Tarragon and coriander infuse carrots with unexpected flavor.
Bring a large saucepan of water to a boil; add salt. Prepare an ice-water bath; set aside. Quarter carrots lengthwise; cook until just tender, about 3 minutes. Immediately transfer with tongs to the ice-water bath. Drain well; transfer to a large bowl.
Bring 2 cups water, the vinegar, tarragon, coriander seeds, peppercorns, and 2 tablespoons salt to a boil in a medium saucepan. Reduce heat; simmer 4 minutes. Pour brine over carrots; let cool completely, about 30 minutes. Transfer to airtight containers; refrigerate at least 1 week (pickles will keep 3 weeks more).