NGRIP CH<sub>4</sub> concentration from 120 to 10 kyr before present and its relation to a δ<sup>15</sup>N temperature reconstruction from the same ice core

Abstract

Abstract. During the last glacial cycle, Greenland temperature showed many rapid temperature variations, the so called Dansgaard-Oeschger (DO) events. The past atmospheric methane concentration closely followed these temperature variations, which implies that the warmings recorded in Greenland were probably hemispheric in extent. Here we substantially extend and complete the North Greenland Ice Core Project (NGRIP) methane record from Termination 1 back to the end of the last interglacial period with a mean time resolution of 54 yr. We relate the amplitudes of the methane increases associated with DO events to the amplitudes of the NGRIP temperature increases derived from stable nitrogen isotope (δ15N) measurements, which have been performed along the same ice core. We find the sensitivity to oscillate between 5 parts per billion by volume (ppbv) per °C and 18 ppbv °C−1 with the approximate frequency of the precessional cycle. A remarkably high sensitivity of 25.5 ppbv °C−1 is reached during Termination 1. Analysis of the timing of the fast methane and temperature increases reveals significant lags of the methane increases relative to NGRIP temperature for the DO events 5, 9, 10, 11, 13, 15, 19, and 20. We further show that the relative interpolar concentration difference of methane is 4.6 ± 0.7% between the DO events 18 and 19 and 4.4 ± 0.8% between the DO events 19 to 20, which is in the same order as in the stadials before and after DO event 2 around the Last Glacial Maximum.

Glacial/interglacial wetland, biomass burning, and geologic methane emissions constrained by dual stable isotopic CH4ice core records

“…We propose that the baseline level of atmospheric methane (2, 106) is in fact determined by AxCax wetlands (located in Sundaland and other AxCax regions) and that its decline to the lowest levels observed in ice cores after MIS 3 is caused by the drying of tropical wetland systems. We observe that the CH 4 response reported for Greenland interstadials (DO 2/3, 18/19/20, and 22/23) during periods of falling sea level is generally small (8,107,108). In other words, [CH 4 ] only shows large stadial/interstadial increases during periods of rising (local) sea level when insolation and increased monsoon precipitation could, in principle, boost wetland CH 4 emissions (2, 4, 19, 25, 70, 106, 109).…”

“…The lowest values of around 360 ppb are measured in ice cores during glacial maxima, whereas for the last eight interglacials, [CH 4 ] typically ranged between 600 and 700 ppb (4). Fast and significant stadial/interstadial [CH 4 ] increases occurred within a few decades during glacials in parallel to DansgaardOeschger events (8). Furthermore, [CH 4 ] levels in the Northern Hemisphere are mostly higher than those in the Southern Hemisphere (9).…”

Temporal and spatial structure of multi-millennial temperature changes at high latitudes during the Last Interglacial

“…This is indeed observed during Termination I as well as during millennial-scale DansgaardeOeschger events (e.g. Chappellaz et al, 1993;Huber et al, 2006;Baumgartner et al, 2013). On Fig.…”

Millennial‐ to Orbital‐Scale Responses of Western Equatorial Atlantic Thermocline Depth to Changes in the Trade Wind System Since the Last Interglacial

“…In addition, the onset of the LIG was defined by aligning the Ti/Ca record of core GL‐1248 with the Antarctic methane record from EPICA Dome C (Loulergue et al, ) at approximately 129 ka on the AICC2012 timescale (Veres et al, ), similarly to previous studies (e.g., Govin et al, ). The rationale behind this alignment is that abrupt Greenland warming events occurred simultaneously with methane increases during millennial‐scale events of the last glacial period and the last deglaciation (Baumgartner et al, ; Chappellaz et al, ; Huber et al, ). We estimated the error for the defined tie points by taking into account (1) the mean resolution of the Ti/Ca record from GL‐1248, (2) the mean resolution and dating uncertainty of the reference curves, and (3) an estimated matching error when defining a tie point.…”