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Tan shades indicate areas where the ice sheet is growing, blue shading indicates areas where it is shrinking.
Tan shades indicate areas where the ice sheet is growing, blue shading indicates areas where it is shrinking.
Thawing permafrost widespread evidence of melting to melt all the permafrost will take centuries locally disruptive melting is occurring methane is liberated when permafrost melts remote possibility that methane in minerals may be released interaction with forest fires; shrubs encroaching on tundra permafrost thawing will be accelerated if summer sea ice continues to retreat
Photo at left is from the parking lot of the Gophysical Institue, University of Alaska at Fairbanks
Snow cover
from the IPCC Fourth Assessment Report, 2007
Snow cover
Based on analyses by David Robinson, Rutgers University. These charts are on line at www.tamino.wordpress.com
Most of the loss of snow cover is due to the summer season.
The changes in the cryosphere are dramatic and wide ranging
Important implications for
ecosystems
water resources
exploitation of the Arctic
geopolitics
Some of these changes are probably linked to global warming
The bottom line
How long has the permafrost been thawing? Are there places where it is advancing? Are changes in land use a factor?
Is the trend in snow cover independent of the shrinking of summer glaciers and snow fields?
Why is sea ice retreating? Are changes in wind playing a role?
Why is it retreating in the Arctic but not in the Antarctic?
Is the summer melting of the Greenland ice cap unprecedented?Is the trend real?Will the melting accelerate?
How far back in time can the retreat of the mountain glaciers be traced?
Outstanding scientific issues
The Oceans (text p. 106-127)
From sticks to satellites: measuring sea levelMonitoring the ocean below the surfaceBalancing the sea level budgetHow high the sea?Climate change and El NiñoWill the Atlantic turn cold on BritainLiving in a changing seaCoral reefs at risk ocean acidification
Sea level : the tides
An animation
Sea level: tsunamis
An animation
From sticks to satellites: measuring sea level
In records like these, tides and events like tsunamis are smoothed out.
Monitoring the ocean below the surface
Monitoring the ocean below the ocean surface
Argo floats
Argo floats
Stephen Riser, Oceanography
TOGA TAO mooringsNOAA / PMEL
Processes that determine local sea level change
Lifting or subsiding of Earth’s crust
Changes in atmospheric pressure
Changes in ocean currents
Changes in storage of stored in lakes, rivers and ground
Thermal expansion of sea water as it warms
Melting of continental ice sheets and glaciers
Lifting or subsiding of Earth’s crust.... isostatic adjustment
Model Derived from GPS
+
–
–+
Lifting or subsiding of Earth’s crust.... isostatic adjustment
from “Sea Level Rise in the Coastal waters of Washington State”, a report for the State Department of Ecology written by Philip Mote and other members of the University of Washington’s Climate Impacts Group. Available on line on the course web site
Changes in atmospheric pressure
Changes in ocean currents
Processes that determine global-mean sea level change
Changes in storage of stored in lakes, rivers and ground
Thermal expansion of sea water as it warms
Melting of continental ice sheets and glaciers
Evidence that sea water is warming. Based on XBT data (ocean temperature measurements from soundings dropped from ships).
Sea level rise in mm from 1860 onward based on a merging of three different datasets.
A more detailed representation of the satellite altimetry measurements of sea level.
IPCC projections based on the assumption of no further changes in the mass of the Greenland ice sheet and a modest thickening of the Antarctic ice sheet due to enhanced snowfall as the climate warms. So far, the observations are tracking the most pessimistic estimate.
1961 to 2003
1993 to 2003
The message: sea level is rising faster than can be accounted for by taking into account the thermal expansion of sea water as it warms and estimates of the melting of the continental ice sheets that has occurred thus far. Note that rates of change are larger in the 1993-2003 data.From the 2007 IPCC report.
Regions colored black are less than a meter above the current sea level; red less than 3 m. The current rate of sea level rise is around 3 mm per year or 1 meter per 3 centuries. If major pieces of the Greenland ice sheet or West Antarctic ice sheet begin to melt at an accelerated rate, sea level would begin to rise faster.
The current rate of sea level rise is around 3 mm per year or 1 meter per 3 centuries. If major pieces of the Greenland ice sheet or West Antarctic ice sheet begin to melt at an accelerated rate, sea level would begin to rise faster.
The current rate of sea level rise is around 3 mm per year or 1 meter per 3 centuries.
Regions colored black are less than a meter above the current sea level; red less than 3 m.
A few more comments about sea level rise
sea level rise is a delayed response to global warming
IPCC projections for the 21st century may be overly conservative
melting of sea ice does not cause sea level to rise
A few more comments about sea level rise
sea level rise is a delayed response to global warming
IPCC projections for the 21st century may be overly conservative
melting of sea ice does not cause sea level to rise
global sea level has dropped by 120 m since the peak of the last ice age
sea level rise is a delayed response to global warming
IPCC projections for the 21st century may be overly conservative
melting of sea ice does not cause sea level to rise
global sea level has dropped by 120 m since the peak of the last ice age
“The Day After Tomorrow” had it wrong: sea level should have dropped!
