Please enable JavaScript.
Coggle requires JavaScript to display documents.
Stable isotopes - Coggle Diagram
Stable isotopes
Alley 2000- 'climate is like a drunk- when left alone, it sits; when forced to move, it staggers'
Sub-Milankovitch events= high frequency climate oscillations (80-20ka BP- 'climate's flickering switch)
-includes interstadials and stadials within glacial/interglacial cycles.
-temp changes between stages and abrupt start
-gradual decline (saw-tooth pattern)
-found in Greenland ice cores.
Dansgaard-Oeschger cycles (D-O events)- rapid climate fluctuations during the last cold stage, 1000-2000yr periodicity, written off as 'noise'.
Bond cycles- longer term cooling cycles 1000-15000 years long during the last cold stage, followed by abrupt warming
Heinrich events- marked by layers rich in IRD in marine sediment cores, massive iceberg discharge (binge and purge cycles of ice sheets, MacAyeal 1992) with a cyclic occurrence, coincide with the end of bond cycles.
Sub-Milankovitch forcing factors= thermohaline circulation which is sensitive to freshwater input and slows down sink, affects NADW overturn. Ice-rafted debris (Heinrich layers and ice sheet binge/purge cycles), six layers detected in NA sediment cores, Laurentide ice sheet and Fennoscandian ice sheets
Ice sheet cyclical growth and decay important for iceberg and freshwater flux to the ocean, influences thermohaline circulation
-
the number of neutrons an element has determines the atomic weight- these are added to the number of protons to generate isotopes of mass
018 is heavier and 015 is lighter, 018 is known as a stable isotope and some are unstable and don't exist in nature.
Variations in the ratio of o16 and o18 indicate changing isotopic composition of ocean waters between glacials and interglacials.
-
-
During glacials- o16 is evaporated more easily, so ocean waters are enriched in o18 more, ice sheets are enriched in o16
-
-
-
-
Proxy data sources: biogenic sediments from the skeletal remains of calcareous organisms (planktonic and benthic foraminifera), inorganic/terrigenous sediment and ice rafted debris (increases during glaciations)
Ice cores- show temp, gas content if atmos, dust (aeolian activity), volcanic eruptions and annual layers- famous ones include Camp Century 1966, Vostok Antarctica 1985, GRIP 1992, EPICA 2000
-
-
Lowe and Walker ch7- association of D/O events with ice sheet collapse in the Nordic seas and freshwater/iceberg release, might weaken ocean circulation, which would increase warming in Antarctica (bipolar seesaw)
