Sea Level Rise

Question 1

what is the mean sea level

Answer 1

is the average height of the sea over longer periods of time (usually a month or year)

Question 2

what timescale are we interested in for sea level rise?

Answer 2

range from months to thousands of years

Question 3

when was the last interglacial?

Answer 3

125,000 years ago

Question 4

at the last interglacial, how high was the sea level compared to today?

Answer 4

5 m above that of today

Question 5

during the last ice age, how low did the sea level fall?

Answer 5

100 metres, as water was trapped in ice sheets.

Question 6

how varied has sea level been in the last 2,000 years?

Answer 6

little change at all from 2,000 years to the start of the 19th century

Question 7

how much has the sea level changed during the late 19th century and early 20th?

Answer 7

1.7 mm per year

Question 8

1993-2021, how much has sea level risen?

Answer 8

3.3 mm per year

Question 9

where are there the highest risks with sea level?

Answer 9

coastal zones with: 
dense population
low elevation
apprciable rates of subsidence
and/or inadequate adaptive capacity

Question 10

why do certain areas have more risk with changes to MSL?

Answer 10

A lot of these areas do not have enough space for adaptive capacity. Low lying islands, there is nowhere for the population or ecosystems to go, so those areas are particularly prone and vulnerable to being affected by mean sea level rise.

Question 11

what does MSL stand for?

Answer 11

mean sea level

Question 12

what are 2 processes which cause natural variability in SL?

Answer 12

ENSO
ocean currents

In terms of el nino southern oscillations, ENSO, as well as changes in the ocean currents.

Question 13

what are the 3 major contributors to MSLR

Answer 13

thermal expansion
glaciers
ice sheets (Greenland and Antarctica)

Question 14

what are ocean properties referred that influences ocean circulation?

Answer 14

temperature, salinity and density.

Question 15

how does seasonality cause glaciers and polar ice caps melting and solidifying?

Answer 15

summer, naturally melts back. winter, snow balances out the melting

Question 16

with the melting of glaciers and polar ice caps, what is caused by rising temperatures?

Answer 16

greater than average summer melting

reduced snowfall

Question 17

why has there been ice loss in Greenland and west Antarctica?

Answer 17

there has been the melting of small glaciers and polar ice sheets
melting of greenalnd ice sheet
melting of Antarctica ice sheet

Question 18

what is the projected melting of the Greenland ice sheet?

Answer 18

7.2 m

Question 19

what is the projected melting of the Antarctica ice sheet?

Answer 19

61

Question 20

what are the 6 impacts of sea level rise?

Answer 20

inundation
flood and storm damage
wetland migration and coastal squeeze
erosion
Saltwater intrusion
rising water tables

Question 21

what does the Kwajalein Atoll show?

Answer 21

shows the effects of MSLR in terms of overwash.

there are greater wave heights, greater wave driven run-up, raised groundwater levels and salinised freshwater lens

Question 22

how are atolls impacted by sea level rise

Answer 22

Influence the sea level rise has on wave heights, the wave driven RUN up, flooding and the result of groundwater in the Atoll.

Question 23

why are atolls and the subsequent effect of sea level rise bad for the residents there?

Answer 23

Large wave event in 2014, and this shows the wave driven run up and sea water that was flooding the island during the wave event in march. And this caused substantial overwash of the island. At the peak, the wave driven flooding overwashed the whole island and raised the ground water levels, which caused them to become saline.
This has significant implications to the people living there.

Question 24

what is wetland migration coastal squeeze

Answer 24

If there is no seawall present, no buildings or infrastructure, the marsh will get further and further inland. The seaward edge will erode away.
In areas wehre there are sea walls present, the salt marsh will get squeezed in, as it is prevented from migrating inland, this is called the coastal squeeze.

Question 25

what are the 3 potential wetland migration?

Answer 25

1- no sea wall present, the saltmarsh can migrate landward
2- the sea wall is present, and landward migration is prevented
3- naturally rising land, landward migration prevented

Question 26

how do you prevent UK marsh vulnerability?

Answer 26

mapping the probability for marshes to be able to retreat.

Question 27

what is saltwater intrusion, and how is this an impact of SLR?

Answer 27

Amount of freshwater a lens contains depends on the size of the island, the amount of rainfall, the amount of water that is being extracted, as well as the permeability of the rock beneath the island.
These can be really shallow underneath the surface, can be as shallow as 4-8 inches, or several metres, it is very specific.

Sea level rise can have a BIG impact on these, with signficiant implications ecologically and for the people living there.

Question 28

what is a rising water table, and how is this a SLR impact?

Answer 28

Marine inundation. That is localised plain flooding due to a rise of ground water due to sea level rise as it gets pushed up.
They measured how much the water table is going to change, under different sea level rise scenarios. Overall the flooding will mostly occur within about 1km stretch zone across the shoreline, which is the quite significant distance in land.
SLR of about 30cm will have little impact on inundation. BUT by the time you get to 60cm SLR. the imapcts on inundation are much more pronounced.