From the University of Colorado at Boulder
Warming North Atlantic water tied to heating Arctic, according to new study
The temperatures of North Atlantic Ocean water flowing north into the Arctic Ocean adjacent to Greenland — the warmest water in at least 2,000 years — are likely related to the amplification of global warming in the Arctic, says a new international study involving the University of Colorado Boulder.
Led by Robert Spielhagen of the Academy of Sciences, Humanities and Literature in Mainz, Germany, the study showed that water from the Fram Strait that runs between Greenland and Svalbard — an archipelago constituting the northernmost part of Norway — has warmed roughly 3.5 degrees Fahrenheit in the past century. The Fram Strait water temperatures today are about 2.5 degrees F warmer than during the Medieval Warm Period, which heated the North Atlantic from roughly 900 to 1300 and affected the climate in Northern Europe and northern North America.
The team believes that the rapid warming of the Arctic and recent decrease in Arctic sea ice extent are tied to the enhanced heat transfer from the North Atlantic Ocean, said Spielhagen. According to CU-Boulder’s National Snow and Ice Data Center, the total loss of Arctic sea ice extent from 1979 to 2009 was an area larger than the state of Alaska, and some scientists there believe the Arctic will become ice-free during the summers within the next several decades.
“Such a warming of the Atlantic water in the Fram Strait is significantly different from all climate variations in the last 2,000 years,” said Spielhagen, also of the Leibniz Institute of Marine Sciences in Keil, Germany.
According to study co-author Thomas Marchitto, a fellow at CU-Boulder’s Institute of Arctic and Alpine Research, the new observations are crucial for putting the current warming trend of the North Atlantic in the proper context.
“We know that the Arctic is the most sensitive region on the Earth when it comes to warming, but there has been some question about how unusual the current Arctic warming is compared to the natural variability of the last thousand years,” said Marchitto, also an associate professor in CU-Boulder’s geological sciences department. “We found that modern Fram Strait water temperatures are well outside the natural bounds.”
A paper on the study will be published in the Jan. 28 issue of Science. The study was supported by the German Research Foundation; the Academy of Sciences, Humanities and Literature in Mainz, Germany; and the Norwegian Research Council.
Other study co-authors included Kirstin Werner and Evguenia Kandiano of the Leibniz Institute of Marine Sciences, Steffen Sorensen, Katarzyna Zamelczyk, Katrine Husum and Morten Hald from the University of Tromso in Norway and Gereon Budeus of the Alfred Wegener Institute of Polar and Marine Research in Bremerhaven, Germany.
Since continuous meteorological and oceanographic data for the Fram Strait reach back only 150 years, the team drilled ocean sediment cores dating back 2,000 years to determine past water temperatures. The researchers used microscopic, shelled protozoan organisms called foraminifera — which prefer specific water temperatures at depths of roughly 150 to 650 feet — as tiny thermometers.
In addition, the team used a second, independent method that involved analyzing the chemical composition of the foraminifera shells to reconstruct past water temperatures in the Fram Strait, said Marchitto.
The Fram Strait branch of the North Atlantic Current is the major carrier of oceanic heat to the Arctic Ocean. In the eastern part of the strait, relatively warm and salty water enters the Arctic. Fed by the Gulf Stream Current, the North Atlantic Current provides ice-free conditions adjacent to Svalbard even in winter, said Marchitto.
“Cold seawater is critical for the formation of sea ice, which helps to cool the planet by reflecting sunlight back to space,” said Marchitto. “Sea ice also allows Arctic air temperatures to be very cold by forming an insulating blanket over the ocean. Warmer waters could lead to major sea ice loss and drastic changes for the Arctic.”
The rate of Arctic sea ice decline appears to be accelerating due to positive feedbacks between the ice, the Arctic Ocean and the atmosphere, Marchitto said. As Arctic temperatures rise, summer ice cover declines, more solar heat is absorbed by the ocean and additional ice melts. Warmer water may delay freezing in the fall, leading to thinner ice cover in winter and spring, making the sea ice more vulnerable to melting during the next summer.
Air temperatures in Greenland have risen roughly 7 degrees F in the past several decades, thought to be due primarily to an increase in Earth’s greenhouse gases, according to CU-Boulder scientists.
