Snöggar breytingar í átt að kólnun á Norður-Atlantshafinu á síðari hluta Nútíma: þáttur sjávarstrauma, andrúmslofts og hafíss

Fréttatilkynning verkefnisstjóra.

17.10.2016

Contents:

• A short abstract, results and impact.
• Information on how the results will be applied.
• A list of the projects output (reports, journal articles or manuscripts). 

In light of the Arctic's inherent sensitivity to abrupt climate change it is imperative to place current Arctic warming in the context of long-term natural variability. This is especially pertinent in the northern North Atlantic, where episodes of abrupt and sustained regional climate shifts have occurred; often resulting in persistent decreases of summer temperature. Considering ice caps are the most reliable proxy for past summer temperature variability, we constrained the Holocene evolution Iceland's northernmost ice cap, Drangajökull, to assess the potential driving mechanisms by comparing to regional climate records. Our toolbox included a suite of lake sediment cores surrounding the ice cap, dating dead vegetation emerging from the receding margin and geomorphic mapping of terminal moraines. During the early Holocene, our results suggest a combination of elevated Northern Hemisphere summer insolation and local sea surface temperatures forced rapid ice cap recession between ~10.3 and 9.2 ka, ultimately driving it to complete extinction by ~8 ka. As regional temperatures began to cool ~5.5 ka, we document the regrowth of Drangajökull at ~2.3 ka and subsequent expansion to its maximum Late Holocene dimensions during the Little Ice Age. The episodic nature of its late Holocene expansion was likely driven by enhanced import of sea ice from East Greenland and associated cooler summer temperatures. Our results benefit ongoing numerical modeling efforts to constrain the evolution of Drangajökull over the Holocene by providing important spatiotemporal datasets to test the validity of our model outputs and the identification of key climate forcing parameters.

Heiti verkefnis: Abrupt transitions to a cold North Atlantic in the late Holocene: Testing the roles of ocean, atmosphere and sea ice / Snöggar breytingar í átt að kólnun á Norður-Atlantshafinu á síðari hluta Nútíma: þáttur sjávarstrauma, andrúmslofts og hafíss
Verkefnisstjórar: Áslaug Geirsdóttir og Gifford H. Miller
Tegund styrks: Verkefnisstyrkur
Styrkár: 2013-2015
Fjárhæð styrks: 20 millj. kr. alls
Tilvísunarnúmer Rannís: 130775-05 

Snöggar breytingar í átt að kólnun á Norður-Atlantshafinu á síðari hluta Nútíma: þáttur sjávarstrauma, andrúmslofts og hafíss. 

Mikilvægt er að setja þá hlýnun sem nú á sér stað á Norðurslóðum í lengra tímasamhengi til þess að skilja betur eðli snöggra loftslagsbreytinga. Þetta á sérstaklega við um norðurhluta Norður-Atlantshafs, þar sem hvort tveggja viðvarandi og skyndilegar svæðisbundnar veðurfarsbreytingar í formi lækkunar á sumarhitastigi, hafa átt sér stað á nútíma (síðustu ~ 11 þús. ár). Jöklar endurspegla vel breytileika í sumarhitastigi. Í þessu verkefni var rannsóknum beint að sögu Drangajökuls með kortlagningu á jökulmenjum í kringum jökulinn, rannsóknum á veðurvísum og efnafræði sets í aðliggjandi stöðuvötnum, auk kolefnisaldursgreininga á fornum gróðurleifum sem hafa komið fram undan hörfandi jökli við núverandi hlýnun. Með því að aldursgreina þessar fornu gróðurleifar er möguleiki á að segja til um stærð og virkni jökulsins á fyrri tímum þegar hann gekk síðast fram og huldi gróðurinn. Niðurstöður sýna að á fyrri hluta Nútíma fyrir ~ 10.300 til 9.200 árum, hófst mikil bráðnun á forvera Drangajökuls vegna samspils hækkandi sumarinngeislunar og yfirborðshitastigs nærliggjandi sjávarmassa. Þetta hlýindatímabil stóð í um það bil 3500 ár eða frá því fyrir um 8.900 til 5.500 árum síðan, þó stutt truflun hafi orðið til kólnunar fyrir um 8.200-8.000 árum. Þegar fór að kólna á ný samfara lækkandi sólarinngeislun fyrir ~ 5.500 árum, sköpuðust aðstæður til nýmyndunar Drangajökuls, sem gekk enn frekar fram fyrir um 2.300 árum uns hámarksútbreiðslu var náð á seinni hluta Nútímans á tímum Litlu ísaldarinnar (1250-1850 CE). Þessi stigvaxandi útbreiðsla Drangajökuls var að öllum líkindum knúin áfram af lækkandi sjávarhita og aukinni hafískomu frá Grænlandi. Niðurstöður okkar verða nýttar í reiknilíkönum sem vinna að því að tengja vöxt og hörfun Drangajökuls á Nútíma við sumarhitastig í þeim tilgangi að varpa ljósi á helstu orsakir og afleiðingar snöggra loftslagsbreytinga.

