressure

Inverted barometer

Days

Ocean currents

Variations

Weeks to months

Annual temperature cycle

Annual cycle

One year

El Niño/Southern Oscillation

Interannnual oscillations

Years

Interdecadal Pacific Oscillation

Interdecadal oscillations

Decades

Long-term global temperature changes

Long-term sea-level change

Multiple decades to centuries

Some influences affect sea levels on short timescales (less than one year) including seasonal factors, weather systems and variability of ocean water properties such as temperature and salinity. The physical properties of the ocean water mass change with mixing and ocean currents, and can cause significant variations in sea level lasting from weeks to months.

Larger scale phenomena, like the El Niño Southern Oscillation (ENSO), the nodal tide and the Interdecadal Pacific Oscillation (IPO), can cause fluctuations in sea level spanning years to decades and are more difficult to isolate from sea level trends.

There is a distinct seasonal signature in most sea level records. For example, the Fort Denison (Sydney) record (which has been collected from 1886 until present) has a strong positive (high) bias in autumn and a negative (low) bias in spring, compared with long-term averages.

Longer term, larger scale meteorological influences such as ENSO can influence sea levels on cycles from three to eight years (National Tidal Centre 2010). The inter-annual variability in sea level around Australia correlates with ENSO (Amin 1993; Feng, Li & Meyers 2004; Church, White et al 2004; Church, Hunter et al 2006; Haigh, Eliot et al 2011).

The range of lunar influences on tides occurs over a cycle of about 18.6 years. Throughout this cycle, the moon induces a small amplitude harmonic influence on the position of mean sea level at a fixed location. The influence is at a maximum at the poles with no influence on the equilibrium nodal tide at latitudes of around 35°N and 35°S (Pugh 1987). The tide gauges in NSW are situated between 28°S and 38°S so the amplitude of the nodal tide for the NSW tidal records is therefore considered negligible (less than 4-5mm). Larger values than the theoretical maximum amplitude of the nodal tide have been measured in tide gauge records (Houston & Dean 2011).

At multidecadal time scales sea level also varies with the IPO, which operates over time frames of 20 to 30 years (National Tidal Centre 2010; Holbrook, Goodwin et al 2010). This long period oscillation is a lengthy interdecadal fluctuation in atmospheric pressure and sea surface temperature. When the IPO is low, cooler than average sea surface temperatures occur over the central North Pacific, and vice versa. During the 20th century the IPO exhibited three major phases: it was positive (southeastern tropical Pacific warm) from 1922 to 1946 and 1978 to 1998, and negative between 1947 and 1976. During positive phases of IPO more El Niño like conditions prevail and sea levels in Eastern Australia are lower than average. During negative phases more La Nina like conditions prevail and sea levels are higher than average.

Tide gauge data provides a measure of the water level “relative” to a fixed, land-based reference mark. However, the land upon which the tide gauge is positioned may be moving. Many processes can contribute to the land moving including:
solid earth tides (relatively small movements of the Earth’s surface caused by the gravity of the moon and sun)
plate tectonics (movements of the Earth’s crust)
glacial isostatic adjustment (the rise of ground levels previously depressed by the weight of ice sheets during the last glacial period, also known as post-glacial rebound)
localised factors including aquifer extraction, reclamation and development loadings.

To accurately estimate sea level change, these processes need to be taken into account. The land itself at a tide gauge might be moving up or down at long term rates comparable with the actual rate of sea level rise. This needs to be considered in isolating the real component attributable to sea level rise.

Sea level rise along the NSW coast can be more accurately determined since the installation in mid-2012 of Continuously Operating Reference Stations at Newcastle and at Fort Denison in Sydney Harbour. These reference stations were funded by OEH to measure any ground movement which could affect the sea level recordings. This will complement the similar sea level monitoring station at Port Kembla operated by the Bureau of Meteorology. These three stations will provide useful data on sea level trends in the medium-long term.

Challenges of isolating long term trends from sea level records

It is difficult to isolate the smaller signal of long-term changes in sea levels from these larger dynamic influences which operate over different time and spatial scales (Zhang & Church 2012). Sea level records which are sufficiently long need to be used so that the more dynamic and cyclical influences do not obscure the long term trend.

