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Course webpagehttps://www.bgc-jena.mpg.de/bgi/index.php/Lectures/HydroBioClimClimateChange
1
Lesson 7
The oceans: Sea level rise
1) Arctic Sea ice
2) Sea level rise
Arctic Sea ice
Strong seasonal variationsMinimum in September
Akclimate.org
2
Arctic Sea ice
Arctic could become (seasonally) ice-free Large uncertainties through model and scenario differences
Maloney et al. (2013)
3
Arctic Sea ice shrinking mostly off the shore of
Russia & Alaska
IPCC (2013)
Arctic Sea ice4
Also Antarctic sea ice is threatened by climate
change
IPCC (2013)
5
Summary
● Arctic sea ice extent varies seasonally with a minimum in September
● This minimum extent has halved in recent years compared to pre-industrial, seasonally ice-free Arctic during this century is possible
Lesson 7
The oceans: Sea level rise
1) Arctic Sea ice
2) Sea level rise
Past Sea level rise
Sea level has risen by approx. 120 m since last glacial maximum
Comparatively little change in past 6000 years
wikipedia.org
6
Past Sea level rise
Sea level has risen by approx. 20 cm since 1900
About ¼ of this is due to thermal expansion
IPCC (2013)
7
Past Sea level rise
Sea level rise is spatially heterogenous
IPCC (2013)
8
Past Sea level rise
Sea level rise is spatially heterogenous
eea.europa.eu
9
Past Sea level rise
Why sea level rises spatially heterogenous
- changes in surface winds (North Pacific, North Atlantic)
- post-glacial rebounds (Scandinavia, Canada)
- tectonics (subsidence off the coast of South America)
- changes in the Earth’s gravity field (through ice melting)
- local effects (groundwater or gas extraction)
10
Past Sea level rise
Local effects (groundwater or gas extraction)
11
Sea level rise
Hypothetic experiment: Melting of Greenland and Antarctic ice sheets
Less sea level increase close to melting areas due to loss of gravity
IPCC (2013)
12
Summary
● Arctic sea ice extent varies seasonally with a minimum in September
● This minimum extent has halved in recent years compared to pre-industrial, seasonally ice-free Arctic during this century is possible
● Sea level has risen by approx. 20 cm since 1900, due to melting glaciers and ice sheets, and thermal expansion
● Sea level rise not spatially uniform, but impacted by local-regional effects such as e.g. wind, post-glacial rebound, groundwater/gas extraction
Future Sea level rise
Sea level rise projected to accelerate
IPCC (2013)
13
Future Sea level rise
Strong differences across scenarios
IPCC (2013)
14
Future Sea level rise
Updated assessments projects higher sea level rise for the same scenarios
IPCC (2013)
15
Comparing projections 2006 (AR4) and 2013 (AR5)
Comparing projections 2013 (AR5) and 2019 (SROCC)
IPCC SROCC (2019)
Future Sea level rise
Differences across models for projecting global sea level in 2100
IPCC (2013)
16
Future Sea level rise
Temperature responds increased greenhouse gas emissions
with delay of decades,sea level responds with delay of
centuries
→ Sea level rise might continue for centuries
IPCC (2013)17
Future Sea level rise
Projected sea level rise until 2100 according to RCP8.5 scenario
Impacts all over the globe
IPCC SROCC (2019)
18
Future Sea level rise
Strongest impacts on coastal lowlands & harbour cities
eea.europa.eu
19
Future Sea level rise
Strongest impacts on coastal lowlands & harbour cities
IPCC (2013)
20
Storm surges will threaten areas not affected in the past
Future Sea level rise ucsusa.com
21
Millions of people potentially affected by inundation
Future Sea level riseIPCC (2013)
22
In Cuxhafen, a 50-year high tide event will become a 10-20-year event, and20-year event sea levels will be 10% or 20% higher at the end of the century
Future Sea level rise23
IPCC SROCC (2019)
Ext
rem
e s
ea level
In Venice, a 50-year high tide event will become a 0.5-2-year event, and
20-year event sea levels will be 30%-50% higher at the end of the century
Future Sea level rise24
IPCC SROCC (2019)
Ext
rem
e s
ea level
Summary
● Arctic sea ice extent varies seasonally with a minimum in September
● This minimum extent has halved in recent years compared to pre-industrial, seasonally ice-free Arctic during this century is possible
● Sea level has risen by approx. 20 cm since 1900, due to melting glaciers and ice sheets, and thermal expansion
● Sea level rise not spatially uniform, but impacted by local-regional effects such as e.g. wind, post-glacial rebound, groundwater/gas extraction
● Projected additional sea level rise of 40-60 cm until 2100, and continued rise afterwards
● Impacts on coastal population, so far unaffected areas at risk of storm surges
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