Sentences with phrase «kyr for»

It took on the order of 100 kyr for the oxygen and carbon isotopic signals in the ocean to return to their original steady - state values after the PETM.

Not exact matches

In comparison, stages 9 and 5 remained below 3.6 o / oo for 13 and 12 kyr, respectively, and the Holocene interglacial has lasted 11 kyr so far.

In addition, current insolation values are not predicted to return to the high values of late MIS 11 for another 65 kyr.

This idea might be considered esoteric were it not for the fact that there are reasons to think that just such a hierarchical disintegration by a very large comet had occurred within the past 20 - 30 kyr, the largest remnant being Comet Encke.

As for the «not stable environment» bit, I think thats wrong: the holocene (last 10 kyr) * has * been fairly stable, and the rise of civilisation is sometimes attributed to that — William]

See Page 4 - 22, Figure 9: Geomagnetic field intensity level derived from composite volcanic records, not sea floor sediments, for the past 45 kyr.

The lake variability index was calculated by collating the published geological evidence for the appearance of either deep ephemeral or shallow alkaline lakes in seven major Basins in 50 kyrs sections over the last 5 Myrs [15], [17], [23]--[27], [34]--[37].

The 14C ages were corrected for mass - dependent fractionation with measured δ13C values, 33 and compared with samples of Pleistocene whale bone or calcite (backgrounds, > 48 14C kyr BP), late Holocene bison bone (∼ 1,850 14C BP), late AD 1800s cow bone and OX - 2 oxalic acid standards for calibration.

FYI: Michael, for the past million years the general warming and cooling cycle revolves around 100 kyr cycles

As for the «not stable environment» bit, I think thats wrong: the holocene (last 10 kyr) * has * been fairly stable, and the rise of civilisation is sometimes attributed to that — William]

Periods that are of possibly the most interest for testing sensitivities associated with uncertainties in future projections are the mid-Holocene (for tropical rainfall, sea ice), the 8.2 kyr event (for the ocean thermohaline circulation), the last two millennia (for decadal / multi-decadal variability), the last interglacial (for ice sheets / sea level) etc..

The paleoclimate record (8.2 kyr, and earlier «large lake collapses») shows a dramatic drop in surface temperatures for a substantial period of time when the ocean circulation shuts off or changes, but is that actually what would be expected under these warming conditions?

For the 300 Gton model run, 17 % remained after 1 kyr, and for 1000 Gton, it was 19For the 300 Gton model run, 17 % remained after 1 kyr, and for 1000 Gton, it was 19for 1000 Gton, it was 19 %.

[Response CO2 levels are currently higher than for any time when we have direct measurements (directly, from 1950; before that, from air trapped in ice cores), which amounts to the last 780,000 years (see, e.g., a picture here for the last 400 kyr).

Over very long time periods such that the carbon cycle is in equilibrium with the climate, one gets a sensitivity to global temperature of about 20 ppm CO2 / deg C, or 75 ppb CH4 / deg C. On shorter timescales, the sensitivity for CO2 must be less (since there is no time for the deep ocean to come into balance), and variations over the last 1000 years or so (which are less than 10 ppm), indicate that even if Moberg is correct, the maximum sensitivity is around 15 ppm CO2 / deg C. CH4 reacts faster, but even for short term excursions (such as the 8.2 kyr event) has a similar sensitivity.

Horizontal lines are the mean values of temperature and CO2 for the time periods 799 — 650, 650 — 450, 450 — 270 and 270 — 50 kyr bp.

To illustrate this difference in the CO2 / temperature relationship before and after MIS 16, we calculate mean values for four different time intervals (799 — 650, 650 — 450, 450 — 270 and 270 — 50 kyr bp).

At the beginning of MIS 16, CO2 remains below 180 p.p.m.v. for 3 kyr, most probably reflecting more pronounced glacial carbon storage in the ocean.

This slope is similar to the five glacial — interglacial transitions of the past 450 kyr (see Supplementary Information for a detailed comparison).

Carbon dioxide measurements on Dome C ice, focusing on the interval 390 to 650 kyr before present, bp (2,700 — 3,060 m) 4, confirmed the strong coupling between CO2 and Antarctic temperature found1 in the Vostok ice core for the past 420 kyr.

«A different behavior is observed for the 1/23 kyr − 1 peak where, for a moderate amount of tuning, the significance of the peak increases dramatically.

later, «For ODP 1218 the estimated autocorrelation coefficient is ϕ = 0.87 and the variance of the ∈ disturbances is 0.41 at a time step of 4.3 kyr.»

Despite multiple careful studies, uncertainties in the ice — gas age differences for the Vostok ice core remain of the order of 1 kyr.

