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part 1a > Cryosphere > Flashcards

Cryosphere Flashcards

1
Q

define the cryosphere (IPCC)

A

the components of the Earth System at and below the land and ocean surface that are frozen, including snow cover, glaciers, ice sheets, ice shelves, icebergs, sea ice, lake ice, river ice, permafrost and seasonally frozen ground

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1
Q

what are CIDs

A

climate impact drivers
from AR6
physical climate system conditions that affect an element of society or ecosystems
can be detrimental, beneficial or neutral

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2
Q

SCE

A

snow cover extent
is the aerial extent of snow covered ground

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3
Q

SCD

A

snow cover duration is how long snow continuously remains on the land surface
Aka the period between snow on and snow off dates

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4
Q

Snow persistence

A

the probability of the persistence of snow at a given place at a given time of the year/through a time interval

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5
Q

SWE

A

snow water equivalent
the depth of liquid water if the snow were to melt completely

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6
Q

6 manual field observations of calculating snow cover

A

snow pillows, precipitation gauges, stakes, snow sampling tubes, sonar, snow pict analysis

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7
Q

3 compiled datasets of snow cover

A

ECCC environment and climate change Canada

SNOTEL for USA

Global Historical Climatology Network GHCN

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8
Q

satellite used for SCE and a bit about it!

A

MODIS on NASA’s terra satellite

Spectroradiometer that measures visible light
extends to 2000

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9
Q

satellite used for SWE and a bit about it!

A

Microwave radiometers on Nimbus 7 that read passive microwave radiation
this indicates the depth of snow and thus accumulation and ablation indicate snow persistence

this depth is then calculated with density to SWE

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10
Q

what is reanalysis

A

synthesis of observational data and numerical models to generate continuous and comprehensive datasets of past weather and climate conditions.

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11
Q

what are the possible drawback of reanalysis

A

we are reliant on the data being accurate that is inputted

often reanalysis products are built on each other, meaning errors could carry forward

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12
Q

what spheres are in coupled climate models

A

atmosphere, hydrosphere cryosphere, and bits of biosphere

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13
Q

Outline climate modelling

A
  • computer programmes that simulate the earths climate system
  • they use mathematical equations to represent the interactions between the various components of the earth
  • they help understand how element of climate work and may change in the future
  • simulate processes like atmospheric circulation, ocean currents and carbon cycle and how they are influenced by forcing
  • often presented as a gridded product, mapping the flows across grids
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14
Q

examples of forcings for climate models

A

changes to atmospheric composition, radiation receipts, land use change

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15
Q

what are the models used in Ar5 and AR6

A

CMIP5 and 6

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16
Q

CMIP stands for

A

Climate model intercomparison project

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17
Q

what are the pathways called in AR5 and 6

A

Representative Concentration pathways
RCPs

Shared socioeconomic pathways SSPs

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18
Q

1 thing that CMIP6 improves on CMIP5

A

has a better modelling and understanding of snow cover feedbacks like albedo and soil moisture

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19
Q

define permafrost

A

Ground (soil or rock, including ice and organic material) that remains at or below 0 degreesC for at least two consecutive years

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20
Q

what is the active layer

A

Layer of ground above permafrost subject to annual thawing and freezing.

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21
Q

define talik

A

A layer or body of unfrozen ground in a permafrost area due to a local anomaly in thermal, hydrological, hydrogeological or hydrochemical conditions.

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22
Q

Define thermokarst

A

Process by which characteristic landforms result from thawing of ice-rich permafrost or melting of massive ice.

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23
Q

outline the 4 permafrost zones and their % cover

A

continuous permafrost - 90%+
discontinuous permafrost - 50-90%
sporadic permafrost - 10-50%
isolated permafrost - <10%

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24
Q

main way of calculating permafrost in situ and a bit about it!

A

boreholes

they are drilled vertically into the ground to access the underlying permafrost
instruments measure temperature as well as composition and stability

cores can also be extracted to analyse layers

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25
Q

satellites to measure permafrost and a bit about it!

A

ERS satellite by the ESA looks at ground temperature and land cover to estimate PF extent. we can’t measure directly

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26
Q

what is the main reanalysis for permafrost and how accurate are they

A

ERA5 and ERA land
overestimates temperature in N America but underestimates at lower latitudes like Tibet

27
Q

example of compiled dataset for permafrost and a bit about it!

A

Zhang et al 1999
contains 3 gridded products showing permafrost extent, permafrost thickness and permafrost zones

28
Q

what do models show of permafrost extent

A

both CMIP 5 and 6 predict an average loss of 60% extent by 2100
40-80% depending on scenario

29
Q

what area of the world is permafrost

A

around 22 x 10^6 km2

30
Q

what % of N hemisphere land is permafrost

A

15%

31
Q

_% of unglacierised land is covered in permafrost above _

A

50% north of 60 degrees N latitude

32
Q

how much of global permafrost is in mountain ranges

A

28%

33
Q

what does borehole data show us about permafrost temperature change (AR6)

A

temperatures increasing over the last 40 years with some regional variations

colder permafrost (under -2 degrees) has increased more in temperature than warmer permafrost

stronger warming also in continuous zone than discontinuous zones

34
Q

how has permafrost ALT changed recently

A

In Arctic there has been a broad increase
in N America a steady rise since 2000
in Tibetan Plateau ALT has risen by 20cm a decade

