Alaska and the MWP
In the last issue of Quaternary Science Reviews Thursday, December 23, 2010
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an interesting study by Clegg et al., Entitled 
Six Millennia of summer temperature variation based on analysis of lake sediments from Midge
Alaska (pdf . Format, 690 KB) published Six Millennia of summer temperature variation based on analysis of lake sediments from Midge The authors note in the introduction: We analyzed
sediments of the past 6000 years from Moose Lake (61 ° 22:45 'N, 143 ° 35.93' W, 437 m asl) in south-central Alaska for midge assemblages at decadal to centennial resolution. Here we report the results and use data to derive the assemblage mean July air temperature (T
July ) estimates using the transfer function of (Barley et al. 2006) [1]. The reliability of this approach at Moose Lake is evaluated by comapring midge-based TJulyestimates with weather station and treering-based temperature data from the same region (Davi et al., 2003) [2]. We then discuss temperature fluctuations at centennial and Millennial Time Scales over the past six Millennia and explore the factors causing these fluctuations.
for us is of interest in particular the analysis of the data in section 4.3: "Temperature fluctuations over the past 2000 years: comparison with previous results. Wir lesen:
A number of recent paleoclimate studies in Alaska and elsewhere have focused on high-resolution reconstructions over the past two millennia (e.g. Hu et al., 2001; Loso et al., 2006; McKay et al., 2008)[3]. Comparisons of the T
record from Moose Lake with other Alaskan temperature records suggest that the regional coherency observed in instrumental temperature records (e.g. Wiles et al., 1998; Gedalof and Smith, 2001; Wilson et al., 2007)[4] extends broadly to at least 2000 cal BP. For example, climatic events such as the LIA and the Medieval Climate Anomaly (MCA; peak warmth around 1000 cal BP) occurred largely synchronously between our T
July record from Moose Lake (Fig. 4C) and a delta18O-based temperature record from Farewell Lake on the northwestern foothills of the Alaska Range (Hu et al, 2001;. Fig. 4D).We can therefore safely say, that was found in the present study evidence for the existence of a MWP (I still consider the term climate anomaly in this regard as misleading and one may be led Fig. 3 A, and description to heart , which for me is a clear increase in temperature from 600 AD to 1200 AD with a peak you can).
But what about the other studies, with the studies by Hu et al, 2001;.. Loso et al, 2006; McKay et al, 2008. works not mentioned - used by Ljungqvist, in its latest study - such as D'Arrigo et al. Loso 2006 or 2009?
The oldest, mentioned regional long-term study of Alaska is by Hu et al., Published under the title
Pronounced climatic variations in Alaska during the last two Millennia . It seems as we will cite the quote to be the first high-quality long-term study of Alaska, so it is appropriate also to begin here.Hu et al. designed
multi proxy geochemical analyzes of a sediment core from Farewell Lake (62 ° 33 'N, 153 ° 38' W, 320 m altitude) in the northwestern foothills of the Alaska Range (Fig. 1A).
theory analysis Provide the first high-resolution (multidecadal) quantitative last record of Alaskan climate variations that spans the two Millennia.
Hu et al. 10552nd
They came here the following results:
SWT reconstruction at Farewell
of interest [Fig 3rd;. The higher average temperatures in the Middle Ages to the Little Ice Age are, in my opinion
claire
distinct and legible, WVB] Hu et al. 10555.
Quaternary Research
[pdf format, 1 MB]) is also evidence for the existence of a MWP in the investigation area. published workA 1500-year record of temperature and glacial response inferred from varved Iceberg Lake, southcentral Alaska
run in the following way:
Loso et al., 13.
Um letztlich konkludieren zu können:
Relative to the entire period of record, temperatures suggested by the chronology were lowest around 600 A.D., increased slowly and sporadically from then until reaching a relatively stable value in the Medieval Warm Period between A.D. 1000 and 1250, cooled again towards a sustained period of Little Ice Age cold between A.D. 1500 and 1850, and have increased dramatically since then.
Loso et al., 23.
