Hello, I was wondering what the "I####" code in the remaks section of a METAR means.

Example:
kbis 111650Z 36009kt 1 1/2sm r31/5500vp6000ft -sn br bkn009 ovc014 m09/m11 a2962 rmk ao2 upb11e13fzrae1554snb1554e11b13 cig 008v012 p0000 I1000

At the very end there is I1000, because there is a 1 directly after the "I" that makes me think that it may be related to a negative temperature but I am not sure especially sense there is just 000 that comes after.
Any help you guys can provide will be greatly appreciated!