Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
Little to No Summer ice in the Arctic
#1
Journal of Quaternary Science

Holocene variability in sea ice cover, primary production, and Pacific-Water inflow and climate change in the Chukchi and East Siberian Seas (Arctic Ocean)

Ruediger Stein,et al

Version of Record online: 27 FEB 2017

ABSTRACT

In this study, we present new detailed biomarker-based sea ice records from two sediment cores recovered in the Chukchi Sea and the East Siberian Sea. These new biomarker data may provide new insights on processes controlling recent and past sea ice changes. The biomarker proxy records show (i) minimum sea ice extent during the Early Holocene, (ii) a prominent Mid-Holocene short-term high-amplitude variability in sea ice, primary production and Pacific-Water inflow, and (iii) significantly increased sea ice extent during the last ca. 4.5k cal a BP. This Late Holocene trend in sea ice change in the Chukchi and East Siberian Seas seems to be contemporaneous with similar changes in sea ice extent recorded from other Arctic marginal seas. The main factors controlling the millennial variability in sea ice (and surface-water productivity) are probably changes in surface water and heat flow from the Pacific into the Arctic Ocean as well as the long-term decrease in summer insolation. The short-term centennial variability observed in the high-resolution Middle Holocene record is probably related to solar forcing. Our new data on Holocene sea ice variability may contribute to synoptic reconstructions of regional to global Holocene climate change based on terrestrial and marine archives.

[Image: Arctic-Sea-Ice-Holocene-Stein-17-768x496.jpg]

LINK
#2
Open Access Paper

Quaternary Science Reviews

Arctic Ocean perennial sea ice breakdown during the Early Holocene Insolation Maximum

15 May 2014

Christian Stranne,et al

Abstract

Arctic Ocean sea ice proxies generally suggest a reduction in sea ice during parts of the early and middle Holocene (∼6000–10,000 years BP) compared to present day conditions. This sea ice minimum has been attributed to the northern hemisphere Early Holocene Insolation Maximum (EHIM) associated with Earth's orbital cycles. Here we investigate the transient effect of insolation variations during the final part of the last glaciation and the Holocene by means of continuous climate simulations with the coupled atmosphere–sea ice–ocean column model CCAM. We show that the increased insolation during EHIM has the potential to push the Arctic Ocean sea ice cover into a regime dominated by seasonal ice, i.e. ice free summers. The strong sea ice thickness response is caused by the positive sea ice albedo feedback. Studies of the GRIP ice cores and high latitude North Atlantic sediment cores show that the Bølling–Allerød period (c. 12,700–14,700 years BP) was a climatically unstable period in the northern high latitudes and we speculate that this instability may be linked to dual stability modes of the Arctic sea ice cover characterized by e.g. transitions between periods with and without perennial sea ice cover.

LINK
#3
Taylor & Francis online

Birds and Climatic Change

Kenneth Williamson (1975) Birds and Climatic Change, Bird Study, 22:3,143-164, DOI: 10.1080/00063657509476459

Published online: 24 Jun 2009

“HISTORICAL REVIEW

Between 1000 and 1300 average summer temperatures were about 1°C higher than today, with the mean annual temperature higher by perhaps 4°C in a largely ice-free Arctic. Eric the Red, a renowned world citizen of that time, has been much maligned as the first progressive publicity man for giving Greenland a false image in order to attract settlers; but in truth, the southwest of that vast country was warmer and greener by far than at any time until the Fieldfares Turdus pilaris arrived there in the mid-1930s. The sea-temperature of the Atlantic was higher than it has been since, and there appears to have been none or very little ice to hinder the Vikings’ communications between Iceland, Greenland,Newfoundland and Labrador (Mowat 1965). Indeed Brooks (1926) considers thatthe polar ice-cap may have disappeared entirely during the summer months, tobuild anew each winter.”

LINK
#4
Watts Up With That?

NSIDC’s Dr. Walt Meier – part 2

“Can the Arctic really become sea ice-free during summer?

It has been suggested that the Arctic really can’t lose all its sea ice during summer because there isn’t enough energy to melt all of the ice in the short summer. There are a couple of reasons why this thinking is faulty.

First, we know the Arctic can potentially lose all its sea ice during summer because it has done so in the past. Examination of several proxy records (e.g., sediment cores) of sea ice indicate ice-free or near ice-free summer conditions for at least some time during the period of 15,000 to 5,000 years ago (Polyak et al., 2010) when Arctic temperatures were not much warmer than today.”

