There are a number of key indicators, beyond our rising global temperature, that show Earth’s climate is changing. One of these is Arctic sea ice.
Measured via satellite since the late 1970’s, the extent and thickness of sea ice tend to vary from year to year but both have been in an overall decline for decades. According to NASA, the melt season in the Arctic has increased by 37 days since 1979.
Sea ice extent, the area of ocean with at least 15% sea ice, has a strong seasonal cycle. It typically peaks in March as winter ends and then declines during the summer, reaching a minimum in September. In March 2017, it hit a record low maximum for the third year in a row. The record minimum occurred in September 2012.
According to the National Snow and Ice Data Center, the average age of Arctic sea ice is also changing. Thick multi-year ice – the ice that lasts through at least one melt season – has decreased 11% per decade since the satellite era began. That means there is more first-year ice, which tends to be thin and brittle. This is troublesome because it is more vulnerable to warming temperatures and wave action.
Sea ice is frozen ocean water. It forms, grows, and melts in the ocean. In contrast to land ice (glaciers), it does not contribute to sea level rise. However, as it melts it creates a global warming feedback loop. Ice is lighter in color and reflects more sunlight than dark ocean water. So, as more ocean water is exposed, more of the sun’s energy is absorbed. This drives temperatures up even further and causes more ice to melt.
The Arctic is now warming twice as fast as the rest of the planet – a phenomenon known as “Arctic amplification.” At this rate, scientists expect the region to be ice-free in summer by the 2030s.
On Monday night, a group of teenagers fell through the thin ice on a body of water in Central Park known as The Pond. Luckily, all were saved by the quick actions of good samaritans and NYC’s outstanding first responders. That said, this unfortunate incident is a salient reminder about safety issues for all winter activities that take place on the ice.
Winter is usually the time for ice-skating, ice-fishing, cross-country skiing, and snowmobiling. This year, however, unseasonably mild conditions have limited the opportunities for many of these popular pursuits. While there have been a few blasts of cold air, they have not lasted long enough to produce ice that can sustain significant weight. Below are some guidelines on how thick the ice needs to be to support different activities.
It is also important to remember that the thickness of ice can vary dramatically at different locations on the same body of water. Therefore, it is always best to follow the instructions of local officials and posted signs. Moreover, as the old saying goes: “If in doubt, don’t go out!”
Most people often associate spring with flowers and mild weather. But as a transitional season, it can also produce some serious cold spells. Wearing shorts one day and a parka the next, you start to wonder when the cold will finally fade away.
The answer to that question largely depends on where you live. Below is a map from NOAA that shows the typical final freeze dates across the continental US. While actual weather conditions vary from year to year, the dates shown are based on climatology – a thirty-year average of temperature data.
Here in New York City, our last spring freeze usually comes in mid-April.
How cold has it been in New England recently? Cold enough for ocean waves to partially freeze along the coast of Nantucket Island in Massachusetts.
Photographer Jonathan Nimerfroh captured these unusual slushy waves on February 20th, when the local air temperature reached a high of only 19°F. While freshwater freezes at 32°F, seawater – owing to its salt content – has a lower freezing point of 28.4°F.
To see more images of this uncommon wintry phenomenon, visit the photographer’s website.
Image Credit: Jonathan Nimerfroh
Icicles are a classic symbol of cold winter weather. In order to form, however, they need a mix of both warm and cold conditions.
These hanging pieces of tapered ice develop when the air temperature is below freezing, but there is enough heat from the sun – or in the case of a building, a poorly insulated roof – to thaw some snow. As the melt water runs off the edge of a surface, it re-freezes in the cold air. Starting with only a few water droplets, an icicle can begin to form. Over time, as melt water continues to drip and re-freeze, an icicle gains both layers of thickness and length.
Often seen forming along the edge of roofs, icicles can also be found on tree branches, power lines, and rocks where water seeps out of the ground. The size and shape of an icicle, according to experts at the National Snow and Ice Data Center, depends on a few different factors. These include the shape of the surface on which it forms and the number of different directions from which melt water approaches the growing icicle.
Icicles can range in size from a few inches to tens of feet.
