Kent captain Sam Northeast hit a match-winning 118 not out as the South sealed a series win against the North in Dubai.
The 27-year-old struck twelve fours and a six in the highest score of the series so far as he played a perfectly paced innings to see the South through to 346 for six after being invited to bat first.
After an excellent unbeaten 92 in game one, county colleague Daniel Bell-Drummond was dismissed in the first over without scoring before the South rebuilt through Middlesex’s Dawid Malan (78) and James Vince of Hampshire (46).
Jack Leaning removed Malan and Alsop in successive balls in different overs before Northeast shared a 170-run stand with Hampshire all-rounder Liam Dawson (83) which proved too much for the North.
In reply, an early onslaught by Northants and England opener Ben Duckett (64) and Lancashire’s Liam Livingstone (26) couldn’t last long enough as the South attack struck regularly.
Yorkshire and England all-rounder Tim Bresnan (74) provided the main resistance as scoreboard pressure told with seven players fell to catches, including one from Northeast to remove Worcestershire's Joe Clarke.
The wickets were shared around with two each for Tom Curran, Dawson, Steven Finn and Malan with one apiece for Toby Roland-Jones in a 47-run win.
The third and final 50-over match of the series takes place in Abu Dhabi on Tuesday morning.