Archive for the ‘snow’ Category

Greenland Update

October 8, 2022

In July 2021 I showed how summer minimum snow cover in Greenland has grown by about 100,000 square kilometres over the past 30 years, and that Greenland could be completely covered by snow all year round in about 45 years.

I explained why this is worth monitoring:

Many scientists think glacial periods start when summer insolation at 65 degrees North decreases enough so that winter snowfall is not completely melted and therefore year by year snow accumulates.  Eventually the area of snow (which has a high albedo i.e. reflects a lot of sunlight) is large enough to create a positive feedback, and this area becomes colder and larger.  Ice sheets form, and a glacial period begins.  This is a gradual process that may take hundreds of years.

Well before global temperatures decrease, the first sign of a coming glacial inception will be an increasing area of summer snow in north-eastern Canada, Baffin Island, and Greenland.

Here is an update with a further two summers of data from Rutgers University.

Figure 1:  Greenland snow area for every month of the year.

Greenland snow cover has been increasing, at an average rate of nearly 1,000 square kilometres a month.

There is a maximum limit:  2,149,412 which is 100% of Greenland (not 2,166,000 – I was mistaken.)

The minimum at the end of summer fluctuates from year to year, and was much less in the past.

Figure 2: Greenland snow area anomalies from monthly means

Snow cover was hundreds of thousands of square kilometres less in the 1960s and 1970s, with an abrupt change in 1978, and a smaller change in the late 1990s.  Before 1978 monthly anomalies above the means were very rare, with large excursions below the means; from 1978 to 1998 there were small decadal fluctuations above and below monthly means; and since 1999 negative values have been rare.

Figure 3: Minimum snow area at the end of summer

There is an increase in the area of unmelted summer snow.   The trend of over 4,000 summer results from step changes in the late 1970s and late 1990s, with the trend continuing.

When we consider the percentage of Greenland covered by snow at the end of summer, the trend is even more startling.

Figure 4:  Percentage of Greenland covered by unmelted snow after summer

Since 1997, the area of unmelted summer snow has remained above 90% of Greenland.  The trend is 0.2% increase each year.  I have extended the x-axis to 2065, and extrapolated the trend line and recent higher and lower values.  IF the trend continues, Greenland may have 100% snow cover for at least one summer by 2030 (8 years from now), and permanent snow cover by about 2063.  (IF)

For comparison I now look at data for North America.

Figure 5: North American snow cover

North America is a very large continent, so there is no upper limit to snow cover.  Snow cover was higher in the past.

Figure 6:  North American summer snow cover

Interesting- when Greenland summer snow cover was low, North American snow was high.  The trend since the mid-1980s is much less steep but still negative- summer snow is still decreasing. 

Now let’s look at winter.

Figure 7:  North American winter snow cover

There’s a surprise.  Winter snow cover is stable- not decreasing- and half a million square kilometres more than 25 years ago.

Figure 8: North American winter snow cover since 1997

Since the late 1990s, winter snow area- as with Greenland summer snow area-has been slowly increasing.

If  this applies to Greenland as well It makes sense- more and thicker snow in Greenland will take longer to melt, so summer snow area will increase.

As I have said previously, short term trends are weather and may not continue, but Greenland is one area that must be watched.