“We must assume that the accelerated decrease of the Arctic sea ice cover and the warming of the ocean and atmosphere of the Arctic measured in recent decades are in part related to an increased heat transfer from the Atlantic,” said Spielhagen.
This statement prompts some things I’d point out that temper it:
“Air temperatures in Greenland have risen roughly 7 degrees F in the past several decades”.
In those remote locations like Nuuk, Greenland, what have we there? Remote pockets of humanity. Humanity building little cities of warmth in the cold Arctic, growing cities:
With 15,469 inhabitants as of 2010, Nuuk is the fastest-growing town in Greenland, with migrants from the smaller towns and settlements reinforcing the trend. Together with Tasiilaq, it is the only town in the Sermersooq municipality exhibiting stable growth patterns over the last two decades. The population increased by over a quarter relative to the 1990 levels, and by nearly 16 percent relative to the 2000 levels.
Nuuk population growth dynamics in the last two decades. Source: Statistics Greenland
Nuuk is not only a growing city, where UHI might now be a factor (but don’t take my word for it, see what NASA had to say about it at AGU this year), it is also a place where the official GHCN thermometers used by NASA are right next to human influences…like turboprop jet exhaust, such as this one in Nuuk’s airport right on the tarmac:
Hmmm, I wonder what happened in Nuuk? The plot below is from NASA GISS (see it yourself here). That “instant global warming” line seems out of character for natural variation in Nuuk. Note the data discontinuity. Often that suggests a station move and/or a change in station environment.
Sometimes a line like that with indicates airport construction near the thermometer, something I documented here.
And here’s the interesting thing. Nuuk is just one data point, one “raging red” anomaly in the sparsely spaced hands-on-human-measured NASA GISS surface temperature dataset for the Arctic. The patterns of warm pockets of humanity with airports and GHCN stations repeat themselves all over the Arctic, because as anyone who has visited the Arctic knows, aviation is the lifeline of these remote communities. And where do they measure the weather data? At the airport of course. Aviation doesn’t work otherwise.
See my complete report on the weird temperatures from Nuuk here. And while you are at it, read my report about the weird temperatures from Svalbaard, another warm single data point from NASA GISS. Interestingly, at that station a local citizen did some science and proved the UHI effect at the airport.
Yes these are just two examples. But there is no denying these facts:
- Remote communities in the Arctic are islands of anthropogenic warmth
- These communities rely of aviation as a lifeline
- The weather is measured at these airports, it is required for safety
- Airports release huge amounts of waste heat, from exhaust, de-icing, terminal buildings, and even tarmac in the sun.
- The majority of GHCN weather stations (used by NASA GISS) in the Arctic are at airports.
Remember Nuuk and Svalbarrd’s thermometers, and then ask Jim Hansen why NASA GISS, a “space studies agency”, doesn’t use satellite data but instead relies upon a surface record that another division of NASA says likely has significant UHI effects that NASA GISS doesn’t filter out sensibly (they only allow for 0.05°C downward adjustment).
And finally, can you really trust data from an organization that takes incoming data for that station and shifts it more than an entire degree C in the past, making a new trend? See the difference between “raw” (which really isn’t raw, it has a scads of adjustments already from NOAA) compared to the GISS final output in this chart:
The data is downloaded from GISS for the station, datasets 1 and 2 were used (raw-combined for this location and homogenized) which are available from the station selector via a link to data below the charts they make on the GISS website. The data is plotted up to the data continuity break, and again after. The trend lines are plotted to the data continuity break, and there’s no trend in the raw data for the last 100+ years.
The curious thing is that there’s no trend in the raw data at Nuuk until you do either (or both) of two things:
1. You use GISS homogenized data to plot the trend
2. You use the data after the discontinuity to plot the trend
I believe the data discontinuity represents a station move, one that exposed it to a warmer local environment. And clearly, by examining the GISS data for Nuuk, you can see that GISS adds adjustments that are not part of the measured reality. What justification could there possibly be to adjust the temperatures of the past downwards? What justification in a growing community (as shown by the population curve) could there be for doing an adjustment that is reverse of waste energy UHI?