Area 1 - Landing
Ok so we start the mission big. At the start hide behind the crates and the good thing is that you have a Threat Detection weapon, which is awesome. After clearing a little bit the area you HAVE move forward otherwise you won't be able to reach the enemies. Use the snow dunes that are throughout the area and slowly continue. Use your Threat Grenades to locate the enemies and stay away from them as they like to throw grenades.
There's an MDL somewhere around the beginning of the mission. Make sure to grab it because we have some ASTs coming up. Stay behind the dunes and even a tank comes out. Shoot until you fall down the pit.
Area 2 - Ice Caverns
After crossing the water and the slow-mo event, we're left in a room filled with Atlas enemies. Quickly jump up to the right side of the cave, shoot the three enemies here and the ones down the path. Stay behind the large pillars because even more enemies will come get you. Stay on the upper ledge when you see more enemies dropping down and quickly dispose of them. Do the same thing in the next part of the cavern, stay behind the pillars and take quick and short peeks to see where the enemies are.
Area 3 - Sniping spot
In this place take the MORS and start shooting the enemies down one after the other. You can pretty much take care of most of the enemies from up here, if you don't want to just jump down and use the snow dunes on either side as cover while you take care of the enemies with the MDL (if you still have it).