Icicles in the sunshine. Credit: MLE
It is now June, the first month of meteorological summer, but it seems winter is only just coming to a close on the Great Lakes.
For the first time since November, according to NOAA, the Great Lakes are ice-free. This marks the latest total thaw on the lakes since record keeping began in the 1970s. Back in March, during one of the coldest winters the region has seen in decades, more than 92% of the Great Lakes were covered by ice. That was the second highest percentage on record.
While a recent string of warm days in the area helped to melt the lingering ice, the U.S. Coast Guard also played a key role. They have reported conducting over 2000 hours of ice-breaking operations throughout this past winter and spring.
Only recently thawed, water temperatures in the lakes are expected to remain rather chilly for most of the summer.
After a frigid winter, the Great Lakes are finally ice-free. Image Credit: NOAA
Persistent frigid temperatures this winter across the Mid-West and Northeast have caused many rivers and lakes to freeze. These include the Great Lakes – the largest group of fresh water lakes on the planet.
According to NOAA’s Great Lakes Environmental Research Laboratory, 91.8% of the Great Lakes are currently covered with ice. That is the second highest percentage on record. The largest was 94.7% in 1979. On average, peak ice coverage each winter is roughly 51%.
This extensive ice cover has its pluses and minuses. On one hand, it has reduced the amount of lake effect snow – the heavy precipitation produced when cold air blows across the expansive and relatively warm lake water. When the lakes are frozen, moisture cannot be evaporated and this process shuts down. On the other hand, it has slowed shipping traffic, which has economic impacts. Also, given their massive size, the frozen lakes will likely keep regional temperatures cooler than average this spring.
While this year’s ice cover on the Great Lakes is near record-breaking, researchers say the ice extent varies annually and that there has been an overall decline since the early 1970’s.
Ice covers more than 90% of the Great Lakes. Image Credit: NOAA/Great Lakes Environmental Research Laboratory.
Winter, like all seasons, has its pluses and minuses. With freezing temperatures and accumulating snow, it can produce travel problems and other difficulties. On the other hand, it also creates the opportunity for a variety of outdoor activities like skiing, sledding, ice-skating, snowshoeing, and of course, the Winter Olympics.
Love of Winter, a painting by George Bellows from 1914, captures the spirit of those who embrace the season. A personal favorite, it portrays the movement of skaters on a frozen pond. Filled with activity and color, the scene conveys the joy of being outdoors on a crisp winter day.
Love of Winter, 1914 by George Bellows. Oil on Canvas (32.5 x 40.5 inches). The Art Institute of Chicago, Friends of American Art Collection.
Coming on the heels of a very snowy January, a series of winter storms slammed the midwest and northeastern U.S. this week. From snow to sleet to freezing rain, the region saw a bit of everything.
Here in New York City, Monday’s storm dumped 8 inches of heavy, wet snow in Central Park – setting a new daily snowfall record. Only two days later, another weather system brought the Big Apple a wintry mix that included 4 inches of snow topped with about 0.25 inches of ice.
These two storms brought the city’s monthly snowfall total up to 12 inches and it is only the first week of February. On average, we usually receive 8.8 inches for the entire month. Overall, local snowfall has been running above average this winter season with 40.3 inches of accumulation to date.
While more snow is on deck for the weekend, NYC is not expecting significant accumulation, contrary to earlier reports.
A rare winter storm paralyzed large sections of the southeastern United States yesterday. Serious impacts from snow, sleet, and freezing rain were felt from the Gulf Coast to Virginia.
According to the NWS, 2.6 inches of snow fell in Atlanta, GA – a new daily record for the region’s largest city. As a whole, the Deep South is not accustomed to wintry precipitation and most cities and towns are not equipped to deal it. Salt spreaders and snowplows are in short supply across the region. As a result, major roads turned into sheets of ice creating very hazardous travel conditions.
The timing of the storm made the situation even worse. Arriving in the afternoon, many people were caught on the roads trying to make their way home. Officials have reported hundreds of traffic accidents and stranded vehicles. Many people were even forced to shelter in place overnight in cars, schools, and stores.
Snow and ice bring travel to a stand still near Atlanta, GA. Image Credit: GuardianLV.com