Peat accumulation in drained thermokarst lake basins in continuous, ice‐rich permafrost, northern Seward Peninsula, Alaska

Abstract

[1] Thermokarst lakes and peat-accumulating drained lake basins cover a substantial portion of Arctic lowland landscapes, yet the role of thermokarst lake drainage and ensuing peat formation in landscape-scale carbon (C) budgets remains understudied. Here we use measurements of terrestrial peat thickness, bulk density, organic matter content, and basal radiocarbon age from permafrost cores, soil pits, and exposures in vegetated, drained lake basins to characterize regional lake drainage chronology, C accumulation rates, and the role of thermokarst-lake cycling in carbon dynamics throughout the Holocene on the northern Seward Peninsula, Alaska. Most detectable lake drainage events occurred within the last 4,000 years with the highest drainage frequency during the medieval climate anomaly. Peat accumulation rates were highest in young (50-500 years) drained lake basins (35.2 g C m À2 yr À1 ) and decreased exponentially with time since drainage to 9 g C m À2 yr À1 in the oldest basins. Spatial analyses of terrestrial peat depth, basal peat radiocarbon ages, basin geomorphology, and satellite-derived land surface properties (Normalized Difference Vegetation Index (NDVI); Minimum Noise Fraction (MNF)) from Landsat satellite data revealed significant relationships between peat thickness and mean basin NDVI or MNF. By upscaling observed relationships, we infer that drained thermokarst lake basins, covering 391 km 2 (76%) of the 515 km 2 study region, store 6.4-6.6 Tg organic C in drained lake basin terrestrial peat. Peat accumulation in drained lake basins likely serves to offset greenhouse gas release from thermokarst-impacted landscapes and should be incorporated in landscape-scale C budgets.

Holocene ice-wedge polygon development in northern Yukon permafrost peatlands (Canada)

“…5). Thermokarst lakes commonly drain suddenly; and sometimes catastrophically (Mackay, 1986;Jones et al, 2011Jones et al, , 2012Jones and Arp, 2015). We suggest lake drainage as the process associated with the split in the record because of gully incision from southerly direction.…”

“…This cycle includes initiation, expansion, drainage and eventual re-initiation (Van Huissteden et al, 2011). Their lifetime e in contrast to the onset e largely depends on local factors such as geomorphology, ground-ice conditions, hydrology and groundsurface stability (Jones et al, 2011(Jones et al, , 2012Jones and Arp, 2015). The initiation of many thermokarst lakes in northwest Canada, Alaska, and Siberia is related to increasing air temperatures, available moisture and permafrost thaw in response to short-term warming events during the Pleistocene-Holocene transition or later on during the Holocene thermal maximum (Rampton, 1988;Brosius et al, 2012;Walter Anthony et al, 2014).…”

Sources and sinks of carbon in boreal ecosystems of interior Alaska: A review

“…Lake drainage Elementa: Science of the Anthropocene • 2: 000032 • doi: 10.12952/journal.elementa.000032 can also result in peat accumulation within a matter of decades, and the accumulation of peat in these basins act as a carbon sink ( Jones et al, 2012) and has the potential to offset losses of CH 4 and CO 2 , but only after centuries to millenia. A recent data and modeling analysis of the radiative forcing of thermokarst lakes since the last deglaciation has revealed that despite being CH 4 sources, thermokarst lakes as a whole became carbon sinks ∼5,000 years ago (Walter-Anthony et al, 2014).…”

“…Lakes can also emit a substantial amount of CO 2 (Kling et al, 1991;Cole et al, 1994;Algesten et al, 2004). Although lakes are large CH 4 and CO 2 sources, they also have the potential to sequester carbon as lake sediments and peat accumulate with time ( Jones et al, 2012;Walter-Anthony et al, 2014).…”

Can C-band synthetic aperture radar be used to estimate soil organic carbon storage in tundra?

“…Peat deposits can have similar surface properties but variable depths. Peat accumulation is related to age, and the accumulation rates decrease exponentially in thermokarst basins (Jones et al, 2012).…”