Porisjokull (Thorisjokull) is a small 25 square kilometer ice cap southwest of Langjokull. The top elevation of the icecap is just 1350 m. This ice caps outlet glaciers have been in retreat as have almost all Iceland glaciers in the last decade (Helgi Björnsson and Finnur Pálsson, 2008). Examination of Landsat images from 2000, 2002, 2011 and 2012, shown in that order below, are used to identify changes in Porisjokull. The primary changes in the periphery are retreat of two lobes on the east side of the icecap at the yellow and red arrow and loss of ice at glacier connections green arrow and purple arrow. The comparison of the 2000 and 2011 images in particular illustrate the complete loss of the lobes at the yellow and red arrow. Between outlets of the icecap areas of glacier area have diminished significantly at the green and purple arrow. The lobe at the yellow arrow has been lost, this represents a retreat of 500 m. At the red arrow the lobe has also been lost, a retreat of 400 m. In the Google Earth images below the lobes still exist. At the green arrow the glaciated area declined from 1.2 square kilometers to 0.5 square kilometers. At the Purple arrow the margin of this intermediate lob has retreated 300 m. The icecap changes has mirrored that of nearby Langjokull, Gudmundsson et al (2008) identified thinning across the accumulation zone of Langjokull from 2000-2007. This led to retreat of the largest outlets of Langjokull.
Bjornsson and Gislason (2010) have examined the climate change that is driving the response of the glaciers.