Antarctica is the coldest, driest place on earth, so you'll definitely want to dress for cooler temperatures -- luckily it only drops into the 20s and 30s during the Austral summer. On some sailings, you won't be getting off the ship, but you may spend a considerable amount of time watching the scenery from out on deck or on your private balcony.
For maximum comfort, layering is best, especially with sweatshirts or silk or wool turtlenecks. You'll probably want to carry fleece gloves and a hat as well. A pair of comfortable, sturdy, non-skid, rubber-soled walking shoes is a must for walking on deck.
On many Antarctica sailings, you'll travel to shore via small boats that depart from the ship, and there additional packing considerations for these cruises. Unless you've already traveled to a very cold climate, you will probably have to purchase a number of items from an outdoor outfitter for your trip.
You'll need waterproof polypropylene or fleece gloves, a hat and warm, waterproof pants, which can be layered over casual pants such as jeans, corduroys, sweatpants or thermal underwear.
You'll also be required to carry a waterproof parka (some cruise lines will provide this) and knee-high rubber boots for excursions on land. If you're departing from Ushuaia, you may be able to rent these items, but keep in mind that during peak times, this gear may be hard to find.
It's also important to keep airline weight restrictions in mind when deciding what to take. Fortunately, the dress code on Antarctica cruises that offer shore landings is generally casual, and most ships feature some sort of laundry facility in case you need it.
Below are some additional tips for packing. Your Vacations To Go expedition cruise specialist will also be able to provide you with a more detailed packing list.