Climate change and El Niño
The orange shading denotes the region in which sea surface temperature tends to be above normal during El Niño events.
D
SST
Variations in equatorial Pacific sea surface temperature (SST) are referred to as El Niño (EN), the Spanish word for the Christ Child. Pressure at Darwin is an indicator of the Southern Oscillation (SO). Since the two vary these variations are viewed as manifestations of a single coupled atmosphere-ocean phenomenon, referred to as ENSO.
El Niño
La Niña
Sea surface temperature is represented by the colored shading. The arrows show the surface winds. Easterlies along the equator drive upwelling, which brings nutrients up to the surface.
Left: sea level as inferred from satellite altimetry data. Right; cross section of winds and ocean currents along the equator in the Pacific. Upper panel represents normal conditions and the lower panel indicates how conditions change during El Nino. From a primer on El Niño at http://www.atmos.washington.edu/gcg/RTN/rtnt.html
El Niño
La NiñaM
El Niño
La Niña
M
G
G
Shading represents the regions of heavy rainfall and arrows denote surface winds. M denotes Marshall Islands, G the Galapagos Is;ands
Rainfall anomalies during El Niño yearswetter than normal drier than normal
Most continental regions are anomalously dry during El Niño years, while desert islands in the equatorial Pacific experience heavy rainfall.
ENSO modulates tropical rainfall
Most continental regions tend to be drier than normal during El Niño years
It appears likely that global warming will make tropical climate more El Niño-like, with drier conditions over most of the tropical continents
No indication that this is happening yet
Climate change and El Niño
1997 Indonesian wildfires
The waters shaded green have high chlorophyll content due to phytoplankton blooms. The phytoplankton (plant plankton) feed on the nutrients brought up to near the surface by the wind-driven equatorial upwelling. Phytoplankton are at the bottom of the food web.
La Niña
El Niño
(a) cryosphere
Coral reefs at riskWhy is El Ninõ of interest in a global warming course?
It provides an example of widespread climate impacts and how ecosystems and society adapt to them
Climate models indicate a shift in the mean climate toward a more “El Niño-like” state as the Earth warms. Hence “El Nino” is an analog for global warming.
Coral reefs at risk
Coral reefs at risk
Coral reefs at riskCoral bleaching
Coral reefs at riskCoral bleaching
Coral reefs at riskCoral bleachinga vivid sign of corals responding to stress which can be induced by: ▪ increased or reduced water temperatures (often attributed to global warming) ▪ increased solar irradiance (photosynthetically active radiation and ultraviolet band light) ▪ changes in water chemistry (in particular ocean acidification) ▪ starvation caused by a decline in zooplankton levels as a result of overfishing ▪ increased sedimentation (can be contributed to silt runoff) ▪ pathogen infections ▪ changes in salinity
Coral bleaching is the loss of color of corals, due to stress-induced expulsion of symbiotic unicellular algae or due to the loss of pigmentation within the algae
Another risk to coral: ocean acidification
Coral reefs at riskCoral bleaching
.................Coca Cola
Coral reefs at riskCoral bleaching
Sparkling mineral water is a negligible cause of dental erosion. While the dissolution potential of sparkling water is greater than still water, levels remain low: by comparison, soft drinks cause tooth decay at a rate of several hundred times that of regular sparkling water. De-gassing of a sparkling mineral water reduces its dissolution potential, but the total levels are still relatively low, suggesting that carbonation of drinks may not be an important factor in causing dental erosion.
Coral reefs at riskCoral bleachingWhen CO2 dissolves in seawater, carbonic acid is produced via the reaction:
This carbonic acid dissociates in the water, releasing hydrogen ions and bicarbonate:
The increase in the hydrogen ion concentration causes an increase in acidity, since acidity is defined by the pH scale, where pH = -log [H+] (so as hydrogen increases, the pH decreases). This log scale means that for every unit decrease on the pH scale, the hydrogen ion concentration has increased 10-fold.
One result of the release of hydrogen ions is that they combine with any carbonate ions in the water to form bicarbonate:
Chemistry of ocean acidification
Coral reefs at riskCoral bleachingWhen CO2 dissolves in seawater, carbonic acid is produced via the reaction:
This carbonic acid dissociates in the water, releasing hydrogen ions and bicarbonate:
The increase in the hydrogen ion concentration causes an increase in acidity, since acidity is defined by the pH scale, where pH = -log [H+] (so as hydrogen increases, the pH decreases). This log scale means that for every unit decrease on the pH scale, the hydrogen ion concentration has increased 10-fold.
One result of the release of hydrogen ions is that they combine with any carbonate ions in the water to form bicarbonate:
Chemistry of ocean acidification
Coral reefs at riskCoral bleaching
the source of the carbonate ions is calcium carbonate CaCO3
In your stomach or in the ocean, the chemistry is the same
Coral reefs at riskCoral bleaching
Pre-industrial (1700s) 8.18Recent past (1990s) 8.102050 (2×CO2 = 560 ppm) 7.952100 (IS92a) 7.82
Ocean AcidificationpH
Decreasing pH means increasing acidity. Note that the tropics have thus far been spared from large changes.
Harmful algal blooms (HABs)