Large inter-annual and inter-decadal sea level fluctuations associated with climate variability (such as ENSO and IPO) are difficult to distinguish from underlying long-term trends of sea level rise in shorter data sets. Long record lengths spanning ENSO and IPO cycles are recommended to help distinguish between trends and long-period relative sea level fluctuations in individual records (Douglas, Kearney & Leatherman 2001; You, Lord & Wilson 2009) and even then great care needs to taken in the interpretation of measured trends.

Analysis (such as filtering and averaging) can be applied to tidal records of sufficient length to smooth dynamic sea level influences and reveal low amplitude sea level rise.

Measuring sea level in NSW

OEH supports a system of tide gauges which measures ocean water levels continuously at recording sites along the NSW coast, and on Lord Howe and Norfolk Islands. This tide gauge system is managed and maintained by Manly Hydraulics Laboratory. Data from these sites have been presented in a range of reports, including the NSW Ocean and River Entrance Tidal Levels Annual Summary 2011-2012 report.

Analysing historic sea level data

OEH is working with collaborators from CSIRO, University of Tasmania, University of Western Australia, Australian National University and Southampton University (UK) to analyse Australian recorded historical sea levels and determine trends, regional variability and influencing factors.

The team are using publicly available tide-gauge records and satellite-altimeter data around Australia. They will also assess the quality of long term Australian sea level data, review relevant Australian sea level research, investigate spatial and temporal variability of sea level data, and analyse long-term sea level trends around Australia. The results will be interpreted in the context of global sea-level change and will be published in a refereed scientific journal.

Past trends provide valuable evidence in preparing for future environmental change but, by themselves, are insufficient for assessing the risks associated with an uncertain future (Parris, Bromirski et al 2012).

Page last updated: 15 March 2013

Ocean Plankton Sponge Up Nearly Twice the Carbon Currently Assumed

Mar. 17, 2013 — Models of carbon dioxide in the world’s oceans need to be revised, according to new work by UC Irvine and other scientists published online Sunday in Nature Geoscience. Trillions of plankton near the surface of warm waters are far more carbon-rich than has long been thought, they found. Global marine temperature fluctuations could mean that tiny Prochlorococcus and other microbes digest double the carbon previously calculated. Carbon dioxide is the leading driver of disruptive climate change.

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In making their findings, the researchers have upended a decades-old core principle of marine science known as the Redfield ratio, named for famed oceanographer Alfred Redfield. He concluded in 1934 that from the top of the world’s oceans to their cool, dark depths, both plankton and the materials they excrete contain the same ratio (106:16:1) of carbon, nitrogen and phosphorus.

But as any gardener who has done a soil test knows, amounts of those elements can vary widely. The new study’s authors found dramatically different ratios at a variety of marine locations. What matters more than depth, they concluded, is latitude. In particular, the researchers detected far higher levels of carbon in warm, nutrient-starved areas (195:28:1) near the equator than in cold, nutrient-rich polar zones (78:13:1).

“The Redfield concept remains a central tenet in ocean biology and chemistry. However, we clearly show that the nutrient content ratio in plankton is not constant and thus reject this longstanding central theory for ocean science,” said lead author Adam Martiny, associate professor of Earth system science and ecology & evolutionary biology at UC Irvine. “Instead, we show that plankton follow a strong latitudinal pattern.”

He and fellow investigators made seven expeditions to gather big jars of water from the frigid Bering Sea, the North Atlantic near Denmark, mild Caribbean waters and elsewhere. They used a sophisticated $1 million cell sorter aboard the research vessel to analyze samples at the molecular level. They also compared their data to published results from 18 other marine voyages.

Martiny noted that since Redfield first announced his findings, “there have been people over time putting out a flag, saying, ‘Hey, wait a minute.’” But for the most part, Redfield’s ratio of constant elements is a staple of textbooks and research. In recent years, Martiny said, “a couple of models have suggested otherwise, but they were purely models. This is really the first time it’s been shown with observation. That’s why it’s so important.”

