I think the hard part of this is predicting how the global jet stream and polar vortex winds might change in response to disruption of the Atlantic currents. It

I think the hard part of this is predicting how the global jet stream and polar vortex winds might change in response to disruption of the Atlantic currents. It already changes for North America in response to the Pacific subtle temperature oscillation we call El Nino / La Nina. The proximity to the ocean and the general westerly winds of the mid latitudes mean that the west coast gets a moderating marine influence. The cold ocean surface provides us "air conditioning" in summer and yet is also a mild "heater" in winter, helping keep coastal air above freezing temperatures. But, this general background pattern is regularly disrupted by large high and low pressure systems that wander through the region and give us our weather of storms, cold snaps, and heat waves. These cyclonic systems can both carry a somewhat distinct air mass inside them and also disrupt the normal westerly surface flow. And the jet stream is largely in control of steering these systems, making them track further north or south or even helping them stall out temporarily in their generally eastward course.