Als nächste Arbeit wollen wirOn the long-term context for late twentieth century warming(pdf format, 920 KB) by D'Arrigo et al. cite, published in the Journal of Geophysical Research
. D'Arrigo et al. "Develop two new tree-ring-based reconstructions of NH temperatures that address several priorities recommended for the generation of searchable records" (2). The proxy data located in Alaska, which go back far enough, have a MWP, clear to read in Table 1, the data "Seward" and "Coastal Alaska", 2 in Figure Generally in relation to the NH konkludieren D'Arrigo et al. hereinafter
We have presented STD and RCS NH temperature reconstructions for the past years 1259th In so doing, we have addressed several recommended priorities [Esper et al., 2005b], [8] for the development of large-scale reconstructions (see above). ... The NH RCS reconstruction displays pronounced variability, including significant "MWP" and "LIA" departures. D'Arrigo et al, 11
The study by McKay et al. Biogenic silica concentration as a high-resolution, quantitative temperature proxy at Hallet Lake, south-central Alaska
(pdf format, 1.35 MB), published in Geophysical Research Letters
shows a MWP. The authors write:
BSi-inferred summer temperatures were warmer than the long-term (2kA) average (3.1 ° C) from about 100 to about 500 AD, before decreasing rapidly to about 2 ° C by 600 AD (Figure 3). This cooling coincide with a period of glacial advance in the Chugach Range and the Kenai Mountains and St. Elias [Wiles et al., 2008] [9]. After about 600 AD, summer temperature gradually icreased from 2 to about 4 ° C average by 1300 AD, and Remained above the 2 ka until about 1500 AD.
Mc Kay et al., 5
The last study, Summer temperatures during the Medieval Warm Period and Little Ice Age inferred from varved proglacial lake sediments in southern Alaska
, (pdf format, 620 KB ) published in the Journal of Paleolimnology , as can "update" to his study of Loso made in 2006 to be seen and also shows clearly a MWP in the study area to. The Abstract summarizes Loso together:
A Medieval Warm Period is evident from 1000 to 1100 AD, but the temperature reconstruction suggest it was less then warm recent decades - an observation supported by independent geological evicence of recent glacier retreat that is unprecedented over the period of record.
Loso, 117
writes in his elaboration of the temperature reconstruction Lobo further:
Temperatures were higher than average gene rally from 950 to 1350 AD, and after a brief rise around 1850 AD reached their highest levels after 1950 AD. Ultimately Loso konkludiert follows:
Second, the Medieval Warm Period is evident in the record, and based on that and other evidence I suggest that it most clearly and consistently manifest itself in southern Alaska during the eleventh century AD .
Loso, 127
Let us remember:
The new study by Clegg et al. (2010) can be viewed by many studies as one that provides the evidence for the claim that there was a MWP in Alaska.
[1] Barley, EM, Walker IR, Kurek J., Cwynar, LC, Mathewes, RW, Gajewski, K., Finney, BP, 2006. A northwest North American training set: distribution of freshwater midges in relation to air temperature and lake depth. Journal of Paleolimnology 36, 295-314.
[2] Davi, NK, Jacoby, GC, Wiles, GC, 2003. Boreal temperature variability inferred from maximum late wood density and tree-ring width data, Wrangell Mountain region, Alaska. Quaternary Research 60, 252-262.[3] which studies the course of the post will be discussed.
[4] Wiles, GC, D'Arrigo, R., Jacoby, G., 1998. Gulf of Alaska atmosphere-ocean variability over recent centuries inferred from coastal tree-ring records. Climatic Change 38, 289-306. Gedalof, Z., Smith, DJ, 2001. Interdecadal climate variability and regime-scale shifts in Pacific North America. Geophysical Research Letters 28, 1515-1518.
Wilson, R., Wiles, G., D'Arrigo, R., Scope, C., 2007. Cycles and shifts: 1,300 years of multi-decadal temperature variability in the Gulf of Alaska. Climate Dynamics 28, 425-440.
[5] Stine, S. (1994) Nature (London)
369, 546-549.
, 1497-1499.
[6], Briffa, KR, Bartholin TS, Eckstein, D., Jones, PD, Karlen, W., Schweingruber, FH & Zetterberg, P. (1990) Nature (London)
346, 434-439 .
Briffa, KR, Jones, PD, Bartholin TS, Eckstein, D., Schweingruber, FH, Karlen, W., Zetterberg, P. & Eronen, M. (1992) Climate Dyn.
7, 111-119.
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