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Irish feel ‘animosity’ from Top Enders

By Andrew Thompson, ABCMarch 18, 2013, 11:39 am

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Some Irish people living in Darwin say they have experienced hostility as increasing numbers move to the Top End looking for work.

Anthony McCann from Belfast said he, like many other Irish people, left home to escape the recession gripping his country.

Mr McCann said he and his friends had noticed growing animosity from some Australians as more Irish people moved to the Top End.

“Coming here to Australia at the start I was like ‘ahh, Australia, it’s class, it’s good’, but now I actually feel a wee bit marginalised too because Aussies are starting to feel, like, as if there’s too many Irish,” he said.

“In Darwin you get that feeling, there’s like a bit of…there’s a bad atmosphere…because there is too many Irish here and there’s lots of fights.

“Not with me or all of us, but it is happening.”

Territory government delegations visited Ireland in recent years as part of efforts to poach skilled workers to plug holes in the local workforce.
The Master Builders Association NT estimated in late 2011 there would be at least 20,000 job vacancies created in the NT over the next decade.

Tracks laid for NSW South West link

AAPMarch 18, 2013, 11:51 am

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Six kilometres of track have been laid for the long-awaited South West Rail Link, the NSW government says.

The continuous rail corridor stretching between Glenfield and Leppington is the first instalment of a 11.4 kilometre rail line that will link residents in Sydney’s southwest to the rest of the city network.

Stations are now being built at Leppington and Edmondson Park, near Camden.

Transport Minister Gladys Berejiklian on Monday said after four months of work, construction on the $2.1 billion link was ahead of schedule.

“These were empty paddocks last year, now you’ve got the structures of the two new stations, the entire corridor is outlined, six kilometres of new truck – I couldn’t be more pleased and more proud,” she told reporters gathered at the Leppington construction site.

“The progress is remarkable and what is really pleasing to see is the light at the end of the tunnel.

“Residents who have waited for the rail link so long here on the southwest will be able to get that rail link and use the trains in the not-too-distant future.”

Premier Barry O’Farrell said the area had been earmarked as a residential hub in the government’s 20-year growth strategy for Sydney, announced over the weekend.

“What we’re seeing here is the infrastructure being delivered prior to those houses arriving,” he said.

“Ultimately the population of Canberra will live in this district.”
Ticket prices for rail services along the line would match those for services on other parts of the CityRail network once the southwest services opens to passengers in 2016, he said.

Gillard faces challenging week as voters desert her

Date March 18, 2013 81 reading now

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No poll relief for Gillard

John Stirton analyses the latest Nielsen/Fairfax poll, whose numbers confirm Labor’s continued strife and the prospects of a Coalition landslide.
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I will not flinch, says defiant PM
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Julia Gillard enters a politically dangerous last sitting week before the May budget, with support for her government stuck in the basement and her standing with voters losing ground to a more popular Tony Abbott.

A sharp drop in support for the ALP in February, which sent shockwaves through the party and fuelled leadership anxiety, is now showing signs of becoming entrenched with less than six months to go to the federal election on September 14.

The latest Age/Nielsen poll has confirmed Labor’s share of the primary vote is languishing at a landslide-losing 31 per cent – up a statistically insignificant 1 point from February.

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This compares with support for the Coalition being unchanged on 47 per cent.

The telephone survey of 1400 people, taken from Thursday, March 14, to Saturday, March 16, also showed Ms Gillard’s satisfaction rating continuing to drop and Mr Abbott’s continuing to improve with the Opposition Leader now preferred prime minister by 49 per cent of voters against Ms Gillard on 43 per cent – down 2 points.

The two-party-preferred split sits at 44per cent for Labor and 56 per cent for the Coalition, which represents a 6 per cent swing to the Coalition from the 50/50 result in 2010 and would leave the ALP electorally devastated if carried through to the election.

