A recent paper and a sudden melting of the Greenland ice sheet bring the expectation of high levels of rising seas even closer (if it wasn’t enough so far).
The paper is ‘Deglacial rapid sea level rises caused by ice sheet saddle collapses’ by Gregoire, Payne and Valdes published in Nature (from Bristol University).
It looks at the mechanism for rapid ice sheet melt and identifies a “saddle” effect where as a portion of the ice sheet that is lower melts, it lowers in altitude, thus increasing the melt in a positive feedback effect. The authors were surprised when they compared this mechanism with two periods of rapid melt at the end of the last ice age when saddles between higher ice sheets melted within a period of 500 years giving rise to multiple meters of sea level rise.
They found their model matched the Melt Water Pulse 1a (9m of rise in 500 years around 14,500 BCE) and another event around 8,500 BCE (2.5m of rise from one particular ice sheet, again in a few centuries).
The important point is that we are becoming able to model ice sheet collapse as more research is done. Enter Antarctica – the sleeping giant!
The other point regards melting of Greenlands entire ice surface during a period of a few days from 8th to 12th of July. Most of this melt will have re-frozen soon after but the fact that 97% of the greenland ice sheet surface had a melting event is unprecedented. If this event occurs again in coming years it would bode a serious acceleration in ice melt with resulting consequences for sea level rise. Current high estimates of 1.2 to 1.8m by 2100 may need to be revised upwards.
In our Woy Woy Forum on the 25th Aug (Woy Woy Community Centre, 1 – 4pm) we hope to hear the latest report on climate change from our visiting scientist, Alex Sen Gupta (http://web.maths.unsw.edu.au/~alexg/). Alex researches the interaction of oceans with the atmosphere. This covers the influence of the Indian Ocean Dipole and El Nino/La Nina that so strongly affect Australia’s climate. He is working with John Church of Hobart Uni who is a leading scientist on sea level rise.