In a small saucepan bring the water and the wine to a boil with the gingerroot, the black peppercorns, and the bay leaf and let the mixture stand, off the heat, for 5 minutes.
In a large buttered baking dish arrange the salmon, skin side down, and sprinkle it with salt to taste. Add the wine mixture and poach the salmon, covered tightly with foil, in the middle of a preheated 400°F oven for 20 to 25 minutes, or until it just flakes and is cooked through.
Make the sauce while the salmon is poaching:
In a bowl whisk together the sour cream, the mayonnaise, the mustard, the gingerroot, the zest, the juice, the green peppercorns, the sugar, the vinegar, and salt to taste and let the mixture stand at room temperature for 20 minutes to let the flavors develop.