A list of the projects output (reports, journal articles or manuscripts).
Publications based on or related to the project – 2013-2016

Harning,D., Geirsdóttir, Á., Miller, G.H., Zalzal, K., in review. Very early Holocene deglaciation of Drangajökull, Vestfirðir, Iceland. Quaternary Science Reviews.

Harning, D., Geirsdóttir, Á., Miller, G.H., Anderson, L., in review. Episodic expansion of Drangajökull, Vestfirðir, Iceland, over the last 3 ka culminating in its maximum dimension during the Little Ice Age. Quaternary Science Reviews.

Florian, C.R., Geirsdóttir, Á., Crump, S., Miller, G.H., Zalzal, K., in review. Catchment geometry influences proxy response in late Holocene records from two proximal lakes located in north Iceland. Journal of Paleolimnology.

Alsos, I.G., Ehrich, D., Seidenkrantz, M-S., Bennike, O., Kirchhefer, A.J., Geirsdóttir, Á. 2016. The role of sea ice for vascular plant dispersal in the Arctic. Biology Letter. Royal Society, London Solomina, O.N., Bradley, R.S., Jomelli, V., Geirsdóttir, Á., Kaufman, D.S., Koch, J., McKay, N.P., Masiokas, M., Miller, G, Nesje, A., Owen, L.A., Putnam, A.E., Wanner, H., Wiles, G., Yang, B., 2016. Glacier fluctuations during the past 2000 years. Quaternary Science Reviews 149, 61-90. http://dx.doi.org/10.1016/j.quascirev.2016.04.008

Sejrup, H.P., Seppä, H., McKay, N.P., Kaufman, D.S., Geirsdóttir, Á., de Vernal, A., Rensen, H., Husum, K., Jennings, A.E., Andrews, J.T., 2016. North Atlantic –Fennoscandian Holocene climate trends and mechanisms. Quaternary Science Reviews, online.

Capedo-Sanz, P., Belt, S.T., Jennings, A.E., Andrews, J.T., Geirsdóttir, Á., 2016. Variability in drift ice export from the Arctic Ocean to the North Icelandic Shelf over the last 8000 years: A multi-proxy evaluation. Quaternary Science Reviews 146, 99-115 http://dx.doi.org/10.1016/j.quascirev.2016.06.012

Geirsdóttir, Á., Miller, G.H., Larsen, D.J., 2016. Glacial landforms in Hvítárvatn, central Iceland. Dowdeswell, J.A., Canals, M., Jakobsson, M., Todd,, B.J., Dowdeswell, E.K., & Hogan, K.A. (eds), Atlas of Submarine Glacial Landforms: Modern, Quaternary and Ancient. Geological Society, London, Memoirs xx, 1-4. @The Geological Society of London 2016. DOI:xx.xxx/xxx__x_

Jónsdóttir, I.R., Ólafsdóttir, S., Geirsdóttir, Á., 2015. A 2000 year record of marine climate variability from Arnarfjörður, NW Iceland. JÖKULL 65.

