Complex sentence: Johansen, in particular, was critical, believing it was too cold on the barrier so early in the season, but Amundsen overruled him, and as the sun rose of 24 August the seven sledges were ready.
Split into simpler sentences: Johansen, in particular, was critical; he warned Amundsen that it was too cold on the barrier so early in the season. But Amundsen overruled him, and as the sun rose on 24 August the seven sledges were ready.