rising seas
TRANSCRIPT
by Kate Potter
Oceans cover almost three quarters of the planet’s surface and contain 97 percent of the water on Earth. It’s hard to believe, but this vast amount of water is getting bigger. As a result, sea levels are rising. So what does that mean for those who live close to the sea?↓A roller coaster is swallowed by the Atlantic ocean in the aftermath of Hurricane Sandy.
Photograph: “Restore the Shore” by Hypnotica Studios Infinite from http://goo.gl/mflFW3 is licensed under CC BY 2.0, edited from original
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WHY IS THAT?
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Photograph: “Breakwater” by tiffany terry from http://goo.gl/B3pYgM is licensed under CC BY 2.0Illustrated boat, waves, clouds: Copyright © Di Fuller, used with permission 2
Sea levels are rising because of global warming. For about one hundred years, they have been rising by 1 or 2 millimetres per year. That doesn’t sound like much, but it’s about ten times faster than during the previous three thousand years. And things aren’t slowing down – if anything, the change in sea levels is increasing. Looking at the evidence, some scientists think that by 2100, the sea could be 80 centimetres to 2 metres higher than it is now.
What’s happeningto the sea?
↑This is a breakwater – a barrier designed to protect the coast from sea damage. These tetrapod (four-footed) structures are designed so that water flows around them rather than against them. As a result, the force of incoming waves becomes weaker. Sea levels are on the rise, so it is becoming important to protect our coastlines.
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Why are rising seas a problem?Imagine that you have built a great sandcastle at the beach. Suddenly a big wave comes and washes over your masterpiece. As the wave pulls back, it takes some of your sandcastle with it. Rising sea levels can do the same thing to the shoreline. We call this erosion. Rising sea levels mean that tides now reach higher than they did in the past. Sea water is getting to places where it never used to reach. This can cause problems for roads, houses, and crops.
Another effect of global warming is that cyclones are now happening more often. A cyclone is a wild storm with strong winds and heavy rain. When there is a cyclone, the air has low pressure, which means that sea levels are higher than normal, and powerful winds push water onto the land. This is called a storm surge. Storm surges can do a lot of damage to roads and houses, especially in places where the land isn’t very high. Many people who live on islands in the Pacific get their fresh drinking water from wells. If an island floods with sea water, salt gets into the wells and the people can no longer use the water. If you have ever swallowed a mouthful of sea water at the beach, you’ll know why!
↑This house in Ngawi, at the southern tip of the North Island, will soon be destroyed due to coastal erosion.
Photograph: Copyright © Dave Turnbull, used with permission ← Previous →Next
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How can youmeasure sea levels?Scientists need evidence to be absolutely certain about how fast sea levels are rising. But working out the “height” of the sea isn’t easy. Sea levels go up and down because of tides, waves, water temperature, and the weather. The land can also sink or rise because of the effects of erosion, earthquakes, and volcanoes. To get a picture of how much the sea has dropped or risen, scientists use information from different sources, such as tide gauges and satellites. They look at data from long periods of time to see whether there are patterns.
In New Zealand, three ports (Auckland, Wellington, and Lyttleton) have been measuring sea levels for over one hundred years. Look at the graph below.
What trend can you see?
Illustrated shark, waves, clouds: Copyright © Di Fuller, used with permissionGraph: Copyright © Di Fuller, used with permission ← Previous →Next
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In 2010 and 2011, a surprising thing happened – sea levels around the world went down. Scientists wondered whether their ideas about sea levels had been wrong. Then they found that the answer to the puzzle lies with our neighbour, Australia. In 2010 and 2011, unusual weather patterns meant that the rain that normally falls on the oceans fell on Australia, causing big floods. Normally, rainwater slowly makes its way back to the sea, but the dry earth in Australia soaked up the water like a giant sponge. Over time, that water has slowly evaporated. A change back to more usual weather patterns means that once again more rain is falling on the oceans than on the land. As a result, sea levels are rising again. ↑
Why did the sea level drop in 2010 and 2011? Because Australia soaked up a lot of the water that usually would have fallen in the oceans.
Australia – a giant sponge
Scientists were able to work out what happened by using data from satellites and from floats that take measurements in the oceans. Using this data, scientists were able to work out that the mass of Australia increased after lots of rain had fallen there.
