Simplot at Bathurst are a leading food processor of products including Edgles Birdseye and Chico rolls and although inland, they are exposed to enough moisture to cause ice problems in -20C stores. The site has multiple entrances and use of Desiccants to reduce the incoming dewpoint was the final solution.
Seibu Giken DST modell RA061R (1450m3/hr) desiccant dehumidifier is a reliable option, as it is electro mechanical control means it can be locally services without circuit cards to confuse any diagnosis. Its stainless steel construction is also useful in food crade areas which are frequently washed. Installed into the dock area and able to remove 10kg/h or water vapour, the units would control to 0Cdp at doc temperatures around 10C. With the dry air directed towards the freezer door at -30Cdp the dryness of the infiltrating air would be adequate to avoid icing issues.
http://tomgrafix.com/sites/somafm/80s.html Americold reduce ice from 15 busy truck doors
In larger loading docks with multiple dock doors the CFA series provides more substantial capacity and ability to locate outdoors and use waste heat effectively.