Blair, C., Geirsdóttir, Á., Miller, G.H., 2015. A high resolution multi-proxy lake record of Holocene environmental change in southern Iceland. Journal of Quaternary Sciences 30 (3) 281-292 ISSN 0267- 8179, DOI: 10,1002/jqs.2780.

Larsen, D.J. Geirsdóttir, Á. & Miller, G.H. 2015. Precise chronology of Little Ice Age expansion and repetitive surges of Langjökull, central Iceland. Geology 43, 167-170., doi:10.1130/G36185.1

Florian, C.R., Miller, G.H., Fogel, M.L., Wolfe, A.P., Vinebrooke, R.D., Geirsdóttir, Á., 2015. Algal pigments in Arctic lake sediments record biogeochemical changes due to Holocene climate variability and anthropogenic global change. J. Paleolimnol 54, 53-69.

Jennings, A., Thordarson, Th., Zalzal, K., Stoner, J., Hayward, C., Geirsdóttir, Á., Miller, G. 2014. Holocene tephra from Iceland and Alaska in SE Greenland shelf sediments. Geological Society, London, Special Publications, 398, 2014, 157-193. Geological Society of London.

Geirsdóttir, Á., Miller, G.H., Larsen, D.J., Ólafsdóttir, S. 2013. Abrupt Holocene climate transitions in the northern North Atlantic region recorded by synchronized lacustrine records in Iceland. Quaternary Science Reviews 70, 48-62.

Larsen, D.J., Miller, G.H., Geirsdóttir, Á., 2013. Asynchronous Little Ice Age glacier fluctuations in Iceland and European Alps linked to shifts in subpolar North Atlantic circulation. Earth and Planetary Science Letters 380, 52-59.

Miller G.H., Brigham-Grette J., Alley R.B., Anderson L., Bauch H.A., Douglas M.S.V., Edwards M.E., Elias S.A., Finney B.P., Fitzpatrick J.J., Funder S.V., Geirsdóttir A., Herbert T.D., Hinzman L.D., Kaufman D.S., MacDonald G.M., Polyak L., Robock A., Serreze M.C., Smol J.P., Spielhagen R., White J.W.C., Wolfe A.P. and Wolff E.W. (2013) Paleoclimate History of the Arctic. In: Elias S.A. (ed.) The Encyclopedia of Quaternary Science, vol. 3, pp. 113-125. Amsterdam: Elsevier.

Miller, G.H., Briner, J.P., Refsnider, KA., Lehman, S.J., Geirsdóttir, Á., Larsen, D.J., Southon, J.R., 2013. Substantial agreement on the timing and magnitude of Late Holocene ice cap expansion between East Greenland and the Eastern Canadian Arctic: a commentary on Lowell et al., 2013 Quaternary Science Reviews 77, 239-245, 2013

Ólafsdóttir, K.B., Geirsdóttir, Á., Miller, G.H., Larsen, D.J., 2013. Evolution of NAO and AMO strength and cyclicity derived from a 3-ka varve-thickness record from Iceland. Quaternary Science Reviews 69, 142-154, 2013

Ólafsdóttir, S., Geirsdóttir, Á., Miller, G.H., Stoner, J.S., Channell, J.E.T. 2013. Synchronizing Holocene lacustrine and marine sediment records using paleomagnetic secular variation Geology 41 (5), 535-538.

Meeting and conference presentations 2013-2016

Harning, D., Geirsdóttir, Á., Miller, G.H., Belart, J.M.C., 2015. An abrupt and sea-ice driven LIA expansion of Drangajökull, Vestfirðir, Iceland. 2015 GSA (The Geological Society of America) Annual Meeting in Baltimore, Maryland, USA (1-4 November 2015).

Anderson, L., Geirsdóttir, Á., Miller, G.H., 2015. Using modern gridded climate data to help interpret terrestrial paleoclimate records: Application to Iceland and the North Atlantic region. 45th Arctic Workshop 2015, Bergen, Norway 10-13 May 2015.