With some Labor MPs and ministers favouring a late leadership change back to Kevin Rudd or perhaps a third candidate, the poll showed Mr Rudd was easily the most popular choice among voters for prime minister, out-pointing Ms Gillard 2 to 1, with 62per cent up against the PM’s 31 per cent.

However, low voter enthusiasm for three other Labor leadership possibilities – cabinet ministers Bill Shorten, Greg Combet, and Bob Carr – suggest the party would not improve its September chances with any of them installed as prime minister. Of the three, the Foreign Minister, Senator Carr, had the most support with 41 per cent to Ms Gillard on 50 per cent.

Pollster John Stirton said that this showed voters were taking the view that if it is not to be Kevin Rudd in charge, they would prefer no change at all.

On the separate index of approval ratings, 38 per cent approved of the way Ms Gillard was handling her job compared to 58 per cent who disapproved. This put her net approval rating at negative 20 per cent, a deterioration of four points in a month.

Mr Abbott’s net approval rating was half as bad on negative 10 per cent (an improvement of three points) with 43 per cent approving his performance and 53 per cent disapproving.

The shifting approval ratings and the preferred prime minister findings confirm that neither leader is particularly popular with voters, but that sentiment may be moving in the direction of the alternative prime minister, Mr Abbott.

The poll comes as dispirited Labor MPs began filing into Canberra on Sunday hopeful, if not confident, that a series of populist appeals by Ms Gillard in recent weeks – including a new campaign against foreign workers, and moves to protect penalty rates – might have begun turning things around.

Yet the poll suggested that Ms Gillard’s tough rhetoric had failed to spark a recovery.

Labor’s one-point improvement in the primary vote came from the Greens, which dropped one point to 10 per cent.

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Government ‘wasting millions’ on prescription drugs

By Naomi Woodley and staff, ABCUpdated March 18, 2013, 11:06 am

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The Federal Government is wasting $1.3 billion a year on prescription drugs and Cabinet ministers should not have a say in which drugs are listed on the PBS, according to a new report.

Drugs are currently assessed for safety, quality and cost-effectiveness before the Pharmaceutical Benefits Pricing Authority decides on an appropriate price.

It is then up to the Health Minister and Federal Cabinet to decide if the medicine should be subsidised by listing it on the PBS.

But a report by the Grattan Institute says Australians should be paying lower prices for their prescription drugs, with a new independent body set up to determine pricing.

It says Cabinet ministers are not qualified to make decisions about which drugs to fund.

Professor Stephen Duckett, former secretary of the federal health department and the director of the institute’s health program, says the process is costing Australia billions of dollars each year compared to other countries.

“Australia is probably wasting $1.3 billion a year because we pay too much for generic drugs, that are drugs that are off patent,” he said.

He says Cabinet should be involved in setting a cap for the PBS, but that is it.

“What’s the skill that Cabinet brings to this decision? They’re not the experts, none of them are clinicians, none of them have actually been involved and seen the detail of the cost effectiveness work,” he said.

“So they’re just an unnecessary overlay that’s second-guessing expert decisions.”

Professor Duckett says Australians should demand lower prices for generic drugs, and delays in adding drugs to the PBS should be ironed out.

He says the time is right for the Government to act, because the current five-year pricing agreement with Medicines Australia expires in July next year.

“Consumers themselves would save money,” he said.

‘More choice’

But Federal Health Minister Tanya Plibersek says the Government is already acting.

“On the pricing of generic drugs, I’d say that price disclosure has meant that 1,400 brands over 127 medicines are up to 87 per cent cheaper over the last four years, and in fact another 60 drugs will go down in price on April 1,” she said.

“It’s certainly true that using the market-based system that we use in Australia it can take up to 18 months to see that price drop.

“The advantage of our system over the sort of tendering system that this report calls for is that we still have a much greater range of choice for patients.”

Ms Plibersek says while the Grattan report is good, there are also risks in following the lead of countries like New Zealand and Canada.

“Lowest price is not always best value because we need to have certainty of supply, we need to have a range of products available so that consumers can use the ones that suits them most, and we also have a much healthier pharmaceutical manufacturing industry in Australia,” she said.
She says the Government will always look to get the best value for consumers.