Blog, coast, coastal flooding, energy, flooding, Journal paper, science, sea level, waves

New paper just published in Coral Reefs – Influence of the Great Barrier Reef on wave attenuation

We have just had a new paper (The large-scale influence of the Great Barrier Reef matrix on wave attenuation) published in the journal Coral Reefs. Click here to see a copy. This was our press release:

New research has found that the Great Barrier Reef, as a whole, is a remarkably effective wave absorber, despite large gaps between the reefs. This means that landward of the reefs, waves are mostly related to local winds rather than offshore wave conditions. 

As waves break and reduce in height over reefs, this drives currents that are very important for the transport of nutrients and larvae. This reduction in wave height also has implications for shoreline stability. Transition 

The Great Barrier Reef in Australia is the largest coral reef system in the world, extending 2,300 km alongshore. The reef matrix is a porous structure consisting of thousands of individual reefs, with gaps in between. The porosity varies in that is it much lower in the north where the continental shelf is narrow and there is extensive reef flats; and is greater in the south where the shelf reaches up to 300 km wide and there are extensive lagoons. 

Previously, there have been several studies investigating how individual reefs in the Great Barrier Reef influence ocean waves. However, this was the first, comprehensive, large-scale study of the influence of an entire offshore reef system on ocean wave transmission. The researchers used a 16-year record of satellite altimeter measurements of wave heights. 

The team was led by Dr Shari Gallop, Research Fellow in Geology and Geophysics at the University of Southampton, and included Dr Ivan Haigh, also from the University of Southampton; Professor Ian Young, Vice-Chancellor of the Australian National University (ANU); Professor Roshanka Ranasinghe, Professor of Climate Change Impacts and Coastal Risk (UNESCO-IHE, Deltares, ANU), and Dr Tom Durrant (Bureau of Meteorology, Australia). 

The aim was to see how wave height reduction is influenced by the porosity of the reef matrix, sea level and wind speed. Dr Gallop says: “There was no evidence that in less porous areas wave heights are lessened. This is because individual reefs, like islands, cast a ‘wave shadow’ over a large area, so that a matrix of individual reefs is remarkably efficient at reducing waves.” 

Dr Haigh adds: “As sea level varies, due to tides and storm surges, the submergence of the reef in water also varies. Wave heights are not strongly affected by water level over the reef matrix.” 

Professor Young says: “A number of previous studies have investigated the attenuation (height reduction) of ocean waves as they spread across individual coral reefs. This research is unique as it looks at the impact of a large scale reef matrix, such as the Great Barrier Reef, on wave height. Such studies are important in providing wave climate information for physical, biological and planning processes in such areas.” 

This new research, published in Coral Reefs, has important implications for wave modelling near reef systems. This is because models that consider individual reefs only may underestimate the wave reduction potential of a full reef matrix. 

Professor Ranasinghe comments: “Plans are under-way to investigate the wave attenuation characteristics over the reef in more detail, using sophisticated numerical modelling. It is of critical importance to know the potential impacts of climate change effects, such as sea level rise and variations in wave conditions, on wave attenuation and current circulation on the Great Barrier Reef. This will aid in the sustainable management of this natural wonder and the surrounding marine national park.”

 

 

 

 

Blog, coast, Journal paper, science, sea level

New paper in Nature Climate Change – Shifting perspectives on coastal impacts and adaptation

Here is our new paper in Nature Climate Change. The below is from our press release:

Coastal regions under threat from climate change and sea-level rise need to tackle the more immediate threats of human-led and other non-climatic changes, according to a team of international scientists.

The team of 27 scientists from five continents, led by Dr Sally Brown at the University of Southampton, reviewed 24 years of Intergovernmental Panel on Climate Change (IPCC) assessments (the fifth and latest set being published in 2013 and 2014). They focused on climate change and sea-level rise impacts in the coastal zone, and examined ways of how to better manage and cope with climate change. 

They found that to better understand climate change and its impacts, scientists need to adopt an integrated approach into how coasts are changing. This involves recognising other causes of change, such as population growth, economic development and changes in biodiversity. Dr Brown emphasised that: “Over the last two and half decades, our scientific understanding of climate change and sea-level rise, and how it will affect coastal zones has greatly increased. We now recognise that we need to analyse all parts of our human and natural environments to understand how climate change will affect the world.”