35
Q

what limits our understanding of permafrost ALT change

A
  1. uneven distribution of observing sites
  2. large variability among existing sites, strongly influenced by local conditions (soil constituents and moisture, snow cover, vegetation)
  3. inter annual variability
  4. thaw settlement on ice rich terrain
36
Q

3 other signs of permafrost degredation

A
  1. ground subsiding and other landscape change like thermokarst and slope instability since mid 20th cent
  2. destabilising rock glacier complexes
  3. increasing size and frequency of avalanches
37
Q

how much of the earth surface and oceans is sea ice

A

7%, 12%

38
Q

what are the classifications of sea ice on its ability to drift and a bit about them!

A

fast ice- frozen - fastened - to shoreline or between shoals or to grounded icebergs

drift (pack) ice further offshore across wide areas and can move with winds and currents. boundary is fast ice boundary

39
Q

what are the classifications of sea ice on its age to drift and a bit about them!

A

new ice - recently frozen seawater that does not yet make solid ice

Nilas - sea ice crust up to 10cm thick. further divided into dark (under 5cm) and light (over 5cm)

young ice - 10-30cm thick, not as flexible as niles and tend to break under wave action

first year sea ice - thicker than young ice but less than 1yr growth

perennial ice - has survive at least 1 melt season. divided into second year ice and multiyear ice

40
Q

what are leads and polynya’s and a bit about them!

A

Both are open water areas between sea ice allowing for interaction between ocean and atmosphere

leads are narrow and linear varying greatly in length, water freezes in winter but is thinner

polynyas are more uniform and larger. 2 types:

sensible heat polynya’s caused by upwelling of warm water

latent heat polynya’s caused from persistent coastal wind

41
Q

3 different ways we can measure Sea ice and bit about them!

A

Sea ice concentration SIC - % of ocean covered by SI

Sea ice area SIA - area of ocean covered by sea ice, linear measure that does not depend on grid resolution

sea ice extent SIE - calculated for gridded products. a binary measure with a threshold of 15% to determine a grid “covered”

42
Q

how is Sea ice thickness calculated

A
  • sonar profiling from submarines since 1953, compiled by Rothrock after cold war
  • altimeters on ERS, ICEsat then Cryosat 2.
43
Q

how is SIA calculated

A

while originally written records by shipping and whaling companies indicated area, now it is satellites

Microwave radiometers on Nimbus and Seasat

44
Q

what is an example of a reanalysis product for sea ice

A

PanArctic Ice Ocean Modelling Assimilation System

PIOMAS

45
Q

how has SIA changed recently

A

decline by around 13% each decade since 1979 (start of satellite)
this is every month of the year

highest losses in summer
arctic SIA is around 25% smaller now than 1980s

46
Q

how has fast ice changed since 1976 and cite!

A

declined by 7% per decade (Yu et al, 2014)

47
Q

model for sea ice

A

SIMIP 2016

works on the shortcomings of CMIP5 and is compiled in CMIP6

48
Q

what has happened to drift speed of sea ice

A

satellites have seen it increase in all seasons
this is because it is less thick

49
Q

where has the antarctic increased and decreased in sea ice in summer

A

increased in Weddell and Ross seas but decreased in Bellingshausen and Amundsen seas

50
Q

how have models shown that anthropogenic forcings have caused a decline in SIA

A

models are run simulating SIA with all possible natural forcing - solar and volcanic - and this shows results nowhere near observed trend

51
Q

what are the difficulty in quantifying forcing and internal variability in terms of SIA

A

large inter model differences

sea ice is increasing in places

52
Q

why has sea ice increased in some places

A

Antarctic ice sheet has melted, leading to increased freshwater fluxes, thus surface ocean cooling, thus sea ice formation

53
Q

what happened in the Weddell sea in 2017 and why

A

largest polyna since 1970, over 40,000 km2, emerged

caused by a subsurface ocean heat flux and changes in ocean circulation

54
Q

for all SSPs in AR6, what does CMIP6 predict to happen to SIA by 2050

A

all will be gone!
less than 15% of SIA of 1980s

55
Q

borehole drawback and cite!

A

preferential slope orientation at the sites, causing temp bias

Biskaborn et al 2015

56
Q

what is the SLSTR

A

sea and land surface temperature radiometer. used by the ESA to estimate PF extent

57
Q

outline ERA5

A

reanalysis product, hourly estimates of atmospheric, land and sea variables. 31km grids.

58
Q

drawback of ERA5 and cite

A

chu et al 2020
overestimated soil temp in Siberia and n America
underestimated in tibet

59
Q

what’s a drawback of CMIP for permafrost and cite

A

not deep enough soil profile
no improvement on summer thaw between 5 and 6
(burke et al, 2020)

60
Q

what have satellites shown us about PF (AR6)

A

ground subsiding and thermokarst indicates slope instability

61
Q

what has reanalysis projected about pf decline

A

its declined by 7% since 197u0

62
Q

how is an increase in snow cover in the arctic affecting PF

A

it is leading to more insolation, thus decadal thawing

63
Q
A
64
Q
A

part 1a (9 decks)

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