The calculation is actually very straightforward. The measurement dubious. One need only calculate the moment of interia of the water spread uniformly over the world’s oceans. Assuming a spherical shell is more than good enough for a couple of decimal places accuracy, but one can easily find displacement for the polar axis as a function of latitude and oceanic boundries therefrom and calculate the angulur inertia of the displaced mass. Repeat the calculation for the impounded mass of water, take the difference over the undisplaced moment and multiply by 86000 (24 x 60 x 60) seconds. They figure approximately a 0.00000000006944444444444% increase in the earth’s moment of inertia around the polar axis. IOW, a rainy day in Brazil.
It’s the angular shift, not the speed of rotation that’s impacting climate/weather. The speed of rotation didn’t change North Atlantic weather patterns. Speed is a red herring.