November 18, 2019

Arctic Sea Ice: Effects on the Climate 1. Introduction

Arctic Sea Ice: Effects on the
Climate

1.    Introduction

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In the Arctic’s north
polar region in the middle of the Northern Hemisphere covering an area of about
14.06 million km² is the Arctic sea ice. A frozen multifaceted surface that
varies in texture, layers and characteristics. Most of this ice is 2 – 3 meters
thick with some of the regions around 4 – 5 meters. The Arctic’s ice follows a
repetitive cycle throughout the year. The ice grows during the winter season freezing
more water and getting thicker, reaching the highest extent in March and then melting
until mid-September where it reaches the lowest coverage. The cycle is then underway
again with the cooling of temperatures and shorter days starting the ice cap
reformation.

This expanse of frozen
sea water holds significant importance to our Earths global climate. It
regulates the atmospheres temperature, helps moderate global climate and reduce
radiation, controls storm activity, and regulates ocean circulation. How is the
Arctic sea ice declining over time and how does that decline affect the Earth’s
climate?

2.    Changes
in the Sea Ice Extent

Since the late 1970’s the
Arctic sea ice extent has been in increasing long-term decline. Each year in September
the sea ice is at it’s lowest annual extent. This annual extent has been
recorded to get lower and lower by about 13 percent per decade and continues to
do so on average. In 2017 ice was found to be at the eighth lowest ever recorded
coverage (Blumberg, 2017). Shown on the graph below you can observe how significant
and consistent this decrease has been, starting in 1979 and continuing to current
day 2017.

Table
1 – Average Monthly Arctic Sea Ice Extent (millions of square kilometers) in September
1979 – 2017. The graph shows the decline of 13.2 percent per 10 years.
(National Snow and Ice Data Center, 2017). The blue line shows the median,
where black shows exact data marks recorded.

This
past year in March, when the ice is to be at it’s fullest and greatest extent, we
hit a record low with the smallest extent for the year at 4.6 square kilometres
(National Snow and Ice Data Center, 2017). With a very warm winter, the ocean
waters high temperatures made freezing much more difficult come March. This
cycle makes it very hard to bring back to “normal” as the decrease aids in more
decrease next year and so on. The amount of sea ice that is five years or older
is a lot less now then in the past with the young sea ice growing in
comparison. This means that there is less ice staying around throughout all
seasons and each melt. Evidence shows that two thirds of all the ice loss that
has happened has occurred in the 12 years following the
year 2000 (Naam, 2012). When the ice melts earlier in the season the open dark
ocean is exposed and therefore absorbs more heat from the Suns rays. The
process of ice loss is then speed up and the warmed water contributes to the
process, as seen this past March. This first climate effect is observed because
of this is radiation and absorption of heat in the atmosphere.

 

3.    Radiation
and Absorption of Heat: Albedo Effect

In
the winter the Arctic ice and snow insulates the ocean water. The exception to this
is where the ice has separated, exposing the open water. This enables the
exchange of heat and water vapor from ocean to Earth’s atmosphere. This open space
gets greater the less ice present and therefore the exchange increases.

The
Arctic’s polar ice and snow insulation is our Earth’s natural atmosphere
cooling system. With the increasing decline of this ice we are losing what helps
control and stabilize earth’s climate system. This can be explained through the
albedo effect, which is determined by the amount of radiation reflected away
compared to how much gets absorbed. The lower this albedo affect the more
radiation absorbed by the planet. The incoming radiation from the Sun through
our Earth’s atmosphere gets reflected off the ice and snow and back into space.
When a great extent of ice is present, nearly all the sunlight that hits the
ice surface is reflected into space because the ice is white and very
reflective (high albedo). This keeps the climate cool in the polar regions as
not much of the sun’s energy and therefore heat is absorbed. With less and less
ice in the Arctic and in it’s place open dark water, there is a less reflective
surface and so more heat is absorbed (low albedo). Below the diagram
illustrates this process and shows just how significant the present of the
Arctic sea ice really is.

Figure 1- The Albedo effect shown through
the amount of radiation absorbed by the water with ice and without. With ice
the snow and ice keep the water cool and reflects 90% back into space and only
10% into warming the water. Without the ice only 6% gets reflected into space,
and 94% absorbs into the water and energy transferred into heat.

