Limits...
A century of variation in the dependence of Greenland iceberg calving on ice sheet surface mass balance and regional climate change.

Bigg GR, Wei HL, Wilton DJ, Zhao Y, Billings SA, Hanna E, Kadirkamanathan V - Proc. Math. Phys. Eng. Sci. (2014)

Bottom Line: A century-long record of Greenland icebergs comes from the International Ice Patrol's record of icebergs (I48N) passing latitude 48° N, off Newfoundland.I48N exhibits strong interannual variability, with a significant increase in amplitude over recent decades.We also suggest that GrIS calving discharge is episodic on at least a regional scale and has recently been increasing significantly, largely as a result of west Greenland sources.

View Article: PubMed Central - PubMed

Affiliation: Department of Geography , University of Sheffield , Sheffield S10 2TN, UK.

ABSTRACT
Iceberg calving is a major component of the total mass balance of the Greenland ice sheet (GrIS). A century-long record of Greenland icebergs comes from the International Ice Patrol's record of icebergs (I48N) passing latitude 48° N, off Newfoundland. I48N exhibits strong interannual variability, with a significant increase in amplitude over recent decades. In this study, we show, through a combination of nonlinear system identification and coupled ocean-iceberg modelling, that I48N's variability is predominantly caused by fluctuation in GrIS calving discharge rather than open ocean iceberg melting. We also demonstrate that the episodic variation in iceberg discharge is strongly linked to a nonlinear combination of recent changes in the surface mass balance (SMB) of the GrIS and regional atmospheric and oceanic climate variability, on the scale of the previous 1-3 years, with the dominant causal mechanism shifting between glaciological (SMB) and climatic (ocean temperature) over time. We suggest that this is a change in whether glacial run-off or under-ice melting is dominant, respectively. We also suggest that GrIS calving discharge is episodic on at least a regional scale and has recently been increasing significantly, largely as a result of west Greenland sources.

No MeSH data available.


Related in: MedlinePlus

Annual GrIS SMB (c), in km3 yr−1, LSST (b) anomaly, in °C, and North Atlantic Oscillation (NAO; a), standardized to 1 s.d., for 1900–2008. The solid line in each panel shows the annual average, and the dashed line is a 5 year running mean. See §2a for a description of the origin of these three datasets.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4042714&req=5

RSPA20130662F1: Annual GrIS SMB (c), in km3 yr−1, LSST (b) anomaly, in °C, and North Atlantic Oscillation (NAO; a), standardized to 1 s.d., for 1900–2008. The solid line in each panel shows the annual average, and the dashed line is a 5 year running mean. See §2a for a description of the origin of these three datasets.

Mentions: The iceberg calving flux is a major component of the total mass balance of the Greenland ice sheet (GrIS). Past work, using a variety of approaches, has found that one of the components of the GrIS total mass balance, namely the surface mass balance (SMB; figure 1) of the GrIS, has high interannual variability, but with two periods of significant decline over the past century, during 1930–1960 [1] and again in the last decade [1,2]. By contrast, current estimates of one measure of the other key component, the solid ice loss, since the early 1990s, namely the ice flux across the GrIS grounding line, suggest this latter function varies much more smoothly on the ice sheet scale [2] but has increased by approximately 20% since the 1990s. These ice loss estimates exhibit no linear correlation with SMB, except when smoothed and considered over the long term [3]. Three questions are raised by these analyses. Is the iceberg discharge, rather than grounding line ice flux, smoothly varying, given the large background flux, the doubling in estimates of its size in the last decade (cf. [2] with [4–6]) and historical [7] and recent palaeoceanographic [8] records of strong variability? How has this discharge varied over longer time scales than can be measured from satellites? What are the major environmental variables driving these changes?Figure 1.


A century of variation in the dependence of Greenland iceberg calving on ice sheet surface mass balance and regional climate change.

Bigg GR, Wei HL, Wilton DJ, Zhao Y, Billings SA, Hanna E, Kadirkamanathan V - Proc. Math. Phys. Eng. Sci. (2014)

Annual GrIS SMB (c), in km3 yr−1, LSST (b) anomaly, in °C, and North Atlantic Oscillation (NAO; a), standardized to 1 s.d., for 1900–2008. The solid line in each panel shows the annual average, and the dashed line is a 5 year running mean. See §2a for a description of the origin of these three datasets.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4042714&req=5

RSPA20130662F1: Annual GrIS SMB (c), in km3 yr−1, LSST (b) anomaly, in °C, and North Atlantic Oscillation (NAO; a), standardized to 1 s.d., for 1900–2008. The solid line in each panel shows the annual average, and the dashed line is a 5 year running mean. See §2a for a description of the origin of these three datasets.
Mentions: The iceberg calving flux is a major component of the total mass balance of the Greenland ice sheet (GrIS). Past work, using a variety of approaches, has found that one of the components of the GrIS total mass balance, namely the surface mass balance (SMB; figure 1) of the GrIS, has high interannual variability, but with two periods of significant decline over the past century, during 1930–1960 [1] and again in the last decade [1,2]. By contrast, current estimates of one measure of the other key component, the solid ice loss, since the early 1990s, namely the ice flux across the GrIS grounding line, suggest this latter function varies much more smoothly on the ice sheet scale [2] but has increased by approximately 20% since the 1990s. These ice loss estimates exhibit no linear correlation with SMB, except when smoothed and considered over the long term [3]. Three questions are raised by these analyses. Is the iceberg discharge, rather than grounding line ice flux, smoothly varying, given the large background flux, the doubling in estimates of its size in the last decade (cf. [2] with [4–6]) and historical [7] and recent palaeoceanographic [8] records of strong variability? How has this discharge varied over longer time scales than can be measured from satellites? What are the major environmental variables driving these changes?Figure 1.

Bottom Line: A century-long record of Greenland icebergs comes from the International Ice Patrol's record of icebergs (I48N) passing latitude 48° N, off Newfoundland.I48N exhibits strong interannual variability, with a significant increase in amplitude over recent decades.We also suggest that GrIS calving discharge is episodic on at least a regional scale and has recently been increasing significantly, largely as a result of west Greenland sources.

View Article: PubMed Central - PubMed

Affiliation: Department of Geography , University of Sheffield , Sheffield S10 2TN, UK.

ABSTRACT
Iceberg calving is a major component of the total mass balance of the Greenland ice sheet (GrIS). A century-long record of Greenland icebergs comes from the International Ice Patrol's record of icebergs (I48N) passing latitude 48° N, off Newfoundland. I48N exhibits strong interannual variability, with a significant increase in amplitude over recent decades. In this study, we show, through a combination of nonlinear system identification and coupled ocean-iceberg modelling, that I48N's variability is predominantly caused by fluctuation in GrIS calving discharge rather than open ocean iceberg melting. We also demonstrate that the episodic variation in iceberg discharge is strongly linked to a nonlinear combination of recent changes in the surface mass balance (SMB) of the GrIS and regional atmospheric and oceanic climate variability, on the scale of the previous 1-3 years, with the dominant causal mechanism shifting between glaciological (SMB) and climatic (ocean temperature) over time. We suggest that this is a change in whether glacial run-off or under-ice melting is dominant, respectively. We also suggest that GrIS calving discharge is episodic on at least a regional scale and has recently been increasing significantly, largely as a result of west Greenland sources.

No MeSH data available.


Related in: MedlinePlus