The scientists also acknowledged that long-term adaptation to climate change can greatly reduce impacts, but further research and evaluation is required to realise the potential of adaptation. “Many parts of the coast can, with forward planning, adapt to sea-level rise, but we need to better understand environments that will struggle to adapt, such as developing countries with large low-lying river deltas sensitive to salinisation, or coral reefs and particularly small, remote islands or poorer communities,” said Dr Brown.

For example, in the Maldives, many small, remote low-lying islands are at risk from climate change and will struggle to adapt. But around the densely populated capital city and airport, adaptation has already occurred as land claim is a common practice in order to relive population pressure. Sea-level rise has already been considered into newly claimed land. Thus in decades to come, potential climate change impacts, such as flooding, will be reduced for this island, benefiting both the local population and economy.

Dr Jochen Hinkel from Global Climate Forum in Germany, who is a co-author of this paper and a Lead Author of the coastal chapter for the 2014 IPCC Assessment Report added: “The IPCC has done a great job in bringing together knowledge on climate change, sea-level rise and is potential impacts but now needs to complement this work with a solution-oriented perspective focusing on overcoming barriers to adaptation, mobilising resources, empowering people and discovering opportunities for strengthening coastal resilience in the context of both climate change as well as existing coastal challenges and other issues.”

This new research, published as a commentary in Nature Climate Change, will help in the understanding of the impacts of climate change and how to reduce impacts via adaptation. Its multi-disciplinary approach could be useful if future IPCC assessment reports are commissioned.

Australia, Blog, coastal flooding, Journal paper, science, sea level, storm surge

New paper just published – land sinks around parts of Australia with passage of tropical cyclones.

We have just had a new paper (‘Non-linear motions of Australian geodetic stations induced by non-tidal ocean loading and the passage of tropical cyclones’) published in the journal of Journal of Geodesy – see here.

In this paper we examined movements in land around Australia using time-series from stations fitted with continuous GPS. Most people think the land is completely stable, but actually the land moves each day by a few millimetres for a variety of reasons. Here we show that land around parts of Australia sunk when cyclone Yasi crossed the Australian coast in January/February 2011. This cyclone generated a large storm surge and the extra weight of this large volume of water near the coast actually resulting in the land dropping slightly.

A earlier study (see here) showed the same thing happens around the North Sea coastlines when big storm surges happen there.

 

 

 

 

Australia, Blog, coast, coastal flooding, extreme events, flooding, Journal paper, science, sea level, storm surge, tides

New paper, just published: Australian Sea Levels – Trends, Regional Variability and Influencing Factors

While there has been significant progress in describing and understanding global-mean sea-level rise, the regional departures from this global-mean rise are more poorly described and understood. In this new paper, which you can view here, we present a comprehensive analysis of Australian sea-level data from the 1880s to the present, including an assessment of satellite-altimeter data since 1993.

We find that After the influence of El Niño Southern Oscillation is removed and allowing for the impact of Glacial Isostatic Adjustment and atmospheric pressure effects, Australian mean sea-level trends are close to global-mean trends from 1966 to 2010, including an increase in the rate of rise in the early 1990s. Given that past changes in Australian sea level are similar to global-mean changes over the last 45 years, it is likely that future changes over the 21st century will be consistent with global changes.

 

Blog, coast, Journal paper, science, sea level

New journal paper in Nature Communications – Timescales for detecting a significant acceleration in sea level rise

Very pleased to announce our new paper – published this month in Nature Communcations, called ‘Timescales for detecting a significant acceleration in sea level rise’.

The paper is open access and you can read it here:

http://www.nature.com/ncomms/2014/140414/ncomms4635/full/ncomms4635.html

 

 

 

 

 

 

Blog, Journal paper, science, sea level, tides

Trends in extreme high sea levels along the German North Sea coastline compared to regional mean sea level changes

The following paper has just been published:

Mudersbach, C., Wahl, T., Haigh, I.D., Jensen, J., 2013. Trends in extreme high sea levels along the German North Sea coastline compared to regional mean sea level changes. In press Continental Shelf Research.