Photograph: “Horsham Flood 2011 - photo 27” by Wimmera from http://goo.gl/me6BKI is licensed under CC BY 2.0Illustrated waves, cloud: Copyright © Di Fuller, used with permission ← Previous →Next
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Making sure we’re preparedHumans are good at adapting to change. We do it all the time. But change is easier when you know it’s coming. That’s why we need to keep measuring sea levels. If sea levels keep rising, we’re going to need to work together to help the people whose lives are affected.
adapting – changing to suit new conditions
erosion – the process by which land is worn away by water or wind
evaporated – when water has turned from liquid into gas, or water vapour (In the water cycle, this happens as the result of heat from the sun.)
global warming – an increase in average temperatures around the world most probably caused by human activities(These activities are increasing gases such as carbon dioxide in the atmosphere. These gases trap heat, a bit like the glass in a greenhouse traps heat.)
sea levels – the average heightsof the surfaces of the seas
tide gauges – large, long pipes with small holes below the waterline. The water level inside the pipes is almost still and can be read accurately – even when waves are moving up and down outside the pipes
Glossary
←Rising sea levels are likely to affect life in New Zealand, with higher tides and larger waves causing erosion, flooding, and other damage.
Take action. Rising sea levels are connected to climate change. You can learn about ways to make a difference to climate change by playing
“Play it cool”. Go to www.climatechange.govt.nzand click on School stuff.
Illustrated boat, waves: Copyright © Di Fuller, used with permissionPhotograph: “Storm wellington south coast dsc4518” by Dave Allen, NIWA from http://goo.gl/6LQVkL is used under a CC BY 3.0 licence, cropped from original.
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Additional digital content slides for students
The following slides contain multimedia that supports the article.
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Tide Gauges video
↑ Find out how the tide gauge at Lyttelton Port measures the sea level. Click here to view the video. The video opens in a new tab.
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A collection of images showing the effects of climate change and rising
sea levels
Use the following photographs to illustrate your own text and for research.
These images can also be downloaded from Google Drive.
10← Previous"Glaciers and Sea Level Rise" by NASA Goddard Space Flight Center from http://goo.gl/9RHZvAis licensed under CC BY 2.0 →Next
Melting glacier↑
11← Previous"Glaciers and Sea Level Rise" by NASA Goddard Space Flight Center from http://goo.gl/lgzsFK is licensed under CC BY 2.0 →Next
Large chunks of ice break off the front of the Perito Moreno glacier in Argentina. This process is called calving.↑
12← Previous"Sea level rise at Alligator River Refuge" by U.S. Fish and Wildlife Service Headquarters from http://goo.gl/Tcuxcm/ is licensed under CC BY 2.0 →Next
An aerial view of submerged trees after a storm.↑
13← Previous"Bloom in the Ross Sea [detail]" by NASA Goddard Space Flight Center from http://goo.gl/I24ehg is licensed under CC BY 2.0 →Next
Bloom in the Ross Sea, south of New Zealand, in Antarctica. The bloom is an annual massive growth of phytoplankton in response to increased sunlight.
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14← Previous"Hawk's Crag, Buller Gorge, New Zealand 1977" by Phillip Capper from http://goo.gl/cAFciS is licensed under CC BY 2.0 →Next
The height of flooding in Buller Gorge (every few years the river in flood covers the road: in the late 1960s it reached the top of the telephone pole).
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15← Previous"Flood damage" by Aidan from http://goo.gl/GQa4ZR is licensed under CC BY 2.0 →Next
Mud left by a flood↑
16← Previous"Eroded Road at Whatarangi Bluff, Palliser Bay" by Karora from http://goo.gl/nHCyJZ is in the public domain →Next
Eroded coastal road at Whatarangi Bluff, Palliser Bay.↑
17← Previous"Eroded Road at Whatarangi Bluff, Palliser Bay-2" by Karora from http://goo.gl/nbGzeX is in the public domain →Next
Eroded coastal road from the other direction, Whatarangi Bluff, Palliser Bay.↑
18← Previous"wedge" by Craig Berry from http://goo.gl/J3t3Qh is licensed under CC BY 2.0 →Next
A 20+ foot wave at Newport Beach, California, USA.↑
19← Previous"Hurricane Dora" by Ana Rodríguez Carrington from http://goo.gl/CukfLt is licensed under CC BY 2.0 →Next
Waves after a tropical storm↑
20← Previous"HMNZS WELLINGTON encounters rough seas in Ross Sea" by New Zealand Defence Force from http://goo.gl/OiHXew is licensed under CC BY 2.0 →Next
HMNZS WELLINGTON encounters rough seas in the Ross Sea↑
21← Previous"Water level moitoring in Chesapeake City" by NOAA's National Ocean Service from http://goo.gl/FoyimI is licensed under CC BY 2.0 →Next
Chesapeake City Tide Station, an active water level gauge, Maryland, USA↑
