Lecture 8: Contrasting impacts of extreme events & trend CC on Arctic ecosystems

Question 1

Arctic is warming, some regions __ DC warmer than in 1950’s

Answer 1

2-3 degrees C

• due to polar amplification
• poles warm more than rest of world
• • arctic +0.09 DC / decade
• • global av +0.06 DC/ decade

Question 2

polar amplification -

Answer 2

greater warming a the poles

Question 3

warming effect on terrestrial ecosystems =

Answer 3

• snow is melting earlier
• longer snow free period
• longer growing season
• • = arctic greening as plants have longer to establish & warmer temperature
• • looking at NDVI satellite images you can see greener land
• – longer growing season or bigger plants

Question 4

“greening” of the arctic: shrubs

Answer 4

• shrubification

increase in shrub abundance 28% on hilltops to 160% floodplains between 1950 -2000

Question 5

Arctic “shrubification” alters

Answer 5

• photosynthesis
• priming of soil C decomposition
• influence permafrost thaw
• alter surface energy balance (transpiration/albedo)

– carbon balance unknown, C into ground. microbes respire, release etc

Question 6

arctic warming = more intense in summer/winter

Answer 6

more in winter than summer

- with more extreme climatic events

Question 7

extreme winter events:

Answer 7

1) extreme winter warming
2) frost-drought
3) icing

Question 8

Extreme winter warming

Answer 8

• e.g. Dec 2007 North-west Scandinavia
• max temp 4-12 DC for 5-12days
• ground surveys: 50% loss live biomass
• 26% reduction in NDVI
• – warming causes bud to burst (plants think its spring) & lose their freeze tolerance

Question 9

frost-drought

Answer 9

• less snow so plants aren’t protected
• winter solar radiation on canopies but soil frozen -
• plants try to transpire BUT roots are frozen
• desiccation damage
• evergreen shrubs particularly vulnerable

Question 10

icing

Answer 10

• rain on snow (refreezing) & winter warming
• ice encasement of vegetation
• High CO2 or hypoxia, AS encasing stops gas exchange BUT questionable –> (Preece et al 2012 & 2013)

Question 11

arctic browning & biotic drivers

Answer 11

Frost drought
icing
extreme winter warming BUT OTHER THINGS TO
- biotic drivers accelerate browning
- maritime & warmer arctic may be early warming
– arctic browning now becoming an issue

Question 12

things that make arctic brown

Answer 12

frost drought
icing
extreme winter warming

Question 13

things that make arctic green

Answer 13

• warming

- shrubification

Question 14

arctic green/ brown

Answer 14

in 2015, 4 years browning trend (2010-2014)

• recent return to greening overall, but major uncertainty
• all models predict greening!!

Question 15

where are we heading? (arctic environment)

Answer 15

• -> trends dominate, = greening!! with some browning episodes
• events dominate = browning will occur!
• • hard to predict

Question 16

trends =

Answer 16

greening

Question 17

events =

Answer 17

browning

- events are sporadic, temporary (recover), hard to predict, and hard to monitor

Question 18

extreme events in wine are ___ in frequency

Answer 18

increasing

Question 19

extreme events caused

Answer 19

widespread plant mortality, often to dominant species

– have major impacts on community structure & C balance