TY - JOUR

T1 - Mountain building and the initiation of the Greenland Ice Sheet

AU - Solgaard, Anne Munck

AU - Bonow, Johan

AU - Langen, Peter Lang

AU - Japsen, Peter

AU - Hvidberg, Christine Schøtt

PY - 2013/12/15

Y1 - 2013/12/15

N2 - The effects of a new hypothesis about mountain building in Greenland on ice sheet initiation are investigatedusing an ice sheet model in combination with a climate model. According to this hypothesis, low-relief landscapesnear sea level characterised Greenland in Miocene times until two phases of km-scale uplift in the lateMiocene and in the latest Miocene–Pliocene (beginning at 10 and ~5 Ma, respectively) initiated the formationof the present-day mountains. The topography of Greenland, prior to these uplift events is reconstructed fromthe present-day, isostatically compensated bedrock by mapping the two main steps in the landscape thatresulted from the two uplift phases. Ice sheet initiation is studied using the topography before uplift and aftereach phase of uplift by applying different forcing conditions relevant for the late Cenozoic, which wascharacterised by long-term cooling superimposed by cold and warm excursions. The modelling results showthat no ice initiates in the case of the low-lying and almost flat topography prior to the uplifts. However, the resultsdemonstrate a significant ice sheet growth in response to the orographically induced increase in precipitationand the cooling of surface temperatures accompanying the uplift. Large amounts of ice are able to formafterthe first uplift event, but the ice sheet is sensitive to changes in climate. The results showthat the second phase ofuplift facilitates ice sheet build-up further and increases the stability of the ice sheet by providing anchoringpoints which are not available to the same extent in the lower topographies. However, the results also reveal aFöhn effect that inhibits ice sheet expansion into the interior Greenland and thus shifts the threshold of formationof inland ice towards colder temperatures. Under conditions that are colder than the present, the ice can overcomethe Föhn effect, flow into the interior and form a coherent ice sheet. The results thus indicate that theGreenland Ice Sheet of today is a relict formed under colder conditions. The modelling results are consistentwith the observed climatic variability superimposed on the general cooling trend in the late Cenozoic: e.g., icerafted debris in late Miocene deposits off southeast Greenland and the mid-PlioceneWarmth. The late Cenozoicmountain building in Greenland augments the effects of the climatic deterioration leading to the Northern Hemisphereglaciations, and without the second phase of uplift, the Greenland Ice Sheet would have been more sensitiveto the changes in climate over the past millions of years.

AB - The effects of a new hypothesis about mountain building in Greenland on ice sheet initiation are investigatedusing an ice sheet model in combination with a climate model. According to this hypothesis, low-relief landscapesnear sea level characterised Greenland in Miocene times until two phases of km-scale uplift in the lateMiocene and in the latest Miocene–Pliocene (beginning at 10 and ~5 Ma, respectively) initiated the formationof the present-day mountains. The topography of Greenland, prior to these uplift events is reconstructed fromthe present-day, isostatically compensated bedrock by mapping the two main steps in the landscape thatresulted from the two uplift phases. Ice sheet initiation is studied using the topography before uplift and aftereach phase of uplift by applying different forcing conditions relevant for the late Cenozoic, which wascharacterised by long-term cooling superimposed by cold and warm excursions. The modelling results showthat no ice initiates in the case of the low-lying and almost flat topography prior to the uplifts. However, the resultsdemonstrate a significant ice sheet growth in response to the orographically induced increase in precipitationand the cooling of surface temperatures accompanying the uplift. Large amounts of ice are able to formafterthe first uplift event, but the ice sheet is sensitive to changes in climate. The results showthat the second phase ofuplift facilitates ice sheet build-up further and increases the stability of the ice sheet by providing anchoringpoints which are not available to the same extent in the lower topographies. However, the results also reveal aFöhn effect that inhibits ice sheet expansion into the interior Greenland and thus shifts the threshold of formationof inland ice towards colder temperatures. Under conditions that are colder than the present, the ice can overcomethe Föhn effect, flow into the interior and form a coherent ice sheet. The results thus indicate that theGreenland Ice Sheet of today is a relict formed under colder conditions. The modelling results are consistentwith the observed climatic variability superimposed on the general cooling trend in the late Cenozoic: e.g., icerafted debris in late Miocene deposits off southeast Greenland and the mid-PlioceneWarmth. The late Cenozoicmountain building in Greenland augments the effects of the climatic deterioration leading to the Northern Hemisphereglaciations, and without the second phase of uplift, the Greenland Ice Sheet would have been more sensitiveto the changes in climate over the past millions of years.

M3 - Journal article

VL - 392

SP - 161

EP - 176

JO - Palaeogeography, Palaeoclimatology, Palaeoecology - An International Journal for the Geo-Sciences

JF - Palaeogeography, Palaeoclimatology, Palaeoecology - An International Journal for the Geo-Sciences

SN - 0031-0182

ER -