A personal observation is that the young clades appear reach peak frequencies in various littoral zones, excluding Central Europe which obviously a product of the Bronze Age.
Of course any haplogroup will have a peak frequency near water, after all, that's where people live. But if you break this down further to include the island nations in the Mediterranean, Atlantic and North Sea, it seems there could be a maritime element.
If I can get a copy of the presentation or paper, I'll put it up.
"Disentangling the expansion of major European mitochondrial DNA lineages"
Dulias, Fichera, Silva, Gandini, Rito, Edwards, Pala, Soares, Richards. University of Hutterfield, 2017
"Phylogenetics aims to investigate the evolutionary history within or between species by identifying relationships between DNA sequences comparing multiple genomes. Looking at the female line of descent, the majority of the modern-day European population (~40%) belongs to mitochondrial (mt)DNA haplogroup H. However, its sister clades within HV(xH,V) are observed at higher frequencies in Southern Europe and the Near East and most of these show a post-glacial expansion, suggestive of a Near Eastern origin and subsequent Mesolithic spread into Europe. On the other hand, analysis of ancient DNA infers that haplogroup H first appeared in the Early Neolithic, with the lineages that subsequently came to dominate across Europe becoming established during the Middle Neolithic period. H reached higher frequencies again during the appearance of the Bell Beaker culture in the Copper Age, but its complex evolutionary history makes it still uncertain when and how H became the dominant European haplogroup. Its most common subclades in Western Europe are H1 and H3, which peak in their abundance in modern Iberia. Using phylogenetic and founder analysis, we estimate arrival times of HV(xH,V), H1 and H3 in Central Europe and the British Isles, thus disentangling population movements out of Iberia at different times. Our results show differences in the arrival times of H1 and H3 to Central Europe and the British Isles, with H1 having been involved in more expansions than H3."