LINK
#5
Quaternary Science Reviews

New insights on Arctic Quaternary climate variability from palaeo-records and numerical modelling

December 2010

Martin Jackobsson, et al

Abstract

Terrestrial and marine geological archives in the Arctic contain information on environmental change through Quaternary interglacial–glacial cycles. The Arctic Palaeoclimate and its Extremes (APEX) scientific network aims to better understand the magnitude and frequency of past Arctic climate variability, with focus on the “extreme” versus the “normal” conditions of the climate system. One important motivation for studying the amplitude of past natural environmental changes in the Arctic is to better understand the role of this region in a global perspective and provide base-line conditions against which to explore potential future changes in Arctic climate under scenarios of global warming. In this review we identify several areas that are distinct to the present programme and highlight some recent advances presented in this special issue concerning Arctic palaeo-records and natural variability, including spatial and temporal variability of the Greenland Ice Sheet, Arctic Ocean sediment stratigraphy, past ice shelves and marginal marine ice sheets, and the Cenozoic history of Arctic Ocean sea ice in general and Holocene oscillations in sea ice concentrations in particular. The combined sea ice data suggest that the seasonal Arctic sea ice cover was strongly reduced during most of the early Holocene and there appear to have been periods of ice free summers in the central Arctic Ocean. This has important consequences for our understanding of the recent trend of declining sea ice, and calls for further research on causal links between Arctic climate and sea ice.

LINK
#6
Open Access paper

Quaternary Science Review

The dynamic Arctic

15 May 2014

Martin Jackobsson, et al

Abstract

Research campaigns over the last decade have yielded a growing stream of data that highlight the dynamic nature of Arctic cryosphere and climate change over a range of time scales. As a consequence, rather than seeing the Arctic as a near static environment in which large scale changes occur slowly, we now view the Arctic as a system that is typified by frequent, large and abrupt changes. The traditional focus on end members in the system – glacial versus interglacial periods – has been replaced by a new interest in understanding the patterns and causes of such dynamic change. Instead of interpreting changes almost exclusively as near linear responses to external forcing (e.g. orbitally-forced climate change), research is now concentrated on the importance of strong feedback mechanisms that in our palaeo-archives often border on chaotic behaviour. The last decade of research has revealed the importance of on-off switching of ice streams, strong feedbacks between sea level and ice sheets, spatial and temporal changes in ice shelves and perennial sea ice, as well as alterations in ice sheet dynamics caused by shifting centres of mass in multi-dome ice sheets. Recent advances in dating techniques and modelling have improved our understanding of leads and lags that exist in different Arctic systems, on their interactions and the driving mechanisms of change. Future Arctic research challenges include further emphases on rapid transitions and untangling the feedback mechanisms as well as the time scales they operate on.

LINK


Additional Excerpt:

"Several studies suggest that the Early Holocene (∼6000–10,000 years BP) experienced less summer-sea ice than at present. …. [S]ea ice during the Early Holocene potentially could have moved over to a seasonal regime with sea ice-free summers due to the insolation maxima the Earth experienced at that time."
#7
A full comment from HERE


David, here’s more historical-geological evidence re. the ice-free status of far-northern Greenland (Hans Tausen ice cap) pre the ‘record’.

(1)Textures, fabrics and meltlayer stratigraphy in the Hans Tausen ice core, North Greenland – indications of late Holocene ice cap generation? in: (U.C. Hammer, ed.) The Hans Tausen Ice Cap Glaciology and Glacial Geology , Meddelelser om Grønland, Geoscience, 39 , pp. 97-114 . 


A thin section study of crystal structure has been carried out on a 345 m long ice core drilled to bedrock on Hans Tausen Iskappe, 1995. In addition, a meltlayer stratigraphy was set up showing how the fraction of meltlayer-ice in the core increases with depth. Main characteristics of crystal structure are increasing mean crystal size from top to bottom in the core and development of a weak single maximum c-axis fabric. The rate of ice crystal growth in the well dated upper half of the core is much lower than expected from studies of the normal grain growth regime in other polar ice cores. Probably the grain boundary movements are impeded by impurities, which are present in relatively high concentrations in the Hans Tausen ice. Assuming the applicability of the calculated growth rate throughout the core, a late Holocene origin of the oldest ice is suggested by the size of the crystals close to the bedrock. Presented data furthermore implies that bottom ice temperatures were never near the melting point and it is concluded that there was no ice cap on the Hans Tausen plateau earlier in Holocene.


(2)On the Holocene evolution of Hans Tausen Iskappe (Greenland)
Zekollari, Harry; Huybrechts, Philippe
EGU General Assembly 2015, held 12-17 April, 2015 in Vienna, Austria. id.1540

Hans Tausen Iskappe (Greenland), situated at 82.5°N, 27.5°W, is world’s northernmost ice cap. During several field campaigns in the 70s and 90s, its ice thickness was measured, mass balance and meteorological measurements occurred, and a 345 m deep ice core was drilled. From this ice core it is known that the ice cap (largely) disappeared during the Holocene Thermal Maximum. The present-day ice cap started building up some 3500-4000 years ago in a wetter and warmer climate than at present. 