22← Previous"4 Inches of rain in 6 hours" by Tony Alter http://goo.gl/taH0hw is licensed under CC BY 2.0 →Next
Rain gauge↑
23← Previous"Tide gauge" by Alex Healing from http://goo.gl/mkKguV is licensed under CC BY 2.0 →Next
Tide gauge↑
24← Previous"cgs00995" by NOAA Photo Library from http://goo.gl/FkKrs2 is licensed under CC BY 2.0. Credit: Personnel of NOAA Ship THOMAS JEFFERSON; Collection of Gretchen Imahori, NOAA/NOS/OCS.NOAA Photo Library →Next
Checking the equipment used to monitor water level↑
25← Previous"Housing on Fakaofo atoll, Tokelau, 2007. Tokelau’s low-lying atolls are susceptible to rising sea levels. Photo: New Zealand Ministry of Foreign Affairs and Trade" by New Zealand Ministry of Foreign Affairs and Trade from http://goo.gl/C5XFxW is licensed under CC BY 2.0 →Next
Houses on Tokelau that could be affected by rising sea levels↑
26← Previous"Aerial view of Tuvalu’s capital, Funafuti, 2011. Photo: Lily-Anne Homasi / DFAT" by Lily-Anne Homasi / Australian Government Department of Foreign Affairs and Trade from http://goo.gl/sz5sL4 is licensed under CC BY 2.0 →Next
Aerial view of Tuvalu’s capital, Funafuti. Tuvalu is a country of low lying atolls, making it vulnerable to rising sea levels.↑
27← Previous"Kiribati 2009. Photo: Jodie Gatfield, AusAID" by Jodie Gatfield, AusAID from http://goo.gl/r53YNa is licensed under CC BY 2.0 →Next
Kiribati.↑
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This visualization shows the extent of Arctic sea ice on August 26, 2012, the day the sea ice dipped to its smallest extent ever recorded in more than three decades of satellite measurements. The line on the image shows the average minimum extent from the period covering 1979-2010. Every summer the Arctic ice cap melts down to what scientists call its “minimum” before colder weather builds the ice cover back up.
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"Arctic Sea Ice Shrinks To New Low In Satellite Era" by Scientific Visualization Studio, NASA Goddard Space Flight Center from http://goo.gl/HfrHlB is licensed under CC BY 2.0
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This little church, thought to date from the 1300s, is in danger of falling into the sea off the coast of north-west Denmark.↑
"Coastal erosion - Maarup" by John Nuttall from http://goo.gl/QmC9bu is licensed under CC BY 2.0
30← Previous"London Arch, Victoria, Australia" by Kelly Hunter from https://www.flickr.com/photos/inspirekelly/5678063966/ is licensed under CC BY 2.0 →Next
The London Arch, Great Ocean Road, Victoria, Australia, used to be called the London Bridge. A section of it collapsed due to erosion in 1990 and left two tourists stranded on the new island it formed. They were rescued by helicopter.
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31← Previous"Tuvalu - Funafuti - Beach #3" by Stefan Lins from http://www.flickr.com/photos/mrlins/304273860/ is licensed under CC BY 2.0 →Next
A beach and wharf on Funafuti Atoll in Tuvalu↑
32← Previous"Brisbane Floods - Gailes Queensland" by Martin Howard from https://www.flickr.com/photos/martinhoward/5349077346 is licensed under CC BY 2.0 →Next
A submerged train line and motorway in Gailes, Brisbane↑
33← Previous"Rockhampton in flood" by Tatiana Gerus from https://www.flickr.com/photos/tgerus/5305820211 is licensed under CC BY 2.0 →Next
Floods at Rockhampton, Australia, 2010, taken from a plane↑
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Play the video to view the article as it is read aloud.
Larger version (mp4, 209.7MB, easier to read text on screen)Use this link on newer computers; Apple iPad 2, 3, 4, Mini; iPhone 4S, 5; and Apple TV 3.
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LinksLook at maps showing what Earth would look like if the ice caps melted.http://www.smh.com.au/photogallery/environment/what-earth-would-look-like-if-the-ice-caps-melted-20131107-2x2qq.htmlSydney Morning Herald
Watch a video about the risks of rising sea levels. http://media.smh.com.au/news/environment-news/getting-a-rise-out-of-sea-level-predictions-4903430.htmlSydney Morning Herald
Take the “Sea Change”, “Warm Up”, or “Sea Salt” quiz to find out how much you know about global climate change.http://climate.nasa.gov/interactives/quizzesNASA
Visit the NASA website to read articles, watch videos, and do activities to find out more about climate change.http://climatekids.nasa.gov/NASA
Watch a video of Arctic ice melting (2011).https://www.flickr.com/photos/24662369@N07/6150172293/flickr
Watch a video about global warming.http://video.nationalgeographic.com/video/101-videos/global-warming-101National Geographic
Watch a video about changing your lifestyle to take action for climate change.http://vimeo.com/90515199Vimeo
Read the story about New Zealand ocean currents and tides.http://www.teara.govt.nz/en/ocean-currents-and-tidesTe Ara
Read about how rising sea levels will affect some island nations. http://www.businessinsider.com.au/sea-level-rise-cause-island-evacuation-2012-10Business Insider Australia
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