Gulf Stream and Global Warming?

Question

How will rising global temperatures (natural or manmade) influence the Gulf Stream, which is responsible for moderating Europes winter climate?

With an increase in cold fresh water input into the Nth Atlantic ocean, surely this will cause the Gulf Stream to fail (as it may already be doing so - with a 30 % reduction in water flows since 1990). As a result, wouldn't Europe/Greenland be plunged into an Ice age of sorts, effectively cancelling out the expected effect of global warming?

Answer 1

What a coincidence, the history channel did a documentary today discussing about this topic.

Answer 2

We don't know for sure--but that is the scenario that most analysis suggests. So it's pretty much the working hypothesis.

With one change--Greenland (except for the southern tip) is not affected by the Gulf Stream.  However, the eastern seaboard of North America is.  Thee --and in the north-northwest parts of Europe, the British Isles, Iceland, and possibly the Scandanavian region would be affected.

Answer 3

I disagree with the premise that this could ever happen, but assuming it did...wouldn't you be far more concerned with keeping the East and West Greenland and Labrador currents moving?

Ice bergs and glaciers have been melting for thousands of years, as well as coastal ice shelf breakup (calving).  There is no effect from this melting on the northern currents as your idea would suggest from the additional fresh water.  By now, it would be a major event.  

The gulfstream, flowing from south to north and then eastwards (therefore much less vulnerable) is not affected either.  Some years there is tremendous ice shelf melting, other years almost none.

Answer 4

The total global effect of having a lot of cold fresh water over the Arctic and N,Atlantic will mostly depend on whether the Arctic is largely ice free in summer. If it is, the earth continues to absorb sunlight in summer. Otherwise we regain reflectivity and global warming might stall.

Answer 5

Well sort of.

I do not think that they will necessarily be plunged into an ice age, but winters will be a bit harsher, and summers probably less pleasant.  

Plants that are used to the warmer climates will either die out, or possibly adapt. If they die out, then chances are some animals will follow. This could lead to an ecosystem collapse, which would make the land a bit more barren.

This however would not only be limited to just Iceland and some parts of Europe.  Everywhere else that the gulfstream leads will experience problems too.

This is also assuming that the current stops completely. Apparently there is research showing that the Gulfstream had some problems in the past, but did not shut down. This is partly due to the fact that, at the very least, a small part of the current is driven by the wind. As long as the wind keeps up, the Gulfstream will keep on chugging along. (Theoretically, of course)