Evidence for an Early Recent Warm Interval in Northwestern Alaska

McCulloch, David S.; Hopkins, David M.

doi:10.1130/0016-7606(1966)77[1089:efaerw]2.0.co;2

Cited by 76 publications

(48 citation statements)

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“…The timing of this warm period at the study site is in agreement with the early Holocene warm period identified previously by other workers in northern and northwestern Alaska (McCulloch and Hopkins, 1966;Detterman, 1970;Nelson and Carter, 1987;Mann et al, 2010) as well as Northwest Canada (Ritchie et al, 1983). In contrast to the work of , who reconstructed a very early HTM culminating before 12 ka cal BP and already ending ca 11 ka cal BP, the dating of the HTM-representing sample Kit 1e3, coincides well with the early Holocene warming peak around 9.2 ka cal BP in Alaska.…”

Section: Warm Summers On the Northern Seward Peninsula During The Earsupporting

confidence: 75%

“…Thermokarst lake formation during that time falls within the range of other published thermokarst lake basal dates for the Seward Peninsula (Spiker et al, 1978;Kaufman and Hopkins, 1985) and the circum-arctic (Walter et al, 2007;Reyes and Cooke, 2011). The age of the lowermost dated sample in unit D of 8370 AE 50 yr BP falls in the period of a pronounced early Holocene climate warming in NW North America (McCulloch and Hopkins, 1966;Detterman, 1970;Ritchie et al, 1983;, a time when thermokarst lake formation peaked in Alaska and other high latitude regions (Walter et al, 2007) and intense peatland formation occurred in Alaska (Jones and Yu, 2010). Our fossil record therefore gives us a clear picture of the environmental conditions in Central Beringia during a period of warm summer growing conditions.…”

Section: Tablementioning

confidence: 55%

“…This spruce twig is currently the only verified and dated spruce macrofossil from the early Holocene in western Alaska. The spruce wood reported in McCulloch and Hopkins (1966) was later retracted by Hopkins et al (1981). While slender evidence for the presence of spruce, the Picea twig is clearly identifiable as such, and the date on the twig itself precludes the possibility of its being reworked from older sediments into the newly forming earlyHolocene thaw lake.…”

Section: Spruce and Early-holocene Treeline In Northwest Alaskamentioning

confidence: 99%

“…12d). Permafrost degradation during this warm period was expressed by formation of ice-wedge casts (McCulloch and Hopkins, 1966) and thermokarst lakes (Hopkins and Kidd, 1988). Throughout the Holocene, thermokarst processes have continued to operate, gradually lowering the original land surface.…”

Section: Tablementioning

confidence: 99%

“…Several palaeoenvironmental records from the Seward Peninsula that cover large parts of the late Quaternary were produced in previous decades from the Imuruk Lake region (Hopkins, 1959b(Hopkins, , 1963Colinvaux, 1964;McCulloch and Hopkins, 1966) and the Kotzebue Sound region (McCulloch and Hopkins, 1966;Matthews, 1974a;Hopkins et al, 1976;Jordan and Mason, 1999). Some studies focused on specific important palaeoenvironmental indicators, such as fossil soil properties (Höfle and Ping, 1996;Höfle et al, 2000), pollen (Colinvaux, 1964), plant macrofossils (Goetcheus et al, 1994;Goetcheus and Birks, 2001), insects (Elias, 2000(Elias, , 2001Kuzmina et al, 2008), and tephra (Begét et al, 1992(Begét et al, , 1996.…”

Section: Introductionmentioning

confidence: 99%

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Late Quaternary environmental and landscape dynamics revealed by a pingo sequence on the northern Seward Peninsula, Alaska

Wetterich

Grosse

Schirrmeister

et al. 2012

Quaternary Science Reviews

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a b s t r a c tA terrestrial sediment sequence exposed in an eroding pingo provides insights into the late-Quaternary environmental history of the northern Seward Peninsula, Alaska. We have obtained the first radiocarbondated evidence for a mid-Wisconsin thermokarst lake, demonstrating that complex landscape dynamics involving cyclic permafrost aggradation and thermokarst lake formation occurred over stadiale interstadial as well as glacialeinterglacial time periods. High values of Picea pollen and the presence of Larix pollen in sediments dated to 50e40 ka BP strongly suggest the presence of forest or woodland early in MIS 3; the trees grew within a vegetation matrix dominated by grass and sedge, and there is indirect evidence of grazing animals. Thus the interstadial ecosystem was different in structure and composition from the Holocene or from the preceding Last Interglacial period. An early Holocene warm period is indicated by renewed thermokarst lake formation and a range of fossil taxa. Multiple extralimital plant taxa suggest mean July temperatures above modern values. The local presence of spruce during the early Holocene warm interval is evident from a radiocarbon-dated spruce macrofossil remain and indicates significant range extension far beyond the modern tree line. The first direct evidence of spruce in Northwest Alaska during the early Holocene has implications for the presence of forest refugia in Central Beringia and previously assumed routes and timing of post-glacial forest expansion in Alaska.

