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FROZEN HEAT

58

Figure 3.5:

Current values and future changes in Arctic bottom-water temperatures. Left: Map of the modern bottom-water temperatures in

an ocean model at 1/2° resolution (1985-2004). Right: Trend in bottom-water warming under elevated pCO

2

as predicted by the Kiel Climate

Model (KCM) (in °C per 100 years). The contour line depicts the 400-metre water-depth contour (From Biastoch

et al.

(2011)).

-2

-1

0

1

2

Mean bottom water temperature (1985-2004), °C

Arctic bottomwater temperature

400 metres isobath

Source: redrawn from Biastoch, A.,

etal

., Rising Arctic Ocean

temperatures cause gas hydrate destabilization and ocean acidi…cation

Arctic Ocean

Laptev

Sea

European

Nordic Sea

-2 -1 0

3 4

1 2

5

Mean trend per 100 years, °C

Trend in Arctic bottomwater temperature

400 metres isobath

Source: redrawn from Biastoch, A.,

etal

., Rising Arctic Ocean

Arctic Ocean

Laptev

Sea

European

Nordic Sea

duces a pressure increase at the sea floor and may help to sta-

bilize marine gas hydrates. However, IPCC projections of eu-

static sea-level rise are generally less than two metres by 2100

and not expected to significantly enhance the stability of gas

hydrates, which are more sensitive to temperature than pres-

sure (Ruppel 2000, 2011; Reagan and Moridis 2008). For

example, modelling by Tishchenko

et al.

(2005) shows how

the complete breakdown of the Greenland ice sheet, and the

seven-metre sea level rise it would cause, would only protect

gas hydrates from a ~0.2 °C temperature increase. In fact, as

discussed in Section 3.5.4, sea level rise might actually have

accelerated gas hydrate dissociation along Arctic shelves by

submerging and warming the sediment. Other changes in

the ocean regime, such as sea-ice cover in the Arctic, wave

and current regime, or hydrology, are also not expected to

have a great influence on gas hydrate stability.