We ask what happened to Anne Caroline and notice a new baby Carrie.
Perhaps this interment list will shed some light:
If this Anne M Sorenson that passed away at 1 year 3 months in August 1869 belongs to Anne Margrethe then their second daughter, Anne Caroline, that migrated with them also must have passed away after arriving in America. It is a fourth daughter, then, that shows up in the 1870 census as Carrie Sorensen born about January 1870.
Also notice, Anne H Sevinson died at age 47 years, 10 months in November 1879. This matches the age of Anne Margrethe Nielsdatter Sorensen. So is this person on the interment list the same? It is in Familysearch as such.
Finally notice the death of Soren Sorenson August 1904, age 77.
Again notice the research that could be done to account for this family in the United States.