Cryosphere 3- Case-studies – ice-sheet influence on ocean currents and heat transport Flashcards
What causes the release of heat from the North east Atlantic?
Gulf stream
North Atlantic drift
What is responsible for heat movement to higher latitudes?
Atmosphere
What is one of the main ocean drivers of the gulf stream/ North Atlantic drift?
Squeezing on the edge of gyre systems
What processes cause the movement of heat to the atmosphere from the ocean?
Evaporation and latent heat
What is another name for the movement of heat via the gulf stream and north Atlantic drift?
Thermohaline circulation
What is thermohaline circulation?
when currents are driven by heat (thermo) and salinity (hals)
Why are the surface waters of the Nordic and Labrador sea unusual?
they become dense enough to sink to depths below 2 km (during winter
time) sinking compensated by influx warmer equatorial water
What is North Atlantic drift?
when the gulf stream extends across the Atlantic
What is the average depth of the ocean and does wind interact with this?
4000m deep wind can only affect 1000m
What does wind only affecting 1000m depth of ocean mean must be the driver of deep ocean currents?
varying temp and salinity and how this affects their density
What can the movement rate of deep ocean currents be across an ocean basin?
decades to centuries
What outflow adds salinity and thus increases density further driving north Atlantic drift?
Mediterranean (which is warm but doesn’t sit on surface due to high salinity and thus density)
What is brine rejection?
when salt water freezes salt is expelled as brine
What happens when brine is rejected?
drains into ocean in narrow channel due to cold and saline sinks in plume which freezes water it comes into contact with
What was North Atlantic drift like during summer in the LGM?
algae records suggest warm surface water open up sea ice in Nordic sea
Deep currents for thermohaline circulation dont form
What was North Atlantic drift like during winter in the LGM?
Warm surface currents and thermohaline circulation pushed south and northward heat transport is greatly reduced from 30°N
What will happen if their is sediment instead of rock under a glacier?
will deform easier allowing quicker movement
Thought quaternary ice sheet margin were prone to collapse
How do Heinrich events/ layers form?
Wind from Sahara can carry fine sand but not coarse sand or gravel but icebergs are the only thing that can carry larger material
What is a H event?
a dramatic collapse or increase in freshwater slowing or stopping North Atlantic drift to higher latitudes
What was N. Atlantic circulation during a H event?
Lid of cold freshwater laden with interrupted ocean conveyor system
Climate affected
Air passing across ice field causes temp on land to plummet
What are Heinrich events associated with?
Coldest phases of last glacial and ice berg release
What are D/O cycles?
rapid warming and cooling through last glacial
What does DO cycles stand for?
Dansgaard-Oeschger cycles
What is the length of the cold warm period of D/O cycles?
1-2kyr
Where can D/O cycle evidence be found?
First in Greenland ice cores
marine and terrestrial records
intense in North Atlantic regions
What was the younger dryas?
last big climatic event of the late Quaternary before the Holocene
When was the younger dryas?
return towards glacial conditions 12.9 to 11.65ka
What was the younger dryas responsible for in the UK?
Loch Lomond stadial
What was the younger dryas caused by?
massive flow glacial meltwater in north Atlantic which restricted overturning circulation
Where was the largest meltwater/ iceberg discharge?
into Arctic via NW passage
What was the 8.2 ka event?
The biggest climatic event in the Holocene in the N Atlantic region
How was the 8.2 ka event like compared to the younger dryas?
less severe
What do Greenland ice cores show the 8.2ka event was like?
cold (less accumulation, lower d 18 O,
windy (more salts (Cl-) and dust (Ca2+ )
dry (decreased CH 4 )
What are tipping points?
points in earths climate where one change can lead to uncontrolled runaway climate change
