Splits. Clean out dust and debris. Coat the trough with asphalt roofing compound. Smooth freezer-grade aluminum foil into this. Then cover with more roofing compound.
If splits are bad, try to nail wood together. If this is impossible, tack a large sheet of heavy aluminum flashing to bottom of gutter. Then use asphalt roofing compound and aluminum foil in the trough. However, it may be smarter to have gutter replaced entirely.
Ice builds up in gutter, backs up water, which leaks through roof. See
gutter, metal.