Just last night I happened upon a program that brought to light the recent discovery of a gigantic impact crater on Greenland that may have been responsible for ending the last ice age.
Search on Hiawatha Glacier, or Hiawatha Crater for in-depth information about it.
In a nutshell, the crater is as wide as the city of Paris. The impactor itself is estimated to have been a mile in diameter, and five cubic miles in volume.
"Scientists have discovered a 31km wide impact crater beneath the Hiawatha glacier in Greenland. The discovery, published in Science Advances, was made using airborne radar surveys which unveiled a circular bedrock depression beneath the ice.The presence of quartz and other grains and features on the ground helped the team confirm the finding – these showed signs of having been subjected to large shock pressures. Analysis of the grains also shows that the impact was most likely made by an iron meteorite more than 1km wide. It would have occurred during the Pleistocene, between about 12,000 and 3m years ago."
Huge crater discovered in Greenland – here’s how the impact may have wiped out the mammoths
The Earth did suffer massive bombardments of asteroids and comets in the past, but this happened billions of years ago, whereas the most recent ice started ending roughly 12,000 years ago.
That probably refers to the so-called Late Heavy Bombardment -- besides the recently identified Greenland impact you mentioned, epic impacts have occurred a number of times even since the Chicxulub impact that ended the Cretaceous, two that come to mind (thanks to the late Eugene Shoemaker) are the Ries Basin impact and the Meteor Crater impact.
links to a couple of topics about the Greenland impact:
http://www.freerepublic.com/focus/chat/2749085/posts?page=77#77