Magnússon, E., Belart, J.M.C., Pálsson, F., Anderson, L., Jarosch, A., Chrochet, P., Berthier, E., Ágústsson, H., Gunnlaugsson, Á.G. and Geirsdóttir, Á. 2015. International Glaciological Society – Nordic Branch Meeting 2015, Copenhagen 29-31 October 2015.

Florian, C., Geirsdóttir, Á., Miller, G., 2015. A High-Resolution Multi-proxy Lake Sediment Record from Torfdalsvatn Suggests a Temperature Gradient Between North and South Iceland During the Early Holocene. EGU (European Geosciences Union General Assembly) Vienna, Austria, 12-17 April 2015

Geirsdóttir Á., Miller, G.H., Briner, J., Schweinsberg, A., Pendleton, S., Larsen, D., Florian, C., 2015. Abrupt centennial-scale departures superimposed on Holocene insolation forcing across the northern North Atlantic. 45th Arctic Workshop 2015, Bergen, Norway 10-13 May 2015.

Florian, C.R., Miller, G.H., Geirsdóttir, Á., Fogel, M.L., Wolfe, A.P., Vinebrooke, R.D., 2015. Algal pigments display varying response to Holocene climate variability between lakes in Baffin Island and Iceland. 45th Arctic Workshop 2015, Bergen, Norway 10-13 May 2015.

Geirsdóttir, Á., Miller, G.H., Larsen, D.J., Pendleton, S., Florian, C., 2015. Abrupt transitions to a cold North Atlantic in the late Holocene. EGU (European Geosciences Union General Assembly) Vienna, Austria, 12-17 April 2015

Geirsdóttir, Á., Miller, G.H., Briner, J., Lehman, S., Landvik, J., Larsen, D., Pendleton, S., Schweinsberg, A., 2015. Nonlinear climate response to Holocene insolation forcing across the North Atlantic Arctic. XIX INQUA (International Union for Quaternary Research) NAGOYA, JAPAN 27 July－2 August, 2015, p.103

Th., Sanz, P.C.Blair, C., Harning, D., Gunnarson, S. 2015. Holocene Climate and Catchment-Specific Responses to Climate Change, Recorded in a Transect of Icelandic Lakes. AGU Fall Meeting, San Francisco, 14-18 December 2015.

Magnússon, E., Belart, J.M.C., Pálsson F., Anderson, L., Berthier, E., Crochet, P., Ágústsson, H., Gunnlaugsson, Á.Þ. and Geirsdóttir, Á. 2015. The subglacial topography of Drangajökull ice cap,  surface and volume evolution in 1946-2014. Haustráðstefna JFÍ, 20. Nóvember 2015.

Alsos, I, Seidenkrantz, M-S, Bennike, O., Kirchhefer, A., Ehrich, D., Geirsdóttir, Á., 2015. The role of sea Ice for Vascular Plant Dispersal in the Arctic. AGU Fall Meeting, San Francisco, 14-18 December 2015.

Harning D., Geirsdóttir Á., Miller G. 2015. Holocene climate and ice cap evolution in Vestfirðir, Iceland. 45th Arctic Workshop 2015, Bergen, Norway 10-13 May 2015.

Jónsdóttir, I.R., Ólafsdóttir, S., Geirsdóttir, Á. 2015. A 2000 year record of marine climate variability from Arnarfjörður, NW Iceland. 45th Arctic Workshop 2015, Bergen, Norway 10-13 May 2015

Gunnarson, S., Geirsdóttir, Á., Miller, G.H., 2015. Coastal to Central: Integrating late-Holocene lacustrine climate proxies in NW Iceland. 45th Arctic Workshop 2015, Bergen, Norway 10-13 May 2015.

Crump, S., Florian, C., Miller, G.H., Geirsdóttir, Á., Zalzal, K., 2015. A tale of two lakes: Catchment- Specific responses to late Holocene cooling in Northwest Iceland. AGU Fall Meeting, San Francisco, 14-18 December 2015.