This
absorption of heat from the lack of ice causes the water to warm and in turn, contributes
to more of the ice melting. This affects how much solar radiation is reflected
off the surface and absorbed every year. We now experience the Arctic absorbing
large amounts of this solar radiation in the summer, and the water temperatures
in turn are rising way above average. One recent study estimates that the extra
heat in the water is the equivalent of adding another 25 percent to global
greenhouse emissions (Wadhams, 2016).

 

 

4.   
Water circulation

The
circulation of the ocean water is affected and changed by the Arctic sea ice
loss. The surface waters are circulated by the wind moving the warmer water
sitting on top. The deeper water circulation is caused by the difference in
water density. The wind pushing the surface warmer waters carries it towards
the poles. This allows the seawater to move across the Earth’s oceans. As this
warmer water reaches the poles it begins to get cooler and cooler, the difference
in temperature and saline causes this water to sink deeper into the ocean. This
movement is part of the thermohaline circulation or the Global Ocean Conveyor.
(UCAR Center for Science Education, 2017). The melting Artic sea ice affects
this procedure as we see rising freshwater from the melting ice it causes the
seawater at high latitudes to become less salty and in turn as we have
discovered, less dense. With the surface water having a lower than normal
density the water is unable to sink and circulate. So how does this
interruption of the thermohaline process affect the climate? The process of
circulation brings heat from the equator and carries it northward where it cools,
then sinks and returns back south.

Figure 2 – The
Global Ocean Conveyor or Thermohaline process above shows the moving of the
water of deep and surface ocean water worldwide (News Archive – The Earth
Institute – Columbia University, 2005).

With
this process slowed or even potentially stopped by the melting of the Arctic
sea ice the ramifications of this would be severe. Without these ocean currents
the climates temperatures would drop, shifting animal, plant and human conditions.
This would be seen particularly in Europe and countries in the North Atlantic where
they could experience long periods of freezing temperatures. The slippery slope
effect would be appropriate in this as more negative consequence would be produced
in response such as the economy in specifically agriculture.

 

5.    Increased
Storm Activity

The
extremity of the storms we experience are regulated in part by the Arctic sea ice.
The smaller amounts of ice present in the Arctic combined with the rising sea
levels from this melting ice, allows for greater wind-induced wave energy to be
created. More waves can be produced because of the now open waters in the
summer. These waves pull apart the larger chunks of ice breaking them into smaller
pieces, allowing the Sun to melt them quicker. The Arctic’s lack of ice allows the
storms to feed off the open waters and mixes the water. This brings up heat that
was absorbed during the summer. As the water warms and stays warm, the air
above warms as well and moves across the land. This land absorbs more heat and
further warms the Arctic narrowing the temperature difference between the
Arctic and areas of lower latitudes. This lower temperature difference means
that the winds are weaker and move slower.

Figure
3
– (Mason, John, 2013) The above figure shows how the jet stream’s slower speed waivers
and brings cold polar air down while the warm tropical air moves up. This
causes pockets and moves into cyclonic spins and anti-cyclonic spins.

The
jet stream shown above is driven by this difference and causes the wind to move
around the north pole. The jet stream is now 14% slower and weaker than it was
in 1980 (Naam, 2012).  With the slower
speed the more defined swings of the jet stream extend farther north and south
as it moves from west to east, allowing warmer, more dense air to move
northward.

This
warmer climate causes more of the water vapor from the ocean to be evaporated
into the atmosphere which traps radiation and holds heat closer to the Earth’s
surface, and thus produces more extreme weather such as heat waves. The loss of
sea ice is a huge positive feedback effect as the changes caused by the melting
of the Arctic sea ice emphasise and lead to more warming and loss of ice. The
energy used to produce these storms or hurricanes come from the warm ocean
water. The very top of the Arctic ocean water increases in temperature making
these tropical storms stronger with faster winds and heavier rain.

The
loss of sea ice has significant impacts on our Earth, it’s connections reaching
far past climate and atmosphere effects discussed.

6.    Conclusion
 

The Arctic sea ice has been and continues to greatly
affect our climate and atmosphere. With the information provided it’s clear
that major changes are happening. As time progresses these processes will
continue to accelerate leading to more heightened and extreme effects and
conditions. The Arctic sea ice will continue to melt from the decreasing Albedo
in the Arctic from lack of ice and snow. Water circulation, which helps control
climate as well by warming and cooling parts of the Earth is slowed and could
potentially be halted by the melting freshwater diluting the seawater and
lowering the density. The increasing temperature of the water and air makes
tropical storms stronger with faster winds and heavier rain

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