ICE Core Agedepth Model Calculator
Free Ice core age–depth model Calculator for cryosphere & climate. Enter variables to compute results with formulas and detailed steps.
Reviewed by Daniel Agrici, Founder & Lead Developer
Formula
age = -(H / a) x ln(1 - z / H)
Where H = total ice thickness (m), a = accumulation rate (m/yr), z = depth (m). The Nye model assumes uniform vertical strain.
Worked Examples
Example 1: Greenland Ice Sheet Sample
Problem:An ice core from a site with 3000 m thickness and 0.25 m/yr accumulation. Estimate age at 1500 m.
Solution:Nye: age = -(H/a) x ln(1 - z/H)\nage = -(3000/0.25) x ln(0.5) = -12000 x (-0.6931) = 8317 years\n\nApproximately 8,317 years old, in the early Holocene.
Result:Nye Age: 8317.8 yr | Layer: 12.50 cm | Thinning: 50.0%
Example 2: Deep Antarctic Core
Problem:Dome C: H = 3200 m, accumulation 0.03 m/yr. Estimate age at 3000 m depth.
Solution:Nye: age = -(3200/0.03) x ln(1 - 3000/3200)\nage = -106667 x ln(0.0625) = 295,745 years\n\nRoughly 296 kyr ago, well within glacial-interglacial cycles.
Result:Nye Age: 295,745 yr | Layer: 0.19 cm | Thinning: 6.3%
Frequently Asked Questions
What is an ice core age-depth model and why is it important?
An ice core age-depth model is a mathematical relationship that assigns calendar ages to specific depths within an ice core. These models are essential because direct annual layer counting becomes impossible at greater depths where layers are thinned beyond resolution. The models account for ice flow dynamics, compaction of firn into ice, and basal conditions. Accurate age-depth models allow scientists to correlate ice core records with other climate archives and establish precise chronologies spanning hundreds of thousands of years.
How does the Nye model calculate ice core ages?
The Nye model is one of the simplest analytical age-depth relationships, assuming uniform vertical strain throughout the ice sheet. The formula is age = -(H/a) times ln(1 - z/H), where H is total ice thickness, a is the surface accumulation rate, and z is the depth. This model assumes a constant accumulation rate over time and a linear decrease in annual layer thickness with depth. It provides reasonable first-order estimates but tends to underestimate ages near the base of the ice sheet.
What is the Dansgaard-Johnsen model and how does it improve on Nye?
The Dansgaard-Johnsen model refines the Nye approach by dividing the ice sheet into two zones with different strain rate behaviors. Above a critical depth the vertical strain rate is constant, while below it decreases linearly to zero at the bed. This better represents real ice flow where basal friction and temperature-dependent deformation create a shear zone near the bottom. The model produces older ages at depth and more closely matches independently dated volcanic tephra markers.
How does basal melting affect ice core chronology?
Basal melting removes ice from the bottom of the ice sheet, effectively shortening the total record and causing the oldest layers to be lost. When basal melt is significant the age at the bottom of the core is finite rather than approaching infinity as predicted by simple models. Melt rates range from near zero in cold East Antarctic sites to several millimeters per year in areas with elevated geothermal heat flux. Correcting for basal melt is essential for accurately estimating the maximum age of recoverable ice.
References
Reviewed by Daniel Agrici, Founder & Lead Developer · Editorial policy