Geirsdóttir Á. 2014. Abrupt Holocene climate transitions in the northern North Atlantic region recorded by synchronized lacustrine and marine records in Iceland. Invited lecture at the University of Bergen. 30. janúar 2014

Florian, C., Miller, G.H., Geirsdóttir, Á., 2014. A Multi-Decadal 11,5 ka Sedimentary Pigment Record of Aquatic Productivity and Landscape Stability from Torfadalsvatn, North Iceland. AGU Fall Meeting 15-19. December 2014. (PP23E-04)

Avsar,U., Hubert-Ferrari, A., Jónsson, S., De batist, M.A.O., Fagel, N., Geirsdóttir, Á., Thordarson, Th., Miller, G.H., 2014. Examples of Subaqueous Paleoseismological techniques from Turkey and Iceland: With Special Emphasis on the Importance of Constructing Precise Sediment Chronologies. AGU Fall meeting San Francisco 15-19 December 2014. (T43B-4718, T52A-06)

Harning, D., Geirsdóttir, Á., Miller, G., 2014. Reconstructing Holocene Climate and Glacial Extent of Drangajökull, Vestfirðir, Iceland. 44th International Arctic Workshop – Boulder, Colorado. 15-16 March 2014. http://instaar.colorado.edu/aw/about/index.html

Larsen, D.J , Miller, G.H., Geirsdóttir, Á., 2014. Dynamic Terminus Fluctuations Of Langjökull Ice Cap During The Little Ice Age. 44th International Arctic Workshop – Boulder, Colorado. 15-16 March 2014. http://instaar.colorado.edu/aw/about/index.html

Geirsdóttir, Á., Miller, G.H., Briner, J., Lehmann, S., Landvik, J., Pendleton, S., Schweinsberg, A., 2014. Similar timings for the onset of persistent cold summers during Neoglaciation across the northern North Atlantic. PAGES co-sponsored workshop on Holocene climate change Timberline Lodge at Mount Hood on October 13th - 16th, 2014 (http://www.timberlinelodge.com/).

Avsar, Ulas et al. 2014. Paleoseismic evidence for pre-historic earthquakes in the sedimentary record of Botnsvatn Lake on the Húsavík-Flatey Fault, North Iceland. EGU 2014.

Avşar,U., Hubert-Ferrari,A., Jónsson, S., De Batist, M., Fagel,N., Geirsdóttir, Á. and Miller, G.H. 2014. A semi-quantitative method to estimate organic matter content of lake sediments using ITRAX micro-XRF core scanner data. SSP3.1.5 Limnogeology - reading the geological record of lakes (Sponsored by IAS). EGU 2014.

Avsar, U., Jónsson, S., Geirsdóttir, Á., Thordarson, Th., Miller, G.H., 2014. Sedimentary Records of Past Earthquakes during the Last 2400 Years in Botnsvatn Lake on the Húsavík-Flatey Fault, North Iceland. AGU Fall meeting San Francisco 15-19 December 2014. (T43B-4718, T52A-06)

Bergþórsdóttir, H.B., Geirsdóttir, Á., Miller, G.H., 2014. A 3000 Year Multi-proxy Record Of Environmental Change From Gripdeild, Eastern Iceland. 44th International Arctic Workshop – Boulder, Colorado. 15-16 March 2014. http://instaar.colorado.edu/aw/about/index.html

Jónsdóttir, I. R.,Ólafsdóttir, S., Geirsdóttir, Á. 2014. A 2000 Year Record Of Marine Climate Variability From Arnarfjörður, NW Iceland. 44th International Arctic Workshop – Boulder, Colorado. 15-16 March 2014. http://instaar.colorado.edu/aw/about/index.html

Florian, C.R, Crump, S.E., Geirsdóttir, Á., Miller, G.H., Zalzal, K.S 2014. A Two-thousand Year Record Of Northern Iceland Late Holocene Cooling From Lakes Bæjarvötn And Torfadalsvatn 44^th International Arctic Workshop – Boulder, Colorado. 15-16 March 2014. http://instaar.colorado.edu/aw/about/index.html