(3) In the seventies two firn cores were drilled a bit south of the Central Dome. One of the main discoveries was that the ice cap did not survive the higher temperatures of the Climatic Optimum 6000-8000 years ago. Different studies of the ice core show that the age estimate of the ice cap lies in the range 3500-4000 years Madsen and Thorsteinsson [2001]; Clausen et al. [2001]; Hammer et al. [2001].

The Hans Tausen Iskappe is not the only ice cap not to survive the warming of the climate following the last ice age and to regrow in the second half of the Holocene. Koerner and Fisher [2002] found from climate proxy data from ice cores that this is the case for many smaller ice caps throughout the Arctic.


The present Hans Tausen Iskappe is only 3500-4000 years old as indicated by different studies of the ice core drilled to bedrock at the central dome. With the onset of the Holocene (our present warm period) around 10000 years ago [Lowe and Walker, 1997] temperatures started to rise and deglaciation began culminating during the Climatic Optimum 6000-8000 years ago. The Hans Tausen Plateau became ice free prior to 8100 BP while the deglaciation in the outer parts of the Independence Fjord (See Fig A.3 for location) occurred some thousand years before. During the deglaciation even the highest located parts of the ice cap were below the equilibrium line and experienced surface melt. The decay occurred by a lowering of the surface and not by horizontal recession. The warmer climate meant that the fjords were seasonally ice free from the period 6700 − 6300 years BP documented by finds of driftwood at Kap Bopa and the eastern end of Nordpasset. In Jørgen Brønlund Fjord finds extend this period to 6600 − 2550 years BP.


During the last ice age Hans Tausen Iskappe is thought to have been confluent with the Greenland Ice Sheet. Studies in Nordpasset show evidence that the northern part of Hans Tausen Iskappe was part of an ice sheet that covered the adjacent area during the same period. [Landvik et al., 2001; Bennike, 1987] At present the ice cap lies ~20 km north of the Greenland Ice Sheet. Studies of sedimentation rates from a lake near Jørgen Brønlund Fjord show a richer vegetation than presently in the period 5000-3300 BP probably caused by an increase in precipitation due to the seasonally open fjords [Landvik et al., 2001]. This interval fits well with the age of the ice cap at the drill site, 3500 − 4000 years assessed by studies of stratigraphy, ice crystals and annual layer thickness by Madsen and Thorsteinsson [2001] and Clausen et al.[2001]. The build-up of the ice cap probably began as a response to the increased precipitation rate. The sedimentation rate dropped at 3500 years BP and 2100 years BP marking the transition to colder summers. During the last century up until 1978 the glacier margins seem to be stable or show a slight retreat of 10-100 m from aerial photographs [Weidick, 2001]. Recession is generally related to north and western facing glaciers. The oldest moraines in the area are ~100 years old, and therefore the culmination of re-advance of local glaciers following the Climatic Optimum is believed to be at the end of the Little Ice Age (1900 AD) Weidick [2001].
#8
Go-o-o-o-o-o-o-o-o-od afternoon everyone,............................... S6
___________________________________________________________________________________________________

"INSIDE EVERY PROGRESSIVE IS A TOTALITARIAN SCREAMING TO GET OUT" - David Horowitz

#9
With 24 hours of daylight for about 4 months, imagine the growing season.
'It's not who votes that matters, it's who counts the votes'  |  György Schwartz, Budapest, Hungary
#10
(10-09-2018, 07:10 PM)Canuknucklehead Wrote: With 24 hours of daylight for about 4 months, imagine the growing season.

In Anchorage the longest sunny day is about 21 hours.  On the longest day of summer it would get to dusk, from about 11PM to 1AM.  Something like that.  Most people arriving at Ft. Richardson/Elmendorf AFB started out with light shades on all the windows.  Some people had a hard time going to sleep with it so light outside.  After a while, most folks ignored the light shades, and the light didn't bother them.  

During the shortest day of the year it got dark around 4:30PM.  But the longest and shortest days didn't last too long.  Next thing you know, its pretty much back to some semblance of normal.  

But the growing season in the Palmer area, which is just north of Anchorage, really did/does have a great growing season.  When I was there, the record cabbage was a 39 pounder.  But since then the record has gone up beyond 100 pounds.  Things really, Really do grow big in the Matanuska Valley.

I Am A Giant Cabbage Farmer | INDIE ALASKA





Why Vegetables Get Freakish In The Land Of The Midnight Sun  Shock

[Image: giant-vegetable-2_sq-eeee1afd81fdd8efeec...00-c85.jpg]
Alaska grower Brittney Kauffman holds two zucchinis she entered in a giant vegetable competition in 2013. "Alaska is just a hotbed for gardening, believe it or not," says Alaska State Fair crops superintendent Kathy Liska. "Everybody thinks that we're always under ice — no!"
___________________________________________________________________________________________________

"INSIDE EVERY PROGRESSIVE IS A TOTALITARIAN SCREAMING TO GET OUT" - David Horowitz



Forum Jump:


Users browsing this thread: 1 Guest(s)