UR COOKED

What climate proxies can we measure in ice cores?

18O ice
air bubble composition
melt layers
ash
borehole temperatures
layer thickness (accumulation rate)
dust/impurities

Lake accumulate sediments from

surrounding environment

Autochthonous material

sediment from within the lake basin

Examples of autochthonous material

biogenic diatoms, aquatic insect parts, aquatic plant fragments, inorganic precipitates

Allochthonous material

sediment originating from outsideof the lake basin

Examples of allochthonous material

river sediment, landslides, overland flow, terrestrial organisms, windblown seds, pollen grains

Chironomids

larvae shed chitinous head capsules that are preserved in lake sediments

When was the Holocene

11,700 ka

A fairly strong relationship has been found between chironomid types and

summer temperature

Pollen preserved in lake sediments provides

information about local to regional vegetation, which reflects climate

Plants that have been recently exposed by melting of cold-based glaciers can be to reconstruct intervals of __

14C, past snowline lowering

Under certain conditions, past glacier extent can be

translated into a temperature and precipitation signal

Trees grow rings in

annual layers, which can be used to reconstruct climate

Tree ring width and/or density can be calibrated against or in the _ period

temperature, precipitation, instrumental

Name three proxies that can be used to reconstruct Holocene climate. For each proxy, indicate the season it should represent

pollen- spring/summer
chironomids- summer
tree rings- growing season for a species
glaciers- summer t, winter p
ice cores- (ice, acc rates) winter (melt layers) summer

From 10ka to present, what does the summer insolation in the northern hemisphere look like?

gradual decline, with ice sheet extent and atmospheric co2 concentration at interglacial levels by 7ka

In Greenland, Holocene temperatures cooled after peak warmth at

~10 ka

In Greenland, the 9.3 and 8.2 ka events were

drops of 2-3°C within ~100-150 years
Summer temperatures on Baffin Island also abruptly fell

Marine and terrestrial proxies suggest a global occurred between ~10-6 ka

Holocene Thermal Maximum

Proxies also suggest a general cooling trend through the middle to late Holocene-called the which culminated in the _

Neoglacial, Little Ice Age

Repeated explosive volcanism + low summer insolation across the northern hemisphere likely caused

the low temps of the LIA

Low temps accompanied by

expanded sea ice + AMOC weakening

Orbital forcing (+ice-albedo and veg-albedo feedbacks)

influenced millennial-scale trends in preindustrial Holocene global temps

After the mid-Holocene, cooling was likely driven by

land cover changes, decreasing solar irradiance, and increasing volcanic activity

Climate models simulate a

global annual mean warming throughout the Holocene

This disagreement between Holocene proxy and model temperatures is called the

Holocene Temperature Conundrum

Did the onset of northern hemisphere glaciation influence human evolution?

No

The sparse fossil record makes it difficult to

test hypotheses about the relationship between climate and human evolution

Human migration in SE Asia driven by _ during Meltwater Pulses 1A and 1B

rapid sea level rise

An example of climate change providing new opportunities for humans

16th century flooding helped the Dutch break away from the Spanish empire

Reason for anomalous atmospheric CO2 rise beginning 7 ka

European deforestation for agricultural purposes

The spread of _ in SE Asia from ~5-1 ka emitted large amounts of CH4

rice irrigation

Holocene ice core and ocean sediment trends are

anomalous compared to previous interglaciations