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Section: Warm Summers On the Northern Seward Peninsula During The Earsupporting

confidence: 75%

Section: Tablementioning

confidence: 55%

Section: Spruce and Early-holocene Treeline In Northwest Alaskamentioning

confidence: 99%

Section: Tablementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Late Quaternary environmental and landscape dynamics revealed by a pingo sequence on the northern Seward Peninsula, Alaska

Wetterich

Grosse

Schirrmeister

et al. 2012

Quaternary Science Reviews

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Natural and historical variability in fluvial processes, beaver activity, and climate in the Greater Yellowstone Ecosystem

Persico

Meyer

2012

Earth Surf Processes Landf

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Two centuries of human activities in the Greater Yellowstone Ecosystem (GYE) have strongly influenced beaver activity on small streams, raising questions about the suitability of the historical (Euro-American) period for establishing stream reference conditions. We used beaver-pond deposits as proxy records of beaver occupation to compare historical beaver activity to that throughout the Holocene. Forty-nine carbon-14 ( 14 C) ages on beaver-pond deposits from Grand Teton National Park indicate that beaver activity was episodic, where multi-century periods lacking dated beaver-pond deposits have similar timing to those previously documented in Yellowstone National Park. These gaps in the sequence of dated deposits coincide with episodes of severe, prolonged drought, e.g. within the Medieval Climatic Anomaly 1000-600 cal yr BP, when small streams likely became ephemeral. In contrast, many beaver-pond deposits date to 500-100 cal yr BP, corresponding to the colder, effectively wetter Little Ice Age. Abundant historical beaver activity in the early 1900s is coincident with a climate cooler and wetter than present and more abundant willow and aspen, but also regulation of beaver trapping and the removal of wolves (the beaver's main predator), all favorable for expanded beaver populations. Reduced beaver populations after the 1920s, particularly in the northern Yellowstone winter range, are in part a response to elk overbrowsing of willow and aspen that later stemmed from wolf extirpation. Beaver populations on small streams were also impacted by low streamflows during severe droughts in the 1930s and late 1980s to present. Thus, both abundant beaver in the 1920s and reduced beaver activity at present reflect the combined influence of management practices and climate, and underscore the limitations of the early historical period for defining reference conditions. The Holocene record of beaver activity prior to Euro-American activities provides a better indication of the natural range of variability in beaver-influenced small stream systems of the GYE.

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Palaeoenvironmental Interpretation of Yedoma Silt (Ice Complex) Deposition as Cold‐Climate Loess, Duvanny Yar, Northeast Siberia

Murton

Goslar

Edwards

et al. 2015

Permafrost & Periglacial

124

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Uncertainty about the geological processes that deposited syngenetically frozen ice‐rich silt (yedoma) across hundreds of thousands of square kilometres in central and northern Siberia fundamentally limits our understanding of the Pleistocene geology and palaeoecology of western Beringia, the sedimentary processes that led to sequestration of hundreds of Pg of carbon within permafrost and whether yedoma provides a globally significant record of ice‐age atmospheric conditions or just regional floodplain activity. Here, we test the hypotheses of aeolian versus waterlain deposition of yedoma silt, elucidate the palaeoenvironmental conditions during deposition and develop a conceptual model of silt deposition to clarify understanding of yedoma formation in northern circumpolar regions during the Late Pleistocene. This is based on a field study in 2009 of the Russian stratotype of the ‘Yedoma Suite’, at Duvanny Yar, in the lower Kolyma River, northern Yakutia, supplemented by observations that we have collected there and at other sites in the Kolyma Lowland since the 1970s. We reconstruct a cold‐climate loess region in northern Siberia that forms part of a vast Late Pleistocene permafrost zone extending from northwest Europe across northern Asia to northwest North America, and that was characterised by intense aeolian activity. Five litho‐ and cryostratigraphic units are identified in yedoma remnant 7E at Duvanny Yar, in ascending stratigraphic order: (1) massive silt, (2) peat, (3) stratified silt, (4) yedoma silt and (5) near‐surface silt. The yedoma silt of unit 4 dominates the stratigraphy and is at least 34 m thick. It is characterised by horizontal to gently undulating subtle colour bands but typically lacks primary sedimentary stratification. Texturally, the yedoma silt has mean values of 65 ± 7 per cent silt, 15 ± 8 per cent sand and 21 ± 4 per cent clay. Particle size distributions are bi‐ to polymodal, with a primary mode of about 41 μm (coarse silt) and subsidiary modes are 0.3–0.7 μm (very fine clay to fine clay), 3–5 μm (coarse clay to very fine silt), 8–16 μm (fine silt) and 150–350 μm (fine sand to medium sand). Semidecomposed fine plant material is abundant and fine in‐situ roots are pervasive. Syngenetic ice wedges, cryostructures and microcryostructures record syngenetic freezing of the silt. An age model for silt deposition is constructed from 47 pre‐Holocene accelerator mass spectrometry (AMS) 14C ages, mostly from in‐situ roots and from three optically stimulated luminescence (OSL) ages of quartz sand grains. The 14C ages indicate that silt deposition extends from 19 000 ± 300 cal BP to 50 000 cal BP or beyond. The OSL ages range from 21.2 ± 1.9 ka near the top of the yedoma to 48.6 ± 2.9 ka near the bottom, broadly consistent with the 14C age model. Most of the yedoma silt in unit 4 at Duvanny Yar constitutes cryopedolith (sediment that has experienced incipient pedogenesis along with syngenetic freezing). Mineralised and humified organic remains dispersed within cryopedolith indicate in...

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Evidence for an Early Recent Warm Interval in Northwestern Alaska

Cited by 76 publications

References 0 publications

Late Quaternary environmental and landscape dynamics revealed by a pingo sequence on the northern Seward Peninsula, Alaska

Late Quaternary environmental and landscape dynamics revealed by a pingo sequence on the northern Seward Peninsula, Alaska

Natural and historical variability in fluvial processes, beaver activity, and climate in the Greater Yellowstone Ecosystem

Palaeoenvironmental Interpretation of Yedoma Silt (Ice Complex) Deposition as Cold‐Climate Loess, Duvanny Yar, Northeast Siberia

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