3 New Papers: Greenland 3-5°C Warmer With 40 Kilometers Less Ice Area 4,000-10,000 Years Ago
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Greenland Cooling Since 2005
Arctic Region Cooler Now Than Most Of The Last 10,000 Years
It’s official. According to a new paper published in the journal Scientific Reports, Greenland has been cooling slightly since 2005.
This trend development may be a harbinger of what may be in store for the coming years. Shifts in North Atlantic temperatures typically lead changes in the Arctic by a few years. And throughout the North Atlantic, rapid cooling has been underway since 2005, plunging below the levels reached in the 1950s.
Kobashi et al., 2017
“For the most recent 10 years (2005 to 2015), apart from the anomalously warm year of 2010, mean annual temperatures at the Summit exhibit a slightly decreasing trend in accordance with northern North Atlantic-wide cooling. The Summit temperatures are well correlated with southwest coastal records (Ilulissat, Kangerlussuaq, Nuuk, and Qaqortoq).”
A Few Thousand Years Ago, The Greenland/Arctic Region Was 3-5°C Warmer Than Now
Between 10,000 and 4,000 years ago, atmospheric CO2 concentrations were almost 150 ppm lower than they are now (~260 ppm). Despite such low CO2 levels, the Arctic region was several degrees Celsius warmer than it has been in recent decades. Arctic summers were likely sea ice-free during these much warmer years.
Mangerud and Svendsen, 2017
“Shallow marine molluscs that are today extinct close to Svalbard, because of the cold climate, are found in deposits there dating to the early Holocene. The most warmth-demanding species found, Zirfaea crispata, currently has a northern limit 1000 km farther south, indicating that August temperatures on Svalbard were 6°C warmer at around 10.2–9.2 cal. ka BP [10,200 to 9,200 years ago], when this species lived there. … After 8.2 cal. ka, the climate around Svalbard warmed again, and although it did not reach the same peak in temperatures as prior to 9 ka, it was nevertheless some 4°C warmer than present between 8.2 and 6 cal. ka BP. Thereafter, a gradual cooling brought temperatures to the present level at about 4.5 cal. ka BP. The warm early-Holocene climate around Svalbard was driven primarily by higher insolation and greater influx of warm Atlantic Water, but feedback processes further influenced the regional climate.”
Lasher et al., 2017
“This paper presents a multi proxy lake record of NW Greenland Holocene climate. … Summer temperatures (2.5–4 °C warmer than present) persisted until ∼4 ka [4,000 years ago] … Continual cooling after 4 ka led to coldest temperatures after 1.2 ka, with temperature anomalies 2-3°C below present. Approximately 1000 km to the south, a 2-3°C July temperature anomaly (relative to [warmer than] present) between 6 and 5 ka [thousand years ago] was reported based upon chironomid assemblages near Illulisat and Jakobshavn (Axford et al., 2013). Across Baffin Bay on northeastern Baffin Island, HTM [Holocene Thermal Maximum] summer temperatures were an estimated ~5°C warmer than the pre-industrial late Holocene and 3.5°C warmer than present, based upon chironomid assemblages (Axford et al., 2009; Thomas et al., 2007).”
Kobashi et al., 2017
“After the 8.2 ka event, Greenland temperature reached the Holocene thermal maximum with the warmest decades occurring during the Holocene (2.9 ± 1.4 °C warmer than the recent decades [1988-2015]) at 7960 ± 30 years B.P.”
No Net Warming For The Greenland Ice Sheet In 90 Years
Kobashi et al., 2017
Zhao et al., 2016
Hanna et al., 2011
Greenland Ice Sheet Had Retreated 20-60 Kilometers Behind Present Margins ~8,000 Years Ago
Lasher et al., 2017
“Following deglaciation, the GrIS [Greenland Ice Sheet] retreated behind its present margins (by as much as 20-60 km in some parts of Greenland) during the HTM [Holocene Thermal Maximum] (Larsen et al., 2015; Young and Briner, 2015).”
Briner et al., 2016
“The Greenland Ice Sheet retracted to its minimum extent between 5 and 3 ka [5,000 and 3,000 years ago], consistent with many sites from around Greenland depicting a switch from warm to cool conditions around that time.”
A Long-Term Context
Greenland has warmed 20-24 times the magnitude reached during the last century multiple times. During these abrupt warming events (10°C to 15°C temperature rise within decades), CO2 concentrations were stable and hovered below 200 parts per million. This indicates that the Arctic climate is not significantly influenced by CO2 variations nor human activity in general, as the past 100 years are well within the range of natural variability.
Easterbrook, 2016
“In the past 500 years, Greenland temperatures have fluctuated back and forth between warming and cooling about 40 times, with changes every 25–30 years. … Comparisons of the intensity and magnitude of past warming and cooling climate changes show that the global warming experienced during the past century pales into insignificance when compared to the magnitude of profound climate reversals over the past 25,000 years. At least three warming events were 20–24 times the magnitude of warming over the past century, and four were 6–9 times the magnitude of warming over the past century.”
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July 10, 2017 at 05:20AM
Iowa Climate Science Education 