Oceans cover most of the Earth's surface and contain nearly all of its water. Sea levels are rising at about 10 times the rate over the past 3,000 years due to global warming. As a result, coastal areas are experiencing problems like erosion and damage from higher tides and stronger storms. Scientists predict that by 2100, sea levels could be 0.8 to 2 meters higher than today if warming continues unabated.

1. 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?
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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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2. Photograph: “Breakwater” by tiffany terry from http://goo.gl/B3pYgM is licensed under CC BY 2.0
Illustrated 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 happening
to the sea?
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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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3. 3
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!
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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

4. 4
How can you
measure 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 permission
Graph: Copyright © Di Fuller, used with permission ← Previous →Next

5. 5
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.
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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 2.0
Illustrated waves, cloud: Copyright © Di Fuller, used with permission ← Previous →Next

6. 6
Making sure we’re prepared
Humans 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 heights
of 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
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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.nz
and click on School stuff.
Illustrated boat, waves: Copyright © Di Fuller, used with permission
Photograph: “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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7. 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↑

8. 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.↑

9. 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.↑

10. 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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11. 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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12. 15← Previous"Flood damage" by Aidan from http://goo.gl/GQa4ZR is licensed under CC BY 2.0 →Next
Mud left by a flood↑

13. 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.↑

14. 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.↑

15. 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.↑

16. 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↑

17. 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↑

18. 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↑

19. 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↑

20. 23← Previous"Tide gauge" by Alex Healing from http://goo.gl/mkKguV is licensed under CC BY 2.0 →Next
Tide gauge↑

21. 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↑

22. 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↑

23. 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.↑

24. 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.↑

25. 28← Previous →Next
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.
↑
"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

26. 29← Previous →Next
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

27. 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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28. 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↑

29. 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↑

30. 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↑