Notes on the sea-ice along the east coast of Greenland. 205 
aided by the comparatively warmer spring-weather eats large holes into 
the floes, weakening them very much and forming a line of breakage. 
The melting having proceeded so far, the year-old ice-field breaks 
up, and its destruction is accelerated by the constant crush and grinding 
along its edges of older floes. 
The year-old ice is thus at an early period broken up in many small 
floes, and the waves, warmer weather, melting water etc. get a larger 
surface to demolish, which also accelerates matters. 
The greater part of this comparatively thin ice, which during the 
winter has filled all the open spaces between the older floes, will probably 
have disappeared at the end of July — if not before. 
The effect of the comparatively warm weather during the spring 
will not make itself felt on the older ice, before some time has elapsed, 
partly owing to the non-conducting snowlayer on its surface, and partly 
on account of the low temperature, which the ice has retained from the 
preceding winter. The temperature of the ice and snow must first rise al- 
most to zero, after which the melting begins all of a sudden. 
But this will not happen at the earliest before the end of June or 
the beginning of July, and in conjunction with the above-mentioned 
causes this will have the effect that the ice-belt decreases most from 
June to July and less again from July to August, when the greater part 
of the year-old ice has disappeared, so that the decrease in the extent 
of the ice-belt for the rest of the season can only be caused by the demo- 
lishing effects of the ice-crushing waves and melting. 
The outer edge of the pack-ice recedes on an average 150 miles 
during the period from April to August, between 77° N. Lat. and 67° 
N. Lat. 
This receding of the edge of the pack-ice has been discussed at 
some length by PETTERSON, who on the strength of the observations 
of one year, published in "The State of the Ice in the Arctic Seas” (1896) 
calculated that the edge receded westward with the rate of about 5 miles 
a day, durmg April and May. This however is not the case, but it 
may be brought to mind that the limits of the ice were unusually 
easterly during this year (1896). The mean of nineteen years of obser- 
vations shows — as stated above — that the ice recedes 150 miles in 
about as many days, or only one mile a day. PETTERSON maintains!) 
that we must look for the cause of this receding in the melting of the 
ice, caused by an underlying layer of water from the Gulf-Stream, which 
comes within a couple of hundred metres of the surface, but it is difficult 
to understand, why this heat should be able to influence the melting of 
the pack-ice through 200 metres of cold surface-water, particularly as 
the ice is never stationary, but drifts rather rapidly to the south over 
the places, where the Gulf-Stream sends branches towards the east 
coast of Greenland. 
1 Ymer. (1900, pag. 176. 