For the time interval during the LIG in which GMSL was above present, there is high confidence that the maximum 1000 - year average rate of GMSL rise associated with the sea level fluctuation exceeded 2 m kyr — 1 but that it did not exceed 7 m kyr — 1.

This issue, known as the 100 - kyr problem, is compounded by a lack of explanation for the transition of the length of the cycles from 41,000 to 100,000 years at the mid-Pleistocene transition 1.2 million years ago.

To quote «Proof is obtained by considering the contrary: ice sheet forcing approximately 3W / m ^ 2 and a 5 kyr timing gap between forcing and response, as appears to be the case at Termination IV (figure 2c), is 15,000 W yr / m ^ 2, enough to warm the upper kilometre of the ocean by approximately 160 C» (pdf page 7) This is his justification for modifying the data - not my «characterization» of what he said.

I suppose it depends on the nature of the cold event, which is not the same for the 8.2 kyr event and the 5.2 kyr event.

«The onset of the LEAP occurred within less than two decade, demonstrating the existence of a sharp threshold, which must be near 416Wm - 2, which is the 65N July insolation for 118 kyr BP (ref.

And I don't believe that there is any such strong negative feedback to the Antarctic to account for the 8.2 kyr warm spike.

Padre Cave in Brazil shows it wetter through 8.2 kyr BP, that should be less El Nino for that region of Brazil to be wetter.

Averages over 3, 7 and 10 kyrs from the CALSxk models (Figs. 2b — 2d) suggest that, although there are zonal differences of minimum field intensity, the southern Atlantic is no preferred location for the minimum field strength.

While Genevey et al. (2008) conclude that regional weighting can improve VADM results from the presently available data for the past 3 kyrs and acknowledge that, due to the lack of southern hemisphere data, VADM results might be geographically biased towards western Eurasia, Knudsen et al. (2008) consider the differences they find over the last 10 kyrs insignificantly small.

The LR04 age model establishes that MIS 11 spans two precession cycles, with 18O values below 3.6 o / oo for 20 kyr, from 398 - 418 ka.

The number of available data is relatively high for the past 2 kyrs, but drops dramatically for older times.

We used the higher resolution CALS3k.3 and CALS3k.4 dipole estimates for comparisons using the same filters on the geomagnetic and the radionuclide dipole reconstructions for the past 3 kyrs (Fig. 6), and computed the correlation coefficients among all four records for the time series with low - pass filters between 1/200 and 1/1000 yrs.

In comparison, stages 9 and 5 remained below 3.6 o / oo for 13 and 12 kyr, respectively, and the Holocene interglacial has lasted 11 kyr so far.

Recent spherical harmonic models for the past 3 and 10 kyrs have improved considerably compared to earlier versions.

For the recent 3 kyrs, CALS3k.4 should be the best choice, although its comparatively low dipole moment estimate is surprising.

Figure 3: The phasing of CO2 concentration and temperature for the global (grey), Northern Hemisphere (NH; blue) and Southern Hemisphere (SH; red) proxy stacks based on lag correlations from 20 — 10 kyr ago in 1,000 Monte Carlo simulations.

«The onset of the LEAP occurred within less than two decades (see the core photograph in Fig. 4), demonstrating the existence of a sharp threshold, which must be near 416 W / m2, which is the 65N July insolation for 118 kyr BP (ref.

Anyway, if the problem was huge, then the oldest ice cores should show a lower CO2 / temperature ratio, which is not the case for either Vostok (420 kyr) or Dome C (800 kyr).

A Fourier analysis of each 4 kyr interval can then be used to produce a local «prediction» for the subsequent 1 ka, based on the putative cycles in the preceding 4 kyr.

Even longer term records exist for few sites: the recent Antarctic EPICA core reaches 800 kyr; many others reach more than 100,000 years.

Given that current low orbital eccentricity will persist over the next tens of thousand years, the effects of precession are minimised, and extremely cold northern summer orbital configurations like that of the last glacial initiation at 116 ka will not take place for at least 30 kyr (Box 6.1).

It was then forced with a global carbon isotope curve for 100 kyr by adding 13C - depleted carbon -LRB--25 ‰) into the oceans to reproduce the 5 - 6 °C warming in tropical oceans.

[1] Also, Archer and Ganopolski (2005) report that probable future CO2 emissions may be enough to suppress the glacial cycle for the next 500 kyr.»

The estimates of how much water was released into the N. Atlantic around 8000 yrs ago (potentially triggering the 8.2 kyr «event») are around 2.5 to 5 Sv years (1 Sv year is a volume flux of 10 ^ 6 m3 / s maintained for a year = 3.1 × 10 ^ 13 m3) delivered over 1 year (Clarke et al, 2004).